作 者 ：陈德祥,班小泉,李意德,肖文发,骆土寿,林明献,许涵
期 刊 ：生态学报 2008年 28卷 9期 页码：4059~4069
Keywords:neighborhood interference, intra-specific competition, gas exchange, Tectona grandis L. f., Jianfengling,
摘 要 ：研究以海南岛尖峰岭21a生的珍贵树种柚木人工林为对象，以邻体干扰指数为干扰强度评价指标，用Li-6400（Li-cor, Inc., USA）便携式光合作用测定系统研究了邻体干扰强度对柚木个体CO2气体交换的日动态和季节变化特性，光合-光响应特性及光合-CO2响应特性的影响。结果表明：邻体干扰并未改变个体叶片光合作用日进程，但对日净光合速率（Pn）的影响差异较大，表现为弱、中、强和极强度干扰下日Pn时段均值比为2.5∶2.3∶1.7∶1.0，弱干扰下日最大净光合速率为极强干扰下的2.8倍；随着干扰强度的增加，柚木叶片的蒸腾速率、气孔导度等特征参数也出现不同程度的下降。邻体干扰对光合-光响应和光合-CO2响应特征参数的影响明显，弱干扰下柚木叶Asat、Qsat 、αA、CE、Vcmax和Jmax分别是极强干扰下的2.7、1.3、1.4、2.7、1.9和2.8倍，Qcomp和Rd则受邻体干扰的影响不明显。干扰强度对光合光响应和光合CO2响应特征的影响随光环境和CO2浓度的改变而有所差异，光环境的改变对弱干扰下柚木个体的影响明显要强于强度以上干扰的个体，而CO2浓度的改变对弱干扰个体的影响则明显要弱于强度干扰以上个体的影响。因此，在林分结构相对单一、经营管理措施基本一致的人工林内，邻体干扰是个体竞争的主要影响因素之一，干扰强度的不同将影响种内个体光合碳同化能力出现差别，导致个体生长差异。可以基于邻体干扰指数评价柚木人工林内种内竞争程度的大小，并以此为依据合理调整柚木人工林的林分结构，达到对环境资源的最合理利用。
Abstract:The growth performance of individual plants in a population was well recognized to be affected by the plant–plant interactions, which we called neighborhood interference. Though relevant mechanisms are still unclear, the variations in gas exchange parameters in relation to the neighborhood interference between individual plants are crucial for evaluating the effects of plant plant interactions. CO2 assimilations in leaves of teak under natural conditions during dry season (November to next April) and wet season (May to October) and its responses to variations in light flux density and CO2 concentration in different neighborhood interference were simultaneously measured with Li-6400 portable photosynthesis system in a 21-years old tropical plantation forest at Jianfengling, Hainan Island. This article deals with the rule of the changes of neighborhood interference on trees characteristics of gas exchange and its dynamic responses to light environments by individual plants. Empirical models of photosynthetic light response and photosynthetic CO2 response were developed to predict the daytime carbon gain by fitting measured data into a non-rectangular hyperbola nonlinear model with the following parameters: the light-saturated photosynthetic rate (Asat), the light-saturated constant (K, equal to the PPFD, which is required to produce one-half of the light-saturated photosynthetic rate), apparent quantum yield (αA, the initial slope of the curve) and dark respiration rate (Rd). Values of the parameters of the maximum rate of carboxylation by Rubisco (Vcmax), carboxylation efficiency (CE), the PAR saturated rate of electron transport (Jmax) were estimated use these models. Diurnal courses of photosynthesis of individuals were not affected by neighborhood interference, but net photosynthetic rates showed a negative relationship with the intensity of neighborhood interference. The ratio of daily average Pn in weak, moderate, strong and heavy neighborhood interference was 2.5∶2.3∶1.7∶1.0, and daily maximum of Pn in weak interference was 2.8 times of that in heavy interference. Leaf transpiration and stomatal conductance were decreased with the increasing of interference intensity. Characteristics of photosynthetic light response and CO2 response was changed by the neighborhood interference, and values of leaf gas exchange parameters including Asat , Qsat, αA, CE, Vcmax and Jmax in weak interference were enhanced by 2.7, 1.3, 1.4, 2.7, 1.9 and 2.8 times respectively than those in heavy interference. But the changes in those parameters were partly depended on light environment and CO2 concentrations, the influence resulted from the changes in light environment on weak interference individuals was significantly stronger than on heavy interference. While beyond the growth CO2 concentrations, the influence resulted from the changes in CO2 concentration on heavy interference individuals was obviously stronger than on weak interference. In conclusion, neighborhood interference can be described as a major means of intra-specific competition of population in a plantation forest with uniform forest structure and consistent management. Carbon assimilation will be affected by the neighborhood interference, and result in divergence in growth performance. Indices of neighborhood interference can be used to evaluate the intra-specific competition, and make the maximum usage on resources after stand structure well adjusted based on that.
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