Aljona Lukjanova

The influence of storm-induced microsites to tree regeneration patterns in boreal and hemiboreal forest

We reviewed studies dealing with regeneration under variable conditions in boreal and hemiboreal forests as affected by different microsite types by tree species functional groups. Generally, the importance of storm-induced microsites for regeneration dynamics in boreal forests depends on several factors: (1) distribution and type of microsites (generated by storm characteristics and stand conditions); (2) viable seed supply (stand history, species dispersal traits and status of surviving trees) and their species’ life history strategy; (3) climatic and site conditions (pre-storm conditions and storm-induced changes); and (4) delayed storm effects, such as retarded falling of trees, favoured vegetation growth, etc. Studies acknowledging the significance of microsites were mostly related to intermediate or severe events, causing sufficient changes in resource levels and growth conditions, and influencing extrinsic factors such as frost heaving, erosion and browsing. Also, the dispersal traits of available tree species, including sprouting and response of surviving trees, such as canopy expansion, should be considered in evaluating microsite importance in individual cases. In intermediate to severe windstorm events, pioneer species are generally profiting most from the additional offer in microsites, requiring bare mineral soil and elevated locations for their establishment and growth. Under gap dynamics, shade-tolerant species benefit from dead wood and elevated locations as these offer safe sites in stands with abundant understorey vegetation.

State of Scots pine (Pinus sylvestris L.) under nutrient and water deficit on coastal dunes of the Baltic Sea

The aim of the present study was to assess the ecophysiological state of Scots pine (Pinus sylvestris L.) growing at different heights on one of the typical coastal sand dunes in the dune field situated in southwestern Estonia. Dependence of the anatomical structure, morphological parameters, nutrients accumulation and biochemical characteristics of needles on the location of the site on the dune and on the concentration of nutrients in soil and in needle tissues was established. Correlation analysis revealed the dependence of chlorophyll a on the concentration of N and Mg in soil as well as in needles. The mesophyll area and chlorophyll concentration in needles were smallest on the top of the dune. The proportion of epidermis in the total needle cross-section area from the top was a little larger than in the needles from the bottom; the epicuticular wax layer on needles decreased towards the top. The length of needles and shoots was the lowest on the top of the dune, where the growth substrate contains notably less nutrients and water than needed for optimum growth of trees. The t test showed statistically significant larger average tree-ring width of the pines growing at the bottom. The pines on the top and at the bottom of the dune were not sensitive to temperature conditions. The radial growth of pines on the top of the dune was positively correlated with the total precipitation of the previous year.

Anatomical structure and localisation of lignin in needles and shoots of Scots pine (Pinus sylvestris L.) growing in a habitat with varying environmental characteristics

Anatomical structure and localisation of lignin in needles and shoots of Scots pine (Pinus sylvestris L.) growing in a habitat with varying environmental characteristics We investigated the influence of a habitat with varying environmental characteristics on the anatomical structure and localisation of lignin in needles and shoots of Scots pine (Pinus sylvestris L.). A dune in South-West Estonia was chosen as the study area because it has extreme environmental characteristics: primitive sandy soil, deficiency of water, heavy winds and high light exposure. Analysis showed that the needles of all age and the current-year shoots of pines growing on the foot of the dune had the largest average cross section, mesophyll and parenchyma areas. The degree of the lignification of needles at the foot, on the slope and on the top of the dune differed distinctly. Intensive lignification of the cellular walls of the xylem was observed in needles and shoots of the pines, growing at the foot, but not in the trees growing on the top of the dune. Analysis showed that the anatomical structure and localisation of lignin, both in needles and in shoots, depend on their age, the trees location (foot, slope or top of the dune) and soil mineral composition. Hariliku männi (Pinus sylvestris) okaste ja võrsete anatoomiline ehitus ja lignifikatsioon ökoloogiliselt erinevates kasvutingimustes Okaste ja võrsete anatoomilist ehitust ja lignifikatsiooni uuriti Tõotusemäe luite jalamil, nõlval ja harjal kasvavatel mändidel. Okaste ja võrsete ristlõigete analüüs näitas, et nende anatoomiline ehitus ja lignifikatsioon sõltuvad puude kasvukohast luitel ja substraadi mineraalsest koostisest. Luite jalamil kasvate mändide okkad ja võrsed olid suurema ristlõike üldpindalaga ja assimilatsioonikoe pindalaga, võrreldes nõlval ja harjal kasvate puude okaste/võrsetega. Luite harjal kasvavate mändide jooksva aasta okkad olid väiksema ksüleemi ja juhtkoe pindalaga, nende mändide jooksva aasta võrsetel aga vastupidi - juhtkimbu ja ksüleemi osa oli suurim. Suuremal osal analüüsitud okastest ja võrsetest oli lignifitseerumisprotsess hästi jälgitav. Ligniini akumulatsioon algab okaste ja võrsete ksüleemi ja epidermi rakukestades. Vanemates okastes ligniini hulk suureneb, kuigi ligniini koguvate kudede pindala ei suurene - jooksva aasta okastes ksüleemi, epidermi ja sklerenhüümi osakaal oli 13,2%, esimese ja teise aasta okastes vastavalt 13,5% ja 12,6%. Luite harjal kasvavatel mändidel oli lignifitseerumisprotsess vähem intensiivne nii okastes kui ka võrsetes, võrreldes luite jalamil ja nõlval kasvavate mändidega.

Use of biofuel ashes in forestry

Bioenergeetikas tekkivate jäätmete kasutamine metsanduses Negative environmental impacts of fossil fuel combustion have increased the use of biomass for energy production. As a consequence of the increased use of biofuels, the production of ashes will increase greatly in the near future. Because of relatively high contents of plant nutrients, biofuel ashes can be recycled as mineral fertilisers to compensate for the loss of nutrients resulting from tree harvesting. The present review aims to summarise the available information on factors affecting the quality of the wood and peat ash and the implications arising from ash application as fertiliser in the forest ecosystems. The understanding of the wood ash as fertiliser originates from the traditional slash-and-burn agriculture. During combustion most elements in wood are retained in the ash. The quality and chemical composition of ashes depends on many factors. The major elements in the ashes are calcium, potassium, magnesium, manganese, sodium, iron, phosphorus and sulphur. Trace elements found in different ash include barium, boron, cadmium, copper, mercury and zinc. The most abundant elements in peat ash are silicon, iron and aluminium. Ashes are characterised by high alkalinity with pH in the range from 11 to 13. Ashes raise the pH and reduce the total acidity in the humus layer and in the top of the mineral soil. The addition of wood ash does not result in a significant growth increase on mineral soils but increases the tree growth on peat soils. The Cd in wood ash did not become bioavailable and harmful to forest biota. The application of wood ash did not change or even decreased the 137Cs activity within forest soil. Wood ash application increased the coverage of the ground vegetation in upland forests and on peatland. Increase in microbial activity and growth rate after ash treatment was observed. Use of biofuel ashes in forestry The positive effect of wood ash on plant growth was understood long ago as better growth of grasses on areas burnt by natural fires was noticed. Scientific study of the effects of ashes began in the first half of the 20th century when the fertilisation experiments with wood ash were started in Sweden (1918) and in Finland (1937). Experiments of fertilisation with wood ash of drained peatlands in Finland are classical and the plots are used for studies up to now. The quality and chemical composition of ashes depends on many factors, including type of the fuel, tree species, type of the plant tissue, degree of the processing of the fuel before combustion, type of the burner and incineration conditions, and proportion of bottom and fly ash in the end product. The major elements in the ashes are calcium, potassium, magnesium, manganese, sodium, iron, phosphorus and sulphur. Ash is generally low on nitrogen because it is vaporises during combustion. Trace elements found in different types of ash include barium, boron, cadmium, copper, mercury and zinc. Compared to wood ash, peat ash contains essentially less mineral elements. The most abundant elements in peat ash are silicon, iron and aluminium. Ashes are characterised by high alkalinity with the pH ranging from 11 to 13. When applied to a soil, ashes will raise its pH and reduce the total acidity in the humus layer and in the top of the mineral soil. A rise in the concentration of base cations has been reported. Wood ash application has been found to increase the levels of extractable phosphorus in humus layer when higher ash doses are used and has little impact on total nitrogen concentrations in soil due to its low levels in the ash. The addition of wood ash does not result in a significant growth increase of trees on mineral soils. The limiting factor for tree growth on mineral soils is in most cases the availability of nitrogen. Wood ash promotes the growth of trees and improves the growth conditions on peat soils, and these positive effects are long lasting. Application of low peat ash doses did not increase the biomass production of trees but has a positive effect when larger amounts are applied. The effects of cadmium on ecosystems and a hazard to human health are of particular concern. There is currently not enough scientific knowledge available to recommend restrictions on the wood ash use as forest fertilizer due to high cadmium concentrations. Generally, the cadmium in wood ash did not become bioavailable and harmful to forest biota. Radionuclide content of forest biomass harvested for energy is related with wood ash application. Results based on experiments show that the application of wood ash does not change or even decreases the 137Cs activity within forest soil and vegetation. On peatlands an increase in the coverage of herbs and grasses and colonisation by nitrophiles has been observed. In addition, sphagnum mosses are substituted by forest mosses. However, wood ash may cause burn damages to bryophytes and lichens. According to some published data, the effect of wood ash on fauna consists in changes in the concentrations of heavy metals and radionuclides in body tissues. In most wood ash studies increased microbial activity and growth rate after ash treatment are reported.

Impact of Alkalisation of the Soil on the Anatomy of Norway Spruce (Picea abies) Needles

In this study, we evaluated the needle anatomy of Norway spruce trees growing on a territory that was exposed to different alkaline dust pollution. The anatomy of the needles of spruce growing on a polluted site in the vicinity of the Kunda cement plant (Northeast Estonia) was compared with the anatomy and physiological state of the needles from an unpolluted site. The needles from polluted sites had a significantly larger average mesophyll area and thicker epidermis. These needles also had significantly smaller average vascular bundles and xylem areas than needles from the unpolluted site. Although in the alkalised growth conditions, the mesophyll area enlarged, the number of damaged mesophyll cells increased, and as a result, the concentration of chlorophylls decreased reducing the photosynthetic potential of trees. Our study indicates that even though cement dust pollution has practically ceased in the area, the alkalised soil is affecting physiological processes in trees for a long time.