基于虚拟植物的幼龄杉木生长模拟

为估算树木在不同生长环境下的生长量及评价树木与环境之间的相互关系,本文以幼龄杉木为对象,从个体尺度上,根据形态结构生长发育规律,定义了幼龄杉木生长的基本单元,耦合用于表达树木形态发育的L-系统和生理生态模型,形成了L-系统的杉木结构—功能模型.在LSTree软件基础上,集成光合作用、生物量分配等模型,扩展了冠层光合有效辐射(PAR)的空间分布模拟,计算每个叶片上分布的PAR值,为光合作用模型提供核心参数.以福州3-4年生杉木的生长盛期为例,计算不同时刻净光合速率,从而计算各生长阶段的生物量,再把生物量分配到各器官.在生物量驱动下,树木形态结构发生变化,通过迭代,实现生物量驱动下的树木动态生长模拟.净光合速率估算结果与已有相关研究对比,比较合理.这种方法可定量分析、解释植物与环境之间关系.

Growth Simulation of Young Chinese Fir Based on Virtual Plant

Energy fixation and organic matter production of forest ecosystem were dominated by plants, which are impacted by their growth environment. The forest ecosystem has the characteristic of long life- span, which makes its research laborious and costly using field experiment. The virtual geographical envi- ronment can provide a new way for its research due to its character of trying to exceed the limit of time and space. In order to estimate the biomass and evaluate relationships among tree and environments, an L-sys- tems based functional-structural model was developed for simulating the development of tree architecture, taking into account tree physiology and environment. The L-systems was used to represent the morpho- logical development of tree. The basic growth unit was described in line with the development of young Chinese fir （Cunninghamia lanceolata）. LSTree system integrated the photosynthesis, photosynthates al- location and morphogenesis models. The spatial distribution of solar radiation in tree canopy was simula- ted for calculating photosynthetically active radiation （PAR） of each leaf obtained. PAR is a key parame- ter for photosynthesis model to estimate biomass. The dynamic growth of an individual 3-to-4-year-old Chinese fir in Fuzhou was simulated in growing season. Based on the 2010 Fuzhou weather and Chinese fir photosynthetic characteristic, net photosynthesis rate and product were calculated for each stage. The a- mount of photosynthates allocated to the growth of new segments and leaves or branches and leave ampli- fication are based on source-sink theory. The growth of tree is driven by available photosynthetic products after respiration losses were accounted for. The morphogenesis change in the young Chinese fir in re- sponse to environment was simulated dynamically in three dimensional representations. The result of net photosynthesis was compared to the previous field observation research, and it showed the simulation re- sult was reasonable. The methodology has promising benefits to depicting the interaction of plant and en- vironment, which will be valuable for estimation of organic matter production too.