Wetland compensation and its impacts on β-diversity

The recovery of soil eukaryotic alpha and beta diversity after wetland restoration

Soil eukaryotes play an important role in regulating the ecological processes and ecosystem functioning. However, the recovery potential of soil eukaryotic diversity during wetland restoration is largely unknown. We compared the alpha and beta diversity of soil eukaryotes of farmlands and natural and restored wetlands to explore the underlying abiotic and biotic driving forces in the Sanjiang Plain, China. We found that there was no significant difference of the alpha diversity of soil eukaryotes, while the beta diversity of soil eukaryotes differed significantly between the three land use types, with the mean values in the restored wetlands in between those in the natural wetlands and farmlands. The composition of soil eukaryotic communities were less diverse in farmlands compared to restored and natural wetlands. Network property of soil eukaryotes community (positive: negative edges) increased from farmlands to restored wetlands to natural wetlands, indicating enhanced species positive: negative interactions during restoration. The structural equation modeling indicated that species positive: negative interactions and soil nutrients directly affected soil eukaryotic beta diversity. Soil pH and soil water content indirectly affected soil eukaryotic beta diversity by directly affecting species interactions. Our findings suggest that wetland restoration could change soil environment, strengthen microbial cooperation, and increase eukaryotic beta diversity. However, it may take a very long time to reach the original level of soil eukaryotic structure and diversity.

Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃⁺–N), and ammonia nitrogen (NH₄⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.

Environmental adaptation is stronger for abundant rather than rare microorganisms in wetland soils from the Qinghai-Tibet Plateau

Disentangling the biogeographic patterns of rare and abundant microbes is essential in order to understand the generation and maintenance of microbial diversity with respect to the functions they provide. However, little is known about ecological assembly processes and environmental adaptation of rare and abundant microbes across large spatial-scale wetlands. Using Illumina sequencing and multiple statistical analyses, we characterized the taxonomic and phylogenetic diversity of rare and abundant bacteria and fungi in Qinghai-Tibet Plateau wetland soils. Abundant microbial taxa exhibited broader environmental thresholds and stronger phylogenetic signals for ecological traits than rare ones. By contrast, rare taxa showed higher sensitivity to environmental changes and closer phylogenetic clustering than abundant ones. The null model analysis revealed that dispersal limitation belonging to stochastic process dominated community assemblies of abundant bacteria, and rare and abundant fungi, while variable selection belonging to deterministic process governed community assembly of rare bacteria. Neutral model analysis and variation partitioning analysis further confirmed that abundant microbes were less environmentally constrained. Soil ammonia nitrogen was the crucial factor in mediating the balance between stochasticity and determinism of both rare and abundant microbes. Abundant microbes may have better environmental adaptation potential and are less dispersed by environmental changes than rare ones. Our findings extend knowledge of the adaptation of rare and abundant microbes to ongoing environmental change and could facilitate prediction of biodiversity loss caused probably by climate change and human activity in the Qinghai-Tibet Plateau wetlands.

Wetland Compensation and Landscape Change in a Rapidly Urbanizing Context

While there are regulatory requirements that regulators should assess the impact of landscape-scale changes on the success of US Clean Water Act wetland compensatory mitigation sites, these requirements are poorly specified and very little work has been done to characterize how landscape change impacts CWA compensation sites. We created a rapid assessment method with both site-based and landscape-scale components, and used it to assess a population of wetland compensation sites in suburban St. Paul, Minnesota in 1997. We resampled the sites in 2010. The watersheds of these 22 compensation sites are characterized by rapid urbanization, the increase in impervious surfaces, and the loss of agriculture. This has resulted in extreme hydrographs at compensation sites and a fragmenting landscape context of more and smaller undeveloped patches. The ecosystem services provided by these compensation sites in 2010 are not significantly different than in 1997, indicating resilience in the face of landscape change, but not showing a trajectory of improvement. Reference sites were established for each ecosystem service, but two reference sites declined dramatically; results point to the importance of understanding ongoing landscape change even at benchmark sites. Compensation sites are typically located in rapidly changing and fragmenting landscapes, and understanding the relationship between landscape and compensation site will be important to ensuring appropriate compensation for impacts regulated by the Clean Water Act.

Cannot see the diversity for all the species: Evaluating inclusion criteria for local species lists when using abundant citizen science data

Abundant citizen science data on species occurrences are becoming increasingly available and enable identifying composition of communities occurring at multiple sites with high temporal resolution. However, for species displaying temporary patterns of local occurrences that are transient to some sites, biodiversity measures are clearly dependent on the criteria used to include species into local species lists. Using abundant opportunistic citizen science data from frequently visited wetlands, we investigated the sensitivity of α- and β-diversity estimates to the use raw versus detection-corrected data and to the use of inclusion criteria for species presence reflecting alternative site use. We tested seven inclusion criteria (with varying number of days required to be present) on time series of daily occurrence status during a breeding season of 90 days for 77 wetland bird species. We show that even when opportunistic presence-only observation data are abundant, raw data may not produce reliable local species richness estimates and rank sites very differently in terms of species richness. Furthermore, occupancy model based α- and β-diversity estimates were sensitive to the inclusion criteria used. Total species lists (all species observed at least once during a season) may therefore mask diversity differences among sites in local communities of species, by including vagrant species on potentially breeding communities and change the relative rank order of sites in terms of species richness. Very high sampling effort does not necessarily free opportunistic data from its inherent bias and can produce a pattern in which many species are observed at least once almost everywhere, thus leading to a possible paradox: The large amount of biological information may hinder its usefulness. Therefore, when prioritizing among sites to manage or preserve species diversity estimates need to be carefully related to relevant inclusion criteria depending on the diversity estimate in focus.