Gotowa bibliografia na temat „Streambank planting”

To understand the timescales and magnitude of responses that can be expected following catchment and riparian rehabilitation, we forecast changes to selected stream ecosystem attributes following tree planting in a pastoral catchment. All planting scenarios were predicted to lead to decreases in daily maximum water temperature after 15-20 years to levels that would be suitable for sensitive invertebrate species. Cooling and reheating were rapid so that most benefits to water temperature along the mainstem were forecast to accrue from shading all of the stream channel network. All planting scenarios were predicted to increase sediment yields over the status quo over the 25-year timeframe examined, with maximal sediment yield occurring about 15 years after planting due to expected erosion of the streambanks under the developing forest shade. Sediment yield was greatest for full catchment planting over 25 years, although sediment yield would be lowest with this scenario over longer timescales. A macroinvertebrate biotic index was predicted to increase by 25% over 15 years if whole catchment afforestation were implemented, compared to 9% if only the 4th order mainstem were planted with riparian trees. The use of ecological forecasting to predict likely outcomes for a range of scenarios should prove useful for prioritising rehabilitation actions.

Black willow (Salix nigra) stem cuttings are commonly used to stabilize eroded streambanks with survival dependent on rapid development of adventitious roots to maintain plant water balance, absorb nutrients, and provide anchorage and support especially during flood and drought events. Soaking cuttings in water prior to planting increases survival and growth rates, but it is not known whether oxygen content in the soaking water affects the rate of early root and shoot initiation and growth. A laboratory experiment tested the hypothesis that cuttings treated with high oxygen (>95% saturation, 8.62 mg O2l–-1) soaking exhibit more rapid initiation and growth of roots and shoots than cuttings treated with low oxygen (<15% saturation, 1.24 mg O2l-1) soaking and control (unsoaked). Root initiation was enhanced in both high and low O2soaking treatments compared to control (100, 93, and 41%, respectively, n = 27). High O2soaking led to greater root length than low O2soaking during the fourth week after planting (26.5 and 12.3 cm on day 22; 27.7 and 19.1 cm on day 27, respectively). Shoot growth was greater in high O2compared to low O2soaking on days 36 and 56 after planting (9.3 and 6.3 cm on day 36, 10.7 and 7.2 cm on day 56, respectively). Shoot and root biomass production was stimulated in both soaking treatments, with 200% more biomass production by day 59 compared to control. Results of this study demonstrated that a high oxygen soaking treatment has potential for improving early root and shoot growth, and survival in willow cuttings planted at riparian restoration sites.

While stream restorations are increasingly being adopted to mitigate sediment and nutrient inputs and to meet water quality regulatory targets, less information is available on the drivers behind the design, implementation, effectiveness, and cost of restorations. We address these issues for a $4.2 million stream restoration for legacy sediments implemented for a rural Piedmont stream in Maryland, USA. A total of 1668 m of stream was restored in three phases, which included the partial removal of legacy sediments, the grading of streambanks, floodplain creation, channel reshaping with meanders and pool-riffle forms, the raising of the stream bed, and the planting of riparian vegetation. The sediment, nitrogen, and phosphorus concentrations and fluxes were monitored before- and during the restoration phases. The sites selected for restoration had legacy sediments vulnerable to erosion and were on state-owned land. The restoration design was based on the need to maintain mature riparian trees and preserve existing sensitive wetland habitats. Water quality monitoring indicated that the sediment and nutrient fluxes increased during the restoration phase and were attributed to disturbance associated with construction activities and increased runoff. We also recommend that soil health needs to be included as an integral component to enhance the effectiveness and resilience of stream restorations.

This thesis provides baseline information on the ecological processes involved in the recruitment and regeneration of riparian vegetation. As there has been a paucity of basic ecological studies on riparian vegetation in Australia, the project is broad in scope, and gives a general picture of the factors influencing, the regeneration of riparian vegetation and provides a starting point for more detailed work. The project focuses on factors determining recruitment events and the life history traits of particular species in a river in the cool temperate zone of south western Australia (Blackwood River) and on a river in the dry tropics of the Kimberley region of north-western Australia (Ord River). By studying two contrasting river systems in different climatic zones, the influence of the physical environment and biotic factors in vegetation persistence and recruitment in the riparian zone can be distinguished. This will contribute to providing an ecological basis for the rehabilitation and management of riparian vegetation in these types of systems. The structure of the vegetation on the Blackwood River consists of an overstorey dominated by Eucalyptus rudis, with a shrub understory at ungrazed sites and with annual species dominant in areas grazed by livestock. On the Ord River there is a much more diverse overstsorey and a species-poor understorey dominated by perennial grasses. Fencing to exclude stock, or to at least manage grazing, is a fundamental step towards achieving rehabilitation of degraded riparian sites where recruitment may be severely limited. Exclosure experiments in the Blackwood River show little improvement in recruitment after three years, with only minor increases in the occurrence and cover of native species. Establishment of these species may be difficult with the increase in abundance of exotic grasses and annual herbs which has occurred as a result of the absence of grazing. These results are however for the short-term and a much longer period is required to look at the vegetation dynamics and successional processes of these sites. In the riparian zone, regeneration of the vegetation from soil seedbanks is important for annual species of herbs and grasses but of only minor significance for perennial species. For perennial species, particularly the overstorey, direct seedfall from existing vegetation occurs, and enhanced dispersal by floating downstream with flood debris is a consequential recruitment mechanism. Hence, reproductive phenology of the four species monitored in this study appears to be well adapted to the hydrological regime on the respective rivers. Position in the riparian landscape where seedlings manage to establish is strongly related to environmental conditions that provide adequate moisture but protect seedlings from flooding. Historical flow records can be used to develop an understanding of the natural flow regime for a particular river which can then be related to patterns of vegetation development in terms of reproductive phenology, seedling establishment and population structure, as well as plant community patterns in the riparian zone. Variability in natural flow regimes, as a disturbance, can therefore be used in conjunction with other abiotic and biotic factors in developing a model of vegetation dynamics for the riparian zone. For example, the regime of intermittent high frequency large flood disturbances on the Ord River prevents the establishment of stable states of the vegetation and the ecosystem is characterised by long periods of transition between short-lived stable states. This riparian ecosystem is thus driven by physical (allogenic) processes rather than by vegetation successional (autogenic) processes. In contrast, lower energy seasonal flooding on the Blackwood River allows mature stands of trees to develop throughout the river profile. Recruitment is continual, although species can also respond to large flood events. This disturbance regime results in long periods of stable status with short periods of transition. The vegetation is thus subject to longer periods of autogenic processes and, because of lower frequency flooding disturbance, shorter periods of allogenic processes. These results highlight the effect of the different fluvial regimes of the two rivers on the respective vegetation dynamics. Management of the riparian vegetation should therefore take into account the frequency and rate of change in the vegetation and that disturbed states and long periods of transition between states, particularly on the Ord River, are part of the natural process. This would suggest that altering the natural flow regimes, such as through river regulation, would have significant effects on riparian vegetation dynamics. This work has relevance to all aspects of riparian zone vegetation, including management of natural systems unaffected by man-made disturbances, for systems affected by stock grazing, for areas requiring rehabilitation and on regulated rivers. It highlights the importance of fluvial processes to riparian vegetation and indicates that understanding the natural flow regime of a target river is a critical first step in the management of riparian vegetation and in the planning of riparian vegetation zone rehabilitation. Where the riparian zone is highly modified, through, for example, livestock grazing and/or weed invasion, natural regeneration of the riparian vegetation may be a long term process. If intervention, such as replanting, is appropriate, care should be taken that species selected are adapted to particular site conditions, such as flooding regime, landscape position and river geomorphology.

Agriculture is key to New Zealand�s economy with land-use conversions in response to market forces occurring regularly. Recently, high-intensity dairy farming has replaced low-density livestock farming, often degrading surrounding waterways. Of particular concern is that dairy cattle can be a source of the parasite Giardia, which in humans is a common cause of gastrointestinal infection. Thus, this thesis evaluated whether dairy farm conversions posed significant consequences for public health. First I examined the prevalence of Giardia in calves in a rapidly intensifying dairying region of New Zealand. A total of 1190 faecal samples were collected from calves one to seven weeks old during two spring calving seasons and screened by direct immunofluorescent microscopy. Giardia cysts were detected in 31% of samples. To evaluate the potential risk that this environmental source of Giardia posed to the human population, molecular genotyping was used to compare forty Giardia strains isolated from calves with thirty isolates from humans collected in the same region and period. Sequencing the β-giardin gene, Giardia duodenalis assemblages A and B were identified from both hosts, with genotype comparisons revealing substantial overlap of identical genotypes for both assemblages, implying zoonotic transmission. Environmental agencies routinely promote the planting of streamside edges to decrease nonpoint pollution from dairy farms entering waterways. However, current methods for tracking pathogens across farmland and into waterways via surface runoff are limited and typically have been developed using artificially created landscapes. Furthermore, no studies have investigated how Giardia moves across the landscape in farm surface runoff. I developed a field-based tracking method specific for Giardia and used this technique to compare the ability of recently planted vegetation strips with bare soil strips cleared of vegetation at decreasing pathogen concentrations; a typical scenario when planting barriers to reduce waterway contamination. A spike containing a bromide tracer and inactivated Giardia cysts was applied in drip-irrigated surface runoff, with one-minute samples collected from the bottom of the plot. A significant treatment effect was identified for Giardia, with 26% fewer detected in runoff from the planted strip, highlighting the immediate benefit of vegetation planting in removing pathogens. Next I evaluated the effects of four riparian treatments on Giardia runoff: exotic pasture grass and weeds growing in the absence of cattle grazing due to fencing, in comparison to monocultural plantings of three New Zealand native grassland species. Runoff experiments were performed after planting, both prior to and following the main summer growing season. Bromide recovery was high from all four treatments (54 - 99%), with no significant treatment effects. By comparison, Giardia recovery was low (1 - 13%). Prior to summer, two native species reduced Giardia in runoff more than the pasture grass/weed treatment which was almost vegetation-free at this time. After summer, Giardia recoveries were uniformly lower in all treatments. These results demonstrate that after one growing season, fencing waterways produces riparian buffers, via the growth of exotic pasture plants released from grazing, that decrease pathogen concentrations in surface runoff to concentrations indistinguishable from native plantings. Given infectious organisms are known to be in the environment, it is important to assess the risk these pose to human populations. Findings from this research can be used to improve currently available risk-assessment models for Giardia transmission from infected dairy animals via water to humans.

The US Army Corps of Engineers Regional Sediment Management (RSM) program funded research to assess the longevity and effectiveness of cedar tree revetments for sediment reduction. Between 1988 and 1997, the Missouri Department of Conservation (MDC) constructed multiple cedar tree revetments, plantings, and a grade-control structure at an experimental stream management area on Locust Creek within the Locust Creek Conservation Area (LCCA). For the first few years, MDC also replaced missing trees as needed. MDC monitored these sites with photographs and cross sections until 2004. This study evaluated bank stability on Locust Creek from 1970 to 2019 using aerial imagery, lidar, ground surveys, and a December 2019 site visit to estimate the areal change in streambanks and the volume of sediment eroded over the years. Based on their dates of construction, the project compared preproject, with-project, and postfailure conditions at each site. The project included cedar tree revetments, other hardwood revetments, plantings, and a grade-control structure. This research found a 50% to 64% reduction in erosion for approximately 14 years. As of December 2019, all tree revetments had failed, and banks were bare and steep. The grade-control structure remained intact and continued to stabilize bed and banks immediately upstream.