Competitive strategies in adult beech and spruce: space-related foliar carbon investment versus carbon gain
Competitive strategies in adult beech and spruce: space-related foliar carbon investment versus carbon gain
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成年山毛榉和云杉的竞争策略：与空间相关的叶面碳投资与碳增益
作者：
I. Reiter;K. Häberle;A. Nunn;C. Heerdt;H. Reitmayer;Rüdiger Grote;R. Matyssek
在中欧，欧洲水青冈和欧洲云杉在叶型、树冠结构和生长季节长度方面代表了截然不同的极端。为了研究这两个共存物种的竞争策略，我们测试了以下假设：（1）阳枝的叶子所占据的空间的特征在于与阴枝相比更大的叶质量投资，（2）每单位占据空间的碳（C）增益在阳枝中比在阴枝中更大，（3）在单位占地碳增益低的地方，植物维持占地的年碳和水分成本低。这些调查在成熟的森林在德国南部。审查是根据对与空间有关的资源投资和植物收益的年度评估进行的。树枝周围的叶状空间被认为是地上资源可用性的相关体积。占树冠空间每站立的叶质量是较高的遮阳比山毛榉的太阳分支，而没有差异存在的树冠体积每叶质量之间的太阳和阴影的云杉分支（假设1接受山毛榉，但拒绝云杉）。然而，山毛榉占据更多的空间，每叶质量比云杉。每占用树冠体积的碳增益是在阳光下比在荫枝（假设2接受），但没有不同的物种。每呼吸和蒸腾成本占用空间的金额没有不同的物种之间或阳光和阴影分支。在山毛榉和云杉中，叶片投资在阳枝和阴枝年度碳平衡中的比例保持相当稳定，而呼吸成本在阴枝中明显增加。因此，荫蔽树枝是占用空间的昂贵结构，只能实现低的甚至是负的碳平衡（拒绝假设3），这与树枝的C自治权相冲突。我们的研究结果表明，竞争力是由立叶质量和每年的分支体积增量，而不是每年的投资在树叶。如本文所示，在空间相关资源投资与回报方面表现出竞争力，有可能促进对植物-植物相互作用的机械理解。
In Central Europe, Fagus sylvatica and Picea abies represent contrasting extremes in foliage type, crown structure and length of growing season. In order to examine the competitive strategies of these two co-occurring species, we tested the following hypotheses: (1) the space occupied by the foliage of sun branches is characterized by greater foliar mass investment compared to shade branches, (2) the carbon (C) gain per unit of occupied space is greater in sun than in shade branches, and (3) annual C and water costs of the foliage for sustaining the occupied space are low, wherever C gain per unit of occupied space is low. These were investigated in a mature forest in Southern Germany. The examination was based on the annual assessment of space-related resource investments and gains of the foliage. The foliated space around branches was regarded as the relevant volume with respect to aboveground resource availability. Occupied crown space per standing foliage mass was higher in shade compared to sun branches of beech, whereas no difference existed in crown volume per foliage mass between sun and shade branches of spruce (hypothesis 1 accepted for beech but rejected for spruce). However, beech occupied more space per foliage mass than spruce. The C gain per occupied crown volume was greater in sun than in shade branches (hypothesis 2 accepted) but did not differ between species. The amount of occupied space per respiratory and transpiratory costs did not differ between species or between sun and shade branches. In beech and spruce, the proportion of foliage investment in the annual C balance of sun and shade branches remained rather stable, whereas respiratory costs distinctly increased in shade foliage. Hence, shade branches were costly structures to occupy space, achieving only low and even negative C balances (rejection of hypothesis 3), which conflicts with the claimed C autonomy of branches. Our findings suggest that competitiveness is determined by the standing foliage mass and the annual branch volume increment rather than annual investments in foliage. Expressing competitiveness in terms of space-related resource investments versus returns, as demonstrated here, has the potential of promoting mechanistic understanding of plant–plant interactions.