Impact of litter quality on mineralization processes in managed and abandoned pasture soils in Southern Ecuador
Impact of litter quality on mineralization processes in managed and abandoned pasture soils in Southern Ecuador
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DOI：
10.1016/j.soilbio.2009.09.025
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发表时间：
2010-01-01
影响因子：
9.7
通讯作者：
Makeschin, Franz
中科院分区：
文献类型：
--
作者：
Potthast, Karin;Hamer, Ute;Makeschin, Franz
热带地区目前正经历着土地利用变化的显着速度，同时改变了对土壤的废弃物投入。在厄瓜多尔南部的广大地区，森林被砍伐，并被用作牧场。这些牧场经常被蕨菜侵入，当蕨菜成为主要牧场时，生产力下降，这些牧场被遗弃。在本研究中，入侵蕨对土壤生态地球化学性质的影响进行了研究。土壤样品（0-5厘米），从一个活跃的牧场与狗尾草为主要草，从一个废弃的牧场杂草丛生的蕨。草（C-4植物）和蕨（C-3植物）凋落物，不同的C：N比（33和77，分别）和木质素含量（Klason-木质素：18%和45%，分别），培养在土壤中的相应位置，反之亦然，在22 ℃下28天。未经修改的微宇宙只包含相应的土壤或凋落物作为对照。在孵育期间，在不同的时间间隔测定CO2的量及其Δ C-13-特征。此外，土壤微生物群落结构（PLFA分析）以及KCl提取的C和N的浓度进行了监测。对比研究表明，弃耕后狗尾草大量被蕨类植物取代，其特征是pH值降低，土壤速效有机碳和氮含量降低，微生物生物量降低，活性降低，放线菌相对丰度增加。CO2的三角洲C-13-签名表明，在牧场控制土壤中，草源有机碳的优先矿化。在与草凋落物的土壤中，土壤有机质的矿化被推迟（负启动效应），也是一个容易获得的有机物质来自草凋落物的优先利用是显而易见的。与其他处理相比，牧草凋落物改良的牧场土壤中的微生物群落结构表现出相反的变化，真菌的相对丰度较低。在废弃的牧场土壤添加蕨凋落物后，一个积极的引发效应似乎是支持在孵化结束时的N限制。这伴随着革兰氏阳性与革兰氏阴性细菌PLFA标志物的比率的增加。草地和蕨菜凋落物质量的差异是土地利用方式转变后土壤生态地球化学和微生物性质变化的重要触发因素。(C)2009爱思唯尔有限公司保留所有权利。
Tropical regions are currently undergoing remarkable rates of land use change accompanied by altered litter inputs to soil. In vast areas of Southern Ecuador forests are clear cut and converted for use as cattle pastures. Frequently these pasture sites are invaded by bracken fern, when bracken becomes dominant pasture productivity decreases and the sites are abandoned. In the present study implications of invasive bracken on soil biogeochemical properties were investigated. Soil samples (0-5 cm) were taken from an active pasture with Setaria sphacelata as predominant grass and from an abandoned pasture overgrown by bracken. Grass (C-4 plant) and bracken (C-3 plant) litter, differing in C:N ratio (33 and 77, respectively) and lignin content (Klason-lignin: 18% and 45%, respectively), were incubated in soils of their corresponding sites and vice versa for 28 days at 22 degrees C. Unamended microcosms containing only the respective soil or litter were taken as controls. During incubation the amount Of CO2 and its delta C-13-Signature were determined at different time intervals. Additionally, the soil microbial community structure (PLFA-analysis) as well as the concentrations of KCl-extractable C and N were monitored. The comparison between the control soils of active and abandoned pasture sites showed that the massive displacement of Setaria-grass by bracken after pasture abandonment was characterized by decreased pH values accompanied by decreased amounts of readily available organic carbon and nitrogen, a lower microbial biomass and decreased activity as well as a higher relative abundance of actinomycetes. The delta C-13-signature Of CO2 indicated a preferential mineralization of grass-derived organic carbon in pasture control soils. In soils amended with grass litter the mineralization of soil organic matter was retarded (negative priming effect) and also a preferential utilization of easily available organic substances derived from the grass litter was evident. Compared to the other treatments, the pasture soil amended with grass litter showed an opposite shift in the microbial community structure towards a lower relative abundance of fungi. After addition of bracken litter to the abandoned pasture soil a positive priming effect seemed to be supported by an N limitation at the end of incubation. This was accompanied by an increase in the ratio of Gram-positive to Gram-negative bacterial PLFA marker. The differences in litter quality between grass and bracken are important triggers of changes in soil biogeochemical and soil microbial properties after land use conversion. (C) 2009 Elsevier Ltd. All rights reserved.