Abstract
Little is known on soil organic carbon (SOC) stocks in karst areas worldwide, although many of them have seen long-term application of agroforestry systems with a potential for carbon sequestration. Therefore, our study aimed to assess landscape-level SOC concentration and stock in the Silica Plateau, a part of the Slovak Karst Biosphere Reserve located in the Western Carpathians (Slovakia) with a centuries-long agroforestry record. The most represented local soil units are Chromi-Rendzic Leptosols and Chromic Cambisols with clayey loam texture, C/N ratio 9–12, and \( {\text{pH}}_{{{\text{H}}_{2} {\text{O}}}} \) 6.6–6.2 in their organo-mineral surface horizons. Mull surface humus form prevails under mixed forest stands dominated by hornbeam (Carpinus betulus L.), oak (Quercus petraea L.), and beech (Fagus sylvatica L.). A total of 2,700 soil samples were collected from 150 soil pits. Both SOC concentrations and stocks were determined for the 0–60 cm mineral soil layer. Soil stoniness was accounted for by means of electrical resistivity tomography. According to the analysis of covariance, cropland SOC concentration (0.026 g g−1) is significantly lower compared to forestland (0.040 g g−1) and pastureland (0.041 g g−1) (P < 0.01). During the period of 130 years after forest clearing, cropland SOC stock has been reduced at an exponential decay rate of ca 0.002 year−1, while the SOC stock in pastureland has increased following land use change from cropland by approximately 30% during the same period of time. Irrespective of land use history, overall SOC stock is high reaching on average 207.4 Mg ha−1, out of which 66% are stored within 0–30 cm and 34% within 30–60 cm soil layers.
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Introduction
Soil organic carbon (SOC) is essential in determining the physical and chemical properties of soils, as well as in the sustenance of primary production in terrestrial ecosystems and the process of trapping atmospheric CO2 (Santore et al. 1995; Post and Kwon 2000). Global soil organic matter exceeds the sum of the atmospheric and biotic pools (Bouwman and Leemans 1995; Schlesinger 1997; Lal 2004). Carbon stock in soils depends on geological substrate, precipitation and temperature (Turrión et al. 2009; Luo and Zhou 2006; Davidson and Janssens 2006), terrain topography and microtopography (Bergstrom et al. 2001a; Stoeckel and Miller-Goodman 2001; Eglin et al. 2008), land use and soil tillage (Baker et al. 2007), and other factors, such as soil depth under consideration (Jobbágy and Jackson 2000). The relative importance of these factors is scale dependent (e.g. Bergstrom et al. 2001b; Corstanje et al. 2007). Although carbon bound in the biomass may exceed the amount of SOC stored within surface humus and topsoil (0–50 cm) of European forest, the overall SOC content is still very significant, ranging from ca 60 to 230 Mg ha−1 (Bauer et al. 2000).
The carbon balance results from C fluxes driven by photosynthesis and respiration, the latter process being dominated by root and microbial soil respiration (Valentini 2003). Generally, soil organic matter (SOM) mean residence time depends on SOM quality and the level of its physical and chemical protection (e.g. Jenkinson and Rayner 1977; Stevenson 1994; Sollins et al. 1996; Zaccone et al. 2011). Consequently, ca 1,500 Pg of organic carbon in the upper meter of mineral soils (Jobbágy and Jackson 2000) consists of several pools with characteristic turnover times (Parton et al. 1987). Thus, approx. 200–300 Pg C in SOM exist in forms that recycle during a century or less (Schimel 1995; Potter and Klooster 1997), while the remainder is stable on time scales of centuries to millennia (Trumbore 2000). Harrison et al. (2000) reported SOM mean resident times ranging from decades to several 100 years in European beech and spruce forests. Importantly, significant proportion of SOC found bellow 10 cm was locked up in stable forms, illustrating the importance of forest soils for the terrestrial carbon cycling in Europe in comparison with the more vulnerable organic carbon stored in agricultural soils and drained peats. The annual SOC loss caused by changes in land use can be considerable, although large variation exists in different parts of the world (Bouwman and Leemans 1995). For example, while forest management has little effect on SOC (Johnson and Curtis 2001), soils of the world’s agroecosystems are often depleted of their SOC pool by 25–75% depending on climate, soil type, and historic management (Lal 2011). On the other hand, Montagnini and Nair (2004) estimated average carbon storage by agroforestry practices at 63 Mg ha−1 in temperate regions, suggesting that agroforestry systems with perennial crops may be important carbon sinks. Also, agroforestry systems involve trees or shrubs, agricultural crop, and possibly pasture as their main components (Mosquera-Losada et al. 2009), thus preserving their attractiveness from ecological and socio-economic points of view (Franco et al. 2001).
However, few landscape-level SOC stock data sets are available for agroforestry systems in karst areas, despite their high representation in Europe and worldwide (e.g. Rivera et al. 2000; Wang et al. 2004; Vidrih et al. 2009). In karst areas, SOC stock calculations heavily depend on visual stoniness assessment in the field, which may be uncertain. For example, Wirth et al. (2004) established that soil stoniness was overestimated by 40%, which would imply an underestimation of SOC stock. Therefore, our study aimed to quantitatively assess SOC stock and variability within a temperate zone agroforestry system, as well as to estimate the impact of past and present land use on SOC concentration in a karst landscape, using electrical resistivity tomography as a non-destructive auxiliary approach.
Materials and methods
Description of study area
Silica Plateau is located within the Slovak Karst Biosphere Reserve in the Western Carpathians, Slovakia. Our experiment was conducted within the area extending between 48°33′51.22″ and 48°36′26.63″N and 20°29′33.81″ and 20°33′03.30″E. The plateau is composed of impermeable Lower Triassic sediments overlain by the Middle Triassic limestone-dolomite complex that contain ca 2% of insoluble remains, mainly illite, montmorillonite, feldspars, quartz, and mica (Šály 1978; Mello et al. 1996). Area’s mean altitude is approximately 600 m a. s. l. Silica Plateau falls to the warm, moderately humid region with cold winter (Lapin et al. 2002) with the mean annual air temperature 5.7–8.5°C and annual average precipitation 630–990 mm (400–595 mm during the vegetation period). Local soils are mostly represented by Rendzic Leptosols, Chromi-Rendzic Leptosols, and Chromic Cambisols (acc. to WRB; FAO 2006), the latter being bound to accumulation positions. Both Rendzic and Chromi-Rendzic Leptosols have \( {\text{pH}}_{{{\text{H}}_{2} {\text{O}}}} \cong 6.6 \) within 0–40 cm. In Chromic Cambisols, \( {\text{pH}}_{{{\text{H}}_{2} {\text{O}}}} \cong 6.2 \). The C/N ratio in soils ranges 9–12. Average cation exchange capacity in the humus-rich topsoil reaches ca 450–500 mval kg−1 and it decreases with depth. Concerned soil units fall into the clayey loam textural class. The dominant clay mineral phase in the clay fraction of the Silica soil is illitic material. Soils depth ranges from 20 to 40 cm on ridges to more than 1 m in accumulation positions (Kobza 1994; Šály 1994; Miko et al. 2003).
According to field survey, current forestland is covered by mixed stands of common hornbeam (Carpinus betulus L., 50%), sessile oak (Quercus petraea L., 30%), and European beech (Fagus sylvatica L., 20%) that fall into several alliances and sub-alliances, mainly Carici pilosae-Carpinenion betuli, Quercion pubescentis-petraea, and Cephalantero-Fagenion. Tree litter of the respective broadleaved mixture has a comparatively low C/N ratio of ca 44 due to the dominance of hornbeam tree litter (C/N ratio ≅ 34) (Bublinec 1994; Hättenschwiler and Gasser 2005). Occurrence of conifers (Picea abies K.; tree litter C:/N ratio ≅ 50) is very limited (1–2%) and confined to sink holes in the northern part of the plateau. The shrubland vegetation belongs to several alliances, mainly the xerophytic Prunion fruticosae, represented by Prunus spp., mainly Prunus fruticosa with tree litter C/N ratio ≅ 78 (Lorenz et al. 2004). Prunus spp. are accompanied by other shrubs, notably Rosa galica L., Crataegus monogyna L., and Berberis vulgaris L. Pastureland is covered by perennial grasses from the alliance Cynosurion cristati Tüxen 1947, for example, Festuca rupicola Heuff., Briza media L., Lolium perenne L., and a smaller portion of legumes (Trifolium repens L.). Avg. C/N ratio of the grassland vegetation litter (approx. 45) is an estimate adopted from Hegyhátsál (Hungary), botanically related and geographically close locality (Tomelleri 2007; Janišová et al. 2007). The pastureland provides sustenance for roaming herds of cattle and sheep. Their fresh feces and urine have C/N ratio about 23 and 1, respectively (Kirchmann 1985). Cropland has been used to produce cereal grains, mainly rye (Secale cereale L.) and common oat (Avena sativa L.), whose C/N ratio in the crop residues ranges 75–100 (Axmann et al. 1990), as well as alfalfa (Medicago sativa L.) with a much lower crop residues C/N ratio ≅ 13 (Troeh and Thompson 1993). Average annual addition of mineral N through fertilization has been ca 20–100 kg ha−1 year−1 since 1967 (Rozložník and Karasová 1994).
Land use history
The land cover mosaic has been changing during past centuries, as documented by map surveys carried out in 1780, 1850, and 1880, as well as modern-time aerial photography data (1950) and current CORINE Land Cover data (2010). The spatio-temporal changes reflect several turning points, starting with the Great Turkish War that played out mainly during the seventeenth century’s 2nd half. The war caused significant decline in the population density and land abandonment on the concerned territory (Wessely 1973). As a result, large tracts of land survived as forests or they were re-claimed by forests (Fig. 1a). By the eighteenth century’s 2nd half, new clearings appeared amidst continuous forests covering Silica Plateau owing to population recovery and the return of refugees to the former war zone. Larger clearings were turned into cropland and pastureland. During the 1st half of the nineteenth century, the woodland cover was further reduced and converted into pastureland. By and throughout the nineteenth century’s 2nd half, less profitable soil tillage in the more remote parts of Silica plateau gave way to the process of secondary succession and forest restoration, and large portion of cropland and forestland were converted to pastureland. As a result, the area of pastureland and shrubland had increased by 1950. Area-wise land cover developments are captured by Table 1. For the purpose of further analysis, we included strongly fragmented shrubland into forestland because of uncertainties inherent to historical map surveys and the tree species demography across the invasion front. This front can extend ca 200 m from forest boundary toward pastureland (Dovčiak et al. 2008).
Soil survey and sampling scheme
One hundred and fifty sampling points were obtained using random numbers generator (Mathematica 8.1; Wolfram Research, Inc., Champaign, IL) and projected on a rectangle area 3 km wide and 5 km long, designated within the Silica Plateau. At each point, soil depth and stoniness were surveyed by electrical resistivity (ER) tomography (ARES, GF system, Brno, Czech Republic) and subsequent imaging of soil/bedrock interface. ER (Ω-m) was acquired by an arrangement of 32 electrodes with a spacing of 0.8 m according to Rey et al. (2006). The processing and reconstruction of 2-D resitivity profiles was implemented in RES2DINV program (Geotomo Software, Gelugor, Malaysia). Coarse fragments content (hereinafter also referred to as stoniness), needed for the establishment of the corresponding calibration relationship with ER, was determined on six soil profiles, which were prepared by a specially designed sledge-hammer-driven spade. The profiles were photographed and the photographs were corrected for geometric distortion. Area occupied by rocks was determined by image analysis, that is, color-based segmentation using the minimum average pixel classification error (Kittler and Illingworth 1986) according to the routine in Mathematica Digital Image Processing 1.1 (Wolfram Research, Inc., Champaign, IL). Stoniness within concerned soil depth (0–60 cm) was determined as the sum of: (1) the relative volume of stones (20–200 mm) and boulders (>200 mm), which is proportional to their relative area on the profile wall in soil pits (Folk 1951; Alexander 1982), previously established by the image analysis; (2) the volume of gravel (2–20 mm). It was measured in undisturbed soil samples (200 cm3), also collected for the determination of fine earth bulk density. They were taken from fifteen profiles representing all land covers (cropland, pastureland, and forestland) at 6 depths (10, 20, …, 60 cm). Mineral soil samples for SOC determination were taken from profiles exposed by pick, spade and shovel on all 150 points. Samples were carved out from six layers (0–10, 10–20, …, 50–60 cm) by means of knife with triple replication along vertical lines, 20 cm apart. Samples weighing ca 500 g were collected in plastic bags. A total of 2,700 samples were collected.
Soil analyses
Soil samples were air-dried, ground, and passed through a 2-mm mesh sieve. Visible plant residues, gravel, and stones were removed manually with a pair of tweezers, while the small root fragments were removed by electrostatically charged stick (Kuzyakov et al. 2001). The C and N contents in the fine earth (<2 mm) were determined by Vario MACRO Elemental Analyzer (CNS version, Elementar GmbH, Hanau, Germany), which employs the dry combustion (DC) method. Because elemental analyzer provides total carbon contents, inorganic C content was measured separately for each sample by a volumetric device (Fiala et al. 1999) and subtracted from the total carbon in order to obtain SOC mass concentration [M M−1]. The commensurability of our SOC concentration analysis with a different method under site-specific conditions was assessed by comparing our preliminary forestland SOC concentration values, determined by DC method (SOCCDC, n 1 = 12), with the full set (n 2 = 12) of forestland SOC concentrations (SOCCWO), previously obtained in the area of interest and available in Šály (1994). SOCCWO were determined by a wet oxidation (WO) titrimetrical method according to Tyurin (1931; also see Kononova 1966). To assess the difference between the two sample means (avg. SOCCDC = 0.40, SD: 0.02; avg. SOCCWO = 0.36, SD: 0.02), the t test (Sokal and Rohlf 1995) was applied to both data sets with and without the application of general conversion coefficient between DC and WO methods compiled by Jankauskas et al. (2006). Based on the test results, alternative hypothesis about significant difference between sample means was rejected (P = 0.83–0.57).
Because we knew bulk density and volume of the soil (i.e., fine earth plus soil pores, without coarse fragments with diameter > 2 mm), SOC stock was computed by summing up the C content in all six 10 cm layers at each sampling point according to
where SOCS, BD i , SOCC i , d i , and cf i , are, respectively, SOC stock [M L−2], soil bulk density [M L−3], SOC concentration [M M−1] in layer i, ith layer thickness [L], volumetric fraction of coarse fragments in layer i [L3 L−3]. Similar relationships were used by Rodríguez-Murillo (2001), Stevens and van Wesemael (2008) and others.
Data evaluation
Differences among average soil bulk densities according to land cover were assessed by ANOVA, including Tukey-HSD post hoc comparison test. The analysis of covariance (ANCOVA) (Sokal and Rohlf 1995) was used to evaluate the effect of historical and current land covers on SOC concentration, in that land cover and stoniness entered the analysis as categorical (predictor) and continuous (confounding) variables, respectively. Average SOC stock (Mg ha−1) was calculated for the whole area of interest based on all sampling points and whole soil profiles (0–60 cm). All analyses were performed within Statistica 9 (StaSoft, Inc., Tulsa, USA). Furthermore, we used the method of chronosequences by calculating the rates of SOC stock depletion or recovery following two land use changes (LUC) (1) from forestland to cropland and (2) from cropland to pastureland for points featuring similar soil depths and stoniness. Because two military surveys (1850 and 1880) were separated by just 30 years, we omitted the 1850 map and data, as capturing transition rather than at least temporary steady state in further analyses.
Results and discussion
Soil depth, stoniness, and bulk density
Soils depth and stoniness were instrumental to our study. Both variables were surveyed using the relationship between ER and stoniness. The relationship was fitted by a decadic logarithm function (Fig. 2) with corresponding root-mean-square error. Our calibration corresponds well to data provided by Marescot (2006), who gave ER about 1,000 Ω-m and above for limestone materials. Examples of soil profiles featuring near-zero and high skeleton contents are given in Fig. 3.
Leaning on the calibration, our ER tomography survey revealed coarse fragments content across the entire area (Fig. 4). Such an irregular distribution is typical of karstic surfaces that include both erosive and accumulation positions such as rocky slopes and ridges, grike fields, dolines, sinkholes, and other characteristic features. The comparison between Figs. 1a–e and 4 illustrates a correspondence between extensively (forestland and pastureland) or intensively (cropland) managed land covers on one hand, and stony or finely grained soil patches on the other hand. Such overlap patterns are common to land use and forest cover histories in Europe (Pichler et al. 2011). Obviously, the non-destructive survey provided a sound and less labor and time-consuming alternative to quantitative soil pits method, which could not be applied due to the large volume of stones and boulders.
Soil bulk density for distinct land covers is given in Table 2. The bulk density increases with soil depth and from forestland to cropland due to higher SOC concentration in the topsoil and in forest soils. Also, coarse fragments below the soil surface, abundantly present in forestland and, to a lesser degree, in pastureland, support the existing soil structure and reduce soil compactibility (Poesen and Lavee 1994).
SOC stock and variability
Our SOC stock calculation was based on a calibrated stoniness–ER relationship. The stock within the 15 km2 area of interest averaged 207.4, 136.8, and 70.7 Mg ha−1 in 0–60, 0–30, and 30–60 cm soil layers, respectively. This high amount of organic carbon (e.g., 103.3 Mg ha−1 within 0–20 cm layer) fell slightly above the 75% CI for the mean SOC stock calculated for Rendzic Leptosols (also within 0–20 cm), but well below the maximum value 126.3 Mg ha−1 (Baritz et al. 2010). This is probably due to the role of Ca2+ in the cation bridging of organic colloids, condensation and stabilization of organic matter (Oades 1988), formation of thin carbonate coatings on particulate organic matter (Duchaufour 1976), and SOM physical protection from decomposition through cementation of soil aggregates by CaCO3 (Oyonarte et al. 1994). Average SOC concentration in Silica soils was 0.039 g g−1 (range: 0.015–0.077 g g−1), 0.049 g g−1 (range: 0.019–0.105 g g−1), and 0.027 g g−1 (range: 0.006–0.070 g g−1) for 0–60, 0–30, and 30–60 cm, respectively. These are comparatively high values, but lower than 0.050–0.150 g g−1 as found in tropical semiarid calcareous soils of northwestern Yucatán, Mexico (Shang and Tiessen 2003). However, the latter work provides certain analogy to our results, in that higher SOC concentrations were found in shallow black lithosols surrounding rock outcrops, while lower SOC concentration was usually established in deeper red rendzinas at slightly lower relief. Also, despite increasing soil respiration rates, greater biological activity in limed soils leads to plant C inputs being processed and incorporated into resistant soil organo-mineral pools (Fornara et al. 2011). However, the variation of SOC stock within the relatively small study area was considerable with a SD of 85.7 Mg ha−1. This formidable variability, resulting from highly variable SOC concentration, rock fragments content, bulk density, and land cover could explain the rareness of SOC stock estimates from karstic soils.
SOC concentration in the fine earth according to land cover
To assess SOC dependence on land cover, we preferred to analyze SOC concentration instead of SOC stock, because calculation of the latter variable involves strongly fluctuating stoniness and, to a lesser degree, soil bulk density. Intrinsic connection between SOC concentration and stoniness is implicitly assumed by various authors, but it was directly suggested only by few, for example, Schaetzl (1991) and Tate et al. (2005). In addition, stoniness and land use were linked through the process of land allocation for specific uses. In fact, dispersion of SOC concentration in cropland was limited because soil tillage was confined to the least stony soils. This is obvious from Fig. 5, which reproduces the location and distribution of SOC concentration according to land cover. Existing collinearity among SOC concentration, land cover, and stoniness (Figs. 5, 6) was controlled for and handled by ANCOVA, in which land cover, stoniness, and SOC concentration represented categorical variable (fixed factor), continuous (confounding) variable, and dependent variable, respectively. The results of ANCOVA, as performed for land cover mosaics representative of four different periods of time, are given in Table 3.
The analysis of covariance suggests that SOC concentration imprint of current (2010) land cover is significant in that SOC concentration in cropland (0.026 g g−1) is lower compared to forestland (0.040 g g−1) and pastureland (0.041 g g−1) (P < 0.01 according to ANCOVA, including the Tukey-HSD post hoc test). Šamonil (2007) reported similar SOC concentrations (ca 0.04 g g−1) in Rendzic Leptosols under forest fragments covering parts of the Bohemian Karst. In our study, the effect of the most recent land cover was also detected in the subsoil (30–60 cm) (P < 0.05). Although similar effect of the previously recorded land cover (1950) probably still persists (P < 0.13), the probability fell sharply for older periods of time (P < 0.24, 0.47) owing mainly to more frequent land use swaps between cropland on the one hand and forestland or pastureland on the other hand. Thus, expectedly, the supposed effects of land use on SOC concentrations, for example, due to soil tillage in the NW part of the area of interest back in 1780 (Fig. 1a), have become intractable due to SOC recovery following secondary forest succession or grazing. Because SOC concentrations under forestland and pastureland have been almost identical in the Silica soil, our investigation confirms that the general assumption about the capacity of both forestland and pastureland to retain more SOC compared with cropped land use (e.g. Martens et al. 2003) is also valid for karstic soils. Stark contrast between cropland and the two remaining land covers also shows in the vertical distribution of SOC concentration (Fig. 7), which was satisfactorily fitted by an exponential function, usually applied in similar studies (e.g. Bernoux et al. 1998).
Soil organic carbon stock depletion, recovery, and reallocation
To achieve a more reliable and conservative comparison between SOC stocks under certain land cover histories, we only considered SOC stocks within 0–60 cm for points with stoniness → 0. Respective SOC stocks under these constraints are given in Table 4.
The data provide an opportunity to assess the rate of SOC stock depletion or recovery due to forestland → cropland and cropland → pastureland LUCs, respectively, during the last 130 years. Since the LUC (1880), the respective Silica cropland soil has lost ca 25% of its initial SOC stock, which is less than an average of 32% after only 23 years, based on several studies evaluated by Poeplau et al. (2011). This was probably owing to the high initial SOC stock, and its effective clay and silt protection in the Silica soil, but also because available studies were mostly concerned only with to the topsoil (approx. 0–30 cm), where the relative loss was probably more pronounced and faster. Although statistical significance could not be established due to small number of observations, we can use exponential decay model (Olson 1963) to assess the rate of SOC stock depletion between land use histories 1 and 2 (Table 4):
In (2–4), SOCS t represents SOC stock at a time t counted from forestland → cropland LUC in 1880, λ is the exponential rate of decay, and SOCS0 is the initial SOC stock (land use history No. 1 acc. to Table 4). From Table 4 and (4), we obtain λ = 0.002 year−1, which is at the bottom of the range compiled by Tiessen et al. (1982). The reasons for tillage-induced SOC depletion include reduced litter inputs, increased soil aeration, and the loss of silt and clay protected C (Six et al. 2002). Also, the input of nutrients from crop residues and fertilization affected the soil biogeochemical cycle. Average C/N ratio in cropland soil (10) was significantly lower (P < 0.05) than in forestland and pastureland soils (12). Although the inputs of the organic C and N strongly contributed to this difference, the particular role of N in SOC dynamics depends on N input rate, initial SOC content, and lignin input to soils. Under low to moderate N input, for example, 40–100 kg N ha−1 year−1, SOC concentration slightly increased or remained constant during several years of fertilization (e.g. Nyborg et al. 1995; Dijkstra et al. 2004; Šimon 2008). As opposed to that, fertilization rates beyond crop N requirements promotes SOC decline (Khan et al. 2007). Given relatively low to moderate amounts of mineral N added to the Silica Plateau cropland soils (20–100 kg ha−1 year−1), we speculate that fertilization did not play dominant role in their SOC dynamics.
Table 4 also demonstrates SOC stock recovery after LUC from cropland to pastureland. The observed, moderate rise in SOC stock was probably sustained and affected by multiple factors. First, above- and below-ground litter, as well livestock feces may provide sufficient amount of C to maintain SOC stock in pastureland on levels similar to forestland (Takahashi et al. 2007). Besides, grazing normally leads to greater root allocation of C in the perennial plants (e.g. Briske et al. 1996; Stewart and Metherell 1999). Finally, SOC accumulation in pastureland may be supported by comparatively high resistance of humic acids from permanent meadows soils to microbial degradation reported by Filip and Tesařová (2005). On the other hand, SOC stock rise in pastureland was slow: it increased by only ca 30% during 130 years. It means that the corresponding rate of recovery was only about one-fourth of the average rate reported by Poeplau et al. (2011). Although SOC stock in pastureland has eventually reached forestland levels, it is also possible that its slower-than-expected rise and the low rate of SOC depletion in cropland have been mutually related through erosive losses and subsequent accumulation. Erosion was reported to play important role in local SOC depletion (e.g.Voroney et al. 1981; Kimble et al. 2001; Schwanghart and Jarmer 2011). In our case, a portion of the C-rich topsoil material from grazed patches in the ridge and slope positions was likely transported to terrain depressions, mainly sinkholes and dolines. Thus, erosive losses and accumulation within the Silica Plateau affect not only soil depth (Miko et al. 2003), but most likely also contribute to the observed spatio-temporal variability of SOC stock.
Conclusions
The application of electrical resistivity tomography, leaning on the electrical resistivity—stoniness calibration, allowed us to acquire a detailed overview of the coarse fragments distribution over a 15 km2 area located on the top of the Silica Plateau in the Slovak Karst Biosphere Reserve. Combined with SOC concentration data obtained from 150 sampling points, it was possible to assess landscape-level SOC stock contained in the mosaic of local Rendzic Leptosols, Chromi-Rendzic Leptosols, and Chromic Cambisols. Our estimates confirm that calcareous soils have the capacity to maintain high SOC stocks even under centuries-long agroforestry management that has resulted in a temporally very dynamic mixture of forestland, pastureland, and cropland. When averaged over the entire area, SOC stock reached ca 200 Mg ha−1 within 0–60 cm layer, but its spatial variability was at the same time also exceptionally high with 43% coefficient of variation. Therefore, it would have hardly been possible to achieve the study goals by the quantitative pits method or similar. Despite the variability of stoniness, ANCOVA revealed the effect of land use on the SOC concentration. While forestland and pastureland featured practically identical SOC concentrations of about 0.040 g g−1, the concentration in cropland was 0.026 g g−1. The chronosequence analysis indicates that the crop production has been reducing SOC stock at a comparatively low rate of ca 0.002 year−1 and that the grazing regime has restored SOC stock back to the forestland level. It appears that favorable SOC retention properties of the calcareous soils provide a broad maneuvering space for land managers in order to use temperate zone agroforestry approaches for offsetting SOC depletion or even achieving SOC accumulation.
References
Alexander EB (1982) Volume estimates of coarse fragments in soils: a combination of visual and weighing procedures. J Soil Water Conserv 37:62–63
Axmann H, Sebastianelli A, Arrillaga JL (1990) Sample preparation techniques of biological material for isotope analysis. In: Hardarson G (ed) Use of nuclear techniques in studies of soil–plant relationships. IAEA-TCS-2, IAEA, Vienna, pp 41–53
Baker JM, Ochsner TE, Venterea RT, Griffis TJ (2007) Tillage and soil carbon sequestration—what do we really know? Agric Ecosyst Environ 118:1–5. doi:10.1016/j.agee.2006.05.014
Baritz R, Seufert G, Montanarella L, Van Ranst E (2010) Carbon concentrations and stocks in forest soils of Europe. For Ecol Manag 260:262–277. doi:10.1016/j.foreco.2010.03.025
Bauer GA, Gebauer G, Harrison AF, Högberg P, Högbom L, Schinkel H, Taylor AFS, Novak M, Buzek F, Harkness T, Persson T, Schulze E-D (2000) Biotic and abiotic controls over ecosystem cycling of stable natural nitrogen, carbon and sulphur isotopes. In: Schulze ED (ed) Carbon and nitrogen cycling in european forest ecosystems. Ecol Stud 142, Springer, Dordrecht, pp 189–214
Bergstrom DW, Monreal CM, St Jacques E (2001a) Spatial dependence of soil organic carbon mass and its relationship to soil series and topography. Can J Soil Sci 81:53–62
Bergstrom DW, Monreal CM, St Jacques E (2001b) Influence of tillage practice on carbon sequestration is scale-dependent. Can J Soil Sci 81:63–70
Bernoux M, Arrouays D, Cern CC, Bourennane H (1998) Modeling vertical distribution of carbon in oxisols of the western Brazilian Amazon (Rondonia). Soil Sci 163:941–951
Bouwman AF, Leemans R (1995) The role of forest soils in the global carbon cycle. In: McFee WW, Kelly JM (eds) Carbon forms and functions in forest soils. SSSA, Madison, WI, pp 503–526
Briske DD, Boutton TW, Wang Z (1996) Contribution of flexible allocation priorities to herbivory tolerance in C4 perennial grasses: an evaluation with 13C labeling. Oecologia 105:151–159. doi:10.1007/BF00328540
Bublinec E (1994) Koncentrácia, akumulácia a kolobeh prvkov v bukovom a smrekovom ekosystéme. [Concetration, accumulation and cycling of elements in beech and spruce ecosystems]. Acta dendrobiologica, VEDA, Bratislava (In Slovak with English abstract)
Corstanje R, Schulin R, Lark RM (2007) Scale-dependent relationships between soil organic carbon and urease activity. Eur J Soil Sci 58:1087–1095. doi:10.1111/j.1365-2389.2007.00902.x
Davidson EA, Janssens IA (2006) Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature 440:165–173. doi:10.1038/nature04514
Dijkstra FA, Hobbie SE, Knops JMH, Reich PB (2004) Nitrogen deposition and plant species interact to influence soil carbon stabilization. Ecol Lett 7:1192–1198. doi:10.1111/j.1461-0248.2004.00679.x
Dovčiak M, Hrivnák R, Ujházy K, Gömöry D (2008) Seed rain and environmental controls on invasion of Picea abies into grassland. Plant Ecol 194:135–148. doi:10.1007/s11258-007-9280-2
Duchaufour P (1976) Dynamics of organic matter in soils of temperate regions: its action on pedogenesis. Geoderma 15:31–40. doi:10.1016/0016-7061(76)90068-9
Eglin T, Walter C, Nys C, Follain S, Forgeard F, Legout A, Squividant H (2008) Influence of waterlogging on carbon stock variability at hillslope scale in a beech forest (Fougères forest—West France). Ann For Sci 65:202
FAO (2006) World reference base for soil resources. World soil resources reports, 103. Food and Agriculture Organization of the United Nations, Rome
Fiala K, Kobza J, Matušková L, Brečková V, Makovníková J, Barančíková G, Búrik V, Litavec T, Houšková B, Chromaničová A, Varádiová D, Pechová B (1999) Záväzné metódy rozborov pôd. Čiastkový monitorovací systém—pôda [Obligatory methods of soil analysis. Partial monitoring system—soil]. Soil Science and Conservation Research Institute, Bratislava, Slovakia (in Slovak). ISBN 80-85361-55-8
Filip Z, Tesařová M (2005) Microbial processing of humic substances from meadow and forest soils. In: Binkley D, Menyailo O (eds) Tree species effects on soils: implications for global change. Springer, Dordrecht, pp 193–212
Folk RL (1951) A comparison chart for visual percentage estimation. J Sediment Petrol 21:32–33. doi:10.1306/D4269413-2B26-11D7-8648000102C1865D
Fornara DA, Steinbeiss S, McNamara N, Gleixner G, Oakley S, Poulton PR, MacDonald AJ, Bardgett RD (2011) Increases in soil organic carbon sequestration can reduce the global warming potential of long-term liming to permanent grassland. Glob Chang Biol 17:1925–1934. doi:10.1111/j.1365-2486.2010.02328.x
Franco D, Mannino I, Zanetto G (2001) The role of agroforestry networks in landscape socioeconomic processes: the potential and limits of the contingent valuation method. Landsc Urban Plan 55:239–256. doi:10.1016/S0169-2046(01)00158-X
Franke R, Nielson G (1980) Smooth interpolation of large sets of scattered data. Int J Numer Methods Eng 15:1691–1704. doi:10.1002/nme.1620151110
Harrison AF, Harkness DD, Rowland AP, Garnett JS, Bacon PJ (2000) Annual carbon and nitrogen fluxes in soils along the European forest transect determined using 14C-bomb. In: Schulze ED (ed) Carbon and nitrogen cycling in European forest ecosystems. Ecol Stud 142, Springer, Dordrecht, pp 237–256
Hättenschwiler S, Gasser P (2005) Soil animals alter plant litter diversity effects on decomposition. Proc Natl Acad Sci USA 102:1519–1524. doi:10.1073/pnas.0404977102
Janišová M, Michálková D, Škodová I, Uhliarová E, Zaliberová M (2007) Cynosurion cristati Tüxen 1947. In: Janišová M, Hájková P, Hegedüšová K, Hrivnák R, Kliment J, Michálková D, Ružičková H, Řezníčková M, Tichý L, Škodová I, Uhliarová E, Ujházy K, Zaliberová M (eds) Travinnobylinná vegetácia Slovenska—elektronický expertný systém na identifikáciu syntaxónov. (Grassland vegetation of Slovakia—electronic expert system for syntaxa identification). Botanický ústav SAV, Bratislava, pp 110–118
Jankauskas B, Slepetiene A, Jankauskiene G, Fullen MA, Booth CA (2006) A comparative study of analytical methodologies to determine the soil organic mater content of Lithuanian Eutric Albeluvisols. Geoderma 136:763–773
Jenkinson DS, Rayner JH (1977) The turnover of soil organic matter in some of the Rothamsted classical experiments. Soil Sci 123:298–305
Jobbágy EG, Jackson RB (2000) The vertical distribution of soil organic carbon and its relation to climate and vegetation. Ecol Appl 10:423–436. doi:10.1890/1051-0761(2000)010
Johnson DW, Curtis PS (2001) Effects of forest management on soil C and N storage: meta analysis. For Ecol Manag 140:227–238. doi:10.1016/S0378-1127(00)00282-6
Khan SA, Mulvaney RL, Ellsworth TR, Boast CW (2007) The myth of nitrogen fertilization for soil carbon sequestration. J Environ Qual 36:1821–1832. doi:10.2134/jeq2007.0099
Kimble JM, Lal R, Mausbach M (2001) Erosion effects on soil organic carbon pool in soils of Iowa. In: Stott DE, Mohtar RH, Steinhardt GC (eds) Sustaining the global farm. Proceedings of 10th ISCO Conference 1999, pp 472–475
Kirchmann H (1985) Losses, plant uptake and utilisation of manure nitrogen during a production cycle. Acta Agric Scand 24
Kittler J, Illingworth J (1986) Minimum error thresholding. Pattern Recogn 19:41–47. doi:10.1016/0031-3203(86)90030-0
Kobza J (1994) Agricultural soils. In: Rozložník M, Karasová E (eds) Chránená krajinná oblasť—Biosférická rezervácia Slovenský kras [Protected landscape area—biosphere reserve Slovak Karst]. Osveta, Martin, pp 70–76 (in Slovak)
Kononova MM (1966) Soil organic matter, 2nd edn. Pergammon Press, Inc., Oxford
Kuzyakov Y, Biriukova O, Turyabahika F, Stahr K (2001) Electrostatic method to separate roots from soil. J Plant Nutr Soil Sci 164:541–545. doi:10.1002/1522-2624(200110)164:5
Lal R (2004) Soil carbon sequestration to mitigate climate change. Geoderma 123:1–22. doi:10.1016/j.geoderma.2004.01.032
Lal R (2011) Sequestering carbon in soils of agro-ecosystems. Food Policy 36:33–39. doi:10.1016/j.foodpol.2010.12.001
Lapin M, Faško P, Melo M, Šťastný M, Tomlain J (2002) Climatic regions. In: Miklós L, Maráky R, Klinda J (eds) Landscape atlas of the Slovak Republic. Ministry of Environment of the Slovak Republic Bratislava, Slovakia
Lorenz K, Preston CM, Krumrei S, Feger KH (2004) Decomposition of needle/leaf litter from Scots pine, black cherry, common oak and European beech at a conurbation forest site. Eur J For Res 123:177–188. doi:10.1007/s10342-004-0025-7
Luo Y, Zhou X (2006) Soil respiration and the environment. Academic Press/Elsevier, London/San Diego
Marescot L (2006) Introduction à l’imagerie électrique du sous-sol. Bull Vaudois Des Sci Nat 90:23–40
Martens DA, Reddy TE, Lewis DT (2003) Soil organic carbon content and composition of 130-year crop, pasture, and forest land-use managements. Glob Chang Biol 10:65–78. doi:10.1046/j.1529-8817.2003.00722.x
Mello J, Elečko M, Pristaš J, Reichwalder P, Snopko L, Vass D, Vozárová A (1996) Geologická mapa Slovenského krasu [Geological map of the Slovak Karst]. Geological Service of the Slovak Republic, Bratislava
Miko S, Durn G, Adamcová R, Covic M, Dubiková M, Skalsky R, Kapelj S, Ottner F (2003) Heavy metal distribution in karst soils from Croatia and Slovakia. Environ Geol 45:262–272. doi:10.1007/s00254-003-0878-y
Montagnini F, Nair PK (2004) Carbon sequestration: an under-exploited environmental benefit of agroforestry systems. Agrofor Syst 61:281–295. doi:10.1023/B:AGFO.0000029005.92691.79
Mosquera-Losada MR, McAdam JH, Romero-Franco R, Santiago-Freijanes JJ, Rigueiro-Rodríguez A (2009) Definitions and components of agroforestry practices in Europe. In: Rigueiro-Rodríguez A, McAdam J, Mosquera-Losada MR (eds) Agroforestry in Europe. Current status and future prospects. Springer, Dordrecht, pp 3–19
Nyborg M, Solberg ED, Malhi SS, Izaurralde RC (1995) Fertilizer N, crop residue, and tillage alter soil C and N content in a decade. In: Lal R, Kimble J, Levine E, Stewart BA (eds) Soil management and greenhouse effect. Lewis Publishers/CRC Press, Boca Raton, FL, pp 93–99
Oades JM (1988) The retention of organic matter in soils. Biogeochemistry 5:35–70. doi:10.1007/BF02180317
Olson JS (1963) Energy storage and the balance of producers and decomposers in ecological systems. Ecology 44:322–331. doi:10.2307/1932179
Oyonarte C, Pérez-Pujalte A, Delgado G, Delgado R, Almendros G (1994) Factors affecting soil organic matter turnover in a Mediterranean ecosystem from Sierra de Gador (Spain): an analytical approach. Commun Soil Sci Plant Anal 25:1929–1945. doi:10.1080/00103629409369164
Parton WJ, Schimel DS, Cole CV, Ojima DS (1987) Analysis of factors controlling soil organic mater levels in Great Plain Grasslands. Soil Sci Soc Am J 51:1173–1179. doi:10.2136/sssaj1987.03615995005100050015x
Pichler V, Godinho-Ferreira P, Zlatanov T, Pichlerová M, Gregor J (2011) Changes in Forest Cover and its Diversity. In: Bredmeier M, Cohen S, Godbold D, Lode E, Pichler V, Schleppi P (eds) Forest Management and the Water Cycle. Ecol Stud 212, Springer, Dordrecht, Heidelberg, London, New York, pp 209–224
Poeplau Ch, Don A, Vesterdal L, Leifeld J, Van Wesemael B, Schumacher J, Gensior S (2011) Temporal dynamics of soil organic carbon after land-use change in the temperate zone—carbon response functions as a model approach. Glob Chang Biol 17:2415–2427. doi:10.1111/j.1365-2486.2011.02408.x
Poesen J, Lavee H (1994) Rock fragments in top soils: significance and processes. Catena 23:1–28
Post WM, Kwon KC (2000) Soil carbon sequestration and land-use change: processes and potential. Glob Chang Biol 6:317–327. doi:10.1046/j.1365-2486.2000.00308.x
Potter CS, Klooster SA (1997) Global model estimates of carbon and nitrogen storage in litter and soil pools—response to changes in vegetation quality and biomass allocation. Tellus B 49:1–17. doi:10.1034/j.1600-0889.49.issue1.1.x
Rey E, Jongmans D, Gotteland P, Garambois S (2006) Characterisation of soils with stony inclusions using geoelectrical measurements. J Appl Geophys 58:188–201. doi:10.1016/j.jappgeo.2005.06.003
Rivera LW, Zimmerman JK, Aide TM (2000) Forest recovery in abandoned agricultural land in a karst region of the Dominican Republic. Plant Ecol 148:115–125. doi:10.1023/A:1009825211430
Rodríguez-Murillo JC (2001) Organic carbon content under different types of land use and soil in peninsular Spain. Biol Fertil Soils 33:53–61. doi:10.1007/s003740000289
Rozložník M, Karasová E (eds) (1994) Chránená krajinná oblasť—Biosférická rezervácia Slovenský kras [Protected landscape area—biosphere reserve Slovak Karst]. Osveta, Martin (in Slovak)
Šály R (1978) Pôda, základ lesnej produkcie [Soil as a basis of forest production]. Príroda, Bratislava (in Slovak)
Šály R (1994) Forest soils. In: Rozložník M, Karasová E (eds) Chránená krajinná oblasť—Biosférická rezervácia Slovenský kras [Protected landscape area—biosphere reserve Slovak Karst]. Osveta, Martin, pp 55–70 (in Slovak)
Šamonil P (2007) Uniqueness of limestone soil-forming substrate in the forest ecosystems classification. J For Sci 53:149–161
Santore RC, Driscoll CT, Aloi M (1995) A model of soil organic matter and its function in temperate forest soil development. In: McFee WW, Kelly JM (eds) Carbon forms and functions in forest soils. Soil Science Society of America, Madison, WI, pp 275–298
Schaetzl RJ (1991) Factors affecting the formation of dark, thick epipedons beneath forest vegetation, Michigan, USA. J Soil Sci 42:501–512. doi:10.1111/j.1365-2389.1991.tb00426.x
Schimel DS (1995) Terrestrial ecosystems and the carbon cycle. Glob Change Biol 1:77–91. doi:10.1111/j.1365-2486.1995.tb00008.x
Schlesinger WH (1997) Biogeochemistry, an analysis of global change. Academic Press, San Diego, CA
Schwanghart W, Jarmer T (2011) Linking spatial patterns of soil organic carbon to topography—a case study from south-eastern Spain. Geomorphology 126:252–263. doi:10.1016/j.geomorph.2010.11.008
Shang C, Tiessen H (2003) Soil organic C sequestration and stabilization in karstic soils of Yucatan. Biogeochemistry 62:177–196. doi:10.1023/A:1021123728639
Šimon T (2008) The influence of long-term organic and mineral fertilization on soil organic matter. Soil Water Res 3:41–51
Six J, Conant RT, Paul EA, Paustian K (2002) Stabilization mechanisms of soil organic matter: implications for C-saturation of soils. Plant Soil 241:155–176. doi:10.1023/A:1016125726789
Sokal RR, Rohlf FJ (1995) Biometry, 3rd edn. Freeman, New York
Sollins P, Homann P, Caldwell BA (1996) Stabilization and destabilization of soil organic matter: mechanisms and controls. Geoderma 74:65–105. doi:10.1016/S0016-7061(96)00036-5
Stevens A, van Wesemael B (2008) Soil organic carbon dynamics at regional scale as influenced by land use history: a case study in forest soils from southern Belgium. Soil Use Manag 24:69–79. doi:10.1111/j.1475-2743.2007.00135.x
Stevenson FJ (1994) Humus chemistry; genesis, composition, reaction, 2nd edn. John Wiley and Sons, New York
Stewart DPC, Metherell AK (1999) Carbon (13C) uptake and allocation in pasture plants following field pulse-labelling. Plant Soil 210:61–73. doi:10.1023/A:1004668910787
Stoeckel DM, Miller-Goodman MS (2001) Seasonal nutrient dynamics of forested floodplain soil influenced by microtopography and depth. Soil Sci Soc Am J 65:922–931. doi:10.2136/sssaj2001.653922x
Takahashi S, Nakagami K, Sakanoue S, Itano S, Kirita H (2007) Soil organic carbon storage in grazing pasture converted from forest on Andosol soil. Grassl Sci 53:210–216. doi:10.1111/j.1744-697X.2007.00095.x
Tate KR, Wilde RH, Giltrap DJ, Baisden WT, Saggar S, Trustrum NA, Scott NA, Barton JR (2005) Soil organic carbon stocks and flows in New Zealand: system development, measurement and modelling. Can J Soil Sci 85:481–489. doi:10.4141/S04-082
Tiessen H, Stewart JWB, Bettany JR (1982) Cultivation effects on the amounts and concentration of carbon, nitrogen and phosphorus in grassland soils. Agron J 64:831–835
Tomelleri E (2007) Modeling the Carbon Cycle and its Interactions with Management Practices in Grasslands. PhD Thesis, Universita degli Studi di Padova, Padova
Troeh FR, Thompson LM (1993) Soils and soil fertility, 5th edn. Oxford University Press, New York
Trumbore S (2000) Age of soil organic matter and soil respiration: radiocarbon constraints on belowground C dynamics. Ecol Appl 10:399–411. doi:10.1890/1051-0761(2000)010[0399:AOSOMA]2.0.CO;2
Turrión MB, Schneider K, Gallardo JF (2009) Carbon accumulation in Umbrisols under Quercus pyrenaica forests: effects of bedrock and annual precipitation. Catena 79:1–8. doi:10.1016/j.catena.2009.04.004
Tyurin IV (1931) A new modification of the volumetric method of determining soil organic matter by means of chromic acid. Pochvovedenie 26:36–47
Valentini R (2003) EUROFLUX: An integrated network for studying the long-term responses of biospheric exchanges of carbon, water, and energy of European forests. In: Valentini R (ed) Fluxes of carbon, water and energy of European forests. Ecol Stud 163, Springer, Dordrecht, Heidelberg, London, New York, pp 1–8
Vidrih M, Vidrih T, Kotar M (2009) In Slovenia: management of intensive land use systems. In: Riguero-Rodríguez A, McAdam J, Mosquera-Losada MR (eds) Agroforestry in Europe: current status and future prospects. Advances in Agroforestry 6, Springer, Dordrecht, Heidelberg, London, New York, pp 397–414
Voroney RP, van Veen JA, Paul EA (1981) Organic C dynamics in grassland soils. 2. Model validation and simulation of the long-term effects of cultivation and rainfall erosion. Can J Soil Sci 61:211–224. doi:10.4141/cjss81-026
Wang L, Lee D, Zuo P, Zhou Y, Xu Y (2004) Karst environment and eco-poverty in southwestern China: a case study of Guizhou Province. Chin Geogr Sci 14:21–27. doi:10.1007/s11769-004-0004-4
Wessely K (1973) The development of the Hungarian military frontier until the middle of the eighteenth century. Austrian Hist Yearb 9:55–110. doi:10.1017/S0067237800019007
Wirth C, Schulze ED, Schwalbe G, Tomczyk S, Weber GE, Weller E (2004) Dynamik der Kohlenstoffvorräte in den Wäldern Thüringens. Thür. Landesanstalt für Wald, Jagd und Fischerei in Zusammenarbeit mit dem Max-Planck-Institut für Biogeochemie, Gotha, Jena
Zaccone C, Casiello G, Longobardi F, Bragazza L, Sacco A, Miano TM (2011) Evaluating the ‘conservative’ behaviour of stable isotopic ratios (δ13C, δ15N, and δ18O) in humic acids and their reliability as paleoenvironmental proxies along a peat sequence. Chem Geol 285:124–132. doi:10.1016/j.chemgeo.2011.03.018
Acknowledgments
This contribution is the result of the project implementation: Extension of the Centre of Excellence ”Adaptive Forest Ecosystems,” ITMS: 262201200149, supported by the Research & Development Operational Programme funded by the ERDF (80%) and the Scientific Grants Agency of the Ministry of Education and the Slovak Academy of Sciences no. 1/0252/11 (20%). Authors thankfully appreciate the assistance of Messrs. Pavol Gregor, MSc., Peter Gregor, and Miroslav Úradník, PhD., during the indicator experiment and SOC determination, as well as kind co-operation of the Slovak Karst National Park − Biosphere Reserve administration. We also thank to two anonymous reviewers for their valuable comments and suggestions that helped us substantially improve our manuscript.
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Communicated by A. Merino.
This article originates from the international symposium “Managed Forests in Future Landscapes. Implications for Water and Carbon Cycles (COST action FP 0601 FORMAN)”.
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Ahmed, Y.AR., Pichler, V., Homolák, M. et al. High organic carbon stock in a karstic soil of the Middle-European Forest Province persists after centuries-long agroforestry management. Eur J Forest Res 131, 1669–1680 (2012). https://doi.org/10.1007/s10342-012-0608-7
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DOI: https://doi.org/10.1007/s10342-012-0608-7