Effects of brash removal after clear felling on soil and soil-solution chemistry and field-layer biomass in an experimental nitrogen gradient

Biofuels, such as brash from forest fellings, have been proposed as an alternative energy source. Brash removal may affect the sustainability of forest production, e.g., through a change in the availability of cations and N in the soil. We report initial effects of brash removal on inorganic N content in humus and mineral soil, soil-solution chemistry, and field-layer biomass after clear felling an N-fertilisation experiment in central Sweden. The experiment comprised six different fertiliser levels, ranging from 0 to 600 kg N ha(-1). Urea was given every 5th year during 1967 to 1982 to replicated plots, giving total doses of 0 to 2400 kg N ha(-1). Clear felling took place in 1995, 13 years after the last fertilisation. The removal of brash decreased the NO3- content in the humus layer after clear felling. A decrease in the NO3- concentration of the soil solution was indicated during most of the study period as well. No effect of the previous N fertilisation was found in the humus layer, but in the mineral soil there was an increase in NO3- content for the highest N dose after clear felling ( p = 0.06). The soil-solution chemistry and the field-layer biomass showed an irregular pattern with no consistent effects of brash removal or previous fertilisation.     

Long term effects of whole tree harvesting on soil carbon and nutrient sustainability in the UK

The practice of harvesting forest residues is rapidly increasing due to rising demand for renewable energy. However, major concerns have been raised about the sustainability of this practice and its net impact on long term soil ability to support forest productivity, particularly through second and subsequent rotations. In this study, soil chemical properties such as acidity, total N and C, available NO₃–N and NH₄–N and exchangeable cations were measured in all horizons in peaty gleys soils under one of the oldest experiments in Europe—a 28-year-old second rotation stand of Sitka spruce (Picea sitchensis), in Kielder forest, UK. Treatments included Whole Tree Harvesting (WTH—of all above ground biomass), Conventional stem-only harvesting (CH) of the first rotation crop, and repeated Fertilisation (FE) after the planting of the second rotation forest. This study demonstrates the soil changes underpinning the reduced second rotation tree productivity on these acidic upland sites under WTH, a further 18 years after the investigation by Proe and Dutch (1994). Overall, WTH increased soil acidity significantly (p < 0.05) and reduced soil base saturation whilst FE reduced soil acidity (p < 0.05) and increased soil base saturation as compared to CH. Soil moisture was significantly higher (p < 0.01) under WTH compared to CH and FE plots. There was no evidence that WTH decreased soil organic carbon (SOC) and soil nitrogen (N), but to the contrary there were significantly (p < 0.01) higher concentrations and stocks of total C and N in the WTH soils compared with CH and FE. The depletion of SOC and N in CH and FE plots was attributed to much higher soil mineralisation rates associated with the brash and fertilisation as compared to the WTH plots, where significantly less soil available NO₃–N (p < 0.01) was found. In the long term WTH on peaty gley soils appears positive for soil C and N storage. However, WTH had a long term negative impact on soil and tree nutrition of K⁺ and P, which are currently at deficient levels, but has had a stabilising effect on tree N nutrition as measured in twigs and needles. These results suggest that whilst WTH lead to a reduction in aboveground tree biomass compared to conventional harvest, these practices on selected soil types and certain sites may be beneficial for soil C and N sequestration. The overall findings of this study imply that cost benefit analyses for each site should be carried out before decisions are made on the appropriate type of forest operations (harvesting and replanting), considering both geology and soils in order to serve both environmental benefits, long term sustainability and the available biomass production for timber and biofuel.     

Recovery of pristine boreal forest floor community after selective removal of understorey, ground and humus layers

In boreal spruce forests that rarely experience extensive disturbances, fine-scale vegetation gaps are important for succession dynamics and species diversity. We examined the community implications of fine-scale gap disturbances by selective removal of vegetation layers in a pristine boreal spruce forest in Northern Finland. The aim was to investigate how the speed of recovery depends on the type of disturbance and the species growth form. We also wanted to know if there appeared changes in species composition after disturbance. Five different treatments were applied in the study: Control, removal of the ground layer (bryophytes and lichens), removal of the understorey layer (dwarf shrubs, herbs and graminoids), removal of both the ground and understorey layers, and complete removal of the vegetation and humus layers above the mineral soil. The vegetation recovery was monitored in terms of cover and species numbers over a 5-year period. Understorey layer cover, composed mainly of clonal dwarf shrubs, recovered completely in 4 years in treatments where the humus layer remained intact, whereas ground layer cover did not reach the control level in plots from where bryophytes and lichens were removed. Recovery was faster in terms of species number than species cover. Bryophytes, graminoids and dominant dwarf shrubs appeared in all disturbed plots quickly after disturbance. Seedlings of trees appeared exclusively in disturbed plots. Graminoids dominated after the removal of humus layer. The results indicate that the regeneration of forest floor after small gap disturbance occurs mainly by re-establishment of the dominant species. Although destruction of the humus layer leaves a long-lasting scar to the forest floor, exposing of mineral soil may enhance the sexual reproduction of dominant species and the colonization of weaker competitors.     

Soil Formation and Vegetation Establishment on the Cliff Face of Abandoned Quarries in the Early Stages of Natural Colonization

The large number of abandoned quarries in many countries presents challenges for restoration of these extremely degraded habitats. To understand soil and plant development in these extreme habitats at a most critical stage of restoration, we evaluated the edaphic conditions and natural vegetation of three large quarries in southern China 3, 5, and 7 years following abandonment. Although soil fertility (organic matter, and N, P, K concentrations) did not differ significantly over a few years, it was much higher than would be expected from newly weathered soil and was comparable to that of the adjacent garden soil on level ground with no slope. This suggests that soil formation on the steep slopes of quarry cliffs is a secondary migration process rather than a primary weathering process. Vegetation cover increased from 10.6 to 18.6 and 23.4%, and species abundance increased from 8 to 11 and 12 species, and from 3 to 6 and 7 families. Plant species composition changed from predominantly annual and perennial herbaceous species to a more diverse community with drought-tolerant and heliophilous shrubs. The vegetation cover was highly positively correlated with soil depth and soil volume ( p < 0.001), and also significantly correlated with soil organic matter, total N, and available N and P concentrations ( p < 0.05). This suggests that vegetation succession is more limited by available soil volume than by soil fertility during the early stages of quarry restoration.     

Effects of Retention Felling on Epixylic Species in Boreal Spruce Forests in Southern Finland

We studied the effects of patch retention felling and soil scarification by harrowing on the coverage and species richness of epixylic species in boreal Norway spruce (Picea abies) forests in Southern Finland. The epixylics were investigated from both the retention tree groups (RTGs) and the surrounding felling areas before and after fellings and after scarification on consecutive years. The cover percentage of all included species groups was shown to decrease after the felling, especially in the felling areas (vascular plants, ?0.4%; mosses, ?27.8%; liverworts, ?4.0%; and lichens,?2.1%). The decrease was considerable also in the RTGs. The amount of dead moss increased in both the areas indicating microclimatic changes. Species richness also declined rapidly after the first year, especially in the felling areas (vascular plants, ?2.2%; mosses, ?27.3%; liverworts, ?30.3%; and lichens, ?22.9%). Scarification also decreases covers and species richness of bryophytes. After the second year, the covers of the species groups generally started to regain, especially in the untreated RTGs. The size of RTG was in positive correlation with the total species number. Another main result indicates that it is possible to maintain much higher initial vegetation abundance and diversity in the RTGs than in the felling areas. Coarse woody debris formed by the frequent tree uprootings may also enhance the long‐term survival of epixylics over forest regeneration period. RTGs should be at least 10 times larger than the size used in current Finnish forestry, so that they could function as species refugia.     

Establishment and persistence of target species in newly created calcareous grasslands on former arable fields

The effects of different restoration measures and management variants on the vegetation development of newly created calcareous grasslands were studied in southern Germany from 1993 to 2002. In 1993, fresh seed-containing hay from a nature reserve with ancient calcareous grasslands was transferred onto ex-arable fields with and without topsoil removal. Nine years after start of the restoration, the standing crop was lower and the cover of bare soil was higher on topsoil-removal sites than on sites without soil removal. Topsoil removal had a positive effect on the proportion of target species (class Festuco-Brometea), because the number and cover of productive meadow species (class Molinio-Arrhenatheretea) were reduced. Persistence of hay-transfer species and the number of newly colonizing target species were highest on topsoil-removal sites. On plots with and without soil removal, species richness and the number of target species increased quickly after hay transfer and were always higher on hay-transfer plots than on plots that had not received hay in 1993. In 2002, differences induced by hay transfer were still much more pronounced than differences between management regimes. Management by mowing, however, led to higher species richness, a greater number of target species and a lower number of ruderals in comparison to no management on restoration fields without soil removal. A detrended correspondence analysis (DCA) indicated that vegetation composition of the hay-transfer plots of the restoration fields still differed from the vegetation of ancient grasslands in the nature reserve. Vegetation of an ex-arable field in the nature reserve (last ploughed in 1959) showed an intermediate successional stage. In general our results indicate that the transfer of autochthonous hay is an efficient method for the restoration of species-rich vegetation, which allows not only quick establishment but also long-term persistence of target species.     

Variation in Aboveground Cover Influences Soil Nitrogen Availability at Fine Spatial Scales Following Severe Fire in Subalpine Conifer Forests

Following fire, fine-scale variation in early successional vegetation and soil nutrients may influence development of ecosystem structure and function. We studied conifer forests burned by stand-replacing wildfire in Greater Yellowstone (Wyoming, USA) to address two questions: (1) How do the variability and spatial structure of aboveground cover and soil nitrogen availability change during the first 4 years following stand-replacing fire? (2) At fine scales (2–20 m), are postfire soil inorganic N pools and fluxes related to aboveground cover? Aboveground cover, soil N pools, and annual net N transformations were measured from 2001 to 2004 using a spatially explicit sampling design in four 0.25-ha plots that burned during summer 2000. Within-stand variability (coefficient of variation) in postfire live vegetative cover declined with time since fire, whereas variability in bare mineral soil, charred litter and fresh litter was greatest 2-3 years postfire. The soil nitrate pool was more variable than the soil ammonium pool, but annual net nitrification was less variable than annual net N mineralization. Spatial structure (quantified by semivariograms) was observed in some aboveground cover variables (for example, graminoids and fresh litter), but there was little spatial structure in soil N variables and no obvious congruence in spatial scales of autocorrelation for soil N and aboveground cover. Significant Spearman correlations (at the sample point) indicated that aboveground cover and soil N were coupled following severe fire, and the dominant influence was from aboveground cover to soil N, rather than from soil N to vegetation. Initial patterns of fire severity and re-vegetation contributed to fine-scale heterogeneity in soil N availability for at least 4 years after severe fire.     

Litter legacy after spruce plantation removal hampers initial vegetation establishment

Restoration of areas used for intensive even-aged Norway spruce (Picea abies Karst.) plantations often involves felling and subsequent spontaneous vegetation succession. However, the accumulated litter layer may hamper vegetation development, and thereby postpone recovery or even change the outcome.We studied effects of the litter layer on vegetation establishment during two seasons following a clear-cut of Norway spruce in Denmark. We experimentally assessed the response of multiple vegetation properties to litter removal, with and without wildlife exclusion by fencing, and in combination with sowing of trees, while fencing. Burning was tested as an alternative way to remove the litter layer.Vegetation establishment was poor, when the litter layer was intact, and cover developed slowly remaining below 10% after two years, irrespective of fencing. In contrast, litter removal and fencing together gave significantly faster recovery and reached nearly 60% mean cover. Vegetation cover was driven by few dominant species, especially the sedge Carex pilulifera. Species richness was similar in all treatments, but increased with sowing of trees. Fencing resulted in taller birch seedlings independently of litter removal, but enhanced by seedling density. Litter removal seemed to favor species with lighter seeds, lower specific leaf area (SLA) and lower Ellenberg N value, i.e. associated with relative infertile conditions. Disturbing the litter by burning seemed to have an effect comparable to mechanical removal, and could be a management alternative.Our results showed that a persistent litter layer after spruce plantation removal may hamper the initial vegetation establishment. Actively removing litter may serve as an additional restoration intervention to overcome this legacy. However, as grazing can keep this potential in check, wildlife exclusion may be necessary as well. To speed up recovery and diversify vegetation structure after spruce plantation removal, we suggest patchy disturbance of the litter, essentially combined with wildlife exclusion.     

Droughting a megadrought: Ecological consequences of a decade of experimental drought atop aridification on the Colorado Plateau

Global dryland vegetation communities will likely change as ongoing drought conditions shift regional climates towards a more arid future. Additional aridification of drylands can impact plant and ground cover, biogeochemical cycles, and plant–soil feedbacks, yet how and when these crucial ecosystem components will respond to drought intensification requires further investigation. Using a long-term precipitation reduction experiment (35% reduction) conducted across the Colorado Plateau and spanning 10 years into a 20+ year regional megadrought, we explored how vegetation cover, soil conditions, and growing season nitrogen (N) availability are impacted by drying climate conditions. We observed large declines for all dominant plant functional types (C₃ and C₄ grasses and C₃ and C₄ shrubs) across measurement period, both in the drought treatment and control plots, likely due to ongoing regional megadrought conditions. In experimental drought plots, we observed less plant cover, less biological soil crust cover, warmer and drier soil conditions, and more soil resin-extractable N compared to the control plots. Observed increases in soil N availability were best explained by a negative correlation with plant cover regardless of treatment, suggesting that declines in vegetation N uptake may be driving increases in available soil N. However, in ecosystems experiencing long-term aridification, increased N availability may ultimately result in N losses if soil moisture is consistently too dry to support plant and microbial N immobilization and ecosystem recovery. These results show dramatic, worrisome declines in plant cover with long-term drought. Additionally, this study highlights that more plant cover losses are possible with further drought intensification and underscore that, in addition to large drought effects on aboveground communities, drying trends drive significant changes to critical soil resources such as N availability, all of which could have long-term ecosystem impacts for drylands.     

Woody Debris Amendment Enhances Reclamation after Oil Sands Mining in Alberta,Canada

Mining disturbs large forested areas around the world, including boreal forests after oil sands mining in Canada. Industrial companies are expected to reclaim degraded land to ecosystems with equivalent land capability. This research showed the value of woody debris for reclamation of dramatically disturbed landscapes with a forest ecosystem end land use. Adding woody debris during reclamation can facilitate recovery of flora, soil nutrient cycling and water and nutrient holding capacity. Combined with forest floor material, woody debris can provide native plant propagules that would be otherwise commercially unavailable. Sites with and without woody debris on forest floor material containing identifiable litter (L), fragmented and fermented litter (F), and humus (H) (LFH), and peat mineral soil mix (peat) cover soils were studied. Within 2 years, woody debris decreased bare ground and created microsites which were positively associated with greater vegetation cover and woody plant density. Woody debris treatments had lower soil available nitrate and soil under woody debris had a lower temperature range and higher soil volumetric water content than control treatments without woody debris. Woody debris did not affect first year microbial biomass carbon or mycorrhizae, but both were greater on LFH than peat cover soil. LFH was associated with lower bare ground and greater vegetation cover, species richness, and soil phosphorus and potassium than peat cover soil, which had greater soil sulfate .     

Chemical composition of forest floor and consequences for nutrient availability after wildfire and harvesting in the boreal forest

In boreal forests of eastern Canada, wildfire has gradually been replaced by clearcut harvesting as the most extensive form of disturbance. Such a shift in disturbance may influence the chemical properties of the forest floor and its capacity to cycle and supply nutrients, with possible implications for forest productivity. We compared the effects of stem-only harvesting (SOH), whole-tree harvesting (WTH) and wildfire on the chemical composition of forest floor organic matter and nutrient availability for plants, 15–20 years after disturbance in boreal coniferous stands in Quebec (Canada). The forest floor on plots of wildfire origin was significantly enriched in aromatic forms of C with low solubility, whereas the forest floor from SOH and WTH plots was enriched with more soluble and labile C compounds. The forest floor of wildfire plots was also characterized by higher N concentration, but its high C:N and high concentration of ¹⁵N suggest that its N content could be recalcitrant and have a slow turnover rate. Total and exchangeable K were associated with easily degradable organic structures, whereas total and exchangeable Ca and Mg were positively correlated with the more recalcitrant forms of C. We suggest that the bulk of Ca and Mg cycling in the soil–plant system is inherited from the influx of exchangeable cations in the forest floor following disturbance. The buildup of Ca and Mg exchangeable reserves should be greater with wildfire than with harvesting, due to the sudden pulse of cation-rich ash and to the deposition of charred materials with high exchange capacity. This raises uncertainties about the long-term availability of Ca and Mg for plant uptake on harvested sites. In contrast, K availability should not be compromised by either harvesting or wildfire since it could be recycled rapidly through vegetation, litter and labile organic compounds.     

Effects of pre-harvest soil acidification,liming and N fertilization on the survival,growth and needle element concentrations of Picea abies L. Karst. seedlings

There are concerns that the anthropogenic acidification of Swedish forest soils may have severe effects on forest yield, and it has been suggested that liming could be used to counter this problem. The aim of this study was to investigate the survival, growth and element concentrations of C+1 needles of Picea abies (L.) Karst. seedlings planted on plots that had been acidified (in 12 annual treatments totalling 600 or 1200 kg S ha^–1 in the form of elemental sulphur), limed (12×500=6000 kg lime ha^–1 in the form of CaCO₃) or N-fertilized (3×200=600 kg N ha^–1 in the form of urea) prior to harvest. Seedlings growing on plots given a combination of the N plus low S treatments were also tested. None of the treatments, given to triplicate plots, significantly influenced seedling survival during the first five growing seasons. Furthermore, none of the treatments significantly affected growth, although the average growth rate was slightly higher for limed plots. The survival and growth of the seedlings are discussed in relation to differences in the cover of field-layer vegetation between the treatments after the final felling. Needles from seedlings in the limed plots showed significantly lower concentrations of Mn and Al, and higher concentrations of Ca and Zn compared with needles from seedlings in the other plots (i.e. control, high S or N-treated). The K concentration in the needles was significantly higher in limed plots than in high-S plots. Changes of element concentrations observed in the soil, associated with the treatments, where in some cases reflected in the needle concentrations.     

Vegetation of tuscan ultramafic soils in relation to edaphic and physical factors

Vegetation and soil sampling were carried out in 80 plots located in five different ultramafic (serpentine) sites of Tuscany, central Italy. The physical and chemical features of each plot were determined and the species composition and cover recorded. The exchangeable fraction of soil metals was analysed because it gives a measure of their concentrations available to plants. The plots were classified by cluster analysis and ANOVA was used to compare the environmental variables of the groups of plots. Canonical correspondence analysis was used to detect the principal factors for gradients of species composition within the plant communities. A higher content of exchangeable metals was found under the more evolved and structured plant communities, suggesting that serpentine vegetation of Tuscany is not strongly limited by soil metals, such as chromium, cobalt, nickel and magnesium, typically associated with ultramafic soils. The low nutrient content of the soils and drought stress mainly due to topographical features, appear to have a more significant role in determining the typical scattered vegetation of the Tuscan ultramafics.     

The effect of harvesting intensity on the fate of applied 15N-ammonium to the organic horizons of a coniferous forest in N. Wales

¹⁵N-ammonium sulphate equivalent to 0.5 kg N/ha was added as a tracer to lysimeters containing the organic horizons of an acid forest soil. The effect of logging debris (brash), vegetation and second rotationPicea sitchensis seedlings on the amount of the¹⁵N found in various soil, vegetation and leachate pools was followed over a period of 60 days. Transformation of¹⁵N-ammonium to nitrate occurred within 24 hours. Although total nitrate leachate losses were high, tracer-derived nitrate represented only 0.4%–4.2% of the applied¹⁵N-ammonium. The atom % excess of the KCI-extractable organic-N pool was initially lower than for the inorganic species but due to the large pool size, consistently represented 3–6% of the applied¹⁵N-ammonium. The similarity of the atom % excess of the ammonium and nitrate pools indicated an autotrophic nitrification pathway.A significant proportion of the¹⁵N-ammonium passed through the microbial biomass which contained between 16 and 48% of the¹⁵N-ammonium 2 days after addition of the¹⁵N-ammonium. This nitrogen was in a readily available form or short-term pool for the first two weeks (with no change in the overall biomass pool), after which the nitrogen appeared to become transformed into more stable compounds representing a long-term pool. Total recovery of the¹⁵N was between 68% and 99% for the different treatments. The presence of brash reduced microbial immobilisation of the¹⁵N-ammonium and total retention in the organic matter. This is suggested to be a consequence of greater nitrification and denitrificatiion rate in organic horizons beneath a brash covering due to different microclimatic conditions.     

An Evaluation of Reclamation Success on Idaho's Phosphate Mines

To evaluate reclamation success on the Wooley Valley phosphate mine in southeastern Idaho, we compared vegetation structure and soil physical, chemical, and elemental properties of several different reclamation treatments with those of a nearby reference area (a native Artemisia tridentata vaseyana/Festuca idahoensis association) after 14 years. Vegetation data had been collected four years after reclamation, and we were able to compare differences in biomass and species composition between dates on the reclaimed area. Four years after reclamation there were no differences in total biomass between topsoil or spoil or between seed only, seed + mulch, or control treatments on the different soil types. Most treatments were dominated by seeded perennial grasses. Fourteen years after reclamation there were no differences in biomass or cover between spoil and topsoil plots, but on spoil plots the seeded and mulched treatment had higher total biomass and vegetation cover than on control or seed-only treatments. The seeded perennial legume Medicago sativa was codominant with the seeded forage grasses on all of the treatments. High initial fertilization rates probably facilitated the early establishment and dominance of the forage grasses; once nutrient levels, especially nitrogen, began to decline, the legume increased in abundance. Similarity between the reclaimed area and the reference or native area was low. Reclaimed treatments had higher biomass but lower species richness. The topsoil and spoil plots had similar soil texture, bulk density, pH, cation exchange capacity, electrical conductivity, and phosphorus. Differences in organic carbon, total nitrogen, carbon: nitrogen ratios, and available moisture were related more to treatments than to soil type. High biomass and, thus, litter input on the seed + mulch treatment on spoil plots resulted in both higher OC and TN than any on other soil/treatment combination. The reclaimed area had lower OC, TN, and available moisture than did the reference area on all but seed + mulch spoil plots. Bulk density was higher on reclaimed plots. The long-term differences observed between the reclaimed and reference areas parallel those obtained for other western reclamation sites. Although successional trajectories depend on the attribute measured, similarity to native reference areas depends on the initial reclamation methods. We discuss reclamation methods that would increase the structural and functional similarity of reclaimed and reference areas on the Wooley Valley phosphate mine.     

Floristic composition and analysis of spontaneous vegetation of Sabkha Djendli in north-east Algeria

We conducted a phyto-ecological analysis of the Sebkha Djendli located in the semi-arid lands of the north-eastern Algeria in order to contribute in the understanding of flora composition, diversity and factors controlling plant zonation. Eight plots, distributed on the cardinal and intercardinal points of the site, were sampled. A floristic analysis (species richness, life forms, spatial occurrence, plant cover rate and similarity) and an assessment of the effect of soil salinity and pH on the cover of dominant halophytes were performed. The results of the floristic approach showed the presence of 51 species belonging to 21 families and 45 genera. The most frequent biological types were therophytes (58%) followed by chamaephytes (18%). Vegetation cover rate ranged from 50% to 95%. The distribution of vegetation all around the edges of the Sabkha revealed the dominance of halophytic species belonging to the family Chenopodiaceae. The variation of total halophytic vegetation cover over all sampled plots seems to be affected neither by the distance from waterbody nor by plot orientation nor by the electrical conductivity and pH of soil.     

Nitrogen transformation rates are affected by cover soil type but not coarse woody debris application in reclaimed oil sands soils

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for reclamation of open‐pit oil sands mining disturbed land in northern Alberta, Canada; coarse woody debris (CWD) is another source of organic matter for land reclamation. We investigated net nitrogen (N) transformation rates in FMM and PMM cover soils near and away from CWD 4–6 years after oil sands reclamation. Monthly net nitrification and N mineralization rates varied over time; however, mean rates across the incubation periods and microbial biomass were greater (p < 0.05) in FMM than in PMM. Net N mineralization rates were positively related to soil temperature (p < 0.001) and microbial biomass carbon (p = 0.045). Net N transformation rates and inorganic N concentrations were not affected by CWD; however, the greater ¹⁵N isotope ratio of ammonium near CWD than away from CWD indicates that CWD application increased both gross N mineralization/nitrification (causing N isotope fractionation) and gross N immobilization (no isotopic fractionation). Microbial biomass was greater near CWD than away from CWD, indicating the greater potential for N immobilization near CWD. We conclude that (1) CWD application affected soil microbial properties and would create spatial variability and diverse microsites and (2) cover soil type and CWD application had differential effects on net N transformation rates. Applying FMM with CWD for oil sands reclamation is recommended to increase N availability and microsites.     

Translocation of Herb-Rich Grassland from a Site in Wales Prior to Opencast Coal Extraction

Reinstatement of vegetation to a similar condition to that prior to disturbance is often required in industrial restoration schemes. Seeding with specially prepared seed mixes containing species suited to local soils is often the preferred option on grounds of practicality and cost. Turf translocation is more difficult and costly but, if successful, meets the reinstatement requirement more precisely. In a pilot study at a proposed opencast coal site in Wales, we compared the effectiveness of whole-turf translocation of herb-rich mesic grassland communities, with a less technically demanding and more cost-effective technique involving spreading turf over twice the area at the receiver site and rotovating it into the underlying soil. The translocated whole turf and rotovated turf plots were cut annually and the vegetation removed to simulate grazing that had occurred prior to translocation. Both the whole-turf and rotovated turf transplant techniques gave successful re-establishment of 50% or more of the species originally present. After three years, the cover and species composition were similar in “whole-turf” and “spread and rotovated” plots. This suggests that the “spread and rotovate” technique provides a satisfactory ecological alternative to whole-turf translocation. However, plant communities changed, in some cases substantially, after translocation using either technique. Altered soil hydrology and nutrition combined with the substitution of cutting for grazing are probably the main causes of these changes.     

Flood-deposited wood debris and its contribution to heterogeneity and regeneration in a semi-arid riparian landscape

We investigated whether large woody debris (LWD) piles create nodes of environmental resources that contribute to the recovery of riparian vegetation and that also augment the heterogeneity and resilience of the riverine system. River and riparian systems are typified by a large degree of heterogeneity and complex interactions between abiotic and biotic elements. Disturbance such as floods re-distribute the resources, such as LWD, and thereby add greater complexity to the system. We examined this issue on a semi-arid savanna river where a ~100-year return interval flood in 2000 uprooted vegetation and deposited substantial LWD. We investigated the micro-environment within the newly established LWD piles and compared this with conditions at adjacent reference sites containing no LWD. We found soil nutrient concentrations to be significantly higher in LWD piles compared with the reference plots (total N +19%, available P +51%, and total C +36%). Environmental variables within LWD piles and reference sites varied with landscape position in the river–riparian landscape and with LWD pile characteristics. Observed differences were generally between piles located in the terrestrial and riparian areas as compared to piles located on the macro-channel floor. After 3 years the number and cover of woody species were significantly higher when associated with LWD piles, regardless of landscape position or pile type. We conclude that LWD piles formed after large floods act as resource nodes by accumulating fine sediments and by retaining soil nutrients and soil moisture. The subsequent influence of LWD deposition on riparian heterogeneity is discerned at several spatial scales including within and between LWD piles, across landscape positions and between channel types. LWD piles substantially influence the initial developmental of riparian vegetation as the system regenerates following large destructive floods.     

Ecological indicators for assessing management effectiveness: A case study of horse riding in an Alpine National Park

Recreation activities and visitor use often have deleterious ecological impacts in protected areas. Management agencies then face the difficult task of providing recreation and tourism opportunities without compromising environmental values. This study assessed the success of efforts aimed at conserving alpine vegetation along the Mt Bogong Massif in Victoria, Australia, through controlling the use of horses. Vegetation condition was assessed in 2001 to coinciding with restrictions on the use of horse riding on trails and then resurveyed 10 years later. Sampling was undertaken in track plots that included the trail and surrounding vegetation, and control plots located away from the trail. There were significant differences in the amount of bare ground, the height of shrubs and ground layer vegetation, and shrub cover between track and control plots in 2001. Ten years later, track plots were recovering with reductions in bare ground and changes in vegetation, with improved ground layer vegetation height. Results show that vegetation condition has improved with restrictions of horse numbers. The indicators selected were sensitive to changes in vegetation condition and hence should be used for ongoing assessment of the effectiveness of this and similar management interventions.