Browsing by Subject "SILVER BIRCH"

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  • Kaarakka, Lilli; Hyvönen, Riitta; Strömgren, Monika; Palviainen, Marjo; Persson, Tryggve; Olsson, Bengt A; Launonen, Erno; Vegerfors, Birgitta; Helmisaari, Heljä-Sisko (2016)
    The use of forest-derived biomass has steadily increased in Finland and Sweden during the past decades leading to more intensive forest management practices in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting results in a direct removal of stump and coarse-root carbon (C) from the stand and can cause extensive soil disturbance, which has been suggested to increase C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied in two different clear-felled Norway spruce (Picea abies) sites in Central Finland. The treatments were whole-tree harvesting (WTH, removal of stems and logging residues), and WTH and stump harvesting (WTH + S). Both sites, Honkola (2 stands) and Haukilahti (6 stands) were mounded. In both treatments, soil samples were taken from different soil layers down to a total depth of 20 cm in the mineral soil from (i) mounds, (ii) undisturbed soil and (iii) pits. The sampling was performed 11-12 years after treatments. Soil C and N mineralization rates were determined in laboratory incubation experiments. In addition, total C and N pools (g m(2)) were estimated for each disturbance class and soil layer. Soil C and N pools had a tendency to be lower following stump harvesting, but no statistically significant treatment effect was detected. Stump harvesting increased soil mixing as indicated by a significant decrease in C concentration in the mound disturbance class. There was no significant effect of stump harvesting on soil C mineralization rates. A combination of mineralization rates and soil pool data showed that field C mineralization (g CO2-C m(-2) yr(-1)) did not significantly differ between stands where stumps were removed or were retained. Further, stump harvesting did not seem to have any stimulating effect on soil CO2 efflux 11-12 years after treatment. (C) 2016 Elsevier B.V. All rights reserved.
  • Kaitaniemi, Pekka; Lintunen, Anna; Sievänen, Risto; Perttunen, Jari (2018)
    Foliar nitrogen is one of the key traits determining the photosynthetic capacity of trees. It is influenced by many environmental factors that are often confounded with the photosynthetic photon flux density (PPFD), which alone strongly modifies the nitrogen content and other foliar traits. We combined field measurements and computational estimates of light transmittance in 3D stands with different combinations of Scots pine (Pinus sylvestris) and silver birch (Betula pendula) to decouple the effect of PPFD from other potential effects exerted by the species of neighbouring trees on the leaf nitrogen content per unit leaf area (Narea) and leaf mass per area (LMA). Independent of the level of PPFD, silver birch had a significantly lower Narea and LMA when Scots pine was abundant in its neighbourhood compared with the presence of conspecific neighbours. In Scots pine, Narea and LMA were only dependent on PPFD and the branching order of shoots. In both species, the relationships between PPFD and Narea or LMA were nonlinear, especially at intermediate levels of PPFD. The levels of PPFD did not show any dependence on the species of the neighbouring trees. The responses of silver birch suggest that the species composition of the surrounding stand can influence foliar nitrogen, independent of the level of PPFD within the canopy.
  • Härkönen, Sanna; Lehtonen, Aleksi; Manninen, Terhikki; Tuominen, Sakari; Peltoniemi, Mikko (2015)
    Leaf area index (LAI) is a key variable for many ecological models, but it is typically not available from basic forest inventories. In this study, we (1) construct a high-resolution LAI map using k nearest-neighbor (k-NN) imputation based on National Forest Inventory data and Landsat 5 TM images (Landsat-NFI LAI), and (2) examine a moderate-resolution LAI map produced based on reduced simple ratio derived from MODIS reflectances (MODIS-RSR LM). The maps cover all the forested areas in Finland. Country-level averages of Landsat-NFI and MODIS-RSR LAI were at same level, but several geographical and land-use related differences between them were detected. Difference was the largest in the lake district of Finland and in northern Finland, and it increased with decreasing share of forests and increasing share of deciduous trees. As MODIS-RSR LAI does not take into account the sub-pixel variation in land use, Landsat-NFI LAI was found to produce more reliable estimates.
  • Ding, Yiyang; Leppälammi-Kujansuu, Jaana; Helmisaari, Heljä-Sisko (2019)
    Abstract 1. Fine root turnover plays a critical role in carbon and nutrient cycling in forest ecosystems. In this study, we focused on the most abundant deciduous species in Nordic countries, silver birch (Betula pendula Roth) and its fine root dynamics, including the amount of litter produced by fine roots as well as by aboveground vegetation. 2. The minirhizotron method was used to quantify fine root longevity of silver birch and understory fine roots and rhizomes in northern Finland. Fine root biomass per basal area and ectomycorrhizal short root numbers per mg were also quantified. The fine root litter production was estimated by fine root biomass and longevity, and then compared with the aboveground litter collected with litter traps. 3. Birch fine root biomass was 1.4-fold higher than that of understory fine roots and rhizomes (234 ± 22, 171 ± 19 g m−2 respectively). Fine root longevity of birch (372 days) was significantly (P < 0.05) shorter than that of understory vegetation (643 days). The birch fine root longevity was positively related to root diameter and soil depth. Hazard analysis showed that thicker roots, long roots, roots produced late in the growing season, and roots growing deeper in the soil had relatively lower mortality hazard compared to the reference data. The total annual soil C input, including both birch and understory, was 283 g C m−2 yr−1. The proportion of understory annual C input was 35% of the total. Total annual belowground C input was 1.4-fold greater than that of aboveground. 4. Our study indicated that the total annual belowground litter production was greater than that of the aboveground litter in a boreal deciduous forest stand. Therefore, more emphasis should be put to quantify the C cycling of both above- and belowground parts of different tree species as well as understory in boreal forests.
  • Leppälammi-Kujansuu, Jaana; Aro, Lasse; Salemaa, Maija; Hansson, Karna; Kleja, Dan Berggren; Helmisaari, Heljä-Sisko (2014)
  • Larjavaara, Markku; Berninger, Frank; Palviainen, Marjo; Prokushkin, Anatoly; Wallenius, Tuomo (2017)
    Improved understanding of carbon (C) accumulation after a boreal fire enables more accurate quantification of the C implications caused by potential fire regime shifts. We coupled results from a fire history study with biomass and soil sampling in a remote and little-studied region that represents a vast area of boreal taiga. We used an inventory approach based on predefined plot locations, thus avoiding problems potentially causing bias related to the standard chronosequence approach. The disadvantage of our inventory approach is that more plots are needed to expose trends. Because of this we could not expose clear trends, despite laborious sampling. We found some support for increasing C and nitrogen (N) stored in living trees and dead wood with increasing time since the previous fire or time since the previous stand-replacing fire. Surprisingly, we did not gain support for the well-established paradigm on successional patterns, beginning with angiosperms and leading, if fires are absent, to dominance of Picea. Despite the lack of clear trends in our data, we encourage fire historians and ecosystem scientists to join forces and use even larger data sets to study C accumulation since fire in the complex Eurasian boreal landscapes.
  • Kaitaniemi, Pekka; Lintunen, Anna; Sievanen, Risto (2020)
    We demonstrate the efficacy of power-law models in the analysis of tree branch growth. The models can be interpreted as allometric equations, which incorporate multiple driving variables in a single scaling relationship to predict the amount of growth within a branch. We first used model selection criteria to identify the variables that most influenced (1) the length of individual elongating annual shoots and (2) the total length of all elongating annual shoots in the individual branches of silver birch (Betula pendula Roth). We then applied the two resulting power-law equations as dynamic models to predict the trajectories of crown profile development and accumulation of branch biomass during tree growth, using total branch length as a proxy for biomass. In spite of the wide size range and geographical distribution of the study trees, the models successfully reproduced the dynamic characteristics of crown development and branch biomass accumulation. Applying the model to predict long-term growth of a single branch that was initiated at the crown top generated a realistic crown profile and produced a final basal branch size that was well within the range of field observations. The models also predicted a set of more subtle and non-trivial features of crown formation, including the increased rate of growth towards the tree apex, decrease in growth towards the lowest branches, the effect of branching order on the amount of elongation, and the higher vigour of thick branches when the effect of branch height was controlled. In contrast, a simple allometric model of the form Y = aX(b) was incapable of capturing all the variability in growth of individual branches and of predicting the features of crown shape and branch size that are associated with the slowing-down of growth towards the crown base. We conclude that power-law models where the parameter a is refined to include spatial information on branch features shows good potential for identifying and incorporating actual crown construction processes in dynamic models that utilize the structural features of tree crowns.
  • Zeleznik, Peter; Westergren, Marjana; Bozik, Gregor; Eler, Klemen; Bajc, Marko; Helmisaari, Heljä-Sisko Marketta; Horvath, Aniko; Kraigher, Hojka (2019)
    European beech (Fagus sylvatica L.) is commercially and ecologically important tree species in Central European forests but its intra-specific variability in drought and temperature tolerance might endanger its future distribution in Europe. Beech phenological and growth traits have been studied in large-scale international beech provenance trials, yet the growth and turnover of its fine roots (FR) has not been included among the observations. FR growth dynamics and FR architectural traits of three beech provenances in the international beech provenance trial Straza/Kamenski hrib, established in Slovenia in 1998, and from a natural beech regeneration site growing at its border, were studied from 2007 to 2010. We studied FR biomass using soil cores (SC), root production using ingrowth soil cores (IC), and root longevity using minirhizotrons (MR). Significant differences in FR biomass (live and dead) between the provenance P37 and other provenances were discovered in SC, FR biomass of P37 being significantly higher than FR biomass of latter, which could be connected with overall excellent growth performance of P37 due to favourable environmental conditions at trial. Values of specific root length (SRL) in IC varied significantly among P37 and P54. The turnover rates in IC were at the end of the experiment close to MR results. Median MR-based longevities of FR varied between 625 and 934 days. Survival curve of the slowest growing provenance (considering its aboveground characteristics) was significantly different from the other two, median longevities of the latter being higher. Death of FR, older than two years, occurred most likely in the winter. Our results suggest that there are significant differences in FR longevity among provenances, which might contribute to their adaptation to future environmental conditions. Furthermore, the calculated annual C investment into FR growth per ha differs up to twofold between provenances, contributing to different C dynamics of their future stands.
  • Mäki, Mari; Krasnov, D.; Hellén, H.; Noe, S. M.; Bäck, J. (2019)
    The forest floor is a significant contributor to the stand-scale fluxes of biogenic volatile organic compounds. In this study, the effect of tree species (Scots pine vs. Norway spruce) on forest floor fluxes of volatile organic compounds (VOC) was compared in boreal and hemiboreal climates.