Stimulation of soil nitrification and denitrification by grazing in grasslands: do changes in plant species composition matter?
Stimulation of soil nitrification and denitrification by grazing in grasslands: do changes in plant species composition matter?
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DOI：
10.1007/s00442-003-1367-4
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发表时间：
2003-11-01
期刊：
影响因子：
2.7
通讯作者：
Louault, F
中科院分区：
文献类型：
--
作者：
Le Roux, X;Bardy, M;Louault, F
长期放牧（几年到几十年）对不同草地生态系统硝化和反硝化作用的刺激作用已被广泛报道。然而，放牧通常会引起植物物种组成的重要变化，以及硝化和反硝化的变化是否主要是由于植被组成的变化从未被测试过。我们比较了土壤硝化和硝化酶活性（NEA和DEA，分别）半天然草地网站经历密集（IG）和轻（LG）放牧/割草制度13年。平均NEA和DEA（即从随机土壤采样观察）在IG高于LG网站。NEA/DEA比值在IG高于LG网站，表明更高的硝化刺激。植物物种组成的显着变化，观察到在响应放牧/割草制度。特别是，IG地点的披碱草比植物量低于LG地点，而IG地点的多年生黑麦草比植物量高于LG地点。相比之下，处理之间的绒毛草，早熟禾和高杆蒿的比容没有显着差异。草地草丛下的土壤采样的最后三个物种表现出较高的DEA，NEA和NEA/DEA比在IG比LG网站。在一定的放牧条件下，植物种类对土壤DEA、NEA和NEA/DEA比值的影响不显著。因此，植物物种组成的修改是不是在半天然草地生态系统经历长期密集放牧的硝化和反硝化的变化驱动的主要因素。因素，如践踏，动物排泄物中的N返回，和/或修改的N吸收和C分泌频繁落叶植物可能是负责增强微生物活性。
Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems. However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested. We compared soil nitrification- and denitrification-enzyme activities (NEA and DEA, respectively) between semi-natural grassland sites experiencing intensive (IG) and light (LG) grazing/mowing regimes for 13 years. Mean NEA and DEA (i.e. observed from random soil sampling) were higher in IG than LG sites. The NEA/DEA ratio was higher in IG than LG sites, indicating a higher stimulation of nitrification. Marked changes in plant species composition were observed in response to the grazing/mowing regime. In particular, the specific phytomass volume of Elymus repens was lower in IG than LG sites, whereas the specific volume of Lolium perenne was higher in IG than LG sites. In contrast, the specific volume of Holcus lanatus, Poa trivialis and Arrhenatherum elatius were not significantly different between treatments. Soils sampled beneath grass tussocks of the last three species exhibited higher DEA, NEA and NEA/DEA ratio in IG than LG sites. For a given grazing regime, plant species did not affect significantly soil DEA, NEA and NEA/DEA ratio. The modification of plant species composition is thus not the primary factor driving changes in nitrification and denitrification in semi-natural grassland ecosystems experiencing long term intensive grazing. Factors such as trampling, N returned in animal excreta, and/or modification of N uptake and C exudation by frequently defoliated plants could be responsible for the enhanced microbial activities.