| Taking the endemic Chinese torreya as an example the paper carried out researches on the relationship between habitat selection and environmental factors based on information technology. Firstly, spatial database was established based on remote sensing image, DEM, soil, geology and meteorological data. Secondly, the key factors affecting its spatial distribution and site selection was analyzed by spatial analysis methods. Finally, the Logistic regression model was introduced into the suitability evaluation and the most suitable distribution zone was successfully predicted using the model. The results would be beneficial for understanding the ecological requirements and would provide scientific basis for preferable site selection and sustainable use of this rare species. The main contents are summarized as follow:(1)Extraction of distribution information of Chinese torreya based on object-oriented method from IKONOS imageryBased on the IKONOS satellite images, the object-oriented technology was used to extract the Chinese torreya information by building feature space from spectrum, shape and texture characteristics. The accuracy assessment demonstrated that the overall accuracy reached 81.67%, the accuracy of Torreya classification reached 74.32% and KAPPA coefficient was 0.75, which was 6%, 15.65% and 10.39% higher than that using supervised classification method respectively. The results showed that the accuracy of classification results using IKONOS image and the object-oriented method could meet the requirements of inventory and habitat analysis of Chinese torreya in the study area.(2) Analysis of geology, soil characteristics and microclimate factorsQuantitative analysis and statistics of environmental features of habitats including geology, soil and microclimate elements were carried out in the study area based on GIS.88.9% of Torreya trees were distributed in the acid tuff. This rare species demanded on soil fertility, and 70% were found to present on mountain yellow earth and yellow earth; 75.2% of Torreya distributed on areas with soil organic matter content greater than 2%; 61.6% were located at regions with soil thicontrol plotness greater than 70 cm. The results showed that the soil nutrient is one of the important factors affecting the distribution of Chinese torreya. Compared with controlled areas, the microclimate characteristics in original habitat are featured by higher relative humidity, cool and rainy in summer and precipitation periodic variation in its growth season. During July and September, The number of＞35℃days was 32 days less than control areas whereas the rainy days and the rainfall was 5 days and 55.6 mm more than control areas respectively. These results demonstrated that the meteorological features in the original habitat were highly agreed with the climatic requirements of Chinese torreya.(3) Habitat structure characteristics of Chinese torreya based on digital terrain analysisThe spatial distribution map of rare Chinese torreya from IKONOS image is over-lapped with 8 topographical factors derived from Digital Elevation Models using digital terrain analysis method. The results showed that 47.76% of the rare plant records occur in areas within 50 m to valley line, and 96.16% were restricted in areas less than 150 meters away from the valley line. The spatial pattern of Chinese torreya exhibited high selectivity of topographical factors such as elevation, slope, aspect and slope position.76.15% occurred at the elevation belts between 400-600m,97.52% grew on the slopes less than 30°74.43% belonged to sunny or half-sunny slope, and 95.55% occurred on the midslope and downslope. Those areas less than 150 m to valley line with slopes less than 30°, altitudes between 400-600 m, and concave surfaces could be identified as the most suitable region for this rare plant. The main cause of topographic differentiation may be highly correlated with the high selectivity of environmental factors during its seedling growth stage.(4) Habitat factor analysis and ecological suitability evaluationThe special habitat factors for Chinese torreya were analyzed with Principal Component Analysis (PCA) and a series of environmental factors including distance to valley line, elevation, slope, topographical wetness index, solar radiation index, soil texture and soil organic matter. The results of PCA analysis indicated that the main environmental factors of affecting habitat of Chinese torreya were in order of importance:moisture, heat and soil nutrient. And moisture might be one of the most important ecological factors for Chinese torreya due to its unique biological and ecological characteristics. A Logistic regression was used to calculate a model for the relationship using topographical attributes. It is concluded that 8 explanatory variables are noted to be significant and 3 topographical factors (distance to valley line, solar radiation index and soil organic matter) may be the important factors influencing its habitat selection. The results from Logistic model evaluation showed that the acreage of the high and moderate suitable zone for Chinese torreya planting accounted for 61.7% of the total area. This result indicated that the study area showed great potential for cultivation of Chinese torreya.(5) Relationship of yield and quality of Chinese torreya with environmental factorsRegression analysis showed that the yield of Chinese torreya highly related with solar radiation, altitude, slope, soil organic matter and potassium content. Soil nutrient factors, especially organic matter content and potassium content influenced its yield significantly. Nutrient analysis of Chinese torreya from different habitats showed that unsaturated fatty acids, amino acids and protein content, potassium content and selenium of dry seeds in origin habitat were higher than that in introduction area. Whereas the contents of calcium, copper, zinc, iron, manganese, magnesium and other mineral elements were lower than that in introduction area. Those torreya trees in origin habitat were rich in nutrients compared to that in introduction area, and their comprehensive quality was significantly higher than that from introduction area.
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