放牧对草原生态系统碳、氮循环的影响：整合分析

发布时间：2019-07-06 16:44

【摘要】：放牧是草原生态系统的主要利用方式之一。不合理的放牧活动不仅威胁到草原生态系统的生物多样性和稳定性,同时还可以显著改变草原生态系统的结构和功能,引起碳和氮流失。近年来,尽管全球范围内开展了大量关于放牧对草原生态系统碳、氮循环影响的研究,但放牧对碳、氮循环,特别是地下过程,影响的一般规律仍然存在广泛争议。本文通过整合分析方法通过设定标准,从全球超过2500篇文献里筛选出105篇关于放牧对草原生态系统碳、氮循环过程影响的论文,建立分析数据库。分析数据库主要包括植物地上碳库、植物地下碳库、土壤碳库、凋落物碳库、微生物量碳库、植物地上部分氮库、植物地下部分氮库、土壤氮库、凋落物氮库、微生物量氮库、土壤碳氮比、植物根系碳氮比、微生物碳氮比、凋落物碳氮比、土壤呼吸通量、土壤净氮矿化速率、土壤净氮硝化速率、土壤容重、土壤酸碱度、土壤温度和土壤湿度等参数。基于数据库和整合分析方法,深入分析探讨放牧对草原生态系统碳、氮循环过程的一般规律。结果表明,放牧活动显著减少土壤碳库、植物地下部分碳库、土壤微生物量碳库和凋落物碳库,减少幅度分别为10.28,13.72,21.62和8.93%,同时显著减少土壤氮库、植物地下部分氮库、土壤微生物量氮库和凋落物氮库,减幅分别为13.38,4.40,24.40和10.39%;与其他参数相比,微生物量碳库和氮库的减幅都是最大的。相反的,放牧显著增加土壤和根系碳氮比但减低了微生物和凋落物碳氮比。放牧活动显著增加草原生态系统土壤呼吸通量、土壤净氮矿化和硝化速率,增幅分别为4.25,30.63和12.88%。此外,放牧活动增加了土壤容重、酸碱度和温度但减少了土壤湿度。放牧密度显著改变着碳氮循环的大小甚至方向。轻度放牧显著增加土壤碳库和土壤氮库,增加幅度分别为0.78%和3.24%,但中度和重度放牧显著减少土壤碳库和土壤氮库,对土壤碳库的减幅分别为3.45%和9.92%,土壤氮库减幅分别为8.41%和13.04%。相似地,轻度放牧分别增加植物地下部分碳库和凋落物碳氮比2.99%和10.14%,中度和重度分别减少植物地下碳库3.17%和24.1%,凋落物碳氮比22.61%和30.18%。与中度和重度放牧相比,轻度放牧下微生物氮和凋落物氮的减幅都是最大的。对于通量而言,轻度放牧显著增加土壤呼吸11.53%,但中度和重度放牧显著减少呼吸通量分别为12.7%和32.6%。土壤净氮矿化速率的加权响应比从轻度到重度放牧减幅介于48.87%到10.85%。但轻度放牧对土壤净氮硝化速率影响不明显,而中度和重度放牧显著减少土壤净氮硝化速率13.43%和103.06%。研究结果还表明,生物和非生物等环境因子显著影响着草原生态系统碳、氮循环对放牧活动的响应。半湿润区/湿润区的放牧干扰活动对土壤碳库、植物地下碳库、土壤氮库和植物地下氮库的减少幅度显著高于干旱/半干旱区。相似地,半湿润区/湿润区的土壤呼吸的加权响应比为0.099±0.023(P0.01),轻微高于干旱/半干旱区。但干旱/半干旱区微生物碳库和凋落物碳库的响应幅度,相对于半湿润区/湿润区而言,表现出更明显的减弱幅度。不同放牧类型显著改变了多数观测变量对放牧活动的响应大小甚至方向。放牧时间和年平均温度与土壤碳库响应比和土壤氮库响应比呈现显著的相关关系。年平均降雨量与土壤碳库响应比呈显著相关关系,但与土壤氮库响应比之间相关性不明显。此外,土壤碳库响应比与土壤氮库响应比呈现显著正相关关系。总体而言,放牧活动在全球尺度上影响草原生态系统碳、氮循环过程,同时改变了地上和地下碳、氮库分配格局。放牧密度显著改变了不同碳库和氮库对放牧活动的响应大小甚至响应方向。未来陆地生态系统模型在预测评估草原生态系统对全球碳、氮收支平衡时应综合考虑放牧密度和气候因子对碳、氮循环过程的影响。
[Abstract]:Grazing is one of the main ways of the grassland ecosystem. Unreasonable grazing activity not only threatens the biological diversity and stability of the grassland ecosystem, but also can obviously change the structure and function of the grassland ecosystem and cause the loss of carbon and nitrogen. In recent years, although a large number of studies on the effects of grazing on the carbon and nitrogen cycle of the grassland ecosystem have been carried out worldwide, the general rules of grazing on the cycle of carbon and nitrogen, especially the underground process, still have a wide range of disputes. In this paper, through the setting of the standard,105 papers on the effects of grazing on the carbon and nitrogen cycle of the grassland ecosystem were selected from over 2,500 articles of the world, and the analysis database was established. the analysis database mainly comprises a plant ground carbon library, a plant underground carbon library, a soil carbon library, a litter material carbon pool, a microbial biomass carbon pool, a plant ground part nitrogen bank, a plant underground part nitrogen bank, a soil nitrogen bank, a litterfall nitrogen bank, a microbial biomass nitrogen bank and a soil carbon-nitrogen ratio, The parameters such as the carbon-nitrogen ratio, the microbial carbon-nitrogen ratio, the carbon-nitrogen ratio of the litters, the soil respiration flux, the soil net-nitrogen mineralization rate, the soil net-nitrogen nitrification rate, the soil bulk density, the soil pH value, the soil temperature and the soil humidity, and the like are the root system carbon-nitrogen ratio, the microbial carbon-nitrogen ratio, the litter-litter carbon-nitrogen ratio, the soil The general rule of the process of carbon and nitrogen cycling in the grassland ecosystem is analyzed in depth based on the database and the integral analysis method. The results showed that the grazing activity significantly reduced the carbon pool of soil, the carbon pool of the underground part of the plant, the amount of soil microbial biomass and the carbon pool of litters, with the reduction of 10.28, 13.72, 21.62 and 8.93%, respectively. The reduction was 13.38, 4.40, 24.40, and 10.39%, respectively; the reduction of the amount of microbial biomass and nitrogen was the largest compared to other parameters. In contrast, grazing significantly increased the carbon-to-nitrogen ratio of the soil and the root system, but decreased the carbon-to-nitrogen ratio of the microorganism and the litter. Grazing activity significantly increased the soil respiration flux of the grassland ecosystem, the net nitrogen mineralization and the nitrification rate of the soil, and the growth rate was 4.25, 30.63 and 12.88%, respectively. In addition, grazing activities increased soil bulk density, pH and temperature, but reduced soil moisture. Grazing density significantly changes the size or even the direction of the carbon-nitrogen cycle. The increase of the soil carbon pool and the soil nitrogen bank was 0.78% and 3.24%, respectively. However, the soil carbon pool and the soil nitrogen bank were significantly reduced with moderate and severe grazing, and the reduction of the soil carbon pool was 3.45% and 9.92%, respectively, and the reduction of the soil nitrogen bank was 8.41% and 13.04%, respectively. Similarly, mild grazing increased the carbon and nitrogen ratio of the underground part of the plant to 2.99% and 10.14%, respectively, and the medium and the severe decreased the underground carbon pool of the plant by 3.17% and 24.1%, the carbon-nitrogen ratio of the litter was 22.61% and 30.18%, respectively. In comparison with moderate and severe grazing, the reduction of microbial nitrogen and litter nitrogen under mild grazing is the largest. For flux, mild grazing significantly increased the respiration of the soil by 11.53%, but moderate and severe grazing significantly reduced the respiratory flux by 12.7% and 32.6%, respectively. The weighted response ratio of the soil net nitrogen mineralization rate was from 48.87% to 10.85% from mild to severe grazing. However, the effect of mild grazing on the Nitrification rate of the soil is not obvious, while the moderate and severe grazing significantly reduces the net nitrogen nitrification rate of the soil by 13.43% and 103.06%. The results of the study also show that the environmental factors such as biological and non-biological factors have a significant effect on the response of the carbon and nitrogen cycle of the grassland ecosystem to the grazing activities. Grazing disturbance in the semi-humid area/ wet area is significantly higher than that of the arid/ semi-arid area for the soil carbon pool, the plant underground carbon pool, the soil nitrogen bank and the plant underground nitrogen bank. Similarly, the weighted response ratio of the soil respiration in the semi-humid area/ wet zone was 0.099-0.023 (P0.01), slightly above the arid/ semi-arid area. In the arid/ semi-arid area, the response amplitude of the carbon pool and the litter carbon pool shows a more significant reduction in the half-humid area/ wet area. The different grazing types significantly changed the response and even the direction of most of the observed variables to the grazing activity. Grazing time and annual average temperature were significantly related to the response ratio of soil carbon bank and the response ratio of soil nitrogen bank. There was a significant correlation between the annual average rainfall and the response ratio of the soil carbon reservoir, but the correlation between the response ratio of the soil and the soil was not obvious. In addition, the response ratio of the soil carbon reservoir is positively related to the response ratio of the soil nitrogen bank. In general, grazing activities affect the carbon and nitrogen cycle of the grassland ecosystem on the global scale, and the distribution pattern of carbon and nitrogen in the ground and the ground is changed. Grazing density significantly changes the response and even response of different carbon and nitrogen banks to grazing activities. The effects of grazing density and climate factors on the process of carbon and nitrogen circulation should be considered in the future land ecosystem model in the prediction and assessment of the global carbon and nitrogen balance of the grassland ecosystem.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S812

【相似文献】