Foliar nutrient content and resorption efficiency of Pinus massoniana in the subtropical red soil erosion region Variation of Chloroplast Pigments of Various Age Leaves along Elevation Gradients of Dominant Species in Castanopsis carlessi Forests in Lingshishan National Forest Park Effect of Short-Day Photoperiod on Adzuki Bean (Phase-out angularis) Seedlings at Different Leaf Ages