Biological soil crusts (BSCs) are an important source of organic carbon, and affect a range of ecosystem functions in arid and semiarid environments. Yet the impact of grazing disturbance on crust properties and soil CO 2 efflux remain poorly studied, particularly in African ecosystems. The effects of burial under wind-blown sand, disaggregation and removal of BSCs on seasonal variations in soil CO 2 efflux, soil organic carbon, chlorophyll a and scytonemin were investigated at two sites in the Kalahari of southern Botswana. Field experiments were employed to isolate CO 2 efflux originating from BSCs in order to estimate the C exchange within the crust. Organic carbon was not evenly distributed through the soil profile but concentrated in the BSC. Soil CO 2 efflux was higher in Kalahari Sand than in calcrete soils, but rates varied significantly with seasonal changes in moisture and temperature. BSCs at both sites were a small net sink of C to the soil. Soil CO 2 efflux was significantly higher in sand soils where the BSC was removed, and on calcrete where the BSC was buried under sand. The BSC removal and burial under sand also significantly reduced chlorophyll a , organic carbon and scytonemin . Disaggregation of the soil crust, however, led to increases in chlorophyll a and organic carbon. The data confirm the importance of BSCs for C cycling in drylands and indicate intensive grazing, which destroys BSCs through trampling and burial, will adversely affect C sequestration and storage. Managed grazing, where soil surfaces are only lightly disturbed, would help maintain a positive carbon balance in African drylands.
", "keywords": ["Chlorophyll", "2. Zero hunger", "Conservation of Natural Resources", "Botswana", "Indoles", "Chlorophyll A", "Temperature", "Water", "04 agricultural and veterinary sciences", "Carbon Dioxide", "15. Life on land", "Poaceae", "Carbon", "Fires", "Carbon Cycle", "Soil", "Phenols", "13. Climate action", "Animals", "0401 agriculture", " forestry", " and fisheries", "Herbivory", "Seasons", "Desert Climate", "Ecosystem", "Soil Microbiology"], "contacts": [{"organization": "Andrew D. Thomas", "roles": ["creator"]}]}, "links": [{"href": "https://doi.org/10.1098/rstb.2012.0102"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Philosophical%20Transactions%20of%20the%20Royal%20Society%20B%3A%20Biological%20Sciences", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1098/rstb.2012.0102", "name": "item", "description": "10.1098/rstb.2012.0102", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1098/rstb.2012.0102"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2012-11-19T00:00:00Z"}}, {"id": "10.1111/j.1438-8677.2012.00627.x", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-19T16:17:25Z", "type": "Journal Article", "created": "2012-06-05", "title": "Physiological And Biochemical Responses Ofquercus Pubescensto Air Warming And Drought On Acidic And Calcareous Soils", "description": "AbstractThe drought\uffe2\uff80\uff90 and thermo\uffe2\uff80\uff90tolerant Quercus pubescens, a tree species growing on both acidic and calcareous soils in the sub\uffe2\uff80\uff90Mediterranean region, was exposed to soil drought (\uffe2\uff88\uff9260% to \uffe2\uff88\uff9280% soil water content) and air warming (+1.2\uffe2\uff80\uff83\uffc2\uffb0C daytime temperature), singly and in combination. The experiment was conducted on two natural forest soils with similar texture but different pH (acidic and calcareous soils). The physiological (photosynthesis) and biochemical (antioxidant system) responses of Q.\uffc2\uffa0pubescens were investigated. On acidic soil, Q.\uffc2\uffa0pubescens had a higher reactive oxygen species (ROS) content than on calcareous soil, confirming that this species is better adapted to the latter soil type. A down\uffe2\uff80\uff90regulation of ascorbate\uffe2\uff80\uff90glutathione cycle enzymes suggests that ROS were used as signalling molecules. Air warming stimulated stomatal opening, while soil drought induced stomatal closure in the late afternoon and reduced Rubisco carboxylation efficiency. Photosynthetic performance in the combined treatment was higher than under single drought stress and similar to control and air warming. Q.\uffc2\uffa0pubescens biochemical responses depended on soil pH. On acidic soil, Q.\uffc2\uffa0pubescens trees exposed to air warming used ROS as signalling molecules. On calcareous soil, these trees were able to balance both soil drought and air warming stress, avoiding ROS toxic effects by increasing antioxidant enzyme activitiy and maintaining a high enzymatic antioxidant defence. When combined, drought and air warming induced either more severe (higher oxidative pressure and impairment of the light\uffe2\uff80\uff90harvesting complex) or different responses (decline of the thermal energy dissipation capacity) relative to the single stressors. Overall, however, Q.\uffc2\uffa0pubescens preserved the functionality of the photosynthetic apparatus and controlled the antioxidant system response, thus confirming its drought and thermo\uffe2\uff80\uff90tolerance and therefore its potential to adapt to the ongoing climate change.
", "keywords": ["0106 biological sciences", "0301 basic medicine", "Hot Temperature", "Climate", "Ribulose-Bisphosphate Carboxylase", "Light-Harvesting Protein Complexes", "Down-Regulation", "Global Warming", "01 natural sciences", "Antioxidants", "Quercus", "Soil", "03 medical and health sciences", "Antioxidant enzyme; ascorbate-glutathione cycle; chlorophyll a fluorescence; gas exchange; oak", "Stress", " Physiological", "Photosynthesis", "Ecosystem", "Antioxidant enzyme; ascorbate-glutathione cycle; chlorophyll a fluorescence; gas exchange; oak.", "Air", "Water", "15. Life on land", "Hydrogen-Ion Concentration", "Adaptation", " Physiological", "6. Clean water", "Droughts", "Oxidative Stress", "13. Climate action", "Plant Stomata"]}, "links": [{"href": "https://doi.org/10.1111/j.1438-8677.2012.00627.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Plant%20Biology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1438-8677.2012.00627.x", "name": "item", "description": "10.1111/j.1438-8677.2012.00627.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1438-8677.2012.00627.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2012-06-05T00:00:00Z"}}, {"id": "10.1594/pangaea.615227", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-19T16:17:59Z", "type": "Dataset", "title": "Chlorophyll and phaeopigments in surface sediment profile PE236-20", "description": "Chlorophyll a and Phaeopigments were extracted with acetone 90% from freezed dried sediment following the method of Yentsch & Menzel (1963): A method for the determination of phytoplankton chlorophyll a and phaeophytin by fluorescence. Deep-Sea Res 10: 221-231. Chlorophyll a and Phaeopigments were measured with a Turner 700 fluorometre following Shuman and Lorenzen (1975): Quantitative degradation of chlorophyll by a marine herbivore, Limnology and Oceanography, 20.", "keywords": ["Replicates", "PE2xx", "bottom max", "Chlorophyll a", "Depth", "Depth", " top/min", "DEPTH", " sediment/rock", "Hotspot Ecosystem Research on the Margins of European Seas HERMES", "Chlorophyll pigment equivalents", "sediment rock", "Chloroplastic pigment equivalents", "Phaeopigments", " standard deviation", "Chloroplastic pigment equivalents", " standard deviation", "European Margin Strata Formation (EuroSTRATAFORM)", "DEPTH", "top min", "Earth System Research", "Depth", " bottom/max", "14. Life underwater", "standard deviation", "Phaeopigments", "Chlorophyll a", " standard deviation", "European Margin Strata Formation EuroSTRATAFORM", "Hotspot Ecosystem Research on the Margins of European Seas (HERMES)", "MultiCorer"], "contacts": [{"organization": "Garcia, Rosa, Thomsen, Laurenz,", "roles": ["creator"]}]}, "links": [{"href": "https://doi.org/10.1594/pangaea.615227"}, {"rel": "self", "type": "application/geo+json", "title": "10.1594/pangaea.615227", "name": "item", "description": "10.1594/pangaea.615227", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1594/pangaea.615227"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2007-01-01T00:00:00Z"}}, {"id": "10451/59767", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-19T16:21:16Z", "type": "Journal Article", "created": "2018-11-03", "title": "\u03b415N of lichens reflects the isotopic signature of ammonia source", "description": "Although it is generally accepted that \u03b415N in lichen reflects predominating N isotope sources in the environment, confirmation of the direct correlation between lichen \u03b415N and atmospheric \u03b415N is still missing, especially under field conditions with most confounding factors controlled. To fill this gap and investigate the response of lichens with different tolerance to atmospheric N deposition, thalli of the sensitive Evernia prunastri and the tolerant Xanthoria parietina were exposed for ten weeks to different forms and doses of N in a field manipulation experiment where confounding factors were minimized. During this period, several parameters, namely total N, \u03b415N and chlorophyll a fluorescence, were measured. Under the experimental conditions, \u03b415N in lichens quantitatively responded to the \u03b415N of released gaseous ammonia (NH3). Although a high correlation between the isotopic signatures in lichen tissue and supplied N was found both in tolerant and sensitive species, chlorophyll a fluorescence indicated that the sensitive species very soon lost its photosynthetic functionality with increasing N availability. The most damaging response to the different N chemical forms was observed with dry deposition of NH3, although wet deposition of ammonium ions had a significant observable physiological impact. Conversely, there was no significant effect of nitrate ions on chlorophyll a fluorescence, implying differential sensitivity to dry deposition versus wet deposition and to ammonium versus nitrate in wet deposition. Evernia prunastri was most sensitive to NH3, then NH4+, with lowest sensitivity to NO3-. Moreover, these results confirm that lichen \u03b415N can be used to indicate the \u03b415N of atmospheric ammonia, providing a suitable tool for the interpretation of the spatial distribution of NH3 sources in relation to their \u03b415N signal.", "keywords": ["Air Pollutants", "Nitrates", "Lichens", "Nitrogen Isotopes", "Chlorophyll A", "0211 other engineering and technologies", "02 engineering and technology", "Models", " Theoretical", "chlorophyll a fluorescence", "01 natural sciences", "nitrogen deposition", "Xanthoria parietina", "Species Specificity", "Ammonia", "13. Climate action", "source spatial distribution", "biomonitoring", "physiological response", "Photosynthesis", "Environmental Monitoring", "0105 earth and related environmental sciences"]}, "links": [{"href": "https://repositorio.ulisboa.pt/bitstream/10451/59767/1/1-s2.0-S0048969718343560-main.pdf"}, {"href": "https://doi.org/10451/59767"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Science%20of%20The%20Total%20Environment", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10451/59767", "name": "item", "description": "10451/59767", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10451/59767"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2019-02-01T00:00:00Z"}}, {"id": "11585/582157", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-19T16:21:25Z", "type": "Journal Article", "created": "2017-01-04", "title": "The cost of surviving nitrogen excess: energy and protein demand in the lichen Cladonia portentosa as revealed by proteomic analysis", "description": "Different nitrogen forms affect different metabolic pathways in lichens. In particular, the most relevant changes in protein expression were observed in the fungal partner, with NO 3- mostly affecting the energetic metabolism and NH 4+ affecting transport and regulation of proteins and the energetic metabolism much more than NO 3- did. Excess deposition of reactive nitrogen is a well-known agent of stress for lichens, but which symbiont is most affected and how, remains a mystery. Using proteomics can expand our understanding of stress effects on lichens. We investigated the effects of different doses and forms of reactive nitrogen, with and without supplementary phosphorus and potassium, on the proteome of the lichen Cladonia portentosa growing in a 'real-world' simulation of nitrogen deposition. Protein expression changed with the nitrogen treatments but mostly in the fungal partner, with NO3- mainly affecting the energetic metabolism and NH4+ also affecting the protein synthesis machinery. The photobiont mainly responded overexpressing proteins involved in energy production. This suggests that in response to nitrogen stress, the photobiont mainly supports the defensive mechanisms initiated by the mycobiont with an increased energy production. Such surplus energy is then used by the cell to maintain functionality in the presence of NO3-, while a futile cycle of protein production can be hypothesized to be induced by NH4+ excess. External supply of potassium and phosphorus influenced differently the responses of particular enzymes, likely reflecting the many processes in which potassium exerts a regulatory function.", "keywords": ["Chlorophyll", "Proteomics", "0301 basic medicine", "570", "mycobiont", "Lichens", "Nitrogen", "Cell Respiration", "Nitrate", "Mass Spectrometry", "Molecular mechanism", "03 medical and health sciences", "nitrate", "Ammonia", "Electrophoresis", " Gel", " Two-Dimensional", "Photosynthesis", "Ammonium", " Molecular mechanism", " Mycobiont", " Nitrate", " Photobiont", " Stress response", "Ammonium; Molecular mechanism; Mycobiont; Nitrate; Photobiont; Stress response; Genetics; Plant Science", "0303 health sciences", "Nitrates", "Stress response", "Chlorophyll A", "stress response", "Mycobiont", "ammonium", "Photobiont", "photobiont", "molecular mechanism", "Energy Metabolism", "Ammonium"]}, "links": [{"href": "http://link.springer.com/content/pdf/10.1007/s00425-017-2647-2.pdf"}, {"href": "https://doi.org/11585/582157"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Planta", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "11585/582157", "name": "item", "description": "11585/582157", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/11585/582157"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2017-01-04T00:00:00Z"}}], "links": [{"rel": "self", "type": "application/geo+json", "title": "This document as GeoJSON", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=Chlorophyll+A&f=json", "hreflang": "en-US"}, {"rel": "alternate", "type": "text/html", "title": "This document as HTML", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=Chlorophyll+A&f=html", "hreflang": "en-US"}, {"rel": "collection", "type": "application/json", "title": "Collection URL", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main", "hreflang": "en-US"}, {"type": "application/geo+json", "rel": "first", "title": "items (first)", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=Chlorophyll+A&", "hreflang": "en-US"}, {"rel": "last", "type": "application/geo+json", "title": "items (last)", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=Chlorophyll+A&offset=7", "hreflang": "en-US"}], "numberMatched": 7, "numberReturned": 7, "distributedFeatures": [], "timeStamp": "2026-09-20T13:05:41.562889Z"}