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Strip-cutting management has been proposed as an alternative to clear-cuts in drained boreal peatland pine (Pinus sylvestris L.) forests. We explored the hydrological feasibility of strip cutting, that is, under which conditions the post-harvest water table (WT) in peat remains sufficiently deep (here, a WT of −0.35 m during the late growing season) to enable undisturbed tree growth. We approached the question by (1) measuring the WTs in a harvested strip and an adjacent unharvested stand in peatland forests in southern Finland and (2) by simulating the WTs in different strip cut layouts, unharvested peatland, and clear-cut cases using a process-based hydrological model. The measured WTs were, on average, 0.06–0.12 m closer to the peat surface in the harvested strips than in the unharvested stands. The hydrological feasibility of strip cutting increased along with increasing site productivity and improving climate conditions. Strip cutting resulted in the rise in the WTs of adjacent unharvested stands, which can have undesired consequences. Depending on the stand density and strip cut layout, the share of the well-drained area in the harvested strips was slightly larger or even two times larger compared to a complete clear-cut of the forest. Narrow strips (here, 13 m in width) indicated better drainage in the harvested area than wider (20–30 m in width) strips. Even though strip cutting has limited capacity to maintain efficient drainage in the harvested strip on low hydraulic conductivity peat, the increase in the WT was smaller than after clear-cut. [ABSTRACT FROM AUTHOR]

Dendrochronological investigations of Scots pine ( Pinus sylvestris L.) growing on Männikjärve peatland in central Estonia showed that annual tree growth of peatland pines can be used as a proxy for past variations of water table levels. Reconstruction of past water table levels can help us to better understand the dynamics of various ecological processes in peatlands, e.g. the formation of vegetation patterns or carbon and nitrogen cycling. Männikjärve bog has one of the longest water table records in the boreal zone, continuously monitored since 1956. Common uncertainties encountered while working with peatland trees (e.g. narrow, missing and wedging rings) were in our case exacerbated with difficulties related to the instability of the relationship between tree growth and peatland environment. We hypothesized that the instable relationship was mainly due to a significant change of the limiting factor, i.e. the rise of the water table level due to human activity. To test our hypothesis we had to use several novel methods of tree-ring chronology analysis as well as to test explicitly whether undetected missing rings biased our results. Since the hypothesis that the instable relationship between tree growth and environment was caused by a change in limiting factor could not be rejected, we proceeded to find possible significant changes of past water table levels using structural analysis of the tree-ring chronologies. Our main conclusions were that peatland pines can be proxies to water table levels and that there were several shifting periods of high and low water table levels in the past 200 years. [ABSTRACT FROM AUTHOR]

The need to regenerate peatland forests is expected to increase in the near future in Finland due to harvest of large amounts of peatlands drained during the 1950s and 1960s. In anticipation of this, a new type of excavator-mounted rototiller for soil scarification in peatlands has been developed in Finland to improve the moisture conditions of the seedbed by mixing the ground vegetation, raw humus layer, and peat. The regeneration result of the new rototiller was compared with traditional patch scarification (i.e. scalping) in direct seeding of Scots pine in three forestry-drained peatland sites in eastern Finland. After two growing seasons, rototilling offered no advantage over scalping in terms of the number of established seedlings, probability of empty patches, or seedling height. Seedling establishment was on average higher on scalping (10%) than on rototilling (8%). The main problem in rototilling may have been the loose and porous structure of the seedbed resulting in drought and frost damages. [ABSTRACT FROM AUTHOR]

The effect of drainage in peatland forests has been studied in Estonia but research on bog pine (Pinus sylvestris L.) stands is lacking and mixed opinions on the expediency of amelioration in this site type are found. In order to obtain more information on the post drainage effects, measurements were conducted in a drained oligotrophic bog Scots pine stand (with a relatively thin peat layer) in Järvselja. Relationship between stand characteristics and distance from the drainage ditch was described and measurement data was compared with data that had been collected 59 years earlier in the same stand. Over time the stand structure and productivity had changed. Due to lengthy drainage, increase in several stand characteristics became evident: mean height 84% (8.60 ± 0.39 m), mean DBH 48% (6.55 ± 0.59 cm), basal area 59% (10.6 ± 3.4 m2 ha-1) and growing stock 179% (169 ± 32 m3 ha-1). Growth conditions had improved (site class improvement 1.8 units) and since earlier comparison data was from an already drained stand, actual change in stand characteristics and productivity compared to pre-drained state, has to be even greater. The studied stand is a good example of successful forest drainage in a bog pine forest and these results contribute to a better understanding of post drainage developments in these types of forests [ABSTRACT FROM AUTHOR]

In boreal-drained peatland forests, tree growth is retarded by the gradual deterioration of drainage ditch networks. In order to avoid the development of suboptimal growth conditions, ditch network maintenance (DNM) operations (ditch cleaning and/or complementary ditching) are annually conducted on an area of about 70,000 ha in Finland. The previous studies indicate that the depth of the water table prior to DNM may influence the magnitude of the growth response to DNM. Tree growth does not necessarily increase after DNM at sites with large stand volume and subsequent low water levels due to tree stand evapotranspiration. We investigated how the pre-treatment water table depth (pre-WTD) in late summer relates to the growth of Scots pine (Pinus sylvestris L.) stands after the DNM operation in 12 field experiments. The increase in mean annual volume growth caused by DNM was negatively related to the pre-WTD, with the highest growth response in stands where the pre-WTD was less than 25–30 cm. DNM did not clearly increase stand growth in sites where the pre-WTD was more than 35–40 cm below the soil surface. There was a high variation in growth response to DNM between the water levels from 20 to 35 cm below the soil surface, indicating that factors other than water table depth are also needed as decision criteria for assessing the appropriate timing of ditch network maintenance. [ABSTRACT FROM PUBLISHER]

Fertilizers are applied in drained peatland forests to correct nutrient imbalances, but few models have been developed for predicting the stand growth response. We used 10- to 34-year-long stem growth increment data from 51 fertilization experiments involving ash, PK, and NPK treatments (doses of P, K, and N varying between 35 and 45, 60 and 80, and 80 and 90 kg·ha-1, respectively) and controls to model the volume growth response of young Scots pine ( Pinus sylvetris L.) stands to fertilization in drained peatland sites of middle and northern Finland. We used the linear mixed models method to express the stand-level growth response as a function of time (5-year periods), site type group, location, and the fertilization treatment (ash-PK combined and NPK). Different growth responses were obtained for nitrogen-rich sites with PK treatment and nitrogen-poor sites with NPK treatment. The PK fertilization in nitrogen-rich sites resulted in the largest volume growth response and longest temporal effect (1.0-2.0 m3·ha-1·a-1 higher mean growth for at least 35 years), with quicker and stronger effects in more southern conditions where average temperature sums were greater than 1000 degree-days (°C). NPK fertilization in nitrogen-poor sites gave a modest response (0.4-0.8 m3·ha-1·a-1 in 35 years). [ABSTRACT FROM AUTHOR]

Abstract: Increasing use of wood fuels for energy production in Finland since the 1990s implies that large quantities of the generated ashes will be available for forest fertilization. The aim of this study was to analyse the effect of wood ash application on 137Cs activity concentrations in Scots pine (Pinus sylvestris L.) needles and certain berries and mushrooms on drained peatlands. The study was based on field experiments carried out on two mires in Finland in 1997–1998. Two different types of wood ash were applied at dosages of 3500, 3700, 10 500 and 11 100 kg ha−1. Wood ash did not increase 137Cs activity concentration in plants in the second growing season following application. On the contrary, a decrease in 137Cs activity concentration was seen in the plants of the ecosystem on drained peatlands. This result is of importance, for instance, when recycling of ash is being planned. [ABSTRACT FROM AUTHOR]

The quantitative relationship between stand growth rate and water table level in peatland forest sites has not been fully ascertained in the literature. In this study, we investigated this relationship by means of a bivariate regression model. Tree and stand attributes, including volume and past 5-year volume growth as well as median water table depth (WTM) during the 1984 growing season, were observed in 69 Scots pine (Pinus sylvestris L.) sample stands with three subplots established in each stand. All stands were located in deep-peated, moderately rich to poor organic soil sites in Central Finland (61°45′–62°26′N, 22°40′–28°29′E) that had been ditched for forestry about 25 years earlier (1959–1961). Prediction models for the fixed mean functions for 5-year volume growth and WTM as well as estimates for variances and the correlation of random effects at plot and subplot levels were estimated simultaneously using bivariate regression methods. The correlation of model residuals at the plot level was highly significant. The model was applied to simulate stand volume development for a period of 20 years. Simulations illustrated the dynamic interaction of stand volume, volume growth, and soil water levels: deep initial WTM resulted in stand growth and volume-development increases and subsequently further deepened the WTM in the stand. The model can be applied to southern boreal drained Scots pine peatlands to estimate the WTM in different stand volume conditions and to assess the effect of stand management on WTM. La relation quantitative entre le taux de croissance d’un peuplement et le niveau de la nappe phréatique dans les tourbières boisées n’a pas été clairement établie dans la littérature. Dans cette étude, avons étudié cette relation à l’aide d’un modèle de régression bivariée. Les caractéristiques des arbres et du peuplement, incluant le volume, l’accroissement en volume des cinq dernières années et la profondeur médiane de la nappe phréatique (NPM) pendant la saison de croissance 1984, ont été observées dans 69 peuplements de pin sylvestre (Pinus sylvestris L.) à l’intérieur desquels trois sous-placettes ont été établies. Tous les peuplements étaient établis sur des sols organiques profonds, modérément riches à pauvres, situés au centre de la Finlande (61°45′–62°26′N, 22°40′–28°29′E) et qui avaient été drainés environ 25 ans plus tôt (1959–1961). Des modèles de prévision pour les fonctions fixes moyennes dans le cas de l’accroissement quinquennal en volume et de la NPM, de même que l’estimation de la variance et de la corrélation entre les effets aléatoires, aux échelles de la placette et de la sous-placette, ont été estimés simultanément à l’aide d’une méthode de régression bivariée. La corrélation des résidus du modèle à l’échelle de la placette était hautement significative. Le modèle a été utilisé pour simuler l’évolution du volume du peuplement pendant une période de 20 ans. Les simulations illustrent l’interaction dynamique entre le volume du peuplement, l’accroissement en volume et le niveau de la nappe phréatique. Ainsi, une NPM initialement basse a entraîné une augmentation de la croissance du peuplement et du volume, ce qui a par la suite abaissé davantage la NPM dans le peuplement. Le modèle peut être appliqué aux tourbières de pin sylvestre drainées situées au sud de la zone boréale pour estimer la profondeur de la NPM dans des peuplements supportant différents volumes et pour évaluer les effets de l’aménagement forestier sur la NPM. [ABSTRACT FROM AUTHOR]