Does accelerated soil organic matter decomposition in the presence of plants increase plant N availability?
Does accelerated soil organic matter decomposition in the presence of plants increase plant N availability?
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DOI：
10.1016/j.soilbio.2009.02.013
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发表时间：
2009-06-01
影响因子：
9.7
通讯作者：
Cheng, Weixin
中科院分区：
文献类型：
--
作者：
Dijkstra, Feike A.;Bader, Nicholas E.;Cheng, Weixin
植物根系可通过根际引发效应提高微生物活性和土壤有机质分解能力。植物种类和土壤类型之间的启动效应差异如何影响氮素矿化和植物吸收几乎是未知的。在温室试验中，我们测试了在三种不同土壤类型上生长的白杨和黄皮松的引发效应是否增加了植物有效氮。我们测量了种植和非种植处理之间土壤来源的CO2-C通量的差异。我们计算了“过剩植物速效氮”，即种植和不种植处理之间植物速效氮的差异(根据试验开始和结束时土壤无机氮和植物氮库的变化估计)。在所有处理中，在植物存在的情况下，105d的总N矿化显著更大，而同时测量的微生物N不受植物存在的影响。氮素矿化总量与引发速率呈极显著正相关。不同土壤类型对植物速效氮的影响并不一致。在一种土壤类型中，植物速效氮在弗氏假单胞菌处理中增加，而在黄瓜假单胞菌处理中没有增加，而在另外两种土壤中，两种植物的作用相反。在试验的前107天，当所有种植土壤中的无机氮仍然丰富时，引发C的累积量与植株过剩的速效氮之间没有关系。然而，在试验的后半部分(108-398天)，当种植处理的土壤无机氮被植物吸收耗尽时，累积的底碳总量与过剩的植物速效氮显著正相关，底质C解释了6种植物-土壤组合中5种植物有效氮变异的78%。在同一种-土壤类型组合中，过量的植株速效氮不能从累积的底物碳量中预测出来。可能是由于大量输入低氮浓度的根际沉淀物而导致的更大的微生物氮固定，可能降低了植物速效氮，或者我们可能低估了植物速效氮，因为在这种处理中，氮通过根分泌物流失而死亡。我们得出的结论是，土壤氮素有效性不能仅由土壤性质决定，而是受到根-土相互作用的强烈影响。爱思唯尔有限公司出版。
Plant roots can increase microbial activity and soil organic matter (SOM) decomposition via rhizosphere priming effects. It is virtually unknown how differences in the priming effect among plant species and soil type affect N mineralization and plant uptake. In a greenhouse experiment, we tested whether priming effects caused by Fremont cottonwood (Populus fremontii) and Ponderosa pine (Pinus ponderosa) grown in three different soil types increased plant available N. We measured primed C as the difference in soil-derived CO2-C fluxes between planted and non-planted treatments. We calculated "excess plant available N" as the difference in plant available N (estimated from changes in soil inorganic N and plant N pools at the start and end of the experiment) between planted and non-planted treatments. Gross N mineralization at day 105 was significantly greater in the presence of plants across all treatments, while microbial N measured at the same time was not affected by plant presence. Gross N mineralization was significantly positively correlated to the rate of priming. Species effects on plant available N were not consistent among soil types. Plant available N in one soil type increased in the P. fremontii treatment but not in the P. ponderosa treatment, whereas in the other two soils, the effects of the two plant species were reversed. There was no relationship between the cumulative amount of primed C and excess plant available N during the first 107 days of the experiment when inorganic N was still abundant in all planted soils. However, during the second half of the experiment (days 108-398) when soil inorganic N in the planted treatments was depleted by plant N uptake, the cumulative amount of primed C was significantly positively correlated to excess plant available N. Primed C explained 78% of the variability in plant available N for five of the six plant-soil combinations. Excess plant available N could not be predicted from cumulative amount of primed C in one species-soil type combination. Possibly, greater microbial N immobilization due to large inputs of rhizodeposits with low N concentration may have reduced plant available N or we may have underestimated plant available N in this treatment because of N loss through root exudation and death. We conclude that soil N availability cannot be determined by soil properties alone, but that is strongly influenced by root-soil interactions. Published by Elsevier Ltd.