Effects of thinning intensities on reproductive modules of Quercus liaotungensis in Huanglong and Qiaoshan Mountains, Northwest China

Abstract

Taking the Quercus liaotungensis middle-aged forests in Huanglong and Qiaoshan Mountains as study objects, the average size of individual trees of Q. liaotungensis, yield and rate of its reproductive modules, as well as their spatial distribution characteristics were investigated in five years after thinning at different intensities (CK, 10%, 20% and 30%), in order to demonstrate the impact of thinning intensity on reproductive modules of Q. liaotungensis. Thinning intensity had no significant effect on average height and average DBH, while it had significant positive correlation with crown area and crown volume. The yield of generative shoots, young fruits and mature fruits increased with thinning intensity, but vegetative shoots, staminate inflorescence, staminate flowers and pistillate flowers of Q. liaotungensis had little change. The yield of generative shoots, young fruits and mature fruits had raised significantly under 20% thinning, and reached the maximum under 30% thinning intensity. The rate of generative shoots and fruit setting rate increased with thinning intensity, and reached significant level under 20% or 30% thinning compared with the control. About three-quarters of the generative shoots, female and male flowers centered in the upper canopy, and the rest were in the lower part. Numbers of reproductive modules at sunny side accounted for about 65% of the total. The lower crown, shaded generative shoots, pistillate flowers and staminate inflorescence increased with the increasing thinning intensity, and the upper crown, sunny generative shoots, pistillate flowers and staminate inflorescence showed a decreasing trend with the increasing thinning intensity. Thinning at the intensity of 30% (canopy density 0.6) was the best, which could greatly improve the fruit set percentage of Q. liaotungensis and its mature rate, so as to improve the seed yield and quality, providing the guarantee for the seed collection and natural regeneration of Q. liaotungensis forests.