Contrasting photosynthetic characteristics of forest vs. savanna species (Far North Queensland, Australia)
Contrasting photosynthetic characteristics of forest vs. savanna species (Far North Queensland, Australia)
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DOI：
10.5194/bg-11-7331-2014
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发表时间：
2014-01-01
期刊：
影响因子：
4.9
通讯作者：
Lloyd, J.
中科院分区：
文献类型：
--
作者：
Bloomfield, K. J.;Domingues, T. F.;Lloyd, J.
森林和稀树草原是热带地区的两种主要植被类型，两者共有的树种很少。在广泛的范围内，人们早就认识到，这两个生物群落的分布主要受降水及其季节性的影响，但土壤的物理和化学性质也可能很重要。从一系列的森林和热带稀树草原网站在澳大利亚远北昆士兰州，我们比较了叶片的光合能力，结构和营养浓度的特点。基于面积的光合能力是较高的稀树草原物种与陡峭的坡度光合氮（N）的关系相比，森林组。更高的叶质量每单位叶面积的稀树草原树木来自密集，而不是较厚的叶子，并没有出现限制光饱和光合速率时，无论是在面积或质量的基础上表示。在所有地点，叶片氮磷（P）的中位数比值都相对较高（> 20），但我们没有发现森林或稀树草原树木光合作用的显性P限制的证据。一个简约的混合效应模型的面积为基础的光合能力保留植被类型和N和P作为解释条款。所得模型拟合预测表明与观测数据拟合良好（R-2 = 0.82）。该模型的随机成分发现，基于区域的光合响应的变化在物种之间（响应方差的71%）要比在不同地点（9%）大得多。这些结果表明，在叶面积的基础上，热带稀树草原树木的远北昆士兰州，澳大利亚，能够在其共同的边界的光合作用优于森林物种。
Forest and savanna are the two dominant vegetation types of the tropical regions with very few tree species common to both. At a broad scale, it has long been recognised that the distributions of these two biomes are principally governed by precipitation and its seasonality, but with soil physical and chemical properties also potentially important. For tree species drawn from a range of forest and savanna sites in tropical Far North Queensland, Australia, we compared leaf traits of photosynthetic capacity, structure and nutrient concentrations. Area-based photosynthetic capacity was higher for the savanna species with a steeper slope to the photosynthesis nitrogen (N) relationship compared with the forest group. Higher leaf mass per unit leaf area for the savanna trees derived from denser rather than thicker leaves and did not appear to restrict rates of light-saturated photosynthesis when expressed on either an area or mass basis. Median ratios of foliar N to phosphorus (P) were relatively high (> 20) at all sites, but we found no evidence for a dominant P limitation of photosynthesis for either forest or savanna trees. A parsimonious mixed-effects model of area-based photosynthetic capacity retained vegetation type and both N and P as explanatory terms. Resulting model-fitted predictions suggested a good fit to the observed data (R-2 = 0.82). The model's random component found variation in area-based photosynthetic response to be much greater among species (71% of response variance) than across sites (9 %). These results suggest that, on a leaf-area basis, savanna trees of Far North Queensland, Australia, are capable of photosynthetically outperforming forest species at their common boundaries.