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Maoli Lake is the water source for local residents and a national nature protected area. However, due to intensive agriculture development, the water quality has deteriorated over the past decades. An effective measure to improve water quality is to control the agricultural non-point source (NPS) pollution through elaborate schemes based on eco-compensation. In order to develop such eco-compensation schemes, three scenarios of agricultural activity adjustment were designed: S1 (halving fertilization every year), S2 (fallow every other year), and S3 (returning agricultural land to forest). A Soil and Water Assessment Tool (SWAT) model was adopted to simulate runoff, total nitrogen, and total phosphorus. Based on SWAT results, a multi-criteria spatial evaluation model considering the environmental, economic, and social effects of eco-compensation was created for best scenario decision. The results reveal the following: (1) the total nutrients loss of agricultural land reduces in all scenarios, but S2 has more reduction compared to S1 and S3; (2) from the comprehensive perspective of environment–economy–society effects, S2 is the best scenario for rice land and dry land; (3) the comprehensive effect of eco-compensation at the grid scale has a significant spatial difference, and therefore, we highlight the necessity and significance of controlling agricultural NPS pollution by eco-compensation on a precise spatial scale. This study can broaden the application field of the SWAT model and provide a scientific basis and experience for the evaluation and spatial design of agriculture eco-compensation.

Background: Sapindus is an important biodiesel, biomedical, and multifunctional economic forest species in Asia, however its germplasms have been persistently damaged or lost. It is imperative to conserve the diversity of Sapindus. This study aimed to reveal the potential habitat distribution patterns of Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in response to current environment and future climate change, and identify hotspots of habitat degradation/expansion to facilitate climate change-adaptive biological conservation. Methods: Using current environmental data and future climate projections (2021–2100), we simulated the present and potential future habitats of Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in east and southeast Asia using a maximum entropy (MaxEnt) model that was developed based on 2041 occurrence records. Results: The model showed that precipitation may play an important role in framing the potential habitats of Sapindus; however, S. delavayi was more sensitive to minimum temperatures (-2 °C to 3 °C) and elevation (1200-2000 m), while S. rarak was more demanding in terms of solar radiation (annual mean Uvb of 4600 to 5000 J/m2/day). Under the current environment, S. mukorossi has the widest suitable habitat distribution (250.24 × 104 km2), followed by that of S. rarak (173.49 × 104 km2), and S. delavayi (78.85 × 104 km2). Under future climate change scenarios, the habitat distribution of S. mukorossi will expand and contract, that of S. delavayi exhibited significant expansion. In contrast, future S. rarak habitat distribution exhibited significant contraction. Conclusions: There were significantly distinct ecological adaptations among Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in east and southeast Asia. The contraction areas should be subject to germplasm collection and ex situ conservation preferentially. The modelled unchanged areas should be used for potential future Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak conservation and utilization.

Sapindus mukorossi Gaertn. (S. mukorossi) is a deciduous tree of the Sapindus L. (Sapindus) in the Sapindaceae Juss. family, which is widely distributed in warm temperate to tropical regions in Asia, especially China and Southeast Asian countries. Because of the high yield of its seed oil (26.15% to 44.69%) (Liu et al., 2017;Sun et al., 2017), it is suitable for biodiesel production according to American Society for Testing and Materials (ASTM) D6751 and European Standards (EN) 14214 (Chakraborty and Baruah, 2013;Sun et al., 2019). Crude extracts from the fruit pericarps of S. mukorossi are rich in triterpenoid saponins (4.14% to 27.04%) and sesquiterpenoids (Liu et al., 2019;Liu et al., 2017), which exhibit excellent surface activity as well as antibacterial, elution, pharmacological, and physiological effects (Xu et al., 2018). Saponin serves as an efficient natural