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Environmental control of CO2-assimilation and leaf conductance in Larix decidua Mill. (1981)

Benecke, U. ; Schulze, E. -D. ; Matyssek, R. ; [et al.]

Springer

Oecologia 50 (1981), S. 54-61

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary CO2-assimilation and leaf conductance of Larix decidua Mill. were measured in the field at high (Patscherkofel, Austria) and low (Bayreuth, Germany) elevation in Europe, and outside its natural range along an altitudinal gradient in New Zealand. Phenology of leaf and stem growth showed New Zealand sites to have much longer growing seasons than in Europe, so that the timberline (1,330 m) season was almost twice as long as at the Austrian timberline (1,950 m). The maximum rates of photosynthesis, A max, were similar at all sites after completion of leaf growth, namely 3 to 3.5 μmol m-2 s-1. Only the sun needles of the Bayreuth tree reached 3.5 to 5 μmol m-2 s-1. Light response curves for CO2-assimilation changed during leaf ontogeny, the slope being less in young than in adult leaves. The temperature optimum for 90% of maximum photosynthesis was at all sites similar between ca. 12–28°C for much of the summer. Only at the cooler high altitude timberline sites were optima lower at ca. 10–16°C in developing needles during early summer. A linear correlation existed between A max and leaf conductance at A max, and this showed no difference between the sites except for sun needles at Bayreuth. Leaf conductance responded strongly to light intensity and this was concurrent with the light response of CO2-uptake. A short-term and a long-term effect were differentiated. With increasing age maximum rates of CO2-uptake and leaf conductance at A max increased, whereas short-term response during changes in light declined. The stomata became less responsive with increasing age and tended to remain open. The stomatal responses to light have a significant effect on the water use efficiency during diurnal courses. A higher water use efficiency was found for similar atmospheric conditions in spring than in autumn. Stomata responded with progressive closure to declining air humidity in a similar manner under dissimilar climates. Humidity response thus showed insensitivity to habitat differences. From the diurnal course of gas-exchange stomata were more closed at timberline (1,330 m) than at lower elevations but this did not lead to corresponding site differences in CO2-exchange suggesting Larix may not be operating at high water use efficiency when air is humid. The main difference between habitats studied was in the time necessary for completion of needle development. Similarity in photosynthesis and leaf conductance existed between sites when tree foliage was compared at the same stage of development. Length of growing season and time requirement for foliar development appear to be a principle factor in the carbon balance of deciduous species. The evergreen habit may be more effective in counterbalancing the effects of cool short summers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00378793

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Carbon uptake and respiration in above-ground parts of a Larix decidua × leptolepis tree (1988)

Matyssek, R. ; Schulze, E. D.

Springer

Trees 2 (1988), S. 233-241

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ISSN: 1432-2285

Keywords: Larix ; Carbon uptake ; Respiration ; Carbon balances ; Water loss ; Sun and shade branches

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Shade needles of hybrid larch (Larix decidua × leptolepis) had the same rates of photosynthesis as sun needles per dry weight and nitrogen, and a similar leaf conductance under conditions of light saturation at ambient CO2 (Amax). However, on an area basis, Amax and specific leaf weight were lower in shade than in sun needles. Stomata of sun needles limited CO2 uptake at light saturation by about 20%, but under natural conditions of light in the shade crown, shade needles operated in a range of saturating internal CO2 without stomatal limitation of CO2 uptake. In both needle types, stomata responded similarly to changes in light, but shade needles were more sensitive to changes in vapor pressure deficit than sun needles. Despite a high photosynthetic capacity, the ambient light conditions reduced the mean daily (in summer) and annual carbon gain of shade needles to less than 50% of that in sun needles. In sun needles, the transpiration per carbon gain was about 220 mol mol−1 on an annual basis. The carbon budget of branches was determined from the photosynthetic rate, the needle biomass and respiration, the latter of which was (per growth and on a carbon basis) 1.6 mol mol−1 year−1 in branch and stem wood. In shade branches carbon gains exceeded carbon costs (growth + respiration) by only a factor of 1.6 compared with 3.5 in sun branches. The carbon balance of sun branches was 5 times higher per needle biomass of a branch or 9 times higher on a branch length basis than shade branches. The shade foliage (including the shaded near-stem sun foliage) only contributed approximately 23% to the total annual carbon gain of the tree.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00202378

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