Global‐scale characterization of turning points in arid and semi‐arid ecosystem functioning

Ecosystems in drylands are highly susceptible to changes in their way of functioning due to extreme and prolonged droughts or anthropogenic perturbation. Long-standing pressure, from climate or human action, may result in severe alterations in their dynamics. Moreover, changes in dryland ecosystems functioning can take place abruptly (Horion et al., 2016). Such abrupt changes may have severe ecological and economic consequences, disturbing the livelihood of drylands inhabitants and causing increased poverty and food insecurity. Considering that drylands cover 40% of Earth&#8217;s land surface and are home to around one-third of the human population, detecting and characterizing hotspots of abrupt changes in ecosystem functioning (here called turning points) becomes even more crucial.BFAST, a time series segmentation technique, was used to detect breakpoints in time series (1982-2015) of rain-use efficiency. An abrupt change in rain-use efficiency time series points towards a significant change in the way an ecosystem responds to precipitation, allowing the study of turning points in ecosystem functioning in both natural and anthropogenic landscapes. Moreover, we here proposed a new typology to characterize turning points in ecosystem functioning, which takes into account the trend in ecosystem functioning before and after the turning point, as well as differences in the rate of change. Case studies were used to evaluate the performance of the new typology. Finally, ancillary data on population density and drought were used to have some first insights about the potential determinants of hotspots of turning point occurrence.Our results showed that 13.6% of global drylands presented a turning point in ecosystem functioning between 1982 and 2015. Hotspots of turning point occurrence were observed in North America (where 62.6% of the turning points were characterized by a decreasing trend in ecosystem functioning), the Sahel, Central Asia, and Australia. The last three hotspot regions were mainly characterized by a positive trend in ecosystem functioning after the turning point. The ancillary data pointed to an influence of both droughts and human action on turning point occurrence in North America, while in Asia and Australia turning point occurrence was higher in areas with higher anthropogenic pressure. In the grasslands of the Sahel, turning points were potentially related to drought.&#160;By detecting where and when hotspots of turning points occurred in recent decades, and by characterizing the trends in ecosystem functioning before and after the turning points, we advanced towards better supporting decision making related to ecosystems conservation and management in drylands. Moreover, we provided first insights about the drivers of ecosystem functioning change in hotspots of turning point occurrence in global drylands (Bernardino et al., 2019).&#160;References:Bernardino PN, De Keersmaecker W, Fensholt R, Verbesselt J, Somers B, Horion S (2019) Global-scale characterization of turning points in arid and semi-arid ecosystems functioning. Manuscript submitted for publication.Horion S, Prishchepov A V., Verbesselt J, de Beurs K, Tagesson T, Fensholt R (2016) Revealing turning points in ecosystem functioning over the Northern Eurasian agricultural frontier. Global change biology, 22, 2801&#8211;2817.

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Remote Sensing Methods for the Biophysical Characterization of Protected Areas Globally: Challenges and Opportunities

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi10060384 ◽

2021 ◽

Vol 10 (6) ◽

pp. 384

Author(s):

Javier Martínez-López ◽

Bastian Bertzky ◽

Simon Willcock ◽

Marine Robuchon ◽

María Almagro ◽

...

Keyword(s):

Remote Sensing ◽

Protected Areas ◽

Large Scale ◽

Anthropogenic Activities ◽

Global Scale ◽

Area Network ◽

Biophysical Characterization ◽

Challenges And Opportunities ◽

Scale Characterization

Protected areas (PAs) are a key strategy to reverse global biodiversity declines, but they are under increasing pressure from anthropogenic activities and concomitant effects. Thus, the heterogeneous landscapes within PAs, containing a number of different habitats and ecosystem types, are in various degrees of disturbance. Characterizing habitats and ecosystems within the global protected area network requires large-scale monitoring over long time scales. This study reviews methods for the biophysical characterization of terrestrial PAs at a global scale by means of remote sensing (RS) and provides further recommendations. To this end, we first discuss the importance of taking into account the structural and functional attributes, as well as integrating a broad spectrum of variables, to account for the different ecosystem and habitat types within PAs, considering examples at local and regional scales. We then discuss potential variables, challenges and limitations of existing global environmental stratifications, as well as the biophysical characterization of PAs, and finally offer some recommendations. Computational and interoperability issues are also discussed, as well as the potential of cloud-based platforms linked to earth observations to support large-scale characterization of PAs. Using RS to characterize PAs globally is a crucial approach to help ensure sustainable development, but it requires further work before such studies are able to inform large-scale conservation actions. This study proposes 14 recommendations in order to improve existing initiatives to biophysically characterize PAs at a global scale.

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Characterization of the Gene Cluster Responsible for Cylindrospermopsin Biosynthesis

Applied and Environmental Microbiology ◽

10.1128/aem.01988-07 ◽

2007 ◽

Vol 74 (3) ◽

pp. 716-722 ◽

Cited By ~ 193

Author(s):

Troco Kaan Mihali ◽

Ralf Kellmann ◽

Julia Muenchhoff ◽

Kevin D. Barrow ◽

Brett A. Neilan

Keyword(s):

Gene Cluster ◽

Global Scale ◽

Open Reading Frames ◽

Cyanobacterial Blooms ◽

Cylindrospermopsis Raciborskii ◽

Economic Losses ◽

Cyanobacterial Toxin ◽

Significant Public Health ◽

Scale Characterization

ABSTRACT Toxic cyanobacterial blooms cause economic losses and pose significant public health threats on a global scale. Characterization of the gene cluster for the biosynthesis of the cyanobacterial toxin cylindrospermopsin (cyr) in Cylindrospermopsis raciborskii AWT205 is described, and the complete biosynthetic pathway is proposed. The cyr gene cluster spans 43 kb and is comprised of 15 open reading frames containing genes required for the biosynthesis, regulation, and export of the toxin. Biosynthesis is initiated via an amidinotransfer onto glycine followed by five polyketide extensions and subsequent reductions, and rings are formed via Michael additions in a stepwise manner. The uracil ring is formed by a novel pyrimidine biosynthesis mechanism and tailoring reactions, including sulfation and hydroxylation that complete biosynthesis. These findings enable the design of toxic strain-specific probes and allow the future study of the regulation and biological role of cylindrospermopsin.

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Isotopic Measurements: A New Tool for Studying Global Carbonyl Sulfide

10.5194/egusphere-egu2020-3528 ◽

2020 ◽

Author(s):

Sophie Baartman ◽

Elena Popa ◽

Maarten Krol ◽

Thomas Röckmann

Keyword(s):

Measurement System ◽

Gross Primary Production ◽

Carbonyl Sulfide ◽

Global Scale ◽

Trace Gas ◽

Promising Tool ◽

Long Lifetime ◽

Scale Characterization ◽

Isotopic Measurements

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth&#8217;s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.Within the framework of the COS-OCS project, we developed a new pre-concentration and measurement system at Utrecht University, that can measure d33S and d34S from COS from 2 to 5 L air samples, with a current precision of about 5&#8240; and 2&#8240; for d33S and d34S, respectively. The aim of the project is to perform a global-scale characterization of COS isotopes by measuring seasonal, latitudinal and altitudinal variations in the troposphere and stratosphere. Here, I will present the details of the new measurement system and results from various atmospheric samples.

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