Alm, Jukka

Lehto, Tarja

Repo, Tapani

Roitto, Marja

Sutinen, Sirkka

Wang, Aifang

English

Jukuri

Metla/640053/LKar/07.2010IntroductionClimate change may increase the risk of flooding  □in winter and early spring in boreal forests.Flooded soil is low in oxygen, which disturbs  □root and rhizosphere function. Also, metabolism and growth of plants can be severely affected.The aim of this study was to evaluate the  □effects of flooding and soil frost on Scots pine saplings during their winter dormancy.Responses of Scots pine to wintertime floodingMarja Roitto1,  Aifang Wang1, Sirkka Sutinen1,  Tarja Lehto2,  Jukka Alm1 and Tapani Repo1AcknowledgmentsThe study was financed by the Academy of Finland (Project 640053) and the Finnish Forest Research Institute (project 3489).ConclusionsIn general, pines tolerated hypoxic root  □conditions during the dormancy period.Soil frost caused water stress, changes in  □carbohydrate metabolism and reduced shoot growth. Root growth analyses are in progress.Material and methodsFour-year-old Scots pine saplings from a  □forest plantation site were replanted into root containers (Fig 2, Table 1).The FLOOD and FROST treatments  □took place during winter.FLOOD: the pots were filled with lake water.•	NONFLOOD. •	FROST: soil temperature -2 ºC.•	NONFROST soil temperature +2 ºC.•	FROST+FLOOD: soil was frozen after water •	addition. Needles were sampled for dark-adapted  □chlorophyll fluorescence (Fv/Fm), water potential and starch analyses.Trunk sap flow was measured by a heat  □balance method by two trees per treatment. The biomass of the above-ground  □parts of the trees was measured.ResultsSoil:  □Oxygen concentration was low in the •	flooded pots during the simulated winter (Fig 3).Shoots: □Chlorophyll fluorescence: recovery •	after low levels in the winter (Fig 4).The lowest sap flow was recorded in •	FROST+FLOOD after the treatments (Fig 5).FROST reduced foliar water potential •	in winter and in the beginning of the following growing season (Fig 6).FROST increased starch •	concentration in the needles in the following growing season (Fig 7).FROST tended to decrease shoot •	growth (Fig 8).Growth season I Winter Growth season IIDuration (weeks) 9 3 6 9 3Photon flux density(µmol m-2 s-1)300 200 200 300 200Photoperiod (day/night) h18/6 6/18 6/18 18/6 6/18Air temperature(day/night) °C20/15 20/15 4/2 20/15 20/15Soil temperature–FROST–NONFROST15 15- 2+215 15Figure 2. The study was performed in a special type of growth chambers, dasotrons, where air and soil conditions can be controlled independently. Photo: Eija Koljonen.Table 1. Chamber conditions during the experiment. The season was changed gradually.Figure 4. Chlorophyll fluorescence (Fv/Fm) in the needles. Stars indicate the difference between the frost treatments (P<0.05). Figure 5. Trunk sap flow.Figure 6. Water potential in the Scots pine needles.  Stars indicate differences between the frost (   ) and flood (   ) treatments (P<0.05).FINNISH FOREST RESEARCH INSTITUTEFigure 8. The biomass of current year needles in Scots pine saplings. Means + SD. 020406080100120Soil oxygen (%)Frost + FloodFrost + NonfloodNonfrost + FloodNonfrost + Nonflood0                    50                  100                150                 200                 250                 300Time (days)summer winter00.10.20.30.40.50.60.70.80.90 50 100 150 200 250 300Chlorphyll fluorescnecn (Fv/Fm)Time (days)Frost + FloodFrost + NonfloodNonfrost + FloodNonfrost + Nonfloodsummer winter0200400600800100012000                    50                  100                150                 200                 250                 300Time (days)summer winterSap flow (g day-1)Frost + FloodFrost + NonfloodNonfrost + FloodNonfrost + NonfloodFigure 1. Springtime flooding in the forest in Karsikko, Joensuu. Photo: Leena Karvinen.Frost + FloodFrost + NonfloodNonfrost + FloodNonfrost + Nonflood-1.80-1.60-1.40-1.20-1.00-0.80-0.60-0.40-0.200.000 50 100 150 200 250 300Water potential (MPa)Time (days)summer winterStarch (%)8.07.57.06.56.05.55.04.54.03.53.00                    50                  100                150                 200                 250                 300Time (days)summer winterfrost+floodfrost+nonfloodnonfrost+floodnonfrost+nonflood020406080100120140160Frost + FloodFrost + NonfloodNonfrost + FloodNonfrost + NonfloodDry mass (g)Figure 3. Six weeks flooding caused hypoxia in soil. Time refers to days from the beginning of the experiment.Figure 7. Starch concentration in the needles. Stars indicate the difference between the frost treatments (P<0.05).1  Finnish Forest Research Institute, Joensuu,  Yliopistokatu 6, P.O. Box 68, FI-80101 Joensuu, Finland. Email: marja.roitto@metla.fi2 School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, P.O. Box 111, FI-80101 Joensuu, Finland

Responses of Scots pine to wintertime flooding

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Responses of Scots pine to wintertime flooding

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