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盐碱土无机CO2通量的分离和量化
王忠媛
学位类型博士
导师李彦
2016
学位授予单位中国科学院大学
学位授予地点北京
学位专业生态学
关键词土壤co2通量 大气co2浓度 Co2溶解 盐碱土 土壤无机co2通量
摘要土壤CO2通量是陆地生态系统碳循环的第二大通量,其很小的变化就能严重改变大气CO2浓度的平衡,在调控区域及全球尺度的碳循环上起着十分关键的作用。干旱区盐碱土无机CO2吸收是一个崭新、独特的科学现象,打破了土壤表面CO2通量完全来自于生物源的假设,可能使干旱区成为地球上除海洋以外的又一具有特殊意义的碳汇区。然而,盐碱土无机CO2通量在土壤CO2通量和全球碳循环中的重要性还缺乏分离和量化依据,因而存在很大的不确定性。本研究在中科院新疆阜康荒漠生态站展开。针对盐碱土的无机CO2吸收现象,通过观测野外土壤CO2通量,解析盐碱土负通量产生的原因。用高压灭菌的方法,将无机CO2通量从土壤CO2通量中分离出来,量化无机CO2通量对土壤CO2通量的贡献。通过观测不同盐碱土无机CO2通量,探索盐碱土无机CO2通量的控制因子。在此基础上,根据CO2的溶解化学,建立盐碱土土壤-大气无机CO2通量模型,模拟土壤无机过程中CO2的运动转化,并用观测数据验证模型。主要结果如下: (1)盐碱土土壤负CO2通量形成的原因有两方面:一方面是夜间大气CO2浓度的剧烈升高及土壤有机呼吸的减小。另一方面是土壤的无机化学过程。 (2)盐碱土的无机CO2通量是土壤CO2通量的重要组分,土壤CO2通量的大部分(60%-90%)波动都来源于无机CO2通量,无机CO2通量的强度是有机呼吸强度的1.3-1.6倍。忽略土壤无机CO2通量,将低估土壤有机呼吸的强度。 (3)在土壤类型一定时,土壤无机CO2通量主要受温度控制;低温利于CO2吸收,高温有利于CO2释放。土壤pH可作为指示盐碱土潜在无机溶解碳库大小的指标;在低温和高温阶段,pH对无机CO2通量的作用效果不同。土壤pH相同时,盐分含量越高,潜在无机溶解碳库越大;但较大的盐分变化,才能造成土壤无机CO2通量的差异。 (4)通过土壤-大气无机CO2通量模型的验证,确定了土壤中无机化学过程是CO2的溶解化学过程。土壤溶液中,CO2以溶解碳酸盐的各种不同形式存在,并相互转化。 (5)夜间大气CO2浓度的作用超过温度,主导土壤CO2通量。忽略大气CO2浓度的作用,将高估温度对土壤CO2通量的作用和通量温度敏感性,运用到预测全球变化的气候模型中,将会造成较大的误差。 综上所述,土壤无机CO2通量是土壤CO2通量的重要组成部分,是生态系统碳循环不可忽略的潜在贡献;对土壤无机CO2通量的研究,将完善对土壤CO2通量和全球碳循环的认知。大气CO2浓度,应该包含在温度以外,共同刻画土壤CO2通量的日过程。在全球变化模型中加入土壤CO2通量对大气CO2浓度的响应模块,将显著提高对未来生态系统碳循环的预测能力。
其他摘要Soil CO2 flux is the second largest flux of carbon cycle in terrestrial ecosystems, and can result in a significant change to the atmospheric CO2 concentration with slight modification in its rate. Thus, soil CO2 flux is a critical ecological process for future atmospheric CO2 concentration, and is considered as an important regulator of regional and global carbon cycle. The abiotic absorption of atmospheric CO2 in saline/alkaline soil is a unique and brand-new phenomenon, which break the assumption that soil CO2 fluxes are purely biological in origin, leading arid and semi-arid lands as a large sink for CO2 beside the oceans. However, due to lacking differentiation standard and quantification data, the significance of abiotic CO2 flux to soil CO2 flux and global carbon cycle is still uncertainty. The experiment was carried out from 2009 to 2012 at Fukang Station of Desert Ecology. The cause of negative CO2 flux was analyzed by monitor In situ soil CO2 flux in field. To determine the potential contribution of abiotic CO2 flux to soil CO2 flux, the abiotic CO2 flux was differentiated by sterilization treatment with pressure steam chamber. The controlling factors were identified by comparing abiotic CO2 flux among various sterilized saline/alkaline soils. Based on the theory of CO2 dissolution chemistry, the saline/alkaline soil abiotic CO2 flux model was established to simulate the movement and transformation of CO2 in the soil, and validated by measurement. The main results are as follows: (1) Along with weakened soil biotic CO2 flux during night time, the negative soil CO2 flux in the saline/alkaline soil were attributed to the atmospheric CO2 concentration fluctuation and an abiotic chemical processes in the soil. (2) As a significant components of soil CO2 flux in saline/alkaline soil, soil abiotic CO2 flux accounted for 60%-90% variation of soil CO2 flux. The strength of abiotic CO2 flux was 1.3-1.6 multiple than soil biotic CO2 flux. Thus, the soil biotic CO2 flux was significantly underestimated by neglecting soil abiotic CO2 flux. (3) For certain saline/alkaline soil, temperature is the main factor which dominated the soil abiotic CO2 flux. Saline/alkaline soil tends to absorb CO2 at low temperature, and release CO2 at high temperature. Soil pH was a good indicator for the potential abiotic soluble carbon pool. The pH had different impact on soil abiotic CO2 flux while the temperature was low or high. Although potential abiotic soluble carbon pool was also increased with soil salinity, it required considerable soil salinity difference to change the abiotic CO2 flux. (4) By the validation of abiotic CO2 flux model, the soil abiotic chemical process was confirmed to be the dissolution of CO2 in soil. CO2 was existed as different kinds of carbonate species in soil solution and transformed from one to another. (5) At the diel scale, the variation of atmospheric CO2 concentration rather than temperature dominated soil CO2 flux at night. The consequence of ignoring the effects of atmospheric CO2 concentration is overestimated the effects of temperature on soil CO2 flux and overestimated the temperature sensitivity of soil CO2 flux, which would cause large errors in climate model for prediction global climate change. Therefore, the non-negligible role of soil abiotic CO2 flux as potential contribution to the ecosystem carbon cycle requires further investigation towards a better understanding of soil CO2 flux and global carbon cycle. Our study highlights the need to include atmospheric CO2 concentration than temperature to characterize the diel variation of soil CO2 flux. Recruiting the atmospheric CO2 concentration module into global change model will dramatically improve our ability to predict future patterns of ecosystem carbon cycling.
学科领域生态学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14761
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
王忠媛. 盐碱土无机CO2通量的分离和量化[D]. 北京. 中国科学院大学,2016.
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