1999
Bergey, Elizabeth A.
Crevices as refugia for stream diatoms: Effect of crevice size on abraded substrates Journal Article
In: Limnology and Oceanography, vol. 44, no. 6, pp. 1522-1529, 1999, ISSN: 0024-3590, (Note that the file size exceeds the maximum allowable for the Angelo database. Please see the attached stable URL for a link to the PDF.).
Abstract | Links | BibTeX | Tags: algal communities, colonization, disturbance, habitat structure, marine-invertebrates, New England, rocky intertidal community, species-diversity, tidal community, upland stream
@article{Bergey1999,
title = {Crevices as refugia for stream diatoms: Effect of crevice size on abraded substrates},
author = {Elizabeth A. Bergey},
editor = {ROCKY INTERTIDAL COMMUNITY; MARINE-INVERTEBRATES; ALGAL COMMUNITIES; SPECIES-DIVERSITY; HABITAT STRUCTURE; TIDAL COMMUNITY; UPLAND STREAM; NEW-ENGLAND; DISTURBANCE; COLONIZATION},
url = {http://www.jstor.org/stable/2670734},
issn = {0024-3590},
year = {1999},
date = {1999-09-00},
journal = {Limnology and Oceanography},
volume = {44},
number = {6},
pages = {1522-1529},
abstract = {This study explored the mechanisms by which crevices act as refugia for small algae during abrasive disturbances. Four substrates with different crevice features were subjected to three levels of abrasion in a stream-based experiment. Substrates were sand-grain caddisfly cases and three glass rod substrates that mimicked caddisfly cases in size and shape, as well as forming a gradient of larger crevices (i.e., smooth with no crevices, sanded with shallow pits, and scratched with deeper grooves). Substrates were subjected to no, low, or high abrasion levels during 18 d of incubation by pulling substrates through a sand-gravel mixture in floating enclosures that housed the experiment. Diatom density, relative biovolume, location in crevices, detritus accumulation, and filamentous algal density were compared among substrate types and abrasion levels. Across all abrasion levels, diatom and filamentous algal densities were higher on caddisfly cases than on all three glass rod substrates. Although abrasion greatly reduced overall diatom density, diatoms within crevices were largely protected. Crevice size influenced diatom size and composition. The small crevices of sanded rods contained primarily small diatoms of a single species (Achnanthidium minutissimum), whereas the larger crevices of scratched rods and caddisfly cases contained a greater range of diatom size and, consequently, greater species diversity. Detritus accumulated in all crevices, and accumulation increased with level of abrasion. Diatom biovolume decreased and location in crevices increased with the level of abrasion on the less textured smooth and sanded glass rods. Abrasion level had little effect on algal assemblages on caddisfly cases. This study demonstrates that crevices can be important refugia from abrasive disturbances, and that the size of crevices relative to organismal size can influence the protective value of crevices.},
note = {Note that the file size exceeds the maximum allowable for the Angelo database. Please see the attached stable URL for a link to the PDF.},
keywords = {algal communities, colonization, disturbance, habitat structure, marine-invertebrates, New England, rocky intertidal community, species-diversity, tidal community, upland stream},
pubstate = {published},
tppubtype = {article}
}
This study explored the mechanisms by which crevices act as refugia for small algae during abrasive disturbances. Four substrates with different crevice features were subjected to three levels of abrasion in a stream-based experiment. Substrates were sand-grain caddisfly cases and three glass rod substrates that mimicked caddisfly cases in size and shape, as well as forming a gradient of larger crevices (i.e., smooth with no crevices, sanded with shallow pits, and scratched with deeper grooves). Substrates were subjected to no, low, or high abrasion levels during 18 d of incubation by pulling substrates through a sand-gravel mixture in floating enclosures that housed the experiment. Diatom density, relative biovolume, location in crevices, detritus accumulation, and filamentous algal density were compared among substrate types and abrasion levels. Across all abrasion levels, diatom and filamentous algal densities were higher on caddisfly cases than on all three glass rod substrates. Although abrasion greatly reduced overall diatom density, diatoms within crevices were largely protected. Crevice size influenced diatom size and composition. The small crevices of sanded rods contained primarily small diatoms of a single species (Achnanthidium minutissimum), whereas the larger crevices of scratched rods and caddisfly cases contained a greater range of diatom size and, consequently, greater species diversity. Detritus accumulated in all crevices, and accumulation increased with level of abrasion. Diatom biovolume decreased and location in crevices increased with the level of abrasion on the less textured smooth and sanded glass rods. Abrasion level had little effect on algal assemblages on caddisfly cases. This study demonstrates that crevices can be important refugia from abrasive disturbances, and that the size of crevices relative to organismal size can influence the protective value of crevices.
1997
Kotanen, Peter M.
Effects of experimental soil disturbance on revegetation by natives and exotics in coastal Californian meadows Journal Article
In: Journal of Applied Ecology, vol. 34, no. 3, pp. 631-644, 1997, ISSN: 0021-8901.
Abstract | Links | BibTeX | Tags: biological invasions, colonization, grasses, introductions
@article{Kotanen1997,
title = {Effects of experimental soil disturbance on revegetation by natives and exotics in coastal Californian meadows},
author = {Peter M. Kotanen},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Kotanen_AppliedEcology1997.pdf},
issn = {0021-8901},
year = {1997},
date = {1997-09-00},
journal = {Journal of Applied Ecology},
volume = {34},
number = {3},
pages = {631-644},
abstract = {1. Disturbance is widely believed to facilitate invasions by exotic plants, but is also important for the persistence of many native species. Here, I report the results of a series of field experiments designed to investigate the effects of soil disturbance on natives and aliens in Californian grassland vegetation. I also compare the effects of different types of soil disturbance to establish whether some favour aliens to a greater degree than others.
2. In two experiments, conducted at different locations, three types of soil disturbance (excavation, burial and simulated gopher mounds) were created, and their revegetation was compared with changes in undisturbed control plots over the next three years. A third experiment was used to provide data on the effects of soil disturbance on soil temperature, moisture and KCl-extractable nitrogen.
3. Disturbance affected both soil temperature and chemistry. Buried plots contained the most KCl-extractable nitrogen, and were also the warmest. Effects on soil moisture were relatively small.
4. Initially, most disturbances greatly reduced the numerical abundance both of groups dominated by natives (perennial graminoids and bulbs) and of groups dominated by aliens (annual graminoids). Disturbance also reduced maximal (summer) species richness, but in some cases increased the fraction of richness contributed by natives.
5. In subsequent years, richness rebounded as natives and exotics re-invaded. Native bulbs and perennial graminoids were slow to recover; instead, most disturbances sr increasingly became numerically dominated by exotic annual grasses, accentuating the effects of a multi-year drought.
6. The differing effects of experimental disturbances on aliens and natives can best be explained by considering relationships between sources of propagules, life histories and geographical origins.
7. Some types of disturbance were less damaging to native-dominated groups than others, but most ultimately favoured exotics. Consequently, it may be difficult to develop management strategies that preserve the diversity of disturbance-dependent natives while still excluding weedy aliens.},
keywords = {biological invasions, colonization, grasses, introductions},
pubstate = {published},
tppubtype = {article}
}
1. Disturbance is widely believed to facilitate invasions by exotic plants, but is also important for the persistence of many native species. Here, I report the results of a series of field experiments designed to investigate the effects of soil disturbance on natives and aliens in Californian grassland vegetation. I also compare the effects of different types of soil disturbance to establish whether some favour aliens to a greater degree than others.
2. In two experiments, conducted at different locations, three types of soil disturbance (excavation, burial and simulated gopher mounds) were created, and their revegetation was compared with changes in undisturbed control plots over the next three years. A third experiment was used to provide data on the effects of soil disturbance on soil temperature, moisture and KCl-extractable nitrogen.
3. Disturbance affected both soil temperature and chemistry. Buried plots contained the most KCl-extractable nitrogen, and were also the warmest. Effects on soil moisture were relatively small.
4. Initially, most disturbances greatly reduced the numerical abundance both of groups dominated by natives (perennial graminoids and bulbs) and of groups dominated by aliens (annual graminoids). Disturbance also reduced maximal (summer) species richness, but in some cases increased the fraction of richness contributed by natives.
5. In subsequent years, richness rebounded as natives and exotics re-invaded. Native bulbs and perennial graminoids were slow to recover; instead, most disturbances sr increasingly became numerically dominated by exotic annual grasses, accentuating the effects of a multi-year drought.
6. The differing effects of experimental disturbances on aliens and natives can best be explained by considering relationships between sources of propagules, life histories and geographical origins.
7. Some types of disturbance were less damaging to native-dominated groups than others, but most ultimately favoured exotics. Consequently, it may be difficult to develop management strategies that preserve the diversity of disturbance-dependent natives while still excluding weedy aliens.
2. In two experiments, conducted at different locations, three types of soil disturbance (excavation, burial and simulated gopher mounds) were created, and their revegetation was compared with changes in undisturbed control plots over the next three years. A third experiment was used to provide data on the effects of soil disturbance on soil temperature, moisture and KCl-extractable nitrogen.
3. Disturbance affected both soil temperature and chemistry. Buried plots contained the most KCl-extractable nitrogen, and were also the warmest. Effects on soil moisture were relatively small.
4. Initially, most disturbances greatly reduced the numerical abundance both of groups dominated by natives (perennial graminoids and bulbs) and of groups dominated by aliens (annual graminoids). Disturbance also reduced maximal (summer) species richness, but in some cases increased the fraction of richness contributed by natives.
5. In subsequent years, richness rebounded as natives and exotics re-invaded. Native bulbs and perennial graminoids were slow to recover; instead, most disturbances sr increasingly became numerically dominated by exotic annual grasses, accentuating the effects of a multi-year drought.
6. The differing effects of experimental disturbances on aliens and natives can best be explained by considering relationships between sources of propagules, life histories and geographical origins.
7. Some types of disturbance were less damaging to native-dominated groups than others, but most ultimately favoured exotics. Consequently, it may be difficult to develop management strategies that preserve the diversity of disturbance-dependent natives while still excluding weedy aliens.