Soil Ecology and Tree Health: Implications for Management of Urban Forests and Ornamental Landscapes Dan Herms Department of Entomology The Ohio State University Ohio Agricultural Research and Development Center email@example.com
Acknowledgements: Students and Post-Docs Jim Blodgett, Rodrigo Chorbadjian, Carolyn Glynn, Bethan Hale, Nate Kleczewski, Joe LaForest, John Lloyd, Marie Egawa Collaborators Enrico Bonello, Robert Hansen, Harry Hoitink, Bill Mattson, Ben Stinner Funding Sources: TREE Fund USDA National Urban Community Forestry Advisory Council
The Ornamental Landscape as an Ecosystem: Implications for Pest Management Herms et al. (1984) J. Arboriculture 10:303-307. “Understanding the ecological interactions between the biotic and abiotic factors within a landscape enables more effective management of pests.”
Objective: Understand how trees allocate their resources in different environments, and the implications for the care of trees. Approach: Develop framework based on carbon allocation that can be used to predict tree behavior in different environments. Conduct experiments to test this framework.
Framework: carbon allocation patterns of trees Herms, D.A. 2002. Effects of fertilization on insect resistance of woody ornamental plants: reassessing an entrenched paradigm. Environmental Entomology 31:923-933. Herms, D.A. 2001. Resource allocation trade-offs in trees. Arborists News 10(5):41-47. Herms, D.A. 2001. Fertilization and pest control. Tree Care Industry 12(5):8-10,12,14. Herms, D.A. 1998. Understanding tree responses to abiotic and biotic stress complexes. Arborist News 7(1):9-15. Herms, D.A., and W.J. Mattson. 1997. Trees, stress, and pests. pp. 13-25. In J.E. Lloyd, ed. Plant Health Care for Woody Ornamentals, International Society of Arboriculture, Savoy, IL. Herms, D.A., and W.J. Mattson. 1992. The dilemma of plants: to grow or defend. Quarterly Review of Biology 67(3):283-335.
Different patterns of resource allocation and acquisition work in different environments
Concepts to emphasize: • resource acquisition vs. resource allocation • carbon budgets and allocation tradeoffs • integration of above- and below-ground growth • acclimation to stressful environments
Resource acquisition vs. allocation (Income vs. budgeting)
Whole plant carbon budget: • photosynthesis rate per unit leaf area • total leaf area
Allocation tradeoffs: plants have limited resources to support: • growth • maintenance • reproduction • storage • defense
The chemical arsenal of plants: defense and stress tolerance • Tannins • Phenolic glycosides • Terpenes • Alkaloids • Cyanogenic compounds • Defensive proteins
Resource allocation patterns • In faster growing plants: • high allocation to total leaf area • high photosynthesis rate • lower allocation to root growth • lower levels of defensive compounds • In slower growing plants: • lower allocation to total leaf area • high photosynthesis rate • higher allocation to root growth • higher levels of defensive compounds
Computer-controlled fertigation system to study responses of willow to nutrient availability Glynn et al. (2007) New Phytologist 176:623-634
Nutrient availability and carbon acquisition: • no effect on photosynthesis rate / leaf area • increased total leaf area
Source / Sink Interactions: carbon moves from sources to sinks via phloem transport
Mechanisms of photosynthetic acclimation: • Nitrogen allocation and specific leaf mass • Root:shoot ratios
Nitrogen deficiency does not cause chlorosis in plants that have had time to acclimate to their environment. Harris, R. W. 1992. Root-shoot ratios. J. Arboriculture 18: 39-42
Stable root:shoot ratios between days 40-85 consistent with equilibrium patterns of resource allocation
Soil fertility and insect resistance: “Properly fertilized trees are better able to ward off both insect and disease damage." “Fertilizing landscape plants promotes their general health and vitality, making them more resistant to insect and disease attack." "Fertilization promotes vigorous growth, disease, and insect resistance, and stress tolerance."
Fertilization decreased the insect resistance of woody plants in almost every study. No study showed increased resistance. Herms, D.A. 2002. Effects of fertilization on insect resistance of woody ornamental plants: reassessing an entrenched paradigm. Environmental Entomology 31:923-933.
Fertilizer Treatment (ANSI standard): Rate: 4.1 lb N / 1000 ft2 / yr 200 kg N / ha / yr 178 lb N / acre / yr Formulation: 18:5:4 NPK (56 % N slow release) Timing: early May and mid-Sept (split application)
Fertilization increased growth of Sphaeropsis tip blight lesions by 50% Blodgett et al. 2005. Forest Ecology and Management 208:273-382.
Effects of nursery fertility regime on crabapple following transplanting (Lloyd, J.E., et al. 2006. HortScience 41:442-445) 1997: three fertility treatments in container nursery 1998: transplanted to low maintenance landscape.
Greater impact of drought stress on photosynthesis of high fertility plants.
Fertilization and stress tolerance: • decreased root:shoot ratio • increased water requirements • decreased secondary metabolites
Fertilization decreased drought stress tolerance: • Red oak, chestnut oak (Kleiner et al. 1992) • American elm (Walters and Reich 1989) • Monterey pine (Linder et al. 1987) • Red pine (Miller and Timmer 1994) • Loblolly pine (Green et al. 1994) • Scots pine (Nilsen 1990) • Norway spruce (Nilsen 1995)
Nutrient cycling in a forest: the ultimate slow release fertilizer
Soil quality: the central role of organic matter (SOM) • Key determinant of soil structure: • oxygen, drainage, water / nutrient holding • capacity. • Source of essential nutrients for plants. • Foundation of soil food web. • Continuously depleted and replenished.
The living soil: In an average cup of healthy soil: Bacteria: 200 billion Fungi: 60 miles of hyphae Protozoa: 20 million Nematodes: 100,000 Arthropods: 50,000 From: S. Frey, Ohio State University
Nutrient Flow: The Central Role of Microbes Organic Matter Soil Microbes Plants
Nutrient Cycling in Ornamental Landscapes Organic Matter (Mulch) Decomposition Organic N Fertilizer Mineralization Microbial Turnover Mineral N (NH4,, NO3) Microbial Uptake Immobilization Plant Uptake