Tree spatial patterns of Abies alba and Fagus sylvatica in the Western Carpathians over 30 years

The decline of Abies alba (fir) in natural fir–beech forests in Europe has fascinated scientists for over a century. During this period, Fagus sylvatica (beech) became the dominant species in this forest type. We hypothesised that (1) the success of beech over fir is significantly connected with the fact that beech suffers less than fir from the presence of conspecific neighbours; that (2) shade tolerance is not a factor which favours beech over fir; and that (3) this is due to a significantly reduced proportion of litter treethrow mounds with suitable conditions for the successful regeneration of fir. We investigated these hypotheses by means of tree spatial pattern analysis. Eight rectangular plots (2–8 ha) were analysed in mountain fir–beech forests of the Outer Western Carpathians, Czech Republic. Various types of the pair correlation function and L function were used to describe the tree density variability of trees with DBH ≥10 cm. The analyses were carried out on datasets from the 1970s, 1990s and 2000s. Our results suggest that negative density dependence is not responsible for the current decline of fir. It seems that a higher shade tolerance of the advanced regeneration could be one of the factors which favour beech over fir. It is evident that fir trees have a markedly stronger positive association to mounds than beech trees.     

Frost damage to planted Norway spruce seedlings — influence of site preparation and seedling type

Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by summer frost was monitored on 10 clear-cuttings of various ages to which slash removal and four types of site preparation had been applied. The clear-cuttings were established on two sites (5 on each) in southern Sweden from 1989 through 1993 and planted each year from the year of cutting until 1993. In total, 7680 seedlings were analysed for frost injuries during the first three years following planting. The site preparation methods evaluated were: application of herbicide to ground vegetation; mowing of ground vegetation; scarification (mounding); and control. Two seedling types, bare-rooted and containerised seedlings, were evaluated.Periods of frost susceptibility were calculated using data on bud and shoot development during 1997 together with weather data for each of the studied years and sites. The date of flushing was well correlated to the air temperature sum (+5°C threshold value) in spring. Frost damage varied considerably between sites and study years. The lowest measured minimum air temperature and the frost-day sum during the frost-susceptible period were correlated to the frequency of frost damage. Soil scarification reduced frost damage in the first growing season. Bare-rooted seedlings had a considerably lower frequency of frost injury compared with containerised ones, possibly because flushing of the former was delayed. There was no statistically significant effect of herbicide application, mowing or slash removal on the frequency of frost damage. Seedling growth was significantly reduced by frost injury, especially in cases where injuries were sustained during several years. Survival was only slightly affected by frost damage.     

Element concentrations and storage in the aboveground biomass of limed and unlimed Norway spruce trees at Höglwald

Twenty years after the application of dolomitic limestone to a well growing, mature Norway spruce stand at Höglwald, Southern Germany an amount of magnesium equal to the input by liming has left the rooting zone. However, 80% of the applied calcium was retained by the ecosystem. A detailed biomass investigation was carried out in order to elaborate whether the stand shows any nutritional benefits and if the aboveground tree biomass represents a sink for calcium and magnesium after liming. Stem wood, bark, branches, twigs, and needles were analysed for the major nutrients. Needles showed higher calcium and magnesium concentrations and significantly lower potassium concentrations on the limed plot. Surprisingly, limed trees had significantly lower magnesium concentrations in the bark but higher concentrations in twigs and needles than unlimed trees. In addition, significantly lower concentrations for potassium, sulphur, and phosphorus were measured in the bark of limed trees, whereas the element concentrations in the wood were rather similar between the two treatments. The low potassium concentrations in bark and needles indicate an impeded potassium uptake after liming presumably due to a calcium potassium antagonism. Magnesium is probably used to compensate the relative lack of potassium. The small differences in the calculated nutrient storage of limed and unlimed trees, however, suggest that the aboveground biomass can be excluded as a relevant sink for the applied calcium and magnesium at the Höglwald site.     

Genetic and historical studies on the origin of Norway spruce in Białowieża Primeval Forest in Poland

Białowieża Primeval Forest lies within the boreal part of the Norway spruce range, which, according to pollen data, was formed by a refugium located in the Russian Upland. However, recent genetic studies have indicated that spruce from the Eastern Carpathian refugium also occurs in Białowieża Forest. In order to investigate whether the Norway spruce from the Eastern Carpathian refugium migrated naturally into the boreal part of the Norway spruce range, we assessed the refugial origin of 234 of the oldest Norway spruce individuals from Białowieża Forest using mitochondrial marker mt15-D02. Out of the trees that we studied, 64.8% carried mitotype 1, which is specific to the Carpathian refugium, while 35.2% had mitotype 3, specific to the Russian refugium. Our genetic analysis, combined with historical data on forest management in this part of Europe, argues for a natural contribution of spruce from the Eastern Carpathian refugium during postglacial recolonization of Białowieża Primeval Forest.     

Finding the meeting zone: Where have the northern and southern ranges of Norway spruce overlapped?

The goal of the work was to define where migration routes of Norway spruce running from its Weichselian refuges could have intersected and formed a hybrid zone. Based on available pollen data, we have hypothesized that the central European disjunction, also called the “spruceless zone”, could be an overlapping area of boreal and southern ranges.     

Mortality of silver fir and Norway Spruce in the Western Alps — a semi-parametric approach combining size-dependent and growth-dependent mortality

Question

Tree mortality can be modeled using two complementary covariates, tree size and tree growth. Tree growth is an integrative measure of tree vitality while tree diameter is a good index of sensitivity to disturbances and can be considered as a proxy for tree age which may indicate senescence. Few mortality models integrate both covariates because classical model calibration requires large permanent plot data-sets which are rare. How then can we calibrate a multivariate mortality model including size and growth when permanent plots data are not available?

Location

To answer this question, we studied Abies alba and Picea abies mortality in the French Swiss and Italian Alps.

Method

Our study proposes an alternative semi-parametric method which includes a random sample of living and dead trees with diameter and growth measurements.

Results

We were able to calibrate a mortality model combining both size-dependent and growth-dependent mortality. We demonstrated that A. alba had a lower annual mortality rate (10%) than P. abies (18%) for low growth (< 0.2 mmyear^?1). We also demonstrated that for higher diameters (DBH ≥ 70 cm), P. abies had a higher mortality rate (0.45%) than A. alba (0.32%).

Conclusion

Our results are consistent with the mechanisms of colonization-competition trade-off and of successional niche theory which may explain the coexistence of these two species in the Alps. The method we developed should be useful for forecasting tree mortality and can improve the efficiency of forest dynamics models.     

Does the mutualism between wood ants (Formica rufa group) and Cinara aphids affect Norway spruce growth?

Ant–aphid mutualisms, in which ants tend aphids, which in turn provide honeydew to the ants, are widespread and have been shown to affect plant growth. In boreal forests the effect of ant–aphid mutualism on tree growth can vary with stand age, because forest clear-cutting harms the ecologically most dominant ant partner in such mutualisms, wood ants (Formica rufa group). We studied whether the mutualism between wood ants and Cinara aphids affects the growth of boreal Norway spruces (Picea abies L. Karst.) in stands of different ages. In boreal forests, conifers, unlike deciduous trees, have only few defoliating insects, and therefore we expected the growth loss of conifers due to sap sucking by aphids not to be compensated by reduced insect herbivory due to predation by wood ants. The study was conducted in medium-fertile spruce-dominated stands in eastern Finland. We used stands of four different age classes (5, 30, 60 and 100 years) and selected ten spruces heavily visited and ten spruces lightly visited by ants around five medium-sized ant mounds in each stand age class. The access of ants was blocked on half of the trees in both groups. In the 5-year-old stands, the mean annual height growth of individual heavily visited seedlings was 16.3% greater than in the ones where ant traffic was blocked, but this difference was not significant. In the 30-year-old stands, the mean annual radial growth of the heavily visited spruces was 7.3% smaller than in trees where ant traffic was blocked, and this difference was significant. The mutualism had no significant effect on the radial growth in the 60- and 100-year-old stands. In the 60-year-old stands, however, the spruces that were visited heavily prior to the beginning of the study grew significantly less relative to their past growth than the initially lightly visited trees during the study. This suggests that the ant–aphid mutualism may have long-term effects on tree growth. The ant–aphid mutualism had no significant effect on the growth at the stand level. The results indicate that ant–aphid mutualism can have a significant effect on the growth of individual spruces, but the effect is negligible at ecosystem level.     

Estimation of LAI in the forested watershed using ASTER data based on Price’s model in summer and winter

Leaf area index (LAI) is an important parameter to identify the water balance in forested watershed as a biological factor influencing directly on the evapotranspiration in the forest area. The purpose of this study was to estimate the LAI in a small forested watershed in summer and winter by applying the Terra/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data to the LAI estimation method. In this study, the estimation was based on the absorption and scattering processes of the solar radiation in the vegetation canopy and the spectral reflectance characteristics of soil vegetation. First, we estimated LAI based on Price’s model by application of ASTER data on the forested watershed located in the Tenzan Mountains of Saga, Japan. To validate the results of LAI estimation, secondly, we compared them to the measured LAI obtained by a plant canopy analyzer (LAI-2000) on the observation area inside the target region. This study showed that the LAI estimation method was a feasible and accurate method as indicated by the high relationship (r = 0.97) between LAI derived from ASTER data and LAI measured by LAI-2000. This paper is the first report on LAI estimation using Terra/ASTER data based on Price’s model and field investigation. This LAI estimation method is a reliable and applicable method.     

An analysis of Norway spruce stem quality in Baden-Württemberg: results from the second German national forest inventory

Additional information concerning the quality of growing stock in forests has been obtained for the first time in Baden-Württemberg and Rheinland-Pfalz during the course of Germany’s second national forest inventory (BWI 2; conducted during the period 2001–2002). In this article, the quality assessment—called stem quality rating method—is described with a special focus on its potential to provide the basis for a more detailed investigation of the growing stock’s quality distribution. As a main result, the article presents and illustrates a model-based quantification of single tree and stand/site variable effects on the quality distribution of Norway spruce. Single tree variables showing a significant effect are diameter at breast height (DBH), height–DBH-ratio (h/d-value), age and distance to forest edge. Additional stand/site variables which have a significant effect are altitude, terrain slope, stand type and inventory team. Due to the ordinal type of the response variable, a categorical regression model is applied. Non-linear effects of predictor variables were detected and modeled by integration of smoothing spline terms. Validating model predictions with regard to expert knowledge in forestry led to the integration of simple constraints in the linear predictor, which controls whether category-specific effects are fitted or not. The resulting model could be described as a vector generalized additive non-proportional odds regression model. This improved insight into the determination of stem quality could be applied in optimization studies to derive optimal silvicultural treatments and in the setting up of management guidelines. Assuming constant relationships between predictor and response variables over time, the combined application with growth simulators allows for a prediction of future joint quality and size class assortment distributions. Finally, the model would allow for a sustainability control of stem quality over time if a consecutive inventory will be conducted during the course of the third German national forest inventory (BWI 3).     

The effects of partial cutting on stand structure and growth of western hemlock–Sitka spruce stands in southeast Alaska

The effects of partial cutting on species composition, new and residual-tree cohorts, tree size distribution, and tree growth was evaluated on 73 plots in 18 stands throughout southeast Alaska. These partially cut stands were harvested 12–96 years ago, when 16–96% of the former stand basal area was removed.Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effects on tree species composition. The establishment of new-tree cohorts was positively related to the proportion of basal-area cut. The current stand basal area, tree species composition, and stand growth were significantly related to trees left after harvest (p<0.001). Trees that were 20–80 cm dbh at the time of cutting had the greatest tree-diameter and basal-area growth and contributed the most to stand growth. Diameter growth of Sitka spruce and western hemlock was similar, and the proportion of stand basal-area growth between species was consistent for different cutting intensities.Concerns about changing tree species composition, lack of spruce regeneration, and greatly reduced stand growth and vigor with partial cuts were largely unsubstantiated. Silvicultural systems based on partial cutting can provide rapidly growing trees for timber production while maintaining complex stand structures with mixtures of spruce and hemlock trees similar to old-growth stands.     

Soil–water content and air-filled porosity affect height growth of Scots pine in afforested arable land in Finland

We examined the soil–water content (SWC) and air-filled porosity (AFP) of afforested arable land in situ and related them with tree growth, which was expressed as the total length of 5-year-height growth above 2.5 m stem height. A total of 34 randomly selected sites in western Finland afforested with Scots pine (Pinus sylvestris L.) were sampled and SWC was measured using time domain reflectometry (TDR). Increasing AFP up to 30% and correspondingly decreasing SWC significantly increased tree growth while concentrations of foliar nutrients and contents of soil nutrients had no effect. Increasing organic matter content (OMC) and decreasing bulk density (BD) were accompanied by increasing SWC and decreasing AFP in the 0–10 cm soil layer. SWC values above 70% indicated critical AFP below 10%. It was found that 44% of the studied sites had mean AFP lower than 10%. The results obtained indicate that the afforested Finnish arable land with high soil OMC is commonly characterized by high SWC and low soil aeration, which can limit tree growth.     

Measurement of standard and off-axis elastic moduli and Poisson’s ratios of spruce and yew wood in the transverse plane

It is well known that in the radial–tangential plane of softwoods, the elastic modulus in the principal directions is clearly higher than the off-axis elastic moduli, which decrease to a minimum at a growth ring angle α of about 45°. However, this angular dependency was experimentally proven by only a few early publications. The aims of this study were (1) to analyze this relationship with up-to-date equipment in compression tests on miniature softwood specimens with varying growth ring angles and (2) to compare the experimental results with those calculated by a tensor transformation to assess whether it is admissible to treat the investigated wood species as orthotropic materials. Two softwoods with distinctly different anatomic structures (Norway spruce and common yew) were chosen, and further properties such as Poisson’s ratios were determined. The results confirm the above-mentioned angle-dependent tendency for spruce elasticity, but also show that it is not valid for softwoods in general since the behavior of yew was completely different. The tissue textures of both species, particularly density and density distribution, were discussed as possible reason for these observed differences. The determined Poisson’s ratios for principal and off-axis load directions may be useful for modeling of material behavior.     

Coarse root–shoot allometry of Pinus radiata modified by site conditions in the Western Cape province of South Africa

The relationship between root and shoot growth and how it is modified by chronic or episodic drought stress is so far not well understood. Allometric partitioning theory (APT) supposes a constant root–shoot allometry. Optimal partitioning theory (OPT) assumes that plants’ root growth is enhanced under water limitation. However, recent studies show that fine and coarse roots react differently. This paper draws attention to the root–shoot allometry of adult Monterey pines (Pinus radiata D.Don) and its dependency on site conditions in South Africa. For assessment of the root–shoot-diameter relationship as an allometric relationship in general and for comparison with APT we used a sample of nine radiata pines from Jonkershoek and three maritime pines (Pinus pinaster Aiton) from Napier. In order to test for a site-dependency of the root–shoot allometry we sampled increment cores from stem and coarse roots of 48 radiata pines along a gradient from moist to dry sites in the Western Cape province. Tree ring analysis revealed an allometric relationship between root diameter (dr) and shoot diameter (ds) (ln(dr) = a + α _dr,ds × ln(ds)). Despite strong variation of the allometric exponent α _dr,ds we found a systematic deviation from 1.0 as would be predicted by APT. We also found α _dr,ds to decrease with drought stress, which is contradictory to both APT and OPT. However, on sites with more pronounced drought stress we detected greater allometric factors a. We hypothesise that fine root growth, and also fine root mortality, is higher on dry sites. On these sites coarse roots seem to be less necessary for matter transport compared with moist and fertile sites. On the latter, fine roots are less ephemeral and require larger coarse roots for transport. We conclude that combined root shoot tree ring analyses have the potential for improving understanding and modelling ecosystems and better assessment of forest functions such as resource use efficiency, stand stability and belowground carbon storage.     

Effects of phosphorus and potassium addition on growth and nodula- tion of Dalbergia sissoo in the nursery

A study was conducted to test the influence of different inorganic fertilizers （phosphorous and potassium） on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combinations of P, K fertilizers were incorporated with the nutrient-deficient natural forest soils, and then amended with cowdung （soil： cowdung = 3：1）. Nodulation status （nodule number, shape, fresh weight, dry weight and color） in the roots and the plant growth parameters （length of shoot and root, collar diameter, fresh and dry weight of shoot and root） were recorded 60 days after seeds sowing. Nodulation status and growth of the plants varied significantly （P〈0.05） in the soils amended with fertilizers in comparison to the control. The highest nodule number （62）, fresh （0.50 g） and dry （0.07 g） weights were recorded with the dose of PK at the rate of 160 kg/hm2. Nodule shape and color also varied widely in different treatments. In case of plant growth parameters, shoot and root length, collar diameter, fresh and dry weight of the plants took on a significant difference （P〈0.05） among various combination of fertilizers. From the study, it is revealed that PK at the rate of 160 kg/hm^2 fertilizer with soil and cowdung mixture （soil： eowdung = 3：1） is recommended for optimum growth and nodule formation of D. sissoo in degraded soils at a nursery level.     

Lumber recovery and value of dead and sound black spruce trees grown in the North Shore region of Québec

Context

To increase the wood supply to its industry, the government of Québec has allocated dead and sound wood (recently dead merchantable stems, DSW) to the wood supply chain in addition to the annual allowable cut of living trees. However, DSW is often criticized by sawmillers for its perceived poor quality and lower value.

Aims

The objective of this study was to compare the lumber visual grade yield and value from live and recently dead merchantable trees in three different states of wood decomposition.

Methods

In total, 162 black spruce trees [Picea mariana (Mill.) BSP] were felled from three different sites comprising three different states of wood decomposition and three diameter classes. The state of decomposition of each standing tree was categorized following Hunter??s classification (decay stages 1 & 2, 3 and 4) and the DSW classification developed by the Government of Québec.

Results

Large trees (> 20?cm) of the Hunter 4 class have a lower value as a result of inferior quality.

Conclusion

Considering the current economic difficulties facing the forest industry and the requirements of ecosystem-based management, we recommend leaving in the forest trees that have reached such a state of deterioration.     

Fungi occurring in the roots and basal parts of one‐ and two‐year‐old spruce and pine stumps

The occurrence of fungi in the underground parts of 1‐ and 2‐year‐old conifer stumps (Pimis sylveslris and Picea abies) was studied in two clear‐felled areas of eastern Uppland in Sweden, and most fungal isolates were identified to species.

Decay fungi (Basidiomycetes) were more frequent in spruce stumps than in pine stumps, and their incidence was highest in 2‐year‐old stumps. The occurrence of blue‐stain fungi and hyaline mycelia did not differ significantly between stumps of different species or age. Within stumps, decay fungi were most frequent in large roots close to the cut surface, whereas blue‐stain fungi and hyaline mycelia were most abundant in small roots. The occurrence of yeasts, bacteria and fast‐growing moulds was also recorded.     

Development and commercialisation of the Pinus patula × P. tecunumanii hybrid in response to the threat of Fusarium circinatum

During the last 20 years a program to develop and commercialize the Pinus patula × Pinus tecunumanii hybrid, as a replacement for P. patula, has been successfully implemented. The first crosses were initiated during the early 1990s and lead to establishment of field trials across a wide variety of sites. This work gained further impetus when it became apparent that Fusarium circinatum, was causing poor post-planting survival of newly established stands of P. patula. P. tecunumanii, has been shown to be tolerant to this disease and thus a second, more comprehensive hybrid testing phase was implemented. Improvements in controlled pollination techniques and propagation methods, as well as access to genetically improved parent-stock and the use of molecular marker technology for fingerprinting was effectively utilized to greatly improve the process during this second phase. The use of artificial inoculation trials have demonstrated that the hybrid, in particular when using the low elevation (LE) provenances of P. tecunumanii, had substantially greater tolerance to F. circinatum than P. patula and survival figures from field trials support these results. Four-year volumes also indicate large growth improvements, although frost damage on certain sites presents a challenge for deployment on colder sites; and this is being tackled through breeding and accurate mapping of frost risk. Large-scale controlled pollinations and vegetative multiplication are now utilized commercially to produce the P. patula × P. tecunumanii (LE) hybrid as an alternative to P. patula.     

Effects of sludge on germination and initial growth performance of Leucaena leucocephala seedlings in the nursery

A study was carried out to determine the influence of different types of sludges （municipal, industrial and residential） on field germination, growth and nodulation of L. leucocephala seedlings in the nursery. Before sowing of seeds, different combinations of sludges were incorporated with the nutrient deficient natural forest soils. Field germination, nodulation status and physical growth parameters of seedlings （shoot and root length, vigor index, collar diameter, leaf number, fresh and dry weight of shoot and root and total dry biomass increment） were recorded after three and six months of seed sowing. Field germination, nodulation status and growth parameters were varied significantly in the soil amended with sludges in comparison to control. The highest number of nodule was recorded from soil amended with residential sludge （ 1：1 ） and highest fresh and dry nodule weight was also found from the same combination in both three and six month old seedlings. In case of growth parameters, the highest growth was recorded from soil and residential sludge （ 1：1 ） combination compared to control. From the study, it can be recommended that soil amended with residential sludge （ 1：1 ） provide better field germination, growth and nodule formation of L. leucocephala in degraded soil.