DNA methylation plays important roles in many biological processes, such as silencing of transposable elements, imprinting, and regulating gene expression. Many studies of DNA methylation have shown ...its essential roles in angiosperms (flowering plants). However, few studies have examined the roles and patterns of DNA methylation in gymnosperms. Here, we present genome-wide high coverage single-base resolution methylation maps of Norway spruce (Picea abies) from both needles and somatic embryogenesis culture cells via whole genome bisulfite sequencing. On average, DNA methylation levels of CG and CHG of Norway spruce were higher than most other plants studied. CHH methylation was found at a relatively low level; however, at least one copy of most of the RNA-directed DNA methylation pathway genes was found in Norway spruce, and CHH methylation was correlated with levels of siRNAs. In comparison with needles, somatic embryogenesis culture cells that are used for clonally propagating spruce trees showed lower levels of CG and CHG methylation but higher level of CHH methylation, suggesting that like in other species, these culture cells show abnormal methylation patterns.
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Despite its small share of total forest biomass, ground vegetation plays an important role in biogeochemical cycles, being able to modify carbon (C) and nutrients fluxes. Global climate warming may ...affect plant nutrient uptake and the carbon:nitrogen:phosphorus (C:N:P) stoichiometry, the release of nutrients from the soil and soil organic matter, as well as significantly influence the tree stand nutrient supply. In this context, the response of Norway spruce (Picea abies (L.) H.Karst) stands' ground vegetation to warming is uncertain. An open-top chamber soil-warming simulation, lasting two growing seasons, was conducted in a spruce forest. At the end of each of the two growing seasons, before leaf senescence, European blueberry (Vaccinium myrtillus L.) aboveground biomass (leaves and stems) and mineral topsoil samples were collected from the plots. The C, N, P, micronutrient, and macronutrient concentrations were estimated in the samples. Warming caused significant decreases in C, N, and P in the soil. Warming also decreased the C:P and N:P stoichiometric ratios in the soil and increased the C:P ratio in plant stems. Significant increase in foliar C and decrease in foliar P in warmed plots were observed. The most evident effect was reduction of N and P in the soil, which directly affected the plant C:P and soil N:P stoichiometry. Our results show that warming has caused a significant decrease in the content of some nutrients in the aboveground plant tissues of blueberries. Given that N is a limiting factor of ecosystems productivity, its reduction in the soil caused by warming may be a serious threat to proper nutrient uptake and cause disruption of biogeochemical cycles. The decrease in nutrient content in aboveground tissues due to warming can result in disruptions to physiological processes.
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•A two-season lasting warming experiment was performed in Norway spruce stand.•Warming significantly decreased C, N and P content in mineral topsoil.•Warmed European blueberry leaves had higher C and lower P content.•Warming reduced Cu, Fe, Mg, Mn and Na content in aboveground parts of blueberries.•N may be a limiting element for biomass production of forests threatened by warming.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Low soil moisture reduced stem growth of Norway spruce in southern Sweden.•High temperature sums and nitrogen deposition tended to increase growth.•Ozone exposure and start of ...growing season could not be shown to influence growth.
Associations between the annual stem basal area increment growth and soil moisture, nitrogen deposition, ground level ozone exposure, air temperatures and the timing of the start of the growing season have been investigated for a twenty four-year period, 1990–2013, based on tree-ring width measurements from seventeen monitoring sites with Norway spruce (Picea abies) forests in southern Sweden. The stem growth-environment associations were analyzed using a fixed effect regression model, with annual stem basal area increment (BAI) as the dependent variable and annual values for a soil moisture index, ozone exposure estimated as AOT30, bulk deposition of nitrogen, summed air temperatures above a threshold and the timing of the start of the growing season as explanatory variables. The statistical analysis was made with and without taking clustering of the sampled trees into account, i.e. that several different tree observations were made at the same monitoring site. The annual number of days with soil moisture below a threshold was the only explanatory variable that could be demonstrated to be negatively associated with changes in BAI, regardless of statistical approach. Positive associations between temperature sums as well as nitrogen deposition with changes in BAI were indicated by low p values using standard p-values, but not when clustering was taken into consideration. Associations between ozone exposure as well as the start date of the growing season with changes in BAI could not be demonstrated since the estimated p values were high regardless of statistical approach. The results show that soil water deficit may considerably limit forest growth in northern European forests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Young forests may return to carbon sinks already eight years after reforestation.•Increased forest productivity shortens the time needed to return to carbon sink.•Harvest of logging residues/stumps ...for bioenergy may improve the carbon balance.
We analyzed ecosystem carbon fluxes from eddy-covariance measurements in five young forests in southern Sweden where the previous stand had been harvested by clear-cutting or wind-felled: three stands with Norway spruce (Picea abies (L.) Karst.), one with Scots pine (Pinus sylvestris) and one with Larch (Larix x eurolepis A. Henry). One of the spruce stands had the stumps harvested, one was fertilized and one without any special treatments. These stands returned from positive (sources) to negative (sinks) annual carbon fluxes 8–13 years after disturbance, depending on site productivity and management. This corresponds to approximately 15% of the rotation periods at these sites. Extrapolation in combination with chronosequence data suggests that conventionally regenerated stands reach a neutral carbon balance after approximately 30% of the rotation period. The lowest carbon emissions and shortest recovery time was observed in a stand where the stumps of the trees, in addition to the stems and logging residues, were removed after harvest. This stand not only returned to a carbon sink within this time period but the total carbon gains since disturbance also equaled the total losses after only 11 years. These results stress that production stands in southern Sweden are carbon sources during a relatively small part of the rotation period, and that this part can be considerably shortened by measures that increase productivity or reduce the amount of woody debris left after disturbance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Effects of species interaction were studied in a mature mixed beech-spruce forest.•A broad spectrum of parameters was included at organ (leaf, fine root, ECM), tree and stand scale.•Mixture with ...beech exacerbated soil water accessibility for spruce.•Exacerbated soil water accessibility in mixture did not increase drought susceptibility of spruce.•Group-wise mixture appears to buffer putatively negative effects of beech competition on spruce.
Mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) frequently over-yield, when compared to respective monospecific stands. Over-yielding is attributed to enhanced resource uptake efficiency through niche complementarity alleviating species competition, for example through enhanced root stratification in mixture. Under severe and frequent summer drought, however, water limitation may become crucial in modifying the prevailing competitive interaction in mixed beech-spruce forests. We hypothesize, therefore, that under drought (H I) inter-specific interaction with beech reduces water accessibility for spruce more than intra-specific conditions, thus (H II) exacerbating drought susceptibility of spruce in terms of reduced photosynthesis and stem growth. Reactions at the organ (leaf, fine root), tree and stand scale were analysed in a mature forest with beech-spruce group mixture. Under inter-specific conditions spruce’s fine-root production and depth of water uptake (assessed via δ18O of xylem water) shifted to shallow, drought-prone soil horizons, in agreement with H I. Overall, lowered fine root production and ramification along with a reduction in long-distance explorative ectomycorrhizal types resulted in decreased soil exploitation in spruce when growing together with beech. Spruce’s drought sensitivity was exemplified by a distinct decrease in stomatal conductance, net CO2 uptake rate and stem growth during periods of water limitation. Notwithstanding, species interaction effects were absent in leaf gas exchange and stem diameter growth, during a six-week summer drought period in 2013 as well as in the extremely dry year of 2003, hence rejecting H II. Based on results from soil moisture measurements and water uptake depth, we interpret the conflicting findings for H I and H II to result from: (i) seasonal shifts between positive (during spring drought) and negative (during summer drought) effects of beech neighbourhood on soil water availability for spruce, possibly overriding each other in their effect on annual stem diameter growth and (ii) the group-wise mixture pattern, where spruce is exposed to competition with beech only along group edges, i.e. laterally only, so that the putatively adverse beech effect on water accessibility stays limited. Our results suggest, compared to single tree mixture, group-wise mixture of beech and spruce to be a favourable silvicultural option in the face of climate change.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•We fitted growth models suitable for both continuous cover and rotation forestry stands.•Sensitivity to climate was restricted by using only temperature sum.•Species-specific symmetric and ...asymmetric competition affected tree growth.
Forest growth models employed in Fennoscandia have been generally targeted at rotation forestry (RF) stands, relying on age as a key predictor. Uneven aged, irregular stands, such as the ones managed with continuous cover forestry, are becoming of increasingly common. New models suited for all kind of management approaches (i.e., age-independent) have been developed in Fennoscandia. Although the ongoing climate change is projected to strongly affect tree growth in boreal regions, climatic variables included in current models are usually restricted to temperature sum averages with simple links.
The objectives of our research were: 1) fitting a new age independent empirical tree basal area increment model (B2023) with inclusion of additional climatic variables for the main Nordic tree species (Norway spruce, Scots pine, and birches); 2) using independent data to validate both the new model and other two age-independent published empirical models (P2013, P2021); and 3) investigating the sensitivity of growth predictions of all the empirical models to climate change.
Our results showed that the new model B2023 was as accurate as P2013 when independently validated. Both models performed well in different forest structures and management alternatives (namely rotation forestry, continuous cover forestry, two-storied stands, and old-growth natural forests), although with few differences, and on average slightly better than P2021. At plot level, the new model B2023 showed slight underprediction for the overstorey pine layer in continuous cover forestry and two-storied stands. The predicted climate change scenarios increased simulated growth in all models, although P2021 showed very high values for spruce. We failed to include additional climatic variables than temperature sum in B2023, thus not improving much its accuracy under historical data, nor its sensitivity to future climate.
Concluding, the individual tree models here presented can be applied to a wide range of forest structures and managements in Fennoscandia. For long-term simulation scenarios, different approaches to improve the climate sensitivity of empirical, individual tree model should be explored.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Microscopic X-ray computed tomography (XµCT) aided finite element (FE) modelling is a popular method in material science to relate material properties to heterogeneous microstructures. Recently, a ...methodology was developed for the XµCT aided FE modelling of wood, which characterises the process from specimen preparation to estimation of material properties. In the current research, this methodology is tested on branches of Norway spruce (Picea abies (L.) Karst.) to estimate the hygroexpansion coefficients of opposite (OW) and compression wood (CW). These properties are largely unknown and have engineering implications. The study is complemented by measurements of density, moisture content (MC) and elastic moduli. Results showed that the methodology assisted in the design of an integrated process and the identification of bottlenecks. It was seen that the level of detail of the numerical model had a strong influence on the obtained hygroexpansion properties. CW from branches showed higher density and longitudinal shrinkage coefficients, and elastic moduli less affected by MC. These differences are unlikely caused by MC, but more likely by the characteristics of the microstructure.
•Advance regeneration was studied after the 2014 ice storm and the 2017 windstorm.•Rapidly light-exposed stands and regularly managed mixed stands were compared.•Quantum yield was measured three ...years after each large-scale disturbance.•Increased light on damaged plots negatively affected fir and favoured deciduous trees.•Ice storm caused more damage and slower recovery than windstorm.
Physiological response to rapid light exposure due to canopy disintegration in young beech, fir, Norway spruce and sycamore trees was measured in three consecutive years after the severe ice storm in 2014 and after windthrow in 2017. Nitrogen amount (Ntot), maximum assimilation response to light (Amax) and quantum yield (Φ) were measured in three categories of different light intensities under closed canopy with indirect site factor (ISF) < 15%, at the forest edge (15% <ISF < 25%) and in the open (ISF > 25%). Tree responses with number of seedlings per hectare were compared between damaged and undamaged sites, with young trees gradually adapting to light conditions in the two years following the two disturbance events.
Nitrogen levels were in the optimal range for all species studied. Rapid exposure to elevated light reduced efficiency in fir and increased efficiency in beech and especially sycamore. No differences in response were observed in spruce. Assimilation efficiency, where both tree species were equal, shifted towards shade. Recovery was similar for all species studied after both disturbances: better after the windstorm, compared to the ice storm, indicating the severity of the event. Reductions in seedling numbers followed the pattern observed for physiological traits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Non-native Norway spruce (NS) shows a limited invasive capacity in Eastern Canada.•Most NS regeneration was found in plantation understory and edges.•Beyond the plantation edge, NS regeneration ...spread the most in open habitats.•Balsam fir could regenerate almost as NS in the understory of NS plantations.
Introduced species are used more and more for timber production throughout the world. This raises much debate about their impact on natural ecosystems. In Quebec, Canada, similar concerns are expressed regarding Norway spruce (Picea abies (L.) H. Karst.), which was introduced in the early 1900s and is currently the main non-native conifer used for planting. The purpose of the present study was to evaluate the current spread of Norway spruce in Quebec and to assess under which circumstances it can regenerate and become established. We studied Norway spruce regeneration dynamics over 5 years in the understory, edge and surroundings of 10thinned Norway spruce plantations aged 36 to 65 years. Most Norway spruce regeneration was found in the understory and near the edge of plantations, and beyond the plantation border on a few sites. Norway spruce seedling density was highly variable in the understory and at the plantation edge (0.6–30.7stems·m−2 and 0–8.5stems·m−2, respectively). Beyond the edge, high densities of Norway spruce regeneration (0.1 to 1.2 seedlings·m−2) were found in 2 recent clearcut areas and in only 2 intolerant hardwood high forests, as far as 28 m from Norway spruce plantations. Overall, Norway spruce regeneration was young (less than 16 years for 98% of seedlings) and relatively slow-growing (on average, 1.1–7.9 cm·year−1, depending on transect location and height class). Balsam fir (Abies balsamea (L.) Mill), a native species, regenerated well (mean density of 3.1stems·m−2) in the understory and the edge of 5 of the 10 studied plantations. When regeneration of both species was present, mean seedling age, growth and height were similar, but balsam fir had a better survival rate than Norway spruce (84% vs.65%). These findings suggest that Norway spruce shows a limited invasive capacity, particularly in the closed canopy of natural forests. Moreover, the presence of native balsam fir in the understory of Norway spruce plantations indicates that the successional pathway could move the stand towards a more natural ecosystem. These results can be useful to target surveys of the most sensitive ecosystems and to develop proactive management strategies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Drought stress impacts seedling establishment, survival and whole-plant productivity. Molecular responses to drought stress have been most extensively studied in herbaceous species, mostly ...considering only aboveground tissues. Coniferous tree species dominate boreal forests, which are predicted to be exposed to more frequent and acute drought as a result of ongoing climate change. The associated impact at all stages of the forest tree life cycle is expected to have large-scale ecological and economic impacts. However, the molecular response to drought has not been comprehensively profiled for coniferous species. We assayed the physiological and transcriptional response of Picea abies (L.) H. Karst seedling needles and roots after exposure to mild and severe drought. Shoots and needles showed extensive reversible plasticity for physiological measures indicative of drought response mechanisms, including changes in stomatal conductance (gs), shoot water potential and ABA (abscisic acid). In both tissues the most commonly observed expression profiles in response to drought were highly correlated with ABA levels. Still, root and needle transcriptional responses contrasted, with extensive root-specific downregulation of growth. Comparison between previously characterized A. thaliana drought-response genes and P. abies revealed both conservation and divergence of transcriptional response to drought. In P. abies, transcription factors belonging to the bZIP AREB/ABF (ABA Response Element Binding/ABRE Binding Factors) ABA-dependent pathway had a more limited role. These results highlight the importance of profiling both above- and below-ground tissues and provide a comprehensive framework to advance understanding of the drought response of P. abies. The results demonstrate that short term, severe drought induces severe physiological responses coupled to extensive transcriptome modulation and highlight the susceptibility of Norway spruce seedlings to such drought events.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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