Nitrogen fixation by biological soil crusts and heterotrophic bacteria in an intact Mojave Desert ecosystem with elevated CO2 and added soil carbon
Nitrogen fixation by biological soil crusts and heterotrophic bacteria in an intact Mojave Desert ecosystem with elevated CO2 and added soil carbon
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DOI：
10.1016/s0038-0717(03)00011-7
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发表时间：
2003-05-01
影响因子：
9.7
通讯作者：
Evans, RD
中科院分区：
文献类型：
--
作者：
Billings, SA;Schaeffer, SM;Evans, RD
生物土壤结皮和自由生活的异养土壤微生物对氮的固定提供了土地中生态系统氮的很大一部分。为了更好地了解 CO2 升高如何影响干旱地区生态系统中的 N-2 固定，我们在暴露于 CO2 升高的完整莫哈韦沙漠生态系统中测量了 C2H2 减少量，作为生物土壤结皮中固氮酶活性的代表，为期 2 年，以及添加或不添加葡萄糖-C 的土壤为期 1 年。我们还测量了地壳和土壤 delta(15)N 和总 N，以评估氮源的变化，并测量了地壳的 delta(13)C，以确定随着 CO2 升高，地壳物种的功能变化。生物土壤结皮对C2H2的平均还原率为76.9+/-5.6μmol C2H4·m(-2)·h(-1)。 CO2 没有显着的影响，但植物间隙的结皮随着 CO2 的升高而表现出固氮酶活性的高度可变性。添加葡萄糖-C 对土壤中 C2H2 的还原率有积极影响。 CO2 升高对土壤固氮酶活性没有影响。植物覆盖影响土壤对碳添加的响应，其中植物间隙的响应最大。添加或不添加C的土壤中C2H2的平均还原率分别为8.5±3.6μmol C2H4·m(-2)·h(-1)和4.8±2.1μmol·m(-2)·h(-1)。地壳和土壤 delta(15)N 和 delta(13)C 值不受 CO2 处理的影响，但确实显示出覆盖类型的影响。植物间隙中的地壳和土壤样本的两次测量值均最低。使用瑞利蒸馏模型对土壤和地壳 [N] 和 delta(15)N 数据进行的分析表明，任何植物群落随 CO2 升高而发生的变化以及随之而来的凋落物组成的变化可能会压倒 N-2 固定的任何生理变化。 (C) 2003 Elsevier Science Ltd. 保留所有权利。
Fixation of N by biological soil crusts and free-living heterotrophic soil microbes provides a significant proportion of ecosystem N in and lands. To gain a better understanding of how elevated CO2 may affect N-2-fixation in aridland ecosystems, we measured C2H2 reduction as a proxy for nitrogenase activity in biological soil crusts for 2 yr, and in soils either with or without dextrose-C additions for 1 yr, in an intact Mojave Desert ecosystem exposed to elevated CO2. We also measured crust and soil delta(15)N and total N to assess changes in N sources, and delta(13)C of crusts to determine a functional shift in crust species, with elevated CO2. The mean rate of C2H2 reduction by biological soil crusts was 76.9 +/- 5.6 mumol C2H4 m(-2) h(-1). There was no significant CO2 effect, but crusts from plant interspaces showed high variability in nitrogenase activity with elevated CO2. Additions of dextrose-C had a positive effect on rates of C2H2 reduction in soil. There was no elevated CO2 effect on soil nitrogenase activity. Plant cover affected soil response to C addition, with the largest response in plant interspaces. The mean rate of C2H2 reduction in soils either with or without C additions were 8.5 +/- 3.6 mumol C2H4 m(-2) h(-1) and 4.8 +/- 2.1 mumol m(-2) h(-1), respectively. Crust and soil delta(15)N and delta(13)C values were not affected by CO2 treatment, but did show an effect of cover type. Crust and soil samples in plant interspaces had the lowest values for both measurements. Analysis of soil and crust [N] and delta(15)N data with the Rayleigh distillation model suggests that any plant community changes with elevated CO2 and concomitant changes in litter composition likely will overwhelm any physiological changes in N-2-fixation. (C) 2003 Elsevier Science Ltd. All rights reserved.