锦鸡儿属灌丛化对草原化荒漠区土壤线虫群落组成和代谢足迹的影响

调查了内蒙古草原化荒漠区3种锦鸡儿垫状锦鸡儿(Caragana tibetica)、荒漠锦鸡儿(C.roborovskyi)和狭叶锦鸡儿(C.stenophylla)]灌丛内、外土壤线虫群落多样性、组成和代谢足迹，以及相关的土壤理化性质和植物群落特征，旨在探讨锦鸡儿属灌丛对土壤线虫群落的影响，并分析这种影响是否具有灌木种间差异，同时从线虫功能团水平上探究灌丛如何通过非生物因素和生物因素影响线虫群落组成。结果表明：锦鸡儿属灌丛对土壤线虫多度、丰富度和多样性无显著影响，但却显著影响土壤线虫群落组成。原因是灌丛对土壤线虫群落具有物种选择性；灌丛可能主要是通过根系分泌物、凋落物质量等因素，而不是通过土壤理化性质和林下植物影响线虫群落组成。土壤线虫组成的变化引起线虫代谢足迹发生明显变化。灌丛内土壤线虫功能代谢足迹大于灌丛外(除狭叶锦鸡儿外),说明灌丛内土壤线虫群落对碳的利用率更高。3种锦鸡儿属灌木中，狭叶锦鸡儿的结构代谢足迹最大，表明狭叶锦鸡儿对捕食杂食类线虫代谢活性的促进作用更强。土壤线虫组成的变化通过线虫代谢足迹导致土壤食物网结构发生显著性变化。狭叶锦鸡儿灌丛土壤干扰程度低，营养富集状况好...

Effects of Caragana shrub encroachment on soil nematode community composition and metabolic footprints in steppe desert region

Woody encroachment has become a common phenomenon in arid and semi-arid grassland worldwide. Soil nematodes are important in promoting organic matter decomposition and nutrient cycling. Although the effects of shrubs on species diversity and functional indices of soil nematode communities have been well studied, the effects of shrubs on the functional diversity, phylogenetic diversity, and metabolic footprint of soil nematode communities are still not well understood. Environmental factors affecting nematode community composition at functional group level and interspecific differences in the effects of shrubs on nematode community composition remain unclear. In this study, we investigated the diversity, composition and metabolic footprint of soil nematode communities, as well as the associated soil physicochemical properties and plant community characteristics outside and inside canopies of three Caragana shrub species (Caragana tibetica, C. roborovskyi and C. stenophylla) in the Inner Mongolia. We aimed to examine the effects of shrubs on soil nematode communities, analyze whether such effects are species specific, and explore how shrubs affect the nematode community composition through environmental factors at nematode functional group level. Our results showed that Caragana shrubs had no significant effects on nematode abundance, richness and diversity, but significantly altered nematode community composition. The possible reasons were that Caragana shrubs had selective effect on nematode species, the effects of shrubs on nematode communities were likely mainly through root exudates, litter quality and other factors, not through soil physicochemical properties and understory plants. The changes in nematode composition led to significant changes in nematode community metabolic footprint. The functional metabolic footprint of nematode community under shrub canopies was higher than that in the open areas (except for C. stenophylla), indicating that soil nematode communities under shrub canopies had higher carbon use efficiency. Among the three Caragana species, C. stenophylla had highest structural footprint, suggesting that it had the strongest facilitation effects on the metabolic footprint of omnivores-predators. The changes in nematode community composition led to the significant changes in soil food web structure through nematode metabolic footprint. The soil nutrient status of C. stenophylla was better with lower disturbance level, and the soil food web was more mature and stable; the soil nutrient status of C. tibetica and C. roborovskyi was moderate with higher disturbance level, and the soil food web tended to degrade. In conclusion, Caragana shrubs altered soil nematode community composition and structure, and such changes were shrub species dependent. Changes in nematode composition caused shifts in metabolic footprints, which further led to variation in soil food web structures.