Maxwell C Wilson’s research while affiliated with Arizona State University and other places

Background Damming disrupts rivers and destroys neighboring terrestrial ecosystems through inundation, resulting in profound and long-lasting impacts on biodiversity and ecosystem processes far beyond the river system itself. Archipelagos formed by damming are often considered ideal systems for studying habitat fragmentation. Methods Here we quantified the island attributes and landscape dynamics of the Thousand Island Lake (TIL) in China, which is one of the several long-term biodiversity/fragmentation research sites around the world. We also synthesized the major findings of relevant studies conducted in the region to further ecological understanding of damming and landscape fragmentation. Results Our results show that the vegetations on islands and the neighboring mainland were both recovering between 1985 and 2005 due to reforestation and natural succession, but the regeneration was partly interrupted after 2005 because of increasing human influences. While major changes in landscape composition occurred primarily in the lakefront areas and near-lakeshore islands, landscape patterns became structurally more complex and fragmented on both islands and mainland. About 80 studies from the TIL region show that the genetic, taxonomic, functional, and phylogenetic diversity on these islands were mainly influenced by island area at the patch scale, but fragmentation per se also affected species composition and related ecological processes at patch and landscape scales. In general, islands had lower species diversity but a steeper species-area relationship than the surrounding mainland. Fragmentation and edge effects substantially hindered ecological succession towards more densely vegetated forests on the islands. Environmental heterogeneity and filtering had a major impact on island biotic communities. We hypothesize that there are multiple mechanisms operating at different spatial scales that link landscape fragmentation and ecological dynamics in the TIL region, which beg for future studies. By focusing on an extensive spatiotemporal analysis of the island-mainland system and a synthesis of existing studies in the region, this study provides an important foundation and several promising directions for future studies.

Microbes, similar to plants and animals, exhibit biogeographic patterns. However, in contrast with the considerable knowledge on the island biogeography of higher organisms, we know little about the distribution of microorganisms within and among islands. Here, we explored insular soil bacterial and fungal biogeography and underlying mechanisms, using soil microbiota from a group of land-bridge islands as a model system. Similar to island species-area relationships observed for many macroorganisms, both island-scale bacterial and fungal diversity increased with island area; neither diversity, however, was affected by island isolation. By contrast, bacterial and fungal communities exhibited strikingly different assembly patterns within islands. The loss of bacterial diversity on smaller islands was driven primarily by the systematic decline of diversity within samples, whereas the loss of fungal diversity on smaller islands was driven primarily by the homogenization of community composition among samples. Lower soil moisture limited within-sample bacterial diversity, whereas smaller spatial distances among samples restricted among-sample fungal diversity, on smaller islands. These results indicate that among-island differences in habitat quality generate the bacterial island species-area relationship, whereas within-island dispersal limitation generates the fungal island species-area relationship. Together, our study suggests that different mechanisms underlie similar island biogeography patterns of soil bacteria and fungi.

Context The study of habitat fragmentation is fraught with definitional and conceptual challenges. Specifically, a multi-scale perspective is needed to address apparent disagreements between landscape- and patch-based studies that have caused significant uncertainty concerning fragmentation’s effects. Objectives Here we test the hypothesis that habitat fragmentation alters biological communities by creating hierarchically nested selective pressures across plot-, patch-, and landscape-scales in the Thousand Island Lake, China. We assess the variation in fragmentation-diversity relationships contextualize the interplay of scale-dependent relationships. Methods This work utilized two datasets. At the island scale, islands were sampled to adequately capture the vast majority of species on each island using 5 × 5 m sampling cells. To capture intra-island variation, we sampled 400 m² plots set up along an edge gradient on each island. The variation in species richness at each scale was then compared using Wilcoxon tests, Spearman rank correlations, generalized linear models, and single-large-or-several-small (SLOSS) simulations. Results We find that edges have little impact on plot α-diversity and between-plot β-diversity, but increase the amount of β-diversity that can be attributed to nestedness at the plot-scale. We also find that the percent habitat in the surrounding landscape has a positive effect on species richness at the patch-scale and that small islands accumulate species faster than large islands of equal total size at the landscape-scale. Conclusions By observing interdependent effects at each scale, we find support for the hypothesis that habitat fragmentation’s effects are hierarchically structured. Therefore, multi-scale approaches are needed to understand the patterns, processes, and consequences of fragmentation.

Background: How habitat fragmentation affects the relationship between local richness and the variation in community composition across space is important to both ecology and conservation biology, but this effect remains poorly understood. Methods: Here, we present an empirical study to address this topic in a fragmented landscape, the Thousand Island Lake (TIL), an artificial land-bridge island system with more than 1,000 islands, which provides an "experimental" fragmented landscape with a homogeneous matrix and similar successional history. We measured species composition and plant functional type (PFT) on 29 islands, and tested the effects of island area and isolation on the relationship between α- and β-diversity. General Linear Models were applied to test the impact of habitat fragmentation. In addition, variation partitioning was used to decouple α-diversity dependent and α-diversity independent spatial turnover in β-diversity of the plant community and across different PFTs. Results: We found habitat fragmentation influences β-diversity of plants primarily by modifying local α-diversity, not spatial turnover in the TIL system. We also found area-dependent environmental filtering and differential plant responses across functional types were the most likely underlying driving mechanisms. Discussion: These results highlight the importance of hierarchical linkages between components of biodiversity across scales in fragmented landscapes, and have practical conservation implications.

Aim Small, old‐growth forest fragments generally have more small‐seeded plants than large patches, due to the disappearance of large seed dispersing vertebrates. This pattern may differ for secondary forest fragments where differential migration ability rather than persistence of seed dispersers may be driving plant community assembly. In this study, we investigated the effect of habitat fragmentation on seed dispersers and plant community structure in regenerating forests. Location The Thousand Island Lake, China. Taxon Plants, birds and mammals. Methods We compiled diversity and abundance data for birds and mammals on islands in the Thousand Island Lake, China. We also surveyed the secondary plant communities and measured seed dispersal traits. Results Community‐weighted mean seed size of woody plants decreased with island size. This pattern was related to compositional difference of the dispersers. We found that mammal diversity and abundance was only weakly or not related to island size; whereas bird diversity and abundance increased strongly with island size. Density of bird‐dispersed plants was significantly positively related with island size. Since birds tend to disperse smaller seeds than mammals, the trend in seed size may have been a consequence of the shift in relative abundance of the two disperser guilds. Main Conclusions Differential responses of seed dispersers to habitat fragmentation may lead to pervasive shifts in the plant community structure of regenerating forest fragments. Our study highlights the importance of keeping large continuous forests in order to retain mammals and their dispersal capabilities.

Agricultural activity is widely recognized as a leading driver of natural wetland loss in many parts of the world. However, little is known about the spatiotemporal patterns of conversion between natural wetlands and farmland in China. This information deficiency has limited decision-making for the sustainable management of natural wetland ecosystems. In this study, we explicitly quantified bidirectional natural wetland-farmland conversions during the periods of 1990-2000 and 2000-2010 at multiple spatiotemporal scales. Our results revealed that about 60% (15,765km2) of China's lost natural wetlands were due to agricultural encroachment for grain production, 74.7% (11,778km2) of which occurred from 1990 to 2000. Natural wetland conversion to farmland was highest in Northeast China (13,467km2 or 85.4%), whereas the natural wetlands in Northwest China demand extra attention because of a notable increase of agricultural encroachment. Natural wetlands in the humid zone experienced tremendous agricultural encroachment, leading to a loss of 10,649km2, accounting for 67.5% of the total agriculture-induced natural wetland loss in China. On the other hand, a total of 1369km2 of natural wetlands were restored from farmland, with 66.3% of this restoration occurring between 2000 and 2010, primarily in Northeast China and the humid zone. Although a series of national policies and population pressure resulted in agricultural encroachment into natural wetlands, there are also policies and management measures protecting and restoring natural wetlands in China. The spatial differences in natural wetland-farmland conversions among different geographic regions and climatic zones suggest that China must develop place-based sustainable management policies and plans for natural wetlands. This study provides important scientific information necessary for developing such policies and implementation plans.

Context The relationship between biodiversity and ecosystem functioning (BEF) has been a central topic in ecology for more than 20 years. While experimental and theoretical studies have produced much knowledge of how biodiversity affects ecosystem functioning, it remains poorly understood how habitat fragmentation affects the BEF relationship. Objectives To develop a framework that connects habitat fragmentation to the BEF relationship from a landscape perspective. Methods We reviewed the literature on habitat fragmentation, BEF, and related fields, and developed a framework to analyze how habitat fragmentation affects the BEF relationship through altering biodiversity, environmental conditions, and both, based on the pattern-process-scale perspective in landscape ecology. Results Our synthesis of the literature suggests that habitat fragmentation can alter BEF relationship through several processes. First, habitat fragmentation causes the non-random loss of species that make major contributions to ecosystem functioning (decreasing sampling effect), and reduces mutualistic interactions (decreasing complementarity effects) regardless of the changes in species richness. Second, environmental conditions within patches and ecological flows among patches vary significantly with the degree of fragmentation, which potentially contributes to and modulates the BEF relationship. Conclusions Habitat fragmentation can affect the BEF relationship directly by altering community composition, as well as indirectly by changing environmental conditions within and among habitat patches on both local and landscape levels. The BEF relationship obtained from small plots and over short time periods may not fully represent that in real landscapes that are fragmented, dynamic, and continuously influenced by myriad human activities on different scales in time and space.

Understanding a species' functional traits allows for a directed and productive perspective on the role a species plays in nature, thus its relative importance to conservation planning. The functional trait ecology of the plateau pika Ochotona curzoniae (Hodgson, 1858) is examined to better understand the resilience and sustainability of the high alpine grasslands of the Qinghai-Tibetan Plateau (QTP). The key functional traits of plateau pikas are their abundance and behavior of digging extensive burrow systems. Plateau pikas have been poisoned over a significant part of their original geographic distribution across the QTP, allowing comparison of ecological communities with and without pikas. Nearly all mammalian and avian carnivores, most of which are obligate predators on pikas, have been lost in regions where pikas have been poisoned. Most endemic birds on the QTP nest in pika burrows; when pikas are poisoned, burrows collapse, and these birds are greatly reduced in number. Due to the biopedturbation resulting from their burrows, regional plant species richness is higher in areas with pikas than without. The presence of pika burrows allows higher rates of infiltration during heavy monsoon rains compared to poisoned areas, possibly mitigating runoff and the potential for serious downslope erosion and flooding. Thus the functional traits of plateau pikas enhance native biodiversity and other important ecosystem functions; these traits are irreplaceable. As plateau pikas are not natural colonizers, active re-introduction programs are needed to restore pikas to areas from which they have been poisoned to restore the important functional ecological traits of pikas.

Sustainability indices (SIs) have become increasingly important to sustainability research and practice. However, while the validity of SIs is heavily dependent on how their components are weighted and aggregated, the typology and applicability of the existing weighting and aggregation methods remain poorly understood. To close the knowledge gap regarding when to use which weighting and aggregation methods for constructing SIs, we review the most commonly used methods for weighting and aggregating SIs, discuss their benefits and drawbacks, and suggest a process-oriented approach for choosing appropriate weighting and aggregation methods depending on research objectives. Our review synthesis was based on peer-reviewed journal articles, books, and reports by international organizations, governmental agencies, and research institutions. After carefully examining their principles, characteristics, and applications, we selected and classified the frequently used methods for indicator weighting and aggregation. We systematically discuss the benefits and drawbacks of nine weighting methods and three aggregation methods. We propose a four-step process for choosing the most suitable weighting and aggregation methods based on: research purposes, spatial and temporal scales, and sustainability perspectives. In this research, we chose the most commonly used methods for weighting and aggregating SIs and analyzed the characteristics, strengths and weaknesses of each method. We found that choosing appropriate weighting and aggregation methods for a specific sustainability assessment project is an extremely important and challenging task. To meet this challenge, we propose a process-oriented approach for properly selecting methods according to the purpose, scale and sustainability concept. This approach can facilitate the proper selection of these methods in sustainability research and practice.

China’s South–North Water Transfer Project (SNWTP) has the potential to transfer as much as 44.8 km³ year⁻¹ of water from the Yangtze River basin to the Yellow River basin. However, the SNWTP has not been assessed from a sustainability perspective. Thus, in this study we evaluated the SNWTP’s economic, social, and environmental impacts by reviewing the English literature published in journals that are part of the Web of Science database. We then synthesized this literature using a Triple Bottom Line framework of sustainability assessment. Our study has led to three main findings: (1) whether the SNWTP is economically beneficial depends largely on model assumptions, meaning that economic gains at the regional and national level are uncertain; (2) the SNWTP requires the resettlement of hundreds of thousands of people and challenges existing water management institutions, suggesting possible social concerns beyond the short term; and (3) evidently large environmental costs in water-providing areas and uncertain environmental benefits in water-receiving areas together point to an uncertain environmental future for the geographic regions involved. Thus, the overall sustainability of SNWTP is seriously questionable. Although much work has been done studying individual aspects of SNWTP’s sustainability, few studies have utilized the multi-scale, transdisciplinary approaches that such a project demands. To minimize environmental risks, ensure social equity, and sustain economic benefits, we suggest that the project be continuously monitored in all three dimensions, and that integrated sustainability assessments and policy improvements be carried out periodically.