红壤丘陵区土地可持续利用中的干旱约束与调控研究

Drought restriction and its management in sustainable land use in earth hilly area

本文选择红壤丘陵区江西余江县作为研究样点 ,运用Zi指数等定量方法衡量区域干旱问题 ,辨识区域存在的干旱及其类别等级 ;运用“制约强度指数”衡量干旱对土地农业利用的约束程度。研究表明 ,红壤丘陵区一定频度的干旱 ,制约着土地利用的过程、形式与效果及其时空变异性 ,其制约强度与土地利用的方式及其结构、作物种类等密切相关。旱地的盲目扩展等不适当人为活动 ,在水利效用受局限之后对干旱成灾的影响作用日渐突出。科学的调控不仅需要完善水利工程网络建设 ,对水源利用采取蓄、引、节、保措施 ,也需要改进土地利用模式与技术 ,重视修订总体规划并进行土地利用的结构性调整。

In view of sustainable land use, the frequencies, characteristics and reasons of drought are studied in red earth hilly area of southern China. The intensity of drought restricting to land use and its temporal and spatial variations, relation between the pattern of land use and the degree of drought as well as measures taken to control drought are dealt with in this paper. Yujiang County of Jiangxi Province was chosen for a case study, the regional drought was assessed by using quantitative methods such as Zi index, coefficient of variation and departure value of precipitation. High frequency and types of drought in the hilly area are distinguished during the period 1951 to 2000. Compared to the case of northern China, the degree of drought was more tiny and alleviated. Drought restricts the three dimensional distribution of landuse and consumably occupies cultivated land resource. Restricting strength index (K) was used to quantify the effect of drought on the restricting degree of agricultural land. Taking a very drought year, the results indicated the K value of the effect of drought on paddy rice is 0.08～0.11, belonging to low restricting strength;that on the dryland is 0.46, high restricting strength; and on farmland for comprehensive evaluation is 0.21, moderate restricting strength. The reasons of drought in red earth hilly area are becauseof the seasonal change of atmosphere circumfluence in eastern China, lower availability in soil moisture,inappropriate human activities and lack of socio-economic ability in combating drought. The regional drought has a high tendency as the human-controlling factors change their condition. Such measures to alleviatethe drought should be taken as follows: (1)including seepage control of dykes several hundred kilometers long in the area, intensification of canalized irrigation networks and development of mini electromechanical irrigation project in hummocks; to perfect irrigation canal system and expand irrigated area by diverting other water resources;(2) to construct small scale water storage ponds in remote and high hummocks; (3) to popularize water-saving agricultural techniques such as intercropping forest and grain plant straw mulching technique, drought-resistant crop(e.g. peanuts)selecting, terracing and scale pitting; (4) to control strictly dryland development in the area and return part of cultivated land to forest on north-south hummocks; and (5) to increase appropriately the ratio of land used for construction and optimize the structure of landuse.