Forest Floor Humus Research Articles

Volatiles from Eucalyptus Trunks and Forest Floor Humus Influence the Habitat Transfer, Host Selection, and Aggregation of Endoclita signifer Larvae

Endoclita signifer is a major wood-boring pest of eucalyptus trees in China, and its third instar larvae can accurately find and infest eucalyptus trees in mixed-species forests, although it can also feed on another 51 tree species in the same planted area. A total of 34 volatile compounds were identified from eucalyptus trunks, including non-infested and infested trunks with single or multiple (more than three) larval entrance cover packets, and forest floor humus. Of these, o-cymene showed a strong gas chromatography-electroantennographic detection (GC-EAD) activity and significant attraction of the third instar E. signifer larvae. Higher abundance of alpha-phellandrene, o-cymene, and the unique 2-phenyl-2-propanol in the volatile profile from infested eucalyptus trunks indicated that they were herbivore-induced plant volatiles (HIPVs). The larvae showed significantly higher attraction to volatile blends, especially those from infested eucalyptus trunks, than to single volatiles. A blend of the three HIPVs, α-pinene, D-limonene, and n-butyl ether may serve as an attractant for the control of E. signifer larvae in eucalyptus plantations. Further, exposure of third instar E. signifer larvae to some of these volatiles which also elicited electroantennogram and behavioral responses, influenced expressions of some olfactory proteins. Our results show that third instar E. signifer larvae can recognize o-cymene from host eucalyptus trunks and are attracted to the trunk by the three HIPVs when they shift their habitats from the forest floor humus to the tree trunks.

After the Storm: Fate and Leaching of Particulate Nitrogen (PN) in the Fluvial Network and the Influence of Watershed Sources and Moisture Conditions

Large storms can erode, transport, and deposit substantial amounts of particulate nitrogen (PN) in the fluvial network. The fate of this input and its consequence for water quality is poorly understood. This study investigated the transformation and leaching of PN using a 56-day incubation experiment with five PN sources: forest floor humus, upland mineral A horizon, stream bank, storm deposits, and stream bed. Experiments were subjected to two moisture regimes: continuously moist and dry–wet cycles. Sediment and porewater samples were collected through the incubation and analyzed for N and C species, as well as the quantification of nitrifying and denitrifying genes (amoA, nirS, nirK). C- and N-rich watershed sources experienced decomposition, mineralization, and nitrification and released large amounts of dissolved N, but the amount of N released varied depending on the PN source and moisture regime. Drying and rewetting stimulated nitrification and suppressed denitrification in most PN sources. Storm deposits released large amounts of porewater N regardless of the moisture conditions, indicating that they could readily act as N sources under a variety of conditions. The inputs, processing, and leaching of large, storm-driven PN inputs become increasingly important as the frequency and intensity of large storms is predicted to increase with global climate change.

The history of mercury pollution near the Spolana chlor-alkali plant (Neratovice, Czech Republic) as recorded by Scots pine tree rings and other bioindicators

We assessed >100years of mercury (Hg) pollution recorded in the tree rings of Scots Pine near a Czech chlor-alkali plant operating since 1941. Hg concentrations in tree rings increased with the launching of plant operations and decreased when Hg emissions decreased in 1975 due to an upgrade in production technology. Similar to traditional bioindicators of pollution such as pine needles, bark and forest floor humus, Hg concentrations in Scots Pine boles decreased with distance from the plant. Mean Hg in pine bole in the 1940s ranged from 32.5μg/kg Hg at a distance of 0.5km from the plant to 5.4μg/kg at a distance of >4.7km, where tree ring Hg was the same as at a reference site, and other bioindicators also suggest that the effect of the plant was no longer discernible. Tree ring Hg concentrations decreased by 8–29μg/kg since the 1940s at all study sites including the reference site. The lack of exact correspondence between changes at the plant and tree ring Hg indicated some smearing of the signal due to lateral translocation of Hg from sapwood to heartwood. Bole Hg concentrations reflected local and regional atmospheric Hg concentrations, and not Hg wet deposition.

Spatiotemporal Changes in Atmospheric Deposition Rates Across The Czech Republic Estimated in The Selected Biomonitoring Campaigns. Examples of Results Available For Landscape Ecology and Land Use Planning

Abstract Several large-scale and fine-scale biomonitoring surveys were carried out in the Czech Republic to estimate current and long-term accumulated atmospheric deposition rates using moss, spruce bark and forest floor humus as bioindicators since the end of 1980s. The results of the bioindicator analyses significantly correlated with available figures of deposition rates detected at the EMEP or Czech national measurement stations. The moss monitoring programmes revealed position of about 7 hot spots of high deposition loads of about 35-40 elements and indicated spatiotemporal decrease in the element deposition rates caused by restructuralization of industry, desulphurization of coal power plants and ceased distribution of leaded petrol. The deposition loads of toxic and risk elements have significantly decreased since the end of 1980s; however, increasing atmospheric deposition rates of reactive nitrogen has been bioindicated recently. The fine-scale moss monitoring campaigns, for example, delimited deposition zones around selected emission sources, revealed changes in deposition rates after introducing new technologies or delimited contaminated area in the surroundings of a chlor-alkali plant after a catastrophic flood episode. Deposition ranges of main pollution sources were mapped depicting the aerial distribution of stable lead isotopic ratios in moss, because the isotopic ratios are highly specific for each pollution source. Monitoring the spruce bark parameters enabled to recognise the distribution of acid rain, dust and sulphate deposition rates and their spatiotemporal changes across the country between 1987 and 2010. The bark investigations along altitudinal profiles showed diminishing effect of air pollution on spruce bark parameters with increasing elevation. This phenomenon can be explained by a decreasing capacity of reduced tree crowns to trap air pollutants in the mountain environment. The mapping of element content in forest floor humus revealed position of long-term spots of high accumulation of industrial pollutants and Chernobyl-derived 137Cs in forests. Knowledge of these hot spots is important for health and environmental protection mainly in the areas where most of the former emission sources were cancelled and the current low atmospheric deposition rates may make a false impression of the clean landscape. The data of the Czech national moss biomonitoring surveys were accepted and stored in the database of UN ECE ICP-Vegetation for checking of air pollution and its possible effects on vegetation in Europe.

A quarter century of biomonitoring atmospheric pollution in the Czech Republic.

The Czech Republic (CZ) had extremely high emissions and atmospheric deposition of pollutants in the second half of the 1980s. Since the beginning of the 1990s, moss, spruce bark and forest floor humus have been used as bioindicators of air quality. In the first half of the 1990s, seven larger areas were found to be affected by high atmospheric deposition loads. Six of these "hot spots" were caused by industrial pollution sources, mainly situated in coal basins in the NW and NE part of the country, and one large area in the SE was affected by increased deposition loads of eroded soil particles. After restructuring of industry in CZ, these hot spots were substantially reduced or even disappeared between 1995 and 2000. Since 2000, only two larger areas with slightly increased levels of industrial pollutant deposition and a larger area affected by soil dust have repeatedly been identified by biomonitoring. The distribution of lead isotope ratios in moss showed the main deposition zones around important emission sources. Very high SO2 emissions led to extreme acidity of spruce bark extracts (pH of about 2.3) at the end of the 1980s. The rate of increasing bark pH was strikingly similar to the rate of recovery of acid wet deposition measured at forest stations in CZ. By about 2005, when the median pH value in bark increased to about 3.2, the re-colonisation of trees by several epiphyte lichen species was observed throughout CZ. An increase in the accumulation of Chernobyl-derived 137Cs in bark was detected at about ten sites affected by precipitation during the time when radioactive plumes crossed CZ (1986). Accumulated deposition loads in forest floor humus corresponded to the position of the moss and bark hot spots.

The impact of juvenile tree species canopy on properties of new forest floor

To keep forest soils fertile, forest practitioners plant mixed stands that are composed of both economically efficient trees such as conifers and soil-improving broadleaves. This is a mandated practice in the Czech Republic. As the new forest grows, it creates a dense canopy. The canopy is a principal source of organic matter to the forest soil. The formation of new forest humus is particularly important in first-generation forests on the former agricultural soil. Former meadow is a suitable site for forest floor and soil investigation since forest-floor humus covering the surface of the soil is a completely new layer.  Both pure evergreen conifer and mixed treatments were planted in 2001. The experimental plot was established in order to investigate performance of tree species and restoration of forest-site conditions. We sampled dead-plant material and 0–10 cm topsoil to investigate their properties under the 10-year-old stands. We compared the treatments by descriptive statistics using both univariate and multivariate techniques. Dry mass (medians of weight) varied among the treatments from 11 to 19 Mg·ha<sup>–1</sup>. The forest floor nutrient concentrations appeared to be dependent on the presence of admixed deciduous tree species (sycamore maple, small-leaved linden and European larch) as these forest floors (EL1, EL2, NS3, SM) were higher in base cations and phosphorus compared to pure spruce (NS1, NS2) and pure Douglas fir (DF) treatments. The first axis of PCA ordination plot revealed 45% of total variability and showed a clear distinction between evergreen coniferous and mixed species treatments. Young plantations produced forest floors of different quality; however it was not reflected in the topsoil properties.  

Effect of stand density and humus removal on regeneration of Pinus densiflora seedlings in a mixed conifer and broad-leaved forest

We studied the impact of stand density and forest floor humus removal on regeneration of Pinus densiflora in a mixed conifer and broad-leaved forest on the Daimonji-Yama Mountain, Kyoto, Japan. Three levels of stand density were set, i.e., a clear-cut site, a heavily thinned site and a lightly thinned site. In each density treatment, comparisons were carried out between humus removal (A0-free) and humus intact (A0-intact) subplots. We counted the emergence of sown pine seeds and measured survival and growth of pine seedlings over the next four years. In addition, light conditions and the recovery of understory were monitored. Results show that thinning intensity and humus removal promoted the establishment and growth of seedlings. One exception, however, was that seedling growth was minimal in the heavily thinned A0-intact subplots. This was due to a strong response of understory vegetation growth on the treatment combination, which hindered the pine seedling growth. Furthermore, we found that the canopy openness measured at 1.3-m height remained at least 35% for the heavily thinned site in 2008. The results suggest that the removal of the A0 layer after heavy thinning is the most effective and labor-saving operation for P. densiflora regeneration.

Spatial distribution of lead and lead isotopes in soil B-horizon, forest-floor humus, grass (Avenella flexuosa) and spruce (Picea abies) needles across the Czech Republic

Abstract Lead concentrations were determined in samples of soil B-horizon ( N = 258), forest-floor humus (O-horizon, N = 259), grass ( Avenella flexuosa , N = 251) and spruce ( Picea abies , N = 253) needles (2nd year) collected at the same locations evenly spread over the territory of the Czech Republic at an average density of 1 site/300 km 2 . Median Pb concentrations differ widely in the four materials: soil B-horizon: 27 mg/kg (3.3–220 mg/kg), humus: 78 mg/kg (19–1863 mg/kg), grass: 0.37 mg/kg (0.08–8 mg/kg) and spruce needles: 0.23 mg/kg (0.07–3 mg/kg). In the Pb distribution maps for humus, grass and spruce a number of well-known Pb-contamination sources are indicated by unusually high concentrations (e.g., the Pb smelter at Pribram, the metallurgical industry in the NE of the Czech Republic and along the Polish border, as well as the metallurgical industry in Upper Silesia and Europe’s largest coal-fired power plant at Bogatynia, Poland). The ratio 206 Pb/ 207 Pb was determined in all four materials. The median value of the 206 Pb/ 207 Pb isotope ratio in the soil B-horizon is 1.184 (variation: 1.145–1.337). In both humus and grass the median value for the 206 Pb/ 207 Pb isotope ratio is 1.162 (variation: 1.130–1.182), in spruce needles the median ratio is 1.159 (variation: 1.116–1.186). In humus, grass and spruce needles the known contamination sources are all marked by higher 206 Pb/ 207 Pb isotope ratios in the maps. Furthermore, the soil B-horizon, humus, grass and spruce needles show distinctly different spatial distribution patterns of the 206 Pb/ 207 Pb isotope ratios. The B-horizon does not provide a viable background value for metal concentrations in the O-horizon or plant materials. None of the maps provides evidence for the importance of traffic-related emissions for the observed isotope ratios at the scale of the Czech Republic.

Linking chemical elements in forest floor humus (O h-horizon) in the Czech Republic to contamination sources

While terrestrial moss and other plants are frequently used for environmental mapping and monitoring projects, data on the regional geochemistry of humus are scarce. Humus, however, has a much larger life span than any plant material. It can be seen as the “environmental memory” of an area for at least the last 60–100 years. Here concentrations of 39 elements determined by ICP-MS and ICP AES, pH and ash content are presented for 259 samples of forest floor humus collected at an average sample density of 1 site/300 km 2 in the Czech Republic. The scale of anomalies linked to known contamination sources (e.g., lignite mining and burning, metallurgical industry, coal fired power plants, metal smelters) is documented and discussed versus natural processes influencing humus quality. Most maps indicate a local impact from individual contamination sources: often more detailed sampling than used here would be needed to differentiate between likely sources.

Production and humus form development in forest stands established on agricultural lands - Kostelec nad Černými lesy region

The afforestation of agricultural lands was carried out under different site and ecological conditions, including lower and medium elevated localities. The present study documents the rapidity of accumulation of surface layers and their characteristics in stands of Scots pine (<I>Pinus sylvestris</I>), Norway spruce (<I>Picea abies</I>), birch (<I>Betula verrucosa</I>) and Douglas fir (<I>Pseudotsuga menziesii</I>) in the territory of the Training Forest Enterprise in Kostelec nad Černými lesy, at the altitude 430 m a.s.l., on the site of nutrient-poor gleyed soils. The plots were compared with the neighbouring continuously forested site covered with old pine-spruce stand and with near-situated arable field. During the first roughly 40 years, considerable changes were documented on the afforested plots. Forest-floor humus layers in the coniferous stands have already been formed, the humus forms being more favourable compared with the old forest site. Acidification and loss of nutrients run in the upper mineral horizons. These processes were also responsible for the less favourable character of the forest soil in the old stand. Birch showed minor shifts of soil properties in the mineral horizon compared to the conifers; the surface humus accumulation was not observed there yet. The lowest degradation among conifers was shown in Douglas fir, intensively taking up deficient nutrients on the other hand.

Comparison of the impact of blue spruce and reed Calamagrostis villosa on forest soil chemical properties

The impact of blue spruce (<I>Picea pungens</I>) and reed <I>Calamagrostis villosa</I>) cover on quantity and quality of upper soil layers was investigated. The research was conducted in the Jizerské hory Mts., Czech Republic (altitude 880 m, acidic spruce forest site type – 8K). Mean weight of dry matter of holorganic horizons was similar under both variants. Totally, there were accumulated 153 t/ha of dry matter of humus horizons in blue spruce and 174 t/ha in reed. Soil pH (KCl) varied from 3.7 to 3.2 under blue spruce stand and from 3.6 to 3.3 under reed. The differences of concentrations of nutrients (P, K, Ca, Mg) were not found significant either. Only L horizon showed significant differences: there were higher values of cation exchangeable capacity (T) and higher content of exchangeable bases (S) under reed. We found very similar forest-floor humus properties under both species. Therefore we can not state worsening of the soil conditions under blue spruce compared to areas covered with tested forest weed species.

Mercury distribution around the Spolana chlor-alkali plant (central Bohemia, Czech Republic) after a catastrophic flood, as revealed by bioindicators

The current mercury concentrations in moss Hypnum cupressiforme, in forest floor humus and in oak and pine bark were determined in a 10-km radius around a chlor-alkali plant affected by a flood in 2002. Similar distribution patterns of Hg had accumulated in four bio-indicators, irrespective of different Hg concentrations in the analysed biological matrices. No accumulation of extremely Hg-contaminated materials was found in the flooded parts. The bio-indicators, used alone or in combination, can be recommended for effective and reliable determination of Hg contamination levels around Hg sources.

Exceedance of critical loads of nitrogen and sulphur and its relation to forest conditions

The calculation of critical loads and their exceedance is one method to describe the vulnerability of forests to environmental stress caused by anthropogenic impact. Exceedance of critical loads for acidifying inputs and nitrogen was compared to different indicators of the soil and forest conditions in the German part of the extensive forest monitoring (ICP Forests/EU Level I), including more than 1,800 plots. In addition, an empirical relationship between the C/N ratio of the forest floor humus layer (C/NHumus) and the estimated nitrogen output for ten plots of the intensive monitoring (ICP Forests/EU Level II) was established in order to estimate the potential nitrogen output on Level I plots dominated by Norway spruce. Regarding all tree species assessed, the exceedance of critical loads for nitrogen and sulphur is negatively correlated with pH and base saturation up to 30 cm soil depth. The sulphur deposition and the exceedance of critical loads are highly correlated with the sulphur content of leaves and needles, whereas the respective relations for nitrogen were lower. The crown condition was weakly positively related to the sulphur content in tree leaves and needles. For Norway spruce sites, high exceedance of critical loads for nitrogen and nitrogen deposition corresponded well with low C/NHumus. In regions with high nitrogen load and low C/N ratios in the humus layer, the calculated nitrogen output was high. The results support the concept of critical thresholds in that way that their exceedance can impair forest ecosystem functions like nitrogen retention.

Effects of fire severity and initial tree composition on understorey vegetation dynamics in a boreal landscape inferred from chronosequence and paleoecological data

AbstractQuestion and Location:How does soil burn severity and early post‐fire tree composition affect long‐term understorey vegetation dynamics in the coniferous forests of eastern Canada?Method:Vegetation dynamics were assessed using paleoecological methods and a chronosequence analysis of extant stands. The relation between environmental factors and succession was evaluated using ordination techniques on the chronosequence data. Understorey succession was studied by regression analysis on the chronosequence data and through within‐site Markovian transition probabilities between successive 1‐cm layers of plant macroremains from soil organic matter profiles.Results:Initial tree composition (Picea mariana and Pinus banksiana) had little effect on understorey composition. Soil burn severity (measured as the thickness of the residual forest floor humus) significantly affected temporal changes in understorey species. Following fires of high severity, stands underwent a gradual paludification with a net increase in Sphagnum and ericaceous shrubs (Ledum groenlandicum), and a decrease in feathermosses. Paludification was accelerated after low severity fires, which led to the dominance of Sphagnum less than 200 years after fire, and of L. groenlandicum shortly after fire. In situ paleo‐ecological work confirmed results obtained with the chronosequence analysis.Conclusions:One vegetation gradient related to time after disturbance is insufficient to account for the full complexity of long‐term changes in understorey composition following fire. Current forestry practices that protect the forest floor humus may induce a premature paludification.

Effects of fire severity and initial tree composition on understorey vegetation dynamics in a boreal landscape inferred from chronosequence and paleoecological data

Question and Location: How does soil burn severity and early post-fire tree composition affect long-term understorey vegetation dynamics in the coniferous forests of eastern Canada? Method: Vegetation dynamics were assessed using paleoecological methods and a chronosequence analysis of extant stands. The relation between environmental factors and succession was evaluated using ordination techniques on the chronosequence data. Understorey succession was studied by regression analysis on the chronosequence data and through within-site Markovian transition probabilities between successive 1-cm layers of plant macroremains from soil organic matter profiles. Results: Initial tree composition (Picea mariana and Pinus banksiana) had little effect on understorey composition. Soil burn severity (measured as the thickness of the residual forest floor humus) significantly affected temporal changes in understorey species. Following fires of high severity, stands underwent a gradual paludification with a net increase in Sphagnum and ericaceous shrubs (Ledum groenlandicum), and a decrease in feathermosses. Paludification was accelerated after low severity fires, which led to the dominance of Sphagnum less than 200 years after fire, and of L. groenlandicum shortly after fire. In situ paleo-ecological work confirmed results obtained with the chronosequence analysis. Conclusions: One vegetation gradient related to time after disturbance is insufficient to account for the full complexity of long-term changes in understorey composition following fire. Current forestry practices that protect the forest floor humus may induce a premature paludification.

Distribution of 36 Element Deposition Rates in a Historic Mining and Smelting Area as Determined Through Fine-Scale Biomonitoring Techniques. Part II: Relative Long-Term Accumulated Atmospheric Deposition Levels

The content of 36 elements in the H horizon of coniferous forest floor humus was determined for 56 sampling plots situated in linear transects running out radially to a distance of 14 km from a lead smelter. Fine-scale contour maps of element content in humus revealed five types of basic patterns for the positions of hot spots. Using PCA and contour maps the following four dominant pollution sources were identified that had influenced the accumulation of some elements in humus in the area (615 km2): operation of a lead smelter (Ag, Bi, Cd, Cu, Fe, Hg, In, Pb, S, Sb, Zn), gravel production from stones from uranium pit heaps (Al, Be, Co, Cr, Ga, Mn, Sc, Se, Th, U, V), operation of works processing heat resistant steel (Mo) and anthropogenic or local geogenic factors (Ce, Co, La, Nd, Pr, Y). Except in the case of Pb, Cd, Zn, (As, Hg), high current and long-term accumulated loads of the other elements named above have not previously been indicated in the literature for this area. In addition, no patterns of accumulated elements in humus in details of registers and allotments are known for this area. The interpolated hot spot area for heavy forest humus contamination was found to be 5–80 km2, however, U, Cd and Pb were highly accumulated in humus at 100, 320 and more than 630 km2, respectively. At a distance of 200 m and 22 km windward and 600 m and 22 km leeward from the lead smelter, the Pb content in the forest floor humus was 78 500 and 131 μg g-1 windward and 81 050 and 175 μg g-1 leeward, respectively. The normal Pb content in forest floor humus is less than 100 μg g-1 in the Czech Republic. Also patterns of accumulated elements in humus in details of registers and allotments have not been known for the area up to now. The distributions of the long-term accumulated elements in humus related to the distance from the source could be described nearly perfectly by exponential equations, while elevation, topography, leeward/windward exposure, and the geology of the sampling plots have not significantly influenced accumulation ofmost elements. Results of the forest floor humus analysis were fully supported by the parallel moss monitoring results. Humus monitoringtechniques can reliably determine the long-term effects of pollutionsources and reveal the hidden accumulated loads of elements in details in the landscape.

A contribution to the effect of liming on forest soils: review of literature

Extensive forest areas were ameliorated by large-scale liming in the last years in order to prevent proceeding acidification and degradation of forest soils. The hitherto knowledge of liming effects on the function of forest soils still appears insufficient for an unambiguous evaluation. Sorption properties of soils and acidity are favourably affected by liming and the favourable effect is usually manifested in the layer of forest floor humus and in mineral soil within ten years. Reduction of soil acidity stimulates development of a bacterial component of microflora, soil edaphon, and good prerequisites are formed for a release of nutrients from soil organic matter. Improvement of some physical parameters of soils and negative effect of liming on the depth of rooting in spruce, availability of nutrients at some sites and in connection with mechanical soil preparation were also described. A key point of liming effect on forest soils is nitrogen dynamics. Mineralization of nitrogen is stimulated at nitrogen-rich sites with C/N < 30. Nitrogen-limited sites show nitrogen mineralization inhibited by liming with signs of pronounced deficiency in spruce nutrition. A positive effect of liming on nutrition with bases is generally accompanied by an adverse influence on N dynamics in acidic soils under spruce monocultures. Therefore it is possible to state that liming induces relatively marked changes in the soil but the actual growth response of woody species cannot be derived only from these changes.

Effects of past fly ash deposition on the forest floor humus chemistry of pine stands in Northeastern Germany

Humus morphology and chemical characteristics of forest soils subjected to long-term deposition of alkaline and acid air pollutants were studied in pine forests on sandy substrates in Northeastern Germany. High emission rates of fly ash in the past caused an accumulation of mineral particles and ferromagnetic fly ash constituents in the organic layer. Mass and total ash content of organic horizons and magnetic susceptibility measurements suggested that fly ash was mainly accumulated in the F and H horizons of the forest soil. Total mass of organic layers at sites with heavy deposition loads were as high as 132 t ha −1. The F and H horizons of fly ash affected forest soils showed mineral contents of up to 59 and 79%, respectively. By measurements of magnetic susceptibility, it was shown that magnetic fly ash particles were found in the fine fractions (125–63 and <63 μm). Fly ash deposition significantly increased the pH values in the L, F and H horizon and mineral topsoil (0–10 cm). Lower pH values in the L layer compared to F and H horizons indicated a re-acidification of these forest soils due to reduced depositions of alkaline ash. Significantly higher concentrations of NH 4Cl extractable cations (i.e. ‘effective cation exchange capacities’) and ‘base saturations (BS)’ of >90% were found in the humic horizons at sites where pH was increased due to high fly ash emissions. Stocks of basic cations were dominated by Ca 2+ and decreased significantly along the fly ash deposition gradient from 46.33 to 6.91 kmol IE ha −1. Proportions of water extractable cations on NH 4Cl extractable cations increased in the forest soil with decreasing deposition loads. Particularly monovalent cations (i.e. K and Na) are more mobile in fly ash influenced soils than bivalent cations (i.e. Ca, Mg). Stocks on organic C and total N decreased along the deposition gradient from 26.7 to 17.5 t C ha −1 and from 1.257 to 0.792 t N ha −1. In contrast, C/N ratios of the organic horizons increased from about 20 to 22 for F and H horizons. Measurements of hot water and cold water extractable organic C suggest that the availability of soil organic matter is reduced in soils with high historical fly ash loads.

Near-surface soil characteristics and understory plants as predictors of Pinus contorta site index in southwestern Alberta, Canada

The physical and chemical properties of forest floor humus (inclusive of L–F–H horizons) and the uppermost 10 cm of the mineral soil zone (i.e. the primary nutrient absorption zone), and understory plant species abundance were compiled for 42 native Pinus contorta Doug. ex Loud. var. latifolia Engelm. ex S. Watson (lodgepole pine) stands located on mesic till sites in the Lower Boreal–Cordilleran ecoregion of southwestern Alberta. Stand ages ranged from 78 to 146 years. These fire-origin stands were stratified into three site index (SI 50) classes, which represented a productivity gradient in terms of height growth. Extractable Ca and bulk density of humus, extractable Ca in the mineral soil and pH, Bm horizon thickness, and sand content were positively associated with increasing SI 50; while humus and Ae horizon thickness, silt, Fe and Al content of the mineral soil were negatively related. Differences occurred in nutrient regime classes and humus form frequencies among the SI 50 classes. About 60 regression equations ( P<0.05) based on one or two independent variables were developed to predict P. contorta SI 50. The amount of explained variance among these equations differed by the type of variable: soil physical (maximum r 2 of 22%) < soil chemical (29%) < plant species (45%) < plant growth-forms (63%) ≈ humus form (67%) variables. Standard errors of the estimate for the 12 best regression equations ranged from 1.6 to 2.4 m, with coefficients of variation ranging from 7 to 10%. Most of the better regression models were based on understory plant growth-forms. Greater abundances of deciduous shrubs, forbs, and pteridophytes were associated with sites that had better tree height growth, while ericaceous species, bryophytes, and lichens were common on poorer sites.

Distribution of Sulphur and Heavy Metals in Forest Floor Humus of the Czech Republic

Forest humus, which has a large cation binding capacity (up to 550 meq/100 g), and provides relatively very stable bindings with elements and their compounds, can effectively adsorb elements from atmospheric deposition and retain them overa long period. In order to test the monitoring potential of usingforest humus to retain the recent and long-term accumulated loadsof 14 elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, S, V,and Zn), samples of coniferous forest floor humus (H or Oh horizon) were collected over an area of 78 864 km2 using a 20 × 20 km scale grid of sampling points overlaid on theentire territory of the Czech Republic (CZ). Data from 192 pointsand the distribution of the concentrations of individual elementsin forest floor humus are presented here. The extent of relatively very high loading covers 18% of CZ and includes thefollowing four hot spots: an area in the western part of centralBohemia, northwestern Bohemia in the lignite coal mining area, the cross-border area in the Sudeten mountains in northern Bohemia, and the black coal mining area and industrial centre innorthern Moravia. Relatively high, moderate and low loads of theelements were observed in 42, 30, and 28%, respectively, of CZ.Coniferous forest floor humus is evenly spread in the Central European territory and has proved to be a suitable and sensitiveindicator of long-term relative atmospheric deposition loads.