Effects of Forest Management Practices on Carbon Storage Coeli M. Hoover USDA Forest Service, Northern Research Station Forest PLUS, Washington DC December 6, 2013

Trail Map Management effects on aboveground C stocks – Long-term thinning studies Management treatment effects on forest floor and soil C stocks – State of knowledge – Results from field study Questions

Management Effects on Aboveground Carbon Stocks

Long-term Thinning Studies Thinning studies with long measurement records can be used to investigate the carbon consequences of different management practices Studies are usually of similar design, and apply a variety of thinning levels Structure study at Kane EF was designed specifically to look at effect of method, using a single density Challenges – lack of documentation, control plots, irregular measurement intervals, etc.

Structure Study - KEF

Crop Tree Thinning - BEF

Mixed Oak Stocking- Vinton Furnace EF

Mixed Oak Stocking

Summary Over the long term, plots will often end up with about the same amount of live biomass carbon across treatments rate However, the rate of accumulation may be quite different, especially in the period following treatment Are your goals short- or long-term?

Management Impacts on Forest Floor and Soil C Stocks

Mini literature review – mineral soil Overall, significant effects of harvesting on soil C have not been detected – Some evidence that boreal soils may respond Some cases of short-term increases in C in surface soils A few cases of short-term decrease in C in either the surface or deeper soils Some evidence that changes may occur at depth over longer time frames, but few studies have addressed this topic

Mini literature review - forest floor Literature includes chronosequences and control/treatment studies Problem of mixing of forest floor and mineral soil often complicates interpretation of results Good evidence that forest floor carbon stocks often decline after harvest – Recovery may take several decades

Most recent meta-analysis Nave et al (Forest Ecology and Management) Analyzed C content (t/ha) and concentration (% C) 75 publications met criteria – Control and harvest – Temperate forest Analyzed 432 response ratios from papers published between Largest analysis to date

Overall results from Nave et al Forest floor – C storage declined by 30±6% after harvest – Significantly different between hardwoods and softwoods Conifer/mixed stand: -20% Hardwood stand: -36% Mineral soil – No significant overall effect – Variation best explained by soil taxonomy

Overall results… Nave et al. 2010

Digging deeper… Nave et al. 2010

Results from regional work Investigated surface soil and forest floor C stocks in long-term thinning studies Variety of treatments: clearcutting, thinning to different densities – e.g., 90 ft 2, 60 ft 2, 30 ft 2, 70% RD, 40% RD All sites northern hardwood States included WV, NY, PA, WI, NH Some sites treated once, others twice Results in Carbon Balance and Management 2011(C. M. Hoover)

Forest Management Effects Study Sites Argonne Bartlett SUNY Heiberg Kane Fernow Middle Mountain

Results Summary Forest floor stocks were variable, ranging from mtC/ha – General trend of increasing S to N – No significant effects related to treatment Surface (0-20 cm) soil stocks range from a low of 32 to a high of 78 mtC/ha – Most sites fall between mtC/ha – Overall, no treatment effects on C stocks or C concentrations – Similar patterns for 0-5 cm depth as 0-20 cm

Forest floor - % C = light thin, = heavy thin Hoover 2011

Kane Experimental Forest (PA)

Mineral soil, 0-5 cm tC/ha, clearcut and control %C, clearcut and control Hoover 2011

Forest Floor C Stocks – Thinned and Control

Forest Floor C Stocks – Clearcut and Control

Fernow Experimental Forest (WV) Whole tree harvest

Soil C Stocks (0-20 cm)- Thinned and Control

Soil C Stocks (0-20 cm)- Clearcut and Control

In summary... rate Thinning treatments may not change the standing C stock over time, but can strongly affect the rate of C accumulation – Thinning method matters! Common management treatments may cause a reduction in forest floor C stocks not Strong evidence that common management treatments do not result in meaningful reductions in SOC stocks or concentrations

Points to ponder Short-and long-term responses often differ – This is true both above and below ground Surface and deep soil layers may respond differently Site specific factors may come into play – Hardwood/softwood types – Soil order Existing studies covered “standard” rotation lengths – not biomass harvests or industrial plantations Your mileage may vary!

Questions?