PrACE GEOGrAfICzNE, zeszyt 143 Instytut Geografii i Gospodarki Przestrzennej UJ Kraków 2015, 85 – 102 doi : 10.4467/20833113PG.15.027.4628 Variability of throughfall and stemflow deposition in pine and beech stands ( Czarne lake catchment, gardno lake catchment on wolin island ) Robert Kruszyk, Andrzej Kostrzewski, Jacek Tylkowski Abstract : The research sought to determine the range of conversion of the chemical composition of precipitation in a beech stand located in the Gardno Lake catchment ( Wolin Island ) and a pine stand in the Czarne Lake catchment ( Upper Parsęta catchment, West Pomerania Province ). The presented results cover three hydrological years : 2012, 2013 and 2014. The research focused on the chemical composition of bulk precipitation ( in the open ), throughfall and stemflow ( in a forest ). The obtained results confirm that after precipitation has had contact with plant surfaces there is an increase in its mineral content. This is due to the process of enrichment of throughfall and stemflow with elements leached out of needles + 2+ + – + 2+ 2– – and leaves ( K , Mg ) and coming from dry deposition ( NH 4, Cl , Na , Mg , SO 4 , NO 3 ) washed out from plant surfaces. The research, based on the canopy budget model, indicates that in the case of potassium, its load leached out of needles and leaves accounted for 75.6 % and 73 %, respectively, of its total deposition on the forest floor. Calcium leaching was not detected in either of the two stands. In comparison with potassium, the range of magnesium leaching was smaller and amounted to 34 % under beech and 26.5 % under pine. As to loads of potassium and magnesium in the beech stand, they were more than twice as large as the ones observed in the pine stand. In spite of the fact that coniferous trees capture aerosols present in the air much more effectively, a higher mineral content was recorded in the beech – 2– + 2+ stand. It applies primarily to ions of marine origin ( Cl , SO 4 , Na , Mg ). It was only when ammonium ions originated from agriculture that their higher concentrations and loads were found in the pine stand. Keywords : forest ecosystem, throughfall, stemflow, ion deposition, canopy budget model, Scots pine, European beech 86 Prace GeoGraficzne, zeszyt 143 introduction Precipitation flowing through the canopy in the form of throughfall ( Tf ) and stemflow ( Sf ) substantially alters its physico-chemical properties when in contact with plant surfaces. The main factors which affect the course, character and intensity of these processes include : an atmospheric supply of various ions and their concentration levels in leaves, the species composition and age of a stand, and the abundance of nutrients in a habitat ( Stachurski 1987 ; Swank 1986 ). These processes include the enrichment of precipitation through washing off dust and gas pollutants deposited on plant surfaces as well as through leaching elements from needles and leaves ( van der Mass, Pape 1991 ; Likens, Borman 1995 ; Grodzińska, Laskowski 1996 ; Dambrine et al. 1997 ; Draaijers et al. 1997 ; Walna, Siepak 1999 ; Polkowska et al. 2005 ; Małek et al. 2008 ; Kozłowski et al. 2012 ). Consequently, despite much lower precipitation totals in the forest ( interception ), its soil is provided with a much larger flux of mineral and organic components than an open area. It is assumed that coniferous trees modify the chemical properties of precipitation much more than deciduous ones ( Shubzda et al. 1995 ; Fernandez-Sanjurjo et al. 1997 ; Herrmann et al. 2006 ; Kozłowski et al. 2012 ). Having needles throughout the year and a larger reception surface ( compared with leaves ), they contribute to increased supplies of pollutants to the soil. The processes taking place in the canopy affect the acid-alkaline balance of precipitation in woodland. Airborne nitrogen and sulphur compounds can be adsorbed on plant surfaces and acidify throughfall and stemflow ( Gower et al. 1995 ; Walna, Siepak 1999 ; Kvaalen et al. 2002 ; Bochenek et al. 2008 ). On the other hand, in the case of deciduous trees, the canopy neutralises acidic compounds. As a result, the pH of throughfall is higher than of precipitation in the open. The primary objective of the research was to : – get familiar with the process of modification of the chemical composition of precipitation in tree stands of different species composition, – determine the total canopy leaching of Ca2+, Mg2+ and K+, – identify changes which take place in the tree canopy in terms of precipitation acidity. study area The research sites were located in the Czarne Lake catchment in West Pomerania ( the upper Parsęta catchment ), 8 km north-west of Szczecinek ( the pine stand ) and on the Wolin Island in the Gardno Lake catchment ( the beech stand ) ( fig. 1 ). The upper Parsęta catchment is situated on the border between two mesoregions : Variability of throuGhfall and stemflow dePosition ... 87 the Drawskie Lakeland and the Byto- wskie Lakeland ( Kondracki 2013 ). The area of the Czarne Lake catchment is 17.66 ha, 3.1 ha of which is the lake itself. The catchment is thoroughly covered with woodland, mostly composed of clusters of fresh pine trees. The research was conducted in a pine stand situated in the Szczecinek forest Division, the Szczecinek forest district, division 36d. This stand is 95 years old and represents a suboceanic Leucobryo-Pinetum fresh pine type of fig. 1. Location of the research sites forest. The pine is the dominant tree Source : authors’ own study. species ( 85.8 % ) with an estimated canopy density of 70 %. Its average D B H ( diameter at breast height ) is 33.8 cm and the average height is 25 m. Apart from pines, there are also silver birches ( Betula pendula ) – 2.3 %, European beeches ( Fagus sylvatica ) – 4.3 %, and common oaks ( Quercus robur ) – 6.6 %. The soil cover at the first research site was classified as a subtype of podzolic rustic soil formed from medium-grained sand sediments. The other research site was in the Gardno Lake catchment, 2.65 km 2 in area, situated in the Uznam and the Wolin mezo-region. The individual character of the catchment derives from its coastal location, proximity to the cliff coast and its full afforestation. The site was located in a forest ecosystem, in a poor habitat of acidophilic beeches referred to as a Luzulo-pilosae-Fagetum association. Predominant in its species composition was the European beech ( Fagus sylvatica ), at 90 %, estimated to be 113 years old. The rest was composed of the Scots pine ( Pinus sylvestris ) aged 103. Their average D B H ( diameter at breast height ) was 35 cm and 42 cm, respectively, and the average height was 26 m for both species. The canopy density was found to be full. Beeches grow on sandy soils composed of medium-grained loose ( rarely weakly loamy ) sands. They form sandy luvisols with some glossic features, podzolised, with a very acidic pH, especially in the upper part of the soil profile. During the study period, the total annual atmospheric precipitation and the mean annual air temperature in the upper Parsęta catchment amounted to 698.3 mm and 8.1 °C ( 2012 ), 582.2 mm and 7.5 °C ( 2013 ), and 539.9 mm and 9.2 °C ( 2014 ). According to a thermal-precipitation classification ( Lorenc 1999 ), the period can be regarded in thermal terms as average ( the years 2012 and 2013 ) and very warm ( 2014 ). In terms of annual precipitation totals, the year 2012 was average, 2013 dry, and 2014 very dry. These values were obtained at the Research Station in Storkowo located 88 Prace GeoGraficzne, zeszyt 143 at a distance of 5 km from the Czarne Lake catchment. As for the other catchment, the total annual precipitation and average annual temperatures were : 575.5 mm and 9.3 °C ( 2012 ), 629.5 mm and 8.8 °C ( 2013 ), and 592.9 mm and 10.4°C ( 2014 ) ( the Biała Góra Research Station ). Against the background of multi-annual figures ( the years 1956 – 2014, Dziwnów ) the period of the hydrological years 2012 – 2014 was relatively warm in thermal terms and average in precipitation terms. research methods The presented results cover a period of three hydrological years : 2012, 2013 and 2014. The measuring system in the pine tree stand consisted of 12 throughfall collectors located under the tree canopy at nodes of a regular grid, distanced every 4 metres ( Photo 1 ). Collector inlets were placed 20 cm above the ground and secured with a mesh to prevent contamination with organic material. The total inlet area of the collectors was 1.356 cm 2. The funnels and receptacles were made of plastic which did not affect the chemical composition of precipitation. In order to reduce any water losses through evaporation, the containers were buried in the ground with P V C pipes placed in the middle. In the beech stand the measuring system consisted of 10 collectors arranged in a grid. Every collector inlet was placed at a height of 1 m above the ground. The total inlet area of the collectors was 2.000 cm 2. The differences in the organisation of the measuring system relate to those in the structure of the tree stands examined ( their canopy density, vertical structure, species composition ). In the beech stand stemflow was monitored as well. Three beeches located in the study area were selected for this purpose. In the pine stand, on the basis of studies conducted in the years 1995 – 1999 the proportion of stemflow in the inflow of water Photo 1. Throughfall collectors in the beech stand ( A ) and pine stand ( B ) Variability of throuGhfall and stemflow dePosition ... 89 and dissolved substances to the forest floor was found to be negligible : the inflow of water averaged 0.2 % ( 0.0 – 0.7 ) of the figure noted in the open ( Kruszyk 2001 ).