PARENT SESSION
Oral Session 5: Disturbance Ecology I: Scaling, Wind, and Ice.
Presiding: D McKenzie
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 113.
Calcium addition to watershed at Hubbard Brook LTER reduces red spruce winter injury.
Hawley, Gary*,1, Schaberg, Paul2, Eagar, Christopher3, Borer, Cathy1, 1 The University of Vermont, Burlington, Vermont, USA2 USDA Forest Service, Burlington, Vermont, USA3 USDA Forest Service, Durham, New Hampshire, USA
ABSTRACT- Research from our laboratory has established that acid rain can directly leach calcium (Ca) from red spruce (Picea rubens Sarg.) foliage, preferentially displace Ca ions from the plasma membranes of mesophyll cells, destabilize membranes, deplete Ca pools thought to be important to plant stress response systems, and significantly reduce the cold tolerance of red spruce current-year foliage. Additional work has verified that Ca depletion instigated through protracted soil nitrogen additions can induce this same mechanistic sequence and result in experimentally-induced stand decline. However, no evidence to date implicates soil Ca depletion accelerated by ambient pollution additions to the physiological dysfunction and decline of native red spruce. The aftermath of a severe region-wide red spruce winter injury event in 2003 provided a unique opportunity to test the impact of existing soil Ca loss on red spruce freezing injury and explore how site Ca nutrition may influence tree response and potential recovery from dramatic foliar losses. We measured the mortality of current-year foliage and buds of 6 to 7, 1/10 ha plots of red spruce trees on both watershed one (a Ca-addition site) and watershed six (a reference watershed) at the Hubbard Brook LTER. Results from this assessment showed that dominant and co-dominant red spruce from the Ca addition watershed had significantly lower levels of current-year foliar winter injury than trees from the reference watershed (24.7 versus 74.4 %, P < 0.01). In addition to foliar losses, dominant and co-dominant red spruce in the Ca addition watershed had significantly less bud and shoot mortality compared to trees in the reference watershed (21.0 versus 43.6 %, P < 0.01). The greater foliar and bud mortality of trees from the reference watershed where deposition-induced Ca leaching is well documented, provide support for the contention that ambient Ca losses are having a meaningful influence on tree physiology and health. We are now evaluating the impacts of the severe 2003 winter injury on the long-term productivity, health and function of red spruce forest ecosystems at this research site.
Key words: forest decline,