Litter removal effectively alleviates the nitrogen limitation in grazing exclusion alpine meadows

IF 5.4 1区 农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Jiangqin Song , Yali Yin , Wen Zhao , Qiqi Sui , Jiuyan Huo , Wenxian Zheng , Shixiong Li
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Abstract

Litter accumulation in the alpine meadows after long-term grazing exclusion hinders the restoration efforts of degraded or mismanaged grassland ecosystems. Little is still known about how removing the litter affects the soil’s nutrient cycling and microbial metabolism. Here, we sampled soils in alpine meadows after four years grazing exclusion along a mass gradient of litter removal (MGLR) and a time gradient of litter removal (TGLR) in the northeastern region of the Qinghai-Tibet Plateau, China. Five soil extracellular enzyme activity (EEA, including carbon-, nitrogen-, and phosphorus- acquiring enzymes), and soil environmental variables were measured, and microbial metabolic limitation was calculated using vector analysis. The results indicated that short interval TGLR had no significant effect on soil enzyme activity. Meanwhile, the MGLR increase eventually promoted the activity of the soil C-, N-, and P-acquiring enzymes, which was beneficial for nutrient cycling. Microbial C limitation displayed the maximum value (1.47) after 50% removal of the litter. Litter removal effectively relieved the pressure on N limitation. The study further provided evidence that the dissolved organic carbon-to-soil available nitrogen ratio (DOC:SAN) and the soil available nitrogen-to-soil available phosphorus ratio (SAN:SAP) were the main environmental factors influencing microbial C limitation and nutrient limitation, respectively. The microbial C (1.33–1.35) and N (34.00°­34.09°) limitation were relatively low when the MGLR was 70%-90%, which was conducive to the element balance and efficient utilization of soil nutrient resources. Altogether, these findings indicated that litter removal had a significant impact on enhancing the activity of EEA and alleviating nutrient limitation despite the other unknown drawbacks. Litter removal and increasing the number of nitrogen-fixing plants may be the effective methods at present to alleviate nitrogen limitation in alpine meadows.
去除凋落物可有效缓解放牧隔离高寒草甸氮素限制
长期放牧后高寒草甸凋落物的积累阻碍了退化或管理不善的草地生态系统的恢复。对于清除凋落物如何影响土壤的养分循环和微生物代谢,人们知之甚少。以青藏高原东北地区为研究对象,采用凋落物质量梯度(MGLR)和凋落物去除时间梯度(TGLR)对放牧4年后的高寒草甸土壤进行了采样。测定5种土壤胞外酶活性(包括碳、氮、磷获取酶)和土壤环境变量,并利用载体分析法计算微生物代谢极限。结果表明,短间隔TGLR对土壤酶活性无显著影响。同时,MGLR的增加最终促进了土壤C-、N-和p获取酶的活性,有利于养分循环。微生物C限制在去除50%后达到最大值(1.47)。凋落物清除有效缓解了氮素限制的压力。研究进一步证明,土壤溶解有机碳与土壤有效氮比(DOC:SAN)和土壤有效氮与土壤有效磷比(SAN:SAP)分别是影响微生物C限制和养分限制的主要环境因子。MGLR为70% ~ 90%时,微生物C(1.33 ~ 1.35)和N(34.00°~ 34.09°)限制较低,有利于元素平衡和土壤养分资源的有效利用。综上所述,这些研究结果表明,尽管存在其他未知的缺陷,但清除凋落物对增强EEA活性和缓解营养限制有显著影响。清除凋落物和增加固氮植物的数量可能是目前缓解高寒草甸氮素限制的有效方法。
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来源期刊
Catena
Catena 环境科学-地球科学综合
CiteScore
10.50
自引率
9.70%
发文量
816
审稿时长
54 days
期刊介绍: Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.
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