Impacts of experimental trampling on tall alpine herbfields and subalpine grasslands in the Australian Alps

The Australian Alps, which are of high conservation value, are popular summer bushwalking destinations. Experimental trampling trials using a standardized methodology were conducted to determine the resistance and resilience of the two common vegetation types: tall alpine herbfield and subalpine grasslands. Vegetation parameters were measured in lanes subject to control (no trampling), 30, 100, 200, 500 and 700 passes at five sites prior to trampling, immediately post trampling, 2 weeks, 6 weeks and 1 year post trampling. Vegetation height, cover of graminoids and herbs, as well as net species richness all declined with trampling, while litter cover increased. Thresholds for damage varied between the two communities and among the different vegetation parameters. The resistance indices for the two communities (number of passes resulting in 50% reduction in vegetation cover), however, were similar at around 440–450 passes indicating that these two communities are among the most resistant of the 19 alpine–subalpine communities that have been tested around the world, but only of moderate resistance compared to non-alpine communities. The two communities showed limited recovery with damage still evident 1 year post trampling. This indicates that they have only moderate tolerance to damage due to moderate resistance, but low resilience.     

Trampling resistance of tropical rainforest soils and vegetation in the wet tropics of north east Australia

Controlled trampling was conducted to investigate the trampling resistance of contrasting high fertility basaltic and low fertility rhyolitic soils and their associated highland tropical rainforest vegetation in north east Australia's Wet Tropics. Although this approach has been taken in numerous studies of trampling in a variety of ecosystem types (temperate and subtropical forest, alpine shrubland, coral reef and seagrass beds), the experimental method does not appear to have been previously applied in a tropical rainforest context. Ground vegetation cover and soil penetration resistance demonstrated variable responses to trampling. Trampling, most noticeably after 200 and 500 passes reduced organic litter cover. Bulk density increased with trampling intensity, particularly on basalt soils as rhyolite soils appeared somewhat resistant to the impacts of trampling. The permeability of the basalt and rhyolite soils decreased markedly with increased trampling intensity, even after only 75 passes. These findings suggest physical and hydrological changes may occur rapidly in tropical rainforest soils following low levels of trampling, particularly on basalt soils.     

Differences in resistance of three subtropical vegetation types to experimental trampling

Experimental trampling trials using a standardized methodology were undertaken in 10 replicate blocks in three vegetation types in an urban reserve in the subtropics of Australia. In each block different intensities of trampling (controls, 10, 25, 50, 100, 150, 200, 250, 300, 400 and 500 passes) were applied, and vegetation parameters were measured pre-trampling, immediately after trampling and 2 weeks later. A Fern understorey had low resistance to trampling intensity, with reductions in relative vegetation height and cover with as few as 10 passes. A Tussock grass understorey showed moderate resistance with reduction in height at 25 passes and cover at 50 passes. A Disturbed grassland dominated by lawn grasses had the highest resistance, with reductions in vegetation height at 100 passes, but cover was affected by as few as 10 passes. The resistance indices (number of passes required to reduce vegetation cover by 50%) of three vegetation types were 210, 360 and 860 passes, respectively. When these values were compared with those for 52 other vegetation types considerable variation was found within life forms, climatic zones and vegetation types indicating that the response of a specific community may not always be predictable.     

The response of two arctic tundra plant communities to human trampling disturbance

A 4-year study was conducted to evaluate the consequences of human trampling on dryas and tussock tundra plant communities. Treatments of 25, 75, 200 and 500 trampling passes were applied in 0.75 m2 vegetation plots at a time of approximately peak seasonal biomass. Immediately after and 1 and 4 years after trampling, plots were evaluated on the basis of plant species cover, percent bare ground, vegetation height, and soil penetration resistance. One year after trampling, soils were collected for nitrogen analysis in highly disturbed and control plots. Immediately after trampling, 500 trampling passes resulted in approximately 50% cover loss in the dryas tundra and 70% cover loss in tussock tundra, but both communities showed a substantial capacity for regrowth. Plots where low and moderate levels of trampling were applied returned to pre-disturbance conditions by 4 years after trampling, but impact was still evident in plots subjected to high levels of disturbance. These results suggest that these tundra communities can tolerate moderate levels of hiking and camping provided that use is maintained below disturbance thresholds and that visitors employ appropriate minimum-impact techniques. By utilizing this information in a visitor education program combined with impact monitoring and management, it is possible to allow dispersed camping and still maintain these vegetation communities with a minimum of observable impact.     

Scale-dependent inconsistencies in the effects of trampling on a forest understory community

The response of forest understory vegetation to trampling applied at different temporal and spatial scales was determined in a cliff-edge forest in Ontario, Canada. Three frequencies (0, 50, 500 passes per year) of short-term trampling (one year) were applied to plots previously undisturbed. Existing trails that had received three frequencies (approx. 100, 500, 25,000 passes per year) of long-term trampling (18 years) were also studied. Community composition, species richness, and individual species frequency were recorded in plots within 4 m and (or) 1 m of the patch centerline. The quantitative and qualitative form of plant response to increased trampling was compared for short-term and long-term treatments, both within 4 m and within 1 m of the path centerline, to judge the consistency of trampling effects at different temporal and spatial scales. As trampling frequency increased, community composition changed progressively, but consistently, in plots both within 4 m and 1 m of the path centerline. Species richness was less affected by trampling and only decreased within 1 m of the path centerline at the highest level of trampling (25,000 passes per season for 18 years). Effects of trampling on individual species frequency were much less consistent at different temporal and spatial scales of trampling. The scale-dependence results suggest that field workers and resource managers both should try explicitly to include and define multiple scale components when trying to ascertain the response of vegetation to human disturbance factors.     

Assessing the impacts of mountain biking and hiking on subalpine grassland in Australia using an experimental protocol

Mountain biking is an increasingly popular, but sometimes controversial, activity in protected areas. Limited research on its impacts, including studies comparing biking with hiking, contributes to the challenges for mangers in assessing its appropriateness. The impacts of mountain bike riding off trail were compared to those of hiking on subalpine grassland in Australia using a modification of a common trampling experimental methodology. Vegetation and soil parameters were measured immediately and two weeks after different intensities of mountain biking (none, 25, 75, 200 and 500 passes across slope, 200 pass up and down slope) and hiking (200 and 500 passes across slope). There were reductions in vegetation height, cover and species richness, as well as changes in species composition and increases in litter and soil compaction with riding. Riding up and down a moderate slope had a greater impact than riding across the slope. Hiking also affected vegetation height, cover and composition. Mountain biking caused more damage than hiking but only at high use (500 passes). Further research including other ecosystems, topography, styles of riding, and weather conditions are required, but under the conditions tested here, hiking and mountain biking appear to be similar in their environmental impacts.     

A survey of trampling effects on vegetation and soil in eight tropical and subtropical sites

Impacts of recreation, especially of vehicles and walkers, were studied in eight tropical or subtropical public sites in Queensland. In each site, plant species number, vegetation cover, plant height, and species cover and frequency in untrampled, slightly trampled, moderately trampled, and heavily trampled areas were counted or measured. Soil penetration resistance and soil organic matter were also recorded. In two of these eight sites, plant cover, height, leaf length, leaf width, and leaf thickness of each species were measured. Some species of grass such asCynodon dactylon were present in areas subject to all degrees of trampling impact and some tussock species, particularlyEragrostis tenuifolia andSporobolus elongatus, were only present in trampled areas. Woody plants occurred only on untrampled areas. The number of species and all the vegetative measurements mentioned above were reduced as wear increased. Plant height was reduced dramatically by even light trampling. Tall plants appeared to be more sensitive to trampling than short plants. No clear relationship between soil organic matter content and trampling intensity was found.     

Vegetation and soil recovery in wilderness campsites closed to visitor use

Recreational use of wilderness results in impacts to vegetation and soil in trails and campsites. Traditionally, campsite impact studies have compared campsites receiving various levels of use with unused control areas. Field studies in Sequoia National Park, California, indicate that the degree of impact to vegetation and soils also varies within campsites. The central areas of campsites, where trampling is concentrated, show lower plant species diversity, differences in relative species cover, more highly compacted soils, and lower soil nutrient concentrations than do peripheral, moderately trampled, and untrampled areas within the same campsite. Three years after closure to visitor use, the central areas show less increase in mean foliar plant cover, and soils remain more highly compacted than in previously moderately trampled areas of the same sites. Changes in relative species cover over time are used to assess both resiliency to trampling and species composition recovery within campsites closed to visitor use.     

Quantifying the effects of trampling and habitat edges on forest understory vegetation – A field experiment

We investigated the effects of human trampling on boreal forest understory vegetation on, and off paths from suburban forest edges towards the interiors and on the likelihood of trampling-aided dispersal into the forests for three years by carrying out a trampling experiment. We showed that the vegetation was highly sensitive to trampling. Even low levels of trampling considerably decreased covers of the most abundant species on the paths. Cover decreased between 10 and 30% on paths which had been trampled 35 times, and at least by 50% on those trampled 70–270 times. On-path vegetation cover decreased similarly at forest edges and in the interiors. However, some open habitat plant species that occurred outside the forest patches and at forest edges dispersed into the forests, possibly through the action of trampling. A higher cover percentage of an open habitat species at the forest edge line increased its probability to disperse into the forest interior. The vegetation community on, next to, and away from lightly trampled paths remained the same throughout the trampling experiment. For heavily trampled paths, the community changed drastically on the paths, but stayed relatively similar next to and away from the paths. As boreal vegetation is highly sensitive to the effects of trampling, overall ease of access throughout the forest floor should be restricted to avoid the excessive creation of spontaneous paths. To minimize the effects of trampling, recreational use could be guided to the maintained path network in heavily used areas.     

Impact of human trampling in different zones of a coral reef flat

The effects of trampling on the coral communities of the outer reef flat and reef crest were investigated at Heron Island at the southern end of the Great Barrier Reef. Eighteen months of trampling at various intensities increased the percentage cover of unoccupied substrate and the cover of mobile rubble. The morphology of the coral was the most important feature relating to trampling resistance. Branching corals were reduced on the outer reef flat, and most broken branches were recorded in the initial phases of the experiment. The reef crest was much more resistant.A short-term trampling experiment showed that trampling detached a greater mass and larger fragments of coral on the outer reef flat than on the reef crest. Further trampling reduced the sizes of the detached fragments on the outer reef flat. A drift experiment indicated that greatest movement of fragments occurred on the reef crest and here the largest fragments moved greater distances.We concluded that all habitats would be changed by reef walking and that by one measure the outer reef flat was 16 times more vulnerable than the reef crest. The routes taken by reef walkers need to be chosen in relation to the trampling resistance of the habitat.     

Responses of Three Heathland Shrubs to Single or Repeated Experimental Trampling

In the last few decades, trampling has become a cause of major disturbance to natural areas. Trampling can occur regularly either seasonally or throughout the year, or as a single impact depending on a recreational activity or an event. This study, carried out on a coastal heathland in north Brittany (France), was based on the hypothesis that the vegetation response can differ depending on whether the trampling is repeated or due to a single event. The aim was to compare the resistance and the short-term recovery capacity of selected species in coastal heathland communities subjected to a trampling experiment, applied once or five times (with equal total number of passes from 0 to 800). The temporal distribution of the trampling did not affect the response of Erica ciliaris, whereas for Erica cinerea and Ulex gallii, trampling was slightly less damaging when applied once rather than five times. These differences could be linked to the lower resistance and the higher recovery capacity of E. ciliaris, compared with the two other species. This study also emphasized the influence of site location by comparing observations with previous studies. Plant resistance calculated here appeared to be lower than that calculated for a less stressful site. The relationship between plant traits and response to trampling was also investigated. The effects of the different times between disturbance application and observations of the short-term response of woody vegetation to experimental trampling is also discussed.     

Sheep grazing effects on Mojave Desert vegetation and soils

Some effects of domestic sheep grazing on vegetation and soils were measured at four sites in the western Mojave Desert. Although sheep have grazed the Mojave Desert for the past 50–100 years, the effects of grazing on the desert ecosystem are largely unknown.The results reflect only short-term effects of grazing, because fenced control areas were not available for study. Heavy grazing caused a 60% reduction in the above-ground biomass under creosote bushes (Larrea tridentata), and sheep trampling caused an increase in soil strength and decreased intershrub annual densities 24 and 28% in two areas. The average area per individual (cover) of burrobush (Ambrosia dumosa) decreased 16–19% and the cover of spiny hop-sage (Grayia spinosa) decreased 29% under grazing pressure. The volumes of individual Ambrosia were 21 and 65% less in two heavily grazed areas than in two lightly grazed areas; the volume of goldenhead (Acamptopappus sphaerocephalus) was 68% less in one heavily grazed area.These changes indicate that the range quality of the Mojave Desert is deteriorating under sheep grazing pressures. Trampling reduces annual cover and disrupts the soil surface, thus promoting wind erosion. The loss of annual biomass and shrub cover should adversely affect reptiles and rodents by removing food sources and protection. Soil strength increases may retard future growth of annuals, further contributing to erosion and food source losses. Studies should be initiated to determine the long-term effects of grazing in the Mojave Desert.     

Trampling Impacts on Thermotolerant Vegetation of Geothermal Areas in New Zealand

Geothermal features such as geysers, mud pools, sinter terraces, fumaroles, hot springs, and steaming ground are natural attractions often visited by tourists. Visitation rates for such areas in the Taupo Volcanic Zone of New Zealand are in the order of hundreds of thousands annually. These areas are also habitat for rare and specialized plant and microbial communities that live in the steam-heated soils of unusual chemical composition. We evaluated historical and current trampling impacts of tourists on the thermotolerant vegetation of the Waimangu and Waiotapu geothermal areas near Rotorua, and compared the results to experimental trampling at a third site (Taheke) not used by tourists. Historical tourism has removed vegetation and soil from around key features, and remaining subsoil is compacted into an impervious pavement on which vegetation recolonization is unlikely in the short term. Social tracks made by tourists were present at both tourist sites often leading them onto hotter soils than constructed tracks. Vegetation height and cover were lower on and adjacent to social tracks than further from them. Thermotolerant vegetation showed extremely low resistance to experimental trampling. This confirms and extends previous research that also shows that thallophytes and woody shrubs, life forms that dominate in thermotolerant vegetation, are vulnerable to trampling damage. Preservation of these vulnerable ecosystems must ensure that tourist traffic is confined to existing tracks or boardwalks, and active restoration of impacted sites may be warranted.     

Monitoring of Vegetation Impact Due to Trampling on Cadillac Mountain Summit Using High Spatial Resolution Remote Sensing Data Sets

Cadillac Mountain—the highest peak along the eastern seaboard of the United States—is a major tourist destination in Acadia National Park, Maine. Managing vegetation impact due to trampling on the Cadillac Mountain summit is extremely challenging because of the large number of visitors and the general open nature of landscape in this fragile subalpine environmental setting. Since 2000, more intensive management strategies—based on placing physical barriers and educational messages for visitors—have been employed to protect threatened vegetation, decrease vegetation impact, and enhance vegetation recovery in the vicinity of the summit loop trail. The primary purpose of this study was to evaluate the effect of the management strategies employed. For this purpose, vegetation cover changes between 2001 and 2007 were detected using multispectral high spatial resolution remote sensing data sets. A normalized difference vegetation index was employed to identify the rates of increase and decrease in the vegetation areas. Three buffering distances (30, 60, and 90?m) from the edges of the trail were used to define multiple spatial extents of the site, and the same spatial extents were employed at a nearby control site that had no visitors. No significant differences were detected between the mean rates of vegetation increase and decrease at the experimental site compared with a nearby control site in the case of a small spatial scale (≤30?m) comparison (in all cases P?>?0.05). However, in the medium (≤60?m) and large (≤90?m) spatial scales, the rates of increased vegetation were significantly greater and rates of decreased vegetation significantly lower at the experimental site compared with the control site (in all cases P?<?0.001). Research implications are explored that relate to the spatial extent of the radial patterns of impact of trampling on vegetation at the site level. Management implications are explored in terms of the spatial strategies used to decrease the impact of trampling on vegetation.     

Effects of Trampling Limitation on Coastal Dune Plant Communities

Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1–2 years) and effective method for improving and safeguarding the diversity of dune plant communities.     

Response of Three Plant Communities to Trampling in a Sand Dune System in Brittany (France)

Dunes that are protected because of their very rich and diverse plant communities are often exposed to excessive visitor pressure. The effects of trampling on the habitat must be known from a conservation viewpoint but also are important for management. To determine the response of plant assemblages to trampling by people, an experimental study was conducted on the state-owned dunes at Quiberon (Brittany, France). Indices of resistance and resilience were used to compare three typical plant communities belonging to the various landscape units: mobile dune, semifixed dune, and fixed dune. The strong contrasts between communities belonging to different successional stages reflect their ecological functioning. The mobile dune and semifixed dune with their low resistance contrasted with the fixed dune. Only the vegetation cover of the semifixed dune benefited from long-term trampling and had a very high resilience (134%). This response could be explained by a good balance of two opposite factors: soil compaction increasing soil stability and moisture content, and vegetation destruction. Because of their low resilience, trampling seems to be harmful for fixed dunes in the long term. The tourist pressure seems easier to integrate in to the mobile dunes and the semifixed dunes if periods of recovery are included in the management.     

Recovery in Naturally Dynamic Environments: A Case Study from the Sperrgebiet,Southern African Arid Succulent Karoo

Little is known about the process of vegetation recovery and associated time frames in the Succulent Karoo Biome of southern Africa. This study investigated the recovery of vegetation on sites impacted by mining (different types of dumps and mined areas) in the arid succulent karoo. The main aim of this study was to determine the state of recovery, time frames, successional stages, and the influence of environmental factors on recovery of coastal dune and sand plain plant communities. For this purpose, vegetation was recorded on some 121 sites throughout a coastal strip of approximately 100 × 3 km in Namibia’s restricted diamond area (Sperrgebiet). Using the species pool concept to derive vegetation reference sites and dominance-diversity curves, recovery of vegetation (measured in terms of species richness and cover) in these altered landscapes reached about 46% on the oldest, 51-year-old mine dumps. However, based on species richness, richness levels similar to the undisturbed reference sites were recorded after 30 years, following a logarithmic trend. Successional stages of natural recovery were indicated in this dynamic coastal environment and Cladoraphis cyperoides and Galenia fruticosa appear to be early successional species. Scaling up of studies to landscape level and developing a target community using the species pool concept are discussed as means to measure recovery in dynamic biological communities. On these altered, man-made landforms, the availability of seed may be the bottleneck to achieve vegetation cover comparable to undisturbed vegetation in the surrounding. Hence, restoration efforts should focus on this aspect.     

Ground flora trampling studies: Five years after closure

Trampling as an ecological factor is a major concern of the management of park, forest, nature preserves, and wilderness areas as recreational resources. Of particular importance to the management concept of carrying capacity is the relative resistance of native plant communities, to trampling and the resilience or the capacity of impacted communities to recover. This information can be used by management to establish seasonal use limits to prevent irreversible degradation of these resources. The purpose of this study was to follow the recolonizaton of experimental trail surfaces barren of vegetative cover and hiked at three levels of use intensity. Results of this study indicate that soil compaction as measured by soil penetration resistance increased progressively with use level while the total number of species, species diversity, and dominant index scores declined. A major finding was that the greatest degree of change occurred at the first level of hiking, indicating that major floristic measures were most affected by the least amount of hiking. Recolonization of impacted areas that received 100 trampling passes as measured by plant cover, dominant indices, floristic dissimilarity, and species diversity was similar to areas receiving four and eight times more trampling, despite major differences in soil penetration resistance. These data suggest limited use delivered at one time can be as damaging as increasing levels of use delivered at over time.     

Persistence and developmental transition of wide seismic lines in the western Boreal Plains of Canada

This study examined the fate of seismic lines utilized in oil and gas exploration in Canada's western Boreal Plains. It retrospectively followed the persistence, recovery and developmental transition of seismic lines established between the 1960s and the mid-1970s through to 2003. We examined lines that passed through three forest types; aspen, white spruce, and lowland black spruce. In general, the recovery rates of seismic lines to woody vegetation were low. After 35 years, 8.2% of seismic lines across all forest types had recovered to greater than 50% cover of woody vegetation. Only the upland forest types recovered; aspen and white spruce. Most seismic lines ( approximately 65% at 35 years) remained in a cleared state with a cover of low forbs. The most common transition for seismic lines was to tracked access ( approximately 20% at 35 years). Transition to other anthropogenic developments such as roads, pipelines, buildings, and timber harvest blocks was 5% after 35 years. The pulse of industrial activity initiated in the mid-1990s greatly increased the transition rate of seismic to tracked access for a short period of time. The discussion focused on natural and anthropogenic factors that hinder recovery and on the management directions that would facilitate greater recovery rates.     

Impacts of Experimentally Applied Mountain Biking and Hiking on Vegetation and Soil of a Deciduous Forest

Many recent trail degradation problems have been attributed to mountain biking because of its alleged capacity to do more damage than other activities, particularly hiking. This study compared the effects of experimentally applied mountain biking and hiking on the understory vegetation and soil of a deciduous forest. Five different intensities of biking and hiking (i.e., 0, 25, 75, 200 and 500 passes) were applied to 4-m-long × 1-m-wide lanes in Boyne Valley Provincial Park, Ontario, Canada. Measurements of plant stem density, species richness, and soil exposure were made before treatment, two weeks after treatment, and again one year after treatment. Biking and hiking generally had similar effects on vegetation and soil. Two weeks after treatment, stem density and species richness were reduced by up to 100% of pretreatment values. In addition, the amount of soil exposed increased by up to 54%. One year later, these treatment effects were no longer detectable. These results indicate that at a similar intensity of activity, the short-term impacts of mountain biking and hiking may not differ greatly in the undisturbed area of a deciduous forest habitat. The immediate impacts of both activities can be severe but rapid recovery should be expected when the activities are not allowed to continue. Implications of these results for trail recreation are discussed.