Study on causes and occurrence rules of seasonal drought in subtropical red soil hilly region Seasonal drought problems in the red soil hilly region of the middle subtropical zone of China Study on Lotononis bainesii Mixed Sowing Respectively with Three Kinds of Perennial Forage Grasses Relationships between initial chemical composition of forest leaf litters and their decomposition rates in degraded red soil hilly region of Southern China. GPP and NPP study of Pinus elliottii forest in red soil hilly region based on BIOME-BGC model