Background and Justification

Transcription

1 Quantifying the influence of winter injury on carbon sequestration for red spruce trees within the Northern Forest: assessing forest health to inform policy and economics Principal Investigator: Gary J. Hawley Affiliation/Institution: UVM-RSENR Mailing address: 81 Carrigan Drive, Burlington, VT Co-Principal Investigators: Paul G. Schaberg Affiliations/Institutions: USDA-FS-NRS s: Collaborators and Affiliations: N/A Completion date: June 30, 2013 The region-wide red spruce winter injury event of 2003 resulted in at least 3 years of reduced woody growth a carbon equivalent of burning about 280 million gallons of gasoline. Since 2007, yearly growth for study trees has been the highest recorded in the last 100 years. The cause of this surprising growth surge is unknown. Funding support for this project was provided by the Northeastern States Research Cooperative (NSRC), a partnership of Northern Forest states (New Hampshire, Vermont, Maine, and New York), in coordination with the USDA Forest Service.

2 Project Summary Rationale: Red spruce winter injury is the result of foliar freezing injury that can lead to crown thinning and eventual tree mortality. Although winter injury is a strong contributor to red spruce decline in the Northern Forest, a quantitative assessment of the influence of winter injury on long-term carbon (C) storage in red spruce trees had not been conducted. Methods: We collected woody increment cores from dominant red spruce trees in 30 forest plots in VT, NH and MA. Cores were used to measure annual radial growth (expressed as basal area increment). Growth data was combined with published allometric equations and USDA Forest Service Forest Inventory and Analysis (FIA) data and used to estimate impacts on aboveground carbon sequestration for the species across the region. Major findings: Foliar loss from winter injury reduced tree growth for three or more years following the 2003 event. Although the reduction in growth was not extensive for any one tree, the cumulative loss for red spruce trees across the region was substantial about 673,000 metric tons of carbon (roughly equivalent to burning 280 million gallons of gasoline). Importantly, trees injured in 2003 have experienced a surprising growth rebound. For the trees in this study, yearly growth is now at he highest level in the last 100 years nearly 2 times the average growth over the last century. Implications for the region: The surprising growth rebound is good news for red spruce a species best known for growth reductions and tree mortality associated with inputs of acid deposition. The new question for researchers and managers is WHY this growth surge is occurring is it associated with pollution reductions, warmer winter temperatures or other changes in the Northern Forest?

3 Background and Justification Acid deposition increases the susceptibility of red spruce to foliar winter (freezing) injury. Foliar loss to winter injury reduces tree growth and can lead to tree mortality. Although the connection between red spruce winter injury and decline is well understood, a quantitative assessment of winter injury and the amount and persistence of reduced growth that follows is lacking. A quantitative analysis of this would allow for a more integrated regional analysis of the influence of winter injury on forest carbon pools in the Northern Forest.

4 Since the 1960s there has been widespread decline of red spruce in the northeast Reddening of current-year foliage visible midwinter to early spring. Caused by freezing damage to current-year foliage. Trees can lose up to 100% of current-year foliage and have bud mortality. Dieback of lateral and apical branches. Photo: A. Kosiba Photo: P. Schaberg

5 Three factors combine to increase the probability and extent of winter injury for red spruce Limited inherent foliar cold tolerance Weather events that predispose or incite injury Severe winter injury Reductions in cold tolerance from acid deposition and Ca depletion

6 Average damage in 2003: 65% loss of current-year foliage to dominant and co-dominant red spruce Photo: G. Hawley

7 Winter injury severity in 2003 and reduced growth Growth 1 year after injury Growth 2 years after injury From Schaberg et al. 2011

8 Methods - overview Used woody increment cores to measure the yearly growth of dominant and co-dominant red spruce over the last 60 years. Trees were from plots where winter injury was quantified during the 2003 regional injury event. Emphasis was placed on assessing growth reductions following the 2003 injury event. Used allometric equations and FIA data to expand growth reductions to estimate biomass loss across the region. The influence of elevation on growth reductions and the substantial growth rebound post injury was also evaluated.

9 Materials & Methods 30 forest plots at 14 locations in VT, NH, & MA Elevation range: m Divided into 3 elevation categories Quantified for current-year foliar damage in 2003: Visual assessment of damage to current-year foliage ranging from 0-100% Plots selected to represent all damage classes dominant and co-dominant trees per plot

10 Plot locations

11 Methods, continued Collected 2 xylem increment cores per tree at breast height (DBH; n = 758). Measured ring widths (MeasureJ2X), cross-dated (COFECHA). Converted raw ring widths to basal area increment (BAI, cm 2 /year). Calculated change in BAI after winter injury ( ) relative to BAI for the same trees in ( pre-winter injury ). Used USDA Forest Service Forest Inventory and Analysis (FIA) online EVALIDator for total number of red spruce in region. Used allometric equations to estimate total above ground biomass for red spruce based on DBH.

12 Results - overview Foliar winter injury in 2003 resulted in at least 3 years of woody growth reduction. Growth reductions were small for any one tree, but cumulative reduced growth resulted in a substantial reduction in biomass gain across the region. Estimated that red spruce captured about 673,000 metric tons less of carbon following winter injury. This is the carbon equivalent of combusting about 280 million gallons of gasoline. Following injury-induced growth reductions, trees experienced a large increase in growth. This growth surge was greatest at middle elevations. The cause of this growth surge is currently unknown.

13 Mean BAI (cm 2 ) Mean BAI (±SE) for 30 red spruce plots * Year with winter injury event * 2003 Winter injury event * * * * 4 Year

14 Elevation (m) Winter injury severity and elevation y = x R² = P < * winter injury (%)

15 Change in BAI (%) BAI by elevation category A AB B Low elevation: <765m Mid elevation: m High elevation: >920m A A B A A B A AB B A B B A B B A AB B A A A -80 Year Different letters denote significant differences

16 Mid-elevation red spruce may be in an optimum location for growth in recent years High elevation Greatest level of foliar and bud mortality in the 2003 injury event Expected to have the greatest lingering growth reductions Environmental constraints may slow growth following injury Low elevation Suffered less winter injury Subject to the greatest competition from hardwoods Mid elevation Experienced moderate injury Dominant canopy species Less competition from hardwoods Growing conditions more moderate/favorable than high elevations

17 Mean net change in BAI (%) Net cumulative growth AB A P = Low elevation Mid elevation High elevation < 765 m m > 920 m B Different letters denote significant differences

18 Reductions in above ground C sequestration Minor for tree: Tree with NO winter injury = kg Tree with 100% winter injury = kg More consequential when calculated region-wide: Reduced C sequestration of 673,000 metric tons of C = 2.4 million metric tons of CO 2 Photo: R. Strimbeck Photo: P. Schaberg Photo: G. Hawley

19 Mean BAI (cm 2 ) Mean BAI (±SE) for 30 red spruce plots * Year with winter injury event Surprising, recent surge in growth * * * * * Year

20 Conclusions: (i) Following the 2003 winter injury event, all red spruce stands in this study had reduced growth. (ii) Winter injury and reductions in growth were linearly and significantly related for 3 years postinjury.

21 Conclusions: (iii) Elevation was positively and significantly related to winter injury severity and may account for variability in rebound post-injury. (iv) Mid-elevation sites had a net positive cumulative growth, and rebounded sooner than other elevations. May be explained by red spruce s dominance and established ecological niche here, but possible that changes in pollutant inputs and climate may also influence this recent boom in growth.

22 Implications for the Northern Forest Red spruce winter injury can result is substantial reductions in carbon sequestration within regional forests. Reductions in growth, rebounds from these losses, and cumulative changes in carbon sequestration over time vary with elevation. High elevation forests appear most vulnerable to protracted reductions in carbon sequestration. Despite elevational patterns, red spruce across the region are now experiencing an unprecedented surge in growth. This growth surge is a welcome reprise for red spruce a species extensively damaged by acid deposition. The cause for this upsurge is unknown, but could have important implications regarding the many ecosystem services (e.g., timber, wildlife habitat, etc.) that red spruce support.

23 Future directions New research will focus on identifying the cause(s) for this recent upsurge in red spruce growth. In particular, the influence of 1) recent reductions in sulfur and nitrogen pollution, and 2) climate change (especially higher winter temperatures) will be evaluated. Understanding the cause(s) of this growth surge will inform policy regarding pollution control and climate change. Understanding this will also influence regional management of red spruce a species of once great regional economic and ecological importance.

24 List of products MS Thesis - Kosiba, A.M Quantifying the influence of winter injury on the carbon sequestration of red spruce trees in the northeastern United States. Burlington, VT: University of Vermont. 65p. M.S. Thesis. The core of this thesis was accepted for publication in Forest Ecology and Management. Peer-reviewed journal article - Kosiba, A.M.; Schaberg, P.G.; Hawley, G.J.; Hansen, C.F Quantifying the legacy of foliar winter injury on woody aboveground carbon sequestration of red spruce trees. Forest Ecology and Management. 320: Presentations at meetings - Kosiba, A.M.; Schaberg, P.G.; Hawley, G.J.; Hansen, C.F Quantifying the influence of winter injury on the carbon sequestration of red spruce trees in the northeastern United States. Northern New England Forests Symposium, The University of Vermont, Burlington, VT. December 16, p. 12 (Abstract). - Schaberg, P.G Acid deposition, calcium depletion, and forest health/productivity: mechanisms and implications. Harvard University Herbaria Seminar Series, Cambridge, MA, April 30, 2013.

25 List of products Web page this research and the associated manuscript in Forest, Ecology and Management were highlighted on the featured research link on the USDA Forest Service Northern Research Station web page starting September 2013: News release The Northern Research Station also produced a news release about this research on August 31, This release is visible at:

26 Thanks to: Dr. Shelly Rayback, Dr. Jennifer Pontius, Dr. Josh Halman, Paula Murakami, Randy Morin, Eric Niebylski, Nick Huntington, Emily Russell-Roy, and Luke Ingram Funding: Northeastern States Research Cooperative (NSRC), USDA McIntire-Stennis, USDA Forest Service Northern Research Station