Using physiological and morphological methods for comparison: is mixed Phyllostachys edulis and Carya illinoinensis a reasonable mixed forest model?

AbstractThe purpose of this study was to investigate whether thePhyllostachys edulis-Carya illinoinensisco-plantation is a feasible forest model. Two treatments and one control were evaluated. The control was a low-densityC. illinoinensisforest (CK), and the treatments were a high-densityC. illinoinensis forest(DF), and aC. illinoinensis-P. edulisco-plantation forest (MF). Gas exchange and chlorophyll fluorescence parameters, leaf physiology, macromorphology, and anatomical structure ofC. illinoinensiswere measured and principal component analysis (PCA) was used to evaluate treatment effects. The highest net photosynthetic rate (Pn), which was 13.72 .µmol CO2·m-2·s-1, was recorded forC. illinoinensisunder the CK treatment, while the corresponding values for MF and DF treatments were 8.98 and 5.25 µmol CO2·m-2·s-1, respectively. The JIP test revealed that plastoquinone libraries were inhibited under both MF and DF, particularly in the latter. Compared with CK, antioxidant substances in MF and DF leaves increased to a certain extent, again, particularly in the latter. Leaf macromorphology and anatomical structures under the different treatments also changed to acclimated to different environments. The leaf area of MF became lower, and the vascular tissue of DF petiole became larger. Finally, based on the main data, the order of the PCA scores was CK > MF > DF. The results indicated that both co-plantation and high-density planting caused both interspecific and intraspecific competition. Photosynthesis was inhibited inC. illinoinensisto varying degrees under both cultivation models. Nonetheless, the stress levels inC. illinoinensiswere significantly lower under the co-plantation forest than under high-density planting. These findings indicate thatC. illinoinensisgrowth was not severely inhibited by co-plantation withP. edulis, as it still developed well. Hence, co-plantation ofP. edulisandC. illinoinensisis a promising mixed-forest model.