Effects of moisture stress on Douglas-fir physiology and growth

1. Effects of moisture stress on Douglas-fir physiology and growth Tom Hinckley, College of Forest Resources, University of Washington, Seattle, WA

2. Preface Introduction Context Methods Impacts Water & Nitrogen • Climate, climate change • Future • • Jeremy Littell • • Dave Spittlehouse • Past • • Renee Brooks Sun: Quantity, vapor pressure gradient Snow: quantity, elevation, rain-on-snow, etc. Rain, cloud, & fog: Quantity, intensity, timing Content of January 29 meeting - 1

3. Preface Introduction Context Methods Impacts Water & Nitrogen Hydraulic redistribution • Frederick Meinzer Soil moisture • Jeffrey McDonnell Soil properties Soil water content Hydraulic Conductivity Groundwater Content of January 29 meeting -2

4. Preface Introduction Context Methods Impacts Water & Nitrogen Climate: Weather Site: Microclimate & topography Physiology & Growth • Tom Hinckley Water Use Efficiency • Andy Black Content of January 29 meeting -3

5. Preface Introduction Context Methods Impacts Water & Nitrogen Outline • Context • Major physiological processes affected by moisture stress • Methods for assessing tree moisture stress • Water-use requirements • Soil water tensions and plant water potential thresholds that result in growth reductions to growth cessation • Does fertilization improve water-use efficiency?

6. Preface Introduction Context Methods Impacts Water & Nitrogen Whole Plant Context • An integrated system • Water loss at foliage level • Water transport • Water uptake • Important to note that nitrogen stress has been regarded as the main control of growth & productivity in Douglas-fir in PNW

7. Preface Introduction Context Methods Impacts Water & Nitrogen Abovegrd stress: • light • ozone • herbivory Belowgrd stress: • nutrients • water • oxygen Water & Nutrient Carbon Carbon Leaf Growth Utilization Storage Production Water & Nutrient Root Growth Uptake Simple Model of How Trees Might Respond to Stress • Does the model work?

8. Preface Introduction Context Methods Impacts Water & Nitrogen Responses To Belowground Stress • Tree Scale Reich et al. (1980. Forest Science 26: 590) Quercus spp. Borchert (1975. Physiologia Plantarum 35: 152) Quercus spp.

9. Preface Introduction Context Methods Impacts Water & Nitrogen Individual Tree Response Cont. • Experiment with Douglas-fir and nitrogen (Friend et al. 1990. Can. J. For. Res.)

10. Preface Introduction Context Methods Impacts Water & Nitrogen Site II- Site II- Site IV+ Site IV+ Stand Response • Keyes and Grier (1981.CJFR): young and high site 40-year-old Douglas-fir Aboveground Aboveground Net Primary Productivity Net Primary Productivity Belowground Belowground Changes with Fertilization

11. Preface Introduction Context Methods Impacts Water & Nitrogen Broader Geographic Comparison Pseudotsuga menziesii Tsuga heterophylla Lee et al. (2007. Forest Ecology & Management 242: 195)

12. Preface Introduction Context Methods Impacts Water & Nitrogen Site Water Balance & Productivity Soil depth & texture Water holding capacity Full April 1 Output: Pan AET Input: PPT Climate change • Grier and Running. 1977. Ecology Pisi Tshe Mixed Psme Juoc

13. Preface Introduction Context Methods Impacts Water & Nitrogen Take-home Messages • Water and nutrients intertwined in PNW • Young soils • Climatic regime • Water long enough, would change site class • Leaf area (tree/stand) sets the productivity potential (species, site, length of time when temperature/light + and water also+) • Climate change • Length of growing season • Shifts in distribution of snow pack, cloud and fog

14. Preface Introduction Context Methods Impacts Water & Nitrogen Methods • Scholander-Hammel Pressure Bomb (PMS) • Leaf or stomatal conductance • Sap velocity, sap flux • Soil moisture • Canopy microclimate (eddy flux) • Remote sensing including air & ground-based LiDAR • Air spade, ground penetrating radar

15. Warmer, longer, drier ‘summers’: • Stomatal closure (decreases in carbon gain; offset partially by increases in CO2 [WUE]; vpg may increases, however) • Allocation to roots • Decreases in tree/stand leaf area Preface Introduction Context Methods Impacts Water & Nitrogen Physiological Processes Impacted • Stomatal closure • Reductions in photosynthesis • Reductions in growth • Changes in carbon allocation • Senescence & abscission of foliage • Decreases in nutrient uptake • Cavitation of conducting elements • Die-back, mortality

16. Preface Introduction Context Methods Impacts Water & Nitrogen Water Used & Thresholds • Water used: 0 - 500 l (kg) per day • Water used: 0 - 5 mm per day • Winter desiccation • Wilting • Length of ‘growing season.’ • Site • Height Soil water holding capacity is often associated with nutrition

17. Preface Introduction Context Methods Impacts Water & Nitrogen Irrigation • Dale Cole: It makes no sense to irrigate (PNW) • Re-examine that statement • Lessons from the SE • Series of studies conducted by T. Albaugh, L. Allen, T. Dean, P. Dougherty, B. Ewers, E. Jokela, K. Johnsen, L. Kress, T. Martin, R. Oren, L. Samuelson, R. Teskey • Loblolly pine (FL, GA, LA, NC, OK)

18. Preface Introduction Context Methods Impacts Water & Nitrogen Leaf Area, Water & Fertilization • Water use: IF (1.8 mm), F (1.2 mm)*, I and C (0.7 mm). • Growth efficiency (SMI/LAI): IF (2.9 Mg/ha•y•LAI), F (2.7), I (2.4), C (1.9) • Soil water availability poor predictor of productivity. • Soil nutrient availability much better • Understory control (nutritional) • Genetics/disease control • Genetic potential in its native range • Fertilization provides greatest gain * Improved depth of rooting

19. Preface Introduction Context MethodsImpacts Water & Nitrogen Summary • Site nutrient availability is critical • Water (or competition for) is critical early for root establishment. • Water likely to become more critical in the future • Unknowns

20. Orphaned Slides (not used in formal talk • Experiment with corn and water (John Boyer)

21. Role of N mineralization on fine root production • Grier et al. (1981. CJFR): young vs. old-growth Pacific silver fir High Includes high & low site Psme, young and old Abam and young Tshe Percentage of Total NPP allocated to fine roots Low N Mineralization

22. Preface Introduction Context Methods Impacts Water & Nitrogen What’s ‘new’ in Douglas-fir water relations • Role of height (Bond, Meinzer, Ryan) • Role of storage (Bond, Cermak, Meinzer) • Role of hydraulic redistribution (Brooks, Meinzer) • Role of night-time transpiration (Ferrell) • Role of roots - microorganisms - guild

23. Critical Role of Leaf Area in NPP • Data from Abam (cited in Hinckley et al. 1999. Phyton). First measures 80 - 82; foliage re-measured 1995)