Timing of snowmelt. SnoEco

Transcription

1 SnoEco: High Arctic ecosystem responses to chnges in snow cover Elisbeth J. Cooper - study t the plot nd lndscpe scle UiT- The Arctic University of Norwy Tromsø, Norwy Timing of snowmelt..is very importnt determintor of strt of growing seson. => How does winter snow depth, timing of snow melt, winter/ summer temperture nd moisture ffect plnt growth nd ecosystem processes? => By mnipulting snow cover nd observing on the lndscpe scle, we cn strt to investigte these reltionships. SnoEco Decomposers Soil invertebrtes Microbes: bcteri + fungi Respirtion rtes SnoEco PLOT COMMUNITY LANDSCAPE Snow depth Winter soil temp Snow free period Herbivores Plnt phenology Growing Seson Length Plnt qulity & growth Soil nutrient sttus Plnt phenology Growing Seson Length Plnt qulity & growth Decgon NDVI sensors mounted t 2 m height progrmmble (every 4hrs) wvelengths 65 nm nd 8 nm Tetrcm NIR digitl cmer mounted on hillside t ~25 msl fully progrmmble (4 imges dily) wvelengths pprox. equl to TM bnds 2, 3, 4 GrdenWtch cmer mounted t 2 m height progrmmble (every 4hrs) RGB wvelengths 1

2 Experimentlly mnipulted snow in Adventdlen, Svlbrd, 78N 12 Snowfences nd 12 controls, 2 vegettion types (Heth nd Medow). Also nturlly erly melt nd removed snow plots. Fences: 6m x 1,5m Perpendiculr to min winter wind direction - from est Experimentlly incresed snow => lter snowmelt Drys octopetl Cssiope tetrgon Slix polris Sxifrg oppositifoli Alopecurus borelis Luzul rcut Bistort vivipr Oxyri digyn Ppver dhlinum Stellri crssipes Pediculris hirsut Cerstium rcticum Crdmine bellidifoli PhDs: Philipp Semenchuk, Nnn Bggesen Msters: Sbine Rumpf, Holly Abbndonto, Judith Winkler, Cecilie Amtorp. PostDocs: Mrk Gillespie, Helen Anderson 8 Vegettive stges 4 Reproductive stges 144 plots, weekly resolution (213) 215 Phenology Growth Cooper et l 211 Mllik et l 211 Semenchuk et l 213, 215 Rumpf et l 214 timing of development uickly to climtic fctors 24 July 28 Slix polris Dely in every spect of phenologicl development Julin Dys Slix polris, Vegettive 27 Blck = Untreted Red = Fence Julin Dys Slix polris, Reproductive 27 Blck = Untreted Red = Fence Before Seson Strt of Seson Furled Flower Buds Flowers Flowers Senesced Ripe Seedheds Green Leves Senescence 25% 5% 75% Senesced Senescence All yers Senescence 5 All tretments Senescence 5 Dy of Yer Dy of snowmelt Dy of snowmelt Weeks since 2 July Heth, Medow, Moist Medow Depth -2, 2-5cm Yer Similr pttern s snowmelt but responds to tretments. Dely in senescence smller thn dely in snowmelt Abbndonto et l in prep Deep snow enhnced soil N content ( NO3 nd NH4), especilly in the moist res. Dee 2

3 et l 215 Chlorophyll content of Slix leves higher in deeper snow thn control plots N content of Slix leves were higher under deep snow thn in control plots l 215 GROWTH Leves of Bistort nd Luzul were lrger in deep snow thn in control plots Sesonl shoot growht (cm) Cssiope shoot growth Control Tretment b No. of leves / sesonl shoot Cssiope lef production Control Tretment 8 b Fence estblishment +1 Yers since tretment strted Fence estblishment +1 Yers since tretment strted Lower growth behind fences Mllik et l 211 GROWTH Species respond differently. Thwing Degree Dy of snow free period best reltionship to size. =>Temperture determines plnt size. Plnts tht strt growing erly, lso stop growing erly (periodic species). => Some species responded positively to deeper snow (Bistort, Drys, Alopecurus, Luzul): incresed nutrient vilbility. Lter flowering nd fewer flowers behind fences Rumpf et l 214 Cooper et l 211 3

4 Cssiope 27 % Seed germintion # Seeds/ Cpsule Seed germinition (%) Seed germintion 5 Number of seeds b Control Fenced Control Fenced No. of seeds per cpsule Mllik et l 211 Germintion 28: reduced for seeds from fence plot plnts Cssiope Drys Cssiope Drys Number of flowers 28, 29, 211: Fewer flowers behind fences in deep snow plots. Lter melt out, shorter time for flower development? Flower bud primordi ffected previous yer? However: 2, 212: Fewer flowers fter wrm event in winter Semenchuk Snow cting et l s 213, n protective 215 lyer Semenchuk et l 213 shrubby Cssiope, 15-2 cm bove the ground Experimentlly mnipulted snowdepth nd melt Phenology: erlier green up with erly melt if subsequent wrmer temps, lte melt delyed erly seson phenology. Senescence: some response to snow melt, prtly light controlled. GSL: species specific: some re periodic species, others just kept growing.. Drys is more compct, only old sed heds exposed Growth: relted to Thwing Degree Dys: generlly reduced growth nd higher % BG with lter snow melt- BUT deeper snow => higher nutrients, some species benefitted (eg Bistort). Reproductive success: generlly relted to GSL => reduced flowering nd vible seeds with lter melt- BUT deep snow protected flower buds in mild periods with snow melt midwinter. 4

5 Soil nd ir temperture ( C) 1/7/7 1/8/7 1/9/7 1//7 1/11/7 1/12/7 1/1/8 1/2/8 1/3/8 1/4/8 1/5/8 1/6/8 1/7/8 1/8/8 Wter content (%Vol) B C Soil moisture Controls Snow depth Controls Temp difference Men: 6.5C, Mx: 17C Soil moisture Fences Snow depth Fences Fences Controls Air temperture t 4 m Behind fences deep snow: wrmer nd more stble soil tempertures Snow built up c1m deeper behind fences Hethfence / snow effect Snow depth (cm) Ecosystem CO 2 flux gcm Autumn / Winter Spring/ Summer 64% 42% 64% 56% % 36% 58% 36% Heth Control Heth Fence Medow Control Medow Fence 12 non gs Heth Control Heth Fence gs Medow Control Medow Fence 8 6 Heth Control Heth Fence Medow Control Medow Fence Ecosystem CO 2 flux gcm -2 2 Autumn / Winter Spring/ Summer 4 2 Under deep snow nnul respirtion incresed from 125=> 144 gcm -2 in Heths nd 162=>196 gcm -2 in Medows Non-growing-seson respirtion incresed from 56% (Heths) nd 42% (Medows) => 64% (both) Morgner et l 2 Dely of phenophse due to fence (# weeks lter thn control) Green-up Flowering Senescence Seed dispersl Length of time needed from snowmelt to rech phenophse. Difference (in weeks) due to fence Green-up Flowering Senescence Seed dispersl 5

6 Chnge in durtion due to fence Length of growing seson (dte of senescence-green-up) Length of reproductive period (dte of seed dispersl- dte of flowering) 6