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首页> 外文学位 >Changes in soil labile-carbon indicated by the ratio of microbial biomass-carbon to total organic-carbon in a semi-arid grassland undergoing desertification.
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Changes in soil labile-carbon indicated by the ratio of microbial biomass-carbon to total organic-carbon in a semi-arid grassland undergoing desertification.

机译：半干旱草原荒漠化地区微生物生物量碳与总有机碳的比值表明土壤不稳定碳的变化。

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摘要

Changes in the abundance and spatial distribution of biologically-available (labile) organic carbon fractions in soils can alter the productivity of arid and semi-arid ecosystems, often leading to desertified conditions. Early indicators of this shift are inevitably linked to microbial activity, which responds more rapidly to environmental changes than does total organic-C stored in the soil. To study changes in labile-C in a Chihuahuan desert grassland in southern New Mexico, microbial biomass-C (C{dollar}sb{lcub}rm mic{rcub}{dollar}) and total soil organic-C (C{dollar}sb{lcub}rm org{rcub}{dollar}) were measured along a gradient of long-term grazing impacts, with an ungrazed site chosen to represent steady state conditions with respect to soil organic matter.; Microbial biomass-C estimated using the chloroform fumigation-extraction method ranged from 28.4 {dollar}mu{dollar}g C g{dollar}sp{lcub}-1{rcub}{dollar} to 423.2 {dollar}mu{dollar}g C g{dollar}sp{lcub}-1{rcub}{dollar} for three soil sample categories that included (1) beneath grass canopies, (2) beneath shrub canopies, and (3) in non-vegetated interspaces. Abundances of total soil organic-C ranged from 1.57 mg C g{dollar}sp{lcub}-1{rcub}{dollar} to 6.53 mg C g{dollar}sp{lcub}-1{rcub}{dollar}, and were generally lower in highly-impacted sites. Using the C{dollar}sb{lcub}rm mic{rcub}{dollar} to C{dollar}sb{lcub}rm org{rcub}{dollar} ratio as an indicator of labile-C, values at all sites were near the steady state level beneath grass canopies, suggesting that abundances remain unchanged with higher grazing-related impacts. Beneath shrub canopies, ratio values were generally higher than the steady state level, an indication that soil labile-C fractions are accumulating. In bare soil interspaces, ratio values along the gradient indicated increasingly significant losses of labile-C with higher grazing impacts relative to the steady state level.; The C{dollar}sb{lcub}rm mic{rcub}{dollar} to C{dollar}sb{lcub}rm org{rcub}{dollar} ratio is a better indicator of soil labile-C in this semi-arid ecosystem than either variable alone. The C{dollar}sb{lcub}rm mic{rcub}{dollar} to C{dollar}sb{lcub}rm org{rcub}{dollar} ratio may thus provide a tool for monitoring changes in soil productivity that occur with desertification. (Abstract shortened by UMI.)
机译：土壤中可生物利用的（不稳定的）有机碳组分的丰度和空间分布的变化会改变干旱和半干旱生态系统的生产力，常常导致荒漠化。这种变化的早期迹象不可避免地与微生物活动有关，微生物活动对环境变化的反应比土壤中存储的总有机碳更快。为了研究新墨西哥州南部奇瓦瓦沙漠草原中不稳定碳的变化，需分析微生物生物量碳（C {dollar} sb {lcub} rm mic {rcub} {dollar}）和土壤总有机碳（C {dollar} sb {lcub} rm org {rcub} {dollar}）是沿着长期放牧影响的梯度进行测量的，并选择了未磨砂的位置代表土壤有机质的稳态条件。使用氯仿熏蒸-提取方法估算的微生物生物量碳范围为28.4 {dol} mu {dol} g C g {dol} sp {lcub} -1 {rcub} {dol}至423.2 {dol} mu {dol} g三种土壤样品类别的C g {dollar} sp {lcub} -1 {rcub} {dollar}，包括（1）草冠下，（2）灌木冠下和（3）非植被空间。土壤总有机碳的丰度范围为1.57 mg C g {dollar} sp {lcub} -1 {rcub} {dollar}至6.53 mg C g {dollar} sp {lcub} -1 {rcub} {dollar}，以及在受影响较大的地区通常较低。使用C {dollar} sb {lcub} rm mic {rcub} {dollar}与C {dollar} sb {lcub} rm org {rcub} {dollar}的比率作为不稳定C的指标，所有位点的值都接近草冠层下方的稳态水平，表明与放牧相关的影响较高时，丰度保持不变。在灌木冠层下，比率值通常高于稳态水平，这表明土壤中不稳定的C组分正在积累。在裸露的土壤空间中，沿梯度的比率值表明不稳定C的损失越来越大，相对于稳态水平而言，放牧影响更大。 C {dollar} sb {lcub} rm mic {rcub} {dollar}与C {dollar} sb {lcub} rm org {rcub} {dollar}的比值是此半干旱生态系统中土壤不稳定碳的较好指标而不是任何一个变量。因此，C {dollar} sb {lcub} rm mic {rcub} {dollar}对C {dollar} sb {lcub} rm org {rcub} {dollar}的比率可能提供了监测荒漠化引起的土壤生产力变化的工具。 （摘要由UMI缩短。）

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