Waterlogging tolerance of trees Tapani Repo, Metla Silviculture in Changing Environment, Nov. 24-25, 2014
Contents Motivation Background concerning waterlogging tolerance An example of dormancy waterlogging
Motivation Maintenance of ditch network Increased wintertime precipitation with climate change
Water vs. growth Growth Shortage of water Excess of water Soil water content
Soil composition water air Pore volume mineral soil Waterlogging leads to decline in air space and soil oxygen in peat!
Oxygen (O 2 ) 21% in air and some less in soil Roots need constant supply of O 2 for their functioning! Cell respiration: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + energy Oxygen deprivation leads to an energy crisis!
Waterlogging tolerance (WT) Depends on: Degree of oxygen deprivation (normoxia hypoxia anoxia) Exposure time State of water (stagnant/streaming) Annual phase of development
0 o GS: Spring bud break (SBB) 90 o GS: Maturity induction point (MI) 180 o GS: Vegetative maturity (VM) 270 o GS: Maximum rest (MR) 315 o GS: End of rest (ER) Growth phase Long roots Relative growth Dormancy Dormancy Short roots Time, days
Waterlogging tolerance (WT) Depends on: Degree of oxygen deprivation (normoxia hypoxia anoxia) Exposure time State of water (stagnant/streaming) Annual phase of development Species, ecotypes and age Conifers/deciduous trees No standard method for WT-assessment!
Effects of waterlogging o Changes in soil conditions o Short- and longterm responses in trees Changes in soil conditions: Oxygen deprivation, accumulation of CO 2 Changes in soil ph (increase or decrease) Breakdown of soil aggregates Decrease in decomposition rate of organic matter Change in bacterial composition Production of soil gases and other compounds by anaerobic bacteria
Tree responses to waterlogging Shortterm responses: Physiology Longterm responses: Morphology and growth (in addition to physiolgy) Physiology Stomatal closure (?) Photosynthesis carbohydrate content Rate of translocation of photosynthesis products Ethylene production Biochemical changes (carboxylation enzymes, chlorophyll) Uptake of mineral nutrients Amount and composition of mycorrhizas Re-oxidation phase critical (postanoxic injury)!
Tree responses to waterlogging Morphology Adventitious roots and lenticels (aeration and release of toxic compounds) Root and shoot growth root/shoot ratio Leaf area Black root formation (chemical reaction) Mortality (appears with delay)!
An example: Waterlogging of Scots pine and silver birch in the dormancy phase 16 pines and 16 birches
Schedule Growth phase I 9+3 wk Enter to dormancy 3 wk Winter Soil frost Flood Posttreatment, dormancy 4 wk Growth phase II 9+3 wk Final harvest 6 wk
Treatments in the dormancy phase Air +4/2 ºC -2 ºC -2 ºC +2 C +2 C Flood No flood Flood No flood Soil frozen Soil not frozen
Trunk sapflow Scots pine Silver birch summer
Short root production in pine 200 180 Short root length production (mm) 160 140 120 100 80 60 40 NOFROST+NOFLOOD NOFROST+FLOOD FROST+NOFLOOD FROST+FLOOD 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Growth season 1 Winter Growth season 2
Fine root biomass Scots pine Silver birch
Shoot phenology Pine: Shoot elongation Birch: Leaf expansion 12/16/2014 19
Biomass of needles and leaves Scots pine: new needles Silver birch: leaves
Conclusions on dormancy waterlogging Shoot phenology: Clear effect of soil freezing but not waterlogging Trunk sap flow: Different patterns between species in FROST & FLOOD Fine root production: Delayed by FROST & FLOOD in pine, compensatory growth occurred Fine root biomass: Elevated in FROST & FLOOD as compared with FLOOD only 12/16/2014 21
Waterlogging of Scots pine Phase: mid of growing season Start of flood End of flood Fv/Fm 0.5 1 3 5 Time from start of flood, wk
Implications of waterlogging on silviculture Excess of water harmful, especially in the growing season Growth losses Trees prone to wind throw due to superficial root system Increased risk for drought stress due to declined root system
Kiitos