The large pine weevil (
) is a major regeneration pest in commercial forestry. Pesticide application has historically been the preferred control method, but pesticides are now being phased out in ...several countries for environmental reasons. There is, thus, a need for alternative plant protection strategies. We applied methyl jasmonate (MeJA), salicylic acid (SA) or oxalic acid (OxA) on the stem of 2-year-old Norway spruce (
) plants to determine effects on inducible defenses and plant growth. Anatomical examination of stem cross-sections 9 weeks after application of 100 mM MeJA revealed massive formation of traumatic resin ducts and greatly reduced sapwood growth. Application of high concentrations of SA or OxA (500 and 200 mM, respectively) induced much weaker physiological responses than 100 mM MeJA. All three treatments reduced plant height growth significantly, but the reduction was larger for MeJA (~55%) than for SA and OxA (34-35%). Lower MeJA concentrations (5-50 mM) induced comparable traumatic resin duct formation as the high MeJA concentration but caused moderate (and non-significant) reductions in plant growth. Two-year-old spruce plants treated with 100 mM MeJA showed reduced mortality after exposure to pine weevils in the field, and this enhanced resistance-effect was statistically significant for three years after treatment.
Heat-induced weight loss (WL) and chemical and dimensional changes of small specimens of beech (
Fagus sylvatica L.), Scots pine (
Pinus sylvestris L.) and Norway spruce (
Picea abies L.) wood were ...examined after thermal modification in the 190–245 °C temperature range. Treated specimens exhibited reductions in their oven-dry weight in line with the severity of the treatment, with the effect of increasing the temperature of exposure being greater than extending the period of treatment. Wood polysaccharides were found to be distinctly more labile than the lignin constituent; the latter increased possibly as a result of repolymerisation reactions trapping some degradation products in the process. Specimens shrank in the transversal plane in a tangential to radial ratio of 2:1 regardless of the treatment regime, while their length increased marginally for WL < 10–12%. It is proposed that the thermal modification leaves the cell wall material in a permanent strained state.
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•The first generalized H-D model was developed for Romanian forests.•Used stand predictors measure tree competition and stand structure.•Calibrating both effects of the mixed model ...reduces the sampling effort.•High accuracy achieved by sampling six trees around the median and the thickest tree.
Tree height measurements are laborious and require more time and effort compared to tree diameter measurements. That being the case, height-diameter (H-D) models are usually used to predict individual tree heights, which are necessary for estimating the tree volume and the site index, as well as for projecting the stand development over time. Using a permanent sampling network (400x400m) from Retezat National Park in Romania, twenty-one (H-D) functions were evaluated for their fit performance, sensitivity to outliers and prediction ability for Norway spruce in mixed uneven aged stands. A set of twenty-three stand variables, both spatial and non-spatial, were used to describe the stand structure, species inter-mingling and competition, in order to be used as stand predictors in a generalized H-D model. Nonlinear mixed effects model was used in modelling the H-D relationship of Norway spruce. We developed the first generalized height-diameter model in Romania using three stand predictors as measures of the stand vertical structure, density and competition. Random and fixed effects calibration techniques were compared, testing various sampling designs in order to improve the height prediction accuracy of the model on a new dataset. Measuring six trees around the median and the thickest tree gave the best result in calibrating both fixed and random effects. On average, the best calibration design increased the accuracy of the prediction by 50 cm compared to the fixed effects prediction. The use of the estimated coefficients and the calibration design will significantly decrease the amount of work done by forest management planners, while ensuring high accuracy and reducing costs.
•Radial xylem sap flow profiles are rarely studied, especially under abiotic stress.•A beech/spruce forest was exposed to repeated seasonal drought and recovery.•HFD and TD type sensors were applied ...to measure the xylem sap flow density profile.•Repeated drought reduced the xylem sap flow profile in spruce but not in beech.•Radial sap flow profiles are altered by drought-induced leaf area reductions.
Water consumption of trees is one of the most important processes connected to their survival under ongoing climate change and extreme events such as drought. Radial profiles of xylem sap flow density are an integral component to quantify the water transport for the level of an individual tree and that of ecosystems. However, knowledge of such radial profiles, in particular under stress, is very scarce. Here we show the radial profile of the xylem sap flow density in mature European beech (Fagus sylvatica L) and Norway spruce (Picea abies (L) Karst.) under repeated summer drought induced by throughfall exclusion (TE) and subsequent recovery compared to untreated control trees (CO). We measured xylem sap flow density (udaily in L dm−2 d−1) down to 8 cm sapwood depth at breast height using two different approaches, a thermal dissipation system and the heat field deformation method. In beech, repeated throughfall exclusion did not affect the radial xylem sap flow profile. However, in spruce, udaily was strongly reduced across the profile under repeated drought, changing the profile from a linear to a logarithmic regression. Even two years after drought release, the xylem sap flow profile did not fully recover in TE spruce. The reduction of udaily along the radial profile was accompanied by a reduction of the leaf area in TE spruce by c. 50%, while sapwood depth remained constant. The reduction of the xylem sap flow density along the profile reduced the calculated water consumption of TE spruce trees by more than 33% compared to CO trees, also after drought release. The impact of stressors such as repeated drought on the xylem sap flow density across the radial profile and its consequences for trees’ and stands’ water consumption needs to be addressed in more detail to minimize uncertainties in quantifying ecosystem water cycles.
The challenge to the sustainable development of forestry in the Eurasian temperate - boreal zone is the increase in the frequency and severity of natural disturbances due to global climate change. In ...this study, a mathematical model for predicting the risk of wildfires in spruce stands growing in the territory of Slovak Paradise National Park under climate change has been proposed and tested. Wildfire risk is described in terms of the observed probabilities of the destruction of spruce stands in relation to their age for a period of 10 years. As the indicators of assumed climate change, the time series of daily values of four fire weather indices (Angstrőm, Nesterov, Baumgartner, and the Meteorological Forest Fire Risk Index) for the period 1951–2019 have been analysed. The results obtained indicated the significant dependence of the observed increasing annual population proportions of burnt areas on the gradually increasing annual population proportions of risky days recorded and evaluated by using the common scales of risk classification. We found that ongoing climate change has a significant impact on increasing the risk of fires. The Meteorological Forest Fire Risk Index has proven to be the most suitable measure for predicting the probability of fire occurrence under the climate conditions in the experimental territory. The indicated risk of fire occurrence in spruce stands under the assumption of a climatic change is substantially higher than in the case when this assumption is neglected. This information can also serve as a basis for the formulation of efficient landscape fire protection measures focused on building the infrastructure to support the efficient retardation of propagation, including the quick suppression of this detrimental natural hazard.
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•We proposed and tested a new mathematical model for wildfire risk prediction.•Climate and hazard data observed in spruce forest stands in Slovakia.•As the annual numbers of dangerous days grow, the fire occurrence hazard increases.•Risk in prediction models should be included in forest management planning methods.
The study of xylogenesis or wood formation is a powerful, yet labor intensive monitoring approach to investigate intra-annual tree growth responses to environmental factors. However, it seldom covers ...more than a few growing seasons, so is in contrast to the much longer lifespan of woody plants and the time scale of many environmental processes. Here we applied a novel retrospective approach to test the long-term (1926-2012) consistency in the timing of onset and ending of cambial activity, and in the maximum cambial cell division rate in two conifer species, European larch and Norway spruce at high-elevation in the Alps. We correlated daily temperature with time series of cell number and lumen area partitioned into intra-annual sectors. For both species, we found a good correspondence (1-10 days offset) between the periods when anatomical traits had significant correlations with temperature in recent decades (1969-2012) and available xylogenesis data (1996-2005), previously collected at the same site. Yet, results for the 1926-1968 period indicate a later onset and earlier ending of the cambial activity by 6-30 days. Conversely, the peak in the correlation between annual cell number and temperature, which should correspond to the peak in secondary growth rate, was quite stable over time, with just a minor advance of 4-5 days in the recent decades. Our analyses on time series of wood anatomical traits proved useful to infer on past long-term changes in xylogenetic phases. Combined with intensive continuous monitoring, our approach will improve the understanding of tree responses to climate variability in both the short- and long-term context.
•Data from even- and uneven-aged spruce stands used to assess response to cuttings.•A stand basal area growth model predicted cutting responses without bias.•Growth rate of uneven-aged stands was 20% ...lower than in even-aged stands.•Growth response to cuttings was notably quicker in even-aged spruce stands.
This study evaluated the basal area growth of Norway spruce stands subjected to different management strategies; specifically, even-aged (EA) stands treated with thinning from below and uneven-aged (UEA) stands treated with selective cutting. Analysis was based on extensive empirical data obtained from permanent long-term experiments established in 23 even-aged and 26 uneven-aged Norway spruce (Picea abies (L.) Karst.) stands in Southern and Central Finland. The specific goals were to determine whether there are differences in: (a) the relationship between the stocking level and the stand basal area growth, (b) the stand basal area growth rates at a given stocking level, and (c) the stand basal area growth responses to cuttings between EA and UEA stands.
A model-based approach was adopted in the analysis. Modelling was used to describe general trends and patterns in the data, emphasising the effects of overall stand density, cutting intensity, and management strategy on post-treatment stand growth. A model for a stand basal-area growth was fitted as a mixed linear model to the pooled data from EA and UEA stands. Model simulations were conducted to elucidate how the treatment of stands affects the predicted stand basal area growth.
The analysis revealed a clear general effect of stocking level on stand basal area growth for all data. Growth increased with increasing stocking density. There was a significant difference in the stand basal area growth of EA stands and UEA stands. The growth of UEA stands was ca. 20% smaller than that of EA stands. There were also major differences in the timing and magnitude of the growth response to cutting between EA and UEA stands. Post treatment growth was noticeably slower in UEA stands than in EA stands, especially during the first 10 years after cutting. The results clearly show that the growth response of the trees remaining in EA stands is faster and greater than that in UEA stands, enhancing the stand basal area growth.
Dendrogeomorphic dating of past landslide events is a valuable tool for the assessment of landslide activity, providing unique data for the analysis of triggers or the modelling of landslide ...behaviour in the future. Unfortunately, tree-ring-based methods as well as dating approaches suffer from some limitations. One of the less frequently addressed limits of dendrogeomorphic analysis concerns the changing capacity of trees to record landslide events in their tree-ring series with increasing age. This study uses, to date, the most extensive database of tree-ring series (1736) of 868 disturbed individuals of Picea abies (L.) H. Karst. subjected to 20 landslides in the Outer Wester Carpathians for the assessment of their age-dependent sensitivity. The distribution of the total number of 1485 growth disturbances (reaction wood - RW and abrupt growth suppression - GS) throughout all decades of tree life shows evidence of distinct changes in the capacity for trees to record landslide signals with increasing age. The occurrence of RW dominated in the juvenile decades of tree life and then increased again in the 9th decade. The frequency of GS gradually increased and culminated during the 7th and 8th decades. The two intensities of growth disturbance (strong and moderate) expressed temporally balanced ratios, suggesting an effect of disturbance intensity rather than changing tree age. The important factors controlling age-dependent tree sensitivity to landslide movements based on the results seem to be changing stem elasticity, decreasing annual increment rates, root system development and increasing tree body weight. Moreover, this study demonstrates that landslide type (e.g., rigid block vs. plastic flow-like landslides) and bedrock geology distinctly modify age-dependent sensitivity that should be taken into account during the sampling of trees for landslide dating.
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•Age-dependent sensitivity was defined based on a large sample size of 868 trees.•Reaction wood dominated in juvenile decades of tree life.•Growth suppression culminated in the 7th–8th decades.•Landslide type and geology distinctly modify tree age-dependent sensitivity.
► Barks of Norway spruce and Scots pine have a significant content of extractives. ► Both barks fractionated well by milling and with similar fraction yield profile with a low proportion of fine ...particles. ► The fractions with the smaller particle size concentrated higher amounts of inorganic material and of extractives. ► Milling and particle size separation may be used in bark utilization as pretreatment for selective enrichment or reduction of targeted components and applications.
The composition of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) barks was studied after grinding and fractioning into different particles sizes.
Both barks fractionated well and with similar fraction yield profile. The yield of fines was low and the major fractions were larger particles, i.e. 2.4% and 3.1% of particles under 0.425mm and 66.0% and 50.3% of particles over 2mm, respectively for spruce and pine bark.
The chemical composition of spruce and pine barks, as a mass weighed average of all granulometric fractions was, respectively: ash 3.3 and 4.6%; total extractives 21.6 and 18.8% (hydrophilic extractives were dominant), lignin 27.9 and 33.7% and holocellulose 42.7 and 37.6%. Suberin accounted for 1.3% and 1.6% of spruce and pine bark, respectively. The non-cellulosic monosaccharides showed in both barks predominance of arabinose followed by xylose and mannose.
Ash elemental composition showed that N represented about 35% of the total inorganics, Ca 35% and K 17%. Zn, Cu, Ni, Cr and Pb were present in both barks at levels under 1% of the total inorganics. Spruce bark had in average higher contents compared to pine bark, except for Pb and Cr.
Size reduction of spruce and pine bark did not apply randomly to the different components and instead resulted into partial separation of the inorganic and organic matter into different size particles. Fine particles concentrated higher amounts of inorganic material and of extractives.
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