Development of a evaluation method of environmental effect on a forested ecosystem using a biogeochemical model based on stream-water hydrochemical processes

综述了扰动引起的森林生态系统环境变化的研究进展。在生物地球化学物质循环模拟模型中，我们考虑了针对美国北部森林开发的PNET模型对模拟日本森林长期环境变化的适用性。在定期采伐的森林流域获得的观测结果被输入到PNET-CN模型中，以模拟溪水的水质。该模型较好地再现了不同树龄小流域硝酸盐(NO3-)浓度的变化，但模拟结果与实测值存在一定差异。测井后20年内，测井对河流NO_3~-浓度的影响与观测结果一致。结果表明，高达40%的采伐率不会改变溪流…中NO_3~-的浓度水平再多一点。成功地模拟了木本植物生物量的长期变化和叶片含氮量的下降规律。然而，观测值和模拟值之间存在很大差距。它建议，应从水和营养条件以及核层发育的角度对模型中包含的参数进行仔细设置。为了弄清河流水质与流域环境条件之间的关系，我们对日本全国范围内的河流水化学进行了调查。我们收集了1270多个地点的溪水，并分析了离子浓度。结果表明，河流NO3-浓度在很大程度上受流域大气氮沉降的影响。与1950年S的前次调查相比，50年间日本溪流中NO_3~-浓度升高。流域内的地质特征影响了磷的浓度。较少

Studies on environmental changes in forested ecosystems caused by perturbations have been summarized. Among simulation models for biogeochemical material cyclings, we considered the applicability of the PnET model, which has been developed for northern American forests, for simulating the long-term environmental changes in forests in Japan. Observational results obtained in the forested watershed, where periodic logging has been conducted, were input to the PnET-CN model to simulate the water qualities of the streamwater. The model was well reconstructed the changes in the nitrate (NO_3^-) concentration among small catchments having different tree ages, although there were some difference in the level of concentrations between the observation and simulation. Effect of the logging on stream NO_3^- concentration can be found for 20 years after logging, coinciding with observations. It was suggested that logging rates up to 40% did not change the NO_3^- concentration level in the streamwa … More ter. The patterns of the long-term change in the woody biomass and the decrease in the leaf nitrogen content were successfully simulated. However, there were large gaps between observational and simulated values. It suggests that the careful setting of parameters included in the model should be done from viewpoints of water and nutrient conditions and the development of the rizosphere. Forest renewal and hydrologic processes should be taken into considerations to improve the simulation results.In order to clarify the relationship between stream water qualities and watershed environmental conditions, we conducted the nationwide survey on the stream hydrochemistry in Japan. We collected stream waters from more than 1270 sites and analyzed the ionic concentrations. It was suggested that the stream NO_3^- concentration was largely governed by the atmospheric nitrogen deposition to the watershed. From the comparison with previous survey in 1950's, the stream NO_3^- concentration in Japan increased during 50 years. Geologic characteristics in the watershed affected the phosphorus (PO_4^<3->) concentration. Less