| Climate is the main determinative factor of the vegetation type and distribution, climatevariation results in the change of vegetation distribution and plant community. Pinusyunnanensis, unique species in Southwestern China and characterized by high ecologicaladaptability, it's of great significance to research. In this thesis, studies on geographicaldistribution,communities and ecological adaptability of P. yunnanensis were discussed.Geographic distribution and Temperature and Moisture indexs of P. yunnanensis are studied,Detrended canonical correspondence analysis (DCCA) was used to analyze the effect of eachlandform and climatic factor on the number of plant species and the structure of plant speciesdistributions and diversity in different strata of Pinus yunnanensis forest and the relationshipamong these factors. The spatiotemporal change characteristics of climate resources in Yunnanand suitable area's changes of P. yunnanensis were analysed based on the geographicinformation system(GIS). The results showed that:(1)P. yunnanensis is distributed mainly in Yunnan, Sichuan, Guizhou, Guangxi and Tibet.The distribution area terrain is complex and changeful following with big altitude difference,presents the obvious northwest tall, southeast low terrain, tilt is not uniform and multistagestepped down. The distribution area has a subtropical plateau monsoon climate generally. P.yunnanensis's Warmth Index(WI) range is32.1~204.3℃·month, optimal range is86.065~159.705℃· month and mean value is122.885℃·month, the limitrange(Minimum~Maximum) is wide and several other indexes also show the same pattern, thisshows that P. yunnanensis distribute with a wide range of climate. It's BiologicalTemperature(BT) range is6.142~22.025℃, optimal range is12~18℃and mean value is15.208℃, this shows that the warm and cool climate are suitable for growth ofP. yunnanensis.However, it's Coldness Index(CI) mean value is-0.398℃·month and minimum value is-20.7℃· month, this shows thatP. yunnanensis has somewhat ability to withstand freezing but the optimum growth temperature is relatively high. Annual precipitation is478mm~1870mm,1009.319mm of average value, Xu's Humidity Index(HI) is3.431~32.616, average8.920, theratio of temperature and precipitation of the year is13.300~46.800, average25.892,Holdridge potential evapotranspiration ratio is0.331~1.874, average0.921, frost-free period131days to359days, average292days. The hydrothermal indexes show that the distributionof P. yunnanensis is wide and elevation, distribution condition of the climate inside the area iscomplex, but it's adapted to climate change. The Coldness Index of upper limit distribution of P.yunnanensis-20.7is very low, it's-3.4in north limit position, higher than that in upper limit.WI is32.1in upper limit position and93.7in north limit position, former is lower than latter,that shows the same pattern. Coldness index is a significant cultural factors that limits P.yunnanensis upward and northward distribution. Finally, the major climatic factors effectingthe distribution of P. yunnanensis were screened out by statistical analysis software SPSS in theorder of temperature＞humidity＞the temperature difference between mean warmest monthtemperature and mean coldest month temperature.(2) The basic character of P. yunnanensis community is simple, tree layer species are notdiverse, majority P. Yunnanensis. The factors of species distribution, quantity and diversityhave greater regularity, mainly by the mean annual summer (May to Sept.) precipitation, meanannual precipitation, mean annual temperature, the number of frost-free days and elevation ofthe common effect. Different results of DCCA ordination show that landform and climaticfactors have different effects on levels of plant community, tree layer species distribute widely,this means that the tree layer species of P. Yunnanensis have different requirements toenvironment factors and distribute differently. The effect of environmental factor on the speciesdiversity pattern and the plant species distributions of tree layer gave the followingsubsequence (from great to little): mean annual summer (May to Sept.) precipitation, range oftemperature, mean annual precipitation. The result on the shrub layer was: mean annualsummer (May to Sept.) precipitation, mean annual precipitation, the number of frost-free days.The shrub layer vegetation distribution is relatively uniform with less overlapping, the differences among the species numbers over the four quadrants are very little. That meansunder different conditions as climatic and landform factors, there are corresponding andadapted species in the shrub layer of P. Yunnanensis. The result on the herb layer was: thenumber of frost-free days, elevation, mean annual summer (May to Sept.) precipitation. Theplant distribution in herb layer is concentrated with some overlapping. It shows that herb layerspecies have common adaptability to climate and always grow with P. Yunnanensis. Impacts ofhuman disturbance on the shrub layer were much higher than that on the tree and herb layers.(3)The interannual variation curve of Warmth Index(WI) in Yunnan province wassignificantly elevated, from1970121.30℃·month to2002133.57℃·month, and the HumidityIndex(HI) interannual variation curve was downward trend, from197010.97mm/℃·month to20028.92mm/℃·month. WI fluctuation was more significant than CI fluctuation. Themaximum value occurred during1998136.63℃·month, and the minimum value for the1976117.13℃·month. However, the maximum value and minimum value were both belong to theoptimal range of P. Yunnanensis. Under the condition of climate changing in the future, P.Yunnanensis will be centralized in areas of middle Yunnan, but the distribution area will change.The north distributing limitation will move unobviously but the south boundary will atrophyobviously, and the suitable area will decrease stage by stage. By2020, the best suitable area ofP. Yunnanensis will reduce1.88%,2050reduction in8.21%, and in2080reduce9.41%. By2080, the unsuitable area will increase4.79%and it will be accelerating trend. |
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