Horizons Of Forest Soils Research Articles

Soil base saturation affects root growth of European beech seedlings§

AbstractTo assess the potential effects of Al toxicity on the roots of young European beech (Fagus sylvatica L.), seeds were sown in soil monoliths taken from the Ah and B horizons of forest soils with very low base saturation (BS) and placed in the greenhouse. The Ah horizons offered a larger supply of exchangeable cation nutrients than the B horizons. After 8 weeks of growth under optimal moisture conditions, the seedlings were further grown for 14 d under drought conditions. Root‐growth dynamics were observed in rhizoboxes containing soils from the Ah and B horizons. The concentrations of Al3+, base cations, and nitrate in the soil solution and element concentrations in the root tissue were compared with above‐ and belowground growth parameters and root physiological parameters. There was no strong evidence that seedling roots suffered from high soil‐solution Al3+ concentrations. Within the tested range of BS (1.2%–6.5%) our results indicated that root physiological parameters such as O2 consumption decreased and callose concentration increased in soils with a BS < 3%. In contrast to the B horizons, seedlings in the Ah horizons had higher relative shoot‐growth rates, specific root lengths, and lengths and branching increments, but a lower root‐to‐shoot ratio and root‐branching frequency. In conclusion, these differences in growth patterns were most likely due to differences in nutrient availability and to the drought application and not attributable to differences in Al3+ concentrations in the soil solution.

Small-scale distribution of extracellular enzymes, fungal, and bacterial biomass in Quercus petraea forest topsoil

The small-scale distribution of activities of extracellular laccase, Mn-peroxidase, endoglucanase, cellobiohydrolase, β-glucosidase, endoxylanase, β-xylosidase, chitinase, and acid phosphatase were studied in the litter (L) and organic (H) horizons of Quercus petraea forest soil and related to the distribution of microbial biomass. Geostatistical analysis showed that the spatial autocorrelation of the enzyme activities and soil microbial biomass measured as phospholipid fatty acids (PLFA) and ergosterol content occurred at similar scales, typically in the range of tens of centimeters. The size of the spatial structures differed between the L and H horizons; for most of the studied enzymatic processes, litter exhibited a higher spatial variability (smaller autocorrelation distances). The distribution of several enzymes, including laccase, Mn-peroxidase, and some hydrolases, reflected the distribution of fungal biomass. Polysaccharide hydrolases exhibited similar spatial distribution patterns in the L horizon, and their activity coincided with a high fungal/bacterial biomass ratio.

Structure and resilience of fungal communities in Alaskan boreal forest soilsThis article is one of a selection of papers from The Dynamics of Change in Alaska’s Boreal Forests: Resilience and Vulnerability in Response to Climate Warming.

This paper outlines molecular analyses of soil fungi within the Bonanza Creek Long Term Ecological Research program. We examined community structure in three studies in mixed upland, black spruce ( Picea mariana (Mill.) BSP), and white spruce ( Picea glauca (Moench) Voss) forests and examined taxa involved in cellulose degradation at one upland site. We found that soil horizon was the factor by which fungal communities were most strongly structured and that predictable turnover in upland fungal species occurred through succession. Communities from consecutive summers were not significantly different, indicating that interannual variation was small in relation to differences between forest types and soil horizons, yet the community at a seasonal study site underwent significant changes within a year. In each study, mycorrhizal fungi dominated the community. Fungi rather than bacteria appeared to dominate [13C]cellulose degradation, with strongest growth in taxa that were not dominant members of the untreated community, including members of the genus Sebacina . Overall, our results point to considerable interannual resilience juxtaposed with narrow niche partitioning and the capacity of individual taxa in these hyperdiverse communities to respond strongly to resource inputs and changes in other abiotic environmental parameters such as temperature. Our data double the cumulative total of fungal sequences in GenBank and together achieve a better picture of fungal communities here than for any other ecosystem on earth at this time.

Geochemical characterization of placic horizons in subtropical montane forest soils, northeastern Taiwan

Well‐developed placic horizons have been found in subalpine forest soils with large clay contents in Taiwan. We investigated their formation processes in five profiles in a subalpine ecosystem of northeastern Taiwan, using scanning electron microscopy (SEM), energy‐dispersive spectrometry (EDS), electron probe microanalysis (EPMA), differential X‐ray diffraction (DXRD) and chemical extractions. The placic horizons, ranging from 3‐ to 17‐mm thick, always occurred above argillic horizons with abrupt changes in pH and texture between the two horizons. When fully developed, the placic horizons were clearly differentiated between upper and lower sub‐horizons. EDS and chemical extractions revealed that the cementing materials in both were predominantly inorganic Fe oxides. However, contents of aluminosilicates and organically complexed Fe and Al were greater in the lower than in the upper placic sub‐horizon. Results of EPMA indicated that interstitial fine materials in the upper placic sub‐horizon were composed mainly of Fe oxides, whereas Fe oxides were codominant with illuvial clay in the lower sub‐horizon. These analyses identified the migration of Fe and clay as major formation processes in both sub‐horizons. We hypothesize that there is a pedogenic sequence that starts with clay illuviation, followed by podzolization. The resultant textural and permeability differentiation reinforces the tendency to profile episaturation that is already inherent from the heavy rainfall and clayey surface soils. Topsoil Fe is therefore reduced and mobilized, and then illuviated with clay and organically complexed Fe/Al to initiate the lower placic sub‐horizon. The poor permeability of this layer reinforces the moisture conditions in the surface soils, and the further reduction, illuviation and deposition of inorganic Fe to form the upper placic sub‐horizon.

Oribatid mites in soil toxicity testing—the use ofOppia nitens(C.L. Koch) as a new test species

Few soil invertebrate species are available for the toxic assessment of soils from boreal or other northern ecozones, yet these soils cover the majority of Canada's landmass as well as significant portions of Eurasia. Oppia nitens (C.L. Koch) is an herbivorous and fungivorous oribatid mite found in soil throughout Holarctic regions, including Canada. Soil tests using O. nitens were performed using 15 different forest soil types and horizons to investigate test variability in adult survival and reproduction. Adult survival (86.1 +/- 1.1%) was consistent across soil types, with a coefficient of variation (CV) of 15%. However, reproduction varied significantly, ranging from 2.9 (+/-1.1) to 86.2 (+/-11.7) individuals, with a corresponding CV of 118 and 30%, respectively. Of the soil factors assessed (NH(3), NO(3), pH, phosphorus [P], organic matter content (OM), carbon:nitrogen (C:N), sand, silt, clay, and sodium adsorption ratio), soil organic matter (OM) explained 68% of the variation observed for reproduction. Increasing the OM using Sphagnum sp. peat moss resulted in optimal reproduction at 7% OM (8% peat content) with the lowest variability (CV of 20%). When assessing the toxicity of a reference chemical, boric acid, the effect of peat amendment reduced lethality to adults with no observable difference on reproduction. The use an age-synchronized culture reduced the test variability for reproduction relative to the use of unsynchronized cultures. Oppia nitens is a good candidate species for a standardized test design, with adult survival easily assessed in a relatively simple design. A long-term reproduction test with O. nitens will require the use of a synchronized population and, on occasion, OM amendment when testing soils with low organic matter content.

Antimony mobility in lead smelter-polluted soils

Emissions from primary and secondary lead (Pb) smelters are responsible for high concentrations of metallic contaminants (Pb, Cd and Zn) in soils. However, less attention has been paid to volatile metalloids, such as antimony (Sb), which accompanies Pb smelting activities. This paper is focused on geochemistry of Sb in the forest and agricultural soils in the vicinity of the Příbram Pb smelter (Czech Republic), with emphasis on Sb distribution, chemical fractionation and comparison with the behaviour of another toxic metalloid, arsenic (As). Forest soils were enriched in Sb (4.86–2058 mg kg − 1 , mean: 379 mg kg − 1 , median: 155 mg kg − 1 ) with the highest concentrations in the organic horizons. Arsenic was found in significantly lower concentrations in forest soils (9.16–447 mg kg − 1 , mean: 127 mg kg − 1 , median: 82.9 mg kg − 1 ). High concentrations of metalloids in forest soils are related to higher interception of smelter emissions by tree canopies. The Sb/As concentrations ratios ranged between 4.6 and 16.4 in the organic soil horizons, which is in agreement with (i) higher Sb deposition between ∼ 1890 and the 1970s as recorded by 210-Pb dated peat cores from the vicinity of the smelter and (ii) rare historical analytical data on processed concentrates and dust from the smelter flue-gas cleaning system. In contrast to organic horizons of forest soils, the concentrations of the two metalloids are rather similar in agricultural soils and in mineral horizons of the forest soils. Antimony concentrations in agricultural soils were in the range 3.12–131 mg kg − 1 (mean: 39.3 mg kg − 1 , median: 23.8 mg kg − 1 ), whereas As concentrations were in the range 4.33–154 mg kg − 1 (mean: 60.3 mg kg − 1 , median: 42.5 mg kg − 1 ). Factor analysis showed that Sb and As are statistically correlated to oxalate-extractable Fe, corresponding to amorphous or less crystalline Fe-oxides. The 5-step sequential extraction procedure (SEP), which was originally designed for As, and revised BCR SEP were applied to chemically fractionate Sb and As in the most polluted soil profiles. In forest soils, Sb was mostly bound in residual fraction with “mobile” concentrations in the range of 0.6–4% of the total Sb content. In contrast, As was significantly more mobile (1.2–22% of the total content in the “mobile” fractions) with dominant binding to Fe-oxides (up to 57% of total As content). In agricultural soils, Sb was again less “mobile” than As (1.4–5.9% and 0.34–12.1%, respectively of the total concentrations). Whereas Sb was mainly bound to the residual fraction and partly also in the reducible fraction (Fe-oxides), As was predominantly bound to Fe-oxides (up to 71% of the total As content). Good agreement was observed between the two SEP methods in determining the “mobile” concentrations of the metalloids ( R 2 Sb = 0.9918 and R 2 As = 0.9104, p < 0.001). Despite probable similarities in the geochemical behaviour of these two metalloids in polluted soil systems, this study indicates that As is chemically more mobile than Sb.

Sand and clay mineralogy of soils of Garhwal Himalaya, Uttarakhand

Fine sand and clay mineralogy of selected horizons of forest soils representing various landforms of Maldeota, Satengal and Dhanaulti areas of Raipur and Jaunpur ranges of Mussoorie forest division of Garhwal Himalaya were investigated. Light minerals constituted more than 80 percent of total fine sand fractions and consisted of quartz, feldspar and mica in order of their abundance. Heavy minerals occurred in minute amounts and constitute 20 percent of the minerals and were dominated by opaque minerals followed by biotite, chlorite, chloritized mica, zircon, garnet, hornblende, tourmaline, rutile etc. Quartz is the dominant mineral in Maldeota and Satengal sites followed by Dhanaulti while feldspar and mica are abundant in Dhanaulti followed by Maldeota and Satengal. Among the heavy minerals opaque minerals, biotite and calcite are present in appreciable quantity in all the three sites viz. Maldeoata, Satengal and Dhanaulti. The other heavy minerals are present in small quantities at all the three sites. The clay fractions from the soils of Maldeota are characterized by illite as the dominant clay mineral associated with kaolinite, chlorite, vermiculite and quartz. The clays from Satengal contained mixture of illite as dominant mineral followed by mica, mixed layer minerals, vermiculite, chlorite and quartz. The soil clays from Dhanaulti indicates the presence of illite, muscovite, kaolinite, mixed layer minerals, chlorite and small traces of vermiculite, calcite and quartz. Differences in mineralogical make up were mostly associated with nature and composition of parent material and degree of weathering. The study, therefore, suggests that soils of the study area contained low to moderate amount of weatherable minerals indicating their podzolic nature.

Soil Carbon and Nitrogen Accumulation in a Forested Debris Flow Chronosequence, California

The role of forest soils in the biogeochemical cycling of C and N is most dynamic during the early stages of soil development. To define C and N trends that occur with soil development in a mixed coniferous forest, a chronosequence formed by debris flows was studied. The accumulation rates of total organic C (TOC) and total N (TN) were evaluated in soils on 10 debris flow deposits, ranging from &lt;1 to 244 yr old. Analysis of the mineral soils was restricted to the 30‐cm depth, since this was the depth of the shallowest debris flows. Carbon was found to accumulate in the organic horizons at a rate of 26.5 g m−2 yr−1 throughout the time span of the chronosequence. Total organic C accumulation in the mineral horizons (0–30 cm) occurred from 0 to 82 yr at a rate of 13 g m−2 yr−1, and was nearly stable from 82 to 244 yr. Total N accumulated at a rate of 0.57 g m−2 yr−1 in the organic horizons and a rate of 0.17 g m−2 yr−1 in the mineral horizons (0–30 cm) throughout the 244 yr chronosequence. This study suggests that C accumulation in the upper mineral horizons of young forest soils occurs for &lt;100 yr, while N accumulation is a slower process that occurs for &gt;250 yr. Carbon and N accumulation in the organic horizons, however, both follow a linear trend over the 244‐yr period. The rates of C accumulation suggest a rapid recovery of the soil organic C pool following disturbance.

Decomposition of leaf litter from a native tree and an actinorhizal invasive across riparian habitats

Dynamics of nutrient exchange between floodplains and rivers have been altered by changes in flow management and proliferation of nonnative plants. We tested the hypothesis that the nonnative, actinorhizal tree, Russian olive (Elaeagnus angustifolia), alters dynamics of leaf litter decomposition compared to native cottonwood (Populus deltoides ssp. wislizeni) along the Rio Grande, a river with a modified flow regime, in central New Mexico (U.S.A.). Leaf litter was placed in the river channel and the surface and subsurface horizons of forest soil at seven riparian sites that differed in their hydrologic connection to the river. All sites had a cottonwood canopy with a Russian olive-dominated understory. Mass loss rates, nutrient content, fungal biomass, extracellular enzyme activities (EEA), and macroinvertebrate colonization were followed for three months in the river and one year in forests. Initial nitrogen (N) content of Russian olive litter (2.2%) was more than four times that of cottonwood (0.5%). Mass loss rates (k; in units of d(-1)) were greatest in the river (Russian olive, k = 0.0249; cottonwood, k = 0.0226), intermediate in subsurface soil (Russian olive, k = 0.0072; cottonwood, k = 0.0031), and slowest on the soil surface (Russian olive, k = 0.0034; cottonwood, k = 0.0012) in a ratio of about 10:2:1. Rates of mass loss in the river were indistinguishable between species and proportional to macroinvertebrate colonization. In the riparian forest, Russian olive decayed significantly faster than cottonwood in both soil horizons. Terrestrial decomposition rates were related positively to EEA, fungal biomass, and litter N, whereas differences among floodplain sites were related to hydrologic connectivity with the river. Because nutrient exchanges between riparian forests and the river have been constrained by flow management, Russian olive litter represents a significant annual input of N to riparian forests, which now retain a large portion of slowly decomposing cottonwood litter with a high potential for N immobilization. As a result, retention and mineralization of litter N within these forests is controlled by hydrologic connectivity to the river, which affects litter export and in situ decomposition.

Microbial Chlorination of Organic Matter in Forest Soil: Investigation Using 36Cl-Chloride and Its Methodology

Chloride, which comes into the forest ecosystem largely from the sea as aerosol (and has been in the past assumed to be inert), causes chlorination of soil organic matter. Studies of the chlorination showed that the content of organically bound chlorine in temperate forest soils is higher than that of chloride, and various chlorinated compounds are produced. Our study of chlorination of organic matter in the fermentation horizon of forest soil using radioisotope 36Cl and tracer techniques shows that microbial chlorination clearly prevails over abiotic, chlorination of soil organic matter being enzymatically mediated and proportional to chloride content and time. Long-term (>100 days) chlorination leads to more stable chlorinated substances contained in the organic layer of forest soil (overtime; chlorine is bound progressively more firmly in humic acids) and volatile organochlorines are formed. Penetration of chloride into microorganisms can be documented by the freezing/thawing technique. Chloride absorption in microorganisms in soil and in litter residues in the fermentation horizon complicates the analysis of 36Cl-chlorinated soil. The results show that the analytical procedure used should be tested for every soil type under study.

Seven Decades of Calcium Depletion in Organic Horizons of Adirondack Forest Soils

We used repeated sampling of the forest floor to determine if there was a net loss of Ca from organic horizons of Adirondack forest soils between 1930 and 2004. In 1984, we established 48 permanent plots in spruce–fir, northern hardwood, and pine stands located in areas sampled by Carl C. Heimburger in the early 1930s. Following Heimburger's protocols and analytical methods, we measured pH and dilute‐HCl‐extractable Ca in Oe and Oa horizons, and determined that there was a statistically significant decrease in Ca concentration during the 1932 to 1984 interval. In the 36 plots that we could locate in 2004, we again sampled organic horizons. During the &gt;70‐yr interval, HCl‐extractable Ca concentrations in the Oe and Oa horizons decreased in each forest type (P &lt; 0.05). We also measured NH4Cl‐extractable Ca and Al in the 1984 and 2004 samples and found a significant decrease in Ca concentration in the pooled Oe horizons. High‐elevation spruce–fir plots showed a Ca loss rate between 1984 and 2004 of 7.6 to 9.8 kg ha−1 yr−1 This compares well with a 4‐yr Ca cycling study conducted in an equivalent spruce–fir forest at Whiteface Mt. in the Adirondacks, which showed an annual forest floor Ca loss of 8.4 kg ha−1 yr−1 Based on uptake and anion flux data from the Whiteface Mt. study, we estimated that about 25 to 30% of the 1984 to 2004 forest floor Ca loss in the spruce–fir plots is attributable to leaching driven by atmospheric SO42− deposition.

Quantifying Carbon Dioxide and Methane Emissions and Carbon Dynamics from Flooded Boreal Forest Soil

The boreal forest is subject to natural and anthropogenic disturbances, but the production of greenhouse gases as a result of flooding for hydroelectric power generation has received little attention. It was hypothesized that flooded soil would result in greater CO(2) and CH(4) emissions and carbon (C) fractionation compared with non-flooded soil. To evaluate this hypothesis, soil C and nitrogen (N) dynamics, CO(2) and CH(4) mean production rates, and (13)C fractionation in laboratory incubations at 14 and 21 degrees C under non-flooded and flooded conditions and its effect on labile and recalcitrant C sources were determined. A ferro-humic Podzol was collected at three different sites at the Experimental Lakes Area, Canada, with a high (19,834 g C m(-2)), medium (18,066 g C m(-2)), and low (11,060 g C m(-2)) soil organic C (SOC) stock. Soil organic C and total N stocks (g m(-2)) and concentrations (g kg(-1)) were significantly different (p < 0.05) among soil horizons within each of the three sites. Stable isotope analysis showed a significant enrichment in delta(13)C and delta(15)N with depth and an enrichment in delta(13)C and delta(15)N with decreasing SOC and N concentration. The mean CO(2) and CH(4) production rates were greatest in soil horizons with the highest SOC stock and were significantly higher at 21 degrees C and in flooded treatments. The delta(13)C of the evolved CO(2) (delta(13)C-CO(2)) became significantly enriched with time during decomposition, and the greatest degree of fractionation occurred in the organic Litter, Fungal, and Humic forest soil horizons and in soil with a high SOC stock compared with the mineral horizon and soil with a lower SOC stock. The delta(13)C-CO(2) was significantly depleted in flooded treatments compared with non-flooded treatments.

Relationship between Aluminum in Soils and Soil Water in Mineral Horizons of a Range of Acid Forest Soils

Previous studies suggest that the solubility of Al in acid forest soils may be expressed as the log Al3+ activity = −n pH + log KH‐Al + log Alp/Cp concentration ratio, with Alp and Cp representing pyrophosphate‐extractable Al and C, respectively, and KH‐Al is the binding constant of Al to protonated complexation sites on soil organic matter (SOM). We show that a slightly modified model, in which Alp is replaced by Alorg (= Alp − KCl‐extractable Al), successfully describes the concentration of Al in A and B horizons of a wide range of acid forest soils (Typic Dystochrepts) developed in different parent materials from a large number of spruce [Picea abies (L.) Karst.] and mixed forest stands in southern Poland. Analysis of the data suggests a reaction stoichiometry of n = 1.27 and log KH‐Al = 1.98 with R2 = 0.76. Furthermore, statistical analysis of a large set of published data, in addition to our own data from the Polish soils, indicates that log[Alorg/Cp] is significantly correlated with soil pH measured in 1 mol L−1 KCl (pHKCl), suggesting that the Al binding to SOM is less at small pHKCl due to increased competition with H+: log[Alorg/Cp] = 0.82 pHKCl − 4.16 (R2 = 0.77, n = 276). Combining the two equations gives a simple Al solubility model for mineral horizons in acid forest soils: log Al = −1.27pH + 0.82pHKCl − 2.18 (R2 = 0.82, n = 127). In this equation, pHKCl relates to chemical soil properties, whereas the pH of soil water also depends on solution characteristics like ionic strength. The equation may be applied to acid forest soils having a soil solution pH in the range of 3.0 to 4.2. Such conditions are rather common in surface horizons (A, E, and upper B) of acid forest soils of the temperate and boreal zones.

Chemical properties and pedogenesis of yellowish/yellow brown forest soils in the submontane and mountain zones of Kyushu district, southwestern Japan

This study aimed to clarify pedogenetic processes and classification of yellowish Brown Forest Soils according to the Classification of Forest Soils in Japan and the Yellow Brown Forest soils according to the Unified Soil Classification System of Japan in the warm and cool temperate forest of Kyushu district, Japan. In addition, the study aimed to clarify a problem with the Unified Soil Classification System of Japan. Thirty-six soil profiles of Brown Forest Soils, including 13 yellowish Brown Forest Soils and 15 Yellow Brown Forest soils, were compared with regard to their chemical properties and the relationship with climatic conditions was assessed. The yellowish Brown Forest Soils had thin A horizons, low pH and low levels of free oxides in the B horizons, and a low amount of silica and a high aluminum and iron to silica ratio. These features were related to the paleo reddish weathering. The immaturely developed A horizon of the yellowish Brown Forest Soils was caused by these weathered, low-activity substances. The Yellow Brown Forest soils had low levels of active iron oxides and a low activity ratio of free iron oxides compared with the Haplic Brown Forest soils in the same thermal climatic conditions. The activity ratio of free iron oxides was correlated to mean annual air temperature with the carbon stocks and with many other chemical properties. Accordingly, classification of Brown Forest Soils was clearer according to thermal climatic conditions. The activity ratio of free iron oxides can become an effective index that distinguishes Yellow Brown Forest soils under warm temperate lucidophyllous forest and Haplic Brown Forest soils under cool temperate broad-leaved deciduous forest with considerable vertical soil zonality.

The effect of afforestation with Scots pine (Pinus silvestris L.) of sandy post-arable soils on their selected properties. II. Reaction, carbon, nitrogen and phosphorus

Despite the extensive literature on the effect on soil properties of afforestation of former arable land, we still lack full understanding of whether the changes proceed in the same direction and at the same rate, and of how long is required to achieve a state of soil equilibrium typical of a natural forest ecosystem. Therefore, as part of a study comparing post-arable sandy soils (Dystric Arenosols) afforested with Scots pine (Pinus silvestris L.) with arable soils and soils of continuous coniferous forests, the range and direction of changes in pH, organic carbon (Corg), total nitrogen (Ntot), ammonium (N-NH4) and nitrates (N-NO3) in soil solution, total (Ptot) and available (Pav) phosphorus were determined. The studies were carried out in south-east Poland (51°30′-51°37′N, 22°20′-22°35′E). Ten paired sites of afforested soils (five with 14- to 17-year-old stands and five with 32- to 36-year-old stands) with adjacent cultivated fields, and five sites of continuous forest with present stands of ca. 130–150 years old were selected. Soil samples were taken from the whole thickness of master horizons and, in the case of the A horizon of the afforested soils, from three layers: 0–5 (A0–5), 5–10 (A5–10) and 10–20 cm (A10–20). The cultivated soils in the Ap horizon showed higher pH (by ca. 1.0 unit), lower Corg and C:N, similar Ntot, lower N-NH4, higher N-NO3, higher Ptot and Pav contents compared with the Ah horizon of continuous forest soils. The results indicated decreased soil pH in the former plough layer of the afforested soils, with the greatest decrease observed in the 0–5 cm layer. In these soils, the Corg content was considerably higher in the A0–5 layer, but lower in the two deeper layers and in the whole A horizon (0–20 cm) compared with the Ap horizon of the arable soils. The results indicate that the Corg content, after an initial phase of decline, again achieved a level characteristic of arable soils. The Ntot content in all layers of the A horizon of the afforested soils was lower than in the Ap horizon of the arable soils, and showed a reduction with stand age, especially in deeper layers. The C:N ratios in the mineral topsoil increased with stand age. N-NH4 content increased and N-NO3 decreased after afforestation. The Ptot and Pav contents in all layers and in the whole A horizon of the afforested soils, on stands of both ages, was lower than in the Ap of the cultivated soils. From the results, it could be concluded that, after more than 30 years of tree growth, the soils of the A horizon were still more similar to arable than to continuous forest soils with respect to Corg, Ptot and Pav. With respect to pH, N-NH4 and N-NO3, especially in the 0–5 cm layer, they were more similar to continuous forest soils than to cultivated soils, but with respect to Ntot and C:N ratio they were somewhere in between.

Carbon Quality and Stocks in Organic Horizons in Boreal Forest Soils

We investigated the mechanisms that determine the quality and quantity of organic carbon (C) stocks in boreal forest soils by analyzing both qualitative and quantitative changes in the organic fractions in the soil organic matter (OM) in a vertical gradient in the decomposition continuum of the organic horizon [litter layer (L), fermentation layer (F), and humus layer (H)] in forest soils using a sequential fractionation method at two forest types along a climatic gradient in Finland. We predicted that the concentrations of water-soluble (WSE) and non-polar (NPE) extractives should decrease and those of the acid-soluble (AS) fraction and acid-insoluble residue (AIR) should increase from the L to the F, and from the F to the H layers, but the C/N ratio of soil OM should stay constant after reaching the critical quotient. We also predicted that the AIR concentrations should be higher in the south than north boreal, and in sub-xeric than mesic forests. Consistent with our hypothesis, the concentrations of WSE and NPE fractions decreased and concentrations of AIR increased in the vertical soil gradient. The highest concentrations of the AS fraction were found in the F layer. The C/N ratio was lowest in the F layer, and the highest in the H layer, indicating that soil OM is depleted in N in relation to C along the vertical soil gradient. Concentrations of WSE and NPE were lower, and concentrations of AIR were higher in the south than in north boreal forests, which is in agreement with our hypothesis that higher soil temperatures may enhance accumulation of slowly decomposable OM in the soil. The concentrations of AIR were higher in the sub-xeric than mesic forests. Contrary to our expectations, however, the differences in the chemical quality in soil OM between the site types were amplified from the L to the H layer. The size of the C storage was significantly larger in south than north boreal sites, and larger in the mesic than in the sub-xeric sites.

Soil surface properties in Mediterranean mountain ecosystems: Effects of environmental factors and implications of management

Understanding soil processes is fundamental to the success of forest restoration programs. We compared different types of soils in Mediterranean mountain forests with respect to their edaphic environments and influence of vegetation cover and lithology. We then used this information to determine the suitability of current forest restoration programs in these ecosystems. Twenty-four surface horizons in forest soils in two zones of contrasting lithology (calcareous and metamorphic) and different types of vegetation cover or management (shrubland, autochthonous forest and reforested forest) were sampled. A set of their essential soil properties were analysed and a series of parameters considered as indicators of surface soil processes was selected: aggregate size, structural stability, water repellency, mineralisation rate and fungal activity. Results confirm that the lithological origins of soils determines the properties defined by the geochemical environment of soilscapes (texture, pH, exchange complex and free oxides), and does not much influence organic properties. On the other hand, the type of plant cover and management do not influence the geochemical properties of the soil decisively, but do maintain a relative control of organic properties, especially those that define their quality (C/N ratio). The variability of surface properties is not well explained by environmental factors, and it is assumed that a large part may be related to the historical use of the soils. The specificity of soilscapes implies differences in vulnerability to forest management: the surface horizons in siliceous environments are more vulnerable than calcareous environments. It is necessary to better characterize soil properties in these forests and accordingly re-evaluate forest restoration efforts with respect to them.

Extraction of water‐soluble organic matter from mineral horizons of forest soils

AbstractDissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H2O, 0.01 M CaCl2, and 0.5 M K2SO4. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K2SO4 extracted the largest amounts of WSOC (up to 126 mg C kg–1) followed by H2O followed by CaCl2. The H2O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol–1 cm–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K2SO4 bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.

Molecular size distribution and hydrophilic and hydrophobic properties of humic acids isolated from forest soil

The aim of the present paper was to determine hydrophilic and hydrophobic properties and the degree of polydispersity of humic acids depending on their degree of maturity and the properties of the plant material participating in the process of humification. The study involved humic acids isolated from samples taken from organic and mineral horizons of forest soils. The samples were taken under the tree stands of: pine with an admixture of hardbeam, European beech, elm, fir, spruce, and thuja. It was demonstrated that the properties of humic acids of the organic horizon and mineral horizons are determined by the kind of plant litter, mainly by the tree species. The humification process is connected with an increase of the proportion of humic acids of lower molecular size as compared to the proportion of molecules greater in size, and with an increase of hydrophilic fractions and a decrease of hydrophobic fractions. Based on the correlation relationships, it was shown that the degree of polydispersity of molecules of humic acids is related to their hydrophilic and hydrophobic properties. Humic acids with a larger proportion of high-molecular fractions demonstrate also a higher proportion of hydrophobic fractions.

Mapping particulate pollution loads using soil magnetometry in urban forests in the Upper Silesia Industrial Region, Poland

The central part of the Silesian Province, Upper Silesian Industrial Region (USIR), is the most urbanized region of Poland and one of the largest urban and industrial areas of Central Europe. The area is surrounded by a protective forest belt with some smaller urban forests, woods and parks, which are commonly used by the local population for daily and weekend recreation. Long-term exploitation of the natural resources of this land together with industrialization and urbanization has caused its physical and chemical degradation, which has in turn resulted in large geochemical and magnetic anomalies. The aim of this study was to apply the method of field magnetometry to quickly and efficiently obtain proxy data for ecological quality assessment of urban forests in the USIR. Surface measurements of magnetic susceptibility ( κ) were performed in two areas of urban forest. The first, “Makoszowy Wood” located in Zabrze (the western part of USIR) and the second area, comprised of two forests “Panewnik Forests” and “Kochlowice Forests” (in the central part of USIR), located in the city regions of Katowice, Chorzow and Ruda Slaska. The spatial variability of κ values measured in the topsoil were large (10–120 × 10 −5 SI units), requiring a relatively dense measurement network when pollution screening is undertaken. In both study areas, some local magnetic anomalies were observed, mostly located close to housing areas or local industrial or urban sources of emission. In sites of enhanced κ values, the content of some heavy metals was considerably high, often exceeding the national threshold values. Study of the vertical distribution of κ values in topsoil profiles, based on 30 cm cores, indicated that contaminants deposited over many years of industrial and urban activity have persisted in the organic horizon of forest soils, which function as an “irreplaceable environmental filter”. Such vast concentrations of contaminants in a relatively small area may be an “ecological time bomb” that may represent a true ecological hazard. Very low soil pH usually favors the release of heavy metals and other toxic elements into the soil environment, and through the soil, directly into the forest ground flora and underground water system.