Modeling long-term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition
Modeling long-term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition
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DOI：
10.1002/eap.1413
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发表时间：
2017-01-01
影响因子：
5
通讯作者：
Kwiatkowski, Bonnie L.
中科院分区：
文献类型：
--
作者：
Jiang, Yueyang;Rastetter, Edward B.;Kwiatkowski, Bonnie L.
为了研究火灾后控制冻土带碳(C)和养分长期恢复的潜在机制，我们使用多元素限制(MEL)模型模拟了火灾后200年内沿烧伤严重程度梯度的三个地点的生物地球化学变化，以响应气温、二氧化碳浓度、氮(N)沉积和磷(P)风化速率的增加。这些模拟是针对严重燃烧、中度燃烧和未燃烧的北极冻土带进行的。我们的模拟表明，火灾后碳平衡的恢复主要取决于生态系统各组成部分之间养分的内部再分配(受气温控制)，而不是来自外部的养分供应(如氮的沉积和固定、磷的风化)。气温和大气CO2浓度的升高导致(1)养分从土壤有机质向植被的净转移；(2)植被和土壤有机质中C：养分比的增加。这些变化导致了植被生物量碳的增加，但土壤有机碳储量的净损失。在气候变暖的情况下，野火中失去的养分很难恢复，因为变暖导致养分循环的加速，导致系统通过淋溶进一步净流失养分。在燃烧和未燃烧的冻土带中，气候变暖导致的养分循环加速和生态系统碳储量的增加最终受到土壤C：养分比率增加的限制，这增加了微生物对土壤中植物有效养分的保留。养分的加速周转、碳的流失和土壤温度的升高可能会导致植被的变化，从而进一步调节长期的生物地球化学演替。我们的分析应该有助于评估冻土带C的预算和火灾后生物地球化学功能的恢复，而这反过来又是维持野生动物栖息地和冻土带植被所必需的。
To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-yr post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO2 concentration, nitrogen (N) deposition, and phosphorus (P) weathering rates. The simulations were conducted for-severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e. g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO2 concentration resulted in (1) a net transfer of nutrient from soil organic matter to vegetation and (2) higher C : nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C : nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra vegetation.