QQ客服 官方微博 反馈留言

题名	盐生荒漠和绿洲农田土壤CO2通量的对比研究
作者	谢静霞
学位类别	博士
答辩日期	2007
授予单位	中国科学院．新疆生态与地理研究所
导师	李彦，中科院新疆生态与地理研究所
关键词	土壤呼吸
其他题名	A Comparative Study on Soil CO2 Flux between a Saline Desert and a Cropped-Oasis Farmland
中文摘要	土壤表面CO2通量作为导致全球气候变化的关键生态过程，已经成为全球碳循环研究的核心问题，其动态变化将对全球碳平衡产生深远的影响。因此研究不同类型陆地生态系统土壤CO2通量的源汇特征及其主要影响因素对于深入理解全球气候变化和解释当今大气中失踪汇等科学难题具有极为重要的科学意义。本研究采用LI-8100自动土壤CO2通量系统观测了阜康原始盐生荒漠和绿洲农田的土壤CO2通量。结果表明：在2005年整个生长季节（05～10月）内，农田平均土壤CO2通量为3.19 μmolCO2?m-2?s-1，盐生荒漠为0.08 μmolCO2?m-2?s-1，农田是盐生荒漠的近40倍；农田土壤CO2通量的日过程呈单峰型，峰值出现在当地时间12：00前后，盐生荒漠则呈双峰型，第一峰值出现在09：00前后，第二峰值在17：00前后；在整个生长季内，农田土壤CO2通量远高于盐生荒漠，盐生荒漠夜间的土壤CO2通量均为负值；农田和盐生荒漠土壤CO2通量的月均最高值分别出现在7月（4.67 μmolCO2?m-2?s-1）和6月（0.17 μmolCO2?m-2?s-1），从9月起，盐生荒漠土壤CO2通量的月均值降为负值。农田和盐生荒漠的土壤CO2通量与土温的相关性都随土壤深度增加而减小，与气温的关系最密切，而且回归系数表明农田土壤CO2通量对温度变化更敏感；湿润事件（灌溉或降雨）对农田和盐生荒漠的土壤CO2通量具有促进作用。盐生荒漠开垦为农田后土壤CO2通量发生了显著变化，不仅改变了土壤CO2通量的量级，甚至改变了通量的方向。由于在2005年观测过程中，发现盐生荒漠夜间的土壤CO2通量呈向下的负值，表现为CO2吸收。为了确定盐碱土CO2的纯吸收通量，2006年比较观测了盐生荒漠、弃耕地和绿洲农田测点灭菌与未灭菌土壤的CO2通量，证实了盐土对大气CO2的吸收是一个单向的无机过程。对盐土CO2通量影响因素的分析表明，盐土的CO2通量分别与0～5 cm、5～10 cm、10～15 cm的土壤电导率（EC）、土壤pH值之间呈显著线性负相关（P<0.0001），且随不同土壤深度呈规律性的变化；灭菌前后土壤的日均CO2通量与气温、2 cm土温、5 cm土温表现为正相关关系，且相关性随土壤深度增加而降低；灭菌后盐土的CO2通量与土壤含水量呈显著线性正相关关系（P<0.0001）。同时证实了碱土也具有和盐土同样的CO2吸收现象，两者吸收强度基本相同。综合考虑各种影响因素确定了盐碱土的日均CO2吸收通量约为0.1～0.5 μmol m-2s-1，结合全球盐碱土的总面积，最后估测出全球7.00亿hm2盐碱土的CO2吸收值约为0.44×1015～4.4×1015 g，其数量级与全球碳循环中的失踪汇相同，进一步证实了盐碱土是大气CO2的一个重要的汇。这对全球碳收支的准确计算以及全球变化趋势的探讨具有重要的科学意义。Soil surface CO2 flux as a key ecological process causing globally climatic change has become a core issue of the global carbon cycle, of which the variation will bring far-reaching influence on the balance of global carbon. As a result, to study the source-sink characteristic and main determinatives of soil CO2 flux in terrestrial ecosystems of different types is of crucially scientific significance for thorough understanding of globally climatic change and explanation of the scientific puzzle of missing sink. In present study, the soil CO2 fluxes were continuously measured at a saline desert and a cropped-oasis farmland reclaimed from the native desert using LI-8100 Automated Soil CO2 Flux system. The results showed that the soil CO2 flux of the farmland averaged 3.19 μmolCO2?m-2?s-1 in the growing season, 39 times higher than that of the saline desert (0.08 μmolCO2?m-2?s-1). The diurnal course of soil CO2 flux was characterized by single-peaked curve for the farmland, but bimodal curve for the saline desert. In addition, the peak of soil CO2 flux in the saline desert appeared at about 8:00 and 17:00 (local time), but 10:00 in the farmland. Soil CO2 fluxes in the farmland were always higher than that in the saline desert throughout the growing season while soil CO2 flux of the saline desert was negative during night. Soil CO2 fluxes also exhibited different seasonal variations at the two sites, with the maximum monthly mean value occurring in June for the saline desert (0.17 μmolCO2?m-2?s-1) and in July for the farmland (4.67 μmolCO2?m-2?s-1). Interestingly, monthly mean soil CO2 flux of the saline desert became negative after September. The CO2 flux was closely related to the air temperature 10 cm above the ground, and its correlation with soil temperature weakened with soil depth at both sites. However, the regression analysis indicated that soil CO2 flux in the farmland was more sensitive to the temperature than that in the saline desert. Furthermore, soil CO2 flux at both sites tended to increase rapidly after typical wetting events (rainfall for the desert and irrigation for the farmland). These results indicated that the soil CO2 flux not only changed its magnitude greatly but also change its direction after the saline desert was reclaimed. Because soil CO2 fluxes in the saline desert appeared negative and downwards to the atmosphere during night in 2005, we measured soil CO2 fluxes contrastively between sterilized and unsterilized soil for saline desert, abandoned farmland and cropped oasis farmland to determine the absorptive CO2 flux of the saline soil. Then we find CO2 absorption by the saline soil is an inorganic and nonreversing process of soils. The analysis of factors influencing the intensity of soil CO2 fluxes in saline soil showed that the soil CO2 fluxes in saline soil before and after sterilization exhibited a significantly (P<0.0001) positive correlation with soil electrical conductivity (EC) and pH values at 0～5 cm、5～10 cm、10～15 cm depth. Differently, the soil CO2 fluxes in saline soil before and after sterilization were positively correlated with air temperature and soil temperature at 2 cm, 5 cm depth, and the correlation with soil temperature weakened with soil depth at both sites. The sterilized soil CO2 fluxes in saline soil were positively correlated with soil water content significantly (P<0.0001). Furthermore, we confirmed that the intensity of CO2 absorption of saline and alkaline soil was very close. After general consideration of various influencing factors，we estimate that the overall daily average of CO2 absorption is 0.1~0.5 μmolCO2?m-2?s-1 for all saline/ alkaline soils globally. Finally, the overall C absorption by the 700 million hm2 saline/alkaline soils on earth is estimated at 0.44×1015 to 4.4×1015 g of C per year, which approximately matches the missing sink in global carbon cycle in magnitude. It approves that saline/alkaline soil is an important CO2 sink of atmosphere and is of crucially scientific significance for exact estimation of global carbon balance and discussion of global change trend.
语种	中文
学科主题	农学
公开日期	2010-11-12
页码	共125页
内容类型	学位论文
源URL	[http://ir.xjlas.org/handle/365004/7984]
专题	新疆生态与地理研究所_中国科学院新疆生态与地理研究所(2010年以前数据)
推荐引用方式 GB/T 7714	谢静霞. 盐生荒漠和绿洲农田土壤CO2通量的对比研究[D]. 中国科学院．新疆生态与地理研究所. 2007.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。