The need for green and atmospheric water governance Wierik, Sofie A.; Gupta, Joyeeta; Cammeraat, Erik L. H. ...
Wiley interdisciplinary reviews. Water,
March/April 2020, Letnik:
7, Številka:
2
Journal Article
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A review of the literature on water governance reveals that most studies focus on blue water governance; while there is some literature on green and atmospheric water, explicit literature on how to ...govern green and atmospheric water is lacking. Hence, this paper addresses the question: What are the arguments for governing green and atmospheric water? In order to address this question, we have undertaken a scoping analysis of the literature on green and atmospheric water. We conclude that water governance must proactively address green and atmospheric water since: (a) blue water represents only a part of the available fresh water; (b) blue river basins represent only a subset of the wider systemic nature of water; (c) land use change has significant impacts on various water flows, which all may need to be governed; (d) climate variability and change influences blue, green, and atmospheric water availability; (e) an understanding of the socio‐ecological uses of the different colors of water is critical for a more optimal and legitimate governance of water; (f) new water technologies make it increasingly possible to modify the use of green and atmospheric water; and (g) global trade infrastructures pressurize local green water resources. Neglecting the need for explicit governance of green and atmospheric water could create new forms of “water grabbing” that would impact water availability beyond the basin scale.
This article is categorized under:
Human Water > Water Governance
Science of Water > Hydrological Processes
Water and Life > Stresses and Pressures on Ecosystems
Graphical of the seven arguments that are in favor of explicitly governing green and atmospheric water (inner ring) and the associated implications for water governance (outer ring).
In the past years, extracellular polymeric substances (EPS) produced by soil microorganisms received an increasing interest, as they not only protect microbes against environmental stresses, but seem ...to play a pivotal role in soil structure formation as well. Within soils, root deposits provide an important source of easily accessible energy and nutrients, stimulating microbial growth to produce EPS. Especially under semiarid climates, where a full vegetation cover cannot be sustained, large gradients in living conditions for microbes can be found between the root-soil interface and barren intercanopy spaces.
In this study, we aimed to elucidate the plant-specific effects on microbes, EPS production and soil aggregation. At two sites in southern Spain, differing in carbonate and graphite content, legume shrubs of Anthyllis cytisoides and grass tussocks of Macrochloa tenacissima were selected. Soil samples were taken in the adjacent bare interspace, under the canopy and of the rhizosphere. From these samples the microbial community (here bacteria and archaea), EPS(-saccharide) content and soil aggregation (<1 mm) were analysed. DNA extracted from the microbial cells detached from the surface of the sampled roots (rhizoplane), was subjected to 16S rRNA gene amplicon sequencing.
The rhizoplane microbial communities differed strongly between plant species and sites, whereby site was the most important factor shaping the communities. The plant species effect on microbial communities diminished strongly with distance to the root surface. At the carbonate-poor Rambla Honda site (site 1), plant species-specific effects were observed in the rhizoplane and rhizosphere, whereas in the carbonate-rich Alboloduy site (site 2) almost no plant species-specific effects were found at the genus level. The larger heterogeneity in microbial communities at site 1 was reflected in EPS-saccharide contents and subsequent soil aggregation, while no difference in soil aggregation was found at site 2. Both parameters increased strongest in the Anthyllis cytisoides rhizosphere at site 1.
Despite the lack of a strong gradient with distance from the root at the carbonate-rich site 2, microbial taxa were found by network analysis that positively correlated to EPS-saccharide contents and/or soil aggregation. The relationship between the identified taxa and EPS and/or aggregation relationships were clearest at the root-soil interface, while several other taxa were found to be widely occurring in the other soil compartments too.
In conclusion, we found in all compartments potential EPS producers, which could have influenced soil aggregation. Nevertheless, microbes with higher relative abundance in the rhizoplane were linked to higher EPS contents, especially in conjunction with legume shrubs, and subsequently related to soil aggregation. The spatial extent of the root effect was only governed by carbonate contents, as higher carbonate content diminished the observed root effects on the microbial community and subsequent soil aggregation.
•Microbial communities in rhizoplane differed depending on plant species.•Soil parent material had the strongest influence on microbial communities.•EPS-saccharide content and aggregation decreased from rhizosphere to bare soil.•Spatial extent of root effect on microbes diminished with higher carbonate contents.•Identified microbial taxa were correlated to EPS-saccharide and soil aggregation.
In the barren semiarid landscape individual plant species improve soil structure, reducing the erosion risks, whereby microaggregates form the most fundamental soil structural components. ...Extracellular polymeric substances (EPS) are considered as an important glue determining aggregation in addition to inorganic binding agents such as carbonates. However, the role of the prokaryotic community in EPS formation and consequently for microaggregation in natural environments is not substantially clarified yet. EPS should be particularly important under semiarid conditions as it forms a protection mechanisms of the prokaryotes against desiccation. Therefore, we examined the influence of the prokaryotic community on soil EPS content and subsequently on soil microaggregation in semiarid grasslands, depending on the parent material, common plant species and the distance to the plant. Soil samples were taken over a distance gradient from two major semiarid grassland plant species in Southern Spain, the legume shrub Anthyllis cytisoides and the grass tussock Macrochloa tenacissima, to the surrounding bare soil at two sites, rich and poor in carbonates. Total community DNA and EPS were extracted, followed by quantification of EPS-saccharide and bacterial abundance and examination of the prokaryotic community composition. Further, the particle size distribution of the microaggregate fraction was determined as an indication of microaggregation. We found that the overall prokaryotic community composition differed between the two sites, but not between plant species. Nonetheless, a link between the community composition and EPS content was established, whereby soil organic matter (OM) seems to be a regulating factor as increasing soil OM contents resulted in more EPS-saccharide. Furthermore, microaggregation was enhanced by the canopy, especially at the edge of Macrochloa tussocks. Contrary to the expectation that increasing inorganic C contents would diminish importance of EPS, the parent material richest in inorganic C results in a significant effect of EPS-saccharide content on microaggregation. For the inorganic C poor site, EPS-saccharide had no observed direct effect on microaggregation. Based on our results we conclude that the availability of decomposable OM influences the prokaryotic community composition and thereby triggers EPS production whereas large contents of polyvalent cations promote the stabilizing effect of EPS on microaggregates.
Soil erosion, rapid geomorphological change and vegetation degradation are major threats to the human and natural environment. Unmanned Aerial Systems (UAS) can be used as tools to provide detailed ...and accurate estimations of landscape change. The effect of flight strategy on the accuracy of UAS image data products, typically a digital surface model (DSM) and orthophoto, is unknown. Herein different flying altitudes (126-235 m) and area coverage orientations (N-S and SW-NE) are assessed in a semi-arid and medium-relief area where terraced and abandoned agricultural fields are heavily damaged by piping and gully erosion. The assessment was with respect to cell size, vertical and horizontal accuracy, absolute difference of DSM, and registration of recognizable landscape features. The results show increasing cell size (5-9 cm) with increasing altitude, and differences between elevation values (10-20 cm) for different flight directions. Vertical accuracy ranged 4-7 cm but showed no clear relationship with flight strategy, whilst horizontal error was stable (2-4 cm) for the different orthophotos. In all data sets, geomorphological features such as piping channels, rills and gullies and vegetation patches could be labeled by a technician. Finally, the datasets have been released in a public repository.
Recent studies indicate that climate change influences soil mineralogy by
altering weathering processes and thus impacts soil aggregation and organic
carbon (SOC) stability. Alpine ecosystems of the ...Neotropical Andes are
characterized by high SOC stocks, which are important for sustaining ecosystem
services. However, climate change in the form of altered precipitation
patterns can potentially affect soil aggregation and SOC stability with
potentially significant effects on the soil's ecosystem services. This study
aimed to investigate the effects of precipitation and lithology on soil
aggregation and SOC stability in the Peruvian Andean grasslands, and it
assessed whether occlusion of organic matter (OM) in aggregates controls SOC
stability. For this, samples were collected from soils on limestone and
soils on acid igneous rocks from two sites with contrasting precipitation
levels. We used a dry-sieving method to quantify aggregate-size
distribution and applied a 76 d soil incubation with intact and crushed
aggregates to investigate SOC stability's dependence on aggregation. SOC
stocks ranged from 153±27 to 405±42 Mg ha−1, and the
highest stocks were found in the limestone soils of the wet site. We found
lithology rather than precipitation to be the key factor regulating soil
aggregate-size distribution, as indicated by coarse aggregates in the
limestone soils and fine aggregates in the acid igneous rock soils. SOC
stability estimated by specific SOC mineralization rates decreased with
precipitation in the limestone soils, but only minor differences were found
between wet and dry sites in the acid igneous rock soils. Aggregate
destruction had a limited effect on SOC mineralization, which indicates that
occlusion of OM in aggregates played a minor role in OM stabilization. This
was further supported by the inconsistent patterns of aggregate-size
distribution compared to the patterns of SOC stability. We propose that OM
adsorption on mineral surfaces is the main OM stabilization mechanism
controlling SOC stocks and stability. The results highlight the interactions
between precipitation and lithology on SOC stability, which are likely
controlled by soil mineralogy in relation to OM input.
The fate of soil‐derived organic C (SOC) transported during erosion is a large uncertainty in assessing the impact of soil erosion on aquatic environments and in balancing C budgets. In our study, we ...determined C mineralization from solid soil organic C and dissolved organic C (DOC) translocated from a loess soil into surface water. We used runoff generated during rainfall simulation experiments. Both total runoff C and DOC were incubated to measure CO2 evolution during 28‐d experiments. Cumulative CO2 emissions from runoff accounted for 3.9 to 4.8% of initial runoff C. It was estimated that 3.3 to 3.7% of initial solid SOC was mineralized contributing to 69 to 80% of total C mineralization from runoff. Mineralization of DOC was larger (7.3–30.2% of initial DOC) and showed a much larger variability than mineralization from solid SOC. However, DOC mineralization contributed to 20 to 31% of total C mineralization from runoff only because of the much smaller amounts of DOC than solid SOC. We could confirm a preferential removal of labile C from soils by water erosion. Nevertheless, the majority of this C will contribute to an aquatic C sink with less than 5% being potentially mineralizable. Our results indicated that the base level of C mineralization from translocated C was derived from the solid phase whereas the variability depends largely on DOC.
Deforestation can lead to an increase in the availability of nutrients in the soil and, in turn, have an impact on the quality of water in receiving water bodies. This study assesses the impact of ...deforestation by evaluating the in-stream concentrations of dissolved organic carbon (DOC) and nitrate, their internal relationship, and those with stream discharge in the Wüstebach headwater catchment (Germany). This catchment has monitored stream water and associated environmental parameters for over a decade as part of the TERENO initiative. Additionally, there is a paired undisturbed forested catchment that serves as a reference stream. Our approach included a more advanced correlation analysis, namely wavelet analysis, that assists in determining changes in the correlation and lag time between the variables of interest over different time scales. This study found that after deforestation, there was an immediate increase in in-stream DOC concentrations, followed by an increase in nitrate ~1 year later. Overall, the mean DOC concentration increased, and mean nitrate concentration decreased across the catchment post-deforestation. Elevated stream water nutrient levels peaked around 2 to 3 years after the clear-cutting, and returned to pre-deforestation levels after ~5 years. The deforestation had no influence on the anti-correlation between DOC and nitrate. However, the correlation between both compounds and discharge was likely altered due to the increased soil nutrients availability as a result of deforestation. Wavelet coherence analysis revealed the “underlying” changing strengths and directions of the main correlations between DOC, nitrate and discharge on different time scales resulting from severe forest management interventions (here deforestation). This information provides new valuable impact insights for decision making into such forest management interventions.
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