Aims Atmospheric nitrogen(N)deposition influences tree hydraulic architecture and thus the growth and survival;but the responses of leaf hydraulic traits remain uncertain,and may vary with species or plant functional ...Aims Atmospheric nitrogen(N)deposition influences tree hydraulic architecture and thus the growth and survival;but the responses of leaf hydraulic traits remain uncertain,and may vary with species or plant functional types.Methods We used the 16-year N addition experiment(10 g N m−2 year−1)on Fraxinus mandshurica(ash,broadleaf angiosperm)and Larix gmelinii(larch,conifer gymnosperm)plantations in northeastern China and examined the effect of N addition on their leaf hydraulics.We measured the leaf pressure–volume traits by the bench drying method and quantified the maximum leaf hydraulic conductance(K_(leaf_max))and resistance to embolism(P50leaf)by the timed rehydration method.Important Findings Larch had higher K_(leaf_max)and stronger drought tolerance(i.e.,lower relative water content at turgor loss point(RWC_(tlp))and modulus of elasticity(ε),and more negative P50leaf)than ash.N addition increased the leaf osmotic potential at turgor loss(πtlp)and full turgor(π0),and leaf capacitance(Cleaf_mass)for ash but not for larch,indicating that ash is more sensitive to N addition.N addition consistently increased K_(leaf_max)and P50leaf values for both species.πtlp andπ0 were positively while Cleaf_mass was negatively correlated with leaf density(LD)for ash.K_(leaf_max)was positively but P50leaf was negatively related with LD for larch.There were negative relationships between K_(leaf_max)and P50leaf for both species.Overall,our findings suggest that long-term N addition decreases the leaf drought tolerance for these two important tree species,which improve the understanding of the tree hydraulic performance under N deposition.展开更多
基金This work was supported by the National Natural Science Foundation of China(31901278)the National Science and Technology Support Program of China(2011BAD37B01)the Program for Changjiang Scholars and Innovative Research Team in Universities(IRT_15R09).
文摘Aims Atmospheric nitrogen(N)deposition influences tree hydraulic architecture and thus the growth and survival;but the responses of leaf hydraulic traits remain uncertain,and may vary with species or plant functional types.Methods We used the 16-year N addition experiment(10 g N m−2 year−1)on Fraxinus mandshurica(ash,broadleaf angiosperm)and Larix gmelinii(larch,conifer gymnosperm)plantations in northeastern China and examined the effect of N addition on their leaf hydraulics.We measured the leaf pressure–volume traits by the bench drying method and quantified the maximum leaf hydraulic conductance(K_(leaf_max))and resistance to embolism(P50leaf)by the timed rehydration method.Important Findings Larch had higher K_(leaf_max)and stronger drought tolerance(i.e.,lower relative water content at turgor loss point(RWC_(tlp))and modulus of elasticity(ε),and more negative P50leaf)than ash.N addition increased the leaf osmotic potential at turgor loss(πtlp)and full turgor(π0),and leaf capacitance(Cleaf_mass)for ash but not for larch,indicating that ash is more sensitive to N addition.N addition consistently increased K_(leaf_max)and P50leaf values for both species.πtlp andπ0 were positively while Cleaf_mass was negatively correlated with leaf density(LD)for ash.K_(leaf_max)was positively but P50leaf was negatively related with LD for larch.There were negative relationships between K_(leaf_max)and P50leaf for both species.Overall,our findings suggest that long-term N addition decreases the leaf drought tolerance for these two important tree species,which improve the understanding of the tree hydraulic performance under N deposition.
