Hortonian Scaling of Coupled Hydrological and Biogeochemical Responses Across an Intensively Managed River Basin

Structural and functional attributes across fractal river networks have been characterized by well-established and consistent hierarchical, Hortonian scaling patterns. In most of the global river basins, spatial patterns of human settlements also conform to similar hierarchical scaling. However, emergent spatial hierarchical patterns and scaling of heterogeneous anthropogenic nutrient loads over a river basin are less known. As a case study, we examined here a large intensely managed river basin in Germany (Weser River; 46K km(2); 8M population). Archived data for point-/diffuse-sources of total Phosphorus (P-tot) input loads were combined with numerical and analytical model simulations of coupled hydrological and biogeochemical processes for in-stream P-tot removal at the network scale. We find that P-tot input loads scale exponentially over stream-orders, with the larger scaling constant for point-source loads from urban agglomerations compared to those for diffuse-source contributions from agricultural and forested areas. These differences in scaling patterns result from hierarchical self-organization of human settlements, and the associated clustering of large-scale, altered land-cover. Fraction of P-tot loads removed through in-stream biogeochemical processes also manifests Hortonian scaling, consistent with predictions of an analytical model. Our analyses show that while smaller streams are more efficient in P-tot removal, in larger streams the magnitude of P-tot loads removed is higher. These trends are consistent with inverse scaling of nutrient removal rate constant with mean discharge, and downstream clustering of larger cumulative input loads. Analyses of six nested sub-basins within the Weser River Basin also reveal similar scaling patterns. Our findings are useful for projecting likely water-quality spatial patterns in similar river basins in Germany, and Central Europe. Extensions and generalizations require further examination of diverse basins with archetype spatial heterogeneities in anthropogenic pressures and hydroclimatic settings

Emergent spatial patterns of competing benthic and pelagic algae in a river network: A parsimonious basin-scale modeling analysis.

Algae, as primary producers in riverine ecosystems, are found in two distinct habitats: benthic and pelagic algae typically prevalent in shallow/small and deep/large streams, respectively. Over an entire river continuum, spatiotemporal patterns of the two algal communities reflect specificity in habitat preference determined by geomorphic structure, hydroclimatic controls, and spatiotemporal heterogeneity in nutrient loads from point- and diffuse-sources. By representing these complex interactions between geomorphic, hydrologic, geochemical, and ecological processes, we present here a new river-network-scale dynamic model (CnANDY) for pelagic (A) and benthic (B) algae competing for energy and one limiting nutrient (phosphorus, P). We used the urbanized Weser River Basin in Germany (7th-order; ~8.4 million population; ~46 K km2) as a case study and analyzed simulations for equilibrium mass and concentrations under steady median river discharge. We also examined P, A, and B spatial patterns in four sub-basins. We found an emerging pattern characterized by scaling of P and A concentrations over stream-order ω, whereas B concentration was described by three distinct phases. Furthermore, an abrupt algal regime shift occurred in intermediate streams from B dominance in ω≤3 to exclusive A presence in ω≥6. Modeled and long-term basin-scale monitored dissolved P concentrations matched well for ω>4, and with overlapping ranges in ω<3. Power-spectral analyses for the equilibrium P, A, and B mass distributions along hydrological flow paths showed stronger clustering compared to geomorphological attributes, and longer spatial autocorrelation distance for A compared to B. We discuss the implications of our findings for advancing hydro-ecological concepts, guiding monitoring, informing management of water quality, restoring aquatic habitat, and extending CnANDY model to other river basins

Resilience trinity: Safeguarding ecosystem functioning and services across three different time horizons and decision contexts

Ensuring ecosystem resilience is an intuitive approach to safeguard the functioning of ecosystems and hence the future provisioning of ecosystem services (ES). However, resilience is a multi‐faceted concept that is difficult to operationalize. Focusing on resilience mechanisms, such as diversity, network architectures or adaptive capacity, has recently been suggested as means to operationalize resilience. Still, the focus on mechanisms is not specific enough. We suggest a conceptual framework, resilience trinity, to facilitate management based on resilience mechanisms in three distinctive decision contexts and time‐horizons: 1) reactive, when there is an imminent threat to ES resilience and a high pressure to act, 2) adjustive, when the threat is known in general but there is still time to adapt management and 3) provident, when time horizons are very long and the nature of the threats is uncertain, leading to a low willingness to act. Resilience has different interpretations and implications at these different time horizons, which also prevail in different disciplines. Social ecology, ecology and engineering are often implicitly focussing on provident, adjustive or reactive resilience, respectively, but these different notions of resilience and their corresponding social, ecological and economic tradeoffs need to be reconciled. Otherwise, we keep risking unintended consequences of reactive actions, or shying away from provident action because of uncertainties that cannot be reduced. The suggested trinity of time horizons and their decision contexts could help ensuring that longer‐term management actions are not missed while urgent threats to ES are given priority

Balancing security, resilience, and sustainability of urban water supply systems in a desirable operating space

The security, resilience, and sustainability of urban water supply systems (UWSS) are challenged by global change pressures, including climate and land use changes, rapid urbanization, and population growth. Building on prior work on UWSS security and resilience, we quantify the sustainability of UWSS based on the performance of local sustainable governance and the size of global water and ecological footprints. We develop a new framework that integrates security, resilience, and sustainability to investigate trade-offs between these three distinct and inter-related dimensions. Security refers to the level of services, resilience is the system’s ability to respond to and recover from shocks, and sustainability refers to local and global impacts, and to the long-term viability of system services. Security and resilience are both relevant at local scale (city and surroundings), while for sustainability cross-scale and -sectoral feedbacks are important. We apply the new framework to seven cities selected from diverse hydro-climatic and socio-economic settings on four continents. We find that UWSS security, resilience, and local sustainability coevolve, while global sustainability correlates negatively with security. Approaching these interdependent goals requires governance strategies that balance the three dimensions within desirable and viable operating spaces. Cities outside these boundaries risk system failure in the short-term, due to lack of security and resilience, or face long-term consequences of unsustainable governance strategies. We discuss these risks in the context of poverty and rigidity traps. Our findings have strong implications for policy-making, strategic management, and for designing systems to operate sustainably at local and global scales

Palaeohexaploid Ancestry for Caryophyllales Inferred from Extensive Gene-Based Physical and Genetic Mapping of the Sugar Beet Genome (Beta vulgaris)

Dohm JC, Lange C, Holtgräwe D, et al. Palaeohexaploid Ancestry for Caryophyllales Inferred from Extensive Gene-Based Physical and Genetic Mapping of the Sugar Beet Genome (Beta vulgaris). The Plant Journal. 2012;70(3):528-540.Sugar beet (Beta vulgaris) is an important crop plant accounting for 30% of the world's sugar production annually. The genus Beta is a distant relative of currently sequenced taxa within the core eudicotyledons, and genomic characterization of sugar beet is essential in order to make its genome accessible to molecular dissection. Here, we present comprehensive genomic information in genetic and physical maps covering all nine chromosomes. Based on this information we identified the proposed ancestral linkage groups of rosids and asterids within the sugar beet genome. We generated an extended genetic map comprising 1127 single nucleotide polymorphism markers prepared from expressed sequence tags and bacterial artificial chromosome (BAC) end sequences. To construct a genome-wide physical map we hybridized gene-derived oligomer probes against two BAC libraries with 9.5 fold cumulative coverage of the 758 Mbp genome. More than 2500 probes and clones were integrated both in genetic maps and the physical data. The final physical map encompasses 535 chromosomally anchored contigs containing 8361 probes and 22,815 BAC clones. By using the gene order established with the physical map we detected regions of synteny between sugar beet (order Caryophyllales) and rosid species involving 1400-2700 genes in the sequenced genomes of Arabidopsis, poplar, grapevine, and cacao. The data suggest that Caryophyllales share the palaeohexaploid ancestor proposed for rosids and asterids. Taken together, we here provide extensive molecular resources for sugar beet enabling future high-resolution trait mapping, gene identification, and cross-referencing to regions sequenced in other plant species. © 2011 The Authors. The Plant Journal© 2011 Blackwell Publishing Ltd

Carbon and nutrient export regimes from headwater catchments to downstream reaches

Excessive amounts of nutrients and dissolved organic matter in freshwater bodies affect aquatic ecosystems. In this study, the spatial and temporal variability in nitrate (NO3-), dissolved organic carbon (DOC) and soluble reactive phosphorus (SRP) was analyzed in the Selke (Germany) river continuum from three headwaters draining 1-3 km(2) catchments to two downstream reaches representing spatially integrated signals from 184-456 km(2) catchments. Three headwater catchments were selected as archetypes of the main landscape units (land use x lithology) present in the Selke catchment. Export regimes in headwater catchments were interpreted in terms of NO3-, DOC and SRP land-to-stream transfer processes. Headwater signals were subtracted from downstream signals, with the differences interpreted in terms of in-stream processes and contributions from point sources. The seasonal dynamics for NO3- were opposite those of DOC and SRP in all three headwater catchments, and spatial differences also showed NO3- contrasting with DOC and SRP. These dynamics were interpreted as the result of the interplay of hydrological and biogeochemical processes, for which riparian zones were hypothesized to play a determining role. In the two downstream reaches, NO3- was transported almost conservatively, whereas DOC was consumed and produced in the upper and lower river sections, respectively. The natural export regime of SRP in the three headwater catchments mimicked a point-source signal (high SRP during summer low flow), which may lead to overestimation of domestic contributions in the downstream reaches. Monitoring the river continuum from headwaters to downstream reaches proved effective to jointly investigate land-to-stream and in-stream transport, and transformation processes

Isolation and linkage analysis of expressed disease-resistance gene analogues of sugar beet (Beta vulgaris L.)

Hunger S, Di Gaspero G, Mohring S, et al. Isolation and linkage analysis of expressed disease-resistance gene analogues of sugar beet (Beta vulgaris L.). Genome. 2003;46(1):70-82.Sequence conservation among resistance genes (R genes) was exploited to identify 47 R gene analogues (RGAs) from sugar beet (Beta vulgaris L.). Using degenerate primers, 11 RGAs were amplified from genomic DNA and 7 from leaf or beet cDNA. Twenty-nine were selected from an EST sequencing program. Twenty-one RGAs contained structures similar to the nucleotide binding site (NBS)--leucine rich repeat (LRR) domain, a motif commonly found in several R genes. Among the remaining RGAs, 19 revealed similarity to the serine (threonine) protein kinase domain of R genes, 4 showed features related to the LRR region of the rice disease resistance gene Xa21, 1 RGA resembled the sugar beet nematode resistance gene Hs1pro-1, and 2 had homologies to other gene products associated with disease resistance. For 20 EST-derived RGAs, transcript levels were compared in leaf and root tissue revealing organ-specific transcription in 7 cases. Thirty-three RGAs were spread over all nine sugar beet chromosomes, except for a cluster of nine closely linked RGAs on chromosome 7. The analysis of linkage between RGAs and loci for rhizomania and Cercospora resistance identified alleles associated with resistance in both cases