1Biology and Ecology of ConifersWhat is the effect of conifers being evergreen?How do conifers live to a great age and grow so tall? Why do conifer forest burn so often?L6 S1Foliage retentionMaureen KennedyTrunkCurrent year1 year-old234567What is the effect of conifers being evergreen?Needles store nutrients andcarbohydrate that is mobilizedin spring for new growthL6 S2Douglas fir, Pseudotsuga menziesiiWhy aren’t all plants evergreen?Why is so much of Washingtoncovered by evergreen conifers?What is the advantage of beingdeciduous rather than evergreen? Most conifers are evergreenThe Evergreen StateL6 S3MONTANECONIFEROUSFORESTNORTHERNCONIFEROUSFORESTALPINETUNDRADECIDUOUSFORESTTROPICALFORESTTROPICALFORESTTEMPERATEDECIDUOUSFORESTARCTICTUNDRAConifer distributionHighElevationLowMoisture Availability LowHighLife on the edge of the good times!L6 S4What is the advantage of the deciduous habitover the evergreen habit?Deciduous plants are frequently faster growing than evergreenplants and can rapidly exploit favorable and reliable habitats. Theirleaves do not require to withstand severe cold or desication, theirphotosynthetic rates are higher, and leaf abscission enables nutrientsand carbohydrates to be withdrawn into the plant for re-useWhy is so much of Washington covered byevergreen conifers?Frequent periods of summer drought but mild wet winters may favorslower growth outside of summer rather than dependence on rapidsummer growth.In general, conifers may succeed over deciduous trees when the summer growthperiod short, for example reduced by drought, or late spring and early winter.L6 S5Forest fires in natural ecosystemsYellowstone National Park 1988Why do conifer forest burn so often?L6 S62Many conifer species are adapted to withstandfire and/or regenerate following fireForest fire occurs naturallyThick fire resistant bark,Sequoiadendron, PinusponderosaOver much of the western USA conifer speciesform ‘dry’ land forestsSerotinous cones, ecotypes ofPinus contorta, and PinusattenuataL6 S7Satellite photograph of the Biscuit Fir, S.W. Oregon August 14, 2002L6 S8The Biscuit Fire started as a result of a series of lightning strikeson July 13, 2002 on the Siskiyou National ForestIt cost an estimated $135m to suppress at the date of containment.The fire grew to 499,570 acres over two monthsOn July 11, 2002, a Red Flag Warning was issued for dry lightningacross southwestern Oregon beginning July 12.There were a number of lightening strikes from the samelightening cell and a number of fires were started on hill tops withno road access. Some fire staff had already been sent to NewMexico and Colorado fires.There was difficult, i.e., not safe access, and initially the fire hadlow regional priority.L6 S9Forest Fires in the United StatesNote the frequency and distribution of lightning caused firesL6 S10An estimated 16 million thunderstorms occur each year on earth,causing some 100 lightning strokes to the ground per second.Between 50 and 80 percent of forest fires in western NorthAmerica are lightning caused. There are some 4,871 lightningfires per year on federally-owned land in the US.Lightning never strikes twice?http://www.chaseday.com/lightning.htmL6 S11Plant of the DayPinus attenuata, knobcone pineSerotinous cones3Why are forest fires a problem?Fire suppression has resulted in theaccumulation of high fuel loadsL6 S12Fire in ponderosa pine forestPrior to 1900 low elevation ponderosa pine forests burned every 5 to 30 yearsMost fires burned only the forest floor reducing fuel and killing small trees This produced open stands of large trees with grassy understories, some shrubsand occasional thickets of young trees.L6 S13Effects of fire exclusion in Ponderosa pineFire exclusion has produced a dense understory of young Douglas firDeep woody debris and duff give hotter longer lasting fires and poor germinationSince the advent of fire fighting some forests have missed 8 to 10 fire rotationsL6 S14These photos were taken at Lick Creek in theBitterroot Valley of Montana over an eighty-yearperiod. Notice how the old growth ponderosa pinestand is replaced by dense Douglas-fir after firesuppression begins in the 1920s.The consequences of fireprotection in Ponderosa pineExit PowerPointL6 S15Controlled burningGround fireWhat conditions of fuelload, moisture content,temperature and windproduce a fire thatburns the excessundergrowth and smalltrees without burningthe dominant trees?East side of theCascades set in late fallL6 S16The effect of a controlled burnBeforeAfterThe effect of a controlled burnHas sufficient material been removed to prevent a major conflagration?in a Pinus ponderosa forestCrater Lake, lower elevation forest burnt in early spring4Bristlecone pineMale coneFemale conePinus longaevaThe oldest aged specimen is 5,600 yCurrent yearLast year’sempty sporangiaHow do conifers live to a great age and grow so tall? L6 S18Koch et al. 2004.Nature 428, 851-854Reiteration of foliage from existing branch structurePlasticity in foliage as water deficits increaseSequoia sempervirensAbility to transport water to ~125m depends uponwood structureL6 S19Things you need to knowBe Able to describe the function of evergreen foliage and itsadvantage and disadvantage when copared to deciduous foliage and how these relate to different ecologies.L6 S20Be Able to describe adaptations to fire by conifer species. Be Able to describe the effects of fire exclusion inPinus ponderosa forestBe Able to define three contributing factors that enable Sequoia sempervirens to grow to a large