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A Comparative Study of Tree Establishment in Abandoned Pasture and Mature Forest of Eastern Amazonia

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Abstract

In Amazonia, millions of hectares of forest have been converted to cattle pasture then abandoned. On sites with histories of heavy use, forest recovery is slow. We compared the process of tree establishment in an abandoned pasture with a history of heavy use and in a mature forest through a series of field studies in northeastern Amazonia. Tree seedling and sprout emergence was greater than or equal to 20 times lower in the abandoned pasture than in forest understory and forest gaps. Tree emergence was restricted in the abandoned pasture by a lad: of tree seeds in the soil (3 tree genera vs 15 in the forest), and a low rate of tree and liana seed deposition by birds and bats in the open vegetation of the abandoned pasture (2 m(-2) yr(-1)). Tree and liana seed deposition in the abandoned pasture was higher beneath treelets (990 m(-2) yr(-1)). Rates of seed removal and consumption by ants and rodents were also higher in the abandoned pasture (>80% removal within 20 d for 6 tree species) than in forest understorey and forest gaps. Cutter ants (Atta sexdens) hindered tree seedling survivorship and growth in the abandoned pasture by clipping leaves and stems, and preferred tree seedlings to grass and shrub seedlings. In the absence of herbivores, survivorship and height growth of seedling transplants in the abandoned pasture were generally lower than in experimental treefali gaps, and were correlated with harsh environmental conditions in the former. Air temperature, air vapor pressure deficit and soil moisture stress in the abandoned pasture exceeded conditions measured in both treefall gaps and intact forest during the 5-month dry season. Seedling growth in the abandoned pasture was also restricted during the wet season. These barriers to tree establishment help explain the low density and emergence rates of tree seedlings in this abandoned pasture relative to the adjacent mature forest.
... Succession on post-agricultural lands is influenced by a variety of site-specific biotic and abiotic factors that may collectively facilitate or inhibit the development of a functioning plant community (Lennox et al., 2018;Lindenmayer et al., 2006;Moonen et al., 2019). The substrate and microclimate of a site are transformed by clearance for agriculture in variable ways that affect the pathways of secondary forest development (Moonen et al., 2019;Nepstad et al., 1996;Steininger, 2000;Villa et al., 2018). The type and intensity of prior agricultural land use is a key factor that determines the rate of forest recovery after abandonment (Mesquita et al., 2015;Moran et al., 2000) and the additional factors impacted directly by land-use history (e.g. ...
... Agricultural practices can be classified based on the intensity of the impact they have on successional pathways (Chazdon, 2014b;Colón and Lugo, 2006;Villa et al., 2018), differentiating traditional shifting cultivation from practices that create pastures or involve heavy machinery that tend to compact soils and increase nutrient leaching (Marquardt et al., 2013). The rate of biomass accumulation is lower following these more intensive forms of land-use (Chazdon et al., 2007;Jaramillo et al., 2003;Kauffman et al., 1993;Mesquita et al., 2015;Moonen et al., 2019;Negrete-Yankelevich et al., 2020;Nepstad et al., 1996;Uhl, 1987;Uhl et al., 1982;Villa et al., 2018), but in many cases it is unclear what mechanism determines that difference. ...
... For deriving predictions of AGB accumulation at a finer scale, our results suggest that information on the intensity of land-use prior to abandonment should be used when it is available. The importance of land-use intensity for biomass accumulation after the abandonment of agricultural activities in the tropics has been noted in previous research (Chazdon et al., 2007;Jaramillo et al., 2003;Kauffman et al., 1993;Mesquita et al., 2015;Moonen et al., 2019;Nepstad et al., 1996;Gomes et al., 2020;Uhl, 1987;Uhl et al., 1982). This finding is supported by our predicted values of AGB in trees (> 5 cm DBH) at 20 years post-abandonment of 41 ± 33 Mg ha -1 and 120 ± 32 Mg ha -1 for sites abandoned after intensive agriculture vs traditional shifting cultivation respectively. ...
Article
There has been widespread clearance of tropical forests for agriculture, but in many cases the cultivation phase is only transient. The secondary forests recovering on these abandoned sites may contribute to mitigation of greenhouse gas emissions and protection of biodiversity, but the rates of recovery may be dependent on land-use intensity and changes in soil properties during cultivation. However fine-scale details on these changes are poorly known for many tropical forest locations. We quantified soil properties and recovery of woody biomass in 42 tropical forest fragments representing a chronosequence following two types of agricultural land-uses, and in 15 comparable reference old growth forests, between the Andes and the Amazon in Peru. Soil fertility, particularly base cation concentrations, responded negatively to increasing intensity of agricultural land-use, and either decreased or increased with time after abandonment dependent on prior land-use. The predicted mean recovery rate of woody biomass over the first 20 years following abandonment matched that predicted by a general model for the Neotropics, but recovery was three-fold higher on sites abandoned following traditional agriculture than on sites recovering from intensive agriculture. Estimated total biomass recovered to just above half that of reference old growth forests within 71 years. The inclusion of the biomass of lianas and smaller tree stems did not modify the apparent rate of ecosystem biomass recovery, however the proportion of the total biomass stored in small stems was greater following intensive than traditional agriculture, which suggests that patterns of stand structural development are sensitive to land-use history. We conclude that effects of historic land use on soil nutrient concentrations and their changes through time are required for a more complete interpretation of variation in biomass recovery rates at local scales. These results also highlight the critical importance of contemporary agricultural intensification for carbon storage in tropical forests.
... Succession in cleared habitats and abandoned pastures is dependent upon forest seeds that arrive to these areas (Holl 1999). Here I consider seed dispersal patterns in currently active sites, in contrast to previous studies that have analyzed forest regeneration through seed dispersers in abandoned pastures (Kappelle 1993;Aide et al. 1995;Nepstad et al. 1996;Holl 1998;Duncan and Chapman 1999;Holl 1999;Zimmerman et al. 2000;Hooper et al. 2002;Hooper et al. 2004;Hooper et al. 2005). ...
... Therefore, planting a mix of the aforementioned species in the disturbed habitats away from natural forests may increase the rate of secondary succession. Some plant species would potentially have to be planted in later successional stages (depending on the conditions of the land), as strong barriers to establishment would prohibit their growth relative to adjacent forested zones (Nepstad et al. 1996;Zimmerman et al. 2000). Nonetheless, the compiled results in Table 2 indicate that enhancing the biodiversity of vegetation (and their respective sizes) in non-forested zones can only increase the amount of perching observations one would see, thereby increasing the probability of varying seed dispersal. ...
... Forest seedling availability (and avian seed dispersal) into non-forested regions is the limiting factor for forest regeneration (Nepstad et al. 1996), and even when seeds arrive to these regions, tropical montane vegetation regeneration is limited at all early stages of succession: colonization, establishment, growth and survival (Holl 1999;Hooper et al. 2004). Holl (1999) proposes that planting native woody seedlings to increase canopy structure, setting up bird perching structures and planting bushy vegetation that matures and fruits quickly may be viable options to overcome barriers to seed dispersal. ...
... Fig. 3), but did not significantly differ due to altitude variations among the vegetations (P>0.45). Moreover, altitude had no significant effect on the Shannon diversity index (F (1,32) =0.11, P=0.92). ...
... The variations in canopy cover may mediate the woody species recruitment processes [26,[28][29][30]4] for vegetations with dense canopy cover in moisture deficit areas may reduce evapotranspiration and conserve soil moisture that which is essential to enhance regeneration and the overall vegetation recruitment and the variation of which across spatial scales may result in the variations in spatial patterns of the recruitment structures in dry vegetation [31]. However, previous findings also reported that woody species develop adaptive mechanisms through massive seed production, dispersal abilities over long distances, ability to sprouting after damaged by grazing, low palatability, clonal reproduction and production of large seeds [27,32,33,8,34,3]. ...
Article
The spatial variations in woody species composition and recruitment structures are less explored in arid and semi-arid ecosystems. We aimed to fill this gap by undertaking the study on three sites which were purposively selected from Awash River Basin based on their area extent and altitudinal gradients. In each vegetation site, we laid out one transect line and on each transect 12 sample plots (each size: 50 × 50 m) were placed with 200 m intervals, resulting in 36 sample plots. Woody species composition difference among the three sites was tested using Adonis2 function. Nonmetric multidimensional scaling ordination analysis was run to visualize the species composition in relation to the vegetation sites in ordination space. The difference in species richness among the sites and the effect of altitudinal variation were tested using a generalized linear model with the Poisson family. The results showed that the species composition was different among the sites and significantly dependent on altitudinal variation (P=0.001). The species richness and number of unique species was higher at Mille site when compared with other two sites, and the alpha diversities of vegetations were reciprocally related to the magnitude of beta diversity. The recruitment structure was poor in sites where the species richness was lower, although the overall patterns vary across sites. Our overall results suggest that restoration schemes need to take onto account the recruitment structure of specific species to enhance the overall health of the vegetation ecosystems, especially in arid and semi-arid ecosystems.
... Fig. 3), but did not significantly differ due to altitude variations among the vegetations (P>0.45). Moreover, altitude had no significant effect on the Shannon diversity index (F (1,32) =0.11, P=0.92). ...
... The variations in canopy cover may mediate the woody species recruitment processes [26,[28][29][30]4] for vegetations with dense canopy cover in moisture deficit areas may reduce evapotranspiration and conserve soil moisture that which is essential to enhance regeneration and the overall vegetation recruitment and the variation of which across spatial scales may result in the variations in spatial patterns of the recruitment structures in dry vegetation [31]. However, previous findings also reported that woody species develop adaptive mechanisms through massive seed production, dispersal abilities over long distances, ability to sprouting after damaged by grazing, low palatability, clonal reproduction and production of large seeds [27,32,33,8,34,3]. ...
Article
Full-text available
The spatial variations in woody species composition and recruitment structures are less explored in arid and semi-arid ecosystems. We aimed to fill this gap by undertaking the study on three sites which were purposively selected from Awash River Basin based on their area extent and altitudinal gradients. In each vegetation site, we laid out one transect line and on each transect 12 sample plots (each size: 50 × 50 m) were placed with 200 m intervals, resulting in 36 sample plots. Woody species composition difference among the three sites was tested using Adonis2 function. Nonmetric multidimensional scaling ordination analysis was run to visualize the species composition in relation to the vegetation sites in ordination space. The difference in species richness among the sites and the effect of altitudinal variation were tested using a generalized linear model with the Poisson family. The results showed that the species composition was different among the sites and significantly dependent on altitudinal variation (P=0.001). The species richness and number of unique species was higher at Mille site when compared with other two sites, and the alpha diversities of vegetations were reciprocally related to the magnitude of beta diversity. The recruitment structure was poor in sites where the species richness was lower, although the overall patterns vary across sites. Our overall results suggest that restoration schemes need to take onto account the recruitment structure of specific species to enhance the overall health of the vegetation ecosystems, especially in arid and semi-arid ecosystems.
... Fungus cultivators are ants, mostly of the Attini tribe, which grow fungus in their nests using plant parts, faeces, insect carcasses and organic matter to feed them (Della Lucia et al.1993;Mariconi 1970). They play a significant role in the fertility and structure of tropical soils (Coutinho 1984;Brener & Silva 1995) and in the establishment and regeneration of tropical biomes (Nepstad et al. 1996). The results may be linked to the availability of resources, which is higher where the largest vegetation cover (reference area) occurs (Hansen 2000;Wardle et al. 2001;De Deyn et al. 2004;Bardgett et al. 2005). ...
Article
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Topsoil transposition has been identified as an environmental restoration technique capable of accelerating regeneration in degraded areas. In addition to the seed bank, topsoil contains invertebrates and microorganisms essential in ecological succession. This study evaluated the temporal variation in the macrofauna community structure in an experiment with topsoil transposition. We hypothesized that the morphospecies richness, functional groups and macrofauna biomass would be higher in the plots with topsoil and native vegetation compared with plots with no topsoil. We further hypothesized that the composition of macrofauna community and the proportion of functional groups in the topsoil and the reference plots would become more similar over time. The community was compared between plots that received topsoil, plots that did not receive topsoil and plots in a natural vegetation, over 14 months. The macrofauna biomass and the diversity of functional groups were equivalent in the degraded area and the topsoil. The effect of treatment on richness depended on time, and it was possible to observe higher values of macrofauna richness in the topsoil compared with the degraded area in some months. The compositions of the macrofauna communities in the degraded area and the topsoil showed greater similarity to each other. In contrast, the reference area showed the greatest dissimilarity with the other treatments. In general, the macrofauna community in the topsoil remained more similar to the degraded area. However, in the topsoil plots, we found higher macrofauna richness during rainy months and an increase in predator biomass. In conclusion, the macrofauna community in the topsoil, which has changed over time, presented higher values of morphospecies richness in some months and the increase in predator biomass, indicating an increase in the complexity of the community. Besides, the topsoil can improve biodiversity, but this does not produce the natural communities found at reference sites, in a small‐time scale experiment.
... predominantly focused on the Neotropics (Cavelier et al., 1998;Flores et al., 2016;Silverio et al., 2013;Veldman & Putz, 2011), typically in the context of invasive exotic grasses, El Niño-fuelled droughts and deforestation (Barlow & Peres, 2004;Barlow & Peres, 2008;Nepstad et al., 1996;Silverio et al., 2013;Veldman & Putz, 2011). This work provides invaluable insights into the potential processes of savannization, which includes the susceptibility of forest trees to fire-induced mortality (Barlow & Peres, 2008;Staver et al., 2020), the invasion of grassy fuels following repeat fires (Silverio et al., 2013, Veldman & Putz, 2011 and finally the formation of no-analogue grassy systems that differ from old-growth savannas (Veldman & Putz, 2011). ...
Article
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1. Fires in savannas limit tree cover, thereby promoting flammable grass accumulation and fuelling further frequent fires. Meanwhile, forests and thickets form dense canopies that reduce C4‐grass fuel loads and creating a humid microclimate, thereby excluding fires under typical climatic conditions. However, extreme fires occasionally burn into these closed‐canopy systems. Although these rare fires cause substantial tree mortality and can make repeat fires more likely, the long‐term consequences of an extreme fire for closed canopy vegetation structure and potential to convert to savanna (hereafter “savannization”) remain largely unknown. 2. Here, we analysed whether an extreme fire could, alone, alter species composition, vegetation structure, and fire regimes of closed‐canopy ecosystems in an intact savanna‐forest‐thicket mosaic, or whether successive fires after an initial extreme fire were necessary to trigger a biome transition between from forest to savanna. 3. We found that forests that only burned once recovered, whereas those that burned again following an initial extreme fire transitioned from closed‐canopy forests towards open, grassy savannas. While thickets had less tree mortality in fires than forests, repeat fires nonetheless precipitated a transition towards savannas. Colonization of the savanna tree community lagged behind the grass community, but also began to transition. 4. Synthesis. Our results suggest that rare extreme fires, followed by repeated burning can indeed result in savannization in places where savanna and forest represent alternative stable states.
... Fungus cultivators are ants, mostly of the Attini tribe, which grow fungus in their nests using plant parts, faeces, insect carcasses and organic matter to feed them (Della Lucia et al.1993;Mariconi 1970). They play a significant role in the fertility and structure of tropical soils (Coutinho 1984;Brener & Silva 1995) and in the establishment and regeneration of tropical biomes (Nepstad et al. 1996). The results may be linked to the availability of resources, which is higher where the largest vegetation cover (reference area) occurs (Hansen 2000;Wardle et al. 2001;De Deyn et al. 2004;Bardgett et al. 2005). ...
... Moreover, seeds of tree or shrub species are rapidly predated, tend to immediately germinate or die after a certain latency time (Hardwick et al. 2004). Consequently, after long periods of disturbance, it is unlikely that the pre-existing soil seed bank will contribute signi cantly to the regeneration of vegetation (Nepstad et al. 1996 Unfortunately, the barriers that get in the way of restoration processes are multiple and diverse. Areas recovering from disturbance may be more susceptible than mature ecosystems to invasion by nonnative species present in the landscape (Huebner and Tobin 2006;McCay et al. 2009). ...
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The lack of seeds represents one of the highest difficulties to overcome for the ecological restoration of areas that have been deforested. This study evaluates the effectiveness of artificial perches in increasing the abundance and species richness of bird-dispersed seeds and the similitude of seed rain composition (origin and habit of plant seeds), of deforested areas with and without artificial perches in relation to woodland remnants that serve as seeds source. The experiment took place in two sites of the Espinal ecoregion, Argentina. We found that in deforested areas, perches increased seed abundance and species richness in the seed rain in comparison with deforested areas without artificial perches. The species composition under artificial perches was similar to the seed rain dispersed in the woodland. However, a decrease in the richness of native species was significant in the deforested area, probably due to behavioral differences between opportunistic and obligate frugivorous. Seed of trees and shrubs species were well represented in the seed rain under artificial perches. Results from this study contribute to the understanding of nucleation and recovery mechanisms used by nature that reflect ecosystem resilience. We recommend using artificial perches in deforested areas with potential for recovery because it is an efficient technique to promote the entry of birds and increase seed rain, preserving features of the original environment. However, using artificial perches should be avoided in sites with potentially invasive non-native species.
... Species dispersed by wind may move longer distances in open areas (Nathan, 2006) than those dispersed by animals, that will arrive to open areas if their dispersal agents are attracted (Wunderle, 1997;Laborde et al., 2008). Once seeds arrive and germinate, the conditions under which they must grow are highly adverse, so most species have high establishment limitation (failure of seedlings to survive and grow) in pastures (Nepstad et al., 1996;Hooper et al., 2005;Martínez-Ramos et al., 2016, de la Peña-Domene and. The fastest changes in tree richness and density during succession have been registered in the first 10 years, driven by fast growing earlysuccessionals but recovery of composition may take centuries (Bechara et al., 2016;Rozendaal et al., 2019). ...
Article
Restoration interventions aim to accelerate forest recovery by skipping the early stages of succession where short-lived early-successional tree species dominate. Large trees (≥30 cm of Diameter at Breast Height [DBH]) provide ecosystem functions, such as carbon storage and acting as stepping stones for the movement of animals through the landscape. Here, we evaluated two mixtures of planted and, unplanted areas to figure out which restoration treatment was more successful in skipping the early stages of succession. For this, we measured forest structure of large trees in restoration settings after 10 years in Los Tuxtlas, Veracruz, Mexico. In 2006, cattle grazing was excluded from 24 plots (30 × 30 m). Eight of those plots were planted with 12 wind-dispersed species, eight plots were planted with 12 animal-dispersed species (a total of 2,304 planted trees), and eight plots were left to undergo natural succession without plantings. Planted and naturally recruited trees have been assessed periodically since 2007. A total of 835 planted and naturally recruited trees of 45 species reached large size. Including all trees (planted and recruited), the richness and abundance of late-successional trees was higher in plantings than under natural succession while richness of large recruits of late-successional species was as higher in plantings as in natural succession. Also, including all trees, plantings of animal-dispersed species have higher richness and abundance of trees dispersed by bats and both bats and birds; while species and trees dispersed by birds were present equally at all treatments. Richness and abundance of bat-dispersed recruits were similar in plantings and natural succession while plantings of wind-dispersed species had higher bird-dispersed recruits. Composition heterogeneity, driven by natural recruitment, was largest for early-successional trees in natural succession. After 10 years, the first stages of succession (20–30 years) were skipped in plantings: plantings have higher abundance of large seeded late-successional species. For an overall increase in composition heterogeneity in permanent agricultural landscapes, we suggest establishing areas to undergo natural succession along with plantings that include a higher percentage of late-successional species with large seeds.
... Al progresar el tiempo de descanso existe competencia y también ocasiona que se hagan más extremas las condiciones de luminosidad, temperatura y falta de humedad, sobre todo durante la estación seca. Al quedar el suelo desnudo en la superficie, se incrementan los niveles de mortalidad por causa de la desecación(Nepstad et al., 1996). ...
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Chapter
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Effects of herbivory and competition on plant mortality and reproduction were compared on a hollow to ridge topographic gradient in an abandoned pasture. Plots with herbivores excluded and (or) vegetation removed were set up along with control plots in hollows and on ridges. Plants of three perennial forbs (Medicago lupulina L., Centaurea nigra L., Taraxacum officinale Weber.) that occurred naturally less often in hollows than on ridges were transplanted into plots. Transplant mortality and reproduction were recorded over a sixteen month period. Where transplants were not protected from herbivores and vegetation was left intact, significantly more plants died in hollows than on ridges. In contrast, none of the transplants protected from herbivores died either in hollows or on ridges. Removing vegetation did not affect the mortality of protected transplants. The number of inflorescences produced per transplant did not differ significantly between hollows and ridges when vegetation and (or) herbivores were present or absent. Results indicate that hollow-ridge variation in the frequency of the three forbs reflects differential mortality from herbivory rather than differential effects of competition on mortality or reproduction. These results support theories that consider differential herbivory to be a primary control of plant frequency on a gradient.