Pub Date : 2009-06-16DOI: 10.2174/1874213000902010052
U. Visser, K. Wiegand, V. Grimm, K. Johst
In the context of agricultural landscapes, conservation biocontrol practitioners attempt to secure and enhance the presence and effectiveness of natural enemies of insect pest species, for example parasitoids. Conservation biocontrol aims at maximizing both parasitoid persistence and parasitation rate. It is, however, still poorly understood how the amount, fragmentation and isolation of non-crop habitat of the host and its parasitoid affect persistence and parasitation rate. We developed a spatially explicit simulation model of a host and its specialized parasitoid and simulated their spatiotemporal population dynamics in virtual landscapes. We found that the total habitat amount in the landscape modulates the impact of fragmentation on parasitoid persistence. If habitat is abundant, parasitoid persistence decreases with fragmentation, whereas if habitat is scarce, persistence is highest at intermediate levels of fragmentation. In any case, persistence is best for intermediate levels of isolation. Parasitation rate, on the other hand, is negatively influenced by fragmentation and isolation regardless of the habitat amount. Our results suggest that in landscapes with abundant habitat, both parasitation rates and parasitoid persistence can be increased by arranging habitat to be as clumped as possible. However, if habitat is scarce, landscape management can optimize either parasitation rates or parasitoid persistence but not both simultaneously.
{"title":"Conservation Biocontrol in Fragmented Landscapes: Persistence and Parasitation in a Host-Parasitoid Model","authors":"U. Visser, K. Wiegand, V. Grimm, K. Johst","doi":"10.2174/1874213000902010052","DOIUrl":"https://doi.org/10.2174/1874213000902010052","url":null,"abstract":"In the context of agricultural landscapes, conservation biocontrol practitioners attempt to secure and enhance the presence and effectiveness of natural enemies of insect pest species, for example parasitoids. Conservation biocontrol aims at maximizing both parasitoid persistence and parasitation rate. It is, however, still poorly understood how the amount, fragmentation and isolation of non-crop habitat of the host and its parasitoid affect persistence and parasitation rate. We developed a spatially explicit simulation model of a host and its specialized parasitoid and simulated their spatiotemporal population dynamics in virtual landscapes. We found that the total habitat amount in the landscape modulates the impact of fragmentation on parasitoid persistence. If habitat is abundant, parasitoid persistence decreases with fragmentation, whereas if habitat is scarce, persistence is highest at intermediate levels of fragmentation. In any case, persistence is best for intermediate levels of isolation. Parasitation rate, on the other hand, is negatively influenced by fragmentation and isolation regardless of the habitat amount. Our results suggest that in landscapes with abundant habitat, both parasitation rates and parasitoid persistence can be increased by arranging habitat to be as clumped as possible. However, if habitat is scarce, landscape management can optimize either parasitation rates or parasitoid persistence but not both simultaneously.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"2 1","pages":"52-61"},"PeriodicalIF":0.0,"publicationDate":"2009-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-04-23DOI: 10.2174/1874213000902010029
R. Loyola
I performed an exploratory analysis of four broad-scale hypotheses (area availability, energy availability, habi- tat heterogeneity and geometric constraints) for changes in species richness over Central American mayfly species, and compared their outcomes at different taxonomic levels. I employed an eigenvector-based spatial filtering to control spatial autocorrelation effects and conducted multiple spatial eigenvector regressions to identify the strongest predictors of spe- cies, genus and family richness. The usefulness of higher-taxa as surrogates for species richness was assessed by Pearson correlations. Mayfly species richness is characterized by a patchy pattern. None of the variables accounted for observed patterns. Only area availability was an effective predictor of mayfly genus and family richness, although both habitat het- erogeneity and energy presented marginal effects on genus richness. I did not observe any relationship between species and higher-taxa richness. Broad-scale hypotheses did not explain species richness patterns of mayflies, which instead can be explained by interactions among studied variables and spatial structure.
{"title":"Broad-Scale Hypotheses do not Account for Species Richness Patterns of Central American Mayflies","authors":"R. Loyola","doi":"10.2174/1874213000902010029","DOIUrl":"https://doi.org/10.2174/1874213000902010029","url":null,"abstract":"I performed an exploratory analysis of four broad-scale hypotheses (area availability, energy availability, habi- tat heterogeneity and geometric constraints) for changes in species richness over Central American mayfly species, and compared their outcomes at different taxonomic levels. I employed an eigenvector-based spatial filtering to control spatial autocorrelation effects and conducted multiple spatial eigenvector regressions to identify the strongest predictors of spe- cies, genus and family richness. The usefulness of higher-taxa as surrogates for species richness was assessed by Pearson correlations. Mayfly species richness is characterized by a patchy pattern. None of the variables accounted for observed patterns. Only area availability was an effective predictor of mayfly genus and family richness, although both habitat het- erogeneity and energy presented marginal effects on genus richness. I did not observe any relationship between species and higher-taxa richness. Broad-scale hypotheses did not explain species richness patterns of mayflies, which instead can be explained by interactions among studied variables and spatial structure.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"2 1","pages":"29-36"},"PeriodicalIF":0.0,"publicationDate":"2009-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68052673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-04-23DOI: 10.2174/1874213000902010037
J. Hewitt, S. Thrush
The relationship between stress and population variability is essential for predicting whether communities will exhibit stability and resilience when faced with stress. Stress is generally considered to increase biological variability, even before mean responses exhibit change. However, generalities related to spatial variability of populations have not emerged, as large-scale perturbations tend to reduce variability in affected areas (i.e., a homogenising effect), and a posi- tive relationship between mean and variance is expected at all scales. To investigate whether stress does increase the spa- tial variability of macrobenthic species abundances, we analysed the response of survey and experimental data, collected over a variety of space (50 m to 5 km) and time scales (15 d to 15 yr), to two different stressors. We observed no consis- tent increase in variability as a response to stress, even within studies. Moreover, a complex relationship was observed be- tween spatial variance and mean abundances that was not represented by a simple power law. However, one consistent re- sponse was observed across stressors and study type; the number of common species exhibiting changes (either increases or decreases) to their spatial variability, beyond natural levels, increased with stress. It seems likely that having species within a community whose spatial variability responds in different ways to stress (rather than spatial variability of all spe- cies increasing) may be crucial to smoothing out tensions between species and increasing resilience.
{"title":"Do Species’ Abundances become More Spatially Variable with Stress?","authors":"J. Hewitt, S. Thrush","doi":"10.2174/1874213000902010037","DOIUrl":"https://doi.org/10.2174/1874213000902010037","url":null,"abstract":"The relationship between stress and population variability is essential for predicting whether communities will exhibit stability and resilience when faced with stress. Stress is generally considered to increase biological variability, even before mean responses exhibit change. However, generalities related to spatial variability of populations have not emerged, as large-scale perturbations tend to reduce variability in affected areas (i.e., a homogenising effect), and a posi- tive relationship between mean and variance is expected at all scales. To investigate whether stress does increase the spa- tial variability of macrobenthic species abundances, we analysed the response of survey and experimental data, collected over a variety of space (50 m to 5 km) and time scales (15 d to 15 yr), to two different stressors. We observed no consis- tent increase in variability as a response to stress, even within studies. Moreover, a complex relationship was observed be- tween spatial variance and mean abundances that was not represented by a simple power law. However, one consistent re- sponse was observed across stressors and study type; the number of common species exhibiting changes (either increases or decreases) to their spatial variability, beyond natural levels, increased with stress. It seems likely that having species within a community whose spatial variability responds in different ways to stress (rather than spatial variability of all spe- cies increasing) may be crucial to smoothing out tensions between species and increasing resilience.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"15 1","pages":"37-46"},"PeriodicalIF":0.0,"publicationDate":"2009-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-04-01DOI: 10.2174/1874213000902010025
R. Borsuk, A. Budden, Roosa Leimu, L. Aarssen, C. Lortie
Citation metrics are widely used as a surrogate measure of scientific merit; however, these indices may be sensitive to factors and influences unrelated to merit. We examined citation rates for 5883 articles in relation to number of authors, first author's primary language, and gender. Citation rates were unrelated to primary language and gender but increased with author number. These findings add to a growing body of indirect evidence for potential attitudinal bias in the perceived merit of publications within ecology.
{"title":"The Influence of Author Gender, National Language and Number of Authors on Citation Rate in Ecology","authors":"R. Borsuk, A. Budden, Roosa Leimu, L. Aarssen, C. Lortie","doi":"10.2174/1874213000902010025","DOIUrl":"https://doi.org/10.2174/1874213000902010025","url":null,"abstract":"Citation metrics are widely used as a surrogate measure of scientific merit; however, these indices may be sensitive to factors and influences unrelated to merit. We examined citation rates for 5883 articles in relation to number of authors, first author's primary language, and gender. Citation rates were unrelated to primary language and gender but increased with author number. These findings add to a growing body of indirect evidence for potential attitudinal bias in the perceived merit of publications within ecology.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"2 1","pages":"25-28"},"PeriodicalIF":0.0,"publicationDate":"2009-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68052659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-02-13DOI: 10.2174/1874213000902010007
C. Dormann, Jochen Fründ, N. Blüthgen, B. Gruber
Many analyses of ecological networks in recent years have introduced new indices to describe network properties. As a consequence, tens of indices are available to address similar questions, differing in specific detail, sensitivity in detecting the property in question, and robustness with respect to network size and sampling intensity. Furthermore, some indices merely reflect the number of species participating in a network, but not their interrelationship, requiring a null model approach. Here we introduce a new, free software calculating a large spectrum of network indices, visualizing bipartite networks and generating null models. We use this tool to explore the sensitivity of 26 network indices to network dimensions, sampling intensity and singleton observations. Based on observed data, we investigate the interrelationship of these indices, and show that they are highly correlated, and heavily influenced by network dimensions and connectance. Finally, we re-evaluate five common hypotheses about network properties, comparing 19 pollination networks with three differently complex null models: 1. The number of links per species ("degree") follow (truncated) power law distributions. 2. Generalist pollinators interact with specialist plants, and vice versa (dependence asymmetry). 3. Ecological networks are nested. 4. Pollinators display complementarity, owing to specialization within the network. 5. Plant-pollinator networks are more robust to extinction than random networks. Our results indicate that while some hypotheses hold up against our null models, others are to a large extent understandable on the basis of network size, rather than ecological interrelationships. In particular, null model pattern of dependence asymmetry and robustness to extinction are opposite to what current network paradigms suggest. Our analysis, and the tools we provide, enables ecologists to readily contrast their findings with null model expectations for many different questions, thus separating statistical inevitability from ecological process.
{"title":"Indices, Graphs and Null Models: Analyzing Bipartite Ecological Networks","authors":"C. Dormann, Jochen Fründ, N. Blüthgen, B. Gruber","doi":"10.2174/1874213000902010007","DOIUrl":"https://doi.org/10.2174/1874213000902010007","url":null,"abstract":"Many analyses of ecological networks in recent years have introduced new indices to describe network properties. As a consequence, tens of indices are available to address similar questions, differing in specific detail, sensitivity in detecting the property in question, and robustness with respect to network size and sampling intensity. Furthermore, some indices merely reflect the number of species participating in a network, but not their interrelationship, requiring a null model approach. Here we introduce a new, free software calculating a large spectrum of network indices, visualizing bipartite networks and generating null models. We use this tool to explore the sensitivity of 26 network indices to network dimensions, sampling intensity and singleton observations. Based on observed data, we investigate the interrelationship of these indices, and show that they are highly correlated, and heavily influenced by network dimensions and connectance. Finally, we re-evaluate five common hypotheses about network properties, comparing 19 pollination networks with three differently complex null models: 1. The number of links per species (\"degree\") follow (truncated) power law distributions. 2. Generalist pollinators interact with specialist plants, and vice versa (dependence asymmetry). 3. Ecological networks are nested. 4. Pollinators display complementarity, owing to specialization within the network. 5. Plant-pollinator networks are more robust to extinction than random networks. Our results indicate that while some hypotheses hold up against our null models, others are to a large extent understandable on the basis of network size, rather than ecological interrelationships. In particular, null model pattern of dependence asymmetry and robustness to extinction are opposite to what current network paradigms suggest. Our analysis, and the tools we provide, enables ecologists to readily contrast their findings with null model expectations for many different questions, thus separating statistical inevitability from ecological process.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"2 1","pages":"7-24"},"PeriodicalIF":0.0,"publicationDate":"2009-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-02-05DOI: 10.2174/1874213000902010001
J. Laundré, J. M. M. Calderas, L. Hernández, C. Juárez
Under predation risk, prey species are more abundant in areas of low predation risk even at the expense of forage quality. As a result two predictions are possible, 1) predators should choose to hunt in areas with fewer but easier to catch prey than areas where they are more abundant but harder to catch; and 2) the frequency of prey species in the diet of predators using low risk areas should be greater than, or at least equal to, the diet of predators using high risk areas. To test these two predictions, we used data on coyote Canis latrans abundance and diet composition from two habitats in the Chihuahuan Desert of Mexico that have different abundances of jackrabbits (Lepus californicus) and rodents. We used the number of coyote scats found in transects in the two areas to assess coyote abundance and analyzed the contents of these scats to determine diet composition. We found significantly more coyote scats/yr (22.6 ± 4.7 (SE) vs. 12.2 ± 2.4 scats/yr, d.f. = 7, paired t = 3.80, P = 0.007) in the habitat with less jackrabbits and more rodents. However, the percent occurrence of jackrabbits (54.3 ± 6.7% vs. 60.1 ± 7.7%) and rodents (32.6 ± 6.5% vs. 30.1 ± 6.0%) in coyote scats did not differ between the two habitats. These results supported both the above cited predictions and the hypothesis that prey vulnerability can influence habitat use by coyotes.
在捕食风险下，低捕食风险地区的猎物种类更丰富，即使以牺牲饲料质量为代价。因此，有两种预测是可能的:1)捕食者应该选择在猎物较少但容易捕获的地区捕猎，而不是在猎物较多但不易捕获的地区捕猎;2)低风险区捕食者饮食中被捕食物种的频率应大于或至少等于高风险区捕食者的饮食。为了验证这两种预测，我们使用了来自墨西哥奇瓦瓦沙漠两个栖息地的土狼(Canis latranans)丰度和饮食组成的数据，这些栖息地有不同丰度的长耳野兔(Lepus californicus)和啮齿动物。我们使用在这两个地区的样带中发现的土狼粪便的数量来评估土狼的丰度，并分析这些粪便的含量来确定饮食组成。结果表明，在大野兔较少、啮齿动物较多的生境中，土狼的数量明显多于土狼(22.6±4.7 (SE) vs. 12.2±2.4 (SE) /yr, d.f = 7，配对t = 3.80, P = 0.007)。大野兔(54.3±6.7% vs. 60.1±7.7%)和啮齿动物(32.6±6.5% vs. 30.1±6.0%)在土狼粪便中出现的比例无显著差异。这些结果支持了上述预测和假设，即猎物的脆弱性会影响土狼对栖息地的利用。
{"title":"Foraging in the Landscape of Fear, the Predator's Dilemma: Where Should I Hunt?","authors":"J. Laundré, J. M. M. Calderas, L. Hernández, C. Juárez","doi":"10.2174/1874213000902010001","DOIUrl":"https://doi.org/10.2174/1874213000902010001","url":null,"abstract":"Under predation risk, prey species are more abundant in areas of low predation risk even at the expense of forage quality. As a result two predictions are possible, 1) predators should choose to hunt in areas with fewer but easier to catch prey than areas where they are more abundant but harder to catch; and 2) the frequency of prey species in the diet of predators using low risk areas should be greater than, or at least equal to, the diet of predators using high risk areas. To test these two predictions, we used data on coyote Canis latrans abundance and diet composition from two habitats in the Chihuahuan Desert of Mexico that have different abundances of jackrabbits (Lepus californicus) and rodents. We used the number of coyote scats found in transects in the two areas to assess coyote abundance and analyzed the contents of these scats to determine diet composition. We found significantly more coyote scats/yr (22.6 ± 4.7 (SE) vs. 12.2 ± 2.4 scats/yr, d.f. = 7, paired t = 3.80, P = 0.007) in the habitat with less jackrabbits and more rodents. However, the percent occurrence of jackrabbits (54.3 ± 6.7% vs. 60.1 ± 7.7%) and rodents (32.6 ± 6.5% vs. 30.1 ± 6.0%) in coyote scats did not differ between the two habitats. These results supported both the above cited predictions and the hypothesis that prey vulnerability can influence habitat use by coyotes.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"2 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2009-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-08-08DOI: 10.2174/1874213000801010014
L. Aarssen, T. Tregenza, A. Budden, C. Lortie, J. Koricheva, Roosa Leimu
When choosing where to submit their research for publication, most ecologists are concerned with journal impact factor, but they are also concerned with the likelihood that their manuscripts will be accepted. Based on a survey of ecologists, we found different degrees of relative concern for these journal attributes depending on author experience and gender. However, the ability of authors to choose among journals based on these journal attributes is limited: while journal impact factors are published regularly, journal rejection rates are not. We obtained, by permission, rejection rate data for a sample of 60 ecology journals for the year 2004. As expected, journals with higher impact factors also have higher rejection rates, but the ratio of (rejection rate) / (impact factor) increases sharply with decreasing impact factor below 1.76. Journals with impact factors below this value therefore provide relatively low payback in terms of impact against cost as estimated by rejection rate. We discuss alternative possible interpretations of this relationship and alternative criteria that might affect an author's decision about journal choice. Most importantly, our analysis indicates that the ability to make informed choices requires that journals publish their rejection rates annually. PREAMBLE How does an author decide where to submit a paper for publication? This important decision is made routinely throughout the career of a typical researching scientist/academic. The choices made can profoundly affect the trajectory, rate of progress, and status of one's research career. Necessarily, the subject category of the journals under consideration must be concordant with the research topic of the paper. However after this, most authors in the field of ecology at least, are usually still presented with more than one choice of a topically suitable subset of candidate journals. And, when the paper is rejected (an experience that few if any manage to avoid completely), the author is commonly inclined to iteratively select alternative journals.
{"title":"Bang for Your Buck: Rejection Rates and Impact Factors in Ecological Journals","authors":"L. Aarssen, T. Tregenza, A. Budden, C. Lortie, J. Koricheva, Roosa Leimu","doi":"10.2174/1874213000801010014","DOIUrl":"https://doi.org/10.2174/1874213000801010014","url":null,"abstract":"When choosing where to submit their research for publication, most ecologists are concerned with journal impact factor, but they are also concerned with the likelihood that their manuscripts will be accepted. Based on a survey of ecologists, we found different degrees of relative concern for these journal attributes depending on author experience and gender. However, the ability of authors to choose among journals based on these journal attributes is limited: while journal impact factors are published regularly, journal rejection rates are not. We obtained, by permission, rejection rate data for a sample of 60 ecology journals for the year 2004. As expected, journals with higher impact factors also have higher rejection rates, but the ratio of (rejection rate) / (impact factor) increases sharply with decreasing impact factor below 1.76. Journals with impact factors below this value therefore provide relatively low payback in terms of impact against cost as estimated by rejection rate. We discuss alternative possible interpretations of this relationship and alternative criteria that might affect an author's decision about journal choice. Most importantly, our analysis indicates that the ability to make informed choices requires that journals publish their rejection rates annually. PREAMBLE How does an author decide where to submit a paper for publication? This important decision is made routinely throughout the career of a typical researching scientist/academic. The choices made can profoundly affect the trajectory, rate of progress, and status of one's research career. Necessarily, the subject category of the journals under consideration must be concordant with the research topic of the paper. However after this, most authors in the field of ecology at least, are usually still presented with more than one choice of a topically suitable subset of candidate journals. And, when the paper is rejected (an experience that few if any manage to avoid completely), the author is commonly inclined to iteratively select alternative journals.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"1 1","pages":"14-19"},"PeriodicalIF":0.0,"publicationDate":"2008-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-08-07DOI: 10.2174/1874213000801010008
R. Zinck, V. Grimm
The quantitative study of wildfire data world wide revealed that wildfires exhibit power-law like frequency- area distributions. Although models exist to predict the spread of a specific fire, there is as yet no agreement on the mechanism which drives wildfire systems on the landscape scale. A classical model in this context is the Drossel-Schwabl cellular automaton (DS-FFM) which robustly produces a power-law like frequency-area statistic for fire sizes. This model originated in statistical physics where it was used to illustrate the concept of self-organized criticality. A conjecture has been made in the literature that this model is not able to produce the spatial patterns of actual wildfires and hence is of no ecological significance. We test this conjecture by comparing the shape of simulated fires in the DS-FFM to those of 68 fires in the boreal forests of Alberta, Canada. Our results suggest that, contrary to the conjecture, the Drossel-Schwabl model performs well in producing realistic fire shapes. It can hence not be excluded as a candidate mechanism behind wildfire systems. We do show, however, that the performance depends on the size of the fire. Best results are obtained for fires of 400-2,000 ha. Very large fires of 2,000-20,000 ha and smaller fires of 20-200 ha differ from the simulated burn scars in the distribution and median size of islands of unburnt vegetation. Nevertheless, the overall fit remains good even for these size classes.
{"title":"More Realistic than Anticipated: A Classical Forest-Fire Model from Statistical Physics Captures Real Fire Shapes","authors":"R. Zinck, V. Grimm","doi":"10.2174/1874213000801010008","DOIUrl":"https://doi.org/10.2174/1874213000801010008","url":null,"abstract":"The quantitative study of wildfire data world wide revealed that wildfires exhibit power-law like frequency- area distributions. Although models exist to predict the spread of a specific fire, there is as yet no agreement on the mechanism which drives wildfire systems on the landscape scale. A classical model in this context is the Drossel-Schwabl cellular automaton (DS-FFM) which robustly produces a power-law like frequency-area statistic for fire sizes. This model originated in statistical physics where it was used to illustrate the concept of self-organized criticality. A conjecture has been made in the literature that this model is not able to produce the spatial patterns of actual wildfires and hence is of no ecological significance. We test this conjecture by comparing the shape of simulated fires in the DS-FFM to those of 68 fires in the boreal forests of Alberta, Canada. Our results suggest that, contrary to the conjecture, the Drossel-Schwabl model performs well in producing realistic fire shapes. It can hence not be excluded as a candidate mechanism behind wildfire systems. We do show, however, that the performance depends on the size of the fire. Best results are obtained for fires of 400-2,000 ha. Very large fires of 2,000-20,000 ha and smaller fires of 20-200 ha differ from the simulated burn scars in the distribution and median size of islands of unburnt vegetation. Nevertheless, the overall fit remains good even for these size classes.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"1 1","pages":"8-13"},"PeriodicalIF":0.0,"publicationDate":"2008-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-03-24DOI: 10.2174/1874213000801010001
S. Ferguson, S. Larivière
Many hypotheses for larger body size with increasing latitude invoke environmental explanations, such as de- creasing temperature. We propose a novel explanation that links environmental selection pressures and body size with spacing behaviour. We test for causal pathways between (1) environment (snow, latitude, primary productivity, seasonal- ity, and temperature) and (2) spacing behaviour (home range size and population density) and (3) body size and sexual size dimorphism using structural equation modelling of independent contrasts derived from 101 mammalian terrestrial carnivore species. Although strong intercorrelations existed among all five environmental variables, primary productivity and seasonality best related to body size and size dimorphism. Using information-theoretic approach to select optimal model fit established that body size was not influenced directly by environment but rather through the intermediary vari- ables, home range or density. For example, species living in highly seasonal environments were associated with larger home ranges and low density that in turn selected for larger body mass and greater sexual size dimorphism. Thus, spacing behaviour provides an important evolutionary link explaining interspecific body size variation.
{"title":"How Social Behaviour Links Environment and Body Size in Mammalian Carnivores","authors":"S. Ferguson, S. Larivière","doi":"10.2174/1874213000801010001","DOIUrl":"https://doi.org/10.2174/1874213000801010001","url":null,"abstract":"Many hypotheses for larger body size with increasing latitude invoke environmental explanations, such as de- creasing temperature. We propose a novel explanation that links environmental selection pressures and body size with spacing behaviour. We test for causal pathways between (1) environment (snow, latitude, primary productivity, seasonal- ity, and temperature) and (2) spacing behaviour (home range size and population density) and (3) body size and sexual size dimorphism using structural equation modelling of independent contrasts derived from 101 mammalian terrestrial carnivore species. Although strong intercorrelations existed among all five environmental variables, primary productivity and seasonality best related to body size and size dimorphism. Using information-theoretic approach to select optimal model fit established that body size was not influenced directly by environment but rather through the intermediary vari- ables, home range or density. For example, species living in highly seasonal environments were associated with larger home ranges and low density that in turn selected for larger body mass and greater sexual size dimorphism. Thus, spacing behaviour provides an important evolutionary link explaining interspecific body size variation.","PeriodicalId":39335,"journal":{"name":"Open Ecology Journal","volume":"1 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2008-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68053043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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