杉木人工林生态系统中氮素的动态特征

DYNAMC PROPERTIES OF NITROGEN IN THE CHINESE FIR PLANTATION ECOSYSTEM

本文介绍会同县18年生杉木人工林生态系统中氮素的分布、转化、消长和循环方面的初步研究。结果表明,该系统总氮量为12287.6公斤/公顷,其中约有97％存在土壤库中,植物固定的氮仅占总氮量的2.5％。杉木枝叶中的氮含量因受“稀释效应”的影响,表现为随时间的推移而降低,尤其是在当年生枝叶的萌发初期。该生态系统每年经水文学途径获得7.35公斤N/公顷,径流输出0.98公斤N/公顷,即该系统每年以6.37公斤/公顷的速率净积累氮,表明杉木林生态系统对氮素的保存和利用的能力较高。文章还建立了氮素动态数学模型并进行初步模拟。

This paper presents recent studies on distribution, growth and decline, transformation and cycling of nitrogen in the Chinese fir plantation ecosystem. The results show that the total quantity of nitrogen in the ecosystem is 12287.6 kg/ha and the majority of the nitrogen of the system (about 97%) is found in the soil compartment as organically bound nitrogen, and only 2.5% is located in the vegetation. Nitrogen content in the branch at d leaf decreases with increasing time because of 'dilution effect'. Nitrogen inputs to the system in bulk precipitation r.re greater than losses via leaching. Of the estimated 7.35kg/ha籥 entering the ecosystem by precipitation, about 86.7% is held or accreted within the ecosystem, as it accumulaties netly 6.37kg N/ha annually. These facts show that the Chinese fir plantation ecosystem has great ability for conserveing and utilizeing nitrogen. Besides, the dynamic mathematical model of nitrogen of the system has been established and primarily simulated.