氮素添加对青藏高原高寒草甸植被和土壤氮素供应能力的影响

发布时间：2018-04-01 22:26

本文选题：高寒草甸　切入点：氮素添加　出处：《兰州大学》2015年硕士论文

【摘要】：青藏高原草地占我国草地面积的三分之一,在维护边疆稳定、民族团结中发挥着重要作用。高寒草甸是青藏高原主要的草地类型,其生态环境异质性高、生态稳定性波动大,草地生产力一直以来是草牧业发展的首要关注点。虽然高寒草甸土壤有机碳含量相对较高,但其生态系统生产力一致被认为受氮素限制,而高寒草甸土壤氮素供应能力以及在不同利用方式下草地土壤氮素有效性仍未开展系统的研究。本研究以甘肃省甘南藏族自治州夏河县高寒草甸为对象,通过连续2年的野外定位研究,测定了在围封和放牧条件下,氮肥添加对草地植物群落及土壤氮含量的影响,结合室内长期间歇淋洗好氧培养和温室盆栽生物测试等方法,进一步分析了草地的氮素有效性特征。得到以下主要结果:1.氮素添加对高寒草甸植被及土壤氮素养分的影响(1)氮素添加当年草地生物量增加,其中禾本科生物量较对照增幅为1.2%~85.9%;毒草生物量所占总生物量比例较对照降低10%左右。施氮次年,围封样地禾本科生物量开始降低,毒草和杂类草生物量增加。(2)氮素添加显著增加了施氮当年土壤矿质氮含量和施氮次年围封样地土壤硝态氮含量。氮素添加对草地土壤矿质氮的影响主要在表层(0~10 cm)土壤,围封草地矿质氮含量对氮素添加更加敏感。2.温度和有机氮对高寒草甸土壤氮素矿化潜力的影响(1)实验室长期间歇淋洗好氧培养下,土壤有机氮铵化速率、硝化速率随着有机氮(牛粪)添加浓度的增加先升高后降低。有机氮添加对土壤氮素的矿化有激发效应,提高了了培养初期氮矿化速率。(2)草地土壤氮素矿化量在25℃条件下明显高于15℃和5℃。高寒草甸土壤氮素矿化以铵态氮为主体,放牧可以促进土壤硝态氮的矿化。铵态氮和硝态氮矿化量此消彼长。(3)一级指数方程Nt=N0(1-e-kt)+C0能较好地反应不同温度和有机氮添加下土壤氮素矿化能力。温度决定了高寒草甸土壤氮素矿化势N0,但对矿化速率k的影响不明显。添加15~45 kg/hm2氮素增加了围封利用下土壤氮素矿化速率。3.有机氮添加对高寒草甸土壤供氮能力影响的生物测试(1)温室盆栽条件下,有机氮添加对生长于高寒草甸土壤的连续种植的3次燕麦花期生物量均无促进作用。3次燕麦的生物量、叶面积指数和根系总长度依次大幅降低。(2)温室条件下,有机氮添加降低了燕麦全株的吸氮量,增加了燕麦种植后土壤残余氮,增加了土壤有机氮矿化量,最高达到对照的3.5倍。有机肥氮素矿化率随着施肥量的增加而降低,在N15(15 kg N/hm2)处理下最大达到47.1%。本研究通过野外监测、好气培养以及生物测试方法,较系统地分析了围封和放牧利用下高寒草甸土壤氮素矿化特征对氮素添加及温度的响应,三种方法所获结论相对一致,一次氮素添加对草地的影响的持续时间在两年以上,不同利用方式下草地氮素矿化能力及其对外界环境的响应不同。围封草地的异质性较低,对氮素添加的响应更加敏感,施用45 kg/hm2的牛粪有机氮对土壤氮素供应能力的增加效果最好。
[Abstract]:Qinghai Tibet Plateau grassland grassland area in China accounted for 1/3, in the maintenance of stability in border areas, play an important role in national unity. Alpine meadow is the main grassland types in Tibetan Plateau, the ecological environment heterogeneity, ecological stability, grassland productivity has been the primary focus of the development of animal husbandry. Although soil organic carbon the content of the alpine meadow is relatively high, but the ecosystem productivity consistent with that by nitrogen limitation, and alpine meadow soil nitrogen supply capacity and the research has not yet effective grassland soil nitrogen system in different utilization ways. This study in Gansu Province, Gannan Tibetan Autonomous Prefecture in Xiahe County meadow as the object, through the research field for 2 the determination of the fencing and grazing conditions, nitrogen fertilizer effects on grassland plant communities and soil nitrogen content, combined with the indoor long period of rest Leaching aerobic incubation and pot bioassay method, further analysis of the characteristics of nitrogen availability of grassland. The main results are as follows: the effects on alpine meadow vegetation and soil nitrogen in 1. nitrogen (1) nitrogen addition that grassland biomass increased, Gramineae biomass compared with an increase of 1.2%~85.9%%; the proportion of the total biomass of weeds biomass decreased about 10%. N the following year, Wai grass biomass sample began to decrease, poisonous weeds and forbs biomass increased. (2) nitrogen addition significantly increased the nitrogen in the soil mineral nitrogen content and nitrogen the enclosed plots of soil nitrate nitrogen content. The effects of nitrogen addition on grassland soil mineral nitrogen mainly in the surface soil (0~10 cm), enclosed grassland mineral nitrogen content of nitrogen added.2. was more sensitive to temperature and organic nitrogen on alpine meadow soil nitrogen mineralization potential Effect of (1) laboratory long-term intermittent leaching aerobic incubation, soil organic nitrogen ammonium nitrification rate, with the rate of organic nitrogen (Niu Fen) increasing concentration increased first and then decreased. The organic nitrogen addition on soil nitrogen mineralization with excitation effect, improve the early culture of nitrogen mineralization rate of soil nitrogen (2). The mineralization of grassland under the condition of 25 DEG C was significantly higher than that of 15 degrees and 5 degrees. The soil nitrogen mineralization in alpine meadow with ammonium nitrogen as the main body, grazing can promote soil nitrate nitrogen mineralization. Ammonium nitrogen and nitrate nitrogen mineralization flux. (3) an exponential equation Nt= N0 (1-e-kt) +C0 can to add soil nitrogen mineralization ability of different reaction temperature and organic nitrogen. The temperature determines the soil nitrogen mineralization potential in alpine meadow N0, but the effect on the mineralization rate of K was not obvious. Adding 15~45 kg/hm2 nitrogen increased enclosure with soil nitrogen mineralization rate of organic nitrogen Tim.3. The alpine meadow soil N-supplying capacity influence biological test (1) greenhouse condition, organic nitrogen adding 3 oat flowering biomass on continuous cropping on growth of alpine meadow soil had no effect to promote biomass.3 oat, leaf area index and total root length were significantly reduced (2). Under greenhouse conditions, organic nitrogen addition decreased the nitrogen uptake of oat whole plant, increase the soil residual nitrogen after planting oats, increase soil organic nitrogen mineralization, up to 3.5 times higher than that of control. Organic fertilizer nitrogen mineralization rate along with the increase of fertilization amount decreased in N15 (15 kg N/hm2) treatment the maximum 47.1%. based on field monitoring, incubation and biological test method, systematically analyzes the response of enclosure and grazing in alpine meadow soil nitrogen mineralization characteristics of nitrogen addition and temperature, the relative conclusions obtained by three different methods The duration, add a nitrogen effect on grassland in more than two years, the mineralization capacity of grassland under different land use patterns and its response to the external environment. The heterogeneity of enclosed grassland is low, more sensitive in response to nitrogen addition increased, the best effect of cow manure organic nitrogen fertilizer on soil nitrogen 45 kg/hm2 supply capacity.

【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S812

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