Introduction

Land use change directly reflects the interaction between human activities and the natural environment. It provides crucial theoretical support for studying Earth’s climate, ecological processes, biodiversity, and biochemical cycles. Rational allocation of land resources profoundly impacts these systems1,2. The acceleration of urbanization, marked by the rapid conversion of non-building land to building land, has resulted in significant land use changes and associated environmental problems3,4. Consequently, research on land use change is essential for understanding urbanization, monitoring environmental shifts, and informing urban and rural planning.

Land use change encompasses alterations in land use types, shapes, sizes, quantities, and spatial arrangements. With significant progress in socioeconomic development5 land use has undergone profound conversions, leading to a series of serious ecological and environmental problems6,7 such as soil erosion8 water pollution9 and land degradation10. Shi Peijun et al.11 used methods such as land use transfer matrices and multiple regression to study land use changes in Shenzhen, concluding that the tertiary industry, as an external factor, drives urban land use expansion by occupying agricultural land. Liu Jiyuan et al.12 used multi-source time-series remote sensing images to monitor land use dynamics in China from 2010 to 2015, finding that the building land area in China increased during this period, primarily at the expense of grasslands and cultivated land. Consequently, land degradation and cultivated land development contributed to a decline in the ecological environment quality of the study area. Currently, extensive research on land use change has been conducted at different scales and using various methods, including land use dynamics and land use transition matrices13,14,15,16. While providing important information for understanding spatial patterns, these studies often focus on static interpretations of spatial indices, failing to fully reveal the dynamic evolution process and underlying mechanisms of land use change17,18,19. The center-of-gravity model has quickly become a common evaluation method due to its ability to assess the trend and direction of land use change.

The center-of-gravity model, a spatial analysis method initially applied to macroeconomic and demographic trend analysis, has gradually been introduced into the field of geography in recent years2,20,21,22. Based on Landsat remote sensing images and basic geographic data, Zhou et al.23 analyzed the land use structure characteristics, spatiotemporal land use change patterns, and center-of-gravity migration characteristics of Wuhan City over the past 20 years using a land use transfer matrix and the center-of-gravity migration model. Their study showed that the dynamic changes and center-of-gravity migration of cultivated land were the most pronounced among different land use types in the study area, while the dynamic changes and center-of-gravity migration of other land use types were less pronounced. Yao Yao et al.24 researched a single type of land use, proposing that the conversion of urban building land use reflects a process of urban building land form conversion corresponding to regional social development and economic conversion over time, manifested as urban spatial expansion and functional conversion. The center of gravity, as an important indicator reflecting changes in land use types, has consistently received widespread attention from scholars both domestically and internationally. By analyzing the distance and direction of center-of-gravity movement, the spatial fluidity and temporal evolution trend of regional elements can be thoroughly examined25. Currently, while the center-of-gravity model is widely used in land use studies, existing research remains limited in its application depth. Current research is mainly limited to studying a single land use type or conducting general analyses of center-of-gravity. A dynamic analysis of the overall trend of the transfer, conversion, and change of the center of gravity of different land use types, as well as refined research on these aspects, is still lacking.

Rapid urbanization significantly alters land use patterns, profoundly impacting regional ecosystems and socioeconomic development. This study analyzes the transfer, conversion, and change processes of different land use types within the rapidly urbanizing main urban area of Zhengzhou. Utilizing multi-temporal remote sensing imagery and land use cover data from 2010 to 2020, combined with a center-of-gravity migration model, this research aims to provide a scientific basis for regional land spatial planning and explore universal urban land use planning strategies by analyzing land use dynamics. Specifically, this study constructs a comprehensive “transfer-conversion-change” analysis framework based on the centroid model, integrating spatial visualization and quantitative analysis to reveal the spatial interactions between different land use types and provide a visual representation of their dynamic changes. By analyzing the relationships of “transfer-conversion-change,” this research seeks to offer deeper insights into the driving mechanisms of urban land use change, contributing to a more nuanced understanding of urbanization processes and informing sustainable land management practices.

Study area

Our study area was located in the transitional zone between Funiu Mountain and Huanghuai Plain (112°42′—114°14′E, 34°16′—34°58′N) with a total area of 7.57 × 105 ha. It is the core growth city of the Central Plains Economic Zone and the comprehensive transportation hub of our country. In recent decades, as a regional development centre, Zhengzhou City had a rapid process of urbanization and apparent changes in surface land use, according to the statistical yearbook. Hence, study area for this research focused on the main urban area of Zhengzhou City. The scope of the research area extends from the Yellow River in the north to the Xinmi and Xinzheng boundaries in the south, the Zhongmou boundary in the east, and the Xingyang boundary in the west, with a total area of 1.06 × 105 ha (Fig. 1).

Fig. 1
figure 1

Location of the study area.

Materials and methods

Data source and processing

Landsat series (30 m×30 m) and GF-1 (8 m×8 m) remote sensing data were obtained from standardized sources, including the Geographic Spatial Data Cloud (https://www.gscloud.cn/) and the Natural Resources Satellite Remote Sensing Cloud Service Platform (https://www.sasclouds.com), covering three periods (2010, 2015, and 2020) as detailed in Table 1. Using the ArcGIS 10.8 software platform, we employed a hierarchical manual interpretation method to prioritize stable land types (e.g., water bodies and built-up areas) and address dynamic seasonal variations (e.g., vegetation and bare land). During the interpretation process, a minimum mapping unit of 10 × 10 pixels was set to generate land use data at a resampled spatial resolution of 10 m×10 m. The classification system comprised six categories: building land (BL), forest land (FL), cultivated land (CL), unused land (UL), water area (WA), and grassland (GL) (Fig. 2).

Fig. 2
figure 2

Land use types in different periods (a: 2010; b: 2015; c: 2020).

Table 1 Data source Description.

Research method

Land use transition matrix

The land use transition matrix reflects both the static information of various land use types at a specific time point and their dynamic changes over time. Therefore, we applied the land use transition matrix in our study to analyze land use changes from 2010 to 2020. The mathematical expression is as follows:

$$\:{S}_{ij}=\left[\begin{array}{cccc}{S}_{11}&\:{S}_{12}&\:\cdots\:&\:{S}_{1n}\\\:{S}_{21}&\:{S}_{22}&\:\cdots\:&\:{S}_{2n}\\\:\cdots\:&\:\cdots\:&\:\cdots\:&\:\cdots\:\\\:{S}_{n1}&\:{S}_{n2}&\:\cdots\:&\:{S}_{nn}\end{array}\right]$$
(1)

Where Sij represents the area of land use type i at the beginning of the study period and is transformed into land use type j at the end of the study period, and n indicates the number of land classes. The sum of each row represents the area of such land at the beginning of the study period and the value of each row represents the direction and quantity of land transfer.

The sum of each column represents the area of this type of land at the end of the study period, and the value of each column represents the direction and quantity of this type of land conversion.

Centre of gravity model

The centre of gravity model can more intuitively represent the spatiotemporal evolution process of land use conversion and socio - economic development by displaying the changing trends of different land use types:

$$\:{Y}_{t}=\sum\:_{i=1}^{n}\left({C}_{ti}\times\:{X}_{i}\right)/\sum\:_{i=1}^{n}{C}_{ti}$$
(2)
$$\:X_{t} = \sum {\:_{{i = 1}}^{n} } \left( {C_{{ti}} \times \:X_{i} } \right)/\sum {\:_{{i = 1}}^{n} } C_{{ti}}$$
(3)

Where Xt and Yt represent the gravity centres’ longitude and latitude coordinates of a land use type in the t year, respectively. Xi and Yi are the gravity centres’ longitude and latitude coordinates of land use type i, separately. And Cti represents the area of the land use type i in the t year.

At the same time, we used mathematical formulas to calculate the migration directions and distances of centres of gravity in different land use types. Assuming the geographic coordinates of the gravity centre for the nth and n + 1 years are (Xn, Yn) and (Xn+1, Yn+1) respectively, then the direction T in which the centre of gravity for the nth year moves towards the gravity centre for the n + 1 year Tθ. The equations are as follows:

$$\:{T}_{\theta\:}=arctan\frac{\left({Y}_{n+1}-{Y}_{n}\right)}{\left({X}_{n+1}-{X}_{n}\right)}$$
(4)
$$\:{D}_{n}=\sqrt{{\left({X}_{n+1}-{X}_{n}\right)}^{2}-{\left({Y}_{n+1}-{Y}_{n}\right)}^{2}}$$
(5)

In addition, three cases in the centre of gravity of land use were divided in this paper: “transfer” of the centre of gravity in different land use types, “conversion” of the centre of gravity in different land use types, and “change” of the centre of gravity in different land use types. The detailed descriptions are as follows:

Transfer of the centre of gravity in different land use: The transfer directions and transfer distances of the centres of gravity in six land use types among three periods (2010, 2015, 2020). For example, the location changes of the centre of gravity in cultivated land during three periods (Fig. 3).

Fig. 3
figure 3

Sketch map of the centre of gravity in cultivated land. (a: the position of the centre of gravity of cultivated land in 2010; b: the position of the centre of gravity after the transfer of cultivated land from 2010 to 2015; c: the position of the centre of gravity after the transfer of cultivated land from 2015 to 2020).

Conversion of the centre of gravity in different land use: Directions and distances of movement after different land use types convert to other land use types from 2010 to 2015 to 2015–2020. For example, changes in the location of centres of gravity after conversion from cultivated land to building land, cropland, and water area, respectively. The conversion of the centre of gravity can clearly demonstrate the trend of mutual conversion between different land use types (Fig. 4).

Fig. 4
figure 4

Sketch map of location changes in the centre of gravity after cultivated land converted to other land use types. (a: the position of the centre of gravity of cultivated land during the period from 2010 to 2015; b: land use conversion of cultivated land during the period of 2015 to 2020; c: the position of the centre of gravity of unchanged cultivated land; d: the centre of gravity position after converting cultivated land into building land; e: the position of the centre of gravity after converting cultivated land into forest land; f: the position of the centre of gravity after converting grass land into grass land; g: the position of the centre of gravity after converting grass land into water; h: the position of the centre of gravity after converting cultivated land into unused land).

Change of the centre of gravity in different land use: Overall directions and distances of movement after changes of six land use types in two periods from 2010 to 2015 to 2015–2020. For instance, changes in the centres of gravity of all changed cultivated patches, e.g., after conversion to forest land, unused land, building land, grass land, and water area, during two periods from 2010 to 2015 to 2015–2020 (Fig. 5). Changes in the centres of gravity visualize the overall trend of. use types in the city.

Fig. 5
figure 5

Sketch map of overall changes in the centre of gravity position in cultivated land where land use has changed. (a: location of cultivated land during the 2010 − 215 Period; b: schematic diagram of converting cultivated land into building land; c: schematic diagram of converting cultivated land into forest land; d: schematic diagram of converting grass land into grass land; e: schematic diagram of converting cultivated land into water area; h: schematic diagram of converting cultivated land into unused land; g: the overall centre of gravity position after converting cultivated land into other land use types during the period of 2015 to 2020).

Result

Analysis of changes in land use types

From 2010 to 2020, areas of building land, forest land, and grass land in the main urban area of Zhengzhou City continued to increase, while the cultivated land area continued to decrease. The conversion between patches of different land use types was frequent, and there was a significant transfer from cultivated land and grass land to other land use types. Among them, the transfer from cultivated land to building land was the largest, with a total of 2.510 ha, followed by the transfer from cultivated land to forest land, with 0.774 ha. Grass land was mainly transferred to building land and forest land. However, the transferred areas from grass land to unused land, cultivated land, and water area were all tiny, with 0.020 ha, 0.013 ha, and 0.006 ha, respectively (Figs. 6, 7 and 8).

Fig. 6
figure 6

Dynamic changes of different land use types in Zhengzhou City from 2010 to 2015 (ha).

Fig. 7
figure 7

Dynamic Changes of Different Land Use Types in Zhengzhou City from 2015 to 2020 (ha).

Exploring the specific transfer area of different land use types, we found that from 2010 to 2015, the cultivated land in the main urban area of Zhengzhou City decreased by 1.404 ha, with 1.063 ha converted to building land and 0.445 ha converted to forest land, respectively. The forest land had increased by 0.535 ha, mainly from cultivated land and building land, with 0.232 ha and 0.445 ha, separately. The water area had decreased by 0.197 ha, converted primarily into building land. The building land had increased by 0.859 ha, of which 1.063 ha had been transferred from cultivated land (Figs. 6 and 8).

During the two periods 2010–2015 and 2015–2020, there were some similar changes in land use transfer in the main urban area of Zhengzhou City, but also some slight differences. The similarity was that cultivated land provided many transfer resources. The difference was that the area of other land use types increased from 2015 to 2020, while the unused land area decreased by 0.077 ha. The building land and forest land area increased by 0.425 ha and 0.526 ha respectively, while the cultivated land decreased by 0.086 ha. The areas converted from cultivated land to building land and forest land were 0.621 ha and 0.329 ha, respectively. The size of unused land transferred to building land was 0.167 ha, while there was less transfer of water area to other land use types (Figs. 7 and 8).

During the two periods 2010–2015 and 2015–2020, the proportion of building land was the same, at 40.1%. From 2010 to 2015, the proportion of cultivated land was as high as 41.94%, while the proportion of unused land was the lowest, only accounting for 2.8%. From 2015 to 2020, the proportion of cultivated land remained only 35.13%. The proportion of forest land increased from 6.47% in 2010–2015 to 11.16%.

Fig. 8
figure 8

Transfer areas (m2) and proportions among six land use types from 2010 to 2020.

Analysis of the centre of gravity centre in different land use types

Transfer analysis of the centre of gravity in different land use types

During the two periods of 2010–2015 and 2015–2020, there were a significant transfer in the centre of gravity in different land use types in the main urban area of Zhengzhou City. The centre of gravity of grass land transferred 4.27 km towards southeast in 2010–2015 and 3.07 km heading northwest in 2015–2020. Overall, the centre of gravity in grass land showed a significant swing from southeast to northwest. In addition, the centres of gravity in the water, cultivated land, and unused land continued to transfer towards the southwest. Among them, the centre of gravity of the water area transferred the least, moving only 1.54 km. The transferred cultivated land and unused land moved 5.40 km and 4.14 km, respectively. The centres of gravity in forest land and building land moved first to the southeast and northwest, and eventually both transferred to the southwest. The centre of gravity transfer in building land and forest land presented a south-north-south and west-north-south swing, respectively (Table 2; Fig. 9).

Table 2 Transfer distances of centres of gravity in different land use types during two periods (km).
Fig. 9
figure 9

Transfers of centres of gravity in different land use types from 2010 to 2020.

Movements in the centre of gravity after land use types conversion

The centres’ locations of gravity in building land, unused land, and cultivated land in the main urban area of Zhengzhou City were around 113°35’— 113°50’E, 34°45’30″N, and 113°35’E— 113°45’E, 34°51’N around for water area from 2010 to 2020. However, the centres of gravity in forest land and grass land were relatively scattered (Fig. 10).

Table 3 Movement distances of the centre of gravity after land use type conversions(km).

During the two periods of 2010–2015 and 2015–2020, the centres of gravity also changed after the conversion of land use types in the study area. The centres of gravity after conversion from grass land to other land use types (building land, forest land, cultivated land, water area, and unchanged grass land), from building land to unused land and grass land, from unused land to forest land and unchanged unused land, from water area to cultivated land, and the unchanged forest land, all headed southeast. Among them, the movement distance of the centre of gravity after the conversion from grass land to cultivated land was the farthest, while from water area to cultivated land was the shortest, with movements of 183.98 km and 1.45 km, respectively (Table 3; Fig. 10).

The direction of the centre of gravity after the conversion of land use types showed partial consistency. The centres of gravity after the conversion of forest land to other land use types (including building land, grass land, cultivated land, water area, and unchanged forest land), water area to building land, forest land and grass land, cultivated land to grass land, water area and unchanged cultivated land, as well as unused land to grass land and unchanged building land, all headed northeast. The movement distances of the centres of gravity from forest land to cultivated land and from unused land to cultivated land were 15.71 km and 11.46 km, respectively. After the conversion from building land to other types of land (the gravity centre of forest land, cultivated land, and water area), from grass land to unused land, and from unused land to water area, the whole centres of gravity moved towards the southwest. Among them, the distance of gravity centre change from building land to forest land was the shortest, at 0.46 km. The centres of gravity all moved towards the northwest after the conversion from cultivated land to building land, forest land, and unused land, from unused land to building land, and grass land. The centre of gravity moved 11.46 km towards the northwest after the unused land was converted to grass land. Generally speaking, after the conversion of land use types, the centre of gravity of grass land mainly moved southeast, that of forest land and water moved northeast, and those of building land and cultivated land moved southwest and northwest, respectively (Table 3; Fig. 10).

Fig. 10
figure 10

Movement of the centre of gravity after the conversion of different land use types in the two periods of 2010–2015 and 2015–2020.

Movement of the centre of gravity after change of different land use types

The centres of gravity also moved after different land use types changed in the main urban area of Zhengzhou City from 2010 to 2020. Firstly, the centre of gravity moved to the southeast after the grass land change, while the forest and water change moved to the northeast. The centre of gravity of the changed cultivated land and unused land were relatively consistent, both moved towards the northwest. Nevertheless, the movement of the centre of gravity in building land significantly differed from other land use types, with parallel heading to the west. The movement distances of centres of gravity in changed grass land and forest land were similar, with 7.48 km and 7.21 km respectively. However, the centre of gravity centre in changed water only moved by 1.51 km (Table 4; Fig. 11).

Table 4 Movement distances after changed land use types during the two periods of 2010–2015 and 2015–2020 (km).
Fig. 11
figure 11

Movement of the centre of gravity after land use type change during the two periods of 2010–2015 and 2015–2020.

Discuss

Changes in different land use types

Change in research focus

Research on land use change is crucial for understanding global environmental change, promoting sustainable development, supporting policy-making, and predicting future trends. Studying the center of land use can effectively illuminate changing trends, facilitate better management of surface resources, protect the environment, and inform land planning decisions26,27,28. Previous researchers have published numerous articles on the study of the center of land use29,30primarily describing the shift of the center of land use. These studies align with the “transfer” aspect in this article’s “transfer-conversion-change” model. This study further utilizes the center-of-gravity model to analyze the “conversion” and “change” of land use, thus revealing the dynamic process of land use change more comprehensively. In addition, this study combines the center-of-gravity model to accurately analyze the migration direction and distance of the “transfer-conversion-change” of the center of gravity, reflecting the development trend of land use more finely and providing a basis for the high-quality development of cities.

Reasons analysis of the changes in the centre of gravity

Traditional articles often focus solely on the shift of the center of gravity of land use31,32,33without considering a multi-faceted analysis of the reasons behind the shift, conversion, and change. For example, this study found that the overall center of land use in Zhengzhou has shifted towards the southwest, consistent with the city’s urban development strategy of “expanding from the west to the south,” indicating that government planning plays an important role in guiding urban spatial expansion. However, unlike traditional research that only analyzes the causes of land use change34,35,36,37this study shifts its focus to regional socio-economic development trends and local policies, thus better revealing the spatial characteristics of land use change in the study area. Similar to the study by Li et al.38 in the Wuhan urban agglomeration, this article also emphasizes the significant impact of government planning on urban land use change.

In summary, this study on land use changes and the shift, conversion, and changes of the urban center of gravity in Zhengzhou City over the past 10 years provides a valuable understanding of urban development trends and the underlying logic. Combining this with a detailed analysis of driving factors in future research can lead to even more accurate results.

Conclusion

In our study, we analysed the “transfer-conversion-change” of the centre of gravity in different land use types of Zhengzhou City over the past years by incorporating the centre of gravity model. The specific conclusions are as follows:

  1. (1)

    The speed of transfer in the gravity centre reflects the pace of urbanization to a certain extent. From 2010 to 2020, the areas of building land, forest land, and grass land in the main urban area of Zhengzhou City increased by 1.284 ha, 1.061 ha, and 0.232 ha, respectively. Nevertheless, the areas of cultivated land decreased by a total of 2.264 ha. The frequent conversions between different land use types from 2010 to 2020, along with the increase in building land and decrease in cultivated land, reflect the speed of urbanization in Zhengzhou City.

  2. (2)

    The directions of the centre of gravity’s conversion and change reflect the demands of urban development. The centres of gravity after conversion from a certain type of land use into building land, water area, unused land, grass land, cultivated land, and unchanged certain type of land use mainly moved to the east or north in the two periods of 2010–2015 and 2015–2020. The centre movement of gravity after conversion from grass land to cultivated land was farthest at 183.98 km, and the centre movement of gravity from building land to forest land was nearest at 0.46 km. In general, the movement of the centre of gravity after the conversion and change in different land use types in Zhengzhou City headed to the northeast, which overall reflected the urban development directions of Zhengzhou City to a certain extent.

  3. (3)

    The transfer and change directions of the centre of gravity reflect the ecological change directions. During the two periods 2010–2015 and 2015–2020, the urban building plan in the northeast of Zhengzhou City has been gradually improved. It is reflected in the increasing area of forest land, the gradual completion of the water area’s water network distribution system, while the area of building land shows a more reasonable adjustment. At the same time, the centre of gravity after building land change moved towards the southwest, while the centre of gravity for the changed forest land and water area moved towards the northeast. It reflects that the ecology in the northeast direction of Zhengzhou City is constantly improving, the quality of urban development is getting higher, and the urbanization building is becoming much more perfect.