Sunlight Doubles Aboveground Carbon Loss in a Seasonally Dry Woodland in Patagonia
Sunlight Doubles Aboveground Carbon Loss in a Seasonally Dry Woodland in Patagonia
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DOI：
10.1016/j.cub.2020.06.005
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发表时间：
2020-08-17
期刊：
影响因子：
9.2
通讯作者：
Austin, Amy T.
中科院分区：
文献类型：
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作者：
Berenstecher, Paula;Vivanco, Lucia;Austin, Amy T.
由于暴露于太阳辐射，地上衰老植物材料（植物凋落物）的光降解已被确定为半干旱生态系统中碳（C）损失的主要控制因素[1]，颠覆了仅基于可用水分和凋落物质量的传统C循环模型。除了有机物的光化学矿化作用[1，2]，阳光也会改变植物凋落物中细胞壁的化学性质[3，4]，使其更容易受到后续生物降解的影响[5-7]。然而，阳光照射，气候季节性和生物分解对碳周转的交互作用在陆地生态系统中仍然没有得到解决。我们在这里表明，暴露在阳光下加速凋落物分解在巴塔哥尼亚林地有一个显着的干燥的夏季。对初始分解的控制随季节而变化，从干燥夏季的直接光化学矿化到潮湿冬季的生物降解。通过操纵植物凋落物使用光谱过滤器，衰减紫外线和短波可见光接收到的阳光，我们表明，直接光降解及其遗产，与增加微生物获得不稳定的碳水化合物，是负责地上碳周转在这个地中海型气候加速。在2年的时间里，在整个植物物种中，暴露在全太阳光谱下的垃圾分解速度是接受衰减阳光的垃圾的两倍。由于预计干旱和旱季长度增加而导致的植被覆盖或生物多样性变化[8]可能会加剧阳光照射引起的地上垃圾中的碳损失，对特别容易受到全球变化影响的生态系统中的碳平衡产生负面影响[9]。
Photodegradation of aboveground senescent plant material (plant litter) due to exposure to solar radiation has been identified as a dominant control on carbon (C) loss in semi-arid ecosystems [1], upturning traditional models of C cycling based only on available moisture and litter quality. In addition to the photochemical mineralization of organic matter [1, 2], sunlight alters the chemistry of cell walls in plant litter [3, 4], making them more susceptible to subsequent biotic degradation [5-7]. Nevertheless, the interactive effects of sunlight exposure, climate seasonality, and biotic decomposition on C turnover remain unresolved in terrestrial ecosystems. We show here that exposure to sunlight accelerated litter decomposition in a Patagonian woodland with a marked dry summer season. Controls on initial decomposition varied seasonally from direct photochemical mineralization in the dry summer to biotic degradation in the wet winter. By manipulating sunlight received by plant litter using spectral filters that attenuated ultraviolet and short-wave visible light, we demonstrate that direct photodegradation and its legacy, associated with increased microbial access to labile carbohydrates, are responsible for the acceleration of aboveground C turnover in this Mediterranean-type climate. Across plant species and over a 2-year period, litter exposed to the full solar spectrum decomposed twice as fast as litter that received attenuated sunlight. Changes in vegetation cover or biodiversity due to projected increased drought and dry season length [8] will likely exacerbate C losses from aboveground litter due to sunlight exposure, negatively impacting the C balance in ecosystems that are particularly vulnerable to global change [9].