中国科学院水利部水土保持研究所机构知识库

近年来中国随着退耕还林还草工程的不断推进以及城市化进程的加快，土地利用/覆被变化（LUCC）极为明显。对于水土流失频发的黄土高原地区来说，LUCC下的水土保持效应研究有十分重要的意义。本研究以兰州市城关区为研究对象，对2000-2020年LUCC水土保持效应进行了初步研究与评价。研究中选用了百合地（N1）和牡丹地（N2）两个耕地，油松+侧柏混交林地（L1）和刺槐+侧柏混交林地（L2）两个林地，撂荒地（C1）、苜蓿地（C2）和天然草地（C3）三个草地，以及挖方样地（W1）、填方样地1（T1）和填方样地2（T2）三个未利用地，对不同土地利用/覆被的水土保持性能进行了测定。选用的水土保持性能指标包括土壤抗蚀性、土壤抗冲性和入渗能力。土壤抗蚀性采用对原状土样干筛-湿筛的方法得到不同粒级的比例，并计算水稳性团聚体平均质量直径（MWD_w）、水稳性团聚体几何平均直径（GMD_w）、水稳性团聚体颗粒分形维数（D_w）、团聚体破坏率（PAD）以及>0.25 mm水稳性团聚体占比[M_w（>0.25）]，在0～30 cm深度内每5cm取一个样。土壤抗冲性测定时使用室内放水冲刷表层原状土样的方法，得到每个样品的土壤冲刷量（M_s），并求算出土壤抗冲系数（AS）。土壤入渗能力测定时使用了单环双水头入渗仪，得到了饱和导水率（K_s）。再计算出耕地、林地、草地和未利用地四种土地利用/覆被的水土保持性能指标值，同时估计了建设用地的水土保持性能相关指标值。然后通过遥感和GIS的方法对兰州市城关区2000-2020年LUCC进行了分析，使用土地利用/覆被转类指数概念，结合不同土地利用/覆被水土保持性能数据，计算出LUCC水土保持效应。主要结果如下：

（1）兰州市城关区各土地利用/覆被表层土壤抗蚀性：MWD_w林地和草地显著大于耕地和未利用地；GMD_w林地＞草地＞耕地＞未利用地，各土地利用/覆被间差异显著；D_w林地显著小于草地和耕地，未利用地最大；PAD林地和草地显著小于耕地，未利用地最大；M_w（>0.25）林地最大，草地和耕地次之，未利用地最小。土壤抗冲性：M_s未利用地显著大于耕地、林地和草地；AS草地＞林地＞耕地＞未利用地，草地AS的值为36.29 L/g，未利用地仅为0.32 L/g。土壤入渗能力：K_s林地＞草地＞耕地＞未利用地，K_s的值依次为0.19、0.12、0.10和0.01 cm/min，林地、耕地和未利用地之间差异的显著性好。

（2）土壤有机质和植物根系与土壤抗蚀性指标和土壤入渗能力指标极显著相关；土壤抗冲性指标与土壤有机质极显著相关，随着根系生物量的增加，土壤抗冲性有增加的趋势。土壤电导率与土壤抗蚀性、抗冲性和入渗能力多为极显著负相关。碱解氮与土壤抗蚀性、抗冲性和入渗能力的相关性好，多为极显著正相关，这是因为碱解氮是易被植物吸收的营养元素且植物的需求量大，对植物生物量的累积尤为重要。较多的有机质累积，会使土壤结构疏松，孔隙度变大，容重变小，入渗能力增强。

（3）2000-2020年兰州市城关区LUCC主要表现为草地的减少、建设用地和未利用地的增加，以及耕地的减少和林地的增加。其中，建设用地的增加面积和增加幅度都为最高水平，值为25.96 km²和46.15%，草地的减少面积最大，减少幅度也较大，值为27.68 km²和28.88%。草地向建设用地的转移面积最大，为12.05 km²，其次为草地向未利用地的转移，为10.02 km²，耕地和林地向建设用地的转移面积也较大，分别为7.42 km²和7.12 km²。

（4）兰州市城关区2000-2020年LUCC水土保持效应主要表现为整体土壤抗蚀性的增强、整体土壤抗冲性的减弱以及整体土壤入渗能力的减弱，草地、建设用地和未利用地面积的变化对此产生了主要的作用。城市扩展工程是影响兰州市城关区LUCC水土保持效应的主要方面。

In recent years, China has experienced significant Land use and land cover change (LUCC) with the continuous promotion of Grain for Green Project and the accelerated urbanization process. For the Loess Plateau region, where soil erosion is frequent, the study of soil and water conservation effects of LUCC is very meaningful. In this study, the soil and water conservation effects of LUCC from 2000 to 2020 were investigated and evaluated preliminarily in Chengguan District, Lanzhou City. In the study, two cultivated land plots, lily land (N1) and peony land (N2), two forest land plots, mixed forest land of Pinus tabulaeformis and Platycladus orientalis (L1) and mixed forest land of Robinia pseudoacacia and Platycladus orientalis (L2), three grassland plots, abandoned land (C1), alfalfa land (C2) and natural grassland (C3), and three unused land plots, dug plot (W1), filled plot 1 (T1) and filled plot 2 (T2), were selected to investigate the soil and water conservation performance of different land use and land cover was measured. The selected soil and water conservation performance indicators include soil anti-erodibility, soil anti-scourability and soil infiltration capacity. Soil anti-erodibility was obtained by dry-wet sieving of undisturbed soil samples to derive the proportion of different grain classes and calculate mean weight diameter of soil water-stable agglomerates (MWD_w), geometric mean diameter of soil water-stable agglomerates (GMD_w), fractal dimension of soil water-stable agglomerates (D_w), percentage of aggregates destruction (PAD), and the percentage of water-stable agglomerates >0.25 mm [M_w（>0.25）], samples were taken at every 5 cm layer in the soil layer from 0 to 30 cm depth. Soil anti-scourability was determined by using an indoor water flushing method for surface undisturbed soil samples to obtain the amount of soil loss weight (M_s) for each sample and to calculate the soil anti-scourability coefficient (AS). Soil infiltration capacity index soil saturated hydraulic conductivity (K_s) was determined using a single-ring dual-head infiltrator. Soil and water conservation performance indicators values were then calculated for four types of land use and land cover: cultivated land, forest land, grassland, and unused land, the values of indicators related to soil and water conservation performance of construction land were also estimated. Then the LUCC 2000-2020 in Chengguan District, Lanzhou City, was analyzed by remote sensing and GIS methods, and the LUCC soil and water conservation effects were calculated using the concept of land use and land cover conversion index, combined with different land use and land cover soil and water conservation performance data. The main results were as follows.

(1) The surface soil anti-erodibility of each land use and land cover in Chengguan District, Lanzhou City, was as follows: MWD_w showed that forest land and grassland were significantly larger than cultivated land and unused land; GMD_w showed that forest land > grassland > cultivated land > unused land, with significant differences among land use and land cover; D_w showed that forest land was significantly smaller than grassland and cultivated land, and unused land was the largest; PAD showed that forest land and grassland were significantly smaller than cultivated land, and unused land was the largest; M_w（>0.25） showed that the largest was forest land, followed by grassland and cultivated land, and the smallest in unused land. The soil anti-scourability showed that M_s of unused land was significantly larger than that of cultivated land, forest land and grassland; AS showed that grassland > forest land > cultivated land > unused land, and the value of AS of grassland was 36.29 L/g, while that of unused land was only 0.32 L/g. The soil infiltration capacity index K_s showed that forest land > grassland > cultivated land > unused land, and the values were 0.19, 0.12, 0.10 and 0.10 cm/min, respectively, with good significance of the differences between forest, cultivated and unused land.

(2) Soil organic matter and plant roots were significantly correlated with soil anti-erodibility index and soil infiltration capacity index; soil anti-scourability index was significantly correlated with soil organic matter, and soil anti-scourability tended to increase with the increase of root biomass. Soil electrical conductivity was highly significant negative correlated with soil anti-erodibility, soil anti-scourability and soil infiltration capacity. The correlation between alkaline nitrogen and soil anti-erodibility, soil anti-scourability and soil infiltration capacity was significantly positive, because alkaline nitrogen is easily absorbed by plants, which is particularly important for the accumulation of plant biomass. A higher accumulation of soil organic matter will result in a looser soil structure, greater porosity, smaller capacity and increased infiltration capacity.

(3) The LUCC in Chengguan District of Lanzhou City from 2000 to 2020 mainly shows the decrease of grassland, the increase of construction land and unused land, as well as the decrease of cultivated land and the increase of forest land. Among them, the increase area and increase rate of construction land are at the highest level, with values of 25.96 km² and 46.15%, and the decrease of grassland area is the largest, and the decrease rate is also larger, with values of 27.68 km² and 28.88%. The transfer of grassland to construction land is the largest with 12.05 km², followed by the transfer of grassland to unused land with 10.02 km², and the transfer of cultivated land and forest land to construction land is also large with 7.42 km² and 7.12 km² respectively.

(4) The soil and water conservation effect of LUCC in Chengguan District of Lanzhou City from 2000 to 2020 is mainly manifested by the enhancement of overall soil anti-erodibility, the weakening of overall soil anti-scourability and the weakening of overall soil infiltration capacity, and the changes in the area of grassland, construction land and unused land play a major role in this. The urban expansion project is the main aspect affecting the soil and water conservation effect of LUCC in Chengguan District, Lanzhou City.

第1章  绪论... 1

1.1  研究背景... 1

1.2  研究进展... 2

1.3  研究目的与意义... 8

1.4  研究内容... 9

1.5  研究思路与技术路线... 10

第2章  材料与方法... 11

2.1  研究区概况... 11

2.2  试验设计与样品采集... 12

2.3  样品处理及指标测定... 18

2.4  数据处理与分析... 22

第3章  结果... 25

3.1  不同土地利用/覆被土壤抗蚀性... 25

3.2  不同土地利用/覆被土壤抗冲性... 34

3.3  不同土地利用/覆被土壤入渗能力... 37

3.4  水土保持性能指标相关性分析... 40

3.5  兰州市城关区土地利用/覆被变化... 43

3.6  土地利用/覆被变化水土保持效应... 48

第4章  讨论... 57

4.1  水土保持性能差异的影响因素分析... 57

4.2  土地利用/覆被变化水土保持效应分析... 60

第5章  结论与展望... 63

5.1  主要结论... 63

5.2  创新与展望... 64

参考文献... 67

致  谢... 73

作者简介及攻读硕士期间发表的学术论文与研究成果... 75