Seasonal variations of leaf nutrient element concentrations and their stoichiometric characteristics in Fraxinus mandshurica plantations

ObjectiveExploring seasonal dynamics of C, N, P concentrations and their ecological stoichiometric characteristics in Fraxinus mandshurica, Larix olgensis, Picea koraiensis, Pinus koraiensis leaves, this paper aims to provide theoretical basis to the optimization management of Fraxinus mandshurica plantations.

MethodTaking 29 years of pure Fraxinus mandshurica plantation, Fraxinus mandshurica×Larix olgensis mixed plantation, Fraxinus mandshurica× Picea koraiensis mixed plantation and Fraxinus mandshurica× Pinus koraiensis mixed plantation, which were planted on the natural forest narrow strip clear cutting land in the Forest Cultivation Experiment Station of Northeast Forestry University as materials, using the method of combining field investigation and experimental analysis, the seasonal dynamics of leaf C, N, P concentrations and their ecological stoichiometric characteristics were studied.

Result(1) Total trend of C, N and P concentrations in Fraxinus mandshurica leaves of Fraxinus mandshurica plantations was gradually reduced from 556.71, 32.61 and 3.62g/kg to 446.15, 18.74 and 1.26g/kg, respectively, and that of C/N, D/P and N/P in Fraxinus mandshurica leaves of Fraxinus mandshurica plantations was gradually increased from 17.06, 150.60 and 9.10 to 23.81, 350.56 and 16.98, respectively. (2) C concentration in the leaves of mixed Larix olgensis, Picea koraiensis and Pinus koraiensis was fluctuations, so did the N concentration and P concentration in the leaves of Picea koraiensis and Pinus koraiensis. N and P concentrations in the leaves of Larix olgensis reduced gradually. While C/N and C/P in the leaves of Larix olgensis rose steadily, C/N and C/P in the leaves of Picea koraiensis continuous declined, C/N and C/P in the leaves of Pinus koraiensis fluctuated. While N/P in the leaves of Larix olgensis and Pinus koraiensis declined after rising first, that of Picea koraiensis declined before it was smooth. (3) N and P concentrations in the leaves of Fraxinus mandshurica and Larix olgensis were significantly higher than those of Picea koraiensis and Pinus koraiensis, C/N and C/P of which were significantly lower than those of Picea koraiensis and Pinus koraiensis.

ConclusionCultivating mixed Fraxinus mandshurica × Larix olgensis plantation and pure Fraxinus mandshurica plantation should be better than cultivating mixed Fraxinus mandshurica× Picea koraiensis plantation and mixed Fraxinus mandshurica × Pinus koraiensis plantation. Enough nitrogen fertilizer should be ensured in the beginning of growth season. Suitable nitrogen and phosphorus fertilizer should be used in the middle growing season.