香港芒萁群落养分的研究

 本文研究香港芒萁群落养分的分配、季节动态和循环。研究结果表明：(1)N、P、K浓度在活物质大于死物质，地上部分大于地下部分。(2)植物的养分贮量是活物质大于死物质，地下部分大于地上部分。(3)当年生芒萁地上部养分贮量随生物量的增加而增加，但是，干物质生产率超过养分吸收率，使得N、P、K浓度由于生物量的增加而降低。(4)虽然芒萁群落的净第一性生产力大于其邻近的草地和灌木林，但其净第一性生产量中的N和P量却小于灌木林。(5)以土壤中的总N和总P来计算，生态系统中的N和P主要贮存于土壤库中，但以土壤有效K来计算，则有大约36％～50％的K贮存于植被中。(6)在研究期间，立枯体和死地被物中的N、P、K贮量逐渐增加，这表明在火灾后生态系统的立枯体和死地被物养分库有一个累积过程。(7)N、P、K通过枯枝落叶的归还量分别占它们在地上部净第一性生产量中的49.1％、30.8％和13.1％，而地上部净第一性生产量中的N和P的31.2％和46.6％来自于养分的内部循环。

A STUDY OF NUTRIENTS IN FERNLAND OF HONG KONG

The study deals with distribution, seasonal dynamics and cycling of nutrients in a Dicranopteris dichotoma community of Hong Kong.The results show that: 1) concentrations of N,P and K in live materials were greater that in dead materials, but greater in aboveground plant parts than in belowground plant parts. 2) Nutrient contents were greater in live materials than in dead materials, but greater in belowground plant parts than in above plant parts. 3) Above ground nutrient contents of current plants increased with increment of phytomass. However ,the production rate of dry matter exceeded uptake rate of nutrients so that the relative concentrations of N,P and K were reduced due to phytomass increase. 4)Although net primary production in the fernland was greater than those in the grassland and scrubland which are near the fernland, the N and P mass in net primary production of the fernland was less than that in the scrubland. 5) Most of N and P in the ecosystem were stored in the soil, in terms of their proportion to their total values. However, the vegetation contributed to about 36%～50% of K in the ecosystem, in terms of available K in the soil. 6) The contents of N,P and K in standing dead matter and litter increased gradually during the study period. This means that there was an accumulative process in the nutrient pool consisting of standing dead matter and litter of the ecosystem after fire. 7) The return of N, P and K by litterfall explained their 49. 1%,38.0% and 13.1%, respectively, in net aboveground primary production (NAPP). 1.2% and 46.6% of N and P in NAPP came from the internal cycling.