[Turbulence micro-meteorological characteristics over the plantation canopy.]

Based on the eddy-covariance system monitoring during leaf germination (15^th March to 15^th April 2015) and leaf forming (15^th July to 15^th August), the turbulence characteristics, turbulence intensity, normalized standard variance of turbulent wind speed and bulk transfer coefficient over forest plantation canopy in the Xiaolangdi Ecosystem Location Research Station were analyzed, aiming to deepen the understanding of the micro-meteorological characteristics of the forest ecosystem and provide scientific basis for the further studies of energy balance and material exchange. Results showed that turbulence spectrum of the plantation had a peak frequency in the low frequency zone and the inertial subarea had an obvious dissipation tendency, which was basically in accor-dance with the law of -5/3. Turbulence intensity was significantly affected by canopy structure. When the turbulence was strong, the wind speed was less than 3 m·s^-1 in spring and less than 2 m·s^-1 in summer. Normalized standard variance of turbulent wind speed in horizontal direction was better than that in vertical direction, which conformed to the similarity law of 1/3 power. The ratio of normalized standard deviation and the friction velocity in u, v, w components of canopy wind speed was 2.55, 2.06 and 1.30 in spring, 2.61, 2.45 and 1.21 in summer, respectively. The bulk transfer coefficient decreased with the increases of stability, with a difference of 1-2 orders of magnitude or more between unstable and stable conditions. Canopy structure had direct influence on the turbulence of the wind speed in each direction, and thereby changed the diffusion direction of the canopy material and energy.