title: Diurnal and seasonal change in stem respiration of Larix principis-rupprechtii trees, northern China.
abstract: Stem respiration is a critical and uncertain component of ecosystem carbon cycle. Few studies reported diurnal change in stem respiration as well as its linkage with climate. In this study, we investigated the diurnal and seasonal change in stem respiration and its linkage with environmental factors, in larch plantations of northern China from 2010 to 2012. The stem respiration per unit surface area (RS) showed clear diurnal cycles, ranging from 1.65±0.10 to 2.69±0.15 µmol m(-2) s(-1), increased after 6∶00, peaked at 15∶00 and then decreased. Both stem temperature and air temperature show similar diurnal pattern, while the diurnal pattern of air relative humidity is just the opposite to Rs. Similar to the diurnal cycles, seasonal change in RS followed the pattern of stem temperature. RS increased from May (1.28±0.07 µmol m(-2) s(-1)) when the stem temperature was relatively low and peaked in July (3.02±0.10 µmol m(-2) s(-1)) when the stem temperature was also the highest. Further regression analyses show that RS exponentially increases with increasing temperature, and the Q10 of Rs at mid daytime (1.97±0.17 at 12∶00 and 1.96±0.10 at 15∶00) is significantly lower than that of mid nighttime (2.60±0.14 at 00∶00 and 2.71±0.25 at 03∶00) Q10. This result not only implies that Rs is more sensitive to night than day warming, but also highlights that temperature responses of Rs estimated by only daytime measurement can lead to underestimated stem respiration increase under global warming, especially considering that temperature increase is faster during nighttime.
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhao
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China ; Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America.
authors.forename: Xiangtao
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
authors.forename: Zhenzhong
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
authors.forename: Guodong
authors.initials: G
authors.lastname: Yin
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China.
authors.forename: Shilong
authors.initials: S
authors.lastname: Piao
mesh_terms: D002681:China; D002940:Circadian Rhythm; D028221:Larix / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology*; D012621:Seasons