Picea Abies Stands Research Articles

Comparing the Effectiveness of Exome Capture Probes, Genotyping by Sequencing and Whole-Genome Re-Sequencing for Assessing Genetic Diversity in Natural and Managed Stands of Picea abies

Conifer genomes are characterized by their large size and high abundance of repetitive material, making large-scale genotyping in conifers complicated and expensive. One of the consequences of this is that it has been difficult to generate data on genome-wide levels of genetic variation. To date, researchers have mainly employed various complexity reduction techniques to assess genetic variation across the genome in different conifer species. These methods tend to capture variation in a relatively small subset of a typical conifer genome and it is currently not clear how representative such results are. Here we take advantage of data generated in the first large-scale re-sequencing effort in Norway spruce and assess how well two commonly used complexity reduction methods, targeted capture probes and genotyping by sequencing perform in capturing genome-wide variation in Norway spruce. Our results suggest that both methods perform reasonably well for assessing genetic diversity and population structure in Norway spruce (Picea abies (L.) H. Karst.). Targeted capture probes were slightly more effective than GBS, likely due to them targeting known genomic regions whereas the GBS data contains a substantially greater fraction of repetitive regions, which sometimes can be problematic for assessing genetic diversity. In conclusion, both methods are useful for genotyping large numbers of samples and they greatly reduce the cost involved with genotyping a species with such a complex genome as Norway spruce.

Differences in biomass production and carbon sequestration between highland and lowland stands of Picea abies (L.) H. Karst. and Fagus sylvatica L.

Despite different levels of complexity among biomass models, it is unclear how much patterns of biomass production and allocation differ between mountain and lowland forests, and how much neglecting this difference biases carbon pool estimations. To address this question, we studied chronosequences of 24 Fagus sylvatica and 24 Picea abies stands in Poland, located both in lowlands and highlands (12 stands of each species per category). We cut and weighted 192 sample trees, and we measured carbon content in wood, bark, branches and leaves. We also developed allometric tree- and stand-level models of biomass and carbon mass. Using log-transformed linear models we checked the effect sizes of elevation category (lowland and highland) on estimate output. We found small, statistically insignificant differences in biomass allocation patterns, carbon content and allometric trajectories in trees between lowland and highland stands. Tree-level allometric models without elevation category had higher accuracy than models including elevation category and explained 96.8–99.8% of biomass variability. Biomass and carbon stock of species studied was positively correlated with stand volume, age, basal area and height, and negatively with stand density. However, the differences between lowlands and highlands were low and did not exceed 38 Mg ha−1 (for P. abies foliage biomass, with model root mean squared error of 37.638 Mg ha−1). Our results revealed transferability of models developed using lowland and highland populations of the studied species. This will increase confidence in methods used to estimate carbon pools.

Biological inhibition of soil nitrification by forest tree species affects Nitrobacter populations.

Some temperate tree species are associated with very low soil nitrification rates, with important implications for forest N dynamics, presumably due to their potential for biological nitrification inhibition (BNI). However, evidence for BNI in forest ecosystems is scarce so far and the nitrifier groups controlled by BNI-tree species have not been identified. Here, we evaluated how some tree species can control soil nitrification by providing direct evidence of BNI and identifying the nitrifier group(s) affected. First, by comparing 28 year-old monocultures of several tree species, we showed that nitrification rates correlated strongly with the abundance of the nitrite oxidizers Nitrobacter (50- to 1000-fold changes between tree monocultures) and only weakly with the abundance of ammonia oxidizing archaea (AOA). Second, using reciprocal transplantation of soil cores between low and high nitrification stands, we demonstrated that nitrification changed 16 months after transplantation and was correlated with changes in the abundance of Nitrobacter, not AOA. Third, extracts of litter or soil collected from the low nitrification stands of Picea abies and Abies nordmanniana inhibited the growth of Nitrobacter hamburgensis X14. Our results provide for the first time direct evidence of BNI by tree species directly affecting the abundance of Nitrobacter.

Decreased variation of forest understory vegetation is an effect of fertilisation in young stands of Picea abies

The substitution of fossil fuels with biofuels to mitigate climate change has caused increased interest in enhancing forest biomass production through fertilisation. We investigated the effects of different fertilisation frequencies on the diversity of understory vegetation in young stands of Picea abies on five sites distributed in regions in the middle and south of Sweden. The treatments included fertilisation conducted annually, every second year or every third year, as well as an unfertilised control. A lower number of vascular plant species was observed on fertilised plots than on control plots, whereas the number of bryophyte species remained unchanged. Fertilised plots also showed a lower variance in species composition and a lower Shannon's diversity index than unfertilised plots. Fertilised plots were more similar to each other than unfertilised plots were to each other over the geographical range. The two most intensive fertilisation treatments had similar effects on the vegetation, whereas the effects of fertilisation conducted every third year were not as substantial. However, the treatment in which fertilisation occurred every third year implies a lower stem-wood production, and there is little knowledge of the long-term differences between the treatments. We conclude that fertilisation of young stands will lead to long-term changes in understory vegetation at the stand scale, whereas the effects at the landscape level are still largely unknown.

A new Late-glacial and Holocene record of vegetation and fire history from Lago del Greppo, northern Apennines, Italy

Detailed Late-glacial and Holocene palaeoenvironmental records from the northern Apennines with a robust chronology are still rare, though the region has been regarded as a main area of potential refugia of important trees such as Picea abies and Abies alba. We present a new high-resolution pollen and stomata record from Lago del Greppo (1,442 m a.s.l., Pistoia, northern Apennines) that has been dated relying on 12 terrestrial plant macrofossils. Late-glacial woodlands became established before 13000 cal b.p. and were dominated by Pinus and Betula, although more thermophilous taxa such as Quercus, Tilia and Ulmus were already present in the Greppo area, probably at lower altitudes. Abies and Picea expanded locally at the onset of the Holocene at ca. 11500 cal b.p. Fagus sylvatica was the last important tree to expand at ca. 6500 cal b.p., following the decline of Abies. Human impact was generally low throughout the Holocene, and the local woods remained rather closed until the most recent time, ca. a.d. 1700–1800. The vegetational history of Lago del Greppo appears consistent with that of previous investigations in the study region. Late-glacial and Holocene vegetation dynamics in the northern Apennines are very similar to those in the Insubrian southern Alps bordering Switzerland and Italy, across the Po Plain. Similarities between the two areas include the Late-glacial presence of Abies alba, its strong dominance during the Holocene across different vegetation belts from the lowlands to high elevations, as well as its final fire and human-triggered reduction during the mid Holocene. Our new data suggest that isolated and minor Picea abies populations survived the Late-glacial in the foothills of the northern Apennines and that at the onset of the Holocene they moved upwards, reaching the site of Lago del Greppo. Today stands of Picea abies occur only in two small areas in the highest part of the northern Apennines, and they have become extinct elsewhere. Given the forecast global warming, these relict Picea abies stands of the northern Apennines, which have a history of at least 13,000 years, appear severely endangered.

Changes in understory composition following catastrophic windthrow and salvage logging in a subalpine forest ecosystem

Catastrophic windthrow and postdisturbance salvage logging each have the potential to profoundly influence understory vegetation communities. This study compared understory vegetation cover, composition, and diversity in Routt National Forest, a subalpine forest in northwestern Colorado that sustained a 10 000 ha blowdown in 1997 and was partially salvage logged in 1999. Understory and edaphic variables were measured in five heavily wind-disturbed Picea–Abies stands, five stands salvage logged 20 months after the blowdown, and five intact stands. Understory species cover and diversity were greater in blown down areas than in salvage-logged or control areas. Community composition of each treatment area was distinct and related to a gradient in organic soil depth, which reflected the severity of understory disturbance. Composition and diversity in blowdown areas relative to control areas stabilized in the 5 years following the blowdown, but vegetation cover continued to increase. Blowdown areas contained early and late successional species. Salvage-logged areas exhibited a shift towards graminoid dominance. This structural change could delay future conifer seedling establishment. The interaction among disturbance severity, understory vegetation composition, and regeneration dynamics should be considered in future decisions to salvage log similar areas because the long-term effects of salvage logging are unknown.

Experimental verification of microsatellite null alleles in Norway spruce (Picea abies [L.] Karst.): Implications for population genetic studies

Three stands ofPicea abies [L.] Karst. with different density in the Harz Mountains (Lower Saxony, Germany) were characterized at 4 microsatellite loci. An excess of homozygotes was observed in all 3 stands at 1 simple sequence repeat (SSR) locus, suggesting the presence of null alleles. To test for the segregation of a null allele, 24 openpollinated seeds (haploid megagametophytes and embryos) from apparently homozygous mother trees were analyzed. For 1 of 3 trees that could be identified as heterozygous for a null allele, no significant deviation from the expected 1∶1 segregation into marker absence (null allele) and marker presence of the second maternal allele could be observed in the haploid megagametophyte. Concordantly, the numbers of embryos heterozygous for the null allele and for the other maternal allele were not significantly different from each other. Inheritance analyses in seedlings and corresponding megagametophytes of gymnosperms were used as a direct experimental verification of microsatellite null alleles in single-tree progeny. Microsatellites with an abundance of null alleles should be discarded from further analysis because inclusion of these loci results in incorrect estimation of allele frequencies.

Modeling infection and spread of Heterobasidion annosum in even-aged Fennoscandian conifer stands

Heterobasidion annosum (Fr.) Bref. s. lato causes severe damage to forests. This study describes a model for simulating the infection and spread of Heterobasidion spp. in stands of Picea abies (L.) Karst. and Pinus sylvestris L. The model includes submodels for stand dynamics (plot simulation, growth and yield, and cross-cutting of trees) and disease dynamics: (i) spore infection, (ii) stump colonization, (iii) colonization of stump roots, (iv) vegetative transfer to tree roots, (v) spread of disease in tree roots, (vi) spread of decay in stems, and (vii) disease effect on tree growth and survival. To illustrate the model, a simulation was carried out on a Swedish Norway spruce stand where logging occurred during the high-risk season for spore infection. The model provides a means of incorporating the impact of root disease into forest planning. A change of parameters indicated that model predictions were sensitive to the spread rate and presence of initial disease centers. Further research is called for in areas related to the development of coarse root systems of various tree species and the probability and rate of transfer of disease from various sources of inoculum to healthy trees.

Age-related effects on leaf area/sapwood area relationships, canopy transpiration and carbon gain of Norway spruce stands (Picea abies) in the Fichtelgebirge, Germany.

Stand age is an important structural determinant of canopy transpiration (E(c)) and carbon gain. Another more functional parameter of forest structure is the leaf area/sapwood area relationship, A(L)/A(S), which changes with site conditions and has been used to estimate leaf area index of forest canopies. The interpretation of age-related changes in A(L)/A(S) and the question of how A(L)/A(S) is related to forest functions are of current interest because they may help to explain forest canopy fluxes and growth. We conducted studies in mature stands of Picea abies (L.) Karst. varying in age from 40 to 140 years, in tree density from 1680 to 320 trees ha(-1), and in tree height from 15 to 30 m. Structural parameters were measured by biomass harvests of individual trees and stand biometry. We estimated E(c) from scaled-up xylem sap flux of trees, and canopy-level fluxes were predicted by a three-dimensional microclimate and gas exchange model (STANDFLUX). In contrast to pine species, A(L)/A(S) of P. abies increased with stand age from 0.26 to 0.48 m(2) cm(-2). Agreement between E(c) derived from scaled-up sap flux and modeled canopy transpiration was obtained with the same parameterization of needle physiology independent of stand age. Reduced light interception per leaf area and, as a consequence, reductions in net canopy photosynthesis (A(c)), canopy conductance (g(c)) and E(c) were predicted by the model in the older stands. Seasonal water-use efficiency (WUE = A(c)/E(c)), derived from scaled-up sap flux and stem growth as well as from model simulation, declined with increasing A(L)/A(S) and stand age. Based on the different behavior of age-related A(L)/A(S) in Norway spruce stands compared with other tree species, we conclude that WUE rather than A(L)/A(S) could represent a common age-related property of all species. We also conclude that, in addition to hydraulic limitations reducing carbon gain in old stands, a functional change in A(L)/A(S) that is related to reduced light interception per leaf area provides another potential explanation for reduced carbon gain in old stands of P. abies, even when hydraulic constraints increase in response to changes in canopy architecture and aging.

Modelling age- and density-related gas exchange of Picea abies canopies in the Fichtelgebirge, Germany

Differences in canopy exchange of water and carbon dioxide that occur due to changes in tree structure and density in montane Norway spruce stands of Central Germany were analyzed with a three dimensional microclimate and gas exchange model STANDFLUX. The model was used to calculate forest radiation absorption, the net photosynthesis and transpiration of single tree s, and gas exchange of tree canopies. Model parameterizations were derived for six stands of Picea abies (L.) Karst. differing in age from 40 to 140 years and in density from 1680 to 320 trees per hectare. Parameterization included information on leaf area dist ribu- tion from tree harvests, tree positions and tree sizes. Gas exchange was modelled using a single species-specific set of physio logical parameters and assuming no influence of soil water availability. For our humid montane stands, these simplifying assumptions appeared to be acceptable. Comparisons of modelled daily tree transpiration with water use estimates from xylem sapflow measure - ments provided a test of the model. Estimates for canopy transpiration rate derived from the model and via xylem sapflow measur e- ments agreed within ± 20%, especially at moderate to high air vapor pressure deficits. The results suggest that age and density dependent changes in canopy structure (changes in clumping of needles) and their effect on light exposure of the average needle lead to shifts in canopy conductance and determine tree canopy transpiration in these managed montane forests. Modelled canopy net photosynthesis rates are presented, but have not yet been verified at the canopy level. norway spruce / xylem sapflow / canopy transpiration / canopy light use efficiency / biosphere-atmosphere interactions

Crown Density and Growth Relationships Between Stands of Picea abies in Norway

Relationships between the crown density and growth of Norway spruce (Picea abies L. Karst.) stands are presented, after removal of the effects of major natural influences. Crown density was assessed annually from 1991 to 1996 on 569 monitoring plots comprising 40000 trees. Stand growth was determined from measurements of diameter and height in 1991 and 1996. Various models explaining mean crown density and annual growth of the stands as a function of natural factors, such as age and site index, were compared. The influence of the natural factors was then removed by recalculating crown density to residual values from one preferred model, and by recalculating growth to relative values given as a percentage of model predictions. Crown density and its residuals were positively correlated to growth. These relationships were weak in terms of their ability to explain variation (low R2). However, the various relationships consistently indicated that approximately 1% change in crown density corresponded to 1% change in growth. This relationship also included common spatial variation over Norway: a large part of south - east Norway had unexplained low crown density and unexplained low growth. Some other, smaller regional consistencies were also found. The study supports the use of crown density assessments and encourages the use of growth data in the search for major stress factors responsible for present forest condition.

Effect of Traffic by Lightweight Forest Machinery on the Growth of Young Picea abies Trees

The effect of traffic by lightweight forest machinery (5–9 Mg) on soil properties and tree growth was assessed in young stands of Picea abies (L.) Karst. Seven sites in the central and southern part of Sweden were monitored for 3 yrs after cleaning operations had been carried out in them. Leader length and diameter of the young trees as well as rut depth and cone penetrometer resistance were measured. The machines made 1–2-cm-deep ruts which had decreased in depth by 40% after 1 yr. Cone penetrometer resistance was slightly increased in the ruts, indicating that the soils were subjected to some degree of traffic-induced compaction. The growth of the trees (n=1073) measured did not differ statistically significant between trees at a distance of 0–1 m from the rut and those>2 m from the rut. In conclusion, traffic by lightweight machinery in young forest stands can occur without affecting tree growth.

Does Tree Age Predict the Occurrence and Abundance of Usnea Longissima in Multi-Aged Submontane Picea Abies Stands?

In boreal Scandinavia Usnea longissima is a rare epiphytic lichen associated with old spruce (Picea abies) forests. To test whether tree age was an important determinant of the occurrence and abundance of U. longissima at the scale of a forest stand we estimated thallus numbers on 1008 trees within three submontane spruce stands in south-central Norway. The stands were of all ages and multi-layered and had been selectively cut previous to the 1940s. There was no relationship between number of U. longissima thalli and tree age among trees with dbh of ≥ 10 cm. The most consistent pattern was a positive relationship between occurrence and number of thalli and stem diameter. After controlling the covariance of stem diameter, there was a tendency for a negative relationship between number of thalli and tree age. The results suggest that in old-growth resembling stands, with already established U. longissima populations, tree size (here measured as stem Diameter) is a better predictor of thallus number than tree age. This does not contradict the possibility that other environmental characteristics, associated with stands of older age, may be important for the establishment and growth of U. longissima populations.

Crown Condition and Growth Relationships within Stands of Picea abies

Relationships within stands between growth and crown condition are presented. The data set contained about 25 000 trees on 500 plots. Growth of single trees was determined by diameter measurements in 1991 and 1996. Diameter increments were recalculated to relative values in two steps; firstly relative to their stem diameter, and secondly relative to reference values for trees in the same plot, having no defoliation or no discoloration. These relative increment values, or growth indices, were distributed on a scale common for all plots, rendering them influenced neither by site and stand properties, nor by social status of each tree. The correlation between crown condition and growth, although of moderate strength, did validate crown condition assessments as a meaningful, but rough measure of forest health or vigour. The relationships were concave, and considerable growth depressions were already found at slight levels of defoliation and discoloration. Growth approached zero as defoliation and discoloration increased towards 100%. These relationships applied for all plots, regardless of their site productivity, development stage or regeneration method.

Estimation of dispersal gradients of S‐ and P‐type basidiospores of Heterobasidion annosum

SummaryThe number of airborne deposits of the root pathogen Heterobasidion annosum was counted with a wood disc method at distances 5–1000 m from one S‐type and one P‐type infection centre in stands of Picea abies in June, July and August, 1995. The level of background deposition in the area was determined in four healthy control stands. Based on intersterility group determination of deposits, only measurements within 100 m of the infection centres could be used in estimations of dispersal gradients owing to confusion with background deposition. A power law gradient model adequately described the reduction of deposits with increasing distance from the infection centres. Gradients were fairly similar in four directions around the infection centres as the wind speeds were low (3.2m/s) during the collection periods. The gradients were steeper around the P‐type centre, probably due to its lower spore production capacity. The background deposition level (2.8 colonies/m2× h) was reached at distances 1255 m and 98 m from the S‐type and P‐type centre, respectively.

Small scale pH buffering in organic horizons of two boreal coniferous forest stands

Factors behind the small-scale variaton of pH were examined in O horizons (humus layers) developed under two stands of Picea abies (L.) Karst. (Site F and K) by combining data on the composition of the cation exchange complex with data from titrations of corresponding H+-saturated samples. Cations extractable in 0.5 M CuCl2 (S=cmolc kg−1 [2Ca+2Mg+2Mn+K+Na]), aluminium extractable in 1.0 M KCl (Ale=cmolc kg−1 [3Al]) and in 0.5 M CuCl2 (Alorg=cmolc kg−1 [3Al]), as well as pH measured in 0.01 M CaCl2 (pHCa) were analysed in one-cm-layers of 13 O horizon cores at each site. Composite samples representing each of the one-cm-layers at each site, as well as samples with two different levels of Al saturation at Site K, were H+ saturated and titrated with NaOH to chosen end points of pHCa=4.0 and 5.5 in a 0.01 M CaCl2 ionic medium. The Acid Neutralisation Capacity (ANC) was estimated as the amount of base needed to increase pHCa of the composite H+-saturated samples to the mean pHCa of the corresponding natural samples. The ANC was found to be similar in magnitude or higher than the amount of sites binding S+Ale, which suggests that 1.0 M KCl exchangeable Al ions are nonacidic in acid O horizons. The relative contribution from i) the capacity of acidic functional groups, ii) their acid strength and iii) their degree of neutralisation to differences in pHCa between sites, among cm-layers and between samples with different levels of Al saturation were estimated from titration curves adjusted to hold two out of three factors (i, ii and iii) to be constant. The degree of neutralisation explained most of the differences in pHCa between the two sites, as well as between samples with different levels of Al saturation at Site K. The pHCa decrease by depth at site F was, however, partly explained by an increasing acid strength. The study emphasizes the importance of examining not only changes in the degree of neutralisation, but also changes in the acid strength and the capacity of buffering functional groups before conclusions about causes behind acidification processes can be made. Difficulties of accurately estimating the degree of neutralisation (base saturation) of acidic functional groups from the composition of adsorbed cations, owing to the unknown acidity of adsorbed Al, was also demonstrated.

Examination of low‐pathogenicity isolates of Armillaria mellea from natural stands of Picea abies in Middle‐Europe

AbstractIn certain indigenous Picea abies Karst. stands in the Thuringian Forest (Middle‐Europe), the incidence of butt rot and die‐back of saplings caused by Armillaria mellea (Vahl ex Fr.) Karst. is conspicuously low in spite of a general spread of this fungus on stumps of clear‐fellings. The majority of 43 isolates of A. mellea recovered from 13 highland infection centres were unable to form the brown type of rhizo‐morphs (BR) in soil but could form the white type rhizomorphs (WR) on sterile substrates. In contrast, 17 isolates from lowland hardwood stands of average disease incidence produced both types of rhizo‐morphs on both substrates. Results of inoculation of excised stem and root sections of Picea abies and Fagus sylvatica L. and saplings of P. abies associated with soils of different fertility levels indicated that the low disease index of certain P. abies stands is caused by the dominance of low‐pathogenicity strains of A. mellea which lack the ability to form BR and penetrate non‐injured bark of roots. Moreover, the poor podzolic highland soil types may contribute more to increase the survival rate and resistance of transplanted P. abies saplings than to reduce the spread of A. mellea.

Picea-Abies forests in the highlands of Northern Alberta

Thirty stands of Picea-Abies dominated forest in highland areas of northern Alberta were studied quantitatively. The highlands are cooler and receive more precipitation than the adjacent lowlands in summer. Orthic Grey Luvisols are the most common soil type.