Prediction and Evaluation of Suitable Habitats for Carya illinoinensis in China Based on an Optimized MaxEnt Model and Land Use Types

Carya illinoinensis (C. illinoinensis) (Pecan), as a characteristic agricultural and economic nut tree species, has been widely cultivated in multiple provinces across China in recent years. This study aimed to provide a scientific basis for the scientific layout of the C. illinoinensis industry by investigating and predicting its suitable habitats and land resources in China.

First, based on the optimized Maximum Entropy (MaxEnt) model, 29 environmental variables, including climate, topography, and soil factors from 167 C. illinoinensis cultivation sites in China were analyzed. Then the dominant environmental factors were screened out, and the potential suitable habitats of C. illinoinensis in China under the current climate scenario were predicted. Second, the available cultivation area for C. illinoinensis was extracted and predicted by overlaying the forest distribution data of China.

The MaxEnt model performed optimally with Feature Class (FC)=Linear-Quadratic (LQ) and Regularization Multiplier (RM) = 2. The AUC value of the ROC curve was 0.93, and the mean TSS of the optimized model was 0.7655, demonstrating that the optimized MaxEnt model exhibits exceptionally high reliability and accuracy. The suitable habitats of C. illinoinensis were mainly influenced by temperature and altitude. The primary dominant environmental factor was the minimum temperature of the coldest month (bio6), followed by altitude, isothermality (bio3), and temperature seasonality (bio4). The corresponding suitable threshold ranges were as follows: -5 ℃ to 5 ℃ for the minimum temperature of the coldest month (bio6), below 1000 m for altitude, 15-30 and 50-57 for isothermality (bio3), and 400-1000 for temperature seasonality (bio4). Ten provinces in China were identified as moderately to highly suitable habitats for C. illinoinensis, with a medium-suitable area of 9208.69×10⁴ hm², accounting for 10% of China's total land area, and the high suitable area of 6411.22×10⁴ hm², accounting for 7% of China's total land area. By overlaying with the forest distribution data of China, the actual available cultivation area for C. illinoinensis in China was 1360.53×10⁴ hm².

In China, C. illinoinensis has potentially suitable habitats in Anhui, Hubei, Henan, Jiangsu, Hunan, Jiangxi, Zhejiang, the central part of Yunnan, south-central Shaanxi, and southwestern Shandong. After overlaying the suitable habitat map with China's forest land distribution data, the actual usable area was significantly reduced. At the provincial scale, Hubei Province had the largest area of highly suitable forest land, reaching 343.35×10⁴ hm², followed by Hunan Province with 305.57×10⁴ hm². Jiangxi and Anhui ranked third and fourth, with 219.81×10⁴ and 161.83×10⁴ hm², respectively, making them important potential main producing areas for pecans. Combining the optimized MaxEnt model with land use types can effectively predict and scientifically evaluate the suitable areas for pecans in China, thereby providing a scientific basis for the development of the pecan industry in China.