The effect of soil freezing on N cycling: comparison of two headwater subcatchments with different vegetation and snowpack conditions in the northern Hokkaido Island of Japan
The effect of soil freezing on N cycling: comparison of two headwater subcatchments with different vegetation and snowpack conditions in the northern Hokkaido Island of Japan
复制标题
DOI：
10.1007/s10533-008-9189-4
复制
发表时间：
2008-03-01
期刊：
影响因子：
4
通讯作者：
Mitchell, Myron J.
中科院分区：
文献类型：
--
作者：
Christopher, Sheila F.;Shibata, Hideaki;Mitchell, Myron J.
气候变化模型预测，温带森林的积雪将发育得更晚，也更浅，导致土壤冻结的倾向更高。在日本最北部的岛屿北海道，积雪深度从西向东递减。这种积雪深度梯度为测试不同积雪和土壤冻结对氮生物地球化学的影响提供了独特的机会。北海道东部石北峡试验林的石北峡北部流域为落叶乔木，年平均积雪量为0.7 m；北海道西部乌里游试验林M3流域为落叶与针叶树混合树种，年平均积雪量为2.0 m。作者于2004年10月至2005年4月进行了一项研究，以确定石巴查和乌尔渝土壤可提取氮、氮矿化和硝化作用的差异是否受到冬季土壤冻结变化或影响森林地面质量的树种组成的控制。乌林林底落叶与针叶混交林的C:N比（25.0比22.4）、木质素：N比（15比8.8）和木质素浓度（0.28比0.18 g木质素g(-1)）较高。森林地表质量的差异导致石别查的净氮矿化和硝化作用高于乌玉。在什别查，土壤在整个研究过程中一直处于冻结状态。对于乌尔尤来说，除了早期气温较低且没有降雪外，土壤基本上是不冻结的。由于冬初寒冷期和土壤冻结，可提取土壤NH4+没有变化，但NO3-有所增加。在石北峡和乌玉之间进行0 ~ 5 cm矿质土的反向移植，并在0、5和30 cm处进行冬季培养，结果表明，无论土壤来源如何，土壤冻结导致净氮矿化增加，而硝化作用降低。在评价具有土壤冻结倾向的温带生态系统间氮动态差异时，应考虑土壤冻结的影响。
Climate change models predict that the snowpacks of temperate forests will develop later and be shallower resulting in a higher propensity for soil freezing. In the northern most island of Japan, Hokkaido, snowpack depth decreases from west to east. This snowpack depth gradient provided a unique opportunity to test the effects of variable snowpack and soil freezing on N biogeochemistry. The Shibecha Northern Catchment in Shibecha Experimental Forest, eastern Hokkaido had deciduous trees and a mean annual snowpack of 0.7 m while the M3 catchment in Uryu Experimental Forest, western Hokkaido had mixed deciduous and coniferous tree species and a mean annual snowpack of 2.0 m. We conducted a Weld study (October 2004-April 2005) to determine if differences in Shibecha and Uryu soil extractable N, N mineralization, and nitrification were controlled by the variability in soil freezing during winter or tree species composition that affected the quality of the forest floor. The mixed deciduous and coniferous trees forming the Uryu forest floor had a higher C:N ratio (25.0 vs. 22.4 at Shibecha), higher lignin: N ratio (15 vs. 8.8), and higher lignin concentrations (0.28 vs. 0.18 g lignin g(-1)). These differences in forest floor quality contributed to higher net N mineralization and nitrification in Shibecha compared to Uryu. In Shibecha, soil remained frozen for the entire study. For Uryu, except for an early period with cold temperatures and no snow, the soil generally remained unfrozen. As a result of the early winter cold period and soil freezing, extractable soil NH4+ did not change but NO3- increased. Reciprocal 0-5 cm mineral soil transplants made between Shibecha and Uryu and incubated during winter at 0, 5, and 30 cm suggested that soil freezing resulted in greater net N mineralization yet lower nitrification regardless of the soil origin. The effect of soil freezing should be considered when evaluating differences in N dynamics between temperate ecosystems having a propensity for soil freezing.