The Bialowieza Primeval Forest (BF) is one of the well-known forests in Central Europe. The most common tree species in BF was Norway spruce (Picea abies (L.) H. Karst), comprising 26%. However, a mass dieback of spruce has occurred during recent years. The spruce dieback in Bialowieza Forest is directly caused by the spruce bark beetle. However, the mass appearance of this pest can be a consequence of global warming and drought. Changes in air temperature were presented and drought indices were calculated as follows: standardized precipitation index, Palmer drought severity index, climatic water balance and soil water storage deficit. The warming of the climate of Bialowieza from 1950 to 2015 is comparable to that observed throughout central Europe. The temperature increased by 1.27 °C. The occurrence of drought from 1950 to 1966 and from 1985 to 2015 had a similar frequency. From 1963 to 1966, the volume of removed deadwood from the managed part of Bialowieza Forest was 27 thousand m3 but from 2012 to 2016, the volume was more than one million m3.
Management for sustainable river valleys requires balancing their natural values against the need for agricultural and recreational development on surrounding lands. The Southern Całowanie Peatland near the city of Warsaw sits on a sandy terrace and has well preserved Carex and Molinia stands existing in part of the area, especially where water tables are less than 1.5 m below the surface. The existing drainage network in this southern part has been poorly maintained and could be reestablished to help raise water levels for restoration of the peatland. Modflow was used to look at influence of drainage channel water levels on the overall water table height in the area. By raising water levels in the drainage system by 0.5 m it was found that 29% of the area would become suitable for increasing Carex and Molinia communities.
This paper presents the results of a study carried out on a Scots pine stand, aged over 70 years, growing on ICP Forests land. The stand underwent late thinning, this being the last operation performed prior to complete felling, which will take place when the trees reach an age of approximately 100 years. The thinning, which reduced the basal area by 20%, caused a decrease in LAI by approximately 30% on average and an increase in the gap fraction by almost 50%. The thinning of the tree canopy increased by more than 40% the quantity of light reaching the lower levels of the tree stand and the soil. Comparison of the results for actual evapotranspiration and tree transpiration with potential evapotranspiration (T ETP -1 , EVT ETP -1) revealed an 8% increase in tree transpiration, while the actual evapotranspiration of the ecosystem increased by 14% after thinning. This increase was partly the result of the higher tree transpiration, but another factor may have been the increased evapotranspiration of forest floor vegetation and the soil, resulting from the greater quantity of light reaching the forest floor. The ratio of the pines' transpiration to the actual evapotranspiration of the ecosystem (T EVT -1 ) was practically unchanged, from 0.60 before thinning to 0.61 after. Modelling was also carried out (based on a Plant Water model) for average meteorological conditions to determine the effect of thinning on the rate at which the trees depleted supplies of soil water. This effect was greatest in September, when plant available water was present for 9 days longer than prior to thinning. In the months with the highest levels of transpiration (from May to August) the period in which plant available water was present lengthened by 2-3 days.
Drought in the forest is not only a prolonged state of water shortage, but also an occasion where interactions between plants and fungi are affected. Water efficiency accelerates a range of pathologies in interactions between organisms, influencing the ecosystems and their interacting biological components. This study focuses on the role of mycorrhizal and endophyte fungi in alleviating the effects of soil water shortage, and on the impact of their altered activity during drought on the health of trees. The issues presented here show the fundamental role of the mycorrhizal mycelium and the mechanism of water transport to the plant in the course of other phenomena (withering, pathogenesis, endophytes biology) that occur in trees under influence of drought, with particular attention on managed coniferous stands. Conclusions resulting from published information on this topic emphasize the negative impact of soil moisture deficiency on the ectomycorrhizal fungi functioning and, in contrast, on the promotion of the growth of some endophytes, pathogens and hemi-parasitic mistletoes (Viscum spp.).
The impact of beaver ponds on tree stand in a river valley
The number of beavers in Poland rapidly increases which may result in conflicts between man and beavers. Despite the fact that beaver ponds play important role in increasing of biodiversity, water retention and soil moisture, they may also cause the die out of tree stands in river valleys and lead consequently to disappearance of typical riparian forest communities. Field studies demonstrated that long term flooding inhibited tree growth. Many trees died after 2 years of flooding. Long flooding caused the death of 80% of trees.
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