*3.1. Land Use Changes during the Period 1995–2015*

After reclassifying land use sensing data of Hubei province in five periods from 1995 to 2015, the land use type distribution map is obtained (Figure 2). According to the results, from 1995 to 2015, forest land and cropland were the main land use types in Hubei province, and the built-up land mainly concentrated in Wuhan city and the center of each urban area in central Hubei province was in an inverted "herringbone" shape in the trend of water flow along the river at the center of Wuhan. There was an expanding trend toward wetland mainly along both sides of the Yangtze River and Han River. The water area was mainly distributed in the relatively flat Jianghan Plain.

The area and change of each land use type in the study area in five periods were obtained by zoning statistics of the reclassified data (Table 2). On the whole, the significant expansion of the built-up land and the reduction of cropland and forest were the most significant characteristics of land use change in Hubei province in the past 20 years. During the past 20 years, the area of the built-up land increased the most, which was 2148.49 km2, and the area increased sharply from 2010 to 2015, accounting for more than 70% of the total increased area. The area of cropland decreased the most, reaching 2047.36 km2, and the area decreased accounted for nearly 60% of the total area decreased from 2010 to 2015. Hubei province covered the largest area of forest, followed by cropland.


**Table 2.** Changes in the area of each category from 1995 to 2015.

According to the land use transfer matrix (Table 3) from 1995 to 2015, the characteristics of land use transformation in Hubei province were as follows: (1) From 1995 to 2015, the area of cropland and forest land eventually decreased. Cropland was mainly converted into forest land and the built-up land, with an area of 12,598.13 and 4323.12 km2, respectively. Forest land was mainly converted into cropland and grassland, with an area of 12,996.31 and 3356.11 km2, respectively. (2) Although water areas and wetlands had been developed and used for 20 years, they eventually increased. In terms of land use types occupied, waters occupied the largest area of cropland at 3450.73 km2, and wetland also occupied the largest area of cropland at 526.92 km2. The increase in the area of water areas and wetlands may be related to the policy of "returning farmland to lakes" implemented in the middle reaches of the Yangtze River. (3) The area of the built-up land had increased the most in 20 years, mainly occupying 4323.12 km<sup>2</sup> of cropland and 862.23 km2 of forest land. The occupied land area was mainly used for urban construction. The built-up land was the land use type with the most thorough artificial transformation and the most affected by urbanization. The difference between the area transferred to the built-up land and the area transferred from the built-up land was the largest, which are 5729.23 and 3576.65 km2, respectively. Therefore, the expansion of the built-up land was the most dramatic during the study period. The occupation of crop land and forest land while the expansion of the built-up land became a significant land use transformation feature in the period of rapid urbanization in Hubei Province. During the study period, with the rapid development of urbanization and the increase of urban and rural incomes, the demand for housing, travel and consumption has increased, and the proportion of secondary and tertiary industries in Hubei province has increased, which has promoted the occupation of urban and rural built-up land to cropland, forest land and other ecological land.


**Table 3.** Transition area matrix of LULC from 1995 to 2015 (km2).

#### *3.2. Temporal Response of Ecosystem Service Values to Land Use Change*

3.2.1. Changes in Ecosystem Service Values of Different Land Use Types

Driven by the rapid urbanization development in Hubei province, land use transition has led to the fluctuation of ecosystem services value (Table 4). As a large amount of cropland and forest land were occupied by the built-up land expansion, the ecosystem services value of cropland and forest land showed a decreasing trend during the study period, in which the loss of forest land was the largest (USD 1.00 billion), and the loss of cropland was the largest (2.96%). From 1995 to 2015, the ESV of water area and wetland increased by USD 2.03 billion and 1.20 billion, respectively, with the largest increment of water area, but the largest increment of wetland, reaching 56.90%. Overall, the total value of ESV in Hubei province increased by USD 1.84 billion in 20 years, and the total ESV showed an increasing trend from 1995 to 2010. From 2010 to 2015, when the expansion of the built-up land invaded cropland and forest land was the most serious, the loss of ESV in Hubei province was nearly USD 320 million. The policy of returning cropland to lake in the middle reaches of the Yangtze River in 1998 may be responsible for the increase of ecosystem services value of water area and wetland, while the rapid development of urbanization may be responsible for the loss of ecosystem services value of cropland and forest land.


**Table 4.** ESVs for different land use types in Hubei Province from 1995 to 2015 (USD).

3.2.2. Changes in Individual Ecosystem Service Values

According to land use and land cover change and ESV coefficient, the contribution of each ecosystem function caused by land use transition to the overall ESV was investigated (Table 5). From the services value of each single ecosystem, hydrological regulation, climate regulation, soil conservation and biodiversity maintenance contribute the most to the overall ESV in the study area. Since 1995, with the rapid development of urbanization in Hubei province, the expansion of the built-up land has occupied a large number of cropland and forest land, and the problem of cropland conversion has intensified, which inevitably leads to the weakening of the ecosystem service function of cropland and forest land. From 2010 to 2015, food production, raw material production, climate regulation, gas regulation, soil conservation and nutrient supply, as the main ecosystem service functions of cropland and forest land, suffered losses to varying degrees, totaling USD 0.50 billion, accounting for the overall ESV losses of the main position. This indicated that the sharp decrease of cropland and forest land caused by rapid urbanization was the main source of ESV loss in the study area. From the perspective of the four service functions of the ecosystem, the largest loss was the regulation service, with a total loss of USD 270 million, followed by the supporting service, with a loss of USD 120 million, and the supply service had a relatively small loss, with a total loss of USD 110 million. In conclusion, the urbanization driven land use transition in Hubei province had the greatest impact on ecosystem regulation services, and the single ecosystem service function of the greatest impact was climate regulation. As the main ecosystem service function of waters and lakes, water supply and hydrological regulation have been increasing, with an increase of USD 250 million and 1790 million, respectively, in the past two decades. The temporal change of ecosystem services value is directly affected by land use transition. The drastic change of land use structure leads to the tightening of resources and environment in the study area, which breaks the balance of original ecosystem and leads to the decline in corresponding ecosystem service function of the region.

**Table 5.** ESVs for different functions in Hubei Province from 1995 to 2015 (USD).


Note: FP, food production; RMP, raw material production; WS, water supply; GR, gas regulation; CR, climate regulation; PE, purifying environment; HR, hydrological regulation; SC, soil conservation; MNS, maintaining nutrient supply; MB, maintaining biodiversity; AL, aesthetic landscape.

#### *3.3. Spatial Response of Ecosystem Service Values to Land Use Transformation*

To explore the spatial response from ecosystem services value to land use transition, Global Moran's I statistic was used to measure spatial autocorrelation based on factor location and attribute to value. The spatial correlation of ecosystem services value in Hubei province in the past 20 years was analyzed. As shown in Figure 3, Moran's I values from 1995 to 2015 were greater than 0, and the county units in Hubei province were mostly in the first and third quadrants, indicating that there was a positive spatial correlation between ecosystem services value of Hubei province from 1995 to 2015. Spatial distribution had a certain spatial correlation and presented spatial aggregation distribution pattern.

**Figure 3.** Global Moran's I in Hubei province from 1995 to 2015.

The hot spot analysis (Formula (7)**–**(9)) was used to reveal the local expression of the change of ecosystem service value in space. The hot spot analysis results (Figure 4) showed that the hot spots of ecosystem service value from 1995 to 2015 are mainly located in the western region where urbanization is relatively slow and rich in forest resources, and the distribution area is large and contiguous. Shennongjia Forestry District in the west was always a hot spot area with 99% confidence. The forest land in Shennongjia Forestry District accounts for more than 85%, the population is small, and the impact of human activities on the ecosystem is small. Fang County, Yun County, Zhushan County, Xingshan County in the northwest, and Lichuan County and Enshi City in the southwest were hot spots, with confidence levels greater than 90%, and they made a great contribution to the overall ESV. Most of these areas are mountainous areas with relatively high forest coverage and good ecosystem conditions. Xishui County in the east and Zhongxiang City and Yunmeng County in the middle were cold spots of ecosystem services value. During this period, the pace of urban construction in this area has accelerated, industry has developed rapidly, and construction land has expanded significantly.

From the number of cold spots and hot spots, from 1995 to 2005, the hot spots with 99% confidence and 95% confidence in Hubei Province decreased, and the cold spots did not change. From 2005 to 2015, the 95% confidence hot spots and 90% confidence hot spots in Hubei Province increased, and Jiangling and Gong'an counties with 90% confidence in the central region were no longer cold spots. Jiangling County and Gong'an County are close to the Yangtze River. During this period, the government paid attention to the prevention and control of water pollution and the protection of the ecological environment, so the ecosystem condition has improved. From the results of the hot spot analysis, in areas with slow urbanization development, the expansion of construction land is not obvious, and the original vegetation coverage is relatively high, so the ecosystem status is relatively stable. In addition, the Yangtze River passes through the territory of Hubei Province. Strengthening the protection of the Yangtze River will help the ecosystem in the Yangtze River Basin to improve.

**Figure 4.** Hot spot analysis in Hubei province from 1995 to 2015.

The calculation of geographical gravity center can help to more accurately grasp the temporal and spatial pattern of ESV from a dynamic perspective. As shown in Figure 5, From 1995 to 2010, the gravity center of ESV shifted from northwest to southeast, with an offset angle of 23.5◦ and an offset distance of 5.099 km. From 2010 to 2015, the rapid development of urbanization in Hubei province led to a sharp decrease in cropland and forest land, which reduced the value of ecosystem services. The center of ecosystem services value shifted in the opposite direction, with an offset angle of 2.5◦, but the deviation distance was not large. During the study period, the focus of ESV was within the boundary of Jingmen City. The results showed that the provision of ecosystem services in Hubei province showed a positive trend from 1995 to 2010, and the ecology in the eastern region was recovering. The ecosystem situation in Hubei province rebounded from 2010 to 2015, which was consistent with the change of ecosystem service values in Hubei province.

**Figure 5.** The trajectory of the center of gravity of ecosystem services value in Hubei province from 1995 to 2015.

#### **4. Discussion**

Under the background of rapid urbanization development in Hubei province, this study explored the characteristics of land use transformation by using land use transfer matrix and evaluated ESV of the study area. On this basis, the ways of ESV responding to land use transformation in time and space were analyzed. There has been much research on ESV responses to land use overturning changes, but little is known about ESV responses driven by rapid urbanization [33,60,74]. By constructing the analytical framework of "urbanization—land use transformation—ecosystem services value response", the study further simulates this "social economic—nature" process.

Hubei province, as an important part of China's key urban agglomeration—the middle reaches of the Yangtze River urban agglomeration, is a typical representative of China's rapid urbanization development. Under the background of rapid urbanization, a large number of labor force migrate to urban areas, regional economy develops rapidly, urban and rural income increases substantially, and demand for housing and consumption surges [75], thus promoting the occupation of urban and rural built-up land to cropland and forest land. The encroachment of the built-up land on cropland and forest land leads to the increase of the intensity and frequency of human activities' interference to the ecosystem, which directly threatens the service functions of the ecosystem [76,77]. These functions are mainly food production, climate regulation, soil conservation and so on.

As an ecological security barrier in the Shennongjia Forestry District in Hubei Province, lakes and waters in the Yangtze and Han River basins have made outstanding contributions to the overall ESV. Therefore, in future development planning, the background advantages of the ecosystem should be fully maintained and the negative impact of urbanization on land use transformation and the ecosystem should be weakened. The Yangtze River Protection Law just passed on 26 December 2020, is the first river basin law in China to protect the ecosystem of the whole Yangtze River Basin, which reflects the attention paid by the state and society to the ecological environment of the Yangtze River Basin. The tourism industry in Shennongjia Forestry District is relatively developed. While developing the tourism industry, we must always place "protecting ecological balance" first. Judging from the difference between the eastern, central and western parts of Hubei Province, the western part of Hubei Province is mostly mountainous areas, with relatively low levels of urbanization, high forest coverage, and high ecosystem security capabilities. Therefore, the ESV of each county is also high. From 1995 to 2015, the central region of Hubei Province accelerated urbanization, with rapid expansion of construction land, mostly in plain areas, with low forest coverage, so the average ESV in the central region was the lowest. The eastern region has the highest level of urbanization development, but the river system here is well−developed and contributes a lot to the overall ESV, so the average ESV in the eastern region is at a medium level. From the perspective of ESV hot spots, the distribution is relatively concentrated and the area is large in the past 20 years. Therefore, the synergistic effect of hot spots can be continued and enhanced, and ecological policies such as "encouraging social capital to participate in ecological protection and restoration policies" [78] and "ecological protection compensation policy" [79] can be used to further support the enhancement of local ecological effects. The main goal of cold spot development is to coordinate the contradiction between economic development and ecological protection. The level of urbanization in Hubei Province is still in the upgrading stage, and the built-up land is still in the expansion stage. It is a major challenge for Hubei province to ensure the economic development while maintaining the ecosystem service function and value. Hubei Province can rely on abundant higher education resources and combine its own scientific research advantages to provide intellectual support for enhancing the service functions of the ecosystem. When making plans, we should weigh various factors to avoid improper utilization of resources. We can incorporate the local index of "Ecosystem services value" into the local government performance assessment. For the cold spot area, we should first identify the reasons for the low ecosystem services value. Then, according to the degree of cropland occupied by the expansion of the built-up land, the degree of river pollution and whether the land layout is reasonable, formulate targeted plans, such as strictly controlling the building density, appropriately increasing the proportion of green space, increasing forest reserves, etc. Enhancing people's understanding of the relationship between with ecological environment and the ecological management of government departments [80] are of great significance for realizing regional sustainable development [81] and steadily improving the capability of ecosystem service assurance.

#### **5. Conclusions**

In this study, taking Hubei province in central China as the research area, we analyzed the characteristics of land use transformation driven by urbanization and the response of ecosystem service value to land use transformation from 1995 to 2015 at the county scale. The results showed that:

(1) Urbanization is an important inducement of land use transformation in Hubei province. From 1995 to 2015, with the continuous improvement of urbanization level in Hubei province, the land use structure changed constantly, and the continuous expansion of the built-up land occupying a large amount of cropland and forest land became the most significant feature of land use transformation. In addition, affected by the policy of "returning farmland to lakes" in the Yangtze River Basin, the area of water area and wetland increased during the study period, second only to construction land.

(2) The spatial and temporal distribution pattern and evolution of ecosystem services value are directly affected by land use transformation. During the study period, the value of ecosystem services in Hubei province increased from USD 118.08 billion in 1995 to USD 119.93 billion in 2015, showing an overall trend of growth. However, from 2010 to 2015, a large number of cropland and forest land in the study area were transformed into the built-up land, resulting in a total ESV loss of USD 480 million for food production, raw material production, climate regulation, gas regulation, soil conservation and other single ecological functions, which became the main reason for the ESV loss in the study area. Therefore, paying close attention to the development trend of urbanization and relevant policies, timely optimizing the land use structure and controlling the area of ecological land occupied by construction land is the focus of the work of relevant government departments in the future. The well−developed water system in Hubei province and the rich forest resources in the west have contributed greatly to the overall ESV of Hubei province. Strengthening the protection of the forest areas in the west and the waters of the Yangtze River and Han River is of great significance to maintaining the stability of the ecosystem service value in Hubei province.

(3) Affected by rapid urbanization and land use changes, the ecosystem services value in Hubei province was high in the west and low in the middle and the east. The hot spots were mainly concentrated in the western regions with slow urbanization development and high vegetation coverage, while the cold spots were mainly distributed in the central regions with strong interference from human activities. In the last five years, when the expansion of the built-up land was the most drastic, the center of gravity of ESV broke the original deviation direction, showing a rebound of migration. Using a variety of spatial analysis methods to analyze the development trend and spatial characteristics of ecosystem services value can help us formulate differentiation policies according to the actual situation of different regions, so as to help the local improve the ecological environment and enhance the ecosystem services value. In general, the response of ecosystem services value to land use transformation is the result of the interaction and synergistic development of the complex system of "society−economy−nature" driven by urbanization.

**Author Contributions:** Conceptualization, X.C.; Data curation, C.L.; Funding acquisition, G.Z.; Investigation, L.S., J.L., J.Z., and Y.J.; Methodology, C.L.; Project administration, X.C.; Supervision, G.Z.; Visualization, L.S.; Writing—original draft, C.L.; Writing—review and editing, X.C., L.S., J.L., J.Z., and Y.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** National Social Science Foundation of China: 16BGL154; China Postdoctoral Science Foundation: 2019M651885; Project of Graduate Teaching and Education Reform (High−quality Teaching Cases), Zhongnan University of Economics and Law: JXAL202104.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data generated or analyzed during this study are included in this published article.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


**Ariany Zulkania 1,2, Rochmadi Rochmadi 1, Muslikhin Hidayat <sup>1</sup> and Rochim Bakti Cahyono 1,\***


**Abstract:** Currently, fossil fuels are still the primary fuel source and reducing agent in the steel industries. The utilization of fossil fuels is strongly associated with CO2 emissions. Therefore, an alternative solution for green steel production is highly recommended, with the use of biomass as a source of fuel and a reducing agent. Biomass's growth consumes carbon dioxide from the atmosphere, which may be stored for variable amounts of time (carbon dioxide removal, or CDR). The pellets used in this study were prepared from a mixture of low-grade iron ore and palm kernel shells (PKS). The reducing reactivity of the pellets was investigated by combining thermogravimetric analysis (TGA) and laboratory experiments. In the TGA, the heating changes stably from room temperature to 950 ◦C with 5–15 ◦C/min heating rate. The laboratory experiments' temperature and heating rate variations were 600–900 ◦C and 10–20 ◦C/min, respectively. Additionally, the reduction mechanism was observed based on the X-ray diffraction analysis of the pellets and the composition of the reduced gas. The study results show that increasing the heating rate will enhance the reduction reactivity comprehensively and shorten the reduction time. The phase change of Fe2O3 → Fe3O4 → FeO → Fe increases sharply starting at 800 ◦C. The XRD intensities of Fe compounds at a heating rate of 20 ◦C/min are higher than at 10 ◦C/min. Analysis of the reduced gas exhibits that carbon gasification begins to enlarge at a temperature of 800 ◦C, thereby increasing the rate of iron ore reduction. The combination of several analyses carried out shows that the reduction reaction of the mixture iron ore-PKS pellets runs optimally at a heating rate of 20 ◦C/min. In this heating rate, the reduced gas contains much higher CO than at the heating rate of 10 ◦C/min at temperatures above 800 ◦C, which encourages a more significant reduction rate. In addition, the same reduction degree can be achieved in a shorter time and at a lower temperature for a heating rate of 20 ◦C/min compared to 10 ◦C/min.

**Keywords:** biomass; iron ore; reduction reactivity; reduction degree; pellet
