China's land use classification system mainly includes comprehensive classification, morphological classification and functional classification, among which comprehensive classification is the main classification system at present, and the first-level classification of some classification systems is shown in table 1- 1. On June 5438+1 October12002, the National Land Classification (Trial) integrated the classification of urban and rural land use, and added some classification types that can more accurately reflect the current situation of land use in China, such as livestock and poultry breeding land, protective agricultural land and industrial and mining land. , and the ground production sites and tailings storage sites such as mining, quarrying, sand mining, salt pans and brick kilns are divided into this classification system, and the classification of agricultural land types is still emphasized, but the secondary industrial land such as industrial land and mining land is not subdivided (Pinghui Liu et al., 2003), and the land destroyed by industrial activities such as mining is not subdivided, such as subsidence land, excavation land, occupied land and abandoned land.

According to the existing land use classification and land use evaluation system, both involve unused land. Unused land usually implies two meanings or one of them: one is that people don't use land resources enough or have limited utilization ability, and land resources are idle and wasted; Second, the quality of local land resources is poor, and its utilization value is low or difficult and uneconomical, but it has great "ecological utilization" value. From the perspective of development, there is almost no land that is not used by human beings, so the land that is not directly used by human beings can be regarded as reserve land resources (Jian Yue et al., 2003). However, in the current land use classification, unused land is divided into unused land and other land, and further subdivided into grassland, saline-alkali land, swamp, sandy land, bare land, bare rock gravel land and other unused land, and other land is further subdivided into river water surface, lake water surface, reed land, tidal flat, glacier, permanent snow and so on. And schools, abandoned land, land damaged by natural disasters and other land that cannot be used at present are not subdivided.

Table 1- 1 Comparison of Main Land Use Classification Systems in China

Up to now, the Technical Specification for Investigation and Evaluation of Cultivated Land Reserve Resources (TD/T 1007-2003) issued by the Ministry of Land and Resources (hereinafter referred to as the Specification) divides the types of land to be reclaimed into excavation, subsidence, waste rock residue, abandoned buildings or garbage, and "three wastes" polluted land. The "Regulations" adopts a three-level classification system, which classifies the cultivated land reserve resources according to the natural attributes and surface morphology of the land, the reasons and types of damage and abandonment, and the objects of land consolidation. The classification system comprehensively and systematically classifies the land to be reclaimed and the land to be sorted for the first time. The land to be reclaimed can be divided into five secondary categories according to the causes, damage degree and morphological characteristics, including excavation damage, subsidence, land occupation, pollution damage and natural disaster damage, among which subsidence is divided into stable subsidence and unstable subsidence. Compaction land is divided into three types: waste rock and fly ash accumulation land, slag, earth and stone dumping land and garbage occupation land (table1-2); According to the causes, pollution damage can be divided into three types: "three wastes" pollution area, sewage irrigation pollution area and chemical pollution area in agricultural production. Natural disaster damage can be divided into six categories: flood damage area, landslide collapse damage area, debris flow damage area, sandstorm damage area, earthquake damage area and other natural disaster damage areas.

Table 1-2 Some Land Use Types in Technical Specification for Investigation and Evaluation of Cultivated Land Reserve Resources

Land destruction is a process. With the development of economy and society, especially the intensification of urbanization and industrialization, the area of land destruction caused by human factors is gradually increasing, and the unused land caused by the destruction will become the main body of unused land. Therefore, this classification system subdivides the unused land due to mining, industry and construction activities, such as excavation, collapse, occupation (including municipal solid waste and abandoned buildings), pollution and natural disaster damage. That is, pay attention to the types of land that have changed greatly in morphological characteristics and can be reclaimed as cultivated land. The regulation defines unused land caused by damage as damaged wasteland. The object of classification is mainly aimed at various artificial and natural factors that change the shape or physical and chemical properties of the surface (or topsoil), so that the land that cannot be reused, such as agricultural land and construction land, loses its original land use value due to the destruction, collapse and occupation caused by mining, industry and construction activities, and completely loses its original productivity due to the destruction of land by natural disasters. This classification system provides a good reference for the classification study of degraded wasteland, but it lacks attention to non-unused land types such as abandoned land, abandoned land and degraded land, that is, it mainly focuses on land abandonment, abandoned land and idle land caused by various human and natural factors, or the physical and chemical properties of the surface (or topsoil) change, which leads to the reduction of land productivity, but the land that is still available or being used is not considered.

(2) Classification of mine wasteland

There are three types of wasteland, namely agricultural wasteland, industrial wasteland and land destroyed by natural disasters. Among them, agricultural wasteland refers to idle land that has not been used for many years due to returning farmland, abandoning farmland or other reasons. Domestic research mainly focuses on its dynamic research and natural ecosystem evolution, and there are many studies on industrial wasteland, mainly focusing on mining wasteland. Li Hongyuan and others (2005) believe that industrial wasteland refers to the land that was once used for industrial production or traffic, transportation and storage related to industrial production, and then abandoned, such as abandoned mines, quarries, factories, railway stations, docks and industrial waste dumps. Mining wasteland is an important part of industrial wasteland. There are many names for mining wasteland in China, such as mining wasteland and mining wasteland. The same connotation is the land destroyed by mining activities that cannot be used without treatment (Mergel R. P, 1987), including open-pit mining sites, dumping sites, tailings ponds, subsidence areas and heavy metal pollution during mining.

Zhu (2002) classified the abandoned farmland in Guizhou into natural disaster wasteland, mining wasteland, industrial wasteland and construction wasteland. Chen Fangqing et al. (2004) classified the wasteland into mining wasteland, engineering wasteland, landfill, debris flow, landslide, incineration, deforestation and abandoned farmland. Debris flow, landslide, fire and logging wasteland are mostly steep slopes and high slopes with poor soil, and their vegetation types are mostly grasslands or shrubs, and the degree of vegetation degradation is relatively light. Mining wasteland includes abandoned rock and soil dumped in mining area, abandoned slag accumulation area, mining subsidence area, etc. The original vegetation on the first two kinds of wasteland was covered, forming a special bare land, which seriously polluted the environment; In the latter wasteland, some plant species died and the vegetation gradually degraded. Engineering wasteland and landfill are typical wasteland produced by human activities, which are mainly formed by dumping, stacking and landfill of some construction waste, industrial waste and domestic waste. Because the main components are industrial and domestic garbage, the environmental pollution is serious.

Based on the goal of mine land use and environmental protection, many researchers also put forward many classification systems in their respective case studies, especially for the damaged land and idle land caused by mine land use and mine land use. According to the direction and goal of land use in mining areas, the classification system of land use in mining areas can be divided into four types (Cao et al., 2007): ① According to the degree of land destruction in mining areas, it can be divided into excavated land, occupied land, occupied land and undisturbed land (original landform). Excavated land refers to the land type left after the original surface morphology, geological strata and biological population are directly destroyed by mining activities; Land occupation refers to the loss of productivity of the original land caused by the abandoned rock and soil piled up on the original land during the excavation and destruction process; Occupied land refers to the original land type affected by human factors, and its original topography has changed, such as the establishment of industrial squares to accommodate factories, coal preparation yards, coal railways, dump roads, power supply and ventilation lines, water supply and drainage pipelines, etc. Undisturbed land refers to the original land type that has not been occupied by digging or dumping soil after the land is requisitioned by the mine. (2) According to the land reclamation situation in the mining area, it is divided into destroyed reclaimed land, destroyed uncultivated land and reclaimed land to be destroyed. Destruction of reclaimed land refers to the type of land covered, leveled and reclaimed after the mining area is excavated or occupied; Land destroyed and not reclaimed refers to the type of land that cannot be reclaimed after the land is destroyed due to digging and occupation. , the surface condition may change in a short time; Land to be destroyed and reclaimed refers to undisturbed areas. ③ According to the site characteristics of the mining area, it can be divided into reclaimed sloping land, reclaimed terrace, uncultivated sloping land and uncultivated terrace. Reclamation and slope construction refers to the land type formed by covering the slope formed after dumping and then reclaiming it. Generally, the gentle slope is 5 ~ 15, and the steep slope is generally greater than 36. Reclamation platform refers to the land type formed by covering and reclaiming the broad mesa of stepped terrain formed after soil abandonment, and the slope of reclamation platform is generally controlled between 0 and 5; The uncultivated slopes and platforms refer to the types of land that are not covered and leveled after dumping. (4) According to the use of reclaimed land and different vegetation coverage, it can be divided into reclaimed forest, grassland and cultivated land from the perspective of soil and water conservation and ecological security in mining areas.

According to the source and formation process, mining wasteland can be divided into the following types: stripping topsoil, waste rock pile wasteland formed by mining rock fragments and low-grade ore accumulation, mining pit wasteland formed by a large number of mined-out areas and subsidence areas caused by mining, and tailings wasteland formed by discharging and accumulating mined-out ore residues (Guo Huancheng,1990; Song et al; Xi guest, 200 1), some scholars further expand its connotation, and think that mine wasteland includes not only the land occupied by mining stripping soil, waste pits, tailings, gangue and sediment of washing wastewater, but also the land occupied first and then abandoned by mining operation surface, mechanical facilities, mine auxiliary buildings and mine roads (Wu Minghui et al., 2001; Mai Shaozhi et al., 2005; Sun et al., 2005; Wei Yan et al., 2007; Li Haiying et al., 2007). See table 1-3 for classification.

Table 1-3 Types of Mining Wasteland (by Source)

Many scholars have studied the types of mine wasteland according to the research needs. Ru Lin et al. (2000) divided mine wasteland into dump, subsidence, barren grass slope and so on. Dump refers to the area formed by layered stripping of dump and occupation of cultivated land; Subsidence refers to the area where the mining of underground minerals causes the movement and deformation of overlying strata, resulting in large-scale surface subsidence and water accumulation; The wasteland in the mine refers to the abandoned land originally distributed between large and small mines on stony hills and slopes. The soil is mostly chestnut cinnamon soil, with solid soil quality, poor water permeability and large slope. Bai Zhongke (2006) investigated the soil environmental problems in mining areas, and divided the excavated land, occupied land and subsided land into two subcategories, divided the excavated land into open-pit and brick kiln borrow sites, divided the occupied land into open-pit dump and fly ash field, and divided the subsided land into coal gangue hill and mine subsided land. Su Guangquan (1998) evaluated the suitability of the abandoned land in the mining area. According to the original landform, climate, slope and other indicators, the abandoned land in the mining area was divided into 5 categories and 25 subcategories. The division indicators include topography (ground slope, altitude, relative height difference), climate (humidity, precipitation), hydrology (runoff, groundwater depth, groundwater recharge), soil (soil thickness, soil texture, pH value), minerals and mining methods (underground operation, open-pit mining), etc. According to the principle and basis of division, the division of abandoned land in mining area is shown in Table 65438+.

It can be seen from table 1-4 that the types of mining wasteland can be covered according to the classification of occupation, excavation and collapse, and can be further subdivided as needed, so as to effectively monitor and evaluate mining wasteland by using remote sensing technology. With the wide application of remote sensing data, many scholars have discussed the classification system of land use/cover in mining areas based on remote sensing data. Xie Hongquan et al. (2004) think that according to the actual situation of land use/land cover in the study area and the resolution of remote sensing, the classification system of land use/land cover in mining areas can adopt two modes: ① single mode, namely, dump, gangue hill, subsided water pit, industrial and mining area, etc. Taking guye district City of Tangshan City as an example, the land use/cover classification was carried out based on TM remote sensing images, and the classification was divided into ponding pit, pit pond and mining area. (2) Multi-level model, the first level can be consistent with the national land classification system, that is, agricultural land, construction land and unused land; The second category can be determined according to the actual situation. Dumps, abandoned mountains, puddles, etc. caused by collapse are classified as unused land. Reclaimed large-area surface fish ponds or intensive fish ponds can be classified as agricultural land, and the mine location can be classified as construction land. Other classifications can refer to the second or third categories of national land classification according to the actual situation. While determining the classification system, it is also necessary to describe the image characteristics, interpretation marks and specific meanings.

Table 1-4 Type system and main division indexes of abandoned land in mining area

sequential

Source: Su Guangquan, He, Guo Huancheng. 1998. suitability evaluation of abandoned soil resources in mining areas [J]. advanced geological exhibition, 17 (4): 39 ~ 46.

(3) Classification of other abandoned land

1. Damaged land

Land damaged by natural disasters refers to land damaged by natural disasters such as earthquakes, rainstorms, mountain torrents, mudslides, landslides, collapses and sandstorms. According to the external driving force of land destruction, the land destroyed by natural disasters includes floods, landslides, collapses, mudslides, sandstorms, earthquakes and other natural disasters. According to the degree of land destruction, Wu Shuren et al. (2002) classified the land destroyed by landslide into three categories, namely, complete destruction, partial destruction and tensile destruction. The complete destruction of land mainly refers to the rapid sliding of all-soil landslide or rock-soil mixed landslide. After a certain distance of violent displacement and uneven movement, the surface rock and soil (including land and cultivated land) turned over, dumped, re-piled and buried, which completely destroyed the surface land and made it impossible to cultivate. The local destruction of land mainly refers to the local deformation and sliding of slope and slide, which causes the local dumping, overturning and accumulation of surface land, destroys the original soil structure and makes it impossible to cultivate in that year. In the process of long-term deformation and creep, the surface soil of the sliding mass cracks, tears and collapses locally, which destroys the land structure and makes it impossible to irrigate and cultivate.

2. Other wasteland

Other abandoned land includes abandoned land and abandoned homestead. Pinghui Liu et al. (2003) put forward a land classification system based on the division of land use industrial structure. In this system, the rural idle homestead is divided into a land use level, and initially classified as a subordinate utilization level of rural houses in primary industrial land. After the optimization of the classification system, they are classified as reserved industrial land, and rural idle land is separated, covering three levels of idle homestead, wasteland and other rural idle land. Idle homestead refers to the land that is intended to be used as a homestead for production or life because the original houses in rural Kuqa have collapsed or been damaged but have not been rebuilt or vacant on its basis; Wasteland refers to the land developed and utilized without artificial reclamation, artificial input or grazing and breeding, excluding saline-alkali land, marshland and bare land; Other rural idle land refers to the cultivated land abandoned by farmers, which is barren because it has not been cultivated for many years. In addition, the National Land Use Classification (Trial) has set up idle homestead under residential land, which refers to idle old house bases and other idle land in the village. However, in the classification of land use status, idle homestead is classified as unused land, but neither of them gives a detailed and accurate definition of idle homestead.

Regarding the study of wasteland, Tan Shukui (2003) divided wasteland into two situations: open land and underground land. Land reclamation refers to the phenomenon that farmers should plant (usually at most one season) without planting any crops, making the fields barren; Hidden shortage means that farmers are still sowing crops in the fields, but the people, money and materials invested in the fields are consciously reduced (obviously not up to the requirements or below the normal level), resulting in a decline in the utilization rate and output level of cultivated land. In this study, abandoned farmland means wasteland, and scholars pay more attention to the succession of abandoned farmland ecosystem. For example, Jia et al. (2004) studied the effect of returning farmland to forest on the accumulation and activity of soil organic carbon, and made a comparative analysis of abandoned wasteland in 1, 3, 5, 7, 10, 15 and 25 years. Hao et al. (2005) studied the succession of abandoned farmland in the hilly region of the Loess Plateau in northern Shaanxi, and adopted the method of classification according to the years of abandoned farmland. In addition, most scholars divide land abandonment into perennial abandonment and seasonal abandonment according to time. Perennial abandonment refers to the abandonment of land for more than 1 year caused by farmers' contracted land not being cultivated or unwilling to cultivate; Seasonal fallow refers to the fallow caused by farmers not farming in a certain season for some reasons, and some seasonal fallow is caused by fallow (Wen Huacheng et al., 2003).