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Unburnt Areas (unburnt + area)
Selected AbstractsEffect of fire on benthic algal assemblage structure and recolonization in intermittent streamsAUSTRAL ECOLOGY, Issue 6 2006AMANDA L. COWELL Abstract: Dry biofilm on rocks and other substrata forms an important drought refuge for benthic algae in intermittent streams following the cessation of flow. This dry biofilm is potentially susceptible to disturbance from bushfires, including direct burning and/or scorching and damage from radiant heat, particularly when streams are dry. Therefore, damage to dry biofilms by fire has the potential to influence algal recolonization and assemblage structure in intermittent streams following commencement of flow. The influence of fire on benthic algal assemblages and recolonization was examined in intermittent streams of the Grampians National Park, Victoria, Australia, using a field survey and manipulative field experiment. The field survey compared assemblages in two intermittent streams within a recently burnt area (within 5 months of the fire) with two intermittent streams within an unburnt area. The two burnt streams were still flowing during the fire so most biofilms were not likely to be directly exposed to flames. Considerable site-to-site and stream-to-stream variation was detected during the field survey, which may have obscured potential differences attributable to indirect effects of the fire. The manipulative field experiment occurred in two intermittent streams and consisted of five treatments chosen to replicate various characteristics of bushfires that may influence dry biofilms: dry biofilm exposed directly to fire; dry biofilm exposed to radiant heat; dry biofilm exposed to ash; and two procedural controls. After exposure to the different treatments, rocks were replaced in the streams and algae were sampled 7 days after flow commenced. Differences occurred across treatments, but treatment differences were inconsistent across the two streams. For example, direct exposure to fire reduced the abundance of recolonizing algae and altered assemblage structure in both streams, while radiant heat had an effect on assemblage structure in one stream only. The manipulative field experiment is likely to have represented the intensity of a small bushfire only. Nonetheless, significant differences across treatments were detected, so these experimental results suggest that fire can damage dry biofilms, and hence, influence algal recolonization and assemblage structure in intermittent streams. [source] The role of environmental gradients in non-native plant invasion into burnt areas of Yosemite National Park, CaliforniaDIVERSITY AND DISTRIBUTIONS, Issue 2 2006Rob Klinger ABSTRACT Fire is known to facilitate the invasion of many non-native plant species, but how invasion into burnt areas varies along environmental gradients is not well-understood. We used two pre-existing data sets to analyse patterns of invasion by non-native plant species into burnt areas along gradients of topography, soil and vegetation structure in Yosemite National Park, California, USA. A total of 46 non-native species (all herbaceous) were recorded in the two data sets. They occurred in all seven of the major plant formations in the park, but were least common in subalpine and upper montane conifer forests. There was no significant difference in species richness or cover of non-natives between burnt and unburnt areas for either data set, and environmental gradients had a stronger effect on patterns of non-native species distribution, abundance and species composition than burning. Cover and species richness of non-natives had significant positive correlations with slope (steepness) and herbaceous cover, while species richness had significant negative correlations with elevation, the number of years post-burn, and cover of woody vegetation. Non-native species comprised a relatively minor component of the vegetation in both burnt and unburnt areas in Yosemite (percentage species = 4%, mean cover < 6.0%), and those species that did occur in burnt areas tended not to persist over time. The results indicate that in many western montane ecosystems, fire alone will not necessarily result in increased rates of invasion into burnt areas. However, it would be premature to conclude that non-native species could not affect post-fire succession patterns in these systems. Short fire-return intervals and high fire severity coupled with increased propagule pressure from areas used heavily by humans could still lead to high rates of invasion, establishment and spread even in highly protected areas such as Yosemite. [source] The importance of post-fire regrowth for sable antelope in a Southern African savannaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Francesca Parrini Abstract Burning is commonly used in savannas to stimulate grass regrowth for grazing ungulates. We recorded the relative use of burns occurring at different stages in the seasonal cycle, as well as in different regions of the landscape by two herds of sable. We also recorded behavioural measures of foraging efficiency and faecal nutrient contents as an indication of nutrient gains. Sable consistently concentrated their grazing on burned areas provided there was sufficient green regrowth during the dry season. In these circumstances they grazed for longer per feeding station, showed a slower step rate while foraging, and shorter between-patch moves, and a higher probability of encountering acceptable food per step taken while foraging than on unburnt areas. In the year when only a burn with insufficient regrowth was available, sable continued to forage in the area that had been burned during the previous year. Faecal crude protein was substantially higher at the end of the dry season in the year when burned areas were utilized. Accordingly early dry season fires can be important in helping sable bridge the nutritional limitations posed by the dry season, provided sufficient soil moisture remains to promote adequate grass regrowth. Résumé Les feux sont fréquemment utilisés dans les savanes pour stimuler la repousse des herbes consommées par les ongulés herbivores. Nous avons enregistré l'utilisation relative des aires brûlées à différents stades du cycle saisonnier, et dans différentes régions du paysage, par deux hardes d'antilopes sable. Nous avons aussi enregistré des mesures comportementales de l'efficacité du nourrissage et le contenu en nutriments des matières fécales pour avoir une indication du gain en nutriments. Les antilopes sable concentraient leur pâturage de façon continue sur les aires brûlées pour autant que la repousse de verdure fût suffisante au cours de la saison sèche. Dans ce cas-là, elles paissaient plus longtemps par station de nourrissage, présentaient un nombre de pas plus faible en mangeant et se déplaçaient moins entre les arrêts, et la probabilité qu'elles rencontrent une nourriture acceptable par pas franchi en cherchant leur nourriture était plus grande que dans les zones non brûlées. L'année où ne fut disponible qu'une zone brûlée où la repousse était insuffisante, les antilopes ont continuéà brouter dans la zone qui avait été brûlée l'année précédente. Le taux de protéines brutes des matières fécales était substantiellement plus haut à la fin de la saison sèche l'année où les zones brûlées ont été utilisées. En fonction de cela, on peut dire que les feux du début de la saison sèche peuvent être importants pour aider les antilopes sable à passer le cap des limites nutritionnelles imposées par la saison sèche, à condition qu'il reste suffisamment d'humidité dans le sol pour favoriser une repousse d'herbes adéquate. [source] Throughfall, runoff and soil erosion after prescribed burning in gorse shrubland in Galicia (NW Spain)LAND DEGRADATION AND DEVELOPMENT, Issue 1 2005J. A. Vega Abstract The first-year effect of two different prescribed burning treatments on throughfall, runoff and soil erosion was evaluated in gorse shrubland (Ulex europaeus L.) in Galicia (NW Spain). The treatments compared were: intense burn, light burn and control (no burn). Accumulated annual throughfall represented between the 81 and 87,per,cent of total rainfall in intensely burned and lightly burned areas, respectively, whereas in the unburnt areas it was 60,per,cent. No significant differences between burning treatments were found for the annual throughfall. However, runoff was significantly greater in intensely burned plots (1·5-times) than in lightly burned plots. Burning also resulted in a significant increase in runoff (between 2·5 and 1·7-times, respectively) compared with controls. Total soil losses were small in all treatments, but the intense burn caused significantly greater soil erosion (5·8-times) compared with the unburned areas. Soil losses after the light burn did not significantly differ from the control although they were higher (2·3-times). The relationships obtained between erosion and several rainfall parameters were significantly different in burned areas compared to the control. The same response was observed for runoff. Annual erosion losses showed a strong dependence on percentage of bare soil even for small values of this variable. Litter thickness was also a very important variable influencing on erosion rates. This study indicated that by combining ignition techniques and high litter moisture content to maintain the percentage of bare soil below 85,per,cent, soil erosion was low. Nevertheless, this result was constrained by the low rainfall that occurred during the study. Copyright © 2005 John Wiley & Sons, Ltd. [source] Resprouting of saplings following a tropical rainforest fire in north-east Queensland, AustraliaAUSTRAL ECOLOGY, Issue 8 2005MATTHEW J. MARRINAN Abstract In 2002, fire burnt areas of Mesophyll- and Notophyll Vine Forest in the Smithfield Conservation Park near Cairns, Australia. We assessed the ability of rainforest plant species to persist through fire via resprouting. Natural rates of mortality and resprouting in unburnt areas were assessed for all saplings (stems < 2 m) via 13, 2 × 50 m belt transects, and compared to estimates of mortality and resprouting in 26 transects in burnt areas. We also tested the resprouting ability per-individual stem of each species against all other stems with which it co-occurred. Totals of 1242 stems (138 species) were sampled in burnt transects and 503 stems (95 species) in unburnt transects (total number of unique species = 169). There was no difference in the number of stems existing prior to the fire in burnt and unburnt areas when expressed on a per-sample area basis. Resprouting from basal shoots and root suckers was significantly greater in burnt than in unburnt areas, but rates of stem sprouting were not different. In burnt areas 72 species were tested for resprouting ability and most (65/72) resprouted at similar rates. All species analysed contained individuals that resprouted. The resprouting response of five species was significantly lower, and in two species was significantly higher. For these species especially, fire may act as a mechanism altering relative abundances. The fire coincided with an extreme El Niño event. Current predictions indicate El Niño conditions may become increasingly common, suggesting fire events within rainforest could become more frequent. Resprouting as a general phenomenon of rainforest species, and differential resprouting ability between species should therefore be an important consideration in assessing the potential path of vegetation change in rainforests after fire. [source] | ||||||||||