Article

The Outcome of Alien Tree Invasions in Puerto Rico

Authors:
  • International Institute of Tropical Forestry
To read the full-text of this research, you can request a copy directly from the author.

Abstract

Invasive alien tree species in Puerto Rico often form monospecific stands on deforested lands that were previously used for agriculture and then abandoned. Most native pioneer species are incapable of colonizing these sites, and thus introduced species have little competition from native trees. Alien trees may dominate sites for 30 to 40 years, but by that time native species begin to appear in the understory. By 60 to 80 years, unique communities comprising both alien and native species are found on these sites. This phenomenon is a response to a change in the disturbance regime of Puerto Rico's landscape, brought about by intensive agricultural land use and abandonment. The invasion of a site and the formation of an alien-dominated forest serve important ecological functions, such as repairing soil structure and fertility, and restoring forest cover and biodiversity at degraded sites.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... Examples of alien tree species as nurse plants, i.e., plants supporting the establishment of native tree species, are also well documented (De Pietri, 1992;Svriz et al., 2013). As such, alien species can help to restore forest cover and species richness (Lugo, 2004). ...
... Similarity of species composition did not show significant difference between L. kaempferi plantations and other vegetation types (Fig. 5), suggesting that the recovery of species composition tends to be slower than that of species richness (Chazdon et al., 2009;Matos et al., 2020). While deer fencing has certain effects on local vegetation recovery in various regions worldwide (Côté et al., 2004;Nishizawa et al., 2016), it is not a panacea given the multiple challenges for forest restoration. Specifically, synergistic influences between deer overgrazing and prevailing winds make restoration challenging in Shiretoko National Park. ...
... We also found that the cover of native tree species was high in alien plantations ( Fig. 6; Group 1). This could be the result of functional differences between L. kaempferi and native species, such as leaf phenology (deciduous vs. evergreen) and light requirement, as reported elsewhere (Lugo, 2004). Furthermore, A. sachalinensis, which can survive under low light because of its high shade tolerance, originally dominates the regeneration in L. kaempferi plantations. ...
Article
Restoring forests has recently received considerable attention in the context of sequestering carbon and supporting biodiversity. Although considering alien species as a tool for natural forest restoration still remains controversial, harnessing alien species when they are already present in an ecosystem might result in overall benefits for nature and society. In this study we evaluated whether the presence of an alien tree species supports or hinders the establishment of naturally regenerating forests in Shiretoko National Park, Japan. In particular, we focused on Larix kaempferi, which is widely present yet non-native to the region, and examined how this alien species affects two factors influencing the success of restoration: wind disturbance and deer herbivory. We examined the following effects of L. kaempferi plantations on natural regeneration: (1) the windbreak function for protecting native tree growth and (2) the nursery function to promote the regeneration of native tree saplings and seedlings under high herbivory pressure. We assessed tree height and regeneration, using large-scale remotely sensed data and terrestrial inventory data in five major vegetation types. We found that L. kaempferi plantations can protect native species from predominant winds. Additionally, L. kaempferi canopy cover promoted abundance and species richness in understory saplings and seedlings compared to other vegetation types such as primary and secondary forests, even under excessive browsing pressure. No regenerating L. kaempferi individuals were observed during the field census, suggesting the species is likely not invasive in our study system. The positive relationship between alien tree species and the regeneration of native tree assemblages emphasizes that existing alien species have the potential to act as nurse plants. Our findings imply that the presence of alien species can contribute to natural forest restoration by improving the local environmental conditions for native species in the short-term. Given the multiple ecological and social needs in our changing world, careful consideration is required to evaluate the long-term consequences of alien species. Especially in ecosystems in which alien species have already established, using their positive functions rather than swiftly eradicating them from the landscape might be beneficial for long-term restoration goals. We conclude that managers need to be aware of the context-dependency of alien species to make restoration more effective.
... First, restoration is a way to combat species invasion, especially under the stresses of climate change and the expanding influence of human activities (Esler et al. 2010;Gaertner et al. 2012;Hobbs and Richardson 2011;Kerns and Guo 2012). Second, restoration has been increasingly used to provide much-needed ecosystem services such as sequestering carbon (Carter 2013) and providing wood, biofuels, and other products, partly because the sites needing restoration are often close to human populations and thus undergo greater ongoing disturbances and degradation (Hill 2007;Lugo 2004;Roe 2010). Therefore, today's restoration efforts face much greater challenges than ever before, and the cost for restoration is drastically increasing through time. ...
... • In highly degraded or totally destroyed habitats, carefully selected exotic species could be used for early restoration or recovery (Guo and Norman 2013;Ren et al. 2014). Such species are often regarded as pioneer species and/or nitrogen fixers, which could facilitate native species colonization as nurse plants during the initial recovery Lugo 2004;Lugo and Erickson 2017;Ren et al. 2008Ren et al. , 2009 (Fig. 2). • Lessons from grassland experiments around the world (e.g., restoration on the Great Plains of the United States) and experimental forests, including plantations (e.g., USDA-Forest Service), have not been extensively and effectively used. ...
... Such nonnative species could subsequently create suitable conditions for native species. However, caution is strongly urged to ensure that there is a high possibility that such nonnative species will be eventually replaced by native species and not be invasive and difficult to eradicate (Guo and Norman 2013;Lugo 2004;Ren et al. 2008). ...
Article
Full-text available
Common practices for invasive species control and management include physical, chemical, and biological approaches. The first two approaches have clear limitations and may lead to unintended (negative) consequences, unless carefully planned and implemented. For example, physical removal rarely completely eradicates the targeted invasive species and can cause disturbances that facilitate new invasions by nonnative species from nearby habitats. Chemical treatments can harm native, and especially rare, species through unanticipated side effects. Biological methods may be classified as biocontrol and the ecological approach. Similar to physical and chemical methods, biocontrol also has limitations and sometimes leads to unintended consequences. Therefore, a relatively safer and more practical choice may be the ecological approach, which has two major components: (1) restoration of native species and (2) biomass manipulation of the restored community, such as selective grazing or prescribed burning (to achieve and maintain viable population sizes). Restoration requires well-planned and implemented planting designs that consider alpha-, beta-, and gamma-diversity and the abundance of native and invasive component species at local, landscape, and regional levels. Given the extensive destruction or degradation of natural habitats around the world, restoration could be most effective for enhancing ecosystem resilience and resistance to biotic invasions. At the same time, ecosystems in human-dominated landscapes, especially those newly restored, require close monitoring and careful intervention (e.g., through biomass manipulation), especially when successional trajectories are not moving as intended. Biomass management frequently uses prescribed burning, grazing, harvesting, and thinning to maintain overall ecosystem health and sustainability. Thus, the resulting optimal, balanced, and relatively stable ecological conditions could more effectively limit the spread and establishment of invasive species. Here we review the literature (especially within the last decade) on ecological approaches that involve biodiversity, biomass, and productivity, three key community/ecosystem variables that reciprocally influence one another. We focus on the common and most feasible ecological practices that can aid in resisting new invasions and/or suppressing the dominance of existing invasive species. We contend that, because of the strong influences from neighboring areas (i.e., as exotic species pools), local restoration and management efforts in the future need to consider the regional context and projected climate changes.
... The answers to these questions are specific to particular species, locations, and points in time. In Puerto Rico, where forest recovery may be further advanced than most jurisdictions in the study, mono-specific stands of non-native plants that once dominated abandoned agricultural sites have since given way to novel forest communities comprised of new combinations of native and non-native species that function and provide multiple ecosystem services at levels similar to or higher than native forests [103,104]. For example, the introduced African tuliptree (Spathodea campanulata) currently accounts for the greatest number of trees and most live tree basal area of all tree species inventoried by the USDA Forest Service FIA program, yet the next three most important tree species are native to Puerto Rico, demonstrating the capacity of native species to regenerate and compete with non-native species and their ability to recolonize secondary forest associations in landscapes significantly altered by human activities [43]. ...
... Third, new or 'novel' assemblages of non-native and native plant species are maturing over large areas and portions of many of the islands, predominately on abandoned agricultural lands cleared of native forests long ago. These forests typically are dominated by non-native and by smaller-(<13 cm dbh) and medium-stemmed (13-28 cm dbh) trees, limiting commercial timber uses, for now at least, but contributing to the restoration and provision of ecosystem services at levels similar to or even higher than native forests [64,103,104,106]. The implications of this trend to sustainability depend greatly on the future trajectory of these novel ecosystems in the specific social-ecological settings in which they occur and how sustainability is defined and delineated in its component parts and processes. ...
Article
Full-text available
Forests across the U.S. and U.S. affiliated islands of the Caribbean and Pacific constitute rich and dynamic social-ecological systems that, while heterogeneous in many ways, share certain characteristics and trends that underscore the utility of sustainability assessments that go beyond single jurisdictional efforts. This paper summarizes a recent effort to assess the sustainability of tropical island forests of and politically affiliated with the U.S. using the Montréal Process criteria and indicator framework (MP C&I), which address ecological, social, economic, and institutional dimensions of forests. Forests cover 45 percent of the total area and more than 50 percent of each island jurisdiction, except Hawaii (36 percent). Forest cover is generally stable over much of the area in terms of recent reference conditions. The history of human occupation and land alteration is a prominent determinant of current conditions throughout the islands, which exhibit relatively high rates of threatened species in comparison to mainland counterparts and particularly where endemism is high. The islands also harbor significant areas of new or novel assemblages of native and non-native forest species, predominately on abandoned agricultural lands cleared of native forests long ago, which have been shown to contribute to the restoration of these degraded lands and provide many other ecosystem services at levels as high as and in some cases higher than native forests. Although industrial-level commercial timber harvest is small to nonexistent on most islands, socioeconomic and cultural linkages to forests are extensive but difficult to quantify. Amassing a foundation of data sufficient to address the MP C&I was challenging, in part due to the heterogeneity of the islands, island geography, and limited reporting capacities. We document significant improvements in the availability of data important for sustainability assessments in the last decade or so, especially with the extension of the U.S. Department of Agriculture Forest Service Forest Inventory and Analysis program to the islands. Likewise, we find the MP C&I to be a useful tool for organizing and presenting information important for assessing forest sustainability. Nevertheless, considerable data gaps remain in the areas of biodiversity, forest functions and processes, and socioeconomic conditions of forests, which are critical elements to track across the islands, particularly in the context of climate change and ongoing anthropogenic pressures.
... Biotic filters become increasingly important in the later stages of succession, while environmental filtering dominates in the early stages and during secondary regeneration (Connell and Slatyer 1977;Letcher 2010;Ding et al. 2012;Letcher et al. 2012;Norden et al. 2012;Purschke et al. 2013;Stadler et al. 2017). Meanwhile, intensity of disturbance has been shown to alter successional trajectories (Chazdon et al. 2003;Lugo 2004;Letcher 2010;Whitfeld et al. 2012). ...
... This species shows an aggressive competitive behavior, forming dense monospecific stands, similar to pioneers species in post disturbance forests (Chazdon 2008;Menon and Carvalho 2012). The novel habitat characteristics promoted by past disturbances, edge effects and human activity creates conditions for the formation of novel assemblages, with alien species being in a competitive advantage, which in the absence of human intervention, will reproduce and trigger new trajectories of succession and ecosystem function (Lugo 2004;Stadler et al. 2017). ...
Article
Full-text available
Urbanization leads to strong modifications of landscape structure and ecosystem functioning, and urban areas are spreading rapidly. The aim of this study was to investigate how phylogenetic diversity and composition of tree species are affected by urbanization itself and land-use history. We found that species richness, rarefied species richness and phylogenetic diversity are all affected by the land-use history of urban forests. Indeed, forests that regenerated from cropland, and particularly those regenerated from denuded landscapes, showed strong phylogenetic clustering, which was also related to their high perimeter-area ratio. Our analyses of phylogenetic composition show that urban forests without land-use history are compositionally indistinguishable from mature, non-urban forests. These two forest types house a diversity of evolutionary lineages and no specific lineage is a strong indicator of these forest types. In contrast, the two urban forest types with anthropogenic land-use history have a few, distinct lineages that are strongly associated with each of them, respectively. Overall, our results suggest that urban forests without previous land-use can house substantial amounts of angiosperm evolutionary diversity, which highlights the importance of preserving natural forest fragments as cities expand. This study highlights the substantial value of tropical urban forests and the importance of considering information on land-use history, even when studying urban environments.
... Puerto Rico's secondary forests represent a legacy of anthropogenic activities with new combinations of both native and introduced tree species (Abelleira-Martínez 2010; Fonseca Da Silva 2014; Lugo 2004Lugo , 2009). Studies characterizing tree species composition in secondary stands of Puerto Rico highlight the critical function of the introduced African tulip tree (Spathodea campanulata P. Beauv.) ( Fig. A8.8) as a novel forest facilitator, along with remnant native forests or trees functioning as seed sources for native species recovery within the subtropical moist and wet forest life zones (Abelleira-Martínez 2010; Brandeis and Turner 2013a). ...
... Sites where the cajeput tree is growing have signs of fire, have been partially drained, and were either farmed in the past or show signs of historical development (Pratt et al. 2005). While the cajeput tree is classified as intolerant of shade (Geary and Woodall 1990), there is no native tree species in Puerto Rico capable of withstanding this combination of flood and fire (Lugo 2004). ...
Chapter
Full-text available
Invasive species in the Southeast and Caribbean region include a wide variety of taxa and affect both terrestrial and aquatic systems. Wood-boring insect species, such as ambrosia beetles and their microbial associates and symbionts, are easily introduced in solid wood packing material; the warm, humid climate facilitates their establishment in southern forests. The climate is also very hospitable to the establishment of new invasive plants, which pose a threat not only through their own ecological effects but also via other organisms (e.g., insects and pathogens) they may harbor upon arrival through international plant trade. In both the terrestrial and aquatic systems of the Southeast, numerous invasive animal species, including birds, reptiles, amphibians, and fish have, been introduced via the commercial pet trade, for which Florida is a major center of activity. Compared to the continental Southeast, the ecosystems of the Caribbean islands of Puerto Rico and the US Virgin Islands, with their diverse sizes and respective levels of anthropogenic activities or land reserve statuses, experience unique environmental and economic effects of non-native invasive species.This chapter highlights invasive species issues of importance in the region, with separate coverage for the continental Southeast and the Caribbean islands.
... In fact, succession theory has profound implications for the management of invasive non-native trees or shrubs ('woody weeds'): weed species that do not regenerate under their own canopy are likely to die out naturally as succession proceeds (providing further disturbance does not occur). If the later successional species regenerating in the understory are predominantly native, then the site could be on a natural trajectory to native dominance, without active management (Lugo 2004). Conversely, woody weed species that do regenerate under their own canopy are more likely to be self-replacing and thus persistent in the long term (Wyckoff & Webb 1996;Vanhellemont et al. 2009). ...
... Additionally, the age of the weed population can influence native regeneration in the understory (Wilson 1994;Carswell et al. 2013). Studies from several countries, including New Zealand (Brockerhoff et al. 2003), South Africa (Geldenhuys 2013) and Puerto Rico (Lugo 2004), have demonstrated that abundance and diversity of native species in the understory of non-native tree stands tend to increase as the stand matures and thins out. It would be useful to know what restricts regeneration of these weed species at some sites, and whether management actions could be applied to elicit the same result. ...
Article
Full-text available
The species composition of the understory can be a key indicator of successional trajectories in the absence of disturbance at forested sites. We surveyed species composition and percent cover in the understory of 132 closed-canopy stands of 41 woody weed species throughout New Zealand as a first step in understanding potential successional trajectories in these weed populations. Twenty-seven weed species had zero, or very few, conspecific seedlings or saplings present beneath their own canopy. Fourteen weed species had medium to high numbers of conspecific seedlings and/or saplings present. Some weed species had variable understory regeneration, with high numbers of conspecific seedlings and saplings present at some sites, but none at others. Twenty-eight weed species had native understory cover of ≥ 50% at one or more sites. Native understory cover was higher at sites close to remnants of native vegetation compared to sites distant from native vegetation. Overall, many more native than non-native species were present in woody weed understories. Melicytus ramiflorus (māhoe) was the most common native species, present at 67% of sites. At least 76 other native species were recorded at five or more sites. Our results demonstrate that (1) woody weed species vary in the extent to which they regenerate under their own canopy, and (2) closed canopy woody weed stands frequently have a predominantly native understory. Further research to determine whether the composition of the understory can be used to predict successional trajectories in woody weed populations would be valuable.
... Aside from the underlying stochastic-like phenomena of extinctions and immigrations, small islands have often suffered from the activities of humans disproportionately more than larger islands or continental areas (Denslow 2003). Anthropogenic land use not only has been widespread on islands but also has changed drastically over time, substantially affecting ecosystem processes, community structure and composition, and species interactions (Lugo 2004;Prasad et al. 2010). Caribbean islands are no exception, as European colonization was often accompanied by a severe reduction in forest cover, to the extent that only 1%-5% of the original forest cover exists on some islands (Wadsworth 1950;Lugo 2004). ...
... Anthropogenic land use not only has been widespread on islands but also has changed drastically over time, substantially affecting ecosystem processes, community structure and composition, and species interactions (Lugo 2004;Prasad et al. 2010). Caribbean islands are no exception, as European colonization was often accompanied by a severe reduction in forest cover, to the extent that only 1%-5% of the original forest cover exists on some islands (Wadsworth 1950;Lugo 2004). While more recent socioeconomic changes have facilitated the recovery of ecological communities and ecosystems, the original forest structure, composition, and interactions have been modified largely because of the influx of alien taxa (e.g., Attena1976; Hubbard1996;Abelleira Martínez et al. 2010;Lugo et al. 2012). ...
Article
Full-text available
Premise of research. Small populations are intrinsically more vulnerable to population decline and extinction. Such populations may be most susceptible when distributed on small islands, which suffer disproportionately more from human influences, both directly and indirectly. Nevertheless, small native populations that occur on multiple islands may have dispersal or life history characteristics that buffer impacts from novel disturbance regimes, and rather than populations contracting, they may be expanding. We monitored three populations of the orchid Brassavola cucullata from Caribbean islands of Sint Eustatius and Saba and asked what is the likelihood of population persistence. Methodology. Over a period of 3-4 years, we recorded growth, fruit production, herbivory, recruitment and mortality for all plants in each of our populations. Because of small sample sizes, we used the Dirichlet distribution to calculate and obtain more realistic parameters estimates for the population projection matrices. We assessed persistence and predicted possible population changes with a mixture of traditional (lambda, elasticities) and more recent (transient dynamics and non-linear elasticities) indices. Pivotal results. Growth, reproduction and predicted population persistence varied among years and islands. Sometimes population size was stable whereas in other years reduction could be as high as 10%, the latter being associated with unusually hot and dry years. Transient dynamic and function analyses suggest that populations would be extremely vulnerable to reduction if small plants dominated, while populations which are dominated by large plants are not as likely to be variable in time, reduction in population density as large as 10% could still be possible. Conclusions. Populations of perennial plants on small islands can fluctuate substantially suggesting a degree of vulnerability. While the current situation for B. cucullata shows a general trajectory of decline, there are some signs of stability despite deforestation and herbivore activity. The outlook is precarious for the Saba population given the predominance of younger plants, and all three populations if spasmodic recruitment fails to occur, which may be the case if disturbance regimes change and the ongoing warming and drying trends persist.
... While many naturalized plant species occur at low densities and go largely unnoticed, others form thick monocultures, with the potential to completely displace native forest ecosystems ( Fig. 23.1b). Although generally unwanted and perceived to have mostly negative effects (Peltzer et al. 2015), invasive non-native species can sometimes provide important services, e.g., by allowing forests to recolonize abandoned agricultural areas (Lugo 2004) and contributing to forest ecosystem services such as erosion control, flood mitigation, and pollination (Branco et al. 2015b). The degree to which the deadwood produced by invasive non-native woody plant species is utilized by saproxylic insects remains mostly unknown, but several recent studies suggest this may depend on the species of tree as well as the insect(s) under consideration. ...
... Major afforestation efforts in China, for instance, are motivated in part by a desire to reduce flooding and erosion and sometimes include areas where forests never grew (Kon et al. 1993). Although generally thought to be bad for biodiversity, non-native plantations can provide important habitats for a wide range of native organisms [including threatened species (Pawson et al. 2010)] and can be particularly beneficial when established on degraded lands rather than displacing native ecosystems (Bremer and Farley 2010;Pawson et al. 2008;Lugo 2004). In their review of this topic, Bremer and Farley (2010) concluded that although non-native plantation forests support fewer specialist species than natural ecosystems, they should not be completely dismissed as "green deserts" by conservation biologists. ...
Chapter
Full-text available
Whether intentionally or accidentally introduced, non-native woody plants now feature prominently in many ecosystems throughout the world. The dying and deadwood produced by these plants represent novel resources for saproxylic insects, but their suitability to these organisms remains poorly understood. We herein review existing knowledge about the utilization of non-native wood species by saproxylic insect communities and also provide several previously unpublished case studies from the USA, Germany, Portugal/Spain, and New Zealand. The first case study suggests that the relative number of beetle species utilizing non-native vs. native wood varies greatly among wood species, with some non-native species (e.g., Albizia julibrissin ) supporting a high beetle diversity. A decomposition experiment found that termites did not readily attack three non-native wood species and did not contribute significantly to their decomposition in contrast to what has been shown for a native pine species. The second case study found two species of non-native wood to support a lower richness of beetles compared to two native wood species in Germany, with Pseudotsuga menziesii supporting particularly few species which formed just a small subset of the community collected from native Picea abies . The third case study, from Iberia, found Eucalyptus to support a relatively small number of insect species with generalist host preferences. The fourth case study provides a list of insects reported from non-native pine and Eucalyptus in New Zealand. Based on our literature review and these new case studies, we conclude that non-native wood species can support diverse insect assemblages but that their suitability varies greatly depending on host species as well as the host specificity of the insect(s) under consideration. Although many generalist species appear capable of using non-native woody resources, more research is needed to determine whether non-native wood species have any value in promoting the conservation of the most threatened taxa.
... Puerto Rico's secondary forests represent a legacy of anthropogenic activities with new combinations of both native and introduced tree species (Abelleira-Martínez 2010; Fonseca Da Silva 2014; Lugo 2004Lugo , 2009). Studies characterizing tree species composition in secondary stands of Puerto Rico highlight the critical function of the introduced African tulip tree (Spathodea campanulata P. Beauv.) ( Fig. A8.8) as a novel forest facilitator, along with remnant native forests or trees functioning as seed sources for native species recovery within the subtropical moist and wet forest life zones (Abelleira-Martínez 2010; Brandeis and Turner 2013a). ...
... Sites where the cajeput tree is growing have signs of fire, have been partially drained, and were either farmed in the past or show signs of historical development (Pratt et al. 2005). While the cajeput tree is classified as intolerant of shade (Geary and Woodall 1990), there is no native tree species in Puerto Rico capable of withstanding this combination of flood and fire (Lugo 2004). ...
... Desde este punto de vista es posible considerar a las especies exóticas como componentes de ecosistemas noveles (Hobbs et al. 2006), con una dinámica propia. Estos nuevos sistemas pueden contribuir a la conservación de las especies nativas tanto en forma directa, mediante mecanismos de facilitación o como catalizadores de la sucesión en áreas degradadas, como en forma indirecta, manteniendo las funciones ecosistémicas y actuando, incluso, como proveedores alternativos de bienes y servicios (Otsamo 2000;D'Antonio and Meyerson 2002;Lugo 2004;Rodríguez 2006;Schlaepfer et al. 2011;Mascaro et al. 2012). ...
Article
Full-text available
The presence of new tree species in forest ecosystems promotes changes in stand dynamics that are reflected by forest structure. These processes are particularly relevant in native forests conservation. Tala (Celtis ehrenbergiana var. ehrenbergiana) and coronillo (Scutia buxifolia) forests are considered among the main forest communities of Buenos Aires province, in Argentina, and are included in several protected areas. In the El Destino Reserve, a very well conserved native forest is currently in the presence of Ligustrum lucidum, which has demonstrated a high invasive potential in other forest of Argentina and the world. The aim of this work was to characterize present structure of these stands and to infer changes in the dynamics promoted by the presence of L. lucidum. We found that these talares are currently dominated by L. lucidum in tree density (93%) and basal area (80%), and that native forest structure has departed from the characteristic values. Around 80% of native trees are dead, widely surpassing the 20% reported natural mortality, and dead tree density is positively associated with L. lucidum density. The exotic species initially established in a non-selective and spatially random pattern and reached current canopy dominance by rapidly exceeding native species total height. Present conditions were reached approximately in 20-25 years, which indicate a high rate of structural change. These results demonstrate these talares have profoundly changed and, considering the degree of modification, could be treated as new ecological systems, either novel or hybrid ecosystems. Whichever the approach, the control of L. lucidum and the active restoration of the native component, as well as the eradication of the exotic species in areas where establishment is still recent, are all of high priority in order to ensure the long-term conservation of these forests.
... Rose apple has the ability of not only to establish its population under heavy shade of forest canopy, but, after establishment it reduces the richness of native plant species. As a result, rose apple can be seen at many places with mono-species groves (Huenneke & Vitousek 1990;MacDonald et al., 1991;Kingston & Waldren, 2003;Lugo, 2004). Due to these reasons, rose apple is often considered as an invasive species owing to its high impact on native biodiversity specifically of oceanic islands. ...
... In contrast, hurricanes topple a small proportion of trees (~13%; Van Bloem et al., 2005), leaving stumps and roots for subsequent sprouting (Van Bloem, Lugo, & Murphy, 2006). Establishment of L. leucocephala stands appears to be a new successional step in recovering forest canopy, consistent with recent descriptions of the role of exotic species in the development of novel forests (Lugo, 2004;Lugo & Helmer, 2004). Indeed, because of its effects on seed arrival and subsequent establishment of native trees, L. leucocephala appears to make Caribbean dry forest more resilient to anthropogenic disturbances. ...
Article
Full-text available
Questions Tropical dry forests that experience severe disturbances (e.g., fires) often remain degraded for long time periods, during which non‐native grasses and trees dominate. One barrier to native tree regeneration in degraded areas may be seed dispersal limitation. To better understand how dispersal limitation influences recovery from degradation, we tested whether the mode and rates of seed dispersal differed in degraded sites dominated either by the exotic tree Leucaena leucocephala or open areas dominated by introduced pasture grasses. We also tested whether L. leucocephala stands facilitate the recruitment of native trees by increasing their seed input compared to open grass areas. Location Guánica Commonwealth Forest, Puerto Rico. Methods Seed rain was measured for one year in traps located within five vegetation types that ranged in degree of forest degradation from open grass to intact native forest. Results In open grass areas, seed rain density was similarly low for L. leucocephala and abiotically dispersed native trees (mean (95% CI) = 50.9 (15.1–171.0) versus 34.2 (10.3–113.5) seeds m⁻² yr⁻¹), whereas it was even lower for animal‐dispersed native trees (0.14 (0.03–0.67) seeds m⁻² yr⁻¹). Compared to open grass areas, L. leucocephala‐dominated stands, even those with grass understories, had higher seed rain density of animal‐dispersed trees (43.0 (12.9–143.6) seeds m⁻² yr⁻¹), but not abiotically dispersed trees (20.8 (6.3–68.5) seeds m⁻² yr⁻¹). Conclusions The dominance of L. leucocephala in disturbed Caribbean dry forests does not appear to be mediated by disproportionate seed arrival in open areas compared to native tree seeds. Rather, subsequent factors such as seed and seedling survival likely favor L. leucocephala in highly degraded areas. Since L. leucocephala stands increase the seed rain of animal‐dispersed native trees, retaining them in highly disturbed Caribbean dry forests may facilitate the regeneration of native forests. This article is protected by copyright. All rights reserved.
... They can cause severe ecosystem damage, including alterations in species composition and trophic structure, displacement of native species, and transmission of pests and diseases (González-Torres et al. 2012). The expansion of invasive species has become a global concern and has motivated substantial scientific investigation and debate regarding the actions which should, or should not, be taken to eliminate them from the landscape (Ewel and Putz 2004;Lugo 2004;Denslow and Johnson 2006). However, the factors that facilitate the success of biological invasions are still poorly understood (Rollins et al. 2013). ...
Article
Full-text available
The expansion of invasive species is a global concern. Within the Orchidaceae there are a number of invasive species. One of the most widely distributed invasive orchids in Mexico is Oeceoclades maculata (Lindl.) Lindl. By examining the population dynamic variations of an invasive species in its range of expansion, we can identify the factors that have contributed to that variation. Life Table Response Experiments (LTRE) were used to describe the dynamic of four populations of O. maculata in different ecosystems in south Chiapas, Mexico. Our goals were to quantify the contributions of differences between years and sites, and their interactions, to overall differences in population growth rate (λ), and to underlying vital rates. Fertility, survival and growth made the largest contributions, both positive and negative, to annual differences in λ. Spatial variations in λ were also found. The largest plants (S3 and S4) made the contributions of greatest magnitude each year and in each site. In seven of eight cases, the inclusion of the interaction term gave a better estimate of the population growth rate. This investigation highlights the need for taking into account life-history variations at different scales when the research goal is to study expansion of an invasive species in a heterogeneous landscape. The usefulness of LTRE studies was also demonstrated to better understand the natural history of the species and thus lay the groundwork for planning efficient management strategies, either for the conservation of rare, endangered species, or for the control of invasive species.
... Increasingly the relevance of diversity's effect on function has risen because of community change and biotic homogenisation caused by introductions of non-indigenous species (NIS) and loss of natives (Byers et al., 2002;Olden & Poff, 2003). NIS can sometimes be a driver of the decline of native species and therefore the subsequent alteration of ecosystem function (Crowl, Crist, Parmenter, Belovsky, & Lugo, 2008;Vaughn, 2010); however, at other times an NIS opportunistically fills an ecological role vacated by missing native species, in which case the NIS can partially compensate for some function lost from native extirpation (Lugo, 2004;Pejchar & Mooney, 2009). ...
Article
Full-text available
• Many communities are shifting composition, with losses of native species and increases of non‐indigenous species (NIS). At its extreme, such alteration of ecological guilds can result in simplification with a single NIS performing an ecological role once carried out by a suite of natives. This alteration has occurred in many rivers of the south‐eastern U.S.A., where the invasive filter‐feeding freshwater clam Corbicula fluminea has proliferated following the nearly complete extirpation of native mussels. • We investigated the factors controlling the distribution and abundance of Corbicula, as well as estimated the ecological service it provides via water filtration. With a nested design, we surveyed multiple transects within four to six sites within each of four rivers that spanned three large catchments in the Georgia piedmont, collecting data on Corbicula density and physical habitat characteristics associated with its presence. • We found Corbicula present in over half of the 1,536 sampled 0.044 m² sampled plots, 90 of the 93 transects that spanned the width of the river, and all 1–2 km sample sites, underscoring the clam's ubiquity in the study region. At the river scale, Corbicula densities ranged from 50–212 Corbicula m⁻², although individual sites ranged from 7–483 Corbicula m⁻². Corbicula was more abundant in areas with higher proportions of gravel, and less abundant with higher proportions of bedrock. A hierarchical model with river, site, and these two substrate variables explained 32% of the variation in Corbicula density. • Using observed densities and published per capita feeding rates, we calculated system‐wide collective filtration rates provided by Corbicula. In the four rivers surveyed and based on estimated residence times for median flows for the summer of 2012, Corbicula is estimated to filter water as many as seven times during median flows and 18 times during minimum flows before water flows out of a 10‐km reach. Due to high abundances and per biomass filtration rates, Corbicula plays an important role in these rivers. • Invasive species, biotic homogenisation, and the loss of functional redundancy may mean that many more rivers are similar to our studied rivers, with a single, often invasive, species dominating ecosystem function. Understanding the influence of biotic homogenisation on ecosystem function is of foremost importance to evaluate the resilience of natural systems.
... It is thus notable that Spathodea stands contain high stocks of these two potentially limiting nutrients. Such high stocks of nutrients can be significant in contributing to the role of these introduced species in supporting the regeneration of native forests and in maintaining site fertility by sequestering and keeping nutrients on site (LUGO, 2004;ABELLEIRA MARTÍNEZ et al., 2010). This is more important for phosphorous and potassium because neither are fixed from the atmosphere as nitrogen, and when leached, they are lost to the system. ...
Article
Full-text available
L'article présente une étude comparative de données de biomasse aérienne, de volume de bois, de stocks de nutriments (N, P, K) et de litière dans différents types de forêts à Puerto Rico. L'objectif de l'étude a été de procéder à une évaluation comparative de nouvelles forêts à Castilla elastica, arbre à caoutchouc, et Spathodea campanulata, tulipier du Gabon, avec des plantations et des forêts naturelles (aussi bien secondaires que matures). Il s'avère que ces deux types de nouvelles forêts peuvent rapidement accumuler en hauteur de grandes quantités de nutriments et de biomasse, produisant ainsi d'importantes chutes de feuillage. Elles peuvent égaler voire dépasser les plantations et les forêts naturelles pour tous les paramètres à l'exception de l'accumulation d'azote au niveau aérien. Ces résultats confirment bien le fait que ces nouvelles forêts peuvent contribuer à la restauration de la biomasse et des nutriments dans les sites déboisés. Cependant, à l'échelle de l'île dans son ensemble, les valeurs obtenues pour la biomasse dans plusieurs types de nouvelles forêts sont inférieures par rapport à celles observées dans cette étude pour les forêts à Spathodea et à Castilla. L'âge des peuplements et les conditions de site seraient ainsi des déterminants critiques du niveau d'accumulation d'éléments nutritifs et de biomasse dans ces forêts.
... Esas especies facilitan el establecimiento de otras exóticas y también de especies nativas. Esos bosques mixtos proveen varios servicios ambientales, como la recuperación de suelos y la restauración y manutención de la diversidad biológica boscosa (LUGO, 2004). Sin embargo, especies cultivadas en jardines a veces causan impactos en fragmentos de bosques urbanos. ...
Article
Full-text available
RESUMEN El crecimiento masivo y global de las ciudades se ha convertido en uno de los más importantes retos socioambientales del siglo XXI. Por lo tanto, es necesario un enfoque más proactivo en la búsqueda de alternativas para la conservación biológica. Este artículo analiza la importancia de los jardines domésticos urbanos como áreas estratégicas para la conservación biológica. Jardines domésticos urbanos (o quintais en portugués) se definen como espacios privados ad-yacentes a las viviendas, y que pueden contener, en grados variados, céspedes, polígonos con vegetación ornamental y alimentaria y fuentes de agua. É común que especies vegetales que han experimentado una disminución severa en sus hábitats silvestres, alcancen altas productividades o densidades en los jardines domésticos urbanos. Esos espacios tienen una enorme capacidad para el suporte de la biodiversidad aunque sea corriente en ellos un predominio de especies vegetales exóticas. Palabras clave: Jardines domésticos de viviendas. Biodiversidad urbana. Ecología urbana. ABSTR AC T The massive and global growth of cities has become one of the most important socio-environmental challenges of the 21st century. Therefore, a more proactive approach is needed in the search for alternatives for biological conservation. This article analyzes the importance of urban domestic gardens as strategic areas for biological
... Esas especies facilitan el establecimiento de otras exóticas y también de especies nativas. Esos bosques mixtos proveen varios servicios ambientales, como la recuperación de suelos y la restauración y manutención de la diversidad biológica boscosa (LUGO, 2004). Sin embargo, especies cultivadas en jardines a veces causan impactos en fragmentos de bosques urbanos. ...
Article
Full-text available
RESUMEN El crecimiento masivo y global de las ciudades se ha convertido en uno de los más importantes retos socioambientales del siglo XXI. Por lo tanto, es necesario un enfoque más proactivo en la búsqueda de alternativas para la conservación biológica. Este artículo analiza la importancia de los jardines domésticos urbanos como áreas estratégicas para la conservación biológica. Jardines domésticos urbanos (o quintais en portugués) se definen como espacios privados ad-yacentes a las viviendas, y que pueden contener, en grados variados, céspedes, polígonos con vegetación ornamental y alimentaria y fuentes de agua. É común que especies vegetales que han experimentado una disminución severa en sus hábitats silvestres, alcancen altas productividades o densidades en los jardines domésticos urbanos. Esos espacios tienen una enorme capacidad para el suporte de la biodiversidad aunque sea corriente en ellos un predominio de especies vegetales exóticas. Palabras clave: Jardines domésticos de viviendas. Biodiversidad urbana. Ecología urbana. ABSTR AC T The massive and global growth of cities has become one of the most important socio-environmental challenges of the 21st century. Therefore, a more proactive approach is needed in the search for alternatives for biological conservation. This article analyzes the importance of urban domestic gardens as strategic areas for biological
... mixes of native and non-native species, including both plants and associated animals, as seen in the case of Puerto Rico and other Caribbean islands, where widespread species-rich secondary forests comprising native and introduced species have developed (Lugo, 2004;Lugo et al., 2012). Further, dominance by non-natives may vary across the landscape and with time, e.g., potentially with biotically mediated declines with time after invasion through accumulation of enemies, plant-soil feedbacks, and evolutionary responses in native species (Flory and D' Antonio, 2015), so local problem cases are not necessarily instructive. ...
... Desde este punto de vista es posible considerar a las especies exóticas como componentes de ecosistemas noveles (Hobbs et al. 2006), con una dinámica propia. Estos nuevos sistemas pueden contribuir a la conservación de las especies nativas tanto en forma directa, mediante mecanismos de facilitación o como catalizadores de la sucesión en áreas degradadas, como en forma indirecta, manteniendo las funciones ecosistémicas y actuando, incluso, como proveedores alternativos de bienes y servicios (Otsamo 2000;D'Antonio and Meyerson 2002;Lugo 2004;Rodríguez 2006;Schlaepfer et al. 2011;Mascaro et al. 2012). ...
Article
Full-text available
La presencia de nuevas especies arbóreas en ecosistemas boscosos desencadena modifcaciones en la dinámica que se reflejan en su estructura. Estos procesos son especialmente relevantes desde el punto de vista de la conservación de bosques nativos. Los bosques de tala (Celtis ehrenbergiana var. ehrenbergiana) y coronillo (Scutia buxifolia) se consideran como una de las principales comunidades boscosas de la provincia de Buenos Aires y se encuentran protegidos en el marco de diversas reservas. En los talares de la Reserva El Destino, reconocidos entre los mejor conservados, se desarrolló un proceso de establecimiento de Ligustrum lucidum, especie que demuestra gran potencial invasor en otros bosques de la Argentina y del mundo. El objetivo de este trabajo fue caracterizar la estructura actual de estos talares e inferir los cambios en la dinámica vinculados con la presencia de esta especie. En la actualidad, estos bosques están dominados por ligustro, tanto en términos de densidad (93%) como de área basal (80%), y la estructura del componente nativo está lejos de los valores característicos. Cerca de 80% de los árboles nativos están muertos, valor muy superior al 20% de mortalidad natural, y se asocian de forma positiva con la densidad de ligustro. La exótica se instaló inicialmente en forma no selectiva y espacialmente aleatoria, y hoy llega a dominar el dosel al superar rápidamente en altura a las especies nativas. El estado actual se alcanzó en aproximadamente 20-25 años, lo cual implica un proceso de cambio estructural muy veloz. Estos resultados indican que estos talares cambiaron profundamente y, dado el grado de modifcación, podrían concebirse como un sistema ecológico nuevo, sean ecosistemas noveles o híbridos. Cualquiera sea el enfoque, el control del ligustro y la restauración activa del componente nativo, así como la erradicación en áreas donde el establecimiento es reciente, resultan prioritarios para asegurar la perpetuidad de estos bosques.
... However, this potentially beneficial role in supporting new or replacing previously lost ecosystem services is studied less often than their negative impacts (Charles and Dukes 2007;Estévez et al. 2015, but see Pyšek et al. 2008;Ewel and Putz 2004;Tassin and Kull 2015). Assessments must recognize that many natural conditions have been altered and nonnative species can be a key part of ecosystem function with potentially beneficial effects on other species (Lugo 2004;Goodenough 2010;Schlaepfer et al. 2011;Eviner et al. 2012;Rodewald 2012;Lugo et al. 2012;Tassin and Kull 2015). ...
Article
Full-text available
The formation of novel ecosystems by non-native species poses management challenges that are both socially and ecologically complex. Negative attitudes towards non-native species can complicate management in cases where non-native species provide ecosystem service benefits. Due to their intentional introduction over a century ago, non-native mangroves in Hawai’i present a unique case study. Although some have called for eradication of mangroves from Hawai’i, an active management approach may ultimately offer the greatest benefits to both the ecosystem and society by allowing mangroves to persist in locations where they provide habitat and crabbing access, while limiting their extent in other locations to protect native bird habitat and allow for beach and ocean access. We evaluated (1) attitudes and perceptions about non-native mangroves, (2) factors influencing these attitudes, and (3) support for different management approaches by surveying residents of Moloka’i, Hawai’i (n = 204). Negative attitudes towards mangroves were influenced by a lack of reliance on mangroves for benefit and a concern about threats to Moloka’i’s coast. Active management was supported by 88% of residents, while 41% supported eradication. Among the 88% in favor of active management, 24% of written in responses expressed a need for maintaining the benefits of mangroves and 67% described reducing the negative impacts, while 4% acknowledged both the benefit and harm the species has on the environment. As successful non-native species management may be dependent on local support, we emphasize that understanding human attitudes and perceptions is beneficial for non-native species managers in any location. Results from our study highlight the importance of understanding social attitudes towards non-native species management strategies from propagation to eradication. We conclude with a framework for integrating stakeholder attitudes and beliefs into novel ecosystem management.
... Invasive species are dominant in many Caribbean TDF, particularly those recovering from disturbance (Ramjohn et al. 2012). While the ecological outcome of novel communities is debated and may not be negative (Lugo 2004), some invasive species are highly drought-and fire-resistant (Wolfe and van Bloem 2012), in contrast to many native species. ...
Article
Full-text available
Tropical dry forest (TDF) is globally one of the most threatened forest types. In the insular Caribbean, limited land area and high population pressure have resulted in the loss of over 60% of TDF, yet local people’s reliance on these systems for ecosystem services is high. Given the sensitivity of TDF to shifts in precipitation regimes and the vulnerability of the Caribbean to climate change, this study examined what is currently known about the impacts of climate change on TDF in the region. A systematic review (n = 89) revealed that only two studies addressed the ecological response of TDF to climate change. Compared to the rapidly increasing knowledge of the effects of climate change on other Caribbean systems and on TDF in the wider neotropics, this paucity is alarming given the value of these forests. We stress the need for long-term monitoring of climate change responses of these critical ecosystems, including phenological and hotspot analyses as priorities.
... They also reduce open water habitat for water birds and other wildlife (Thouvenot et al. 2013a). Removal of invasives may facilitate the establishment or expansion of either native or non-native species into the niche that was created and modified by the invasive (Kl€ otzli and Grootjans 2001, Lugo 2004. Gaertner et al. (2014) highlighted the risk of regime shifts in ecosystems invaded by aggressive non-native species due to feedback mechanisms and ecosystem engineering characteristics of such invasives (Crooks 2002). ...
Article
Full-text available
Invasive species fundamentally change the bio-physical and ecological characteristics of the ecosystems they invade. Rapidly expanding invasive species may facilitate the spread of other invasive species, and successive invasion events may lead to novel species interactions that may push the system beyond its equilibrium state and change successional pathways. Knowing the direction of the invasion front may be useful to predict impacts of invasive species. Water primrose (Ludwigia spp.), one of the invasive floating macrophytes in the Sacramento-San Joaquin River Delta (hereafter, Delta), has increased in cover rapidly over the past three decades likely outcompeting native and non-native species, changing their functional relationships, with cascading effects in the macrophyte communities of the aquatic ecosystem. In this study, we analyze the directionality of water primrose invasion and assess which spaces it occupies, whether it has overcrowded or outcompeted other vegetation communities, and its implications for succession in the Delta. We used imaging spectroscopy data acquired in June of 2004, June of 2008, November of 2014, and October of 2016 for the 2500 km2 of the Delta to map the communities of submerged macrophytes, floating macrophytes, and emergent marsh. We found that water primrose cover increased fourfold in the Delta over the past 13 yr, changing significantly in the central Delta and Liberty Island region from 122 ha in 2004 to 471 ha in 2016. Water primrose expanded first by spreading over open water and submerged macrophytes and, when that habitat was exhausted, primrose invasion switched direction and encroached into emergent marsh. This bilateral expansion to both open water and the marsh is likely to change rates of succession and affect the restoration of the native Delta marshes. Understanding the mechanisms behind the expansion dynamics of this invasive will allow managers to counter its impact on newly established vulnerable marshes.
... However, the species composition of these naturally emerging forests was different from that of historic forests (Lugo and Helmer, 2004) and they have been identified as novel forests (Martinuzzi et al., 2013) in part because the dominant species are naturalized introduced tree species. Understanding the functioning of novel forests is important because they are increasingly common in the world (Hobbs et al., 2013) and can play a significant role in rehabilitating degraded soils (Lugo, 2004). ...
Article
Full-text available
One of the challenges in the restoration of degraded lands is the re-establishment of soil structure and fertility. Novel forests that regenerate on recently abandoned and degraded agricultural lands are among the first biotic systems that begin the process of soil rehabilitation. The rate of litter decomposition and associated element mobility is one of many processes that contribute to the understanding of how ecosystem-level processes restore eroded soils. We studied the stoichiometry of Spathodea campanulata leaves decomposing in novel subtropical moist forests. We found that the speed of leaf decomposition was high (annual decomposition constant of 5.0 to 2.6 or half-life of 51 to 98 days). Spathodea leaf mass loss was particularly fast during the first 16 days of decomposition (half-life of 33 days). Leaf litter was characterized by high chemical quality with low C/N, C/P, and N/P. During the leaf decomposition process, macroelements (N, P, K, Ca, and Mg) were more mobile than microelements (Al, Mn, Fe, and Na). As leaf litter decomposed, nitrogen increased in concentration, the quantity of all macroelements decreased, and microelements tended to increase in both concentration and quantity. Because of the rapid rate of decomposition and high chemical quality of Spathodea leaf litter, it appears that the potential for yielding residual soil organic matter from its leaves is reduced, but this is a tradeoff with the rapid release of elements, which contributes to the high juvenile tree density and primary productivity observed in novel Spathodea forests.
... Under this background, Hobbs et al. (2006) proposed the concept of novel ecosystems, and defined it as having species compositions and relative abundances that have not occurred previously within a given biome; later, Hobbs et al. (2013) redefined it as a system of biotic, abiotic, and social components that differ from those that prevailed historically due to human influence, 1988-2004 2005-2012 2013-2017 1988-2017 having a tendency to self-organize and manifest novel qualities without intensive human management. For example, Lugo (2004) researched the changes of deforested lands that were previously used for agriculture and then abandoned in Puerto Rico, and discovered that unique communities consisting of both alien and native species are found on these sites in 60 to 80 years. Currently, there is still widespread debate on the issue of novel ecosystems Murcia et al. 2014;Kattan et al. 2016;Miller & Bestelmeyer 2016;Miller & Bestelmeyer 2017). ...
Article
Full-text available
Ecological restoration studies have been widely conducted for many years to solve eco‐environmental problems. However, no publications offer a systematic and quantitative analysis of the evolution of the field of ecological restoration. To address this knowledge gap, for the first time, we applied a bibliometric analysis approach to analyse ecological restoration studies. We analysed 3929 articles published between 1988 and 2017 catalogued in the Science Citation Index Expanded database and the Social Sciences Citation Index database. The results show that annual article output stably increased after 2004, and the number of annual articles of each country has also increased notably since then. The USA occupies the leading position in ecological restoration studies, with China attaining a close second position in recent years. Four institutions and seven journals are outstanding in the field of ecological restoration. Academic collaborations of authors or institutions exhibit an increasing trend, but international collaboration needs to be strengthened because eco‐environmental problems are a global challenge. Forest, grassland and wetland ecosystems have received the most attention. Biodiversity, ecosystem services, and climate change are core issues of ecological restoration studies and are predicted to remain the research hotspots in the future. Novel ecosystems are likely to become one of the most important research areas in the near future. More importantly, it is crucial for researchers to places more emphasis on social issues of ecological restoration in the future. This article is protected by copyright. All rights reserved.
... Smith et al., 2016) . Similarly, the post-World War II fallowing of former agricultural lands throughout the islands have demonstrated the need for reforestation after centuries of export agriculture drained the soil and reduced biodiversity (Lugo, 2004;Lugo & Helmer, 2004;Pascarella et al., 2000;Rudel et al., 2000) . Given the extent of environmental harms committed to the islands since colonization, there is a clear need to balance cultivating the lands towards material sovereignty while also caring for the lands to promote environmental restoration, a difficult and contentious balance to weigh (Burnett et al., 2019;Carrière et al., 2002;del Mar López et al., 2001;Hobbs et al., 2014;Pascarella et al., 2000;Rudel et al., 2000;Shelton & Richmond, 2016) . ...
Thesis
Full-text available
Puerto Rico’s food systems are dangerously precarious, with the islands importing about 90% of its food, a consequence of five centuries of colonialism prioritizing foreign profit over local welfare. Particularly in the aftermath of Hurricane Maria, though, there has been a swelling movement towards food sovereignty on the islands, often aligned with overlapping movements towards the resurgence of Taíno identity and culture. Bringing these movements together, this dissertation focuses on Taíno social-environmental systems, using the recorded Taíno language as the primary vantage point in order to understand the dynamics of pre-colonial social-environmental systems on the islands, the cultures that shaped such systems, and how that can guide us to food and material sovereignty on the islands. This dissertation is grounded in a decolonial research methodology, which I develop and provide as a generalized framework such that other researchers can make use of it as well. Delving into Taíno ecolinguistic ontologies – or the worldviews and relations revealed by the nexus between language and the environment – demonstrates a high degree of naming multiplicity in the Taíno lexicon, particularly for plants and animals with which there was greater intimacy in Taíno cultures. Additionally, redundancy was a prominent feature in pre-colonial Taíno bicultural systems, contributing to socioecological resilience, although there were several categories, especially related to spiritual functions, for which certain biota are simply irreplaceable. Although there are numerous critical barriers obstructing food and material sovereignty for Puerto Rico, the lessons gleaned from Taíno culture, particularly Taíno ecolinguistic ontologies and pre-colonial social-environmental systems, indicate several promising opportunities for cultivating sovereignty: research towards decolonization, mass (re)education, land reclamation, land cultivation & restoration, establishing constellations of care, and building a Pan-Caribbean coalition.
... Currently most examples of habitat recovery in the context of invasive species are from freshwater and saltwater systems (Rodriguez, 2006). Examples with the evidence that native species regenerate in invasive exotic species settings in terrestrial settings appear to be few and mostly limited to recovery of the woody forest understorey types (Fischer et al., 2009;Lugo, 2004;Berens et al., 2008). This study has shown that not only can native forest species recover in such settings, even the mid-to upper storey types would. ...
Article
There are many studies on the applicability of natural regeneration for recovery of degraded forests. Studies of the potential of natural regeneration and succession to restore degraded forest areas under invasive exotic plants are few in comparison. This study examined the potential of these processes to bring about the recovery of large areas under the exotic paper mulberry Broussonetia papyrifera in Mabira Forest, Uganda. The areas of focus were degraded by farming but abandoned and invaded by mulberry 30 years ago. Sampling was conducted in three mulberry-dominant stands (Int 1, Int 2, and Hv) that were differentiated by the degree of mulberry cutting by local communities and other anthropogenic disturbances. Primary forest (Nt) was a fourth stand used as a reference. Data were collected using Modified-Whittaker Plots, transects and other plot types adapted to record impact of disturbance. Analyses of stem density showed that both mulberry and native trees occurred in all the stands in varying densities and age classes from seedling to tree class size. Non-metric multidimensional scaling showed Int 1 (a relatively undisturbed stand with fully grown mulberry) to be closest to Nt floristically, followed by Int 2 (a disturbed stand with fully grown mulberry). Hv (a disturbed stand with low stature mulberry) was least similar to Nt. Overall, Int 1 was closer to Nt than to any of the other stands; while Int 2 was closer to Hv than to Int 1 or to Nt. Most analyses of seedling and sapling densities and species diversity of native trees showed a pattern whereby Hv < Int 2 < Int 1 < Nt. Numbers of forest-typical species varied between stands but not significantly. Inter-stand differences in the levels of disturbance were pronounced with Hv and Int 2 having significantly higher incidences of illegal indigenous tree cutting and charcoal kilning than Int 1. Regressions of percent cover values on seedling densities, sapling densities and species richness showed negative relationships between mulberry cover and native tree seedling density and species richness but not sapling density. Indigenous tree sapling densities were positively correlated with indigenous tree species cover. These findings suggest that anthropogenic disturbance and to a smaller extent mulberry factors; and not differences in rates of species colonization and degrees of species performance explain the current state of recovery of the stands. Natural regeneration and succession therefore have potential to recover the degraded sites and reverse the dominance of mulberry if the ongoing human disturbance is stopped.
... Although secondary forests usually have lower species richness in comparison with well-preserved forests, they can provide important habitat for various species, especially in highly degraded and fragmented landscapes (Barlow et al., 2007;Aerts & Honnay, 2011;Edwards et al., 2011;Van Breugel et al., 2013;Lennox et al., 2018). For example, in the year 1940, Puerto Rico had less than 10% forest cover (Lugo, 2004), but following extensive socio-economic changes, forest cover has increased continuously and was estimated to bẽ 55% in 2014 (Marcano-Vega, 2017), providing habitat for diverse native, naturalized, and introduced species. ...
Article
Full-text available
Estimates of forest cover have important political, conservation, and funding implications, but methods vary greatly. Haiti has often been cited as one of the most deforested countries in the world, yet estimates of forest cover range from <1% to 33%. Here, we analyze land change for seven land cover classes (forest, shrub land, agriculture/pasture, plantation, urban/infrastructure, barren land, and water) between 2000 and 2015 using Landsat imagery (30 m resolution) in the Google Earth Engine platform. Forest cover was estimated at 26% in 2000 and 21% in 2015. Although forest cover is declining in Haiti, our quantitative analysis resulted in considerably higher forest cover than what is usually reported by local and international institutions. Our results determined that areas of forest decline were mainly converted to shrubs and mixed agriculture/pasture. An important driver of forest loss and degradation could be the high demand for charcoal, which is the principal source of cooking fuel. Our results differ from other forest cover estimates and forest reports from national and international institutions, most likely due to differences in forest definition, data sources, spatial resolution, and methods. In the case of Haiti, this work demonstrates the need for clear and functional definitions and classification methods to accurately represent land use/cover change. Regardless of how forests are defined, forest cover in Haiti will continue to decline unless corrective actions are taken to protect remaining forest patches. This can serve as a warning of the destructive land use patterns and can help us target efforts for better planning, management, and conservation.
... Rose apple has the ability of not only to establish its population under heavy shade of forest canopy, but, after establishment it reduces the richness of native plant species. As a result, rose apple can be seen at many places with mono-species groves (Huenneke & Vitousek 1990;MacDonald et al., 1991;Kingston & Waldren, 2003;Lugo, 2004). Due to these reasons, rose apple is often considered as an invasive species owing to its high impact on native biodiversity specifically of oceanic islands. ...
Chapter
Full-text available
Patel, CR; Rymbai, H; Patel, NL; Ahlawat, TR; Tandel, YN; Saravaiya, SN; Swamy, GSK; KH, Nataraja; Sabarad, Anil I. 2016. Rose apple (Syzygium jambos (L.) Alston). In: Underutilized Fruit Crops: Importance and Cultivation, Part II, S.N. Ghosh, Akath Singh and Anirudh Thakur (Ed.). Narendra Publishing, Delhi, India. pp 1134-58 Syzygium jambos (L.) Alston (Syn. Eugenia jambos L. or Jambosa vulgaris DC) popularly known as ‘Rose apple’ is an important member of the family Myrtaceae. Due to the ability of not only survive and establish but to raise its populations in wide geographical conditions with different soil and nutrient status, rose apple naturalised inmany countries particularly in coastal regions and islands and often being considered as an invasive species or weed. At many places it is grown as home garden tree due to its fruits as attraction for children or planted as an ornamental tree due to showy foliage & flowers. The Rose Apple is a fabulous fruit tree of the tropics. In Asia, the fruit tree is associated with symbolism and numerous legends. The Rose Apple is said to be the golden fruit of immortality, and Buddha is said to have experienced enlightenment sitting under a Rose Apple tree. Likemany other fruits towhich the word “apple” has been attached, the rose apple in no way resembles an apple, neither in the tree nor in its fruit. It is an excellent fruit and appeals everybody for its nice rosy fragrance, good and spongy texturewhich is neither very soft nor very hard and very low acerbity.
... Some species of the genus, like Acacia auriculiformis and Acacia mangium, were introduced to degraded tropical and subtropical regions to establish forest communities (McNamara et al., 2006;Norisada et al., 2005;Peng et al., 2005). These trees could not only improve soil nutrients, but by shielding against intense radiation and heat load, they could also facilitate colonization by other plants (Lugo, 2004;Parrotta et al., 1997). Therefore, they were considered as nurse plants for understory native species (Yang et al., 2009). ...
... It has become a major invasive species on South Pacific islands (e.g. Cook Islands, Fiji, Guam, Hawaii, Samoa, and Vanuatu; Labrada and Medina 2009), Puerto Rico (Lugo 2004), as well as in the Hawaiian archipelago, where it invades closed forests since seedlings are shade tolerant (Larrue et al. 2014). Farmers remove S. campanulata by hand, but this is time-consuming and labor-intensive. ...
Chapter
Costa Rica is one of the most diverse countries in the Neotropics. It has the highest species concentration per unit area of terrestrial ecosystems. The country has a vascular flora of approximately 10 712 species, of which 1048 (9.7%) are introduced, and of these, 47 (0.4%) are considered invasive. Invasive plants are linked to species extinctions and ecosystem simplification and usually spread from agricultural systems into the natural forest and other environments such as wetlands. Introduced old‐world pastures (especially African) have the potential to invade environments dominated by native grasses such as dry and wet savannas. Although we distinguish environments that are very susceptible to invasive plants, such as oceanic islands (Cocos Island), there is not enough detailed and updated information to design contingency plans to manage and prevent the spread of these species. Costa Rica's legal framework is advanced in this respect, and there is an online list of introduced species. However, there are major research gaps and a lack of monitoring and educational programs reaching out to the general public to prevent the indiscriminate spread of introduced plants. Botanical gardens, commercial nurseries, and organizations doing landscaping services are at a high risk of becoming dispersal foci of invasive species. A more detailed information system on invasive plants is critical to identify risks and educate the public. Also, more systematic monitoring and information systems on invasive plants and invasive organisms, in general, are required at the regional level since this phenomenon is not unique to one country. Establishing regional systems for research and monitoring of introduced organisms represents a major challenge considering that the intensity of human migrations and the exchange of germplasm can only increase in the near future, with both phenomena heightened by the progression of climate change. Therefore, it is likely that cases of invasive organisms will increase in the near future.
... Anthropogenic disturbance is common across the region and includes intentional and accidental fires (Martin and Fahey 2006), and land-use change for agriculture and urban development (Grau et al. 2003, Grau andAide 2008). Land-use change has increased forest fragmentation and introduced nonnative and invasive species from areas that do not experience hurricanes (e.g., Spathodea campanulata [African tulip] and various Albizia species; Lugo 2004, Brandeis et al. 2007 or which are heavily favored by storms (e.g., Pittosporum undulatum [Australian cheesewood]; Bellingham et al. 2018). In Caribbean forests along the hurricane path, fire has also been introduced as a management tool for pasture management or as an accidental or malicious disturbance where introduced pasture grasses that have invaded dry forests are burned (Chinea 2002, Thaxton et al. 2012, Wolfe and Bloem 2012. ...
Article
Full-text available
Over the course of 16 d in the fall of 1998, Hurricane Georges made landfall on five Caribbean Island nations, two U.S. states, and two territories. Along its path, it impacted nearly every type of built environment and terrestrial and marine ecosystem found in the Caribbean and the southeastern United States. We reviewed ecological and sociological research related to Georges in order to demonstrate the potential power of regional synoptic networks despite notable gaps that existed at the time. Most studies examined various effects and responses within four years of the storm, though a few reported longer‐term results. Reduction in forest stem density was the most reported ecological effect and ranged from 7% to 51% among sites in different forest types. Forests previously impacted by Hurricane Hugo in 1989 showed lower mortality from Georges than forests with longer hurricane‐free intervals. Rivers in the storm's path exported heavy loads of sediment to marine systems. For example, 5–10 million tons of sediment was transported to marine systems from Puerto Rico, and suspended sediments increased tenfold in coastal Louisiana. Economic costs directly related to Hurricane Georges ranged from 5% to 200% of annual GDP in the year after the storm. Sociological research indicated that children and college students exposed to Hurricane Georges experienced elevated effects on mental health such as anxiety and depression for up to 2.5 yr. Established research areas and longitudinal studies were valuable in understanding hurricane effects in the context of long‐term trends but fragmented research capacity reduced both local and regional synthetic efforts. Georges provides a template of how future integrated research programs could provide a deeper understanding of how nature, urbanization, human culture, and societal norms interact, respond, and recover from a major hurricane. However, future studies should avoid using the Saffir‐Simpson scale as a shorthand indicator or predictor of storm effects because topographic, historical, ecological, political, infrastructural, and societal factors interact to alter storm effects. The breadth of topics addressed in the research produced after Georges shows the potential for transformative, regionally synthetic research that spans whole watersheds and nearshore areas while integrating ecological and social sciences.
... These successional species are C 3 -photosynthesizers, so their abundance will also cause a decreasing trend in d 13 C. In the recent history of land cover change in the Fajardo watershed, researchers observed the rapid colonization of abandoned pasture by pioneer trees (Lugo and Helmer 2004;Lugo 2004). Taking these abandoned agricultural plots as disturbance analogues, trees have a competitive advantage even in parts of the landscape that are suitable for the growth of tropical grasses. ...
Article
https://authors.elsevier.com/c/1cN6B-4PRxnnu We present cospatial, contemporary archival records of biotic and abiotic terrestrial processes operating over the past ∼25 ky within the Rio Fajardo watershed, in northeastern Puerto Rico. The proxy records were derived from a 5-m-thick stratigraphic section exposed by cut bank incision. We interpreted ecosystem dynamics from changes in the stable carbon isotopic ratio of sedimentary organic material compared to 13C ratios of contemporary carbon sources. Sedimentary organic material had 13C values ranging from −29.715 to −15.291. We derived a record of paleo-erosion rates in the catchment from the concentration of meteoric 10Be in layers of the floodplain sediments. Paleo-erosion rates ranged from 13 to 356 mm ky−1. The chronology of the sediments was constrained with the radiocarbon ages of organic deposits, the oldest age was calibrated to ∼22.4 ky BP (thousand years before present) and retrieved at 440 cm depth. We collected grain size data, clay mineralogies, and analyzed geochemical indices including the chemical weathering index, salinization, and base cation loss down profile. This stratigraphic sequence captures major shifts in the Caribbean climate, the intensification of the El Nino-Southern Oscillation, and the arrival of humans on the island. During the last glacial and early Holocene epochs both biotic (13C) and abiotic proxies (10Bemet and geochemical data) indicated dynamic equilibrium with climate. The past five thousand years (ky) of record are characterized instead by pulsed responses to disturbances in both systems. Colonial-era land use drove changes that significantly exceeded natural variability in any proxy over the period of record.
... What is the conservation value of secondary forests whose composition is altered compared to presumed pre-disturbance assemblages, particularly when stands are dominated by nonnative species (i.e., novel forests; Lugo and Helmer, 2004;Lugo, 2004)? Forested landscapes, regardless of species composition, retard erosion and reduce extreme flooding while providing habitat structure for generalist wildlife. ...
Article
The Luquillo Experimental Forest (LEF) has a long history of research on tropical forestry, ecology, and conservation , dating as far back as the early 19th Century. Scientific surveys conducted by early explorers of Puerto Rico, followed by United States institutions contributed early understanding of biogeography, species endemism, and tropical soil characteristics. Research in the second half of the 1900s established the LEF as an exemplar of forest management and restoration research in the tropics. Research conducted as part of a radiation experiment funded by the Atomic Energy Commission in the 1960s on forest metabolism established the field of ecosystem ecology in the tropics. Subsequent research has built on these early advances to develop new theories on ecosystem response to disturbance regimes and the role of the biota in ecosystem resilience. Recent and current research in the LEF has advanced understanding of resilience to hurricane disturbances, human land use, gamma irradiation, landslides, drought, and warming, showing that even following the most severe disturbances (e.g., landslides, agriculture) forests reestablish within 60 years. Work in the LEF has reversed the paradigm that tropical ecosystems are fragile, but instead exhibit remarkable resilience to many forms of disturbance present at multiple spatial and temporal scales. Current research is already advancing understanding of how climate change and attendant effects on the disturbance regime might affect the composition, structure, and function of tropical forest ecosystems.
... These results, while both informative and intriguing, need to be interpreted with the knowledge that the disturbance regime at JB-BN is shaped by more than just frequent hurricanes. Prior to European colonization, Puerto Rico was 100% forested (Little et al. 1974), but by the late 1940s, only 6% of the island remained forested, and only 1% of the primary forest remained (Lugo 2004;Roberts 1942). The forest at JB-BN is a relatively young forest and may respond differently to hurricane disturbance than an older forest. ...
Article
Full-text available
Background Categorization of topographical features into landform type is a long-standing method for understanding physiographic patterns in the environment. Differences in forest composition between landform types are driven primarily by concurrent differences in soil composition and moisture, but also disturbance regime. Many studies have focused on the interaction between fire disturbance, succession, and landforms, but the effects of hurricane disturbance on compositional differences between landforms are poorly understood. In the study presented here, we assess compositional and structural differences between landform types in the tree community of a young sub-tropical forest that is frequently subjected to hurricanes. Specifically, we ask whether the tree community (1) changed structurally over the study period, (2) experienced compositional change over the study period, (3) is compositionally different between landform types, and (4) exhibits compositional change mediated by landform type. Results The tree community experienced significant structural change over the course of our study, but compositional change was only significant for some landforms. Conclusion Despite large-scale, intense, and frequent hurricane disturbance to our study system, compositional change in the tree community was localized and only significant for some landform types.
... However, alien species that successfully integrate into resident communities can also stabilize networks by increasing network nestedness (Bascompte et al., 2003;Traveset et al., 2013), boost productivity by increasing overall species richness (Cardinale et al., 2006) or provide new ecosystem services to native species (Gleditsch, 2017). Alien species can benefit disturbed communities (Lugo, 2004) or compensate for the loss of native species (Kawakami et al., 2009). I here discuss the possibility that alien species stimulate zoochory of native species by exploring two possible mechanisms: alien species may affect the abundances or behavior of native disperser animals, or may facilitate the arrival of new alien disperser species. ...
Article
Full-text available
Many alien plants use animal vectors for dispersal of their diaspores (zoochory). If alien plants interact with native disperser animals, this can interfere with animal-mediated dispersal of native diaspores. Interference by alien species is known for frugivorous animals dispersing fruits of terrestrial plants by ingestion, transport and egestion (endozoochory). However, less attention has been paid to possible interference of alien plants with dispersal of diaspores via external attachment (ectozoochory, epizoochory or exozoochory), interference in aquatic ecosystems, or positive effects of alien plants on dispersal of native plants. This literature study addresses the following hypotheses: (1) alien plants may interfere with both internal and external animal-mediated dispersal of native diaspores; (2) interference also occurs in aquatic ecosystems; (3) interference of alien plants can have both negative and positive effects on native plants. The studied literature revealed that alien species can comprise large proportions of both internally and externally transported diaspores. Because animals have limited space for ingested and adhering diaspores, alien species affect both internal and external transport of native diaspores. Alien plant species also form large proportions of all dispersed diaspores in aquatic systems and interfere with dispersal of native aquatic plants. Alien interference can be either negative (e.g., through competition with native plants) or positive (e.g., increased abundance of native dispersers, changed disperser behavior or attracting additional disperser species). I propose many future research directions, because understanding whether alien plant species disrupt or facilitate animal-mediated dispersal of native plants is crucial for targeted conservation of invaded (aquatic) plant communities.
... Land-use change (not only related to the establishment of plantings) is also an important driver of NNTs invasions. Abandonment of land can increase the potential for invasion of NNTs or lead to the establishment of plantations (Lugo 2004(Lugo , 2015Sitzia et al. 2012;Mullah et al. 2014;Bravo et al. 2019;Vaz et al. 2019). ...
Article
Full-text available
Sustainably managed non-native trees deliver economic and societal benefits with limited risk of spread to adjoining areas. However, some plantations have launched invasions that cause substantial damage to biodiversity and ecosystem services, while others pose substantial threats of causing such impacts. The challenge is to maximise the benefits of non-native trees, while minimising negative impacts and preserving future benefits and options. A workshop was held in 2019 to develop global guidelines for the sustainable use of non-native trees, using the Council of Europe – Bern Convention Code of Conduct on Invasive Alien Trees as a starting point. The global guidelines consist of eight recommendations: 1) Use native trees, or non-invasive non-native trees, in preference to invasive non-native trees; 2) Be aware of and comply with international, national, and regional regulations concerning non-native trees; 3) Be aware of the risk of invasion and consider global change trends; 4) Design and adopt tailored practices for plantation site selection and silvicultural management; 5) Promote and implement early detection and rapid response programmes; 6) Design and adopt tailored practices for invasive non-native tree control, habitat restoration, and for dealing with highly modified ecosystems; 7) Engage with stakeholders on the risks posed by invasive non-native trees, the impacts caused, and the options for management; and 8) Develop and support global networks, collaborative research, and information sharing on native and non-native trees. The global guidelines are a first step towards building global consensus on the precautions that should be taken when introducing and planting non-native trees. They are voluntary and are intended to complement statutory requirements under international and national legislation. The application of the global guidelines and the achievement of their goals will help to conserve forest biodiversity, ensure sustainable forestry, and contribute to the achievement of several Sustainable Development Goals of the United Nations linked with forest biodiversity.
... When a woody weed population is young and actively growing, stem density is high and light levels in the understory may be insufficient for native (or exotic) seedling establishment. However, as the stand ages and thins, light levels increase, and native seedlings may be better able to recruit (Wilson 1994;Lugo 2004;Carswell et al. 2013;Geldenhuys 2013). This process has been observed in exotic tree plantations in New Zealand (Allen et al. 1995;Ogden et al. 1997;Brockerhoff et al. 2003;Forbes et al. 2019) and South Africa (Geldenhuys 1997). ...
Article
Full-text available
Invasive exotic tree and shrub species (woody weeds) form dense, monospecific stands in many areas of New Zealand. At some sites, the weed dies out naturally and is replaced by native species as succession proceeds, but at others the weed persists indefinitely. The ability to distinguish between these different trajectories is critical to effective weed management, but the conditions that determine successional outcomes remain poorly understood. However, clues to the successional trajectory at any given woody weed site can be found in the understory, because understory plants represent the potential future plant community (in the absence of disturbance). Of key relevance is whether the woody weed species is regenerating under its own canopy, because this enables it to replace individuals as they die, and thus persist as succession proceeds. Conversely, if the understory is comprised entirely of native species, there is potential for the natives to take over the community as the weed dies out. This process is often termed "passive restoration", because native vegetation is restored without any active management other than (in some cases) the removal of environmental stressors or degrading processes. The likelihood of a native understory developing is affected by site-specific traits such as the natural (historical) vegetation type, proximity to native seed sources, climate, stand age and the presence of herbivores. We present a framework to help land managers use their observations of understory vegetation to assess likely successional trajectories in woody weed stands.
... The generation of novel ecosystems with non-native plants as the main drivers has been well documented within a wide range of habitats around the globe (Lugo, 2004;Rogers & Chown, 2014;Yu, Okin, Ravi, & D'Odorico, 2016). Despite awareness of the various mechanisms through which non-native plants can alter ecosystem composition and processes (Hejda, Pyšek, & Jarošík, 2009;Vilà et al., 2011), the degree of novelty that different taxonomic groups or functional types generate within an ecosystem remains unclear. ...
Article
Full-text available
Aims: Novel ecosystems are self-maintaining ecosystems that support species assemblages without historical precedent. Despite much interest and controversy around novel ecosystems, it remains poorly understood how they are generated, what their capacity to support biodiversity is and what the implications for society are. Here, we address these issues through a global synthesis of non-native palms, since palms are likely generators of novel ecosystems because they are introduced widely beyond their native range and have the capacity to act as ecosystem engineers. Location: Global. Methods: We gathered data on non-native palms from peer-reviewed literature/pa-pers, grey literature and online databases. We extracted data on the biogeographic context of palm invasions, plant functional traits and anthropogenic drivers to quantify their effects on biodiversity, ecosystem functioning and ecosystem services. Results: Of the 2,557 palm species, 3.4% (86 species) were recorded as naturalized and 1.1% (28 species) as invasive, which exceeds the average invasion success across all woody plants. Naturalized palms are present in most tropical and subtropical regions around the world, often in urban areas, reflecting the use of palms in horticulture. Many naturalized palms were taller and more likely to originate from open habitats or dry forest than non-naturalized palms. These features likely represent the naturalized palms' competitive ability, high fecundity and dispersal ability along with ecological matching to human-disturbed environments. Overall, literature on ecological effects of palm invasions was sparse, but we found multiple cases in which palm invasions resulted in strong ecosystem changes or even biome shifts. Main Conclusions: We found strong evidence that palm invasions can generate novel ecosystems. Although there are substantial knowledge gaps on the ecological effects of palm invasion, anthropogenic drivers like urbanization and ongoing global warming will continue to expand palm ranges and promote non-native palms as generators of novel ecosystems. Keywords: alien invasive species, Arecaceae, biological invasions, ecosystem effects, global change, invasion biology, non-native species, novel ecosystems, palms, urban ecology
... The Caribbean region is a hotspot of biodiversity with high priority for conservation due to its remarkable biological richness and high levels of endemism (>70% for Caribbean flowering plants; Acevedo-Rodríguez & Strong, 2012;Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, 2000;Roncal, Nieto-Blázquez, Cardona, & Bacon, 2020;Santiago-Valentin & Olmstead, 2004). Historically, Caribbean islands have played a crucial role as crossroads between continental America, Europe and Africa, resulting in multiple introductions of alien species over centuries as well as changes in land use and biota composition (Lugo, 2004;Rojas-Sandoval et al., 2017). Additionally, the flora of the Lesser Antilles is among the best documented for tropical archipelagos; comprehensive and updated botanical inventories are available providing the information needed for this study. ...
Article
Full-text available
Aim Understanding the factors driving the diversity of alien and native species on islands is crucial for predicting the spread of alien species and for proposing management practices to protect the unique native biodiversity that often occurs in insular ecosystems. The main objective of this study was to evaluate whether native and alien plant species respond similarly to natural biogeographic and human‐related drivers. Location Lesser Antilles, Caribbean. Methods We compiled a dataset with the verified status of native and alien plant species occurring on 15 islands across the Lesser Antilles. We assessed the relationship of native and alien plant species richness and identified the biogeographic and socio‐economic variables that best explain the diversity patterns of both alien and native species on these islands by combining correlation analysis and generalized linear models. Results The final dataset comprises a total of 2,438 plant species with 1,825 native species and 613 alien species. For the 15 islands analysed, native and alien species richness is strongly and positively correlated, but different variables explained their diversity patterns. We found that biogeographic drivers such as island area, elevation and distance to the mainland best explain patterns of native species richness. On the other hand, alien species richness was well predicted by a combination of geographic and socio‐economic variables, with per capita gross domestic product (GDP) and island area having the strongest effect. Species composition of alien floras is also significantly influenced by the historical colonial identity of these islands. Main conclusions While native species are clearly associated with biogeographic variables, alien species are strongly influenced by variables related to human activities and therefore anthropogenic disturbance processes. Modification of natural areas by human activities can result in high alien species richness even on islands with high native species richness.
... We suggest that this period is also the critical stage during which M. maximus can have the greatest influence on local flora; other non-native species may exert similar effects. This dynamic is important to ecosystems with pronounced dry seasons, such as Mediterranean climates, arid regions, tropical dry forests, or habitats with a significant ecological perturbation such as abandoned pasturelands (Holl 1999, Lugo 2004, Maza-Villalobos et al. 2011. In highly degraded ecosystems with strong legacy effects, restoration can be an uphill battle with established abiotic thresholds (Prober et al. 2009, Wolfe andVan Bloem 2012). ...
Article
Invasive grasses can influence the diversity and survival of native species by changing disturbance regimes, e.g., promoting fire and altering nutrient and resource fluxes. The goal of this study was to assess how non-native and native grasses influence the establishment of native woody seedlings in the Guánica subtropical dry forest, Puerto Rico. This forest has been experiencing the influence of introduced non-native plants, altered disturbance regimes, and resultant changes in the forest community over the past decades. We selected 2 field sites with the non-native grass Megathyrsus maximus (Guinea Grass) or the native grass Uniola virgata (Limestone Grass). At each site, we randomly selected 20 grass clumps and 20 adjacent bare soil patches in which to transplant seedlings of 3 native woody species. We recorded seedling survival over a 23-month study period, with soil-moisture content recorded for the first 6-month period. Seedling survival varied from 0–15%, with the best survival in all 3 species occurring in the U. virgata grass edges (15%) as compared to other treatments (0%). Patches of M. maximus displayed drastic fluctuations in moisture levels, which may have inhibited native-species establishment. We observed the highest seedling survivorship in Coccoloba microstachya (Puckhout) and Erythroxylum areolatum (Swamp-redwood) individuals, suggesting that these species are good candidates for restoration.
... One of the most promising approaches to objective research is long-term studies that focus on elucidating complex ecosystem processes that include both native and non-native species. Such is the case for (i) non-native plants that add to the British flora without negative consequences to native diversity (Thomas & Palmer, 2015); (ii) invading oysters that interact with native mussels to form multi-layered mixed reefs in the northern Wadden Sea (Reise et al., 2017); (iii) alien-dominated forests that serve important ecological functions (Lugo, 2004;Mascaro, Hughes, & Schnitzer, 2012); (iv) increases in local richness in an invaded clade of frogs in Lower Middle America (Pinto-Sánchez, Crawford & Wiens, Pinto-Sanchez, Crawford, & Wiens, 2014); (v) local regulation of non-native plant species in New Zealand due to accumulated negative soil feedbacks (Diez et al., 2010); and (vi) the detection of life-history evolutionary processes both in native and exotic species that eventually facilitate coexistence (Lankau et al., 2009;Leger & Espeland, 2010;Phillips, Brown, & Shine, 2010). ...
Article
Herein, I review existing criticisms of the field of invasion biology. Firstly, I identifiy problems of conceptual weaknesses, including disagreements regarding: (i ) definitions of invasive, impact, and pristine conditions, and (ii ) ecological assumptions such as species equilibrium, niche saturation, and climax communities. Secondly, I discuss methodological problems include the misuse of correlations, biases in impact reviews and risk assessment, and difficulties in predicting the effects of species introductions or eradications. Finally, I analyse the social conflict regarding invasive species management and differences in moral and philosophical foundations. I discuss the recent emergence of alternatives to traditional invasion biology approaches, including the concept of novel ecosystems, conciliation biology, and compassionate conservation. Understanding different value systems will be the first step to reconciling the different perspectives related to this controversial topic.
Article
Full-text available
Introduced psittacine birds can become highly invasive. In this study, we assessed invasions of Psittaciformes in Puerto Rico. We reviewed the literature, public databases, citizen science records, and performed in situ population surveys across the island to determine the historical and current status and distribution of psittacine species. We used count data from Ebird to determine population trends. For species whose populations were increasing, we modelled their potential distribution using niche modeling techniques. We found 46 Psittaciformes in Puerto Rico, of which 26% are only present as pets, at least 29 species have been reported in the wild, and of those, there is evidence that at least 12 species are breeding. Our results indicate that most introduced species which have been detected as established still persist, although mostly in localized areas and small populations. Clear evidence of invasiveness was found for Brotogeris versicolurus and Myiopsitta monachus, which have greatly expanded their range in recent years. Psittacara erythrogenys and Eupsittacula canicularis also showed population increases, although to a lesser degree. The niche models predicted suitable areas for the four species, and also indicate the potential for range expansion. We discuss the factors leading to invasion success, assess the potential impacts, and we discuss possible management strategies and research prospects.
Article
Full-text available
The overlapping area between Thap Lan National Park and Thai Samakkhi subdistrict is a popular tourist destination in Nakorn Ratchasima province, Thailand and in recent decades, this area has been extensively developed for both tourism and agriculture. However, such changes have violated Thai national law since most of the developed areas are within Thap Lan National Park. Therefore, the effect of these developments on the natural forest community was studied. A sample size of 111 temporary plots was set up for collecting data on native tree species and exotic plant species of all life-forms. The findings revealed that the vegetation cover could be categorized into two main groups: 1) natural plant communities, consisting of dry evergreen forests, mixed deciduous forests and secondary forests; and 2) plant communities resulting from anthropogenic disturbances, consisting of forest plantations, field crops, orchards, resort parcels, and temple vicinities. The study also found that tree sapling and tree seedling densities and the percentage ground cover were significantly lower in areas developed for tourism and agriculture than in areas of natural plant communities. This reflected the inability of native species to regenerate and disperse naturally in this modified landscape. In addition, in the human-developed areas, several introduced, invasive, alien plants and weeds in field crop, orchard and resort plant communities were found. The development of tourism activities and agriculture were the major factors which substantially threatened the sustainability of the natural ecosystem of the tropical forests in this region.
Article
Full-text available
Invasive alien tree species can exert severe impacts, especially in insular biodiversity hotspots, but have been inadequately studied. Knowledge of the life history and population trends of an invasive alien tree species is essential for appropriate ecosystem management. The invasive tree Bischofia javanica has overwhelmed native trees on Haha-jima Island in the Ogasawara Islands, Japan. We explored forest community dynamics 2 years after a typhoon damaged the Sekimon primary forests on Haha-jima Island, and predicted the rate of population increase of B. javanica using a logistic model from forest dynamics data for 19 years. During the 2 years after the typhoon, only B. javanica increased in population size, whereas populations of native tree species decreased. Stem diameter growth of B. javanica was more rapid than that of other tree species, including native pioneer trees. Among the understory stems below canopy trees of other species, B. javanica grew most rapidly and B. javanica canopy trees decreased growth of the dominant native Ardisia sieboldii . These competitive advantages were indicated to be the main mechanism by which B. javanica replaces native trees. The logistic model predicted that B. javanica would reach 30% of the total basal area between 2017 (in the eastern plot adjacent to a former B. javanica plantation) and 2057 (in the western plot distant from the plantation site), which is a maximum percentage allowing to eradicate under the present guideline of the National Forest. The results suggest immediate removal of B. javanica is required to preserve native biodiversity in these forests.
Article
Exotic woody plants are often used by native organisms, but may also be targets of expensive control justified by nature conservation. We determine the use of a weed of national significance, Gorse (Ulex europaeus L.), by native mammals, birds, reptiles and vascular plants in pastoral areas in an Australian biodiversity hotspot. Large numbers of fauna species were observed using Gorse within our 43 × 1 ha sample sites in riparian, woodland and pasture vegetation. Gorse cover and/or height positively influenced: the detection of mammals as a whole in an interaction with visibility at 50–75 cm above ground, but not their species richness or individual species abundances; bird abundance, but not richness; and, reptile richness but not abundance. In terms of flora, Gorse cover and/or height positively affected: non‐native plant species richness and the height and fecundity, but not the richness, of native grasses and forbs—but Gorse cover negatively influenced the height of native herbs. The only species of conservation significance using Gorse were three mammals, only one of which, the Tasmanian Pademelon (Thylogale billardieri), was sufficiently common to analyse. Its abundance had no relationship with Gorse cover or height. Even in the wider context of complementary work, there is no strong threatened species conservation justification for retaining Gorse thickets in the Northern Midlands pastoral landscape. Equally, expending scarce conservation resources to remove Gorse, as is taking place, is unlikely to achieve any threatened species conservation outcome but may help reduce long‐term loss of native animal and plant species.
Article
Full-text available
The Paraná River ends in a delta that possesses a native riparian forest of outstanding complexity and richness: the monte Blanco (MB). It is located in the highest sectors of the islands, the levees, and has been practically eliminated and replaced mainly by forest plantations. Likewise, many of these forest plantations have been abandoned giving place to post-abandonment secondary forests (PF) where the processes of invasion of exotic species and of recovery of native species make their classification difficult. The main objective of the research was to describe and compare the vegetation of 2 spontaneously developed levee forests in the Frontal Paraná River Delta. Twenty 100 m2 sampling plots of were set in MB and PF and species presence, cover and tree density were recorded. Both forests resulted homogeneous in the coverage of the main growth forms, but variable in terms of their age and the origin of the species that comprise them. These forests preserve a considerable percentage of the original species and, compared to other delta communities, have greater richness and a markedly different composition. Finally, the classification of these forests is discussed and the generic name “levee forest” is proposed to refer to them.
Article
Full-text available
Worldwide the number of non-native species escaping from cultivation into native habitats is steadily increasing with no signs of saturation. Species that eventually become invasive may generate unwanted social and ecological conditions especially in areas of conservation concern. This study built upon prior biodiversity work from 432 residential yards in the San Juan Metropolitan Area of Puerto Rico to evaluate the natural history and functional traits of native and non-native plant species in these green spaces. We reviewed the literature for a total of 361 plant species to extract information on their taxonomy, native distribution range, invasive status (casual, naturalized or invasive), life-form and ecological and biological species attributes. We then evaluated the relationship between their attributes and their probability of escaping cultivation and become invasive. Our results show that non-native species growing in yards are more likely to succeed in becoming invasive if they have vegetative growth, a mixed breeding system, and an unspecialized dispersal mode. We also found that native and non-native species occurring in residential yards share similar adaptive strategy scores. Most plant species that have already become invasive originated from Asia and America a fact that is likely tied to the US nursery trade. We used the combined results of this and prior studies to understand the factors facilitating plant invasion and to generate recommendations for the development of management strategies that may limit the spread of non-native ornamentals with the potential to escape cultivation and become invasive on this island.
Article
Full-text available
In many countries where the economy has shifted from mainly agricultural to industrial, abandoned agricultural lands are lost to urbanization. For more than 4 centuries the Puerto Rican economy depended almost entirely on agriculture, but sociopolitical changes early in the 20th century resulted in a shift to industry. This shift in the economy, and an increase in population, has resulted in an increase in urban areas. This study describes the rate and distribution of urban growth on the island of Puerto Rico from 1977 to 1994 and the resulting influence on potential agricultural lands. Urban extent and growth were determined by interpreting aerial photographs and satellite imagery. The 1994 urban coverage was combined with a soil coverage based on agricultural potential to determine the distribution of urban areas relative to potential farmlands. Analyses showed that in 1977, 11.3% of Puerto Rico was classified as urban. After 17 years, urban areas had increased by 27.4% and urban growth on soils suitable for agriculture had increased by 41.6%. This represents a loss of 6% of potential agricultural lands. If this pattern of encroachment by urban growth into potential farmlands continues, Puerto Rico’s potential for food production in the future could be greatly limited.
Article
Full-text available
Tree growth, biomass productivity, litterfall mass and nutrient content, changes in soil chemical properties and understory forest succession were evaluated over a 8.5-year period in single- and mixed-species (50:50) plantations of two N2-fixing species, Casuarina equisetifolia and Leucaena leucocephala, and a non-fixing species, Eucalyptus robusta. At the optimal harvest age for maximum biomass production (4 years), total aboveground biomass ranged from 63Mgha−1 in the Eucalyptus monoculture to 124Mgha−1 in the Casuarina/Leucaena mixture, and was generally greater in the mixed-species than in single-species treatments due to increased productivity of the N-fixing species in the mixed stands. Total litterfall varied from 5.3 to 10.0Mgha−1 year−1 among treatments, or between 5.9% and 13.2% of net primary production. Litterfall production and rates of nutrient return for N, P, K, Ca and Mg were generally highest for Leucaena, intermediate for Casuarina and lowest for Eucalyptus. These rates were usually higher in the mixed-species than in monospecific stands due to differences in biomass productivity, but varied considerably depending on their species composition. Total system carbon and nutrient pools (in biomass plus soils to 40-cm depth) for N, P, K, Ca, Mg, Mn at four years were consistently greater in the plantation treatments than in the unplanted control plots. Relative to the single-species plantations, these system pools were generally larger in the mixed-species plantations for C (−10% to +10%), N (+17% to +50%), P (−1% to +63%), K (−19% to +46%), Ca (−10% to +48%), Mg (+5% to +57%) and Mn (+19% to +86%). Whole-tree harvests at four years would result in substantial system carbon and nutrient losses, although these estimated losses would not exceed the estimated gains realized during the four-year period of tree growth at this site. At 7.5 years, soil organic matter and effective cation exchange capacity were reduced in all plantation treatments relative to the control. Changes in soil nutrient content from 0 to 7.5 years were highly variable and not significantly different among treatments, although stands containing Leucaena generally showed higher rates of nitrogen and phosphorus accretion in soils than those with Eucalyptus and/or Casuarina. Natural regeneration of secondary forest tree and shrub species increased over time in all plantation treatments. A total of 24 native or naturalized forest species were recorded in the plantations at 8.5 years. Woody species abundance at this age was significantly greater beneath Casuarina than either Eucalyptus or the Eucalyptus/Leucaena mixed stands. Species richness and diversity, however, were greatest beneath stands containing Eucalyptus and/or Leucaena than in stands with Casuarina.
Article
Full-text available
The extensive recovery from agricultural clearing of Puerto Rican forests over the past half-century provides a good opportunity to study tropical forest recovery on a landscape scale. Using ordination and regression techniques, we analyzed forest inventory data from across Puerto Rico’s moist and wet secondary forests to evaluate their species composition and whether the landscape structure of older forest affected tree species composition of recovering forests at this scale. Our results support conclusions from studies conducted in Puerto Rico at smaller scales and temperate forests at larger scales that timing of abandonment and land use history are of overwhelming importance in determining the species composition of recovering forests. Forest recovery is recent enough in Puerto Rico that previous land use is clearly evident in current species composition, and creates new forest communities. As demonstrated in other work, physical factors such as elevation and substrate co-vary with land use history, so that the species composition of the forest landscape results from the interplay between biophysical and socioeconomic forces over time. Our results also indicate that increasing the distance to the largest forest patches occurring in the landscape 12 years previous had a small negative impact on species richness but not species diversity or community composition. We conclude that land use history has as much influence in species composition as biophysical variables and that, at the scale of this study, there is no large influence of forest landscape structure on species diversity or composition.
Article
Full-text available
The introduction of new predators and pathogens has caused numerous well-documented extinctions of long-term resident species, particularly in spatially restricted environments such as islands and lakes. However, there are surprisingly few instances in which extinctions of resident species can be attributed to competition from new species. This suggests either that competition-driven extinctions take longer to occur than those caused by predation or that biological invasions are much more likely to threaten species through intertrophic than through intratrophic interactions. The likely threat of introduced species to resident controphics (species in the same trophic level) can be assessed with the help of existing biodiversity and extinction data sets and of two recent theories: (1) the fluctuating resource availability hypothesis, developed to account for changes in the invasibility of communities, and (2) the unified neutral theory, proposed to account for patterns of biodiversity at the community and metacommunity levels. Taken together, theory and data suggest that, compared to intertrophic interactions and habitat loss, competition from introduced species is not likely to be a common cause of extinctions of long-term resident species at global, metacommunity, and even most community levels.
Article
Full-text available
In lowland tropical and temperate forests, nitrogen (N) and phosphorus (P) resorption from senesced leaves may reflect a mechanism of conservation of a limiting nutrient (Edwards & Grubb 1982, Killingbeck 1996, Proctor et al. 1989, Scott et al. 1992, Songwe et al. 1997, Vitousek & Sanford 1986). At the ecosystem level it has important implications for element cycling. The nutrients which are resorbed during leaf senescence are directly available for further plant growth, which makes a species less dependent on current nutrient uptake. Nutrients which are not resorbed, however, will be circulated through litterfall in the longer term (Aerts 1996).
Article
Full-text available
In western Europe, forest area has been expanding rapidly since the 19th century, mainly on former agricultural land. Previous studies show that plant diversity differs between these recent forests and ancient forests that were already forested at the time of first national cadastral surveys, around 1800. Here, we investigated the duration of such agricultural aftereffects. In northeastern France, large areas were deforested during the Roman occupation and thereafter abandoned to forest. In one such forest that was farmed during the period AD 50–250, we show that species richness and plant communities vary according to the intensity of former agriculture. These variations are linked to long-term changes of chemical and structural soil properties. Hence, we suggest that such effects of past agricultural land use on forest biodiversity may be irreversible on an historical time scale.
Article
Full-text available
The Asian clam, Corbicula fluminea (Bivalvia); Florida applesnail, Pomacea paludosa (Gas-tropoda); and Australian redclaw, Cherax quadricarinatus (Crustacea) have recently become established or possibly established in Puerto Rico. The giant floater, Anodonta grandis (Bivalvia); giant freshwater prawn, Macrobrachium rosenbergii (Crustacea); and red swamp crawfish, Procambarus clarkii (Crustacea), have been introduced but not released. This paper presents the history of these introductions, their potential ecological consequences, and the loopholes that allowed each one to happen. Among the latter were: the danger inherent in C. fluminea was apparently not advertised, very similar snails (P. paludosa and South American applesnails, Pomacea cumingii) were not distinguished, existing enforcement systems were not designed to prevent package-delivery shipments and mass shipments of C. quadricarinatus to individuals, and P. clarkii and A. grandis were introduced by the aquarium industry and transferred to aquaculture.
Article
Full-text available
Regeneration of secondary forests is recognized as an important means for the recovery of native species biodiversity in human-disturbed tropical lands. Native earthworms are often replaced with exotic species after deforestation. We studied changes in earthworm diversity and community structure along a chronosequence of abandoned tropical pastures in the Cayey Mountains of Puerto Rico. This chronosequence consisted of active pastures, young secondary forests 25–40 years old, and mature secondary forests>77 years old. Earthworm diversity increased along successional stages. The exotic soil-feeding earthworm Pontoscolex corethrurus dominated the pastures and young secondary forests. Five native earthworm species ( litter feeders Borgesia sedecimsetae, Estherella sp., Onychochaeta borincana, Neotrigaster rufa, and Trigaster longissimus ) were found in the mature forests, together with P. corethrurus. Earthworm density was highest in the active pastures ( 273 individuals/m² ), decreased as forest regeneration proceeded, and was lowest in the mature forests ( 88 individuals/m² ). Our results suggest that regeneration of mature secondary forests, and the consequent increase in litter biomass on the forest floor, can promote the recovery of earthworm diversity and native species of earthworms in old tropical pastures.
Article
Full-text available
Patterns of understory colonization by native and naturalized trees and shrubs were evaluated in 4.5-year-old plantations of three exotic tree species, Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala, on a degraded coastal grassland site with reference to overstory composition and understory environmental conditions. 19 secondary forest species were established in the plantation understories (with a total area of 0.52 ha), while no natural regeneration occurred in unplanted, though protected, control areas. The majority of these species (90 %) and the total seedling population (97 %) were zoochorous, indicating the importance of frugivorous bats and particularly birds as facilitators of secondary forest species colonization. Understory species richness and seedling densities were affected significantly by overstory composition, the most abundant regeneration occurring beneath Leucaena and least under Casuarina. Understory colonization rates within mixed-species stands were intermediate between those of single-species stands of the trees comprising their overstories. Significant negative correlations were found between understory species richness and seedling density, and forest floor depth and dry mass, especially for small-seeded ornithochorous species. Higher colonization rates near the peripheries of plantation plots relative to plot interiors were due in part to roosting site preferences by frugivores, particularly bats.The study results indicate that overstory species selection can exert a significant influence on subsequent patterns of colonization by secondary forest species and is an important consideration in the design of plantations for ‘catalyzing’ succession on deforested, degraded sites.
Article
Full-text available
Forest structure and species composition were described in abandonedshade and sun coffee plantations and abandoned pastures in Puerto Rico. Foreststructural characteristics were similar to older forest sites afterapproximately 30 yr of recovery. The historical presence of shadecoffee plantations as the dominant agricultural activity in the region hasresulted in the homogenization of secondary forest composition. The continuousdominance of Coffea arabica and species used for shade inabandoned shade coffee contributed to a slower rate of species compositionchange in comparison to abandoned pastures. Abandoned pastures were initiallycolonized by a group of light demanding and/or wind dispersed species and thenby shade tolerant species characteristic of abandoned shade coffee plantations,suggesting that the secondary forests of abandoned shade coffee plantation arethe major source of species in this landscape. The presence of a few isolatedbig trees in sun coffee plantations appeared to facilitate colonization ofwoodyspecies similar in composition to abandoned shade coffee plantations. In amultivariate analysis, time since abandonment and elevation were the variablesthat explained the majority of variability in species composition among sites.However, a few native species (e.g. Guarea guidonia,Casearia sylvestris, Ocotealeucoxylon) were common regardless of land use history or elevation.In contrast, important old forest species (e.g. Sloaneaberteriana, Dacryodes excelsa,Manilkara bidentata) were rare or absent from most of thesecondary forest stands suggesting the need to reintroduce these species. Landmanagement and conservation efforts can be improved by incorporating theeffectsof land use history on secondary forest dynamics.
Article
Full-text available
Resorption efficiency (RE) and proficiency, foliar nutrient concentrations, and relative soil nutrient availability were determined during 3 consecutive years in tree species growing under contrasting topographic positions (i.e., top vs. bottom and north vs. south aspect) in a tropical dry forest in Mexico. The sites differed in soil nutrient levels, soil water content, and potential radiation interception. Leaf mass per area (g m–2) increased during the growing season in all species. Soil P availability and mean foliar P concentrations were generally higher at the bottom than at the top site during the 3 years of the study. Leaf N concentrations ranged from 45.4 to 31.4 mg g–1. Leaf P varied from 2.3 to 1.8 mg g–1. Mean N and P RE varied among species, occasionally between top and bottom sites, and were higher in the dry than in the wet years of study. Senesced-leaf nutrient concentrations (i.e., a measure of resorption proficiency) varied from 13.7 to 31.2 mg g–1 (N) and 0.4 to 3.3 mg g–1 (P) among the different species and were generally indicative of incomplete nutrient resorption. Phosphorus concentrations in senesced leaves were higher at the bottom than at the top site and decreased from the wettest to the the driest year. Soil N and P availability were significantly different in the north- and south-facing slopes, but neither nutrient concentrations of mature and senesced leaves nor RE differed between aspects. Our results suggest that water more than soil nutrient availability controls RE in the Chamela dry forest, while resorption proficiency may be interactively controlled by both nutrient and water availability.
Article
Full-text available
Although deforestation continues to be a major threat to tropical biodiversity, abandonment of agricultural land in Puerto Rico provides an opportunity to study long-term patterns of secondary forest regeneration. Using aerial photographs from 1937, 1967, and 1995, we determined land-use history for 2443 ha in the Cayey Mountains. Pastures were the dominant land cover in 1937 and <20% of the area was classified as forest. Between 1937 and 1995, forest cover increased to 62% due to widespread abandonment of agriculture. To examine the effect of historic land use on current forest structure and species composition, we sampled secondary forests in 24 abandoned pastures, 9 abandoned coffee plantations and 4 old-growth forest sites. Sites were located on two soil types along an elevational gradient (125–710 m) and included a chronosequence from 4 to over 80 years old. After 25–30 years, basal area and species richness in secondary forest sites derived from abandoned pastures and coffee plantations were similar to old-growth forest sites. The species composition of secondary forests derived from abandoned pastures and coffee plantations remained distinct from old-growth forest. In addition to historic land use, age and elevation were important environmental variables explaining variation in secondary forest species composition. Non-indigenous species were common in recently abandoned pastures and coffee plantations, but their importance declined in the older sites. This study demonstrates that secondary forests on private land can be an important component of the conservation of tropical tree biodiversity.
Article
Full-text available
The species composition of forests change continuously as the earth’s biota evolves and adjusts to environmental change. Humans are accelerating the rate of species turnover by moving species around the planet and dramatically changing environmental conditions. Our focus is on new forests in Puerto Rico that emerge naturally on abandoned lands previously converted to agriculture and degraded. These forest stands have combinations of species that are new to the island’s landscapes. New forests exhibit high species dominance during forest establishment, which includes dominance by alien tree species. These alien tree species establish and maintain forest cover, which may facilitate regeneration of native tree species. Landscape analysis and literature review revealed that these emerging stands are highly fragmented (60% were <1 ha in 1991), function as refugia for native organisms, and at 60–80 years old have similar species richness and structural features as native stands of similar age. However, the island’s new forests exhibit important differences from mature native forests on unconverted forestlands. New forests have fewer endemic species and fewer large trees (≥55 cm dbh) than mature native forests; they have higher soil bulk density and lower soil carbon and litter stocks; and they accumulate aboveground biomass, basal area, and soil carbon more slowly than native forests of similar age. We suggest that new forests will become increasingly prevalent in the biosphere in response to novel environmental conditions introduced to the planet by humans.
Article
Full-text available
This paper reviews the characteristics of animal seed dispersal relevant to tropical forest restoration efforts and discusses their management implications. In many tropical regions seed dispersal by animals is the predominant form of dissemination of propagules and has the potential to facilitate recolonization of native vegetation on degraded sites. The site traits relevant for attracting seed dispersers include the availability of perches, the structural complexity of the vegetation and the presence of food resources, especially fruit, as an attractant. Tree plantations with these traits will be particularly attractive to animal seed dispersers and, therefore, will have higher rates of seed rain than plantations lacking these traits. The efficacy of animal seed dispersal to restoration sites can be limited by the degree of isolation from a seed source, absence of animal seed dispersers in the region and by large seed size. In highly degraded regions, where seed sources may be isolated and animal seed dispersers rare, restoration will require direct seeding or planting. However, even under the best of conditions with a full compliment of animal seed dispersers and a nearby seed source, large-seeded species, because of their relative immobility, should be planted if a full return to primary forest is desired.
Article
Full-text available
The literature on tropical secondary forests, defined as those resulting from human disturbance (e.g. logged forests and forest fallows), is reviewed to address questions related to their extent, rates of formation, ecological characteristics, values and uses to humans, and potential for management. Secondary forests are extensive in the tropics, accounting for about 40% of the total forest area and their rates of formation are about 9 million ha yr ⁻¹ . Geographical differences in the extent, rates of formation and types of forest being converted exist. Secondary forests appear to accumulate woody plant species at a relatively rapid rate but the mechanisms involved are complex and no clear pattern emerged. Compared to mature forests, the structure of secondary forest vegetation is simple, although age, climate and soil type are modifying factors. Biomass accumulates rapidly in secondary forests, up to 100 t ha ⁻¹ during the first 15 yr or so, but history of disturbance may modify this trend. Like biomass, high rates of litter production are established relatively quickly, up to 12–13 t ha ⁻¹ yr ⁻¹ by age 12–15 yr. And, in younger secondary forests (< 20 yr), litter production is a higher fraction of the net primary productivity than stemwood biomass production. More organic matter is pro duced and transferred to the soil in younger secondary forests than is stored in above-ground vegetation. The impact of this on soil organic matter is significant and explains why the recovery of organic matter in the soil under secondary forests is relatively fast (50 yr or so). Nutrients are accumulated rapidly in secondary vegetation, and are returned quickly by litterfall and decomposition for uptake by roots. We propose a model of the gains and losses, yields and costs, and benefits and tradeoffs to people from the current land-use changes occurring in the tropics. When the conversion of forest lands to secondary forests and agriculture is too fast or land-use stages are skipped, society loses goods and services. To avoid such a loss, we advocate management of tropical forest lands within a landscape perspective, a possibility in the tropics because land tenures and development projects are often large.
Article
Full-text available
The conversion of tropical forests into pastures has increased dramatically in the last 20 years. Once these lands are abandoned it is not clear if they will recover to forest or if they will become permanent grasslands. Economic changes in Puerto Rico have led to the abandonment of agricultural lands over the last 60 years, providing an opportunity to assess the longer term patterns of forest recovery following human disturbance. This study focuses on the changes in vegetation in abandoned pastures ranging in age from 0 to 60 years or more in two replicate chronosequences. Species richness and density of woody species were very low during the first 10 years following abandonment and woody biomass did not increase substantially until approximately 15 years post-abandonment, Recovery in pastures is greatly delayed in comparison with forest recovery following other types of human and natural disturbance. The successional trajectory is quite different in comparison to those following natural disturbances in the nearby Luquillo Mountains. In particular, the initial colonizing species are not 'typical' pioneer species (e.g. Cecropia sp., Scheffleria morotononi), but a group of shrubs and treelets in the Rubiaceae, Melastomataceae, and Myrtaceae. The presence of grasses and the rapid colonization and growth of ferns and herbaceous species in the abandoned pastures appears to be a major factor inhibiting the establishment of secondary forest and imparts a selective barrier on the colonizing woody species.
Article
Full-text available
The introduction of bamboo to montane rain forests of the Luquillo Mountains, Puerto Rico in the 1930s and 1940s has led to present-day bamboo monocultures in numerous riparian areas. When a non-native species invades a riparian ecosystem, in-stream detritivores can be affected. Bamboo dynamics expected to influence stream communities in the Luquillo Experimental Forest (LEF) were examined. Based on current distributions, bamboo has spread downstream at a rate of 8 m y -1 . Mean growth rate of bamboo culms was 15.3 cm d -1 . Leaf fall from bamboo stands exceeded that of native mixed-species forest by c. 30(k = -0.021), and leaves from another abundant riparian exotic, Syzygium jambos (Myrtaceae) (k = -0.018), decayed at relatively slow rates when submerged in streams in fine-mesh bags which excluded macro-invertebrate leaf processors. In a second study, with leaf processors present, bamboo decay rates remained unchanged (k = -0.021), while decay rates of S. jambos increased (k = -0.037). Elemental losses from bamboo leaves in streams were rapid, further suggesting a change in riparian zone/stream dynamics following bamboo invasion. As non-indigenous bamboos spread along Puerto Rico streams, they are likely to alter aquatic communities dependent on leaf input.
Article
In this study, monthly changes in concentrations of various nutrients (N, P, K, Ca & Mg) and their uptake, accumulation, transfer and release in both plant parts and soil were studied in grasses grown under Albizzia plantation and in the open grazing land in the semi-arid region of Madurai. At both sites, the maximum concentration of all nutrients were recorded in the live shoot, followed by dead shoot, below ground and litter. The average nutrient accumulation in the plant parts as well as in the soil was in the order of N<K<Ca<Mg<P. Among the sites, the nutrients concentration in plant components and the uptake from the soil were significantly higher (P>0.05) in the plantation site than in the open grazing land. The soil moisture content also showed significant increase under Albizzia plantation than in the open grazingland. Of the total uptake about 80% of nutrients, were transferred to above ground plant parts and very little was transferred to below ground parts. At both sites, the nutrients return to the soil through root was lower than that of litter disappearance. The study reveals that Albizzia trees can increase the nutrient content of understorey grasses by their rapid leaf turnover and decomposition of nutrient rich litter, which can result in significant increase in soil fertility.
Article
A 1980 inventory of secondary forests on lands of timber production potential in Puerto Rico showed that about half (52 000 ha) are adequately stocked with poletimber or saplings of timber species to produce a 2nd crop without artificial regeneration. -from Authors
Chapter
Palm brakes growing on steep slopes in the Caribbean are characterized by low species richness, simple community structure, and temporal and spatial variations in community structure. Two Prestoea montana palm forest stands were studied in the Luquillo Experimental Forest over a period of 40 years in order to determine the successional status of the palm brake. The stand with the greater rainfall had fewer tree species, greater species dominance, and lower turnover of species than the stand with less rainfall. Soil structure and chemistry varied widely both vertically and horizontally and could not explain spatial changes in stand structure. Dicotyledonous trees grew larger in the better-drained sites with deeper soils on top of ridges or on steep slopes. Palms dominated swales and waterlogged areas. The combination of geological, climatic (including storms and hurricanes), and geomorphic conditions resulted in a frequently disturbed palm brake environment. The biotic response to such conditions appears to be cyclic successions characterized by a small group of species that replace each other, catastrophic mortalities, rapid growth rates after disturbance, and permanence of the palm forest physiognomy. We suggest that succession in palm brakes follows different directions depending on type of disturbance and site conditions. Site conditions are variable in spite of always being wet and geomorphologically unstable.
Article
Soil organic matter content and loose litter were studied in secondary forests of the subtropical moist- and wet-forest life zones of Puerto Rico to observe patterns due to life zone (climate), type of forest cover, soil group, and topography. Soil organic matter content in the top 23 cm ranged from 8.99 kg/m$^2$ in the moist-forest life zone to 7 30 kg/m$^2$ in the wet-forest life zone, a highly significant difference. Greater amounts of soil organic matter were found under higher timber volumes, but the trend was less pronounced in the wet forest. Significant interactions with life zone were found for organic matter among soil groups (deep volcanic, shallow volcanic, granitic, and limestone) and among forest classes (young secondary, late secondary, abandoned coffee, and active coffee shade). In secondary forests on granitic soils, highly significant differences of 12.98 and 7 32 kg/m$^2$ of organic matter were found in wet and moist forests, respectively. Moreover, highly significant differences were observed by landform and slope in active coffee shade in wet forests, with the lowest values on convex land forms and slopes >45 percent. Mean loose litter storages in moist and wet forests were not significantly different, nor was there a significant interaction with life zone. Significant differences, however, were detected by timber volume class, soil group, and forest class. Within these highly disturbed wet and moist forests, greater timber volumes tended to be associated with greater loose litter accumulation.
Article
Studies are being made of plant microfossils from seven Tertiary formations in Mexico, Panama, and Puerto Rico. The Puerto Rican samples from the Oligocene San Sebastian Formation have yielded 165 morphological forms; 44 have been identified, and 15 of these have no previously known fossil record. Community types include a coastal, brackish-water assemblage of Rhizophora and Pelliciera, an upland tropical to subtropical community, and an arboreal cool-temperate community of Fagus, Liquidambar, and Nyssa. Of the 44 genera identified, 31 presently grow in Puerto Rico, three grow on other islands of the Antilles, seven are found in ecologically comparable habitats elsewhere in Latin America, and only the three temperate trees require habitats not presently available on the island. The temperate element suggests altitudes greater than those of today, and recently available geological data reveal the presence of Oligocene highlands of 13,000 to 15,000 feet elevation. These would be sufficient to provide cool-temperate conditions in an insular environment at 18 degrees north. Ancestral Puerto Rico (Hispaniola, Puerto Rico, and the Virgin Islands) provided an effective landbridge between northern South America, the West Indies, and Mexico (Yucatan). However, the Oligocene seas extended across at least part of peninsula Florida and up to 120 miles inland along the Texas Gulf Coast; thus the barrier to migration from the Antilles into southeastern North America was probably greater than at present. Of the 44 genera identified all have affinities with northern South America, eastern Mexico, and the Antilles; and none have exclusive affinities with the vegetation of southeastern North America. Studies from Panama and Veracruz, Mexico, suggest tropical elements in the modern and fossil floras of southeastern North America were introduced along an Isthmian-coastal Mexico route during the early Tertiary or subsequently through long-distant dispersal into tropical outliers (southern peninsula Florida).
Article
A major cause of tropical deforestation has been the conversion of lowland forest into pastures for cattle grazing. We studied forest structure and species composition following abandonment of cattle pastures in 23 abandoned pastures 9.5-60 yr old and seven forested sites > 60 yr old. Sires were chosen along an elevational gradient from 10-450 m and represented subtropical wet and moist forest life zones. Age since abandonment was the best predictor of stand characteristics. Woody plant density, basal area, species number, and diversity were low 10 yr after abandonment, but increased rapidly after 10 to 15 yr pose-abandonment. Although distance to nearest seed source and hurricane exposure are factors char could affect forest recovery there was little variation among sires and no effects were detected. Elevation and age were significant determinants of species composition. At higher elevations (> 100 m), the shrub Miconia prasina (Melastomataceae) was the dominant pioneer species, bur in the low elevation, a larger group of shrubs and small trees colonized abandoned pastures. At higher elevations, the species composition of recovering sires did nor include many mature forest species. After 40 yr of recovery, secondary forest stands cannot be distinguished from undisturbed sites in terms of density, basal area, species number, or diversity, but it appears that it will require centuries for these sires to return to a species composition similar to undisturbed forests.
Article
Ants were studied on Puerto Rico and 44 islands surrounding Puerto Rico. Habitat diversity was the best predictor of the number of species per island and the distributions of species followed a nested subset pattern. The number of extinctions per island was low, approximately 1–2 extinctions per island in a period of 18 years, and the rates of colonization seem to be greater than the extinction rates. Ant dynamics on these islands do not seem to support the basic MacArthur and Wilson model of island biogeography. The MacArthur and Wilson equilibrium is based on the notion that species are interchangeable, but some extinctions and colonizations can change the composition and number of species drastically.
Article
Melaleuca ( Melaleuca quinquenervia (Cav.) S.T. Blake) is a large tree species that occurs naturally throughout eastern Australia, New Caledonia, Irian Jaya and southern New Guin- ea. In North America, melaleuca has primarily infested the Florida peninsula south of Lake Okeechobee. It is classed as a Federal Noxious Weed in the United States and as a Prohibit- ed Aquatic Plant and Noxious Weed in the state of Florida. In the continental United States, melaleuca has been recorded from Louisiana, Texas and California. Additionally, this tree has become moderately invasive in Puerto Rico and Hawaii. Melaleuca rapidly invades moist, open habitats, both dis- turbed and undisturbed, and forms dense, impenetrable mo- nocultures. In general, invasion is less prominent in forested sites than marshes; however, only dense hammock-type com- munities seem to produce enough shade to prevent invasion. Invasive characteristics of melaleuca include its evergreen hab- it, prolific seed production, frequent flowering, and flood and drought tolerance. This tree threatens biodiversity of native flora and fauna by diminishing the value of their habitat. The large expanses of melaleuca on public lands have cost public agencies in Florida $25 million in control efforts between 1989 and 1999. Estimations of economic impacts of melaleuca on recreation, tourism, fires, loss of endangered species, and more range from $168 million annually to $2 billion over a pe- riod of 20 years. Various methods of control (chemical, me- chanical, manual, biological and integrated) are evaluated.
Article
Changes in land cover from forest to agriculture often alter riparian vegetation, which modifies the physical conditions of streams. To understand the impacts of different categories of land cover on riparian and stream habitats, we sampled riparian vegetation and stream conditions in three adjacent watersheds in southeastern Puerto Rico. Land cover categories (pasture, mixed, and forest) were determined using aerial photographs. Vegetation structure and composition and characteristics of streams were assessed for 35 riparian sites. Sites were located along first-order streams, at 400-600 m elevation in the wet-forest life zone. Understory vegetation in the forest sites was mainly shrubs, herbs, and ferns, whereas the mixed and pasture sites were dominated by grasses, vines, and bare soil. Syzygium jambos and Spathodea campanulata, nonnatives, and Guarea guidonia, a native, were the most common tree species in the riparian areas. Surrounding land cover explained >60% of the variation among stream sites. There was a positive relationship between tree cover and percentage of dissolved oxygen, and a negative relationship between tree cover and percentage of substrata covered by sediments from eroded soil. The amount of woody debris in the streams tended to increase with forest cover. Overall, land cover is a landscape feature that effectively characterized riparian understory cover, tree species composition, and stream condition.