Monitoring research of rainfall penetrating through the forest to the soil surface was conducted in Świętokrzyski National Park between 1994--1995 and 2000-2001 in order to recognize the role of rainfall in the process of acidifying soil and surface waters. In compliance with the assumptions used for monitoring system of water and matter circulation (Fig. 1) the dynamics of chemical composition and acidity were tested in the bulk precipitation (OA) were tested at the height of 30 m over soil - 4 m over crown beech stand, throughfall in the fir-beech stand (OpJd) and beech stand (OpBk) and stemflow of 5 fir trees 180-190 years old (SpJd) and 5 beech trees 80-100 years old (SpBk). In the monthly samples, the content of Cl, SO42-, NO3-, PO43-, NH4+, Ca2+, Mg2+, K+, Mn2+, Pb2+, Fe3+, Al3+ was determined, whereas pH was determined directly after the rainfall in this area. The soils of the investigated forest area developed from quartzite weathering with an admixture of eolic dust are very acid with alkaligenous cation saturation in mineral horizons from 8-11% in the Ah and E horizons to 6-30% in the C and SolDg horizons (Fig. 2). On the basis of the pH measurements it has been stated that between 1994-2001 there was a considerable trend of increasing acidification in rainfall flowing downwards the stand to the surface, especially stemflow in comparison with bulk precipitation (Table 1). The seasonal dynamics of pH in rainfall is considerable, however, with lower pH-values in cold periods and 2,0-2,5 pH higer in warm periods (Table 2, Fig. 3). From the investigated fir-beech stand and beech stand, rain waters leaches considerable amounts of K+, Mn2+, and H+, and also Ca2+, NH4+, Al3+, NO3-, SO42-, Cl-, PO43-, and Mg2+ to the lower degree (Table 2, Fig. 4). This phenomenon is especially sharply manifested in the constant stemflow "pathes", directly to the rhyzosphere. High enrichment of rain waters in hylosphere with anions of strong acids NO3- SO42-, Cl-, and protons H+ may be caused by dry deposition in dry periods of gases coming from emission and in wet periods by decomposition dust and acrosol of deposited on the surface of plants above-ground. The quantity of then cation and anion rinsed from the tree organs depends on the acidity of the soil. The molar rations Ca2+/Al3+, mol*mol-1 and the base saturation degree Ma% of rain waters in hylosphere indicate intensive neutralization of acides by basic ions washed out from trees by acid rain waters (Fig. 5). The calculated Acid Neutralising Capacity ANCaq μmol* μmol 1-1 confirms slight overbalance of acids in the bulk precipitation in years 1994-1995 and 2000-2001 (Table 3, Fig. 6). In the throughfall there was a decreasing trend of basic cation domination and in 2000-2001 with increased dominance of acids over bases. Stemflow in the investigated period shows overbalance of acids in relation to bases with negative values ANCaq. In the dynamics of ANCaq there is considerable dominance of acids components in cold periods. In vegetation periods they are buffered by leaching from the assimilation organs and from bark of basic cations, increasing with the increased concentration of anions of strong acides in waters.
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The programme of the research includes use of the SPAC model, taking into account how soil acidity will influence root density and transpiration of trees. Main results are connected to the simulation of these relation between root density and transpiration of trees, taking into account the actual soil water content and soil water stress (pF of soil water). These relations will indicate how the Mountain forest ecosystem can be influenced and which action would bring the most desirable results in terms of reforestation. In the North-Eastern part of Bohemia (CZ) stress and physiological disorders of higher plants are related to a strong forest decline. Total deforestation in some localities is connected with additional problems of reforestation. Research is directed into the pedo-environmental restriction to forest renovation in terms of soil chemical and physical constraints and the climate effect on the forest health. The knowledge on soil - tree - atmosphere - system using a SPAC model and the soil degradation, rooting density and soil water relations were evalued. The upper elevation coniferous forest trees live on the edge of disaster under continuous stresses. Soils are shallow to bedrock, nutritionally poor, too wet, with severe winters. Anthropogenic factors known from field studies to cause stresses in forest trees are mainly acidity (H2SO4/HNO3) and metal ions. Acidity (low pH) influences root systems and causing death of fine roots, which reduces water and mineral uptake. Sulphur and nitrogen compounds are the major pollutants having deleterious effect on forests. The sulphur deposition is perhaps the highest in the world here, up to 100kg S per ha and year. Decreasing root density is resulting with decreasing of tree transpiration and tree photosynthesis, often with death of the tree. Climatic data of the field were used to simulate diurnal course of the temperature, relative humidity and solar radiation during cloudy and sunny days. Results of simulation are giving the numerical values of root water uptake as a function of changing root density, influenced by soil degradation. The main assumptions were that the forest decline is a result of the water stress of trees. Forest under stress was damaged by insects, like Zeraiphera griseana, attacking several thousands of ha of the stand. Soil acidity under the influence of the acid rain drops even to the level of pH 2.4, standinglater on the level pH 3.4. The wet sulphate sulphur deposition was above 20 kg ha-1 year-1 in 1990 at Mountain Śnieżka, up to 100 kg S ha-1 year-1 in some locations, highest in the world. The annual concentrations of the sulphur dioxide SO2 in the area oscillate around 40-50 μg m-3 of air, while the annual SO2 concentration of 20μg m-3 may have a toxic effect on coniferous forest, especially under unfavourable climatic and edaphic conditions. Acidity influences root systems and soils, causing death of fine roots, reducing water and mineral uptake, altering microflora and litter decomposition, reducing mycorrhizae, resistance and vigor. The molar Ca/Al ratio below 1.0 shown to repress root growth. The working question in this paper was how decreasing root density L[v] cm cm-3 may influence spruce stands, but mainly leaf water negative pressure (water stress), leaf to air temperature (heat stress) and pulse of diurnal transpiration. The result of the simulation using SPAC model was the transpiration rate to leaf water negative pressure loop, given in fig. 2. Data on the root density was collected in the field. Diurnal meteorological data were taken from Pec near Śnieżka, 800 m a.s.l. Day 13th August 2000 (225th day of the year) was selected, sunny. Soil water potential was taken low as pF 2,9. Root penetration depth was shallow, about 50 cm. Root densities in the simulation were 5.0, 1.0, 0.1 and 0.05 cm cm-3, but in the field on the location of the strong forest decline the densities were below 0.4-0.5 and in the location of moderate forest decline the densities were about 1.0 cm cm-3. Critical behaviour of the trees was when root density was lower than 1.0 cm cm-3. Results of simulation may be confronted with the results of field measurements. Conclusions are: forest decline has a similar effect as the clear-cutting of the total stand; acid rain and clear-cutting are creating the conditions like in the acid bogs, with very low pH and low redoxEh; the research is indicating the importance of root regeneration ability, related to micro-topography, spatial variability of soils and phyto-sociology; new seedlings must be not distributed uniformly, but located only on the small "islands" elevated above the bog; biomanipulation and inoculation with microbes and fungi are not helping for seedlings survival; great need is indicated for new soil survey on micro-topography and spatial variability for new locations of the clusters of the seedlings.
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