Unveiling the diversity of regional burning patterns at the Brazilian savanna

2021 ◽  
Author(s):  
Patrícia S. Silva ◽  
Joana Nogueira ◽  
Julia A. Rodrigues ◽  
Filippe L.M. Santos ◽  
Gabriel A. Daldegan ◽  
...  
Keyword(s):  
Dry Season ◽  
Future Climate Change ◽  
Fire Intensity ◽  
Anthropogenic Pressure ◽  
Fire Size ◽  
Regional Patterns ◽  
Fire Scar ◽  
Spatial Coverage ◽  
Fire Patterns ◽  
Temporal And Spatial

<p>Fire is an integral and predictable component of ecological functioning and dynamics in fire-prone biomes. However, the relationships and potential feedback between fire and its drivers are complex, as they depend on the temporal and spatial scales adopted when analyzing the fire regime. A remote sensing approach allows the characterization of fire regimes with larger spatial coverage and temporal homogeneity, especially where fire records are rare, as in the Brazilian savannas (Cerrado). The Cerrado is a mosaic of soil types and topographic settings, with varying regional climate patterns, resulting in a variety of fire resistant/sensitivity vegetation types, and recent disturbances, mostly due to increasing economic and agricultural development, along with changes in climate, are disrupting its natural fire patterns. Most studies characterizing fire activity in Cerrado are either performed at the biome-level or focus on very specific locations with results then extrapolated over the whole biome, which may mask important regional patterns. Here, we aim to characterize the regional fire patterns into the Cerrado’s 19 ecoregions, previously defined based on biophysical parameters which do not include fire. </p><p>We use burned area (BA), fire radiative power and individual fire scar data based on MODIS products (respectively, MCD64A1, MCD14ML and Global Fire Atlas) to evaluate inter and intra annual cycles, spatial anomalies and trends of BA, fire intensity and fire size (small fires: <1000ha, medium: 1000-5000ha and large fires: >5000ha) in each ecoregion from 2001 to 2019. </p><p>Our results show a marked north-south BA gradient, with higher annual BA contributions from the northern ecoregions. These ecoregions are mainly located in the latest agricultural frontier, MATOPIBA, where there are more vegetation remnants that are under high anthropogenic pressure due to recent economic development. Conversely, ecoregions showing low BA are highly fragmented and  have been historically deforested for longer periods. Most fires are of low intensity and higher intensity fires occur towards the end of the dry season period (June to October). Moreover, there are considerable differences in extremely intense events, especially in the eastern ecoregions. We also found that temporal and spatial patterns are highly variable, depending on fire scars size. Infrequent medium and large scars account for most of BA compared to common very small and small scars. Overall, fire seasonality varies substantially depending on fire size class: larger scars occur over a 2-month period within the dry season, whereas the remaining classes are increasingly scattered along the year. BA is increasing and fire intensity decreasing over MATOPIBA’s ecoregions, while in southern ecoregions, is the opposite, with a decreasing over BA and an increase of fire intensity. Smaller scars are overall decreasing, whereas medium and larger scars show positive trends over central and northern ecoregions. </p><p>This study highlights the importance of understanding the diversity of fire dynamics in Cerrado to better inform and prepare refined-scale fire management strategies in light of current regional ecosystem disturbances and future climate change. </p><p>The study was funded by CNPQ (grant 441971/2018-0) and P. S. Silva is supported by FCT (grant SFRH/BD/146646/2019).</p>

Southern African fire regimes as revealed by remote sensing

2010 ◽  
Vol 19 (7) ◽  
pp. 861 ◽  
Author(s):  
S. Archibald ◽  
R. J. Scholes ◽  
D. P. Roy ◽  
G. Roberts ◽  
L. Boschetti
Keyword(s):  
Southern Africa ◽  
Human Activities ◽  
Spatial Information ◽  
Fire Regime ◽  
Fire Regimes ◽  
Fire Intensity ◽  
Fire Size ◽  
Regional Patterns ◽  
Radiative Power ◽  
Fire Radiative Power

Here we integrate spatial information on annual burnt area, fire frequency, fire seasonality, fire radiative power and fire size distributions to produce an integrated picture of fire regimes in southern Africa. The regional patterns are related to gradients of environmental and human controls of fire, and compared with findings from other grass-fuelled fire systems on the globe. The fire regime differs across a gradient of human land use intensity, and can be explained by the differential effect of humans on ignition frequencies and fire spread. Contrary to findings in the savannas of Australia, there is no obvious increase in fire size or fire intensity from the early to the late fire season in southern Africa, presumably because patterns of fire ignition are very different. Similarly, the importance of very large fires in driving the total annual area burnt is not obvious in southern Africa. These results point to the substantial effect that human activities can have on fire in a system with high rural population densities and active fire management. Not all aspects of a fire regime are equally impacted by people: fire-return time and fire radiative power show less response to human activities than fire size and annual burned area.

Impactul activităților umane asupra stării peisajelor geografice din bazinul hidografic Cogâlnic în anii 2004-2014

2020 ◽  
Author(s):  
Nicolae Boboc ◽  
◽  
Valentina Munteanu ◽  
Keyword(s):  
Statistical Data ◽  
Environmental Changes ◽  
Spatial Dynamics ◽  
Anthropogenic Pressure ◽  
Human Pressure ◽  
Republic Of Moldova ◽  
Temporal And Spatial ◽  
The Republic ◽  
High Degree

The high degree of land use in the Republic of Moldova as a whole, and the Cogâlnic river basin in particular, imposes the need to assess the quality of the environment and the characteristics of the anthropogenic pressure on the landscapes in temporal and spatial dynamics and to identifying an adequate of measure system for the purpose to maintain/restore the optimal structure and functioning of landscape systems. Based from the Land Cadastre on data, statistical data of population censuses, bibliographic and cartographic sources, a system, was appraised a system of indicators(of naturalness, of artificialization of landscapes, environmental changes) and quantified human pressure on the environment through agriculture and anthropogenic pressure on forest landscapes from the Cogâlnic catchment area. The values of the indices and the human pressure on the landscapes were processed using GIS techniques and elaborated cartographic models.

Free-living freshwater nematodes from Brazil: checklist of genera and regional patterns of diversity

Nematology ◽  
2021 ◽  
pp. 1-14
Author(s):  
Taciana Kramer de Oliveira Pinto ◽  
Sérgio A. Netto ◽  
André Morgado Esteves ◽  
Francisco José Victor de Castro ◽  
Patricia Fernandes Neres ◽  
...  
Keyword(s):  
Benthic Communities ◽  
Extreme Environments ◽  
Freshwater Ecosystems ◽  
Freshwater Biodiversity ◽  
High Turnover ◽  
Free Living ◽  
Regional Patterns ◽  
Freshwater Nematodes ◽  
Spatial Coverage ◽  
Freshwater Habitats

Summary Brazil has one of the largest varieties of aquatic ecosystems and rich freshwater biodiversity, but these components have constantly been damaged by the expansion of unsustainable activities. Free-living nematodes are an abundant and ubiquitous component of continental benthic communities, occurring in all freshwater habitats, including extreme environments. Despite this, hardly any studies have examined the generic composition of nematodes in different latitudes and the geographic overlap of assemblages. We provide data on nematode genera from six regions in Brazil, over a north-south gradient spanning about 4000 km, encompassing rivers, coastal lakes, and reservoirs with different levels of human impact. Interpolation/extrapolation curves were generated and the zeta diversity was used to assess the overlap of nematode assemblages. Freshwater nematode assemblages comprised 54 families and 132 genera. Mononchidae, Monhysteridae, Chromadoridae, Tobrilidae and Dorylaimidae were the most diverse families. Differences in diversity and high turnover of genera were found among regions, probably related to stochastic processes. Mononchus was the only widely distributed genus. Our results revealed a high biodiversity of free-living freshwater nematodes among the regions. The limited spatial coverage of the data reveals an enormous knowledge gap in a country with 12% of the world’s freshwater resources. The lack of spatial patterns, e.g., latitudinal variation, suggests that freshwater nematode assemblages are primarily structured by the intrinsic properties of habitats. This reinforces the uniqueness of freshwater ecosystems and suggests that the nematode assemblages may be sensitive to environmental disturbances, since the limited distributions of taxa may lead to lower resilience.

scholarly journals Methane gas emissions from savanna fires: What analysis of local burning regimes in a working West African landscape tell us

2021 ◽  
Author(s):  
Paul Laris ◽  
Moussa Koné ◽  
Fadiala Dembélé ◽  
Lilian Yang ◽  
Rebecca Jacobs
Keyword(s):  
Ambient Air ◽  
Methane Emissions ◽  
Dry Season ◽  
West African ◽  
Biomass Composition ◽  
Fire Intensity ◽  
Methane Cycle ◽  
Gas Emissions ◽  
Savanna Fires ◽  
Fire Type

Abstract. Savanna fires contribute significantly to greenhouse gas emissions. While it is recognized that these fires play an important role in the global methane cycle, there are too few accurate estimates of emissions from West Africa, the continent's most active fire region. Most estimates of methane emissions contain high levels of uncertainty because they are based on generalizations of diverse landscapes that are burned by complex fire regimes. To improve estimates we used an approach grounded in the burning practices of people who set fires to working landscapes. We conducted 97 experimental fires collecting data for savanna type, grass type, biomass composition and amount consumed, scorch height, speed of fire front, fire type and ambient air conditions for two sites in Mali. We collected smoke samples for 36 fires using a canister method. We report values for fire intensity, combustion completeness, patchiness, modified combustion efficiency (MCE) and emission factor (EF). Our study finds that methane EFs ranged from 3.71 g/kg in the early dry season (EDS) to 2.86 in the mid-dry season (MDS). We found head fires had nearly double the CH4 EF of backfires (4.89 g/kg to 2.92). Fires during the MDS have the lowest intensity values and the lowest methane emissions 0.981 g/m2 compared with 1.030 g/m2 for EDS and 1.102 g/m2 for the late dry season (LDS). We conclude that policies aimed at shifting the burning regime earlier to reduce methane emissions will not have the desired effects, especially if fire type is not considered. We recommend using the adjusted mean value of 0.862 g/m2—based on the carbon content for West African grasses—for calculating emissions for West African savannas.

scholarly journals Monitoring Beach Topography and Nearshore Bathymetry Using Spaceborne Remote Sensing: A Review

2019 ◽  
Vol 11 (19) ◽  
pp. 2212 ◽  
Author(s):  
Edward Salameh ◽  
Frédéric Frappart ◽  
Rafael Almar ◽  
Paulo Baptista ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Frequency ◽  
Anthropogenic Pressure ◽  
Fundamental Parameters ◽  
Temporal Sampling ◽  
Current State ◽  
Needed Information ◽  
Spatial Coverage ◽  
Remote Sensing Techniques ◽  
Using Data

With high anthropogenic pressure and the effects of climate change (e.g., sea level rise) on coastal regions, there is a greater need for accurate and up-to-date information about the topography of these systems. Reliable topography and bathymetry information are fundamental parameters for modelling the morpho-hydrodynamics of coastal areas, for flood forecasting, and for coastal management. Traditional methods such as ground, ship-borne, and airborne surveys suffer from limited spatial coverage and temporal sampling due to logistical constraints and high costs which limit their ability to provide the needed information. The recent advancements of spaceborne remote sensing techniques, along with their ability to acquire data over large spatial areas and to provide high frequency temporal monitoring, has made them very attractive for topography and bathymetry mapping. In this review, we present an overview of the current state of spaceborne-based remote sensing techniques used to estimate the topography and bathymetry of beaches, intertidal, and nearshore areas. We also provide some insights about the potential of these techniques when using data provided by new and future satellite missions.

scholarly journals Climatology of the mesopause density using a global distribution of meteor radars

2018 ◽  
Author(s):  
Wen Yi ◽  
Xianghui Xue ◽  
Iain M. Reid ◽  
Damian J. Murphy ◽  
Chris M. Hall ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
High Latitudes ◽  
Meteor Radar ◽  
Low Latitude ◽  
Wave Forcing ◽  
Spring Equinox ◽  
Spatial Coverage ◽  
Low Latitudes ◽  
Variation Characteristics ◽  
Temporal And Spatial

Abstract. The existing distribution of meteor radars located from high- to low-latitude regions provides a favourable temporal and spatial coverage for investigating the climatology of the global mesopause density. In this study, we report the climatology of the mesopause density estimated using multiyear observations from nine meteor radars, namely, the Davis Station (68.6° S, 77.9° E), Svalbard (78.3° N, 16° E) and Tromsø (69.6° N, 19.2° E) meteor radars located at high latitudes, the Mohe (53.5° N, 122.3° E), Beijing (40.3° N, 116.2° E), Mengcheng (33.4° N, 116.6° E) and Wuhan (30.5° N, 114.6° E) meteor radars located in the mid-latitudes, and the Kunming (25.6° N, 103.8° E) and Darwin (12.3° S, 130.8° E) meteor radars located at low latitudes. The daily mean density was estimated using ambipolar diffusion coefficients derived from the meteor radars and temperatures from the Microwave Limb Sounder (MLS) on board the Aura satellite. The seasonal variations in the Davis Station meteor radar densities in the southern polar mesopause are mainly dominated by an annual oscillation (AO). The mesopause densities observed by the Svalbard and Tromsø meteor radars at high latitudes and the Mohe and Beijing meteor radars at high mid-latitudes in the Northern Hemisphere show mainly an AO and a relatively weak semiannual oscillation (SAO). The mesopause densities observed by the Mengcheng and Wuhan meteor radars at lower mid-latitudes and the Kunming and Darwin meteor radars at low latitudes show mainly an AO. The SAO is evident in the Northern Hemisphere, especially at high latitudes, and its largest amplitude, which is detected at the Tromsø meteor radar, is comparable to the AO amplitudes. These observations indicate that the mesopause densities over the southern and northern high latitudes exhibit a clear seasonal asymmetry. The maxima of the yearly variations in the mesopause densities display a clear temporal variation across the spring equinox as the latitude decreases; these latitudinal variation characteristics may be related to latitudinal changes influenced by gravity wave forcing. In addition to an AO, the mesopause densities over low latitudes also clearly show a variation with a periodicity of 30–60 days related to the Madden-Julian oscillation in the subtropical troposphere.

Temporal and spatial variation of surface soil water content on karst slopes in dry season

2015 ◽  
Vol 35 (19) ◽  
Author(s):  
张川 Zhang Chuan ◽  
张伟 Zhang Wei ◽  
陈洪松 Chen Hongsong ◽  
聂云鹏 Nie Yunpeng ◽  
叶莹莹 Ye yingying ◽  
...  
Keyword(s):  
Spatial Variation ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Surface Soil ◽  
Dry Season ◽  
Temporal And Spatial Variation ◽  
Temporal And Spatial

Long-term assessment of surface dynamics in the Tyrrhenian Sea

2020 ◽  
Author(s):  
Enrico Zambianchi ◽  
Naomi Krauzig ◽  
Pierpaolo Falco
Keyword(s):  
Sea Level ◽  
Spatial Scales ◽  
Sea Surface ◽  
Extreme Weather Events ◽  
Tyrrhenian Sea ◽  
Surface Dynamics ◽  
Surface Circulation ◽  
Spatial Coverage ◽  
Temporal And Spatial

<p>The variability of surface dynamics has been investigated extensively in the Mediterranean Sea for different temporal and spatial coverage, whereas a specific evaluation for the area of the Tyrrhenian Sea does not exist. Thus, this study is focused on the Tyrrhenian basin, a subbasin of the western Mediterranean, which is considered sensitive to climatic variations due to its small size and isolated nature. The main scope is to provide a comprehensive and up-to-date assessment of the sea surface warming, the sea level changes and the general surface circulation in the Tyrrhenian Sea, as well as to improve the understanding of the relation to large-scale teleconnection patterns and to regional air-sea interaction. The long-term spatio-temporal variability and trends were investigated using satellite-derived, in-situ and reanalysis-based datasets up to the end of 2018. Further, the possible linkage with the occurrence of extreme weather events was assessed using observations from the European Severe Weather Database. The different datasets cover multiple temporal and spatial scales and enable the investigation of the potential physical processes related to the non-homogeneous, time-depended spatial variability. The results indicate a significant increase in sea level and sea surface temperature which appears to be linked with the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO), respectively. Moreover, analysis of the basin’s surface circulation together with local air-sea exchanges of heat, freshwater and momentum indicated a significant influence of the wind-driven Ekman pumping variability.</p>

scholarly journals Spatial and temporal covariability in early ocean survival of Chinook salmon (Oncorhynchus tshawytscha) along the west coast of North America

2014 ◽  
Vol 71 (7) ◽  
pp. 1671-1682 ◽  
Author(s):  
D. Patrick Kilduff ◽  
Louis W. Botsford ◽  
Steven L. H. Teo
Keyword(s):  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Survival Rates ◽  
Central Valley ◽  
Vancouver Island ◽  
Regional Patterns ◽  
Migration Patterns ◽  
The Pacific ◽  
Spatial Coverage ◽  
Correlation Scale

Abstract Knowledge of the spatial and temporal extent of covariation in survival during the critical ocean entry stage will improve our understanding of how changing ocean conditions influence salmon productivity and management. We used data from the Pacific coastwide coded-wire tagging program to investigate local and regional patterns of ocean survival of Chinook salmon (Oncorhynchus tshawytscha) from the Central Valley of California to southeastern Alaska from 1980–2006. Ocean survival of fish migrating as subyearlings covaried strongly from Vancouver Island to California. Short-term correlations between adjacent regions indicated this covariability increased, beginning in the early 1990s. Chinook salmon survivals exhibited a larger spatial scale of variability (50% correlation scale: 706 km) than those reported for other northeast Pacific Ocean salmon. This scale is similar to that of environmental variables related to ecosystem productivity, such as summer upwelling (50% correlation scale: 746 km) and sea surface temperature (50% correlation scale: 500–600 km). Chinook salmon ocean survival rates from southeastern Alaska and south of Vancouver Island were not inversely correlated, in contrast to earlier observations based on catch data, but note that our data differ in temporal and spatial coverage from those studies. The increased covariability in Chinook salmon ocean survival suggests that the marine phase contributes little to the reduction in risk across populations attributable to the portfolio effect. In addition, survival of fish migrating as yearlings from the Columbia River covaried with Chinook salmon survival from the northernmost regions, consistent with our understanding of their migration patterns.

scholarly journals The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

2016 ◽  
Author(s):  
N.J. Cowan ◽  
P.E. Levy ◽  
D. Famulari ◽  
M. Anderson ◽  
J. Drewer ◽  
...  
Keyword(s):  
Temperate Climate ◽  
N2o Emissions ◽  
Future Studies ◽  
Dynamic Chamber ◽  
Spatial Coverage ◽  
Before And After ◽  
Temporal And Spatial ◽  
N2o Fluxes ◽  
Intensively Managed ◽  
Measurement Period

Abstract. Intensively managed grass production in high rainfall temperate climate zones is a globally important source of N2O. Many of these grasslands are occasionally tilled and can lead to increased N2O emissions. This was investigated by comparing N2O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high resolution dynamic chamber and static chamber methods greatly improved the temporal and spatial coverage of N2O fluxes before and after the tillage event and is recommended to be followed in future studies. Total cumulative fluxes calculated for the tilled and un-tilled fields over the 175 day measurement period were 2.45 ± 0.27 and 2.08 ± 0.23 kg N2O-N ha−1, respectively. N2O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately two months after the tillage event contributing to an estimated increase in N2O fluxes of 1.08 ± 0.14 kg N2O-N ha−1. Cumulative fluxes calculated over a 28 day period in August after the application of 70 kg-N ha−1 as ammonium nitrate to both fields were estimated at 0.42 ± 0.15 and 0.75 ± 0.14 kg N2O N ha−1 for the tilled and un-tilled fields, respectively. The tillage event appears to have substantially increased N2O fluxes from the tilled grassland field over a two month period; however, this increase may have been fractionally offset by a decrease in emissions after the August fertilisation event.

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