Mineral soil carbon pool responses to forest clearing in Northeastern hardwood forests

Abstract

Harvesting forests introduces substantial changes to the ecosystem, including physical and chemical alterations to the soil. In the Northeastern United States, soils account for at least 50% of total ecosystem C storage, with mineral soils comprising the majority of that storage. However, mineral soils are sometimes omitted from whole-system C accounting models due to variability, lack of data, and sample collection challenges. This study aimed to provide a better understanding of how forest harvest affects mineral soil C pools over the century following disturbance. We hypothesized that mineral soil C pools would be lower in forests that had been harvested in the last one hundred years vs. forests that were >100 years old. We collected mineral soil cores (to 60 cm depth) from 20 forest stands across the Northeastern United States, representing seven geographic areas and a range of times since last harvest. We compared recently harvested forests to >100-year-old forests and used an information theoretic approach to model C pool dynamics over time after disturbance. We found no significant differences between soil C pools in >100-year-old and harvested forests. However, we found a significant negative relationship between time since forest harvest and the size of mineral soil C pools, which suggested a gradual decline in C pools across the region after harvesting. We found a positive trend between C : N ratio and % SOM in harvested forests, but in >100-year-old forests a weak negative trend was found. Our study suggests that forest harvest does cause biogeochemical changes in mineral soil, but that a small change in a C pool may be difficult to detect when comparing large, variable C pools. Our results are consistent with previous studies that found that soil C pools have a gradual and slow response to disturbance, which may last for several decades following harvest.

Evaluation of forest management effects on the mineral soil carbon pool of a lowland, mixed-species forest in Maine, USA

“…Petrenko and Friedland (2014) found that average mineral soil C stocks were 34.9, 32.1, and 26.4 Mg ha −1 for 0-10, 10-20, and 20-30 cm depth increments in recently (<100 yr old) harvested stands across the northeastern USA. The corresponding C concentrations for these depth increments (7.2%, 4.6%, and 3.3%) were higher than our values, which may partially explain the lower mineral soil C stocks observed at our study site.…”

“…This analysis indicated that the probability of detecting a significant treatment effect was only 6%. Other studies on soil C have also shown that their effect tests had low power due to low replication (McLaughlin and Phillips 2006;Kurth et al 2014;Petrenko and Friedland 2014). For example, Petrenko and Friedland (2014) found that between 60 and 230 stands meeting their study's criteria would be required to detect significant differences in mineral soil C pools depending on the depth increment sampled.…”

“…In the same analysis, Spodosols showed a significant loss of deep mineral soil C stocks, but no significant declines in C stocks were found for the soil profile as a whole. However, a recent study conducted across the northeastern US found a negative relationship between time since harvest and mineral soil C storage (Petrenko and Friedland 2014). In studies involving simultaneous measurements of soil C pools on sites with similar soil types and past histories, Chatterjee et al (2009) and Powers et al (2011) found no significant differences in mineral soil C stocks among various silvicultural and harvesting treatments.…”

“…However, there is concern about how the type of forest management used to achieve these goals will affect soil C pools and productivity (Johnson and Curtis 2001;Jandl et al 2007;Berger et al 2013). Although much research has been conducted on the influence of clearcutting on the mineral soil C pool Petrenko and Friedland 2014;Vario et al 2014), less attention has been focused on the influence of other even-aged silvicultural systems and repeated partial harvesting. Furthermore, the studies that have compared the influence of various silvicultural and harvesting treatments on soil C pools (see, for example, Chatterjee et al (2009) ;Powers et al (2011)), rarely consider the potential effect of other soil properties besides C concentrations on these comparisons.…”

Evidence for Losses From Strongly Bound SOM Pools After Clear Cutting in a Northern Hardwood Forest

“…Several studies have observed soil C release from certain horizons in temperate forest soils after harvest (Grand and Lavkulich, 2012;Nave et al, 2010). Studies specific to northern New England have observed C decreases in mineral soil horizons after clear cutting (Zummo and Friedland, 2011;Petrenko and Friedland, 2014).…”