河北太行山区河谷土地空间分异规律研究

Study on the spatial differentiation of valley lands in Taihang mountain areas in Hebei Province

河谷是集自然的精华与众多的人文景观于一体的带状地域 ,在山丘区的可持续发展战略中具有举足轻重的地位。在山丘区退化河流生态系统的恢复和洪水过后的灾后重建过程中 ,河谷土地的空间分异特征以及洪水干扰对河谷景观安全的制约作用 ,是确定河谷土地利用策略和指导河岸植被带建设的重要依据。本文以景观生态学原理为指导 ,调查了河北太行山地区的 7条河流 ,在全面分析主流河谷土地利用格局及 96.8洪灾格局的基础上 ,深入研究了太行山地区河谷土地的空间分异规律。以洪水干扰为主导因素 ,提出由上至下在纵向上把河谷划分为 5个区段 ,即上游侵蚀区 ,上中游侵蚀 -堆积区 ,中游侵蚀堆积区 ,中下游堆积 -侵蚀区 ,下游堆积区 ;由河道向两侧山体在横向上把河谷土地划分为弹性利用带、脆弱利用带和稳定利用带 3条土地带 。

River valley is a strip of zone in which the natural cream and numerous human landscapes are congregated.In Taihang mountain areas of Hebei province,river valley occupies only about 10 percent of the total area of mountain and hill region,but it gathers almost all the inhabitant construction land and farmland with the highest productivity level.River valley holds the key position in sustainable development strategy in the areas.On 4 th and 5 th August 1996,a great flooding rarely in the local history occurred in Tainhang mountain area in Hebei province.The losses from the flooding were serious in the riverine area.The comprehensive human activities led to the degradation of watershed environment and became the cause for the frequency flood.So the foundation of flood control and river ecological restoration is predicated on the scientific recognition to the rules of flood disaster and the spatial differentiation of valley lands,and also based on the establishment of adaptive policy.The core of the policy was to using lands reasonably to make the land use patterns adapt the spatial differentiation of valley lands and possible flood in the area.In this paper,using landscape theories and methods,the problem was studied. The outside inverstigation was performed from June to July in 1997 and May to June in 1998.Based on a case study of the 96.8 flood,the cahnges of valley lana use patterns were investigated completely.The main valleys of 7 rivers Yanzhi,Dasha,Beiliu,Banyu and Yaozi located in Fuping county,Beisha and Zhulong located in Yuanshi county,were selected to be the typical research locations.Walking down from headstream along the river,the status of land use and 96.8% flood disaster were surveyed by interviewing with local people who experienced the event.The status of land use was described by 4 phases of pre flood,during flood,after flood and present.Meanwhile the changes of land use patches,river characteristics and the range of land affected by flood were evaluated by land measuring and drawing on the present land use status map.We used the reach as the basic researching unit.In order to compare the differences between regions and rivers,classification was carried out according to the practical situations of land use before 1996 and after 96.8 flood disaster in valley of Taihang mountain areas.The land use patch was classified into seven types farmland,village,forest land,orchard,reservoir or pond,barren sands or beach,and reed field;while the 96.8 flood disaster was classified into three types destroyed,flooded and sedimentated patch. Using the corridor analyzing method of landscape ecology,the river corridor was to divide into three sections of matrix,patch and corridor.Based on comprehensive analysis of land use and flood patterns in main river valleys of 7 rivers,and emphasized Yanzhi river for a case study,the spatial differentiation of valley lands were studied in longitudinal and cross direction.The results were as follows: 1.The whole trends of valley characteristics in longitudinal direction were that:along with the extending of river from headstream to downstream,the grain composition of riverbed matrix reduced,valley landform tended to gentle and valley gradually widened in steps,and this process was usually related to branch converge and swerve.The erosion process gradually weakened while deposition process enhanced.Valley lands are disturbed exitensively by human being actions because of being the central zone for producing and living.Artificial landscape types took up the main parts of the valley landscape except the residual natural landscape types occurred in upstream valley.The proportion of artificial land use area increased from headstream to downstream,the human disturbance index was 55.48%,and the reserved watercourse 20.88%.Besides the influence of landforms,we could also obtained the same result from the changes of other 6 river valleys. Based on those characteristics,we could divided a valley into five zones in longitudinal direction:(1)upstream erosion section i