Biogeosciences报道了中科院植物研究所万师强课题组在内蒙古典型温带草原开展的全球变化生态学的研究成果,肯定了该项研究的重要意义。
气候变化与陆地生态系统反馈关系的模拟和预测存在很大的不确定性。大尺度模型通常采用平均温带作为气候驱动因子来模拟陆地生态系统碳循环对气候变暖的响应和反馈;这些模型包括了两种潜在的假设:(1)均匀的白天和夜间增温幅度;(2)全天增温的效应等于白天和夜间的增温效应之和。然而,过去半个世纪全球的温度纪录显示,夜间最低温度的增温幅度比白天最高温度的增温幅度高出一倍,因此第一种假设被否定。虽然来自北美洲矮草草原植物和菲律宾水稻产量的证据显示昼夜不对称增温和对称增温对陆地植物的生长和碳积累的影响可能不同,但是到目前为止,还没有关于昼夜不对称增温如何影响陆地生态系统碳循环的直接实验证据和报道,因此也不能证实和否定上述第二种假设。
针对这一问题,植物所万师强课题组于2006年4月开始,在内蒙古典型温带草原开展了一个包括四种处理的实验:对照,白天增温(早上6点到晚上6点)、夜间增温(晚上6点到早上6点)和全天增温(24小时)。经过3年的处理和对土壤呼吸的测定,研究人员发现:不论是对土壤呼吸代表的碳释放还是总生态系统生产力代表的碳吸收而言,全天增温的效应均小于白天和夜间的增温效应之和。该研究结果说明不能利用全天增温的效应来预测自然条件下发生的昼夜不对称增温对陆地生态系统碳循环的影响,从而否定了利用平均温度作为气候驱动因子的模型中的第二种假设。同时为改进和完善气候变化-碳循环反馈关系的模型模拟和预测提供了直接、关键的实验证据和参数估计。
该研究项目在国家自然科学基金委重大研究计划“全球变化与区域效应”重点项目“全球变暖背景下白天和夜间增温对温带草原群落结构和生态系统功能的特异性影响”资助下完成。(生物谷Bioon.com)
生物谷推荐原始出处:
Biogeosciences, 6, 1361-1370, 2009
Effects of diurnal warming on soil respiration are not equal to the summed effects of day and night warming in a temperate steppe
J. Xia1,2, Y. Han1,2, Z. Zhang1,2, Z. Zhang1,2, and S. Wan1
1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing 100093, China
2Graduate School of Chinese Academy of Sciences, Yuquanlu, Beijing 100049, China
Abstract. The magnitude of daily minimum temperature increase is greater than that of daily maximum temperature increase under climate warming. This study was conducted to examine whether changes in soil respiration under diurnal warming are equal to the summed changes under day and night warming in a temperate steppe in northern China. A full factorial design with day and night warming was used in this study, including control, day (06:00 a.m.–06:00 p.m., local time) warming, night (06:00 p.m.–06:00 a.m.) warming, and diurnal warming. Day warming showed no effect on soil respiration, whereas night warming significantly increased soil respiration by 7.1% over the 3 growing seasons in 2006–2008. The insignificant effect of day warming on soil respiration could be attributable to the offset of the direct positive effects of increased temperature by the indirect negative effects via aggravating water limitation and suppressing ecosystem C assimilation. The positive effects of night warming on soil respiration were largely due to the stimulation of ecosystem C uptake and substrate supply via overcompensation of plant photosynthesis. Changes in both soil respiration (+20.7 g C m?2 y?1) and GEP (?2.8 g C m?2 y?1) under diurnal warming are smaller than their summed changes (+40.0 and +24.6 g C m?2 y?1, respectively) under day and night warming. Our findings that the effects of diurnal warming on soil respiration and gross ecosystem productivity are not equal to the summed effects of day and night warming are critical for model simulation and projection of climate-carbon feedback.