Research On Land Use Changes And Ecological Effects In Lijiang River Basin

Land-use/land-cover(LULC) changes are considered as a key issue of global changes, which is influencing and altering ecosystem structures and services at different scales. Understanding LULC changes and its ecological effects is important to enhancing ecosystem sustainability and maintaining ecological security. The Lijiang River basin, as one of the most famous travel destinations, has a typical karst landform and sensitive environment. With the rapid urbanization and intensive tourism in recent, this area increasingly faces a serial of environmental challenges, including LULC changes, pollutions, biodiversity decrease, and land deterioration, etc. Thus, the study on LULC changes and its ecological effects in the Lijiang River Basin is significant to regional ecosystem management. In this study, we aim to reveal human-induced disturbances’ effects on regional ecosystem structure and functions. We will:(1) quantify the LULC changes in the Lijiang River basin;(2) estimate its ecological effects based on remote sensing and geographical information technique; and(3) develop a framework for improve ecosystem management in the Lijiang River basin, along “pattern-process-effect” guideline. Combing with field survey, a set of remote sensing images was used to extract the LULC data in Lijiang River basin to quantify the LULC changes and its ecological effects. Our results will supply a reference to ecological environment construction and decision-making.The main results include:(1) Significant LULC changes were observed in the Lijiang River basin during 1973-2013 a. In this area, woodland was the primary LULC type. Various LULC types showed different change trends across whole stage. Woodland, construction land and unused land increased while farmland decreased. Water body increased first and then decreased, whereas the grassland was on the contrary. Moreover, the distribution of LULC types showed significant differences in slope degree and elevation. Most of Woodlands located in the area more than 8° in slope degree while the farmlands and construction lands were found in the area under 8°. Water body and unused lands mainly appeared in the area under 15°. Additionally, most woodlands were exist at the elevation zones in 200-500 m and 500-800m; farmlands, construction lands, water body and unused lands appeared at the elevation zones blow 500m; grasslands were concentrated on the elevation zone of 200-500 m. In the past four decades, comprehensive dynamic degree of land use showed an increase trend after decrease. The peak value appeared at 2000-2013 a, indicating dramatically changes of LULC in the study area. The single dynamic degree of woodland and farmland showed a continuously increase trend. Compared with change of water, the change speed of construction land was higher than other LULC types.The fragmentation degree increased due to dispersed urban sprawling and fruit planting in the Lijiang River basin during 1973-2000 a. In this stage, patch complexity increased and drove the whole landscape to fine-grain landscape. However, an opposite trend appeared after 2000 a, since concentrated urban sprawling and farming, as well as the gain-for-forest. Thus, landscape fragmentation decreased in this stage. Across whole stage, the fragmentation degrees of woodland and construction land decreased after increasing, the fragmentation degrees of farmland increased. Unused land tended to be concentrated.The primary influence factors of LULC changes can be explained as the adjustment of agricultural planting structure and agriculture and forestry development during 1973-1986 a. However, the effects were different for various study stages. During 1986-2000 a, urbanization and fruit industry development were the main influencing factors to landscape transform, while urbanization, industrialization, rapid tourism development and gain-for-forest were the main forces during 2000-2013 a.(2) The ecosystem service value(ESV) kept a continuous increase during the 40 years with the net value increased 8.27×108 yuan, and the ESV of woodland was the largest. The ESV per unite area increased with the slope, the slope zones above 25° had the largest ESV per unite area and the slope zones between 15~25° had the largest ESV in different periods. The ESV per unite area was increased with altitude, the ESV per unite area of high altitude localities was the larger and the altitude belt within 200~500m had the largest ESV in all the periods.Little change of the contribute ratio of each single service value within 1973-2000 a, and water conservation service decreased sharply in 2000-2013 a with the rapid growth of construction land area. The regulation and support service function of ecosystem in Lijiang River basin was far more than production and culture function. Within the four periods, the climate and gas regulation service, formation and protection of soil service, biodiversity conservation service, raw materials, entertainment and culture service was continuous increased; water conservation service increased firstly and then decreased; waste treatment and food production service was continuous decreased.In the whole period, Woodland and water body converted into other land use types led to the loss of ESV, and farmland, construction land, grassland and unused land converted into other land use types led to the increase of ESV. Different land use types converted into construction land caused the loss of ESV, whereas different land use types converted into water body brought the increase of ESV due to the highest ecological value coefficient of water body and the lowest ecological value coefficient of construction land.(3) Most of the towns in Lijiang River basin were located at the highest and higher ESV region in the past 40 years, and the overall distribution pattern of ESV was basically stable, which showed the characteristic of north and east higher, central and south lower. The high ESV region mainly distributed at Hua Jiang, Lan Tian, Qing Shi Tan, Liang Shui, Zhong Feng, Jie Shou, Rong Jiang, where had a larger area of forest and water body; the low ESV region was mainly concentrated in Guilin city and surrounding townships, where had a high degree of urbanization and human intense disturbance.The ESV level of most districts was basically stable, and the changing zones mainly concentrated at central area of Lijing River basin.In order to accurately describe the internal differences of ESV in each administrative unit, grid method has been taken into this research. The results showed that the ESV of Lijiang River basin was in a high level and increased continuously, but part of low ESV region tended to be centralized from scattered distribution. Moreover, the spatial distribution of ESV showed a significant spatial positive correlation. Most of grid cells belonged to highest and higher ESV region, and the number was continuous increased. Region with high ESV mainly distributed at forest area in the north and mid-eastern of Lijiang River basin, and region with Low ESV concentrated in the tourism economical belt of Xingan county town-Lingchuan county town-Guilin city-Yangshuo county town.(4) The overall ecological risk of Lijiang River basin kept at a lower level and slightly decreased during 1973-2013 a, whereas the ecological risk in local region was sharply increased. The spatial distribution of ecological risk showed a significant spatial positive correlation in four periods. lowest and lower ecological risk areas were dominant in Lijiang River basin, and showed a trend of gradual increase. The areas of higher and moderate ecological risk were decreased and the areas of highest ecological risk expanded quickly. Region with significant ecological risk changes was distributed in Guilin city and Yangshuo county. The spatial distribution of ecological risk was basically stable and showed an obvious ring structure, and gradually decreased from the axis of Xingan county town-Lingchuan county town-Guilin city-Yangshuo county town to other regions. Region with low ecological risk value mainly distributed in forest area in the north and mid-eastern of Lijiang River basin, and region with high ecological risk value concentrated in the urban area along Lijiang River. The total area of low ecological risk region converted to high ecological risk region was 296.13 km2, and the contrary converted area was 965.44 km2, the area of high risk converted to low risk was continuous increased and the conversion rate was continuous accelerating.(5) The ecological risk distribution of Lijiang River basin has significant slope, altitude, and land use differences, highest and higher ecological risk mainly concentrated in 0~3° and 3~8° slope zones, lowest and lower ecological risk mainly concentrated in 8~15°, 15~25° and above 25° slope zones. The ecological risk decreased with slope increased. From the aspects of altitude, lowest ecological risk was mainly distributed at 500~800m and 800~1200m altitude belt, lower ecological risk was mainly distributed at 200~500m altitude belt, and moderate, higher and highest ecological risk were mainly distributed at 0~200m and 200~500m altitude belt. The ecological risk decreased with altitude increased. The majority of farmland, grassland, water body and unused land belonged to lower and moderate ecological risk areas and woodland belonged to the lowest and lower ecological risk areas, whereas the construction land belonged to the higher and highest ecological risk areas.(6) With respect to ecosystem management, the main ecological function zones were distinguished as ecological conservation area, ecological agriculture and forest area, comprehensive ecological development area, and eco-city construction area based on the ecosystem services, ecological risk and LULC status. Different development policies in four zones were also provided to optimizing LULC structure. Moreover, we suggest some ecological projects, including water conserving project, soil erosion treatment, karst landscape protection, farmland conservation, and the tourism improvement. This paper supplied an effective support to regional ecosystem management for both Lijiang River Basin and other similar areas.