nasa-gesdisc/es-publications-researchareas huggingface dataset:
Satellite Retrievals of Probabilistic Freeze-Thaw Conditions from SMAP and AMSR Brightness Temperatures (2022)

The freeze-thaw (FT) status of soil regulates ecological and hydrologic processes and is, therefore, a vital component of land surface models. This study utilizes a hidden Markov model (HMM) to retrieve surface FT status from L-band [Soil Moisture Active Passive (SMAP)] and Ka-band [Advanced Microwave Scanning Radiometer (AMSR)] satellite microwave brightness temperatures in cold-constrained lands north of  $45 ^\circ \textN$ . The HMM, parameterized on a per-gridcell basis such that there are two possible states and emissions probabilities are assumed to be a two-component Gaussian Mixture, produces the posterior probability (a continuous variable between 0 and 1) that the surface is frozen given the radiometer input. HMM classification accuracy, averaged over five core validation networks, is acceptable (Ap > 80%) when judged against in situ air and soil temperature measurements from individual validation sites and is comparable to that of current FT products that produce a discrete state. Patterns in performance across variable land class, open water fraction, and elevation are assessed from 91 sparse network weather stations within 87 gridcells in the domain. The resulting satellite data record provides a continuous variable estimate of the daily probability of frozen conditions over northern land areas experiencing widespread thawing of permafrost and a shrinking frozen season due to global warming.

Research areas: Land Surface/Agriculture Indicators
An Improved Method for Pan-Tropical Above-Ground Biomass and Canopy (2021)

An improved method for retrieving Above-ground Biomass (AGB) and Canopy Height (CH) based on an observable from Cyclone Global Navigation Satellite System (CYGNSS), soil moisture from Soil Moisture Active Passive (SMAP) and location is proposed. The observable derived from CYGNSS is more sensitive to vegetation. The CYGNSS observable, soil moisture and the location are used as the input features of an Artificial Neural Network (ANN) to retrieve AGB and CH. The sensitivity analysis of the CYGNSS observable to target parameters shows that the proposed observable is more sensitive to AGB/CH than the conventional observable. The AGB/CH retrievals of the improved method show that it has better performance than that of the traditional method, especially in the areas with AGB in the range of 0 to100 Mg/ha and CH in the range of 0 to10 m. For AGB retrievals, the root mean square error (RMSE) and correlation coefficient are 64.84 Mg/ha and 0.80 in the range of 0 to 550 Mg/ha. Compared with the traditional method, the RMSE is decreased by 11.63%, while the correlation coefficient is increased by 5.26%. For CH retrievals, the RMSE and correlation coefficient are 5.97 m and 0.83 in the range of 0 to 45 m. The RMSE is decreased by 12.59%, while the correlation coefficient is increased by 5.06%. The analysis of the improved method in different areas shows that the performance of the improved method over the area with high vegetation is better than the area with low vegetation. The results obtained here further strengthens the capability of GNSS-R for global AGB/CH retrievals as well as different land cover areas.

Research areas: Validation
Modelling temporal variability of in situ soil water and vegetation isotopes reveals ecohydrological couplings in a riparian willow plot (2022)

Abstract. The partitioning of water fluxes in the critical zone is of great interest due to the implications for understanding water cycling and quantifying water availability for various ecosystem services. We used the tracer-aided ecohydrological model EcH2O-iso to use stable water isotopes to help evaluate water, energy, and biomass dynamics at an intensively monitored study plot under two willow trees, a riparian species, in Berlin, Germany. Importantly, we assessed the value of in situ soil and plant water isotope data in helping to quantify xylem water sources and transit times, with coupled estimates of the temporal dynamics and ages of soil and root uptake water. The willows showed high water use through evapotranspiration, with limited percolation of summer precipitation to deeper soil layers due to the dominance of shallow root uptake (>80 % in the upper 10 cm, 70 %78 % transpiration/evapotranspiration). Lower evapotranspiration under grass (52 %55 % transpiration/evapotranspiration) resulted in higher soil moisture storage, greater soil evaporation, and more percolation of soil water. Biomass allocation was predominantly foliage growth (57 % in grass and 78 % in willow). Shallow soil water age under grass was estimated to be similar to under willows (1517 d). Considering potential xylem transit times showed a substantial improvement in the model's capability to simulate xylem isotopic composition and water ages and demonstrates the potential value of using in situ data to aid ecohydrological modelling. Root water uptake was predominately derived from summer precipitation events (56 %) and had an average age of 35 d, with xylem transport times taking at least 6.28.1 d. By evaluating isotope mass balances along with water partitioning, energy budgets, and biomass allocation, the EcH2O-iso model proved a useful tool for assessing water cycling within the critical zone at high temporal resolution, particularly xylem water sources and transport, which are all necessary for short- and long-term assessment of water availability for plant growth.

Research areas: Ecosystems, Land Surface/Agriculture Indicators
Land Use and Climate Change Altered the Ecological Quality in the Luanhe River Basin (2022)

Monitoring and assessing ecological quality (EQ) can help to understand the status and dynamics of the local ecosystem. Moreover, land use and climate change increase uncertainty in the ecosystem. The Luanhe River Basin (LHRB) is critical to the ecological security of the BeijingTianjinHebei region. To support ecosystem protection in the LHRB, we evaluated the EQ from 2001 to 2020 based on the Remote Sensing Ecological Index (RSEI) with the Google Earth Engine (GEE). Then, we introduced the coefficient of variation, TheilSen analysis, and MannKendall test to quantify the variation and trend of the EQ. The results showed that the EQ in LHRB was relatively good, with 61.08% of the basin rated as good or excellent. The spatial distribution of EQ was low in the north and high in the middle, with strong improvement in the north and serious degradation in the south. The average EQ ranged from 0.58 to 0.64, showing a significant increasing trend. Furthermore, we found that the expansion of construction land has caused degradation of the EQ, whereas climate change likely improved the EQ in the upper and middle reaches of the LHRB. The results could help in understanding the state and trend of the eco-environment in the LHRB and support decision-making in land-use management and climate change.

Research areas: Ecosystems
Satellite footprint data from OCO-2 and TROPOMI reveal significant spatio-temporal and inter-vegetation type variabilities of solar-induced fluorescence yield in the US … (2020)

Solar-induced chlorophyll fluorescence (SIF) measured from space has been increasingly used to quantify plant photosynthesis at regional and global scales. Apparent canopy SIF yield (SIFyield apparent), determined by fluorescence yield (F) and escaping ratio (fesc), together with absorbed photosynthetically active radiation (APAR), is crucial in driving spatio-temporal variability of SIF. While strong linkages between SIFyield apparent and plant physiological responses and canopy structure have been suggested, spatio-temporal variability of SIFyield apparent at regional scale remains largely unclear, which limits our understanding of the spatio-temporal variability of SIF and its relationship with photosynthesis. In this study, we utilized recent SIF data with high spatial resolution from two satellite instruments, OCO-2 and TROPOMI, together with multiple other datasets. We estimated SIFyield apparent across space, time, and different vegetation types in the U.S. Midwest during crop growing season (May to September) from 2015 to 2018. We found that SIFyield apparent of croplands was larger than non-croplands during peak season (JulyAugust). However, SIFyield apparent between corn (C4 crop) and soybean (C3 crop) did not show a significant difference. SIFyield apparent of corn, soybean, forest, and grass/pasture show clear seasonal and spatial patterns. The spatial variability of precipitation during the growing season could explain the overall spatial pattern of SIFyield apparent. Further analysis by decomposing SIFyield apparent into F and fesc using near-infrared reflectance of vegetation (NIRV) suggests that fesc may be the major driver of the observed variability of SIFyield apparent.

Research areas: Agriculture, Land Surface/Agriculture Indicators
Disentangling the effects of hydro-climatic factors and land use intensification on wetland vegetation dynamics in the Lower Delta of the Paraná River (2021)

The non-insular portion of the Lower Delta of the Parana River is part of the largest mosaic of wetlands in Argentina. However, it is being altered by intensification of cattle grazing and the increasingly rapid implementation of water management infrastructure. In this context, studying the relationship between hydro-climatic variables and vegetation growth is urgent to ensure sound management and conservation. To overcome the limitation of high cloud cover in the area which has hampered the construction of regularly spaced high-resolution time series, we implemented the recently developed spatio-temporal vegetation index image fusion model (STVIFM). In order to understand the relationship between vegetation growth and hydro-climatic factors, we performed pixel-wise correlation analyses between the newly synthesized monthly (30m) NDVI time series and hydro-climatic variables. Then, we tested whether water control infrastructure alters these relationships. Based on the accurate performance of STVIFM, we provide quantitative and spatially accurate evidence on the positive, complementary and heterogeneous relationships between vegetation growth, temperature, rainfall and the flood pulse. Our results show that water management infrastructure decouples certain areas from its natural hydrological regime, decreasing water availability and altering vegetation growth dynamics. In this context, urgent action is needed aimed towards implementing land planning measures that consider the natural variability and hydrologic regime of the system while balancing production and conservation.

Research areas: Land Surface/Agriculture Indicators
An Integrated Approach for Detection and Prediction of Greening (2020)

The combined study of vegetation coverage (VC) and land use change provides important scientific guidance for the restoration and protection of arid regions. Taking Hongjian Nur (HJN) Lake in the desert region as a case study, the VC of this area was calculated using a normalized difference vegetation index (NDVI), which is based on a mixed pixel decomposition method. A grey forecasting model (GM) (1, 1) was used to predict future VC. The driving factors of VC and land use change were analyzed. The results indicate that the average VC of the whole watershed showed a gradual increase from 0.29 to 0.49 during 20002017. The prediction results of the GM VC showed that the greening trend is projected to continue until 2027. The area of farmland in the watershed increased significantly and its area was mainly converted from unused land, grassland, and forest. The reason for increased VC may be that the combination of the exploitation of unused land and climate change, which is contrary to the countrys sustainable development goals (SDG; goal 15). Therefore, the particularities of the local ecological environment in Chinas desert area needs to be considered in the development of ecological engineering projects.

Research areas: Land Surface/Agriculture Indicators
THE RESILIENCE OF ETHIOPIAN CHURCH FORESTS: INTERPRETING AERIAL (2017)

Church forests collectively represent the only surviving remnants of the original montane forest, serving as critical sanctuaries for many of Ethiopia's endangered and endemic plant and invertebrate taxa. Modern inventories of church forests suggest that they are vulnerable to degradation because of their small size and isolation. The aim of this study is to use historical air photos from the period of the Italian occupation of Ethiopia (1935–1941) to measure changes to church forests over a ~80‑year time span. We find little evidence that church forests in the study region around Debra Tabor in the northern Ethiopia highlands are declining in size. Rather, church forests have proven to be remarkably resilient on the landscape despite decades of dramatic change to the world around them. Our findings, therefore, highlight the effectiveness of religion‑based forest stewardship. Results also indicate, however, that while many church forests used to be buffered from intensive agricultural activity (e.g., cultivation and pasture) today, they find themselves significantly more isolated and vulnerable to edge effects as a result of a general decrease of trees and bushlands surrounding the forests. Copyright

Research areas: Ecosystems
Assessing Multi-Temporal Global Urban Land-Cover Products Using (2022)

In recent years, the availability of multi-temporal global land-cover datasets has meant that they have become a key data source for evaluating land cover in many applications. Due to the high data volume of the multi-temporal land-cover datasets, probability sampling is an efficient method for validating multi-temporal global urban land-cover maps. However, the current accuracy assessment methods often work for a single-epoch dataset, and they are not suitable for multi-temporal data products. Limitations such as repeated sampling and inappropriate sample allocation can lead to inaccurate evaluation results. In this study, we propose the use of spatio-temporal stratified sampling to assess thematic mappings with respect to the temporal changes and spatial clustering. The total number of samples in the two stages, i.e., map and pixel, was obtained by using a probability sampling model. Since the proportion of the area labeled as no change is large while that of the area labeled as change is small, an optimization algorithm for determining the sample sizes of the different strata is proposed by minimizing the sum of variance of the users accuracy, producers accuracy, and proportion of area for all strata. The experimental results show that the allocation of sample size by the proposed method results in the smallest bias in the estimated accuracy, compared with the conventional sample allocation, i.e., equal allocation and proportional allocation. The proposed method was applied to multi-temporal global urban land-cover maps from 2000 to 2010, with a time interval of 5 years. Due to the spatial aggregation characteristics, the local pivotal method (LPM) is adopted to realize spatially balanced sampling, leading to more representative samples for each stratum in the spatial domain. The main contribution of our research is the proposed spatio-temporal sampling approach and the accuracy assessment conducted for the multi-temporal global urban land-cover product.

Research areas: Habitat Conversion/Fragmentation, Validation
Environmental accounting for ecosystem conservation: Linking societal and ecosystem metabolisms (2017)

This paper proposes an approach to environmental accounting useful for studying the feasibility of socio-economic systems in relation to the external constraints posed by ecological compatibility. The approach is based on a multi-scale analysis of the metabolic pattern of ecosystems and societies and it provides an integrated characterization of the resulting interaction. The text starts with a theoretical part explaining (i) the implicit epistemological revolution implied by the notion of ecosystem metabolism and the fund-flow model developed by Georgescu-Roegen applied to environmental accounting, and (ii) the potentials of this approach to create indicators to assess ecological integrity and environmental impacts. This revolution also makes it possible to carry out a multi-scale integrated assessment of ecosystem and societal metabolisms at the territorial level. In the second part, two applications of this approach using an indicator of the negentropic cost show the possibility to characterize in quantitative and qualitative terms degrees of alteration (crop cultivation, tree plantations) for different biomes (tropical and boreal forests). Also, a case study for land use scenarios has been included. The proposed approach represents an integrated multi-scale tool for the analysis of nature conservation scenarios and strategies.

Research areas: Ecosystems
Ecosystem services from southern African woodlands and their future under global change (2016)

Miombo and mopane woodlands are the dominant land cover in southern Africa. Ecosystem services from these woodlands support the livelihoods of 100 M rural people and 50 M urban dwellers, and others beyond the region. Provisioning services contribute $9  2 billion yr1 to rural livelihoods; 76% of energy used in the region is derived from woodlands; and traded woodfuels have an annual value of $780 M. Woodlands support much of the region's agriculture through transfers of nutrients to fields and shifting cultivation. Woodlands store 1824 PgC carbon, and harbour a unique and diverse flora and fauna that provides spiritual succour and attracts tourists. Longstanding processes that will impact service provision are the expansion of croplands (0.1 M km2; 20002014), harvesting of woodfuels (93 M tonnes yr1) and changing access arrangements. Novel, exogenous changes include large-scale land acquisitions (0.07 M km2; 20002015), climate change and rising CO2. The net ecological response to these changes is poorly constrained, as they act in different directions, and differentially on trees and grasses, leading to uncertainty in future service provision. Land-use change and socio-political dynamics are likely to be dominant forces of change in the short term, but important land-use dynamics remain unquantified.This article is part of the themed issue Tropical grassy biomes: linking ecology, human use and conservation.

Research areas: Land Surface/Agriculture Indicators, Habitat Conversion/Fragmentation
Scaling functional traits from leaves to canopies (2020)

Abstract
            In this chapter, we begin by exploring the relationship between plant functional traits and functional diversity and how this relates to the characterization and monitoring of global plant biodiversity. We then discuss the connection between leaf functional traits and their resulting optical properties (i.e., reflectance, transmittance, and absorption) and how this related to remote sensing (RS) of functional diversity. Building on this, we briefly discuss the history of RS of functional traits using spectroscopy and imaging spectroscopy data. We include a discussion of the key considerations with the use of imaging spectroscopy data for scaling and mapping plant functional traits across diverse landscapes. From here we provide a review of the general methods for scaling and mapping functional traits, including empirical and radiative transfer model (RTM) approaches. We complete the chapter with a discussion of other key considerations, such as field sampling protocols, as well as current caveats and future opportunities.

Research areas: Ecosystems
Molecular Detection and Characterization of Intestinal and Blood (2021)

Wild chimpanzee populations in West Africa (Pan troglodytes verus) have dramatically decreased as a direct consequence of anthropogenic activities and infectious diseases. Little information is currently available on the epidemiology, pathogenic significance, and zoonotic potential of protist species in wild chimpanzees. This study investigates the occurrence and genetic diversity of intestinal and blood protists as well as filariae in faecal samples (n = 234) from wild chimpanzees in the Dindefelo Community Nature Reserve, Senegal. PCR-based results revealed the presence of intestinal potential pathogens (Sarcocystis spp.: 11.5%; Giardia duodenalis: 2.1%; Cryptosporidium hominis: 0.9%), protist of uncertain pathogenicity (Blastocystis sp.: 5.6%), and commensal species (Entamoeba dispar: 18.4%; Troglodytella abrassarti: 5.6%). Entamoeba histolytica, Enterocytozoon bieneusi, and Balantioides coli were undetected. Blood protists including Plasmodium malariae (0.4%), Trypanosoma brucei (1.3%), and Mansonella perstans (9.8%) were also identified. Sanger sequencing analyses revealed host-adapted genetic variants within Blastocystis, but other parasitic pathogens (C. hominis, P. malariae, T. brucei, M. perstans) have zoonotic potential, suggesting that cross-species transmission between wild chimpanzees and humans is possible in areas where both species overlap. Additionally, we explored potential interactions between intestinal/blood protist species and seasonality and climate variables. Chimpanzees seem to play a more complex role on the epidemiology of pathogenic and commensal protist and nematode species than initially anticipated.

Research areas: Ecosystems
Flow structures over mesophotic coral ecosystems in the eastern Gulf of Mexico (2020)

Simultaneous time series of current velocity profiles are used to characterize flow structures over intermediate-depth coral ecosystems in the eastern Gulf of Mexico. Understanding of temporal variability and spatial coherence in flow is necessary to establish connectivity among these ecosystems. Time series were collected at Pulley Ridge (the westernmost site), Northern Dry Tortugas, and Southern Dry Tortugas. Overlapping data spanned the period from March 22, 2013 to June 20, 2015. The strongest currents were approximately 1 m s-1 southeastward at Pulley Ridge. Subtidal velocities from the three sites were decomposed into real-vector, concatenated empirical orthogonal functions (EOFs). Results from EOFs indicated that Mode 1, which explained 63% of the subtidal variance, was roughly in the same direction at each of the three sites. Mode 1 directionality indicated potential interconnectivity between Pulley Ridge and Southern Dry Tortugas, and between Northern Dry Tortugas and Pulley Ridge. Mode 1 also suggested limited to no connectivity between the two Dry Tortugas sites as the flows over the two sites were parallel. Mode 2 explained close to 24% of the variance and showed incoherence among the three sites. Wavelet analysis of EOF coefficients indicated dominance of >1 week variability in this region. Flow variability may be associated with wind forcing and Loop Current variability as confirmed by satellite altimetry. Wind forcing caused part of the intra-monthly (<1 month) periodicity in flows. Sea level in the area of the Loop Current, as derived from EOF application on altimetry data during the period of velocity measurements, was related to Mode 1 of the currents at sub-monthly (>1 month) periods. The relationship was more robust, but inverse, when comparing sea level off the northwestern coast of Cuba to the Mode 1 of the currents. These results characterize physical connectivity among South Florida coral ecosystems and have biophysical implications for coral fish populations.

Research areas: Ecosystems