Undisturbed Forest Soils Research Articles

Hydraulic properties for a wide range of undisturbed and compacted French forest soils: in situ measurements and estimation with the BEST method

Key messageThe dataset provides hydraulic properties estimated using the Beerkan Estimation of Soil Transfer (BEST) method, on undisturbed and on compacted and rutted French forest soils. It allows a reliable assessment of the effect of traffic on soil permeability. However, hydraulic properties could not be estimated on extremely rutted soils, underscoring the necessity for tailored protocols for these conditions.

Short‐term survival and growth of 32 native boreal plants on treated oil sands tailings

AbstractThe consolidation of oil sands tailings is a cost‐ and time‐consuming process that requires treatment via active (e.g., centrifugation) and passive (e.g., self‐weight consolidation) methods. The use of plants to dewater tailings is a promising concept and has previously been evaluated using agronomic grass species in greenhouse studies. This greenhouse study evaluated the short‐term survivorship and growth of 32 upland and lowland native plant species (12 forbs, 14 graminoids, and six woody plants) in centrifuged tailings and benchmarked their performance against reclamation soil and undisturbed forest soil. All plant species were propagated from seed and transplanted as seedlings into containers filled with one of the three substrates. After 42 days, the height (woody species only) and total aboveground biomass were determined for all living plants. As expected, the mortality of seedlings in tailings was higher than plants grown in the other two substrates. Graminoid species, regardless of species community type (wetland or upland), had higher survival probabilities and growth compared to forb or woody species across all substrates. Of forbs and woody species evaluated, Geum aleppicum and Populus tremuloides showed the most promise amongst the upland species, and Rumex occidentalis was the wetland equivalent.

Application of Soil Multiparametric Indices to Assess Impacts of Grazing in Mediterranean Forests

In this study, the effects of different stocking rates were quantified in three study areas in a Mediterranean forest (Cuenca, Spain) by applying a multiparametric soil quality index (SQI) developed from undisturbed forest soils (>40 years). The main objective was to advance the development and application of multiparametric indices that allow for soil condition assessment. To fulfill this objective, the effectiveness of the developed multiparametric soil quality index (SQI) was analyzed as an indicator of livestock impacts on soil in the Mediterranean forest. The control areas without livestock activity were forest stands of different ages (a thicket forest stand of <30 years; a high-polewood forest stand of 30–60 years; and an old-growth forest stand of >60 years), which were compared with areas subjected to various grazing intensities (areas with permanent livestock passage: a sheepfold that had been inactive for 2–3 years and an active sheepfold; areas with intermittent livestock passage: a bare-soil area, a pine stand and a scrubland). The applied multiparametric soil quality index (SQI) was sensitive to changes in forest ecosystems depending on the stocking rates. However, to obtain greater precision in the assessment of the effects of stocking rates, the multiparametric index was recalibrated to create a new index, the Soil Status Index by Livestock (SSIL). The correlation between the quality ranges obtained with both indices in different study areas suggests that the SSIL can be considered a livestock impact reference indicator in Mediterranean forest soils.

The impact of reclamation and vegetation removal on compositional and functional attributes of soil microbial communities in the Athabasca Oil Sands Region

Large-scale mining for oil extraction in the boreal forests of Northern Alberta has led to a disturbance footprint of ~900 km2 of land; which must be reclaimed to equivalent land capabilities. Microorganisms are sensitive to anthropogenic disturbances and play an essential role in the cycling of soil nutrients and plant growth, making them potential indicators of ecosystem function. Thus, the objective of this work was to determine the impact of land reclamation on the composition and function of soil microbial communities in the Athabasca Oil Sands Region (AOSR). We evaluated bacterial community composition via high throughput sequencing of 16S rRNA genes and soil functional diversity by community-level physiological profiling (CLPP). The ranges of variability for these factors observed in soils reclaimed with either peat-mineral mix (PMM), forest floor-mineral mix (FFM), or FFM diluted with sand (Sand-FFM), were compared to that of undisturbed reference soils (NS) and a vegetation removed soil (VR). Differences between reclamation soils and natural soils were clearly discernible, with reclamation imposing a more drastic disturbance to the boreal forest than that of removal of vegetation alone. VR changed the structure of the soil microbial community and increased the overall diversity, within-community interactions, and heterogeneity; while reclamation shifted the microbial community structure to an even greater extent, placing it outside the range of natural variability. Among reclamation substrates, FFM showed the highest level of similarity to the range of natural variability and PMM showed the least. Altogether, our findings underscore the profound impact of anthropogenic activities associated with large-scale mining on soil biological activity, microbial communities, and edaphic profiles. These alterations are of such magnitude that they render the affected soils significant divergent from the reference undisturbed boreal forest soil.

Application of a Soil Quality Index to a Mediterranean Mountain with Post-Fire Treatments

In Mediterranean areas, fire has increased soil degradation and erosion. For this reason, the application of soil quality indices can help to determine soil recovery and degradation levels. By using a multiparameter soil quality index fitted to undisturbed forest soils, we can show the right information on soil functionality. In this study, the objectives were to evaluate soil functionality after suffering a fire, to subsequently treat with various soil treatments (wood mulching), and then check a soil quality index (SQI) to assess the soil quality recovery in burned Pinus nigra stands. For this purpose, a burned area was selected in the Cuenca Mountain range (Spain) under a Mediterranean climate. Experimental plots were established in the study area, with three slope gradients and applying three methods of covering soil using: (1) wood chips; (2) piles of branches; and (3) trunks of contour-felled logs. The experiment was conducted for 4 years. Results showed that the properties of soil were enhanced under wood chips and logs as a surface-covering material, and in a short time (less of 3 years). In consequence, the values of the SQI index were higher after applying these two treatments, thus reflecting the effectiveness of the SQI for monitoring post-fire recovery.

Morpho-molecular characterization of Clonostachys rosea and deciphering its biomolecules untangles the anti-fungal action against Fusarium oxysporum f.sp. lycopersici

Clonostachys rosea, a promising mycoparasite, has great biological control abilities against a variety of fungal plant diseases, insects and nematode pests. In the present study, three isolates of Clonostachys rosea were isolated from carrot, undisturbed forest and black gram rhizosphere soils respectively, out of 50 soil samples taken from different field and horticultural crops. Out of 15 onion plant samples from various locations, one isolate of C. rosea was isolated from root samples of onion. Two isolates of C. rosea from mycoparasitized sclerotia on cabbage head rot infected sample and naturally deceased whitefly in cotton was isolated respectively. They were morphologically and molecularly confirmed as C. rosea based on the fungal taxonomical keys and PCR amplification with ITS, translation elongation factor 1 alpha (TEF-1α), species specific primer sets respectively. The antagonistic ability of C. rosea against Fusarium oxysporum f.sp. lycopersici (Fol) has been shown using confrontation assay. Molecular docking of biomolecules of C. rosea using AutoDock vina module in PyRx 0.8 software reported dl-Glyceraldehyde dimer and 2(3H)-Furanone, dihydro-4-hydroxy as best hits with highest binding energy in the range of – 7.1 to −5.6 kcal/mol against target protein Global transcription regulator sge1 (SIX Gene Expression 1) of Fol. We also observed comparatively less binding energy for commercially available fungicide on docking against the target protein of Fol.

Loss of soil carbon and nitrogen indicates climate change-induced alterations in a temperate forest ecosystem

Climate warming is expected to influence terrestrial biogeochemical cycles by modifying the quality and quantity of plant litter input to soils. Although a growing number of studies recognize the importance of plant litter input in influencing the loss of soil organic matter (SOM) through a phenomenon called the priming effect (PE), the exact mechanisms behind PE are not well known. Importantly, most PE research is based on short term pot experiments in which fresh organic matter (FOM) input is represented by a single addition of compounds of unnaturally simple chemical composition. Furthermore, only a few studies exist in which the PE was explored in terms of organic C (SOC) and total N content in the soil. Here, we report results of a 3-year long litter manipulation study conducted under natural conditions in a broadleaved Korean pine forest in N-E China. We show that the extra supply (twice the normal input) of aboveground tree litter composing of conifer needles, leaves and small twigs was associated not only with slightly decreased SOC (by 5%) but especially that of soil total N (STN) (by 15%) content in the top soil (0–5 cm depth). In contrast, removal of litter resulted in an increased (ca. 15%) amount of both SOC and STN during the study when compared to control soils receiving natural litter input. Despite the enhanced leaf litter decomposition rate in the treatment receiving extra litter, the changes in SOC and STN were related neither to soil microbial biomass nor to community composition. The amount of N lost (40.0 g m−2) in the soil due to litter addition was ca. three times the amount of N added (12.3 g m−2) via the litter, while the amount of C lost (238 g m−2) was about one third of that added (940 g m−2), suggesting that soil N in our research site is more prone to the PE than soil C. As we did not manipulate belowground FOM input, our results suggest that input of aboveground litter rather than that by roots explained the PE in our study. Results of our long-term study conducted under natural conditions in undisturbed forest soils highlight the large potential of recalcitrant, aboveground litter to affect the PE, which should not go unnoticed when predicting the role of forest soils under conditions (such as climate warming) when these soils act as C sinks.

A Simple Method to Assess Key Soil Hydraulic Properties

We devised a simple infiltrometer to easily assess soil infiltration capacity and key soil hydraulic properties considering the impact of soil structure on soil infiltration. We conducted two series of five in situ infiltration experiments each on undisturbed forest and grassland soil of contrasting bulk densities and saturated hydraulic conductivity (Ks), and one on six soil columns with mineral soil and various textures without structure. Finally, we measured Ks, saturated water content and the van Genuchten parameters of these soils. Based on the obtained results, we found the best correlations to be exponential correlations between clay content and infiltrated water volume on the one hand and between clay content and the hydraulic properties on the other hand in all cases. Considering the infiltrated volume obtained by the infiltrometer and the measured soil parameters in mineral soil columns as references, we hypothesized that any change in hydraulic parameters of the natural soil is proportional to the change in infiltration volume. Thus, a second term accounting for water volume changes was therefore included in the correlation equations. The first validations of Ks values in forest soil showed good agreement with the laboratory measurements. Further investigations are needed to extend our validation to other soils with various textures.

Pioneer biocrust communities prevent soil erosion in temperate forests after disturbances

Abstract. Soil erosion continues to be one of the most serious environmental problems of our time and is exacerbated by progressive climate change. Until now, forests have been considered an ideal erosion control. However, even minor disturbances of the forest floor, for example, from heavy vehicles used for timber harvesting, can cause substantial sediment transport. An important countermeasure is the quick restoration of the uncovered soil surface by vegetation. To date, very little attention has been paid to the development of nonvascular plants, such as bryophytes, in disturbed areas of temperate forests and their impact on soil erosion. This study examined the natural succession of pioneer vegetation in skid trails on four soil substrates in a central European temperate forest and investigated their influence on soil erosion. For this purpose, rainfall simulations were conducted on small-scale runoff plots, and vegetation was continuously surveyed during the same period, primarily to map the development of bryophytes and the occurrence of biological soil crusts (biocrusts). Biocrusts appeared immediately after disturbance, consisting primarily of bryophyte protonemata and cyanobacteria as well as coccoid and filamentous algae that lost their biocrust characteristics as succession progressed. They were present from April to July 2019, with a particular expression in the skid trail that was on shale clay (Psilonotenton Formation) and silty clay loam substrate. In general, skid trails on clayey substrates showed considerably higher bryophyte cover and species richness. Although bryophytes were subsequently overtopped by vascular plants, they managed to coexist until their growth was restricted due to leaf litter fall. Brachythecium rutabulum and Oxyrrhynchium hians were the most important and persistent pioneer bryophyte species, while Dicranella schreberiana and Pohlia lutescens were volatile and quickly disappeared after spreading in the summer. Sediment discharge was 22 times higher on disturbed bare soil compared with undisturbed forest soil and showed the largest sediment removal in the wheel tracks. Counteracting this, soil erosion decreased with the recovery of surface vegetation and was particularly reduced with growing pioneer biocrusts in summer, but it again increased in winter, when vascular vegetation became dominant. This leads to the conclusion that the role of bryophyte-dominated biocrusts in forests has been underestimated so far, and they can contribute more to soil conservation at specific times of succession than vascular plants.

Post-harvest recovery of soil methane oxidation on skid trails and landings in a managed northern hardwood forest

Skid trails and landings are features within managed forest landscapes where soils are moderately to extremely disturbed by forestry vehicles. They have been found to exhibit reduced methane (CH4) oxidation or CH4 emissions six months to a year after a harvest has ended, but little is known about when these changes begin to occur (either during or after harvests) or how they recover over a longer timeframe. We took periodic measurements of soil CH4 flux from skid trails and landings during a harvest, and also quantified CH4 flux rates from sites that had been harvested up to 15 years prior to form a replicated chronosequence of soil recovery. In the thirteen-week period of active harvesting soil CH4 oxidation steadily declined, with small emissions occurring by the end of the measurement period. The chronosequence measurements revealed high rates of CH4 emissions the first year after harvest followed by a decrease in the following years. Emissions were particularly strong from landings and skid trails that had experienced high amounts of traffic and were located on lower slopes. By the end of the 15-year chronosequence landing and skid trail soils had returned to acting as CH4 sinks; however, the rates of oxidation remained lower than undisturbed forest soils. Further, integration of models created to predict CH4 flux over time indicates that CH4 flux from these soils are unlikely to reach a full recovery within a 20-year period - the average length of time of a harvest cycle in this region. On landings the change from emissions back to oxidation was correlated with soil temperatures, which decreased over time. On some skid trails CH4 flux was correlated with soil moisture content, which initially increased from buried wood’s increased water holding capacity and then decreased over time. The results suggest that remediation measures ought to be implemented immediately after harvest to avoid the high emissions that occur in the following few years and should prioritize the removal or prevention of incorporation of wood fragments.

Effects of Elemental Sulfur on Soil pH and Growth of Saskatoon Berry (Amelanchier alnifolia) and Beaked Hazelnut (Corylus cornuta) Seedlings

The land disturbed by open-pit oil sands mining must be restored to support the survival and growth of native boreal plants. Because tailings sand and sodic shale overburden are commonly used as an underlying parent substrate that is capped by boreal forest cover soils, the soil pH in reclamation sites is often higher compared with undisturbed boreal forest soil. Sulfur is a major byproduct of oil sands refining and could potentially be used as an amendment to lower the soil pH on reclamation sites. In this study, we examined the effects of soil pH and elemental sulfur on growth and physiological responses in Saskatoon berry and beaked hazelnut seedlings. We found that elemental sulfur was effective in lowering soil pH. However, addition of elemental sulfur to a forest soil of pH 5.7 lowered the soil pH to around 3, which impaired the growth and physiological performance of both plant species. The addition of 5 and 25 g kg−1 elemental sulfur to the pH 8.5 soil did not substantially improve the examined growth and physiological parameters in Saskatoon berry and beaked hazelnut seedlings. Further, excess addition of elemental sulfur in high pH soil could reduce the uptake of nitrogen, phosphorus, and calcium in Saskatoon berry. The results demonstrate that the amount of sulfur applied to the soil would need to be carefully determined for different soil types and pH levels to avoid potential toxicity effects.

Substratum-dependent moss microhabitat types alter soil nematode community structure in the mixed coniferous forest of Dachigam National Park, Jammu and Kashmir

Mosses although lack a proper rhizosphere, and poorly exploit the substratum on which they grow, still play complex role in ecological processes by providing nutrients and shelter to various organisms. Among the moss fauna, nematodes are the most abundant inhabitants. Keeping this in mind, the present study investigates how nematode communities differ among substratum-dependent moss microhabitats from forest soil. For this, samples were collected from five different microhabitats (FS: forest soil, MS: mosses on soil, MR; mosses on rocks, MLT: mosses on lower tree trunk and MUT: mosses on upper part of tree trunk), from the mixed coniferous forest of Dachigam National Park, Srinagar, Jammu & Kashmir. Results showed that the distribution pattern of nematode assemblages mirror the variation of microclimate. Total nematode abundance, trophic abundance (bacterivores, fungivores, herbivores, predators) and diversity (Shannon index, Simpson index) were highest in FS and lowest in MUT. Maturity index indicated more stable nematode communities in forest soil compared to different moss microhabitats. Results from NMDS showed clear separation of samples between microhabitats forming isolated clusters. Enrichment index depicted more enriched condition in MUT and least in FS. In general, our findings provide insights that more abundant, diverse and stable nematode communities are supported in undisturbed forest soil compared to desiccation-prone moss microhabitats.

Quantification of soil element changes in long-term agriculture: A case study in Northeast China

Anthropogenic measures that are implemented to improve the nutrient status of soil for growing food can lead to soil and environmental contamination. The influence of agricultural measures (cultivation and fertilization) on a cropland soil can be explained and quantified by exploring the variety and distribution of elements (calcium iron, rubidium, titanium, etc) in the soil profile. In this study, a cropland soil subjected to long-term (1948–2019, 72 years) anthropogenic agricultural activity was compared with a natural, undisturbed forest soil. Results showed that the anthropogenic activity affected the correlation of different elements in the cropland soil to different degrees, with the degree of the effects ranked as follows: calcium (Ca) > iron (Fe) = rubidium (Rb) > titanium (Ti) = chromium (Cr) > potassium (K) = zirconium (Zr) = strontium (Sr) > sulfur (S) = nickel (Ni) = scandium (Sc) > manganese (Mn) > vanadium (V) = zinc (Zn) = tungsten (W) > copper (Cu) = lead (Pb) = cobalt (Co). The elements were distributed much more evenly throughout the profile of the natural forest soil than the disturbed cropland soil. Some elements, such as Fe, Ti, V, Pb, Cr, Rb, K, Ca, Mn, Sc, Sr, and Cu, can be absorbed by vegetable growth and participate in the plant physiological cycle, while others, such as K, Rb, Cr, and Ti, may be lost readily as the soil is tilled. Elements such as Pb, Sc, Zn, and Sr, gradually accumulate over time from continuous fertilizer applications. In order to maintain the health of cropland soils, both farmers and policy makers should strive to mitigate elemental pollution by carefully managing applications of micronutrient fertilizers.

Soil carbon dynamics in diverse organic land use systems in North Eastern Himalayan ecosystem of India

Land use management exerts a tenacious impact on soil organic carbon (SOC) dynamics; however, the impact varies with climate, soils, and management practices. Therefore, an in-depth understanding of changes in SOC pools and its fractions is necessary to reduce carbon (C) emissions and adopt efficient land use planning for sustainable soil management in the North Eastern Himalayan (NEH) region of India. The soils under five prominent land uses [e.g., alder (Alnus nepalensis) + large cardamom (Amomum subulatum), alder + turmeric (Curcuma longa), ginger (Zingiber officinale) + maize (Zea mays), ginger and undisturbed forest] were sampled down to 45 cm depth to assess the impacts of land use systems on SOC content and storage, its fractions, microbial biomass carbon (MBC) and the dehydrogenase (DHA) activities. Results demonstrated that undisturbed forest soil had the highest organic carbon (OC, 145.8 Mg ha−1), active C (AC, 73.7 Mg ha−1), passive C (PC, 72.1 Mg ha−1) pools, MBC and DHA activities followed by alder + large cardamom system (140.7 Mg OC ha−1, 70.9 Mg AC ha−1, and 69.8 Mg PC ha−1, respectively). The soils under undisturbed forest and alder + large cardamom system had a higher share of the very labile C fractions for all depths than other land uses. Conversely, soils under sole ginger and ginger + maize land uses had a greater proportion of non-labile C (NLC) fractions; however, absolute values of the NLC pool were the highest under undisturbed forest soil. Alder + large cardamom land use system had the highest AC: PC pool ratio (1.13) and C stratification (1.02–1.05) compared to the other land uses. Of the various land uses, SOC pools (0–45 cm) in six years were reduced nominally under alder + large cardamom system (4.2%), while the reduction was maximum under the ginger system (11.2%) as compared to the SOC pools of undisturbed forest. The study demonstrated that the cultivation of crops like maize and/or ginger is more degrading and will always have a negative impact on the fertility and overall health of the Himalayan soil. Hence, alder + large cardamom system may be promoted to restore the soil C in the Sikkim Himalayan region of NEH, India, and other similar regions of the world.

Soil Recovery Assessment after Timber Harvesting Based on the Sustainable Forest Operation (SFO) Perspective in Iranian Temperate Forests

Minimizing the impact of timber harvesting on forest stands and soils is one of the main goals of sustainable forest operation (SFO). Thus, it is necessary to make an accurate assessment of forest operations on soil that is based on the SFO perspective. The present study was conducted according to SFO principles to investigate the time required for the natural recovery of soil after disturbance by skidding operations in some Iranian forests. The physical, chemical, and biological properties of soil found in abandoned skid trails from different time periods were compared with undisturbed forest soils. The soil bulk density, the penetration resistance, and the microporosity of a 25-year-old skid trail were 8.4–27.4% and 50.4% greater, and the total porosity, macroporosity, and soil moisture were 1.9–17.1% and 4.6% lower than the undisturbed area. In a 25-year-old skid trail, the values of pH, Electrical conductivity (EC), C, N, available P, K, Ca, and Mg, earthworm density, and biomass were lower than in the undisturbed area, and the C/N ratio value was higher than in the undisturbed area. High traffic intensity and slope classes of 20–30% in a three-year-old skid trail had the greatest impact on soil properties. In order to have sustainable timber production, SFO should be developed and soil recovery time should be reduced through post-harvest management operation.

Soil organic matter mobilization by re-compaction of old forest skid trails

Wood harvesting is restricted to a system of permanent skid trails in order to minimize the soil disturbance and damage. Therefore, it is not the compaction of previously undisturbed forest soil, but the re-compaction of already existing skid trails that is of practical relevance when investigating machinery-induced wood harvest effects on soil properties. This study investigated the effects of machinery-induced re-compaction on soil physical, chemical, and microbiological properties of an old skid trail in a spruce forest by wheeling 8 times with a maximum total load of 32.2 Mg, using a genuine old skid trail as a control. Re-compaction significantly increased the bulk density and reduced the porosity, whereas the soil organic carbon (SOC) and total nitrogen (N) contents were not significantly affected. However, re-compaction reduced the SOC/total N ratio by 10%, suggesting considerable SOC mineralization after re-compaction. K2SO4 extractable C contents were increased by 94% at 0–3 cm and 67% at 7–10 cm depth after re-compaction. This led to 20% and 90% increased microbial biomass C/soil organic C (MBC/SOC) ratios at 0–3 cm and at 7–10 cm depth, respectively. In contrast, the ergosterol/MBC ratio was significantly decreased by 10% at 0–3 cm and by about 30% at 7–10 cm depth by re-compaction, apparently due to the promotion of bacteria and mobilization of soil organic matter.

Slow Recovery of Major Soil Nutrient Pools during Reclamation in a Sub-Alpine Copper Mine Area, Southeastern Edge of the Tibetan Plateau, Sichuan Province, SW China

Improvement of soil nutrients is crucial for the long-term development and stability of restored ecosystems in mine areas. However, knowledge about the variation in soil nutrients and their influencing factors during the reclamation of sub-alpine metal mine soil is still scarce. We assess the status of soil organic carbon (SOC), total nitrogen (TN), N fractions, total phosphorus (TP), and available P in reclaimed soil at a copper mine site (2702 m above sea level) in the southeastern edge of the Tibetan Plateau, southwest China. The mine area had been reclaimed by distributing stockpiled topsoil (~15 cm) in 2008, sowing seeds of ryegrass (Lolium perenne L.) in 2009, and planting seedlings of A. ferdinandi-coburgii and Rosa omeiensis f. pteracantha in 2010. We found that, eight years after the reclamation, although the concentrations of SOC (24.3 g kg−1) and TN (2.21 g kg−1) in the reclaimed soil increased by 25% and 29% compared with the stockpiled topsoil, respectively, they only accounted for about half of the levels in the undisturbed topsoil. In contrast, the concentration of TP (498–570 mg kg−1) did not significantly change between the reclaimed and stockpiled topsoil. The concentrations of NH4-N (30.1 g kg−1), NO3-N (17.2 g kg−1), and available P (11.1 mg kg−1) in the reclaimed soil were 2.2, 1.3, and 1.6 times the levels in stockpiled topsoil, respectively, but still lower than those in undisturbed soil. The concentrations of microbial C, N, and P in the reclaimed soil had a similar variation pattern to the available nutrients. The soil C:P and N:P ratios and microbial biomass C:P and N:P ratios in the reclaimed soil were significantly lower than the levels in the undisturbed forest soil. The average accumulation rates of SOC and TN in the reclaimed soil were 85.3 and 11.4 g m−2 year−1, respectively. The rates are much lower than those of reclaimed mine soils with similar reclaim duration but better climate conditions. Relatively slow development of vegetation and soil microorganisms and leaching due to a freeze–thaw cycle controlled by the sub-alpine climate are likely responsible for the slow recovery of soil SOC and TN.

Temporal distribution of Fukushima-derived 137Cs in coniferous forest soil evaluated based on compartment-exponential model

Based on the compartment and exponential models, the distribution of Fukushima-derived 137Cs was evaluated at four sampling dates in undisturbed coniferous forest soil. The compartment model was employed to evaluate the dynamic of 137Cs in the three sub-sections of the forest floor (FF), namely undergrowth (UG), litter layer (OL), and fragmented litter layer (OF), while the exponential model was administrated to describe its distribution below the FF. According to the compartment model, the derived ecological half-life of 137Cs in the UG, OL, and OF layers was 0.97, 1.1, and 4.9 years, respectively, indicating 137Cs resides much longer in the OF layer. Hence, this soil section remains a potential source of radiation dose mainly due to its high 137Cs content associated with low attenuation effect. Below the OF layer, the 137Cs distribution was well described by exponential model and its derived relaxation lengths were in the range of 0.8-1.4 cm, implying the migration of 137Cs in mineral soil is very slow and almost intact during the observation time. Collectively, our results highlighted that the compartment model for the FF and the exponential model for the soil below the FF are adequate enough to generate essential information. Thus, the potential decontamination measures should have to be chosen on their effect on the FF's 137Cs. Graphical abstract.

Dye Tracer Visualization of Infiltration Patterns in Soils on Relict Charcoal Hearths

Anthropogenically modified soils are often characterized by a high heterogeneity of substrates and show unique patterns of water infiltration. Such effects are not limited to intensively used or disturbed agricultural and technogenic soils, but can also occur as legacies of former land use in forested areas. The remains of historic charcoal hearths represent a widespread legacy of historic land use. Soils at relict charcoal hearths (RCHs) are most prominently altered by the deposition of a layer of charcoal-rich substrate on top of the natural soil surface. The presence of such a technogenic layer can considerably influence infiltration and soil wetness patterns on the sites. This study describes the spatial patterns of infiltration and soil wetness at charcoal hearth sites compared with undisturbed sandy forest soils for a historic charcoal production area north of Cottbus, Germany. We characterized six plots on RCH and reference soils under pine, oak and mixed forest by visualizing preferential flow patterns of infiltrating water in dye tracer experiments. Additionally, we characterized bulk density, soil organic matter contents and water repellency, using water drop penetration time (wdpt) tests, of the RCH and reference soil horizons. The results reflect that the persistence of water repellency of both the technogenic substrates and the natural topsoils is extremely high under dry conditions, but is drastically reduced after wet antecedent conditions. The dye tracer experiments reflect increased preferential flow on the RCHs for dry soil conditions, for which infiltration is limited to very few flow paths in the technogenic substrate layer. Differences between RCH and reference soils are less clear for higher antecedent soil wetness, for which the results indicate more uniform wetting of the technogenic substrates. We conclude that the structural properties of the additional technogenic substrate layer of RCHs have characteristic effects on water infiltration, causing a high temporal variation of preferential flow in relation to antecedent soil moisture conditions. These effects can result in high heterogeneity of soil moisture for dry conditions, and generally in a high temporal variation of soil wetness in RCHs soils.

Escorrentía y producción de sedimentos en encinares incendiados de la Sierra Madre Oriental, México

En condiciones de disturbio mínimo, los suelos de los ecosistemas forestales tienen tasas de infiltración altas, y por lo tanto, la magnitud de la escorrentía y la erosión es baja, situación que puede revertirse por el fuego. El objetivo del presente estudio fue evaluar el efecto de tres niveles de severidad de incendios en la escorrentía y producción de sedimentos, mediante simulación de lluvia en encinares de la Sierra Madre Oriental. Por medio de árboles de regresión se identificaron las características de la superficie del suelo que más influencia tienen sobre ambos procesos. La escorrentía promedio, la escorrentía máxima y la producción de sedimentos fueron mayores en áreas con severidad de incendio alta, que en las áreas con severidad moderada y áreas sin quemar. Las variables de con más repercusión fueron la rugosidad de la superficie del suelo, la pendiente y las coberturas de mantillo y fragmentos de rocas. Se concluye que la severidad de incendios es fundamental para entender los procesos hidrológicos superficiales y de erosión, y que las características de la superficie del suelo modificadas por el fuego, como la cobertura y la microtopografía afectan la escorrentía y producción de sedimentos en áreas quemadas. Los resultados son útiles para identificar áreas prioritarias para la restauración de suelos y definir acciones de mitigación de la erosión.