Roberts Matisons

Influence of climate on tree-ring and earlywood vessel formation in Quercus robur in Latvia

We studied the effects of climatic factors on tree-ring width and vessel lumen area (VLA) in earlywood of English oak (Quercus robur L.) in Latvia. Cores were obtained from healthy canopy oaks in 40 stands located across Latvia. Tree-ring widths and VLA were measured. Principal component analysis was used to arrange the sites along gradients of response of tree-ring width and earlywood to environmental factors. Significant relationships of tree-ring width and mean VLA with climatic factors (mean monthly temperature and precipitation sum) were determined by correlation analysis. Relationships between tree-ring, early- and latewood widths were tested in three sampled stands. The patterns of response of VLA and tree-ring width to environmental factors differed in relation to a west–east gradient of increasing continentality. Three regions of Latvia (western, central and eastern) were distinguished along this gradient. Responses to climate differed between tree-ring width and mean VLA. Occurrence of significant correlations between climatic factors and the proxies differed between regions, likely due to regional differences in temperature and precipitation. Tree-ring width correlated with climatic factors (most commonly with March, May and June temperature and August precipitation of the current growing season and July–August temperatures of the previous growing season); VLA was more strongly related to climatic factors, particularly with temperature in winter and spring months. The proportion of significant correlation coefficients with climatic factors differed between the regions. Among sites, significant correlation of tree-ring width with temperature in spring and summer was more frequent in the western region, while correlation with winter temperature of the previous growing season and precipitation in August was more frequent in the eastern region. For VLA, the frequency of significant correlation coefficients with temperature in winter and spring was higher in the eastern region.

Dynamics of natural hemiboreal woodland in the Moricsala Reserve, Latvia: the studies of K. R. Kupffer revisited

Abstract Karl Reinhold Kupffer (1872–1935), an outstanding botanist and plant ecologist, took the initiative that led to the establishment of the first nature reserve in Latvia, on Moricsala Island in 1912. The reserve provided an excellent reference area for natural hemiboreal woodland for future generations. There have been very few studies on the dynamics of natural broadleaved forest in Europe, probably owing to lack of primeval forests of this type. However, Kupffer produced a map of forest types in the reserve with accurate descriptions of the vegetation by layers, and his descriptions include interpretations of forest dynamics processes. This information, together with the present age and diameter structure of mixed pedunculate oak (Quercus robur) stands in the Moricsala Reserve in Latvia, was used to reconstruct the past successional sequences of tree species in 2006–2007. Tree age and diameter at breast height of trees in two transects (total area 6600 m2) and four plots (each 400 m2) were measured. In one transect, located in the most pristine part of the reserve, and in one plot, lime (Tilia cordata) is gradually replacing oak in the canopy. In the second transect, oak is replacing a Scots pine (Pinus sylvestris) overstorey, and a spruce understorey observed there at the start of the twentieth century has been outlived by oak. In mixed oak–spruce stands, wind-induced mortality of spruce is followed by waves of release and self-thinning of spruce, and there is evidence that oak in the understorey can utilize the periods of weak competitive pressure to recruit to higher age and size classes.

Proportion of knotty wood in stems of 28-year old lodgepole and Scots pine in experimental plantation in Zvirgzde, Latvia

Abstract In forestry, alien tree species are planted to maximize yield from a stand by increasing productivity and decreasing environmental risks. In Eastern Europe, lodgepole pine (Pinus contorta var. latifolia) might be used as a source of biomass and industrial wood; however, before any recommendations are given, possible gains of the novel species should be scrupulously evaluated. In this study, we compared volume and proportion of knotty stemwood (VKN) of native Scots pine (Pinus sylvestris) from first generation seed orchards and provenances of alien lodgepole pine [Fort Nelson (58°38’ N, 122°41’ W) and Summit Lake (54°24› N, 122°37› W)] at the age of 27 years growing in central Latvia. We also assessed the relationships between VKN and several morphometric parameters. Stem diameter of both species was similar; however, Summit Lake provenance of lodgepole pine exceeded Scots pine in height, while Fort Nelson provenance was lower than Scots pine. Although Scots pine produced nearly two times less whorls than lodgepole pine, volume of knotless stemwood did not differ significantly between the species; though it was higher for Summit Lake provenance of lodgepole pine compared to Scots pine. In contrast, the proportion of VKN differed significantly between both the species and the provenances. Scots pine showed the lowest proportion of VKN (~ 9%) and Fort Nelson provenances of lodgepole pine showed the highest proportion of VKN (~ 14%). Thus, Summit Lake appears more suitable for the production of industrial wood amongst the provenances of lodgepole pine; nevertheless, higher quantity of leftover material is expected. Some morphometric parameters correlated with VKN and the proportion of VKN, but these relationships differed between species and provenances. The total cross-section of branches was the best predictors of VKN for Scots pine and Fort Nelson provenance of lodgepole pine, while stem diameter showed the strongest correlation for Summit Lake provenance. Number of whorls and mean diameter of living branches were the best predictors of the proportion of VKN for lodgepole pine and Scots pine, respectively. Accordingly, morphometric parameters might be useful for the selection of the best trees of lodgepole pine.