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VR1.0
PT J
AU Ritchie, EG
Martin, JK
Krockenberger, AK
Garnett, S
Johnson, CN
AF Ritchie, Euan G.
Martin, Jennifer K.
Krockenberger, Andrew K.
Garnett, Stephen
Johnson, Christopher N.
TI Large-herbivore distribution and abundance: Intra-and interspecific niche variation in the tropics
SO ECOLOGICAL MONOGRAPHS
AB Determining the biological and environmental factors that limit the distribution and abundance of organisms is central to our understanding of the niche concept and crucial for predicting how species may respond to large-scale environmental change, such as global warming. However, detailed ecological information for the majority of species has been collected only at a local scale, and insufficient consideration has been given to geographical variation in intraspecific niche requirements. To evaluate the influence of environmental and biological factors on patterns of species distribution and abundance, we conducted a detailed, broadscale study across the tropical savannas of northern Australia on the ecology of three large, sympatric marsupial herbivores (family Macropodidae): the antilopine wallaroo (Macropus antilopinus), common wallaroo (M. robustus), and eastern grey kangaroo (M. giganteus). Using information on species abundance, climate,. re history, habitat, and resource availability, we constructed species' habitat models varying from the level of the complete distribution to smaller regional areas. Multiple factors affected macropod abundance, and the importance of these factors was dependent on the spatial scale of analyses. Fire regimes, water availability, geology, and soil type and climate were most important at the large scale, whereas aspects of habitat structure and interspecific species abundance were important at smaller scales. The distribution and abundance of eastern grey kangaroos and common wallaroos were strongly influenced by climate. Our results suggest that interspecific competition between antilopine wallaroos and eastern grey kangaroos may occur. The antilopine wallaroo and eastern grey kangaroo (grazers) preferred more nutrient-rich soils than the common wallaroo (grazer/browser), which we relate to differences in feeding modes. The abundance of antilopine wallaroos was higher on sites that were burned, whereas the abundance of common wallaroos was higher on unburned sites. Future climate change predicted for Australia has the capacity to seriously affect the abundance and conservation of macropod species in tropical savannas. The results of our models suggest that, in particular, the effects of changing climatic conditions on. re regimes, habitat structure, and water availability may lead to species declines and marked changes in macropod communities.
SN 0012-9615
PD FEB
PY 2008
VL 78
IS 1
BP 105
EP 122
UT ISI:000253944400007
ER
PT J
AU Cardoso, MF
Nobre, CA
Lapola, DM
Oyama, MD
Sampaio, G
AF Cardoso, Manoel F.
Nobre, Carlos A.
Lapola, David M.
Oyama, Marcos D.
Sampaio, Gilvan
TI Long-term potential for fires in estimates of the occurrence of savannas in the tropics
SO GLOBAL ECOLOGY AND BIOGEOGRAPHY
AB Aim This study aims to improve the formulation and results of the Brazilian Center for Weather Forecasting and Climate Studies Potential Vegetation Model (CPTEC-PVM) by developing a new parameterization for the long-term occurrence of fire in regions of potential savannas in the tropics. Compared with the relatively slow processes of carbon uptake and growth in vegetation, fast mortality and biomass consumption by fires may favour grasses and reduce tree coverage.
Location The tropics.
Methods For finding large-scale relationships between fires and other environmental factors, we made two main simplifying assumptions. First, lightning is the most important source of ignition for natural fires. Second, over continental areas in the tropics, lightning is mainly related to the zonal flux of moisture transport.
Results The parameterization of fire occurrence was built based on a simple empirical relationship, combining information on mean and intra-annual variance of the zonal wind.
Main conclusions The implementation of this new relationship improved the formulation and the results of the CPTEC-PVM. As a result of this new parameter, the accuracy of the model in allocating the correct vegetation (seasonal forests) instead of savannas for large regions in India and Southeast Asia is now substantially higher than in previous studies.
SN 1466-822X
PD MAR
PY 2008
VL 17
IS 2
BP 222
EP 235
UT ISI:000252966000008
ER
PT J
AU Bajocco, S
Ricotta, C
AF Bajocco, Sofia
Ricotta, Carlo
TI Evidence of selective burning in Sardinia (Italy): which land-cover classes do wildfires prefer?
SO LANDSCAPE ECOLOGY
AB The objective of this paper is to identify land-cover types where fire incidence is higher (preferred) or lower (avoided) than expected from a random null model. Fire selectivity may be characterized by the number of fires expected in a given land-cover class and by the mean surface area each fire will burn. These two components of fire pattern are usually independent of each other. For instance, fire number is usually connected with socioeconomic causes whereas fire size is largely controlled by fuel continuity. Therefore, on the basis of available fire history data for Sardinia (Italy) for the period 2000-2004 we analyzed fire selectivity of given land-cover classes keeping both variables separate from each other. The results obtained from analysis of 13,377 fires show that for most land-cover classes fire behaves selectively, with marked preference (or avoidance) in terms of both fire number and fire size. Fire number is higher than expected by chance alone in urban and agricultural areas. In contrast, in forests, grasslands, and shrublands, fire number is lower than expected. In grasslands and shrublands mean fire size is significantly larger than expected from a random null model whereas in urban areas, permanent crops, and heterogeneous agricultural areas there is significant resistance to fire spread. Finally, as concerns mean fire size, in our study area forests and arable land burn in proportion to their availability without any significant tendency toward fire preference or avoidance. The results obtained in this study contribute to fire risk assessment on the landscape scale, indicating that risk of wildfire is closely related to land cover.
SN 0921-2973
PD FEB
PY 2008
VL 23
IS 2
BP 241
EP 248
UT ISI:000252636100011
ER
PT J
AU Hochkirchi, A
Adorf, F
AF Hochkirchi, Axel
Adorf, Frauke
TI Effects of prescribed burning and wildfires on Orthoptera in Central European peat bogs
SO ENVIRONMENTAL CONSERVATION
AB Fire has become a frequent tool in nature conservation and hazard reduction, but there is still dispute about the responses of many taxa, especially concerning invertebrate populations. While the effects of fire on plants and animals have been examined intensively in prairies, savannahs and coniferous forests, wetlands have rarely been considered in this context, yet wetland ecosystems do experience periodic fires. This study examines the effects of prescribed burning and wildfires on Orthoptera in four Central European peat bogs. All species persisted on the burned plots and none experienced a massive decline in abundance compared to unburned treatments. Generally, differences in species composition and abundance were more distinct between the bogs than between the fire treatments or fire season. One threatened species, Omocestus rufipes, occurred more often in burned than in unburned samples. The abundances of Orthoptera species in the transition zone between burned and unburned plots were either uniform or step-like rather than gradual in nature, conflicting with a hypothesis of post-fire recolonization from unburned plots. This pattern supported by non-metric multidimensional scaling suggests that the vegetation structure plays a substantial role in habitat choice of these insects. Small-scale fires between February and May do not seem to represent a threat to Orthoptera species. However, in the longer term, peat bog restoration may be affected by negative vegetation responses.
SN 0376-8929
PD SEP
PY 2007
VL 34
IS 3
BP 225
EP 235
UT ISI:000252206400007
ER
PT J
AU Gavin, DG
Hallett, DJ
Hu, FS
Lertzman, KP
Prichard, SJ
Brown, KJ
Lynch, JA
Bartlein, P
Peterson, DL
AF Gavin, Daniel G.
Hallett, Douglas J.
Hu, Feng Sheng
Lertzman, Kenneth P.
Prichard, Susan J.
Brown, Kendrick J.
Lynch, Jason A.
Bartlein, Patrick
Peterson, David L.
TI Forest fire and climate change in western North America: insights from sediment charcoalrecords
SO FRONTIERS IN ECOLOGY AND THE ENVIRONMENT
AB Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and vegetation. We highlight several records from western North America and their relevance in reconstructing historical forest dynamics, fire-climate relationships, and feedbacks between vegetation and fire under climate change. Climatic effects on fire regimes are evident in many regions, but comparisons of paleo-fire records sometimes show a lack of synchrony, indicating that local factors substantially affect fire occurrence, even over long periods. Furthermore, the specific impacts of vegetation change on fire regimes vary among regions with different vegetation histories. By documenting the effects on fire patterns of major changes in climate and vegetation, paleo-fire records can be used to test the mechanistic models required for the prediction of future variations in fire.
SN 1540-9295
PD NOV
PY 2007
VL 5
IS 9
BP 499
EP 506
UT ISI:000250659900008
ER
PT J
AU Bibi, F
AF Bibi, Faysal
TI Dietary niche partitioning among fossil bovids in late Miocene C-3 habitats: Consilience of functional morphology and stable isotope analysis
SO PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
AB Teeth of late Miocene bovids referred to Bovini and "Boselaphini" were subjected to enamel stable carbon and oxygen isotope analysis to test paleoecological reconstructions based on dental morphology. Teeth of Bovini possess derived characters-including larger size, higher crowns, and increased enamel surface area-that are indicative of feeding on a more fibrous and gritty diet, probably grass. In contrast, teeth of "Boselaphini" reflect the plesiomorphic condition among bovids-being smaller, lower-crowned, and with simple occlusal morphology- and are indicative of a diet with a greater reliance on softer food items such as browse. Late Miocene bovines are also expected to have inhabited drier, more open habitats than did boselaphines. Stable carbon and oxygen isotopic compositions from 30 fossil teeth (18 bovine, 12 boselaphine) from well-dated localities of between 8.3 and 7.9 Ma in age from the Siwalik deposits, Pakistan, were analyzed to test these paleoecological hypotheses. All delta C-13 values (VPDB) are more negative than -8 parts per thousand, indicating that both bovines and boselaphines at this time had pure C-3 diets. The mean delta C-13 for bovine teeth (-10.4 parts per thousand) is more positive than that for boselaphines (-10.9 parts per thousand), and the differences between these two series are significant (Wilcoxon, p < 0.01;t test,p < 0.05) while the variances are not. Early bovines thus appear to have exploited more open habitats than did their boselaphine counterparts. Lack of a significant difference between variances suggests that the dietary niche breadth of early bovines was not different from that of boselaphines. Mean delta O-18 (SMOW) for bovine teeth (26.3 parts per thousand) is slightly more negative-as might be expected for grazers-but not statistically significant from the boselaphine delta O-18 mean (28.1 parts per thousand, t test,p=0.066). Overlap in delta O-18 values between bovines and boselaphines is high, implying that these two bovid types did not differ greatly in their water intake behaviors. Rather, both fossil bovines and boselaphines probably shared similar obligate drinking habits and dependency on water bodies much as living boselaphines, bovines, and tragelaphines (clade Bovinae) do today.
Stable isotope analysis results, particularly delta C-13 values, suggest that in the late Miocene neither bovines nor boselaphines inhabited dense forest habitats. And while both bovid taxa may have been mixed feeders to different extents, the delta C-13 values support the hypothesis developed on the basis of dental functional morphology that early bovines evolved inhabiting more open habitats than did contemporaneous boselaphines. The scenario whereby the bovine clade owes its origins to a boselaphine lineage that adapted to drier, more open habitats is supported by the general context of climatic and faunal change in Eurasia in the late Miocene, particularly between 11-8 Ma, when faunal assemblages from many sites exhibit significant turnover events through which open-babitat taxa become present in increasing proportions at the expense of closed-habitat taxa. (c) 2007 Elsevier B.V. All rights reserved.
SN 0031-0182
PD SEP 27
PY 2007
VL 253
IS 3-4
BP 529
EP 538
UT ISI:000250255400016
ER
PT J
AU van Wilgen, BW
Govender, N
Biggs, HC
AF van Wilgen, Brian W.
Govender, Navashni
Biggs, Harry C.
TI The contribution of fire research to fire management: a critical review of a long-term experiment in the Kruger National Park, South Africa
SO INTERNATIONAL JOURNAL OF WILDLAND FIRE
AB The present paper reviews a long- term fire experiment in the Kruger National Park, South Africa, established in 1954 to support fire management. The paper's goals are: (1) to assess learning, with a focus on relevance for fire management; (2) to examine how findings influenced changes in fire management; and (3) to reflect on the experiment's future. Results show that fire treatments affected vegetation structure and biomass more than species composition. Effects on vegetation were most marked in extreme treatments (annual burning, burning in the summer wet season, or long periods of fire exclusion), and were greater in areas of higher rainfall. Faunal communities and soil physiology were largely unaffected by fire. Since the inception of the experiment, paradigms in savanna ecology have changed to encompass heterogeneity and variability. The design of the experiment, reflecting the understanding of the 1950s, does not cater for variability, and as a result, the experiment had little direct influence on changes in management policy. Notwithstanding this, managers accept that basic research influences the understanding of fundamental ecosystem function, and they recognise that it promotes appropriate adaptive management by contributing to predictive understanding. This has been a major reason for maintaining the experiment for over 50 years.
SN 1049-8001
PY 2007
VL 16
IS 5
BP 519
EP 530
UT ISI:000250427300002
ER
PT J
AU Pettit, NE
Naiman, RJ
AF Pettit, Neil E.
Naiman, Robert J.
TI Fire in the riparian zone: Characteristics and ecological consequences
SO ECOSYSTEMS
AB We review the current understandings of the frequency, spatial distributions, mechanisms, and ecological consequences of fire in riparian zones. Riparian zones are well known for influencing many ecological processes at local to landscape scales, and fire can have an important ecosystem-scale influence on them. Riparian zones differ from surrounding uplands in their biophysical templates, moisture regimes and disturbance regimes; as a consequence the characteristics and effects of fire are different than in adjacent uplands. Fire impacts on riparian zones vary proportionally with the severity and extent of burning in the catchment and are affected by stream size. Riparian zones can act as a buffer against fire and therefore as a refuge for fire-sensitive species. However, under some circumstances, such as dry pre-fire climatic conditions and the accumulation of dry fuel, riparian areas become corridors for fire movement. Fire incursion into riparian zones creates canopy gaps and drier conditions, which allow subsequent build up of dead wood and establishment of fire adapted species. In concert, this increases fuel loads and the probability of another fire. Secondary effects of riparian fire include altering nutrient fluxes and cycling, increasing sediment loads, and stimulating erosion. We conclude that riparian fires are potentially important in shaping ecological characteristics in many regions, but this is poorly quantified. A better understanding of riparian fire regimes is essential to assess the effects of fire in helping shape the complex ecological characteristics of riparian zones over the longer-term.
SN 1432-9840
PD AUG
PY 2007
VL 10
IS 5
BP 673
EP 687
UT ISI:000249969200001
ER
PT J
AU Diadema, K
Medail, F
Bretagnolle, F
AF Diadema, Katia
Medail, Frederic
Bretagnolle, Francois
TI Fire as a control agent of demographic structure and plant performance of a rare Mediterranean endemic geophyte
SO COMPTES RENDUS BIOLOGIES
AB We examine the effects of fire and/or surrounding vegetation cover on demographic stage densities and plant performance for a rare endemic geophyte, Acis nicaeensis (Alliaceae), in Mediterranean xerophytic grasslands of the 'Alpes-Maritimes' French 'departement', through sampling plots in unburned and burned treatments. Fire increases density of flowering individuals and seedling emergence, as well as clump densities and number of individuals per clump, per limiting vegetation height and cover, and increasing bare soil cover. In contrast, fire has no effect on reproductive success. Nevertheless, two growing seasons after fire, all parameters of demographic stages and plant performance do not significantly differ between the two treatments. Small-scale fire is beneficial for the regeneration of this threatened geophyte at a short-time scale. In this context, a conservation planning with small and controlled fires could maintain the regeneration window for populations of rare Mediterranean geophytes.
SN 1631-0691
PD SEP
PY 2007
VL 330
IS 9
BP 691
EP 700
UT ISI:000249321400007
ER
PT J
AU Scheiter, S
Higgins, SI
AF Scheiter, Simon
Higgins, Steven I.
TI Partitioning of root and shoot competition and the stability of savannas
SO AMERICAN NATURALIST
AB A classic problem in coexistence theory is how grasses and trees coexist in savannas. A popular deterministic model of savannas, the rooting niche separation model, is based on an assumption that is not empirically supported in many savannas. Alternative models that do not rely on the rooting niche assumption invoke intricate stochastic mechanisms that limit their attractiveness as general models of savannas. In this article we develop an alternative deterministic model of grass-tree interactions and use it to analyze the conditions under which grass-tree coexistence is possible. The novel feature of this model is that it partitions aboveground and belowground competition and simulates the fact that fire and herbivory remove only aboveground biomass. The model predicts that stable coexistence of grasses and trees is possible, even when grasses and trees do not have separate rooting niches. We show that when aboveground competition is intense, grasses can be excluded by trees; under such conditions, fire can prevent grasses from exclusion and induce a stable savanna state. The model provides a general framework for exploring the interactive effects of competition, herbivory, and fire on savanna systems.
SN 0003-0147
PD OCT
PY 2007
VL 170
IS 4
BP 587
EP 601
UT ISI:000249307700011
ER
PT J
AU Bucini, G
Hanan, NP
AF Bucini, Gabriela
Hanan, Niall P.
TI A continental-scale analysis of tree cover in African savannas
SO GLOBAL ECOLOGY AND BIOGEOGRAPHY
AB Aim We present a continental-scale analysis that explores the processes controlling woody community structure in tropical savannas. We analyse how biotic and abiotic factors interact to promote and modify tree cover, examine alternative ecological hypotheses and quantify disturbance effects using satellite estimates of tree cover.
Location African savannas.
Methods Tree cover is represented as a resource-driven potential cover related to rainfall and soil characteristics perturbed by natural and human factors such as fire, cattle grazing, human population and cultivation. Within this framework our approach combines semi-empirical modelling and information theory to identify the best models.
Results Woody community structure across African savannas is best represented by a sigmoidal response of tree cover to mean annual precipitation (MAP), with a dependency on soil texture, which is modified by the separate effects of fire, domestic livestock, human population density and cultivation intensity. This model explains c. 66% of the variance in tree cover and appears consistent across the savanna regions of Africa.
Main conclusions The analysis provides a new understanding of the importance and interaction of environmental and disturbance factors that create the broad spatial patterns of tree cover observed in African savannas. Woody cover increases with rainfall, but is modified by disturbances. These 'perturbation' effects depend on MAP regimes: in arid savannas (MAP < 400 mm) they are generally small (< 1% decrease in cover), while in semi-arid and mesic savannas (400-1600 mm), perturbations result in an average 2% (400 mm) to 23% (1600 mm) decrease in cover; fire frequency and human population have more influence than cattle, and cultivation appears, on average, to lead to small increases in woody cover. Wet savannas (1600-2200 mm) are controlled by perturbations that inhibit canopy closure and reduce tree cover by, on average, 24-34%. Full understanding of the processes determining savanna structure requires consideration of resource limitation and disturbance dynamics.
SN 1466-822X
PD SEP
PY 2007
VL 16
IS 5
BP 593
EP 605
UT ISI:000248959300005
ER
PT J
AU Anderson, TM
Ritchie, ME
Mayemba, E
Eby, S
Grace, JB
McNaughton, SJ
AF Anderson, T. Michael
Ritchie, Mark E.
Mayemba, Emilian
Eby, Stephanie
Grace, James B.
McNaughton, Samuel J.
TI Forage nutritive quality in the serengeti ecosystem: the roles of fire and herbivory
SO AMERICAN NATURALIST
AB Fire and herbivory are important determinants of nutrient availability in savanna ecosystems. Fire and herbivory effects on the nutritive quality of savanna vegetation can occur directly, independent of changes in the plant community, or indirectly, via effects on the plant community. Indirect effects can be further subdivided into those occurring because of changes in plant species composition or plant abundance (i.e., quality versus quantity). We studied relationships between fire, herbivory, rainfall, soil fertility, and leaf nitrogen (N), phosphorus (P), and sodium (Na) at 30 sites inside and outside of Serengeti National Park. Using structural equation modeling, we asked whether fire and herbivory influences were largely direct or indirect and how their signs and strengths differed within the context of natural savanna processes. Herbivory was associated with enhanced leaf N and P through changes in plant biomass and community composition. Fire was associated with reduced leaf nutrient concentrations through changes in plant community composition. Additionally, fire had direct positive effects on Na and nonlinear direct effects on P that partially mitigated the indirect negative effects. Key mechanisms by which fire reduced plant nutritive quality were through reductions of Na-rich grasses and increased abundance of Themeda triandra, which had below-average leaf nutrients.
SN 0003-0147
PD SEP
PY 2007
VL 170
IS 3
BP 343
EP 357
UT ISI:000248964000005
ER
PT J
AU Syphard, AD
Radeloff, VC
Keeley, JE
Hawbaker, TJ
Clayton, MK
Stewart, SI
Hammer, RB
AF Syphard, Alexandra D.
Radeloff, Volker C.
Keeley, Jon E.
Hawbaker, Todd J.
Clayton, Murray K.
Stewart, Susan I.
Hammer, Roger B.
TI Human influence on California fire regimes
SO ECOLOGICAL APPLICATIONS
AB Periodic wildfire maintains the integrity and species composition of many ecosystems, including the mediterranean-climate shrublands of California. However, human activities alter natural fire regimes, which can lead to cascading ecological effects. Increased human ignitions at the wildland-urban interface (WUI) have recently gained attention, but fire activity and risk are typically estimated using only biophysical variables. Our goal was to determine how humans influence fire in California and to examine whether this influence was linear, by relating contemporary (2000) and historic (1960-2000) fire data to both human and biophysical variables. Data for the human variables included fine-resolution maps of the WUI produced using housing density and land cover data. Interface WUI, where development abuts wildland vegetation, was differentiated from intermix WUI, where development intermingles with wildland vegetation. Additional explanatory variables included distance to WUI, population density, road density, vegetation type, and ecoregion. All data were summarized at the county level and analyzed using bivariate and multiple regression methods. We found highly significant relationships between humans and fire on the contemporary landscape, and our models explained fire frequency (R-2 = 0.72) better than area burned (R-2 = 0.50). Population density, intermix WUI, and distance to WUI explained the most variability in fire frequency, suggesting that the spatial pattern of development may be an important variable to consider when estimating fire risk. We found nonlinear effects such that fire frequency and area burned were highest at intermediate levels of human activity, but declined beyond certain thresholds. Human activities also explained change in fire frequency and area burned (1960 2000), but our models had greater explanatory power during the years 1960-980, when there was more dramatic change in fire frequency. Understanding wildfire as a function of the spatial arrangement of ignitions and fuels on the landscape, in addition to nonlinear relationships, will be important to fire managers and conservation planners because fire risk may be related to specific levels of housing density that can be accounted for in land use planning. With more fires occurring in close proximity to human infrastructure, there may also be devastating ecological impacts if development continues to grow farther into wildland vegetation.
SN 1051-0761
PD JUL
PY 2007
VL 17
IS 5
BP 1388
EP 1402
UT ISI:000248265700011
ER
PT J
AU Petty, AM
Werner, PA
Lehmann, CER
Riley, JE
Banfai, DS
Elliott, LP
AF Petty, Aaron M.
Werner, Patricia A.
Lehmann, Caroline E. R.
Riley, Jan E.
Banfai, Daniel S.
Elliott, Louis P.
TI Savanna responses to feral buffalo in Kakadu National Park, Australia
SO ECOLOGICAL MONOGRAPHS
AB Savannas are the major biome of tropical regions, spanning 30% of the Earth's land surface. Tree: grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buffalo (Bubalus bubalus), on the mesic savannas of Kakadu National Park (KNP), a World Heritage Park located within the Alligator Rivers Region (ARR) of monsoonal north Australia. The study inverts the experience of the Serengeti savannas where grazing herds rapidly declined due to a rinderpest epidemic and then recovered upon disease control. Buffalo entered the ARR by the 1880s, but densities were low until the late 1950s when populations rapidly grew to carrying capacity within a decade. In the 1980s, numbers declined precipitously due to an eradication program. We show evidence that the rapid population expansion and Sudden removal of this exotic herbivore created two ecological cascades by altering around cover abundance and composition, which in turn affected competitive regimes and fuel loads with possible further, long-term effects due to changes in fire regimes. Overall, ecological impacts varied across a north-south gradient in KNP that corresponded to the interacting factors of precipitation, landform, and vegetation type but was also contingent upon the history of buffalo harvest. Floodplains showed the greatest degree of impact during the period of rapid buffalo expansion, but after buffalo removal, they largely reverted to their prior state. Conversely, the woodlands experienced less visible impact during the first cascade. However, in areas of low buffalo harvest and severe impact, there was little recruitment of juvenile trees into the canopy due to the indirect effects of grazing and high frequency of prescribed fires once buffalo were removed. Rain forests were clearly heavily impacted during the first cascade, but the long term consequences of buffalo increase and removal remain unclear. Due to hysteresis effects, the simple removal of an exotic herbivore was not sufficient to return savanna systems to their previous state.
SN 0012-9615
PD AUG
PY 2007
VL 77
IS 3
BP 441
EP 463
UT ISI:000248379900007
ER
PT J
AU Bader, MY
van Geloof, I
Rietkerk, M
AF Bader, Maaike Y.
van Geloof, Isabel
Rietkerk, Max
TI High solar radiation hinders tree regeneration above the alpine treeline in northern Ecuador
SO PLANT ECOLOGY
AB Many tropical alpine treelines lie below their climatic potential, because of natural or anthropogenic causes. Forest extension above the treeline depends on the ability of trees to establish in the alpine environment. This ability may be limited by different factors, such as low temperatures, excess solar radiation, competition, soil properties, dispersal ability, and fires. In this paper we address the following two questions: Do trees regenerate above the present treeline, and what are the inhibiting factors for tree establishment? To answer these questions we described the spatial pattern of recent tree establishment below and above the present treeline in northern Ecuador. Also, we experimentally transplanted seedlings into the alpine vegetation (paramo) and the forest, and investigated the effect of shade, neighboring plants, and substrate on their survival. The number of naturally occurring tree sprouts (seedlings, saplings and ramets) was highest just outside the forest, and decreased with distance to the forest edge. However, only two species that were radiation-tolerant made up these high numbers, while other species were rare or absent in the pairamo. In the forest, the species diversity of sprouts was high and the abundance per species was relatively low. The transplanted seedlings survived least in experimental plots without artificial shade where neighboring plants were removed. Seedling survival was highest in artificially shaded plots and in the forest. This shade-dependence of most tree species can strongly slow down forest expansion toward the potential climatic treeline. Due to the presence of radiation-tolerant species, the complete lack of forest expansion probably needs to be ascribed to fire. However, our results show that natural processes can also explain both the low position and the abruptness of tropical treelines.
SN 1385-0237
PD JUL
PY 2007
VL 191
IS 1
BP 33
EP 45
UT ISI:000247195000004
ER
PT J
AU Menges, ES
AF Menges, Eric S.
TI Integrating demography and fire management: an example from Florida scrub
SO AUSTRALIAN JOURNAL OF BOTANY
AB In this work, I have used life-history and demographic data to define fire return intervals for several types of Florida scrub, a xeric shrubland where fire is the dominant ecological disturbance but where fire suppression is a major issue. The datasets combine chronosequence and longitudinal approaches at community and population levels. Resprouting shrubs, which dominate most types of Florida scrub, recover rapidly after fires (although their limits under frequent fires are not well known) and also increasingly dominate long-unburned areas. These dominant shrubs can prosper over a range of fire return intervals. Obligate-seeding scrub plants, which often have persistent seed banks, can be eliminated by frequent fire but often decline with infrequent fire. Population viability analyses of habitat specialists offer more precision in suggesting ranges of appropriate fire return intervals. For two types of Florida scrub (rosemary scrub and oak-hickory scrub), plant-population viability analyses narrow the interval and suggest more frequent fires than do previous recommendations, at intervals of 15-30 and 5-12 years, respectively. Variation in fire regimes in time and space (pyrodiversity) is recommended as a bet-hedging fire-management strategy and to allow co-existence of species with disparate life histories.
SN 0067-1924
PY 2007
VL 55
IS 3
BP 261
EP 272
UT ISI:000246571400008
ER
PT J
AU Uhl, D
Abu Hamad, A
Kerp, H
Bandel, K
AF Uhl, D.
Abu Hamad, A.
Kerp, H.
Bandel, K.
TI Evidence for palaeo-wildfire in the Late Permian palaeotropics - charcoalified wood from the Um Irna Formation of Jordan
SO REVIEW OF PALAEOBOTANY AND PALYNOLOGY
AB Charcoalified wood from the lower part of the Late Permian Um Irna Formation of Jordan is described. This charcoal represents the first evidence of palaeo-wildfire during the Late Permian in northern Gondwana. The source locality at the northeastern rim of the Dead Sea has yielded excellently preserved gymnosperm charcoal. Taxonomically most remains are identified as Dadoxylon-type gymnosperm wood. However, one woody specimen exhibits features that suggest a potential taxonomic relationship to the Corystospermales, a group otherwise represented at this locality by compressed fronds assigned to the genus Dicroidium. The occurrence of charcoal in the Um Irna Formation is in accordance with sedimentological data, as well as palaeoclimatic interpretations of this formation that suggest a tropical climate with alternating wet and dry seasons, favourable for the occurrence of wildfires. The charcoalified wood from the Late Permian of Jordan testifies for the first time to the occurrence of palaeo-wildfire in the low latitudes of northern Gondwana during; this period. (c) 2006 Elsevier B.V. All rights reserved.
SN 0034-6667
PD MAY
PY 2007
VL 144
IS 3-4
BP 221
EP 230
UT ISI:000245798500007
ER
PT J
AU Retzer, V
AF Retzer, Vroni
TI Forage competition between livestock and Mongolian Pika (Ochotona pallasi) in Southern Mongolian mountain steppes
SO BASIC AND APPLIED ECOLOGY
AB Nomadic pastoralism is the most suitable form of land use in the semi-arid grasslands of the world and from a pastoralist point of view wild herbivores are considered forage competitors to livestock. Although small mammals are abundant in steppe ecosystems forage competition between small mammals and livestock has rarely been quantified. This study presents the results of an exclosure experiment investigating forage competition between the Mongolian Pika (Ochotona pallasi) and livestock in the Stipa-Allium-steppes of the Gobi Gurvan Saykhan, southern Mongolia. Available forage in the area consists primarily of Stipa krylovii, Agropyron cristatum, and Allium polyrrhizum (representing 80% of available phytomass), all of which are regarded as desirable forage plants. In the drought year of 2001 however, species heights indicated that Allium is avoided by pika and livestock alike while Stipa and Agropyron are intensely browsed.
Pika and livestock populate the same habitat and browse the same limited forage species, leading to the conclusion that both herbivore groups compete for forage. Due to their smaller body size, pika are able to bite down the vegetation to a lower level and thereby consume more of the available forage, giving them a competitive advantage over the livestock. (c) 2006 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.
SN 1439-1791
PY 2007
VL 8
IS 2
BP 147
EP 157
UT ISI:000245005000005
ER
PT J
AU Klimesova, J
Klimes, L
AF Klimesova, Jitka
Klimes, Leoa
TI Bud banks and their role in vegetative regeneration - A literature review and proposal for simple classification and assessment
SO PERSPECTIVES IN PLANT ECOLOGY EVOLUTION AND SYSTEMATICS
AB While sexual regeneration of plants after disturbance is relatively well understood, vegetative regeneration has attracted some attention only recently. Its role along environmental gradients and across biomes is poorly known and standard methods for assessment are not yet established. We review current knowledge about the role of bud banks in vegetative regeneration and the diversity of their modes of functioning. The similarities and differences between bud banks and seed banks are illustrated, focusing on dormancy, dispersability, seasonal dynamics, longevity and storage of carbohydrates. We try to formulate some principles that unity bud bank functioning across habitats and growth forms: (1) the bud banks consist of all buds which may be used for vegetative regeneration, including those formed adventitiously only after injury; (2) vertical distribution of buds reflects avoidance of disturbance; (3) seasonal changes in the bud bank make vegetative regeneration sensitive to timing of disturbance; and (4) ability to form adventitious buds provides a potential for vegetative regeneration from roots, stumps and leaves. Based on these principles, a simple classification of bud banks is presented similar to the classification of seed banks. Bud bank traits are considered in relation to severity, timing and frequency of disturbance. These include vertical distribution and seasonal fluctuations in the number of buds. Methods for quantitative assessment of bud numbers and resprouting capacity are reviewed, and a new approach based on indirect bud counts is proposed. The suggested concept of bud banks may be widely used in studies focusing on plant functional traits in relation to disturbance regimes at the levels of plant individuals, populations and communities. Its further development may incorporate adjustments for areas with lion-seasonal climate and refinements for some growth forms, such as epiphytes. (c) 2007 Rubel Foundation, ETH Zurich. Published by Elsevier GmbH. All rights reserved.
SN 1433-8319
PY 2007
VL 8
IS 3
BP 115
EP 129
UT ISI:000245028200001
ER
PT J
AU Willis, KJ
Birks, HJB
AF Willis, K. J.
Birks, H. J. B.
TI What is natural? The need for a long-term perspective in biodiversity conservation
SO SCIENCE
AB Ecosystems change in response to factors such as climate variability, invasions, and wildfires. Most records used to assess such change are based on short-term ecological data or satellite imagery spanning only a few decades. In many instances it is impossible to disentangle natural variability from other, potentially significant trends in these records, partly because of their short time scale. We summarize recent studies that show how paleoecological records can be used to provide a longer temporal perspective to address specific conservation issues relating to biological invasions, wildfires, climate change, and determination of natural variability. The use of such records can reduce much of the uncertainty surrounding the question of what is "natural" and thereby start to provide important guidance for long-term management and conservation.
SN 0036-8075
PD NOV 24
PY 2006
VL 314
IS 5803
BP 1261
EP 1265
UT ISI:000242215800032
ER
PT J
AU Roberts, PD
Stewart, GB
Pullin, AS
AF Roberts, Philip D.
Stewart, Gavin B.
Pullin, Andrew S.
TI Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine
SO BIOLOGICAL CONSERVATION
AB Review articles are important sources of information and often the only source of evidence used by decision makers in conservation and environmental management to assess effectiveness and impact of interventions and other actions. Recent developments in the field of medicine and public health have established 'systematic review' guidelines to minimise bias and explicitly document methodology, allowing replication and updating in light of further advances. The aim of this article was to assess the methodological and reporting rigour of reviews from the disciplines of conservation, ecology and environmental management (referred to as "ecological reviews"). This was achieved by comparing them to medical systematic reviews, using 27 detailed criteria well established in medicine. When compared with medical systematic reviews, ecological reviews were more likely to be prone to bias, lacking details in the methods used to search for studies, and were less likely to assess the relevance of studies, quality of the original experiments and to quantitatively synthesise the evidence. overall, ecological reviews show lower quality and greater variation in reporting style and review methods. To address this, reviewers could use a systematic review approach and journals could provide more explicit guidelines for the preparation and production of review articles. (c) 2006 Elsevier Ltd. All rights reserved.
SN 0006-3207
PD OCT
PY 2006
VL 132
IS 4
BP 409
EP 423
UT ISI:000241348900001
ER
PT J
AU Kenward, H
AF Kenward, Harry
TI The visibility of past trees and woodland: testing the value of insect remains
SO JOURNAL OF ARCHAEOLOGICAL SCIENCE
AB The reconstruction of woodland history is important in relation to archaeological, ecological, biogeographical and evolutionary problems, and insect remains are a significant source of relevant information. Fully natural interglacial and Holocene 'waterlogged' deposits assumed to have formed in woodland generally contain abundant macrofossils of both plants and insects indicative of trees. In contrast, British archaeological deposits rich in macrofossil remains of trees often lack, or contain very few, tree-associated insects. To cast light on this contradiction, assemblages of insect (Coleoptera and Hemiptera) remains from a range of modern deposits with various spatial relationships to woodland and trees have been analysed. The proportions of tree-associated insects varied greatly. There was a general trend from higher values in woodland and near to isolated trees of species supporting a rich insect fauna, to low or zero values where there were no trees. However, low values sometimes occurred in woods or near trees, so that rarity of tree-associated insects in archaeological deposits does not always carry the implication of a treeless environment. Further investigation is suggested, with emphasis on the importance of identifying isolated trees, scrub and hedges as a resource for humans and wildlife in the past. (c) 2006 Elsevier Ltd. All rights reserved.
SN 0305-4403
PD OCT
PY 2006
VL 33
IS 10
BP 1368
EP 1380
UT ISI:000239894700003
ER
PT J
AU Pons, J
Pausas, JG
AF Pons, J.
Pausas, J. G.
TI Oak regeneration in heterogeneous landscapes: The case of fragmented Quercus suber forests in the eastern Iberian Peninsula
SO FOREST ECOLOGY AND MANAGEMENT
AB Quercus suber recruitment is quantified at local (in different vegetation types) and landscape level in three marginal populations (sites) ranging in size from 70 to 7000 ha and located in the eastern Iberian Peninsula (Spain). We hypothesised that: (1) recruitment of marginal Q. suber populations in eastern Iberia should be higher than in the core area of distribution, western Iberia, (2) within our study area, there should be a trend in the regeneration from north (the largest forest patch) to south (the smallest patch), and (3) within a site, recruitment should not be randomly distributed, but rather some vegetation types should show higher recruitment than other vegetation types. To test these hypotheses, a total of 61 plots measuring 12.5 m x 12.5 m were established on seven vegetation types in five previously selected 3 km x 3 km quadrats. On each plot all Quercus plants shorter than 3 m were labelled and tracked between 2003 and 2005. Results support the first and third hypotheses but not the second one. Q. suber recruitment densities ranged from 0 to 7200 plants per hectare. The complete regeneration process (from recruitment to growth) occurred on old fields; well-established seedling banks were abundant under forest canopies; recruitment in shrublands was practically null. To better understand Q. suber recruitment, both landscape configuration and interactions with other Quercus species should be considered. (c) 2006 Elsevier B.V. All rights reserved.
SN 0378-1127
PD AUG 1
PY 2006
VL 231
IS 1-3
BP 196
EP 204
UT ISI:000239572600021
ER
PT J
AU Ansley, RJ
Boutton, TW
Skjemstad, JO
AF Ansley, R. J.
Boutton, T. W.
Skjemstad, J. O.
TI Soil organic carbon and black carbon storage and dynamics under different fire regimes in temperate mixed-grass savanna
SO GLOBAL BIOGEOCHEMICAL CYCLES
AB [1] We quantified the effects of repeated, seasonal fires on soil organic carbon (SOC), black carbon (BC), and total N in controls and four fire treatments differing in frequency and season of occurrence in a temperate savanna. The SOC at 0 - 20 cm depth increased from 2044 g C m(-2) in controls to 2393 - 2534 g C m(-2) in the three treatments that included summer fire. Similarly, soil total N (0 - 20 cm) increased from 224 g N m(-2) in the control to 251 - 255 g N m(-2) in the treatments that included summer fire. However, winter fires had no effect on SOC or total N. Plant species composition coupled with lower delta C-13 of SOC suggested that increased soil C in summer fire treatments was related to shifts in community composition toward greater relative productivity by C-3 species. Lower delta N-15 of soil total N in summer fire treatments was consistent with a scenario in which N inputs > N losses. The BC storage was not altered by fire, and comprised 13 - 17% of SOC in all treatments. Results indicated that fire and its season of occurrence can significantly alter ecosystem processes and the storage of C and N in savanna ecosystems.
SN 0886-6236
PD JUL 19
PY 2006
VL 20
IS 3
AR GB3006
DI ARTN GB3006
UT ISI:000239578200002
ER
PT J
AU Pineiro, G
Paruelo, JM
Oesterheld, M
TI Potential long-term impacts of livestock introduction on carbon and nitrogen cycling in grasslands of Southern South America
SO GLOBAL CHANGE BIOLOGY
AB Empirical evidence based on grazing exclusion at the scale of years to decades shows that grazing modifies carbon (C) and nitrogen (N) cycling. However, long-term effects at the scale of centuries are less known, yet highly relevant to understand local and global impacts of grazing. Additionally, most studies have focused on the isolated response of C and N, with little understanding of their interactions. Using CENTURY, a process-based biogeochemical model, we analyzed the impacts of 370 years of livestock grazing (i.e. long term, from early European colonization to present) in 11 sites across the Rio de la Plata grasslands and compared them with those resulting from two decades of grazing (i.e. mid-term, typical exclosure experiment). In the long term, livestock grazing primarily altered the N cycle through faster N returns to the soil via urine and dung, which were offset by uninterrupted N outputs by volatilization and leaching. As a result, soil organic N decreased by -880 kg ha(-1) or -19%. Higher N outputs (mainly as NH3) opened the N cycle, potentially decreasing N2O and NOx emissions and increasing N depositions over the region. These greater outputs of N constrained C accumulation in soils, reducing soil organic C by -21 200 kg ha(-1) (-22%, a reduction of -1.5 Pg of C for the whole region) and net primary production by -2192 kg ha(-1) yr(-1) (-24%). Mid-term simulations showed that the effects of livestock introduction in a decadal time scale were substantially different both in magnitude and direction from long-term responses. Long-term results were not substantially affected when atmospheric CO2 content, species composition and fire regime were changed within plausible ranges, but highlighted fire-grazing interactions as a major constraint of long-term C and N dynamics in these grasslands.
SN 1354-1013
PD JUL
PY 2006
VL 12
IS 7
BP 1267
EP 1284
UT ISI:000238352800010
ER
PT J
AU Gongalsky, KB
TI Forest fires as a factor of formation of soil animal communities
SO ZHURNAL OBSHCHEI BIOLOGII
AB Forest fires usually destroy the most of soil animals. However due to the heterogeneity of soil cover some animals can survive in the partially burned patches (refugia). These groups along with the inhabitants of deep soil layers are the first to colonize burned areas. Nevertheless, the leading role in colonization of the burned areas belongs to obligate pyrophilous groups, adapted to discover burned areas and inhabit them. These, mostly saprovorous, groups develop thanks to the plenty of easily available resources (fungi and other microorganisms developing on pyrogenic mineralized organic remains) and lack of competition during first two years after the fire. They are replaced later by the phytophagous and saprovorous groups (facultative pyrophils), which are more successful in competition and gaining burned areas. Once the litter layer reestablished, the groups of other animals not occurring on the newly burned areas colonize them. A large part of those are predators. Fire severity is the most important factor regulating recovery of soil-living animal communities on the burned areas.
SN 0044-4596
PD MAR-APR
PY 2006
VL 67
IS 2
BP 127
EP 138
UT ISI:000237969400004
ER
PT J
AU Moritz, MA
Morais, ME
Summerell, LA
Carlson, JM
Doyle, J
TI Wildfires, complexity, and highly optimized tolerance
SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
AB Recent, large fires in the western United States have rekindled debates about fire management and the role of natural fire regimes in the resilience of terrestrial ecosystems. This real-world experience parallels debates involving abstract models of forest fires, a central metaphor in complex systems theory. Both real and modeled fire-prone landscapes exhibit roughly power law statistics in fire size versus frequency. Here, we examine historical fire catalogs and a detailed fire simulation model; both are in agreement with a highly optimized tolerance model. Highly optimized tolerance suggests robustness tradeoffs underlie resilience in different fire-prone ecosystems. Understanding these mechanisms may provide new insights into the structure of ecological systems and be key in evaluating fire management strategies and sensitivities to climate change.
SN 0027-8424
PD DEC 13
PY 2005
VL 102
IS 50
BP 17912
EP 17917
UT ISI:000234010500008
ER
EF