Spatial regulation design of farmland landscape around cities in China: A case study of Changzhou City

Cities 97 (2020) 102504

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Spatial regulation design of farmland landscape around cities in China: A case study of Changzhou City

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Penghui Jianga,b, , Manchun Lia,b, Yong Shengc a

School of Geographic and Oceanic Sciences, Nanjing University, Nanjing 210023, China Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Nanjing University, Nanjing 210023, China c Anhui Geological Exploration Technologies Institute, Hefei 230001, China b

A R T I C LE I N FO

A B S T R A C T

Keywords: Spatial regulation Landscape structure classification Prime farmland Farmland protection

A key issue faced by land management in China involves finding ways to prevent the degradation of the farmland system, which includes not only the scale and quality but also the ecological function of farmlands. This study uses a classification model of farmland landscapes that categorizes farmlands as core, boundary, perforation, corridor, edge patches, and discrete patches to propose a prime farmland protection zone delineation model that layer-by-layer excludes single factors based on a ‘function, quality, ownership, and environmental identification’ basis. Prime farmland protection zones are delineated based on the quality division of farmland, spatial ownership indicators, and geographic environmental determination. Finally, the spatial regulation of farmland boundaries from a ‘two lines, two zones’ perspective is determined based on conflict and coordination analysis between the prime farmland protection zones and built-up land. The spatial regulation method for farmland protection proposed by this study is based on the strict protection of prime farmland and the maintenance of its structural integrity, which can benefit farmland protection around the cities of China and achieve the goal of orderly urban expansion. This study provides theoretical guidance for protecting productive farmland resources, limiting disorderly urban expansion, and maintaining the heterogeneity of regional landscapes.

1. Introduction Farmlands are an important land resource that help ensure survival, national food security, ecological security, and renewable energy transitions and form an important component of national security (Bakker, Hatna, Kuhlman, et al., 2011; Barrett, 2010; Godfray, Beddington, Crute, et al., 2010; Kastner, Erb, & Haberl, 2014; Liu & Xie, 2013; Sutherland, Peter, & Zagata, 2015). The ecological environments around cities tend to deteriorate in response to socio-economic development and the loss of green space. The ecological functions of agricultural systems are becoming increasingly crucial to the maintenance of regional ecological security (Deslatte, Swann, & Feiock, 2017; Reid, Chen, Goldfarb, et al., 2010). Therefore, to protect farmlands, one should consider their scale, quality, and ecological functions. Further, retaining an integrated farmland landscape system could contribute to a protected farmland system (Jeffrey, 2009; Sayer, Sunderland, Ghazoul, et al., 2013). Regions where significant conflict exists between views on farmland protection and those on urban development are particularly problematic with respect to farmland landscape system planning, and they form the key link for farmland scale, quality, and ecological

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function protection (Girvetz, Thorne, Berry, et al., 2008; Holmes, 2014; Jeffrey, 2009). However, some farmland system degradation processes, such as farmland landscape fragmentation, significantly influence the function, security and productivity of the farmland landscape system (Girvetz et al., 2008; Schipanski, Barbercheck, Douglas, et al., 2014; Su, Luo, Mai, et al., 2014; Su, Yang, Hu, et al., 2014). Worldwide, China has the largest population, and its food security and ecological degeneration problems caused by farmland loss and irrational urban expansion have received global attention. d'Amour, Reitsma, Baiocchi, et al. (2017) simulated the effects of global urban expansion and found that, in the future, about one-quarter of the world's farmland loss would occur in China, mostly in the regions where high-quality farmland is currently concentrated. Accordingly, Kong (2014) argued that China should strictly protect its superior farmland resources to ensure the foundational stability of its food security. China's Thirteen Five-Year plans proposed adherence to the strictest farmland protection system, holding the farmland ‘red line’, and implementing a ‘grain storage based on land and technology’ strategy. Cao (2016) further proposed deepening the theoretical understanding and legal exploration of farmland protection and developing prime

Corresponding author at: School of Geographic and Oceanic Sciences, Nanjing University, Nanjing 210023, China. E-mail addresses: [email protected] (P. Jiang), [email protected] (M. Li).

https://doi.org/10.1016/j.cities.2019.102504 Received 11 April 2019; Received in revised form 24 September 2019; Accepted 4 November 2019 0264-2751/ © 2019 Elsevier Ltd. All rights reserved.

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gradually converting from a perspective of quality and quantity to that of landscape reconstruction (Jiang, Cheng, Zhuang, et al., 2018; LaFevor, 2015; Lausch, Blaschke, Haase, et al., 2015). Despite the importance of farmland ownership, landscape structure, and landscape quality and quantity, previous studies have rarely focused on farmland landscape structure protection (Jiang et al., 2018). Research is required to enable scientific identification of farmland patches adjacent to cities and determine the land units crucial to regional farmland landscape structures. To address this gap in the literature, this study focuses on the Changzhou city region, which is experiencing conflict between farmland conservation and urban development. Using the landscape structure classification model for farmlands, superior farmlands adjacent to the city region were identified, and a delineation of prime farmland protection zones was performed. The urban developmental boundaries were delineated to restrict disorderly urban expansion onto the farmland. In addition, by integrating the urban development boundaries with the prime farmland protection zones, the spatial control boundaries of the farmland landscapes were determined to provide policy suggestions on managing the relationship between construction, farmland conservation, and protection of superior farmlands. In this manner, this study aims to coordinate the conflict between urban expansion and farmland protection by constructing a farmland conservation system around cities.

farmland management and protection technology based on high standards. Currently, the country's spatial regulations for farmlands focus on prime farmland protection zones as a form of conservation (Cheng, Jiang, Chen, et al., 2015; Cheng, Xia, Jiang, et al., 2015; Xia, Wang, Xu, et al., 2016; Zhang, Wang, Li, et al., 2014). However, the implementation of ineffective policies during the prime farmland protection plan period, such as ‘selecting the far but not near’, ‘selecting the bad but not good’, and ‘prime farmlands are farmlands located in the mountains, oceans, and villages’ caused an overall decline in farmland quality. Therefore, finding new ways to improve the management, protection, and uses of farmlands is important to ensure human survival and the development of relationships in the context of China's urbanization. Moreover, the prevention of farmland loss resulting from rapid urban expansion helps prevent the disappearance of China's countryside (Zinda, 2014). Landscape configuration changes to farmland are driven by disturbances to farmland landscapes by human non-farming, construction, and developmental activities, which are currently degrading the comprehensive quality of farmland uses in China (Cheng, Jiang, Chen, et al., 2015; Su, Luo, Mai, et al., 2014; Su, Yang, Hu, et al., 2014; Tan, Li, Xie, et al., 2005; Xie, Mei, Guangjin, et al., 2005). Spatially, this mainly presents as construction activities related to urban expansion overtaking farmland (Chen, Chen, Shi, et al., 2003; Li, Deng, & Seto, 2012; Liu, Liu, & Qi, 2015; Tan et al., 2005). Since the beginning of openness and reform in 1978, the Chinese urbanization process has long been conducted in an uncoordinated manner, with farmland decreasing due to the increasing demand for land for urban construction (Huang, Du, & Castillo, 2019; Liu et al., 2015). How to coordinate the relationship between farmland protection and urban development is crucial to the sustainable socio-economic development of China and the creation of creating sustainable cities (Chen, Zhang, Huang, et al., 2019; Deng, Qiu, Wang, et al., 2011). The spatial regulation of farmland should involve the protection of superior farmland lying adjacent to cities and the limitation of building on farmlands for urban expansion. Specific measures should be implemented to delineate prime farmland protection zones and set boundaries for city development (Cheng, Jiang, Cai, et al., 2017; Jiang, Cheng, Gong, et al., 2016). The delineation of prime farmland protection zones should involve an optimization of the farmland's spatial layout to realize a contiguous distribution of the farmland (either compacted or closely packed), improve agricultural mechanization, and increase agricultural yields and quality (Zhang, Li, Du, et al., 2015). In addition, prime farmland protection zones around cities are important to enable spatial segregation between urban built-up land and farmland because the zones strictly limit the extent of urban expansion, guide cities from scalar expansion to connotative development, and redirect planning from fragmented to grouped planning while enforcing urban development boundaries (Jiang et al., 2016). Mathematical models based on remote sensing technology and geographic information technology have been widely applied to delineate the spatial regulation boundaries of farmland protection urban development (Cheng et al., 2017; Li & Yeh, 2001; Liu, Li, Tan, et al., 2011; Lv, Zheng, Zhao, et al., 2013; Xia et al., 2016). Moreover, the spatial continuity of farmland landscape and periurban farmland protection through governance innovation were found to be highly desirable (Cheng et al., 2017; Perrin, Nougarèdes, Sini, et al., 2018). However, none of these studies considered the management problem, including ownership and landscape structure, in detail. During the implementation process of prime farmland protection zones lacking the constraints of contiguous factors pertaining to spatial ownership, it is difficult to avoid the management chaos caused by unclear ownership (Sklenicka, Janovska, Salek, et al., 2014). Prime farmlands with unique ownership benefit from land management efficiency because of the clear conservation responsibilities. Further, an integrated farmland landscape structure can directly promote agricultural system functioning, with farmland protection strategies

2. Materials and methods 2.1. Study area The study site comprised the areas under the jurisdiction of Changzhou city (Fig. 1). Located downstream from Nanjing on the Yangtze River, the area is a flat terrain of 1861.96 km2. The geomorphology of the site comprises alluvial plains with deep soil layers. The climate is subtropical monsoon, with rain and high temperatures occurring in the same season. Therefore, the farmland conditions of the study site are unique and of high quality. The spatial layout of the farmland is contiguous, and it is one of the major food production areas in China's Yangtze River delta region. The built-up areas of the city increased from 24.44 km2 at the beginning of implementation of the Chinese economic reform in early 1978 to 203.80 km2 in 2014 (Changzhou Municipal Statistics Bureau and Changzhou Investigation Team of the National Bureau of Statistics, 2015). There was large-scale conversion of farmland into built-up land (Cheng, Jiang, Chen, et al., 2015; Cheng, Xia, Jiang, et al., 2015) and, between 1978 and 2014, the total farmland area decreased from 1008.40 km2 to 584.20 km2 (Changzhou Municipal Statistics Bureau and Changzhou Investigation Team of the National Bureau of Statistics, 2015). This significant decrease in farmland seriously threatens regional food security. The rapid economic development of the study site has increased the demand for built-up land and, under the influence of China's new wave of urbanization, the growth rate of built-up land in the area is expected to be retained in the short term, resulting in the intensification of conflicts between urban developmental needs and farmland conservation efforts. Therefore, in the study site, a land development issue that urgently requires resolution involves finding ways to protect the quality and quantity of farmlands and maintain food security while meeting the urbanization needs for land. 2.2. Data sources The data used in this study were land-use survey data (1:50,000), classification and gradation data on farmland quality (1:50,000), administrative division data on the study area (1:50,000), and the database of the third round of overall land-use planning of Changzhou city (Table 1). The Changzhou Land and Resources Bureau provided all the 2

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Fig. 1. The study area. The numbers 010, 020, 030 and 040 refer to constructive expansion permitted zone, constructive expansion conditionally-permitted zone, constructive expansion restricted zone, and constructive expansion prohibited zone respectively.

using the landscape structure classification algorithm developed from a mathematical morphological image processing technology to divide farmland landscape systems. This landscape structure is relatively simple with respect to farmlands, although over-segmentation results in the inability to accurately confirm the ecological functions of a farmland's landscape components. Further, over-segmentation causes significant missegmentation, which is concentrated in the mutual confusion among patches, edges, perforations, and corridor farmlands (Fig. 2). Therefore, based on the classification algorithm formulated by Soille and Vogt (2009), this study classified adjacent pixels of corridor algorithm and core farmland as edge farmland or perforation farmland and defined corridors as linear channels on the peripheries of core farmland to connect non-core farmlands. Simultaneously, the study corrected the missegmentations in the algorithm between edge patches of farmland and edge farmland, and between perforation farmland and corridor farmland. Subsequently, the study created a farmland landscape classification system that improved classification accuracy and simplified the classification system. Subsequently, the farmland landscape structure types were defined based on the spatial location, scale, and its landscape functions (Cheng et al., 2017; Jiang et al., 2018; Soille & Vogt, 2009). Among them, core farmlands form the basis of agricultural production; they determine the potential productivity of regional agriculture along with edge farmlands (Jiang et al., 2018). On the contrary, patch (including edge and discrete patch farmlands) and perforated farmlands are used as indicators of farmland landscape fragmentation. Different from the above-mentioned, bridge farmlands are usually the connectors among multiple independent farmland landscape systems (Soille & Vogt, 2009). Based on the definitions of different farmland landscape types, the details of the farmland landscape structure classification process are as

Table 1 Data resources. Data name

Data types

Data description

Data sources

Land use data Farmland quality gradation Administrative division Construction land regulation zones Remote sensing Landsat 8 data OLI ASTER GDEM

Vector Vector Vector Vector

1:50,000 1:50,000 1:50,000 1:50,000

Changzhou Land and Resources Bureau

Raster

Resolution: 30 m

http://www. gscloud.cn/

required vector data. The land-use survey data were used to perform farmland landscape structural classifications and formed the basic data for planning the spatial regulation of farmlands. The classification and gradation data on farmland quality were the evaluation standard for selecting high-quality farmlands. Further, administrative division data were used to define and unify the ownership properties of every farmland patch. Finally, the database on overall land-use planning displayed the spatial regulation policy on land use in the study area for farmlands and for built-up land for construction. Therefore, we selected the controlled partition of built-up land provided by this database to perform the coordination analysis between farmland protection and urban expansion. 2.3. Methodology 2.3.1. Farmland landscape structure classification model The farmland landscape structure classification model was designed 3

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Fig. 2. Sketch map of farmland landscape structure and design of farmland landscape classification.

patches of farmlands and discrete farmlands. (6) Finally, we distinguished the linear farmlands from the edge patches of farmlands. Further, we defined the linear farmlands that were connected to at least two distinct edge farmlands as corridor farmlands.

follows: (1) Land-use data were classified into farmlands or non-agricultural land-use types. Then, the data were transformed into binary grid data, in which a property contains all the information about the farmland. To maintain the integrity of the ownerships of the farmland patches and reduce error during the data conversion process, the pixel size was set as 10 × 10 m based on the original scale of the land-use data (1:50,000). (2) Based on the binary data, we classified the core farmland by defining it as the farmlands surrounded by farmland pixels without connections to non-farmlands. Subsequently, we selected a structural element with eight neighbourhoods to identify the core farmlands pixel by pixel using the erosion action of the mathematical morphological image processing technique. (3) Using the identified core farmlands as the centre and using the outward dilation action with one pixel of the mathematical morphological image processing technique, we identified the boundary pixel of the core farmlands and non-farmlands. Further, all boundary pixels were defined as edge farmlands. (4) Perforated farmlands were identified based on the core farmland using an inward dilation action with one pixel of the mathematical morphological processing technique. (5) Subsequently, all farmland pixels connected to edge farmlands or surrounded by non-farmlands were defined as edge patches of farmlands or discrete farmlands, respectively. We performed convolution computations between the classified results of edge and perforation farmlands and the structural elements to identify edge

2.3.2. Spatial ownership identification of farmland patches The basic organizational unit of prime farmland protection was the village administrative unit. To achieve unified implementation of prime farmland protection measures, it was necessary to unify information on the ownership of prime farmland protection patches. Spatial ownership identification of farmland patches comprised of the normalization of data format, spatial analysis, and pixel labelling. Since farmland blocks were raster data and village administrative divisions were vector data, the geospatial computations required a data format that conformed to both data types. To ensure the accuracy of land block and contiguous surface coverage data, raster data were used as the data format to identify ownership and label the patches, and the raster pixel size of a farmland block was the standard used to convert the assigned values by village as raster data. Accordingly, we performed raster computing to obtain the prime farmland protection patches labelled with the administrative division information. Subsequently, raster values with the same attributes were combined, the farmland pixels were deleted, and attribute connections to administrative divisions with assigned values were performed to achieve the spatial ownership identification and labelling of prime farmland protection patches and obtain the theoretical prime farmland protection areas. 4

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(3) The selection of land development intensity of prime farmland protection areas was a geographical environmental determining marker that indicated the intensity of non-farm activities on a patch, evaluated the feasibility of conducting conservation activities on prime farmlands, and screened suitable conservation patches for inclusion as prime farmland protection zones (Zhang et al., 2014). Based on these identified zones, prime farmland protection zones were created by the spatial aggregation of the conservation patches.

2.3.3. Identification of geographic environments around farmland landscapes The geographical environments appropriate to concentrated agriculture are regions with low probabilities of urban construction and development; hence, the delineation of prime farmland protection zones should avoid regions with high probabilities of urban construction and development. Quantifying land development intensity can be applied to determine the share of built-up land, which might directly indicate the intensity of regional production and construction activities. Therefore, this study used land development intensity at the village administrative level of the prime farmland protection block to identify the extent of appropriateness of land for inclusion in prime farmland protection zones. Built-up land was the basis for calculating land development intensity. Based on its spatial and socio-economic characteristics, built-up land can be divided into rural, urban, and other built-up land types. Among them, rural built-up land refers to the areas where basic organizational units of farmland production are located, whereas urban built-up land refers to the spaces where non-farm production is concentrated. Therefore, to understand the influence of land development intensity on farmland production interference intensity, this study used the ratio of urban built-up land as the basic data marker, which was calculated from regional land development intensity. The formula was given as follows:

LDIu =

3. Results 3.1. Delineation of prime farmland protection zones 3.1.1. Functional delineation of farmland plots Based on the farmland landscape structure classification method, we divided farmland landscapes into core, edge, and corridor farmlands, as well as edge patches of farmland, discrete patches of farmland, and perforation farmlands (Fig. 4). In the study area, core and edge farmlands were the major landscape types, comprising 77.70% of the area's total farmland. Edge patches and discrete patches of farmland had the next highest share of area, comprising 14.67% of the area's farmland (Fig. 4). Spatially, core farmland was presented as a concentrated contiguous distribution on the peripheries outside the boundaries of the central urban region. These peripheral regions represented the historical farmland regions of Changzhou city, which had insignificant levels of urbanization lags and farmland segmentation resulting from road traffic, built-up areas, and other human activities. Patches of farmland were irregularly scattered in the peripheries of the central city region, where urban construction activities were common and non-farm activities encroached on farmland boundaries, causing the segmentation of farmland by other factors (Fig. 4). The majority of the farmland was surrounded by built-up land, isolating the land as ecological islands in the central city and decreasing spatial contiguity. From a functional perspective, core farmlands had a contiguous distribution, as well as the lowest interference from non-farm activities and highest agricultural productivity among all types. This landscape type functions as farmland production, plays a macroscopic dominant role in farmland landscapes, and forms a basis for maintaining farmland landscapes. Further, the edge farmland is an ecological transition zone between core farmlands and non-farm ecosystems; it helps isolate ecological interference and facilitates the ecological buffering of nonfarm ecosystems and non-farm activities occurring on prime farmlands. Edge farmlands buffer and protect the production functions of core farmlands, and these two farmland types complement each other. Contrarily, corridor farmlands are channels that connect farmlands to each other and function as separations between farmlands and nonfarm ecosystems. Further, edge and discrete patches of farmland include small habitat areas and exist as mosaics within non-farm ecosystems. These landscapes are often affected by various non-farm activities and have low systemic productivity. Their function is similar to that of perforation farmlands, which is mainly the demonstration of the spatial configuration evolutionary process of farmland landscapes. Therefore, the delineation of prime farmlands should consider both edge and core farmlands, account for plot continuity, use the core farmland as the prime farmland template, and use the peripheries of the edge farmland as the borders of basic agricultural fields. Using the landscape structure classification results, functional segmentation, and pixel attribute reclassification, we combined the core farmlands as contiguous farmlands and the edge patches of farmland, discrete patches of farmland, and perforation farmlands as discrete farmlands and defined corridor farmlands as connecting channels. From the perspective of ensuring continuity among farmland landscapes, contiguous farmlands and connecting channels were selected as the theoretical prime farmland protection patches.

Au = Sum {aI (B) = ui | B = U , R} × 100% A

LDIu refers to the land development intensity which was calculated based on the proportions of urban built-up lands per spatial statistical units (the administrative areas of villages or communities), Au refers to the total area of urban built-up lands within the spatial statistical units, A refers to the total area of the spatial statistical units, I(B) refers to classified built-up land types, a refers to area calculating, B refers to built-up lands, U refers to urban built-up lands and R refers to the rural built-up lands. 2.3.4. Single-factor layer-by-layer exclusion This study proposed a single-factor layer-by-layer exclusion method, that is, the use of relevant factors dominating a few natural and cultural characteristics as the sole determining criteria and layer-by-layer screening to optimize the selection of superior farmlands and delineate prime farmland protection zones. The specific processes are as follows (Fig. 3): (1) The functional delineation of farmland landscapes was based on the farmland landscape structure classification model. Further, we defined the functions of different farmland landscape types. Since core and edge farmlands determine the potential productivity of regional agriculture, they should be strongly protected (Cheng et al., 2017; Jiang et al., 2018). Consequently, farmland landscape types dominating regional agriculture production were selected as prime farmland protection patches by using the spatial analysis technology. (2) Subsequently, we evaluated the quality of the prime farmland protection patches by using natural quality grading, utilization quality grading, and economic quality grading of farmlands at the plot level (the data were provided by the Changzhou Land and Resources Bureau). To achieve a more comprehensive evaluation of farmland quality, the integrated quality grading of regional farmlands was classified with the spatial analysis of natural quality grading, utilization quality grading, and economic quality grading of farmlands (Cheng et al., 2017; Xia et al., 2016). Further, the farmland plots that had high grades of natural, utilization, and economic quality were selected as prime farmland plots. Finally, the administrative zoning of preferred farmlands was performed with the confirmation of the prime farmland protection areas. 5

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Fig. 3. Process of the single-factor layer-by-layer exclusion method of abstracting prime farmland protection zones.

attributed to prime farmland protection zones. However, the real quality of farmland landscapes is usually affected by the geographic environments around them, especially the nonagricultural interruptions (Deng et al., 2011). Based on the spatial distribution of land development intensity in the study site, this study found that the land development intensity in areas comprising a concentration of urban built-up lands was greater than 10%, in general, whereas the land development intensity values in regions with a concentration of farmlands were all less than 10% (Fig. 5(e)). This finding indicates that a land development intensity of 10% could be used as the cut-off point to distinguish between regions where agriculture is concentrated and regions where urban construction is concentrated (Fig. 5(e)). Therefore, this study used the cut-off of land development intensity greater than 10% as the screening criterion for further exclusion of theoretical prime farmland protection areas labelled with spatial ownership information.

3.1.2. Quality segmentation and geographic environment control of farmlands The integrated quality of farmlands is found in its natural conditions (including light, temperature, water, air, and soil), uses (development and extents of use under standard agricultural systems and natural background conditions), and economic value (monetized value based on the development and extents of use under standard agricultural systems and natural background conditions). Currently, the standards of farmland quality segmentation refer to the results of the quality grading of farmlands provided by the State Land Administration Bureau. Therefore, this study conducted qualitative segmentation of farmlands using farmland quality grading at the urban block scale of Changzhou city. Farmland quality grading includes natural farmland quality grading (Fig. 5(a)), use quality grading (Fig. 5(b)), and economic quality grading (Fig. 5(c)). To derive the integrated quality grading of farmlands, this study spatially superimposed natural, use, and economic quality gradings (Fig. 5(c)). The threshold intervals of integrated quality grading of the farmlands were divided based on their corresponding division standards of natural, use, and economic quality gradings. Based on the integrated quality grading evaluation results, the lowest integrated quality grade of farmlands inside the Changzhou city limits was 23, which corresponded to the threshold interval of the integrated quality grading of farmlands (Fig. 5(d)). All the farmlands in the study site were of high quality, that is, from the perspective of farmland quality, all the theoretical prime farmland protection patches considered by this study had the natural, use, and economic potentials

3.2. Delineation of theoretical prime farmland protection zones The screening results on prime farmland protection areas described above and the pattern identified from the results provided a theoretical spatial range of prime farmland protection zones in Changzhou city. The results found that the total area of theoretical prime farmland protection zones delineated by the study is 864.26 km2, which comprised 50.97% of the entire study area with the water area is excluded. Land use types in the zones included farmlands and other types. Further, the prime farmland protection zones covered almost all the 6

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Fig. 4. Farmland landscape classes in the municipal district of Changzhou city.

3.3. Design of the spatial regulation boundaries of farmlands

important farmland production areas and achieved the maximum extent of protection of superior farmlands in the city. However, from the perspective of coordinating prime farmland protection with urban construction and development activities, the prime farmland protection zones were mainly distributed on the peripheries of developed areas in the city centre. In this manner, the goal of spatial segregation of urban production spaces and farmland production spaces was realized, the concentration of farmland production spaces was promoted, and basic site conditions for mechanized farmland production and large-scale commodity farmland management were achieved. In addition, by jointly considering integrated production capacities and spatial concentrations of farmlands, we can help protect farmland quality and ensure sustainable uses of farmland. Moreover, as barriers to urban expansion, permanent prime farmlands could limit disorderly urban expansion, guide group-oriented urban development, and improve intensive urban land uses.

While delineating centralized management and protection zones for prime farmlands, the spatial regulation of farmlands should limit the external dynamic factors causing the degradation of farmland landscapes, such as urban expansion. Based on the delineated prime farmland protection zones, the theoretical flexible and rigid urban development boundaries (see Jiang et al., 2016) and existing types of spatial regulation policies on construction land were combined. Flexible boundaries are those that can be changed according to urban development demands, while rigid boundaries are those that are strictly regulated, with change forbidden during a certain time period. To resolve the conflict between farmland conservation and urban construction, this study confirmed the spatial regulation borders of the farmlands within the Changzhou city region.

3.3.1. Spatial conflict between farmland conservation and urban expansion Specifically, the built-up spaces, farmland conservation spaces, and urban built-up central regions delineated by this study represent the 7

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Fig. 5. Farmland quality and land development intensity of the study area. The (d) comprehensive quality rank of farmland was determined by the (a) natural quality rank, (b) utilization quality rank and (c) economic quality rank. The land development intensity was calculated by using the equation provided in the Materials and methods section. Farmlands located in the villages or communities with LDI > 10% were excluded.

conditional construction zones (aside from the small areas that were retained as prime farmlands), the majority of these zones were within the urban development boundaries, as well (Fig. 6(d), (e)). Among them, the sizes of the conflict regions between the theoretical flexible or theoretical rigid urban development boundaries and the theoretical prime farmland protection zones retained as prime farmland protection zones were 14.05 km2 and 29.02 km2, respectively. However, the sizes of the conflict regions delineated as urban development boundaries were 60.78 km2 and 100.03 km2, respectively.

conflicts between the theoretical prime farmland protection zones and the central city region (Fig. 6(a)) and those between the theoretical prime farmland protection zones and theoretical flexible (Fig. 6(b)) and rigid (Fig. 6(c)) urban development boundaries. Therefore, this study employed a spatial superimposition analysis to identify the spatially superimposed urban development and farmland conservation regions. The areas of conflict between the central city region and theoretical prime farmland protection zones were relatively concentrated and mainly distributed in the northern farmland concentration region, having an area of 26.69 km2. The spatial conflict regions of the theoretical flexible or theoretical rigid boundaries and the theoretical prime farmland protection zones were similar and were discretely distributed along the boundary, with areas of 84.22 km2 and 142.88 km2, respectively.

3.3.3. Design of the spatial regulation of farmlands Based on the farmland protection concept of focused management and protection of farmlands and the weakening of non-farm interference mechanisms, this study designed a ‘two lines, two zones’ spatial regulation structure for farmlands. The phrase ‘two lines’ refers to flexible or rigid urban development boundaries, and the term ‘two zones’ means prime farmland protection zones or urban flexible regulation zones (Fig. 7). The goal was to solve the problem of spatial landuse management with respect to conflicts between farmland protection and urban expansion. The specific analytical implementation path followed is discussed here. First, the spatial analytical technology of the Geographic Information Systems (GIS) was used to analyse the basis of conflict between farmland protection and urban expansion through a spatial diagnosis of land spatial management policies and all known background information on the areas experiencing the aforementioned conflict. This step determined the regulatory direction of these areas to determine the final spatial boundaries of prime farmland protection zones and of the flexible urban developmental borders and the rigid urban development boundaries. The exclusion analysis of these urban development boundaries found flexible and adjustable regions with which flexible or rigid urban development boundaries were established as urban spatial expansion limits, prime farmland protection zones with focused management, protection zones for farmlands, and flexible adjustable regions to act as buffers between areas for farmland conservation and areas of urban expansion.

3.3.2. Conflict zone resolution analysis This study analysed solutions based on the spatial regulation divisions of the built-up land in conflict areas and their contexts (Fig. 6(d), (e)). According to the results of the analysis on farmland landscape configurations, the farmland landscape in the central city region was seriously fragmented, and the central city was a developmental core unsuitable for prime farmland protection. Therefore, we did not include the regions of conflict between the theoretical prime farmland protection zones and central city in the prime farmland protection zones. The principles for resolving other types of conflicts include the following: (1) Determination of regulated divisions. All the regulated zones in the conflict regions that were permissible construction and conditional construction zones were within the urban development boundaries; however, all the regulated zones that limited or prohibited construction were within prime farmland protection zones. (2) Determination of context. Large areas of conflict surrounded by built-up land within the urban development boundaries were retained as prime farmland protection zones to ensure the spatial continuity between urban development boundaries and prime farmland protection zones.

3.3.4. Delineation of the spatial regulation boundaries of farmlands The final prime farmland protection zones and flexible and rigid urban development boundaries were delineated based on the resolution direction results on the conflict zones. However, based on the range of

The direction of resolution of the conflict zones was based on the following reasoning: Since the majority of the conflict zones were in urban environments or were generally superimposed on permissible or 8

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Fig. 6. Identification and coordination of the conflict areas between urban development and farmland protection. (a) Conflict areas between urban centre boundary and prime farmland, (b) conflict areas between flexible urban development boundary and prime farmland, (c) conflict areas between rigid urban development boundary and prime farmland, (d) coordination between flexible urban development boundary and prime farmland, (e) coordination between rigid urban development boundary and prime farmland. RPF refers to the conflict areas that were reserved as prime farmlands and RUDB refers to the conflict areas that were reserved as the parts of urban development boundary.

available flexible or rigid urban development boundaries and through the confirmation of the urban flexible and adjustable regions (based on spatial analysis), a two lines, two zones spatial regulation structure was developed for farmlands (Fig. 8). As explained earlier, the phrase ‘two lines’ refers to flexible or rigid urban development boundaries and ‘two zones’ refers to prime farmland protection zones or urban flexible regulation zones. The coverage areas of flexible and rigid urban development boundaries were 566.02 km2 and 700.85 km2, respectively, and the area of the flexible adjustable region was 134.83 km2. This delineation formed two large patches, one in the north along the river and the other comprising the majority of the Changzhou city area (Fig. 8). The area of prime farmland protection zones was 729.58 km2; covered the majority of the farmlands; and formed patches in the northern region, including two patches in the east and west of Lake Ge and two patches in the northeast, that is, a total of four protection area patches (Fig. 8).

In addition, based on the spatial layout of the two lines and two regions, prime farmland protection zones and rigid urban development boundaries nearly overlapped, achieving the goal of using prime farmland protection zones to limit urban expansion. This fulfilled the original design intention of strictly regulating interference arising from urban expansion and weakening non-farm construction and developmental activities on farmlands. Therefore, this study concludes that, by concentrating on the protection target, regional farmland protection efforts should focus on satisfying urban developmental needs while strictly limiting the effects of urban expansion on farmland landscapes. The centralized management of protection efforts and weakening of interference by non-farm activities might achieve improved protection of farmland resources.

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Fig. 7. The ‘two lines, two zones’ spatial regulation structure for farmlands. The ‘two lines’ refers to the flexible urban development boundary and the rigid urban development boundary. The ‘two zones’ refers to the prime farmland protection area and the flexible coordination area.

4. Discussion

farmland quality, and regional geography (Liu et al., 2014; Zhang et al., 2015). Regarding plot morphology and spatial layout, quantitative analyses of landscape configuration indices are currently performed by type, landscape, and patch scale. However, it is difficult to quantitatively characterize the spatial information and system functions of a single plot (Xia et al., 2016). The evaluation of farmland quality and regional geography is mostly determined through comprehensive assessments of numerous elements and factors (Cheng et al., 2017; Xia et al., 2016). Comprehensive evaluation has some reference value for the integrated productivity levels of regional farmlands; however, uncertainty in factor selection and weighting determinations exists. In addition, integrating multiple factors tends to dilute the decisive effects of the major factor on farmland quality and environmental assessment, which distorts the evaluation results. Conventional land-use planning and delineation approaches adopted in prime farmland protection zones tend to emphasize the qualities of the protection target and overall requirements of regional socio-economic development (Cheng et al., 2017; Xia et al., 2016). This approach creates numerous problems, such as a lowered quality of prime farmland protection zones, fragmented morphology, and high

Since there is a significant extent of superimposition between farmland and urban built-up spaces, China has experienced problems associated with the large-scale occupation of superior farmlands as a result of urban expansion. This has been a longstanding problem since the beginning of China's economic reform (d'Amour et al., 2017; Deng, Huang, Rozelle, et al., 2015; Jiang, Deng, & Seto, 2013; Song, Pijanowski, & Tayyebi, 2015). With the rapid growth of the Chinese urban population, the demand for built-up land has been increasing, whereas the quantity and quality of farmlands have been continuously declining. Currently, the potential for food security problems threatens the country's sustainable socio-economic development strategy (Liu & Xie, 2013; Zhang et al., 2014). Therefore, resolving the conflict between efforts for farmland protection and urban expansion is a core aspect of China's spatial planning (Deng et al., 2015; Liu, Fang, & Li, 2014; Song et al., 2015). The delineation of prime farmland protection zones is the basic policy tool to prevent farmland decrease from urban expansion. It involves numerous elements, such as plot morphology, spatial layout, 10

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Fig. 8. Delineation of spatial regulation boundaries according to the two lines, two zones spatial regulation structure of farmlands. The ‘two lines’ refers to the flexible urban development boundary and the rigid urban development boundary. The ‘two zones’ refers to the prime farmland protection area and the flexible coordination area.

The core aspect of the spatial regulation method for farmland protection proposed by this study is its basic emphasis on and attention to farmland resource quality, environment, ownership, and spatial continuity, as well as the strict regulation of the interference created by non-farm activities on superior farmland resources. The exact method used by the study involved delineation of the buffer areas between farmlands and built-up areas to create flexible areas for urban development in advance of its encroachment. These spaces would be established after comprehensively considering the integrated quality of adjacent farmlands to ensure the viability of the structural integrity of the farmland landscapes, confirm as much as possible that superior farmland resources would not be occupied, and minimize interference by non-farm activities in farmlands. Therefore, the two lines of flexible and rigid urban development boundaries would guide the directional and appropriate growth of cities, whereas the prime farmland protection zones would centralize the protection of superior farmland resources. Flexible and adjustable zones are expected to resolve the conflict between farmland conservation and urban expansion efforts. The two lines, two zones method for spatial regulation of farmlands has the following advantages compared to

altitudes with highly gradient farmlands (Cheng, Jiang, Chen, et al., 2015; Cheng, Xia, Jiang, et al., 2015). This delineation approach weakens the ability to retain prime farmlands because it cannot halt disorderly urban expansion or achieve the planning objectives of protecting superior farmland resources and ensuring regional food security. Consequently, this study employed geographical spatial dimension deduction, followed the delineation sequence of ‘prime farmland protection plot, prime farmland protection patch, prime farmland protection zone’, and delineated prime farmland protection zones by spatially scaling them up and performing layer-by-layer aggregation. In this process, the prime farmland protection patches were identified by the farmland landscape structure classification model proposed earlier, which identifies spatially adjacent plots and defines them as prime farmland protection patches. On this basis, the quality grading of farmland plots, plot ownership information, and regional land development intensity were combined to further screen the prime farmland protection patches, which were sequentially combined to form prime farmland protection areas (which are larger than patches but smaller than zones) and prime farmland protection zones. 11

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become the irreplaceable parts of the ideal of ‘Garden City’. Furthermore, controlling the urban growth rate and improving the compactness of urban form through a series if spatial regulation policies, i.e., the delineation of farmland protection zones, will also contribute to the ecological security of the cities (Zhou, Liu, Tan, et al., 2014). Therefore, improved planning of farmland landscape around Chinese cities will not only enhance its culture heritage but also environmental optimization as well.

conventional prime farmland protection zones: (i) Emphasis on the structural integrity of farmland landscapes. Through spatial isolation, regional construction land spaces are strictly divided into farmlands and urban spaces, which are represented by built-up land. This distinction ensures the maintenance of the morphology of farmlands' spatial continuity, which lessens the risk of fragmentation of the farmland landscape configuration. (ii) Emphasis on unified spatial ownership. This study performed spatial aggregation based on the ownership attributes of farmland blocks. While maintaining the continuity of the farmland's spatial morphology, the study ensured the integrity of protection and management of farmlands. This prevents unclear responsibilities for protection, division, and confusion about farmland ownership. (iii) Emphasis on the purity of the production environment. This study performed spatial screening of farmland blocks based on land development intensity to obtain pure farmland production spaces and lower the probability of occurrence of non-farm activities on farmland. Simultaneously, the study used flexible and adjustable regions to isolate farmland spaces from non-farmland spaces, interrupting the transmission channels of industrial pollution to farm production areas and realizing the goal of surrounding the city with crop fields and greening the city's ecological environment.

However, several uncertainties still need to be explored and addressed in future research to minimize errors due to factors such as threshold selection, data resolution, and landscape classification size. For example, currently, farmland quality classification in China are mostly based on the regulation for gradation on agriculture land quality. This gradation is determined by land use coefficient, land economic coefficient, and the standard of farming system at county scale (GB/T 2804, 2012). Therefore, it is hard to evaluate the difference of farmland quality at city level. In order to perform a further evaluation, standard sampling points uniformly distributed across the agricultural areas are selected. However, no uniform rule can be concluded from the thousands of samples because of the complicated agriculture environment of China. As a result, few precise thresholds can be selected to identify the quality of every farmland patch. Likewise, landscape structure classification also faces the question of selecting an appropriate standard to identify farmland landscape structure precisely. Different landscape classification sizes will lead to inconsistent definitions of edge patches and corridor farmland (Riitters, Vogt, & Soille, 2009). Except for this, data resolution also determines the classification effect through eliminating the interference information caused by nonagricultural landscapes. Recent scientific research indicates that high resolution data will further remove the heterogeneous landscape information showed in low-resolution data (Ritters et al, 2009; Wickham & Riitters, 2019) . In conclusion, technical problems related to matters such as evaluation standards and data accuracy still require further research to reduce uncertainty.

Through conflict zones resolution, high quality farmland resources can be well protected while urban development benefits from this design. To create sustainable cities in China, farmland landscape design can contribute to urban development in the following ways: (i) The optimization of urban form. Chinese farmland protection can govern urban expansion and guide urban form (He, Liu, Yu, et al., 2013; Long, Han, Lai, et al., 2013). In order to constrain disorderly urban expansion and prevent farmland loss from urban construction, about 62,466 km2 prime farmland protection zones around cities in China were delineated at the end of 2016 (http://www. mnr.gov.cn/dt/mtsy/201701/t20170113_2328720.html, in Chinese). The primary goal of this work is to maintain food security and promote urban form planning by making full use of ‘forced’ mechanisms to delineate urban development boundary (http:// www.mnr.gov.cn/dt/mtsy/201701/t20170113_2328720.html, in Chinese). Therefore, it is clear that a perfect farmland landscape pattern design will lead to a rational urban form, especially for cities in China which are mostly surrounded by farmlands (Cheng et al., 2017). (ii) Improving utility of land resources. Chinese rapid urbanization processes characterized by substantial increases in construction land scale has led to incomplete urbanization (Du, 2016). As a result, urban diseases like high investment of land resources and low land-use efficiency cause unsustainable urbanization (Guan, Wei, Lu, et al., 2018). China must constrain the urban scale and slow the pace of urban expansion through a series of policy measures, such as a boundaries restricted by other landscapes. Currently, the Chinese government plans to strictly regulate farmland around cities and force cities to implement urban renewal (Cheng et al., 2017; Zheng, Shen, & Wang, 2014). Through such protection, idle and inefficient land resource can be optimized and the comprehensive values of land development maximized. (iii) Beautifying the environment around cities. Farmlands around cities are a significant ecological barrier that is more conducive to agriculture than urban development (Eagle, Eagle, Stobbe, et al., 2014). Since the natural landscapes in peri-urban areas have largely been removed in prior decades because of industrialization and urbanization, farmlands have become a unique green belt around cities (Bryant & Chahine, 2016). In particular, in Chinese cities with histories of agricultural cultivation, farmlands have

5. Conclusions This study employed the landscape structure classification model to farmland and identified prime farmland protection patches based on the functional differences among farmland patches. It determined the integrated quality of prime farmland protection patches based on farmland quality grading and delineation. Further, it ensured the ownership continuity of prime farmland protection patches through spatial ownership identification and labelling. Based on these techniques, a land development intensity value greater than 10% was used as the screening threshold to delineate prime farmland protection patches, which was then used to combine protection patches and delineate theoretical prime farmland protection zones. The study employed the GIS spatial analytical technology to analyse the foundations of conflict between farmland protection and urban built-up land and to perform a spatial diagnosis based on land-use spatial management policies and all known background information on the conflict areas. This step determined the regulatory direction of the conflict areas with which the spatial boundaries of prime farmland protection zones were determined, as well as flexible or rigid boundaries of urban development. The exclusion analytical results of the flexible urban development boundaries, rigid urban development boundaries, and flexible adjustable regions could establish flexible urban development boundaries and rigid urban development boundaries as urban spatial expansion limits. Prime farmland protection zones were identified as focused management and protection zones for farmlands, and flexible adjustable regions were identified as buffer spaces between farmland conservation areas and built-up areas. This step solved the spatial relationship problem between the prime farmland protection zones and 12

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the urban development boundaries by clarifying a spatial regulation structure for farmlands based on the two lines, two zones approach. By solving the conflict between prime farmland protection zones and urban development boundaries, this study established a spatial regulation structure for farmlands based on the two lines, two zones approach, which was established to satisfy regional construction and development requirements, and it integrated the two land-use strategies of spatial regulation of built-up land and concentration and protection of farmlands. This approach could solve the conflict between farmland conservation and urban expansion, realize the goal of optimizing the spatial configuration and quality of construction land.

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