Effects of fine-scale simulation of deer browsing on soil micro-foodweb structure and N mineralization rate in a temperate forest
Effects of fine-scale simulation of deer browsing on soil micro-foodweb structure and N mineralization rate in a temperate forest
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DOI：
10.1016/j.soilbio.2007.10.004
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发表时间：
2008-03
影响因子：
9.7
通讯作者：
S. Niwa;N. Kaneko;H. Okada;K. Sakamoto
中科院分区：
文献类型：
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作者：
S. Niwa;N. Kaneko;H. Okada;K. Sakamoto
低密度的本地浏览哺乳动物对营养循环的影响还没有完全了解。弱的啃食可以提高土壤中的氮（N）矿化，并对森林地面的植物再生产生积极影响。为研究西卡鹿（Cervus nippon）弱食对土壤亚系统的影响，以天然林中以矮生竹（Sasa nipponica）为主的林下植被层为研究对象，采用不同强度的落叶模拟鹿的弱食对土壤亚系统的影响。在夏季以大约1周的间隔进行三次落叶（0-18%的叶子去除）。我们测量了水溶性碳（C）浓度，磷脂脂肪酸（PLFA）配置文件作为微生物群落结构的指标，20：4的PLFA作为原生动物丰度的指标，线虫群落结构在家庭层面上，在28天的孵化和氮矿化率。落叶对每个土壤参数的影响，通过比较落叶前后的值。氮矿化率在第一个10天的孵育表现出单峰响应落叶强度，峰值矿化率在落叶率（去除的叶子/总叶片数）为7.6%，与原生动物PLFA和丰富的Plectidae（最主要的食菌线虫家族）。与此相反，在接下来的18天的培养过程中，氮矿化率单调下降，落叶强度增加，与土壤中的水溶性C浓度和新叶的C含量。这些结果表明，去除<15%的叶片可能诱导了持续不到1周的根系不稳定有机质的脉冲式释放，并在短期内（脱叶后的前1-2周）通过土壤微生物循环促进了氮的矿化。氮矿化，然而，减少与落叶强度的增加，在较长的时间内（3-5周后落叶），可能是因为减少不稳定的有机质供应从根落叶后1周。结果表明，在28天的培养期内，氮矿化率对落叶强度的响应呈单峰模式，峰值较小（落叶率为4.9%），高落叶率（>10%）对氮矿化率有负面影响。本研究表明，在森林地面植物的浏览有积极或消极的影响，土壤氮矿化潜力取决于浏览强度水平。
The effects of low densities of native browsing mammals on nutrient cycling are not fully understood. Weak browsing may improve nitrogen (N) mineralization in soil and positively affect plant regrowth at the forest floor. To investigate the effects of weak browsing by sika deer (Cervus nippon) on soil subsystems, we defoliated a dwarf bamboo (Sasa nipponica)-dominated understory layer in a natural forest at different intensities to realistically simulate deer browsing. Defoliation (0–18% leaf removal) was performed three times at approximately 1-week intervals in summer. We measured water-soluble carbon (C) concentration, phospholipid fatty acid (PLFA) profiles as indicators of microbial community structure, a PLFA of 20:4 as an indicator of protozoan abundance, nematode community structure at the family level, and the N mineralization rate in 28 days of incubation. The effects of defoliation on each soil parameter were determined by comparing before and after defoliation values. The N mineralization rate in the first 10 days of incubation showed a unimodal response to defoliation intensity, with a peak mineralization rate at a defoliation rate (number of removed leaves/total leaves) of 7.6%, correlating with protozoan PLFA and the abundance of Plectidae (the most dominant family of bacterivorous nematodes). In contrast, the N mineralization rate during the following 18 days of incubation decreased monotonically with increasing defoliation intensity, correlating with the water-soluble C concentration in the soil and the C content of new leaves. These results suggest that removing <15% of leaves may have induced a pulse-like release of labile organic matter from roots that lasted for less than 1 week and stimulated N mineralization through microbial loop in soil in the short term (in the first 1–2 weeks after defoliation). N mineralization, however, was reduced with increase of defoliation intensity in the longer term (3–5 weeks after defoliation), possibly because of the reduction in labile organic matter supply from roots 1 week after defoliation. As a result, N mineralization rates over the 28-day incubation period responded to defoliation intensity in a unimodal pattern with a small peak (at a defoliation rate of 4.9%) and were negatively affected by high defoliation rates (>10%). This study suggests that browsing on forest floor plants has positive or negative effects on soil N mineralization potential depending on browsing intensity level.