尕海湿地草甸土退化过程土壤氮矿化演变特征

氮矿化是生态系统循环的重要环节之一，影响着生态系统功能和氮素生物地球化学循环，因此研究高寒湿地退化过程中土壤氮矿化演变特征，对揭示气候变化和人为活动干扰背景下的湿地土壤氮素循环过程具有重要意义。以尕海湿地4种不同退化梯度(未退化、轻度退化、中度退化、重度退化)土壤为研究对象，采用野外树脂芯原位培养方法，通过对植物生长季不同生长阶段(生长初期、生长盛期、枯萎期)土壤氮素矿化作用研究，分析湿地退化演替过程中土壤氮矿化时空变化特征及其与土壤环境因子和酶活性之间的关系。结果表明：尕海湿地退化对土壤氮矿化过程有显著抑制作用，与未退化(0.143 mg kg^-1 d^-1)相比，轻度退化、中度退化、重度退化的土壤净氮矿化速率分别减小了0.018 mg kg^-1 d^-1、0.025 mg kg^-1 d^-1、0.020 mg kg^-1 d^-1;随着退化程度加剧，土壤净氨化速率逐渐减小或者不变，而净硝化速率却增大。随时间推移，各退化...

Evolution characteristics of soil nitrogen mineralization during meadow soil degradation of Gahai wetland

Nitrogen mineralization is one of the important links in ecosystem cycle, which affects ecosystem functions and nitrogen biogeochemical cycle. Therefore, it is important to study the evolution characteristics of soil nitrogen mineralization during the process of alpine wetland degradation, which help us to reveal the process of wetland soil nitrogen cycle in the context of climate change and other human disturbances. Four different wetland degradation gradients (non-degraded, slightly degraded, moderately degraded, and severely degraded) in the Gahai wetland areas were selected as the research objects. Using the in-situ resin core method, the temporal and spatial change characteristics of soil nitrogen mineralization and its relationship with soil environmental factors and enzyme activities were analyzed through the observation of soil nitrogen mineralization at different growth stages (early growth stage, peak growth stage, and wilting stage) in the plant growing season. The results show that the wetland degradation had a significant inhibitory effect on soil nitrogen mineralization. Among them, compared with non-degraded soil (0.143 mg kg^-1 d^-1), the mineralization rate of net nitrogen in slightly degraded, mildly degraded, and severely degraded, the values increased by 0.018, 0.025, 0.020 mg kg^-1 d^-1, respectively; with the intensification of degradation, the soil net ammoniation rates decreased gradually or remained unchange, while soil net nitrification rate increased. As time went by, the soil net nitrogen mineralization rates changed significantly for four degradation gradients. Except for the non-degraded stage, which had a maximum value in August, the maximum values of other degradation stages appeared in July (ranged from 0.217 to 0.305 mg kg^-1 d^-1). Compared with September and October, the value in August decreased by 0.137-0.217 mg kg^-1 d^-1 and 0.173-0.241 mg kg^-1 d^-1, respectively. Repeated-measures two-way ANOVA showed that Wetland degradation and culture time had a significant interaction effect on soil nitrogen mineralization (P<0.05); Redundancy analysis showed that the net nitrification rate was positively correlated with nitrate reductase, urease activity and temperature (P<0.05), but was negatively correlated with protease, nitrite reductase, and water content (P<0.05). However, the net ammoniation rate and net nitrogen mineralization rate were opposite. Soil water content contributed as much as 67.7% to the rate of soil net ammonia, nitrification and nitrogen mineralization, which was the main affecting factor driving the change of soil nitrogen mineralization during the degradation process of Gahai wetland. The research results provide a basis data for the development of mechanism models of nitrogen mineralization process in alpine wetlands under the background of climate change.