Studies on upper timberline: morphology and anatomy of Norway spruce (<i>Picea abies</i>) and stone pine (<i>Pinus cembra</i>) needles from various habitat conditions

Baig, M. N.; Tranquillini, Walter

doi:10.1139/b76-174

Cited by 75 publications

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“…Current-year needles of stone pine thereby were found to exhibit a 2.75-to 4.5-fold lower cuticular transpiration during winter than Norway spruce (Mt. Patscherkofl, Central Austrian Alps; Baig and Tranquillini, 1976). In a recent publication Anfodillo et al (2002) show a 2.8-fold higher cuticle resistance of stone pine compared with Norway spruce growing in the Dolomites (NE Italian Alps).…”

Section: Discussionmentioning

confidence: 95%

Winter at the Alpine Timberline. Why Does Embolism Occur in Norway Spruce But Not in Stone Pine?

2003

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Conifers growing at the alpine timberline are exposed to frost drought and freeze-thaw cycles during winter-stress factors known to induce embolism in tree xylem. The two dominant species of the European Central Alps timberline were studied: Norway spruce (Picea abies [L.] Karst) and stone pine (Pinus cembra), which usually reaches higher altitudes. We hypothesized to find embolism only at the timberline and to observe less embolism in stone pine than in Norway spruce due to avoidance mechanisms. Seasonal courses of embolism and water potential were studied at 1,700 and 2,100 m during two winter seasons and correlated to vulnerability (to drought-induced embolism), leaf conductance, and micrometeorological data. Embolism was observed only at the timberline and only in Norway spruce (up to 49.2% loss of conductivity). Conductivity losses corresponded to low water potentials (down to Ϫ3.5 MPa) but also to the number of freeze-thaw events indicating both stress factors to contribute to embolism induction. Decreasing embolism rates-probably due to refillingwere observed already in winter. Stone pine did not exhibit an adapted vulnerability (50% loss of conductivity at Ϫ3.5 MPa) but avoided critical potentials (minimum Ϫ2.3 MPa): Cuticulare conductance was 3.5-fold lower than in Norway spruce, and angles between needles and axes were found to decrease in dehydrating branches. The extent of conductivity losses in Norway spruce and the spectrum of avoidance and recovery mechanisms in both species indicates winter embolism to be relevant for tree line formation.During the winter season, trees growing at the alpine timberline have to withstand conditions extremely unfavorable for plant water status. Water supply is permanently blocked because soil and stem are frozen, on the other hand, the shoot is exposed to water losses ("Frosttrocknis"; e.g. Michaelis, 1934;Pisek and Larcher, 1954;Larcher, 1972;Tranquillini, 1980) and to frequent freeze-thaw events (Gross et al., 1991).Drought and freeze-thaw cycles are known to induce the formation of gas bubbles in the water transport system of trees. This "embolism" interrupts the transmission of negative pressure to the soil and subsequently the flow of water through xylem conduits ("cohesion theory"; e.g. Boehm, 1893;Dixon and Joly, 1894;Richter, 1972;Jackson and Grace, 1994). Drought stress leads to high tensions in the water columns causing entry of air bubbles (air seeding) from adjacent air-filled conduits through the pits (e.g. Zimmermann, 1983;Tyree et al., 1994). Vulnerability analysis revealed species-specific water potential () thresholds for the onset of cavitation, whereby conifers were found to be very resistant due to their special pit anatomy (see e.g. Sperry and Tyree, 1990;Cochard, 1992;Jackson et al., 1995;Brodribb and Hill, 1999). Freeze-thaw events induce embolism because air is not soluble in ice-remaining gas bubbles can expand during thawing and lead to cavitation. However, this effect was reported to be of minor importance in conifers (e.g. Sucoff, 1969;Ro...

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Section: Discussionmentioning

confidence: 95%

Winter at the Alpine Timberline. Why Does Embolism Occur in Norway Spruce But Not in Stone Pine?

2003

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“…Decreasing carbon balance with altitude is due to the shortening of the growing season (Wardle 1971;Tranquillini 1979;Stevens & Fox 1991), as well as a decline in net photosynthetic rates (Pisek & Winkler 1958;Benecke & Nordmeyer 1982; but see KoÈ rner 1998). Incomplete tissue maturation when carbon balance is reduced makes trees vulnerable to direct factors such as low temperatures or winter desiccation (Michaelis 1934a,b;Wardle 1971;Baig & Tranquillini 1976). Such damage further reduces the energetic reserves of any survivors so that they become progressively more susceptible to environmental pressures (a positive feedback).…”

Section: Introductionmentioning

confidence: 99%

Tree recruitment at theNothofagus pumilioalpine timberline in Tierra del Fuego, Chile

2000

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Summary1 Nothofagus pumilio forms an abrupt alpine timberline (AT) at 690 m a.s.l on Balseiro mountain, 54 S, Tierra del Fuego, Chile. Fruit and seed rain (quantity and quality), emergence, density and survival of seedlings were studied across an altitudinal gradient (450±740 m) from within the forest to above the AT. 2 Fruit rain generally declined with altitude but increased between 630 and 690 m before falling sharply beyond the AT. The proportion of seed-bearing fruits, seed viability and seed mass also declined with increasing altitude, but showed no recovery in the vicinity of the AT. 3 Fruit rain decreased exponentially with distance into the alpine zone, so that e ective dispersal rarely exceeded 20 m beyond the AT and few of these fruits contained seeds. 4 Seedling emergence and density decreased with altitude both within the forest and into the alpine zone so that seedlings were found no more than 10±20 m above the AT. Even in 1996, when fruit production was high, successful seedling recruitment was limited to lower altitudes. 5 There was little correlation between altitude and the percentage survival of naturally occurring seedlings within the forest. However, transplanted seedlings survived better at the AT itself than immediately inside the forest, and showed high mortality in the alpine zone. 6 The most severe bottlenecks for tree recruitment within the forest appeared to be seedling emergence and seed production. Above the AT, seed viability and emergence were the principal bottlenecks. 7 Although not all demographic variables declined altitudinally, the overall probability of adult establishment decreased with increasing altitude and became very low once the protection by the tree canopy became unavailable. A demographic model explaining the origin and abrupt character of the AT studied is presented.

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“…During the late autumn and persisting throughout the winter, soil and stem water freeze, thus becoming largely unavailable to the foliage (Sakai 1982;Sakai and Larcher 1987). Cuticular water loss may greatly exceed impeded absorption during the winter, possibly owing to inadequate cuticle development in a short cool growing season (Wardle 1968;Baig and Tranquillini 1976;Tranquillini 1979) and/or cuticle abrasion by windblown ice particles (Hadley and Smith 1983. Such winter desiccation may be the primary cause of the krummholz growth form (Hadley and Smith 1983) and a major determining factor of timberline in areas subject to a continental climate (Tranquillini 1979).…”

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confidence: 99%

Winter water relations of timberline larch (Larix leptolepis Gord.) on Mt. Fuji

Maruta

1996

Trees

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AbstractmA krummholz mat of larch, Larix leptolepis, is the predominant growth form near the upper limit (near 2500 m) of the timberline ecotone on the south slope of Mt. Fuji, Japan. On the south-eastern slope, the tree line is lowered to 1600 m because of the last volcanic eruption. The extent and causes of winter desiccation were compared in timberline larch between 2500 m and 1600 m elevation over two winters. Bark abrasion due to wind-blown fine volcanic gravels caused a decrease in bark resistance to water loss and resulted in severe desiccation damage to current-year shoots of krummholz larches in the winter of 1986 -87 at 2500 m, whereas abraded shoots at 1600 m maintained high water content during both winters. In the winter of 1985 -86, shoots of krummholz larches at 2500 m did not experience bark abrasion and high water contents were maintained. Experimental abrasion of shoot surfaces resulted in similar results at each elevation. Thus, in timberline larch at 2500 m, abrasion by wind-blown fine volcanic gravels is the primary factor causing winter desiccation damage and krummholz formation. Based on field experiments, the estimated amount of water movement to non-abraded shoots was the same for the two elevations. At 2500 m, water movement to abraded shoots was less than to non-abraded shoots, but the reverse situation was noted at 1600 m. Water supply to abraded shoots at 2500 m was limited and insufficient to compensate for water loss. A cause of limited water supply at 2500 m may be xylem embolism.

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Studies on upper timberline: morphology and anatomy of Norway spruce (Picea abies) and stone pine (Pinus cembra) needles from various habitat conditions

Cited by 75 publications

References 0 publications

Winter at the Alpine Timberline. Why Does Embolism Occur in Norway Spruce But Not in Stone Pine?

Winter at the Alpine Timberline. Why Does Embolism Occur in Norway Spruce But Not in Stone Pine?

Tree recruitment at theNothofagus pumilioalpine timberline in Tierra del Fuego, Chile

Winter water relations of timberline larch (Larix leptolepis Gord.) on Mt. Fuji

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