Soil carbon and nitrogen changes after clearing mulga (Acacia aneura) vegetation in Queensland, Australia:: Observations, simulations and scenario analysis
Soil carbon and nitrogen changes after clearing mulga (Acacia aneura) vegetation in Queensland, Australia:: Observations, simulations and scenario analysis
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DOI：
10.1016/j.soilbio.2007.09.003
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发表时间：
2008-02-01
影响因子：
9.7
通讯作者：
Dalal, Ram C.
中科院分区：
文献类型：
--
作者：
Kirschbaum, Miko U. F.;Harms, Ben;Dalal, Ram C.
在这里报告的工作中，我们研究了土壤（有机）碳和氮的变化后，观察到的立场固氮mulga树（金合欢aneura）水牛草（Cenchrus ciliaris）牧场，不含固氮豆科植物。一系列以前报道的实地测量结果进行了比较，对CenW 3.1，世纪model.The模型的重新制定的版本成功地再现了所观察到的模式，土壤碳，C：N比和氮矿化率下mulga植被。这包括相对较小的变化，碳浓度下降到1米，C：N比约11-13在所有土壤深度，大量的氮矿化率，深度为90厘米，清除后，持续减少土壤有机碳和氮stocks.Interpretation的实验观测是困难的，除了大量的“死”的有机物杀死mulga根清除后。在树木被移除后不久进行的测量中，这种物质可以通过筛分（至2毫米）排除在外，但由于部分分解的物质可能能够通过筛子，因此可以包括在以后的一年采样中。过去的工作通常忽略了死粗根的考虑。对于网站的碳收支，活生物量和地表凋落物的变化显着超过了土壤有机碳的小变化，在腐烂的粗根的变化定量比其他有机碳pools. Modulated氮矿化率的变化更重要的是根据水牛草比那些下mulga和显着的逐年变化，符合不同的降雨量。它没有表现出一致的趋势，在第一个20年后清除，因为减少氮储量的影响是平衡的有机质质量的增加，从富含木质素的mulga凋落物的变化，以较低的木质素浓度的水牛草凋落物。土壤氮矿化速率随氮储量的减少而逐渐降低，但凋落物质量保持稳定。情景分析表明，通过增加豆科植物或停止放牧动物对养分的去除，改变土壤氮收支，可以影响土壤碳氮变化趋势。为了阻止土壤氮的下降，并确保氮储存的长期维持或增加，需要包括豆类。(c)2007爱思唯尔有限公司保留所有权利。
In the work reported here we examine the changes in soil (organic) carbon and nitrogen that are observed after converting a stand of nitrogen-fixing mulga trees (Acacia aneura) to buffel-grass (Cenchrus ciliaris) pasture that contained no nitrogen-fixing legumes. A range of previously reported field measurements was compared against the output of CenW 3.1, a reformulated version of the CENTURY model.The model successfully reproduced the observed patterns of soil carbon, C:N ratios and nitrogen mineralisation rates under mulga vegetation. This included relatively small changes in carbon concentration down to 1 m, C:N ratios of around 11-13 across all soil depths, substantial nitrogen mineralisation rates to a depth of 90 cm and, after clearing, an on-going decrease in soil organic carbon and nitrogen stocks.Interpretation of experimental observations was made difficult by the addition of a large amount of 'dead' organic matter from killed mulga roots after clearance. This material may be excluded through sieving (to 2 mm) in measurements taken shortly after tree removal, but may be included in later-year sampling as the partly decomposed material might be able to pass through sieves. Past work has usually ignored consideration of dead coarse roots. For the site carbon budget, changes in live biomass and surface litter significantly outweighed the small changes in soil organic carbon, and changes in decaying coarse roots were quantitatively more important than changes in other organic carbon pools.Modelled nitrogen mineralisation rates were lower under buffel-grass than those under mulga and showed significant year-to-year variations that were in line with varying rainfall. It showed no consistent trend over the first 20 years after clearing because the effect of decreasing nitrogen stocks was balanced by an increase in organic matter quality with the change from lignin-rich mulga litter to buffel-grass litter with lower lignin concentration. Nitrogen mineralisation rates gradually decreased thereafter as nitrogen stocks continued to decrease but litter quality stabilised.A scenario analysis showed that soil carbon and nitrogen trends could be affected by changing the nitrogen budget through inclusion of legumes or cessation of nutrient removal by grazing animals. Inclusion of legumes was needed to halt the decline in soil nitrogen and to ensure the long-term maintenance, or increase, in nitrogen stocks. (c) 2007 Elsevier Ltd. All rights reserved.