Artikkelit jotka sisältää sanan 'growth'

Should the frequency of drought increase in boreal forests due to climate change, seedlings planted in prepared peat mounds could become more susceptible to soil desiccation. The resistance of Scots pine (Pinus sylvestris L.) seedlings to drought will thus be a key factor in the regeneration success of pine-dominated, forestry-drained peatlands. In this study, we evaluated the physiological, metabolic, and morphological responses of year-old seedlings gradually exposed to extreme drought in highly decomposed Sphagnum-Carex peat blocks. Drought clearly suppressed root and shoot growth as well as fractional colonization of ectomycorrhizal fungi. Sustained declines in photochemical efficiency (Fv/Fm) of previous-year and current-year needles did not occur until the volumetric soil water content had dropped to 30% and 10%, respectively. Polyamine analysis revealed that new needles are preferred in protecting the different parts of the seedlings against drought stress. Despite growth losses, the maintenance of rather high photochemical efficiency in current-year needles under severe water stress would appear to indicate a potential for seedling recovery if water availability in the peat improved. Given the high tolerance exhibited by Scots pine seedlings, death by drought seems a lesser concern.

• Pearson, Finnish Forest Research Institute, Parkano Research Unit, Kaironiementie 15, FI-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo
• Saarinen, Sähköposti: ei.tietoa@nn.oo
• Heiskanen, Sähköposti: ei.tietoa@nn.oo
• Sarjala, Sähköposti: ei.tietoa@nn.oo
• Laine, Sähköposti: ei.tietoa@nn.oo

The effects of potassium (K) fertilisation on the nutrient status and growth of Scots pine (Pinus sylvestris L.) stands on drained peatlands were studied on three field experiments in northern central Finland. The Scots pine stands were at a sapling or pole stage with a dominant height of 3–8 m when the experiments were set up. The stands differed from each other in their nutritional status, for example, the foliar K concentration varied considerably between the experiments. The experiments were fertilised with potassium chloride, rock phosphate (P 42kg ha-1) and urea (N 46kg ha-1) between 1979 and 1980. The potassium doses in terms of elemental K, were 50, 100, 200 and 400kg ha-1. The foliar samples were taken three times during the study period: 7–9 years, 14–15 years and 19–20 years after fertilisation. The stand measurements were done 19–22 years after the fertilisation. The rate and magnitude of stand response due to fertilisation depended essentially on the nutritional status of the trees. The strongest effect of PK-fertilisation was obtained on a nitrogen-rich peatland, where the stands suffered from severe phosphorus and potassium deficiencies (foliar P concentration < 1.2 mg g-1, K concentration < 3.5 mg g-1). During the study period, the annual stand volume growth on fertilised plots ranged from 3.9 to 5.4 m3 ha-1 a-1, and that of the unfertilised plots was 0.78 m3 ha-1 a-1. In other sites, where the lack of phosphorus and potassium was not so drastic, nor did the trees suffer from shortage of nitrogen, the effect of PK-treatment on tree growth was weak or almost non-existent. The foliar K concentrations rose with the amount of potassium chloride applied. The fertilisation effect of the dose of 100kg K ha-1 lasted 15–20 years, after which the foliar K concentration dropped close to the deficiency limit. The effect of the larger doses (200–400kg K ha-1) on the needle K concentration was more pronounced and still visible at the end of the study period. However, the stand growth responses gained with larger potassium applications were not essentially greater than those with the 100 kg ha-1 dose.

• Pietiläinen, Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Vesala, Sähköposti: ei.tietoa@nn.oo

We studied the natural regeneration of a cut-over peat bog in the Sumava Mountains, Czech Republic. The spontaneous revegetation by vascular plants has been limited by extreme abiotic conditions left after peat mining. Only 1-2% of the total area was recolonized by Sphagnum mosses. This was mainly because drainage channels are still drying out the bog. Only plants tolerant to water stress such as Juncus effusus, Molinia caerulea, Eriophorum angustifolium and E. vaginatum were able to establish there. A key species colonizing bare surface is a clonal plant E. angustifolium. It forms circular polycormons of densely aggregated ramets. As in other radially spreading phalanx plants, the oldest (central) part of the system gradually dies, previously connected ramets become separated, and ring polycormon becomes open to recolonization by other plant species. We analyzed the relationships between species richness of the ring and their size, percentage litter cover, distance to seed sources, and soil fertility. The number of plant species was higher in the middle of the polycormons. The soil was more fertile in the central area than in the surroundings. We conclude that the restoration of highly disturbed habitats can be facilitated by clonal behavior of pioneer populations.

• Lanta, Faculty of Bilogical Sciences, University of South bohemia, Branisovska 31, CZ-370 05 Ceske Budejovice, CzechRebuplic Sähköposti: ei.tietoa@nn.oo
• Doležal, Sähköposti: ei.tietoa@nn.oo
• Samata, Sähköposti: ei.tietoa@nn.oo

The nutritional status of Scots pine (Pinus sylvestris L.) stands growing on a nitrogen-rich, drained pine mire in western Finland was studied after refertilization using needle analysis and the response of stand volume growth. The main aim was to find out if K-refertilization alone could maintain or increase the volume growth without causing a nutrient imbalance between K and P. The initial fertilization was carried out in 1961 - 62 using PK fertilizer and refertilized in 1976 and 1989 with different combinations of nitrogen (N), phosphorus (P), potassium (K) and boron (B). Needle samples were taken and the tree stands were measured in 1996 and 2001. Peat samples were taken in 2002. According to the needle analysis results, the concentration of P was above the deficiency level in all the treatments in 1995 and 2000. There was a clear shortage of K in the needles collected from the control treatment, but the concentration of K was still adequate 12 years after the latest K refertilization. The volume growth of the stands clearly responded to the 1976 refertilization with K alone, which was probably due to the fact that trees had been suffering from K deficiency before the first refertilization and 14-15 years thereafter. After the second refertilization, the combination of K and P increased the annual volume growth more than refertilization with K alone. This indicates that about 25 years after the initial fertilization, there was already some shortage of P. The highest stand volume was associated with the combined K (1976) and PK (1989) refertilization treatment. Refertilization with N did not increase stand volumes during the study period.

• Rautjärvi, The Finnish Forest Research Institute, Joensuu Research Centre, Box 68, FIN-80101 Joensuu Sähköposti: ei.tietoa@nn.oo
• Kaunisto, Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo

A viable understorey of Norway spruce often develops under a nurse crop on nutrientrich peatlands drained for forestry. The impact of birch nurse crop density and height equalization of the Norway spruce understorey on the height growth of spruce seedlings was studied on three sites: on a transforming herbrich spruce swamp, an abandoned peat field and a mixed peat/mineral soil field. The nurse crop was managed in 1990: 1) no thinning, 4000 stems ha-1, 2) thinning to 1000 stems ha-1. 3) thinning to 500 stems ha-1, or 4) removal of the nurse crop. In addition, the spruce seedlings over 1 m in height were removed from randomized halves of each plot. The unmanaged nurse crop reduced the growth of the understorey the most on all the sites. On the other hand, the spruce seedlings grew the best on the plots where the nurse crop had been removed. Due to height equalization the growth of the spruce understorey first slowed down, but towards the end of the study period the height growth of the equalized and non-equalized spruce understoreys were almost the same.

• Päätalo, The Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Hilli, Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Tillman-Sutela, Sähköposti: ei.tietoa@nn.oo

A natural understorey of Norway spruce often develops under birch on oligo-mesotrophic peatlands, but spruce can also be planted on these sites. The effects of fertilization and the density of the pubescent birch nurse crop on the height growth and needle nutrient status of a planted spruce understorey on an old drained herb-rich sedge pine fen was investigated in this study. The spruce transplants were planted early in the 1960’s. The nurse crop was removed, thinned to 200 stems ha-1 or left unmanaged in 1988. A number of plots were also fertilized. The height growth of the spruce transplants was measured during two periods after management, and the needle nutrient concentrations were determined before fertilization and again 10 years later. The height growth of the spruce was 40 - 60% greater after removal of the nurse crop than that under the unthinned nurse crop. Even the thinned nurse crop slowed down the growth of the understorey. However, height growth was the best on the plots on which the nurse crop was removed and the plots fertilized.

• Hilli, OSLA, Kirkkotie 1, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Päätalo, Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo
• Piiroinen, Sähköposti: ei.tietoa@nn.oo

This study aimed at finding out the effects of maintaining ditch systems by ditch cleaning and complementary ditching on volume growth of drained Scots pine (Pinus sylvestris L.) stands. Volume growth during the first ten post-treatment years was increased by 0.16 m3 ha-1 a-1 after ditch cleaning, 0.36 m3 ha-1 a-1 after complementary ditching, and 0.48 m3 ha-1 a-1 after the combined treatment. The average growth reactions during the second five-year period were considerably higher than during the first one. No drastic reductions in stand growth, however, occurred in the untreated plots during the post-treatment period of ten years.

• Lauhanen, The Finnish Forest Research Institute, Kaironiementie 54, FIN-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo
• Ahti, Sähköposti: ei.tietoa@nn.oo

The present study looked into the soil properties of twenty-four peat-based field by examining the 0-10, 10-20, 20-30 and 30-40 cm soil layers and thc effect that soil properties have on the initial development of young stands of downy birch growing in Pohjois-Savo, southern Finland. Adding of mineral soil to peat-based fields and the decomposition and subsidence of peat had resulted in increasing the bulk density of the peat, especially in the tilling layer. Also, the amounts of nutrients in the tilling layer were higher than in the layer below. Together with fertilization, the addition of mineral soil had increased the soil's nutrient amounts manyfold compared to virgin mires and mires drained for forestry. Eighthy-one per cent of the trees were alive. The share of viable trees had fallen to half of the planting density, being now just 840 trees per hectar. The increase in the amount of extractable potassium and total copper in the soil improved the growth of young stands and reduced the proportion of trees of inferior quality. Growth disorders were observed in downy birch, and these were probably caused by increases in the ratios of the amounts of main nutrients and micro-nutrients in the soil. The ratio of nitrogen and phosphorus to copper was reflected best of all in the growth of young stands. An increase in the amount of soil nitrogen and phosphorus in relation to the amount of soil copper impaired stand growth and promoted the occurrence of trees afflicted by growth disorders.

• Hynönen, Pohjois-Savo Forestry Centre, P.O. Box 1019, FIN-70101 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo
• Makkonen, Sähköposti: ei.tietoa@nn.oo

Factors affecting the need for ditch network maintenance in northern Finland were studied. In addition, the effect of ditch network maintenance on stand growth was estimated. A dataset containing ditch, tree stand, site type and climate variables was built up on the basis of the permanent sample plots (SINKA) on peatlands. Regression analysis as well as discriminant analysis were used to identify factors and criteria that could be used to identify sites that would respond to ditch network maintenance. Instead of the ditch condition class, ditch age and depth proved to be the variables reflecting the need for ditch network maintenance. The volume of the tree stand was influenced the most by the temperature sum and age of ditching. Stand volume growth was influenced the most by the volume of the tree stand. The site type index or the volume of the tree stand did not give useful information for the planning of ditch network maintenance. When ditch age was 10-40 years, complementary ditching increased annual stand growth of pine mires by 0.6-1.0 and 1.5-1.9 m3 ha-1 a-1 on spruce-birch swamps.

• Lauhanen, The Finnish Forest Research Institute, Parkano Research Station, FIN-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo
• Piiroinen, Sähköposti: ei.tietoa@nn.oo
• Penttilä, Sähköposti: ei.tietoa@nn.oo
• Kolehmainen, Sähköposti: ei.tietoa@nn.oo

The effects of fertilization and refertilization on the growth of pubescent birch (Betula pubescens) stands growing on drained peatlands in northern Finland were studied in eight field experiments. The treatments were: (i) control with no fertilization, (ii) fertilization with nitrogen (N), (iii) fertilization with phosphorus and potassium (PK), and (iv) fertilization with nitrogen, phosphorus, and potassium (NPK). The sites represented four different mesotrophic to eutrophic site types with stand median heights ranging from 7 m to 13 m. Tree growth was monitored at stand level during periods of five to eleven years following the setting up of the experiments and during periods of 4 to 7 years following the repetition of the treatments in 1985. At the end of the second period, sun-exposed leaves were sampled from two stands in August 1990 for the purpose of conducting foliar nutrient analyses. The first-time fertilization treatments did not affect tree growth on any of the site types. Following the repetition of the treatments, the stands responded positively to NPK or PK fertilization on all site types except on the shallow-peated herb-rich peatland forest. There was no response to mere N-fertilization on any of the site types. The growth responses observed were weaker than those reported for Scots pine in similar climatic conditions. Key words: Betula pubescens, foliar nutrients, growth responses, nitrogen, peatland, phosphorus, potassium

• Penttilä, The Finnish Forest Research Institute, Rovaniemi Research Station, P.O.Box 16, FIN-96301 Rovaniemi, Finland Sähköposti: ei.tietoa@nn.oo
• Moilanen, Sähköposti: ei.tietoa@nn.oo

Abstract: The stand-level responses to fertilization and refertilization were studied in seven factorial field experiments established in 1974-1976. The factors were nitrogen fertilization (N) and phosphorus-potassium fertilization (PK). The factorial treatments were applied at two levels: (i) control and (ii) fertilized with a dosage following the currently used Finnish forest fertilization guide-lines. The spruce-dominated stands were selected from areas drained according to normal forestry practises between 1932 and 1969. The sites covered fairly well the trophic variation that occurs on spruce-dominated peatlands in the mid-boreal zone in Finland. Tree growth was monitored during two periods of five to seven years. The second period followed the refertilization in 1985. At the end of the second period, one-year-old sun-exposed needles were sampled from the four southernmost stands for nutrient analyses. The effects of fertilization on tree growth were generally fairly weak and insignificant, especially during the first study period. After refertilization, the effect of N was positive in three stands on mesotrophic sites. The foliar nutrient analyses of unfertilized spruces showed low concentrations of N, P and Cu. PK-fertilization increased foliar P concentrations and, in some cases, also K concentrations. Since the PK-fertilizer included some borate, it also increased foliar B concentrations. N-fertilization did not affect foliar N, P or K concentrations but it decreased foliar concentrations of Ca, Zn, and B in some cases. Both the growth responses and the foliar nutrient analyses indicated that nitrogen was the most deficient macro-nutrient. Key words: foliar nutrients, growth responses, mires, nitrogen, phosphorus, Picea abies, potassium

• Moilanen, The Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Penttilä, Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo

The site index system presented is intended as support for the idea of developing a more hierarchical and integrated forest classification system in Finland. The data used were obtained from stands growing on old permanent experimental plots laid out in drainage areas in southern Finland. The model, describing the post-drainage development of stand dominant height as a function of drainage age (time elapsed since drainage), is based on successive measurement data (465 observations), collected from 89 plots, each representing a single stand. The site indices H40dr are post-drainage dominant height values 40 years since drainage, given in 2-meter classes. Post-drainage dominant height is defined as the difference between the current dominant height and the dominant height at the time of drainage. In classification work, one needs to know (or measure) the two aforementioned height characteristics, together with age since drainage. If the dominant height at the time of drainage is not known, it can be estimated from a function presented herein and based on current dominant height and drainage age. The mean annual volume increments at 40 years since drainage (MAI40) are also presented. There is still a need for examining separately the accuracy of the model with new data from spruce-, pine- and birch-dominated stands, collected for numerical constructions of site index curves. Therefore, the site index model and its characteristics must be seen more as outlines than as a final system for practical application. A well-functioning ditch network is a default when applying the site index curves.

• Gustavsen, The Finnish Forest Research Institute, Joensuu Research Station, P.O.Box 68, FIN-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo

The five-year response of a birch-dominated mixed stand (80% Betula pubescens, 14% Betula pendula) to thinning was studied in a thinning experiment in a mesotrophic, shallow-peated site in Ylitornio, northern Finland. Four thinning intensities (0%, 47%, 57% and 71 % removal of the initial stem number, i.e. 0%, 17%, 27% and 52% removal of the initial basal area), with three replications, were arranged in a randomized block design. At the time of thinning, the stand age was 30 a, and the dominant height was 11.5 m. Light (15%) and normal (27%) thinning decreased the rates of stand-level basal area growth by 12 and 15%, respectively. Thinning resulted in a significant increase in the growth of mean height and a subsequent increase in volume growth in the normally-thinned plots. Following heavy thinning, the volume and basal area growth rates were 35% and 32% less than those in the control treatment. The relative basal area increment, as well as the increase in mean diameter, was at its maximum in the heavily-thinned plots. Keywords: Betula pubescens, forest drainage, growth, thinning

• Hökkä, The Finnish Forest Research Institute, Rovaniemi Research Station, P.O.Box 16, FIN-96301 Rovaniemi, Finland Sähköposti: ei.tietoa@nn.oo
• Penttilä, Sähköposti: ei.tietoa@nn.oo

The post-drainage growth of a simulated model stand according to different thinning methods was predicted for 84 years by spatial single-tree growth models. In thinnings, the post-thinning stand density varied as a function of the distance of the ditch. The best yield and income were obtained by leaving the stand near ditches and extraction road midway between ditches denser than elsewhere. Keywords: growth model, Pinus sylvestris, stand management

• Miina, University of Joensuu, Faculty of Forestry, P.O.Box 111, FIN-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
• Pukkala, Sähköposti: ei.tietoa@nn.oo

Liming (with applications of 1 000 to 8 000 kg ha1) had no long-term (1929-1985) effect on the growth of Scots pine on drained oligotrophic peatlands. Liming plus NPK fertilization had a variable effect on the growth of the stands. The same treatment could result in a very different response in different experimental areas. Both liming alone and liming plus NPK fertilization increased the calcium, magnesium and nitrogen contents of peat and decreased the C/N ratio and acidity. Liming plus fertilization decreased needle boron and manganese and increased calcium and nitrogen concentrations. The results of peat and needle analysis indicated that the changes in nitrogen availability to trees caused by liming have not been sufficient enough to affect tree growth. It was also concluded that boron deficiency was the main reason for the lowered yield. Key words: fertilization, needle nutrients, peat nutrients, Pinus sylvestris, tree growth

• Nieminen, The Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo
• Pätilä, Sähköposti: ei.tietoa@nn.oo

Models reflect reality but also simplify it. The modeller must choose where the balance lies between simplicity plus understanding and complexity plus realism. (1) Two pictorial and descriptive models of the surface of a peat-forming bog are given, and a third shows why the true rate of peat accumulation must diminish over time. (2) A simple quantitative model of the surface layers is described and leads to the conclusion that the surface layer is in a steady state, fixing carbon, losing some by decay, and passing some on to the underlying peat proper. A similar model for the underlying peat shows that if decay is at a rate that is a constant proportion of what remains then there is an upper asymptotic limit to the depth of peat. But if the rate of decay decreases, because the remaining material is more refractory, then peat accumulation continues indefinitely though at an ever-decreasing rate. (3) A simulation model allowing greater realism but diminished understanding is outlined. (4) Models should be aids, not objects in their own right. Keywords: Carbon balance, modelling, peat growth, peatland

• Clymo, School of Biological Sciences, Queen Mary and Westfield College, London El 4NS, UK Sähköposti: ei.tietoa@nn.oo

The study was made in four experimental fields on drained peatland in western Finland (63-66°N). One of the experiments was laid out in 1972; the others in 1978-1979. Treatments included different kinds of wood ash and PK-fertilizer, an ash-imitating mixture and apatite+biotite. Needle analyses and growth measurements were carried out in 1983— 1986. The concentrations of Mg and Mn generally decreased after fertilization. A rise in the foliar P, foliar K and foliar weight correlated with the growth response. Best growth increment was achieved with the ash-imitating mixture and PK-fertilizer, while apatite+biotite did not increase growth. In the first years after fertilization, growth on the ash plots was weaker, but later stronger or equal to growth on PK- and ash-imitating plots. The correlation between initial tree height and post-fertilization growth was similar on the different treatments. The poor growth increment on some ash treatments was probably due to the insufficient amount of nutrients in the ashes used. Key words: Ash fertilization, Finland, growth, needle analysis, peat, Scots pine

• Silfverberg, The Finnish Forest Research Institute, P.O. Box 18, SF-0I301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo

The peat formation time scale in the acrotelm was evaluated using the rate of burial of the root collars and the tree age of buried Scots pine stems in the surface peat. The data were originally presented, but unanalysed, by A.K. Cajander (1906). During the first 30 years after the germination of pine seed the Sphagnum carpet above the root level increased its thickness without noticeable compression and decomposition. During the following 20-30 years the decomposition increased, but the growth of Sphagnum also decreased. A third phase began after 55-60 years during which the growth of Sphagnum was compensated by decomposition. Keywords: Acrotelm, peat formation, Sphagnum growth

• Lindholm, Water and Environment Research Office (Nature Conservation), Water and Environment Research Institute, P.O. Box 250, SF-0010! Helsinki, Finland Sähköposti: ei.tietoa@nn.oo

This study included growth and needle analysis in ash-fertilized spruce and pine stands near Oulu (65 °N, 26 °E). Most of these stands, totalling 770 measured trees, were on peat and fertilized in wintertime 1980 and 1981 as practical work with 40 m3/ha. By 1985 there was a clear increment of growth, especially in spruce stands, probably due to the great amount of phosphorus (375 kg/ha) applied. Keywords: peatland forestry, tree growth, ash-fertilization, phosphorus.

• Silfverberg, Department of Peatland Forestry, The Finnish Forest Research Institu­te, Unioninkatu 40 A, 00170 Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo