【作者】 李秀梅；

【导师】 吴波；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化防治， 2012， 博士

【摘要】 景观动态是区域生态环境变化研究的重要内容。石羊河流域是河西走廊三大内陆河之一，近年来自然和人为干扰导致石羊河流域出现干旱化、盐渍化和植被退化等环境问题，景观变化明显，因此景观动态分析有助于了解自然和人为干扰与流域环境变化的关系。论文基于遥感和GIS技术，根据植被类型划分石羊河流域景观要素类型，形成1974、1995和2006年流域景观图和1959、1974、1987、1995、2001和2006年民勤绿洲景观图。在景观分类与制图基础上，分析了1959年以来石羊河流域的景观动态与成因。主要结论如下：（1）随海拔升高，上游山地依次分布着草地、天然乔木林、亚高山灌丛、高寒荒漠；绿洲—荒漠系统的景观要素类型也呈相似的带状依次分布着人工绿洲、非地带天然植被和人工林、砂砾质和石质荒漠和流动沙漠，流动沙漠边缘的低洼处也存在盐漠和盐生草甸。砂砾质和石质荒漠、草地、流动沙漠和人工绿洲是流域主要的景观要素类型。除了天然乔木林，地带性植被组成的景观要素类型连通性好，非地带性植被组成的景观要素类型只有盐生草甸和盐化荒漠连通性好。（2）流域景观格局特征、景观动态与格局变化有区域差异。上游山地景观格局比流域整体复杂；中、下游绿洲—荒漠系统景观格局比流域整体简单，但是东部比西部盐碱化和景观破碎化程度高；且越往下游越严重，而沙漠和砂砾质荒漠的连通性却增加。1974-2006年石羊河流域景观格局复杂程度增加，是中游和下游景观破碎化增加的结果，越往下游破碎化趋势越严重；而山地景观格局趋于简单，变化幅度较小，但变化速度加快。1974-2006年人工绿洲的面积比例增加了5.96%，且中游远超过下游。砂砾质和石质荒漠减少的最多，为2.32%，中游最明显；其次是人工林，为1.45%，下游最明显；温带落叶灌丛、人工林、盐漠和次生盐碱地损失最严重，分别减少到原来的0.02、0.58、0.64和0.68，盐漠中游损失最明显，其余下游损失最明显。在人工绿洲面积增加和砂砾质和石质荒漠、人工林、盐漠和次生盐碱地面积减少的过程中均产生大量小斑块，格局变复杂；其余景观要素流向的格局趋于简单。（3）流域景观动态与格局变化时间上阶段特征明显。1974-1995年，上游草地流向旱地；中游砂砾质荒漠、旱地和人工林流向人工绿洲；下游盐生草甸、温带落叶灌丛和盐漠流向砂砾质和石质荒漠，盐生草甸和砂砾质和石质荒漠流向人工绿洲和人工林，人工林流向人工绿洲，人工绿洲流向次生盐碱地。结果景观要素类型的面积比例，上游草地减少1.76%；中游砂砾质荒漠、旱地和人工林分别减少4.24%、1.99%和1.81%，人工绿洲增加8.02%；下游人工绿洲、次生盐碱地和人工林分别增加了2.23%、0.02%和0.85%，砂砾质和石质荒漠减少了1.74%。1995-2006年上游旱地流向草地；中游砂砾质荒漠和盐漠流向人工绿洲；下游人工林、次生盐碱地、砂砾质和石质荒漠流向人工绿洲，人工林流向砂砾质和石质荒漠。结果，景观要素类型的面积比例，上游旱地减少0.99%；中游人工绿洲增加4.25%；下游人工绿洲和砂砾质和石质荒漠分别增加3.07%和1.43%，次生盐碱地和人工林分别减少0.45%和3.31%。（4）景观动态变化集中在绿洲，与流域下游总体的变化过程相似，坝区、泉山区和湖区1987年前的水体、温带落叶灌丛、盐生草甸、盐漠和1995年前的砂砾质和石质荒漠大量减少，而人工林和次生盐碱地增加；1987年后人工林和次生盐碱地减少，而人工绿洲和砂砾质和石质荒漠增加。到2007年坝区和泉山区的水体和温带落叶灌丛消失，次生盐碱地、盐生草甸和盐漠也接近消失；坝区的砂砾质和石质荒漠减少3.46%，人工绿洲增加17.87%；泉山区的砂砾质和石质荒漠减少1.26%，人工绿洲增加12.39%；湖区次生盐碱地增加3.20%（约1/2的面积），人工绿洲减少0.11%，砂砾质和石质荒漠增加3.53%，人工林比1974年减少2.62%（约1/2），流动流动沙漠增加1.40%。坝区和泉山区的人工绿洲、人工林和砂砾质和石质荒漠格局复杂程度明显增加；坝区盐生草甸只剩余少量小斑块，盐漠破碎化增加；泉山区的盐漠只剩余少量的小面积斑块。湖区人工林和盐漠破碎化增加；砂砾质和石质荒漠的连通性增强；盐生草甸和次生盐碱地减少的是小斑块，格局趋于简单。（5）从影响因素的时空变化分析了景观动态与格局变化成因。50年代以来不同区域的气候总体趋于暖干，虽然从70年代开始降水增加，但是气温也升高，使流域来水量持续减少，对植被影响不利，非地带天然植被和天然林减少，但是人工绿洲持续扩展，因此，人为干扰是石羊河流域景观变化的最主要原因。50年代修建红崖山水库，导致1987年前下游的民勤绿洲非地带天然植被迅速减少；70年代中游人工绿洲扩张使下游水资源减少而出现次生盐渍化和人工林退化；但是随着盐碱化减轻、开发地下水和种植价格高且耐旱耐盐碱的经济作物，80年代开始下游人工绿洲也扩展，人工林继续减少；最终导致90年代下游砂砾质和石质荒漠也迅速增加。更多还原

【Abstract】 Landscape dynamics is the important part of environments changing analysis. As one ofthe three inland river basin in Hexi corridor, Shiyang river basin was experiencing drouth,salination, vegetation degeneration and obvious landscape change caused by natural and humandisturbers. Therefore landscape dynamics research could contribute to reflect the relationshipbetween disturbers and environments change. On the basis of landscape classificationaccording to the vegetation type,3periods landscape map from1974to2006of Shiyang riverbasin and6periods landscape map from1959to2006of Minqin oasis were obtained using RSand GIS technology.On completion of landscape classification and cartography, dynamicss andcauses of landscape pattern of Shiyang river basin since1959were analyzed using landscapeecological method.（1）Along with the increasing altitude, grassland, natural forest, sub alpine shrub and colddesert were distributed in the up reaches. Similar to up reaches, artificial oasis, salt vegetationand artificial forest together, gravel and lithoid desert and sandy desert were orderly distributedin Oasis Desert System with large area of saline desert and salt meadow distributed in the lowarea of the edge of sandy desert also. Gravel and lithoid desert，grassland, sandy desert andartificial oasis were the main landscape types of Shiyang river basin. Except natural forest,landscape types composed by local vegetation had well connectivity, whereas landscape typescomposed by alien vegetation only salt meadow and saline desert were well connected.（2）Landscape dynamics and pattern changes were different by regions. Compared withthe whole basin, up reaches was more fragmented, whereas middle reaches and lower reach’sstructure were simpler then the hole basin. From the east reaches to west reaches, salinationand landscape fragmentation aggravated, and that enhanced downwards the stream with theconnectivity of sandy desert and gravel and lithoid desert increased. Since1974, the landscapestructure tended to be complicated because of obviously increased fragmentation in the middle and lower reaches, and that enhanced from the middle to lower reaches; while the landscapestructure of the upper reaches tended to be simple, but with changing speed accelerated.Artificial oasis’s area percentage increased5.96%, and middle reaches exceed lowerreaches. Gravel and lithoid desert decreased most obvious by2.32%, especially in middlereaches. Artificial forest decreased obviously by1.45%, especially in lower reaches. Temperatedeciduous shrub, artificial forest, salt desert and secondary salt land, the most severely losslandscape types, were reduced to the original0.02,0.58,0.64and0.68, with salt desert mostobvious in middle reaches and others in lower reaches. Due to mass of small patches increasedin expending of artificial oasis and reducing of gravel and lithoid desert, artificial forest, saltdesert and secondary salt land, their landscape pattern complicated while that of otherssimplified.（3）Landscape dynamics and pattern changed by stage. During1974-1995, grasslandconversed to dry farmland in up reaches; gravel and lithoid desert, dry farmland and artificialforest conversed to artificial oasis in middle reaches; in lower reaches, salt meadow, temperatedeciduous shrub and salt desert conversed to gravel and lithoid desert, salt meadow and graveland lithoid desert conversed to, artificial oasis and artificial forest, artificial forest conversed toartificial oasis, artificial oasis conversed to secondary salt land. Eventually, the area percentageof grassland decreased1.76%in up reaches; gravel and lithoid desert, dry farmland andartificial forest decreased4.24%、1.99%and81%and artificial oasis increased8.02%inmiddle reaches; in lower reaches, artificial oasis, secondary salt and artificial forest increased2.23%、0.02%and0.85%, and gravel and lithoid desert decreased1.74%.During1974-1995, dry farmland conversed to grassland in up reaches; gravel and lithoiddesert and salt desert conversed to artificial oasis in middle reaches; in lower reaches, artificialforest, secondary salt land and gravel and lithoid desert conversed to artificial oasis, artificialforest conversed to gravel and lithoid desert. Eventually, the area percentage of dry farmlanddecreased0.99%in up reaches; artificial oasis increased4.25%in middle reaches; in lower reaches, artificial oasis and artificial forest increased3.07%and1.43%, artificial forest andsecondary salt land decreased0.45%and3.31%.（4）Landscape dynamics changes was concentrated in oasis. Same as the lower reaches,water, salt meadow, temperate deciduous shrub, salt desert and gravel and lithoiddesert(before1995) were decreased obviously but artificial forest and secondary salt land wereincreased in Huqu, Quanshanqu and Baqu before1987, while artificial forest and secondarysalt land were decreased but artificial oasis and gravel and lithoid desert were increased after1987. Until2007, water and temperate deciduous shrub were disappeared and Secondary saltland, salt meadow and salt desert remained few in Baqu and Quanshanqu; gravel and lithoiddesert decreased3.46%and artificial oasis increased17.87%in Bqqu; gravel and lithoid desertdecreased1.26and artificial oasis increased12.395in Quanshanqu; secondary salt land, graveland lithoid desert and sandy land increased3.20%(1/2times)3.53%and1.40%but artificialoasis decreased0.11%and artificial forest decreased2.62%(1/2times) compare to1974.The landscape structure of artificial oasis, artificial forest and gravel and lithoid deserttended to be complicated in, Baqu and Quanshanqu; salt desert fragmentation aggravated andonly few salt meadow patches were left in Baqu; only few salt desert patches were left inQuanshanqu; in Huqu, artificial forest and salt desert fragmentation aggravated and thelandscape structure of salt meadow and secondary salt land tended to be simple due to lossmass of small patches, but the connectivity of gravel and lithoid desert was increased.（5）The causes of landscape dynamics and landscape pattern changes were studied byanalysis Influence factors change. Climate tended to be dry and warm since50`s, although therainfall increased but the temperature was raised simultaneity since70`s led to water resourcesdecreased which had negative affect to vegetation, therefore, salt vegetation and natural forestdecreased, but artificial oasis increased proved that human disturbances were the main reasonof landscape dynamics. On account of building Hongyashan reservoir in50`s, salt vegetation inMinqin oasis decreased quickly before1987. The expansion of artificial oasis in middlereaches led to the shortage of water resources which resulted in secondary salinization and artificial forest’s degradation in lower reaches subsequently. But the artificial oasis increasedsince80`s and gravel and lithoid desert increased in lower reaches since90`s owing tosalinization weakening, groundwater exploitation and planting of high price, salt and droughttolerable economic crops in lower reaches.更多还原