Plant Sciences, Forschungszentrum Juelich GmbH, Wilhelm-Johnen Strasse, Juelich, Germany.
Laboratory of Functional Ecology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
Plant Cell Environ. 2021 Apr;44(4):1072-1094. doi: 10.1111/pce.13968. Epub 2020 Dec 29.
Plant population density is an important variable in agronomy and forestry and offers an experimental way to better understand plant-plant competition. We made a meta-analysis of responses of even-aged mono-specific stands to population density by quantifying for 3 stand and 33 individual plant variables in 334 experiments how much both plant biomass and phenotypic traits change with a doubling in density. Increasing density increases standing crop per area, but decreases the mean size of its individuals, mostly through reduced tillering and branching. Among the phenotypic traits, stem diameter is negatively affected, but plant height remains remarkably similar, partly due to an increased stem length-to-mass ratio and partly by increased allocation to stems. The reduction in biomass is caused by a lower photosynthetic rate, mainly due to shading of part of the foliage. Total seed mass per plant is also strongly reduced, marginally by lower mass per seed, but mainly because of lower seed numbers. Plants generally have fewer shoot-born roots, but their overall rooting depth seems hardly affected. The phenotypic plasticity responses to high densities correlate strongly with those to low light, and less with those to low nutrients, suggesting that at high density, shading affects plants more than nutrient depletion.
植物种群密度是农学和林学中的一个重要变量，提供了一种实验方法来更好地理解植物-植物竞争。我们通过量化 334 个实验中的 3 个林分和 33 个个体植物变量，对均龄单种林分对种群密度的响应进行了荟萃分析，以了解植物生物量和表型特征随密度增加一倍而发生的变化。增加密度会增加单位面积的生物量，但会降低个体的平均大小，这主要是通过减少分蘖和分枝来实现的。在表型特征中，茎直径受到负面影响，但植物高度仍然非常相似，部分原因是茎长与质量比增加，部分原因是更多的分配给茎。生物量的减少是由于光合速率降低，主要是由于部分叶片被遮蔽。每株植物的总种子质量也大幅减少，部分原因是每粒种子的质量降低，但主要是因为种子数量减少。植物通常具有较少的地上根，但它们的整体根系深度似乎几乎不受影响。对高密度的表型可塑性响应与对低光的响应强烈相关，与对低养分的响应相关性较小，这表明在高密度下，遮荫对植物的影响大于养分枯竭。
