根际激发效应的发生机制及其生态重要性

doi:10.3724/SP.J.1258.2014.00007

摘要/Abstract

摘要：

土壤激发效应是指由各种有机物质添加等处理所引起的土壤有机质周转强烈的短期改变。根际是激发效应最主要也是最重要的发生部位。根际激发效应能够反映生态系统土壤碳氮周转的速度, 并影响植物、土壤微生物等对养分的获取和竞争, 维持生态系统各组分间的养分平衡。虽然对根际激发效应的产生机制已取得一定程度的认知, 但是对根际激发效应在土壤碳氮转化过程中的作用机理及其生态重要性依然缺乏足够的理解。该文在论述激发效应的研究历史和主要发生部位的基础上对最新研究进展进行了综合分析, 提出了一个具体的根际激发效应的发生机制, 深入剖析了影响根际激发效应的生物与非生物因素, 并阐释了根际激发效应的生态重要性, 对未来根际激发效应的研究方向进行了展望。

关键词: 胞外酶, 根际沉积物, 根际激发效应, 土壤微生物

Abstract:

Priming effects are defined as “strong short-term changes in the turnover of soil organic matter caused by moderate treatments of the soil”. Rhizosphere is the most important place, where the priming effects take place. Rhizosphere priming effects reflect the turnover rate of soil carbon and nitrogen, and affect the acquisition of competition for nutrients by plants and microorganisms, thus maintaining nutrient balance among the various components of an ecosystem. Although there has been a general understanding on the occurrence of rhizosphere priming effects, the mechanisms underlying their role in soil carbon and nitrogen transformations and their ecological significance are still not fully comprehended. This paper provides a synthesis of the latest advancement in studies of the rhizosphere priming effects. On the basis of reviews of research history and identification of the hotspots, we first put forward a mechanism underlying the occurrence of rhizosphere priming effects, and then examined the biotic and abiotic factors influencing the rhizosphere priming effects. The ecological significance and outlooks of research in the rhizosphere priming effects were discussed and clarified.

Key words: exoenzyme, rhizodeposition, rhizosphere priming effect, soil microorganisms

孙悦, 徐兴良. 根际激发效应的发生机制及其生态重要性. 植物生态学报, 2014, 38(1): 62-75. DOI: 10.3724/SP.J.1258.2014.00007

SUN Yue, XU Xing-Liang, Yakov KUZYAKOV. Mechanisms of rhizosphere priming effects and their ecological significance. Chinese Journal of Plant Ecology, 2014, 38(1): 62-75. DOI: 10.3724/SP.J.1258.2014.00007

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2014.00007

https://www.plant-ecology.com/CN/Y2014/V38/I1/62

图/表 2

图1 土壤激发效应的主要发生部位: 碎屑周际、根际和动物通道(参照Beare et al. 1995和Kladivko, 2001)。

Fig. 1 The hotspots of priming effects: detritusphere, rhizos- phere and drillosphere (after Beare et al. 1995 and Kladivko, 2001).

图2 根际激发效应的发生机制: 当土壤氮受限时, 植物将较多的光合产物投资到地下, 根际微生物利用根际沉积物获取碳和能量, 增加微生物数量和活性, 促进微生物胞外酶的分泌, 分解有机质释放可利用氮, 产生正的根际激发效应(图左); 当土壤氮富集时, 减少了微生物对养分的需求, 根际微生物偏好利用根系分泌物, 减少胞外酶的分泌, 而植物也减少向地下的碳分配, 导致根际微生物数量减少和活性降低, 抑制了有机质分解, 产生负的根际激发效应(图右)。绿箭头、蓝箭头和红箭头分别代表由植物、土壤微生物和胞外酶主导的生态过程; 箭头的粗细表征通量的大小或过程的强弱。可利用性氮库中的黄色代表来自土壤有机质矿化作用产生的可利用性氮, 其色块面积大小代表来自有机质矿化作用的数量。

Fig. 2 Mechanism of rhizosphere priming effects. At low nutrient levels (left), plants allocate more photosynthates to belowground and supply soil microorganisms with carbon and energy. As a result, microbial biomass and activities increase and enhance production of extracellular enzymes by the rhizosphere microorganisms to decompose soil organic matter and release nutrients. Therefore, a positive priming effect takes place. In contrast, at high nutrient levels (right), microorganisms have less demand for nutrients and thus preferentially utilize root exudates, leading to reduced production of extracellular enzymes. Moreover, as plants invest less photosynthates in belowground, microbial biomass and activities will decrease. As a result, the decomposition of soil organic matter slows down and a negative priming effect occurs. The green, blue, and red arrow-lines represent the ecological processes mediated by plants, soil microorganisms, and exoenzymes, respectively. The thickness of an arrow-line indicates its relative magnitude of a flux or intensity of a process. Yellow colour of the available nitrogen pool indicates mineral nitrogen derived from mineralzation of soil organic matter. The area of the yellow colour represents the amount of mineral nitrogen derived from mineralzation of soil organic matter.

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