The use of random parameter models in forestry has been proposed as one method of incorporating different levels of information into prediction equations. By explicitly considering the variance-covariance structure of observations and considering some model parameters as random rather than fixed, one can incorporate more complex error structures in analyzing data. Competition indices and variance component techniques were applied to 92 Scots pine (Pinus sylvestris L.)-dominated permanent sample plots on drained peatlands in northern Finland. By quantifying stand, plot, and tree level variation, it was possible to identify the level (stand, plot, or tree) at which the explanatory variables contributed to the model. The replication of plots within stands revealed little variation among plots within a single stand but significant variation occured at stand and tree levels. Positive and negative effects of inter-tree competition are identified by examining simple correlation statistics and the random parameter model.

Understanding the anthropogenic and natural factors that affect runoff water quality is essential for proper planning of water protection and forest management, particularly in the changing climate. We measured water quality and runoff from 10 unmanaged and 20 managed forested headwater catchments (7-12,149 ha) located in Finland. We used linear mixed effect models to test whether the differences in total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) export and concentrations observed can be explained by catchment characteristics, land use, forest management, soil fertility, tree volume and hydrometeorological variables. Results show that much of variation in TOC, TN and TP concentrations and export was explained by drainage, temperature sum, peatland percentage and the proportion of arable area in the catchment. These models explained 45-63% of variation in concentrations and exports. Mean annual TOC export in unmanaged catchments was 56.4 +/- 9.6 kg ha(-1) a(-1), while in managed it was 79.3 +/- 3.3 kg ha(-1) a(-1). Same values for TN export were 1.43 +/- 0.2 kg ha(-1) a(-1) and 2.31 +/- 0.2 kg ha(-1) a(-1), while TP export was 0.053 +/- 0.009 kg ha(-1) a(-1) and 0.095 +/- 0.008 kg ha(-1) a(-1) for unmanaged and managed, respectively. Corresponding values for concentrations were: TOC 17.7 +/- 2.1 mg L-1 and 28.7 +/- 1.6 mg L-1, for TN 420 +/- 45 mu g L-1 and 825 +/- 51 mu g L-1 and TP 15.3 +/- 2.3 mu g L-1 and 35.6 +/- 3.3 mu g L-1. Overall concentrations and exports were significantly higher in managed than in unmanaged catchments. Long term temperature sum had an increasing effect on all concentrations and exports, indicating that climate warming may set new challenges to controlling nutrient loads from catchment areas.

More reliable assessments of nutrient export to surface waters and the Baltic Sea are required to achieve good ecological status of all water bodies. Previous nutrient export estimates have recently been questioned since they did not include the long-term impacts of drainage for forestry. We made new estimates of the total nitrogen (N), total phosphorus (P) and total organic carbon (TOC) export from forests to surface waters at different spatial scales in Finland. This was done by formulating statistical equations between streamwater concentrations and climate, soil, forest management and runoff variables and spatial data on catchment characteristics. The equations were based on a large, long-term runoff and streamwater quality dataset, which was collected from 28 pristine and 61 managed boreal forest catchments located around Finland. We found that the concentrations increased with temperature sum (TS), i.e. from north to south. Nitrogen, P and TOC concentrations increased with the proportion of drained areas in the catchment; those of N and TOC also increased with the proportion of peatlands. In contrast, with the increasing concentrations of N and TOC with time, P concentrations showed a decreasing trend over the last few decades. According to our estimates, altogether 47,300 Mg of N, 1780 Mg of P and 1814 Gg of TOC is transported from forest areas to surface waters in Finland. Forest management contributes 17% of the N export, 35% of the P export and 12% of the TOC export. Our new forest management export estimates for N and P are more than two times higher than the old estimates used by the environment authorities. The differences may be explained by the long-term impact of forest drainage. The spatial results indicate that peatland forests are hotspots for N, P and TOC export, especially in the river basins draining to the Gulf of Bothnia.

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to -20 or -40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 degrees C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC.

The balance between incoming precipitation (rainfall and snowfall) and outgoing evapotranspiration (ET), runoff and drainage to and from an ecosystem plus changes in soil moisture storage and the water equivalent of the snowpack is known as the water balance. A dominating feature of the water balance in the boreal zone is snowpack accumulation over winter and the spring snowmelt, both of which are affected by forest. In Finland, there are strong north-south gradients in the amount of precipitation, the proportion of rainfall and snowfall and temperature, and therefore latitudinal differences in the water balances components can be expected. Furthermore, the large canopy and deeper rooting of trees, together with the presence of a permanent ground vegetation cover, result in significant differences in interception, infiltration and water balance outputs of forests compared to other forms of land-use. Because of morphological and ecophysiological differences between the trees species, the water balance of Norway spruce and Scots pine dominated forests can be expected to differ. Determining the water balance of forest ecosystems across Finland would, therefore, help in assessing the hydrological ecosystem services provided by forests and form a basis for examining the effects of climate change and forest management on the water balance. This study aimed to compute the daily water balance of six Norway spruce, and three Scots pine dominated mature forest stands (plots) located throughout Finland over a 26-year study period (1990-2015). It was hypothesized that the various water balance components would systematically vary with latitude, a surrogate for climate, and differ between spruce and pine stands. The daily version of the water balance model “WATBAL” developed by Mike Starr (University of Helsinki, Dept. Forest sciences) was used for this study. The model requires daily meteorological data (precipitation, temperature, global radiation), stand parameters (canopy cover, rooting, crop coefficient), soil parameters (including infiltration coefficient, soil moisture contents at permanent wilting point, field capacity and saturation, and two soil moisture parameters for a plant available water content function). Six of the plots had soil developed in till and 3 plots had soil developed in sorted glaciofluvial deposits. Plot meteorological data for 1990-2015 was derived using spatially interpolated gridded data. If the daily air temperature was ≤0°C, any precipitation was assumed to be snowfall. The stand and soil parameters were derived from data collected from the 9 study plots by Luke (formerly Metla). The nine plots belong to the Finnish network of ICP-Forest level II plots that have been established throughout Europe. Pedotransfer functions (PTF) based on soil texture and organic matter contents were used to derive initial values for the soil hydraulic parameters. Time domain reflectometry (TDR) measured soil moisture data was available for 7 of the plots and, after carrying out careful quality control and rejection of outliers, used for calibration of modelled soil moisture and optimization of soil hydraulic parameters for those plots. Optimization was carried out using the non-linear Marquardt regression method. Goodness-of-fit for soil moisture was evaluated using correlation and R2 values from linear regression. After computing the daily water balance with the WATBAL model (using optimized soil hydraulic parameter values for the 7 plots and initial PTF values for the remaining 2 plots) the long-term mean annual and mean daily water balance components (with a 7-day moving average smoothing) were calculated. The water balances were computed for the humus layer plus 0-40 cm soil layer, which, based on literature, would have included most if not all of the roots. The dependence of the mean annual water balance components on latitude was evaluated using correlation analysis and linear regression, and the effect of tree species was tested for using the t-test on pairs of spruce-pine plots located close to each other. The raw TDR data was found to contain a considerable amount of gaps and erroneous (too high) values, often associated with the spring snowmelt. Optimization of the soil hydraulic parameters using the measured soil moisture contents calculated from the “cleaned” TDR data for the snow-free period resulted in a highly significant (p<0.001) Pearson correlation of +0.85 (R2 = 0.75) for the fit between measured and modelled soil moisture contents calculated across all 7 plots. The correlations for the individual plots were also highly significant. Based on the optimized WATBAL output, the fraction of plot mean annual precipitation as snowfall ranged from 20 to 29%. Corresponding ranges for ET, drainage and runoff were respectively 33 to 57%, 24 to 42%, and 18 to 25%. The mean annual water balance components were found to be significantly correlated to latitude, reflecting trends in precipitation and temperature. Evapotranspiration decreased with increasing latitude while maximum snow-on-ground, snowmelt and associated runoff increased with increasing latitude. Spruce mean annual ET was 9% higher than pine in one of the paired plot sets and 37% higher in the other set. For drainage, pine was 15% greater than spruce in one of the paired plot set and 74% higher in the other set of paired plots. There were no significant differences between spruce and pine plots for snowmelt and runoff. Variation around these trends were related to differences in soil hydraulic properties among the plots which, in turn, were related to differences in parent material and soil texture. The overall conclusion from this study was that the daily water balance of the forested plots could be realistically modelled using such a relatively simple water balance model as WATBAL. The importance of spatially representative and accurate soil moisture measurements for model calibration purposes was highlighted. While the importance of snowfall on the water balance increased northwards regardless of tree species, evapotranspiration was determined by both latitude and by species. Climate change can therefore be expected to have a significant impact on the water balance of Finnish forests resulting in environmentally important changes in leaching and runoff.

Viime vuosina julkaistujen tutkimusten mukaan metsäojitettujen soiden vesistö kuormituksen epäillään olevan moninkertaisesti aiemmin arvioitua suurempaa. Syynä tähän on se, että kuormitusta syntyy aiemmista käsityksistä poiketen silloinkin, kun ojitusalueilla ei ole vuosikausiin tehty mitään toimenpiteitä. Tässä työssä arvioitiin metsäojitusalueilta syntyvä vesistökuormitus ottamalla huomioon sekä tämä nykyisistä metsätaloustoimenpiteistä riippumaton ”ojituslisä” että kunnostusojituksen, lannoituksen ja hakkuiden aiheuttama kuormitus. Tehdyn arvion mukaan metsätaloudesta ojitetuilla soilla syntyy Suomessa vuosittain typpikuormitusta noin 8500 Mg ja fosforikuormi tusta 590 Mg. Kun ojituslisä otetaan huomioon, typpikuormitus on noin 18-kertainen ja fosforikuormitus 6–7-kertainen aiempiin vain eri toimenpiteiden kuormitukset huomioon ottaviin arvioihin verrattuna. Vesiensuojelun kannalta oleellista olisi selvittää, mitkä tekijät ojitusalueilla aiheuttavat ojituslisän muodossa tapahtuvaa pysyvää kuormitusta ja mitä tämän kuormituksen torjumiseksi on tehtävissä.