Data from: Mammalian engineers drive soil microbial communities and ecosystem functions across a disturbance gradient

The effects of mammalian ecosystem engineers on soil microbial communities and ecosystem functions in terrestrial ecosystems are poorly known. Disturbance from livestock has been widely reported to reduce soil function, but disturbance by animals that forage in the soil may partially offset these negative effects of livestock, directly and/or indirectly by shifting the composition and diversity of soil microbial communities. Understanding the role of disturbance from livestock and ecosystem engineers in driving soil microbes and functions is essential for formulating sustainable ecosystem management and conservation policies.
We compared soil bacterial community composition and enzyme concentrations within four microsites: foraging pits of two vertebrates, the indigenous short-beaked echidna (Tachyglossus aculeatus) and the exotic European rabbit (Oryctolagus cuniculus), and surface and subsurface soils along a gradient in grazing-induced disturbance in an arid woodland.
Microbial community composition varied little across the disturbance gradient, but there were substantial differences among the four microsites. Echidna pits supported a lower relative abundance of Acidobacteria and Cyanobacteria, but a higher relative abundance of Proteobacteria than rabbit pits and surface microsites. Moreover, these microsite differences varied with disturbance. Rabbit pits had a similar profile to the subsoil or the surface soils under moderate and high, but not low disturbance.
Overall, echidna foraging pits had the greatest positive effect on function, assessed as mean enzyme concentrations, but rabbits had the least. The positive effects of echidna foraging on function were indirectly driven via microbial community composition. In particular, increasing activity was positively associated with increasing relative abundance of Proteobacteria, but decreasing Acidobacteria.
Our study suggests that soil disturbance by animals may offset, to some degree, the oft-reported negative effects of grazing-induced disturbance on soil function. Further, our results suggest that most of this effect will be derived from echidnas, with little positive effects due to rabbits. Activities that enhance the habitat for echidnas or reduce rabbit populations are likely to have a positive effect on soil function in these systems.

哺乳动物生态系统工程师（mammalian ecosystem engineers）对陆地生态系统中土壤微生物群落与生态系统功能的影响，目前尚缺乏充分研究。已有大量研究报道，家畜活动造成的扰动会降低土壤功能，但在土壤中觅食的动物所带来的扰动，可能通过直接或间接改变土壤微生物群落的组成与多样性，部分抵消家畜活动带来的负面影响。明确家畜与生态系统工程师造成的扰动在驱动土壤微生物群落及生态系统功能中的作用，对于制定可持续的生态系统管理与保护政策至关重要。

本研究在一片存在放牧诱导扰动梯度的干旱林地中，对比了四种微生境的相关指标：两种脊椎动物的觅食坑——本土短喙针鼹（Tachyglossus aculeatus）与外来欧洲野兔（Oryctolagus cuniculus）的觅食坑，以及表层土壤与亚表层土壤。

微生物群落组成在不同扰动梯度间差异较小，但四种微生境之间存在显著差异。与野兔觅食坑及表层微生境相比，针鼹觅食坑中酸杆菌门（Acidobacteria）与蓝细菌门（Cyanobacteria）的相对丰度更低，而变形菌门（Proteobacteria）的相对丰度更高。此外，这些微生境间的差异随扰动程度发生变化：野兔觅食坑的群落组成谱与中度、高度扰动下的亚表层土壤或表层土壤相似，但与低度扰动下的情况存在显著不同。

总体而言，以平均酶浓度衡量的土壤功能，在针鼹觅食坑中得到的正向提升最为显著，而野兔觅食坑的提升效果最弱。针鼹觅食活动对土壤功能的正向影响，是通过微生物群落组成间接介导的。具体而言，土壤功能活性的提升与变形菌门相对丰度的增加呈正相关，而与酸杆菌门相对丰度的减少呈正相关。

本研究表明，动物造成的土壤扰动可在一定程度上抵消已有研究广泛报道的放牧扰动对土壤功能的负面影响。进一步而言，本研究结果显示，此类抵消效应主要源自针鼹的活动，野兔活动几乎不会带来正向影响。因此，有利于针鼹栖息的生境保护措施，或是降低野兔种群数量的管控手段，均有望对该类生态系统的土壤功能产生积极作用。