The effects of drought and timing of precipitation on the inter-annual variation in ecosystem-atmosphere exchange in a Mediterranean grassland
The effects of drought and timing of precipitation on the inter-annual variation in ecosystem-atmosphere exchange in a Mediterranean grassland
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DOI：
10.1016/j.agrformet.2011.01.008
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发表时间：
2011-05-15
影响因子：
6.2
通讯作者：
Pio, Casimiro Adriao
中科院分区：
文献类型：
--
作者：
Jongen, Marjan;Pereira, Joao Santos;Pio, Casimiro Adriao
我们研究了季节和年际变化的碳，水和能量通量在地中海草地生态系统在葡萄牙，占主导地位的一年生物种，使用涡度协方差技术。研究期间，从2004年到2008年，其特点是高的年内和年际降水变化：2004-2005年和2007-2008年的水文年降水量低于平均水平（“干旱”年），而其他两个水文年的降水量高于平均水平能量分配到感热（H）和潜热（λ E）通量的变化与土壤含水量的变化，与植物的出苗和衰老相一致。年综合生态系统净碳交换（NEE）对干旱高度敏感，在“湿润”年表现为碳汇（如CO2，CO2）。2005-2006年，-190克C m（-2）y（-1）），在“干旱”年份（例如，2004-2005年，+49 g Cm（-2）y（-1））。年综合NEE与年降水量呈负相关（r（2）=0.78）。然而，降水的时间影响NEE，个别雨事件在旱季导致大脉冲的生态系统呼吸（R-eco）。生长季节高峰期的低降水量，如2007年春季，减少了碳固存。NEE年际变化的最佳描述因子是叶面积持续期（LAD），可解释96%的变异，平均辐射利用效率（芸香）为1.59 g MJ（-1），内在水分利用效率（IWUE）为24.6 g C hPa kg（-1）H2O。芸香和IWUE的年际变化趋势相似，反映了生产力和降水时间的差异，我们的研究表明，在地中海环境中的碳和能量通量强烈依赖于水的可用性。(C)2011 Elsevier B. V.保留所有权利。
We studied the seasonal and inter-annual variation in carbon, water and energy fluxes over a Mediterranean grassland ecosystem in Portugal, dominated by annual species, using the eddy-covariance technique. The study period, from 2004 to 2008, was characterised by high intra- and inter-annual precipitation variation: the hydrological years 2004-2005 and 2007-2008 had precipitation below average ('dry' years) whereas the other two hydrological years had precipitation above average ('wet' years).The variation in energy partitioning into sensible heat (H) and latent heat (lambda E) fluxes was associated with changes in soil water content, coinciding with plant emergence and senescence. The ecosystem was lambda E-dominated in those periods with soil water content above 15%, and became H-dominated when soil water content fell below 15%.Annually integrated net ecosystem carbon exchange (NEE) was highly sensitive to drought, varying from a carbon sink in 'wet' years (e.g., 2005-2006, -190 g C m(-2) y(-1)), to a carbon source in 'dry' years (e.g., 2004-2005, +49 g C m(-2) y(-1)). There was a negative correlation between annually integrated NEE and annual precipitation (r(2) =0.78). However, timing of precipitation influenced NEE, with individual rain events in the dry season resulting in large pulses of ecosystem respiration (R-eco). Low precipitation at the peak of the growing season, as in the spring of 2007, decreased carbon sequestration. The best descriptor for inter-annual variation in NEE was leaf area duration (LAD), which explained 96% of the variance.Average radiation-use efficiency (RUE) was 1.59 g MJ(-1) and inherent water-use efficiency (IWUE) was 24.6 g C hPa kg(-1) H2O. RUE and IWUE had similar trends in inter-annual variation, reflecting differences in productivity and timing of precipitation.Our study showed that carbon and energy fluxes in this Mediterranean environment depended strongly upon water availability. (C) 2011 Elsevier B.V. All rights reserved.