Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of ex...Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of extremely geographic situation. This study was designed to examine soil CO<sub>2</sub> efflux characteristics of diurnal and seasonal variation, thus obtaining estimates of carbon balance of <em>Kobresia pygmaea</em> meadow in Qinghai-Tibet plateau. The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared. Composite model which was set by soil respiration rate, soil moisture content and temperature (atmospheric temperature and soil temperature) could explain better the variations of soil respiration rate. The variation range of <em>Q</em><sub>10</sub> ranged from 1.28 to 2.34, which was sensitive to temperature in green-up period and late growth stage, and decreased in growth peak period. Meanwhile, during the growing seasons the observed amount of annual carbon fixation via primary production for <em>Kobresia pygmaea</em> meadow ecosystem was about 120.21 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>. The carbon dioxide output via soil heterotrophic respiration was about 37.54 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>. So carbon budget had more input than output. The <em>Kobresia pygmaea</em> meadow ecosystem has stronger potential to absorb carbon dioxide, it was a sink of atmospheric CO<sub>2</sub>, and the plant community had a net carbon gain of 82.67 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>.展开更多
Tillage practices can potentially affect soil organic carbon （SOC） accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a doubl...Tillage practices can potentially affect soil organic carbon （SOC） accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice （Oryza sativa L.） field in Hunan Province of China. Three tillage treatments, no-till （NT）, conventional plow tillage （PT）, and rotary tillage （RT）, were laid in a randomized complete block design. Concentrations of SOC and bulk density （BD） of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass （ESM） basis and fixed depth （FD） basis. Soil carbon budget （SCB） under different tillage systems were assessed on the basis of emissions of methane （CH4） and CO2 and the amount of carbon （C） removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT （on an ESM basis） was as high as 129.32 Mg C ha-1, significantly higher than those under PT and RT （P 〈 0.05）. The order of SOC stocks in the 0-80 cm soil layer was NT 〉 PT 〉 RT, and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced effects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage effects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.展开更多
北方森林因其面积大、土壤碳储量高以及对全球暖化响应敏感而在全球碳平衡和气候系统中起着至关重要的作用。土壤呼吸和木质残体分解释放出的 CO2 通量是北方森林生态系统输入大气圈的最主要的碳源。量化这个通量并深刻理解其中的机理过...北方森林因其面积大、土壤碳储量高以及对全球暖化响应敏感而在全球碳平衡和气候系统中起着至关重要的作用。土壤呼吸和木质残体分解释放出的 CO2 通量是北方森林生态系统输入大气圈的最主要的碳源。量化这个通量并深刻理解其中的机理过程 ,是评价和预测北方森林在全球变化中的作用必不可少的内容。综述了北方森林生态系统土壤呼吸和木质残体分解释放出的 CO2 通量随生态系统类型及环境条件而变化的一般格局以及自养呼吸和异氧呼吸在土壤表面 CO2 通量中的相对贡献 ;分析了影响北方森林土壤呼吸的主要生物物理因子 ;讨论了该领域研究存在的问题和今后的研究方向 ;并强调木质残体分解释放出的 CO2 通量虽然在以往的森林生态系统碳平衡研究中常被忽略 。展开更多
文摘Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of extremely geographic situation. This study was designed to examine soil CO<sub>2</sub> efflux characteristics of diurnal and seasonal variation, thus obtaining estimates of carbon balance of <em>Kobresia pygmaea</em> meadow in Qinghai-Tibet plateau. The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared. Composite model which was set by soil respiration rate, soil moisture content and temperature (atmospheric temperature and soil temperature) could explain better the variations of soil respiration rate. The variation range of <em>Q</em><sub>10</sub> ranged from 1.28 to 2.34, which was sensitive to temperature in green-up period and late growth stage, and decreased in growth peak period. Meanwhile, during the growing seasons the observed amount of annual carbon fixation via primary production for <em>Kobresia pygmaea</em> meadow ecosystem was about 120.21 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>. The carbon dioxide output via soil heterotrophic respiration was about 37.54 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>. So carbon budget had more input than output. The <em>Kobresia pygmaea</em> meadow ecosystem has stronger potential to absorb carbon dioxide, it was a sink of atmospheric CO<sub>2</sub>, and the plant community had a net carbon gain of 82.67 g C<span style="white-space:nowrap;">·</span>m<sup>-2</sup><span style="white-space:nowrap;">·</span>a<sup>-1</sup>.
基金Supported by the Special Fund for Agro-Scientific Research in the Public Interest of China(Nos.200903003 and 201103001)
文摘Tillage practices can potentially affect soil organic carbon （SOC） accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice （Oryza sativa L.） field in Hunan Province of China. Three tillage treatments, no-till （NT）, conventional plow tillage （PT）, and rotary tillage （RT）, were laid in a randomized complete block design. Concentrations of SOC and bulk density （BD） of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass （ESM） basis and fixed depth （FD） basis. Soil carbon budget （SCB） under different tillage systems were assessed on the basis of emissions of methane （CH4） and CO2 and the amount of carbon （C） removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT （on an ESM basis） was as high as 129.32 Mg C ha-1, significantly higher than those under PT and RT （P 〈 0.05）. The order of SOC stocks in the 0-80 cm soil layer was NT 〉 PT 〉 RT, and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced effects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage effects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.
文摘北方森林因其面积大、土壤碳储量高以及对全球暖化响应敏感而在全球碳平衡和气候系统中起着至关重要的作用。土壤呼吸和木质残体分解释放出的 CO2 通量是北方森林生态系统输入大气圈的最主要的碳源。量化这个通量并深刻理解其中的机理过程 ,是评价和预测北方森林在全球变化中的作用必不可少的内容。综述了北方森林生态系统土壤呼吸和木质残体分解释放出的 CO2 通量随生态系统类型及环境条件而变化的一般格局以及自养呼吸和异氧呼吸在土壤表面 CO2 通量中的相对贡献 ;分析了影响北方森林土壤呼吸的主要生物物理因子 ;讨论了该领域研究存在的问题和今后的研究方向 ;并强调木质残体分解释放出的 CO2 通量虽然在以往的森林生态系统碳平衡研究中常被忽略 。
