Mineral Soil Layers Research Articles

Aspen and white spruce productivity is reduced by organic matter removal and soil compaction

Declines in forest productivity have been linked to losses of organic matter and soil porosity. To assess how removal of organic matter and soil compaction affect short-term ecosystem dynamics, pre-treatment and year 1, 5 and 10 post-treatment soil properties and post-treatment plant community responses were examined in a boreal trembling aspen (Populus tremuloidesMichx.)-dominated ecosystem in northeastern British Columbia. The experiment used a completely randomized design with three levels of organic matter removal (tree stems only; stems and slash; stems, slash and forest floor) and three levels of soil compaction (none, intermediate [2-cm impression], heavy [5-cm impression]). Removal of the forest floor initially stimulated aspen regeneration and significantly reduced height growth of aspen (198 cm compared to 472–480 cm) as well as white spruce (Picea glauca [Moench] Voss) height (82 cm compared to 154–156 cm). The compaction treatments had no effect on aspen regeneration density. At Year 10, heights of both aspen and white spruce were negatively correlated with upper mineral soil bulk density and were lowest on forest floor + whole tree removal treatments. Recovery of soil properties was occurring in the 0 cm to 2 cm layer of mineral soil. Bulk density values for the 0 cm to 10 cm depth remained above 86% of the maximum bulk density for the site, a soil condition where reduced tree growth can be expected.

Molecular discrimination of bacteria (organic versus mineral soil layers) of dry woodlands of Argentina

We performed screening of bacteria inhabiting soil organic (O) layers vs mineral (A) layers. Community level and group-specific genetic fingerprinting was used to assess changes in bacterial structures of dry woodlands of Argentina as function of regional climate, season and land use. Multiple factor effects and correlations of soil organic matter, microbial biomass and bacterial structures were found, indicating substrate, soil moisture and moderate temperature as favorable conditions. Fingerprinting data showed distinct soil bacteria inhabiting O vs A layers. At the community level, lower similarities were found in the O layer (28%) than in the A layer (47%); this phenomenon was not always reflected at the group level, providing more accurate insights into environmental change induced shifts in soil bacterial structures (i.e., higher similarities among actinomycetes and ammonium oxidizers inhabiting the O layer with respect to the A layer). Specific bacterial groups were more affected in O than A layers, in wet summer and under moderate regional climate (moisture effect). N2 fixers were found to be the most sensitive community members (i.e., to grazing induced disturbances) and predominate in the O layer. Discrimination of soil bacteria provided evidences about the role of organic layer bacteria in overall organic matter dynamics.

High organic carbon stock in a karstic soil of the Middle-European Forest Province persists after centuries-long agroforestry management

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.

Amount of boron in Norway spruce stands in eastern Finland

The aim of this study was to determine the amount of boron in three Norway spruce (Picea abies (L.) Karst) stands in eastern Finland, where boron deficiency is common. A further aim was to estimate the effects of logging-residue harvest on boron balance and the boron-to-nitrogen ratio on these sites. The data were obtained from a 30-year-old and a 62-year-old healthy spruce stand as well as from a 35-year-old spruce stand with boron deficiency and growth disorders. Altogether 2.1 and 2.4kgha−1 boron, respectively, were bound in trees+organic layer+0–10cm mineral soil layer in the two healthy stands, and 0.9kgha−1 in the boron deficient stand. For the amount of boron in the healthy stands the trees made up 43% and 49%, respectively, and in the boron deficient stand 38%. Stems contained 30% and 40%, respectively, of the boron in trees in the healthy stands and 37% in the boron-deficient stand. Only 11–13% of the tree boron was in the needles. The amount of nitrogen bound in the ecosystem studied was 2.1 and 2.5Mgha−1, respectively, in the two healthy stands and 3.0Mgha−1 in the boron deficient stand. In the ecosystem the trees contained 21–29% of the amount of nitrogen. Stems contained 14–24%, respectively, and needles 26–36%, respectively, of the nitrogen in the trees on the studied stands. In stem-only harvestings, relatively more boron than nitrogen would be removed from a site. In the boron-deficient stand, boron fertilisation for 3years nearly doubled the amount of boron in the ecosystem. Only 38% of the fertiliser boron (2kgha−1) was found in the ecosystem components studied.

The Forest Floor and Mineral Soil Carbon Pools of Six Different Forest Tree Species

The influence of tree species on forest soil properties has been studied for a long time. Recently, the role of soil carbon (C) pools for mitigation of greenhouse gases has highlighted the need for more knowledge on the tree species effects on soil organic C. In Turkey, the effects of six different tree species; Sessile oak (Quercus petraea), Oriental spruce (Picea orientalis), Austrian pine (Pinus nigra), Turkish fir (Abies bormulleriana), Scots Pine (Pinus sylvestris), and Taurus cedar (Cedrus libani) on the carbon pools of the top mineral soil (0-30 cm) and the forest floor were investigated in adjacent stands. Carbon pools of the forest floor varied from 11 Mg ha -1 beneath the Oriental spruce to 20 Mg ha -1 beneath the Scots pine. The C contents of the forest floor were similar among species and there was no significant difference in C mass of forest floors among species. In the 0-30 cm mineral soil layer, the highest soil organic C pool was beneath the Taurus cedar and the lowest was found in the native Sessile oak forest. Total C pools (forest floor + 30 cm mineral soil) increased in the order Quercus petraea < Abies bornmulleriana < Picea orientalis < Pinus sylvestris < Pinus nigra and Cedrus libani from 77 to 126 Mg ha-1. The results suggest that tree species differ in C sequestration rates within the forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after five decades.

Availability and evaluation of European forest soil monitoring data in the study on the effects of air pollution on forests

In the study of air pollution effects on forest ecosystems, solid soil data such as cation exchange capacity, base saturation and other exchangeable cation fractions, soil texture, soil moisture, soil weathering rates, C/N ratio and other variables form an important information base for many air pollution impact models. This paper shows some of the possibilities and the limitations of the soil data that European countries collected on the systematic Level I and on the intensive and permanent Level II monitoring plots within the ICP Forests programme. The soil data date from a first inventory in the 1990s and from a second inventory more than 10 years later. Both surveys were conducted following a common manual on sampling and analysis of soil. An example of the changes in pH(CaCl2) and base saturation in the forest floor and mineral soil on more than 2000 plots till a depth of 80 cm between the two surveys is presented. In this period the pH(CaCl2) significantly increased in the very acid forest soils [with pH(CaCl2) below 4.0] but further decreased in forest soils with pH(CaCl2) above 4.0. Following the trend in pH, the base saturation increased in soils with a very low buffering capacity (soils with a base saturation below 20% in the first inventory) and decreased in forest soils with reference base saturation values above 20%. There is both a decrease of soil pH and base saturation in the forest floor of the Arenosols and Podzols. In the Podzols this decreasing trend could not be established in the mineral soil, though this decreasing trend persisted in a number of mineral soil layers of the Arenosols. The only consistent increasing trend of pH and base saturation when stratifying according to the WRB reference soil groups was seen in the forest floor of the Luvisols and Cambisols.

Tricholoma matsutake dominates diverse microbial communities in different forest soils.

Fungal and actinobacterial communities were analyzed together with soil chemistry and enzyme activities in order to profile the microbial diversity associated with the economically important mushroom Tricholoma matsutake. Samples of mycelium-soil aggregation (shiro) were collected from three experimental sites where sporocarps naturally formed. PCR was used to confirm the presence and absence of matsutake in soil samples. PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting and direct sequencing were used to identify fungi and actinobacteria in the mineral and organic soil layers separately. Soil enzyme activities and hemicellulotic carbohydrates were analyzed in a productive experimental site. Soil chemistry was investigated in both organic and mineral soil layers at all three experimental sites. Matsutake dominated in the shiro but also coexisted with a high diversity of fungi and actinobacteria. Tomentollopsis sp. in the organic layer above the shiro and Piloderma sp. in the shiro correlated positively with the presence of T. matsutake in all experimental sites. A Thermomonosporaceae bacterium and Nocardia sp. correlated positively with the presence of T. matsutake, and Streptomyces sp. was a common cohabitant in the shiro, although these operational taxonomic units (OTUs) did not occur at all sites. Significantly higher enzyme activity levels were detected in shiro soil. These enzymes are involved in the mobilization of carbon from organic matter decomposition. Matsutake was not associated with a particular soil chemistry compared to that of nearby sites where the fungus does not occur. The presence of a significant hemicellulose pool and the enzymes to degrade it indicates the potential for obtaining carbon from the soil rather than tree roots.

The dynamics pattern of soil carbon and nutrients as soil thawing proceeded in the alpine/subalpine forest

Little attention has been given to the dynamics of soil C and nutrients during the soil thawing period in subalpine/alpine forests. To understand the ecological linkages between the non-growing and growing seasons, soil C and nutrients were measured in the primary fir (Abies faxoniana) forest, fir and birch (Betula albosinensis) mixed forest and secondary fir forest in the subalpine/alpine regions of western China. Soils were sampled as soil thawing proceeded from 5 March, 15 March, 25 March, 5 April and 15 April to 25 April 2009, based on monitored soil temperatures. Frequencies of temperature fluctuations (below and above 0 °C) during the soil thawing period depended on the altitude. The soil organic layer showed higher contents and stocks of C, N and P compared with the mineral soil layer. Since the soil organic layer was more directly exposed to environmental changes, the variations of soil C and nutrients in the soil organic layer were more apparent than those in the mineral soil layer. The fluctuations of soil C and nutrients varied with the altitude during soil thawing period. Soil C and nutrient concentrations decreased sharply at the beginning of soil thawing, and thereafter increased in the mixed and secondary forest, which were different to the changes in the primary forest. Soil available nutrients, except for −N in the primary forest, showed an increasing tendency in the early stage of the thawing period, but soil available N and P decreased in the later stage of the thawing period. The increasing soil temperature had little effect on soil nutrient availability during the thawing period. The results indicated that soil carbon and nutrients were significantly affected by the length of freeze–thaw period, which is beneficial towards understanding the interactions between wintertime and the growing season.

Effects of soil aggregate size, moisture content and fertilizer management on nitrous oxide production in a volcanic ash soil

A laboratory incubation study was conducted to determine the effects of soil aggregate size, soil moisture content and manure application on nitrous oxide (N2O) production through nitrification and denitrification. In Southern Hokkaido, soil samples were taken from a mineral soil layer (2.5–10 cm) of a grassland to which chemical fertilizer and manure had been applied. The soil aggregates were air-dried and sieved with 4.5 mm and 2 mm sieves, and the soil moisture was adjusted to 60% and 80% of field water capacity (FWC). Immediately after moistening, incubation was initiated and lasted for 9 days at 20°C. Following the start of incubation, a flush of N2O, carbon dioxide (CO2) and nitric oxide (NO) was observed. Production of all gases was higher in larger aggregates from the manure-applied soil. Productions of CO2 and NO were not significantly influenced by soil moisture content, but N2O production was considerably higher in 80% FWC as compared with 60% FWC. Based on the results of the N2O–nitrogen (N)/NO–N ratio, the process of N2O production was mainly due to nitrification in 60% FWC and denitrification in 80% FWC. Soil chemical properties, especially ammonium–N –N), nitrate–N (NO3–N) and water extractable organic C (WEOC) and microbial biomass C (MBC) also changed immediately after moistening. These changes were higher in larger aggregates from the manure-applied soil. Potential denitrification enzyme activity (DEA) was significantly higher in larger aggregates from manure-applied soil with higher moisture content. The N2O production in both 60% and 80% FWC correlated significantly with MBC and DEA. Regardless of soil moisture conditions, MBC correlated significantly with DEA, WEOC consumption and apparent N mineralization. These facts suggest that larger soil aggregates could have quickly developed suitable internal conditions for microbial activity inside the aggregates and consequently stimulated N2O production through nitrification and denitrification.

Mid-infrared spectroscopy for topsoil layer identification according to litter type and decompositional stage demonstrated on a large sample set of Austrian forest soils

When forest soils are investigated, the identification of litter and soil layers is a key step. Mid-infrared spectroscopy seems to be promising for this due to its capability to provide fingerprint information. In this study, a large data set of mid-infrared spectra of different forest soils (L, FH and Ah horizons of coniferous, mixed and deciduous forests) was available together with general analyses data (among others organic carbon, total nitrogen and carbonate contents). This set was used for devising models for the identification of different soil layers and to follow the characteristics of different forest types in the different layers. Canonical discriminant functions were calculated using nine mid-infrared bands occurring in both organic layers and mineral soil layers. The discriminant analysis of the topsoil layers showed that aliphatic mid-infrared bands dominated the first function and yielded a clear separation of mineral and organic layers. Further, this analysis reflected the higher chemical diversity in the organic layers visible by a high scattering of the calculated data points. Two tests with two separate data sets showed a reliable and reproducible performance of the model. Separations of forest types were best possible in the organic layers, in which the deciduous forests were separated best from mixed and coniferous forests. Also for these discriminations, aliphatic bands were dominating. Advanced degradation of soil organic matter resulted in small distances of equidistant forest-type group-centers in the 5–10 cm layers of the mineral soils. Dominating molecular moieties in the discriminant functions in these layers were carbonates and aliphatic bands. The applied methodology suggests mid-infrared spectroscopy as an appropriate tool for soil layer identification, allowing for unequivocal discrimination between organic and mineral soil layers. Discriminations of forest types delivered information about dominating mid-infrared bands in the single layers and allowed conclusions about functional groups dominating these differences.

Effects of liming on chemical properties of soil, needle nutrients and growth of Scots pine transplants

The effects of limestone (2.0 and 4.0 Mg ha −1) on chemical properties of soil, nutrient concentrations of needles and growth of Scots pine ( Pinus sylvestris L.) transplants were investigated on three reforestation areas on infertile acidic sites in southern Finland. The limestone was applied either on the soil surface (unploughed plots) or was mixed into the topsoil (ploughed plots). All the treatments were replicated four times. Surface broadcast of lime elevated the pH in the organic layer and in the 0–10 cm layer of mineral soil. The increase in the pH of the organic layer after 21 years was, on average, 0.7 and 1.1 pH units, with a dose of lime 2 and 4 Mg ha −1, respectively. On the ploughed plots, the pH in the uppermost 0–10 cm soil layer was 0.4–0.5 units higher than on the corresponding unlimed plots. Both doses of lime significantly increased the amount of exchangeable Ca and the base saturation (BS) in the topsoil on the ploughed plots, and the amount of exchangeable Ca and Mg, as well as the base saturation (BS) in the organic layer + the 0–10 cm layer of mineral soil on the unploughed plots. Regardless of the techniques used for application of lime, after 21 growing seasons the Ca and Mg concentrations in needles were significantly higher on the limed plots than on the controls. In needles, the Ca/Mn ratio was the best indicator for measuring the response to liming. Only on the unploughed plots did liming increase stand volume and dominant diameter of pines. Intensive disc ploughing produced significantly more stems and increased both stand volume and the dominant height of pines compared to unploughed plots.

Survey on composition and bioconcentration potential of 12 metallic elements in King Bolete (Boletus edulis) mushroom that emerged at 11 spatially distant sites

This paper provides data on baseline concentrations, interrelationships and bioconcentration potential of 12 metallic elements by King Bolete collected from 11 spatially distant sites across Poland. There are significant differences in concentrations of metals (Al, Ba, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Sr, Zn) and their bioconcentration potential in King Bolete Boletus edulis at 11 spatially distant sites surveyed across Poland. These have resulted from significant geographical differences in trace metal concentrations in a layer (0-10 cm) of organic and mineral soil underneath to fruiting bodies and possible local bioavailabilities of macro- (Ca, K, Mg, Na) and trace metals (Al, Ba, Cd, Cu, Fe, Mn, Sr, Zn) to King Bolete. The use of highly appreciated wild-grown edible King Bolete mushroom has established a baseline measure of regional minerals status, heavy metals pollution and assessment of intake rates for wild mushroom dish fanciers against which future changes can be compared. Data on Cd, Cu and Zn from this study and from literature search can be useful to set the maximum limit of these metals in King Bolete collected from uncontaminated (background) areas. In this report also reviewed are data on Al, Ba, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Sr and Zn accumulation in King Bolete.

Evolution of the Hydraulic Conductivity of Reclamation Covers over Sodic/Saline Mining Overburden

The evolution of the field saturated hydraulic conductivity of four covers located on a reclaimed saline-sodic shale overburden from oil sands mining is presented. Three covers consisted of a surface layer of peat/glacial topsoil over a mineral, soil. and one cover was a single layer of mixed peat and mineral soil. Measurements of the field saturated hydraulic conductivity of the cover and shale materials were made with a Guelph permeameter between 2000 and 2004. The hydraulic conductivity of the cover materials in the multilayered covers increased by one to two orders of magnitude over the first few monitoring seasons. The hydraulic conductivity of the single-layer cover system, which was placed three years before the multilayered covers, marginally increased from 2000 to 2002 and then remained relatively unchanged. The hydraulic conductivity of the shale underlying all four covers increased approximately one order of magnitude. Soil temperature measurements indicated that one freeze/thaw cycle occurred ...

Shifting sources of soil labile organic carbon after termination of plant carbon inputs in a subtropical moist forest of southwest China

AbstractLabile organic carbon (LOC) is a critical component of soil organic carbon (C) because of its intimate association with soil heterotrophic respiration and role in the decomposition of resistant soil organic matter. In a subtropical moist evergreen broad‐leaved forest of southwest China, we examined changes of LOC and its potential turnover time, microbial biomass C (MBC), and soil microbial activity of the organic and the 0–10 cm mineral soil layers with aboveground plant litter and belowground root treatments. In February of 2004, removal of organic layer, root‐trenching, and tree‐girdling treatments were applied alone and in combination to manipulate plant‐C inputs. In 2006, root‐trenching and tree‐girdling treatments did not significantly change LOC in the organic layer. In the 0–10 cm mineral soil layer, LOC increased substantially due to tree‐girdling treatment, especially in the plots of tree‐girdling and the combinations of three treatments, but this increase was absent in 2007. Soil MBC in these two layers generally did not change markedly after plant‐C inputs manipulations except significant increase under tree‐girdling treatment in 2006. The potential turnover times of LOC increased in all plots with the plant‐C inputs manipulations. The lack of influence of plant‐C inputs manipulations on LOC pools is likely due to high total soil organic C here, while insignificant changes of MBC suggest the soil microbes are not C limited in this forest. The changes of the potential turnover time of LOC imply that the sources of LOC have been shifted from fresh plant litter or root exudates to old soil organic C. Our results suggest that LOC recently derived from plants is preferred by microbes when available, but microbes can also use LOC from soil organic matter when fresh plant C is not available.

Capillary electrophoresis characterisation of humic acids: application to diverse forest soil samples

Environmental contextAnalysis of soil organic matter is important for understanding turnover and stabilisation processes of organic carbon in soils. Capillary electrophoresis is used here to investigate humic acids from soils of diverse forest sites, and show that the patterns of signals are indicative of soil characteristics. The method provides useful information of soil types and complements the existing set of methods for humic acid characterisation. AbstractAnalyses of humic substances provide very useful information about turnover characteristics and stabilisation processes of soil organic matter in environmental soil samples. The present study investigates 113 samples of forest soils from three different layers (undecomposed litter (L), if present, mixed samples of F (intermediate decomposed) and H (highly decomposed) organic matter (FH) and upper mineral soil layers (Ah horizon) from 0 to 5 cm) by extracting humic acids (HAs) and recording electropherograms. Five signals of these electropherograms were evaluated and correlated with basic parameters from soil (organic carbon, Corg, and total nitrogen, Nt, and extraction yields of HAs) and HAs (total carbon, Ct, and Nt), and with signals from photometry, mid-infrared and fluorescence spectroscopy. The developed method was able to separate HAs from different soil layers by calculating a discriminant function based on the five evaluated electrophoretic signals. The dataset of this work opened the opportunity to correlate the observed electrophoretic signals with the other determined soil parameters and spectroscopic signals. This can be seen as a very important step in the direction to assignments of the obtained electrophoretic signals. Soil characteristics were reflected quite well by this method and, combined with the other approaches, it is suitable for applications in further studies.

Long-term nitrogen additions increased surface soil carbon concentration in a forest plantation despite elevated decomposition

Abstract Forests cover one-third of the Earth’s land surface and account for 30–40% of soil carbon (C). Despite numerous studies, questions still remain about the factors controlling forest soil C turnover. Present understanding of global C cycle is limited by considerable uncertainty over the potential response of soil C dynamics to rapid nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application. Here, we present a 15-year-long field study and show an average increase of 14.6% in soil C concentration in the 0–5 cm mineral soil layer in N fertilized (defined as N+ hereafter) sub-plots of a second-rotation Pinus radiata plantation in New Zealand compared to control sub-plots. The results of 14 C and lignin analyses of soil C indicate that N additions significantly accelerate decomposition of labile and recalcitrant soil C. Using an annual-time step model, we estimated the soil C turnover time. In the N+ sub-plots, soil C in the light (a density −3 ) and heavy fractions had the mean residence times of 23 and 67 yr, respectively, which are lower than those in the control sub-plots (36 and 133 yr in the light and heavy fractions, respectively). The commonly used lignin oxidation indices (vanillic acid to vanillin and syringic acid to syringaldehyde ratios) were significantly greater in the N+ sub-plots than in the control sub-plots, suggesting increased lignin decomposition due to fertilization. The estimation of C inputs to forest floor and δ 13 C analysis of soil C fractions indicate that the observed buildup of surface soil C concentrations in the N+ sub-plots can be attributed to increased inputs of C mass from forest debris. We conclude that long-term N additions in productive forests may increase C storage in both living tree biomass and soils despite elevated decomposition of soil organic matter.

ForCent model development and testing using the Enriched Background Isotope Study experiment

The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool 14C signature (Δ 14C) data from the Enriched Background Isotope Study 14C experiment (1999–2006) shows that the model correctly simulates the temporal dynamics of the 14C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass Δ 14C data, and with soil respiration Δ 14C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study 14C experimental treatments on soil respiration Δ 14C values for the different soil organic matter pools. Model results suggest that a two‐pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.

Vegetation, Soils, and Land Use in Calcareous Fens of Eastern New York and Adjacent Connecticut

Calcareous fens are wetlands fed by calcareous groundwater and with predominantly low (< 1 m) vegetation. They are critical habitat for rare species, and development of tall vegetation alters this habitat. Our purpose was to better understand how human activities influence the fen habitat. In 1997 in eastern New York and northwestern Connecticut we located 25 fens using soil maps and field surveys, and delimited these sites using 73 indicator plants classified a priori as fen species, disturbance species, or non-fen woody species. In three plots in each fen we measured species cover, water table depth, organic matter, total inorganic nitrogen, groundwater pH and conductivity, and described land use on and within 100 m of each fen to identify the conditions that may lead to fen degradation. Total inorganic nitrogen correlated most significantly with plant species composition. Fen-species richness was negatively correlated with nitrogen, whereas non-fen woody species richness and cover were positively correlated with nitrogen, suggesting that nitrogen inputs contribute to dominance of tall vegetation in fens. Richness of disturbance indicator species was negatively correlated with soil organic matter. Thus, fens with mineral soil layers may be more susceptible to dominance by non-fen species. Percent cover of disturbance indicator species was greater in fens near public roads. Cover of Lythrum salicaria, an invasive weed, was positively correlated with land-use intensity and was greater near public roads. The use of soil maps, indicator plant richness and cover, inorganic nitrogen, water table, and soil organic matter may be an efficient method for locating, delimiting, and assessing the ecological status of fens.

Determination of Organic and Inorganic Carbon in Forest Soil Samples by Mid-Infrared Spectroscopy and Partial Least Squares Regression

Analyses of organic and inorganic carbon are of great interest in the field of soil analyses. Soil samples from a national monitoring project were provided for this study, including more than 130 forest sites from Austria. We investigated the humus layers (if present undecomposed litter (L), of mixed samples of F- (intermediate decomposed organic matter) and H-(highly decomposed organic matter) (FH)) and upper mineral soil layers (0-5 and 5-10 cm) of the samples. Mid-infrared spectra were recorded and evaluated by their band areas; subsequently we calculated models with the partial least squares approach. This was done by correlating calculated data of the mid-infrared spectra with gas-volumetrically determined carbonate values and measurements of organic carbon from an elemental analyzer. For carbonate determination, this approach gave satisfying results. For measurements of organic carbon, it was necessary to discriminate into humus layers and mineral soils or even more groups to obtain satisfactory correlations between spectroscopically determined and conventionally measured values. These additional factors were the presence of carbonate, the forest type, and the dominant tree species. In mineral soils, fewer subdivisions were necessary to obtain useful results. In humus layers, groupings of sites with more similar characteristics had to be formed in order to obtain satisfying results. The conclusion is that the chemical background of soil organic matter leading to different proportions of functional groups, especially in the less humified organic matter of the humus layers, plays a key role in analyses with mid-infrared spectroscopy. Keeping this in mind, the present approach has a significant potential for the prediction of properties of forest soil layers, such as, e.g., carbonate and organic carbon contents.

Kinetic studies of proteolytic enzyme activity of arctic soils under varying toluene concentrations

Abstract The original focus of this study was an analysis of proteolytic enzyme activity of Alaskan arctic tundra soils, however initial results raised questions regarding the method ( Watanabe and Hayano, 1995 ). Thus, the goals of the study changed to 1) an investigation of the method, and 2) a comparison of enzyme activities of two different soil layers from the arctic tundra. Methodological examination included the impact of toluene, used to prevent immobilization of the product, and blank correction on enzyme activity, and a search for a true 6-h linear rate of activity during a 48-h incubation. We measured native and potential, using casein as an artificial substrate, activities as net amino acid production in mineral and organic soil layer samples. Varying toluene concentration had no clear effect on activity; omitting toluene resulted in zero native activity and reduced potential for the organic samples, but not for the mineral. Comparison of activities with and without blank correction indicated, particularly for potential activity of samples with low native rates, that correction was required for accuracy. Native and potential activity of the organic samples, and native of the mineral were linear during the first 6 h of incubation; linearity was found during the 6–24 h incubation for potential activity of the mineral. Soil layer activity data indicated that native activity was higher in organic soils as compared with mineral. The organic layer potential activity was ten-fold greater than the native, suggesting substrate limitation; potential and native activities did not differ in the mineral layer, indicating substrate sufficiency. Casein addition changed the kinetic pattern for both layers from hyperbolic to sigmoidal for the mineral and linear for the organic, implying different enzyme pools or behavioral changes of existing pools. Native activity based on total soluble protein was higher for the mineral samples relative to the organic, reiterating substrate capacity differences and variations in enzyme/substrate interactions.