CA-TP4 Soil Respiration Data 2008-2018

Soil CO2 emissions or soil respiration (Rs) data were measured at an eastern white pine forest (Pinus strobus L.) planted in 1939 as monoculture stands north of Lake Erie in southern Ontario, Canada. The forest site is part of the Turkey Point Observatory and has been associated with AmeriFlux and global Fluxnet initiatives, where it is known as CA-TP4. The forest is dominated (&gt;82%) by eastern white pine, while other tree species include 11% balsam fir (Abies balsamea L. Mill) and species native to the hardwood forests of North American Eastern Temperate Forest Ecoregion, including 4% Oak (Quercus velutina L., Q. alba L.), 2 % Red Maple (Acer rubrum L.) and some wild black cherry trees (Prunus serotina Ehrh). The forest was thinned in 1983 and winter of 2012, where one-third of trees were randomly removed. <br><br>Soil CO2 efflux was measured using an automated non-steady state chamber system developed by the University of British Columbia in a 50 m × 50 m area located 100 m north from the eddy covariance flux tower at the site from June 2008 to October 2018. Initially four chambers were installed. One measured heterotrophic respiration (FRT1) in the trenched plot whereby live tree roots were removed from surrounding area and other three as controls. chambers and measured total soil CO2 efflux (FS: FS1, FS2, and FS22). One of the control chambers (FS22) was altered in May 2009 to measure the contributions from the mineral-soil horizon (FLR) to total soil respiration, by removing the litter layer. In May 2009, two more control chambers (FS3 and FS4) were added to the chamber system to measure total soil respiration. Finally, in May 2010, two additional chambers were installed, one as a control (FS5) and an additional chamber to measure heterotrophic respiration (FRT2); increasing the total number of chambers in the chamber system to eight. In total, five chambers were measuring total soil CO2 efflux, two chambers measured heterotrophic soil CO2 efflux and one chamber measured contributions from the mineral-soil horizon. Each chamber consisted of a PVC collar and a chamber lid that fit onto the collar. The collars were inserted approximately 2 to 4 cm into the ground. The chamber lid consisted of a transparent plastic dome fixed to a metal frame. Each chamber closed individually for a one-minute interval, where the CO2 concentration was sampled and measured by an infrared gas analyzer (model LI-840, Li-COR Inc.). Measurements were cycled through the eight collars for a total of three cycles per half-hour period. Each half-hour average consisted of three, minute-long CO2 concentration measurements per chamber. One half-hourly value was produced for each collar by averaging the three measurements taken during that half-hour. The measurement chambers remained open when not taking measurements. Throughout the growing season, any vegetation growth was removed from inside the collars to eliminate potential photosynthesis effects. <br>Tree density is 413 (321) tree per ha, Leaf Area Index is 8.5 (5.3), tree heigh 23.4 (22.9) m, and diamter at breat heigh is 39 (37.2) m. Numbers in paranthesis show vales after 2012 thinning. Topography in the area is predominantly flat with occasional 0.5-3.0% undulating slopes. The soil at the site is well drained with a low water holding capacity and classified as brunisolic grey-brown luvisols in the Canadian System of Soil Classification and is composed of ~98% sand. The climate in the region is cool temperate with a 30-year mean annual temperature of 8.0 °C and mean annual precipitation of 1036 mm.