Estimate of productivity in ecosystem of the broad-leaved Korean pine mixed forest in Changbai Mountain

摘要

We measured soil, stem and branch respiration of trees and shrubs, foliage photosynthesis and respiration in ecosystem of the needle and broad-leaved Korean pine forest in Changbai Mountain by LI-6400 CO_2 analysis system. Measurement of forest microclimate was conducted simultaneously and a model was found for the relationship of soil, stem, leaf and climate factors. CO_2 flux of different components in ecosystem of the broad-leaved Korean pine forest was estimated based on vegetation characteristics. The net ecosystem exchange was measured by eddy covariance technique. And we studied the effect of temperature and photosynthetic active radiation on ecosystem CO_2 flux. Through analysis we found that the net ecosystem exchange was affected mainly by soil respiration and leaf photosynthesis. Annual net ecosystem exchange ranged from a minimum of about -4.671 (μmol·m~(-2)·s~(-1) to a maximum of 13.80 μmol·m~(-2)·s~(-1), mean net ecosystem exchange of CO_2 flux was -2.0 μmol·m~(-2)·s~(-1) and 3.9 μmol·m~(-2)·s~(-1) in winter and summer respectively (mean value during 24 h). Primary productivity of tree, shrub and herbage contributed about 89.7%, 3.5% and 6.8% to the gross primary productivity of the broad-leaved Korean pine forest respectively. Soil respiration contributed about 69.7% CO_2 to the broad-leaved Korean pine forest ecosystem, comprising about 15.2% from tree leaves and 15.1% from branches. The net ecosystem exchange in growing season and non-growing season contributed 56.8% and 43.2% to the annual CO_2 efflux respectively. The ratio of autotrophic respiration to gross primary productivity (R_a:GPP) was 0.52 (NPP:GPP=0.48). Annual carbon accumulation underground accounted for 52% of the gross primary productivity, and soil respiration contributed 60% to gross primary productivity. The NPP of the needle and broad-leaved Korean pine forest was 769.3 gC·m~(-2)·a~(-1). The net ecosystem exchange of this forest ecosystem (NEE) was 229.51 gC·m~(-2)·a~(-1). The NEE of this forest ecosystem acquired by eddy covariance technique was lower than chamber estimates by 19.8%.