氮磷添加对青藏高原高寒草甸土壤有机碳降解的影响

发布时间：2018-09-11 17:24

【摘要】：陆地生态系统植物生长主要受氮磷状况的限制。由于独特的环境条件,青藏高原高寒草甸矿化作用较弱,植物生长更加受到养分状况限制。氮磷添加可以提高植物生产力,但同时也会改变植物和土壤的化学组成,影响土壤有机碳的分解。本文以青藏高原高寒草甸的六种优势植物和土壤为研究对象,研究了氮磷添加(N5、N10、N15、N5P5、N10P10、N15P15、CK)对其化学组成的影响,并通过室内培养实验探究了有机碳的分解过程以及不同时期累积碳矿化量与植物和土壤化学组成的关系,以期揭示氮磷添加对土壤有机碳的影响机制。主要结果有:1.氮磷添加显著降低了土壤有机碳含量。2.N10P10处理显著增加了土壤全氮含量;氮磷合施显著增加了土壤全磷含量。3.单施氮肥导致土壤碳氮比(N10除外)和碳磷比有所降低但与对照差异不显著,氮磷合施显著降低了土壤碳氮比和碳磷比。4.氮磷合施降低了垂穗披碱草、早熟禾(N10P10除外)、老鹳草和珠芽蓼的氮含量,显著增加了鹅绒委陵菜的氮含量;氮磷合施显著增加了除黄花棘豆外的五种植物的磷含量,并显著降低了其碳磷比和氮磷比。5.N10P10和N15P15处理均显著降低了除垂穗披碱草外的其它五种植物的木质素含量。6.不论是分解前期还是分解后期,N15P15处理均显著增加了累积碳矿化量(除了添加垂穗披碱草土壤的后期矿化量)。氮磷添加对整个分解过程累积碳矿化量的影响与后期一致。7.分解过程的累积碳矿化量与氮含量显著正相关,与碳氮比、纤维素和木质素含量显著负相关。除了分解前期,添加杂类草的土壤累积碳矿化量与植物氮含量以及碳氮比相关,在整个分解过程中,累积碳矿化量主要受土壤氮含量、碳氮比、纤维素及木质素含量的影响。综上得到以下结论:1.青藏高原高寒草甸植物生长主要受氮限制,单施氮肥尤其是高剂量氮肥(N15)可以缓解氮限制状况;2.分解过程累积碳矿化量主要和土壤N含量正相关、C/N以及植物木质素含量负相关,与微生物量碳并无显著相关性;3.因为氮磷添加普遍降低了土壤C/N和植物木质素含量,所以氮磷添加增大了累积碳矿化量,促进了有机碳的分解,不利于土壤有机碳的积累。
[Abstract]:Plant growth in terrestrial ecosystems is mainly restricted by nitrogen and phosphorus conditions. Because of the unique environmental conditions, the mineralization of alpine meadow in Qinghai-Xizang Plateau is weak, and plant growth is restricted by nutrient status. The addition of nitrogen and phosphorus can improve plant productivity, but also change the chemical composition of plant and soil, and affect the decomposition of soil organic carbon. In this paper, six dominant plants and soils in alpine meadow of Qinghai-Xizang Plateau were studied to study the effects of nitrogen and phosphorus addition (N5 ~ (10) N _ (10) N _ (10) P _ (5) N _ (10) P _ (5) N _ (10) P _ (10) N _ (10) P _ (10) N _ (10) P _ (10) N _ The decomposition process of organic carbon and the relationship between the accumulation of carbon mineralization and plant and soil chemical composition in different periods were investigated through indoor cultivation experiments in order to reveal the mechanism of nitrogen and phosphorus addition on soil organic carbon. The main result was 1: 1. Addition of nitrogen and phosphorus significantly decreased soil organic carbon content. 2.N10P10 treatment significantly increased soil total nitrogen content, and nitrogen and phosphorus combined application significantly increased soil total phosphorus content. The ratio of carbon to nitrogen (except N _ (10) and the ratio of carbon to phosphorus were decreased, but there was no significant difference between the two groups. The ratio of carbon to nitrogen and carbon to phosphorus was significantly decreased by the combination of nitrogen and phosphorus. The nitrogen content of Potentilla tuber and Potentilla spp were significantly increased by nitrogen and phosphorus combination, and the phosphorus content of five plants except Spinia chinensis was significantly increased by the combination of nitrogen and phosphorus, while the nitrogen content of Kentucky bluegrass (except N10P10), geranium and Polygonum hydrogonum was significantly increased by combined application of nitrogen and phosphorus, and the nitrogen content of Potentilla tuber was significantly increased by the combination of nitrogen and phosphorus. The ratio of carbon to phosphorus, the ratio of nitrogen to phosphorus, and the treatment of N15P15 significantly decreased the lignin content of the other five plants. The accumulation of carbon mineralization was significantly increased by N _ (15) P _ (15) treatment both in the early stage of decomposition and in the late stage of decomposition (except for the late mineralization of the soil of Euphorbia spp.). The effect of nitrogen and phosphorus addition on the accumulation of carbon mineralization in the whole decomposition process was consistent with that in the later stage. The accumulation of carbon mineralization in decomposition process was positively correlated with nitrogen content, negatively correlated with C / N ratio, cellulose and lignin content. In addition to the early stage of decomposition, the amount of soil cumulative carbon mineralization was related to plant nitrogen content and C / N ratio. During the whole decomposition process, the cumulative carbon mineralization amount was mainly affected by soil nitrogen content, C / N ratio, cellulose and lignin content. In summary, we get the following conclusion: 1. The growth of alpine meadow plants in Qinghai-Xizang Plateau is mainly restricted by nitrogen, but only applying nitrogen fertilizer, especially high dose nitrogen fertilizer (N15), can alleviate the nitrogen limitation. The accumulation of carbon mineralization in decomposition process was mainly negatively correlated with soil N content, C / N and plant lignin content, but not with microbial biomass carbon. Because the addition of nitrogen and phosphorus generally reduced the content of soil C / N and plant lignin, the addition of nitrogen and phosphorus increased the amount of accumulated carbon mineralization and promoted the decomposition of organic carbon, which was not conducive to the accumulation of soil organic carbon.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S812.2

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