Occurrence patterns of facilitation by shade along a water gradient are mediated by species traits
Occurrence patterns of facilitation by shade along a water gradient are mediated by species traits
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DOI：
10.1016/j.actao.2014.12.001
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发表时间：
2015-01-01
影响因子：
1.8
通讯作者：
Tsuyuzaki, Shiro
中科院分区：
文献类型：
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作者：
Egawa, Chika;Tsuyuzaki, Shiro
在受干扰的生境中，荫蔽通常通过改善水和热胁迫对植物有促进作用。遮荫的促进作用往往随着可用水量的减少而增加。与此同时，几项研究表明，遮荫的促进作用不受水分状况的影响，也不受极端干燥条件下的塌陷影响。我们假设受益植物的性状，特别是在茎和根之间分配生物量的灵活性，会介导阴影促进和水分状况之间关系的变化。为了验证这一假设，我们研究了两种沼泽物种在开采后泥炭地不同水分条件下对树荫的反应。在3个水分水平（干：泥炭含水量53%，湿：77%，对照：71%）× 2个遮荫水平（50%遮荫和50%无遮荫）下播种白纹和茉莉。对两种植物的成活率、生物量和茎根间生物量分配进行了2年的监测。遮荫提高了两种植物的存活率和生物量。然而，遮荫对白筋的促进作用与含水量无关，而对粳稻的促进作用强度随着含水量的降低而增强。白杨在干旱条件下优先将生物量分配给根系，具有较强的耐旱性。日本稻不改变其生物量的分配，以响应阴影或水位，是干旱不耐。我们的研究结果表明，受益植物生物量分配的灵活性介导了沿水梯度阴影促进的发生模式。生物量分配不灵活的物种通过改善水分胁迫对水分胁迫的促进作用随着水分有效性的降低而增加，而生物量分配灵活的物种的促进作用与水分状况无关。这种特定物种的促进将促进不同物种在一个群落中共存。(C) 2014 Elsevier Masson SAS。版权所有。
In disturbed habitats, shade often has facilitative effects on plants by ameliorating water and thermal stresses. Facilitation by shade tends to increase as water availability decreases. At the same time, several studies have suggested that facilitation by shade is not affected by water status or collapses under extremely dry conditions. We hypothesized that traits of beneficiary plants, specifically, the flexibility in the allocation of biomass between shoots and roots, would mediate variation in the relationship between facilitation by shade and water status. To test this hypothesis, we examined the responses of two bog species to shade under various water conditions in a post-mined peatland. The seeds of Rhynchospora alba and Moliniopsis japonica were sown under three water levels (dry: 53% peat water content, wet: 77%, and control: 71%) x two shading levels (50% shaded and unshaded). The survival, biomass, and biomass allocation between the shoots and roots of the two species were monitored for two years. Shade increased the survival and biomass of both species. However, the facilitation of R. alba by shade was independent of water level, whereas the strength of the facilitative effects on M. japonica increased as water content decreased. R. alba preferentially allocated biomass to roots under dry conditions and was highly drought tolerant. M. japonica did not alter the allocation of its biomass in response to either shade or water level and was drought intolerant. Our results suggest that flexibility in biomass allocation of beneficiary plants mediates occurrence patterns of facilitation by shade along a water gradient. The facilitation of species with inflexible biomass allocation by shade through the amelioration of water stress increases as water availability decreases, whereas the facilitation of species with flexible biomass allocation is independent of water status. Such species-specific facilitation would promote the coexistence of diverse species in a community. (C) 2014 Elsevier Masson SAS. All rights reserved.