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Richard M Cowling - One of the best experts on this subject based on the ideXlab platform.
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multi decadal vegetation change in dune vegetation of the south eastern cape floristic region is thicket expansion without fire inevitable
South African Journal of Botany, 2021Co-Authors: Richard M Cowling, M T HoffmanAbstract:Abstract It is hypothesized that in the Holocene dune Fynbos-thicket mosaics of the Cape, decades-long absence of fire results in closed-canopy thicket replacing more open Fynbos shrublands. We tested this hypothesis by analyzing repeat photographs from 16 sites at Cape St Francis in the south-eastern Cape Floristic Region. The period of monitoring ranged from 55 to 17 year and most sites had been last burnt between 30 and 50 years ago. We divided the sites into coastal (salt wind-exposed) and inland zones and computed, for each pair of photographs, the rate of change of four plant types, namely thicket shrubs, Fynbos woody, Fynbos herbaceous and grass. Coastal zone sites showed a significant increase in thicket shrub cover and a significant decline in both grass and Fynbos herbaceous cover. Fynbos woody cover declined in the face of thicket invasion, but increased in grassy sites, most likely due to a decline in herbivory intensity. No significant changes in plant types were observed in the inland sites, although thicket shrub cover did increase marginally at the expense of Fynbos woody plants. However, thicket invasion was restricted to swales and lower dune slopes; the dune Fynbos of the upper slopes and crests remains uninvaded by thicket and surprisingly vigorous after 30–50 year without fire. This is consistent with the notion that Fynbos species occupy drier sites than thicket in these dune landscapes and regular fire is not a prerequisite for its persistence. Overall, we showed a large increase in woody plant cover throughout the study area. While this pattern is consistent with predictions for vegetation change in response to atmospheric [CO2] pollution, it can also be explained by land use changes experienced in the study area, starting in the early 1960s, involving a shift from subsistence agriculture to holiday resort development and tourism.
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historical fire regimes in a poorly understood fire prone ecosystem eastern coastal Fynbos
International Journal of Wildland Fire, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Johan Baard, Sonali DasAbstract:We characterised the historical fire regime (1900–2010) in eastern coastal Fynbos shrublands, which occur in a poorly studied part of the Cape Floral Kingdom (CFK). Natural (lightning-ignited) fires dominated the fire regime. Fire seasonality decreased from west (Outeniqua region) to east (Tsitsikamma region) within the study area, and between the study area and further west in the CFK. This is consistent with a west–east climatic gradient in the CFK, where rainfall is concentrated in winter in the west, and evenly distributed across months in the east. Median fire return intervals (FRIs) (1980–2010) were broadly comparable to other Fynbos areas but estimates varied widely depending on whether or not the data were censored (16–26 years with and 8–13 years without censoring). FRIs appeared to be shorter in the Tsitsikamma, where rainfall and plant growth rates are higher, than in the Outeniqua. The total area burnt annually has increased significantly since 1980, coinciding with an increase in weather conducive to fires, suggesting that fire regimes may be responding to climate change. Frequent recurrence of very large fires and the virtual absence of vegetation in older post-fire age classes are potential causes for concern in achieving Fynbos conservation objectives.
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fire regimes in eastern coastal Fynbos imperatives and thresholds in managing for diversity
Koedoe, 2013Co-Authors: Tineke Kraaij, Richard M Cowling, Brian W Van WilgenAbstract:Until recently, fire ecology was poorly understood in the eastern coastal region of the Cape Floral Kingdom (CFK), South Africa. Rainfall in the area is aseasonal and temperatures are milder than in the winter-rainfall and drier inland parts of the CFK, with implications for the management of fire regimes. We synthesised the findings of a research programme focused on informing ecologically sound management of fire in eastern coastal Fynbos shrublands and explored potential east–west trends at the scales of study area and CFK in terms of fire return interval (FRI) and fire season. FRIs (8–26 years; 1980–2010) were comparable to those elsewhere in the CFK and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success suggested that for biodiversity conservation purposes, FRIs should be ≥ 9 years in eastern coastal Fynbos. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning and post-fire proteoid recruitment suggested that fires in eastern coastal Fynbos are not limited to any particular season. We articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal Fynbos, to guide adaptive management of fire in the Garden Route National Park and elsewhere in the region. Conservation implications: Wildfires are likely to remain dominant in eastern coastal Fynbos, whilst large-scale implementation of prescribed burning is unattainable. Fires occurring in any season are not a reason for concern, although other constraints remain: the need for sufficient fire intensity, safety requirements, and integration of fire and invasive alien plant management.
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proteaceae juvenile periods and post fire recruitment as indicators of minimum fire return interval in eastern coastal Fynbos
Applied Vegetation Science, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Annelise SchuttevlokAbstract:Question Fire management practices aimed at biodiversity conservation are often in conflict with hazard reduction requirements. Particularly in protected areas where such conflict of interest exists, the question is asked: what are the ecological thresholds within which fire should be managed? Location Montane proteoid Fynbos shrublands, eastern coastal part of the Cape Floral Kingdom; coastal slopes of the Tsitsikamma and Outeniqua Mountains, South Africa. Methods Estimates of optimal fire frequencies are often based on the relationship between plant age and the rate of seed accumulation of the slowest-maturing species. We established juvenile periods and recruitment success (measured as the ratio of post-fire recruits to the pre-burn population) after fires at different intervals, of serotinous, reseeding shrubs in the Proteaceae. From this we estimated minimum fire return intervals (FRIs) that would allow for their persistence in eastern coastal Fynbos shrublands. Results Juvenile periods ranged from 4 to 9 yr, which are comparable to ecologically similar proteoids elsewhere in Fynbos and SE and SW Australian shrublands. There was large variability among sites and within species in the degree of flowering at given plant ages, some of which seemed related to the moisture regime. There were no consistent differences among species in their rate of maturation. Post-fire recruitment success was near zero following a fire in 5-yr-old vegetation, always above replacement levels following fires in ≥7-yr-old vegetation, and at a maximum in old (38 yr) Fynbos. There was considerable variation in post-fire recruitment success for any particular FRI, species or site. The lack of a significant relationship between recruitment success and pre-fire vegetation age, suggests that once a critical post-fire age is attained, factors other than seed abundance affect recruitment success. Conclusions From an ecological perspective, our findings imply a minimum FRI of 9 yr for eastern coastal Fynbos. This is not intended to prescribe rigid management of fire according to a fixed rotation and does not negate the need to consider site- or species-specific requirements. Instead it provides a lower threshold for a range of acceptable FRIs below which a significant decline of species populations is predicted.
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fire season effects on the recruitment of non sprouting serotinous proteaceae in the eastern bimodal rainfall Fynbos biome south africa
Austral Ecology, 2008Co-Authors: Brian W Van Wilgen, Serban Proches, Steffen Heelemann, Anthony G Rebelo, Stefan Porembski, Richard M CowlingAbstract:Research in Mediterranean-climate shrublands in both South Africa and Australia shows that recruit- ment of proteoid shrubs (non-sprouting, serotinous Proteaceae) is best after warm-season (summer and autumn) fires and worst after cool-season (winter and spring) ones. This pattern has been attributed to post-dispersal seed attrition as well as size of pre-dispersal seed reserves. Here we investigate patterns of post-fire recruitment for four proteoid species in the eastern part of South Africa's Fynbos biome, which has a bimodal (spring and autumn) rainfall regime. Despite the lack of significant differences in recruitment between cool- and warm-season burns, we find some evidence for favourable recruitment periods following fires in spring and autumn, immediately before, and coinciding with, the bimodal rainfall peaks. This suggests that enhanced recruitment is associated with conditions of high soil moisture immediately after the fire, and that rapid germination may minimize post-dispersal seed attrition. In two of the species, we also find a shift from peak flowering in winter and spring in the Mediterranean-climate part of the Fynbos biome, to summer and autumn flowering in the eastern part. Because these two species are only weakly serotinous, warm-season flowering would result in maximal seed banks in spring, which could explain the spring recruitment peak, but not the autumn one. We conclude that eastern recruitment patterns differ significantly from those observed in the western and central parts of the biome, and that fire management protocols for the east, which are currently based on data and experience from the winter-rainfall Fynbos biome, need to be adjusted accordingly. Fire managers in the eastern Fynbos biome should be less constrained by requirements to burn within a narrow seasonal range, and should therefore be in a better position to apply the required management burns.
Tineke Kraaij - One of the best experts on this subject based on the ideXlab platform.
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historical fire regimes in a poorly understood fire prone ecosystem eastern coastal Fynbos
International Journal of Wildland Fire, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Johan Baard, Sonali DasAbstract:We characterised the historical fire regime (1900–2010) in eastern coastal Fynbos shrublands, which occur in a poorly studied part of the Cape Floral Kingdom (CFK). Natural (lightning-ignited) fires dominated the fire regime. Fire seasonality decreased from west (Outeniqua region) to east (Tsitsikamma region) within the study area, and between the study area and further west in the CFK. This is consistent with a west–east climatic gradient in the CFK, where rainfall is concentrated in winter in the west, and evenly distributed across months in the east. Median fire return intervals (FRIs) (1980–2010) were broadly comparable to other Fynbos areas but estimates varied widely depending on whether or not the data were censored (16–26 years with and 8–13 years without censoring). FRIs appeared to be shorter in the Tsitsikamma, where rainfall and plant growth rates are higher, than in the Outeniqua. The total area burnt annually has increased significantly since 1980, coinciding with an increase in weather conducive to fires, suggesting that fire regimes may be responding to climate change. Frequent recurrence of very large fires and the virtual absence of vegetation in older post-fire age classes are potential causes for concern in achieving Fynbos conservation objectives.
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fire regimes in eastern coastal Fynbos imperatives and thresholds in managing for diversity
Koedoe, 2013Co-Authors: Tineke Kraaij, Richard M Cowling, Brian W Van WilgenAbstract:Until recently, fire ecology was poorly understood in the eastern coastal region of the Cape Floral Kingdom (CFK), South Africa. Rainfall in the area is aseasonal and temperatures are milder than in the winter-rainfall and drier inland parts of the CFK, with implications for the management of fire regimes. We synthesised the findings of a research programme focused on informing ecologically sound management of fire in eastern coastal Fynbos shrublands and explored potential east–west trends at the scales of study area and CFK in terms of fire return interval (FRI) and fire season. FRIs (8–26 years; 1980–2010) were comparable to those elsewhere in the CFK and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success suggested that for biodiversity conservation purposes, FRIs should be ≥ 9 years in eastern coastal Fynbos. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning and post-fire proteoid recruitment suggested that fires in eastern coastal Fynbos are not limited to any particular season. We articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal Fynbos, to guide adaptive management of fire in the Garden Route National Park and elsewhere in the region. Conservation implications: Wildfires are likely to remain dominant in eastern coastal Fynbos, whilst large-scale implementation of prescribed burning is unattainable. Fires occurring in any season are not a reason for concern, although other constraints remain: the need for sufficient fire intensity, safety requirements, and integration of fire and invasive alien plant management.
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proteaceae juvenile periods and post fire recruitment as indicators of minimum fire return interval in eastern coastal Fynbos
Applied Vegetation Science, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Annelise SchuttevlokAbstract:Question Fire management practices aimed at biodiversity conservation are often in conflict with hazard reduction requirements. Particularly in protected areas where such conflict of interest exists, the question is asked: what are the ecological thresholds within which fire should be managed? Location Montane proteoid Fynbos shrublands, eastern coastal part of the Cape Floral Kingdom; coastal slopes of the Tsitsikamma and Outeniqua Mountains, South Africa. Methods Estimates of optimal fire frequencies are often based on the relationship between plant age and the rate of seed accumulation of the slowest-maturing species. We established juvenile periods and recruitment success (measured as the ratio of post-fire recruits to the pre-burn population) after fires at different intervals, of serotinous, reseeding shrubs in the Proteaceae. From this we estimated minimum fire return intervals (FRIs) that would allow for their persistence in eastern coastal Fynbos shrublands. Results Juvenile periods ranged from 4 to 9 yr, which are comparable to ecologically similar proteoids elsewhere in Fynbos and SE and SW Australian shrublands. There was large variability among sites and within species in the degree of flowering at given plant ages, some of which seemed related to the moisture regime. There were no consistent differences among species in their rate of maturation. Post-fire recruitment success was near zero following a fire in 5-yr-old vegetation, always above replacement levels following fires in ≥7-yr-old vegetation, and at a maximum in old (38 yr) Fynbos. There was considerable variation in post-fire recruitment success for any particular FRI, species or site. The lack of a significant relationship between recruitment success and pre-fire vegetation age, suggests that once a critical post-fire age is attained, factors other than seed abundance affect recruitment success. Conclusions From an ecological perspective, our findings imply a minimum FRI of 9 yr for eastern coastal Fynbos. This is not intended to prescribe rigid management of fire according to a fixed rotation and does not negate the need to consider site- or species-specific requirements. Instead it provides a lower threshold for a range of acceptable FRIs below which a significant decline of species populations is predicted.
David M Richardson - One of the best experts on this subject based on the ideXlab platform.
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plant invasions restoration and economics perspectives from south african Fynbos
Perspectives in Plant Ecology Evolution and Systematics, 2012Co-Authors: Mirijam Gaertner, Henning Nottebrock, Helanya Fourie, Sean D J Privett, David M RichardsonAbstract:Abstract Restoration is gaining importance in the management of plant invasions. As the success of restoration projects is frequently determined by factors other than ecological ones, we explored the ecological and financial feasibility of active restoration on three different invaded sites in South Africa's Cape Floristic Region. The aim of our study was to identify cost-effective ways of restoring functional native ecosystems following invasion by alien plants. Over three years we evaluated different restoration approaches using field trials and experimental manipulations (i.e. mechanical clearing, burning, different soil restoration techniques and sowing of native species) to reduce elevated soil nutrient levels and to re-establish native Fynbos communities. Furthermore we investigated the possibility of introducing native Fynbos species that can be used for sustainable harvesting to create an incentive for restoration on private land. Diversity and evenness of native plant species increased significantly after restoration at all three sites, whereas cover of alien plants decreased significantly, confirming that active restoration was successful. However, sowing of native Fynbos species had no significant effect on native cover, species richness, diversity or evenness in the Acacia thicket and Kikuyu field, implying that the ecosystem was sufficiently resilient to allow autogenic recovery following clearing and burning of the invasive species. Soil restoration treatments resulted in an increase of available nitrogen in the Acacia thicket, but had no significant effects in the Eucalyptus plantation. However, despite elevated available soil nitrogen levels, native species germinated irrespective whether sown or unsown (i.e. regeneration from the soil seed bank). Without active introduction of native species, native grasses, forbs and other shrubs would have dominated, and proteoids and ericoids (the major Fynbos growth forms) would have been under-represented. The financial analysis shows that income from flower harvesting following active restoration consistently outweighs income following passive restoration, but that the associated increase in income does not always justify the higher costs. We conclude that active restoration can be effective and financially feasible when compared to passive restoration, depending on the density of invasion. Active restoration of densely invaded sites may therefore only be justifiable if the target area is in a region of high conservation priority.
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a biome scale assessment of the impact of invasive alien plants on ecosystem services in south africa
Journal of Environmental Management, 2008Co-Authors: B W Van Wilgen, David M Richardson, Belinda Reyers, D Le C Maitre, L SchonegevelAbstract:Abstract This paper reports an assessment of the current and potential impacts of invasive alien plants on selected ecosystem services in South Africa. We used data on the current and potential future distribution of 56 invasive alien plant species to estimate their impact on four services (surface water runoff, groundwater recharge, livestock production and biodiversity) in five terrestrial biomes. The estimated reductions in surface water runoff as a result of current invasions were >3000 million m 3 (about 7% of the national total), most of which is from the Fynbos (shrubland) and grassland biomes; the potential reductions would be more than eight times greater if invasive alien plants were to occupy the full extent of their potential range. Impacts on groundwater recharge would be less severe, potentially amounting to approximately 1.5% of the estimated maximum reductions in surface water runoff. Reductions in grazing capacity as a result of current levels of invasion amounted to just over 1% of the potential number of livestock that could be supported. However, future impacts could increase to 71%. A ‘biodiversity intactness index’ (the remaining proportion of pre-modern populations) ranged from 89% to 71% for the five biomes. With the exception of the Fynbos biome, current invasions have almost no impact on biodiversity intactness. Under future levels of invasion, however, these intactness values decrease to around 30% for the savanna, Fynbos and grassland biomes, but to even lower values (13% and 4%) for the two karoo biomes. Thus, while the current impacts of invasive alien plants are relatively low (with the exception of those on surface water runoff), the future impacts could be very high. While the errors in these estimates are likely to be substantial, the predicted impacts are sufficiently large to suggest that there is serious cause for concern.
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ecosystem level impacts of invasive acacia saligna in the south african Fynbos
Restoration Ecology, 2004Co-Authors: Stephanie G Yelenik, William D Stock, David M RichardsonAbstract:Recent efforts to clear invasive plants from the Fynbos of South Africa forces managers to think about how N2-fixing invasives have altered ecosystem processes and the implications of these changes for community development. This study investigated the changes in nitrogen (N) cycling regimes in Fynbos with the invasion of Acacia saligna, the effects of clear-cutting acacia stands on soil microclimate and N cycling, and how altered N resources affected the growth of a weedy grass species. Litterfall, litter quality, soil nutrient pools, and ion exchange resin (IER)-available soil N were measured in uninvaded Fynbos, intact acacia, and cleared acacia stands. In addition, a bioassay experiment was used to ascertain whether the changes in soil nutrient availability associated with acacia would enhance the success of a weedy grass species. Acacia plots had greater amounts of litterfall, which had higher concentrations of N. This led to larger quantities of organic matter, total N, and IER-available N in the soil. Clearing acacia stands caused changes in soil moisture and temperature, but did not result in differences in IER-available N. The alteration of N availability by acacias was shown to increase growth rates of the weedy grass Ehrharta calycina, suggesting that secondary invasions by nitrophilous weedy species may occur after clearing N2-fixing alien species in the Fynbos. It is suggested that managers use controlled burns, the addition of mulch, and the addition of Fynbos seed after clearing to lower the levels of available N in the soil and initiate the return of native vegetation.
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an expert system for screening potentially invasive alien plants in south african Fynbos
Journal of Environmental Management, 1995Co-Authors: K C Tucker, David M RichardsonAbstract:The development and application of an expert system is described for screening alien woody plants for their invasive potential in South African Fynbos. The system is proposed for use by potential introducers to demonstrate low invasive risk before importing woody alien species for cultivation. Rules for the system were derived from empirical evidence by quantifying invasion windows and barriers that have limited the set of widespread woody invaders (trees and shrubs) in Fynbos to fewer than 20, out of several hundred introduced species. The system first compares broad-scale environmental conditions (climate and soil) between the home environment of a species and Fynbos. Features of the plant in its home environment (basic life history traits, population characteristics, regeneration biology, habitat preferences) are then assessed. Finally, an assessment is made of life history adaptations to the prevailing fire regime in Fynbos (juvenile period, fire-survival capacity of adult plants, seed bank longevity). The reasoning is explicit and the steps leading to a conclusion (high risk/low risk) can be retraced. Besides the obvious application in identifying species with a high risk of invading, the system has considerable potential for modelling, and for teaching the concepts of biological invasions. The rules provide an explicit conceptualization of invasion processes in Fynbos and identify multiple paths to invasive success (not all of which have been realized yet). The system can therefore be used in planning control operations (for optimal allocation of control effort to critical stages in invasion), and for predicting the outcome of changes (e.g. in fire frequency) on the dimensions of invasion windows, and for assessing what changes are needed to prevent or reduce the extent of invasion by a given taxon. Application of the system is demonstrated on Pinus and Banksia taxa and a selection of species from Californian chaparral.
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the invasive potential of australian banksias in south african Fynbos a comparison of the reproductive potential of banksia ericifolia and leucadendron laureolum
Austral Ecology, 1992Co-Authors: M A Honig, Richard M Cowling, David M RichardsonAbstract:Several taxa of the Australian Proteaceae have invaded South African Fynbos and require costly management programmes to bring under control. Banksia spp. have been introduced only recently to Fynbos regions. The invasive potential of Banksia ericifolia (Proteaceae) was investigated by comparing its recruitment potential with that of an indigenous proteaceous shrub, Leucadendron laureolum. Both species are overstorey shrubs that are killed by fire and rely on canopy-stored seeds (serotiny) for recruitment. Eight year old B. ericifolia shrubs produced an average of 16 500 seeds per plant, which is thirty times more than the average of 570 seeds produced by 10 year old L. laureolum shrubs. The seed bank of B. ericifolia was not only larger than that of L. laureolum (1098 vs 525 viable seeds m−2 projected canopy cover), but also considerably larger than that described for the species in its native environment (200–330 seeds m−2 in a 9 year old stand north of Sydney). Leucadendron laureoleum released most of its seed a few days after the cones were burnt, whereas seed release in B. ericifolia was spread over 12 weeks. The seeds of B. ericifolia had lower wingloading and fall rates than L. laureolum and were dispersed over greater distances. The relative seedling growth rates of the two species were very similar (0.03 g per day), but below-ground biomass was greater and proteoid roots were more developed in B. ericifolia seedlings than in L. laureolum after 100 days. Four year old B. ericifolia plants growing in the field had attained over twice the height of indigenous pro-teoids and accumulated up to 10 times the fresh biomass of L. xanthoconus, a species which is ecologically similar to L. laureolum. The Bioclimatic Prediction System (BIOCLIM) was used to create a bioclimatic profile of B. ericifolia and identify climatically suitable areas in the Cape Province. Results show that its potential distribution covers most Fynbos areas in the southwestern Cape. It is concluded that B. ericifolia has the potential to be highly invasive in Fynbos.
Brian W Van Wilgen - One of the best experts on this subject based on the ideXlab platform.
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historical fire regimes in a poorly understood fire prone ecosystem eastern coastal Fynbos
International Journal of Wildland Fire, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Johan Baard, Sonali DasAbstract:We characterised the historical fire regime (1900–2010) in eastern coastal Fynbos shrublands, which occur in a poorly studied part of the Cape Floral Kingdom (CFK). Natural (lightning-ignited) fires dominated the fire regime. Fire seasonality decreased from west (Outeniqua region) to east (Tsitsikamma region) within the study area, and between the study area and further west in the CFK. This is consistent with a west–east climatic gradient in the CFK, where rainfall is concentrated in winter in the west, and evenly distributed across months in the east. Median fire return intervals (FRIs) (1980–2010) were broadly comparable to other Fynbos areas but estimates varied widely depending on whether or not the data were censored (16–26 years with and 8–13 years without censoring). FRIs appeared to be shorter in the Tsitsikamma, where rainfall and plant growth rates are higher, than in the Outeniqua. The total area burnt annually has increased significantly since 1980, coinciding with an increase in weather conducive to fires, suggesting that fire regimes may be responding to climate change. Frequent recurrence of very large fires and the virtual absence of vegetation in older post-fire age classes are potential causes for concern in achieving Fynbos conservation objectives.
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fire regimes in eastern coastal Fynbos imperatives and thresholds in managing for diversity
Koedoe, 2013Co-Authors: Tineke Kraaij, Richard M Cowling, Brian W Van WilgenAbstract:Until recently, fire ecology was poorly understood in the eastern coastal region of the Cape Floral Kingdom (CFK), South Africa. Rainfall in the area is aseasonal and temperatures are milder than in the winter-rainfall and drier inland parts of the CFK, with implications for the management of fire regimes. We synthesised the findings of a research programme focused on informing ecologically sound management of fire in eastern coastal Fynbos shrublands and explored potential east–west trends at the scales of study area and CFK in terms of fire return interval (FRI) and fire season. FRIs (8–26 years; 1980–2010) were comparable to those elsewhere in the CFK and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success suggested that for biodiversity conservation purposes, FRIs should be ≥ 9 years in eastern coastal Fynbos. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning and post-fire proteoid recruitment suggested that fires in eastern coastal Fynbos are not limited to any particular season. We articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal Fynbos, to guide adaptive management of fire in the Garden Route National Park and elsewhere in the region. Conservation implications: Wildfires are likely to remain dominant in eastern coastal Fynbos, whilst large-scale implementation of prescribed burning is unattainable. Fires occurring in any season are not a reason for concern, although other constraints remain: the need for sufficient fire intensity, safety requirements, and integration of fire and invasive alien plant management.
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proteaceae juvenile periods and post fire recruitment as indicators of minimum fire return interval in eastern coastal Fynbos
Applied Vegetation Science, 2013Co-Authors: Richard M Cowling, Brian W Van Wilgen, Tineke Kraaij, Annelise SchuttevlokAbstract:Question Fire management practices aimed at biodiversity conservation are often in conflict with hazard reduction requirements. Particularly in protected areas where such conflict of interest exists, the question is asked: what are the ecological thresholds within which fire should be managed? Location Montane proteoid Fynbos shrublands, eastern coastal part of the Cape Floral Kingdom; coastal slopes of the Tsitsikamma and Outeniqua Mountains, South Africa. Methods Estimates of optimal fire frequencies are often based on the relationship between plant age and the rate of seed accumulation of the slowest-maturing species. We established juvenile periods and recruitment success (measured as the ratio of post-fire recruits to the pre-burn population) after fires at different intervals, of serotinous, reseeding shrubs in the Proteaceae. From this we estimated minimum fire return intervals (FRIs) that would allow for their persistence in eastern coastal Fynbos shrublands. Results Juvenile periods ranged from 4 to 9 yr, which are comparable to ecologically similar proteoids elsewhere in Fynbos and SE and SW Australian shrublands. There was large variability among sites and within species in the degree of flowering at given plant ages, some of which seemed related to the moisture regime. There were no consistent differences among species in their rate of maturation. Post-fire recruitment success was near zero following a fire in 5-yr-old vegetation, always above replacement levels following fires in ≥7-yr-old vegetation, and at a maximum in old (38 yr) Fynbos. There was considerable variation in post-fire recruitment success for any particular FRI, species or site. The lack of a significant relationship between recruitment success and pre-fire vegetation age, suggests that once a critical post-fire age is attained, factors other than seed abundance affect recruitment success. Conclusions From an ecological perspective, our findings imply a minimum FRI of 9 yr for eastern coastal Fynbos. This is not intended to prescribe rigid management of fire according to a fixed rotation and does not negate the need to consider site- or species-specific requirements. Instead it provides a lower threshold for a range of acceptable FRIs below which a significant decline of species populations is predicted.
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fire management in mediterranean climate shrublands a case study from the cape Fynbos south africa
Journal of Applied Ecology, 2010Co-Authors: Brian W Van Wilgen, G G Forsyth, Helen Margaret De Klerk, Sonali Das, S Khuluse, Peter Mu SchmitzAbstract:CITATION: Van Wilgen, B. W. et al. 2010. Fire management in Mediterranean-climate shrublands: a case study from the Cape Fynbos, South Africa. Journal of Applied Ecology, 47(3):631–638, doi: 10.1111/j.1365-2664.2010.01800.x.
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fire season effects on the recruitment of non sprouting serotinous proteaceae in the eastern bimodal rainfall Fynbos biome south africa
Austral Ecology, 2008Co-Authors: Brian W Van Wilgen, Serban Proches, Steffen Heelemann, Anthony G Rebelo, Stefan Porembski, Richard M CowlingAbstract:Research in Mediterranean-climate shrublands in both South Africa and Australia shows that recruit- ment of proteoid shrubs (non-sprouting, serotinous Proteaceae) is best after warm-season (summer and autumn) fires and worst after cool-season (winter and spring) ones. This pattern has been attributed to post-dispersal seed attrition as well as size of pre-dispersal seed reserves. Here we investigate patterns of post-fire recruitment for four proteoid species in the eastern part of South Africa's Fynbos biome, which has a bimodal (spring and autumn) rainfall regime. Despite the lack of significant differences in recruitment between cool- and warm-season burns, we find some evidence for favourable recruitment periods following fires in spring and autumn, immediately before, and coinciding with, the bimodal rainfall peaks. This suggests that enhanced recruitment is associated with conditions of high soil moisture immediately after the fire, and that rapid germination may minimize post-dispersal seed attrition. In two of the species, we also find a shift from peak flowering in winter and spring in the Mediterranean-climate part of the Fynbos biome, to summer and autumn flowering in the eastern part. Because these two species are only weakly serotinous, warm-season flowering would result in maximal seed banks in spring, which could explain the spring recruitment peak, but not the autumn one. We conclude that eastern recruitment patterns differ significantly from those observed in the western and central parts of the biome, and that fire management protocols for the east, which are currently based on data and experience from the winter-rainfall Fynbos biome, need to be adjusted accordingly. Fire managers in the eastern Fynbos biome should be less constrained by requirements to burn within a narrow seasonal range, and should therefore be in a better position to apply the required management burns.
Ophélie Ronce - One of the best experts on this subject based on the ideXlab platform.
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Life-History Traits Evolved Jointly with Climatic Niche and Disturbance Regime in the Genus Leucadendron (Proteaceae)
American Naturalist, 2018Co-Authors: Jeanne Tonnabel, Frank Schurr, Florian Boucher, Wilfried Thuiller, Julien Renaud, Emmanuel Douzery, Ophélie RonceAbstract:Organisms have evolved a diversity of life-history strategies to cope with variation in their environment. Persistence as adults and/or seeds across recruitment events allows species to dampen the effects of environmental fluctuations. The evolution of life cycles with overlapping generations should thus permit the colonization of environments with uncertain recruitment. We tested this hypothesis in Leucadendron (Proteaceae), a genus with high functional diversity native to fire-prone habitats in the South African Fynbos. We analyzed the joint evolution of life-history traits (adult survival and seed-bank strategies) and ecological niches (climate and fire regime), using comparative methods and accounting for various sources of uncertainty. In the Fynbos, species with canopy seed banks that are unable to survive fire as adults display nonoverlapping generations. In contrast, resprouters with an underground seed bank may be less threatened by extreme climatic events and fire intervals, given their iteroparity and long-lasting seed bank. Life cycles with nonoverlapping generations indeed jointly evolved with niches with less exposure to frost but not with those with less exposure to drought. Canopy seed banks jointly evolved with niches with more predictable fire return, compared to underground seed banks. The evolution of extraordinary functional diversity among Fynbos plants thus reflects, at least in part, the diversity of both climates and fire regimes in this region.
