The impact of introduced and indigenous woody plants on change of selected soil chemical properties in the Arboretum Mlyňany

© Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources, 2015 http://www.fapz.uniag.sk/ DOI: 10.15414/afz.2015.18.02.44–48


Introduction
Plants introduction, as intentional anthropogenic activity, means the planting of plants transported over large geographical barriers into new territory, which is situated beyond the borders of natural occurrence of particular species.Various anthropogenic activities support plants acclimation, their survival and autoreproduction in new conditions, what leads to their naturalization.It allows plants release into the wild and penetration into natural communities (Eliáš, 2011).In recent decades, the alien species invasions have become a significant cause of species decline and degradation of natural environment (Vitousek et al., 1997).Introduced invasive species are currently considered as the second most serious threat of the world biodiversity (Eliáš, 1999).
In the Arboretum Mlyňany, the intentional anthropogenic introduction of tree species, as well as planting of indigenous trees is performed since 1892, when it was founded as a private collection of Count Ambrózy.Gradually, in the original 40 ha oak-hornbeam forest were planted introduced trees, which over time adapted to new natural conditions, and even some of them extended to the Arboretum surrounding (Tomaško, 1998).Arboretum is divided on: original Ambrozy's park founded in year 1892, area of East-Asia dendroflora in year 1964, area of North America dendroflora in year 1975, area of Korea dendroflora in year 1984 and exposition of Slovak dendroflora in year 1992 (Tábor and Pavlačka, 1992).
Soil characteristics considerably affect not only rooting and plants growth, but also their development, succession and health condition (Tokár and Kukla, 2008).On the other hand, also plants significantly affect soil properties by their root exudates, plant residues, roots penetration (Philips and Marion, 2004;Masarovičová, 2011).Therefore, the change of vegetation has significant and often major influence on soil.
The aim of the study reported here was to investigate the extent, to which selected soil chemical properties of A horizon under original oak-hornbeam growth in the Ambrozy's park were altered by long-term cultivation of introduced and indigenous tree species.

Locality description
Arboretum Mlyňany (48º 19' N, and 18º 21' E) is located in southern Slovakia, in the valley of river Žitava, at an altitude of 165-217 m above sea level, in warm, dry climate area with mean annual temperature 10.6 °C and mean annual total precipitation 541 mm (Figure 1).Undulated terrain is southern spur of Hronský Inovec and Tríbeč.Arboretum site floristically belongs to the Pannonian area, geo-botanically to the Querceto-Carpinteum area.Arboretum is situated on a late Tertiary geological formation, represented by clays, sands and rubble sands (Stenhübel, 1957;Hrubík et al., 2011).This substratum is almost all covered by wind-deposited loess, mostly without carbonates (Cifra, 1958).On majority of Arboretum area was developed Stagni-Haplic Luvisols, other subtypes are Haplic Luvisols and cultivated Stagni-Haplic Luvisols (Polláková and Konôpková, 2012).
Soil samples were collected from A horizons, which reached to the following depths: oaks-hornbeams and spruces to 0.15 m, yews and pines to 0.20 m and cherry laurels to 0.23 m.Different depths of soil sampling were related to the different thickness of A horizons.After drying, from soil samples were removed plant and root residues, samples were grinded and homogenized by sieving through sieves with mesh diameter <2 mm and <0.25 mm.In such prepared soil samples were determined: soil pHpotentiometrically in H 2 O and in 1 mol dm -3 KCl (Hrivňáková et al., 2011); exchangeable base ions (S) and The map of Arboretum Mlyňany site hydrolytical acidity (H) by Kappen's method (Hrivňáková et al., 2011); exchangeable Al by method of Sokolov (Hanes, 1999), available macro-elements phosphorus (P) and potassium (K) were analysed by method Melich III (Melich, 1984), then P was detected colorimetrically on Spectrophotometer Jenway model 6400 and K on atomic absorption spectrophotometer.Total soil organic carbon (C T ) was analysed by Tyurin method (Orlov and Grischina, 1981); total nitrogen content (N T ) by Kjeldahl (Fecenko, 1991).Based on determined C T a N T contents were calculated their relative proportions.
Each analyse was done in 3 repeats and in paper are shown average values.
For statistical evaluation was used one-way analysis of variance, and differences between the variants (tree species) were assessed using Scheffe's test with minimum significance level of P ≤0.05.

Results and discussion
Arboretum Mlyňany is a good site for studying the degree of different tree species influence on soil chemical properties, which were considerably changed by trees action (Polláková and Konôpková, 2012).Original growth in Ambrózy's park was oak-hornbeam forest therefore soil under the rest of this forest was chosen as a control, with which were compared soil chemical properties under growths of introduced and indigenous tree species.The differences were studied in A horizons, since these were the most influenced by trees litter and root residues and exudates.
pH is considered as the most important indicator of soil state, fertility and functioning.It provides information about soil microbial activity, potential chemical degradation, availability of elements to plants.In Arboretum Mlyňany, tree species had statistically significant influence on changes of pH values in A horizons (Table 1).In A horizons, values of pH in H 2 O significantly increased under growths of cherry laurels (11%) and pines (24%) compared to the soil under the rest of original oak-hornbeam forest.Also in pH in KCl were found statistically significant differences caused by various tree species.Compared to control (oak-hornbeam forest), the litter and root exudates of yew significantly decreased pH in KCl values.
In addition to pH, indicators of soil acidity are also cationic composition of sorption complex and soil saturation by aluminum.Šebesta et al. (2011) found that the gradual acidification of anthropogenically undisturbed forest over 60 years decreased pH values by 0.1-0.3 units in A and B horizons, but base saturation decreased by half compared to the original state.
In Arboretum Mlyňany, high production of low-molecular organic acids and fulvic acids during decomposition of poor quality humus material provided by trees, which was moreover in the form of litter deposited on the soil surface, resulted to very strong hydrolytic acidity.
From the results shown in Table 1 follows that in A horizons of examined soils, the tree species had statistically significant effect (P = 0.0000) on the changes of hydrolytic acidity (H), sum of exchange base cations (S), cation exchange capacity (CEC) as well as the degree of sorption complex saturation by base cations (BS).Under the original oak-hornbeam forest and spruces, the values of H were more than 50% higher than under growths of cherry laurels, yews and pines.The lowest values of S and the highest H in A horizons under the original oak-hornbeam forest resulted to the lowest degree of sorption complex saturation by base cations (BS = 24.1%).Stronger soil acidity was probably caused by longer period (more than 112 years) of oaks-hornbeams influence on soil (Arboretum was established in year 1892 in the original oak-hornbeam forest).Since other tree species were younger, the duration of their action on soil was shorter therefore their influence on soil chemical properties was not so distinct.
Exchange aluminum was detected in all studied A horizons.Matúš et al. (2006) stated that aluminum is present in different chemical forms, of which free Al 3+ , Al(OH) 2+ a Al(OH) 2 + are critical for the evaluation of its toxicity, and for determining the impact of protons entry into the soil and surface water.Just these are released into the soil solution due to dissolution of minerals, or ion-exchange reactions (Čurlík et al., 2003).Cronan and Grigal (1995) found that if the degree of base saturation is below 15%, aluminum will probably cause stress to plants.In all studied A horizons of Arboretum, the degree of sorption complex saturation by base cations was more than 24%, what excludes negative effect of aluminum on plants (Table 1).
Compared to the A horizon under the rest of original oak-hornbeam forest, due to changed vegetation were statistically significantly altered contents of nitrogen, phosphorus and potassium (Table 2).The content of nitrogen significantly increased under growth of pines (by 24%).Phosphorus content significantly decreased under growths of spruces (81%), yews (by 35%), cherry laurels (by 73%) and pines (by 81%).The content of potassium significantly decreased under cherry laurels (by 46%) and pines (by 19%), increased under yews (93%).
In the past, the nutrients in Arboretum soil were supplied through farmyard manure.Whereas from year 1965 in the Arboretum are not used any fertilizer it is assumed that N, P, K macronutrients originate from decomposed trees litter.Already Olson (1963) stated that litter represents the input-output system of nutrients in forests.The rate, at which litter accumulates and decomposes, regulates the flow of energy, primary productivity and nutrient cycling in forest ecosystem.According to Hättenschwiler et al. (2005), plant species affects the ecosystem through nutrient turnover, uptake and use by plants, quantity and chemical composition of litter, interaction with rhizosphere, and changes microclimate of environment.
In addition to content, also relative proportion of total carbon (C T ) and nitrogen (N T ) was evaluated.Obtained results showed that tree species had statistically significant effect on changes of C T : N T ratios in A horizons of Stagni-Haplic Luvisol (Table 2).Compared to other trees, significantly narrowest C T : N T ratio was under spruces.The highest statistical difference was found between growth of spruces and cherry laurels.In A horizons, C T : N T ratio significantly decreased under pines (15%) and spruces (32%) compared to the rest of original oak-hornbeam forest.
The content of organic carbon in soil is regulated by the balance between biotic inputs and losses and abiotic conditions involving climate, topography and soil type and also various anthropogenic interventions to soil.The quality of plant residues significantly affects their decomposition and loss of carbon from soil (Vesterdal et al., 2008).The type of vegetation had statistically significant effect on changes of C T content in A horizons (P = 0.0000).Compared to C T content in A horizon under original oak-hornbeam forest, C T significantly increased under cherry laurels (by 17%) and decreased under spruces growth (34%).Quideau et al. (2001) stated that various tree species have different effect on stock and dynamics of organic matter in soil and in addition, changes of land use cause alteration the chemical properties of organic matter.Direct relationship between tree species and soil organic matter composition was ascertained.Also in the soil of Arboretum, anthropogenically changed vegetation affected not only the quantity and quality of soil organic matter, but also the content of essential nutrients, pH values and characteristics of soil sorption complex.

Conclusions
Obtained results showed, that intentional, anthropogenic change of vegetation participated on highly significant change of soil chemical properties in A horizons of Arboretum Mlyňany.The impact of introduced tree species was more distinct than indigenous ones.The most influenced parameters were exchangeable aluminium, exchangeable base cations, degree of sorption complex saturation by base cations, available phosphorus content; and the least influenced parameters were pH H 2 O, total carbon and nitrogen contents, and C T : N T ratio.
The growths of cherry laurels and pines had the greatest impact on the change of chemical properties of A horizons compared to original oak-hornbeam forest and were significantly altered 10 of 12 examined parameters.The smallest impact on chemical characteristics in A horizons had the growth of spruces, since caused significant change in 7 of 12 examined parameters.

Figure 1
Figure 1Mean annual temperature and mean annual total precipitation in Arboretum Mlyňany in years Source:Hrubík and Hoťka, 2007

Table 1
Soil pH and characteristics of sorption complex in A horizons of Stagni-Haplic Luvisol

Table 2
The content of organic carbon and basic nutrients in A horizons of Stagni-Haplic Luvisol C T -total soil organic carbon, N T -total nitrogen content, P -available phosphorus content, K -available potassium content Different letters between lines indicate statistically significant differences -Scheffe's test with minimum significance level at P ≤0.05