| The rocky desertification in karst mountainous areas of southwestern China, a specific phenomenon of land degradation, is one of the most serious environmental problems and a hotspot of ecological research. The critical situation of population, resources and environment restricts seriously the sustainable development of this region. This resulted in the poverty which will become worse and worse. During recent years the central and local governments and the public worked hard to attempt to address this problem. Some of scientific and technological achievements about the comprehensive treatment of rocky desertification have been successfully obtained. However the increasing trend of rocky desertification has not been basically restrained. The governance situation still remains rigorously. The restoration and reconstruction of the Karst desertification ecosystem has become the key issues in deciding the sustainable development of economy and society in southwestern China. Due to the lack of related basic scientific studies, more ecological research is urgently needed.In this study we used Guizhou Proveince as the target area where have extensive distribution of karst morphology and serious rocky desertification. Three aspects related to karst vegetation change and restoration were studied based on field investigation, data collection and synthesis. Firstly, we estimated the biomass of different forest types during 1996-2000 and 2001-2005 in Guizhou Province using the continuous forest inventory data and volume-biomass transfer functions of major forest types. We combined the spatial and temporal changes of biomass pattern with the karst/non-karst landform and focused on the dynamic changes karst forest biomass. Correlation of forest biomass and recent rocky desertification level was further analyzed. This will provide the background information of productivity maintenance mechanism and adaptive rehabilitation for the ecological restoration and rocky desertification control in karst areas. Secondly the current status of plant species selection for ecological restoration of rocky-desertified karst vegetation was investigated in Guizhou province based on data from internet searching, literature review and field surveys. The restoration effectiveness of selected plants was then preliminarily evaluated. Thirdly, we attempted to summarize and synthesize the existing theory, fundamental, and approach of karst rocky desertification treatment. Advice and attentive issues resolving the existing problems of present treatments are provided. Main results are as follows:1. The total biomass of trees and shrubs in forests and non-forest was 3.51×108 ton in Guizhou during 1996-2000. Of them woods in non-karst region accounted for 82% and in karst region 18%. Different types of forests had different total biomass. Forest stand had the highest total biomass among all forest types, accounting for 71.4% of total forest biomass. Forest in karst region had obviously less total biomass than in non-karst terrain. Cunninghamia lanceolata had the highest total biomass (5.38×10' ton) among all dominant species (and species groups). Total biomass of sclerophyll broadleaved woods was 4.99×107 ton. Pinus massoniana, P. yunnanensis and Quercus had total biomass between 2.8-3.5×107 tons. Cupress and malacophyll broadleaved woods reached 1.5×107 ton, respectively. Other dominant species had relative low biomass below 1×10'ton. Based on statistics of political region, total biomass (9.83×107t) and forest stand biomass (5.81×107t) in Qiandongnan were all 2-3 folds higher than those in Zunyi, Tongren and Qiannan. They were far higher than in Qianxinan, Bijie, Guiyang, Anshun and Liupanshui (total biomass 0.53-1.85×107t and forest biomass 0.16-0.86×107t, respectively). High biomass (>400t·hm-2) and middle-high biomass density (100-400 t·hm-2) mainly occurred in bamboo forest and forest stand of the southeast, east and northwest. Middle-low biomass (30-100 t·hm-2) occupied all of forest and non-forest area of the province. Low biomass (0-30t·hm-2) occurred mainly in karst terrain. In general forests in Guizhou have low biomass. This is closely related to the topography of plateau and mountains. The rocky-desertification in karst terrain and the shallow soil layer and dry habitat under karst forest restricted forest growth and then reduced forest biomass. Human activity also has strong disturbance in forest distribution and production.2. Between 2001 and 2005, total biomass of Guizhou forest lands reached 3.43×108t (please note:items are different from the period of 1996-2000 due to data availability). The volume and biomass of forests were much higher than other land types. Total biomass in Qiandongnan was the highest and in Liupanshui it was the lowest. Forest in non-karst terrain had obviously more total biomass than in karst region. From the political region point of view, Anshun had the most severe karst rocky desertification (the ratio of karst rocky desertification to total area of the region is 31.72%) and the Qiandongnan had the lightest situation. Analyses based on landform and rocky desertification level found that there were highly significant correlations between rocky desertification level and slope, soil thickness, tree diameter at the breast height (DBH), tree height, forest age, volume and biomass. Except for a few special examples, the volume and biomass of all the karst forests are lower than non karst forests and the rocky desertification in karst forests is much more serious than non-karst areas.3. Between 1996 and 2005 Guizhou forests had mainly changed as follows: Forest land area increased by 768.00×103 hm2. From forest type point of view, areas of forest land, shrub land and minor forest increased, and woodland and non-forest land areas decreased. From forest utilization point of view areas of shelter forest and special-purpose forest substantially increased, and areas of timber forest and fuel wood forest drastically reduced. In political regions, forest was still mainly located in the east, south-east and north of Guizhou Province (Qiannan, Qiandongnan, Tongren Prefecture, northwest comer of Zunyi). Total biomass of Guizhou forests increased from 2.58×108t in 2000 to 3.43×108 in 2005. Spatial patterns of volume and biomass of different forest types changed very little. Biomass patterns at two periods wer similar in different political regions and karst and non-karst regions. 4. In total 85 plant species were used in vegetation restoration in 328 sites of 78 counties and cities of Guizhou Province. Among them, there are 26 plants of ecological forest (mainly pine, fir, cypress, Chinese toona, poplar and clammy hopseedbush),45 plants of economic forest including 26 Chinese medicines (such as Taizi ginseng and gaxtraodia) and 19 fruit trees (pear, peach, plum, chestnut and honeysuckle),14 pastoral species (white shamrock, ryegrass and alfalfa). These species were planted in assemble or scatter in different comprehensive treatment areas of karst rocky desertification:Area A (western Guizhou plateau and mountain), Area B (middle Guizhou hill plain and mountain), Area C (eastern Guizhou lowland and hills) and Area D (non rocky desertification in southeastern and southern Guizhou). In terms of the effectiveness of restoration activities, the integration of cash crops (such as tea and oil tea), medicinal plants, flowers cultivation, and pastoral husbandry into a restoration project has showed good prospects in regional development of industrialization. Economic and fruit forests such as honeysuckle, chestnut, pear and peach growing in their optimal habitats also benefited local environment and economy. However, there are still problems about plantation and management of artificial forests during the processes of ecological restoration of rocky-desertified vegetation, for example, singularity of tree plantations, simpleness of species configuration, and extensive management. These problems resulted in lower ecological functions and economic values that should be urgently and earnestly improved.5. During the comprehensive treatments of rocky desertification in karst mountainous area of SW China, we should follow some fundamentals. The treatment must accord with natural rules. Both economic development and ecological construction must be equally paid attention to. Different places and different situation of rocky desertification must be treated in different ways, and such different treatments must be performed according to ecological divisions. Furthermore technique and measurement should be exercisable in order to maintain the sustainable development of ecosystems in this degraded mountainous area. Many successful and effective approaches have been explored through the practice of long-term rocky desertification treatments. Such approaches include ecological restoration engineering, essential agricultural construction engineering, exploitation and utilization engineering of water resources, marsh gas pit engineering, ecological migration, pasture and stockbreeding, and ecological agriculture development. Many problems still existed during and after the treatments. Following suggestions of solving the existing problems must be paid more attention:the ecological compensation of returning farmland to forest and grassland (grain for green policy); resettlement of ecological migration and the ability oriented education determination of the range of rocky desertification control; management, maintenance and reformation of marsh gas pit; scope of the pasture, staff training of the awareness of economic management, and improvement of animal husbandry technology in the development of pasture livestock breeding; design, construction and refinement of side-slope in the "transforming hillside to terrace"; and the selection of plant species and combination of afforestation and forest management in "tree planting and afforestation" projects. |
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