Repeated freeze-thaw cycles and their effects on biological processes in two arctic ecosystem types
Repeated freeze-thaw cycles and their effects on biological processes in two arctic ecosystem types
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DOI：
10.1016/s0929-1393(02)00093-8
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发表时间：
2002-10-01
影响因子：
4.8
通讯作者：
Michelsen, A
中科院分区：
文献类型：
--
作者：
Larsen, KS;Jonasson, S;Michelsen, A
分别来自高海拔和低海拔的两个亚北极石南群落的中生态系统，在不同的植被组成下，进行了18个昼夜冻融循环的实验，这些循环在白天温度为+2 ℃和夜间温度为-4 ℃之间波动。与未冻（+2 ℃）和冻（-4 ℃）的围隔生态系统相比，循环围隔生态系统中的围隔生态系统呼吸始终较低和较高。当外推到整个非生长季节时，我们的数据表明非生长季节的碳（C）损失约为20-30 g C m（-2），与每年150-200 g C m（-2）的植物生物量C的可能年结合量相比，这是相当大的。结果支持了冬季碳通量必须包括在北极生态系统的年度碳收支的假设。微生物生物量C仅在循环的围隔生态系统中下降，表明虽然微生物活动主要受温度控制，但微生物生物量受冰点附近温度波动的强烈影响。与微生物碳相反，微生物生物量氮（N）质量在循环围隔中没有变化，导致微生物C/N比降低。第二，土壤中的无机氮浓度下降的循环，表明微生物生存的冻融循环具有很高的潜力，土壤中的N和N，大概是从死微生物释放。这两组的围隔反应非常相似的冻融循环，表明所观察到的响应多个昼夜冻融循环是常见的两种生态系统类型，尽管在植物物种组成和气候的差异。(C)2002爱思唯尔科技有限公司。保留所有权利。
Mesocosms from two subarctic heaths from high and low altitudes, respectively, and differing in the composition of vegetation were experimentally subjected to 18 diurnal freeze-thaw cycles fluctuating between day temperatures of +2degreesC and night temperatures of -4degreesC. Mesocosm respiration was consistently lower and higher in cycled mesocosms compared to mesocosms kept unfrozen (+2degreesC) and frozen (-4degreesC), respectively. When extrapolated to the entire non-growing season, our data suggest a non-growing season carbon (C) loss in the order of 20-30 g C m(-2), which is substantial compared with a likely annual incorporation of plant biomass C of 150-200 g C m(-2) per year. The results support the hypothesis that winter carbon fluxes must be included in annual carbon budgets for arctic ecosystems.Microbial biomass C decreased only in cycled mesocosms, indicating that while microbial activity is mainly controlled by temperature, microbial biomass is strongly affected by temperature fluctuations around the freezing point. In contrast to microbial C, microbial biomass nitrogen (N) mass did not change in cycled mesocosms, leading to decreased microbial C to N ratio. Second, soil inorganic N concentration declined in the soils subjected to the cycles, showing that microbes surviving the freeze-thaw cycles had a high potential for sequestering soil N and N that presumably was released from dead microbes. The two sets of mesocosms responded very similarly to the freeze-thaw cycles, indicating that the observed responses to multiple diurnal freeze-thaw cycles are common for both ecosystem types despite the differences in plant species composition and climate. (C) 2002 Elsevier Science B.V. All rights reserved.