Agriculture erases climate constraints on soil nematode communities across large spatial scales

Abstract

Anthropogenic conversion of natural to agricultural land reduces aboveground biodiversity. Yet, the overall consequences of land‐use changes on belowground biodiversity at large scales remain insufficiently explored. Furthermore, the effects of conversion on different organism groups are usually determined at the taxonomic level, while an integrated investigation that includes functional and phylogenetic levels is rare and absent for belowground organisms. Here, we studied the Earth's most abundant metazoa—nematodes—to examine the effects of conversion from natural to agricultural habitats on soil biodiversity across a large spatial scale. To this aim, we investigated the diversity and composition of nematode communities at the taxonomic, functional, and phylogenetic level in 16 assemblage pairs (32 sites in total with 16 in each habitat type) in mainland China. While the overall alpha and beta diversity did not differ between natural and agricultural systems, all three alpha diversity facets decreased with latitude in natural habitats. Both alpha and beta diversity levels were driven by climatic differences in natural habitats, while none of the diversity levels changed in agricultural systems. This indicates that land conversion affects soil biodiversity in a geographically dependent manner and that agriculture could erase climatic constraints on soil biodiversity at such a scale. Additionally, the functional composition of nematode communities was more dissimilar in agricultural than in natural habitats, while the phylogenetic composition was more similar, indicating that changes among different biodiversity facets are asynchronous. Our study deepens the understanding of land‐use effects on soil nematode diversity across large spatial scales. Moreover, the detected asynchrony of taxonomic, functional, and phylogenetic diversity highlights the necessity to monitor multiple facets of soil biodiversity in ecological studies such as those investigating environmental changes.

Organism body size structures the soil microbial and nematode community assembly at a continental and global scale

“…On the other hand, a higher influence of stochastic processes in temperate coniferous forests emerges likely as a consequence of lower stringency of environmental selection and higher habitat patchiness as a result of biodiversity and system complexity 8 , 42 , 43 . Consistent with our results, the meta-analysis revealed a relative high proportion of stochasticity in agroecosystems, likely due to the regular management of the system that allow for a dynamic community turnover and lowered homogeneity of the system over time 44 .…”

Effects of historical legacies on soil nematode communities are mediated by contemporary environmental conditions

“…To obtain a panorama of the diversity patterns of soil nematodes at large scales, we obtained soil samples from 16 natural sites in mainland China ( Figure S1). We selected the sites by maximizing the geographical and environmental gradients considering both accessibility and affordability (Table S1 and Figure S1; Li et al, 2020). Three plots were selected within each site, and each plot (approximately 20 m 2 ) was at least 100 m apart from each other.…”

“…For each plot, five soil cores (diameter: 3.5 cm; depth: 0-10 cm) were randomly collected and mixed. A total of 48 soil samples were collected from August to October 2016 during the plant growth stage to minimize the seasonal effect in our study (Li et al, 2020). Although the sample size is relatively small, the sampling procedures were highly comparable among these sites.…”

Contrasting beta diversity of spiders, carabids, and ants at local and regional scales in a black soil region, northeast China

“…From these studies it was realized that the most probable cause for this loss and biodiversity simplification is reduced food availability and decreased niche availability by habitat fragmentation, for example, with detrimental effects on ground-dwelling carabids (Hendrickx et al, 2009). Drivers of community assembly are scale dependent and can change with spatial scales (Lindo and Winchester, 2008;Li et al, 2020;Sreekar et al, 2020). Previous studies demonstrated that only limited to single scale may lead to biased conclusions (Sasaki and Yoshihara, 2013;Banaszak-Cibicka and Żmihorski, 2020) and studies at both local and regional scales allow researchers to identify the most important processes operating across multiple spatial scales (Benocci et al, 2015;Hamaoka et al, 2020).…”