增氮增雨对贝加尔针茅草甸草原土壤氮矿化及土壤理化性质的影响

发布时间：2018-07-12 13:51

本文选题：增氮 + 增雨　；参考：《东北师范大学》2015年硕士论文

【摘要】：大气氮沉降加剧与降水格局改变是全球变化的重要表象。水分与氮素均为温带半干旱区草原生态系统初级生产力的限制性因素。氮素增加与降水改变直接或间接地影响草地生态系统的氮循环速率。本文以内蒙古贝加尔针茅草甸草原为研究对象,实施增氮、增雨处理。增氮通过施用硝酸铵和尿素(分别占总施氮量的70%和30%)来实现,施氮量分为高(12 g N m-2 a-1)、中(6 g N m-2 a-1)、低(0 g N m-2 a-1,即自然肥力)三个水平;增雨通过集水槽截流降雨浇灌法来实现,增雨量分为高(增加2/7自然降水)、中(增加1/7自然降水)、低(自然降水)三个水平;增氮、增雨及二者互作一共九种处理组合,每一种处理四个重复,采用PVC顶盖埋管培养技术来测取土壤氮矿化速率,研究增氮、增雨及二者互作对草地土壤无机氮含量、土壤氮矿化速率以及土壤理化性质的影响。主要结论如下:(1)总体来看,在6-8月期间,土壤铵态氮含量的增加幅度明显高于硝态氮含量的增加幅度。从铵态氮含量来看,高氮(N2)条件下土壤8月份的铵态氮含量随着水分增加显著升高,而高水(W2)条件下土壤8月份的铵态氮含量也呈现随着氮素水平增加而显著升高的趋势。可见,增氮、增雨处理在提高土壤铵态氮含量过程中存在相互促进的交互效应。从硝态氮含量来看,增氮、增雨处理无交互效应。增氮处理对于硝态氮含量的影响作用较大,而增雨处理对于土壤硝态氮含量几乎无影响。(2)增氮、增雨以及二者交互效应在6月10日-7月10日、7月10日-8月10日间隔内对土壤净铵化速率及净硝化速率均不显著。然而,增雨处理对于6月10日-8月10日两个月间隔的土壤净铵化速率具有显著影响作用。同样,增氮处理对于6月10日-8月10日间隔的土壤净硝化速率的影响达到显著水平。可见,增氮、增雨处理对草地生态系统土壤氮矿化过程的影响具有时间上的累加效应。(3)水分是影响土壤铵态氮和土壤净铵化速率的主要因子,而氮素水平对土壤硝态氮和土壤净硝化速率影响作用显著。由于土壤硝态氮含量远远高于铵态氮含量,因此,氮素水平对于土壤总无机态氮含量及矿化过程一定程度上掩盖了水分因子的作用效果。综上,不同梯度的增氮和增雨对于贝加尔针茅草甸草原土壤氮矿化过程及土壤氮素含量均具有明显的影响。然而,增氮、增水处理对于土壤铵态氮和硝态氮作用效果不同。增氮会更多地影响土壤硝态氮含量与净硝化速率,进而影响土壤无机态氮含量及氮矿化。总体上,大气氮沉降及降水格局改变背景下草地无机氮及净氮矿化速率的变化可能是枯落物、植物、土壤环境及其土壤微生物等多因素相互作用的结果。
[Abstract]:The increase of atmospheric nitrogen deposition and the change of precipitation pattern are important phenomena of global change. Water and nitrogen were restrictive factors of primary productivity of grassland ecosystem in temperate semiarid region. Nitrogen increase and precipitation change directly or indirectly affect the nitrogen cycling rate of grassland ecosystem. In this paper, Nei Mongol Bekal Stipa meadow grassland as the research object, nitrogen and rain treatment. The nitrogen increase was achieved by applying ammonium nitrate and urea (70% and 30% of the total nitrogen fertilizer, respectively). The nitrogen application amount was divided into three levels: high (12 g N m-2 a-1), middle (6 g N m-2 a-1) and low (0 g N m-2 a-1, I. E. natural fertility). The precipitation increase is divided into three levels: high (increase 2 / 7 of natural precipitation), middle (increase 1 / 7 of natural precipitation), and low (natural precipitation). The rate of nitrogen mineralization in soil was measured by PVC capping tube culture technique. The effects of nitrogen enrichment, precipitation and interaction on the content of inorganic nitrogen, mineralization rate of soil nitrogen and physical and chemical properties of soil were studied. The main conclusions are as follows: (1) in the period of June to August, the increase of soil ammonium nitrogen content was obviously higher than that of nitrate nitrogen content. According to the content of ammonium nitrogen, the content of ammonium nitrogen in August increased significantly with the increase of water content under the condition of high nitrogen (N2), and the content of ammonium nitrogen in August increased with the increase of nitrogen level in high water (W2). It can be seen that there is a mutually reinforcing interaction effect in the process of increasing the content of ammonium nitrogen in soil under the treatment of increasing nitrogen and rain. From the point of view of nitrate nitrogen content, no interaction effect was found between nitrogen increasing and precipitation increasing. The effect of nitrogen treatment on nitrate content was greater than that of rain treatment. (2) nitrogen increasing treatment had little effect on nitrate nitrogen content in soil. (2) nitrogen increasing treatment had little effect on soil nitrate nitrogen content. During the interval of June 10 to July 10, July 10 to August 10, the rate of net ammonium and nitrification of soil were not significant. However, the precipitation treatment had a significant effect on the net ammonium rate of soil between June 10 and August 10. Similarly, the effect of nitrogen addition on the net nitrification rate between June 10 and August 10 was significant. It can be seen that the effects of nitrogen and rain treatment on soil nitrogen mineralization in grassland ecosystem have a cumulative effect on time. (3) Water is the main factor affecting soil ammonium nitrogen and soil net ammonium mineralization rate. The effect of nitrogen level on soil nitrate nitrogen and net nitrification rate was significant. Because the content of soil nitrate nitrogen is much higher than that of ammonium nitrogen, the effect of nitrogen level on the content of total inorganic nitrogen and mineralization process of soil is masked to some extent. In conclusion, the nitrogen mineralization process and soil nitrogen content in the steppe of Stipa baicalensis meadow were significantly affected by nitrogen increasing and rain increasing with different gradients. However, the effects of nitrogen and water treatment on soil ammonium and nitrate were different. The increase of nitrogen will affect the nitrate content and the net nitrification rate, and then affect the inorganic nitrogen content and nitrogen mineralization in the soil. In general, the change of mineralization rate of inorganic nitrogen and net nitrogen in grassland under the background of atmospheric nitrogen deposition and precipitation pattern change may be the result of the interaction of litter, plant, soil environment and soil microorganism.
【学位授予单位】：东北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S812.2

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