Seasonality and drivers of stem CO<inf>2</inf> efflux for four temperate coniferous tree species

Abstract

4种温带针叶树种树干CO 2 释放通量的季节动态及 其驱动因子许 AbstractAims Stem CO 2 efflux (E s ) is an important component of annual carbon budget in forest ecosystems, but how biotic and environmental factors regulate seasonal and inter-specific variations in E s is poorly understood. The objectives of this study were: (1) to compare seasonal dynamics in E s for four temperate coniferous tree species in northeastern China, including Korean pine (Pinus koraiensis), Korean spruce (Picea koraiensis), Mongolian pine (Pinus sylvestris var. mongolica), and Dahurian larch (Larix gmelinii); and (2) to explore factors driving the inter-specific variability in E s during the growing and non-growing seasons.Methods Ten to twelve trees for each tree species were sampled for E s and stem temperature at 1 cm depth beneath the bark (T s ) measurements in situ with an infrared gas analyzer (LI-6400 IRGA) and a digital thermometer, respectively, from July to October 2013 and March to July 2014. The daily stem circumference increment (S i ), sapwood nitrogen concentration ([N]), and related environmental factors were monitored simultaneously. Important findingsThe temporal variation in E s for the four tree species overall followed the changes in T s throughout the study period, with the maxima occurring in the summer months (late May to early July) characterized by higher temperature and more rapid stem growth and the minima in spring (late March to April) or autumn (October) having lower temperature. T s accounted for 42%-91% and 56%-89% of variations in E s during the growing (May to September) and non-growing (other months) seasons, respectively. Furthermore, apart from T s , we also found significant regression relationships between E s and S i , relative air humidity and [N] during the © Chinese Journal of Plant Ecology