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The effect of contrasting meteorological conditions on hydrology, hydrochemistry and input–output budgets of nutrients and metals was examined in a small (2.8 ha) forested watershed of the Masurian Lakeland (NE Poland). The conditions of a frosty and dry continental winter activated an outflow of underground water originating from deeper water resources. The chemical composition of this outflow differed from watershed waters outflowing during mild winters with respect to SO4-S, Ca and Mg, which had lower concentrations, and NH4-N and K, which exhibited higher concentrations. An exceptionally severe winter affected also element fluxes in the examined watershed during the subsequent growing season. In order to show this impact, a comparison was made between the balances of elements moving through the investigated forest ecosystem during the growing seasons following mild and extremely cold winters. A biogeochemical effect of a frosty winter drought in a small post-glacial forested watershed, observed during vegetation growth (April – October), involved increased mineralization of nitrogen and phosphorus: a higher level of DON and DOP retention and a lower level of SRP and NO3-N retention. The increase in mineralization and the “opening” of biogeochemical cycles were also reflected in the loss of metals as K, Na, Ca and Mg.
At the end of July 1997 a premature shedding of one- and two-year-old foliage of Scots pine (Pinus sylvestris L.) was observed in central Poland. We examined the etiology and physiological consequences of this needle shedding event in a 15-year-old Scots pine plantation with diverse populations originating from Sweden, Russia, Latvia, Poland, Germany and France. On average, trees lost 20% of two-year-old foliage, with a local population from Poland having the highest needle loss (28%) and the lowest in a population from France (13%). However, differences among populations in needle loss were only marginally significant (p = 0.1). Phytopathological observations excluded biotic factors as responsible for needle loss. Analysis of thermal conditions in 1997 suggest that premature needle shedding may originate from the combination of winter physiological drought and unusually high (up to 35°C) air temperatures and low precipitation in late spring. We found that winter drought significantly affected the foliage by reducing its water content and concentration of nonstructural carbohydrates. High summer temperatures increased water stress and as a consequence led to reduction in crown density. Our data indicated that the needle shedding may be also related to root system damage due to low soil temperatures. Marginally significant differences among populations in needle shedding may indicate a weak genetic control over premature needle-fall among European Scots pine populations.
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