A new threshold selection method for species distribution models with presence-only data: Extracting the mutation point of the P/E curve by threshold regression.

Selecting thresholds to convert continuous predictions of species distribution models proves critical for many real-world applications and model assessments. Prevalent threshold selection methods for presence-only data require unproven pseudo-absence data or subjective researchers' decisions. This study proposes a new method, Boyce-Threshold Quantile Regression (BTQR), to determine thresholds objectively without pseudo-absence data. We summarize that the mutation point is a typical shape feature of the predicted-to-expected (P/E) curve after reviewing relevant articles. Analysis based on source-sink theory suggests that this mutation point may represent a transition in habitat types and serve as an appropriate threshold. Threshold regression is introduced to accurately locate the mutation point. To validate the effectiveness of BTQR, we used four virtual species of varying prevalence and a real species with reliable distribution data. Six different species distribution models were employed to generate continuous suitability predictions. BTQR and nine other traditional methods transformed these continuous outputs into binary results. Comparative experiments show that BTQR has advantages in terms of accuracy, applicability, and consistency over the existing methods.

Eco-environmental evolution, control, and adjustment for Aibi Lake catchment.

Aibi Lake in north Xinjiang is a typical lake of the arid area, but with a peculiar wetland-arid area ecosystem. Due to the climate becoming drier and the disturbance of human activities, the eco-environment of Aibi Lake catchment has degraded. It was found in our study that there were spatial-temporal changes of vegetation cover, plant species, and soil physical and chemical properties in the catchment. In the upper section of alluvial-fluvial plains, the desertified steppe of Stipa and Artemisia spp. is developed with vegetation cover of some 50%. Haloxylon ammodendron desert occupies the lower section with vegetation cover of some 60%. In these regions with an intensive human disturbance, vegetation has degraded into herb vegetation of annual plant complexes. On the margins of the alluvial-fluvial fans, the lakeshore, and the surrounding regions where the river mouths join the lake, different azonal vegetation-Phragmites communis marsh, Phragmites communis meadow, and Tamarix shrubs-have developed with a vegetation cover of some 80%. On heavier, salinized land, succulent halophyte desert vegetation dominated by Halocnemum strobilaceum has formed with a fractional canopy cover of 10-15%. Haloxylon persicum, Aristida pennata, and other species with a vegetation cover of 30-50% grow in the sand desert zone on the periphery in the lake. In contrast with the 1950s, the vegetation cover around the lakebed and at the river deltas has slightly increased; however, the vegetation cover around the periphery of the lake has decreased and the plant species have still degraded. The surface soils on the windward area and the dried lakebed that have lost vegetation protection have become coarser, whereas the land on the leeward side of the lake has accumulated fine particles. In contrast with the 1980s, soil organic matter has declined markedly. The analyses of climatic data show that the number of days of drifting dust in Jinghe County and Bole City increased in the last 20 years. In the investigation, we found that intensively developed land, the bare lakebed, and abandoned cultivated land provided a great deal of material for drifting dust. In conclusion, we consider the eco-environmental degradation resulting from the inappropriate human activities and put forward recommendations for land-use adjustment and dust control.

[Establishment and application of eco-environmental risk assessment system of highway: a case study from G315 Yitunbulake-Qiemo section of Xinjiang].

The eco-environmental risk assessment system of highway, based on the Analytic Hierarchy Process and specialists' ideas, is set up. To give prominence to the spatial attribute of each assessment index the weight values were determined by the magnitude of special range that was influenced by assessment index. By translating relative maps using GIS the influenced range of environmental factors, the area occupied, was gotten. The lengths impacted by disaster factors were measured by the route reconnaissance and design. The results of applying the assessment system to evaluate the eco-environmental risk assessment of G315 Yitunbulake-Qiemo section of Xinjiang show that the eco-environmental risk indices of the road region, eco-environmental risk assessment (ERA) were between 1.55-3.23. According to the heterogeneity of the ecoenvironmental vulnerability indices (sigma x(i)w(i)) and disasters indices (sigma y(i)w(j)) included in ERA, 4 risk ranks to assess the eight units of landscape ecology in the Yitunbulake-Qiemo section of G315 highway were carried out, which factually reflects the characteristics of the eco-environmental risk for the highway.