| In recent years, with the global warming and extreme weather are more frequently, structure and types of forest are undergoing tremendous changes. As an important part of forest ecosystem forestry diseases have got a lot of impact from the climate change directly or indirectly. Arceuthobium sichuanense is a parasitic seed plant disease that mainly harm to spruce trees have make a seriously economic loss in nature spruce forests of "san jiang yuan" areas now. It is so serious that restrict economic and social development in local areas. This paper focus on studying 3 questions what are suitable areas of Arceuthobium sichuanense, the impact of climate change for Arceuthobium sichuanense, the impact of climate change for extent of injury made by Arceuthobium sichuanense. To get this goal, the niche models and dendrochronology have be used. By studying those questions,3 conclusions have be made in following:(1) The first question, it predicted and analyzed where are the suitable areas of Arceuthobium sichuanense by using GARP and MaxEnt models, points data of Arceuthobium sichuanense known by now and some grid data of environmental variables. Then use the ROC curves to make a test. The result showed range maped by GARP model is more widely than MaxEnt, but the display of every levels is poorer than MaxEnt model. So in this study, two map had been overlayed to one map according to 4:1 weight to get a better display and ROC curves test reveal AUC=0.937(Excellent). The final map showed Arceuthobium sichuanense mainly concentrated in Qinghai, Gansu, Sichuan, Xizang provinces, and the central areas of Arceuthobium sichuanense were the cross land of Qinghai, Gansu, Sichuan. By other hand, GARP and MaxEnt models all revealed temperature variables had a more significant effect, and precipitation variables just have normally effect.(2) The second question, the suitable areas between 1961 years and 2000 years had been analyzed by MaxEnt model. The result showed the central areas were also the cross of Qinghai, Gansu and Sichuan provinces, and suitable areas have a obviously change in size and direction. The range have a trend that suitable areas toward to northwest and southwest and southwest trend was more significant. This part also made a statistical analysis to the range of suitable areas every years, and the result showed that a upward trend year by year, and 1989 years got a maximum. Among those years, most suitable areas had increased 2.70x 103 square kilometers, middle suitable areas were 9.58×104 square kilometers and low suitable areas were 3.73x 104 square kilometers and total increased 1.36x 105 square kilometers.(3) The third question, this paper major study on how were climate change damage to Arceuthobium sichuanense by dendrochronology. The result showed when DMR got the level 3, then tree rings width had a significant change. The statistical analysis of volume increment which DMR>3 level according to time series showed 1992 years occurred a significant reduce compared to other years. In other words that the Arceuthobium sichuanense destroyed their host trees seriously. Temperature compared to precipitation were more correlative with volume increment of host trees, and temperature had a different impact to health and sick spruce what was the former have a positive correlation and the latter have a negative correlation... |
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