Afa 2012 effects of drought jonPresentation Transcript
Effects of Drought on Tree Growth Dr. Jon Barry, RF Assistant Professor Southwest Research and Extension Center
Evidence ofDrought• Death• Less growth• Tree rings• Increased stress
Drought andEstablished Trees • Stress leading often to pest infestation • Decreased growth • Decreased stocking • Changes in vegetation - Ecotone movement between prairie and forest - Elimination of mesic species on xeric sites
Weather Patternfor SWREC • Two years of record rain - Decreased root growth during wet periods Increased top growth during wet - periods • Two years of severe drought - Need more roots and less top during drought • One year moderate drought • Result: Tree stress and pest infection
2008 Rainfall 70Inches 60 50 40 Cum Total 30 Cum Normal 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2009 Rainfall 90Inches 80 70 60 50 Cum Total 40 Cum Normal 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2010 Rainfall 60Inches 50 40 Cum Total 30 Cum Normal 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Simple EnergyBalance Model Photosynthesis Respiration Te mp er atu re r Wate and Light Energy Storage
Water Flow Water Flow impacted by wind, temperature, and humidity. Water Flow controlled by stomates There is still ﬂow when stomates Water moves are closed through xylem Water Holding Capacity of Soil Depth of Soil
Effect of Droughton Photosynthesis • Decreasing water availability decreases photosynthesis • Decreasing production of carbohydrates • Less growth - Less roots • Less production of “natural pesticides”
What is Tree Stress• Trees subject to less than ideal growing conditions.• Strain (reduction or change in function) - Elastic Strain - Plastic Strain Off-site
Stress and Pests• Reduced photosynthesis and increased respiration lends to depleted energy• Lack of energy leads to the lack of resistance to pests• Trees succumb to repeated attacks or are not able to compartmentalize• pest Process can last decades
Stress and Pests• Hypoxylon canker• Bark beetles• Root weevils and leptographium
Managing OlderStands• Maintain vigor - Thin when thinning is needed - Control competing vegetation• Recognize financial and biological maturity
Seedlings andDrought• How do we insure success?• Do we plan for failure during drought years?
Seedling Quality• All nurseries in Arkansas produce quality seedlings.• What is a quality seedling? - Fibrous root system - Pronounced terminal bud - Secondary needles - Proper caliper - Dormant
Proper Storage• Stored in a cooler and planted directly from the cooler• If not kept in a cooler - Don’t leave in sun - Don’t leave in truck• Increasing temperatures increase respiration which decrease energy reserves
Proper PlantingConditions• Don’t Plant with Poor Soil Moisture.• Don’t Plant at Temperatures > 60o• Don’t Plant at Wind Speeds > 15 mph.
Proper Handlingin Field• One tree at a time• NO ROOT PRUNING
Planting• Tight and deep! - Beyond the root collar - As long as the terminal bud is above the ground - Don’t be over-concerned with root deformation - Vertical not at an angle
Strategy to ImproveSuccess• Site preparation - Debris removal - Tillage• Vegetation control - More water• Containerized seedlings - Fall planting
Poor DensityStrategy• Plant more trees - Overstocking
Ford’s Axiom• When environmental conditions are good, the little things matter a little.• When environmental conditions are bad, the little things matter a lot.