| 摘要: |
| 洛川塬是黄土高原第二大黄土塬面，也是黄土高原面积最大的苹果种植区。近几十年来，由于塬面高强度人类活动影响，洛川塬沟道侵蚀剧烈，塬面萎缩呈现逐年加剧的趋势，严重影响了塬区的生产、生活和生态安全。因此，清晰了解近几十年来洛川塬土地利用/覆被变化及人类活动影响，对于洛川塬的保护和水土流失治理至关重要。本文使用遥感、地理信息系统和数学方法，以洛川塬主体洛川县为例，对洛川县1985年、2000年和2015年的土地利用数据进行了解译，分别从土地利用变化速度、转移方向和土地利用程度三方面综合分析了洛川县近30 a土地利用时空变化的规律及人类活动影响。研究结果表明：（1）1985—2015年洛川县主要的土地利用类型为林地、草地和耕地，三者面积占比达91.29%；近30 a土地利用变化最大的特点为建设用地面积持续增加且增幅最大，共增加了117.16 km2，年均增加5.11%，其中1985—2000年建设用地面积增加了38.13 km2，2000—2015年增加了79.03 km2，建设用地面积的增加主要由耕地转入；（2）近30 a人类活动对洛川县土地利用变化的影响主要体现在林地、草地、耕地、建设用地之间的转换；前15 a（1985—2000年）林草地面积减少，耕地和建设用地面积增加；后15 a（2001—2015年）林草地和建设用地面积增加，耕地面积减少；（3）近30 a洛川县的综合土地利用动态度呈现增加趋势但增幅较小，前15 a（1985—2000年）综合土地利用动态指数小于后15 a（2001—2015年），表明后期人类活动对土地利用综合开发利用起到积极的影响。 |
| 关键词: 洛川县 土地利用/覆被变化 人类活动 Landsat影像 |
| DOI：10.7515/JEE222037 |
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| 基金项目:中国科学院战略性先导科技专项（B类）（XDB40000000）；国家自然科学基金项目（41790444） |
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| Land use/land cover change and impacts of human activities in Luochuan tableland in 1985—2015: a case study of the Luochuan County of Shaanxi Province, China |
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ZHANG Ruihua, JIN Zhao, YANG Siqi, PENG Jianbing
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1. School of Geological Engineering and Geomatics, Chang’an University, Xi’an 710054, China
2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
3. CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
4. College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
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| Abstract: |
| Background, aim, and scope Loess tableland is the most valuable land resource on the Chinese Loess Plateau (CLP). However, the plateau surface of the loess tableland has experienced serious soil and water loss due to headward erosion. Luochuan County of Shaanxi Province is the main body of the Luochuan tableland, which is the second largest tableland on the CLP. In recent years, an increasing number of studies have focused on gully consolidation and tableland protection in Luochuan County. However, information on land use and land cover change, especially the expansion of urban areas on the tableland of Luochuan County, is rare. In this study, the land use and land cover change in Luochuan County between 1985 and 2015 was characterized, and the aim was to quantify the dynamics of land use/land cover change and elucidate the impacts of human activities. Materials and methods Landsat images were collected, and the sensor types were TM and OLI. The spatial resolution of the Landsat images was 30 m. All images were pre-processed and classified by ENVI software. ArcGIS and Google Earth software were used to interpret the results of supervised classification to improve the accuracy of the results. Results (1) Woodland, grassland and arable land were the main land use types in Luochuan County between 1985 and 2015, occupying more than 90% of the total land area. During the past 30 years, the area of construction land exhibited the most significant increase; specifically, the area increased by 117.16 km2, and the annual rate of increase was 5.11%. In 1985—2000, the area of construction land increased by 38.13 km2, and in 2000—2015, the area of construction land increased by 79.03 km2. (2) Over the past 30 years, the main characteristics of land use change were the mutual conversions of woodland, grassland, arable land and construction land. In the first 15 years (1985—2000), the woodland and grassland showed a change pattern of first decreasing and then increasing; in the latter 15 years (2001—2015), the arable land showed a change pattern of first increasing and then decreasing. The areas of unused land and waterbodies changed less during the past 30 years. (3) Over the past 30 years, the comprehensive land use dynamics in Luochuan County showed an increasing trend, which indicated that human activities have gradually increased in the area. However, human activities are changing to a conservation role based on the directions of land use change in Luochuan County. Discussion In 1985—2015, the land use and land cover patterns in Luochuan County changed greatly, and the change pattern had a close relationship with the implementation of the national policy, e.g., the policy of converting cropland to woodland and grassland and China western development. For example, the arable land area of Luochuan County first increased and then decreased in 1985—2000, with a total increase of 107.14 km2. This result is related not only to the implementation of the production contract responsibility system in rural areas from 1985 to 1990 but also to the reclamation of most grassland and woodland into arable land. The construction land area of Luochuan County increased continuously from 1985 to 2015, with an average annual growth of approximately 11.60%, mainly from arable land, and this change is indicative of the strong economic development in Luochuan County. With the continuous expansion of the urbanization area and the continuous expansion of the traffic network, the water and soil loss on the tableland and erosion of the ditches have accelerated. Moreover, the soil anti-scourability in the loess area was different under different vegetation conditions. The research results showed that the impact of human activities on land use/cover change in Luochuan County from 1985 to 2015 was mainly reflected by the mutual conversion between woodland, grassland, arable land and construction land, and human activities had an important role in promoting the conversion of land use types and have further affected the water and soil loss and gully erosion in the Loess Plateau area. Conclusions In this study, we conclude that modern human activity, e. g. urbanization, is the major driver of land use change on the Luochuan tableland, which showed the most significant increase of land area. Moreover, the transitions of woodland, arable land, grassland are more influenced by ecological policy implemented on the CLP. Recommendations and perspectives When using software for supervised classification, remote sensing images with a long history have the disadvantage of insufficient resolution, which will result in the results facing the risk of insufficient accuracy. It is suggested that the recognition accuracy can be improved in the future by using a large amount of data training in deep learning. |
| Key words: Luochuan County land use /cover change human activities Landsat imagery |
