| The provisions of "the integrated countermeasure of rocky desertification in karst areas of Guizhou,Guangxi and Yunnan" in《The Tenth Five-year Plan of National Economy and Society Development of the People' s Republic of China》were passedin March.2001.It became a national goal that karst rocky desertification would be controlled and special and degenerative karst ecosystem would be rehabilitated in Southwestern China.However, how are fragile karst ecosystem rehabilitated with optimal technology and high quality engineering? How much are on earth cost and benefit of rehabilitated karst ecosystem? How are the cost and the benefit evaluated ? The above questions must be solved in the integrated countermeasure of karst rocky desertification.Representative researches were included ecology rehabilitation technology of Guohua demonstration zone and ecology rehabilitation mechanism of secondary and economic forest in Longla demonstration one by field observation and demonstration engineering and so on, as a case study of Guohua and Nongla demonstration zone,in Pingguo county and Mashan county,Guangxi.Then,The methods of ecological economic valuation were applied to the value assessment of rehabilitated karst ecosystem,results are as follows:(1) Practised ecology rehabilitation technology in Guohua mainly included techniques of soil improvement,exploitation of ep(?)karst water resources,choice-bred,introduction of karst vegetation.Karst water resources of Guohua were exploitated 2×10~4m~3/a,one of Longla 27317.2m~3/a,high epikarst spring with "storage—diversion" technique;dispersing flow or converging flow of epikarst underground water with "interception—storage—diversion", subterranean rivers of high elevation depression with "lifting—storage—diversion".Areas of cultivated land was increased 150hm~2 by cascaded land consolidation along terrain contour line of peak-cluster depressions.Available N,available K,available P and organic contents in the improved soil respectively went up 90.19μg/g,47.92μg/g,14.28μg/g和0.21%by methods and measures of return of straws into soil,using organic fertilizer and sulfidation process canesugar mill filtered mud.Vegetation density of Guohua went up 75%in 2007 from 10%in 2000,vegetation species also rose from 25 to 32,with introduction of soil seed bank and pioneer plants,techniques of artificially assisted restoration and the adapted compositions of arbors-shrubs-grasses.(2) Regulating capability of water resources in epikarst zones under secondary forest showed that total transpiration of secondary forest was 21319 m~3 in 1 year,with 33%of total precipitation and 42%of infiltration in Landiantang drainage area.These results farther proved that plant transpiration would increase,while plant communities raised a higher succession stage.Therefore,plant species of low transpiration rate should be cultivated or that of high transpiration rate cut down among rehabilitating water-source ecology forest in karst rock desertification areas.The ecological water requirements and the economic water requirements all are kept optimal.(3) Results of measured secondary forest in Nongla,with LI-6400 made in America and the stable carbon isotope technique,showed that water use efficiency(WUE) of all kinds of plant species were different.These plant species could be respectively arranged from high to low as WUE:Engelhardtia roxburghiana,Decaspermum esquirolii Cyclobalanopsis glauca,Lonicer maack,Zenia insignis,Indocalamus latifolius,Alchornea trewioides (Benth.),Foliumllicis Latifoliae,Radermachera sinica,Caesalpinia sepiaria Roxb., Vitex negund,Leucaena leucocephala,Toona sinensis,Callicarpa nudiflora,Bumbusa stenostachia,Eriobotrya japonica.WUE of Engelhardtia roxburghiana,Decaspermum esquirolii Cyclobalanopsis glauca,Lonicer maack,Zenia insignis were more higher,showed that they had eximious drought resistance and drought tolerance.Therefore,Engelhardtia roxburghiana,Decaspermum esquirolii Cyclobalanopsis glauca,Lonicer maack,Zenia insignis should be firstly breeded and introduced during rehabilitating karst ecosystem in rock desertification zones.However,WUE of introduced Leucaena leucocephala,Toona sinensis,Callicarpa nudiflora,Bumbusa stenostachia,Eriobotrya japonica,in Nongla were very low,and,they have fragile drought resistance.As a result,it was very indispensable that native species should be breeded and cultivated.(4) The ecological service value of restored and rehabilitated ecosystem was very high in karst rock desertification areas.Based on the methods of benefit-cost analysis,the total service value of rehabilitated ecosystem in Guohua was RMB31473986 yuan.Deducted from actual expenses during rehabilitation,total ecological economic net value was RMB19586948 yuan.Net value was 8.9 times as much as actual expenses.The total ecosystem service value of Nongla was RMB17466608 yuan yearly,with the market value approach, opportunity cost method,shadow project method and so on.Soil conservation value and example education by demonstration,scientific research value of them were more higher, with RMB2609910 yuan and RMB8600000 yuan respectively.The above results farther showed that restored and rehabilitated ecosystems could play an important role in controlling the soil and water loss,education,scientific research.
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