小体型草本植物对光照环境的调整是其在草地物种混生环境中互补资源利用的策略。
Adjustment to the light environment in small-statured forbs as a strategy for complementary resource use in mixtures of grassland species.
机构信息
UFZ, Helmholtz Centre for Environmental Research, Department of Community Ecology, Theodor-Lieser-Strasse 4, Halle, Germany.
出版信息
Ann Bot. 2011 May;107(6):965-79. doi: 10.1093/aob/mcr044. Epub 2011 Mar 7.
BACKGROUND AND AIMS
The biological mechanisms of niche complementarity allowing for a stable coexistence of a large number of species in a plant community are still poorly understood. This study investigated how small-statured forbs use environmental niches in light and CO(2) to explain their persistence in diverse temperate grasslands.
METHODS
Light and CO(2) profiles and the corresponding leaf characteristics of seven small-statured forbs were measured in monocultures and a multi-species mixture within a biodiversity experiment (Jena Experiment) to assess their adjustment to growth conditions in the canopy.
KEY RESULTS
Environmental conditions near the ground varied throughout the season with a substantial CO(2) enrichment (>70 µmol mol(-1) at 2 cm, >20 µmol mol(-1) at 10 cm above soil surface) and a decrease in light transmittance (to <5 % deep in the canopy) with large standing biomass (>500 g d. wt m(-2)) in the multi-species assemblage. Leaf morphology, biochemistry and physiology of small-statured forbs adjusted to low light in the mixture compared with the monocultures. However, the net carbon assimilation balance during the period of low light only compensated the costs of maintenance respiration, while CO(2) enrichment near the ground did not allow for additional carbon gain. Close correlations of leaf mass per area with changes in light availability suggested that small-statured forbs are capable of adjusting to exploit seasonal niches with better light supply for growth and to maintain the carbon metabolism for survival if light transmittance is substantially reduced in multi-species assemblages.
CONCLUSIONS
This study shows that adjustment to a highly dynamic light environment is most important for spatial and seasonal niche separation of small-statured forb species in regularly mown, species-rich grasslands. The utilization of short-period CO(2) enrichment developing in dense vegetation close to the ground hardly improves their carbon balance and contributes little to species segregation along environmental niche axes.
背景与目的
植物群落中大量物种稳定共存的生态位互补的生物学机制仍知之甚少。本研究调查了矮小草本植物如何利用光和 CO₂ 环境生态位来解释它们在不同温带草地中的持续存在。
方法
在生物多样性实验（耶拿实验）中，在单种培养物和多种物种混合物中测量了七种矮小草本植物的光和 CO₂ 分布以及相应的叶片特征，以评估它们对冠层生长条件的适应。
主要结果
整个季节，地面附近的环境条件随季节变化而变化，CO₂ 大量富集（距地面 2 cm 处>70 µmol mol⁻¹，距地面 10 cm 处>20 µmol mol⁻¹），透光率降低（树冠深处透光率<5%），在多物种组合中，大型立木生物量（>500 g d. wt m⁻²）。与单种培养物相比，矮小草本植物的叶片形态、生物化学和生理学在混合物中适应低光条件。然而，低光时期的净碳同化平衡仅补偿了维持呼吸的成本，而地面附近的 CO₂ 富集则不允许额外的碳增益。叶面积质量与光可用性变化的密切相关性表明，矮小草本植物能够适应利用季节性光供应较好的生态位进行生长，如果多物种组合中透光率大幅降低，则能够维持其碳代谢以生存。
结论
本研究表明，在经常修剪、物种丰富的草地中，适应高度动态的光环境是矮小草本植物物种在空间和季节性生态位分离的最重要因素。在靠近地面的密集植被中产生的短期 CO₂ 富集的利用几乎不能改善它们的碳平衡，并且对沿环境生态位轴的物种分离贡献很小。
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