MS Abstracts

Tatjana Khakimulina 2010. 250 Years of Disturbance Dynamics in a Pristine Old-growth Picea abies Forest in Arkhangelsk Region, North-Western Russia: A Dendrochronological Reconstruction.

To describe the historical patterns of natural disturbance regimes in European boreal forests we conducted a dendroecological study in a primeval old-growth spruce dominated stands and reconstructed the long-term dynamics of canopy disturbances. We treated the radial growth releases of individual sub-canopy trees as the major indicator of sudden openings in the forest canopy. Growth releases were detected by using the formal approach only (strict criteria were applied). The reconstruction of past canopy disturbances was done by GIS-based analysis of spatial information on released trees over the study period.

The study area was located in the transitional vegetation zone of the middle and northern taiga, on the watershed of Northern Dvina and Pinega rivers, North-Western Russia. Spatial and temporal characteristics of canopy disturbances were studied within the area of 1.8 ha along the two transects, 20×450 m2 each. All trees with DBH > 6 cm (dead and alive) and coarse woody debris (DBH > 18 cm) within transects were mapped and described (n = 2126) and all living and recently dead trees were sampled with an increment corer (n = 1678) at the height 40 cm above the root collar.

Stands were composed of Picea abies and Betula pendula, mean standing volume was 211 m3/ha. Spruce was of multiple ages with pronounced regular peaks (cohorts) in trees age distribution. At least four such cohorts were distinguished and represented peaks in spruce regeneration.

No evidence of stand replacing events was found over the 250(300)-year period that the study covered. The dynamics was likely driven by small and middle-size canopy disturbances, occurring at varying frequencies. A detailed spatial disturbances reconstruction reflecting the last 170 (160) years revealed a disturbance rate of about 4% yearly mortality. Periodic increases in disturbance rate however played a major role in forest regeneration. Four such peaks were timed to decades 1850, 1890, 1930 (1920 – for transect 1) and 1980. Disturbance rates at peaking decades were about 60% and never exceeded 75% of the canopy area. Surprisingly little difference in disturbance rates was found among forest types with different soil moisture. Though forests with higher soil moisture had slightly lower disturbance intensity and less pronounced regular peaks in disturbance rate over considered time span.

Keywords: Disturbance, canopy gap, disturbance rate, old-growth forest, Norway spruce, European spruce bark beetle, forest history.

Agnieszka Gawron, 2009. Age determination of Fagus sylvatica L. natural regeneration in southern Sweden – comparison of two methods.

The age estimation methods of European beech (Fagus sylvatica L.) recruitment was investigated in a semi-natural beech-dominated forest located in Biskopstorp estate, Halland county, Southern Sweden. I compared two methods that involved (a) counting of bud scale scars and (b) chronological analysis of the annual rings. In 7 beech dominated stands 175 seedlings of beech advanced regeneration were analyzed on 20 m radius plots (1257 m²).

I found that regeneration occurred in all stands over restricted periods resulting in up to three distinct regeneration pulses (in 1993, 1994, 1996 and 1999). The occurrence and survival of beech regeneration depends mainly on environment created by the mother trees (expressed as canopy openness and , basal area of old growth). Ages estimated by two methods were significantly differed for saplings older than 8 years. The age of saplings seemed to be the only factor affecting the accuracy of age estimation. The visibility of annual marks on the shoot depended on thickness of the bark and occurrence of the lichens, which both were strongly related to the sapling age. Thus, the terminal bud scale scars counting was more reliable in case of saplings younger than 8 years. The annual rings counting was very precise for all saplings on a condition, that within the annual ring there was no additional increment zone. Unfortunately the dendrochronological method is very time consuming and it requires special magnifying equipment and knowledge about growth development. Despite of mentioned-above obstructions concerning the bud scale scar method, for practical forestry purposes this age estimation technique is suggested to be more applicable due to its simplicity.

Igor Saygin, 2008. Masting and dendrochronology of Fagus sylvatica in Southern Sweden.

… coming soon …

Alexander Dobrovolsky, 2007. Dynamics of natural mortality and tree structure in Oranienbaum park.

The increasing attention towards urban forestry encourages the study of temporal changes in green zones and parks close to cities. Studying stands’ dynamics and predicting their structure in the future provides a knowledgeable base to improve stand quality and structure with the focus, among other aspects, on their value as recreational areas. The aim of this study was to analyze the dynamics of growth and development of broadleaved stands near the northern border of their habitat.

We studied Oranienbaum Park (total area is 161 ha) in the North-West part of Russia and used two research studies of park’s vegetation; the first completed in 1981 and the other in the year 2003. The park is located in the southern coast of the Gulf of Finland, 40 kilometers west of St.-Petersburg. These broadleaved species (lime, oak and ash) are dominant in the stand’s composition. The basis for the study was made up by a total of 13256 sample trees which were measured (height, dbh, vitality, status) and mapped at scale 1:500 at two different occasions in the year 1981 and 2003.

For all sites, tree species, and DBH classes, the relative mortality rate was 1.12% per year. Relative mortality rates of less than 1 % per year were observed for larch, fir and lime. Relative mortality rates of more than 1 % per year were observed for birch, maple, black alder, oak, ash, and spruce. The highest mortality rate (2.5% per year), was observed for birch. The analysis of the mortality rates in different age groups of different tree species showed that the greatest mortality rate for the majority of species was observed in young (<40 years old) and old (>100 years old) age groups.

Using the Markov chain model (Shugart, 1984; Botkin, 1993; Feldman, et all, 2004) we

studied the development of the Tilia cordata stands in the Park. “Vitality –class changes” and “diameter-class changes” sub-models were used as a basis for modeling to predict vitality diameter combined changes. The temporal patterns of changes in vitality classes of lime trees show high probability of shifting from 1st and 2nd vitality classes to 2nd vitality class. The probability of the transition from the 3rd vitality class to the 2nd strongly increases when the diameter class increases. The transition probability from the 3rd vitality class to the 4th (dead trees) increases with the decreasing of the initial diameter.

The model predicts that the amount of presently living Tilia trees will be reduced by 50% in the next 70 years and less than 8% of the present living trees will live up to 200 years. It also indicated that the annual mortality rate for Tilia trees will increase during the next 50 years and probably would stabilize in the area of 1.3% per year.

By using the model results with the empirical experiential data it shows that the model

realistically reflects stand tendency in the future and can be a useful tool for park

management under different silvicultural scenarios.

Oxana Shvedova, 2008. Analysis of Growth Dynamics and Climate Response of Scots Pine (Pinus sylvestris) across Different Site Types within Vepsski Forest Nature Park, North-Western Russia

I analyzed growth response of Scots pine to monthly weather variations in stands across a range of site types (dry-to-mesic, mesic and moist) on the territory of Vepsski Forest Nature Park, North-Western Russia. On this territory old-growth stands grow under conditions of low anthropogenic influence. The main goals were (1) to assess the correlation of tree-ring width with monthly climate variables (air temperature and

precipitation), (2) to compare climate-growth relationships across site types, and (3) to

prove or reject the hypothesis about differences between site-specific responses of

growth. The project also included identification of pointer years (years with strong and

consistent growth anomalies) from master chronologies of each plot and their comparison with regional weather anomalies. Similarities in growth pattern were observed for chronologies of plots with analogous site conditions. Response function analyses revealed a strong positive effect of July temperature on the ring increment of pines growing at dry-to-mesic sites, while no significant correlation between the tree growth and temperature was observed at mesic sites. Negative response to the temperature of previous-year September was detected on two out of three moist sites; one moist site showed a positive effect of the March temperature. Precipitation did not have any significant influence on annual growth variations across all sites except at one mesic site where growth was positively responding to February precipitation. Under mesic conditions, I found significant positive influence of July maximum and previous-year December minimum temperatures on pine growth. At moist sites the maximum temperatures of July-August had a positive effect, while the maximum temperatures of April negatively affected ring increment. The most frequent association between the pointer years and maximum/minimum extremes was observed at moist sites.

In general, growth anomalies in pointer years were related to weather anomalies that occurred during the growing season in the same years. Positive growth anomalies were observed in the years with very warm and moist weather in the spring-summer period, occasionally with dry June and excessive January precipitation. Negative growth anomalies were associated with different combinations of extreme weather conditions that occurred during growing season; some negative pointer years were linked with very warm winter-spring period and excessive precipitation during that time, and occasionally with extremely low February temperature. To conclude, ring width in this area responds to monthly air temperature during the growing season months and has no significant response to monthly precipitation.

Ewa Zin 2007. Age structure and dynamics of a semi-natural mixed Scots pine (Pinus sylvestris L.) – Norway spruce (Picea abies L. Karst.) stand in relation to fire regime in the BialowieSa Forest (Poland).

This study showed that fires have shaped the past and present structure and

regeneration dynamics of the investigated mixed Scots pine-Norway spruce stand in the BialowieSa Forest. The recorded regeneration pulses of both species correlate well with two fire events dated in the studied area, in 1825 and 1874. Additionally, no evidence of cutting in relation to these periods of massive tree species recruitment could be found.

The fire suppression as recorded in the last 100 years seems to be responsible for the

observed succession from pine to spruce dominance. The studied example allows for the assumption that fire was a factor of major importance for creating open conditions in the pine dominated woodlands of the BialowieSa Forest. Such conditions seem to have been crucial for successful natural regeneration of Scots pine, which appears to be gradually outcompeted by spruce in the coniferous stands in this area recently.

Still many questions remain and need further investigations that can make a fundamental contribution to the already existing knowledge about forest dynamics in

the BialowieSa Forest [e.g. Falinski 1986; Bernadzki et al. 1998] and in temperate

lowland mixed forests generally.

This study demonstrates that fire has been a crucial factor for determining the

structure and dynamics of forest ecosystems not only in boreal or hemi boreal

landscapes, but also in temperate lowland mixed woodlands. Therefore, its role in

changing the forest character should be reevaluated also in this part of the world.

Susanne Ahlander 2007. Are trees on islands more exposed to lightning-strokes than trees at mainland?. Southern Swedish Forest Research Centre, SLU. Examensarbete / SLU, Institutionen för sydsvensk skogsvetenskap vol. 95.

All vegetation is subject to different kinds of disturbances. Before human intervention, lightning strikes were the principal natural cause of ignition in conifer dominated European forests (Gromtsev 2002; Granström 2001). Spatial variation in strokes can provide valuable information about fire regimes in the past, but is not very well investigated. It has been claimed that ignition occurs more often on islands in lakes, than in corresponding habitat in mainland. The isolation and/or elevation would thus contribute to the high susceptibility to lightning strikes on islands. There may also be a difference in the attraction of lightning by different tree species. In this study, approximately 200 ha forest were investigated for lightning scars in trees on islands in the lake Allgunnen, and on adjacent mainland. To discover potential differences in scars distribution between the areas, the scars were classified into three categories according to the degree of certainty of lightning being the cause of the scar, “confident”, “likely” and “uncertain lightning scars”. More scars were found on islands (37.9/100ha) than in mainland (25.6/100ha). Scots pine (Pinus sylvestris) was incomparably the most frequently damaged species accordingly to tree species distribution in the investigated areas, being struck relatively more than other species. The findings suggest that there may be a difference in lightning strikes in trees on islands in lake Allgunnen compared to trees in corresponding mainland areas. And there may, as well, exist preferences in lightning-scars distribution on different tree species.

Marcin Churski 2006. Age structure and diameter distribution in a southern Swedish beech dominated landscape. Sveriges Lantbruksuniversitet. Examensarbete nr 78, Institutionen för sydsvensk skogsvetenskap, Alnarp juli 2006.

Tree ages and tree diameters were investigated in an 800 ha south Swedish beech dominated landscape with old-growth associated conservational values. Ca. 1200 trees from 53 sites with beech present were used in the analysis. At landscape level, the tree diameter distribution revealed a rotated sigmoid pattern without logarithmic transformation, well in accordance with existing models of size structure and suggesting that the forest is under a small-scale disturbance regime. The age distribution at the landscape scale was irregular with prominent peaks and absent recruitment periods, suggesting occurrence of disturbances. The analysis of age over diameter showed that there was a low age-diameter correlation. Age distribution revealed existence of three cohorts that originated in the periods 1720-1760, 1850-1900 and 1930-1950 between which low recruitment of regeneration occurred. Forest utilisation is suggested to be a major reason for the irregular age structure and the different cohort history.