渭北黄土高原合理放牧对退耕草地土壤呼吸和侵蚀的影响

发布时间：2018-03-09 18:40

本文选题：退耕草地　切入点：合理放牧　出处：《中国农业科学院》2016年硕士论文　论文类型：学位论文

【摘要】：黄土高原是我国土壤侵蚀严重区域之一,自1999年实施退耕还林(草)以来该区生态环境得到较大改善,但同时也带来一些社会、经济问题。在该区采取必要措施在保护生态环境的同时又能促使农民增收的显得尤为重要。本研究选择黄土高原渭北旱原坡地,建立退耕草地放牧,退耕草地不放牧和传统农耕地三种处理的对比试验小区,定量研究了在退耕草地开展合理放牧在减少土壤呼吸和土壤侵蚀方面的作用及其影响因素。本试验在建立的三种试验小区,利用LI-8100碳通量自动测量仪原位监测植物生长期(4~9月)和植物非生长期(10~12月)三种处理土壤CO2排放速率的变化,同时利用时域反射仪(TDR 300)测定表层0~10cm土壤含水量,用地温表测定2cm和5cm表层土壤的温度。利用环境放射性核素7Be示踪技术,监测较大降雨事件引起的土壤侵蚀速率,同时取样测定侵蚀区土壤有机碳含量,比较不同处理小区侵蚀导致的土壤有机碳流失量。结果表明:(1)在植物生长期3种处理土壤CO2平均排放速率大小顺序为:退耕草地[3.69±0.39μmol/(m2?s)]退耕草地放牧[3.00±0.44μmol/(m2?s)]传统农耕地[1.99±0.22μmol/(m2?s)],且3种处理土壤CO2平均排放速率有显著性差异(P0.05);坡耕地退耕还草后土壤CO2排放增加了85%,合理放牧使退耕草地土壤CO2排放量减少了19%;在植物生长期,放牧后退耕草地土壤CO2排放减少主要与动物踩踏引起土壤容重明显增加及草类植被地上部分向土壤中输入的有机碳的减少有关。在植物非生长期,3种处理土壤CO2平均排放速率大小顺序为:退耕草地[0.76±0.21μmol/(m2?s)]传统农耕地[0.68±0.13μmol/(m2?s)]退耕草地放牧[0.51±0.13μmol/(m2?s)],但3种处理土壤CO2平均排放速率无显著性差异(P0.05);植物非生长期合理放牧对退耕草地土壤呼吸影响不大,土壤呼吸主要受土壤温度的影响。(2)在植物生长期,水分、温度影响因子无法解释三种处理间土壤CO2排放差异;在植物非生长期温度变化可以解释三种处理间土壤呼吸变化的50%以上,尤其是放牧地,温度变化可解释土壤呼吸变化的86.61%。(3)在退耕草地实施合理放牧可有效减少土壤侵蚀和土壤有机碳的流失。两次较大降雨事件后退耕草地放牧相较于退耕草地不放牧土壤侵蚀量平均减少了75%,土壤有机碳流失量平均减少了78%。合理放牧期间动物的踩踏作用引起草地土壤容重的增加是退耕草地土壤侵蚀减少的主要原因。本研究结果揭示,在我国黄土高原和类似的退耕还草地区,在植物生长期开展合理放牧既可以促进当地畜牧业生产,又能有效控制土壤侵蚀,减少土壤CO2排放;在植物非生长期围栏禁牧,用饲料喂养牲畜,可以减轻草地负担,有利于牧草的恢复生长,是一种值得探究的退耕草地可持续发展管理模式。
[Abstract]:The Loess Plateau is one of the serious areas of soil erosion in China. Since 1999, the ecological environment of this area has been greatly improved, but at the same time it has brought some societies. Economic problems. It is particularly important to take necessary measures to protect ecological environment and increase farmers' income in this area. A comparative experimental plot of three treatments, the non-grazing and the traditional agricultural land, of returning cultivated grassland, The effect of rational grazing on reducing soil respiration and soil erosion and its influencing factors were studied quantitatively. The change of soil CO2 emission rate was monitored by using LI-8100 carbon flux automatic measuring instrument in situ during plant growth period (4 ~ September) and plant non-growth period (10 ~ December). The soil water content of 0 ~ 10 cm surface layer was measured by time domain reflectometer (TDR 300). The soil erosion rate caused by heavy rainfall events was monitored by using the environmental radionuclide 7Be tracer technique, and the soil organic carbon content was measured by sampling. The soil organic carbon loss caused by soil erosion in different plots was compared. The results showed that the average CO2 emission rate of the three treatments in plant growth stage was in the order of returning farmland to grassland [3.69 卤0.39 渭 mol / m ~ (2)]? (3. 00 卤0. 44 渭 mol / m ~ (2)? Traditional farming land [1.99 卤0.22 渭 mol / m ~ (2)? The average CO2 emission rate of the three treatments was significantly different (P0.05N), the soil CO2 emission increased by 85% after the conversion of sloping farmland to grass, and the soil CO2 emission decreased by 19% by rational grazing. The decrease of soil CO2 emission after grazing was mainly related to the increase of soil bulk density caused by animal stampede and the decrease of organic carbon input from the aboveground part of grass vegetation to soil. The order of the average emission rate is: returning grassland [0.76 卤0.21 渭 mol / m ~ 2]? Traditional farming land [0.68 卤0.13 渭 mol / m ~ (2)? S) [0.51 卤0.13 渭 mol / m ~ (2) 路m ~ (2)] for grassland grazing [0.51 卤0.13 渭 mol / s]? However, there was no significant difference in the average CO2 emission rate among the three treatments (P 0.05), and reasonable grazing had little effect on soil respiration in returning grassland, and soil respiration was mainly affected by soil temperature. The difference of soil CO2 emission between the three treatments could not be explained by the temperature influencing factors, and more than 50% of the changes of soil respiration between the three treatments, especially in grazing land, could be explained by the temperature change in the non-growth period of plants. Soil erosion and soil organic carbon loss can be effectively reduced by rational grazing in return grassland, which can be explained by temperature change. 86.61% of soil respiration change. Two heavy rainfall events compared with non-grazing grassland after two heavy rainfall events, conversion grassland grazing can reduce soil erosion and soil organic carbon loss. Soil erosion decreased 75%, soil organic carbon loss decreased 78%. The increase of soil bulk density caused by animal stampede during reasonable grazing was the main reason of soil erosion reduction. In the Loess Plateau of China and similar areas of returning farmland to grass, reasonable grazing during plant growth period can not only promote local animal husbandry production, but also effectively control soil erosion and reduce soil CO2 emission. Feeding livestock with fodder can lighten the burden of grassland and is beneficial to the recovery and growth of forage grass. It is a sustainable development management mode of grassland which is worth exploring.
【学位授予单位】：中国农业科学院
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S812.2

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