Seasonal controls on patterns of soil respiration and temperature sensitivity in a northern mixed deciduous forest following partial-harvesting

• Published in: Forest ecology and management Vol. 348; pp. 208 - 219
• Main Authors: Shabaga, Jason A., Basiliko, Nathan, Caspersen, John P., Jones, Trevor A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2015
• Subjects: Autumn; Basal respiration; Bioenergy; biomass; Biomass harvest; carbon dioxide; deciduous forests; forest ecosystems; forest soils; Forests; growing season; Harvesting; microclimate; necromass; Phenology; pruning; Q10; regression analysis; regrowth; Respiration; respiratory rate; Selection silviculture; Soil (material); soil respiration; Soil temperature; stand basal area; Summer; Thinning; trees; understory; Q10; Selection silviculture; Bioenergy; Biomass harvest; Phenology; Basal respiration
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2015.03.022

•Soil respiration was elevated for three years following partial harvesting.•Respiration differences between harvesting and control treatments varied seasonally.•Large autumn differences were linked to increased fine woody debris.•Low summer differences and were associated with reduced tree cover.•Increasing relative Q10 values in harvested plots linked to understorey regrowth. Disturbances can alter CO2 efflux from soils (FCO2) by altering the microclimate, structure, and biogeochemical properties of forest ecosystems. Results of prior studies are unclear if and how partial harvesting of northern deciduous forests affects FCO2. These mixed responses may be due to differences in harvesting levels, time since harvest, and the spatial and seasonal heterogeneity of treatment effects and soil properties. To account for this spatio-temporal dependence, we produced subject-level regression models from regular measurements of FCO2 and soil temperatures during the 2010–2012 growing seasons following tree-length (TL) and more intensive biomass (BIO) harvests. In this paper, we compare seasonal and inter-annual post-harvest recovery trends for measured and temperature-corrected soil respiration rates and the sensitivity of soil respiration to temperature (as Q10). FCO2 values from TL/BIO treatments exceeded unharvested controls, recurrently peaking in the autumn (average for TL/BIO: 28%/17%, p⩽0.05) and waning in the summer (14%/10%, not significant). A comparison of measured FCO2 vs. modelled respiration values corrected for temperature differences indicated that higher soil temperatures following canopy thinning accounted for 34–41% of these differences in 2010 but <15% by 2012. Initially lower in 2010, Q10 and summer respiration values for harvested treatments exceeded those of controls by 2012, and despite waning temperature differences, average annual effect sizes corrected for temperature differences did not decline. Autumn and basal respiration rates were correlated with post-harvest fine woody debris volumes in 2010 (r2=0.58/0.57, p=0.01), summer rates in all years decreased with harvested tree basal area (r2=0.43–0.58, p⩽0.05), and the post-harvest basal area of understorey vegetation predicted increasing Q10 effect sizes from 2010 to 2012 (r2=0.81, p⩽0.01). With consideration to studies demonstrating that the contribution of root respiration (RR) to FCO2 is highest in summer, we propose that partial harvesting initially restricts RR and peak summer respiration rates, but compensates for this decline by increasing basal respiration rates and FCO2 through elevated soil temperatures and decomposition rates from canopy thinning and harvest residue substrate inputs (i.e., woody debris and root necromass). During post-harvest recovery, forest understorey regrowth reduces soil temperatures but influences patterns of FCO2 by increasing summer respiration and Q10 values in harvested treatments, likely by increasing RR.