Miroslav Šrůtek

Neighbourhood interactions and environmental factors influencing old-pasture succession in the Central Pyrenees

Abstract The shrub Buxus sempervirens and the trees Abies alba and Fagus sylvatica have recently recolonized old-pastures in the Central Pyrenees. We mapped all live and dead individuals (> 1.3 m tall) in a large forest plot in Ordesa Valley to examine the importance of density-dependent processes during recolonization. Biotic interactions were inferred from changes in horizontal structure and the influences of neighbours on tree survival. Buxus differentially influenced establishment and survival of tree species, thereby controlling future canopy composition and spatial structure. The rapidly invading Abies formed denser patches on elevated sites less occupied by Buxus, whereas Fagus preferentially established within shrubs. Abies reached densities which led to intense intraspecific competition and high mortality rates among saplings. Self-thinning in Abies led to smaller numbers of regularly spaced survivors, and greater relative dominance of Fagus. Disregarding intraspecific effects and abiotic environment, Abies survival was significantly lower under Buxus shrubs, which suggests that the spatial location and abundance of Abies was constrained by the location of Buxus. Fagus survival was not related to Buxus density, but remained significantly lower in denser Abies patches. The higher mortality of Fagus in denser Abies patches, and the resulting spatial segregation of the species, reflects asymmetric interspecific competition. Inhibition from Buxus shrubs and intraspecific competition prevent invading Abies from dominating and may therefore help in maintaining a mixed Abies-Fagus stand.

Vegetation structure along the altitudinal gradient at the treeline of Mount Paektu, North Korea

Vegetation structure of the treeline was studied on the southeastern slope of Mount Paektu (North Korea). Fifteen temporary plots (20m×20m) were situated along the altitudinal transect. Seven square samples (phytosociological relevés 5 m×5 m) were analyzed in each plot. Although the character of the vegetation was rather continuous altitudinally, five similar groups of vegetation samples were distinguished by the TWINSPAN procedure. The distribution of samples in the classification showed not only the effect of altitude but also the effect of competition between the tree and the shrub layers and other factors. In the canonical correspondence analysis (CCA) ordination several environmental variables were used (such as altitude of each plot, distance of each plot from the forest edge and the cover percentage of tree, shrub, herb and moss/lichen layers). The variable ‘cover of tree layer’ had the strongest relation to the species data. Continuous changes of species richness along the altitude were confirmed. Species richness decreased significantly with altitude.

Vegetation-environment Relationships within and among Selected Natural Forests in North Korea

The set of 234 forest vegetation samples from North Korean forests was subdivided into two homogenous groups, i.e. coniferous forests, and broad-leaved and mixed forests. The indirect (i.e. the detrended correspondence analysis, DCA) and direct (i.e. canonical correspondence analysis, CCA) gradient analyses were used to recognize relationships between forest communities and several environmental variables (mean annual precipitation, slope orientation and inclination, altitude, cover of particular forest strata, mean annual Kira’s warmth (WI) and coldness (CI) indices). Although relatively little variation in species composition is explained by the indirect ordination, environmental gradients were recognizable in both mountain coniferous forests and mixed pine-oak forests. Altitude and precipitation, and their interdependence, seem to be good predictors of forest composition, particularly in the mountain coniferous forests. In fact, these variables generally are the most important factors affecting species distribution and vegetation zonation along environmental gradients. Nevertheless, understanding the ecology of these forest ecosystems will not be complete without investigation of the effects of other biotic and abiotic factors, such as latitude, distance from the sea, air humidity, prevailing wind direction, temperature, light intensity, evapotranspiration, soil features and various kinds of natural and human-caused disturbances. This is an area for future research in the region. The change in species diversity (Hill’s index) did not show any distinct pattern in relation to any environmental gradient. This is true across the whole data set and within the two main forest types.

Regeneration and Seedling-habitat Relationships of the Marginal Population of Pitch Pine (Pinus rigida) After Prescribed Burning, Eastern Ontario, Canada

Abstract Post-fire seedling establishment in relation to microsite conditions and relationships of seedlings (saplings) to older tree individuals was studied in two treatments (i.e., burned and unburned sites) in an area known as the pitch pine (Pinus rigida) ridge on Hill Island, St. Lawrence Islands National Park, Eastern Ontario. Pinus rigida is a rare tree species in Canada at the northern limit of its range. Pinus strobus (eastern white pine) and Quercus alba (white oak) are also common species of the site. The negative correlation between density of mature P. rigida trees and total canopy cover and hardwood density was con.rmed in unburned plots on the ridge. On the other hand, P. strobus density was positively correlated with those parameters. The density of P. rigida seedlings is higher (by 48%) and P. strobus seedlings lower (by 82%) in burned plots than in unburned plots. Seedling recruitment was also dependent on the occurrence of seed trees of both species. The density of P. strobus seedlings was generally higher than that of P. rigida seedlings, especially in unburned plots. The long absence of .re, high seed production of P. Strobus, and relatively low number of P. rigida seed-producing trees, which have a low amount of fertile cones, are probably the main factors in.uencing seedling recruitment on the ridge. Discriminant analysis con.rmed different seedbed requirements of both species. Pinus strobus seedlings occurred within both treatments, especially on deeper soil pro.les with thicker litter depth, although, for seed regeneration, a mineral soil seedbed or a greatly reduced organic layer was also important. Pinus rigida seedling recruitment on burned and unburned plots was comparatively higher on mineral soil, thinner litter layer, and moss and lichen cushions.

Species and Spatial Structure of Forests on the Southeastern Slope of Paektu-san, North Korea

The forest vegetation was analyzed on the southeastern slope of Paektu-san (2744 m), the highest peak of the Korean Peninsula, along the border with China. Nine temporary plots (50 by 10 m) were established along an altitudinal gradient (ca. 26 km, from 1380 to 1920 in), in order to document vegetation spatial patterns and allometric relationships. Thirty-three vegetation samples (area 250 m2 to 400 m2) were collected in or near the temporary plots for the description of particular vegetation types. Seven groups of vegetation types, which can be differentiated from each other relatively well, were suggested by divisive hierarchical classification. These vegetation types correspond roughly to the altitudinal vegetation belts. Altitude was confirmed statistically as the key factor in the variability of plant communities, as evaluated by canonical correspondence analysis. Species richness (number of species), however, does not show any distinct pattern with respect to altitude. Spatial pattern differed considerably, both among particular plots and among species in the same plot. There was, however, no consistent trend with altitude. On the other hand, nrorphometry and allometric relationships of Larix olgensis, the dominant tree, show consistent trends with altitude.