Ecohydrology 

About: Ecohydrology is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Evapotranspiration & Riparian zone. It has an ISSN identifier of 1936-0584. Over the lifetime, 1337 publications have been published receiving 35249 citations. The journal is also known as: eco-hydrology.

Hydrological feedbacks in northern peatlands

Abstract: Northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). However, these ecosystems face increases in the severity, areal extent and frequency of climate-mediated (e.g. wildfire and drought) and land-use change (e.g. drainage, flooding and mining) disturbances that are placing the future security of these critical ecosystem services in doubt. Here, we provide the first detailed synthesis of autogenic hydrological feedbacks that operate within northern peatlands to regulate their response to changes in seasonal water deficit and varying disturbances. We review, synthesize and critique the current process-based understanding and qualitatively assess the relative strengths of these feedbacks for different peatland types within different climate regions. We suggest that understanding the role of hydrological feedbacks in regulating changes in precipitation and temperature are essential for understanding the resistance, resilience and vulnerability of northern peatlands to a changing climate. Finally, we propose that these hydrological feedbacks also represent the foundation of developing an ecohydrological understanding of coupled hydrological, biogeochemical and ecological feedbacks. Copyright © 2014 John Wiley & Sons, Ltd.

A synthetic review of feedbacks and drivers of shrub encroachment in arid grasslands

Abstract: Many arid grasslands around the world are affected by woody plant encroachment and by the replacement of a relatively continuous grass cover with shrub patches bordered by bare soil. This shift in plant community composition is often abrupt in space and time, suggesting that it is likely sustained by positive feedbacks between vegetation and environmental conditions (e.g. resource availability) or disturbance regime (e.g. fire or freeze). These feedbacks amplify the effects of drivers of shrub encroachment, i.e. of conditions favouring a shift from grass to shrub dominance (e.g. overgrazing, climate change). Here, we review some major drivers and feedbacks and identify the basic stages in the transition from grassland to shrubland. We discuss some possible scenarios of interactions between drivers and feedbacks that could explain the transition from a stage to the next and the potential irreversibility of the shift from grass to shrub dominance. We introduce a simplistic modelling framework that can integrate the various drivers to explain the emergence of bistability for shrub-encroached grassland systems. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

Abstract: In arid/semi-arid environments, where rainfall is seasonal, highly variable and significantly less than the evaporation rate, groundwater discharge can be a major component of the water and salt balance of a wetland, and hence a major determinant of wetland ecology. Under natural conditions, wetlands in arid/semi-arid zones occasionally experience periods of higher salinity as a consequence of the high evaporative conditions and the variability of inflows which provide dilution and flushing of the stored salt. However, due to the impacts of human population pressure and the associated changes in land use, surface water regulation, and water resource depletion, wetlands in arid/semi-arid environments are now often experiencing extended periods of high salinity. This article reviews the current knowledge of the role that groundwater–surface water (GW–SW) interactions play in the ecology of arid/semi-arid wetlands. The key findings of the review are as follows: 1.GW–SW interactions in wetlands are highly dynamic, both temporally and spatially. Groundwater that is low in salinity has a beneficial impact on wetland ecology which can be diminished in dry periods when groundwater levels, and hence, inflows to wetlands are reduced or even cease. Conversely, if groundwater is saline, and inflows increase due to raised groundwater levels caused by factors such as land use change and river regulation, then this may have a detrimental impact on the ecology of a wetland and its surrounding areas. 2.GW–SW interactions in wetlands are mostly controlled by factors such as differences in head between the wetland surface water and groundwater, the local geomorphology of the wetland (in particular, the texture and chemistry of the wetland bed and banks), and the wetland and groundwater flow geometry. The GW–SW regime can be broadly classified into three types of flow regimes: (i) recharge—wetland loses surface water to the underlying aquifer; (ii) discharge—wetland gains water from the underlying aquifer; or (iii) flow-through—wetland gains water from the groundwater in some locations and loses it in others. However, it is important to note that individual wetlands may temporally change from one type to another depending on how the surface water levels in the wetland and the underlying groundwater levels change over time in response to climate, land use, and management. 3.The salinity in wetlands of arid/semi-arid environments will vary naturally due to high evaporative conditions, sporadic rainfall, groundwater inflows, and freshening after rains or floods. However, wetlands are often at particular risk of secondary salinity because their generally lower elevation in the landscape exposes them to increased saline groundwater inflows caused by rising water tables. Terminal wetlands are potentially at higher risk than flow-through systems as there is no salt removal mechanism. 4.Secondary salinity can impact on wetland biota through changes in both salinity and water regime, which result from the hydrological and hydrogeological changes associated with secondary salinity. Whilst there have been some detailed studies of these interactions for some Australian riparian tree species, the combined effects on aquatic biodiversity are only just beginning to be elucidated, and are therefore, a future research need. 5.Rainfall/flow-pulses, which are a well-recognized control on ecological function in arid/semi-arid areas, also play an important, though indirect, role through their impact on wetland salinity. Freshwater pulses can be the primary means by which salt stored in both the water column and the underlying sediments are flushed from wetlands. Conversely, increased runoff is also a commonly observed consequence of secondary salinity, and so, wetlands can experience increased surface water inflows that are higher in salinity than under natural conditions. Moreover, changes in rainfall/flow-pulse regimes can have a significant impact on wetland GW–SW interactions. It is possible that in some instances groundwater inflow to a wetland may become so heavy that it could become a major component of the water balance, and hence, mask the role of natural pulsing regimes. However, if the groundwater is low in salinity, this may provide an ecological benefit in arid/semi-arid areas by assisting in maintaining water in wetlands that become aquatic refugia between flow-pulses. 6.There has been almost no modelling of GW–SW interactions in arid/semi-arid wetlands with respect to water fluxes, let alone salinity or ecology. There is a clear need to develop modelling capabilities for the movement of salt to, from, and within wetlands to provide temporal predictions of wetland salinity which can be used to assess ecosystem outcomes. 7.There has been a concerted effort in Australia to collect and collate data on the salinity tolerance/sensitivity of freshwater aquatic biota and riparian vegetation. There are many shortcomings and knowledge gaps in these data, a fact recognized by many of the authors of this work. Particularly notable is that there is very little time-series data, which is a serious issue because wetland salinities are often highly temporally variable. There is also a concern that many of the data are from very controlled laboratory experiments, which may not represent the highly variable and unpredictable conditions experienced in the field. In light of these, and many other shortcomings identified, our view is that the data currently available are a useful guide but must be used with some caution. Copyright © 2008 John Wiley & Sons, Ltd.

Inter-disciplinary perspectives on processes in the hyporheic zone

Abstract: The interface between groundwater and surface water within riverine/riparian ecosystems--the hyporheic zone (HZ)--is experiencing a rapid growth of research interest from a range of scientific disciplines, often with different perspectives. The majority of the multi-disciplinary research aims to elucidate HZ process dynamics and their importance for surface water and groundwater ecohydrology and biogeochemical cycling. This paper presents a critical inter-disciplinary review of recent advances of research centred on the HZ and highlights the current state of knowledge regarding hydrological, biogeochemical and ecohydrological process understanding. The spatial and temporal variability of surface water and groundwater exchange (hyporheic exchange flows), biogeochemical cycling and heat exchange (thermal regime) are considered in relation to both experimental measurements and modelling of these phenomena. We explore how this knowledge has helped to increase our understanding of HZ ecohydrology, and particularly its invertebrate community, the processing of organic matter, trophic cascading and ecosystem engineering by macrophytes and other organisms across a range of spatial and temporal scales. In addition to providing a detailed review of HZ functions, we present an inter-disciplinary perspective on how to advance and integrate HZ process understanding across traditional discipline boundaries. We therefore attempt to highlight knowledge gaps and research needs within the individual disciplines and demonstrate how innovations and advances in research, made within traditional subject-specific boundaries (e.g. hydrology, biochemistry and ecology), can be used to enhance inter-disciplinary scientific progress by cross-system comparisons and fostering of greater dialogue between scientific disciplines.

A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales

Abstract: Land degradation is a problem prolific across semi-arid areas worldwide. Despite being a complex process including both biotic and abiotic elements, previous attempts to understand ecosystem dynamics have largely been carried out within the disparate disciplines of ecology and hydrology, which has led to significant limitations. Here, an ecohydrological framework is outlined, to provide a new direction for the study of land degradation in semi-arid ecosystems. Unlike other frameworks that draw upon hierarchy theory to provide a broad, non-explicit conceptual framework, this new framework is based upon the explicit linkage of processes operating over the continuum of temporal and spatial scales by perceiving the ecosystem as a series of structural and functional connections, within which interactions between biotic and abiotic components of the landscape occur. It is hypothesized that semi-arid land degradation conforms to a cusp-catastrophe model in which the two controlling variables are abiotic structural connectivity and abiotic functional connectivity, which implicitly account for ecosystem resilience, and biotic structural and function connectivity. It is suggested therefore that future research must (1) evaluate how abiotic and biotic function (i.e. water, sediment and nutrient loss/redistribution) vary over grass–shrub transitions and (2) quantify the biotic/abiotic structure over grass-shrub transitions, to (3) determine the interactions between ecosystem structure and function, and interactions/feedbacks between biotic and abiotic components of the ecosystem. Copyright  2008 John Wiley & Sons, Ltd.