scholarly journals Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

2020 ◽  
Vol 12 (19) ◽  
pp. 3264
Author(s):  
Edgard Bontempo ◽  
Ricardo Dalagnol ◽  
Flavio Ponzoni ◽  
Dalton Valeriano
Keyword(s):  
Mixed Models ◽  
Marked Decrease ◽  
Structural Characteristics ◽  
Rank Correlation ◽  
Environmental Data ◽  
Northeast Brazil ◽  
Caatinga Vegetation ◽  
Leaf Level ◽  
Landscape Level ◽  
Heterogeneous Vegetation

Sun-Induced chlorophyll Fluorescence (SIF) relates directly to photosynthesis yield and stress but there are still uncertainties in its interpretation. Most of these uncertainties concern the influences of the emitting vegetation’s structure (e.g., leaf angles, leaf clumping) and biochemistry (e.g., chlorophyll content, other pigments) on the radiative transfer of fluorescent photons. The Caatinga is a large region in northeast Brazil of semiarid climate and heterogeneous vegetation, where such biochemical and structural characteristics can vary greatly even within a single hectare. With this study we aimed to characterize eleven years of SIF seasonal variation from Caatinga vegetation (2007 to 2017) and to study its responses to a major drought in 2012. Orbital SIF data from the instrument GOME-2 was used along with MODIS MAIAC EVI and NDVI. Environmental data included precipitation rate (TRMM), surface temperature (MODIS) and soil moisture (ESA CCI). To support the interpretation of SIF responses we used red and far-red SIF adjusted by the Sun’s zenith angle (SIF-SZA) and by daily Photosynthetically Active Radiation (dSIF). Furthermore, we also adjusted SIF through two contrasting formulations using NDVI data as proxy for structure and biochemistry, based on previous leaf-level and landscape level studies: SIF-Yield and SIF-Prod. Data was tested with time-series decomposition, rank correlation, spatial correlation and Linear Mixed Models (LMM). Results show that GOME-2 SIF and adjusted SIF formulations responded consistently to the observed environmental variation and showed a marked decrease in SIF emissions in response to a 2012 drought that was generally larger than the corresponding NDVI and EVI decreases. Drought sensitivity of SIF, as inferred from LMM slopes, was correlated to land cover at different regions of the Caatinga. This is the first study to show correlation between landscape-level SIF and an emergent property of ecosystems (i.e., resilience), showcasing the value of remotely sensed fluorescence for ecological studies.

scholarly journals Adjustments to SIF Aid the Interpretation of Drought Responses at the Caatinga of Northeast Brazil

2020 ◽  
Author(s):  
Edgard Bontempo ◽  
Ricardo Dalagnol ◽  
Flavio Ponzoni ◽  
Dalton Valeriano
Keyword(s):  
Mixed Models ◽  
Marked Decrease ◽  
Structural Characteristics ◽  
Rank Correlation ◽  
Environmental Data ◽  
Northeast Brazil ◽  
Caatinga Vegetation ◽  
Leaf Level ◽  
Landscape Level ◽  
Heterogeneous Vegetation

Sun-Induced chlorophyll Fluorescence (SIF) relates directly to photosynthesis yield and stress but there are still uncertainties in its interpretation. Most of these uncertainties concern the influences of the emitting vegetation’s structure (e.g., leaf angles, leaf clumping) and biochemistry (e.g., chlorophyll content, other pigments) on the radiative transfer of fluorescent photons. The Caatinga is a large region at northeast Brazil of semiarid climate and heterogeneous vegetation, where such biochemical and structural characteristics can vary greatly even within a single hectare. With this study we aimed to characterize eleven years of SIF seasonal variation from Caatinga vegetation (2007 to 2017) and to study its responses to a major drought in 2012. Orbital SIF data from the instrument GOME-2 was used along with MODIS MAIAC EVI and NDVI. Environmental data included precipitation rate (TRMM), surface temperature (MODIS) and soil moisture (ESA CCI). To support the interpretation of SIF responses we have used red and far-red SIF adjusted by the Sun’s zenith angle (SIF-SZA) and by daily Photosynthetically Active Radiation (dSIF). Furthermore, we have also adjusted SIF through two contrasting formulations using NDVI data as proxy for structure and biochemistry, based on previous leaf-level and landscape level studies: SIF-Yield and SIF-Prod. Data was tested with time-series decomposition, rank correlation, spatial correlation and Linear Mixed Models (LMM). Results show that GOME-2 SIF and adjusted SIF formulations responded consistently to the observed environmental variation and showed a marked decrease in SIF emissions in response to a 2012 drought, that was generally larger than the corresponding NDVI and EVI decreases. Drought sensitivity of SIF, as inferred from LMM slopes, was correlated to land cover at different regions of the Caatinga. This is the first study to show correlation between landscape-level SIF and an emergent property of ecosystems (i.e., resilience), showcasing the value of remotely sensed fluorescence for ecological studies.

Landscape-level variability in the age underestimation of understory black spruce in the northern boreal forest of Quebec

2005 ◽  
Vol 35 (3) ◽  
pp. 633-642 ◽  
Author(s):  
Marc-André Parisien ◽  
Luc Sirois ◽  
Sylvain Parent
Keyword(s):  
Boreal Forest ◽  
Mixed Models ◽  
Black Spruce ◽  
Ground Level ◽  
Simple Linear Regression ◽  
Linear Regression Models ◽  
Growth Rings ◽  
Age Correction ◽  
The Relationship ◽  
Landscape Level

This study examines the variability of the potential aging error for saplings (height ≤1.5 m) of black spruce (Picea mariana (Mill.) B.S.P.) in mature fire-dominated stands (n = 14 stands) of the northern boreal forest of northwestern Quebec. Age underestimation was determined by counting the number of underground bud scars of saplings. The magnitude and variability of age underestimation was compared within and among stands. The relationship between corrected ages (the sum of age underestimation and the number of growth rings at ground level) and ground-level ages was strongly linear and was therefore described with simple linear regression models. To evaluate landscape-level variability in this relationship, the regressions were compared among stands using mixed models. Despite high variability in age underestimation at the stand level, the relationship between corrected and ground-level age was highly significant (p < 0.0001) for all stands except one. However, there were many significant statistical differences between these regressions, indicating high landscape-level variability. The magnitude of age underestimation was found to be highly site specific (means of 7–26 years), the phenomenon being more marked and variable in older stands. Given high landscape-level variability, age underestimation of understory black spruce saplings in northern boreal stands must be documented for every sampled stand to apply a valid age correction in studies that involve multiple stands.

scholarly journals Distance from roads and cities as a predictor of habitat loss and fragmentation in the caatinga vegetation of Brazil

2002 ◽  
Vol 62 (4b) ◽  
pp. 897-905 ◽  
Author(s):  
A. M. SANTOS ◽  
M. TABARELLI
Keyword(s):  
Economic Development ◽  
Species Composition ◽  
Habitat Loss ◽  
Satellite Imagery ◽  
Dry Forest ◽  
Northeast Brazil ◽  
Distance Class ◽  
Positive Correlation ◽  
Caatinga Vegetation ◽  
Habitat Loss And Fragmentation

Roads and cities represent huge sources of degradation for adjacent ecosystems regarding nutrient cycling, energy, water flow and species composition. In this study we test the hypothesis that distance from roads and cities is associated with habitat loss and fragmentation in the caatinga vegetation- a dry forest to scrub vegetation that covers ca. 736,000 km² of northeast Brazil. The study site comprised a 2,828.8 km² piece (64 km x 44.2 km) of Xingó region (09°36'S, 37°50'W), which is located between the States of Alagoas and Sergipe. Based on satellite imagery we mapped the remaining vegetation, 145 km of paved roads and the seven small-sized cities set in the study site. A positive correlation was found between the combined distance from roads and cities and the percentage of remaining vegetation as it dropped from 18% at 12 km distant to 5.9% at 1 km distant from cities and roads. Thus, remaining vegetation was reduced by one third near cities and roads. A positive correlation was also found between distance from cities and roads and the percentage of fragments larger than 200 ha, which ranged from 3.6% (within 3 km distance class) to 23.3% (15 km distance class) of all fragments. Our results suggest a road/city-effect zone of 12 to 15 km width, over which habitat loss and fragmentation extend throughout the caatinga vegetation. These findings should be considered in the regional polices for biodiversity conservation and economic development of the caatinga region.

Spatial and temporal variation in amphibian metacommunity structure in Chiapas, Mexico

2014 ◽  
Vol 30 (6) ◽  
pp. 537-549 ◽  
Author(s):  
Leticia Margarita Ochoa-Ochoa ◽  
Robert James Whittaker
Keyword(s):  
Environmental Changes ◽  
Environmental Variability ◽  
Forest Disturbance ◽  
Rank Correlation ◽  
Environmental Data ◽  
Dynamic Responses ◽  
Temporary Ponds ◽  
Spatial And Temporal Variation ◽  
Short Term ◽  
Metacommunity Structure

Abstract:Amphibians are known to be sensitive to environmental change but their responses at the level of metacommunities to short-term environmental variability are poorly understood. We used field data from two protected areas, La Pera and Nahá (Chiapas, Mexico) to test for variation in metacommunity properties for two consecutive years (2009 and 2010). Amphibians and accompanying environmental data were recorded to a standardized protocol within each landscape, in four or five transects of 50 × 2-m per patch, for 30 and 31 patches, respectively. We found 23 species in La Pera and 30 in Nahá (21 species shared). Metacommunity structure was analysed using reciprocal averaging (RA) ordination by means of metrics for coherence, turnover and boundary clumping, with Spearman rank correlation used to examine relationships with environmental variables. The metacommunity structure varied differentially among the landscapes between years, being classed as quasi-Gleasonian in La Pera in both years, but Clementsian for Nahá in 2009 and Gleasonian for Nahá in 2010. In further illustration of variation between years, in 2009 the principal community gradient (RA axis 1) for La Pera was significantly positively correlated with altitude (r = 0.36), forest disturbance status (r = 0.78), mean canopy cover (r = 0.79) and mean litter depth (r = 0.67), while in 2010 it was correlated with latitude (r = 0.38), mean grass-layer height (r = 0.38), incidence of rainfall prior to sampling (r = 0.35) and presence of temporary ponds (r = 0.45). Our findings support the notion that amphibians respond to short-term environmental changes by individualistic movement within the landscape as well as via population dynamic responses.

scholarly journals Habitat selection of secondary hole-nesting birds in riverine forests along Drava river in Croatia

2020 ◽  
Vol 144 (11-12) ◽  
pp. 558-558
Author(s):  
Mario Slatki ◽  
Jelena Kralj
Keyword(s):  
Tree Species ◽  
Structural Characteristics ◽  
Bird Species ◽  
Rank Correlation ◽  
Basal Area ◽  
Principal Component ◽  
Relative Number ◽  
Bird Community ◽  
Habitat Characteristics ◽  
Mixed Stands

The correlation between secondary hole-nesters community characteristics and floristic and structural characteristics of their habitat was studied in riverine forest stands near river Drava in Croatia. Standard point count method was used for bird community sampling and circular plot method for habitat sampling. Sampling was carried out on 66 points. PCA analysis that included 28 independent habitat variables was used, followed by Spearman rank correlation between principal component scores and bird community variables (number of species and number of pairs). Tree basal area was used as an indication of stand maturity and to classify studied points into four forest types (ash, poplar, alder and mixed). Eight secondary hole-nesting species and 14 tree species were recorded. The average forest age was 59.8 ± 20.5 years, with ash and mixed stands being on average older than alder and poplar stands. Shannon-Wiener index of secondary hole-nesters diversity was highest in stands with dominant ash and was increasing with stand maturity. A significant positive correlation was found between number of bird species as well as number of pairs and older stands with lower number of tree species and lower relative number of poplar and alder. It can be concluded that diversity of secondary hole-nesting bird species as well as their abundance is correlated with structural habitat characteristics and that older stands show greater bird biodiversity and abundance.

Three new species of Graphidaceae (lichenized Ascomycota) from the semi-arid region of northeast Brazil

Phytotaxa ◽  
2017 ◽  
Vol 331 (2) ◽  
pp. 289 ◽  
Author(s):  
JACIELE DE OLIVEIRA DANTAS ◽  
ELAINE SANTOS ALVES ◽  
ROBERT LÜCKING ◽  
MARCELA EUGENIA DA SILVA CÁCERES
Keyword(s):  
New Species ◽  
Fungal Species ◽  
Northeast Brazil ◽  
Additional Material ◽  
Caatinga Vegetation ◽  
The Family ◽  
Three New Species ◽  
Semi Arid Region ◽  
Santa Maria ◽  
Semi Arid

Three new lichenized fungal species in the family Graphidaceae are described from Northeast Brazil. Graphis alba has lirellae with a conspicuous white cover, eventually becoming striate, small, (sub-)muriform ascospores, and stictic acid. Halegrapha redonographoides features somewhat pseudostromatic ascomata with immersed lirellae, a completely carbonized excipulum, and small, submuriform ascospores, in combination with a norstictic acid chemistry. Thelotrema pachysporoides has an ecorticate, white thallus and produces brown, 7–13-septate, 25–35 × 7–10 µm large ascospores. The new species were found in an isolated remnant of Caatinga vegetation, at Fazenda Santa Maria da Lage, Poço Verde, Sergipe state, with additional material of one of the species also detected in the state of Tocantins.

scholarly journals Agronomic, morphogenic and structural characteristics of tropical forage grasses in northeast Brazil

2014 ◽  
Vol 2 (2) ◽  
pp. 214 ◽  
Author(s):  
Rosane C. Rodrigues ◽  
Thiago V.R. Sousa ◽  
Maria A.A. Melo ◽  
Jocélio S. Araújo ◽  
Rogério P. Lana ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Northeast Brazil ◽  
Forage Grasses ◽  
Tropical Forage

Canopy-scale relationships between foliar nitrogen and albedo are not observed in leaf reflectance and transmittance within temperate deciduous tree species

Botany ◽  
2011 ◽  
Vol 89 (7) ◽  
pp. 491-497 ◽  
Author(s):  
Megan K. Bartlett ◽  
Scott V. Ollinger ◽  
David Y. Hollinger ◽  
Haley F. Wicklein ◽  
Andrew D. Richardson
Keyword(s):  
Nitrogen Content ◽  
Near Infrared ◽  
Structural Characteristics ◽  
Nitrogen Concentration ◽  
Deciduous Tree ◽  
Integrating Sphere ◽  
Area Index ◽  
Foliar Nitrogen ◽  
Crown Shape ◽  
Leaf Level

Strong positive correlations between the maximum rate of canopy photosynthesis, canopy-averaged foliar nitrogen concentration, and canopy albedo have been shown in previous studies. While leaf-level relationships between photosynthetic capacity and foliar nitrogen are well documented, it is not clear whether leaf-level relationships between solar-weighted reflectance and nitrogen underlie the canopy-scale patterns. Using an integrating sphere, we measured the reflectance and transmittance (350–2500 nm) of both individual leaves and multileaf stacks. Samples were collected from 12 broadleaf species at the Harvard Forest in central Massachusetts, USA. Across all species, foliar nitrogen (both mass-based nitrogen concentration and area-based nitrogen content) and leaf mass / area ratio were negatively, rather than positively, correlated with solar-weighted reflectance and transmittance in ultraviolet–visible and near-infrared wavelength bands (350–700 nm and 700–2500 nm, respectively). Leaf-level anatomy and biochemistry, therefore, do not appear to drive the canopy-level association between increasing foliar nitrogen content and increasing canopy albedo. This suggests that interactions between leaf optical properties and structural canopy-scale traits that correlate with nitrogen content (perhaps some combination of crown shape, leaf area index, leaf angular distribution, or other structural characteristics of the canopy), may instead underlie the previously observed relationship between nitrogen and canopy-level shortwave albedo.

scholarly journals Effects of Climate Change and Various Grassland Management Practices on Grasshopper (Orthoptera) Assemblages

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Zoltán Kenyeres ◽  
Judit Cservenka
Keyword(s):  
Land Use ◽  
Mixed Models ◽  
National Park ◽  
Management Practices ◽  
Rank Correlation ◽  
Grassland Management ◽  
Climatic Conditions ◽  
Spearman Rank Correlation ◽  
Independent Variables ◽  
Land Use Types

Influence of different grassland management practices on Orthoptera assemblages inhabiting humid grassland areas was studied since 2003 to 2011. The examined sites were within the protected area of Balaton Uplands National Park. The physiognomy and climatic conditions of the studied habitats were similar but their land use types were significantly different. After the preliminary analyses of Nonmetric multidimensional scaling, neighbour joining clustering, and Spearman rank correlation, we examined the possible effects of such independent variables as land use (nonmanagement, mowing, grazing), microclimate (humidity and temperature), regional macroclimate (annual and monthly mean temperatures and rainfall), using General Linear Mixed Models, and canonical correlation analysis. Our results showed that the effect of grassland management practices on the organization of Orthoptera assemblages was at least as important as that of macro- and microclimate. Furthermore, grassland management could intensify the influence of several local and regional parameters. These results can help finding the most suitable type of grassland management to conserve the grasshopper assemblages.

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