Estimation of stress history of trees in declined and deserted forests by carbon isotope analysis

在中国黄土高原，广泛种植油松和刺槐，以防沙治沙。对这两个树种的年轮早材和晚材的碳同位素比值进行了分析。松树的气孔比蝗虫敏感，前年10月到今年6月的气候对早期木材的同位素比值有影响，而现在的6~8月气候对晚期木材的同位素比值有影响。蝗虫的气孔对气候的反应不太敏感，其同位素比值低于松树。结果表明，草地蝗虫的水分利用效率较低，松林土壤水分含量较高，透水性较高，地上植被较丰富，而蝗虫的水分含量较草地低。所有这些结果表明，蝗虫比松树更容易蒸腾水分。松树枯萎病造成的森林衰退。对筑波松林进行了调查，并利用IKONOS遥感数据进行了松林受害情况的监测。用核磁共振显微镜观察了松材线虫病的枯萎过程，认为松材线虫病的枯萎机理为失控的栓塞物。在坦桑尼亚泽山衰退的山毛榉(Fagus Crenata)林中，衰退可能会影响外生菌根多样性。通过对亚高山冷杉林林分消长过程的研究，阐明了两种冷杉树种共存的机制。

In Loess Plateau in China, Chinese pine (Pinus tabulaeformis) and black locast (Robinia pseudoacacia) are widely planted to prevent desertification. For these two species, carbon isotope ratios of early and late wood of tree rings were analyzed. Pine has more sensitive stomata than locust, and climate of previous October to current June was found to affect to the isotope ratio of the early wood, and those of current June to August to the late wood. Locust showed less sensitive reaction of stomata to the climate, and isotope ratio was lower than that of pine. These result suggested lower WUE (water use efficiency) of locust.In the stands planted with pine had higher soil water content and water permeability and richer floor vegetation, while locust showed lower water content than grassland. All of these results suggested that locust tend to transpire water than pine.Forest decline caused by pine wilt disease in Mt. Tsukuba was surveyed and damaged pine stand was detected by remote sensing data of IKONOS. The process of wilting in pine wilt disease was visualized by Magnetic Resonance Microscopy, and mechanism of wilting was suggested to be a runaway embolism. In declined beech (Fagus crenata) forest in Tanzawa Mountains, decline was suggested to affect ectomycorrhizal diversity. In subalpine fir-wave forest of Abies spp., process of stand development and decline was studied, and mechanism of coexistence of two fir species was clarified.