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 changeFuture• Jeremy Littell• Dave SpittlehousePast• Renee Brooks

Preface Introduction Context Methods Impacts Water & Nitrogen

Content of January 29 meeting -2

Preface Introduction Context Methods Impacts Water & Nitrogen

Groundwater

Hydraulic redistribution• Frederick MeinzerSoil moisture • Jeffrey McDonnellSoil properties

Soil water contentHydraulic Conductivity

Content of January 29 meeting -3

Preface Introduction Context Methods Impacts Water & Nitrogen

Site: Microclimate & topography

Physiology & Growth• Tom HinckleyWater 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 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 Respond to Stress

• Does the model work?

Leaf GrowthCarbonProduction

CarbonStorage

Root Growth

Water & NutrientUptake

Water & NutrientUtilization

Belowgrd stress: • nutrients• water• oxygen

Abovegrd stress: • light• ozone• herbivory

Preface Introduction Context Methods Impacts Water & 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 Impacts Water & Nitrogen

Individual Tree Response Cont.

• Experiment with Douglas-fir and nitrogen (Friend et al. 1990. Can. J. For. Res.)

Total of 6 Combined Treatments:

N Concentration of Macroenvironment

0 ppm 20 ppm 100 ppm

0 ppm

200 ppm

Ss

Sn

Is

In

Ns

Nn

N Concentration

of Micro-

environment

2.5 l

0.4 l0.4 l

Macroenvironment

Severe N

Stress (s)

No N

Stress (n)

Micro-

environment

-N +N

-N +N

Nitrogen Stressed

R

F

r2 highr1 low

oots

oliage

r1 low

R

F

r2 high

oots

oliage

Non-Stressed

Preface Introduction Context Methods Impacts Water & Nitrogen

Stand Response

• Keyes and Grier (1981.CJFR): young and high site 40-year-old Douglas-fir

Preface Introduction Context Methods Impacts Water & Nitrogen

Net

Prim

ary

Pro

duct

ivity

Site

IV+ S

ite II

-

Abo

vegr

ound

Bel

owgr

ound

Changes with Fertilization

Net

Prim

ary

Pro

duct

ivity

Site

IV+ S

ite II

-

Abo

vegr

ound

Bel

owgr

ound

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

• Grier and Running. 1977. Ecology

Soil depth & textureWater holding capacityFull April 1Output: Pan AETInput: PPT

Climate change

PisiTshe

PsmeJuoc

Mixed

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 & ground-

based LiDAR• Air spade, ground penetrating radar

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

Preface Introduction Context Methods Impacts Water & Nitrogen

• 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

Warmer, longer, drier ‘summers’:

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

Preface Introduction Context Methods Impacts Water & 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 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

Preface Introduction Context Methods Impacts Water & Nitrogen

Orphaned Slides (not used in formal talk

0-0.4-0.8-1.2

Growing Region Water Potential (MPa)

0

2

4

Leaf

Silk

Stem

Nodal roots

• 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

Per

cent

age

of

Tot

al N

PP

al

loca

ted

to f

ine

root

s

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 Impacts Water & Nitrogen

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)