Sustained impact of drought on wet shrublands mediated by soil physical changes
Sustained impact of drought on wet shrublands mediated by soil physical changes
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DOI：
10.1007/s10533-014-0059-y
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发表时间：
2015-04
期刊：
影响因子：
4
通讯作者：
M. Domínguez;A. Sowerby;Andrew R. Smith;D. Robinson;Susie Baarsel;R. Mills;M. Marshall;Eva K. Koller-E
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文献类型：
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作者：
M. Domínguez;A. Sowerby;Andrew R. Smith;D. Robinson;Susie Baarsel;R. Mills;M. Marshall;Eva K. Koller-E
预计的气候变暖可能会大幅增加潮湿有机土壤的碳排放，从而促进陆地碳循环和气候变化之间的正反馈。有证据表明，在这些土壤中，由于碳基质的大量可利用性，变暖对土壤呼吸的刺激可以持续很长一段时间。然而，湿有机土壤对干旱的长期反应仍不确定。有机矿物土壤可能特别脆弱，因为它们的土壤水分池对缓解干旱事件的作用有限。利用北威尔士(英国)全生态系统气候变化实验，我们发现来自潮湿灌丛的灰化(有机-矿物)土壤的土壤呼吸更容易受到反复干旱的影响，而不是对气候变暖的影响，而且干旱的影响在十年尺度上并没有减弱。干旱对土壤呼吸的刺激与土壤结构的重大变化有关，与对照相比，土壤结构的变化导致持水量下降了54%。苔藓植物的丰富可以缓冲土壤水分的流失，减缓变暖条件下土壤CO2的排放。由于没有证据表明植物生产力的变化抵消了干旱下土壤碳排放的增加，这种反应可能会产生积极的气候反馈。结果表明，次优势植被和土壤物理性质的变化在确定气候变化对土壤碳动态的影响方面可能具有潜在的关键作用。
Projected climate warming may substantially increase carbon emissions from wet organic soils, contributing to a positive feedback between the terrestrial carbon cycle and climate change. Evidence suggests that in these soils the stimulation of soil respiration by warming can be sustained over long periods of time due to the large availability of C substrates. However, the long-term response of wet organic soils to drought remains uncertain. Organo-mineral soils might be particularly vulnerable, because of their limited soil moisture pool to buffer drought events. Using a whole-ecosystem climate-change experiment in North Wales (UK) we show that soil respiration in podzolic (organo-mineral) soils from wet shrublands is more vulnerable to recurrent drought than to warming, and that the drought impact does not attenuate at decadal time scales. Stimulation of soil respiration by drought was linked to major changes in soil structure that led to a 54 % reduction in water holding capacity compared to control. Bryophyte abundance was found to buffer soil moisture losses, moderating soil CO2efflux under warming. As there was no evidence of change in plant productivity to offset the increased soil C emissions under drought, this response may result in a positive climate feedback. The results indicate the potentially critical role that changes in sub-dominant vegetation and in soil physical properties may have in determining climate change impacts on soil C dynamics.