Wang Chuan-Hua, Li Jun-Qing, Yang Ying
China Three Gorges University, Yichang 443000, Hubei, China.
Ying Yong Sheng Tai Xue Bao. 2011 Dec;22(12):3117-22.
To investigate the effects of atmospheric nitrogen deposition on the seedlings regeneration of Liquidambar formosana, a greenhouse experiment was conducted, in which, the low light- and nitrogen supplies were controlled similar to those in typical L. formosana secondary forests, with the effects of different light- and nitrogen supply on the L. formosana seedlings survival, leaf functional traits, biomass allocation, and gas exchange studied. The whole plant light compensation point (LCP(whoIe-plant)) of the seedlings was estimated with a whole plant carbon balance model, and then compared with the understory photosynthetic active radiance (PAR) of the typical secondary forests. Under 3.0% and 6.0% of full sunlight, eutrophic nitrogen supply led to a decrease of seedlings survival (shade tolerance) and specific leaf area (SLA), but had no obvious effects on the seedlings biomass allocation. At eutrophic nitrogen supply, light intensity had significant effects on the leaf area based maximum assimilation rate, whereas increasing nitrogen supply under low light induced the increase of leaf mass based dark respiration rate. Both light intensity and nitrogen supply had significant effects on the mass based leaf respiration rate, and the interaction of light and nitrogen had significant effects on the mass based stem respiration rate. Increasing nitrogen supply increased the LCP(wholeplant), under 3.0%, 6.0%, and 12.0% of full sunlight, but decreased the LCP(whoIe-plant) under 25.0% of full sunlight. The decrease of the seedlings shade tolerance induced by the increasing nitrogen supply under low light was correlated with the variations of the seedlings carbon balance capacity. Under the background of elevated atmospheric nitrogen deposition, the maintenance of L. formosana populations in China would more depend on disturbances and gap regeneration, and the population dynamics would be deeply affected.
为研究大气氮沉降对枫香幼苗更新的影响，开展了一项温室实验，该实验控制低光照和低氮供应，使其类似于典型的枫香次生林，研究不同光照和氮供应对枫香幼苗存活、叶片功能性状、生物量分配和气体交换的影响。利用全株碳平衡模型估算幼苗的全株光补偿点（LCP(whole-plant)），并与典型次生林林下光合有效辐射（PAR）进行比较。在全日照的3.0%和6.0%条件下，富氮供应导致幼苗存活率（耐荫性）和比叶面积（SLA）下降，但对幼苗生物量分配无明显影响。在富氮供应条件下，光照强度对基于叶面积的最大同化率有显著影响，而在低光照条件下增加氮供应会导致基于叶质量的暗呼吸速率增加。光照强度和氮供应均对基于质量的叶片呼吸速率有显著影响，光和氮的交互作用对基于质量的茎呼吸速率有显著影响。增加氮供应会使全日照的3.0%、6.0%和12.0%条件下的LCP(wholeplant)升高，但在全日照的25.0%条件下会使LCP(whole-plant)降低。低光照条件下氮供应增加导致幼苗耐荫性下降与幼苗碳平衡能力的变化相关。在大气氮沉降增加的背景下，中国枫香种群的维持将更多地依赖于干扰和林窗更新，种群动态将受到深刻影响。
