Comparative Analysis of GEDI’s Elevation Accuracy from the First and Second Data Product Releases over Inland Waterbodies

Spaceborne LiDAR altimetry has been demonstrated to be an essential source of data for the estimation and monitoring of inland water level variations. In this study, water level estimates from the Global Ecosystem Dynamics Investigation (GEDI) were validated against in situ gauge station records over Lake Geneva for the period between April 2019 and September 2020. The performances of the first and second releases (V1 and V2, respectively) of the GEDI data products were compared, and the effects on the accuracy of the instrumental and environmental factors were analyzed in order to discern the most accurate GEDI acquisitions. The respective influences of five parameters were analyzed in this study: (1) the signal-over-noise ratio (SNR); (2) the width of the water surface peak within the waveform (gwidth); (3) the amplitude of the water surface peak within the waveform (A); (4) the viewing angle of GEDI (VA); and (5) the acquiring beam. Results indicated that all these factors, except the acquiring beam, had an effect on the accuracy of GEDI elevations. Nonetheless, using VA as a filtering criterion was demonstrated to be the best compromise between retained shot count and water level estimation accuracy. Indeed, by choosing the shots with a VA ≤ 3.5°, 74.6% of the shots (after an initial filter) were retained with accuracies similar to choosing A > 400 (46.2% retained shots), SNR > 15 dB (63.3% retained shots), or gwidth < 10 bins (46.5% of retained shots). Finally, the comparison between V1 and V2 elevations showed that V2, overall, provided elevations with a more constant, but higher, bias and fewer deviations to the in situ data than V1. Indeed, by choosing GEDI shots with VA ≤ 3.5°, the unbiased RMSE (ubRMSE) of GEDI elevations was 27.1 cm with V2 (r = 0.66) and 42.8 cm with V1 (r = 0.34). Results also show that the accuracy of GEDI (ubRMSE) does not seem to depend on the beam number and GEDI acquisition dates for the most accurate GEDI acquisitions (VA ≤ 3.5°). Regarding the bias, a higher value was observed with V2, but with lower variability (54 cm) in comparison to V1 (35 cm). Finally, the bias showed a slight dependence on beam GEDI number and strong dependence on GEDI dates.

The Climate Change Response of Pacific Ocean Squids

Climate change is proving to be a driving factor reshaping the distribution and altering the movement of marine species, dynamics of which are crucial for sustainable development and marine resources management. However, how Pacific Ocean squids – boasting the salient biological features of a one-year life span and strong adaptive abilities, and which support more than 25% of global squid catches – respond to climate change is overlooked. We address this knowledge gap by constructing spatio-temporal generalized additive mixed models based on hundreds of thousands of digitized Chinese squid-jigging logbooks covering three Pacific stocks of two squid species (Ommastrephes bartramii and Dosidicus gigas) spanning 2005 – 2018. Here we show the relationships between environmental variables and local abundance of squids (reflected by response curves) track changes in climate; the squid biomass peaks and troughs coinciding with La Niña and El Niño events, respectively are moderate in contrast to the effects of directional climate change. We find substantial poleward shifts by squids inhabiting low latitude and middle latitudes. These findings have broad implications both for food security and open ocean ecosystem dynamics.

Assessing Potential Safety Zone Suitability Using a New Online Mapping Tool

Safety zones (SZs) are critical tools that can be used by wildland firefighters to avoid injury or fatality when engaging a fire. Effective SZs provide safe separation distance (SSD) from surrounding flames, ensuring that a fire’s heat cannot cause burn injury to firefighters within the SZ. Evaluating SSD on the ground can be challenging, and underestimating SSD can be fatal. We introduce a new online tool for mapping SSD based on vegetation height, terrain slope, wind speed, and burning condition: the Safe Separation Distance Evaluator (SSDE). It allows users to draw a potential SZ polygon and estimate SSD and the extent to which that SZ polygon may be suitable, given the local landscape, weather, and fire conditions. We begin by describing the algorithm that underlies SSDE. Given the importance of vegetation height for assessing SSD, we then describe an analysis that compares LANDFIRE Existing Vegetation Height and a recent Global Ecosystem Dynamics Investigation (GEDI) and Landsat 8 Operational Land Imager (OLI) satellite image-driven forest height dataset to vegetation heights derived from airborne lidar data in three areas of the Western US. This analysis revealed that both LANDFIRE and GEDI/Landsat tended to underestimate vegetation heights, which translates into an underestimation of SSD. To rectify this underestimation, we performed a bias-correction procedure that adjusted vegetation heights to more closely resemble those of the lidar data. SSDE is a tool that can provide valuable safety information to wildland fire personnel who are charged with the critical responsibility of protecting the public and landscapes from increasingly intense and frequent fires in a changing climate. However, as it is based on data that possess inherent uncertainty, it is essential that all SZ polygons evaluated using SSDE are validated on the ground prior to use.

Phages in the Gut Ecosystem

Phages, short for bacteriophages, are viruses that specifically infect bacteria and are the most abundant biological entities on earth found in every explored environment, from the deep sea to the Sahara Desert. Phages are abundant within the human biome and are gaining increasing recognition as potential modulators of the gut ecosystem. For example, they have been connected to gastrointestinal diseases and the treatment efficacy of Fecal Microbiota Transplant. The ability of phages to modulate the human gut microbiome has been attributed to the predation of bacteria or the promotion of bacterial survival by the transfer of genes that enhance bacterial fitness upon infection. In addition, phages have been shown to interact with the human immune system with variable outcomes. Despite the increasing evidence supporting the importance of phages in the gut ecosystem, the extent of their influence on the shape of the gut ecosystem is yet to be fully understood. Here, we discuss evidence for phage modulation of the gut microbiome, postulating that phages are pivotal contributors to the gut ecosystem dynamics. We therefore propose novel research questions to further elucidate the role(s) that they have within the human ecosystem and its impact on our health and well-being.

Dependência, pressão e recuperação de recursos florestais no Parque Nacional do Limpopo (Moçambique)

The general perception is that forest resources exploitation can cause the degradation and loss of resources and biodiversity, promoted by landscape fragmentation and pressure over habitats. But such assumption might not be adjusted to situations where long term exploitation by traditional communities is based on management strategies adapted to recovery, adjusting pressure to kept resources available. In this work, we assess the recovery of the Mopane woodlands considering different land use practices and stand development stages on areas explored by local communities. In detail, we want to explore: i) changes on stem size across plant comunities dominated by Mopane (Kirk ex Benth ex J. Leonard); ii) relationships between the variation in stem size across communities and the associated land use practices and vegetation stand development stage. To answer those questions, an inventory was carried out to collect data from 50 temporary circular plots of different sizes spatially nested, covering four stand development stages. Each nested circular plot was composed of a large plot (0.02 ha), an intermediate plot (0.04 ha), and an inner plot (0.01 ha) for counting stems of different DBH. Data was analysed using Excel, Two-Way Indicator Species Analysis (TWINSPAN) and CANOCO, and several parametric and non-parametric tests. TWINSPAN analysis, using stem counts, grouped the 1746 stems from 29 species (with Mopane as one species) into 5 communities and 10 sub-communities, based on indicator species and eigenvalues (level of stability). This study was carried out in the Limpopo National Park (LNP), in Mozambique, a conservation area established in 2001 and part of the Great Limpopo Transfrontier Park (GLTP) since 2002. Acording to the results, population structure (size class distribution of trees) of Mopane communities showed variation related to stand development stage, as expected. The initial stages show good regeneration, indicating that recovery is not hampered by the exploitation regime in use, a critical aspect once ecosystem dynamics of Mopane woodland has a deep influence on the way that local communities manage harvesting of Mopane products for different uses, and traditional uses do also have influence on recovery dynamics. So, management of such resource is critical to ensure sustainable resource use and guarantee provision for future generations. For that, a zonation of Mopane woodlands within the Park, considering different land uses, might enhance a quick system recovery on specific areas and contribute to woodland productivity, good quality products and reduce used areas, promoting habitat conservation.

Evaluating the Spring-Neap Tidal Effects on Chlorophyll-a Variations Based on the Geostationary Satellite

Tides are the dominant hydrodynamic processes in most continental shelf seas and have been proven to have a significant impact on both marine ecosystem dynamics and biogeochemical cycles. In situ and satellite observations have suggested that the spring-neap tide results in fluctuations of chlorophyll-a concentrations (Chl-a) with a fortnightly period in some shelf waters. However, a large number of missing values and low observation frequency in satellite-observed Chl-a have been recognized as the major obstacle to investigating the regional pattern showing where and to what extent of the effects of spring-neap tide on Chl-a and the seasonal variations in the effects within a relatively large region. Taking Himawari-8 as an example, a simple algorithm appropriate for geostationary satellites was proposed in this study with the purpose of obtaining a tide-related daily climatological Chl-a dataset (TDCD) and to quantitatively estimate the effects of the spring-neap tide on Chl-a variations. Based on the Chl-a time series from TDCD, significant fortnightly signals of Chl-a fluctuations and high contribution together with high explanations of the fortnightly fluctuations for Chl-a variations were found in some specific inshore waters, especially in the East China Sea, Bay of Bengal, South China Sea, and northern Australian waters. The spring-neap tide was found able to induce the spatio-temporal fortnightly fluctuations of Chl-a with an annual amplitude of 12–33% of the mean in these inshore areas. Significant seasonal variations in the fortnightly fluctuation of Chl-a were observed in the temperate continental shelf regions, while levels remained relatively stable in the tropical waters. Further analysis implied that the spatio-temporal fortnightly fluctuations of Chl-a were closely associated with the tidal current differences between the spring and neap tides. Seasonal variations in the tidal current differences were found to be a key driving factor for seasonal fluctuations of the spring-neap tidal effects on Chl-a in the temperate continental shelf regions. This study provides a better understanding of tide-related marine ecosystem dynamics and biogeochemical cycles and is helpful in improving physical–biogeochemical models.

Examining the Role of Marine Mammals and Seabirds in Southeast Alaska’s Marine Ecosystem Dynamics

Primary producers are the foundation of marine food webs and require reliable nutrient sources to maintain their important role with ecosystems. While marine mammals and seabirds can play critical roles in marine nutrient cycling, their contributions are often overlooked. Southeast Alaska’s marine environment supports abundant marine mammal and seabird populations in addition to valuable fisheries. Nonetheless, there is still relatively little known about nutrient sources and fluxes in this region which is a critical component of fisheries management. The goal of our study was to advance knowledge of the role of mammals and seabirds in marine nutrient cycling and to understand how changing marine mammal and seabird populations may alter ecosystem dynamics. We utilized qualitative network models (QNMs) to examine how a simulated Southeast Alaska ecosystem would respond to an increase in marine mammals, seabirds, and nutrients. Researchers are increasingly utilizing QNMs as a first step in the development of ecosystem-based fisheries management plans as their adaptable nature is well suited to address rapidly changing climatic conditions. Our results indicate that marine mammals and seabirds make important contributions to marine nutrient concentrations in the region and that these valuable ecosystem services should not be overlooked.

Ecosystem dynamics after forest fire. Blideen Atlas case

Human disturbances affect the majority of terrestrial ecosystems. The radical changes in the behaviour of ecological systems, partial or total destruction of plant biomass, often with the death of fundamental entities. Of these disturbances, fires affect many terrestrial ecosystems, particularly forests, by changing their floristic composition, their structure and their functioning; the global average annual forest area burned is estimated at 65 million ha. The Mediterranean basin, a hotspot, annually loses between 0.5 and 1 million hectares of forest. In Algeria, the annual average of areas destroyed by fire is between 45,000 and 50,000 ha. Our work set out to study the changes in the plant coverage of the land one year after the passage of fire. We studied the effects at the floristic, ecological and dynamic level in a forest ecosystem located in the north of Algeria (Atlas Blideen). The phytoecological inventory of vegetation (74 surveys, 162 species) was carried out from subjective sampling. To highlight the different groupings in the study area, classical statistical treatments (factorial analysis of correspondences) were applied to the floristic and ecological data. The results of computer processing made it possible to individualize and classify four plant groups according to the degree of the fire. The qualitative and quantitative analysis of these groups shows a therophytization of the flora, due to the regression of the forest cover (disappearance of the phanerophytes) caused by the passage of fire, with a floral procession represented mainly by Asteraceae, Poaceae and Fabaceae and an index disturbance which greatly exceeds 50%. However, some tree and shrub taxa such as cork oak, holm oak and Pistacia lentiscus tree have the capacity to reappear by rejecting the calcined stumps.