Analysis of gas exchange of Merkus pine populations by the optimality approach

We hypothesized that northern and northeastern Thai populations of Merkus pine (Pinus merkusii Jungh. et de Vriese), which differ in the duration of their grass stage and which originate from slightly different climates in terms of water availability, differ in their gas exchange characteristics. We compared CO(2) exchange response to irradiance, diurnal regulation of leaf conductance within a 10-day period and structural properties among the populations. We used a model, which is based on the concept of optimal stomatal regulation, to analyze CO(2) exchange and transpiration rates. The two geographical groups did not differ in CO(2) exchange response to irradiance, diurnal transpiration, or water use. Mean stomatal length was significantly greater in the northeastern population than in the northern populations, but stomatal frequency did not differ among populations. First-year shoot growth and dry matter production, allocation of nitrogen to needles and root:shoot ratios were similar in the two geographical groups. Genotypic variation in the duration of the grass stage was not reflected in variation in gas exchange, indicating that the grass stage is an adaptation to more site-specific conditions. The modeled response of CO(2) exchange rates to irradiance fitted well the rates measured under laboratory conditions. The transpiration model, which utilized maximum leaf conductance and other parameters derived from the CO(2) exchange measurements, also fitted well the transpiration rates measured in a greenhouse under changing environmental conditions.     

Effects of genetic entry and competition by neighbouring trees on growth and wood properties of cloned Norway spruce (Picea abies)

? The aim of this work was to study both the effects of genetic entry and competition by neighbouring trees on growth, yield, wood density traits and fibre properties of 20 Norway spruce clones grown in an experimental trial located in southern Finland. The material included 10 Finnish clones, 2 Russian clones and 8 provenance-hybrids clones, the latter ones representing crosses between Finnish and foreign parent trees.

? We found that, compared to growth and yield, wood density traits and fibre properties showed, on average, lower phenotypic variations. Moreover, significant differences could be observed among the clones regardless of the trait (p < 0.05). Conversely, on average, no clear differences could be found between Finnish, Russian and provenance-hybrids clones in most of the studied traits.

? The marked differences among the clones, and lack of clear differences among the provenances suggested that any ranking, regarding different traits, should be based on individual clones. The phenotypic correlations between different traits ranged from moderate to strong suggesting that selection based on one trait would affect other traits. Regardless of clone, the growth of trees (e.g. breast height diameter) decreased and the wood density increased with increasing competition by neighbouring trees, which was expressed by competition index.

     

Seasonal acclimation of photosystem II in Pinus sylvestris. II. Using the rate constants of sustained thermal energy dissipation and photochemistry to study the effect of the light environment

Photosynthesis in evergreen conifers is characterized by down-regulation in autumn and rapid up-regulation in spring. This seasonal pattern is largely driven by temperature, but the light environment also plays a role. In overwintering Scots pine (Pinus sylvestris L.) trees, PSII is less down-regulated and recovers faster from winter stress in shaded needles than in needles exposed to full sunlight. Because the effect of light on the seasonal acclimation of PSII has not been quantitatively studied under field conditions, we used the rate constants for sustained thermal energy dissipation and photochemistry to investigate the dynamics and kinetics of the seasonal acclimation of PSII in needles exposed to different light environments. We monitored chlorophyll fluorescence and needle pigment concentration during the winter and spring in Scots pine seedlings growing in the field in different shading treatments, and within the crowns of mature trees. The results indicated that differences in acclimation of PSII in overwintering Scots pine among needles exposed to different light environments can be chiefly attributed to sustained thermal dissipation. We also present field evidence that zeaxanthin-facilitated thermal dissipation and aggregation of thylakoid membrane proteins are key mechanisms in the regulation of sustained thermal dissipation in Scots pine trees in the field.     

Analysis of organic and inorganic sulfur constituents and 34S-isotopes in dated sediments of Forest Lakes in southern Finland

A modification of the Jonson-Nishita digestion-distillation apparatus was used to determine the S constituents of sediments from three forest lakes (Munajärvi, Orajärvi, and Sorvalampi) in southern Finland. Lakes Munajärvi and Orajarvi had undergone marked acidification during the past 30 yr or so presumably due to acid deposition as revealed from sedimentary diatom and chrysophycean remains. Organic S constituted a major part of the total S, and during the recent years the portion of C-bonded S increased in the Lakes Munajarvi and Sorvalampi more strongly than the portion of sulfate esters. In the case of Lake Orajärvi the concentration of total S increased by a factor of 2.3 from its preindustrial level which seems to be due to an increase of both C-bonded S and SO₄ ^?2. Coincidentally with the up core increase in total S, the sediment cores of Orajärvi and Munajarvi were strongly depleted of the ³⁴S-isotope (r = ?0.83 in Orajärvi n = 15, and r = ? 0.84 in Munajärvi n = 10). This implies that the recent changes in sedimentary S are related to the increasing input of airborne pollutant S since about 1850 in Orajarvi and 1950 in Munajärvi provided that the ²¹⁰Pb dating of the cores is correct and diagenetic changes have not greatly altered the vertical distribution of S in these sediments.     

Nitrification in forest soil of different pH as affected by urea,ammonium sulphate and potassium sulphate

Nitrification was inhibited by ammonium sulphate and potassium sulphate added to soil from the organic horizon (pH 4.7) of a Myrtillus-type pine forest. Urea did not inhibit nitrification. Soil pH was slightly decreased by the salts but increased by urea. The salts increased soil electrical conductivity more than urea did. The inhibition of nitrification following salt treatments was probably due to a decrease in soil pH and not to osmotic effects. In acid conditions, the salts had a less inhibitory effect on CO₂ production than on nitrification, indicating that nitrifying bacteria were more sensitive than other organisms to the salts.     

Methane oxidation in boreal forest soils: kinetics and sensitivity to pH and ammonium

In soil incubation experiments we examined if there are differences in the kinetic parameters of atmospheric methane (CH₄) oxidation in soils of upland forests and forested peatlands. All soils showed net uptake of atmospheric CH₄. One of the upland forests included also managed (clear-cut with or without previous liming or N-fertilization) study plots. The CH₄ oxidation in the forested peat soil had a higher K_m (510 μl l⁻¹) and V_max (6.2 nmol CH₄ cm⁻³ h⁻¹) than the upland forest soils (K_m from 5 to 18 μl l⁻¹ and V_max from 0.15 to 1.7 nmol CH₄ cm⁻³ h⁻¹). The forest managements did not affect the K_m-values. At atmospheric CH₄ concentration, the upland forest soils had a higher CH₄ oxidation activity than the forested peat soil; at high CH₄ concentrations the reverse was true. Most of the soils oxidised CH₄ in the studied pH range from 3 to 7.5. The pH optimum for CH₄ oxidation varied from 4 to 7.5. Some of the soils had a pH optimum for CH₄ oxidation that was above their natural pH. The CH₄ oxidation in the upland forest soils and in the peat soil did not differ in their sensitivities to (NH₄)₂SO₄ or K₂SO₄ (used as a non-ammonium salt control). Inhibition of CH₄ oxidation by (NH₄)₂SO₄ resulted mainly from a general salt effect (osmotic stress) though NH₄⁺ did have some additional inhibitory properties. Both salts were better inhibitors of CH₄ oxidation than respiration. The differences in the CH₄ oxidation kinetics in the forested peat soil and in the upland forest soils reveal that there are differences in the physiologies of the CH₄ oxidisers in these soils.     

Nitrous oxide emissions from agricultural soils at low temperatures: a laboratory microcosm study

We studied in laboratory microcosms (intact soil cores) N₂O and CO₂ emissions from four different agricultural soil types (organic soil, clay, silt and loam) at low temperatures with or without freezing-thawing events. When the temperature of the frozen soil cores was increased stepwise from −8 °C the N₂O emissions began to increase at −0.5 °C, and peaked at −0.1 °C in the organic, clay and silt soils, and at +1.6 °C in the loam soils. However, a stepwise decrease in soil temperature from +15 °C also induced an increase in the N₂O emissions close to the 0 °C. These emissions peaked between −0.4 and +2.5 °C depending on the soil type and water content. However, the emission maxima were from 2 to 14.3% of those encountered in the experiments where frozen soils were thawed. Our results show that in addition to the well-documented thawing peak, soils also can have a maximum in their N₂O emission near 0 °C when soil temperature decrease. These emissions, however, are less than those emitted from thawing soils. The correlations between the N₂O and CO₂ emissions were weak. Our results suggest that N₂O is produced in soils down to a temperature of −6 °C.     

Cost-benefit analysis of using orchard or stand seed in Scots pine sowing,the case of northern Finland

A cost-benefit analysis of orchard seed versus seed from existing natural stands is presented for the scenario of direct sowing of Scots pine (Pinus sylvestris L.). The differential benefits of orchard seed are seed quality and improved yield due to genetic gain. These benefits are expected to further reduce the total cost of orchard seed. Seedlings from seed orchard seed had 11% better survival rate (p < .001, the best clone over 17%, p < .010) than seedlings from local stand seed. This was observed in a case study of 15 young seeding trials located in Central and North Finland. Expected yield improvements for stands established with orchard seed were obtained from local progeny test results, and they were further simulated on tree growth using the MELA forest simulation program. The cost-benefit analysis showed that, with a 7% yield improvement and a 15% better seed quality, the net cost of orchard seed was less than that of stand seed (discount rate 3%).     

Genetic variation of pedunculate oak (Quercus robur L.) in the urban woodlands of Helsinki

We present a genetic profile of pedunculate oak (Quercus robur L.) in three woodlands of the Helsinki region. We genotyped all mature trees and samples of seedlings to evaluate patterns of genetic variation and gene flow, and evaluate the long-term stability and natural regeneration of these stands. Although five microsatellite loci showed no significant differences in heterozygosity between generations in most locations, significant (p?per se does not interfere with gene flow over the distances represented here. Based on our findings, a minimal-maintenance program reliant upon natural regeneration of oak in the public parks of Helsinki seems plausible.