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Prediction and Evaluation of Suitable Habitats for Carya illinoinensis in China Based on an Optimized MaxEnt Model and Land Use Types
Scientia Agricultura Sinica 2026, 59(14): 3147-3161
Published: 16 July 2026
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Objective

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.

Method

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.

Result

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.

Conclusion

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.

Issue
Identification method for Carya illinoinensis varieties based on scale interactive distillation network
Transactions of the Chinese Society of Agricultural Engineering 2025, 41(5): 209-216
Published: 15 March 2025
Abstract PDF (1.6 MB) Collect
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Pecan (Carya illinoinensis) is one of the highly valuable nut crops in the global agricultural economy, due to its nutritional and economic advantages. There has ever a rising demand for high-quality cultivars of pecan in recent years. Precise and efficient identification is then required for germplasm resource conservation, breeding programs, and commercial production. However, some challenges still remain in identifying the pecan cultivars, owing to their morphological similarities, and environmental and image acquisition, such as lighting, angle, and distance. Traditional cultivar identification can also rely mainly on manual observation and expert knowledge; These manual approaches cannot fully meet large-scale production, due to the time-consuming susceptibility to subjective errors. It is very necessary to develop automatic, scalable, and accurate recognition of the pecan cultivars. In this study, a scale-interactive knowledge distillation network (siKD-Net) was introduced to enhance the accuracy of classification using deep learning. The discriminative features were then extracted from the pecan images, in order to facilitate the highly precise differentiation of cultivar. 9 048 images were captured from the twelve cultivars of widely cultivated pecan, such as Pawnee. An image dataset was established to support the training and evaluation of the improved model. Among them, the different imaging distances also caused variations in the object scales during data acquisition. The inconsistent representation of features seriously deteriorated the classification of the diverse image samples. Fortunately, the SIKD-Net framework performed better to solve the scale variation and feature inconsistency during image classification. The global-local feature was also incorporated with the scale-aware knowledge distillation. A series of experiments were then conducted to evaluate the performance of the SIKD-Net model. The results indicate that the classification accuracy of 96.98% was achieved in the twelve pecan cultivars, significantly surpassing conventional machine learning and deep learning. A comparison was also made on the baseline models, including the standard convolutional neural networks (CNNs) and transformer-based architectures. Moreover, the scale-interactive knowledge distillation substantially enhanced both the robustness and accuracy of the cultivar recognition. The high accuracy of classification was achieved in the pecan cultivar for agricultural and industrial applications. Automatic recognition can be extended to the rest of tree nuts and fruit crops for precise classification. Furthermore, the improved model can be deployed within smart systems for seedling selection, orchard management, and post-harvesting. Therefore, intelligent sorting can be integrated to enhance efficiency, in order to reduce the reliance on manual inspection in commercial settings. In conclusion, deep-learning identification can be expected to significantly enhance the efficiency and accuracy of pecan cultivar recognition. The hyperspectral imaging and multimodal feature fusion can also be integrated to further enhance the performance and the deployment of the SIKD-Net model for the large-scale classification in real-world orchard environment. The findings can also provide a scientifically robust and practically viable solution to pecan germplasm identification in precision agriculture, intelligent crop classification, and food processing.

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