Deadwood heterogeneity is regarded as a primary causal driver of deadwood-associated soil biodiversity, but the underlying mechanisms remain elusive. This is partly due to the technical difficulties in disentangling and quantifying different components (e.g., deadwood is both habitat and food) of heterogeneity to which soil organisms may have context-dependent responses. Furthermore, non-trophic interactions, e.g., facilitation, also add complexity to deadwood heterogeneity-biodiversity relationships, yet their influences are unaccounted for in most deadwood biodiversity studies. To address these research gaps, we sampled isopod communities from 40 logs of two isotopically distinct tree species, which had been cut and incubated reciprocally for eight years in each of two environmentally contrasting sites (e.g., differences in background isotopic signatures and litter turnover rates). We then assessed the extent to which the variation in the biodiversity of isopod communities is explained by deadwood heterogeneity induced by wood-boring beetles. Stable isotope ratios (i.e., δC and δN) were employed to examine the response of trophic diversity of isopod communities to the rarely tested food facet of deadwood heterogeneity. We hypothesized the deadwood heterogeneity is boosted by wood-boring beetles and thereby positively affects the abundance, taxonomic diversity and trophic diversity of isopod communities. Our results supported this hypothesis: the abundance and Shannon and Simpson diversity as well as trophic diversity of isopods were positively correlated to wood-boring beetle tunnel densities in both sites and across the two tree species. We observed significant tree species and reciprocal treatment effects on the δ15N values of isopods in one of the two sites. This result suggested that the use of deadwood as food sources versus habitats by isopods is environmentally dependent. This study demonstrates that there is substantial heterogeneity within deadwood that promotes the diversity and trophic diversity of macroinvertebrates. This relationship is mediated by saproxylic beetle facilitation, with implications for the roles of saproxylic beetles and within-deadwood heterogeneity in determining microbial wood decomposition in temperate forests.

中文翻译：

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促进：同位素证据表明蛀木甲虫驱动二次分解者的营养多样性

枯木异质性被认为是枯木相关土壤生物多样性的主要驱动因素，但其潜在机制仍然难以捉摸。这部分是由于在解开和量化异质性的不同组成部分（例如，枯木既是栖息地又是食物）方面存在技术困难，而土壤生物可能对此有依赖于环境的反应。此外，非营养相互作用，例如促进作用，也增加了枯木异质性-生物多样性关系的复杂性，但它们的影响在大多数枯木生物多样性研究中都没有得到考虑。为了弥补这些研究空白，我们从两种同位素不同的树种的 40 根原木中采集了等足类动物群落样本，这些树种在两个环境对比鲜明的地点中相互砍伐和培育了八年（例如，背景同位素特征和凋落物周转率的差异） 。然后，我们评估了蛀木甲虫引起的枯木异质性在多大程度上解释了等足动物群落生物多样性的变化。采用稳定同位素比率（即 δ13C 和 δ1N）来研究等足类动物群落的营养多样性对很少测试的枯木异质性食物方面的响应。我们假设枯木异质性是由蛀木甲虫增强的，从而对等足类动物群落的丰度、分类多样性和营养多样性产生积极影响。我们的结果支持了这一假设：等足类动物的丰度、香农和辛普森多样性以及营养多样性与两个地点和两个树种的蛀木甲虫隧道密度呈正相关。我们在两个地点之一观察到显着的树种和交互处理对等足类动物 δ15N 值的影响。这一结果表明，等足类动物使用枯木作为食物来源而不是栖息地是环境依赖性的。这项研究表明，枯木内存在显着的异质性，促进了大型无脊椎动物的多样性和营养多样性。这种关系是由腐木甲虫促进介导的，对腐木甲虫和死木内异质性在确定温带森林微生物木材分解中的作用有影响。