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

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

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

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

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 ImpactsWater & 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 ImpactsWater & Nitrogen

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

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

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

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

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

Site Water Balance & Productivity Grier and Running Ecology Soil depth & texture Water holding capacity Full April 1 Output: Pan AET Input: PPT Climate change Pisi Tshe Psme Juoc Mixed Preface Introduction Context Methods ImpactsWater & 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 ImpactsWater & 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 Preface Introduction Context Methods ImpactsWater & 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 Preface Introduction Context Methods ImpactsWater & Nitrogen Stomatal closure (decreases in carbon gain; offset partially by increases in CO 2 [WUE]; vpg may increases, however) Allocation to roots Decreases in tree/stand leaf area Warmer, longer, drier ‘summers’:

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

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 ImpactsWater & 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/hayLAI), 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 ImpactsWater & 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 Preface Introduction Context Methods ImpactsWater & Nitrogen

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

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

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 Preface Introduction Context Methods ImpactsWater & Nitrogen

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