Effects of drought stress on the growth, photosynthetic characteristics, and active oxygen metabolism of poplar seedlings. Growth and Microbial Community Characteristics in the Rhizosphere of Poplar in Respond to Pentachlorophenol Stress Responses of Fagus engleriana Seedlings to Light and Nutrient Availability Regression Models of Above-Ground Biomass of Fargesia nitida in Dengsheng Area in Wolong Nature Reserve