Climate warming is a key factor driving species range shifts. While previous work has focused on shifts of aboveground plant communities, changes in climate and vegetation should affect soil communities and hence ecosystem-level nutrient cycling and ecosystem functioning. High alpine ecosystems are particularly sensitive to climate warming because snow is among the main drivers of ecosystem structure and function. Climate-warming snow cover changes at Niwot Ridge in the Colorado Rocky Mountains have resulted in a consistent plant colonization of previously unvegetated soils generating a natural gradient of soil habitats ranging from unvegetated to increasingly vegetated. We used this gradient of plant communities at different successional stages to determine if nematodes respond to climate-driven changes in this high-alpine landscape and if they play a role in changes in soil C and N. We hypothesized that: 1) there would be clear shifts in nematode communities along the gradient as a function of snow cover, plant richness and density, and water holding capacity but that these shifts would be dependent on nematode feeding habits and their positioning in the soil foodweb and 2) the shifts would be associated with accumulating soil C and N. To test these hypotheses, we measured nematodes, plants, and soil microbes, snow cover, pH, soil water holding capacity, and different forms of soil C and N in 98 plots across the plant successional gradient. As predicted, nematode communities exhibited extensive shifts from a few individuals of a single species in unvegetated soils to hundreds of individuals and tens of species within every feeding group under complex plant communities. Representatives of omnivorous and bacterivorous K-strategists preceded plants and plant parasites and root associates depended on plants most. Linear regression models indicated that plants, microbial communities and soil water holding capacity, but not snow cover, were the most predictive factors of nematode diversity and density across all trophic levels and that all nematode groups were positively related to all measures of soil C and N. Structural equation models confirmed these results, but also indicated that effects of climate warming on nematodes were indirect primarily through shifts in plant and microbial communities and changes of soil water holding capacity. Moreover, nematode trophic group densities, but not their diversity, played a potential role in the accumulation of soil N, and to a lesser degree of soil C. Because nematode communities at Niwot Ridge are largely at their early phases of assembly, with continuing climate warming, we predict their increasing abundance and diversity will likely continue, as will their impact on soil C and N processes.

气候变暖是推动物种范围变化的关键因素。虽然之前的工作侧重于地上植物群落的变化，但气候和植被的变化应该会影响土壤群落，从而影响生态系统层面的养分循环和生态系统功能。高山生态系统对气候变暖特别敏感，因为雪是生态系统结构和功能的主要驱动力之一。科罗拉多州落基山脉 Niwot Ridge 的气候变暖积雪变化导致以前没有植被的土壤的植物持续定植，从而产生了从无植被到越来越有植被的土壤栖息地的自然梯度。我们使用不同演替阶段的植物群落梯度来确定线虫是否对高山景观中气候驱动的变化做出反应，以及它们是否在土壤碳和氮的变化中发挥作用。我们假设：1）会有线虫群落沿梯度的明显变化是积雪、植物丰富度和密度以及持水能力的函数，但这些变化将取决于线虫的摄食习惯及其在土壤食物网中的位置，以及 2) 这些变化是相关的土壤碳和氮积累。为了检验这些假设，我们测量了 98 个样地中植物演替梯度的线虫、植物和土壤微生物、积雪、pH、土壤持水能力和不同形式的土壤碳和氮。正如预测的那样，线虫群落表现出从无植被土壤中单个物种的几个个体到复杂植物群落下每个摄食群体中数百个个体和数十个物种的广泛转变。杂食性和食菌性 K 策略的代表先于植物，植物寄生虫和根系最依赖植物。线性回归模型表明，植物、微生物群落和土壤持水能力，但不是积雪，是所有营养级线虫多样性和密度的最具预测性因素，并且所有线虫群与土壤 C 和 N 的所有测量均呈正相关. 结构方程模型证实了这些结果，但也表明气候变暖对线虫的影响是间接的，主要是通过植物和微生物群落的变化以及土壤持水能力的变化。此外，线虫营养群的密度，而不是它们的多样性，在土壤 N 的积累中发挥了潜在作用，对土壤 C 的影响程度较小。 因为 Niwot Ridge 的线虫群落主要处于组装的早期阶段，气候持续变暖，我们预测它们的丰度和多样性的增加可能会继续下去，它们对土壤碳和氮过程的影响也将继续。