Aims As woody plants encroach into grassland ecosystems, we expect altered plant-soil interactions to change the microbial processes that affect soil carbon storage and nutrient cycling. Specifically, this research aimed to address how (1) soil chemistry, (2) microbial nutrient demand, and (3) the rate and source of potential soil C mineralization vary spatially under clonal woody shrubs of varying size within a mesic grassland. Methods We collected soil samples from the center, the midpoint between the center and edge, the edge, and the shrub-grass ecotone of multiple Cornus drummondii shrubs across a shrub-size gradient in infrequently burned tallgrass prairie. Results Total soil carbon and nitrogen increased with shrub size at every sampling location but the edge. Microbial demand for nitrogen also increased as shrubs increased in size. Across all shrub sizes and sampling locations, potential soil carbon mineralization rates were higher when microbes broke down proportionally more shrub-derived (C 3 ) organic matter than grass-derived (C 4 ) organic matter. Conclusions Our results suggest that the spatio-temporal context of woody encroachment is critical for understanding its impact on belowground microbial processes. In this ecosystem, a longer period of occupancy by woody plants increases potentially mineralizable soil carbon.

中文翻译：

---

由于木本侵占导致土壤微生物过程的空间变化取决于高草草原的灌木大小

目标随着木本植物侵入草原生态系统，我们预计植物-土壤相互作用的改变会改变影响土壤碳储存和养分循环的微生物过程。具体而言，这项研究旨在解决 (1) 土壤化学、(2) 微生物养分需求和 (3) 潜在土壤 C 矿化的速率和来源如何在中等草原内不同大小的无性系木本灌木下发生空间变化。方法 我们从中心、中心和边缘之间的中点、边缘和灌木 - 草丛中收集土壤样品，这些灌木跨越灌木大小的梯度，在很少燃烧的高草草原上。结果除边缘外，每个采样点的土壤总碳和氮随着灌木大小的增加而增加。随着灌木大小的增加，微生物对氮的需求也增加了。在所有灌木大小和采样位置中，当微生物分解的灌木衍生 (C 3 ) 有机质比草衍生 (C 4 ) 有机质成比例时，潜在的土壤碳矿化率更高。结论我们的结果表明，木质侵占的时空背景对于理解其对地下微生物过程的影响至关重要。在这个生态系统中，木本植物占据较长时间会增加潜在的可矿化土壤碳。结论我们的结果表明，木质侵占的时空背景对于理解其对地下微生物过程的影响至关重要。在这个生态系统中，木本植物占据较长时间会增加潜在的可矿化土壤碳。结论我们的结果表明，木质侵占的时空背景对于理解其对地下微生物过程的影响至关重要。在这个生态系统中，木本植物占据较长时间会增加潜在的可矿化土壤碳。