Earthworm bioturbation stabilizes carbon in non-flooded paddy soil at the risk of increasing methane emissions under wet soil conditions
Earthworm bioturbation stabilizes carbon in non-flooded paddy soil at the risk of increasing methane emissions under wet soil conditions
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蚯蚓生物扰动稳定了非淹稻田土壤中的碳，但在潮湿土壤条件下存在增加甲烷排放的风险
DOI：
10.1016/j.soilbio.2015.08.033
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发表时间：
2015
影响因子：
9.7
通讯作者：
Wolters V.
中科院分区：
文献类型：
--
作者：
John K;Marxsen J;Zaitsev A.S;Wolters V.
在以水稻为基础的生态系统中，对蚯蚓的研究往往集中在一些害虫物种上，而这些重要的土壤工程师有益地影响碳储存和循环的潜力被广泛忽视。我们进行了一个微观实验，以量化热带蚯蚓蚯蚓的影响。不同水分饱和度和施氮量对水稻土碳周转的影响。在国际水稻研究所（菲律宾）的低地农场对土壤进行取样。在没有蚯蚓的情况下，土壤呼吸表现出明显的驼峰形的最大值在中间水平的水饱和度（4倍高于手干土壤），并增加1.5倍，随着N施肥量的增加。相比之下，甲烷排放量在低至中等土壤湿度时很小，在水饱和条件下则很高（比手干土壤高80倍）。未观察到对氮添加的响应。蚯蚓抑制呼吸最大值在中间饱和水平（由一个因素的1.4）和刺激的影响，N施肥（1.7倍，在最高施肥水平）。另一方面，蚯蚓强烈增加CH4释放条件下的高水饱和度（3倍）。没有一致的反应，土壤微生物区系（细菌丰度，土壤酶）的活性可以建立。我们的研究结果表明，土壤有机碳的稳定通过微生物生物扰动被限制在土壤湿度的范围内，允许高活性的蚯蚓。在集约化农业条件下，蠕虫的稳定作用甚至可能由于它们抵消了氮肥对微生物呼吸的积极作用而增强。因此，蚯蚓可能在减少稻田土壤转化为非淹没作物（如旱稻或玉米）后的CO2冲刷方面发挥重要作用。然而，在非常潮湿的土壤中甲烷排放的加速表明了某种风险，这与在雨季仍然面临临时洪水的生产系统中甲烷丰度的增加有关。
Studies on earthworms in rice-based ecosystems tend to focus on some pest species, while the potential of these important soil engineers for beneficially affecting carbon storage and cycling is widely ignored. We carried out a microcosm experiment to quantify the impact of the tropical earthwormPheretimasp. on the C turnover in paddy soils under different conditions of water saturation and N fertilization. The soil was sampled at the lowland farm of the International Rice Research Institute (Philippines). In the absence of earthworms, soil respiration showed a distinct hump-shaped maximum at intermediate levels of water saturation (4-fold higher than in hand-dry soil) and increased 1.5-fold with increasing amounts of N fertilization. Amounts of CH4emitted, in contrast, were small at low to moderate soil humidity and became very high under conditions of water saturation (80-fold higher than hand-dry soil). No response to nitrogen addition was observed. Earthworms suppressed both the respiration maximum at intermediate saturation levels (by a factor of 1.4) and the stimulating impact of N fertilization (1.7-fold at maximum fertilizer level). On the other hand, earthworms strongly increased CH4release under conditions of high water saturation (3-fold). No consistent response of the soil microflora (bacterial abundance, soil enzymes) to earthworm activity could be established. Our findings suggest that the stabilization of soil organic C via earthworm bioturbation is confined to the range of soil humidity that allows high activity ofPheretimasp. Under conditions of intensive agriculture, the stabilizing effect of the worms may even be augmented by the fact that they offset the positive effect of N fertilization on microbial respiration. Earthworms may thus play a vital role in reducing the CO2flush from paddy soils after the conversion to non-flooded crops such as aerobic rice or maize. Acceleration of methane emission in very humid soils nevertheless points to a certain risk that is associated with increasing earthworm abundance in production systems that are still exposed to temporary flooding during the wet season.
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