Summary

We measured the distribution of tree biomass and allocation of production in four stands of lodgepole pine (Pinus contorta var. latifolia Engelm.). At the time of sampling the stands were 70-78 years old; two were growing on sites with xeric soil moisture and two on sites with mesic soil moisture regimes. Above-ground biomass ranged from 116.5 t/ha on one xeric site to 313.1 t/ha on one mesic site. Stem biomass represented 68% and 73% of total tree biomass on xeric and mesic sites, respectively, whereas total root biomass represented between 20% and 28% of total lodgepole pine biomass. Fine and small roots represented 4% and 1.5% of total tree biomass on the xeric and mesic sites, respectively. Total net primary productivity (NPP) ranged from 790 g/m2/year (xeric) to 1190 g/m2/year (mesic), and stemwood production represented 20-27% of total NPP (xeric) and 35% (mesic). The below-ground fraction of total productivity was 38-46% (mesic sites) and 55-66% (xeric). Fine and small roots represented 82-94% of below-ground productivity. Allocation of productivity was in the following order: fine and small roots > stems > foliage > coarse roots > branches, for all but the wettest site, where stem production exceeded fine and small root production.

Summary

Nutrient optimisation increased current annual stem volume increment (CAI), after ten years' treatment, from 3 to 14 m3/ha/year, while irrigation had no effect on stem growth. Improved soil nutrient availability increased leaf area index and light-saturated rate of photosynthesis, and changed carbon allocation to stems. Simulations using a boreal-modified version of the BIOMASS model agreed well with field measurements of photosynthesis, and indicated a 20% increase in annual net primary production with simulated climatic warming, due to the earlier start of the growing season.

Summary

The results of two yield optimisation experiments in young Norway spruce stands in northern and south-eastern Sweden are presented, after nine and ten years' treatment, respectively. The experiments aimed to demonstrate the potential yield under given climatic conditions and non-limiting soil water, by optimising the nutritional status of the stands, at the same time as avoiding the leaching of nutrients to groundwater. Fertilisation, with or without irrigation, increased stem volume production by a factor of four in comparison to unfertilised controls.

Summary

The process-based growth model BIOMASS was modified to incorporate low-temperature effects on photosynthetic production in Norway spruce stands growing in northern Sweden. Annual photosynthetic production (or gross primary production, GPP) was simulated for three calendar years, 1990-1992, for stands with low (control) and high (irrigated and fertilised) nutrient availability. The most pronounced loss of 'potential' GPP, caused by low-temperature effects, originated from reduced photosynthetic capacity in spring and early summer, leading to 21-28% losses for control and 19-26% losses for irrigated-fertilised stands.

Summary

Stem respiration rates were measured for ten control and ten irrigated-fertilized (IL) Norway spruce trees, in order to determine effects of stem N concentration on the seasonal course of respiration. The trees, 30 years old and growing in northern Sweden, were measured on seven occasions from June 1993 to April 1994. Total respiration was separated into growth and maintenance respiration for both xylem and phloem bark, in order to explore sources of seasonal variation and mechanisms of fertilization effects on respiration,

Stem respiration increased in response to the IL treatment and was positively correlated with growth rate, volume of living cells and stem N content. No significant effect of IL treatment or N concentration in the living cells was found for respiration per unit volume of live cells. Total stem respiration during the growing season (June to September) was estimated to be 16.7 and 29.7 mol CO2/m2 for control and IL-treated trees, respectively. Growing-season respiration accounted for approximately 64% of total annual respiration. Estimated growth respiration varied between 40 and 60% of total respiration during the growing season, depending on the method. Between 75 and 80% of the live cell volume in the stems was in the phloem, and phloem maintenance accounted for about 70% of maintenance respiration. It was concluded that the best basis for expressing rates of stem growth and maintenance respiration in young Norway spruce trees is stem surface area, because most of the living cells were found in the phloem, and the living xylem cells were concentrated in the outer growth rings.

Axelsson, B., and S. Brakenhielm, pp. 25-64. SWECON investigation sites - biological and physiographical features.

Flower-Ellis, J.G.K., and H. Persson, pp. 125-138. Investigation of structural properties and dynamics of Scots pine stands.

Persson, H., pp. 251-260. Death and replacement of fine roots in a mature Scots pine stand.

Larsson, S., and O. Tenow, pp. 269-306. Needle-eating insects and grazing dynamics in a mature Scots pine forest in Central Sweden.

Ågren, G.I., B. Axelsson, J.G.K. Flower-Ellis, S. Linder, H. Persson, H. Staaf, and E. Troeng, pp. 307-313. Annual carbon budget for a young Scots pine.

Summary

An annual carbon budget was calculated for a typical 14-year old Scots pine in plot IhII at Ivantjarnsheden, Jadraas, based upon independent measurements over the period 1974-76. Net photosynthetic production was estimated at 1723 g C, with carbon utilisation distributed between respiration (173 g C - about 10%), stem growth 145 g C (9%), branch growth 132 g C (8%), current needle growth 286 g C (17%) and fine root growth 960 g C (57%). With an effective ground area per tree of 10 square metres and a dry biomass/carbon ratio of 2.0, these figures may be transformed to give total net primary production in dry biomass terms of 305 g/m2/year (above-ground = 113; below-ground = 192 g/m2/year).

Albrektson, A., pp. 315-327. Relations between tree biomass fractions and conventional silvicultural measurements.

Bringmark, L., pp. 341-361. Ion leaching through a podsol in a Scots pine stand.

Granhall, U., and T. Lindberg, pp. 333-340. Nitrogen input through biological nitrogen fixation.

Persson, T., E. Baath, M. Clarholm, H. Lundkvist, B.E. Soderstrom, and B. Sohlenius, pp. 419-459. Trophic structures, biomass dynamics and carbon metabolism of soil organisms in a Scots pine forest.

Summary

Data are presented on dry matter and N, P, K, Ca and Mg contents and movements in soil and ground vegetation for a 30-year old natural jack pine stand in northern Ontario; 9, 70, 16.5, 1.4, 8.2, 11.2 and 1.8 g/m2, respectively - less than in many pine species of comparable age in other parts of the world. A comparison with nutrient contents in younger (20 yr) and older (65 yr) stands on the same site indicated that most nutrient accumulation in vegetation takes place in the first decades of stand development. Annual nutrient uptake by all vegetation was 3.2, 0.2, 1.9, 2.1, and 0.3 g/m2 N, P, K, Ca, and Mg, respectively. Between 71% and 89% of the elements taken up annually by trees were returned to the soil by litterfall and leaf wash. Forest floor organic matter built up with stand age, and N, P, and Mg accumulated in this material faster than the other elements. Soil reserves of plant-available or mineralizable nutrients were maintained by nutrient replenishment from precipitation and vegetation-soil nutrient cycling. It is concluded that removal of elements from the ecosystem by logging or burning should not result in significant impoverishment of this site.

Summary

Annual amounts of N, P, K, Ca and Mg in litterfall, throughfall and stemflow were measured in a 30-year old jack pine stand on a coarse glacial outwash soil in northern Ontario. Litter from ground vegetation and from the pine overstory was estimated. The nutrient content of precipitation was measured and the quantity of nutrients in leaf wash deteremined. The most important source of N, P, Ca and Mg for the forest floor was tree litter (51-69% of total, depending on the element), wheras throuhgfall supplied most K (54%). Ground vegetation litter contributed significant amounts of nutrients (7-23%) but stemflow added little (1-8% of total). K in throuhgfall was derived primarily from precipitation entering the ecosystem. The forest floor received annual totals of 3.0, 0.2, 1.9, 2.2, and 0.3 g/m2 of N, P, K, Ca, and Mg, respectively from the processes studied. Most of the nutrients in these totals returned to the forest floor from the vegetation.

Summary

Concentration and mass of nutrient elements (N, P, K, Ca, Mg, Cu, Fe, Mn, Na, Zn) were investigated in 110-year old lichen woodland in the subarctic of eastern Canada. Biomass plus soil organic matter contained 41% of the total nutrient mass in the system. Calcium (85%), P (76%), Mg (67%) and K (64%) were found largely in live biomass, whereas N was found equally in biomass plus organic soil (45%) and mineral soil (55%). Micronutrients occurred mainly in the soil inorganic fraction. Nitrogen was acutely deficient for rapid growth. Potential loss of Ca under logging and burning regimes consistently exceeded exchangeable soil reserves. To evaluate these impacts realistically, more complete knowledge is needed of net atmospheric and soil inputs and vegetation requirements. Dominant tree, shrub and lichen genera all differed strongly in the concentration of tissue elements. Among vascular species, total element concentration related inversely to species abundance. Since evergreen perennial plants of low nutrient concentration prevailed at maturity, we suggest that nutrients increasingly limited the abundance of deciduous shrubs.

Moore, T.R. (1980) The nutrient status of subarctic woodland soils. Arctic and Alpine Research 12, 147-160.

Summary

Fifteen lichen woodlands were studied in the sub-arctic of eastern Canada. Results indicate a strong dominance by Picea mariana and Cladonia alpestris. Mean tree density was 556/ha, of which over 75% were P. mariana, with P. glauca and Larix laricina present as only minor components. Lichen (78% of which was C. alpestris) covered 97% of surface area, and shrubs 17%. Total live biomass on a representative site was 4,629 g/m2, of which 75% was P. mariana and C. alpestris; the only other significant species was Betula glandulosa. Biomass was distributed between tree, shrub and ground layer species in the approximate ratio 3:1:1. Lichen and leaves represented one-third of the total; stem and roots constituted 40% and 28% of total biomass. Biomass levels and tissue distribution were similar to other woodlands in the immediate area and to Larix woodlands in the former USSR. Lichen woodland had much lower total biomass, higher root/shoot ratio, and high shrub and ground layer biomass compared with boreal confier and temperate deciduous forest.