The Effects of Snow, Soil Microenvironment, and Soil Organic Matter Quality on N Availability in Three Alaskan Arctic Plant Communities
The Effects of Snow, Soil Microenvironment, and Soil Organic Matter Quality on N Availability in Three Alaskan Arctic Plant Communities
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DOI：
10.1007/s10021-011-9447-5
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发表时间：
2011-08-01
期刊：
影响因子：
3.7
通讯作者：
Bret-Harte, M. Syndonia
中科院分区：
文献类型：
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作者：
DeMarco, Jennie;Mack, Michelle C.;Bret-Harte, M. Syndonia
北极气候变暖可能导致从以禾本科植物为主转变为以灌木为主，进而可能通过灌木对碳(C)和氮(N)的生物地球化学循环的非生物和/或生物控制而改变生态系统的结构和功能。在阿拉斯加图利克湖附近的北极冻土带，我们量化了环境和操纵雪处理下三种不同植物群落的净N矿化速率，这些植物群落的落叶灌木丰度不同。我们的目标有两个：(1)测试北极落叶灌木周围的积雪量是否保持了足够高的冬季土壤温度，以刺激微生物活动并增加土壤N水平(土壤小气候的影响)；(2)通过对N矿化的主要驱动因素-土壤有机质质量与小气候的影响，比较雪和灌木对N有效性的相对影响。冬季雪量增加对土壤氮素矿化速率有正向影响，但对冬季影响不明显。夏季土壤有机质质量对氮矿化的影响是土壤小气候的9倍，冬季只有土壤有机质质量对氮矿化有显著影响。在短时间尺度上，灌木与雪的相互作用可能主要通过对夏季土壤微环境的影响来增加植物有效氮的含量。此外，土壤有机质质量的差异可能会导致净N矿化的差异大于我们在三个地点看到的土壤小气候的变化。
Climate warming in The Arctic may lead to a shift from graminoid to shrub dominance, which may, in turn, alter the structure and function of the ecosystem through shrub influences on the abiotic and/or biotic controls over biogeochemical cycles of carbon (C) and nitrogen (N). In Arctic tundra, near Toolik Lake, Alaska, we quantified net N-mineralization rates under ambient and manipulated snow treatments at three different plant communities that varied in abundance of deciduous shrubs. Our objective was twofold: (1) to test whether the amount of snow that can accumulate around Arctic deciduous shrubs maintains winter soil temperatures high enough to stimulate microbial activity and increase soil N levels (effect of soil microclimate) and (2) to compare the relative effects of snow versus shrubs on N availability via effects on the main drivers of N-mineralization: SOM quality versus microclimate. Winter snow addition had a positive effect on summer, but not winter, N-mineralization rates. Soil organic matter quality had a nine times larger effect on N-mineralization than did soil microclimate in the summer season and only SOM quality had a detectable effect on N-mineralization in the winter. Here we conclude that on a short time scale, shrub interactions with snow may play a role in increasing plant available N, primarily through effects on the summer soil microenvironment. In addition, differences in SOM quality can drive larger differences in net N-mineralization than changes in soil microclimate of the magnitude of what we saw across our three sites.