The ecological stoichiometry of Moso bamboo (Phyllostachys edulis) during the "explosive growth period" (EGP) remains unknown. In a previous study, we showed that the carbon (C) required by shoots during the EGP is derived from attached mature bamboos. In this study, we attempted to answer the following two questions: (1) Is the nitrogen (N) and phosphorus (P) required by shoots during the EGP also derived from attached mature bamboos? (2) Is the ecological stoichiometry of Moso bamboo during the EGP consistent with the growth rate hypothesis (GRH)? We simultaneously investigated changes in the N and P concentrations and N:P ratios of shoots (young bamboos) and attached mature bamboo over an 11-month period. During the EGP of Moso bamboo shoots (April 15-May 29), N and P concentrations in the shoots declined markedly because of the dilution of biomass and the transport to the germinated leaves and branches, and the N:P ratio remained at a low level. The significant correlations between relative height and biomass growth rates and the concentrations of N and P and N:P ratios during the EGP were consistent with the GRH. To meet the needs of "explosive growth," N was presumed to be transferred from the branches and rhizomes of attached mature bamboos to the shoots via underground rhizomes, while P likely came from mature bamboo leaves and branches. After the emergence of the branches and leaves of young bamboo: (1) the N concentration of the new leaves initially decreased and then increased, (2) P concentration exhibited a marked decrease, (3) and N:P ratio gradually increased. Our findings regarding the N:P ratio of shoots (young bamboos) during the EGP are consistent with the GRH, and we surmise that mature bamboo supplies N and P to attached young shoots via underground rhizomes.

Soil dissolved organic carbon (DOC) and nitrogen (DON) play significant roles in forest carbon, nitrogen and nutrient cycling. The objective of the present study was to estimate the effect of management practices and nitrogen (N) deposition on soil DOC and DON in Moso bamboo (Phyllostachys edulis (Carrière) J. Houz) plantations. This experiment, conducted for over 36 months, investigated the effects of four N addition levels (30, 60 and 90 kg N ha −1 year −1 , and the N-free control) and two management practices (conventional management (CM) and intensive management (IM)) on DOC and DON. The results showed that DOC and DON concentrations were the highest in summer. Both intensive management and N deposition independently decreased DOC and DON in spring (p < 0.05) but not in winter. However, when combined with IM, N deposition increased DOC and DON in spring and winter (p < 0.05). Our results demonstrated that N deposition significantly increased the loss of soil DOC and DON in Moso plantations, and this reduction was strongly affected by IM practices and varied seasonally. Therefore, management practices and seasonal variation should be considered when using ecological models to estimate the effects of N deposition on soil DOC and DON in plantation ecosystems.

Plant functional traits are crucial features that modulate plant performance via influencing growth, survivorship, and reproduction (Díaz et al., 2016;Wright et al., 2004). Plant traits largely determine community assembly and the multiple functioning of ecosystems, such as biomass production and carbon storage (Migliavacca et al., 2021; van der Plas et al., 2020). Thus, our ability to understand and predict ecosystem function largely depends on quantifying plant trait distributions and their responses to environmental drivers (Kovenock & Swann, 2018). Climatic drivers shape and shift functional traits and ecological strategies across broad biogeographical gradients (Wieczynsk et al., 2019). However, plant functional traits at fine-grained communities are usually predominantly driven by local soil nutrient levels rather than large-scale climate variables (Bruelheide et al., 2018;Simpson et al., 2016). In addition, there is growing recognition that nutrient addition has become one of the

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Extreme drought is one of the key climatic drivers of tree mortality on a global scale. However, it remains unclear whether the drought-induced tree mortality will increase under nocturnal climate warming. Here we exposed seedlings of two wide-ranging subtropical tree species, Castanopsis sclerophylla and Schima superba, with contrasting stomatal regulation strategies to prolonged drought under ambient and elevated night-time temperature by 2°C. We quantified the seedling survival time since drought treatment by measuring multiple leaf traits such as leaf gas exchange, predawn leaf water potential, and water use efficiency (WUE). The results showed that all seedlings in the ambient temperature died within 180 days and 167 days of drought for C. sclerophylla and S. superba, respectively. Night warming significantly shortened the survival time of C. sclerophylla by 31 days and S. superba by 28 days, respectively, under the drought treatment. A survival analysis further showed that seedlings under night warming suffered a 1.6 times greater mortality risk than those under ambient temperature. Further analyses revealed that night warming suppressed net leaf carbon gain in both species by increasing the nocturnal respiratory rate of S. superba across the first 120 days of drought and decreasing the photosynthetic rate of both species generally after 46 days of drought. These effects on net carbon gain were more pronounced in S. superba than C. sclerophylla. After 60 days of drought, night warming decreased the predawn leaf water potential and leaf WUE of C. sclerophylla but not S. superba. These contrasting responses are partially due to variations in stomatal control between the two species. These findings suggest that stomatal regulation can regulate the response of leaf gas exchange and plant water use to nocturnal warming during drought. This study indicates that nocturnal warming can accelerate tree mortality during drought.