Production in aquatic macrophyte communities: A theoretical and empirical study of the influence of spatial light distribution
Production in aquatic macrophyte communities: A theoretical and empirical study of the influence of spatial light distribution
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DOI：
10.4319/lo.2002.47.6.1742
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发表时间：
2002-11-01
影响因子：
4.5
通讯作者：
Sand-Jensen, K
中科院分区：
文献类型：
--
作者：
Binzer, T;Sand-Jensen, K
许多陆生植物冠层调节叶片密度和叶片倾斜度的空间格局，以在光合组织之间均匀地分配光，并优化光利用效率。然而，无座水生植物不能保持相同的明确的三维结构，因为强大的阻力和流动的水的剪切力。这种冠层结构上的差异被认为是陆地群落的总生产率比水生群落高出三至五倍的原因。为了评估水生生境中的群落结构的影响，我们结合了一个简单的机械模型和经验测量人工结构的大型藻类群落（石莼）不同的叶状体吸收率和社区密度。预测值和测量值对应密切，并显示，在高光环境中的总生产量显着提高了垂直方向的菌体时，吸收率和社区密度都很高。这一结果意味着，高叶状体吸收率和社区密度暴露于强光的水生植物是有限的，在实现高的总生产率，因为他们无法均匀地分配光合组织之间的光子。由于散射和衰减的水柱增加，叶状体结构对生产的影响下降，薄的透明的大型植物是更有效地利用光比厚的不透明的大型植物。研究结果表明，光的低效分布是导致水生生境中大型藻类群落生产率低和不同冠层结构大型藻类形态功能群深度分布的主要原因。
Many terrestrial plant canopies regulate spatial patterns in leaf density and leaf inclination to distribute light evenly between the photosynthetic tissue and to optimize light utilization efficiency. Sessile aquatic macrophytes, however, cannot maintain the same well-defined three-dimensional structure because of the strong drag and shear forces of moving water. This difference in canopy structure has been suggested to account for the three- to five-fold higher gross production rates in terrestrial than aquatic communities. To evaluate the effect of community structure in aquatic habitats, we combined a simple mechanistic model and empirical measurements on artificially structured macroalgal communities (Ulva lactuca) with varying thallus absorptance and community density. Predicted and measured values corresponded closely and revealed that gross production in high-light environments was markedly enhanced by a vertical orientation of thalli when absorptance and community density were both high. This result implies that aquatic macrophytes of high thallus absorptance and community density exposed to high light are limited in attaining high gross production rates because of their inability to distribute photons evenly between the photosynthetic tissues. As scattering and attenuation in the water column increase, the effect of thallus structure on production declines and thin transparent macrophytes are more efficient at utilizing light than thick opaque macrophytes. The results confirm that inefficient distribution of light can account for the low community production rates in aquatic habitats and the depth distribution of form-functional groups of macroalgae with different canopy structure.