Multivariate statistics are commonly used to identify the factors that control the dynamics of runoff or sediment yields during hydrological processes. However, one issue with the use of conventional statistical methods to address relationships between variables and runoff or sediment yield is multicollinearity. The main objectives of this study were to apply a method for effectively identifying runoff and sediment control factors during hydrological processes and apply that method to a case study. The method combines the clustering approach and partial least squares regression (PLSR) models. The case study was conducted in a mountainous watershed in the Three Gorges Area. A total of 29 flood events in three hydrological years in areas with different land uses were obtained. In total, fourteen related variables were separated from hydrographs using the classical hydrograph separation method. Twenty-nine rainfall events were classified into two rainfall regimes (heavy Rainfall Regime I and moderate Rainfall Regime II) based on rainfall characteristics and K-means clustering. Four separate PLSR models were constructed to identify the main variables that control runoff and sediment yield for the two rainfall regimes. For Rainfall Regime I, the dominant first-order factors affecting the changes in sediment yield in our study were all of the four rainfall-related variables, flood peak discharge, maximum flood suspended sediment concentration, runoff, and the percentages of forest and farmland. For Rainfall Regime II, antecedent condition-related variables have more effects on both runoff and sediment yield than in Rainfall Regime I. The results suggest that the different control factors of the two rainfall regimes are determined by the rainfall characteristics and thus different runoff mechanisms.

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most important diseases of oilseed rape in the world. Because of the absence of resistant varieties and the disadvantages of chemical control, application of antifungal microbes has become an eco-friendly and effective measure to control this disease. In this study, Bacillus subtilis strain RSS-1, isolated from soil samples, was identified based on morphological, physiological and biochemical tests, and DNA gyrase subunit A (gyrA), gyrB, DNA-directed RNA polymerase subunit beta (rpoB) and rpoC gene sequence analysis. It significantly inhibited mycelial growth and sclerotial production of S. sclerotiorum in vitro. In greenhouse experiments, all three tested concentrations (10⁶, 10⁷, 10⁸ cfu mL⁻¹) of cell fermentation broth and culture filtrate significantly reduced the severity of sclerotinia stem rot on oilseed rape (P < 0.05). RSS-1 was more effective at reducing disease severity when applied 24 h before inoculation with S. sclerotiorum than at 24 h post inoculation, suggesting that RSS-1 should be applied as a prophylactic rather than a curative biological agent. Colonization tests indicated that the population density of RSS-1 on rapeseed leaves significantly decreased (P < 0.05) over 6 days. However, RSS-1 could stably colonize in rhizospheric soil of rapeseed over 30 days. Challenge inoculation tests showed that RSS-1 significantly inhibited the activities of polygalacturonase and cellulase and accumulation of oxalic acid during the S. sclerotiorum infection. These results suggest that RSS-1 was a potential biological agent for controlling sclerotinia stem rot caused by S. sclerotiorum on oilseed rape.