JOURNAL OF FOREST SCIENCE, 61, 2015 (5): 225–234 doi: 10.17221/6/2015-JFS Eff ects of aff orestation on soil structure formation in two climatic regions of the Czech Republic V. Podrázský1, O. Holubík2, J. Vopravil2, T. Khel2, W.K. Moser3, H. Prknová1 1Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic 2Research Institute for Soil and Water Conservation, Department of Soil Science and Soil Conservation, Prague-Zbraslav, Czech Republic 3U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Flagstaff, Arizona, USA ABSTRACT: The aim of this study was to determine the effect of agricultural land afforestation on soil characteristics. Two sites in two regions of the Czech Republic were evaluated, at lower as well as higher submountain elevations: in the regions of the Orlické hory Mts. and Kostelec nad Černými lesy, afforested, arable and pasture lands were com- pared for basic chemical and physical characteristics. It was determined: pH, CEC, exchangeable nutrients, SOC, bulk density, volume density, porosity (differentiated by pore size), water conductivity and soil aggregate stability. This study demonstrated the important influence of previous land use upon soil characteristics. The characteristics of the arable horizon can persist for many years; in forests, the mineral horizons (15–30 cm) can persist within 15–30 years after afforestation. Afforestation, which caused an increase in soil porosity by decreasing reduced bulk density and increasing capillary and gravitational pores (increasing the water-holding capacity and soil air capacity), is important for maintaining the soil stability. The positive effect on infiltration and retention capacity resulted not only from the presence of a forest overstorey, but also from the presence of permanent grass cover of pasture land. Keywords: water-stable aggregates (WSA); mean weighted diameter (MWD) Forests play a prominent role in carbon (C) est ecosystems with the goal of forest resource sus- transfer fl uxes through photosynthesis and res- tainability. Th e extensive roots of trees and other piration and represent an important carbon pool forest vegetation aff ect microbial biomass in the in terrestrial ecosystems (Brown, Lugo 1990; soil by controlling carbon cycling between the at- Merganiová, Mergani 2010; Sefidi, Mohad- mosphere and the soil (Brown et al. 2002). Land jer 2010; Marková et al. 2011). Occupying roughly use also has an important infl uence on soil proper- 30% of the land surface, forest ecosystems store ties and stabilization (Tisdall, Oades 1982), as do more than 80% of all terrestrial aboveground C and silvicultural treatments (Grashey-Jansen 2012; more than 70% of all soil organic carbon (SOC) (Six Malek, Krakowian 2012). et al. 2002). Th erefore the multiple eff ects of soil With changes in land use, soil microaggregates organic matter (SOM) on nutrient dynamics (Bin- and particles may form macroaggregates through kley 1995), carbon cycling (Nambiar 1996) and the action of temporary and transient binding soil structure formation (Caravaca et al. 2001) agents (Elliott 1986). Th e stability of these soil are important to maintain or enhance SOM in for- aggregates, as measured by water-stable aggregates Supported by Ministry of Agriculture of the Czech Republic, Projects No. QH82090 (20%), MZE0002704902 (30%), and QJ132012 2 (50%). J. FOR. SCI., 61, 2015 (5): 225–234 225 (WSA) and mean weighted diameter (MWD), de- dently of tree species (Gartzia-Bengoetxea et termines the soil structure (Filho et al. 2002). As al. 2009). Th is result may be attributed to diff erenc- an important indicator of soil quality, the soil struc- es in annual organic matter inputs (Kavvadias et ture directly or indirectly infl uences other physical al. 2001) and litter quality (Sariyildiz et al. 2005), and chemical soil properties (Cerda 2000). Th e as well as the enmeshing eff ect of roots and asso- biogeochemical dynamics of forest soil improves ciated mycorrhizal hyphae (Miller, Lodge 1997). soil aggregation compared to soil on agricultural All of these eff ects may contribute to stabilization lands, mainly by the transfer of organic carbon into of topsoil aggregates (Six et al. 2000). deeper soil horizons (e.g. Podrázský et al. 2009). Th e rate of change during the transition from Kaiser et al. (2002) determined that the forest sub- agricultural to forest land use has not been well soil has about 45% of the SOC of the soil profi le; described to date and there is limited knowledge this fraction is bound to clay particles, forming mi- of the impacts of these changes at the landscape/ croaggregates of < 20 μm in diameter. regional level. Our hypothesis is that forest estab- Aff orestation results in signifi cant sequestra- lishment can lead to considerable soil changes in tion of new carbon and stabilizes old carbon pools just a few decades. Th e aim of this study was to de- (physically protected SOM fraction), associated termine the impact of recent aff orestation on soil with the formation of soil stable microaggregates properties and soil structure formation in two re- aff ected by silt and clay content (Del Galdo et al. gions with diff erent climates. We specifi cally stud- 2003). Th e same authors found that aff orestation in- ied changes in soil characteristics 15–30 years from creases the SOC by 23% in the surface soil. SOC se- aff orestation. questration depends on forest species and manage- ment practices (Lal 2002; Del Galdo et al. 2003; Lamlom, Savidge 2003; Blanco-Canqui, Lal MATERIAL AND METHODS 2004). Researchers have found that dominant tree species aff ect the availability and biochemical com- Site descriptions. Th e study was conducted at position of organic matter inputs to soil (Leckie two localities (marked 1, 2) at 21 sites, which rep- et al. 2004). Diff erent properties, exudates and func- resent two typifi ed the soil type and climatic con- tions of various root systems may also have diff er- ditions within the Czech Republic. Th e soil char- ent eff ects on aggregation (Chan, Heenan 1988). acteristics of three land uses (aff orested, pasture, Th e nature and degree of soil improvement depend cultivated) were compared; the factor of forest type not only on the type of forest but also on land use diff erences has not been evaluated in this study. history. Aff orestation is generally found to improve Site (1) – highland was in the Rychnov nad soil carbon compared to cultivated agricultural Kněžnou district in the Orlické hory Protected Land- land but not necessarily compared to pasture land scape Area at an average altitude of 700 m a.s.l. (total (Guo, Gifford 2002). Th e soils of former moor- area of this mountainous region is 204 km2). For this land in the United Kingdom benefi ted from planta- study, we selected an area of 2 km2 (16°25'53–56''E; tions of birch (Betula spp.), but not of pines (Pinus 50°09'29–37''N). Climatic conditions are determined spp.) (Dimbleby 1952). Other studies did not fi nd as a mildly warm and very moist climate classifi ed as a signifi cant diff erence between microbial biomass an MT3 climatic region (Quitt 1971), with mean under aff orested tree species (Priha, Smolander annual temperature of approximately 7°C and mean 1997) despite the diff erent nutrient content of the annual precipitation of 848 mm (Moravec, Votýp- litter under each species. ka 1998). Th e geological bedrock is metamorphic in Th e stability of aggregates in the rhizosphere of origin and consists of paragneiss and phyllites. Th e forest stands is strongly correlated with the C-bio- soil type was identifi ed as Haplic Cambisol (accord- mass and soluble C-fractions as well as with dehy- ing to FAO 2007). drogenase and phosphatase activities. Th e combi- We compared the following cases: nation of residue amendment and level of available – aff orested (6 sites) – a site of forest species mainly low-molecular-weight organic fraction of forest Picea abies/minor species, e.g. Fagus sylvatica, stands signifi cantly improves soil aggregate stabili- Abies alba, Larix decidua, Alnus glutinosa and ty (WSA); the benefi cial eff ect appears to be mainly Betula pendula; the result of reactivation of microbiological activity – pasture (2 sites) – a site dominated by herbaceous (Caravaca et al. 2001). It appears that macroag- species/various grasses (Poaceae); gregates (0.25–2 mm) may play an important role – cultivated (1 site) – a site representing arable land in aggregate dynamics in mature forests, indepen- used for agriculture. 226 J. FOR. SCI., 61, 2015 (5): 225–234 Site (2) – lowland was established in the Prague- particle density (Danielson, Sutherland 1986), East district at an average elevation of 390 m a.s.l. porosity system was defi ned as a sum of capillary It is situated in the vicinity of the town of Kostelec (CP), semi-capillary (SP) and gravitational (GP) nad Černými lesy (total area of 18 km2). Th e experi- pores and calculated by the value of suction capac- mental plots, representing an area of approximately ity (Qs) according to the standard ČSN 13040; (iii) 1 km2 (14°55'27–36''E; 49°56'40–57''N), were estab- Kopecký rings for saturated hydraulic conductiv- lished in 1967 by planting on agricultural soils. Cli- ity (Ksat) described by Klute and Dirksen (1986) matic conditions are determined as a mildly warm and determined according to the standard ČSN and slightly dry climate classifi ed as an MT9 cli- 721020; (iv) samples for determination of aggre- matic region (Quitt 1971), with mean annual tem- gate stability (weight of sample – 3 kg) were air- perature of 8.4°C and mean annual precipitation of dried and sifted through nested sieves (Retch – ISO 591 mm (Moravec, Votýpka 1998).