Forest structure from terrestrial laser scanning – in support of remote sensing calibration/validation and operational inventory

Forests are an important part of the natural ecosystem, providing resources such as timber and fuel, performing services such as energy exchange and carbon storage, and presenting risks, such as fire damage and invasive species impacts. Improved characterization of forest structural attributes is desirable, as it could improve our understanding and management of these natural resources. However, the traditional, systematic collection of forest information – dubbed “forest inventory” – is time-consuming, expensive, and coarse when compared to novel 3-D measurement technologies. Remote sensing estimates, on the other hand, provide synoptic coverage, but often fail to capture the fine- scale structural variation of the forest environment. Terrestrial laser scanning (TLS) has demonstrated a potential to address these limitations, but its operational use has remained limited due to unsatisfactory performance characteristics vs. budgetary constraints of many end-users. To address this gap, my dissertation advanced affordable mobile laser scanning capabilities for operational forest structure assessment. We developed geometric reconstruction of forest structure from rapid-scan, low-resolution point cloud data, providing for automatic extraction of standard forest inventory metrics. To augment these results over larger areas, we designed a view-invariant feature descriptor to enable marker-free registration of TLS data pairs, without knowledge of the initial sensor pose. Finally, a graph-theory framework was integrated to perform multi-view registration between a network of disconnected scans, which provided improved assessment of forest inventory variables. This work addresses a major limitation related to the inability of TLS to assess forest structure at an operational scale, and may facilitate improved understanding of the phenomenology of airborne sensing systems, by providing fine-scale reference data with which to interpret the active or passive electromagnetic radiation interactions with forest structure. Outputs are being utilized to provide antecedent science data for NASA’s HyspIRI mission and to support the National Ecological Observatory Network’s (NEON) long-term environmental monitoring initiatives

Towards scale-invariant aboveground biomass estimation in Savanna ecosystems using small-footprint waveform lidar

Land degradation is becoming an issue of increasing concern in the savanna ecosystems of southern Africa. As a result, there is a growing need to map structural changes at the fine scale, while retaining the ability to aggregate up to landscape level for analysis across land use gradients. Aboveground biomass (AGB) is an important indicator of vegetation structure and therefore is the ideal variable for estimation from light detection and ranging (lidar) data. To avoid the effects of scale, this paper takes a tree-delineation approach for segmentation of the structurally heterogeneous savanna environment. Diameter at breast height (DBH) measurements collected in-field are then regressed against lidar-derived statistics to estimate DBH on a per tree basis, from which biomass follows naturally by allometry. The result is a spatially explicit biomass map of the savanna environment, believed to be one of the first of its kind, that can be scaled by aggregation of per-tree biomass distributions

Serum-Free Cryopreservation of Five Mammalian Cell Lines in Either a Pelleted or Suspended State

Herein we have explored two practical aspects of cryopreserving cultured mammalian cells during routine laboratory maintenance. First, we have examined the possibility of using a serum-free, hence more affordable, cryopreservative. Using five mammalian lines (Crandell Feline Kidney, MCF7, A72, WI 38 and NB324K), we found that the serum-free alternative preserves nearly as efficiently as the serum-containing preservatives. Second, we compared cryostorage of those cells in suspended versus a pellet form using both aforementioned cryopreservatives. Under our conditions, cells were in general recovered equally well in a suspended versus a pellet form

Climatic variability in Mfabeni peatlands (South Africa) since the late Pleistocene

It has been postulated that a bipolar seesaw interhemispheric mechanism dominated the relationship between the Northern and Southern hemisphere climates since the late Pleistocene. A key test for this proposition would be to undertake palaeoenvironmental studies on terrestrial archives in climatically sensitive regions. Southern Africa's contemporary C-3 and C-4 terrestrial plant distributions display a definitive geographical pattern dictated by different growing season rainfall and temperature zones; however, the region is generally archive poor due to its overall semi-arid climate and high relief topography. The Mfabeni peatland, with a basal age of c. 47 k yrs calibrated before present (kcal yr BP), is one of the oldest continuous coastal peat deposits in Southern Africa. Molecular leaf wax isotopes (delta C-13(wax)) were generated for a 810 cm long core, and combined with previously published bulk geochemical (delta C-13(bulk), %TOC), palynological, and stratigraphic data, to reconstruct the late Pleistocene and Holocene palaeoenvironments. We interpreted environmental shifts associated with the Heinrich 4, Last Glacial Maximum, deglacial and Holocene periods, which are consistent with adjacent Indian Ocean sea surface temperature records. However, the other shorter climate perturbations during the Heinrich 5, 3, 2, 1, Antarctic cold reversal and Younger Dryas, were muted, most likely due to local hydrological overprinting on the Mfabeni record. A general anti-phase sequence was observed between the Mfabeni record and better established Northern Hemisphere events, underpinning the bipolar seesaw interhemispheric mechanism proposed for global climate forcing since the Late Pleistocene

Conservation conundrum – red listing of subtropical-temperate coastal forested wetlands of South Africa

Africa’s range-restricted and transitional subtropical-temperate coastal forested wetlands are facing interlinking threats of climate and anthropogenic pressures. We assessed their conservation status using the criteria of the International Union for Conservation of Nature (IUCN). Their total areal extent was hind-casted to the reference epoch 2000, followed by the quantification of subsequent total losses in areal extents for the epochs 2005, 2008, 2011 and 2017. South Africa had 120 km2 of coastal swamp and floodplain forests in 2000 of which the majority (116.5 km2) occurred on the Maputaland Coastal Plain (MCP). By 2011, 20% of the areal extent was lost, and at the lowest rate of decline we estimate that ≥ 80% of the rest will be lost in the next 50 years. An ecosystem collapse assessment therefore indicated that the habitat is very likely Critically Endangered. Fragmentation and types of transformations were used as degradation indices to show functional collapse. These results showed that forest patches became increasingly fragmented, from 511 to 1 145 patches between 2000 and 2017 and that > 23% of the areal extent showed severe transformation. Several faunal species, with a close association to the forested wetlands of the MCP, are considered threatened with numbers declining because of transformation to timber plantations or agriculture and coupled with a prolonged drought. Of these, a sub-species of the Samango monkey, Cercopithecus mitis erythrarchus, considered to be a primary ecosystem engineer of the habitat, was red listed with a restricted distribution, being endemic, Near Threatened and declining. Also under pressure, because of habitat fragmentation and degradation is the Peregrine crab (Varuna litterata), a euryhaline species requiring connectivity across the land-seascape, ranging from freshwater forested wetlands to estuarine and off-shore environments. Functionally, these coastal forested wetlands are therefore also considered Critically Endangered. The final IUCN conservation status of South Africa’s subtropical-temperate coastal forested wetlands are recommended to be very likely Critically Endangered. Irrespective of 62% of the areal extent of these forested wetlands being within protected areas, severe degradation (metrics of fragmentation and transformation) were observed even inside these areas for the past two decades. The conservation conundrum is that despite existing legislation and management measures, there has been no stop or reversal of the negative trends to date. As a supplementary method, we therefore recommend a transdisciplinary community-based approach to conservation practice, continued and improved monitoring of the habitat losses, the identifying priority areas for rehabilitation and addressing data deficiencies in important species associations.CSIR’s Parliamentary Grant Project P1BEO00/P1CCS02, titled “Marine Observational and Predictive System Capabilities (MAROPS)”; as well as the African Union Commission (AUC) Global Monitoring for Environment and Security (GMES) MARCOSOUTH (K8MARCO). The Department of Science and Innovation (DSI) and National Research Foundation (NRF) Chair in Shallow Water Ecosystems (UID 84375) supported time of Prof. Janine Adams.https://www.elsevier.com/locate/ecolindam2022Geography, Geoinformatics and Meteorolog

Terrestrial laser scanning in forest inventories

AbstractDecision making on forest resources relies on the precise information that is collected using inventory. There are many different kinds of forest inventory techniques that can be applied depending on the goal, scale, resources and the required accuracy. Most of the forest inventories are based on field sample. Therefore, the accuracy of the forest inventories depends on the quality and quantity of the field sample. Conventionally, field sample has been measured using simple tools. When map is required, remote sensing materials are needed. Terrestrial laser scanning (TLS) provides a measurement technique that can acquire millimeter-level of detail from the surrounding area, which allows rapid, automatic and periodical estimates of many important forest inventory attributes. It is expected that TLS will be operationally used in forest inventories as soon as the appropriate software becomes available, best practices become known and general knowledge of these findings becomes more wide spread. Meanwhile, mobile laser scanning, personal laser scanning, and image-based point clouds became capable of capturing similar terrestrial point cloud data as TLS. This paper reviews the advances of applying TLS in forest inventories, discusses its properties with reference to other related techniques and discusses the future prospects of this technique

ECOSTRESS: NASA's next generation mission to measure evapotranspiration from the International Space Station

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station ECOSTRESS) was launched to the International Space Station on June 29, 2018. The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as level‐3 (L3) latent heat flux (LE) data products. These data are generated from the level‐2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear‐sky ET product (L3_ET_PT‐JPL, version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear‐sky instantaneous/time of overpass: r2 = 0.88; overall bias = 8%; normalized RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are over‐represented. The 70 m high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1 km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data

Terrestrial laser scanning for plot-scale forest measurement

Plot-scale measurements have been the foundation for forest surveys and reporting for over 200 years. Through recent integration with airborne and satellite remote sensing, manual measurements of vegetation structure at the plot scale are now the basis for landscape, continental and international mapping of our forest resources. The use of terrestrial laser scanning (TLS) for plot-scale measurement was first demonstrated over a decade ago, with the intimation that these instruments could replace manual measurement methods. This has not yet been the case, despite the unparalleled structural information that TLS can capture. For TLS to reach its full potential, these instruments cannot be viewed as a logical progression of existing plot-based measurement. TLS must be viewed as a disruptive technology that requires a rethink of vegetation surveys and their application across a wide range of disciplines. We review the development of TLS as a plotscale measurement tool, including the evolution of both instrument hardware and key data processing methodologies. We highlight two broad data modelling approaches of gap probability and geometrical modelling and the basic theory that underpins these. Finally, we discuss the future prospects for increasing the utilisation of TLS for plot-scale forest assessment and forest monitoring