研究全球变化的植被-气候分类系统

A VEGETATION-CLIMATE CLASSIFICATION SYSTEM FOR GLOBAL CHANGE STUDIES IN CHINA

本文应用Holdridge的生命地带分类系统进行我国的植被-气候分类。计算结果所划分的生命地带与我国的植被分区有较好的对应性。该系统与计算净第一性生产力(NPP)的chikugo模型结合尚可推算各地带的潜在净第一性生产力。文中对CO_2倍增条件下的我国植被演变趋势和生产力变化做了预测,并采用GIS做了图形分析和显示。

The study on vegetation-climate interaction is the basis for research of ecosystem response in global change. By means of quantitative analysis on vegetation-climate interaction or digitized diagram of bioclimatology, vegetation types and their distribution pattern can be corresponded with certain climatic types in a series of mathematical forms. Thus, the climate can be used to predict vegetation types and their distribution, the same is in reverse. Potential evapotranspiration rate is a comprehensive climatological index which combines temperature with precipitation and can be used to evaluate the climatic control of vegetation. In this respect, Holdridge's method has been devoted much attention and widely applied internationally by its simplicity, reasonableness, and close correspondence between vegetation and climate. It is especially applicable for the assessment of sensibility of terrestrial ecosystems and their distribution in accordance with climate change and to predict the changing pattern of vegetation under doubled CO_2 condition. Holdridge's life zone system is an integrated relationship or geometric series of annual biotemperature (BT), annual precipitation, and potential evapotranspiration rate (PER), which constitutes a climatological diagram for natural vegetation. The BT, PER, and life zones of China's biomes or vegetation zones are resulted by applying this system to calculate more than 700 climatological stations in China. Comparing with China's vegetation division map, the distribution map of life zone in China displayed by EIS shows a quite good correspondence with the former one, but there are some differences as follows: 1. China's subtropical vegetation zone mostly belongs to warm-temperate zone in Holdridge's life zone system; 2. The correspondence between vegetation zones and life zonesoin western China is relatively lower. This is owing to that there is no enough climatological stations in there, and also the simulation on high plateau climate and vegetation is insufficient by Holdridge's system; 3. The snow-line of Holdridge's system is too even. It should be higher in elevation on arid mountains than which on moist mountains That means the BT of snow-line would lower on the former one. Therefore, an appropriate correction was made for Holdridge's system. According to the result of analysis by calculating climatological data of vegetation zones using Holdridge's system in China, the BT, potential evapotranspiration (PET), and PER show geographical zonalities. There are close correlation among the climatological parameters and geographical indexes: latitude (L), longitude (G), and altitude (H). Their regression correlations are as follows: BT=44.5275-0.488664L-0.109246G-0.00352548H (r^2=97.1%) PET=2626.64-28.7953L-6.4565G-0.208039H (r^2=97.1％) PER=10^(6.6935+0.05817L-0.074054G-0.00048954H) (r^2=67.5％) In China's continent, while increasing each one degree of latitude towards north, BT would decrease 0.49℃ and PET would decrease 28.8 ram; While increasing each one degree of longirude towards east, BT would decrease 0.11℃ and PET would decrease 6.Smm; While increasing each 100m of altitude, BT would decrease 0.35℃ and PET would decrease 20.8mm. PER has also close correlation with Budyko's radiative dryness index (RDI): RDI=0.55802+0.314O1PER-(9.8624E-3)PER~ + (1.2274E-4)PRE^3 (r^2=90.9%) Thus, the net primary productivity (NPP) which was calculated from RDI in Chikugo Model, now, could be easily obtained by using PER. The regressional correlation of NPP on geographical indexes is as follows: NPP=12.0448-0.560691L+0.152365G-(0.115307E-2)H (r^2=90.0%) That means while increasing each one degree of latitude, NPP would decrease 0.56t/ha.a; while iucreasing each one degree of longitude, NPP would increase 0.15t/ha.a; and while in creasing each 100m of altitude, NPP would decrease 0.116t/ha·a. It is estimated that under the global warming caused by doubled CO_2 content in the atmosphere, the annual mean temperature may increase 2—4℃ and the annual precipitation may increase 20％; according to calculation from Holdridge's system, the forest zones in eastern China's continent may be push towards the north for 2.5—4.5 degree of latitude, the boreal coniferous forest zone will be almost moved out of the northern boundary of the country. The tropical forest zone should expand towards north from southern coast. The temperate steppe zone may be forced to shrink back in the east by the forest zone and by the desert zone in the west. The vegetatiou on the Tibet Plateau seems mostly sensible to be warming and changes tremendously, its alpine desert will mostly transfer to temperate desert, and greatly increase the area of temperate desert in China.