Inter-specific Variations And Relationships In Leaf Traits Of Major Temperate Species In Northeastern China

Leaf traits are key factors contributing to carbon dioxide and water vapor fluxes between vegetation and the atmosphere, and linking the soil-plant-atmosphere biogeochemical cycles. It is very important to study leaf traits for deeply understanding carbon cycling process and constructing mechanistic process model. The temperate forest in northeastern China is sensitive to climate change, and plays a crucial role in national and regional carbon balance. However, the contribution of the different species to forest carbon budgets and its responses to environmental change are poorly understood. In this study, we measured the leaf trait parameters for 52 major species (including 17 tree species:Carpinus cordata, Populus ussuriensis, Malus pallasiana, Populus davidiana, Maackia amurensis, Tilia mandshurica, Ulmus propinqua, Betula costata, Pinus sylvestris var. mongolica, Fraxinus mandshurica, Betula platyphylla, Tilia amurensis, Pinus koraiensis, Juglans mandshurica, Ulmus laciniata, Phellodendron amurense, Rhamnus davuricus; 11 shrubs:Philadelphus schrenkii, Acanthopanax Senticosus, Rosa davurica, Spiraea pubescens, Corylus heterophylla, Syringa amurensis, Spiraea salicifolia, Sorbaria kirilowii, Kalonymus macroptera, Lonicera maakii, Viburmum sargentii and 24 herbs:Adoxa moschatellina, Adonis amurensls, Gagea hiensis, Poa anuua, Ranunculus ussuriensis, Pulsatilla chinensis, Chelidonium majus, Hylomecon vernalis, Taraxacum albo-marginatum kitag, Anemone amurensis, Corydlis remora, Polygonatum humile, Parasenecio hastatus, Vicia cracca, Impatiens noli-tangere, Angelica anomala, Urtica angustifolia, Cardamine leucantha, Lilium brownie, Thalictrum aquilegifolium var. sibiricum, Filipendula palmate, Veronicastrum sibiricum, Viola acuminate, Smilacina dahurica). The measured parameters included:leaf functional traits (light-saturated photosynthetic rate (Pmax_a),maximum rate of Rubisco carboxylation (Vcmax_a), maximum electron transport rate (Jmax_a), triose phosphate use rate (TPU_a) and dark respiration rate (Rd_a) per unit leaf area; light-saturated photosynthetic (Pmax_m), maximum rate of Rubisco carboxylation (Vcmax_m), maximum electron transport rate (Jmax_m), triose phosphate use rate /(TPU_m) and dark respiration rate (Rd_m) per unit dry mass; photosynthetic nitrogen-use efficiency (PNUE)) and leaf structural traits (leaf total nitrogen content (N_a),leaf total carbon content (C_a) and chlorophyll content(Chl_a) per unit leaf area; leaf total nitrogen content (N m) and leaf total carbon content (C_m) per unit leaf dry mass; chlorophyll content per unit leaf fresh mass (Chl_m); leaf mass per area (LMA)). The objectives of this study were to quantify the variability in leaf traits among species and functional groups, and explore the relationships between leaf trait parameters.(1) Leaf functional (Pmax_a, Vcmax_a, Jmax_a, TPU_a, PNUE和Rd_a) and structural (N_a, N_m, C_a, C_m, Chl_a, Chl_m and LMA) traits of trees, shrubs and herbs differed significantly among species (P<0.001). The Pmax and Rd for the trees ranged from 7.79 to 20.86μmol·m-2·s-1 and 0.54 to 1.58μmol·m-2·s-1, respectively; those for the shrubs ranged from 4.4 to 14.56μmol·m-2·s-1 and 0.13 to 0.98μmol·m-2·s-1, respectively; and those for the herbs ranged from 5.27 to 22.33μmol·m-2·s-1 and 0.12 to 1.88μmol·m-2·s-1, respectively.(2)Both leaf functional traits (Pmax_a, Vcmax_a, Jmax_a, TPU_a, PNUE and Rd_a) and structural traits (N_a, N_m, C_a, C_m, Chl_a, Chl_m and LMA) differed significantly among functional groups (P<0.05). And the mean values of Pmax ranked as tree (13.12μmol·m-2·s-1)> herb (11.07μmol·m-2·s-1)> shrub (9.7μmol·m-2·s-1). The tree had highest Rd (0.94μmol·m-2·s-1), whereas the shrub had the lowest Rd (0.52μmol·m-2·s-1), and the former was 1.8 times that of the latter. The contribution of tree and herb to temperate forest carbon budgets in northeastern China was higher than that of shrub.(3) The relationships between leaf traits were:Pmax_a increased with N_a and C_a increased; Vcmax_a,Jmax_a and TPU_a were positively correlated with N_a, C_a and Chl_a, but were not correlated with PNUE; Rd_a was positively correlated with C_a, was not correlated with N_a and PNUE. Pmax_m, Fcmax_m, Jmax_m,TPU_m and Rd_m all were not correlated with N_m; Vcmax_m, Jmax_m and TPU_m were positively correlated with C_m, Chl_m and PNUE; Pmax_m was positively correlated with Chl_m and PNUE; Rd_m increased with PNUE increased. LMA was negatively correlated with Pmax_m, Vcmax_m, Jmax_m, TPU_m, Rd_m, Chl_m and C_m;were positively correlated with Pmax_a, Vcmax_a,Jmax_a, TPU_a, Rd_a, N_a, Chl_a and C_a; but was not correlated with N_m. Our results demonstrate generality of leaf trait relationships. And Pmax_a for herb was higher than tree and shrub at a given N_a. Increase in Pmax_a, Vcmax_a, Jmax_a, TPU a and Rd_a for herb were higher for a given increase in C_a and LMA than tree and shrub too. It implied that the response of herb for growth conditions change was greater than tree and shrub.