Impact of forest conversion to agriculture on carbon and nitrogen mineralization in subarctic Alaska
Impact of forest conversion to agriculture on carbon and nitrogen mineralization in subarctic Alaska
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DOI：
10.1023/a:1024976713243
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发表时间：
2003-03
期刊：
影响因子：
4
通讯作者：
J. Grünzweig;S. D. Sparrow;F. S. Chapin
中科院分区：
文献类型：
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作者：
J. Grünzweig;S. D. Sparrow;F. S. Chapin
土地利用变化可能是高纬度地区全球变化的一个主要组成部分，可能导致土壤碳和氮循环的重大改变。我们解决了完全复制的黑云杉森林和农田的不同年龄（以下毁林），并根据不同的管理制度在阿拉斯加内陆的土地利用变化的地球化学影响。从森林到耕地的变化使夏季表层土壤温度升高了4-5 °C，生物活动季节延长了两到三周。一个共同的基板（燕麦残茬）的分解提高了25%，在外地相比，森林后，垃圾袋埋了一年。在现场特定的土壤中的净氮矿化率在夏季森林和领域是相似的，但在冬季，森林是唯一的网站，净氮固定发生。田间年龄和管理对C和N矿化有显著影响。年分解率，土壤呼吸和夏季净氮矿化倾向于在年轻的比在老领域和较高的休闲比种植的年轻领域。为了确定控制C和N矿化的主要环境因子，研究了土壤温度、水分和N有效性。分解和净氮矿化似乎主要由无机氮的有效性驱动。土壤温度只在比较森林和农田时起作用，而在农田与农田之间的差异中不起作用。从土壤呼吸测量结果证实，在外地的异养呼吸，从而分解温度的敏感性低。此外，土壤呼吸和净氮矿化都受到低土壤水分含量的限制。研究表明：（1）森林采伐促进了亚北极土壤C、N矿化;（2）在控制森林采伐后C、N矿化方面，N有效性比土壤温度更重要。预测高纬度地区土地利用变化的地球化学影响需要更好地了解其与全球变化的其他因素，如气候变化和氮沉降的相互作用。
Land-use change is likely to be a major component of global change at high latitudes, potentially causing significant alterations in soil C and N cycling. We addressed the biogeochemical impacts of land-use change in fully replicated black spruce forests and agricultural fields of different ages (following deforestation) and under different management regimes in interior Alaska. Change from forests to cultivated fields increased summer temperatures in surface soil layers by 4–5 °C, and lengthened the season of biological activity by two to three weeks. Decomposition of a common substrate (oat stubble) was enhanced by 25% in fields compared to forests after litter bags were buried for one year. In-situ net N mineralization rates in site-specific soil were similar in forests and fields during summer, but during winter, forests were the only sites where net N immobilization occurred. Field age and management had a significant impact on C and N mineralization. Rates of annual decomposition, soil respiration and summer net N mineralization tended to be lower in young than in old fields and higher in fallow than in planted young fields. To identify the major environmental factors controlling C and N mineralization, soil temperature, moisture and N availability were studied. Decomposition and net N mineralization seemed to be mainly driven by availability of inorganic N. Soil temperature played a role only when comparing forests and fields, but not in field-to-field differences. Results from soil respiration measurements in fields confirmed low sensitivity of heterotrophic respiration, and thus decomposition to temperature. In addition, both soil respiration and net N mineralization were limited by low soil water contents. Our study showed that (1) C and N mineralization are enhanced by forest clearing in subarctic soils, and (2) N availability is more important than soil temperature in controling C and N mineralization following forest clearing. Projecting the biogeochemical impacts of land-use change at high latitudes requires an improved understanding of its interactions with other factors of global change, such as changing climate and N deposition.