## 2 Materials and Methods  
### Collection and Testing of Soil Samples  
The Xianshan Lake Wetland Park is located in Changxing County, Huzhou City, Zhejiang Province, China. It is situated in the northern part of Zhejiang Province and at the intersection of Zhejiang, Jiangsu, and Anhui provinces. The park covers an area of 2692.2 hectares. It is not only one of the largest wetlands in the province of Zhejiang's north, but it is also one of the most ecologically diverse and unspoiled wetland ecosystems in the Yangtze River Delta, as well as a typical example of the natural wetlands and artificial lakes and wetland systems in Zhejiang. Its geographic structure is shown in Figure 1. The sample region has a diverse range of flora and animals, a thick canopy of vegetation, a subtropical monsoon climate, four distinct seasons, and a variety of landforms. It also has a moderate climate, plenty of sunshine, and abundant rainfall. The average annual temperature is 15.2 degrees Celsius, the average annual sunshine hours are 2074 h, and its soil types are mainly bog soil, paddy soil, and red earth soil.  
The experimental soils in this study were collected in September 2022. A total of 85 soil sample points were collected from different types of 0-15 cm surface soils in the study area, of which five surface soil mixes were taken from each sample point. The well-blended soil samples were brought indoors for natural air drying. They were then ground to eliminate contaminants and underwent screening treatment using a sieve with a pore size of 2 mm. The soil samples were equally divided into two parts for soil spectral information collection and chemical technology for SOM content determination, in which the chemical technology utilized potassium dichromate oxidation to determine the SOM content [14]. The specific process of the chemical method was as follows: Under heating conditions, soil organic carbon was oxidized using an excess of potassium dichromate sulfuric acid solution. The excess potassium dichromate was titrated with a ferrous sulfate standard solution. The  
Figure 1: Geographic location of the study area and distribution of sampling sites.  
amount of potassium dichromate consumed was calculated according to the oxidation correction factor to determine the organic carbon content. This value was then multiplied by the constant 1.724 to obtain the SOM content.  
Soil spectral reflectance was determined using an FX(17) hyperspectral camera with a spectral range of 900-1700 nm and a spectral resolution of 3.5 nm, containing a total of 224 bands. The spectral equipment acquisition device is shown in Figure 2. During the determination process, the light source was provided by six 50 W halogen lamps. The fiber optic probe had a field of view of 10\({}^{\circ}\), and it was positioned at a distance of 20 cm from the surface of the soil samples. Each soil sample was divided into 27 portions and placed in a tray. Before the determination, each sample was calibrated with a white board to reduce instrument-related errors. Subsequently, based on ENVI5.3 software, 27 spectral curves were measured for each soil sample, and the average value was taken as the actual spectral curve for that soil sample after removing the outliers [15].