【作者】 徐当会；

【导师】 王辉；

【作者基本信息】 甘肃农业大学 ， 森林经理学， 2002， 硕士

【摘要】 根据1996年甘肃省河西走廊沙漠化普查资料、以及疏勒河流域中下游TM影像数据，运用景观生态学理论和方法，通过计算景观格局指数、各景观要素之间的转移矩阵、以及土地荒漠化综合值，对河西走廊荒漠化土地和疏勒河流域中下游的景观格局变化机理、以及河西走廊19个县(市、区)的荒漠化程度进行了初步分析和研究，结果如下： 1．河西走廊荒漠化土地景观格局变化机理 (1)景观多样性指数变化态势分析表明：整个河西走廊的景观多样性指数和均匀度指数均呈增加趋势，景观多样性指数从1949年的2.454增加到1995年的2.489，均匀度指数从0.685增加到0.694，说明该区的景观异质性在增大。不同流域五个时期的景观多样性指数与均匀度指数，以疏勒河流域最低，其最高值出现在1970年，分别为2.204和0.615；黑河流域最高，其最低值出现在1949年，分别为2.642和0.737，这说明黑河流域的景观异质性较疏勒河流域高。 (2)景观分离度指数变化态势分析表明：从1949年到1995，特用地、耕地、林地等人工嵌块体的景观分离度在黑河流域和石羊河流域减小，在疏勒河流域增大。黑河流域分别减小了0.120、0.035和0.051，石羊河流域分别减小了157.800、0.350和0.270，疏勒河流域分别增加了0.005、0.260和0.029。流动沙地、半固定沙地、戈壁等半自然嵌块体的景观分离度在三个流域都呈减小趋势。分析表明：景观分离度与人类活动强度有较为密切而复杂的关系，主要表现在两个方面：1)与人类活动密切相关的景观类型，在人类活动较强的流域，景观分离度与人类活动强度成反相关。在人类活动较弱的流域，景观分离度与人类活动强度成正相关；2)对于那些受人类影响残留下的半自然景观类型，景观分离度和人类活动强度成反相关。 (3)景观斑块破碎化指数变化态势分析表明：河西走廊、石羊河流域和黑河流域的景观斑块破碎化指数增加，1949年分别为0.0009、0.0037和0.0036，1995年分别为0.0024、0.0210和0.0065。景观斑块破碎化指数升高，说明上述三区的景观破碎化程度增加，这一结论与平均斑块面积分析结论相矛盾。在疏勒河流域，景观斑块破碎化指数减小，1949年为0.0023，1995年为0.0003，这表明景观破碎化程度减小。这一结论与平均斑块面积分析结论一致。因此，从该指数本身考虑，再结合其计算结果，可认为景观斑块破碎化指数所揭示的结果只能作为衡量一个区域景观破碎化程度的参考指标，而不能作为重要的或唯一的指标。 2．疏勒河流域中下游景观格局变化机理 1990、1994和 1999年，沙地、风蚀劣地和盐渍化土地面积之和占研究区总土地面积分别为57．lO、60．lO和63．6O。1990～1994年，低盖度直地向沙地转化的速率为 1300hln’h，灌木林地向高盖度草地和低盖度草地转化的速率分别为672ho’／。和908 ho’／。。1994－1999，高盖度草地和低盖度草地向耕地转化的速率分别为 1200hlnZ／a和 1558hln～a，向沙地转化的速率分别为 335 hxn勺a和113 hln书。分析表明：疏勒河流域中下游是以戈壁、荒漠、裸土和沙漠化土地构成的以荒漠为景观基质，以天然草甸与林灌植被、人工绿洲和水域等构成的绿洲为景观镶嵌体。其景观空间格局是干旱气候条件和人为活动叠加的产物，受气候波动和人为垦植灌耕等活动影响，景观动态变化范围大、格局各要素之间转化复杂。主要表现在：归）流域中上游人工绿洲的形成与发展常以流域下游天然绿洲大面积荒漠化为代价，如耕地面积的增加以草地转化为流动和半固定沙地为代价。（）该流域的景观格局在向两个方向变化，而且这两个变化方向密切相关。一方面，在靠近水源和流域中上游地带，农耕发达，一般形成集约化、灌溉系统完善的农田景观；另一方面，在远离水源或流域下游地带，则随上游水资源利用程度的不断提高，天然生态体系破坏不断加剧，景观由高度破碎化的天然植被向荒漠化景观发展。 3．土地荒漠化程度综合评价结果 综合评价分析表明：在1995年，属于轻度荒漠化县（市、区）的有玉门市、山丹县、张掖市、肃南县、永昌县；属于中度荒漠化的有阿克塞县、肃北县、安西县、金昌市、酒泉市、金塔县、嘉峪关市，高台县、民乐县和临泽县；属于严重荒漠化的有敦煌市；属于极严重荒漠化的有武威市，民勤县和古浪县。从评价的结果可以看出，河西走廊除少数县（市、区）的荒漠化程度较轻外，大多数为中度、严重或极严重荒漠化区域，说明该区土地荒漠化形式十分严峻。更多还原

【Abstract】 Based on the investigation material of sandy desertification land of Hexi corridor, Gansu province in 1996 and images of middle and lower reaches of Shule river basin, landscape pattern indices, transition matrix of patches and land desertification synthesis value were calculated. The variation mechanism of landscape pattern of desertification land in Hexi corridor and middle and lower reaches of Shule river basin and desertification degree of 19 counties, cities or regions in Hexi corridor were analyzed and discussed on the basis of landscape ecological theory and method. The results and conclusions are summarized up as follows:1. The variation mechanism of landscape pattern of desertification land in Hexi corridor(1) The variation trend of landscape diversity index shows that in Hexi corridor, landscape diversity index and evenness index increased in past 50 years. Landscape diversity index increased from 2.454 to 2.489 and evenness index increased from 0.685 to 0.694 from 1949 to 1995, which indicates that the landscape heterogeneity enhanced. Comparing landscape diversity index and evenness index of five periods in three basins, the minima were in Shule river basin whose maxims carne to 2.204 and 0.615 respectively in 1970, the maxims were in Hei river basin whose minima appeared 2.642 and 0.737 respectively in 1949, which indicates that the landscape heterogeneity in Hei river basin was higher than in Shule river basin.(2) The variation trend of landscape isolation index shows that the landscape isolation index of man-made landscape types such as special utilized land, farmland and forest land decreased in Hei river basin and Shiyang river basin from 1949 to 1995, which decreased 0.120, 0.035, 0.051 and 157.800, 0.350, 0.270 respectively. But in Shule river basin, which increased 0.005, 0.026 and 0.029 respectively. On the other hand, landscape isolation index of remained natural landscape types such as flowing sand dune, semi-flowing sand dune and gobi had a decreasing trend in three basins. Analysis results show that the relationship between landscape isolation index and human activity intensity is complex, which is reflected from two aspects:3(a) For those man-made landscape types, landscape isolation index shows an inverse relationship with human activity intensity in the basins effected intensively by human activity, shows a positive relationship in the basins impacted weakly by human activity, (b) For those remained natural types, the relationship between landscape isolation index and human activity is inverse.(3) The variation trend of landscape patch fragmentation index shows that in Shiyang river basin, Hei river basin and overall Hexi corridor, the landscape patch fragmentation index increased. In 1949, they were 0.0037, 0.0036 and 0.0009 respectively, and in 1995, the}’ were 0.021, 0.0065 and 0.0024 respectively, which shows that the landscape patterns were fragmenting in those regions, this was contrary to the analysis results of mean patch area. But in Shule river basin, this index decreased, in 1949, it was 0.0023 and in 1995, it was 0.0003, which means that the landscape fragmentation degree descended, this coordinates with the results obtained from the mean patch area. Therefore, in order to measure landscape fragmentation degree, the landscape patch fragmentation index results should be taken as a reference index and not as a sole or major index.2. The variation mechanism of landscape pattern in middle and lower reaches of Shule river basinThe area percentage of sandy land, wind eroded land and saline-alkali land to the total in 1990,1994 and 1999 were 57.1%, 60.1% and 63.6% respectively. The transition rate of grassland with low coverage to sandy desert was 1300hnr/a, shrub land to grassland with low and high coverage were 672hm2/a and 908hnr/a respectively in the period of 1990-1994. During the period of 1994-1999, the transition rates of grassland with low coverage and high coverage to farmland were 1200hnr/a and 1558hm2/a respectively, and to sandy land wer更多还原