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- Poyatos, R., et al.
(författare)
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Global transpiration data from sap flow measurements: the SAPFLUXNET database
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 13:6, s. 2607-2649
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Tidskriftsartikel (refereegranskat)abstract
- Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The "sapfluxnetr" R package - designed to access, visualize, and process SAPFLUXNET data - is available from CRAN.
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| 2. |
- Ming, D.W., et al.
(författare)
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Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.
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| 3. |
- Leshin, L.A., et al.
(författare)
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Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 341:6153
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Tidskriftsartikel (refereegranskat)abstract
- Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity’s Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.
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| 7. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Changes in nitrogen cycling in riparian zones along a chronosequence of restored streams in northern Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding how stream restoration affects nitrogen (N) cycling in riparian zones is crucial for setting realistic performance criteria for restored streams. Most streams in northern Sweden were channelized for timber floating, and many streams have now been restored. Channelization disconnected streams from the riparian zone, and reduced the flooding that creates anoxic conditions necessary for many N-cycling reactions. We used a space-for-time substitution consisting of stream reaches restored 2 to 25 years ago, unrestored channelized and natural reference reaches to determine how N-cycling in riparian zones changes with time after restoration. Using stable isotopes of N (δ15N), we found that restoration caused more enriched foliar and root δ15N in recently restored sites, suggesting more gaseous losses of N in younger sites. This enrichment in foliar and root δ15N decreased over the 25-year chronosequence suggesting that the N-cycle becomes tighter and loses less N as it ages. Although the [N] in foliage, roots, and soils did not change over time, understory biomass decreased over time, suggesting that more N was available to plants in younger compared to older sites. Changes in the mechanism of N acquisition (i.e., mycorrhizal colonization, as shown by Δδ15N), plant species richness, and cover of deciduous trees (carbon source), were the most important factors explaining variation in δ15N along with time after restoration. It is clear that the restoration of these streams causes a large and rapid change in nitrogen processing in the riparian zone and this alteration persists for at least 25 years.
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| 8. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Recovery of nitrogen cycling in riparian zones after stream restoration using delta N-15 along a 25-year chronosequence in northern Sweden
- 2017
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 410:1-2, s. 423-436
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Tidskriftsartikel (refereegranskat)abstract
- Swedish boreal streams were modified to transport timber by pushing boulders to stream sides, creating levees that disconnected streams from riparian areas. Many streams have since been restored and our goal was to understand how this affects riparian nitrogen (N) cycling. We compared the natural abundance of delta N-15 isotopes in foliage and roots of Filipendula ulmaria plus soils and litter along streams restored 2-25 years ago. We measured sources of N, potential immobilization of N, namely plant diversity and biomass, and the amount and sources of carbon (C) to determine if these were important for describing riparian N cycling. The delta N-15 of F. ulmaria foliage changed dramatically just after restoration compared to the channelized, disconnected state and then converged over the next 25 years with the steady-state reference. The disturbance and reconnection of the stream with the riparian zone during restoration created a short-term pulse of N availability and gaseous losses of N as a result of enhanced microbial processing of N. With increasing time since restoration, N availability appears to have decreased, and N sources changed to those derived from mycorrhizae, amino acids, or the humus layer, or there was enhanced N-use efficiency by older, more diverse plant communities.
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| 9. |
- Maaroufi, Nadia, et al.
(författare)
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Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity
- 2019
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 25:9, s. 2900-2914
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Tidskriftsartikel (refereegranskat)abstract
- There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha(-1) year(-1)) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha(-1) year(-1)). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (<= 12 kg N ha(-1) year(-1)) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.
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| 10. |
- Metcalfe, Daniel B., et al.
(författare)
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Patchy field sampling biases understanding of climate change impacts across the Arctic
- 2018
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Ingår i: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:9, s. 1443-1448
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Tidskriftsartikel (refereegranskat)abstract
- Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.
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