282 research outputs found
Estimating nonlinear mixing effects for arid vegetation scenes with MISR channels and observation directions
A Monte-Carlo ray-trace model has been applied to simulated sparse vegetation desert canopies in an effort to quantify the spectral mixing (both linear and nonlinear) occurring as a result of radiative interactions between vegetation and soil. This work is of interest as NASA is preparing to launch new instruments such as MISR and MODIS. MISR will observe each ground pixel from nine different directions in three visible channels and one near-infrared channel. It is desired to study angular variations in spectral mixing by quantifying the amount of nonlinear spectral mixing occurring in the MISR observing directions
Active Amplification of the Terrestrial Albedo to Mitigate Climate Change: An Exploratory Study
This study explores the potential to enhance the reflectance of solar
insolation by the human settlement and grassland components of the Earth's
terrestrial surface as a climate change mitigation measure. Preliminary
estimates derived using a static radiative transfer model indicate that such
efforts could amplify the planetary albedo enough to offset the current global
annual average level of radiative forcing caused by anthropogenic greenhouse
gases by as much as 30 percent or 0.76 W/m2. Terrestrial albedo amplification
may thus extend, by about 25 years, the time available to advance the
development and use of low-emission energy conversion technologies which
ultimately remain essential to mitigate long-term climate change. However,
additional study is needed to confirm the estimates reported here and to assess
the economic and environmental impacts of active land-surface albedo
amplification as a climate change mitigation measure.Comment: 21 pages, 3 figures. In press with Mitigation and Adaptation
Strategies for Global Change, Springer, N
A review of methods to measure and monitor historical carbon emissions from forest degradation
In the absence of historical field data, developing countries can rely on consistent current ground data and remote sensing assessments
What lies beneath : detecting sub-canopy changes in savanna woodlands using a three-dimensional classification method
QUESTION : Increasing population pressure, socio-economic development and
associated natural resource use in savannas are resulting in large-scale land
cover changes, which can be mapped using remote sensing. Is a three-dimensional
(3D) woody vegetation structural classification applied to LiDAR (Light
Detection and Ranging) data better than a 2D analysis to investigate change in
fine-scale woody vegetation structure over 2 yrs in a protected area (PA) and a
communal rangeland (CR)?
LOCATION : Bushbuckridge Municipality and Sabi Sand Wildtuin, NE South Africa.
METHODS : Airborne LiDAR data were collected over 3 300 ha in April 2008 and
2010. Individual tree canopies were identified using object-based image analysis
and classified into four height classes: 1–3, 3–6, 6–10 and >10 m. Four structural
metrics were calculated for 0.25-ha grid cells: canopy cover, number of canopy
layers present, cohesion and number of height classes present. The relationship
between top-of-canopy cover and sub-canopy cover was investigated using
regression. Gains, losses and persistence (GLP) of cover at each height class and
the four structural metrics were calculated. GLP of clusters of each structural
metric (calculated using LISA – Local Indicators of Spatial Association – statistics)
were used to assess the changes in clusters of eachmetric over time.
RESULTS : Top-of-canopy cover was not a good predictor of sub-canopy cover.
The number of canopy layers present and cohesion showed gains and losseswith
persistence in canopy cover over time, necessitating the use of a 3D classification
to detect fine-scale changes, especially in structurally heterogeneous savannas.
Trees >3 min height showed recruitment and gains up to 2.2 times higher in the
CR where they are likely to be protected for cultural reasons, but losses of up to
3.2-foldmore in the PA, possibly due to treefall caused by elephant and/or fire.
CONCLUSION : Land use has affected sub-canopy structure in the adjacent sites,
with the low intensity use CR showing higher structural diversity. A 3D classification
approach was successful in detecting fine-scale, short-term changes
between land uses, and can thus be used as amonitoring tool for savannawoody
vegetation structure.
Remove selectedThe Carnegie Airborne Observatory is made possible by the Avatar Alliance Foundation, Margaret A. Cargill Foundation, John D. and Catherine T. MacArthur Foundation,
Grantham Foundation for the Protection of the Environment, W.M. Keck Foundation, Gordon and Betty Moore Foundation, Mary Anne Nyburg Baker and G. Leonard
Baker Jr. and William R. Hearst III. Application of the CAO data in South Africa is made possible by the Andrew Mellon Foundation and the endowment of the Carnegie
Institution for Science.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1654-109X2016-07-31hb201
Unsustainable fuelwood extraction from South African savannas
Wood and charcoal supply the majority of sub-Saharan Africa’s rural energy needs. The
long-term supply of fuelwood is in jeopardy given high consumption rates. Using airborne
light detection and ranging (LiDAR), we mapped and investigated savanna aboveground
biomass across contrasting land uses, ranging from densely populated communal areas to
highly protected areas in the Lowveld savannas of South Africa. We combined the LiDAR
observations with socio-economic data, biomass production rates and fuelwood consumption
rates in a supply–demand model to predict future fuelwood availability. LiDAR-based biomass
maps revealed disturbance gradients around settlements up to 1.5 km, corresponding to the
maximum distance walked to collect fuelwood. At current levels of fuelwood consumption
(67% of households use fuelwood exclusively, with a 2% annual reduction), we calculate that
biomass in the study area will be exhausted within thirteen years. We also show that it will
require a 15% annual reduction in consumption for eight years to a level of 20% of households
using fuelwood before the reduction in biomass appears to stabilize to sustainable levels. The
severity of dwindling fuelwood reserves in African savannas underscores the importance of
providing affordable energy for rural economic development.The CSIR researchers were funded by the CSIR Strategic
Research Panel and the Department of Science and
Technology’s Earth Observation Unit. SUCSES study (Sustainability in Communal Socio-Ecological Systems) which provided data on fuelwood use in
Justicia was funded by the South African National Research
Foundation.
The airborne campaign and analysis was funded by the
Andrew Mellon Foundation.http://iopscience.iop.org/1748-9326am201
Biomass increases go under cover : woody vegetation dynamics in South African rangelands
Woody biomass dynamics are an expression of ecosystem function, yet biomass estimates
do not provide information on the spatial distribution of woody vegetation within the vertical
vegetation subcanopy. We demonstrate the ability of airborne light detection and ranging
(LiDAR) to measure aboveground biomass and subcanopy structure, as an explanatory
tool to unravel vegetation dynamics in structurally heterogeneous landscapes. We sampled
three communal rangelands in Bushbuckridge, South Africa, utilised by rural communities
for fuelwood harvesting. Woody biomass estimates ranged between 9 Mg ha-1 on gabbro
geology sites to 27 Mg ha-1 on granitic geology sites. Despite predictions of woodland depletion
due to unsustainable fuelwood extraction in previous studies, biomass in all the communal
rangelands increased between 2008 and 2012. Annual biomass productivity
estimates (10–14% p.a.) were higher than previous estimates of 4% and likely a significant
contributor to the previous underestimations of modelled biomass supply. We show that biomass
increases are attributable to growth of vegetation <5 m in height, and that, in the high
wood extraction rangeland, 79% of the changes in the vertical vegetation subcanopy are
gains in the 1-3m height class. The higher the wood extraction pressure on the rangelands,
the greater the biomass increases in the low height classes within the subcanopy, likely a
strong resprouting response to intensive harvesting. Yet, fuelwood shortages are still occurring,
as evidenced by the losses in the tall tree height class in the high extraction rangeland. Loss of large trees and gain in subcanopy shrubs could result in a structurally simple landscape
with reduced functional capacity. This research demonstrates that intensive harvesting
can, paradoxically, increase biomass and this has implications for the sustainability of ecosystem service provision. The structural implications of biomass increases in communal
rangelands could be misinterpreted as woodland recovery in the absence of three-dimensional,
subcanopy information.S1 Dataset. Biomass model data. Data include 2012 LiDAR-derived average height and canopy
cover extraction metrics, as well as field-work based allometry. Each line item is per 25 m x
25 m grid cell. Metadata are included in the dataset.S2 Dataset. Biomass and subcanopy data. Data include 2008 and 2012 biomass estimates derived
from biomass models as well as % subcanopy returns for voxel data for the height class
categories: 1-3m, 3-5m, 5-10m and >10m. Each line item is per 25 m x 25 m grid cell. Data are
organized per land extraction category into separate worksheets. Metadata are included in
the dataset.S3 Dataset. Biomass changes (Mg ha-1) in relation to relative height and canopy cover
change. Data include biomass change estimates (2008–2012), percentage height and canopy
cover changes for each 25 m x 25 m grid cell. Each height class (relative to height in 2008) are
shown on separate worksheets. Metadata are included in the dataset.S1 Fig. Site-specific biomass model residuals. The residual spread demonstrates heteroskedasticity
with increasing biomass fitted values for rangelands with a) high, b) intermediate and
c) low extraction pressure.S2 Fig. Biomass changes (%) relative to height-specific change in subcanopy returns (%).
Height categories are: 1–3 m, 3–5 m, 5–10 m and >10 m.The Carnegie Airborne Observatory (CAO)
is made possible by the Avatar Alliance Foundation,
Margaret A. Cargill Foundation, John D. and
Catherine T. MacArthur Foundation, Grantham
Foundation for the Protection of the Environment, W.
M. Keck Foundation, Gordon and Betty Moore
Foundation, Mary Anne Nyburg Baker and G.
Leonard Baker, Jr., and William R. Hearst III.
Application of the CAO data in South Africa is made possible through the Andrew Mellon Foundation and
the endowment of the Carnegie Institution for
Science, the Council for Scientific and Industrial
Research (CSIR), and the South African Department
of Science and Technology (grant agreement DST/
CON 0119/2010, Earth Observation Application
Development in Support of SAEOS). CSIR coauthors
are supported by the European Union’s
Seventh Framework Programme (FP7/2007-2013,
grant agreement n°282621, AGRICAB). PJM
acknowledges funding from the National Research
Foundation (NRF: SFH1207203615). Additionally,
PJM and ETFW acknowledge the DST-NRF Centre
of Excellence in Tree Health Biotechnology (CTHB)
and, PJM and BFNE, the Applied Centre for Climate
and Earth Systems Science (ACCESS). BFNE
acknowledges financial support from Exxaro.http://www.plosone.orgam201
Framing the concept of satellite remote sensing essential biodiversity variables: challenges and future directions
Although satellite-based variables have for long been expected to be key components to a unified and global biodiversity monitoring strategy, a definitive and agreed list of these variables still remains elusive. The growth of interest in biodiversity variables observable from space has been partly underpinned by the development of the essential biodiversity variable (EBV) framework by the Group on Earth Observations – Biodiversity Observation Network, which itself was guided by the process of identifying essential climate variables. This contribution aims to advance the development of a global biodiversity monitoring strategy by updating the previously published definition of EBV, providing a definition of satellite remote sensing (SRS) EBVs and introducing a set of principles that are believed to be necessary if ecologists and space agencies are to agree on a list of EBVs that can be routinely monitored from space. Progress toward the identification of SRS-EBVs will require a clear understanding of what makes a biodiversity variable essential, as well as agreement on who the users of the SRS-EBVs are. Technological and algorithmic developments are rapidly expanding the set of opportunities for SRS in monitoring biodiversity, and so the list of SRS-EBVs is likely to evolve over time. This means that a clear and common platform for data providers, ecologists, environmental managers, policy makers and remote sensing experts to interact and share ideas needs to be identified to support long-term coordinated actions
Search for CP Violation in D^0--> K_S^0 pi^+pi^-
We report on a search for CP violation in the decay of D0 and D0B to Kshort
pi+pi-. The data come from an integrated luminosity of 9.0 1/fb of e+e-
collisions at sqrt(s) ~ 10 GeV recorded with the CLEO II.V detector. The
resonance substructure of this decay is well described by ten quasi-two-body
decay channels (K*-pi+, K*0(1430)-pi+, K*2(1430)-pi+, K*(1680)-pi+, Kshort rho,
Kshort omega, Kshort f0(980), Kshort f2(1270), Kshort f0(1370), and the ``wrong
sign'' K*+ pi-) plus a small non-resonant component. We observe no evidence for
CP violation in the amplitudes and phases that describe the decay D0 to K_S^0
pi+pi-.Comment: 10 pages, 3 figures, also available at
http://w4.lns.cornell.edu/public/CLNS/, submitted to PR
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