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

在我国黄土高原地区，油松和刺槐被广泛种植，以防止荒漠化。对这两个树种的早、晚材年轮碳同位素比值进行了分析。松树的气孔比刺槐敏感，前10月至当年6月的气候影响早材的同位素比值，当年6月至8月的气候影响晚材的同位素比值。刺槐气孔对气候变化的反应较不敏感，同位素比值低于松树。结果表明，刺槐的水分利用效率（WUE）较低，油松林下土壤含水量和透水性较高，地被植被较丰富，而刺槐林下土壤含水量低于草地。这些结果表明，刺槐比松树更易蒸腾水分。利用IKONOS遥感数据对筑波市进行了调查，并对受损的松树林分进行了检测。利用磁共振显微镜观察了松树萎蔫病的萎蔫过程，认为萎蔫的机理是一种失控的栓塞。在丹泽山的山毛榉（毛榉）林衰退，下降的建议，影响外生菌根多样性。在亚高山冷杉冷杉林中，研究了林分的发育和衰退过程，阐明了两种冷杉共存的机制。

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.