274 research outputs found
Comment on "The global tree restoration potential"
Bastin et al. (Reports, 5 July 2019, p. 76) state that the restoration potential of new forests globally is 205 gigatonnes of carbon, conclude that âglobal tree restoration is our most effective climate change solution to date,â and state that climate change will drive the loss of 450 million hectares of existing tropical forest by 2050. Here we show that these three statements are incorrect
Multimodal deep learning for mapping forest dominant height by fusing GEDI with earth observation data
The integration of multisource remote sensing data and deep learning models
offers new possibilities for accurately mapping high spatial resolution forest
height. We found that GEDI relative heights (RH) metrics exhibited strong
correlation with the mean of the top 10 highest trees (dominant height)
measured in situ at the corresponding footprint locations. Consequently, we
proposed a novel deep learning framework termed the multi-modal attention
remote sensing network (MARSNet) to estimate forest dominant height by
extrapolating dominant height derived from GEDI, using Setinel-1 data, ALOS-2
PALSAR-2 data, Sentinel-2 optical data and ancillary data. MARSNet comprises
separate encoders for each remote sensing data modality to extract multi-scale
features, and a shared decoder to fuse the features and estimate height. Using
individual encoders for each remote sensing imagery avoids interference across
modalities and extracts distinct representations. To focus on the efficacious
information from each dataset, we reduced the prevalent spatial and band
redundancies in each remote sensing data by incorporating the extended spatial
and band reconstruction convolution modules in the encoders. MARSNet achieved
commendable performance in estimating dominant height, with an R2 of 0.62 and
RMSE of 2.82 m, outperforming the widely used random forest approach which
attained an R2 of 0.55 and RMSE of 3.05 m. Finally, we applied the trained
MARSNet model to generate wall-to-wall maps at 10 m resolution for Jilin,
China. Through independent validation using field measurements, MARSNet
demonstrated an R2 of 0.58 and RMSE of 3.76 m, compared to 0.41 and 4.37 m for
the random forest baseline. Our research demonstrates the effectiveness of a
multimodal deep learning approach fusing GEDI with SAR and passive optical
imagery for enhancing the accuracy of high resolution dominant height
estimation
Woody encroachment and forest degradation in sub-Saharan Africa's woodlands and savannas 1982-2006
We review the literature and find 16 studies from across Africa's savannas and woodlands where woody encroachment dominates. These small-scale studies are supplemented by an analysis of long-term continent-wide satellite data, specifically the Normalized Difference Vegetation Index (NDVI) time series from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset. Using dry-season data to separate the tree and grass signals, we find 4.0% of non-rainforest woody vegetation in sub-Saharan Africa (excluding West Africa) significantly increased in NDVI from 1982 to 2006, whereas 3.52% decreased. The increases in NDVI were found predominantly to the north of the Congo Basin, with decreases concentrated in the Miombo woodland belt. We hypothesize that areas of increasing dry-season NDVI are undergoing woody encroachment, but the coarse resolution of the study and uncertain relationship between NDVI and woody cover mean that the results should be interpreted with caution; certainly, these results do not contradict studies finding widespread deforestation throughout the continent. However, woody encroachment could be widespread, and warrants further investigation as it has important consequences for the global carbon cycle and landâclimate interactions
Topographic roughness as a signature of the emergence of bedrock in eroding landscapes
Rock is exposed at the Earth surface when rates of erosion locally exceed
rates of soil production. The thinning of soils and emergence of bedrock has
implications spanning geomorphology, ecology and hydrology. Soil-mantled
hillslopes are typically shaped by diffusion-like sediment transport
processes that act to smooth topography through time, generating the
familiar smooth, convex hillslope profiles that are common in low relief
landscapes. Other processes, however, can roughen the landscape. Bedrock
emergence can produce rough terrain; in this contribution we exploit the
contrast between rough patches of bedrock outcrop and smooth, diffusion-dominated soil to detect bedrock outcrops. Specifically, we demonstrate that
the local variability of surface normal vectors, measured from 1 m resolution
airborne LiDAR data, can be used as a topographic signature to
identify areas within landscapes where rock exposure is present. We then use
this roughness metric to investigate the transition from soil-mantled to
bedrock hillslopes as erosion rates increase in two transient landscapes,
Bald Rock Basin, which drains into the Middle Fork Feather River,
California, and Harrington Creek, a tributary of the Salmon River, Idaho.
Rather than being abrupt, as predicted by traditional soil production
models, in both cases the transition from fully soil-mantled to bedrock
hillslopes is gradual and spatially heterogeneous, with rapidly eroding
hillslopes supporting a patchwork of bedrock and soil that is well
documented by changes in topographic roughness, highlighting the utility of
this metric for testing hypotheses concerning the emergence of bedrock and
adding to a growing body of evidence that indicates the persistence of
partial soil mantles in steep, rapidly eroding landscapes
An Effective Method for InSAR Mapping of Tropical Forest Degradation in Hilly Areas
Current satellite remote sensing methods struggle to detect and map forest degradation, which is a critical issue as it is likely a major and growing source of carbon emissions and biodiveristy loss. TanDEM-X InSAR phase height (hÏ) is a promising variable for measuring forest disturbances, as it is closely related to the mean canopy height, and thus should decrease if canopy trees are removed. However, previous research has focused on relatively flat terrains, despite the fact that much of the worldâs remaining tropical forests are found in hilly areas, and this inevitably introduces artifacts in sideways imaging systems. In this paper, we find a relationship between hÏ and aboveground biomass change in four selectively logged plots in a hilly region of central Gabon. We show that minimising multilooking prior to the calculation of hÏ strengthens this relationship, and that degradation estimates across steep slopes in the surrounding region are improved by selecting data from the most appropriate pass directions on a pixel-by-pixel basis. This shows that TanDEM-X InSAR can measure the magnitude of degradation, and that topographic effects can be mitigated if data from multiple SAR viewing geometries are available
On Kinks and Bound States in the Gross-Neveu Model
We investigate static space dependent \sigx=\lag\bar\psi\psi\rag saddle
point configurations in the two dimensional Gross-Neveu model in the large N
limit. We solve the saddle point condition for \sigx explicitly by employing
supersymmetric quantum mechanics and using simple properties of the diagonal
resolvent of one dimensional Schr\"odinger operators rather than inverse
scattering techniques. The resulting solutions in the sector of unbroken
supersymmetry are the Callan-Coleman-Gross-Zee kink configurations. We thus
provide a direct and clean construction of these kinks. In the sector of broken
supersymmetry we derive the DHN saddle point configurations. Our method of
finding such non-trivial static configurations may be applied also in other two
dimensional field theories.Comment: Revised version. A new section added with derivation of the DHN
static configurations in the sector of broken supersymmetry. Some references
added as well. 25 pp, latex, e-mail [email protected]
Evidence For The Production Of Slow Antiprotonic Hydrogen In Vacuum
We present evidence showing how antiprotonic hydrogen, the quasistable
antiproton-proton (pbar-p) bound system, has been synthesized following the
interaction of antiprotons with the hydrogen molecular ion (H2+) in a nested
Penning trap environment. From a careful analysis of the spatial distributions
of antiproton annihilation events, evidence is presented for antiprotonic
hydrogen production with sub-eV kinetic energies in states around n=70, and
with low angular momenta. The slow antiprotonic hydrogen may be studied using
laser spectroscopic techniques.Comment: 5 pages with 4 figures. Published as Phys. Rev. Letters 97, 153401
(2006), in slightly different for
Laryngeal transplantation in minipigs: vascular, myologic and functional outcomes
There is no effective way of replacing all the functions of the larynx in those requiring laryngectomy. Regenerative medicine offers promise, but cannot presently deliver implants with functioning neuromuscular units. A single well-documented laryngeal transplant in man was a qualified success, but more information is required before clinical trials may be proposed. We studied the early response of the larynx to laryngeal transplantation between 17 pairs of NIH minipigs full matched at the MHC2 locus. Following iterative technical improvements, pigs had good swallowing and a patent airway at 1Â week. No significant changes in mucosal blood flux were observed compared with pre-operative measurements. Changes in muscle morphology and fibre phenotype were observed in transplant muscles retrieved after 7Â days: the levels of fast and slow myosin heavy chain (MyHC) protein were reduced and embryonic MyHC was up regulated consistent with denervation induced atrophy. At 1Â week laryngeal transplantation can result in good swallowing, and is not associated with clinical evidence of ischemia-reperfusion injury in MHC-matched pigs
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