Xiuli Chu

(Reports, 5 October 2018, p. 80) report significant increases in forest productivity from monocultures to multispecies mixtures in subtropical China. However, their estimated productivity decrease due to a 10% tree species loss seems high. We propose that including species richness distribution of the study forests would provide more meaningful estimates of forest-scale responses.

Decline of species population, low natural regeneration, and heavy competition on field sites require the planting of large seedling stocks to restore Taxus chinensis and Phoebe chekiangensis in tropical China. In this study, we examined the effects of different formulations and application rates of controlled-release fertilizers (CRF) of nitrogen (N) and phosphorus (P) on nursery seedling growth and nutritional attributes. The objective was to determine optimum formulation (N:P2O5 ratio) and application rate to increase nutrient reserves of the seedlings before transplanting to the field. Four formulations (17-9-13 to 19-6-14 N-P2O5-K2O ratios) and four application rates (1.5 kg m-3 to 4.5 kg m-3) were used in a double-factors factorial design with 3 replications. The results showed that CRF formulation can affect nutritional attributes, while application rate modified seedling growth and nutritional attributes. The optimum seedling response occurred with the 17-6-16 formulation at the rate of 3.5kg m-3. These findings will guide nursery practice in the production of high-quality seedlings for optimum survival and growth in the field.

Exponential fertilization (EF) can feed seedlings with more nutrients than needed for growth and continuous lighting is expected to reduce the risk of loading at high application rate. In this study, red-seed tree (Ormosia hosiei Hemsley & E. H. Wilson) seedlings were raised by EF at a low rate of 160 mg nitrogen (N) plant-1 (conventional) (N-phosphorus [P]-potassium [K], 12-9-12) and a high rate of 600 mg N plant-1 (intensive), which was adapted from previous studies with large-pot-seedlings. Both fertilizer regimes were nested to either of two light spectra from high-pressure sodium (HPS) and light-emitting diode (LED) sources with three replicates for each combined treatment. Seedlings subjected to the conventional regime in the LED spectrum showed better growth and greater biomass accumulation with higher leaf N and P contents than other ones. In the conventional fertilizer regime, the LED spectrum also resulted in higher photosynthesis shown by more pigments and higher N synthesis than the HPS spectrum. The HPS spectrum strengthened P synthesis in the intensive regime. The antioxidative activity was stimulated by a high dose of EF, hence excessive toxicity was likely induced. We recommend using the normal rate of 160 mg N plant-1 for the culture of red-seed tree seedlings with LED lighting to promote seedling quality without causing excessive nutrient toxicity.