Nitrogen retention in the riparian zone of watersheds underlain by discontinuous permafrost

Thesis (M.S.) University of Alaska Fairbanks, 2005Riparian zones function as important ecotones for reducing nitrate concentration in groundwater and inputs into streams. In the boreal forest of interior Alaska, permafrost confines subsurface flow through the riparian zone to shallow organic horizons, where plant uptake of nitrate and denitrification are typically high. Two research questions were addressed in this study: 1) how does riparian zone nitrogen retention vary in watersheds underlain by discontinuous permafrost, and 2) what is the contribution of denitrification to riparian zone nitrogen retention? To estimate the contribution of the riparian zone to watershed nitrogen retention, I analyzed groundwater chemistry using an end-member mixing model. To assess the importance of denitrification as a mechanism of nitrogen retention, I conducted field denitrification assays using the acetylene block technique. Over the summer, nitrogen retention averaged 0.75 and 0.22 mmol N m⁻² d⁻¹ in low and high permafrost watersheds, respectively. Compared with the fluvial export of nitrogen, the retention rate of nitrogen in the riparian zone is 10 - 15% of the loss rate in stream flow. Denitrification accounted for a small proportion (3%) of total nitrogen retention in the riparian zone. Variation in nitrogen retention between watersheds did not account for differences in stream nitrate concentration between watersheds.Introduction -- Factors controlling denitrification -- Riparian zones as nutrient filters -- Models of riparian zone function -- Permafrost and hydrology -- Caribou Poker Creeks Research Watershed (CPCRW) -- References -- Nitrogen retention in the riparian zone of watersheds underlain by discontinuous permafrost -- Conclusions -- References

The Effect of Riparian Buffer Zones of Macroinvertebrate Biodiversity and Stream Health

Riparian buffer zones are the forested areas between a stream and the surrounding land. They help preserve stream quality, and in doing so, help preserve biodiversity. Riparian buffer zones have an affect on a vast array of stream attributes, macroinvertebrate biodiversity, and the health of stream ecosystems; it is for this reason that they are important. Macroinvertebrates are often considered an indicator of ecosystem health and therefore the way that buffer zones affect macroinvertebrate species richness and abundance are often indicative of how they affect the rest of the ecosystem. The purpose of this project was to collect macroinvertebrates to test for differences between riparian and non-riparian zones. The data were collected once during each of the calendar seasons (twice during the fall) in the Yellow Breeches Creek in Cumberland County, Pennsylvania. Richness and abundance are not greater in riparian zones. However, the Shannon index and Becks scales are statistically greater in riparian zones; indicating greater biodiversity in riparian zones

The relationship between riparian zone width and floristic quality in Shenandoah County, Virginia

Riparian zones harbor an above average plant biodiversity. This biodiversity is threatened by invasive species and increasing human disturbance, the latter of which includes deforestation from agriculture and urban development. In this study, I examine relationship between the width of a forested riparian zone and the vegetation growing there. By using floristic quality assessment as a measure of anthropogenic disturbance, one can determine if wider riparian zones foster exclusion of non-native species while providing higher quality habitats for native plants. A randomized block design was used with three forested riparian treatments: deforested, moderately forested (woody vegetationstream), and extensively forested (woody vegetation \u3e50m wide from the stream). There was a significant difference in the floristic quality and percent native species between riparian zones with deforested, moderately forested, and extensively forested riparian zones (

Framework for evaluating the economic benefits, costs, and trade-offs associated with riparian-area management practices and strategies

The purpose of this paper is to provide an overview of the significant economic considerations is the analysis of the management, use, and enhancement of riparian zones in the interior West. Applied demonstration work has been done, including basic biological research relating to the functioning of riparian ecosystems and to the effects of domestic livestock grazing on the performance of the riparian system. The literature relating to that work is reviewed here, with an emphasis on implications for economic analysis. Attention is given to the subject of the costs and benefits of riparian-zone management, use, and enhancement strategies from the private and from the social perspectives. The final part of the paper deals with the types of values riparian zones provide, the social benefits resulting from the improvement of riparian zones, the private and social costs of riparian-zone degradation, and the possibilities for the provision of economic incentives to encourage voluntary private sector participation in riparian improvement projects on both private and public lands

The influence of Mediterranean riparian forests on stream nitrogen dynamics: a review from a catchment perspective

The influence ofMediterranean riparian forests on stream nitrogen dynamics: a review from a catchment perspective Riparian zones are considered natural filters of nitrogen (N) within catchments because they can substantially diminish the exports of N from terrestrial to aquatic ecosystems. However, understanding the influence of riparian zones on regulating N exports at the catchment scale still remains a big challenge in ecology, mainly because upscaling plot scale results is difficult, as it is disentangling the effects of riparian, upland, and in-stream processes on stream water chemistry. In this review, we summarize previous studies examining key hydrological and biogeochemical processes by which Mediterranean riparian zones regulate catchment water and N exports.We focus onMediterranean regions because they experience a marked climatic seasonality that facilitates disentangling the close link between climate, riparian hydrology, and stream N exports. We show that Mediterranean riparian soils can be hot spots of N mineralization and nitrification within catchments given their relatively moist conditions and large stocks of N-rich leaf litter. Extremely large nitrification rates can occur during short-time periods (i.e. hot moments) and lead to increases in stream N loads, suggesting that riparian soils can be a potential source of N to adjacent aquatic systems. Moreover, riparian trees can contribute to decrease riparian groundwater level during the vegetative period, and promote reverse fluxes from the stream to the riparian zone. During periods of high hydrological retention, stream water exports to downstream ecosystem decrease, while stream water chemistry is mostly determined by in-stream processes. Riparian tree phenology can also affect catchment N exports by shaping the temporal pattern of both light and litter inputs into the stream. In spring, light enhances in-stream photoautotrophic N uptake before riparian leaf-out, while riparian leaf litter inputs promote in-stream N mineralization in summer and fall. Finally, we illustrate that the impact of Mediterranean riparian zones on stream hydrology and biogeochemistry increases along the stream continuum, and can ultimately influence catchment N exports to downstream ecosystems. Overall, findings gathered in this review question the well-established idea that riparian zones are efficient N buffers, at least for Mediterranean regions, and stress that an integrated view of upland, riparian, and stream ecosystems is essential for advancing our understanding of catchment hydrology and biogeochemistry

Multitaxonomic Diversity Patterns along a Desert Riparian–Upland Gradient

Riparian areas are noted for their high biodiversity, but this has rarely been tested across a wide range of taxonomic groups. We set out to describe species richness, species abundance, and community similarity patterns for 11 taxonomic groups (forbs & grasses, shrubs, trees, solpugids, spiders, scarab beetles, butterflies, lizards, birds, rodents, and mammalian carnivores) individually and for all groups combined along a riparian–upland gradient in semiarid southeastern Arizona, USA. Additionally, we assessed whether biological characteristics could explain variation in diversity along the gradient using five traits (trophic level, body size, life span, thermoregulatory mechanism, and taxonomic affiliation). At the level of individual groups diversity patterns varied along the gradient, with some having greater richness and/or abundance in riparian zones whereas others were more diverse and/or abundant in upland zones. Across all taxa combined, riparian zones contained significantly more species than the uplands. Community similarity between riparian and upland zones was low, and beta diversity was significantly greater than expected for most taxonomic groups, though biological traits explained little variance in diversity along the gradient. These results indicate heterogeneity amongst taxa in how they respond to the factors that structure ecological communities in riparian landscapes. Nevertheless, across taxonomic groups the overall pattern is one of greater species richness and abundance in riparian zones, coupled with a distinct suite of species

The use of riparian buffer zones for the attenuation of nitrate in agricultural landscapes.

Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2002The focus of this mini-dissertation is the use of riparian buffer zones to manage nitrate pollution of water resources. Riparian buffer zones are vegetated areas adjacent to streams, lakes and rivers, that are managed to enhance and protect aquatic resources from the adverse impacts of agricultural practices. These zones are recognised globally for their function in water quality amelioration. Despite the growing literature, there is little consensus on how to design, assess and manage these riparian buffer zones specifically for nitrate attenuation. For the purpose of this mini-dissertation, a literature review of world-wide research into the nitrate attenuation efficiencies of riparian buffer zones was undertaken. A database was created using the key information from this literature. Two key processes responsible for immobilising and/or removing nitrate from surface and subsurface flows are generally recognised in the available literature, namely: vegetative uptake and the process of denitrification. A comparison of the available riparian studies indicated that there are similar characteristics in riparian buffer zones that may be responsible for enhancing these key mechanisms. Studies where there was shallow lateral subsurface or uniform surface water delivery pathways, vegetation of close structure and composition, high organic matter in the soils and fluctuating soil surface saturation rates showed the most significant nitrate attenuation efficiencies. The mini-dissertation proposes that these similarities can be used to both assess a riparian landscape for its potential to attenuate nitrate, and to size a riparian buffer zone specifically to meet this function. A set of proposed guidelines based on the findings of the dissertation attempt to illustrate how riparian pollution control recommendations can be achieved. These guidelines are an example of how to assist a farmer or similar landowner in achieving good nitrate removal efficiencies from a riparian buffer zone. The guidelines work through three steps, which help to establish and prioritise management zones, assess each zone's potential for nitrate attenuation, and determine adequate riparian buffer widths for each management zone. A case study was used to illustrate the practical application of the guidelines. Full testing of these guidelines was not within the scope of this mini-dissertation, however the guidelines are an indication of how information regarding riparian function can be applied to a system to determine effective management of water resources

An evaluation of the ecology and riparian management of the south branch of the Whareroa Stream, Paekakariki : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Natural Resource Management at Massey University

Whareroa Farm, Mackays Crossing, Paekakariki, was bought by the Department of Conservation in 2005. The goal was to effect the restoration of a corridor for flora and fauna from the Akatarawa Forest in the east to Queen Elizabeth Park and the sea in the west. The south branch of the Whareroa Stream, which arises as a series of tributaries from a ridge 272m above sea level, traverses Whareroa Farm and the adjacent Queen Elizabeth Park. It was thought likely that the stream had been severely affected ecologically during a century of cattle and sheep farming, though the degree to which the ecological degradation had occurred was unknown. Obvious deforestation and land use changes suggested that, in concert with many other New Zealand hill country farms, the ecological changes would be significant. To establish and quantify the degree of degradation, the Auckland Regional Council (ARC) Stream Environment Valuation (SEV) protocol was applied to the Whareroa Stream and its tributaries. Five sites were selected for valuation, varying from open pasture to bush covered and open parkland. The resulting SEV scores showed losses of ecological value ranging from 32% to 46% across the sites. The Macroinvertebrate Community Index (MCI) and the fish Index of Biological Integrity (IBI) were measured at each site. Results indicated that aquatic habitats were unable to sustain adequate assemblages at four of the five sites. The valuations of the riparian zones at each site used the River Environment Classification (REC) and Riparian Management Classification (RMC) protocols. The results indicated that current riparian characteristics showed poor to absent effective riparian zones from the headwaters to the sea at all sites. Riparian zones are pivotal to the provision of stream ecological integrity and are responsible for maintaining the longitudinal, lateral and vertical connectivity between a stream, its network and its surrounding land. The loss of in-stream organic matter from lack of riparian vegetation together with the loss of effective temperature control from lack of shade, impacts negatively on the habitats for macroinvertebrates and fish. This was highlighted in the Whareroa Stream network. While the SEV and RMC evaluations showed that, with best practice management plans, there was great potential for improvement of the Whareroa Stream ecology, any riparian restoration would require sympathetic and improved fencing, withdrawal of stock from stream access and the retirement of headwater land from pastoral use. The loss of ecological integrity that occurs as a result of prolonged land use changes from forest to agriculture is well illustrated by the situation in the south branch of the Whareroa Stream and its tributaries

Nitrogen removal and the fate of Nitrate in Riparian buffer zones

Riparian buffer zones, adjacent to waterways, may protect water quality by intercepting and removing nitrogen in runoff from agricultural land. This research comprised four parts: (1) a field study of nitrogen buffering by differently vegetated riparian zones in a United Kingdom (UK) sheep-grazed pastoral catchment; (2) a field study of surface and subsurface runoff hydrology, and nitrogen flux, in a UK riparian wetland; (3) a laboratory study ((^15)N tracer-isotope dilution) of microbial inorganic nitrogen production and removal processes in the UK riparian wetland soil; and (4) a laboratory microcosm study ((^15)tracer) of nitrate removal processes in bare and plant-inhabited (Glyceria declinata) New Zealand (NZ) riparian wetland soil. Dissolved organic nitrogen and ammonium were generally more important components of subsurface runoff than nitrate in the three UK riparian zones. All riparian zones were poor buffers having minimal effect on the nitrogen concentration of subsurface runoff. In the UK riparian wetland site subsurface (saturated zone) and surface 'preferential flow paths' typically conveyed large quantities of catchment runoff rapidly into, and across the site, and hindered nitrogen buffering. However, under low flow conditions, runoff-riparian soil contact increased and the wetland decreased the catchment nitrogen flux by 27%. In the UK riparian wetland soil most nitrate removal was attributable to denitrification (87- 100%) as opposed to dissimilatory nitrate reduction to ammonium (DNRA) (0-13%) and immobilisation (0-10%). Total ((^14)N+(^15)N) transformation rates for these processes were 1.3-47, 0.5-1.5 and 0.6-2.5 μg N g soil(^-1) hr(^-1) respectively. In the NZ riparian wetland soil Glyceria declinata assimilated 11-15% of nitrate but, more importantly, increased soil oxidation and altered the proportions of nitrate removal attributable to denitrification (from 29% to 61-63%) and DNRA (from 49 to <1%), but not immobilisation (22-26%). Denitrification and, thus, nitrogen buffering might be enhanced, in some riparian zones by increasing the extent of moderately anoxic soil with plants that release oxygen from their roots or with water table management

Characterization of Pan-Mediterranean Riparian Areas by Remote Sensing Derived Phenological Indices

This report aimed at inventorying characteristics of Mediterranean riparian-use zones using statistical analysis of some phenological indices calculated from remote sensing time series. Riparian areas are focused because of their prime importance in offering potential for adapted agricultural landuse and their ecosystem services. The quantity of vegetation cover present in these wider riparian-use zones has been proven to be directly dependent to adjacent landuse and related to the functioning of the zone as wider riparian buffer. Phenological indices derived from low resolution remote sensing time series can be used in complement with other data to assess and monitor dynamics and stresses of the riparian-use zones.JRC.H.7-Land management and natural hazard