[Distribution of fine root biomass of main planting tree species in Loess Plateau, China].

The distribution of fine roots of Pinus tabuliformis, Populus tomentosa, Prunus armeniaca, Robinia pseudoacacia, Hippophae rhamnoides, and Caragana korshinskii was investigated by using soil core method and the fine root was defined as root with diameter less than 2 mm. The soil moisture and soil properties were measured. The results showed that in the horizontal direction, the distribution of fine root biomass of P. tabuliformis presented a conic curve, and the fine root biomass of the other species expressed logarithm correlation. Radial roots developed, the fine root biomass were concentrated within the scope of the 2-3 times crown, indicating that trees extended their roots laterally to seek water farther from the tree. In the vertical direction, the fine root biomass decreased with the increasing soil depth. Fine root biomass had significant negative correlation with soil water content and bulk density, while significant positive correlation with organic matter and total N contents.

[Canopy interception of Pinus tabulaeformis plantation on Longzhong Loess Plateau, Northwest China: characteristics and simulation].

Taking the Pinus tabulaeformis plantation in the Anjiagou catchment on Longzhong Loess Plateau as test object, an observation was made on the characteristics of throughfall, stemflow, interception, and canopy structure of P. tabulaeformi during its growth season (from May to September) in 2011. Based on the observed data, the revised Gash analytical model was adopted to simulate the canopy interception, aimed to understand the ecological hydrological processes of Pinus tabulaeformis plantation and related mechanisms. In the observation period, a total of 19 precipitation events were observed, with a total precipitation of 215.80 mm. The throughfall, stemflow, and canopy interception were 165.24 mm, 2.29 mm, and 48.27 mm, occupying 76.7%, 1.1%, and 22.4% of the total precipitation, respectively. The simulated canopy interception was 41.24 mm, being 7.13 mm lower than the observed value and with a relative error of 14.7%. There were 33.8% and 60.0% of interception were evaporated from the canopy during and after precipitation, respectively. The revised Gash analytical model was highly sensitive to the canopy storage capacity, forest coverage, rainfall intensity, and evaporation, but less sensitive to the stemflow rate and stem water holding capacity.

[Characteristics of rainfall interception by Caragana korshinskii and Hippophae rhamnoides in Loess Plateau of Northwest China].

From May to October 2011, an investigation was conducted on the effects of rainfall and its intensity on the canopy interception, throughfall, and stemflow of Caragana korshinskii and Hippophae rhamnoides, the main shrub species commonly planted to stabilize soil and water in the Anjiagou catchment of Loess Plateau. A total of 47 rainfall events were observed, most of which were featured with low intensity, and the total amount and average intensity of the rainfalls were 208.9 mm and 2.82 mm x h(-1), respectively. As a whole, the rainfall events of 2-10 mm and 0.1-2 mm x h(-1) had the highest frequency. The canopy interception, throughfall, and stemflow of C. korshinski were 58.5 mm (28%), 124.7 mm (59.7%), and 25.7 mm (12.3%), while those of H. rhamnoides were 17.6 mm (8.4%), 153. 1 mm (73.3%), and 38.2 mm (18.3%), respectively. Regression analysis showed that the canopy interception, throughfall, and stemflow of the two shrub species all had significant positive correlations with the rainfall amount, and had exponent or power correlations with the rainfall amount and the maximum rainfall intensity in 10 minutes.