本文選題：高寒草甸　切入點(diǎn)：氮素添加　出處：《蘭州大學(xué)》2015年碩士論文

【摘要】：青藏高原草地占我國(guó)草地面積的三分之一,在維護(hù)邊疆穩(wěn)定、民族團(tuán)結(jié)中發(fā)揮著重要作用。高寒草甸是青藏高原主要的草地類型,其生態(tài)環(huán)境異質(zhì)性高、生態(tài)穩(wěn)定性波動(dòng)大,草地生產(chǎn)力一直以來(lái)是草牧業(yè)發(fā)展的首要關(guān)注點(diǎn)。雖然高寒草甸土壤有機(jī)碳含量相對(duì)較高,但其生態(tài)系統(tǒng)生產(chǎn)力一致被認(rèn)為受氮素限制,而高寒草甸土壤氮素供應(yīng)能力以及在不同利用方式下草地土壤氮素有效性仍未開展系統(tǒng)的研究。本研究以甘肅省甘南藏族自治州夏河縣高寒草甸為對(duì)象,通過(guò)連續(xù)2年的野外定位研究,測(cè)定了在圍封和放牧條件下,氮肥添加對(duì)草地植物群落及土壤氮含量的影響,結(jié)合室內(nèi)長(zhǎng)期間歇淋洗好氧培養(yǎng)和溫室盆栽生物測(cè)試等方法,進(jìn)一步分析了草地的氮素有效性特征。得到以下主要結(jié)果:1.氮素添加對(duì)高寒草甸植被及土壤氮素養(yǎng)分的影響(1)氮素添加當(dāng)年草地生物量增加,其中禾本科生物量較對(duì)照增幅為1.2%~85.9%;毒草生物量所占總生物量比例較對(duì)照降低10%左右。施氮次年,圍封樣地禾本科生物量開始降低,毒草和雜類草生物量增加。(2)氮素添加顯著增加了施氮當(dāng)年土壤礦質(zhì)氮含量和施氮次年圍封樣地土壤硝態(tài)氮含量。氮素添加對(duì)草地土壤礦質(zhì)氮的影響主要在表層(0~10 cm)土壤,圍封草地礦質(zhì)氮含量對(duì)氮素添加更加敏感。2.溫度和有機(jī)氮對(duì)高寒草甸土壤氮素礦化潛力的影響(1)實(shí)驗(yàn)室長(zhǎng)期間歇淋洗好氧培養(yǎng)下,土壤有機(jī)氮銨化速率、硝化速率隨著有機(jī)氮(牛糞)添加濃度的增加先升高后降低。有機(jī)氮添加對(duì)土壤氮素的礦化有激發(fā)效應(yīng),提高了了培養(yǎng)初期氮礦化速率。(2)草地土壤氮素礦化量在25℃條件下明顯高于15℃和5℃。高寒草甸土壤氮素礦化以銨態(tài)氮為主體,放牧可以促進(jìn)土壤硝態(tài)氮的礦化。銨態(tài)氮和硝態(tài)氮礦化量此消彼長(zhǎng)。(3)一級(jí)指數(shù)方程N(yùn)t=N0(1-e-kt)+C0能較好地反應(yīng)不同溫度和有機(jī)氮添加下土壤氮素礦化能力。溫度決定了高寒草甸土壤氮素礦化勢(shì)N0,但對(duì)礦化速率k的影響不明顯。添加15~45 kg/hm2氮素增加了圍封利用下土壤氮素礦化速率。3.有機(jī)氮添加對(duì)高寒草甸土壤供氮能力影響的生物測(cè)試(1)溫室盆栽條件下,有機(jī)氮添加對(duì)生長(zhǎng)于高寒草甸土壤的連續(xù)種植的3次燕麥花期生物量均無(wú)促進(jìn)作用。3次燕麥的生物量、葉面積指數(shù)和根系總長(zhǎng)度依次大幅降低。(2)溫室條件下,有機(jī)氮添加降低了燕麥全株的吸氮量,增加了燕麥種植后土壤殘余氮,增加了土壤有機(jī)氮礦化量,最高達(dá)到對(duì)照的3.5倍。有機(jī)肥氮素礦化率隨著施肥量的增加而降低,在N15(15 kg N/hm2)處理下最大達(dá)到47.1%。本研究通過(guò)野外監(jiān)測(cè)、好氣培養(yǎng)以及生物測(cè)試方法,較系統(tǒng)地分析了圍封和放牧利用下高寒草甸土壤氮素礦化特征對(duì)氮素添加及溫度的響應(yīng),三種方法所獲結(jié)論相對(duì)一致,一次氮素添加對(duì)草地的影響的持續(xù)時(shí)間在兩年以上,不同利用方式下草地氮素礦化能力及其對(duì)外界環(huán)境的響應(yīng)不同。圍封草地的異質(zhì)性較低,對(duì)氮素添加的響應(yīng)更加敏感,施用45 kg/hm2的牛糞有機(jī)氮對(duì)土壤氮素供應(yīng)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.

【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：S812

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