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Study evaluates overall soil arthropod diversity at different geographic scales

Soil arthropods contribute to terrestrial ecosystem functions and services. Previous studies have mainly focused on specific arthropod and non-arthropod taxonomic groups at various geographic scales. However, the patterns of overall soil arthropod community composition and the drivers of taxonomic diversity at different geographic scales remain unevaluated.

In a study in Catena, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences examined the diversity and distribution patterns of soil arthropods in four forests with different latitudinal distributions in Yunnan Province, southwestern China.

To explain the distribution patterns of soil arthropods at both local (relatively small habitat patches) and regional (latitudinally) scales, the researchers explored two hypotheses: the habitat heterogeneity hypothesis, where spatial complexity and variability of habitat allow many species to coexist, and the more-individuals hypothesis, where the amount of resources in itself, regardless of their spatial heterogeneity, increases overall soil arthropod richness and abundance.

The researchers collected soil arthropod samples from four locations including tropical Bubeng, tropical Nabanhe, subtropical Ailaoshan, and subalpine Lijiang across different latitudes in Yunnan, and identified these samples to family or subfamily level.

They then measured soil physicochemical properties to test the relative importance of environmental factors at different spatial scales.

Their analysis showed that soil arthropod richness and abundance increased with rising latitude, which contrasted with the pattern generally known for plants and aboveground animals.

At the regional scale, litter biomass (resources) explained species richness and abundance, which is consistent with the more-individuals hypothesis. While at the local scale, other soil physicochemical properties were more important, supporting the habitat heterogeneity hypothesis.

However, the relative importance of individual soil properties was highly dependent on sites, suggesting that environmental factors at one site do not necessarily reflect those at other sites at different latitudes. Nestedness was not a major component of the regional-scale β-diversity, change in species diversity between different ecosystems.

The study provides the first evidence that regional-scale β-diversity patterns of soil arthropods also follow the same patterns as other groups of terrestrial and freshwater organisms.

"It highlights the importance of considering different spatial scales and environmental factors to better understand and conserve soil biodiversity," said Yang Xiaodong, one of the corresponding authors of the study, and a researcher from XTBG.