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This site moved from Brown University to SUNY-ESF effective 11/17/2010, and now reflects Multiple Element Limitation in Northern Hardwood Ecosystems

Introduction

The investigators responsible for this project seek to clarify relationships between stand age and the cycling of Calcium between biotic and abiotic pools in the northern hardwood forest. The work involves a chronosequence of thirteen stands for extensive research located throughout the White Mountain National Forest, six of which are at Bartlett Experimental Forest in Bartlett, NH, and one of which is at Hubbard Brook Experimental Forest in Woodstock, NH. More intensive research will be conducted in nine stands at the Bartlett Experimental Forest.

Objectives

Our overall objectives are to describe differences in Ca cycling with stand age, and to determine the source of Ca mobilized from mineral soil in young stands. We will test our hypotheses using two experimental approaches: an extensive one involving 13 stands that we have previously studied, and an intensive one using replicate stands of three ages at a single site.

Background

There is growing concern that base cations are being depleted from forest soils in the northeastern United States as a result of acid rain (Baes and McLaughlin 1984, Shortle and Bondietti 1992, Likens et al. 1998). These losses from soil are likely to be compounded by timber harvesting and the associated loss of nutrients, with Ca the element most likely to become limiting (Federer et al. 1989). Recent studies have reported dramatic declines in pools of exchangeable base cations (Johnson et al. 1994, Knoepp and Swank 1994, Huntington et al. 2000). The loss of cations in general and Ca in particular over past decades is thought to have adversely affected forest productivity and health in eastern North America (Baes and McLaughlin 1984, Shortle and Bondietti 1992) and Europe (Ulrich et al. 1980, Graveland et al. 1994).

Environmental stresses such as acid rain may not be the only factors influencing changes in soil Ca over time. We suggest that forest age needs to be considered when interpreting Ca cycling patterns. Our Ca budgets indicate that young northern hardwood stands (<30 yrs old) transfer Ca from mineral soil into aboveground vegetation, forest floor, and drainage water, whereas older stands are in approximate steady state. This suggests that young stands tap a pool of soil Ca that is not as available to older stands. Identification of this pool is essential to predicting the consequences of acid rain and forest management on ecosystem productivity. Our proposed research will explore the effect of forest age on Ca cycling in the northern hardwood forest. Our objectives are to describe differences in Ca cycling in stands of different ages, and to determine the sources of Ca mobilized from mineral soil as a function of stand age.

Broader Implications

The proposed study addresses the question of Ca depletion in northeastern forests, which is critically important for both policy formulation and forest management. At the nearby Hubbard Brook Experimental Forest, exchangeable Ca in soil is predicted to be depleted in less than one harvest cycle, which means that either the productivity of re-growing forests will very soon be limited by Ca availability (Likens et al. 1998), or forests obtain Ca from previously unrecognized pools. The proposed experiment will improve our ability to predict the long-term implications of acid precipitation in the context of forest succession.

Geologists have traditionally put biology in a black box, minimizing the importance of biotic processes to geochemistry, while ecologists have put weathering in a black box, often ascribing to it whatever flux was necessary to balance a budget. The lack of a dialectic between weathering and biotic processes has limited our understanding of how nutrient cycling relates to ecosystem productivity and environmental stress.

In this proposal, we will make measurements that will allow us to define the importance of biotic processes on altering weathering and Ca availability. Understanding the importance of this interaction is key to defining sustainable forest management practices. We need to know how intensively we can manage northern hardwood forests before nutrient depletion limits forest productivity. The proposed research will contribute to identifying sustainable forestry practices in the northern hardwood forests of the northeastern United States.

Quantification of non-silicate mineral sources of Ca (apatite and calcite) to northeastern forest soils is important in calculations of Ca depletion because these Ca sources do not contain Na, which is often used to estimate the rate of Ca release by weathering. For example, Likens et al. (1998) calculated Ca weathering release based on stream sodium fluxes and an assumed Ca/Na weathering release ratio of 0.24 to 0.33. If non-sodium-bearing minerals contribute significant amounts of Ca to the soil, as we suggest, then rates of plant available Ca depletion could be significantly overestimated.

In addition to the intellectual impacts of the study, this project will provide long-term infrastructure for studies of succession and forest age in the northern hardwood forest. Previous advances in our understanding of long-term changes in ecosystem structure and function have relied heavily on chronosequence studies. Such studies are subject not only to random sources of error but also systematic ones: changes in technology and markets for wood products have altered the nature of harvest treatments over time (Arthur and Yanai 2000, Yanai et al. 2000). The proximity and similarity of our experimental study area to the Hubbard Brook Experimental Forest will magnify its utility to a broad spectrum of researchers.

This text was adapted from NSF Grant Proposal # DEB 0235650, "Biotic Control of Calcium Supply: Distinguishing Sources to Regrowing Forests."  Yanai, Hamburg, Arthur, Blum, 2003.


Articles from this project:

Blum, J., A.A. Dasch, S.P. Hamburg, R.D.Yanai, and M.A. Arthur. 2008. Use of foliar Ca/Sr discrimination and 87Sr/86Sr ratios to determine soil Ca sources to sugar maple foliage in a northern hardwood forest.  Biogeochemistry 87(3):287-296  PDF

Yanai, R.D., J.D. Blum, S.P. Hamburg, M.A. Arthur, C.A. Nezat, T.G. Siccama.  2005.  New insights into calcium depletion in northeastern forests.  Journal of Forestry. 103: 14-20.  PDF

Yanai, R.D., R.P. Phillips, M.A. Arthur, T.G. Siccama, and E. Hane.  2005.  Spatial and temporal variation in calcium and aluminum in northern hardwood forest floors.  Water, Air, and Soil Pollution. 160: 109-118. PDF

Hamburg, S,P., R.D. Yanai, M.A. Arthur, J.D. Blum and T.G. Siccama.  2003.  Biotic control of calcium cycling in northern hardwood forests: acid rain and aging forests.  Ecosystems 6: 399-404.  PDF


Contact:

For further information, feel free to contact any of the following people involved in the project:

Principal Investigators and Collaborators:

Mary Arthur
University of Kentucky

Joel Blum
University of Michigan

Melany Fisk
Miami University of Ohio

Steven Hamburg
Brown University

Elizabeth Hane
Rochester Institute of Technology

Matt Vadeboncoeur
University of New Hampshire

Ruth Yanai
SUNY College of Environmental Science and Forestry

 

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The Ca site formerly housed at Brown University was designed and maintained by technician extraordinaire Matt Vadeboncoeur.