Effects of Forest Harvest on Soil Carbon and Related Variables in Canadian Spodosols

Abstract

Knowledge about soil organic carbon (SOC) response to forest harvest in conifer stands is limited. The objective of this study was to determine the short-to medium-term effects of bole-only clearcut harvest on SOC and related variables in a Douglas fir [Pseudotsuga menziesii (Mirbel) Franco]-dominated forest of southwestern British Columbia. We collected soil samples from control (mature forest), cleared (harvested 1-5 yr before sampling), and regenerating (harvested 8-15 yr before sampling) stands and measured SOC, pH, texture, moisture, total N, loss-on-ignition, effective cation exchange capacity (CEC^), and pyrophosphate-extractable Fe and Al. We found that SOC stocks in the forest floor were higher in cleared and regenerating plots than in control. The mineral subsoil played an important role in the overall response of SOC storage after harvest. In mineral horizons, SOC concentration was higher in cleared plots and similar to control levels in regenerating plots. Treatment effects were restricted to SOC associated with the sand size fractions. This suggests that clearcutting resulted in additional soil organic matter (SOM) inputs to the mineral soil, but that these inputs were not stabilized or retained in regenerating plots. Harvest also affected bulk organic matter composition. The C/N and C/SOM ratios were lower in regenerating plots while tbe CEC^/C ratio was higher, suggesting an increase in organic matter maturity and oxidation.

Calcium-mediated stabilisation of soil organic carbon

“…While powerful, these direct spectroscopic techniques require the use of synchrotron light source and can only be applied to small amounts of samples with limited compositional complexity. We are still lacking a method that allows for the routine assessment of inner sphere Ca-SOM complexes and their relative importance in different soils, which constitutes a significant research gap given the potential for inner sphere interactions to stabilise SOM with increased efficiency (Mikutta et al 2007), and perhaps through ecosystem disturbance events (Basile-Doelsch et al 2009;Grand and Lavkulich 2012).…”

Soils of temperate rainforests of the North American Pacific Coast

“…Restricted drainage resulting from podsolization and paludification can lead to the development of thick, C-dense, organic layers, particularly in more northern NAPC rainforests. Even when podsolization does not lead to water-logged conditions, the translocation of Fe and Al can play an important role in SOC stabilization in the mineral layers of temperate rainforest Spodosols by forming organometallic complexes, among other mechanisms (Grand and Lavkulich, 2012). The accumulation of SOC is an important component of total ecosystem C storage, which is exceptionally high in temperate rainforests, even more so than SOC alone (Keith et al, 2009;Smithwick et al, 2002).…”

Disturbance Legacy on Soil Carbon Stocks and Stability within a Coastal Temperate Forest of Southwestern British Columbia, Canada

“…stability) is driven by the intrinsic properties of SOC as well as physiochemical and biological parameters. As an example, in coastal temperate rainforests of British Columbia, the clay fraction can account for one third of the SOC (Grand & Lavkulich, 2012). In addition, Grand and Lavkulich (2012) showed that Fe and Al can form organometallic complexes with SOC.…”

“…As an example, in coastal temperate rainforests of British Columbia, the clay fraction can account for one third of the SOC (Grand & Lavkulich, 2012). In addition, Grand and Lavkulich (2012) showed that Fe and Al can form organometallic complexes with SOC. Yet, as this mechanism enables SOC stabilization, the translocation of Al and Fe in the mineral layers of Podzolic soils (dominant in coastal temperate forests of British Columbia) may enhance SOC storage (Eusterhues et al, 2005).…”

“…The early study of Lavkulich and Rowles (1971) in coastal temperate rainforests of British Columbia reported the effect of land use on Podzolic soil properties, focusing on the overall effects of converting mature forest to agricultural uses. Grand and Lavkulich (2012) showed that harvest (clear-cutting) of mature coastal temperate forests of British Columbia resulted in additional SOM inputs to the mineral soil, but these inputs were not stabilized or retained in recovering second-growth forests. The present study builds on this earlier research by comparing SOC stocks and stability among three forest sites that differ in disturbance history and tree species composition.…”