College of Natural Resources and Environment/State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A & F University, Yangling 712100, China.
College of Natural Resources and Environment/State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A & F University, Yangling 712100, China; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resource, Yangling 712100, China.
Sci Total Environ. 2024 Oct 1;945:174088. doi: 10.1016/j.scitotenv.2024.174088. Epub 2024 Jun 20.
Vegetation degradation in arid and semi-arid regions reduces plant C inputs to the soil, which can impede soil nutrient cycling because of the limited C source for microbial metabolism. However, whether vegetation degradation aggravates microbial nutrient limitation in degraded ecosystems in arid and semi-arid regions is not fully understood. Here, we investigated changes in soil enzyme activity and microbial nutrient limitation along a well-documented gradient of degraded seabuckthorn (Hippophae rhamnoides L.) (slightly degraded, canopy dieback <25 %, moderately degraded, canopy dieback 25 %-75 %, and severely degraded, canopy dieback >75 %) in Liang (long ridge) and gully channel locations in the Pisha Sandstone region of the Loess Plateau, China. We found that as the magnitude of seabuckthorn degradation increased, activities of C-acquiring enzymes and ratios of C:N and C:P enzymes (0.54-0.80 and 0.52-0.77, respectively) increased whereas the N:P enzyme ratio (0.93-0.99) decreased. Stoichiometric modelling further indicated that microorganisms were limited by soil C and P (vector angle >45°) in the seabuckthorn plantation region, and the degradation of seabuckthorn plantation aggravated microbial C and P limitations. Partial least squares path modelling revealed that seabuckthorn degradation (canopy dieback) was the main factor explaining microbial C limitation variations, while soil physicochemical properties (pH and soil moisture content) and understory plant parameters (litter biomass) were the major factors underlying microbial P limitation of long ridge and gully channel formations, respectively. Our findings highlight synergistic changes between aboveground and belowground processes, suggesting an unexpected negative effect of vegetation degradation on soil microbial community and nutrient cycling. These insights offer a direction for the development of plantation nutrients management strategies in semi-arid and arid areas.
在干旱和半干旱地区，植被退化会减少植物向土壤输入的 C，这可能会阻碍土壤养分循环，因为微生物代谢的 C 源有限。然而，植被退化是否会加剧干旱和半干旱地区退化生态系统中微生物的养分限制仍不完全清楚。在这里，我们研究了沿着一个有充分记录的沙棘（Hippophae rhamnoides L.）退化梯度（轻度退化，冠层枯死<25%，中度退化，冠层枯死 25%-75%，严重退化，冠层枯死>75%）在中国黄土高原砒砂岩区梁（long ridge）和沟谷位置的土壤酶活性和微生物养分限制的变化。我们发现，随着沙棘退化程度的增加，C 获取酶的活性和 C:N 和 C:P 酶的比值（分别为 0.54-0.80 和 0.52-0.77）增加，而 N:P 酶的比值（0.93-0.99）下降。化学计量模型进一步表明，在沙棘种植区，微生物受到土壤 C 和 P 的限制（向量角>45°），而沙棘种植的退化加剧了微生物 C 和 P 的限制。偏最小二乘路径模型表明，沙棘退化（冠层枯死）是解释微生物 C 限制变化的主要因素，而土壤理化性质（pH 和土壤含水量）和林下植物参数（凋落物生物量）是沟谷形成微生物 P 限制的主要因素。我们的研究结果强调了地上和地下过程之间的协同变化，表明植被退化对土壤微生物群落和养分循环有意外的负面影响。这些发现为半干旱和干旱地区的种植园养分管理策略的发展提供了方向。
