Quantifying the influence of foliar winter injury on long-term woody carbon sequestration for red spruce in the northeastern forest

Background/Question/Methods

Red spruce (Picea rubens Sarg.) foliar winter injury is freezing injury  that causes the reddening and mortality of current-year foliage that can lead to crown thinning and eventual tree death. Although winter injury is a strong contributor to red spruce decline in the northeastern U.S., a quantitative assessment of the influence of winter injury on aboveground woody carbon (C) storage in red spruce has not been conducted.  In 2005 we conducted a dendrochronological survey of woody growth of dominant and co-dominant red spruce trees growing in 23 plots in three states (VT, NH and MA) that experienced a range of winter injury levels (averaging from 0 to 100% mortality of current-year needles) in 2003 – a year of severe region-wide winter injury. Linear regression analyses showed a significant relationship between winter injury severity and growth reductions for two years after the 2003 event. Growth data was then combined with established allometric equations and USDA Forest Service, Forest Inventory and Analysis (FIA) data to calculate the influence of winter injury on above-ground woody C sequestration of red spruce trees across the region for 2003 and 2004. 

Results/Conclusions

Using this analysis, we estimated a reduction of 394,000 metric tons of C sequestered (approximately 1,438,000 metric tons of CO₂) in red spruce stems ≥ 20 cm in diameter in New York and northern New England during the two years following the 2003 event.  This estimate represents a 1.2% reduction in above ground C sequestration for affected trees.  However, since this analysis was conducted soon after the 2003 event, long-term reductions in woody biomass accumulation and injury-induced mortality were not calculated. Using an expanded sample of forest stands where winter injury was quantified in 2003, we are now quantifying C losses for the eight years after the 2003 event to measure the influence of this event on 1) long-term reductions in growth, and 2) C losses associated with injury-induced mortality. In addition, because past research has shown that acid deposition-induced calcium (Ca) depletion contributed to the severity of the 2003 winter injury event, we are also assessing if the replacement of Ca to soils at the Hubbard Brook Experimental Forest (Thornton, NH) bolstered C storage.  Estimates of reduced C storage could help inform regional management and policy discussions about the interconnections between forest health and C sequestration.