A Tree is a Tree Or Perhaps Not. Nov. 10, Dr. Les Werner UW Stevens Point

Transcription

1 A Tree is a Tree Or Perhaps Not Nov. 10, 2016 Dr. Les Werner UW Stevens Point Les.Werner@uwsp.edu

2 Urban Soils Urban Soils Differ from Natural Soils Natural Soil Urban Soil Photo by L. Werner

3 Urban Soils From a Trees Perspective: Critical Soil Factors (a.k.a. the things that are most often wrong with urban soils) Reduced Soil Fertility Compromised Soil Structure Reduced Soil Volume

4 Urban Soils Causes for Reduced Soil Fertility

5 Urban Soils Causes for Reduced Soil Fertility Organics removed from the site are a net loss to the nutrient cycle lbs N/1000 ft 2 Source: Werner and Miller, 2000, Photos from Web

6 Urban Soils Causes for Reduced Soil Fertility Urban environments tend to be more alkaline ph affects the availability of essential elements Activity of bacteria/fungi

7 Urban Soils ph induced Fe chlorosis Photos by Purdue Plant & Pest Diagnostic Lab

8 Urban Soils Causes for Compromised Soil Structure Urban Soils are Highly Disturbed Mineral sub-soils lack the organic content of the topsoil (A horizon) Photos from web

9 Urban Soils Causes for Compromised Soil Structure Note: Saturated Surface Soil Vertical discontinuities can impede water drainage Original Soil Grade Photo: L. Werner

10 Urban Soils Causes for Compromised Soil Structure Urban soils tend to be highly compacted Increase in Bulk Density (%) # of Trips Compaction increases the mineral fraction and reduces pore space Source: NRCS Urban Soil Primer Source: WI DNR, Forest Management Guidelines

11 Urban Soils Growth Limiting BD Line High bulk density can restrict root penetration Clay ~ 1.4 g/cm3 Loam ~ 1.5 g/cm3 Sand ~ 1.7 g/cm3 Dadow and Warrington, WSDG-TN

12 Urban Soils Compaction (a.k.a. bulk density) affects plant available water Drawn from data in Archer and Smith, 1972

13 25 Soil Oxygen at Varying Bulk Density 20 % Oxygen g/cm3 Hypothetical

14 Urban Soils Causes for Compromised Soil Structure High sodium levels can destroy soil aggregates and increase compaction Divalent Ca 2+ and Mg 2+ form bridges between particles Monovalent Na+ causes the particles to repel Ca 2+ Mg 2+ Deicing salts high in sodium are common in northern cities Na + Na + Na + Na + Ca 2+ Na + Na + Mg 2+ Na + Na +

15 Urban Soils Digging out a soil profile in problem areas can be of great assistance in diagnosing soil structure * Thickness of Organic Layer * Rooting depth * Depth of soil * Depth to restrictive layers * Potential contaminants

16 Urban Soils Evaluating Soil Volume Trees planted at the same time Photo courtesy of Casey Tree

17 Urban Soils How Much Soil Does a Tree Need? Need?

18 Urban Soils Soil Volume is also about structural roots Photo: C. Wells Photo: L. Werner Photo: A. Uhen

19 Towards a better understanding of tree nutrition through soil and tissue analysis Mr. Abraham Nebgen Dr. Les Werner Dr. Bryant Scharenbroch Best Management Practices (BMP s) for Tree and Shrub Fertilization Soil and/or foliar nutrient analysis should be used to determine the need for fertilizer.

20 Bond et al. Tree Physiology 27: Generally, increased resource availability results in greater growth

21 Guidelines for Effective Nutrient Management Growth Health Limitation Deficiency Match the tree s demand for resources with the soils ability to supply resources Whenever possible - mimic nature

22 Unfortunately, the relationship between soil extractions and leaf concentrations is weak Partial List of Sources of Variability Mobility of Elements Season Life Span of Trees Method of Extraction Timing of Extraction Plasticity of Trees Application Across Sites

23 Concentrations of essential elements can change over a growing season

24 Sites vary in their ability to supply resources

25 In Trees, the Demand for Resources is Highly Variable Variable Supply + Variable Demand = Cookbook recipes are not an acceptable management practice

26 Factors that Influence the Annual Demand for Resources by Trees Site Growth Strategy Age Health Environmental Conditions

27 Trees from Nutrient Poor Sites Conservative Consumption Strategy Long lived leaves Low nutrient concentration in tissues High nutrient resorption Slow Litter Decomposition Higher root:shootratios (assumes light is not limiting) Slow rate of growth (Δ biomass/time)

28 Trees from Nutrient Rich Sites Resource Spending Short lived leaves High nutrient concentration Low nutrient resorption Fast Litter Decomposition Lower root:shoot ratios (assumes light is not limiting) Fast rate of growth (Δ biomass/time)

29 High Nutrient Strategy High Nutrient Availability Growth Strategy (successional stage) Succession Low Nutrient Strategy Low Nutrient Availability Rapid Nutrient Uptake Slow Nutrient Uptake High Nutrient Efficient Roots High Turnover Rapid Growth High Turnover High Nutrient Efficient Leaves Low Nutrient Efficient Roots Slow Turnover Slow Growth Slow Turnover Low Nutrient Efficient Leaves Rapid Photosynthesis Slow Photosynthesis Redrawn from Chapin and Van Cleve 1981

30 Features of Early Successional Stage Trees Rapid growth Rapid root and leaf turn over Large below ground biomass Weak inherent defense Higher Nutrient Requirement

31 Features of Late Successional Stage Trees Slow growth Slow root and leaf turn over Large below ground biomass Strong inherent defense Lower Nutrient Requirement

32 Growth Strategy (Leaf Retention) Fast/high rate of resource acquisition associated with leaves that have: High specific leaf area High nitrogen content High P content Short life span Kazakou, E. et al Components of nutrient residence time and the leaf economics spectrum Functional Ecology 12:

33 Growth Strategy (Leaf Retention) Slow/Low rate of resource acquisition associated with leaves that have: Low specific leaf area Low nitrogen content Low P content Long life span Kazakou, E. et al Components of nutrient residence time and the leaf economics spectrum Functional Ecology 12:

34 Age Rapid increases in biomass during the early phases of growth results in a high demand for new resources (i.e. nitrogen)

35 Age Over time the demand for new resources stabilizes

36 Age Leaves are one of the biggest sinks for N Leaf Area stabilizes over time Vertessy et al Factors determining relations between stand age and catchment water balance in mountain ash forests. For. Ecology and Mgt.

37 Age Mature trees use more stored N to meet leaf demands for N Concentration of nitrogen in the leaves of mature trees was similar to young trees NDFF - Foliage Juvenile trees had substantially more fertilizer N than mature trees % NDFF (arc sin square root) Juvenile Mature Werner and Jull, Days after Treatment

38 Health Tree defense systems are fundamentally tied to C stores If the health of the tree is compromised, C reserves are used for defense* Fertilizing a tree with N may compromise ability to defend (C capital is used to acquire N) *Assumes cause of problem is not the result of nutrient deficiency

39 A Supply & Demand Model for Nutrient Management Supply Site Factors Management Factors Demand Tree Factors Prescription based on the likelihood of achieving a desired response

40 Factor Descriptor Supply Value Soil Volume < 1 ft 3 m 2 Low ft 3 m 2 Medium 2 2 ft 3 m 2 High 3 Soil Organic Matter < 2% Low % Medium 2 > 4% High 3 Soil Texture Sand Low 1 Loam High 2 Clay Medium 3 Bulk Density < 1.2 g/cm 3 High g/cm 3 Medium 2 > 1.5 g/cm 3 Low 1 Atmospheric Deposition (total N) Supply Site Factors < 6 kg/ha Low kg/ha Medium 2 > 10 kg/ha High 3 Total

41 Supply Management Factors Factor Descriptor Supply Value Understory Fertilized Routinely, on going High 3 Occasionally Medium 2 Never Low 1 Litter Removal Full removal leaves, clippings, etc. Low 1 Partial removal clippings returned, Medium 2 leaves removed Full return leaves, clippings, etc. High 3 Supplemental Irrigation Never Low 1 Occasionally (i.e. during periods of drought) Medium 2 Frequent High 3 Total

42 Supplying Power (Site + Management Factors) Total Points Interpretation 8 12 Low Supply Medium Supply High Supply

43 Demand Tree Factors Factor Descriptor Demand Value Age Young High 3 Mature Medium 2 Over Mature Low 1 Growth Strategy Deciduous High 3 Coniferous Medium 2 Early Succession High 3 Mid Succession Medium 2 Late Succession Low 1 Health Unhealthy Low 1 Healthy Medium 2 Vigorous High 3 Total Total Points Interpretation < 7 Low Demand 7 9 Medium Demand High Demand

44 Decision Matrix Interpretation Tree Demand Low Supply Medium Supply High Supply Low Growth Response Probable Growth Response Unlikely Growth Response Unlikely Medium Growth Response Likely Growth Response Probable Growth Response Unlikely High Growth Response Likely Growth Response Likely Growth Response Unlikely