Leaf C, N, P Concentrations And Their Stoichiometry Of Peatland Plants In The Great Hing'an Mountains

Boreal peatlands are important terrestrial carbon(C)-fixed ecosystems in China,which are sensitive to environmental changes.Climate warming and increased nitrogen(N)deposition alter the community structure and carbon sequestration potential of peatland plants by affecting their N and phosphorus(P)uptake.Leaf C,N,P concentrations and their stoichiometry can elucidate the uptake abilities and limitation of nutrients in plants and improve the assessment of the changes of C-fixing capacity of peatland ecosystems.This study analyzed differences and its response to environmental factors for leaf C,N,and P concentrations of three graminoids(Eriophorum vaginatum,Carex globularis,Deyeuxia angustifolia),five deciduous shrubs(Betula fruticosa,Salix myrtilloides,Salix rosmarinifolia,Vaccinium vitis-idaea,Vaccinium uliginosum)and three evergreen shrubs(Ledum palustre,Chamaedaphne calyculata,Rhododendron capitatum)across eighteen peatlands in the Great Hing'an Mountains,northeastern China.The results showed:(1)Leaf C,N,P concentrations and C:N,C:P and N:P values of 11 dominant plants in peatland of the Great Hing'an Mountains ranged from 32.7% to 50.5%,0.7% to 2.8%,0.05% to 0.41%,15.1 to 61.5,97.6 to 805.7,and 2.7 to 28.4,respectively.Leaf C,N,and P concentrations of shrubs were higher while leaf C:N,C:P,and N:P values were lower than those of graminoids,indicating that shrubs had higher C fixation and N and P uptake but lower N and P use efficiency than graminoids.Leaf N:P values were less than 10 for Deyeuxia angustifolia,Salix myrtilloides,Salix rosmarinifolia,Rhododendron capitatum.Leaf N:P values ranged between 10 and 16 for Eriophorum vaginatum,Betula fruticosa,Ledum palustre,Chamaedaphne calyculata,Vaccinium vitisidaea,Vaccinium uliginosum and Carex globularis.These results showed that investigated plants were mostly co-limited by N and P and a few were N-limited.(2)The ranking for the spatial coefficient of variance(CV values)of leaf C,N,P parameters was N:P(27.8± 9.6%)> P(25.1± 7.5%)> C:P(24.7± 8.6%)> N(13.3± 6.4%)> C:N(11.8± 6.1%)> C(5.6± 1.8%).The spatial coefficient of variance(CV values)of leaf C,N,P concentrations and C:N,C:P,N:P values for graminoids were higher than shrubs which showed C,N,and P parameters of graminoids were more sensitive to environmental changes than those of shrubs.The inter-species CV values of leaf N for graminoids were higher than deciduous and evergreen shrubs,the inter-species CV values of leaf P for deciduous shrubs were higher than graminoids and evergreen shrubs,respectively,showing that the physiological differentiation of N and P use strategies among graminoids and deciduous shrubs were larger than those of evergreen shrubs.(3)Overall,there was no significant correlation between C,N,P contents and C:N,C:P,N:P values of plant leaves and annual average temperature,annual precipitation and elevation,which may be related to the relatively small range of environmental factors in the peatland distribution area in this study.Among three growth forms,leaf N concentration and C:N values of deciduous shrubs were correlated with annual average temperature and altitude,indicating that N and P uptake of deciduous shrubs were more sensitive to climate change than those of graminoids and deciduous shrubs.Leaf N and P concentration of graminoids decreased with the increase of total N concentration in soil,while that of deciduous shrubs and evergreen shrubs decreased.This indicated that the increase of soil N and P promoted the competition of three growth forms plants for soil nutrients.Except for evergreen shrubs,Leaf N and P concentration of graminoids and deciduous shrubs did not change significantly with the total P concentration in soil,suggesting that the effect of soil P on plant N and P absorption was weak.