Nitrogen alters carbon dynamics during early succession in boreal forest
Nitrogen alters carbon dynamics during early succession in boreal forest
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DOI：
10.1016/j.soilbio.2010.03.026
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发表时间：
2010-07-01
影响因子：
9.7
通讯作者：
Treseder, Kathleen
中科院分区：
文献类型：
--
作者：
Allison, Steven D.;Gartner, Tracy B.;Treseder, Kathleen
北方森林是木材产品的重要来源，可以使用化肥来提高森林产量，特别是在北方地区养分贫乏的地区。随着气候变化，火灾频率可能会增加，导致北方景观在早期演替阶段所占比例更大。由于大多数施肥研究都集中在成熟的北方森林上，被烧毁的北方生态系统对养分供应增加的反应尚不清楚。因此，我们使用氮肥(N)施肥实验来测试最近燃烧的北方生态系统中的C循环将如何响应增加的N有效性。我们假设，施肥将增加分解速度、土壤呼吸和参与碳循环的胞外酶的活性，从而减少土壤碳储量。与我们的假设一致，随着氮素的添加，凋落物质量损失显著增加，纤维素酶和甲壳素降解酶的活性增加了45%-61%。我们还观察到有机土层中的C含量从19.5+/-0.7%显著下降到13.5+/-0.6%，并且在施肥区有降低土壤总碳储量的趋势。与我们的假设相反，三个生长季节的平均土壤呼吸从78.3+/-6.5 mg CO2-Cm(-2)h(-1)下降到54.4+/-4.1 mg CO2-Cm(-2)h(-1)。尽管施N使地上净初级生产力增加了2.5倍，但这些变化还是发生了，并伴随着以子囊菌为主导的真菌群落结构的显著变化。我们的结果表明，早期演替的北方生态系统的C循环对N的添加有很高的响应。施肥会导致土壤碳的初始损失，然后是土壤碳底物的枯竭和真菌群落的形成。微生物总生物量下降和呼吸速率没有跟上植物投入的步伐。这些模式表明，在火灾频发的北方地区，氮肥可能会暂时减少生态系统的碳储量，但随后会增加。(C)2010爱思唯尔有限公司。保留所有权利。
Boreal forests are an important source of wood products, and fertilizers could be used to improve forest yields, especially in nutrient poor regions of the boreal zone. With climate change, fire frequencies may increase, resulting in a larger fraction of the boreal landscape present in early-successional stages. Since most fertilization studies have focused on mature boreal forests, the response of burned boreal ecosystems to increased nutrient availability is unclear. Therefore, we used a nitrogen (N) fertilization experiment to test how C cycling in a recently-burned boreal ecosystem would respond to increased N availability. We hypothesized that fertilization would increase rates of decomposition, soil respiration, and the activity of extracellular enzymes involved in C cycling, thereby reducing soil C stocks. In line with our hypothesis, litter mass loss increased significantly and activities of cellulose- and chitin-degrading enzymes increased by 45-61% with N addition. We also observed a significant decline in C concentrations in the organic soil horizon from 19.5 +/- 0.7% to 13.5 +/- 0.6%, and there was a trend toward lower total soil C stocks in the fertilized plots. Contrary to our hypothesis, mean soil respiration over three growing seasons declined by 31% from 78.3 +/- 6.5 mg CO2-C m(-2) h(-1) to 54.4 +/- 4.1 mg CO2-C m(-2) h(-1). These changes occurred despite a 2.5-fold increase in aboveground net primary productivity with N, and were accompanied by significant shifts in the structure of the fungal community, which was dominated by Ascomycota. Our results show that the C cycle in early-successional boreal ecosystems is highly responsive to N addition. Fertilization results in an initial loss of soil C followed by depletion of soil C substrates and development of a distinct and active fungal community. Total microbial biomass declines and respiration rates do not keep pace with plant inputs. These patterns suggest that N fertilization could transiently reduce but then increase ecosystem C storage in boreal regions experiencing more frequent fires. (C) 2010 Elsevier Ltd. All rights reserved.