Page 100 - JCAU-6-3

Journal of Chinese
Architecture and Urbanism Influence of land-use change on carbon storage

Carbon density data were mainly retrieved from the 3. Results
2010s carbon density dataset of terrestrial ecosystems
in China (Li et al., 2003; Xie et al., 2004; Xu et al., 2019), 3.1. Overview of land-use structure and change
and the average carbon density measurement data were The land-use pattern in Chengdu was dominated by
collected from sampling points within the research area. cultivated land and forest from 2010 to 2020. Over these
The carbon density correction formula was selected based 10 years, cultivated land accounted for 55.22 – 58.30%,
on the principle of similar climate conditions (Alam et al., while forest accounted for 22.69 – 22.92%, with the
2013; Chen et al., 2007; Chen et al., 2023; Giardina et al., proportion of other land types relatively low (Table 2).
2001; Ke & Tang, 2019; Parjuk et al., 2024). The average A land-use transfer matrix of three periods in Chengdu
annual precipitation and temperature of Sichuan province was established using geographic information system
and Yunnan province were substituted into Equations II, III, technology, and a Sankey diagram of land-use transfer was
and V. From 2010 to 2020, the average annual temperatures created to illustrate the quantity and spatial distribution
of Sichuan province and Yunnan province were 15.61°C and characteristics of land-use transfer (Figure 2).
16.07°C, respectively, and the average annual precipitations
were 1070.51 mm and 958.41 mm, respectively. The 3.2. Quantitative characteristics of land-use transfer
corrected coefficient can be obtained by plugging these From 2010 to 2015, land-use transfer in Chengdu mainly
values into the formula, and then, the carbon density can be occurred among cultivated land, forest, and construction land
obtained. The carbon density of dead organic matter in this (Table 3). A considerable amount of cultivated land, totaling
study was considered to be one-tenth of the aboveground 19,008.594 ha, was transferred out, mainly to construction
biomass carbon density (Delaney et al., 1998).
land and forest. In addition, the forest was also transferred
The carbon density of each land type was calculated out, mainly to cultivated land. Meanwhile, construction land
using Equations V and VIII (Table 1). Subsequently, the experienced a net increase, totaling 20,020.811 ha, with the
carbon storage of each land-use type in different periods main source being cultivated land. In addition, grassland and
can be obtained using the InVEST model after inputting unused land were transferred out in much smaller amounts,
the carbon density database and other parameters. mainly converting to forest. There were also some wetlands
that were converted to cultivated land.
2.3.3. Land-use dynamic index
From 2015 to 2020, the land-use transfer trend in
The land-use dynamic index was used to measure the Chengdu was consistent with that of the previous 5 years
transfer speed of a certain land-use type within a specific (Table 3). Cultivated land was mainly transferred into
period. The formula is as follows: construction land and forest, with the transfer area being
S S the largest, reaching 250,92.662 ha. There was also more
R b a 100% (IX)
S T forest transferred out, most of which became cultivated land.
a
During these 5 years, construction land continued to increase
Here, R represents the land-use dynamic index during substantially, with the main source still being cultivated land.
the study period in a specific location, where S and S Compared with 2010 – 2015, the area of wetlands increased
a
b
refer to the area at the beginning and end of the land-use significantly in 2015 – 2020, reaching 17.86%, primarily due
transfer, respectively. In this study, T is either 5 years or to the contribution of cultivated land and forest.
10 years. A “positive” R represents transferred-in, while a In summary, there has been a considerable amount
“negative” R represents transfered-out. of cultivated land transferred out in Chengdu from 2010
to 2020, mainly transferred into construction land and
Table 1. Carbon density (t/ha) of the terrestrial ecosystem in
Chengdu forest (Table 4). The net increase of construction land
was 45,445.131 ha. The increase in forest was 3,295.616
Land‑use type C above_i C below_i C soil_1 C dead_i Combined ha, primarily to fill the gap left by significant conversion
carbon density from cultivated land to construction land. Although many
Cultivated land 30.30 20.00 41.20 3.03 945.30 grasslands were converted to forest, the total amount of
Forest 48.17 10.90 48.17 4.82 1,120.49 grassland remained relatively stable. The unused land did
Grassland 1.04 2.49 1.04 0.10 46.63 not change significantly.
Wetland 1.94 15.37 1.94 0.19 194.51 3.3. Spatial distribution of land-use transfer
Construction land 14.00 2.79 36.17 1.40 543.60 From 2010 to 2020, the aggregation degree of land-use
Unused land 0.51 9.70 0.51 0.05 107.66 transfer in Chengdu exhibited a spatial trend of gradually

Volume 6 Issue 3 (2024) 4 https://doi.org/10.36922/jcau.3069