Microbial residues as indicators of soil restoration in South African secondary pastures
Microbial residues as indicators of soil restoration in South African secondary pastures
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DOI：
10.1016/j.soilbio.2010.12.012
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发表时间：
2011-04
影响因子：
9.7
通讯作者：
Franziska Lauer;Raimund Kösters;C. D. Preez;W. Amelung
中科院分区：
文献类型：
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作者：
Franziska Lauer;Raimund Kösters;C. D. Preez;W. Amelung
南非高地半干旱草原土壤的长期集约耕作导致碳、氮以及相关活和死微生物生物量的显着损失。为了恢复土壤，农民将退化的耕地改造成次要牧场。本研究的目的是阐明微生物在再生阶段对土壤中碳和氮固存的贡献。复合样本取自以前的耕地（即 Plinthustalfs）的表土，这些土地在 1-31 年前已转变为牧场。氨基糖被确定为大块土壤和选定颗粒尺寸部分中微生物残留的标记。结果表明，当次生牧场使用过程中C和N含量增加时，大块土壤（0-5cm）中的氨基糖浓度以类似的幅度恢复，并在大约90年后达到新的稳态水平，这仅相当于原生草地中氨基糖水平的90%。粘土大小部分中的氨基糖浓度恢复到比大块土壤中更高的最终水平，并且年恢复速度也更快。这证实了，尤其是较细的颗粒含有大量的氨基糖，因此有助于恢复微生物来源的碳和氮。大块土壤中氨基糖的不完全恢复只能部分归因于次生草地的质地稍粗糙，这些草地因风蚀而失去了淤泥。尤其是土壤也失去了恢复 5 厘米土壤深度以下微生物残留的能力。总体而言，葡萄糖胺与胞壁酸的比率也随着牧场使用时间的增加而增加，这表明真菌主导了微生物对碳和氮的封存，而细菌细胞壁残留物的重新积累则不太明显。然而，氨基葡萄糖与胞壁酸的比例最终甚至超过了原生草地，这表明以前的集约化作物管理对土壤微生物群落的影响仍然存在一些不可逆转的变化。
Prolonged intensive arable cropping of semiarid grassland soils in the South African Highveld resulted in a significant loss of C, N and associated living and dead microbial biomass. To regenerate their soils, farmers converted degraded arable sites back into secondary pastures. The objective of this study was to clarify the contribution of microorganisms to the sequestration of C and N in soil during this regeneration phase. Composite samples were taken from the topsoils of former arable land, namely Plinthustalfs, which had been converted to pastures 1–31 years ago. Amino sugars were determined to be markers for microbial residues in the bulk soil and in selected particle-size fractions. The results showed that when C and N contents increased during the secondary pasture usage, the amino sugar concentration in the bulk soil (0–5 cm) recovered at similar magnitude and reached a new steady-state level after approximately 90 years, which corresponded only to 90% of the amino sugar level in the primary grassland. The amino sugar concentration in the clay-sized fraction recovered to a higher end level than in the bulk soil, and also at a faster annual rate. This confirms that especially the finer particles contained a high amount of amino sugars and were responsible, thus, for the restoration of microbially derived C and N. The incomplete recovery of amino sugars in bulk soil can only in parts be attributed to a slightly coarser texture of secondary grassland that had lost silt through wind erosion. The soils particularly had also lost the ability to restore microbial residues below 5 cm soil depth. Overall, the ratios of glucosamine to muramic acid also increased with increasing duration of pasture usage, suggesting that fungi dominated the microbial sequestration of C and N whereas the re-accumulation of bacterial cell wall residues was less pronounced. However, the glucosamine-to-muramic acid ratios finally even exceeded those of the primary grassland, indicating that there remained some irreversible changes of the soil microbial community by former intensive crop management.