Rolling in the deep: Priming effects in earthworm biopores in topsoil and subsoil
Rolling in the deep: Priming effects in earthworm biopores in topsoil and subsoil
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DOI：
10.1016/j.soilbio.2017.06.021
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发表时间：
2017-11
影响因子：
9.7
通讯作者：
D. Hoang;S. L. Bauke;Y. Kuzyakov;J. Pausch
中科院分区：
文献类型：
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作者：
D. Hoang;S. L. Bauke;Y. Kuzyakov;J. Pausch
启动效应是指活性碳源的加入引起土壤有机质分解的变化。蚯蚓将有机物纳入其洞穴衬里，从而创造微生物的首选栖息地，但这种洞穴引发效应启动的作用是未知的。在这里，我们研究的机制驱动SOM分解在顶部和底土生物孔隙，并在根际。鉴于表土是在采样前10个月翻耕后新形成的，我们假设（1）有机质可及性、酶活性和酶反应效率（Ka）是生物孔隙与非生物孔隙、根际、底土与表土不同引发效应的主要驱动因素;（2）生物孔隙中微生物酶的产生取决于微生物群落组成。为了验证这些假设，蚯蚓（Lumbricus terrestris L.）从表土（0-30 cm）和两个底土深度（45-75和75-105 cm）取样。此外，根际样品取自表土。测定了土壤总有机碳（Corg）、总氮（TN）、总磷（TP）和碳、氮、磷循环相关酶（纤维二糖水解酶、β-葡萄糖苷酶、木聚糖酶、几丁质酶、亮氨酸氨肽酶和磷酸酶）的活性。结果表明，土壤微生物在生物孔隙中的酶活性（Vmax）和催化效率（Ka）均高于根际和非根际，表明该土壤微生物群落最活跃。一些酶和C：N比在散装土壤中的负相关性解释了较高含量的新鲜有机C在表土，和相应的C和养分限制在底土。土壤酶活性与生物孔隙中的C和TN呈正相关，但与C和TN随孔隙龄的减少有关。在底土中，生物孔隙中的启动效应比非生物孔隙中的启动效应高2.5倍，这是由于生物孔隙中的微生物的有利条件和粘液对微生物活动的刺激。我们的结论是，蚯蚓洞不仅提供了C和养分的顶部和底土之间的联系，但强烈地增加微生物活性和加速SOM在底土的营业额，有助于根系的养分动员。
Priming effect is the change of soil organic matter (SOM) decomposition due to the addition of labile carbon (C) sources. Earthworms incorporate organic matter into their burrow-linings thereby creating preferred habitats for microorganisms, but the roles of such burrows in priming effect initiation is unknown. Here we study the mechanisms driving SOM decomposition in top- and subsoil biopores and additionally in the rhizosphere. Given the topsoil was newly formed after ploughing 10 months prior to sampling, we hypothesized that (1) SOM accessibility, enzyme activities and efficiency of enzymatic reaction (Ka) are main drivers of different priming effect in biopores vs. bulk soil and rhizosphere, subsoil vs. topsoil and (2) the production of microbial enzymes in biopores depends on microbial community composition. To test these hypotheses, biopores formed byLumbricus terrestrisL. and bulk soil were sampled from topsoil (0–30 cm) and two subsoil depths (45–75 and 75–105 cm). Additionally, rhizosphere samples were taken from the topsoil. Total organic C (Corg), total N (TN), total P (TP) and enzyme activities involved in C-, N-, and P-cycling (cellobiohydrolase, β-glucosidase, xylanase, chitinase, leucine aminopeptidase and phosphatase) were measured. Priming effects were calculated as the difference in SOM-derived CO2from soil with or without14C-labeled glucose addition.Enzyme activities (Vmax) and the catalytic efficiency (Ka) were higher in biopores compared to bulk soil and the rhizosphere, indicating that the most active microbial community occurred at this site. Negative correlations between some enzymes and C:N ratio in bulk soil are explained by higher content of fresh organic C in the topsoil, and the corresponding C and nutrient limitations in the subsoil. The positive correlation between enzyme activities and Corg or TN in biopores, however, was associated with the decrease of C and TN with pore age in the subsoil. In the subsoil, priming effect in biopores was 2.5 times higher than bulk soil, resulting from the favorable conditions for microorganisms in biopores and the stimulation of microbial activities by earthworm mucus. We conclude that earthworm burrows provide not only the linkage between top- and subsoil for C and nutrients, but strongly increase microbial activities and accelerate SOM turnover in subsoil, contributing to nutrient mobilization for roots.