Annual Fire Research Articles

Fire and grazing impacts on silica production and storage in grass dominated ecosystems

Grassland ecosystems are an important terrestrial component of the global biogeochemical silicon cycle. Although the structure and ecological functioning of grasslands are strongly influenced by fire and grazing, the role of these key ecological drivers in the production and storage of silicon represents a significant knowledge gap, particularly since they are being altered worldwide by human activities. We evaluated the effects of fire and grazing on the range and variability of plant derived biogenic silica stored in plant biomass and soils by sampling plants and soils from long-term experimental plots with known fire and grazing histories. Overall, plants and soils from grazed sites in the South African ecosystems had up to 76 and 54% greater biogenic silica totals (kg ha−1), respectively, than grazed North American sites. In North American soils, the combination of grazing and annual fire resulted in the greatest abundance of biogenic silica, whereas South African soils had the highest biogenic silica content where grazed regardless of burn frequency. These results as well as those that show greater Si concentrations in grazed South African plants indicate that South African plants and soils responded somewhat differently to fire and grazing with respect to silicon cycling, which may be linked to differences in the evolutionary history and in the grazer diversity and grazing intensity of these ecosystems. We conclude that although fire and grazing (as interactive and/or independent factors) do not affect the concentration of Si taken up by plants, they do promote increased silicon storage in aboveground biomass and soil as a result of directly affecting other site factors such as aboveground net primary productivity. Therefore, as management practices, fire and grazing have important implications for assessing global change impacts on the terrestrial biogeochemical cycling of silicon.

Controls of Aboveground Net Primary Production in Mesic Savanna Grasslands: An Inter-Hemispheric Comparison

Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.

Kyoto Pilgrimage Past and Present

Kyoto Pilgrimage Past and Present Pamela D. Winfield Introduction Kyoto, or Heian‐kyō as it was known for most of its history, is perhaps unlike other pilgrimage cities in the world. It has no one distinguishing landscape feature such as the Ganges in Benares which perennially draws pilgrims to its shores. It does have the Kamo, Katsura, and Uji rivers, but these waters have primarily attracted not pilgrims but rather poets, moon viewing parties and even double love‐suicides to its banks and bridges well into the modern period. Kyoto does not possess any single sacred site such as the sanctuary in Santiago de Compostela to which penitents progress on bended, bloodied knee. Rather, it boasts thousands of Buddhist temples, Shintō shrines, Daoist‐inspired gardens and sacred mountain climbs that are designed to elevate the spirit and cultivate the connection between nature, human nature and Buddha‐nature. It has numerous pilgrimage destinations within the contours of its urban landscape, but at the same time also participates in far‐reaching pilgrimage circuits that extend well beyond the metropolitan center. All roads may lead to Rome as the old adage goes, but in Kyoto’s case, roads run both ways, leading pilgrims as much out beyond the urban setting as drawing them in toward the city center. This essay, accordingly, will address pilgrimage itineraries in and around Kyoto from the perspective of a much larger matrix of pilgrimage activity in the Kansai region. In the process, it will revisit the false dichotomy between pilgrimage and tourism (a theme that Chaucer first brought to light over six‐hundred years ago), and hopefully shed new light on some contemporary pilgrimage practices in Japan by a whole host of players: tourists, school groups, tea aficionados, Reiki practitioners, scholars, and nature‐lovers alike. Mountain pilgrimages around the city Taking our cue from Victor Hugo’s famous bird’s‐eye view of Paris, let us broadly survey the topography and chronology of Kyoto à vol d’oiseau.1 Heian‐kyō (lit. the capital of peace and tranquility) was established in 794 by Emperor Kammu to escape the political intrigues of the Buddhist clergy in the old capital of Nara.2 After a disastrous decade at the short‐lived capital at Nagaoka (784‐794 CE), Heian‐kyō was sited in the flat plain of the Yamashiro basin according to Chinese principles of feng shui geomancy. Mountains (symbolizing the male yang aspect) surround the capital on three sides to the north, and its rivers (symbolizing the female yin aspect) flow south. Buddhist Mt. Hiei to the northeast and proto‐Shintō Mt. Kurama to the northwest protected the capital from evil influences that were believed to emanate from the north. Like most sacred mountains, these peaks were closed to women before the so‐called nyonin kekkai ban was lifted in the nineteenth century, but today both male and female pilgrims are able to make their way up the slopes by bus, funicular, or (rarely) by foot. Many Tendai Buddhist congregations and confraternities organize package tours to their head temple at Enryakuji on Mt. Hiei to pay homage to their founder Saichō (767‐822) and the great Tendai reformers of the medieval period.3 Perhaps the most impressive practice associated with the mountain is the Kaihōgyō or 1,000‐day austerity‐training performed by Tendai “marathon monks.”4 They circumambulate the mountain’s temple complex in sets of 100 or 200 days per year, incessantly chanting the mantra of Fudō myōō, the King of Immovable Wisdom. They run approximately thirty kilometers per day in straw sandals, stopping only to sleep, eat, or pause at approximately 260 worship stops. They culminate their pilgrimage in their seventh year by including the entire city of Kyoto in their circumambulation. On the other side of the city to the northwest, other less organized and less intense pilgrims hike Mt. Kurama to retrace the steps of Mikao Usui (1865‐1926). This modern‐day seeker reputedly discovered the hands‐on healing technique of Reiki in either 1914 or 1922 (the accounts differ) while in retreat on the mountain.5 Other visitors attend the annual Kurama fire festival here which commemorates the transfer and enshrinement of a kami...

Impacts of management legacies on litter decomposition in response to reduced precipitation in a tallgrass prairie

The response of ecosystem processes to current and future climatic events may be affected by historical disturbance regimes. Here, we address the interaction between reduced precipitation and the legacy effects of two contrasting long-term burn regimes in a tallgrass prairie (20 years of annual burning versus fire suppression). We examined rates of decomposition and the response of decomposition to reduced precipitation under rainout shelters in these two prairie types to assess potential interactions between legacy effects and reduced precipitation. To test the legacy effects of the different burn regimes, we placed experimental plots in each prairie type under a standardized management regime. In each plot, we ceased burning, mowed to maintain a standard canopy height, and maintained standard surface litter accumulation. We measured decay rates for surface litter, buried roots, and buried wooden dowels. While decomposition rates of substrates were reduced an average of approximately 29% under reduced precipitation, we found no significant main effects of burn history on decomposition on any of the substrates. However, in the recovery period following 2 years of an experimentally imposed drought, we did find an effect of burn history on decomposition and this effect varied for different substrates. Historical effects of management or natural disturbances on ecosystem processes may often be subtle or negated by compensatory responses, and in this study few legacy effects on decomposition rate were detected.

Pyromineralization of soil phosphorus in a South African savanna

Savannas are shaped by drought, herbivory, nutrient limitation, and fire. We assessed the interactions between two of these factors—nutrient limitation and fire—across a savanna landscape in Kruger National Park, South Africa, by quantifying increases in plant-available forms of soil phosphorus (P) following experimental or simulated burns. Plant-available pools of P were defined for granitic surface soils subjected to four experimental fire regimes (no fire, triennial fire in the wet season, triennial fire in the dry season, and annual fire in the dry season). To provide context for these results, we also fractionated surface soils from a granitic catena after simulating burning of these soils in a furnace. Burned soils showed comparable pyromineralization rates, with the experimental burn plot soils averaging 0.49 ± 0.04 g labile P m − 2 y − 1 and catena soils averaging 0.63 ± 0.12 g labile P m − 2 y − 1 . Only soils from subplots burned triennially during the wet summer season with moderate fire intensities (∼ 1.1 MW m − 1 ) showed significant increases in labile P relative to control soils. Soils from other burned subplots with greater fire intensities showed smaller gains in labile P, suggesting pyromineralization rates may peak at intermediate fire intensities. We estimated ash contributed up to 33% of pyromineralized P. For catena soils, simulated burning led to significant increases in pyromineralized P for the relatively P-rich footslope soils and smaller increases for sandy crest and midslope soils. These pyromineralization P fluxes are of the same order of magnitude as plant P demand estimated using foliar P levels, and about one-half microbial mineralization rates. In P-limited ecosystems where chemical weathering rates are slow, moderate-intensity fires could play a critical biogeochemical role in the supply of labile P.

Annual fire and mowing alter biomass, depth distribution, and C and N content of roots and soil in tallgrass prairie

Management practices, such as fire and mowing, can affect the distribution and quality of roots and soil C and N in grasslands. We examined long-term (13 years) effects of annual fire and mowing on fine (<2 mm) roots and soil C and N content in a native tallgrass prairie at Konza Prairie Biological Station in northeastern Kansas, USA. Using 90 cm deep soil cores, we determined that fire and mowing independently and interactively influenced the quantity and depth distribution of fine root biomass, root C and N concentration, and soil C and N content. Annual burning increased total fine root biomass by 48% and total C storage in roots by 47% compared to unburned unmowed plots, and resulted in a deeper distribution of roots. There was a significant interaction of fire and mowing, whereby mowing reduced root biomass and root C storage by ~30% in annually burned plots, but did not affect total root biomass in unburned plots. Mowing also resulted in shallower distribution of roots regardless of fire treatment. Root N concentration was reduced by 15–25% in plots that were burned, mowed, or both. Mowing effects on soil C and N were restricted to surface soils (0–10 cm), where mowing reduced soil C concentrations by ~20% and N concentrations by 17% regardless of burning treatment. In contrast, burning alone did not significantly influence soil C and N concentrations. In general, root biomass, root C and N mass, and soil C and N concentrations declined with depth, and most responses to burning and mowing exhibited significant interactions with depth. Different long-term fire and mowing regimes can significantly alter belowground root biomass and C and N dynamics in grasslands, and in particular at depths in the profile that are not typically sampled.

Loss of biodiversity and ecosystem functioning in Indo-Malayan peat swamp forests

The tropical peat swamp forests of Indonesia and Malaysia are unusual ecosystems that are rich in endemic species of flora, fauna and microbes despite their extreme acidic, anaerobic, nutrient poor conditions. They are an important refuge for many endangered species including orang utans. Ecosystem functioning is unusual: microbial decomposition is inhibited because the leaves are sclerophyllous and toxic to deter herbivory in the nutrient poor environment, yet bacteria are abundant and active in the surface layers of the peat, where they respire DOC leached from newly fallen leaves. The bacteria are subsequently consumed by aquatic invertebrates that are eaten by fish, and bacterially respired CO2 is assimilated by algae, so bacteria are thus vital to carbon and nutrient cycling. Peat swamp forests are highly sensitive to the impacts of logging, drainage and fire, due to the interdependence of the vegetation with the peat substrate, which relies on the maintenance of adequate water, canopy cover and leaf litter inputs. Even minor disturbances can increase the likelihood of fire, which is the major cause of CO2 emissions from regional peat swamp forests and which impact ecosystems worldwide by contributing to climate change. Indo-Malayan peat swamps affect the hydrology of surrounding ecosystems due to their large water storage capacity which slows the passage of floodwaters in wet seasons and maintains stream base flows during dry seasons. These forests are of global importance yet they are inadequately protected and vanishing rapidly, particularly due to agricultural conversion to oil palm, logging, drainage and annual fires.

Defining a fire year for reporting and analysis of global interannual fire variability

The interannual variability of fire activity has been studied without an explicit investigation of a suitable starting month for yearly calculations. Sensitivity analysis of 37 months of global MODIS active fire detections indicates that a 1‐month change in the start of the fire year definition can lead, in the worst case, to a difference of over 6% and over 45% in global and subcontinental scale annual fire totals, respectively. Optimal starting months for analyses of global and subcontinental fire interannual variability are described. The research indicates that a fire year starting in March provides an optimal definition for annual global fire activity.

Diversity and composition of spider assemblages in five vegetation types of the Terai Conservation Area, India

Abstract This study deals with the comparison of spider diversity and composition in a complex landscape of the Terai Conservation Area (TCA) characterized by alluvial floodplains of tall grassland interspersed with woodland, swamps, and riparian patches. High water table, annual flooding, and annual grassland fire maintain its dynamic complexity. A mosaic of five vegetation types was sampled for spiders from March 2005 to August 2006 by using pitfall traps and other semi-quantitative collection methods along transects. A total of 3666 adult spiders representing 22 families, 60 genera, and 160 species were found. Using the abundance-based estimator, Chao1, the predicted richness for the total area sampled is 173 ± 8.32 (SD) species. This indicates that the inventory was almost complete at the regional scale (92%). With similar proportions of captured species, rarefied richness value showed that species richness was highest in riparian swamp forest. Comparison of different sites revealed that species compo...

Temporal coherence of aboveground net primary productivity in mesic grasslands

Synchrony in ecological variables over wide geographic areas suggests that large‐scale environmental factors drive the structure and function of ecosystems and override more local‐scale environmental variation. Described also as coherence, this phenomenon has been documented broadly in the ecological literature and has recently received increasing attention as scientists attempt to quantify the impacts of global changes on organisms and their habitats. Using a mesic grassland site in North America, we assessed coherence in ecosystem function by quantifying similarity in aboveground net primary production (ANPP) dynamics in 48 permanent sampling locations (PSLs) over a 16‐yr period. Our primary objective was to characterize coherence across a broad geographic region (with similar ecosystem structure and function), and we hypothesized that precipitation and a similar fire frequency would strengthen coherence between PSLs. All 48 PSLs at our site (Konza Prairie Biological Station, Manhattan, KS, USA; KPBS) were exposed to a similar regional driver of ANPP (precipitation); however, local drivers (including differences in fire frequency and soil depth at different topographic positions) varied strongly among individual PSLs. For the purpose of this assessment, the watershed‐level experimental design of KPBS was considered a model, which represented different fire management strategies across the Great Plains Region. Our analyses revealed a site‐level (KPBS) coherence in ANPP dynamics of 0.53 for the period of 1984–1999. Annual fire enhanced coherence among PSLs to 0.76, whereas less frequent fire (fire exclusion or a 4‐yr fire return interval) failed to further increase coherence beyond that of the KPBS site level. Soil depth also strongly influenced coherence among PSLs with shallow soils at upland sites showing strong coherence across fire regimes and annually burned uplands closely linked to annual precipitation dynamics. The lack of coherence in ecosystem function in PSLs with deep soils and low fire frequencies suggests that conservation and management efforts will need to be more location specific in such areas where biotic interactions may be more important than regional abiotic drivers.

Influence of grazing and fire frequency on small‐scale plant community structure and resource variability in native tallgrass prairie

In grasslands worldwide, grazing by ungulates and periodic fires are important forces affecting resource availability and plant community structure. It is not clear, however, whether changes in community structure are the direct effects of the disturbance (i.e. fire and grazing) or are mediated indirectly through changes in resource abundance and availability. In North American tallgrass prairies, fire and grazing often have disparate effects on plant resources and plant diversity, yet, little is known about the individual and interactive effects of fire and grazing on resource variability and how that variability relates to heterogeneity in plant community structure, particularly at small scales. We conducted a field study to determine the interactive effects of different long‐term fire regimes (annual vs four‐year fire frequency) and grazing by native ungulates (Bos bison) on small‐scale plant community structure and resource variability (N and light) in native tallgrass prairie. Grazing enhanced light and nitrogen availability, but did not affect small‐scale resource variability. In addition, grazing reduced the dominance of C4grasses which enhanced species richness, diversity and community heterogeneity. In contrast, annual fire increased community dominance and reduced species richness and diversity, particularly in the absence of grazing, but had no effect on community heterogeneity, resource availability and resource variability. Variability in the abundance of resources showed no relationship with community heterogeneity at the scale measured in this study, however we found a relationship between community dominance and heterogeneity. Therefore, we conclude that grazing generated small‐scale community heterogeneity in this mesic grassland by directly affecting plant community dominance, rather than indirectly through changes in resource variability.

Diurnal, seasonal, and interannual variation in carbon dioxide and energy exchange in shrub savanna in Burkina Faso (West Africa)

Savannas cover large areas of the Earth's surface and play an important role in global carbon cycling. West Africa is dominated by a variety of savanna ecosystems; however, they have been poorly studied up to now. In the present study, energy and carbon dioxide exchange was measured over a 2‐year period using the eddy covariance technique at a southern Sudanian savanna site in Burkina Faso that was not subject to human disturbances except for annual burning. Turbulent energy exchange was dominated by sensible heat flux in the dry season (November–May) and by latent heat flux in the wet season (June–September), with peak values higher than 300 W m−2 and lower than 100 W m−2 for the dominating and the minor component, respectively. The ecosystem was a marginal CO2 source in the dry season, whereas significant CO2 uptake was found in the rainy season. CO2 fluxes showed a clear diurnal pattern, with mean release rates of 0.2 mg CO2 m−2 s−1 during nighttime and mean maximum uptake rates of 1.0 mg CO2 m−2 s−1 in July and August around midday. Diurnal courses of CO2 flux were in phase with photosynthetically active radiation (PAR). Highest CO2 uptake rates of more than 0.8 mg CO2 m−2 s−1 occurred at PAR levels in excess of 1000 μmol m−2 s−1. Total net ecosystem CO2 uptake was 179 ± 98 g C m−2 in the first year and 429 ± 100 g C m−2 in the second year of investigation, including an estimate of annual fire C loss of 149 g C m−2. The remarkable difference in net CO2 uptake between the two years could be explained by higher rainfall in 2006, revealing the sensitivity of the ecosystem to water availability and rainfall distribution that could lead to a significant change in C sequestration patterns under a changing climate.

Cronología de la regeneración del bosque tropical seco en Santa Rosa, Guanacaste, Costa Rica. I. Características edáficas

We characterized soil chemical and physical properties in eight tropical dry forest (TDF) successional sites along a time sequence (10, 15, 20, 40, 60 and >100 years) in Santa Rosa, Costa Rica. Seventeen soils were identified, described, and classified in six orders. Most soils were classified as Entisols and Vertisols, but Mollisols, Alfisols, Inceptisols and Ultisols were also present. All soils showed good fertility that did not constrain species richness. High edaphic variation seemed the result of complex interactions among the pyroclastic origin of Santa Rosa ignimbritic plateau (SRIP), the lithological composition and acidity of ignimbritic rocks, the strong seasonality in rainfall, intense hydric and aeolic erosion, topographic variations within the SRIP, and past human intervention. Correlations performed on soils classified as Entisols (<60 cm deep) showed a depletion of soil cations (Ca, Mg, K, Na and CEC) during the first 20 years of forest regeneration, that later recovered in mature TDF sites. Organic matter content did not change significantly along the TDF chrono-sequence. Substantial increments in macro-pores and soil hydraulic conductivity were observed, probably resulting from higher root biomass and turnover in older successional sites. Soil available water and meso-pore abundance were negatively correlated with TDF successional age. Our results indicate that edaphic changes observed along TDF regeneration might have been due to annual fires in pastures and young TDF sites, addition of decaying litter and fine roots as regeneration progressed, milder microclimate conditions during late regeneration in mature TDF sites, increased nutrient cycling, and the predominance of sandy loam textures among the soils examined. These changes in the soil environment with succession may have physiological and phenological consequences on the species appearing at different stages of TDF regeneration.

Effects of controlled livestock grazing and annual prescribed fire on epigeal termite mounds in a savannah woodland in Burkina Faso

The diversity and abundance of epigeal termite mounds were investigated in response to controlled livestock grazing and annual prescribed fire in a Sudanian savannah-woodland in Tiogo State Forest. Sampling of termite mounds was carried out in 4×4 subplots of 0.25 ha in a split-plot experimental design during the rainy season in 2002. There were two main plots of which one was fenced to exclude livestock grazing and the second exposed to grazing. Each of the main plots included 4 subplots with annual prescribed fire since 1992 and 4 subplots without fire. Data were collected on the number and characteristics of termite mounds. A mean density of 698 mounds ha−1 was recorded. Mounds built by Trinervitermes spp. were the most abundant followed by Cubitermes spp., Macrotermes subhyalinus and M. bellicosus. The large mound-builders Macrotermes spp. dominated the community interms of basal area (96% of the total) and above-ground volume (99%). The diversity of mound types was notaffected by livestock grazing and annual early prescribed fire (P>0.05). There was no statistical effect of livestock grazing on mound density, whereas a strong depressive effect of annual fire was observed for Trinervitermes spp. mound density (P=0.012). In this ecosystem, annual prescribed fire appeared to be the major determinant for termite mound abundance.

Mountain pine beetle and forest carbon feedback to climate change

The mountain pine beetle (Dendroctonus ponderosae Hopkins, Coleoptera: Curculionidae, Scolytinae) is a native insect of the pine forests of western North America, and its populations periodically erupt into large-scale outbreaks. During outbreaks, the resulting widespread tree mortality reduces forest carbon uptake and increases future emissions from the decay of killed trees. The impacts of insects on forest carbon dynamics, however, are generally ignored in large-scale modelling analyses. The current outbreak in British Columbia, Canada, is an order of magnitude larger in area and severity than all previous recorded outbreaks. Here we estimate that the cumulative impact of the beetle outbreak in the affected region during 2000-2020 will be 270 megatonnes (Mt) carbon (or 36 g carbon m(-2) yr(-1) on average over 374,000 km2 of forest). This impact converted the forest from a small net carbon sink to a large net carbon source both during and immediately after the outbreak. In the worst year, the impacts resulting from the beetle outbreak in British Columbia were equivalent to approximately 75% of the average annual direct forest fire emissions from all of Canada during 1959-1999. The resulting reduction in net primary production was of similar magnitude to increases observed during the 1980s and 1990s as a result of global change. Climate change has contributed to the unprecedented extent and severity of this outbreak. Insect outbreaks such as this represent an important mechanism by which climate change may undermine the ability of northern forests to take up and store atmospheric carbon, and such impacts should be accounted for in large-scale modelling analyses.

POST-FIRE RESPROUTING AND MORTALITY IN CERRADO WOODY PLANT SPECIES OVER A THREE-YEAR PERIOD

The objective of this work was to evaluate resprouting features and mortality in Cerrado woody plants after annual controlled fires (in 1998, 1999 and 2000) in a campo sujo area (an open savanna physiognomy) of 2500 m2 at the Reserva Ecológica do IBGE, Brasília-DF, Brazil. The area was protected against fire for 23 years prior to the fires. All plants of the woody layer with diameter larger than 2.0 cm at 30 cm from soil level were tagged and identified. At about one year after each controlled fire the damage type and the number of basal and underground sprouts for each individual were recorded. Stem diameter and height were measured for each marked sprout. A total of 1307 sprouts were tagged and measured. The main impact of fire on resprouting was a decrease in the number of new sprouts after each controlled fire: 684 sprouts after the first burning to 248 after the third burning. Mortality of sprouts was 34.8% and 37.8% after the 1999 and 2000 fires. A decrease in the number of sprouts with a diameter smaller than 1.0 cm after the successive fires was also observed, indicating that fires at one-year intervals resulted in alterations in the structure of the woody vegetation in the area. The species mortality rates were higher after the first controlled fire. However, it seems that there is no relation between sprouting capacity and species survival. The species that show mortality rates lower than 10% also showed a variety of sprouting capacity.

The effects of fire and elephants on species composition and structure of the Niassa Reserve, northern Mozambique

In the Miombo Woodlands Region of south-central Africa, the interaction between fires and elephants is one of the main drivers of vegetation, along with climate, soils and topography. Fire–elephant interaction is particularly important in conservation areas where elephant populations are confined and anthropogenic fires occur every year. The effects of this interaction on vegetation composition and structure have not been extensively studied in the region. The Miombo woodlands of the 42,000 km 2 Niassa Reserve in northern Mozambique are subject to annual anthropogenic fires and an increasing elephant population, but it is not understood whether, the elephant–fire interaction is manifest. We investigate the distribution of plant species composition and ecosystem structure, and their relationships with environmental and disturbance factors within the Niassa Reserve. Fifty sampling plots were established and measurements for vegetation composition and structure, fire and elephant damage to plants, environmental (edaphic and topographic) and disturbance data were collected. We used multivariate statistics analysis including detrended correspondence analysis (DCA), canonical correspondence analysis (CCA) and Principal Component Analysis (PCA) to explore the data. Three groups of species were distinguished according to their abundances: the Miombo group, the eastern Combretacea group and the western Uapaca group. The miombo group was uniformly distributed in the area and independent of environmental and disturbances factors. The Uapaca group followed an elevation gradient from east to west, while the combretacea group was explained by edaphic and disturbance factors. The damage to the woody component was predominant in the east. The damage by fire and elephant to miombo species was concentrated on adults, while these species had low ingrowth.

Contemporary climate variability and forest fires in Deliblatska pescara

Considering the actual scenario of contemporary global climate changes and their possible influence on forest fires, the connections between temperature changes and precipitations on fires have been examined in Deliblatska pescara. The basic characteristics of fires have been analyzed in the area which is considered the most endangered in Serbia. The decreasing trend of annual number of fires was ascertained for period the 1948-2002. However, the trend of annual temperature and precipitation changes is not in accordance with the trend of annual number of fires. Some seasonal aspects related with the change of climate elements cannot also explain the decreasing number of fires. A rising trend of annual fire spread surface have been ascertained, which is in accordance with air temperature rise at the end of the 20th century. However, five extreme values were far above the upper standard deviation, which was explained by non climate factors (increase of surface under pine trees, mistakes during fire extinguishing and similar).

Impact of Protected Areas and Land Use on Regeneration of Acacia Woodland’s in Eastern Burkina Faso

Regeneration success, persistence strategies (seedlings vs. coppicing), and population trend of Acacia spp. were tested under two land-use regimes in eastern Burkina Faso: (i) protected areas shielded to livestock grazing pressure, to logging, and using early annual fire as a management system; (ii) areas with high human impact (heavily and extensive livestock grazing, harvesting for wood and for medicinal plants). Generally, a good regeneration rate of Acacia species was observed in protected areas and a poor regeneration rate in areas with high human impact. Nevertheless, some species affiliated to the subgenus Aculeiferum as A. dudgeoni and A. polyacantha showed a good regeneration under both land use regimes. Juvenile plants less than 25 cm height of A. dudgeoni and A. gourmaensis increased by 116 to 50 % in areas with human impact as compared to their populations in protected areas. With SCD slopes varying from –0.40 to -0.70, the protected Acacia woodland displayed a stable population structure due to abundance of recruitment, and coppicing persistence (more common in the subgenus Aculeiferum) favoured by early annual fire. Consequently, the protected areas are favourable for Acacia woodland regeneration. Conversely, SCD slopes are positive or close to zero in areas of anthropogenic regime and showed a declining population, especially more marked with the subgenus Acacia due to permanent seed and seedling removal by livestock grazing. Nevertheless, the number of seedlings of some species was higher in areas under human pressure than in protected areas, especially for the subgenus Aculeiferum, improving the genetic variability and thus the long-term maintenance of the population

Savanna fires and their impact on net ecosystem productivity in North Australia

AbstractSavannas comprise a large area of the global land surface and are subject to frequent disturbance through fire. The role of fire as one of the primary natural carbon cycling mechanisms is a key issue in considering global change feedbacks. The savannas of Northern Australia burn regularly and we aimed to determine their annual net ecosystem productivity (NEP) and the impact of fire on productivity. We established a long‐term eddy covariance flux tower at Howard Springs, Australia and present here 5 years of data from 2001 to 2005. Fire has direct impacts through emissions but also has indirect effects through the loss of productivity due to reduced functional leaf area index and the carbon costs of rebuilding the canopy. The impact of fire on the canopy latent energy exchange was evident for 40 days while the canopy was rebuilt; however, the carbon balance took approximately 70 days to recover. The annual fire free NEP at Howard Springs was estimated at −4.3 t C ha−1 yr−1 with a range of −3.5 to −5.1 t C ha−1 yr−1 across years. We calculated the average annual indirect fire effect as +0.7 t C ha−1 yr−1 using a neural network model approach and estimated average emissions of fine and coarse fuels as +1.6 t C ha−1 yr‐1. This allowed us to calculate a net biome production of −2.0 t C ha−1 yr‐1. We then partitioned this remaining sink and suggest that most of this can be accounted for by woody increment (1.2 t C ha−1 yr‐1) and shrub encroachment (0.5 t C ha−1 yr‐1). Given the consistent sink at this site, even under an almost annual fire regime, there may be management options to increase carbon sequestration by reducing fire frequency.