Article

Historical contingency in fluviokarst landscape evolution

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

Lateral and vertical erosion at meander bends in the Kentucky River gorge area has created a series of strath terraces on the interior of incised meander bends. These represent a chronosequence of fluviokarst landscape evolution from the youngest valley side transition zone near the valley bottom to the oldest upland surface. This five-part chronosequence (not including the active river channel and floodplain) was analyzed in terms of the landforms that occur at each stage or surface. These include dolines, uvalas, karst valleys, pocket valleys, unincised channels, incised channels, and cliffs (smaller features such as swallets and shafts also occur). Landform coincidence analysis shows higher coincidence indices (CI) than would be expected based on an idealized chronosequence. CI values indicate genetic relationships (common causality) among some landforms and unexpected persistence of some features on older surfaces. The idealized and two observed chronosequences were also represented as graphs and analyzed using algebraic graph theory. The two field sites yielded graphs more complex and with less historical contingency than the idealized sequence. Indeed, some of the spectral graph measures for the field sites more closely approximate a purely hypothetical no-historical-contingency benchmark graph. The deviations of observations from the idealized expectations, and the high levels of graph complexity both point to potential transitions among landform types as being the dominant phenomenon, rather than canalization along a particular evolutionary pathway. As the base level of both the fluvial and karst landforms is lowered as the meanders expand, both fluvial and karst denudation are rejuvenated, and landform transitions remain active.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... What is an appropriate measure of fitness in Earth surface systems (ESS)? A number of hypotheses have been proposed for optimal structures and configurations of, e.g., ecosystems, channel networks, topography, etc. Most, if not all, of these principles can be reduced to (or subsumed under) the idea of efficiency or resistance selection--more efficient and resistant forms and structures are more likely to persist and grow, or to occur repeatedly, than less efficient ones (see Jorgensen, 1997;Fath et al., 2001;Ulanowicz et al., 2006 on ecological systems; Huang and Nanson, 2000;Nanson and Huang, 2008;2018;Paik and Kumar, 2010;Phillips, 2010;2011;Smith, 2010;and Huang et al., 2014 on geomorphic systems;andOzawa et al., 2003 andKleidon et al., 2013 on geophysical phenomena more generally). To the extent that "fitter" (more efficient and/or resistant) geomorphic features and structures are subject to not just preferential preservation, but also enhancement (via positive feedbacks) and/or propagation, then algorithmic evolution models may apply to geomorphology, too--implying the possibility of geomorphic creativity. ...
... Thus creativity and innovation in biological evolution was accompanied by creativity and innovation in fluvial systems. However, selection for maximum efficiency structures and configurations has been shown to operate for a number of abiotic phenomena, including atmospheric fluid flows (Ozawa, et al., 2003); development of subsurface flow networks (Hunt, 2016), and evolution of stream channel networks, planforms, and cross-sections (Huang and Nanson, 2000;Nanson and Huang, 2008;2018;Kleidon et al., 2013;Paik and Kumar, 2010;Phillips, 2010;2011;Smith, 2010;Huang et al., 2014). ...
... Kentucky River case study Previous research (Phillips, 2018) examined a chronosequence of fluviokarst landscape development over ca 1.5 Ma in central Kentucky. That chronosequence is reexamined here with respect to evolution of dolines. ...
Article
In biological evolution, creativity occurs in the appearance of new entities by evolutionary dynamics. This is linked to mutations and genetic drift, which cannot occur in geophysical phenomena. Biota can exhibit evolutionary creativity that influences landforms, but how does creativity (defined here as the capacity for emergence of new entities that increase the adjustedness of the landscape to environmental conditions) occur in landforms and landscapes as entities independent of biota? Creativity in geomorphic evolution does not require any sort of goal functions or purposeful innovation‐‐just that geomorphic development is capable of producing novelties that may be better adapted (more efficient or durable) than predecessors. Independently of biota, evidence exists that landforms may develop to become more or less "fit" in terms of efficiency and/or durability. Thus emergence of novel features may lead to their persistence. Emergence of novel forms is illustrated for the case of karst sinkholes (dolines), which indicates increasing geomorphic diversity over Ma and Ga timescales. A case study of fluviokarst chronosequences in Kentucky demonstrates emergence and elimination of landforms as landscapes evolve. Some of these may represent generally (as opposed to locally) novel landforms. While this paper is more suggestive than demonstrative, results strongly suggest evolutionary creativity in geomorphology both tied to, and independent of, biological evolution. This occurs due to emergence of geomorphic entities that are subject to selection that tends to increase efficiency and durability.
... A direct empirical test of the implications of the model above would have to confirm (or not) the transition from rapid growth in initial stages of epikarst development to slow growth or steady-state later. This is not possible at the moment, though some chronosequences of fluviokarst landform development on the interior of Kentucky River meander bends (Phillips, 2018) might provide future opportunities if sufficient dating resolution could be obtained. However, a means of assessing the implications of the previous section can be developed, as described below. ...
... The Kentucky River has incised roughly 100 m since that time in the inner Bluegrass, carving the Kentucky River gorge. Phillips (2017Phillips ( , 2018 has shown how this incision has driven landform change on the uplands (as well as in the valleys). ...
... The Chenault includes rounded gravels of lithology not found in the local rock, and also sometimes sand, indicating a Kentucky River source. Phillips (2018) showed that some bends have a chronosequence of strath terraces on the erosional slip-off slopes of the bend interiors. Thus the presence of the deeper soils shows that they formed post-Kentucky River incision, and possibly from initially exposed bedrock. ...
Article
Tree roots have biogeomorphic engineering effects on epikarst weathering and soil deepening. This is investigated using a system model describing the interactions among biogeomorphic effects of roots, weathering, and soil-epikarst development. The model shows that the system is dynamically unstable when roots are limited by subsurface accommodation space and water availability, and weathering is moisture limited. Instability indicates relatively rapid, unstable growth of epikarst cavities and soil, driven by positive feedbacks. However, when belowground rooting space and moisture are no longer limiting, and weathering is reaction-limited, the system is dynamically stable, indicating steady state or slow growth of epikarst and soils. Results suggest an important role for biogeomorphic ecosystem engineering (BEE) by tree roots in soil and epikarst development, but that BEE is self-limiting. When moisture storage and supply for both plants and dissolution are adequate and sufficient root space is available, BEE effects become negligible. Supportive data and field observations from the Inner Bluegrass region of Kentucky indicate that BEE effects of trees can produce favorable conditions for tree growth, with these effects becoming negligible as soil thickness increases sufficiently.
... Another used geomorphic signatures to identify karst-to-fluvial and fluvial-to-karst transitions at the landform scale (Phillips, 2017). In a third study, a chronosequence based on fluvial strath terraces was used to examine historical contingency (Phillips, 2018a;Fig. 5.6). ...
... For the landform transitions, positive links were assigned where multiple examples of apparent transitions from one form to another were recognized in the field (Phillips, 2017a), where the "destination" landform did not precede the "origin" landform in the chronosequence (Phillips, 2018a), and where the basic principles of fluviokarst landform development support the transition (Phillips, 2015a(Phillips, , 2017a. Negative links were assigned where no evidence of a transition was observed, and principles suggest that a transition would be extremely unlikely, if not impossible. ...
Chapter
History matters. Global (independent of place and time) principles are necessary to explain landscape evolution, as are place factors (geographical and environmental context). But, by themselves, they are not sufficient. To explain landscape evolution—which by definition has important temporal dimensions—history must also be incorporated. Landscape evolution is historically contingent. This chapter outlines several different types of historical contingency, discusses multiple pathways and outcomes in landscape evolution, and evaluates why some imaginable pathways are rare and others common, and some trends are divergent and others convergent. Methods for evaluating path stability of historical trajectories are introduced and applied to several different Earth surface systems. The chapter concludes with a consideration of landscape evolution in the context of convergence, divergence, and equifinality.
... As dolinas são as formas de relevo mais comuns e representativas das paisagens cársticas, e estão relacionadas à maneira como se deu o processo de formação (morfogênese). Segundo Tavassos (2019, p. 78-81) 2016;BOČIĆ et al., 2015;JERIN;PHILLIPS, 2017;KOŠUTNIK, 2007;PHILLIPS, 2017PHILLIPS, , 2018PHILLIPS et al., 2004;TÎRLǍ et al., 2016). ...
Article
Full-text available
Abstract The vast occurence of Bambuí group carbonate rocks (Neoproterozoic), in Brazilian Central-West region, allows the realocation of great superficial rivers to the fragile underground ambient. In this sense, this work aims the identification of areas with the possibility of occurrence of sinkholes in Rio Corrente Basin, located in the northeast portion of Goiás state. These features are typical in karstic ambients, being responsible for the superficial hydrography capture to the subterranean area. Using the Geographic Information System (GIS), operating the softwares QGIS and SAGA GIS, attempts were made to the location of such areas from visual identification (considering criteria such as hydrography, altitude, contours and vegetation). From the application of these filters 170 polygons of were identified, representing areas of possibility of sinkholes occurrence, being necessary field work to validate them.
... It is considered that the stacking of the structural units leads to erosion and consequently, to the creation of juxtaposed basins to receive fluvial or marine sediments. Whipple and Tucker (1999), Gallen and Wegmann (2017) and Phillips (2018) incorporate rock uplift, U, into a fluvial erosion model to reach the steady state. To try to elucidate the nature of these structural units in northern Tunisia, we have used a digital terrain modeling (DTM) field to understand and model this dynamic in the context of complex tectonic disturbances, and for more or less constant climatic conditions. ...
Article
Full-text available
Digital elevation modeling (DEM) was used to determine key morphological features such as hypsometry, slopes and topographic evolution in correlation with tectonic regimes and erosion mechanisms. This contribution discusses the tectonic model of northern Tunisia, which since 1977 has been described by geologists as an allochthonous unity domain of the Serravallian-Tortonian. This study presents new data from the erosion rate calculation following the establishment of these units and then proposes another view on regional tectonics. Therefore, the example used of Oued Sedjnene gives a rising rate of the order of 0.01 mm/year, almost equivalent to the results found in surrounding medeterranean belt (ex. Italy and Turkey). The structure and geomorphology of northern Tunisia is a result of folding of Cenozoic basin. However located tangential structure are related to transcurrent faults and not overthrust structure.
... In fluviokarst landscapes, the interpretation of river profiles is potentially impacted by other factors governing the evolution of channel networks, such as the relative influence of dissolution and mechanical processes on the erosion of the river bed, diversion of surface flow to the subsurface karst systems, and groundwater sapping (e.g., Dunne, 1980Dunne, , 1990Schorghofer et al., 2004;Anthony and Granger, 2007;Woodside et al., 2015;Francis et al., 2018). Furthermore, repeated transitions from a prevalence of dissolution processes to dominant fluvial erosion can result in hybrid or transitional landforms and complex patterns of erosion that render the interpretation of the fluviokarst landscape in terms of climate or uplift change problematic (Gallen and Wegmann, 2017;Phillips, 2017Phillips, , 2018. ...
Article
The evolution of fluviokarst landscapes results from the interplay of karst and fluvial processes, all driven by rock uplift or base level fall. The fluviokarst landscape of the Murge Plateau in the central Apulian Region (southeastern Italy) is characterized by narrow, steep-sided, V-shaped canyons, locally called ‘Gravine’, and deeply incised into the Plio-Pleistocene deposits of the Bradanic Trough and the underlying Apulian limestone bedrock. Previous studies propose alternative models of canyons development, however identifying a dominant morphogenetic process for the evolution of the ‘Gravine’ fluviokarst drainage basins remains an open question. The results of our regional morphometric analysis reveal a marked transition from the relict, low-relief landscape preserved in the Murge uplands to the steep channel reaches below prominent knickpoints showing evidence of a transient wave of river incision that is propagating inland. We observe anomalies of mean local relief and channel steepness, and the distribution of fluvial knickpoints consistent with a regional uplift affecting the Murge Plateau since Middle-Late Pleistocene. These findings demonstrate that the history of landscape evolution was dominated by fluvial processes. Using transformed river profile analysis we show that χ anomalies in the ‘Gravine’ trunk channels indicate drainage basin instability by drainage area capture. The convex-shape of the hypsometric curves and high hypsometric integrals confirm that the disequilibrium state of the 13 analyzed basins results from a combination of regional uplift and subsequent river network reorganization and plateau area captures. Based on our results, we propose a new model of landscape evolution for the ‘Gravine’ fluviokarst drainage basins.
... At the same time, these features and properties can influence future developmental trajectories. Within the systems approach, this property is identified as part of historical contingency, and is referenced frequently in the geosciences (Phillips, 2013(Phillips, , 2017. ...
Article
In the present paper we report on the only known example of a hummocky meadow in Poland. The area of the Hala Długa in the Gorce Mountains is a hotspot of complex geomorphic edge effects that have been widely studied in relation to human impacts and forest disturbances. Applying an interdisciplinary approach, we aimed to study the geomorphic activity in edge conditions between two contrasting ecosystems, a high-mountain meadow and a forest. Several methods were applied: geomorphic mapping, radiocarbon dating, soil analysis, geomorphometry, wood anatomy, and investigations of historical maps. These methods enabled us to reconstruct the history of the Hala Długa over the past ca 300 years, and to evaluate geomorphic activity and soil dynamics in this area. The treethrow pit-mound microtopography (hummocky meadow, Buckelwiese) of this area was formed under forest conditions, but due to long-term human impacts linked to sheep grazing and mowing, was preserved as a distinct topography for at least 100 years. While this topography was still clearly visible in the 1950s, when it was first reported, it is currently gradually disappearing under trees that have formed a belt around the study area. Soils of the study site were disturbed by tree uprooting, with many key features identified during the soil profile analysis: spots of coarse partly oriented sandstone fragments in pits, patches of organic matter in the metamorphic B horizon, and a large number of root remnants and pieces of charcoal in different parts of treethrow mounds and pits. We suggest a non-linear or even polygenetic soil evolution due to altered vegetation and disturbance regimes. The evaluation of wood remnants revealed that the majority of uprooted tree species were Picea abies (L.) H. Karst and Larix decidua Mill. We conclude that in the Gorce Mountains geomorphic edge effects can form hotspots of geomorphic activity driven by human impacts, natural disturbances, and the specific hydrological regime in the highest parts of the massif.
... Rather, they depend on a combination of fieldwork, soil survey data, and published research to develop a narrative of place formation. Field observations are based on work conducted for both site-specific and regional studies of differential landscape development on inner and outer bends of the Kentucky River gorge (Phillips, 2015), soil spatial complexity (Phillips, 2016a), fluviokarst landform transitions (Phillips, 2016a), and landform evolution on chronosequences associated with Kentucky River incision and lateral migration (Phillips, 2018a). Published soil surveys and related data utilized are shown in Table 2. ...
Article
Nine axioms for interpreting landscapes from a geoscience perspective are presented, and illustrated via a case study. The axioms are the self-evident portions of several key theoretical frameworks: multiple causality; the law–place–history triad; individualism; evolution space; selection principles; and place as historically contingent process. Reading of natural landscapes is approached from a perspective of place formation. Six of the axioms relate to processes or phenomena: (1) spatial structuring and differentiation processes occur due to fluxes of mass, energy, and information; (2) some structures and patterns associated with those fluxes are preferentially preserved and enhanced; (3) coalescence occurs as structuring and selection solidify portions of space into zones (places) that are internally defined or linked by mass or energy fluxes or other functional relationships, and/or characterized by distinctive internal similarity of traits; (4) landscapes have unique, individualistic aspects, but development is bounded by an evolution space defined by applicable laws and available energy, matter, and space resources; (5) mutual adjustments occur between process and form (pattern, structure), and among environmental archetypes, historical imprinting, and environmental transformations; and (6) place formation is canalized (constrained) between clock-resetting events. The other three axioms recognize that Earth surface systems are always changing or subject to change; that some place formation processes are reversible; and that all the relevant phenomena may manifest across a range of spatial and temporal scales. The axioms are applied to a study of soil landscape evolution in central Kentucky, USA.
Article
Full-text available
O carste apresenta regiões de conexões entre os sistemas fluviais e cársticos o fluviocarste, dispondo de feições típicas, como os vales secos. Tais feições vêm sendo estudadas de diversas formas para contribuir no entendimento da dinâmica geomorfológica do carste. Este estudo visa fazer uma revisão sobre vales secos em sistemas cársticos, tendo em vista observar o potencial científico destas áreas para diversas aplicabilidades. A revisão utilizou como principal forma de busca a plataforma Web Of Science (todas as bases), abrangendo o período entre 1945-2020, que abordavam sobre tais feições, com o uso das seguintes palavras-chave: karstic valley, dry valleys, blind valley, relict valley, ancient valley, fossil valley, solution valley, paleovalley e paleokarst valley, resultando em vinte e sete trabalhos, com diversas propostas de análise, evidenciando os fatores envolvidos na dinâmica fluviocárstica. O levantamento permite observar que são poucos estudos considerando a extensão de ocorrência de rochas carbonáticas no mundo, havendo concentração das pesquisas no continente europeu. No Brasil, apesar de dispor de regiões carbonáticas e das várias áreas mapeadas com ocorrência de cavernas, principalmente no bioma Cerrado, não há pesquisas sobre o tema, mesmo que viabilizem a identificação dos fatores que influenciam evoluções dos sistemas fluviocársticos.
Article
Concentrated or preferential flow patterns occur at all scales in hydrologic systems. They shape, and are shaped by, geomorphic and pedologic patterns and structures. Preferential flow patterns in surface channel networks and dual-porosity subsurface flow systems are a way of achieiving maximum efficiency, as predicted by dissipative systems, constructal, network evolution, percolation, and ecohydrological theories. These all converge on the same predictions and interpretations of preferential flow, which satisfactorily answer “why” these patterns form and persist. However, as geomorphic and hydrologic systems have no intentionality or agency, and thus no ability to actively seek improved efficiency, how these systems evolve is an open question. I propose an emergent explanation based on five phenomena. First, concentrated flows form due to principles of gradient and resistance selection. Second, positive feedback reinforces the concentrated preferential flow paths and their relationship to potential moisture storage zones. Third, intersecting flow paths form networks. Fourth, the expansion of concentrated flow paths and networks is limited by thresholds of flow needed for channel, macropore, or conduit growth and maintenance. This results in a “store and pour” flow system that can retain water during dry periods and transport it efficiently during wet periods. These systems survive provided they develop “spillway” and/or secondary storage mechanisms to accommodate excess water inputs. Finally, store-and-pour systems are maintained (selected for) because they are often stable. Store-and-pour structures are advantageous for flow systems, and for vegetation and ecosystems. These entities cannot actively pursue goals, and no laws dictate evolution toward such patterns. Their development is an emergent phenomenon and their persistence a matter of selection, i.e., survival of the most stable.
Chapter
Darwinian natural selection acting on individuals is one of only several types of selection influencing landscape evolution. Ecological filtering and abiotic selection (including the least action principle and preferential flows) apply. The overarching principle is one of efficiency selection, whereby more efficient, stable, and durable forms, structures, patterns, networks, and flux pathways are more likely to occur, grow, and persist than less efficient ones. Particularly important forms are gradient selection, favoring steeper and faster flow paths; resistance selection, whereby more resistant features are preferentially preserved; biogeochemical selection, which favors more rapid elemental cycling; network selection, which makes more efficient flux and interaction networks more likely; and thermodynamic selection, reflecting the advantages of energy use efficiency. Efficiency selection is highly local, however, one of several reasons that landscapes and environmental systems are not always inevitably becoming more efficient overall. A case study illustrating selection principles is given.
Article
Full-text available
Understanding evolution of soils and landforms (and other Earth surface systems) has itself evolved from concepts of single-path, single-outcome development to those that recognize multiple possible developmental trajectories and different maturely developed states. Soil geomorphology and pedology should now move beyond showing that multiple trajectories are possible to investigating why some evolutionary pathways (EPs) are common and persistent, whereas others are rare and transient. A typology of EPs is developed and applied to soil formation in the North Carolina coastal plain. Some EP are impossible because of violation of generally applicable laws or absence of necessary conditions; others are currently impossible, having occurred in the past but requiring conditions that no longer exist. Improbable paths are possible but rare, because necessary circumstances involve rare events or boundary conditions. Inhibited EPs are also possible but rare because of resistance factors or feedbacks that prevent or inhibit them. Transient paths may be common but are not long-lived or well preserved and are thus rarely observed. Recurring but nonrepeating EPs occur in different locations but are irreversible in any given location and cannot recur except in the case of system-resetting disturbance or new inputs. Recurring EPs are not inhibited or self-limited, occur in different locations, and may be repeated because of ongoing or recurrent processes or conditions. Selected path types occur in multiple situations, but with increased probability due to feedbacks or responses that encourage or enhance recurrence and/or persistence. The case study shows examples of all possible EP types.
Article
Full-text available
Flow diversions and landform transitions between channelized surface (fluvial) and concentrated subsurface (karst conduit) flows may be common in fluviokarst landscapes. Identifying landforms associated with fluvialto- karst or karst-To-fluvial transitions shows this to be the case at three study sites in the Inner Bluegrass karst region of Kentucky. Forms representing the capture or diversion of stream flow to subsurface conduits include sinking streams, dry karst valleys, paleovalleys resulting from karst stream piracy, and alluvial collapse dolines. Features indicating karst-To-fluvial transitions include stream incision into dry karst valleys, doline breaching by surface runoff or stream incision, and formation of karst pocket valleys and karst windows. Many smaller transitional landforms also exist (e.g., stream swallets). The three study sites have about three larger transitional landform features per km2, with karst-To-fluvial features slightly more common. Dissolution in bedrock-controlled stream channels leading to karst piracy is the most common cause of fluvial to karst transitions, while general stream incision driven by Kentucky River downcutting is the main driver of karst-To-fluvial shifts. The landform transitions are examined via a network model based on hydrological probability and flow partitioning. The model is dynamically unstable. Instability indicates that local changes and disturbances that modify moisture fluxes, local relief, conduit or surface channel conveyance capacity, or hydraulic slopes are likely to persist and grow, resulting in hydrogeomorphic transitions. Evolution of the Kentucky fluviokarst is best understood as mutual reinforcement, whereby fluvial dissection can be intensified and accelerated by the presence of karst features, and karstification is enhanced by stream incision. © 2017 Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany.
Article
Full-text available
Suspended sediment is a natural part of river systems and plays an essential role in structuring the landscape, creating ecological habitats and transporting nutrients. It is also a common management problem, where alterations to sediment quantity and quality negatively impact ecological communities, increase flood hazard and shorten the lifespan of infrastructure. To address these challenges and develop appropriate sustainable management strategies, we need a thorough understanding of sediment sources, pathways and transport dynamics and the drivers that underlie spatial and temporal variability in suspended sediment transport in rivers. However, research to date has not sufficiently addressed the temporal complexity of sediment transport processes, which is limiting our ability to disentangle the hydro-meteorological, catchment, channel and anthropogenic drivers of suspended sediment transport in rivers. This review critically evaluates previously published work on suspended sediment dynamics to demonstrate how the interpretation of sediment sources and pathways is influenced by the temporal scale and methodology of the study. To do this, the review (i) summarizes the main drivers of temporal variation in suspended sediment transport in rivers; (ii) critically reviews the common empirical approaches used to analyze and quantify sediment sources and loads, and their capacity to account for temporal variations; (iii) applies these findings to recent case studies to illustrate how method and timescale affect the interpretation of suspended sediment transport dynamics; and finally (iv) synthesizes the findings of the review into a set of guidelines for a multi-timescale approach to sediment regime characterization. By recognizing a priori that study design and temporal scale have an impact on the interpretation of SS dynamics and employing methods that address these issues, future research will be better able to identify the drivers of suspended sediment transport in rivers, improve sediment transport modelling, and propose effective, sustainable solutions to sediment management problems.
Article
Full-text available
Biota–soil interactions in natural ecosystems are the subject of considerable research. Our hypothesis is that individual trees play a significant role through biomechanical and biochemical disturbances affecting soil formation in temperate forests, resulting in a complex spatial pattern of disturbance regimes and a close relationship between disturbance histories and soil units. In Žofínský Prales (Czech Republic) – the fourth oldest, continuously protected reserve in Europe and the first site of global research network SIGEO (Smithsonian Institution Global Earth Observatories) in continental Europe – we compared extensive dendrochronological, soil and pit–mound microtopography data both temporally and spatially from an area of anthropogenically unaffected 42 ha collected from 2008–2012. These data sets differ in terms of information complexity and length of memory: tree cores contain complex information about the disturbance history of the past 350 years, footprints of disturbances from the uprooting of a specific tree can persist 1700 years, and soils represent an extensive composite phenotype that has been developing for at least the entire postglacial period (10 500 years). On average, 6.18–13.41% of the canopy on individual soil units was disturbed per decade. Even though the "backbone" of key events in the development of the forest ecosystem remained the same (e.g. the 1870s, 1880s and 1980s), the internal structure of disturbance history often differed among soil units; the most exceptional were Gleysols and Histosols, where important feedback from soil to trees was expected. However, the characteristics of treethrow dynamics as well as the frequencies of stronger releases in core series also significantly differed along a gradient of terrestrial soil weathering and leaching (Haplic Cambisols – Dystric Cambisols – Entic Podzols – Albic Podzols). These results suggest the existence of several disturbance regimes within the forest, controlling fine-scale pedodiversity.
Article
Full-text available
We investigated surface and vegetation dynamics in the artificial initial ecosystem "Chicken Creek" (Lusatia, Germany) in the years 2006–2011 across a wide spectrum of empirical data. We scrutinized three overarching hypotheses concerning (1) the relations between initial geomorphological and substrate characteristics with surface structure and terrain properties, (2) the effects of the latter on the occurrence of grouped plant species, and (3) vegetation density effects on terrain surface change. Our data comprise and conflate annual vegetation monitoring results, biennial terrestrial laser scans (starting in 2008), annual groundwater levels, and initially measured soil characteristics. The empirical evidence mostly confirms the hypotheses, revealing statistically significant relations for several goal variables: (1) the surface structure properties, local rill density, local relief energy and terrain surface height change; (2) the cover of different plant groups (annual, herbaceous, grass-like, woody, Fabaceae), and local vegetation height; and (3) terrain surface height change showed significant time-dependent relations with a variable that proxies local plant biomass. Additionally, period specific effects (like a calendar-year optimum effect for the occurrence of Fabaceae) were proven. Further and beyond the hypotheses, our findings on the spatiotemporal dynamics during the system's early development grasp processes which generally mark the transition from a geo-hydro-system towards a bio-geo-hydro system (weakening geomorphology effects on substrate surface dynamics, while vegetation effects intensify with time), where pure geomorphology or substrate feedbacks are changing into vegetation–substrate feedback processes.
Article
Full-text available
Tlie paper shows how the velocities of the channel waves Pa and 8a, as thus far calculated, are apparent velocities. From such apparent values it is easy to calculate the real velocities, which coincide with the minimum velocity of longitudinal and transversal waves, calculated by 15. Gutenberg and by Miss I. Lehmann for the astenospliere. The canalization of seismic energy is a general phenomenon which, in the case of strong earthquakes with focus ca. 100 km deep, may involve not only the astenospliere, but also tlie earth crust channels. Important examples are alleged. The paper finally shows that also tlie energy developped by deep earthquakes (600 km deep and more) undergoes remarkable canalization. However, this concerns to a significant extent only the astenospliere.
Article
Full-text available
Karst relief of Central Florida and fluvial relief of the Florida Panhandle were analyzed and compared on the basis of standardized samples of karst and fluvial topography derived from digital databases in a GIS environment. Comparative geomorphological analyses of the two distinct genetic relief types were performed on the basis of morphometric parameters derived for each type of relief in general as well as differentially for hypsometric intervals of paleo-marine terraces with the assumption of relative stability of tectonic conditions of the underlying carbonate platform. The comparative analyses conducted indicate overall higher values of the morphometric parameters in the fluvial relief compared to those in the karst relief. This is a consequence of more than two times higher rates of fluvial denudation compared to the karst denudation rates (0.23 vs. 0.11 mm/year, respectively). Differential analyses with respect to the paleo-marine terrace intervals reveal significant quantitative morphological differences between the upper, older and lower, younger terrace intervals in the karst and fluvial relief. In the two older terrace intervals, fluvial and karst denudation rates range from 0.07 to 0.09 mm/year, while in the younger terrace intervals fluvial denudation shows more than two times higher rates than the karst denudation (0.22 and 0.55 vs. 0.11 and 0.19 mm/year), indicating that fluvial processes in the study area are more effective than the respective karst processes. This is clearly reflected in the higher values of vertical dissection and denudated sediment volume in the fluvial relief in the younger terrace intervals, while the increased karst denudation rates are not yet reflected in the respective morphometric parameters due to the slower morphologic response. Overall, long-term karst denudation ranging from 0.07 to 0.19 mm/year is derived by volumetric analysis of the denudated sediment and as such accounts for the effects of both chemical and mechanical denudation. Consequently, they are significantly higher than the previously calculated short-term solutional denudation rates, although their values fall in the mid range of theoretical estimations with respect to climatic conditions of the study area. The obtained fluvial denudation rates ranging from 0.07 to 0.55 mm/year are similar to previous estimates of long-term fluvial denudation.
Article
Full-text available
The complex drainage systems within karst settings can result in atypical longitudinal profiles. Features, such as cave entrances, can be expressed as anomalous ‘bumps’ in the longitudinal profile of a stream if downcutting has continued upstream of the area in which the water is pirated to the subsurface. Horn Hollow, a fluviokarst valley located in Carter Caves State Park Resort in northeastern Kentucky, was examined for these types of features. The objectives of this study were to determine if sediment mobility can be used as a proxy for anomalous areas along the profile of the valley and if detailed cross-sections can reveal and/ or differentiate areas of cave collapse from natural down-cutting of the system. To accomplish these objectives, the longitudinal profile of Horn Hollow and numerous cross-sections through the valley were surveyed. Armor point counts were performed at cross-sections unless the section was predominantly bedrock. Although Horn Hollow’s waters have been predominantly pirated to the subsurface, the longitudinal profile of the system is graded to that of a stream near equilibrium, but anomalous areas are present. The progression of sediment size along the length of the profile does not follow a typical fining-downstream pattern. Some of the largest sediments can be found within the lower segment of the profile. Taken together, the anomalous bumps and the sediment size suggest that the shape of the longitudinal stream profile is strongly influenced by karst processes such as stream piracy and cave collapse.
Article
Full-text available
Chronosequences are a fundamental tool for studying and representing change in Earth surface systems. Increasingly, chronosequences are understood to be much more complex than a simple monotonic progression from a starting point to a stable end-state. The concept of path stability is introduced here as a measure of chronosequence robustness; i.e., the degree to which developmental trajectories are sensitive to disturbances or change. Path stability is assessed on the basis of the largest Lyapunov exponent (λ1) of an interaction matrix consisting of positive, negative, or zero entries based on whether existence of a given system state or stage promotes or facilitates (positive), prevents or inhibits (negative), or has no significant effect on transitions to another state. Analysis of several generic chronosequence structures represented as signed, directed, unweighted graphs indicates five general cases: Path-stable reversible progressions (λ1 < 0); neutrally path-stable irreversible progressions (λ1 = 0); path unstable with very low divergence (0 < λ1 < 1); path unstable with low divergence (λ1 = 1); and complex multiple pathways (λ1 > 1). Path stability is probably relatively rare in chronosequences due to the directionality inherent in most of them. A complex soil chronosequence on the lower coastal plain of North Carolina was analyzed as described above, yielding λ1 = 0.843, indicating very low divergence. This outcome is consistent with pedological interpretations, and derives largely from the presence of self-limiting early stages, and a few highly developed states that inhibit retrogression back to many of the earlier stages. This kind of structure is likely to be common in pedological and hydrological sequences, but this suggestion requires further testing.
Article
Full-text available
What we see now in the landscape is the result of a long history of events with varying degrees of persistence. We have only limited access to much of that history and we know that many current events have only a minimal impact on what we see. Even rather extreme events may have impacts that are not very long-lasting but can have the effect of changing the antecedent states for future events. That means that sampling of sequences of events might be important in understanding the evolution of the catchments. In some cases, however, extreme events can have an impact on the system that persists over hundreds or thousands of years. Any evolution of the landscape is then constrained by those past events, however much it might be also constrained by self-organisational principles. It might be difficult to verify those principles given the epistemic uncertainties about past histories and system properties that are generic to the studies that are possible within a research project or career. These arguments are investigated in a simple slab model of landslip failures in a hillslope hollow subject to stochastic forcing over long periods of time. The complementarity of an event-persistence approach to hydro-eco-geomorphological systems is captured in suggestions for future research questions.
Article
Full-text available
Biota–soil interactions in natural ecosystems are the subject of considerable research. Our hypothesis is that individual trees play a significant role through biomechanical and biochemical disturbances affecting soil formation in temperate forests, resulting in a complex spatial pattern of disturbance regimes and a close relationship between disturbance histories and soil units. In Žofínský Prales (Czech Republic) – the fourth oldest, continuously protected reserve in Europe and the first site of global research network SIGEO (Smithsonian Institution Global Earth Observatories) in continental Europe – we compared extensive dendrochronological, soil and pit–mound microtopography data both temporally and spatially from an area of anthropogenically unaffected 42 ha collected from 2008–2012. These data sets differ in terms of information complexity and length of memory: tree cores contain complex information about the disturbance history of the past 350 years, footprints of disturbances from the uprooting of a specific tree can persist 1700 years, and soils represent an extensive composite phenotype that has been developing for at least the entire postglacial period (10 500 years). On average, 6.18–13.41% of the canopy on individual soil units was disturbed per decade. Even though the "backbone" of key events in the development of the forest ecosystem remained the same (e.g. the 1870s, 1880s and 1980s), the internal structure of disturbance history often differed among soil units; the most exceptional were Gleysols and Histosols, where important feedback from soil to trees was expected. However, the characteristics of treethrow dynamics as well as the frequencies of stronger releases in core series also significantly differed along a gradient of terrestrial soil weathering and leaching (Haplic Cambisols – Dystric Cambisols – Entic Podzols – Albic Podzols). These results suggest the existence of several disturbance regimes within the forest, controlling fine-scale pedodiversity.
Article
Full-text available
Based on a wide range of empirical data we investigated surface and vegetation dynamics in the artificial initial ecosystem "Chicken Creek" (Lusatia, Germany) in the years 2008-2011. We scrutinized three different hypotheses concerning (1) the relations between initial geomorphological and substrate characteristics with surface structure and terrain properties, (2) the effects of the latter on the occurrence of grouped plant species, and (3) vegetation density effects on terrain surface change. Our data comprise annual vegetation monitoring results, terrestrial laser scans twice a year, annual groundwater levels, and initially measured soil characteristics. Using Generalized Linear Models (GLMM) and Generalized Additive Mixed Models (GAMM) we can mostly confirm our hypotheses, revealing statistically significant relations that partly reflect object or period specific effects but also more general processes which mark the transition from a geo-hydro towards a bio-geo-hydro system, where pure geomorphology or substrate feedbacks are changing into vegetation-substrate feedback processes.
Article
Full-text available
The Purón River valley shows a special configuration due to convergence of surficial and groundwater processes in a phreatic conduit. Typical karst processes of dissolution–precipitation have been replaced by fluvial activity, where mechanical water erosion morphologies are dominant. All this seems to relate to a stage of abandonment of the underground environment in favour of the surficial domain. River incision in rock canyons is accomplished in many cases by phreatic conduits evolution, its collapse and opening to the surface. During the initial stages of this process, river piracy and superficial changes in the drainage network occur by capturing in first place the groundwater system. In this context of fluvial activity, numerous sculpted forms, such as potholes, are found in the conduit which is the result of changes and evolution in the cave into a more evolved morphology, pointing to river stream power concentration along certain conduit sections.
Article
Full-text available
Earth surface systems (ESS) are characterized by various degrees of historical contingency, which complicates efforts to relate observed features and phenomena to environmental controls. This article provides a conceptual framework for understanding and assessing historical contingency in ESS that is based on algebraic graph theory. ESS are conceptualized as consisting of components (e.g., climate, topography, and lithology) observed or inferred at time periods. Each component at each time period represents a node of a network or graph, and interactions among components constitute the links or edges. Four indexes are applied: the S-metric, which indicates the extent to which observations of part of the network (e.g., topographic changes between two time periods) are likely to represent the dynamics of the network as a whole; spectral radius, which measures coherence and potential amplification of changes or disturbances; Laplacian spectral radius, an index of the relationship between network stability and time steps and an indication of path dependence; and algebraic connectivity, which measures the inferential synchronizability. For each of these, an index on a 0–1 scale is developed, which represents high and minimum levels of historical contingency for a given n, q. These are applied to several archetypal graph structures that represent various forms of historical contingency in the geosciences and to two specific case studies involving Quaternary evolution of fluvial systems in Texas and Kentucky.
Article
Full-text available
The Cousance karst (located between the valleys of the Saulx and Marne) has been studied to determine the temporal records of river incision in the eastern Paris Basin, around the ANDRA experimental nuclear waste repository. Two generations of karst are recognized. The first is a palaeophreatic karst indicative of an old base level, now uplifted +75 m above the underground streams. It is underlain and drained by a second generation of karst with active sinks, which records the vertical evolution following the entrenchment of the River Marne. Ten U/Th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes, mainly during isotopic stages 3 and 5 (between 102.4 ± 1.2 and 49.4 ± 0.4 ka bp) but also during isotopic stage 2 at 16.3 ± 0.1 and 20.9 ± 0.3 ka bp. These dates provide an absolute age limit for the start of vertical development of the karst, at the latest during isotope stage 5c.
Article
Full-text available
Longitudinal profiles of bedrock streams in central Kentucky, and of coastal plain streams in southeast Texas, were analyzed to determine the extent to which they exhibit smoothly concave profiles and to relate profile convexities to environmental controls. None of the Kentucky streams have smoothly concave profiles. Because all observed knickpoints are associated with vertical joints, if they are migrating it either occurs rapidly between vertical joints, or migrating knickpoints become stalled at structural features. These streams have been adjusting to downcutting of the Kentucky River for at least 1.3 Ma, suggesting that the time required to produce a concave profile is long compared to the typical timescale of environmental change. A graded concave longitudinal profile is not a reasonable prediction or benchmark condition for these streams. The characteristic profile forms of the Kentucky River gorge area are contingent on a particular combination of lithology, structure, hydrologic regime, and geomorphic history, and therefore do not represent any general type of equilibrium state. Few stream profiles in SE Texas conform to the ideal of the smoothly, strongly concave profile. Major convexities are caused by inherited topography, geologic controls, recent and contemporary geomorphic processes, and anthropic effects. Both the legacy of Quaternary environmental change and ongoing changes make it unlikely that consistent boundary conditions will exist for long. Further, the few exceptions within the study area–i.e., strongly and smoothly concave longitudinal profiles–suggest that ample time has occurred for strongly concave profiles to develop and that such profiles do not necessarily represent any mutual adjustments between slope, transport capacity, and sediment supply. The simplest explanation of any tendency toward concavity is related to basic constraints on channel steepness associated with geomechanical stability and minimum slopes necessary to convey flow. This constrained gradient concept (CGC) can explain the general tendency toward concavity in channels of sufficient size, with minimal lithological constraints and with sufficient time for adjustment. Unlike grade- or equilibrium-based theories, the CGC results in interpretations of convex or low-concavity profiles or reaches in terms of local environmental constraints and geomorphic histories rather than as “disequilibrium” features.
Article
Full-text available
Efforts to predict responses to climate change and to interpret modern or paleoclimate indicators are influenced by several levels of potential amplifiers, which increase or exaggerate climate impacts, and/or filters, which reduce or mute impacts. With respect to geomorphic responses and indicators, climate forcings are partly mediated by ecological, hydrological, and other processes which may amplify or filter impacts on surface processes and landforms. Then, geomorphic responses themselves may be threshold-dominated or dynamically unstable, producing disproportionately large and long-lived responses to climate changes or disturbances. Or, responses may be dynamically stable, whereby resistance or resilience of geomorphic systems minimizes the effects of changes. Thus a given geomorphic response to climate could represent (at least) two levels of amplification and/or filtering. An example is given for three fluvial systems in Kentucky, U.S.A, the Kentucky, Green, and Big South Fork Rivers. Climate impacts in the early Quaternary were amplified by glacially-driven reorganization of the ancestral Ohio River system to the North, and by dynamical instability in the down-cutting response of rivers incising plateau surfaces. Effects of more recent climate changes, however, have been filtered to varying extents. Using alluvial terraces as an example, the study rivers show distinctly different responses to climate forcings. The lower Green River has extensive, well-developed terraces recording several episodes of aggradation and downcutting, while the Big South Fork River has no alluvial terraces. The Kentucky River is intermediate, with limited preservation of relatively recent terraces. The differences can be explained in terms of differences among the rivers in (1) filtering effects of constraints on fluvial responses imposed by strongly incised, steep-walled bedrock controlled valleys; and (2) amplifier effects of periodic damming of lower river reaches by glaciofluvial outwash.
Article
Full-text available
The age of single windthrows (single uprooted trees and/or pit/mound microtopographical pairs) in a natural fir-beech forest was assessed in the flysch zone of the Outer Western Carpathians. The following characteristics were evaluated for all 1562 single windthrows occurring in a 10.8 ha area: dimensions; thickness of organic and upper mineral soil horizons both on mounds and in pits; and the presence of new trees taking root on the windthrows. For more recent windthrows, selected quantitative and qualitative characteristics of the uprooted trees were evaluated. A suppositional gradient of age (SGA) was constructed based on the windthrow characteristics using principal component analysis. A representative sample of windthrows was dated along the SGA with the use of dendroecological techniques and historic records from 1972 and 1995. For European beech (Fagus sylvatica L.) we were able to measure the actual threshold of release value – at 12% of growth change. The age of windthrows was determined in 37 of a total of 51 cases. The development of windthrow properties over time was studied. Age explained 33.7% of the variability in the measured windthrow characteristics (F = 19.31, p = 0.0002, measured characteristics see above). A multiple regression model (R2 = 0.844, F = 65.62, p < 1 × 10−6) was constructed to evaluate the age of undated windthrows. The best predictors of age were: ordinal classification of trunk disintegration and thickness of F and A horizons on the mound.
Article
The development pathway of a landscape depends to a degree on the initial spatial distributions of mineral and organic components. The interaction between structures and ecohydrological processes during the critical initial development period is scarcely understood and often difficult to observe. While viable modeling approaches exist for most aspects of initial development (e.g., landscape evolution, vegetation succession), a deeper understanding of the prevailing feedback mechanisms requires a comprehensive, integrated modeling approach. We present a review of the current literature regarding the description of initial structures, the state-of-the-art of research on structure-forming processes and their interaction with existing and newly emerging structures, as well as the corresponding modeling efforts. The most relevant aspects are (i) sediment translocation processes and initial evolution of topography, (ii) surface crusting, (iii) vegetation succession, and (iv) the evolution of the soil pore space. Based on existing conceptions for integrated modeling of the coevolution of structures and ecohydrological behavior, we outline an integrative modeling framework that is based on a three-dimensional spatial structural model of initial sediment distributions, which can be used to: (i) analyze the spatiotemporal development dynamics depending on initial structures; and (ii) relate the simulated structural development to available observations of initial ecohydrological development. We discuss possible validation and generalization strategies of modeling results, and propose to define three-dimensional spatial functional catchment units (process domains) characterized by specific structural dynamics and the dominant ecohydrological processes.
Article
Evolution of Earth surface systems (ESS) comprises sequential transitions between system states. Treating these as directed graphs, algebraic graph theory was used to quantify complexity of archetypal structures, and empirical examples of forest succession and alluvial river channel change. Spectral radius measures structural complexity and is highest for fully connected, lowest for linear sequential and cyclic graphs, and intermediate for divergent and convergent patterns. The irregularity index \(\beta \) represents the extent to which a subgraph is representative of the full graph. Fully connected graphs have \(\beta = 1\). Lower values are found in linear and cycle patterns, while higher values, such as those of divergent and convergent patterns, are due to a few highly connected nodes. Algebraic connectivity (\(\mu (\mathrm{G}))\) indicates inferential synchronization and is inversely related to historical contingency. Highest values are associated with fully connected and strongly connected mesh graphs, whereas forking structures and linear sequences all have \(\mu (G)\) = 1, with cycles slightly higher. Diverging vs. converging graphs of the same size and topology have no differences with respect to graph complexity, so complexity change is dependent on whether development results in increased or reduced richness. Convergent-divergent mode switching, however, would generally increase ESS complexity, decrease irregularity, and increase algebraic connectivity. As ESS and associated graphs evolve, none of the possible trends reduces complexity, which can only remain constant or increase. Algebraic connectivity may increase, however. As improving shortcomings in ESS evolution models generally result in elaborating possible state changes, this produces more structurally complex but less historically contingent models.
Chapter
The Old Kentucky River system was a major contributor to the Teays River, draining southwestern Ohio and much of eastern Kentucky. The trunk river flowed northward from southeastern Kentucky throughout Frankfort and Carrollton, and then past Cincinnati and Dayton, joining the Teays River near Springfield, Ohio. North of the glacial boundary, which lies along the modern Ohio River, the course of the Old Kentucky River has been modified, and is today largely buried by drift. Although dissection is extensive to the south, there are many remnants of this entrenched and broadly meandering Teays-age valley system and of its sub-upland predecessors. These valleys contain areas of upward-fining, deeply weathered gravel, composed mainly of rounded quartz, chert, and silicified limestone pebbles derived from the headwaters of the system. Modern rivers have been entrenched 30 to 100 m below the Old Kentucky River valley and its main tributaries, the Old Licking and South Fork. The Old Kentucky River system was severed from the Teays when glaciation dammed its downstream reaches, forcing a reversal in flow direction between its junction with the Teays in west-central Ohio and Carrollton, Kentucky, and causing westward overflow into the Old Ohio River system. Piracy by the Old Ohio may also have contributed to the integration of the Old Kentucky and Old Ohio River basins. Ponded sediment is present in some of the now-abandoned valley remnants east of Cincinnati. As a result of glacial damming, the headwaters of the Teays River in southeastern Ohio and West Virginia overflowed westward across the Manchester divide into the Old Kentucky River drainage basin. All of these events led to establishment of the modern Ohio River system.
Article
Many landscapes are characterized by a mosaic of patches in various stages of succession. Whether successional paths dampen, track, or magnify extrinsic variation in initial conditions influences how much historical and site-specific detail is required to explain variation in patch composition. I investigated the patterns and importance of historical effects in a successional marine rocky intertidal community on the central coast of Oregon, USA Patches in the mid-intertidal mussel bed (M. californianus) were manually cleared in a way that mimicked natural disturbances. In four separate blocks (large patches ~9 m2), three sets of plots were initiated with their starting dates staggered by one year. Within each set of plots, I manipulated the presence/absence of two groups of early successional sessile species under each of three predator densities. This design allowed me to address the following general questions: (1) What are the separate and interactive effects of successional age, yearly variation, and initial conditions on the temporal changes observed after disturbance? (2) When do interactions between early species act to dampen or magnify natural variation between years or starting dates? Succession in mid-intertidal patches in the mussel bed displayed complex patterns of historical effects, which varied among species and between different stages of succession. Embedded in this potential complexity were some consistent and repeatable successional trends. Some potentially important canalizing, or 'noise-dampening' forces in this system included: (1) physiological and/or life history trade-offs between dispersal ability and competitive ability, (2) strong direct biotic interactions, which buffer environmental variability, and (3) compensatory ('buffering') responses of species within an important functional group. 'Noise-amplifying' forces included: (1) variable indirect effects of predators, (2) prey size escapes, and (3) predator saturation (or prey 'Swamp' escapes). Understanding the patterns and causes of consistency or contingency in succession will be critical for managing variability in landscapes that are increasingly dominated by anthropogenic disturbance regimes.
Article
Evidence is presented demonstrating that in areas of varied tectonic settings - shield, orogenic, platform - relief amplitude has increased over periods of 60-100 My. Slope steepening is characteristic of many of the areas discussed. Of the recognised models of landscape evolution Crickmay's model involving Unequal Activity is closest to that described here. But whereas Crickmay attributed areal inequalities in erosion to disparities between the erosive capacities of major streams and their tributaries draining divides, the present model is based largely in structure, and its control of shallow groundwaters, weathering and erosion, and in consequent reinforcement effects. This model involving increasing relief amplitude readily accommodates the very old palaeosurface remnants reported from various parts of the world. -Author
Article
In order to explore mechanisms of bedrock terrace formation, we have developed a numerical model that couples vertical river incision and meandering. Model results illustrate that flights of unpaired strath terraces can form purely from the internal dynamics of bedrock river meandering in vertically incising channels. Specifically, knickpoints that propagate upstream following meander cutoffs enhance vertical incision, whereas channel lengthening and corresponding slope reduction during meander growth suppresses vertical incision. Analysis of topography from the Smith River, Oregon, USA, suggests terrace formation by this mechanism. Our results introduce an alternative mechanism to climatic or tectonic forcing, namely inherent instability triggered by meander growth and cutoff, that explains both oscillations in rates of vertical bedrock incision and the formation of longitudinally traceable, unpaired bedrock terraces. In addition, our results point to simple topographic criteria for identifying internally generated fluvial bedrock terraces.
Article
Karst plateaus often have a complex geological and geomorphological history. It is widely accepted that their development requires a long period of karst denudation. This study reconstructs the palaeodrainage network of a karst plateau, analyses its properties and establishes its geomorphological significance. The main purpose of this research was to deepen our understanding of a key stage in the evolution of karst plateaus - the transition from a fluvial landsurface to one dominated by karst surface processes. The study was conducted on a large part of the Una-Korana Plateau, the largest plateau in the Dinaric karst. The majority of the plateau is made of carbonate rocks of Triassic, Jurassic and Cretaceous age that set the conditions for the development of the karst. We have reconstructed the palaeodrainage network based on 1:25,000 topographic maps with 10 m contours. The transition of the surface drainage network to the underground karst drainage network is still in progress, so, depending on the degree of karstification, the drainage network was divided into three categories: active, dry and relict. It was found that 90.5% of the pre-existing drainage network has undergone some degree of karstification. The active surface drainage network gradually shifted to a dry network, then to a relict network. The surface drainage network is gradually replaced by a dense network of dolines. Today, the flat and karstified inter-fluvial area is drained underground towards the main watercourses and these drain the entire region over the surface towards the Pannonian basin. This is the largest known karst palaeodrainage network in the Dinaric karst that has been reconstructed in this way.
Article
The archetypal badass is individualistic, non-conformist, and able to produce disproportionate results. The badass concept is applied here to geomorphology. The individualistic concept of landscape evolution (ICLE) is introduced, based on three propositions: excess evolution space, capacity of all landforms to change, and variable selection pressure from environmental factors within and encompassing landscapes. ICLE indicates that geomorphic systems are idiosyncratic to some extent, and that even where two systems are similar, this is a happenstance of similar environmental selection, not an attractor state. As geomorphic systems are all individualistic, those that are also non-conformist with respect to conventional wisdoms and have amplifier effects are considered badass. Development of meander bends on a section of the Kentucky River illustrates these ideas. The divergence of karst and fluvial forms on the inner and outer bends represents unstable amplifying effects. The divergence is also individualistic, as it can be explained only by combining general laws governing surface and subsurface flow partitioning with a specific geographical and environmental setting and the history of Quaternary downcutting of the Kentucky River. Landscape evolution there does not conform to any conventional theories or conceptual frameworks of geomorphology. The badass traits of many geomorphic systems have implications for the systems themselves, attitudes toward geomorphic practice, and appreciation of landforms. Badass geomorphology and the ICLE reflect a view, and approach to the study of, landforms as the outcome of the interplay of general laws, place-specific controls, and history. Badass geomorphology also implies a research style receptive to contraventional wisdoms. Aesthetically, amplifier effects and individualism guarantee an essentially infinite variety of landforms and landscapes that geoscientists can appreciate both artistically and scientifically. Non-conformity makes the interpretation and understanding of this variety more challenging—and while that increases the degree of difficulty, it also makes for more interesting and compelling professional challenges. This article is protected by copyright. All rights reserved.
Conference Paper
The twenty largest perennial springs of Kentucky were identified and ranked over a ten-year period. Since most large springs are not shown on topographic or geologic maps, ranked springs were primarily located from previous hydrogeologic surveys, field reconnaissance, and literature review. Spring flows were ranked by minimum annual discharge, which ranged from 0.15-0.68 m 3/s. These springs are classified as 3rd Magnitude, based on the Meinzer (1923) discharge scale. Unit base flow (the ratio of minimum discharge to basin area) revealed diverse hydrogeologic yield of the karst spring group, ranging from 0.22-12.27 L/s/km 2, suggesting significant unattributed losses and gains. Most large springs are derived from classic fluviokarst basins draining well-developed karst of Mississippian-age limestones. However, one-third result from short stream or meander cutoffs of less than 5 km, which are not necessarily related to well-developed karst terrane. An index of karst basin development can be obtained by the ratio of subsurface flow length to total basin length.
Article
In order to contribute to the debate on the role of fluvial erosion in the shaping of karst, two nearby areas with different karstic landscapes were compared. Areas A and B are located relatively close to each other on the southern side of the Krk Island (Adriatic Sea, Croatia). Both areas are composed of similar limestone with a very high CaCO3 content.Area A is a typical doline or polygonal type (“classical”) of karst with numerous dolines (up to 57/km2) covered with terra rossa (red soil) and Mediterranean maquis shrubland. Dolines are located in zones which correspond to the strike of the main geological structures. Dry karstic valleys are visible only on gently inclined coastal slopes bordering the karstic plateau. In contrast, area B is typical of a bare karst landscape with a strong (palaeo)fluvial imprint. The dolines are absent, and the bedrock is only sporadically covered with terra rossa. Palaeogene marls have been observed in a few elongated depressions and in the coastal zone of area B. Along steep coastal slopes, valleys (up to 460 m/km2) are cut into the carbonates. The traces of episodic surface flows are visible in some of these valleys, in contrast to the valleys in area A. Remnants of a disrupted ancient fluvial network are clearly visible on the elevated karstic plateau in area B.Differences in the recent morphology are attributed mainly to varying thicknesses of the Palaeogene impermeable marly cover, and the intensity of tectonics in the two areas.
Article
The primary goal of this project is to develop a relative chronology of events in the geologic history of the Kentucky River, and to consider the geologic controls on those events. This study utilized published geologic and topographic data, as well as field observations and extensive compilation and comparison of digital data, to examine the fluvial record preserved in the Kentucky River valley in central Kentucky. Numerous fluvial features including abandoned paleovalleys, fluvial terraces and deposits, bedrock benches, and relict spillways between adjacent river valleys were identified during the course of the study. The morphology of the modern valley coincides with bedrock lithology and can be used to describe the distribution and preservation of modern and ancient fluvial deposits and features in the study area. Bedrock lithology is the dominant control on valley morphology and on the distribution and preservation of fluvial deposits and features in the study area. Some stream trends are inherited from the late Paleozoic drainage of the Alleghanian orogeny. More recent inheritance of valley morphology has resulted from the erosion of the river from one lithology down into another lithology with differing erosional susceptibility, thus superposing the meander patterns of the overlying valley style onto the underlying lithology. One major drainage reorganization related to a pre-Illinoisan glacial advance disrupted the northward flow of the Old Kentucky River toward the Teays River system and led to organization of the early Ohio River. This greatly reduced the distance to baselevel, and led to abrupt incision and a change in erosional style for the Kentucky River. The successful projection of valley morphologies on the basis of bedrock stratigraphy, the history of erosion suggested by fission track data and the results of this study, as well as soil thickness and development, all argue against the existence of a midto late-Tertiary, low-relief, regional erosional surface. This study instead hypothesizes that the apparent accordance of ridge-top elevations in the study area is a reflection of a fluvially downwasted late Paleozoic depositional surface.
Article
Subsurface solutional pathways make limestone terrains sensitive to changes in soil properties that regulate flows to the epikarst. This study examines biogeomorphic factors responsible for changed water movements and erosion in fluviokarst slopes deforested 200 years ago along the Kentucky River, Kentucky. In this project, infiltration and water content data from forest and fescue grass soil profiles were analyzed within a detailed overview of system factors regulating hillslope hydrology. Results show that grass has growth and rooting characteristics that tend to create a larger volume of lateral water movement in upper soil layers than occurs under forests. This sets up the current emergent pattern of erosion in which water perches at grass slope bases and overwhelms pre-existing epikarst drainage. Tree roots are able to cause solution at multiple discrete points of entry into fractures and bedding planes, increasing storage capacity and releasing sediment over time. Grass roots do not enter bedrock, and their rooting depth limits diffuse vertical preferential flow in root channels to above one meter. In the areas dense clay soils, flow under grass is conducted sideways either through the regolith or at the bedrock surface. Rapid flow along rock faces in hillslope benches likely moves fines via subsurface routes from the hillslope shoulders, causing the exposure of flat outcrops under grass. Lower growing season evapotranspiration also promotes higher grass summer flow volumes. Gullying occurs at sensitive points where cutters pass from the uphill grassed area into the forest, or where flow across the bedrock surface crosses grass/forest boundaries oriented vertical to the slope. At these locations, loss of the protective grass root mat, coupled with instigation of tree root preferential flow in saturated soils, causes soil pipes to develop. Fluviokarst land management decisions should be based on site-specific slope, soil depth, and epkarst drainage conditions, since zones sensitive to erosion are formed by spatial and temporal conjunctions of a large number of lithologic, karst, soil, climate, and vegetation factors. This study shows that it is the composite of differing influences created by forest and grass that make forests critical for soil retention in high-energy limestone terrains.
Article
In the carbonate aquifers which underlie most karst terrains, groundwater flow is through a dendritic system of solution conduits. In such aquifers, termed shallow conduit-flow aquifers, the methods used to model granular and fracture aquifers are not generally applicable. Investigations were conducted in the Inner Bluegrass Karst Region of central Kentucky with the objective of developing methods of modeling shallow conduit-flow aquifers as well as obtaining quantitative information on a specific portion of the aquifer to assist in its management for water supply purposes.
Article
Geomorphic systems consist of coupled subsystems with traits of small-world networks (SWN), characterized by tightly connected clusters of components, with fewer connections between the clusters. Geomorphic systems based on scale hierarchies often exhibit a connected caveman small-world network (CCSWN) structure. SWNs are efficient for linking a large number of components with a relatively small number of links; but effects of CCSWN structure on synchronization and scale linkage have not been examined. Synchronization is analyzed via graph theory and applied to: (1) relationships among three levels of form–process interaction in stream channels; (2) hierarchical relationships of weathering systems at scales from weathering profiles to landscapes; and (3) interactions in fluviokarst systems at the scale of flow processes and of landscape evolution. Relationships among system components are represented as simple unweighted graphs. The largest eigenvalue of the adjacency matrix (spectral radius) reflects the critical coupling strength required to synchronize the system. The second-smallest eigenvalue of the Laplacian of the adjacency matrix (algebraic connectivity) is a measure of the synchronizability. In all examples both are much less than the maximum for networks of the same number of nodes. The sparseness of the networks is the major contributor to the low synchronization, but the specific pattern of connections (“wiring”) is also significant. Where CCSWN structures arise naturally, they help explain how geomorphic effects are transmitted between disparate scales in the absence of obvious scale linkage. Where CCSWNs are an option for representation of geomorphic systems in models and data structures, they will not improve scale linkage, despite the efficiency of SWNs in other respects. Methods developed here can be applied to evaluating alternative spatial data structures or mapping strategies which either increase synchronization, supporting a lumping or aggregation approach, or decrease synchronization, indicating disaggregation or splitting into scale hierarchies.
Article
The Earth's surface is the dynamic interface of climatic, biotic, and geologic systems and is often described as the Earth's critical zone. Structures and processes within this zone are highly complex and heterogeneous and therefore not yet completely understood, particularly with regard to their interactions. In contrast, parts of the critical zone still in their initial development stages are expected to be less complex and heterogeneous compared to mature systems. Therefore, research approaches concentrating on this crucial initial development period of ecosystems have been recently initiated. A central hypothesis is that the initial ecosystem development phase forms the later state of ecosystems. Similarly, the behavior of mature ecosystems can only be understood if knowledge about their evolution exists. The initial development stages of geo-ecosystems are characterized by highly dynamic abiotic and biotic processes. This results in the rapid formation and alteration of structures, which in turn constitute a new framework for new processes. To disentangle the structure-process interactions, interdisciplinary and integrative research approaches in the fields of geomorphology, ecology, biology, soil science, hydrology, and environmental modeling are required. We discuss ideas that emerged from the fourth Meeting of Young Researchers in Earth Sciences (MYRES IV) held at the Brandenburg University of Technology (BTU) Cottbus in 2010 (www.myres.org), which focused on the overarching question: what are the evolutionary constraints and pathways that govern development of spatiotemporal patterns in ecosystem process and structure? This paper presents a review of the most important aspects of initial ecosystem processes as key factors of landscape development.
Article
Central Kentucky is characterized by a mixture of karst and fluvial features, typically manifested as mosaic of karst-rich/channel-poor (KRCP) and channel-rich/karst-poor (CRKP) environments. At the regional scale the location and distribution of KRCP and CRKP areas are not always systematically related to structural, lithological, topographic, or other controls. This study examines the relationship of KRCP and CRKP zones along the Kentucky River gorge area, where rapid incision in the last 1·5 million years has lowered local base levels and modified slopes on the edge of the inner bluegrass plateau. At the scale of detailed field mapping on foot within a 4 km2 area, the development of karst and fluvial features is controlled by highly localized structural and topographic constraints, and can be related to slope changes associated with retreat of the Kentucky River gorge escarpment. A conceptual model of karst/fluvial transitions is presented, which suggests that minor, localized variations are sufficient to trigger a karst–fluvial or fluvial–karst switch when critical slope thresholds are crossed. Copyright © 2004 John Wiley & Sons, Ltd.
Article
Verleysdonk, S., Krautblatter, M. and Dikau, R., 2011. Sensitivity and path dependence of mountain permafrost systems. Geografiska Annaler: Series A, Physical Geography, 93, 113–135. DOI: 10.1111/j.1468-0459.2011.00423.x This article is an attempt to transfer a classical geomorphological concept – the sensitivity concept by Brunsden and Thornes – onto mountain permafrost systems. Focus is put on the impulses applied on the system and its subsequent response. The system state, the ratio between sensitivity and resistivity, as well as all system components and the external impulses are understood to be variable in space and time. In order to address sensitivity and path dependence in mountain permafrost systems, not only the present system configuration but also their historical development and possible future attractors have to be analysed. Important elements are the system configuration, variable impulses and thresholds, processes and process rates and internal feedbacks. The Zugspitze in the Northern Calcareous Alps at the German/Austrian border is chosen as a test site for the applicability of the sensitivity concept on mountain permafrost systems due to the high quantity of research conducted there and the significant impact of climate change on the periglacial system. Further aspects include the consequences of the Eibsee Bergsturz event in 3700 bp in terms of path dependence and geomorphic response time. With this conceptual approach, we hope (1) to enhance the interlinkage between periglacial geomorphology and other sub-disciplines of geomorphology, (2) to contribute to the strengthening of the conceptual basis of periglacial geomorphology, and, therefore, (3) to strengthen the possibilities for holistic exchange within the cryospheric research community.
Article
The long and complex depositional and tectonic history of the Appalachians has produced a substrate of folded and faulted sandstones, shales, and carbonate rocks (leaving aside the metamorphic and igneous core). The Appalachian fluviokarst is an evolving landscape developed on the carbonate rocks. The erosion of surface streams competes with dissolutional processes in the carbonate rocks, and both compete with tectonic uplift of the eastern margin of the North American plate. The Appalachians have undergone erosion since the Jurassic and 5 to 15 km of sediment have been removed. Many karst landscapes have come and gone during this time period. The earliest cosmogenic-isotope dates place the oldest Appalachian caves in the early Pliocene. Various interpretations and back-calculations extend the recognizable topography to the mid to late Miocene. Much of the present-day karst landscape was created during the Pleistocene. There have been many measurements and estimates of the rate of denudation of karst surfaces by dissolution of the carbonate bedrock and many estimates of the rate of downcutting of surface streams. Curiously, both of these estimates give similar values (in the range of 30 mm ka 21), in spite of the differences in the erosional processes. These rates are somewhat higher than present-day rates of tectonic uplift, leaving the contemporary landscape the result of a balance between competing processes. Introduction of tectonic forces into the interpretation of karst landscapes requires consideration of the long-term uplift rates. In the Davisian point of view, uplift was episodic, with short periods of rapid uplift followed by long static periods that allowed the development of peneplains. In the Hackian point of view, uplift has occurred at a more or less constant rate, so that present topography is mainly the result of differential erosion rates. Attempts to back-calculate the development of karst landscapes requires a conceptual model somewhere between these rather extreme points of view.
Article
Landscapes subject to constant forcing tend to evolve toward equilibrium states in which individual landforms have similar characteristics. Yet, even in landscapes at or near equilibrium, there can be significant variability among individual landforms. Furthermore, sites subject to similar processes and conditions can have different mean landform characteristics. This variability is often ascribed to on-going transient evolution, or to heterogeneity in processes, material properties, forcing, or boundary conditions. Three surprising outcomes of landform evolution models suggest, however, that such variability could arise in equilibrium landscapes without any heterogeneity in the physical processes shaping the topography. First, homogeneous systems subjected to constant forcing can generate a heterogeneous distribution of equilibrium landforms. Second, even simple non-linear systems can have multiple stable equilibrium states. Third, evolving landscapes can exhibit path dependence and hysteresis. We show how these three mechanisms can produce variability in landforms that arises from the characteristics of the initial topographic surface rather than from heterogeneity in geomorphic processes. Numerical experiments on the formation of low-order fluvial valleys and transportational cyclic steps in erodible streambeds illustrate why it is important to consider the influence of initial conditions when comparing models with natural topography, estimating the uncertainty of model predictions, and studying how landscapes respond to disturbances. Copyright © 2011 John Wiley & Sons, Ltd.
Article
Jovan Cvijić was born in western Serbia and studied widely in the Dinaric Kras. His publication of Das Karstphänomen (1893) established that rock dissolution was the key process and that it created most types of dolines, “the diagnostic karst landforms”. The Dinaric Kras thus became the type area for dissolutional landforms and aquifers; Germanicised as “karst”, the regional name is now applied to modern and paleo-dissolutional phenomena worldwide. Cvijić related the complex behaviour of karstic aquifers to development of solutional conduit networks and linked it to a cycle of landform evolution. He is recognized as “the father of karst geomorphology”.
Article
The evolution and flow in a karst aquifer is studied with numerical simulations, based on the KARST model (Karst AquifeR Simulation Tool). The aquifer consists of a three-dimensional interconnected network of conduits representing fractures in the rock, and a porous rock matrix representing the finer fissured system in the rock. Flow through the aquifer can be driven by both diffuse recharge from precipitation and localised sinking streams, and the aquifer drains towards a large karst resurgence representing the base level. Superimposed onto the karst aquifer is a landscape, which can evolve with time by small-scale diffusive processes, large-scale river erosion, and karst denudation.Fractures in the aquifer are enlarged with time by chemical dissolution, enhancing the secondary porosity of the karst aquifer. The enlargement of fractures results in a dramatic increase of the aquifer conductivity over several orders of magnitude, and a change of flow patterns from an initially pore-controlled to a heterogeneous fracture-controlled aquifer. During the evolution, the water table is falling from an initially high position close to the land surface to a lower level coinciding with the actual base level.Two model scenarios are studied to elucidate the karst aquifer evolution in three dimensions. The evolution models are then complemented by event-type spring discharge modelling, which can be used as a predictive tool for karst spring discharge and contaminant transport.