Xiaoyu Liu

Lianas are woody vines that rely on host trees for support to access the forest canopy. Lianas typically occur in tropical and subtropical forests and coexist with trees in subtropical secondary forests, where their interactions strongly influence forests communities and ecosystem functioning. We compared stem and leaf traits of lianas and trees to examine the effects of growth form and leaf habit. We measured 20 functional traits (9 stem anatomical/hydraulic and 11 leaf morphological/nutrient) from 10 liana and 14 tree species coexisting in a subtropical forest of south China. Lianas exhibited 3.5‐fold higher sapwood specific conductivity ( K _s ) than trees, as well as higher predawn leaf water potential (Ψ _predawn ) and hydraulically weighted vessel diameter ( D _h ). Additionally, maximum vessel diameter ( D _max ) of lianas approximately three times higher than that of trees, and theoretical hydraulic conductivity ( K _p ) was ~20 times higher than trees. Functional trait analysis indicated that lianas grouped separately from trees along a leaf and stem economics spectrum: lianas were grouped together at the fast end of the plant economics spectrum, with high hydraulic diameter ( D _h ) and high nitrogen (N) and phosphorus (P) concentration, exhibiting an acquisition‐focused water and nutrient strategy, permitting rapid growth and tissue turnover. Trees were grouped at the low end of the plant economics spectrum, with a high C:N ratio, high vessel thickness/diameter (VT/VD) and high wood density (WD), exhibiting a conservative resource acquisition strategy. Moreover, lianas exhibited significantly higher modularity in their trait networks compared to trees (0.490 vs 0.345; p = 0.043), reflecting stronger local integration of function, with tightly coordinated traits that may enhance system adaptability by limiting the spread of local drought‐induced stress. These findings improve our understanding of the mechanisms shaping ecological strategies across woody plants with different growth forms and leaf habits, and addresses the limited trait‐based knowledge of subtropical forests relative to tropics. This study provides novel insight into how growth form and leaf habit shape resource acquisition and niche partitioning in co‐occurring woody species in a subtropical and secondary forests. Read the free Plain Language Summary for this article on the Journal blog.

Background: Si can be important for the growth, functioning, and stoichiometric regulation of nutrients for high-Si-accumulating bamboo. However, other trees do not actively take up dissolved silicic acid [Si(OH)₄] from the soil, likely because they have fewer or no specific Si transporters in their roots. It is unclear what causes differential growth and C:N:P stoichiometry between bamboo and other trees across levels of Si supply. Results: Si supply increased the relative growth rate of height and basal diameter of bamboo saplings, likely by increasing its net photosynthetic rate and ratios of N:P. Moreover, a high concentration of Si supply decreased the ratio of C:Si in bamboo leaves due to a partial substitution of C with Si in organic compounds. We also found that there was a positive correlation between leaf Si concentration and its transpiration rate in tree saplings. Conclusions: We demonstrated that Si supply can decrease the ratio of C:Si in bamboo leaves and increase the ratio of N:P without altering nutrient status or the N:P ratio of tree saplings. Our findings provide experimental data to assess the different responses between bamboo and other trees in terms of growth, photosynthesis, and C:N:P stoichiometry. These results have implications for assessing the growth and competition between high-Si-accumulating bamboo and other plants when Si availability is altered in ecosystems during bamboo expansion.

Si availability may be altered by bamboo expansion when other trees are replaced by bamboo due to the influence of plant communities on the quantity of phytoliths and Si accumulation. It has been shown that Si availability can modify nutrient-use efficiency (e.g., N and P) of some Si-accumulating plants. However, it is unclear how Si availability might alter N uptake and assimilation between Si-accumulating plants such as bamboo compared to other species, particularly for different chemical forms such as ammonium (NH₄⁺) and nitrate (NO₃⁻). To explore the influences of Si availability on uptake and assimilation rates for different forms of inorganic N between bamboo and other trees, we selected one-year-old seedlings of bamboo (Phyllostachys pubescens) and three other native subtropical species, namely Phoebe bournei, Schima superba, and Cunninghamia lanceolata. We applied three levels of Si and ¹⁵N tracers in a pot experiment and then measured the concentrations of Si (total Si, soluble Si, and exchangeable Si), C, N (total N, NH₄⁺-N, and NO₃⁻-N), and N uptake and assimilation rates for both roots and leaves. We found that there were higher inorganic N root uptake and assimilation rates for bamboo compared to other species, likely due to higher biomass accumulation and quicker turnover of fine roots. Moreover, Si supply did not change the uptake preference for N forms or overall uptake and assimilation rates in most species; however, a high concentration of the Si supply slightly increased NO₃⁻-N uptake and assimilation rates in fine roots and leaves of P. bournei, particularly immediately following the addition of Si. These results have implications for predicting the coexistence and competition between bamboo and other trees through the uptake and assimilation of different forms of inorganic N (i.e., high Si-accumulating plants compared to other plants), particularly when Si availability is altered in ecosystems.