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Relationships between biodiversity and carbon stocks in forest ecosystems: A systematic literature review

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Abstract

A systematic literature review was conducted to explore the relationships between multiple measures of biodiversity (e.g. species diversity, functional divergence and dominance) and carbon (C) stocks (both aboveground and soil organic) in different forest ecosystems. A total of 47 studies, searched in Web of Science or Knowledge, were selected based on different biodiversity indices, strength of the datasets and particularly focusing on C stocks. The majority of relationships between species diversity or richness and C stocks were positive, while only few were negative. The niche complementarity and the mass ratio hypotheses are the two major hypotheses for explaining the effect of functional diversity on C stocks. These two hypotheses did not contradict each other but reflect the two different sides of functional trait attribute i.e., dominance and divergence. The majority of studies suggested that strong dominance by tall and conservative species, rather than a set of coexisting species with diverse heights and acquisitive role, results in more C stocks in various forest ecosystems. Thus, most of the studies supported mass ratio hypothesis instead of the niche complementarity hypothesis in terms of increasing C stocks in forest ecosystems. We concluded that experimental works in other forest ecosystems have shown that each measure of biodiversity often increases C stocks, although the extent to which direct causal relationships exist between biodiversity and C stocks in subtropical forests are still uncertain. Thus, a little is understood how multiple measures of biodiversity affect C stocks, when also considering the effects of biotic and abiotic components of an ecosystem.

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... Forests are a major component in the global carbon cycle and, consequently, they have a potential role in mitigating climate changes attributed to the increase in atmospheric CO 2 (Pan et al. 2011;Ali and Yan 2017). Because of this importance, research has been dedicated to understanding the role of environmental (climate, soil, topography) and biological factors (e.g., dominance, species richness, functional diversity) on carbon dynamics in forests Poorter et al. 2015;Ali and Yan 2017;van der Sande et al. 2017). ...
... Forests are a major component in the global carbon cycle and, consequently, they have a potential role in mitigating climate changes attributed to the increase in atmospheric CO 2 (Pan et al. 2011;Ali and Yan 2017). Because of this importance, research has been dedicated to understanding the role of environmental (climate, soil, topography) and biological factors (e.g., dominance, species richness, functional diversity) on carbon dynamics in forests Poorter et al. 2015;Ali and Yan 2017;van der Sande et al. 2017). The biodiversity effects have particularly well explored due to their great importance in conservation policies, coupled with the intention to develop joint strategies that may benefit biodiversity and conserve/increase carbon stocks (Schwartz et al. 2000;Srivastava and Vellend 2005). ...
... The biodiversity effects have particularly well explored due to their great importance in conservation policies, coupled with the intention to develop joint strategies that may benefit biodiversity and conserve/increase carbon stocks (Schwartz et al. 2000;Srivastava and Vellend 2005). These studies have identified complex and divergent relationships between forest carbon and biodiversity (Ali and Yan 2017), and they have indicated the need for further work with multifaceted diversity metrics, considering the functional components (Paquette and Messier 2011;Prado-Junior et al. 2016; van der Plas 2019), to improve our understanding of how ecosystems function in relation to carbon fluxesin particular, above-ground biomass (AGB). ...
Article
Background: The mass ratio hypothesis (functional dominance) and niche complementarity hypothesis (functional diversity) are two potential approaches for making the link between biodiversity and biomass. It is yet unclear how biodiversity and biomass are related in seasonally dry tropical forest (SDTF) communities where there is a seasonal water limitation. Aims: The objective of this study was to quantify the effects of environmental filtering on ecosystem functioning, especially those related to biodiversity and above-ground biomass. Methods: We estimated biomass and functional traits for all species in five plots at five sites in a SDTF. We related functional diversity and community-weighted trait mean (CWM) values to above-ground biomass (AGB) using linear mixed models. Results: Functional diversity was not related to AGB, while CWM values of vessel density (VD) were positively and the Carlquist Vulnerability Index (CVI) was negatively related to AGB. Conclusion: The CWM values of functional traits related to the trade-off between safety of water transport and the efficiency of water conductivity and conservative strategies (VD and CVI) were good predictors of AGB. The mass ratio hypothesis appears to be a better predictor of AGB than niche complementarity in our study conducted in the SDTF.
... It is worth noting that methodological factors including scale and sampling, and geographic factors can strongly influence elevational species richness. Elevational gradients are modulated by cascading and interlinked effects of biotic and abiotic factors such as rainfall, temperature and humidity, which vary among ecosystems and with spatial and temporal scale (Ali & Yan, 2017). ...
... Lianas as structural parasites generally rely on trees for support (Parren, 2003;Ewango, 2010). This findings aligns with the niche complementarity and mass ratio hypotheses (Ali & Yan, 2017), which explain the effect of functional diversity on carbon stock. ...
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Tropical forests ecosystems remain the most diverse on the planet, and store considerable amounts of biomass and carbon. Despite the importance of tropical forests, sizable knowledge gaps exist regarding species diversity, plant biomass and carbon. These knowledge gaps are particularly large in tropical systems, and even more so in the African tropics. This study provides baseline data on species composition and vegetation structure, and evaluate variation along elevational gradient transecting of four elevation-forest types: lowland, mid-elevation, sub-montane and montane forest in the Rumpi Hills Forest Reserve of Cameroon. We collected data on tree species diversity, above-ground biomass and carbon in 25 1-ha plots sampled in 500 m long x 20 m width transect. Results revealed high species diversity, particularly in lowland forest. Overall, the study enumerated 12,037 individuals (trees ≥ 10 cm dbh) of 441 species. The mean species per plot decreased with increasing elevation, 112 in lowland, 81 in mid-elevation, 60 in submontane and 38 in montane forest. Above-ground carbon averaged 162.88±50 t ha-1. We found the greatest carbon storage and tree and liana species diversity at low elevations. Our results indicate that high species diversity and occurrence of larger tree species are more important in carbon storage in lowland forest than at higher elevations. These findings are useful for management and land use planning of the forests in the Rumpi Hills Forest Reserve.
... The importance of these forests is also highlighted by their larger area, higher carbon stock per unit area and higher productivity than boreal and temperate forests (Galbraith et al., 2013;Mitchard, 2018;Pan et al., 2013). Thus, studies have been carried to investigate the patterns of carbon stock and uptake in tropical forests and also their relationship with environmental and biological variables that can act as drivers (Ali et al., 2019;Ali and Yan, 2017;de Assis et al., 2019;Poorter et al., 2017;Sullivan et al., 2017). Through these studies, such carbon stock and uptake processes have been guidelines for planning conservation strategies, such as the selection of priority areas for conservation, as well as being a proxy for the assessment of the possible response of the global carbon cycle to climate change (Ferreira et al., 2018;Sullivan et al., 2020). ...
... Unlike the classical perspective that considers species richness as the main factor associated with biodiversity, authors have proposed that biodiversity comprises a series of other variables associated with species functionality, structural patterns and heterogeneity that are treated as "biodiversity components" (Van der Sande et al. 2017). In this context, the relationship between the biodiversity components and carbon stock and uptake processes has been questioned, with some mechanisms proposed from the association with taxonomic, functional diversity, structural complexity and beta diversity (Ali et al., 2019;Ali and Yan, 2017;Sullivan et al., 2017;Tilman et al., 2014;van der Plas, 2019;van der Sande et al., 2017). Advances in understanding these relationships have been made to challenge conservation policies based on isolated factors, in which areas are selected for conservation and strategies are made based in just one attribute. ...
Article
Obtaining high-quality information on vegetation attributes directly linked to ecosystem services in tropical forests, such as carbon stock and biodiversity, is essential to develop ecological information to be used in planning conservation strategies. Defining the optimum vegetation sample plots size is an important part of the process of obtaining information, since is crucial for its quality, and also for its financial costs and time required. In this context, we evaluated whether: (i) the optimum plot size selected in two approaches (basal area/carbon stock vs biodiversity) are different since they are associated with different ecological drivers; (ii) different tropical forests vegetation types present different optimum sample plot size due to their ecological specific at-tributes, such as species composition, structure and functioning. For this we evaluated the vegetation sample plots optimum size of different vegetation types of tropical savanna and forest of broad occurrence in the tropics (Atlantic Semideciduous Forest – ASF; Cerrado Woodland – CW; Cerrado Forest – CF; and Seasonally Dry Tropical Forest - SDTF), in two approaches: forest basal area and carbon stock, since they are related variables; and biodiversity variables by species composition similarity and heterogeneity in communities. We used 4 forest fragments in Brazil that were sampled in a way that allowed the arrange of subplots to form different plot sizes. In order to evaluate the optimum sample plot size in the basal area/carbon stock approach we used four methodologies, in which the obtained variability was compared to a reference size (1000 m2). For the biodi-versity approach we used the floristic similarity and composition heterogeneity between units as metric, eval-uating differences in the similarity patterns and possible reductions or increases in variability compared to the reference size. We found there are no significant differences for biodiversity variables between sample plot sizes for all vegetation types, thus the optimum size may be selected using just the basal area/carbon stock approach. In the basal area/carbon stock approach, most of the evaluated methods generally presented lower plot size values compared to the reference size (1000 m2) in all vegetation types, except for the ASF. There are differences between vegetation types that may be grouped in two groups related to the optimum size selected, that are related to their ecological restriction patterns: CW, CF and SDTF with optimum size between 600 and 1000 m2; and the second with ASF, with optimum sample plot size between 1000 m2 and 1400 m2.
... It is worth noting that methodological factors including scale and sampling, and geographic factors can strongly influence elevational species richness. Elevational gradients are modulated by cascading and interlinked effects of biotic and abiotic factors such as rainfall, temperature and humidity, which vary among ecosystems and with spatial and temporal scale (Ali & Yan, 2017). ...
... Lianas as structural parasites generally rely on trees for support (Parren, 2003;Ewango, 2010). This findings aligns with the niche complementarity and mass ratio hypotheses (Ali & Yan, 2017), which explain the effect of functional diversity on carbon stock. ...
... Literature on the relationship between plant diversity and carbon stock in subtropical forest ecosystems is limited and variable. Most studies on diversity-carbon stock are concentrated in tropical and temperate forest ecosystems (Ali and Yang 2017). Generally, a positive relationship between carbon stock and diversity in tropical forest ecosystems has been reported by several researchers (Strassburg et al. 2009;Thomson et al. 2009). ...
Article
Studies on relationship between tree diversity and carbon stock has not been consistent. The present study was undertaken to quantify and compare the plant diversity and carbon stock in a subtropical broadleaved and a subtropical pine forest of Meghalaya, northeast India. Biomass-based carbon estimation was undertaken in two subtropical broadleaved forest stands viz., Mawnai (MBF) and Nongkrem (NBF) and adjacent Pinus kesiya dominated forest stands (MPF and NPF), occurring in similar topography, climatic conditions and soil type. The aboveground and belowground tree biomass was estimated using existing allometric models. Carbon was estimated as 47.4% of the total biomass. Tree species richness was greater in the subtropical broadleaved forest stands at MBF and NBF (117 and 21 species) than in the adjacent pine forests, MPF and NPF (15 and 16 species). The density values were 1294 and 1127 individuals ha−1 in the broadleaved forest stands, and 894 and 1032 individuals ha−1 in the adjacent pine forest stands, respectively. The broadleaved forest stands, MBF and NBF had tree biomass carbon stock of 140.4 Mg C ha−1 and 133.6 Mg C ha−1, respectively, which were significantly greater (F = 26.6; P < 0.05) than the pine forest stands, MPF and NPF (74.7 Mg C ha1 and 63 Mg C ha−1). The contribution of trees belonging to the higher DBH classes (> 66 cm) to the total biomass carbon was greatest in MBF, while the lower diameter trees belonging to 5–15 cm and 16–25 cm were the major contributors to the total biomass carbon in the pine dominated stands.
... I focused strictly on the peer-reviewed research papers in order to find more critical research papers on the relationships between stand structural attributes and forest functioning. The method consisted of four steps following Ali and Yan (2017c), i.e., (i) the development of keywords, (ii) a systematic search of literature, (iii) key findings from the collected papers, and (iv) review synthesis. ...
Article
Species diversity is a part of (forest) stand structure but tree diameter diversity and height diversity alone or combined are typically defined as stand structural diversity or complexity or attributes. There is increasing evidence that stand structural attributes determine forest functioning. Here, I provide a review of forest stand structure and functioning (e.g. aboveground biomass, carbon storage and productivity) in order to explore the current knowledge across worldwide forest ecosystems including (sub-) tropical, temperate and boreal forests, as well as agroforests and experimental plantations or forests. A total of 31 original studies were selected, based on the hypothesized relationships between forest stand structure and functioning, through the systematic literature search in the Web of Science and Google Scholar. Hypothesized studies on forest stand structure and functioning, as compared to species diversity, are under-represented in the highly skewed ecological literature. The synthesis of this review indicates that stand structural attributes often increase aboveground biomass or carbon storage through the positive plant-plant interactions under the niche complementarity effect. Whereas, the influences of stand structural attributes on stand productivity are either negative, positive or nonsignificant. Here, the negative influence is attributable to the asymmetric competition for light, competitive exclusion and selection effect, whereas the nonsignificant effect is attributable to the absolute superiority of specific trees on stand growth. This review highlights that there is no ubiquitous relationship between stand structure and forest functioning, but this relationship greatly depends on the environmental conditions, biotic interactions, stand age and disturbance intensities within a specific forest ecosystem. I anticipate that this review might encourage further studies on the multivariate relationships between stand structural attributes and forest functioning while considering for other abiotic and biotic factors of the forests.
... Little is known about the patterns of biomass change in subtropical remnants of old-growth forests (Ali & Yan, 2017b;Lin, Lai, Muller-Landau, Mi, & Ma, 2012), or about the drivers of tree demographic rates ( Ma et al., 2016 ranges (Oliveira-Filho, Budke, Jarenkow, Eisenlohr, & Neves, 2015;dos Santos, Saraiva, Müller, & Overbeck, 2015), which might impact forest dynamics. As both biotic conditions and abiotic variables may be related to temporal changes in forest ecosystems (Prado-Junior et al., 2016;van der Sande, Peña-Claros, et al., 2017b), studies that incorporate plant traits into this perspective of community dynamics have the potential to enlarge the applicability of observed results to other biogeographic regions and/or environmental conditions. ...
Article
Question: How do biotic forest conditions, in terms of plant functional traits and tree basal area, and soil variables influence old-growth forest dynamics? Location: A subtropical old-growth forest in Southern Brazil. Methods: Forest inventories were conducted in 1999 and 2017, in 24 permanent plots of 500 m2. All trees with a circumference at breast height of ≥ 30 cm were measured, identified to the species level, and tagged. We fitted linear models to evaluate the effect of the biotic variables of initial forest communities (tree basal area, trait community-weighted mean (CWM) and both species and functional diversity metrics) and of soil variables on forest dynamics. These models included biomass dynamics (annual rate of biomass increment and mortality) and demographic rates (recruitment and mortality rates). Furthermore, linear models were used to evaluate the effect of tree survival, recruitment and mortality and biomass increment on the net biomass change. Results: We observed a positive effect of species diversity and a negative effect of CWM leaf phosphorous content on the biomass increment. Biomass loss was positively related to basal area and negatively related to the CWM of leaf nitrogen content. Overall, net biomass change was negatively influenced by biomass loss due to mortality. Recruitment rates were negatively affected by soil potassium content and were positively affected by soil pH and functional evenness of the community. Mortality rates were positively predicted by soil clay content and negatively predicted by species diversity. Conclusions: Community functional traits, basal area and soil variables predicted growth, mortality and recruitment dynamics of this subtropical old-growth forest. This work provides important information about the biomass and demographic dynamics of subtropical forests, showing that initial community characteristics influence the gain and loss of biomass and individuals over a period of almost two decades.
... Trees, freshwater macrophytes, seagrasses, reefforming bivalves, and corals are all examples of such foundation species which create habitat for other species with their own body tissue (Jeppesen et al. 1992, Ellison et al. 2005, Coker et al. 2014, Christianen et al. 2016, van der Zee et al. 2016, Ali and Yan 2017. A major factor thought to underlie foundation species' enhancements of associated communities is their positive effect through their ability to modify their habitat (Govenar 2010). ...
Article
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Foundation species are typically suggested to enhance community diversity non‐trophically by increasing habitat structure and mitigating physical stress, while their trophic role is considered of minor importance. Yet, there is little experimental evidence on the relative importance of trophic and non‐trophic effects and the interaction with patch size. Here, we transplanted different festoon sizes of living Tillandsia usneoides (Spanish moss) and structural mimics assessing the trophic and non‐trophic roles of this habitat‐forming epiphyte in mediating the invertebrate community. Compared to bare branches, mimics enhanced species and feeding guild richness and abundances, but living festoons even more so, demonstrating that trophic and non‐trophic effects jointly stimulated the community. Specifically, our results show that, independent of patch size, 40% of the total species richness and 46% of total guild richness increase could be contributed to habitat structure alone, while Spanish moss trophically stimulated these metrics by another 60% and 54%. As detritivores were particularly enhanced in living festoons, our findings suggest that trophic stimulation occurred primarily through the provisioning of Spanish moss detritus. Our results highlight that foundation species can facilitate their associated communities through both trophic and non‐trophic pathways, calling for studies addressing their indirect trophic role via the brown food web.
... Terrestrial ecosystems vary in carbon sequestration potential and thus influence atmospheric carbon dioxide concentrations (Ardö and Olsson, 2004;Ali and Yan, 2017). This potential makes the system to either release (source) or assimilate (sink) carbon di oxide (CO ). ...
Article
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The extent and distribution of dry forests play an important role in biodiversity conservation and carbon storage. Field measurements were carried out during 2008-2012 at 903 sampling plots in forests of 33 districts of Rajasthan and carbon stock due to trees, shrubs, bamboos, tree saplings, herbaceous vegetation and dead material (litter and coarse woody debris - CWD) were estimated for their spatial variation and to devise a programme of reforestation. There were significant (P<0.05) differences in carbon stock ranging from 0.02-0.91 tons ha-1 for litter, 0.00- 0.39 tons C ha-1 for CWD, 0.005-0.84 tons ha-1 for herbaceous biomass, 0.09-5.22 tons ha-1 for shrubs, 1.17-13.96 tons ha-1 for trees, 0.00-0.29 tons ha-1 for bamboo and 0.01-0.26 tons ha-1 for tree saplings. The variations were found to relate to rainfall pattern. Highest values were in Kota, Karauli, Rajasamand, Pratapgarh, Udaipur and Dungarpur respectively. Contribution of trees, shrubs, bamboos and sapling were 85.5%, 13.0%, 0.39% and 1.30%, respectively signifying the role of trees in terrestrial carbon storage. Lowest carbon stock was in Churu (0.051 million tons) and highest in Udaipur (8.079 million tons) out of total standing carbon stock, wherein 27.31 million tons was above-ground and 11.68 million tons was in root biomass in forests of Rajasthan. Strong spatial variations in component-wise carbon stock and below state average standing carbon stock in almost 15 districts in Rajasthan suggests taking up forest management by enrichment tree planting for increasing diversity and productivity leading to increased carbon sequestration and climate change mitigation. Keywords Biomass Distribution, Carbon-Storage, Dry Forest Ecosystem, Plant Habits.
... This may be due to positive relationships among species that make full use of natural resources. The niche complementarity hypothesis supports this result [74]. With the continuous growth of the forest stand, the AGB continues to accumulate, and the stand CC continues to increase. ...
Article
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Forests are the main body of carbon sequestration in terrestrial ecosystems and forest aboveground biomass (AGB) is an important manifestation of forest carbon sequestration. Reasonable and accurate quantification of the relationship between AGB and its driving factors is of great importance for increasing the biomass and function of forests. Remote sensing observations and field measurements can be used to estimate AGB in large areas. To explore the applicability of the panel data models in AGB and its driving factors, we compared the results of panel data models (spatial error model and spatial lag model) with those of geographically weighted regression (GWR) and ordinary least squares (OLS) to quantify the relationship between AGB and its driving factors. Furthermore, we estimated the tree height, diameter at breast height, canopy cover (CC) and species diversity index (Shannon–Wiener index) of Robinia pseudoacacia plantations in Changwu on the Loess Plateau using field data and remote sensing images by a random forest model and estimated soil organic carbon (SOC) contents using laboratory data by ordinary kriging (OK) interpolation. We estimated AGB using the already estimated tree height and diameter at breast height combined with the allometric growth equation. In this study, we estimated SOC contents by OK interpolation, and the accuracy R2 values for each soil layer were greater than 0.81. We estimated diameter at breast height (DBH), CC, SW and tree height (TH) using the random forest, and the accuracy R2 values were 0.85, 0.82, 0.76 and 0.68, respectively. We estimated AGB with random forest and the allometric growth equation and found that the average AGB was 55.80 t/ha. The OLS results showed that the residuals of the OLS regression exhibited obvious spatial correlations and rejected OLS applications. GWR, SEM and SLM were used for spatial regression analysis, and SEM was the best model for explaining the relationship between AGB and its driving factors. We also found that AGB was significantly positively correlated with CC, SW, and 0–60 cm SOC content (p < 0.05) and significantly negatively correlated with slope aspect (p < 0.01). This study provides a new idea for studying the relationship between AGB and its driving factors and provides a basis for practical forest management, increasing biomass, and giving full play to the role of carbon sequestration.
... Overall, it appears that forest maintenance for biodiversity aligns well with a carbon sequestration objective. With carefully practised management, both can be achieved for a certain period of time [66], although the direct causative relationship between these two ecosystem services is questionable [67]. Moreover, this relationship depends on tree species and vegetative zone and persists only to the point that dieback rates of old trees become significant-that is, when the negative correlation between stand basal area of living trees and the volume of deadwood becomes strong. ...
Article
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As one of the most abundant tree species in the hemiboreal zone, birch is important from both commercial and biodiversity perspectives. While old-growth deciduous stands are important for biodiversity conservation with an emphasis on deadwood availability, the role that deadwood in these stands plays in carbon sequestration remains unclear. We studied mature (71–110 years old) and old-growth (121–150 years old) birch stands on fertile mineral soils. The marginal mean deadwood volume was 43.5 ± 6.4 m3 ha−1 in all mature stands, 51.3 ± 7.1 m3 ha−1 in recently unmanaged mature stands, and 54.4 ± 4.4 m3 ha−1 in old-growth stands; the marginal mean deadwood carbon pool for each stand type was 5.4 ± 0.8 t·ha−1, 6.3 ± 0.9 t·ha−1, and 7.9 ± 0.6 t·ha−1, respectively. Deadwood volume was not related to stand productivity in terms of stand basal area, stand height, or stand age. The difference between mature and old-growth stands remained non-significant (p < 0.05). A high volume of deadwood was almost continuously present throughout the landscape in assessed unmanaged sites; moreover, 88% of sample plots in old-growth stands and 63% of sample plots in mature stands had a deadwood volume higher than 20 m3·ha−1. Old-growth stands had a slightly greater volume of large deadwood than unmanaged mature stands; in both, almost half of the deadwood was more than 30 cm in diameter and approximately one-fifth had a diameter greater than 40 cm. Both groups of stands had similar proportions of coniferous and deciduous deadwood and lying and standing deadwood. Old-growth stands had a higher volume of recently and weakly decayed wood, indicating increased dieback during recent years.
... Such disturbances directly contribute to global climate change through emission from deforestation and forest degradation (D&D) ( Holl and Aide, 2011 ;Van der Werf et al., 2009 ;Miles and Kapos, 2008 ). In tropical countries, such as Bangladesh, D&D is one of the most common disturbances that results in poor biodiversity ( Astiani, 2016 ) and inadequate carbon stock in forest biomass ( Ali and Yan, 2017 ;Poorter et al., 2017 ). Bangladesh has lost nearly 0.9 million ha of forest since 1930 attributed to anthropogenic disturbances . ...
Article
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Forest Protected Area (PA) co-management, which integrates local communities in the forest management structures, was started in Bangladesh in 2004 to effectively manage and conserve forest resources. This study has investigated if the initiative has met its objectives. Using NDVI maps, we applied a stratified random sampling framework to identify sample plots. Phytosociological and carbon-sequestration data were collected from two co-managed PAs (Lawachara National Park and Teknaf Wildlife Sanctuary) and adjacent reserve forests that are not under co-management regime. Results reveal that phytosociological attributes for both mature trees and naturally regenerated seedlings showed better results in co-managed sites than in non-co-managed sites. Plot mean species, genus, and family were 2.69, 2.64, 2.49, respectively, in the non-co-managed sites as opposed to 1.64, 1.60, and 1.46 in the co-3 managed plots. Simpson's Diversity Index was 0.11 and 0.15 in co-managed PAs and control sites, respectively. Given the standard normal distribution, the range of biomass carbon sequestration was (-300, 500) t/ha in the co-managed PAs as opposed to (-200, 400) t/ha in the control sites. Overall, sites without co-management showed better biodiversity status than the sites having co-management practices.
... However, subtropical forests have a mixture of distinct elements of tree species (e.g. seasonal and evergreen, tropical and austral origins), which often co-dominate the ecological communities, thus the effect of functional composition on biomass is still poorly understood (Ali and Yan, 2017b;Souza and Longhi, 2019). ...
Article
Subtropical forests certainly contribute to terrestrial global carbon storage, but we have limited understanding about the relative amounts and of the drivers of above-ground biomass (AGB) variation in their region. Here we assess the spatial distribution and drivers of AGB in 119 sites across the South American subtropical forests. We applied a structural equation modelling approach to test the causal relationships between AGB and environmental (climate and soil), structural (proportion of large-sized trees) and community (functional and species diversity and composition) variables. The AGB on subtropical forests is on average 246 Mg ha − 1. Biomass stocks were driven directly by temperature annual range and the proportion of large-sized trees, whilst soil texture, community mean leaf nitrogen content and functional diversity had no predictive power. Temperature annual range had a negative effect on AGB, indicating that communities under strong thermal amplitude across the year tend to accumulate less AGB. The positive effect of large-sized trees indicates that mature forests are playing a key role in the long-term persistence of carbon storage, as these large trees account for 64% of total biomass stored in these forests. Our study reinforces the importance of structurally complex subtropical forest remnants for maximising carbon storage, especially facing future climatic changes predicted for the region.
... On the other hand, the mass ratio hypothesis assumes that carbon stock in a particular forest stand is mainly determined by the most dominant woody plant species and diverse forest stands would allow higher probability of occurrence for dominant woody plant species that would positively influence the AGC stock (Fotis et al., 2018;Yuan et al., 2018). Woody plant species diversity can also indirectly affect AGC stock through its influence on stand structural diversity (Ali & Yan, 2017;Zhang & Chen, 2015). Interspecific differences in physiological and morphological traits of different woody plant species can lead to complex stand structures (Juchheim et al., 2020), and this in turn would positively influence AGC stock. ...
Article
Aboveground carbon (AGC) stock in forests is affected by several biotic and abiotic factors. Understanding those factors is crucial in managing forests for climate change mitigation and other ecosystem services. This study examined effects of diversity attributes (species and stand structural diversity of woody plants) and topographic attributes (altitude and slope) on AGC stock of a dry Afromontane forest. Data from individual woody plants for estimating AGC were collected from 252 plots (20 × 20 m) established in a systematic grid (2 × 2 km) covering the entire forest area. Woody plant diameter diversity and woody plant height diversity were used as proxies for stand structural diversity. Structural equation modelling was applied to test the effects of the selected attributes on AGC stock, and together they explained 71% of the variation. Stand structural diversity was the most important driving factor for the AGC stock. Woody plant species diversity had both direct and indirect effects on AGC stock, but the indirect effect through its influence on stand structural diversity was more pronounced. Altitude and slope were both negatively but weakly associated with AGC stock. Our results provide insight on the effects of diversity and topographic attributes on AGC stock, which can assist future management of the forest. Enhancing stand structural diversity by means of selection cutting systems and woody plant species diversity by means of enrichment planting can be effective treatments. When considering dry Afromontane forests’ widespread distribution, the potential contribution in carbon sequestration and thereby mitigating climate change is substantial. Hence, the results and management suggestions from the present study may have practical interest for the management of dry Afromontane forests not only in Ethiopia but also in Africa at large.
... The niche complementarity hypothesis holds that diversity can enhance AGB through maximizing resource utilization efficiency among co-occurring species or individuals through niche complementarity or facilitation. The mass ratio hypothesis predicts that AGB is mainly driven by the traits of dominant plant species [7,8]. Many researchers have considered the ...
Article
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Forests regulate air quality and respond to climate change by storing carbon. Assessing the driving factors of forest aboveground carbon (AGC) storage is of great importance for forest management. We assumed that different forest types would affect the relationship between species richness, stand density, individual tree size variation, and AGC. In order to test and verify it, we analyzed the inventory data of 206 fixed plots (20 m × 20 m) of Jingouling Forest Farm, taking advantage of the piecewise structural equation model (pSEM) to explore the effects of species diversity, stand structure attributes, and topography on the AGC storage in the Wangqing Forest in Jilin Province. In addition, in this study, we aimed to investigate whether the fixed factors (species diversity, stand structure attributes, and topography) influenced AGC storage more significantly than the random factor (forest type). According to the results of pSEM, the selected factors jointly explain the impact on 33% of AGC storage. The relationship between stand density and AGC is positive, and the impact of individual tree size variation on AGC storage is negative. Species richness has direct and indirect impacts on AGC storage, and the indirect impact is more significant through individual tree size variation. Both elevation and slope are significantly negatively associated with AGC storage. Forest type explains the impact on 12% of AGC storage, which means the relationship between AGC and predictors varies across forest types. The results provide a scientific basis for the protection and management decision of natural forests in northeastern China.
... The SOC correlates with an ecosystem's capacity to provide nutrients to plants and to retain elements or compounds harmful to the environment or plants (Almendros et al., 2010;Puttaso et al., 2011;Ali and Yan, 2017). Thus, the SOC reflects important functional processes in the soil, such as storage of nutrients, water-holding capacity, stability of aggregates, and microbial activity (Casals et al., 2000;Eaton et al., 2008;Ghimire et al., 2017). ...
Article
Desertification is occurring throughout the mountainous areas of the Mediterranean. These processes lead to reduced soil fertility, increased soil loss, and reduced vegetation cover and species richness. To prevent further damage, it is recommendable to use low-cost approaches that are compatible with the European Strategy of Circular Economy guidelines. We investigated the systemic benefits from recycling of forest clearance residue by adding it to a dry Mediterranean mountainous area. More specifically, we performed afforestation without addition of residue in two control plots (C plots), and afforestation with addition of 10 Mg ha− 1 of clearance residue from a nearby region dominated by Aleppo pine (Pinus halepensis Mill.) in two other plots (PM plots). We conducted the experiments throughout 30 months after the afforestation process. Eighteen months after the intervention, the PM plots had significant increases in the soil organic carbon (SOC), and related increases in ecosystem productivity and stability. More generally, addition of clearance residues improved soil and vegetation recovery, and contributed to more successful afforestation. The improvements may be explained by an increase of infiltration process due to the physical changes in the soil following bio-waste addition. Addition of the forest residues increased the formation of soil macrochannels, and also increased the sink area, thereby improving the hydrodynamics of the ecosystem. Thus, soil loss was reduced by 98.2% in the PM plots relative to the C plots. Our study indicates that application of forest clearance residues to Mediterranean mountainous areas is an effective land management practice that produces very little waste, and it is in accordance with European policy.
Article
Based on the Web of Science Core Collection databases from 1990 to 2018, a scientometric analysis of 1,284 academic works related to forest carbon sequestration is carried out to characterize the intellectual landscape by identifying and revealing the basic characteristics, research power, intellectual base and research hotspots in this field. The results of this work show that: ① the number of publications in forest carbon sequestration research has increased rapidly and the research in this field is in its “growth stage”; Forest Ecology and Management is the most productive journal and Forestry is the most popular subject category; ② the most productive authors and institutions in this subject area are in the USA, China and Canada, with the Chinese Academy of Sciences being the key institution performing such research; ③ in the sample, 9 papers have played a key role in the evolution of the field and laid a solid foundation for future research; ④ Keyword clustering analysis showed that the main research topics in the domain of forest carbon sequestration could be summarized as: (a) temperate forest; (b) forest management; (c) uncertainty analysis; (d) forest floor; (e) REDD; (f) net primary productivity. Meanwhile, keyword bursts analysis showed that the new research hotspots or research frontiers mainly concentrated on changes in the carbon storage and carbon sequestration potential of secondary forests and tropical forests, plant litter carbon storage and contribution to total ecosystem carbon storage, and new national forest inventories (NFIs). Through in-depth analysis of forest carbon sequestration research, this paper provides a better understanding of development trends that have emerged in this field over the past 29 years, which can also offer reference for future research.
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The study of plant diversity and its role in ecosystem functioning is becoming a central issue in ecology. The relationships between carbon storage and tree diversity of natural forest at small scale are still unclear. This research investigated these relationships in an old‐growth forest at Changbai Mountain, Northeast China. It was found that at small scale, tree carbon storage generally increases with increasing tree species richness, but for stands with same species richness, tree carbon storage varies dramatically. At the small scale, tree species evenness has a significantly linear relationship with nature logarithm of total tree carbon storage. The stand carbon storage of trees is mainly controlled by stand tree composition. Fraxinus mandshurica, Pinus koraiensis, Quercus mongolica, Tilia amurensis, and Acer mono contribute more than 85% of stand carbon storage of trees. Stands with similar tree composition at small scale have different soil organic carbon storage and nutrient contents. Tree species evenness has great impact on soil N content at the soil horizon less than 30 cm deep, but its impacts on C/N, P, K, and S contents are small. Tree density has a negative linear relationship with soil organic C and C∶N ratio at the soil horizon is less than 30 cm deep. The implication of our findings here for carbon sequestration in the Kyoto Protocol is also discussed.
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Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors.Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above-ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees ≥10 cm d.b.h. in 62 and 21 1.0-ha plots, respectively. We determined relationships of biomass increments to initial standing biomass (AGBi), biomass-weighted community mean values (CWM) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion).The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGBi, to ‘fast’ stands dominated by trees with soft, nutrient-rich leaves, lighter woods and lower AGBi.We tested whether AGBi and biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis).CWMs were reasonable bivariate predictors of AGBi and biomass increments, with CWM specific leaf area SLA, CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height Hmax and CWM wood specific gravity the most important. AGBi was also a reasonable predictor of the three measures of biomass increment. In best-fit multiple regression models, CWMHmax was the most important predictor of initial standing biomass AGBi. Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGBi was the only predictor for biomass increments from recruits.Synthesis. We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWMHmax is a strong driver of ecosystem biomass and carbon storage and CWM SLA, and other CWM leaf traits are especially important for biomass increments and carbon sequestration.
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Functional diversity has been seen as the key to predicting the stability, invasibility, resource capture, nutrient cycling and productivity of communities. However, it has been unclear how to estimate it. Ten criteria for an index of functional diversity are developed. These include that it should reflect the range of characters present and the abundance of the species with those characters in the community, and be unaffected by the measurement units used or by the number of species. An index that meets all ten criteria, FD var , is investigated. It is based on the variance in characters, weighted by the abundance of the species with those characters. Tested with artificial and randomly generated data, it showed reasonable use of the 0-1 range (mean 0.60, range 0.0009-0.975) and intuitive behaviour. Tested with field data from eight sites in New Zealand, it gave a good spread of values (mean 0.65, range across sites 0.34-0.84), showed good ability to distinguish between the communities and its performance was ecologically intuitive. Illustrative correlations are made with mean annual temperature and soil fertility, determined by a bio-assay. FD var is recommended for general use.
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Tree diversity and biomass (above-and below-ground) were studied under two forest management regimes viz. Wildlife sanctuary (WLS) and Reserved forest (RF). The study was conducted in the undisturbed tropical primary forest (PF) at Siju, a WLS, and five RFs viz. Dambu and Darugiri (MSF1: Sal plantation forest) and Songsak, Rongrengiri and Baghmara (MSF2: Mixed sal-natural forest) of Garo hills, which remained undisturbed during the past 50-60 years. Tree species richness was highest in the WLS (67 species) followed by RFs (MSF2: 49-61 and MSF1: 33-35). Tree density was greater in WLS (846 trees ha-1) than RFs (570-690). Tree biomass (above-and below-ground) in WLS (382 Mg ha-1) was also greater than the RFs (250-332 Mg ha-1). Variations in species composition, density, diameter distribution pattern, biomass and C stock in the WLS and RFs were attributed to two different forest management practices adopted.
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Temperate- and high-latitude forests have been shown to contribute a carbon sink in the Northern Hemisphere, but fewer studies have addressed the carbon balance of the subtropical forests. In the present study, we integrated eddy covariance observations established in the 1990s and 2000s to show that East Asian monsoon subtropical forests between 20°N and 40°N represent an average net ecosystem productivity (NEP) of 362 ± 39 g C m(-2) yr(-1) (mean ± 1 SE). This average forest NEP value is higher than that of Asian tropical and temperate forests and is also higher than that of forests at the same latitudes in Europe-Africa and North America. East Asian monsoon subtropical forests have comparable NEP to that of subtropical forests of the southeastern United States and intensively managed Western European forests. The total NEP of East Asian monsoon subtropical forests was estimated to be 0.72 ± 0.08 Pg C yr(-1), which accounts for 8% of the global forest NEP. This result indicates that the role of subtropical forests in the current global carbon cycle cannot be ignored and that the regional distributions of the Northern Hemisphere's terrestrial carbon sinks are needed to be reevaluated. The young stand ages and high nitrogen deposition, coupled with sufficient and synchronous water and heat availability, may be the primary reasons for the high NEP of this region, and further studies are needed to quantify the contribution of each underlying factor.
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1. Functional traits can be used to describe the composition of communities through indices that seek to explain the factors that drive community assembly, biotic effects on ecosystem processes or both. Appropriately representing functional composition is therefore essential for predicting the consequences of environmental context and management actions for the provisioning of multiple ecosystem services (ESs) in heterogeneous landscapes. 2. Functional indices can be constructed from single or multiple traits; however, it is not clear how they differ in information content or ability to predict biodiversity — ecosystem function relationships in complex landscapes. Here, we compare the utility of analogous single- and multi-trait indices in linking environmental variation and functional composition to ESs in a heterogeneous landscape, relating functional indices based on three plant traits [height, relative growth rate and root density (RD)] to variation in the physical environment and to two ESs (forage production and soil carbon) and their net ES level. 3. Two orthogonal gradients, elevation and soil bulk density (BD), explained significant variation in several dimensions of functional composition comprised of single traits. These traits in turn significantly predicted variation in ESs and their net values. Only one index measured with multiple traits (functional richness) varied with the physical environment, while none predicted variation in ES or net ES levels. 4. One ES, soil carbon, increased with the community-average value of RD, while the other, forage production, was related to the range and community-average value of height. In turn, average RD increased with soil BD while the average and range of height declined with elevation. Due to these environmental patterns, soil carbon and forage production did not covary strongly, leading to moderate net ES levels across the landscape. 5. Synthesis: Single-trait indices of functional composition best linked variation in environmental gradients with productivity and soil carbon. Because the environment—trait functioning relationships were independent of one another, the ESs were independently distributed across the landscape, providing little evidence of synergies or trade-offs. Single- and multi-trait indices contained unique information about functional composition of these communities, and both are likely to have a place in predicting variation in ESs under different scenarios.
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1. Carbon storage in vegetation and soil underpins climate regulation through carbon sequestration. Because plant species differ in their ability to capture, store and release carbon, the collective functional characteristics of plant communities (functional diversity) should be a major driver of carbon accumulation in terrestrial ecosystems. 2. Three major components of plant functional diversity could be put forward as drivers of carbon storage in ecosystems: the most abundant functional trait values, the variety of functional trait values and the abundance of particular species that could have additional effects not incorporated in the first two components. 3. We tested for associations between these components and carbon storage across 16 sites in the Chaco forest of Argentina under the same climate and on highly similar parental material. The sites differed in their plant functional diversity caused by different long-term land-use regimes. 4. We measured six plant functional traits in 27 species and weighted them by the species abundance at each site to calculate the community-weighted mean (CWM) and the functional divergence (FDvar) of each single trait and of multiple traits (FDiv). We also measured plant and soil carbon storage. Using a stepwise multiple regression analysis, we assessed which of the functional diversity components best explained carbon storage. 5. Both CWM and FDvar of plant height and wood-specific gravity, but no leaf traits, were retained as predictors of carbon storage in multiple models. Relationships of FDvar of stem traits and FDiv with carbon storage were all negative. The abundance of five species improved the predictive power of some of the carbon storage models. 6. Synthesis. All three major components of plant functional diversity contributed to explain carbon storage. What matters the most to carbon storage in these ecosystems is the relative abundance of plants with tall, and to a lesser extent dense, stems with a narrow range of variation around these values. No consistent link was found between carbon storage and the leaf traits usually associated with plant resource use strategy. The negative association of trait divergence with carbon storage provided no evidence in support to niche complementarity promoting carbon storage in these forest ecosystems.
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1. Carbon storage in vegetation and soil underpins climate regulation through carbon sequestration. Because plant species differ in their ability to capture, store and release carbon, the collective func-tional characteristics of plant communities (functional diversity) should be a major driver of carbon accumulation in terrestrial ecosystems. 2. Three major components of plant functional diversity could be put forward as drivers of carbon storage in ecosystems: the most abundant functional trait values, the variety of functional trait values and the abundance of particular species that could have additional effects not incorporated in the first two components. 3. We tested for associations between these components and carbon storage across 16 sites in the Chaco forest of Argentina under the same climate and on highly similar parental material. The sites differed in their plant functional diversity caused by different long-term land-use regimes. 4. We measured six plant functional traits in 27 species and weighted them by the species abun-dance at each site to calculate the community-weighted mean (CWM) and the functional divergence (FDvar) of each single trait and of multiple traits (FDiv). We also measured plant and soil carbon storage. Using a stepwise multiple regression analysis, we assessed which of the functional diversity components best explained carbon storage. 5. Both CWM and FDvar of plant height and wood-specific gravity, but no leaf traits, were retained as predictors of carbon storage in multiple models. Relationships of FDvar of stem traits and FDiv with carbon storage were all negative. The abundance of five species improved the predictive power of some of the carbon storage models. 6. Synthesis. All three major components of plant functional diversity contributed to explain carbon storage. What matters the most to carbon storage in these ecosystems is the relative abundance of plants with tall, and to a lesser extent dense, stems with a narrow range of variation around these values. No consistent link was found between carbon storage and the leaf traits usually associated with plant resource use strategy. The negative association of trait divergence with carbon storage provided no evi-dence in support to niche complementarity promoting carbon storage in these forest ecosystems.
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a b s t r a c t Tropical forests play an important role in storing carbon through aboveground biomass (AGB) and are considered the highest biodiversity ecosystem on earth. However, the quantitative relationship between AGB and structure–species diversity is poorly understood. Twenty-eight 1-ha plots from old-growth trop-ical evergreen broadleaf forests and dry dipterocarp deciduous forests, distributed in six ecological regions throughout Vietnam, were used for large tree census (diameter at breast height P 10 cm). Mea-sures of biodiversity (species richness, Shannon index, and evenness) and of structure–species diversity (biomass–species and abundance–biomass–species diversities) were used to determine the patterns and strengths of relationship between each measure and AGB. The linear, logarithmic, and exponential pat-terns were found, however the former dominated. Negative linear and exponential patterns represented relationship between evenness and AGB, while positive linear and logarithmic relationships were most suitable for others. In general, site – specific relationships (R 2 > 0.6) were much stronger than inter – site relationships (R 2 < 0.6). Meanwhile, relationships between measures of biodiversity and AGB (the lowest R 2 = 0.14) were generally weaker than that between measures of structure–species diversity and AGB (the lowest R 2 = 0.31). This finding indicates that structure–species diversity is a sound index represent-ing the role of tropical forest in storing biomass and may suggest that uneven-aged and multistoried plantations should be encouraged for carbon sequestration. Ó 2013 Elsevier B.V. All rights reserved.
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Forests are the dominant terrestrial ecosystem on Earth. We review the environmental factors controlling their structure and global distribution and evaluate their current and future trajectory. Adaptations of trees to climate and resource gradients, coupled with disturbances and forest dynamics, create complex geographical patterns in forest assemblages and structures. These patterns are increasingly discernible through new satellite and airborne observation systems, improved forest inventories, and global ecosystem models. Forest biomass is a complex property affected by forest distribution, structure, and ecological processes. Since at least 1990, biomass density has consistently increased in global established forests, despite increasing mortality in some regions, suggesting that a global driver such as elevated CO2 may be enhancing biomass gains. Global forests have also apparently become more dynamic. Advanced information about the structure, distribution, and biomass of the world’s forests provides critical ecological insights and opportunities for sustainable forest management and enhancing forest conservation and ecosystem services.
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Forests take up and store large quantities of carbon. An analysis of inventory data from across the globe suggests that temperate and boreal forests accounted for the majority of the terrestrial carbon sink over the past two decades.
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The objective of this study was to determine the relationship, or lack thereof, between growth and diversity of tree species and size in conifer stands of western North America. Growth was measured by net basal area growth and its components: survivor growth, recruitment, and mortality. The analysis used inventory data from permanent plots in the Douglas-fir/western hemlock forest type in Oregon and Washington, and in the mixed-conifer forest type in California. The methods consisted of generalized least square regression with spatial autocorrelation, controlling for the effect of other stand characteristics. Other things being equal, in the two forest types under study there was a strong positive relationship between net basal area growth and tree-species diversity. This effect was associated with higher recruitment in stands of higher tree-species diversity. Neither mortality nor growth of survivors was related to tree-species diversity. The relationship between growth and tree-size diversity was less clear. For Douglas-fir/western hemlock, net basal area growth was negatively correlated with tree-size diversity, essentially because recruitment was lower on plots of high tree-size diversity. For mixed conifers, net basal area growth tended also to be lower in plots of high tree-size diversity, but this was mostly because mortality was higher in plots of higher tree-size diversity.
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Analyis of published data for forty-six Costa Rican forest sites indicates a negative correlation between soil nutrient availability and tree species richness. P, K, Ca, Na, total bases, base saturation, and cation exchange capacity showed significnat (P 2 of 0.71. Correlations between species richness, precipitation, tree density, tree height, and soil fertility, are consistent with the interpretation that the highest species richness occurs under poor growth conditions. Results of field and glasshouse fertilization experiments are reviewed.
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THE functioning and sustainability of ecosystems may depend on their biological diversity1-8. Elton's9 hypothesis that more diverse ecosystems are more stable has received much attention1,3,6,7,10-14, but Darwin's proposal6,15 that more diverse plant communities are more productive, and the related conjectures4,5,16,17 that they have lower nutrient losses and more sustainable soils, are less well studied4-6,8,17,18. Here we use a well-replicated field experiment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity. Moreover, the main limiting nutrient, soil mineral nitrogen, was utilized more completely when there was a greater diversity of species, leading to lower leaching loss of nitrogen from these ecosystems. Similarly, in nearby native grassland, plant productivity and soil nitrogen utilization increased with increasing plant species richness. This supports the diversity-productivity and diversity-sustainability hypotheses. Our results demonstrate that the loss of species threatens ecosystem functioning and sustainability.
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Stand structural diversity is useful in forecasting growth and can be indicative of overall biodiversity. Many variables that indicate structural diversity can be measured. However, species, diameter, and height are commonly measured and indicate changes in vertical and horizontal stand structure. Indices based on the distribution of basal area per hectare by diameter, height, and species were derived and evaluated by applying them to simulated and actual data sets with a wide variety of stand structures. Extending the Shannon index of diversity to proportions by species, diameter, and height resulted in reasonable results with more diverse structures having higher values. However, diameter and height ranges must be divided into classes to use these indices. A new index based on the variances of the target stand, relative to the variance of a uniformly distribution stand, showed similar diversity measures to that of the Shannon index, without the need for dividing the diameter and height data into classes. Examination of these indices for use in growth and yield modelling of complex stands is needed.
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Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.
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Humans are modifying both the identities and numbers of species in ecosystems, but the impacts of such changes on ecosystem processes are controversial. Plant species diversity, functional diversity, and functional composition were experimentally varied in grassland plots. Each factor by itself had significant effects on many ecosystem processes, but functional composition and functional diversity were the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and light penetration. Thus, habitat modifications and management practices that change functional diversity and functional composition are likely to have large impacts on ecosystem processes.
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Relationships between stand growth and structural diversity were examined in spruce-dominated forests in New Brunswick, Canada. Net growth, survivor growth, mortality, and recruitment represented stand growth, and tree species, size, and height diversity indices were used to describe structural diversity. Mixed-effects second-order polynomial regressions were employed for statistical analysis. Results showed stand structural diversity had a significant positive effect on net growth and survivor growth by volume but not on mortality and recruitment. Among the tested diversity indices, the integrated diversity of tree species and height contributed most to stand net growth and survivor growth. Structural diversity showed increasing trends throughout the developmental stages from young, immature, mature, and overmature forest stands. This relationship between stand growth and structural diversity may be due to stands featuring high structural diversity that enhances niche complementarities of resource use because trees exist within different horizontal and vertical layers, and strong competition resulted from size differences among trees. It is recommended to include effects of species and structural diversity in forest growth modeling initiatives. Moreover, uneven-aged stand management in conjunction with selective or partial cutting to maintain high structural diversity is also recommended to maintain biodiversity and rapid growth in spruce-dominated forests.
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Maintaining both the structure and functionality of forest ecosystems is a primary goal of forest management. In this study, relationships between structural diversity and aboveground stand carbon (C) stocks were examined in spruce-dominated forests in New Brunswick, Canada. Tree species, size, and height diversity indices as well as a combination of these diversity indices were used to correlate aboveground C stocks. Multiple linear regressions were subsequently used to quantify the relationships between these indices and aboveground C stocks, and partial correlation analysis was also adopted to remove the effects of other explanatory variables. Results show that stand structural diversity has a significant positive effect on aboveground C stocks even though the relationship is weak overall. Positive relationships observed between the diversity indices and aboveground C stocks support the hypothesis that increased structural diversity enhances aboveground C storage capacity. This occurs because complex forest structures allow for greater light infiltration and promote a more efficient resource use by trees, leading to an increase in biomass and C production. Mixed tolerant species composition and uneven-aged stand management in conjunction with selection or partial cutting to maintain high structural diversity is therefore recommended to preserve biodiversity and C stocks in spruce-dominated forests.
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This paper contains a strategy for estimating total aboveground biomass of tropical forests. We developed regression equations to estimate aboveground biomass of individual trees as a function of diameter at breast height, total height, wood density, and Holdridge life zone (sensu Holdridge 1967). The regressions are applied to some 5,300 trees from 43 independent sample plots, and 101 stand tables from large-scale forest inventories in four countries, to estimate commercial and total aboveground biomass per unit area by forest type, and to estimate expansion factors defined as the ratio of aboveground to commercial biomass. The quadratic stand diameter (QSD, i.e., the diameter of a tree of average basal area) in a given forest stand influences the magnitude of the expansion factor. Stands of small trees have large expansion factors (up to 6.4), and as QSD increases, the expansion factor decreases to a constant value (about 1.75). For undisturbed forests in moist, moist transition to dry, and dry life zones respectively, the expansion factors for total aboveground biomass were 1.74, 1.95, and 1.57 respectively. For undisturbed, logged, and nonproductive forest categories used by the FAO to report global commercial wood volume data, we estimated expansion factors of 1.75, 1.90, and 2.00 respectively. Applying these factors to FAO data results in a 28 to 47% increase in previous volume-derived estimates of tropical forest biomass. However, estimates of tropical forest biomass based on small destructive samples continue to be high relative to estimates based on volume data. For. Sci. 35(4):881-902.
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Dry tropical forest communities are among the world's most threatened systems and urgent measures are required to protect and restore them in degraded landscapes. For planning conservation strategies, there is a need to determine the few essential measurable properties, such as number of species and basal area, that best describe the dry forest vegetation and its environment, and to document quantitative relationships among them. This paper examines the relationships between forest basal area and diversity components (number of species and evenness) for a disturbed dry tropical forest of northern India. Data were collected from five sites located in the Vindhyan dry tropical forest of India, selected on the basis of satellite images and field observations to represent the entire range of conditions in terms of canopy cover and disturbance regimes. These sites represented different communities in terms of species composition. The forest was poorer in species richness, and lower in stem density and basal area than wet forests of the tropics. Across sites (communities), the diversity components and tree density were positively related with total tree basal area. Considering basal area as a surrogate of biomass and net production, diversity is found to be positively associated with productivity. A positive relationship between basal area, tree density and species diversity may be an important characteristic of the dry forest, where recurring disturbance does not permit concentration of biomass or stems in only a few strong competitors. However, the relationships of basal area with density, alpha diversity and evenness remain statistically significant only when data from all sites, including the extremely disturbed one, are used in the analysis. In some sites there was a greater coefficient of variation (CV) of basal area than in others, attributed to patchy distribution of stems and resultant blanks. Therefore, to enhance the tree diversity of these forests, the variability in tree basal area must be reduced by regulating local disturbances. Conservation activities, particularly fuelwood plantations near human settlements, deferred grazing and canopy enrichment through multi-species plantations of nursery-raised or wild-collected seedlings of desirable species within the forest patches of low basal area, will be needed to attain restoration goals, but reforestation programmes will have to be made attractive to the forest-dwelling communities.
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At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
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1. Despite recent interest in linkages between above- and below-ground communities and their consequences for ecosystem processes, much remains unknown about their responses to long-term ecosystem change. We synthesize multiple lines of evidence from a long-term ‘natural experiment’ to illustrate how ecosystem retrogression (the decline in ecosystem process rates due to long-term absence of major disturbance) drives vegetation change, and thus above-ground and below-ground carbon (C) sequestration, and communities of consumer biota.
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Adaptive management is to reduce the vulnerability of ecosystems to climate change and to increase their resilience to climate-induced changes in ecological conditions. The forestry activities modify greenhouse gas emissions and increase carbon sequestration. The forest managers and policymakers work to minimize the adverse impacts of climate varaibility and changes.
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Increased global recognition of the role of forests in regulating the biosphere-atmospheric carbon cycle through carbon sequestration, has resulted in a wide range of scientific studies on estimation, mapping, monitoring and the prediction of Aboveground Biomass (AGB) on various scales in sub-Saharan Africa. In many parts of the developing world, specifically in sub-Saharan Africa, the accurate quantification of AGB, although still a challenge, is important for national carbon accounting, REDD+ project payments, sustainable forest management and strategic policy-making. In this review, an overview of remote sensing applications in AGB estimation in sub-Saharan Africa, including research challenges and basic information related to the trade-offs between sensor estimation accuracy and costs, is provided. It is assumed that this review is timely, due to a relative increase in the number of remotely sensed forests carbon studies in the recent years (specifically the period between 1998 and 2013). Remotely sensed data is particularly appealing, due to its robustness, instantaneity and repeated spatio-temporal coverage and hence the ability to successful estimate and map AGB. However, estimation accuracy and image acquisition cost vary with sensor resolution and type. It is assumed that this study will provide guidance in future national carbon accounting studies, which is one of the main objectives of the Kyoto Protocol and the REDD+ (Reducing Emissions from Deforestation and Forest Degradation) project, housed under the United Nations Framework Convention on Climate Change (UNFCCC), particularly for the developing world.
Chapter
This chapter introduces primary productivity in terrestrial ecosystems. Primary production is a complex set of processes in which chemical or solar energy is converted to produce biomass. By far, the main primary producers are green plants, which convert solar energy, carbon dioxide, and water to glucose, and eventually, to plant tissue. Primary productivity is the rate at which energy is converted into biomass. Estimations of primary productivity can be obtained through different methods. The oldest one is by destructive measurements of plant biomass, aboveground and belowground. Frequent samplings are necessary to avoid an underestimation due to the loss of plant material through herbivory or senescence. This method measures the actual accumulation of biomass after some of the products of photosynthesis are expended for the plant's own maintenance through respiration. More recent methods involve the measurement of carbon dioxide fluxes at the vegetation–atmosphere interface. The milestones in the investigation of terrestrial productivity correspond to increased capabilities to integrate measurements over larger scales. This development is largely the outcome of the efforts of international scientific organizations to stimulate research in this field. Two international programs, the International Biological Program (IBP), and subsequently, the International Geosphere–Biosphere Program (IGBP) have been, and are, instrumental in the coordination and direction of research. However, a lot of effort remains to be expended to improve the knowledge at all scales, as well as to influence policy based on this knowledge.
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Natural forest ecosystems are very important because of their potential and primary role in carbon (C) sequestration. However, it is not very clear that whether Functional Trait Diversity (FTD) enhances C stocks in them due to the trait values of the most abundant species (the mass ratio effect; measure as a Community Weighted Mean (CWM) and/or the variety of trait values (the niche complementarity effect; measure as a Functional Divergence (FD) within an ecosystem. In this study, I reviewed the most recent, critical, empirical and original research studies about FTD-C stocks relationship to understand the effects of CWM and FD on C stocks in natural forest ecosystems. The results of their studies suggest that strong dominance by tall and conservative species, rather than a set of coexisting species with diverse heights and exploitative nature, results in greatest C stocks in natural forest ecosystems. Thus, functional dominance (CWM effect) rather than FD effect has strong influence on C stocks in natural forest ecosystems. In conclusions, these evidences reflect that presence of dominant species will finally diminish functional divergence. Therefore, further research is needed to include the abiotic and biotic factors of an ecosystem in the conceptual model to critically test the FTD model of C stocks for full understanding.
Chapter
A quick dip into the literature on diversity reveals a bewildering range of indices. Each of these indices seeks to characterize the diversity of a sample or community by a single number. To add yet more confusion an index may be known by more than one name and written in a variety of notations using a range of log bases. This diversity of diversity indices has arisen because, for a number of years, it was standard practice for an author to review existing indices, denounce them as useless, and promptly invent a new index. Southwood (1978) notes an interesting parallel in the proliferation of new designs of light traps and new permutations of diversity measures.
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Species-specific allometric equations for shrubs and small trees are relatively scarce, thus limiting the precise quantification of aboveground biomass (AGB) in both shrubby vegetation and forests. Fourteen shrub and small tree species in Eastern China were selected to develop species-specific and multispecies allometric biomass equations. Biometric variables, including the diameter of the longest stem (D), height (H), wet basic density (BD), and crown area and shape were measured for each individual plant. We measured the AGB through a non-destructive method, and validated these measurements using the dry mass of the sampled plant components. The AGB was related to biometric variables using regression analysis. The species-specific allometric models, with D and H as predictors (D-H models) accounted for 70% to 99% of the variation in the AGB of shrubs and small trees. A multispecies allometric D-H model accounted for 71% of the variation in the AGB. Although BD, as an additional predictor, improved the fit of most models, the D-H models were adequate for predicting the AGB for shrubs and small trees in subtropical China without BD data.
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Ecologically sustainable management of temperate forests is a complex task that involves balancing potentially conflicting land uses such as wood production and nature conservation. We argue that a variety of strategies implemented at different spatial scales is required for biodiversity conservation in temperate forests where wood production is permitted. This is a form of 'risk-spreading;' if one option is ineffective for a given species, it may still be conserved as a result of the implementation of other approaches. At the largest scale, there is a clear need for reserves to protect representative samples of forest ecosystems. Within landscapes broadly designated for timber harvesting, intermediate-scale strategies such as the implementation of networks of streamside reserves and wildlife corridors are important for biodiversity conservation. At smaller spatial scales within harvested areas, critical habitat components for forest-dependent organisms like large old trees and logs must be provided. We focus on the importance of these fine-scale attributes for the conservation of biodiversity within logged forests using the mountain ash (Eucalyptus regnans) forests of the Central Highlands of Victoria as a case study. Forest managers must develop silvicultural practices that maintain and perpetuate critical stand attributes essential for the conservation of forest-dependent organisms. To this end, a shift is required from the extensive use of clearfelling to the adoption of new silvicultural techniques that maintain more structurally complex multi-aged stands. The maintenance of key structural features should be used as a template to guide harvesting methods to ensure that production forests contribute to biodiversity conservation, not only in mountain ash forests, but also temperate wood production elsewhere around the world.
Book
"Measuring Biological Diversity assumes no specialist mathematical knowledge and includes worked examples and links to web-based software. It will be essential reading for all students, researchers, and managers who need to measure biological diversity."--BOOK JACKET.
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We examined (1) the relationships between aboveground tropical forest C storage, biodiversity and environmental drivers and (2) how these relationships inform theory concerning ecosystem function and biodiversity. Experiments have shown that there is a positive relationship between biodiversity and ecosystem functioning, but intense debate exists on the underlying mechanisms. While some argue that mechanisms such as niche complementarity increase ecosystem function, others argue that these relationships are a selection effect.
Article
In all, 48 sites of subalpine coniferous forest that had undergone natural regeneration for 5–310 years were selected as study locations in the Southwest China. We compared species richness (S), plant diversity (Shannon–Wiener index, H′; Margalef index, R), and above- and below-ground ecosystem carbon (C) pools of six plant communities along a chronosequence of vegetation restoration, and we also examined evidence for a functional relationship between plant diversity and C storage. Our results showed that above-ground C increased significantly (over 52-fold), mainly due to the increase of C in aboveground living plants and surface litter. Soil organic carbon (SOC) content increased from the herb community type (dominated by Deyeuxia scabrescens, P1) to mixed forest type (dominated by Betula spp. and Abies faxoniana, P4), which constituted the main C pool of the system (63–89%), but decreased thereafter (communities P5–P6). The mean C stock in the whole ecosystem – trees, litter layer and mineral soil – ranged from 105 to 730MgCha−1 and was especially high in the spruce forest community type (dominated by Picea purpurea, P6). On the other hand, the relationships between C stocks (soil, aboveground) and mean annual temperature or altitude were generally weak (P>0.05). Moreover, we did not detect a relationship between S and aboveground C storage, while we found a significant negative relationship between H′, R and aboveground C storage. In addition, our experiment demonstrated that total root biomass and litter C/N ratio were significant functional traits influencing SOC, while S, R, and H′ had little effect. Path analysis also revealed that litter C/N ratio predominantly regulated SOC through changes in the quantity of microorganisms and soil invertase enzyme activity.
Article
More attention has been given to tree size diversity in boreal forests over the past few years, mainly because of increased focus on uneven-aged forest management, biodiversity and social values. Objective measures of tree size diversity are needed in order to develop management plans that are sustainable with respect to ecological and economical values. The objective of the present study was to evaluate different indices describing diameter diversity based on criteria related to applications in forest management planning. Eight previously described indices were evaluated based on 16 simulated and 174 empirical diameter distributions. The Gini coefficient was found superior with respect to discriminant ability, capability of providing logical ranking of different distributions and sensitivity to variation in sample size. There is a wide range of possible applications of the Gini coefficient in forest management planning, e.g. to compare tree size diversity in different stands, to assess changes in tree size diversity over time, to quantify the influence of different silvicultural treatments on tree size diversity and to assess areas suitable for certain silvicultural treatments. The coefficient can also be used as an integrated part of growth simulators in order to control the silvicultural treatments in projections.
Article
We analyzed the relationship between species richness and biomass in natural forest communities at two similar sites on Mt. Xiaolongshan, northwest China. At both sites, a wide range of tree layer biomass levels was available by local biomass estimation models. In order to identify underlying mechanism of the species richness-biomass relationship, we included different water resource levels and number of individuals in each plot in our analysis. We sampled 15 and 20 plots (20 m × 20 m), respectively, at both two sites. These plots were sampled equally on the sunny slope and the shady slope. Species richness, number of individuals of each species and diameter at breast height (DBH) as a substitute of biomass of tree layer were recorded in each sample. At one site, the relationship between species richness and biomass was significant on the sunny slope, and this relationship disappeared on the shady slope due to more environmental factors. The relations between species richness and number of individuals and between number of individuals and biomass paralleled the species richness-biomass relation on both slopes. The difference in number of individuals-biomass relationships on the sunny slope and the shady slope revealed “interspecific competitive exclusion” even though the species richness-biomass relationships were not hump-shaped. At the other site, species richness was not related to biomass or to number of individuals. Our study demonstrated the importance of environmental stress and succession of community in the understanding of species diversity-productivity patterns.
Article
Methods are presented to predict some of the effects of management on the tree size diversity of forest stands, measured with the Shannon-Wiener index applied to diameters. The diameter distribution is an indicator of stand structure and a determinant of biological diversity. The methods, which involve linear and nonlinear programming models of managed stands, were applied to northern hardwood forests. The attendant stand growth model was calibrated and validated with remeasured plots. The results suggest that, in this specific case, a natural, undisturbed stand would reach the highest possible sustainable diversity of tree size. Any intervention would decrease that diversity. In particular, economic harvesting policies would reduce tree size diversity by 10 to 20%, depending on the length of the cutting cycle. However, economics and diversity did not necessarily conflict. With the data and model used here, lengthening the cutting cycle up to 30 yr led to higher tree size diversity, while it also increased the soil rent of a stand by decreasing the present value of the cost of re-entry. Similarly, for a given cutting cycle, the soil rent increased with tree size diversity up to about 90% of the sustainable maximum, but decreased sharply thereafter. Real internal rates of return of 2 to 4% could be earned with stands that had either mediocre or very good levels of diversity. Likewise, starting from the same initial stand state, proper choice of a cutting guide could lead to much higher levels of tree size diversity, without decreasing forest value. For. Sci. 40(1):83-103.
Article
Question: What are the determinants of fine-scale plant species richness (SR)? Location: Île-aux-Grues, Québec, Canada. Methods: Elevation, soil organic matter, soil pH, irradiance, tree basal area (BA) and plant SR (herbs, shrubs, and trees) were determined in 100 contiguous 25 m2 quadrats in a deciduous forest. Each variable was analysed for spatial autocorrelation using Moran's I. Path analysis was used to determine the effects of different variables on tree, shrub and herb SR in a hierarchical modelling approach. Results: Most of the variables, except tree BA, PPFD (photo-synthetic photon flux density) and shrub SR, were positively autocorrelated at a scale of ca. 20 m or less. The path analyses explained ca. ll%-40% of the variance in plant SR; however, the model for shrub SR was not significant. Tree SR was positively associated, but herb SR was negatively associated with tree BA. Tree SR had a positive influence on shrub SR, but herb SR remained unaffected by tree or shrub SR. Conclusion: The positive association of tree BA and tree SR suggests that the data from the study site correspond to the left (ascending) portion of the SR-biomass relationship (un-dersaturated SR). The negative effect of tree BA on herb SR is direct and not mediated through reduced PPFD. High tree BA might cause high resource use, induce high litter production and affect soil properties, all of which might significantly affect herb SR. Several factors not considered here might influence fine-scale SR, such as interspecific interactions, fine-scale disturbances and heterogeneity (both spatial and temporal) in resources and abiotic conditions. Within-site variations of SR might be difficult to model with precision because of the relative importance of stochastic vs deterministic processes at this spatial scale.
Article
Is the above-ground biomass in natural temperate forests positively correlated with tree species diversity? . Is this biomass related to the diversity of tree functional groups? Location: We used published data from over 100 permanent plots located in natural temperate forests in the Czech Republic, Poland and Slovakia. Methods: We related the number of tree species and Simpson's index of tree species diversity to the above-ground biomass in natural forest stands, and we repeated the same calculations for the identification of functional groups of trees using PCA analysis of functional traits. Results: Analysed sites ranged from almost pure subalpine spruce stands to mixed deciduous lowland forests with eight tree species per stand. The above-ground biomass accumulation ranged from 169 to 536 tons of dry mass per hectare. For the analysed data set the relationship between tree species diversity and biomass accumulation was not significant but showed a negative trend. Similar results were obtained in analyses employing tree functional groups instead of tree species. A significant negative relationship was found after four stands located in the highest elevations had been removed from the data set. Conclusions: There is a weak negative relationship between tree species diversity and above-ground biomass in natural forests of Central Europe.