Major changes in forest carbon and nitrogen cycling caused by declining sulphur deposition
Major changes in forest carbon and nitrogen cycling caused by declining sulphur deposition
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DOI：
10.1111/j.1365-2486.2011.02468.x
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发表时间：
2011-10
影响因子：
11.6
通讯作者：
F. Oulehle;C. Evans;J. Hofmeister;R. Krejci;Karolina Tahovská;T. Persson;P. Cudlín;J. Hruska
中科院分区：
文献类型：
--
作者：
F. Oulehle;C. Evans;J. Hofmeister;R. Krejci;Karolina Tahovská;T. Persson;P. Cudlín;J. Hruska
硫（S）和氮（N）沉降是陆地碳（C）和氮循环的重要驱动力。我们分析了15年期间在捷克共和国的高度酸化云杉网站在土壤和树木生物量的C和N池的变化。1995年至2009年，硫的总沉降量从5克/米-2年-1减少到1.1克/米-2年-1，而氮的总沉降量没有变化。在同一时期，Oa层的C和N库分别减少了116 g C和4.2 g N m − 2 yr − 1，总减少量分别为47%和42%。这种损失的C和N可能源于有机质（OM），积累在高酸沉降期间，凋落物分解被抑制。Oa层有机质的损失与20世纪90年代的大量沥滤（90厘米处1.3 g N m − 2 yr − 1）和2006年以来几乎没有沥滤（<0.02 g N m − 2 yr − 1）相吻合。林分地表净氮矿化量也呈下降趋势。这对云杉针叶氮浓度（从17.1到11.4 mg kg − 1），凋落物C/N比（从51到63）的增加以及1994年至2009/2010年间Oi + Oe层C/N比（从23.4到27.3）的显着增加产生了影响。与1990年代相比，2000年代的森林增长率较高，树冠落叶率较低。我们的研究结果表明，减少S沉降对森林有机质循环产生了深远的影响，导致历史生态系统N富集的逆转，硝酸盐淋溶的停止，以及累积的有机土壤C和N储量的重大损失。这些结果对我们理解森林和其他生态系统中氮饱和度和碳封存的控制具有重要意义，受到当前或历史的S沉积。
Sulphur (S) and nitrogen (N) deposition are important drivers of the terrestrial carbon (C) and N cycling. We analyzed changes in C and N pools in soil and tree biomass at a highly acidified spruce site in the Czech Republic during a 15 year period. Total S deposition decreased from 5 to 1.1 g m−2 yr−1 between 1995 and 2009, whereas bulk N deposition did not change. Over the same period, C and N pools in the Oa horizon declined by 116 g C and 4.2 g N m−2 yr−1, a total decrease of 47% and 42%, respectively. This loss of C and N probably originated from organic matter (OM) that had accumulated during the period of high acid deposition when litter decomposition was suppressed. The loss of OM from the Oa horizon coincided with a substantial leaching (1.3 g N m−2 yr−1 at 90 cm) in the 1990s to almost no leaching (<0.02 g N m−2 yr−1) since 2006. Forest floor net N mineralization also decreased. This had consequences for spruce needle N concentration (from 17.1 to 11.4 mg kg−1 in current needles), an increase in litterfall C/N ratio (from 51 to 63), and a significant increase in the Oi + Oe horizon C/N ratio (from 23.4 to 27.3) between 1994 and 2009/2010. Higher forest growth and lower canopy defoliation was observed in the 2000s compared to the 1990s. Our results demonstrate that reducing S deposition has had a profound impact on forest organic matter cycling, leading to a reversal of historic ecosystem N enrichment, cessation of nitrate leaching, and a major loss of accumulated organic soil C and N stocks. These results have major implications for our understanding of the controls on both N saturation and C sequestration in forests, and other ecosystems, subjected to current or historic S deposition.