Thinning treatment and litterfall changes influence soil respiration in a Larix principis-rupprechtii plantation
PENG Xinhao;HAN Hairong;XU Xiaofang;CAI Mengke;BAI Yingchen;CHENG Xiaoqin;Forestry College of Beijing Forestry University;
Soil respiration( Rs),the second largest site of carbon flow in the forest ecosystem carbon budget,plays an important role in the global carbon( C) cycle and climate change. Understanding the effects of forest management practices( e.g. thinning) on Rsis crucial for the accurate estimation of forest carbon cycling. Simultaneously,aboveground litter management practices( removal,addition,and so on) can also influence Rs. However,little is known about the response of Rsto thinning and its relationship with the changes in litter production induced by thinning. We aimed to quantify the response of Rsrate to different thinning intensities and to explore the relationships between Rsand soil temperature and moisture as a result of different litter management practices. A thinning manipulation experiment was conducted in a Larix principis-rupprechtii plantation in Shanxi province, China, with the following treatments: heavy thinning, moderatethinning,low thinning and no thinning. In addition,three treatments—litterfall removal,litter addition and normal litterfall—were applied to analyze the relationship between differences in litter input and Rs. Rates of soil respiration were measured twice a month using the LI-8100 Automated Soil CO_2 Flux System from May to October 2016,while soil temperature and moisture at a depth of 5 cm were measured using temperature and moisture probes and data loggers. A significant difference was noted in Rsamong the different thinning treatments( P0.05). Clear monthly variations in Rswere noted in the growing season,and Rsreached its peak value in August. Overall,moderate thinning increased Rsrate during the growing season by 15.7% from that of the no-thinning treatment. During the growing season,the Rsrate was lower by40.16% with litterfall removal than that of normal litterfall; however,Rsrate was higher by 16.06% with litter addition than that of normal litterfall. Moderate thinning increased accumulative Rsby 55. 06 g C/m2 during the growing season. Under litter removal conditions,accumulative Rsdecreased by 153.48 g C/m~2 during the growing season,while accumulative Rs increased with litter addition by 79.87 gC/m~2. During the growing season,Rsexhibited significant exponential relationships with soil temperature,while there were no significant differences in soil moisture among the various treatments. Temperature sensitivity( Q10) values of Rsranged from 2.36 to 3.46 in the various thinning intensities,with the highest Q10 value in the low thinning stand. The Q10 value were lower with the litter removal and litter addition treatments than those of normal litterfall. The interaction of soil temperature and moisture had a significant effect on Rs. The best fitting model with temperature and moisture explained 28% —62% of the variation in Rs. The results indicated that the interaction between thinning treatments and litter changes has a significant effect on the Rsin L. principis-rupprechtii plantations. The compound effect of moderate thinning and litter addition on Rsis significantly greater than that of any single factor. In conclusion,thinning played a considerable role in altering Rsand carbon cycle in forest ecosystems by influencing the soil microenvironment and litter production rates.
【CateGory Index】： S714
【CateGory Index】： S714