Nitrogen availability effects on carbon mineralization, fungal and bacterial growth, and enzyme activities during decomposition of wheat straw in soil
Nitrogen availability effects on carbon mineralization, fungal and bacterial growth, and enzyme activities during decomposition of wheat straw in soil
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DOI：
10.1016/s0038-0717(99)00030-9
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发表时间：
1999-07-01
影响因子：
9.7
通讯作者：
Breland, TA
中科院分区：
文献类型：
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作者：
Henriksen, TM;Breland, TA
我们的目标是：（1）在温度（15℃）和湿度（-10 kPa）可控的微观实验中，研究小麦（Triticum aestivum L.）秸秆分解对氮有效性增加（秸秆干物质含氮量分别为0.5%、0.8%、1.2%和1.9%）的响应；（2）在微生物群落水平阐明潜在机制；（3）根据测量结果建立一个模型。当秸秆干物质中有效氮（秸秆氮和土壤无机氮）浓度低于1.2%时，会显著降低秸秆残留碳矿化速率以及土壤微生物总生物量（氯仿熏蒸 - 提取法测定）的增长。在土壤矿质氮库耗尽后不久，负面影响就会出现。氮对微生物群落的影响主要是由真菌生长（麦角固醇测定）减少引起的，而细菌总生物量（落射荧光显微镜测定）没有受到显著影响。然而，产纤维素酶的菌落形成细菌单位数量随着氮有效性降低而减少。在添加秸秆的土壤中，氮浓度降低会使外切纤维素酶、内切纤维素酶和半纤维素酶的活性降低，而在未添加秸秆的对照土壤中，影响则相反。我们建立了一个模型，根据近似分析（Van Soest法）确定的秸秆残留的三个部分以及一个腐殖质库，假定它们按照一级速率动力学分解。根据微生物测量结果，将微生物群落细分为三组，分别消耗易分解物质、结构物质和腐殖质。当全纤维素分解速率作为氮有效性的函数进行修正时，该模型很好地模拟了氮对碳矿化和微生物生物量增长的影响。我们的实验表明，在氮浓度远高于田间谷物收获后常见浓度时，小麦秸秆矿化可能会受阻，并且在对农业土壤中碳和氮周转进行建模时，应考虑氮有效性的影响。此外，该试验举例说明了一种情况，即需要对分解生物的功能群进行研究，才能令人满意地解释和模拟在过程水平上观察到的差异。（C）1999 Elsevier Science Ltd.保留所有权利。
Our objectives were (1) to investigate the response of wheat (Triticum aestivum L.) straw decomposition to increasing nitrogen availability (0.5, 0.8, 1.2 and 1.9% N of straw dry matter) in a microcosm experiment at controlled temperature (15 degrees C) and moisture (-10 kPa), (2) to elucidate underlying mechanisms at the microbial-community level, and (3) to develop a model according to the measurements. Concentrations of available N (straw N and soil inorganic N) below 1.2% of straw dry matter significantly reduced the rate of carbon mineralization from straw residues and the growth of total soil microbial biomass (chloroform fumigation-extraction). The negative effects appeared shortly after the pool of soil mineral N had been depleted. The N effect on the microbial community was mainly caused by reduced fungal growth (ergosterol), while total bacterial biomass (epifluorescence microscopy) was not significantly affected. However, number of cellulase-producing, colony-forming bacterial units decreased with decreasing N availability. In straw-amended soil, decreasing N concentrations reduced activities of exocellulase, endocellulase and hemicellulase, while in unamended control soil the effects were opposite. We developed a model in which three fractions of straw residues, determined by proximate analysis (Van Soest), and a humus pool were assumed to decay according to first-order rate kinetics. In accordance with the microbial measurements, the microbial community was subdivided into three groups consuming readily decomposable, structural and humus materials respectively. When holocellulose decay rate was modified as a function of N availability, the model simulated N effects on C mineralization and microbial biomass growth very well. Our experiment showed that wheat straw mineralization may be retarded at N concentrations well above those frequently found after grain harvest in the field and that effects of N availability should be taken into account when modelling C and N turnover in agricultural soils. Moreover, the trial exemplified a situation where studies of functional groups of decomposer organisms were required to explain and model satisfactorily differences observed at the process level. (C) 1999 Elsevier Science Ltd. All rights reserved.