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Strategies and Case Studies for Incorporating Ecophysiology into Southern Pine Tree Improvement Programs

2005; Oxford University Press; Volume: 29; Issue: 2 Linguagem: Inglês

10.1093/sjaf/29.2.70

1938-3754

Timothy A. Martin, Phillip M. Dougherty, Mary A. Topa, Steven E. McKeand,

Tree-ring climate responses

Both genetic and environmental influences on tree growth are expressed through physiological processes. This central, integrating role of physiology has made the field of forest ecophysiology a major area of biological research for the past several decades. Specifically, forest ecophysiology is the study of how plants interact with their abiotic and biotic environment to acquire the resources (sunlight, CO2, water, and nutrients) needed to produce assimilates necessary for growth, reproduction, competition with other plants, and defense against insects and disease. Because of their commercial and ecological importance, southern pines, especially loblolly pine (Pinus taeda L.) have been intensively studied by ecophysiologists. Although an exhaustive review of the ecophysiological literature is not possible here, examples of the physiological and morphological determinants of growth that have been studied in southern pines include the following: leaf area development (Gresham 1982, Martin and Jokela 2004), crown and canopy structure (Kinerson et al. 1974, Gillespie et al. 1994), light interception (Dalla-Tea and Jokela 1991, Will et al. 2001), carbon fixation (Bormann 1956, Teskey et al. 1987, Ellsworth 2000, Yang et al. 2002), respiration (Brix 1962, Kinerson et al. 1977, Maier et al. 1998), carbon allocation (Kuhns and Gjerstad 1988, Retzlaff et al. 2001b), tree water relations and stand water balance (Knauf and Bilan 1974, Seiler and Johnson 1985, Fites and Teskey 1988, Phillips and Oren 2001), root structure and function (Sword et al. 1996, Topa and Sisak 1997, Wu et al. 2000), and nutrient uptake and utilization dynamics (Switzer et al. 1966, Birk and Vitousek 1986, Dalla-Tea and Jokela 1994, Barron-Gafford et al. 2003). Important areas of emphasis have included genetic variation in physiology and morphology (Thames 1963, Ledig and Perry 1967, Bilan et al. 1977, Bongarten et al. 1987, McGarvey et al. 2004), physiological responses to silvicultural treatments (Johnson 1990, Murthy et al. 1997, Samuelson et al. 2001), and the potential effects of pollution and climate change on physiology (Sasek et al. 1991, Tissue et al. 1993, Teskey 1997, Oren et al. 2001). Taken together, the broad and deep coverage of ecophysiological investigations with southern pines (in particular, loblolly pine) have enabled a level of biological understanding that is rivaled in only a few other forest tree species, such as Douglas-fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris), and radiata pine (Pinus radiata). Our detailed physiological knowledge of important commercial tree species has laid the groundwork for our modern approach to forest management. Most university forest management curriculums require a formal course in forest ecophysiology, and imparting a mental model of how the various biotic and abiotic components of a forest community interact is the composite goal of all university forestry programs. This goal is established on the realization that to anticipate the long-term consequences of forest management decisions, land managers must understand the mechanisms by which trees interact with their environment. The discipline of ecophysiology is expected to play an even bigger role in forest management in the near future because of the rapid changes that are occurring in our environment (carbon dioxide, ozone, atmospheric nitrogen inputs, temperature, and rainfall); in the forest genetic base being applied to managed forest systems; and in forest composition due to the application of increasingly intensive forest management practices. These rapid changes in forest environments and movement toward management scenarios that differ greatly from the past somewhat lessen the utility of empirical growth and yield models and make it imperative that we develop process-driven growth models capable of simulating forest growth under diverse situations (Landsberg 2003). Over the past two decades, considerable progress has been made in bringing the fruits of forest ecophysiological research to bear on applied forest management problems. NOTE: T. A. Martin can be reached at (352) 846-0866; Fax: (352) 846-1277; tamartin@ufl.edu. Manuscript received August 23, 2003, accepted April 28, 2004. Copyright © 2005 by the Society of American Foresters.