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Effects of moisture stress on Douglas-fir physiology and growth Tom Hinckley, College of Forest Resources, University of Washington, Seattle, WA Preface Introduction Context Methods Impacts Water & Nitrogen Content of January 29 meeting - 1 Sun: Quantity, vapor pressure gradient Rain, cloud, & fog: Quantity, intensity, timing Snow: quantity, elevation, rainon-snow, etc. Climate, climate change Future • Jeremy Littell • Dave Spittlehouse Past • Renee Brooks Preface Introduction Context Methods Impacts Water & Nitrogen Content of January 29 meeting -2 Soil properties Soil water content Hydraulic Conductivity Groundwater Hydraulic redistribution • Frederick Meinzer Soil moisture • Jeffrey McDonnell Preface Introduction Context Methods Impacts Water & Nitrogen Content of January 29 meeting -3 Climate: Weather Site: Microclimate & topography Physiology & Growth • Tom Hinckley Water Use Efficiency • Andy Black 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? 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 Preface Introduction Context Methods Impacts Water & Nitrogen Simple Model of How Trees Might Abovegrd stress: Respond to Stress • light • ozone • herbivory Carbon Storage Carbon Production Leaf Growth Root Growth • Does the model work? Water & Nutrient Utilization Water & Nutrient Uptake Belowgrd stress: • nutrients • water • oxygen 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. 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.) Nitrogen Stressed Non-Stressed Total o +N -N Micro- +N environm ent -N N Concen Foliage Foliage 0.4 l No N Roots Stress (n) r1 low 2.5 l Macroenvironm ent r2 high r1 low 0.4 l Severe N Roots Stress (s) r2 high of Micro- environm Preface Introduction Context Methods Impacts Water & Nitrogen Stand Response Changes with Fertilization Aboveground Belowground Site II- Site IV+ Net Primary Productivity Aboveground Belowground Site II- Site IV+ Net Primary Productivity • Keyes and Grier (1981.CJFR): young and high site 40-year-old Douglas-fir Preface Introduction Context Methods Impacts Water & Nitrogen Broader Geographic Comparison Pseudotsuga menziesii Tsuga heterophylla Lee et al. (2007. Forest Ecology & Management 242: 195) 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 Pisi Tshe Psme Mixed Juoc • Grier and Running. 1977. Ecology 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 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 & groundbased LiDAR • Air spade, ground penetrating radar Preface Introduction Context Methods Impacts Water & Nitrogen Physiological Processes Impacted • Warmer, Stomatal longer, closure drier ‘summers’: • Reductions in photosynthesis • Stomatal closure (decreases in • Reductions in growth carbon gain; offset partially by • Changes in carbon allocation increases in CO2 [WUE]; vpg may • Senescence & abscission of foliage increases, however) • Decreases in nutrient uptake • Allocation to roots • Cavitation of conducting elements • Decreases in tree/stand leaf area • Die-back, mortality 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 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) 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 Preface Introduction Context Methods Impacts 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 Elongation Rate (mm/h) Orphaned Slides (not used in formal talk • Experiment with corn and water (John Boyer) Leaf 4 Silk 2 Nodal roots 0 Stem 0 -1.2 -0.8 -0.4 Growing Region Water Potential (MPa) Role of N mineralization on fine root production • Grier et al. (1981. CJFR): young vs. oldgrowth Pacific silver fir High Percentage of Total NPP allocated to fine roots Includes high & low site Psme, young and old Abam and young Tshe Low N Mineralization 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 Critical Role of Leaf Area in NPP 1995 Remeasure OG (+ 16 years) 24 Net Primary Productivity -1 -1 (Mg ha y ) • Data from Abam (cited in Hinckley et al. 1999. Phyton). First measures 80 - 82; foliage re-measured 1995) Keyes (1982) YL YH 31 (YH) 16 24 (YL) • 200 (OG) 8 0 03 9 16 24 8 Foliar Biomass (Mg ha -1)