Jennifer W. Burt

Summary
1. The importance of site history (including initial disturbance intensity and propagule arrival)
in determining successional trajectories is a key theoretical and applied line of research in
ecology.
2. Abandoned ski slopes provide an opportunity to study successional processes following
differing initial disturbance intensities. Some ski slopes are graded with heavy equipment
when constructed (‘graded’, severe initial disturbance), while others are simply cleared of… Show more

Summary
1. The importance of site history (including initial disturbance intensity and propagule arrival)
in determining successional trajectories is a key theoretical and applied line of research in
ecology.
2. Abandoned ski slopes provide an opportunity to study successional processes following
differing initial disturbance intensities. Some ski slopes are graded with heavy equipment
when constructed (‘graded’, severe initial disturbance), while others are simply cleared of tall
woody vegetation (‘cleared’, lesser initial disturbance).
3. In a blocked chronosequence study of graded and cleared ski slopes abandoned 10–43 years
previously, we found that graded ski slopes did not show predictable recovery trajectories over
many decades. In contrast, cleared ski runs showed significant convergence with adjacent reference
forest communities.
4. Convergence in community composition on cleared ski runs was driven by trees, though
understorey species were more numerous and dominant during succession. Understorey communities
did not predictably change in species or life-form composition over time, regardless
of ski run type.
5. Graded ski runs exhibited little or no edaphic recovery over time, showing neither reductions
in bare ground and visible soil erosion, nor increases in soil depth. Cleared ski runs, in
contrast, showed evidence of recovery in all of these variables except soil depth, which
remained uniformly high.
6. Synthesis and applications. The creation of new ski slopes by tree clearing is preferable to
the grading of new slopes with heavy machinery, because grading reduces ecosystem function
and decreases the predictability of soil and vegetation recovery decades after abandonment.
Existing graded ski slopes (both operational and abandoned) may benefit from restoration of
soils and vegetation.

Media coverage of this publication included Powder Magazine, Tahoe Quarterly, San Francisco Chronicle, Sacramento Bee, Associated Press Newswire Show less

Abstract: Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high… Show more

Abstract: Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high elevation, disturbed soils, open, steep slopes). The most appropriate reference communities for selecting ski slope revegetation species are thus successional, or seral plant communities in similar environments (i.e., other ski slopes). Using results from a broad-scale reference community analysis, I evaluated plant communities naturally occurring on ski slopes from 21 active and abandoned ski areas throughout the northern Sierra Nevada to identify native plant species suitable for use in ski slope restoration. I constructed a baseline planting palette of regionally appropriate plant species (for restoration of either newly created or already existing ski runs) that is functionally diverse and is likely to succeed across a broad range of environments. I also identify a more comprehensive list of species for more specialized planting mixes based on site-specific goals and particular environmental settings. Establishing seral plant communities may be an appropriate restoration goal for many other types of managed lands, including roadsides, firebreaks and utility rights-of-way. This study describes an ecological (and potentially cost-effective) approach to developing restoration planting palettes for such managed lands. Show less

For many, being “green” means finding high-tech : and, by extension, high-cost : fixes for familiar environmental problems.

But sometimes the greenest solutions lie in reviving sensible and economical practices from the past.

Ski run construction presents one clear example.

In bygone days, when skiing operations were smaller in scope, ski runs were mostly created in ways that avoided long-term environmental degradation. In forested areas, ski area operators simply cut down… Show more

For many, being “green” means finding high-tech : and, by extension, high-cost : fixes for familiar environmental problems.

But sometimes the greenest solutions lie in reviving sensible and economical practices from the past.

Ski run construction presents one clear example.

In bygone days, when skiing operations were smaller in scope, ski runs were mostly created in ways that avoided long-term environmental degradation. In forested areas, ski area operators simply cut down trees and tall shrubs in the path of the new run, creating an open slope through the forest. Skiers flew over unseen snow-buried stumps, small shrubs, and undisturbed soils. Because the soils were left undisturbed, these ski runs were not subject to great erosion, and native plant communities regrew vigorously from the existing seedbank.

In subsequent decades, ski run construction changed dramatically. The predominant practice shifted from clearing to grading, or bulldozing ski runs to create a smooth under-snow surface, stripping the slope of vegetation, stumps, rocks, roots and seeds. The topsoil is scraped and often buried beneath the subsoil, and soils are compacted, creating a harsh environment for plant establishment and growth. … Show less

Abstract:
The early phases of biological invasions are poorly understood. In particular,
during the introduction, establishment, and possible lag phases, it is unclear to
what extent evolution must take place for an introduced species to transition
from established to expanding. In this study, we highlight three disparate data
sources that can provide insights into evolutionary processes associated with
invasion success: biological control organisms, horticultural… Show more

Abstract:
The early phases of biological invasions are poorly understood. In particular,
during the introduction, establishment, and possible lag phases, it is unclear to
what extent evolution must take place for an introduced species to transition
from established to expanding. In this study, we highlight three disparate data
sources that can provide insights into evolutionary processes associated with
invasion success: biological control organisms, horticultural introductions, and
natural history collections. All three data sources potentially provide introduction
dates, information about source populations, and genetic and morphological
samples at different time points along the invasion trajectory that can be
used to investigate preadaptation and evolution during the invasion process,
including immediately after introduction and before invasive expansion. For all
three data sources, we explore where the data are held, their quality, and their
accessibility. We argue that these sources could find widespread use with a few
additional pieces of data, such as voucher specimens collected at certain critical
time points during biocontrol agent quarantine, rearing, and release and also
for horticultural imports, neither of which are currently done consistently. In
addition, public access to collected information must become available on
centralized databases to increase its utility in ecological and evolutionary research. Show less

Abstract. In mountain regions around the world, downhill ski areas represent a significant
source of anthropogenic disturbance while also providing recreation and revenue. Ski-run
creation always results in some level of disturbance, but disturbance intensity varies greatly
with construction method. Ski runs may be established either by clearing (cutting and
removing tall vegetation) or by clearing and then machine-grading (leveling the soil surface
with heavy equipment). To… Show more

Abstract. In mountain regions around the world, downhill ski areas represent a significant
source of anthropogenic disturbance while also providing recreation and revenue. Ski-run
creation always results in some level of disturbance, but disturbance intensity varies greatly
with construction method. Ski runs may be established either by clearing (cutting and
removing tall vegetation) or by clearing and then machine-grading (leveling the soil surface
with heavy equipment). To quantify how these different intensities of initial disturbance affect
ecosystem properties, we extensively surveyed vegetation, soils, and environmental characteristics
on cleared ski runs, graded ski runs, and adjacent reference forests across seven large
downhill ski resorts in the northern Sierra Nevada, USA. We found that the greater
disturbance intensity associated with grading resulted in greater impacts on all ecosystem
properties considered, including plant community composition and diversity, soil characteristics
relating to processes of nutrient cycling and retention, and measures of erosion potential.
We also found that cleared ski runs retained many ecological similarities to reference forests
and might even offer some added benefits by possessing greater plant species and functional
diversity than either forests or graded runs. Because grading is more damaging to multiple
indicators of ecosystem function, clearing rather than grading should be used to create ski
slopes wherever practical.

Media coverage of this publication included The New York Times, The Economist, NPR's Marketplace, Capital Public Radio's Insight, and The History Channel's Life After People. Show less

Abstract The aquarium trade is an important and rapidly growing vector for introduced species in the
United States. We examined this vector by surveying pet stores in the San Francisco Bay–Delta region to
compile a list of aquarium fish species commonly stocked. We identified which of these species might be able to survive in the Bay–Delta, and investigated store representatives’ knowledge and attitudes about biological invasions. A restrictive analysis using conservative estimates of… Show more

Abstract The aquarium trade is an important and rapidly growing vector for introduced species in the
United States. We examined this vector by surveying pet stores in the San Francisco Bay–Delta region to
compile a list of aquarium fish species commonly stocked. We identified which of these species might be able to survive in the Bay–Delta, and investigated store representatives’ knowledge and attitudes about biological invasions. A restrictive analysis using conservative estimates of fish temperature tolerances and environmental conditions found that the local aquarium trade includes 5 fish species that can survive in a temperate system such as the Bay–Delta. Under more inclusive parameters, up to 27 fish species met the criteria for survival in the Bay–Delta. We further explored these results by
comparing potential invader incidence between different types of stores. In the more restrictive analysis, three national retail chains stocked significantly more potentially invasive species than independent aquarium stores, but there was no difference in the more inclusive analysis. A significantly
higher percentage of fish taxa were easily identifiable and well-labeled in chain stores than in independent stores. Most aquarium store representatives indicated willingness to take action to reduce the threat of traderelated introductions, although chain store employees were more willing to assign responsibility for reducing this threat to the aquarium industry than were independent store employees. Management efforts for this vector should focus on (a) improving labeling and identification of fish species in stores, (b) expanding the often spotty data on fish physiological tolerances, especially for saltwater species, (c) educating customers and store employees about the risks
posed by pet release, and (d) providing better options for responsible disposal of unwanted fish. Show less

Abstract: Although prevention is the most cost-effective way to avoid the enormous expenses associated with plant invasions, invasive plants continue to be imported as trade commodities for horticultural use. With very little government regulation of horticultural imports of invasive plants, efforts have turned toward fostering voluntary initiatives to encourage self-regulation by the horticulture trade. Our study takes the first step toward evaluating the potential success of these voluntary… Show more

Abstract: Although prevention is the most cost-effective way to avoid the enormous expenses associated with plant invasions, invasive plants continue to be imported as trade commodities for horticultural use. With very little government regulation of horticultural imports of invasive plants, efforts have turned toward fostering voluntary initiatives to encourage self-regulation by the horticulture trade. Our study takes the first step toward evaluating the potential success of these voluntary initiatives. We conducted a survey of nursery professionals to gauge their perceptions of invasive species, the role of the horticulture trade in invasive plant introductions, and their participation—potential and actual—in preventive measures outlined in the St Louis Voluntary Codes of Conduct for nursery professionals. We found nursery professionals to be highly aware of invasive plants and to accept responsibility as a trade for horticultural introductions. Although only 7% of respondents had heard of the St Louis Voluntary Codes of Conduct, the majority (57%) reported having participated in at least two of seven preventive measures, and most (78%) reported willingness to engage in the majority of preventive measures. We found that several factors significantly predict increased participation in preventive measures, particularly awareness of invasive plants and involvement in trade associations. We also identified incentives and obstacles to participating in preventive behaviors, including “concern for the environment” and “lack of information,” respectively. Our results suggest that participation in voluntary initiatives will improve through increased outreach, and we provide specific recommendations for improving participation in voluntary programs in the horticulture trade. Show less

Abstract: Natural habitats vary in the degree to which they are invaded by exotic species, but it is unclear whether they differ in the mechanisms underlying the spatial spread of a given exotic species. To compare the dynamics of invasion in highly invaded non-serpentine oak woodlands and less-invaded serpentine habitats, we used an historical "experiment" consisting of the introduction of several nonnative species for post-mining revegetation, supplemented by a pot experiment and a factorial… Show more

Abstract: Natural habitats vary in the degree to which they are invaded by exotic species, but it is unclear whether they differ in the mechanisms underlying the spatial spread of a given exotic species. To compare the dynamics of invasion in highly invaded non-serpentine oak woodlands and less-invaded serpentine habitats, we used an historical "experiment" consisting of the introduction of several nonnative species for post-mining revegetation, supplemented by a pot experiment and a factorial field experiment. Three species showed significant declines in abundance on transects from revegetated zones into natural habitats, indicating that these species had spread into the natural habitats from revegetated zones. Dactylis glomerata and Trifolium hirtum were found up to 95 m into oak woodland, 35 m into serpentine meadows, and 0-25 m into serpentine seeps and chaparral, while Elytrigia pontica was found up to 45 m into serpentine seeps. The pot experiment showed that this pattern of distribution for Dactylis was not caused or limited by variation in soil properties. The field experiment showed that Dactylis invasion in both oak woodland and serpentine meadow habitats was limited by disturbance and seed supply. Dactylis success was negatively correlated with species richness in oak woodlands, but positively correlated with richness in serpentine meadows, suggesting that the relationships between diversity, invasion, and underlying habitat suitability differed between these habitats. Our results show that in harsh serpentine soils, the spread of recently introduced exotic species is slower than in more fertile and more invaded oak woodlands. However, disturbance and propagule addition are equally important in promoting the spread of invaders in both environments. Show less