Current issue: 57(2)
Under compilation: 57(3)
One-hectare plot in a Scots pine (Pinus sylvestris L.) forest was systemically sampled for surface soil characteristics: humus layer thickness, soil carbon and nitrogen content, pH, electrical conductivity and respiration were determined from 106 samples. The effects of large trees on the plot were mapped and their joint influences at the locations of soil sampling were described as the influence potential, derived from the ecological field theory, and were calculated based on the locations and dimensions of trees.
The range of variation of soil characteristics was from three to sevenfold; no spatial autocorrelation was detected. The calculated influence potential of trees, as determined by their size and spatial distribution, was related to the spatial variation of top soil properties. Top soil properties were also related to thickness of the humus layer but they were poorly correlated with underlying mineral soil characteristics. Humus layer thickness, with the calculated influence potential of trees, may provide a means to predict top soil characteristics in specific microenvironments in the forest floor.
The article is a literature review focusing on the reaction of soil respiration, litter decomposition and microflora of forest soils to various pollutants like acidic deposition, heavy metals and unusual high amounts of basic cations. There is a great deal of evidence indicating that environmental pollution affects soil microbial activity and community structure. Much of the data originates from experimental designs where high levels of pollutants were applied to the soil under field or laboratory conditions. Furthermore, many were short-term experiments designed to look for large effects. These experiments have an indicative value, but it has to be kept in mind that environmental pollution is a combination of many pollutants, mostly at low concentrations, acting over long periods of time. There is therefore consequently a demand for research performed in natural forest environments polluted with anthropogenic compounds.
A third generation of forest tree gas exchange measuring system design for the use in the field is described. The system is designed to produce data for determining the dependence of the rate of tree photosynthesis, respiration and transpiration on environmental factors. The system consists of eight cuvettes, a tubing system, two infrared gas analysers, an air flow controller, a data logger, and a computer. The measuring cuvette is a clap type, i.e. it is mostly open, only closing during measurement. CO2 exchange is measured as the change in the cuvette concentration of CO2, and, transpiration is measured as the increase in water vapour concentration while the cuvette is closed. The environmental factors measured are temperature, irradiance and air pressure. The system was planned in 1987 and constructed in 1988. It worked reliably in late summer 1988 and the quality of data seems to be satisfactory.
The PDF includes an abstract in Finnish.
The use of forest mosses as bioindicators was tested with transplanted experiments. One transplantation experiment was made to study effects of air pollutants on two forest moss species, Hylocomnium splendens (Hedw.) Schimp. and Pleurozium schreberi (Willd. ex Brid.) Mitt. Another transplantation was used to study the nitrogen fixation capacity of blue-green algae in the Hylocomnium and Pleurozium moss layers. The surface structure of the moss species was studied by scanning electron microscopy. The air pollution induced changes in the surface structure of moss cells were observable soon after the transplantation. In polluted industrial areas the fertilizing effect of air-borne nitrogen compounds increased the photosynthetic activity of mosses before their destruction. Stress respiration was also observable in polluted areas. The nitrogen fixing capacity decreased or was almost inhibited in all the air-polluted environments.
A monitoring program is planned for the terrestrial environment around industries in Sweden, which emit acid compounds and heavy metals. Directions for the County Government Boards are being prepared. The paper deals with the present pollution situation in Sweden, based on recent scientific results, the justifications for local monitoring, and the organizing of the monitoring including the parameters suggested.
Four examples from a case study at an oil power station illustrate reporting of the data and the difficulties in interpreting the results. The examples are the distribution of a lichen indicator, heavy metal content and phosphatase activity in the moor layer, soil respiration and tree growth.
Photosynthesis and dark respiration in five families of autochtonous Norway spruce (Picea abies (L.) H. Karst.) and in seedlings from twenty Finnish stands of Scots pine (Pinus sylvestris L.) were investigated in constant environmental conditions. Values of CO2 exchange were compared with the height growth and weight of seedlings in Norway spruce and with the weight alone in Scots pine. No statistically significant differences were found in CO2 exchange among progenies or stands. Photosynthetic efficiency and photosynthetic capacity showed a positive correlation both in spruce and in pine. Growth and net photosynthetic capacity were linearly and positively correlated in pine. Spruce and a higher light compensation point than pine. The use of an open IRGA system with several simultaneous measurements and the trap-type cuvette construction in genetic work are discussed.
The PDF includes a summary in English.
In the literature review the current status of information on the genetic variation of CO2 exchange and some reviews and investigations on this subject are listed. Photorespiration is separately discussed and unpublished data of an electron microscope study of poplar leaf microbodies are presented.
Considerable genetic inter- and intraspecific variation is found in several characteristics that affect CO2 exchange in trees. Photosynthesis in young trees does not correlate well with growth through the whole rotation cycle. A special interest has been shown to marginal environmental conditions (e.g. water deficit, low temperature, and low light intensity), as opposed to optimal conditions often employed in laboratory studies of CO2 exchange in trees.
In an unpublished poplar studies by the author et.al. a preliminary experiment with poplar clones showed variation in the CO2 competition point. This variation was negatively correlated with the photosynthesis efficiency of these clones.
The PDF includes a summary in English.
In this study an attempt was made to use manometric Warburg technique in studying the growing season variations in the respiration rates of the roots of 1–3-year-old seedlings of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.). The respiration rates in both short-roots and long-roots have also been investigated.
According to the results, respiration intensity was the greatest in Scots pine and Norway spruce short-roots but also considerable in the long-root tips at the points of elongation. When the oxygen uptake rate per weight unit in the pine short-roots is given value of 100, the rate in the long-root tips is 61 and in the basal area 36. The corresponding values for spruce are 100, 69 and 43. The relative carbon dioxide release rates are different for the basal parts of the long-roots: pine 53 and spruce 57, when the CO2 release from the short-roots is 100. The CO2 release rate in the basal parts of the long-roots is relatively greater than the oxygen uptake. The respiration rate of the root systems of pine was larger than that of spruce due to the larger size of the root system.
The respiration rate per unit weight of pine roots of the 1- to 3-year-old seedlings decreases significantly with the increasing age. In spruce, the decrease was smaller. The result could have been different if only the short-roots of the same growing season were studied from all seedlings.
During the first growing season the root respiration rate decreased from the middle of the summer towards autumn. An experiment with pine seedlings grown in the mineral soil showed a very rapid increase in respiration rate in the spring. The rate, especially oxygen uptake, is at its greatest in the roots at the time of fastest growth.
Plants assimilate carbon dioxide from the air. Respiration of plants also produce carbon dioxide. Because the carbon dioxide level of the air is only 0.3%, only little carbon dioxide can diffuse in plants. Thus, the carbon dioxide assimilated by the plants is formed mostly in the earth when organic substances are degraded. The article describes a method to measure carbon dioxide level in the air.
The aim of this study was to investigate the ecophysiological and morphological characteristics of two salt-tolerant tree species, Eucalyptus camaldulensis Dehn. and Combretum quadrangulare Kurz. A greenhouse experiment with different levels of NaCl salinity (0, 0.5, 1.0, 1.5, and 2.0%) was set up and the results were compared with those of a field study on non-saline and saline soils. The determination of optimum gas exchange and the development and evaluation of photosynthetic models with and without water deficit were also included in this study.
Morphological characteristics under saline conditions showed that shoot height and diameter growth, shoot internode length, root length/biomass, leaf width and length, leaf area, number and biomass, and shoot/root and leaf/root ratios decreased with salinity, while leaf thickness increased with salinity. More growth was allocated to the roots than to the leaf canopy. Ecophysiological studies in laboratory showed that photosynthesis, stomatal conductance and water potential decreased with salinity, while the CO2 compensation point increased with salinity. Transpiration, dark respiration and photorespiration increased at low salinity but decreased at high salinity levels. In the field study, however, there were no significant differences in stomatal conductance and opening between saline and non-saline soils. Model predictions supported the results of the field measurements. Adaptation to salinity was reflected in an acclimatization of tree structure in the field study. There were both functioning and structural changes of seedlings in the greenhouse experiment
In terms of ecophysiological and morphological characteristics, E. Camaldulensis showed better salt tolerance than C. Quadragulare both in the greenhouse experiment and field study
The PDF includes a summary in Finnish.
Genetic variation in the physiological characteristics and biomass accumulation of Acacia mangium Willd. was studied in both field and laboratory conditions. Variation in the growth characteristics, foliar nutrient concentration, phyllode anatomy and stomatal frequency was analysed in 16 different origins under field conditions in Central Thailand. Family variation and heritability of growth and flowering frequency were calculated using 20 open-pollinated families at the age of 28 months. The effect of environmental factors on diameter growth in different provenances is also discussed.
Under laboratory conditions, such physiological characteristics as transpiration rate, leaf conductance and leaf water potential were measured at varying soil moisture conditions. The responses of photosynthesis, photorespiration and dark respiration as well as the CO2 compensation point to temperature and irradiance were also investigated. All physiological characteristics indicated differences among provenances. An attempt was made to relate the results obtained in the laboratory to the growth performance in the field. Recommendations on provenance selection for the planting of A. mangium in Thailand are also given.
The PDF includes a summary in Finnish.
Soil respiration readings are reported for three ameliorated peatland sites of different types, covering a period of four years, during which the sites were drained and treated with various fertilizers. Respiration is shown to increase exponentially with temperature, varying mostly in the range 100–500 mg CO2 m-2 h-1. The changes in soil respiration followed those in surface temperature with a time-lag of approximately 3–3.5 hours. At one site, where the groundwater table dropped by about 0.5 m after ditching, soil respiration increased 2.5-fold within a few weeks, whereas at the other two sites both the fall in the groundwater table and the resultant changes in soil respiration were small.
The fertilizers tested were slow-dissolving PK, fast-dissolving PK, wood ash, slow-dissolving PK + urea, slow-dissolving PK + Nitroform (urea formaldehyde) and slow-dissolving PK + urea + a micro-element mixture. Application of fast-dissolving PK + urea led to a rapid increase in soil respiration at the site poorest in nutrients, and slow-dissolving PK to a slow increase in respiration. The greatest, steady increase of all was achieved by treatment with ash. At the sites with a higher natural nutrient content the application of fertilizers usually led to a decline in soil respiration lasting 1–2 years, after which the initial level was normally regained. Treatment with micro-elements caused an initial fall in soil respiration values in all three biotopes, followed by a pronounced increase.
The PDF includes a summary in Finnish.
In this study we determined the effect of transformation of a mature sessile oak forest stand into a coppiced forest, and of thinning and throughfall reduction in a coppice stand on soil water content (SWC) and soil CO2 efflux. The precipitation reduction was induced by installing parallel drainage channels in both unthinned and thinned coppice stands. The driving factor for temporal dynamics of soil CO2 efflux in all plots was soil temperature. The other factor was soil water content but only up to about 15%. Above this threshold, there was no more effect on CO2 efflux. We found no clear difference in SWC or soil CO2 efflux between the mature and coppiced stand eight years after harvesting. On the other hand, thinning of the coppice stand resulted in increase in SWC up to 22% in proportion, which we assume to be a result of increased gap fraction of the canopy. However, no effect on soil CO2 efflux was observed two years after the thinning. Installation of the drainage channels in two plots covering 30% of the ground area resulted in decrease in SWC up to a proportional 30.5% and thus contributed up to 50.7% reduction in soil CO2 efflux.
Boreal forest soil contains significant amounts of organic carbon. Soil disturbance, caused for example by site preparation or stump extraction, may increase decomposition and thus lead to higher CO2 emissions, contributing to global warming. The aim of this study was to quantify responses of soil-surface CO2 fluxes (Rs) and litter (needle and root) decomposition rates following various kinds of soil disturbance commonly caused by mechanical site preparation and stump harvest. For this purpose four treatments were applied in a clear-cut site in central Sweden: i) removal of the humus layer and top 2 cm of mineral soil, ii) placement of a humus layer and 2 cm of mineral soil upside down on top of undisturbed soil, forming a double humus layer buried under mineral soil, iii) heavy mixing of the humus layer and mineral soil, and iv) no disturbance (control). Rs measurements were acquired with a portable respiration system during two growing seasons. To assess the treatments’ effects on litter decomposition rates, needles or coarse roots (Ø = 6 mm) were incubated in litterbags at positions they would be located after the treatments (buried, or on top of the soil). The results indicate that site preparation-simulating treatments have no effect or may significantly reduce, rather than increase, CO2 emissions during the following two years. They also show that buried litter decomposes more rapidly than litter on the surface, but in other respects the treatments have little effect on litter decomposition rates.