Understanding the influence of landscape pattern changes on water yield (WYLD) and nutrient yield is a key topic for water resource management and nonpoint source (NPS) pollution reduction. The annual WYLD and NPS pollution were estimated in 2004 and 2015 with the calibrated and validated Soil and Water Assessment Tool (SWAT) in the Hun-Taizi River watershed. The impact of land use and landscape pattern changes on the annual WYLD and NPS loading changes were analyzed with a boosted regression tree (BRT) and redundancy analysis (RDA). The results showed that WYLD had a positive correlation with dry farmland and built-up area; however, a negative correlation with paddy field and water area, with the relative contribution of 42.03%, 23.79%, 17.06%, and 13.55%, respectively. The change in nutrient yield was positively correlated with changes in dry farmland, built-up area, and water area but negatively with forestland, according to the BRT model. Landscape patterns had an important influence on WYLD and NPS pollution. A large unfragmented forestland may improve water quality, while a large concentrated dry farmland results in water quality deterioration due to NPS pollution. Water quality is more likely degraded when land uses are complex and scattered with many small patches in a forestland dominated watershed.

Forest fires are important natural disturbances that influence accurate estimations of forest carbon budgets, largely owing to the uncertainty of carbon emissions from forest fires. Fuel burning efficiency is an important factor affecting accurate estimations of carbon emissions and is difficult to quantify. Here, we quantified burning efficiencies of fuel strata by fire severity and forest types and investigated influencing factors. Burning efficiencies of fuel strata increased with increasing fire severity. The tree stratum had low values of burning efficiency of 0.76, 0.83, 6.84% under low-, moderate-, high-severity fires respectively. The burning efficiency of the herb stratum was the highest, over 95%, followed by the litter stratum between 49 and 85%. Although the tree stratum accounted for the largest carbon storage of aboveground fuels, most carbon consumed during fires came from the shrub and herb strata. Among forest types, the burning efficiency of aboveground fuels in Pinus pumila–Larix gmelinii forest was much higher than the other two studied. Fire Weather Index (FWI) and temperature exerted a positive effect on the burning efficiency of understorey fuels. Precipitation mainly had a negative influence on the burning efficiency of shrub and duff.