Quantifying ecological effects of sedimentation in streams in differing land use management zones

<p>This ecological and geomorphological assessment of Horokiri Stream and Ration Creek was conducted across four longitudinal zones to explore the effects of sediment delivery, run-off, channel form, riparian and in-stream habitat. The Horokiri Stream channel has moved approximately 7 metres westward over the last 20 years, with both banks now covered in long grass, flaxes, natives with a mix of tall canopy trees. Looking at stream, Spearman’s for Ration at Figure 27 (n = 16, rho -0.243, p = 0.36) as deposited sediment increased, MCI decreased, non-significant. Spearman’s for Horokiri at Figure 28 (n = 16, rho 0.247, p = 0.35) as MCI increased with sediment, non-significant. Results from upstream of the riparian zones showed more deposited fine sediment. However, within both the riparian zones the sediment deposition was much lower. The native riparian planting along the stream banks had a positive effect on reducing sedimentation. The findings support the concept that the restoration of riparian zones with buffer widths exceeding 10 metres can improve stream habitat and invertebrate health. There was no relationship between flow and deposition rate P(X2>241.84) = 0.24. Figure 24 shows deposited sediment on MCI depending on land use groups (X2 = 11.81, df = 4, p = 0.019). No statistically significant differences were found (comparing the effect of sediment between different land use management groups). An experiment investigated a disturbance hypothesis in both Ration Creek and Horokiri Stream was conducted during February 2019. The experiment was designed to be long enough to study the effects of four weekly pulse flushing events created by scrapping the stream bed with a drain drag tool and the effects of a press sustained disturbance on the macroinvertebrate community. I measured the sediment and the macroinvertebrate captured in each trap within the experiment site every seven days. My prediction was that macroinvertebrate communities subject to sustained fine sediment delivery (press disturbance) are affected by simulated pulse flushing events (pulse disturbance). A comparison of sediment depositional rate before and after the manipulative experiment (Figure 36) showed higher sediment deposition after the pulse flushing events (1.55 W/A/D) compared to before during the assessment phase (0.88 W/A/D) in Horokiri (t = 2.35, df = 8.95, p = 0.04), but no significant difference before (1.57 W/A/D) or after (1.38 W/A/D) in Ration (t = -0.818, df = 7.71, p = 0.44). It appeared that the smaller riparian buffer width of 2-5m at Ration Creek did not limit sediment deposition. The effects of sediment disturbance in the experiment reflect the rapid ability of macroinvertebrates to respond to sediment by drifting out of unsuitable areas. The weekly pulse disturbance events resulted in increased sediment deposition compared to the background levels of sediment deposition (indicative of a press disturbance) in both streams. As pulse disturbance events increased, the number of macroinvertebrate taxa decreased. Horokiri Stream invertebrate communities declined by 33% compared to Ration Creek which declined by 50%.</p>

Quantifying ecological effects of sedimentation in streams in differing land use management zones

<p>This ecological and geomorphological assessment of Horokiri Stream and Ration Creek was conducted across four longitudinal zones to explore the effects of sediment delivery, run-off, channel form, riparian and in-stream habitat. The Horokiri Stream channel has moved approximately 7 metres westward over the last 20 years, with both banks now covered in long grass, flaxes, natives with a mix of tall canopy trees. Looking at stream, Spearman’s for Ration at Figure 27 (n = 16, rho -0.243, p = 0.36) as deposited sediment increased, MCI decreased, non-significant. Spearman’s for Horokiri at Figure 28 (n = 16, rho 0.247, p = 0.35) as MCI increased with sediment, non-significant. Results from upstream of the riparian zones showed more deposited fine sediment. However, within both the riparian zones the sediment deposition was much lower. The native riparian planting along the stream banks had a positive effect on reducing sedimentation. The findings support the concept that the restoration of riparian zones with buffer widths exceeding 10 metres can improve stream habitat and invertebrate health. There was no relationship between flow and deposition rate P(X2>241.84) = 0.24. Figure 24 shows deposited sediment on MCI depending on land use groups (X2 = 11.81, df = 4, p = 0.019). No statistically significant differences were found (comparing the effect of sediment between different land use management groups). An experiment investigated a disturbance hypothesis in both Ration Creek and Horokiri Stream was conducted during February 2019. The experiment was designed to be long enough to study the effects of four weekly pulse flushing events created by scrapping the stream bed with a drain drag tool and the effects of a press sustained disturbance on the macroinvertebrate community. I measured the sediment and the macroinvertebrate captured in each trap within the experiment site every seven days. My prediction was that macroinvertebrate communities subject to sustained fine sediment delivery (press disturbance) are affected by simulated pulse flushing events (pulse disturbance). A comparison of sediment depositional rate before and after the manipulative experiment (Figure 36) showed higher sediment deposition after the pulse flushing events (1.55 W/A/D) compared to before during the assessment phase (0.88 W/A/D) in Horokiri (t = 2.35, df = 8.95, p = 0.04), but no significant difference before (1.57 W/A/D) or after (1.38 W/A/D) in Ration (t = -0.818, df = 7.71, p = 0.44). It appeared that the smaller riparian buffer width of 2-5m at Ration Creek did not limit sediment deposition. The effects of sediment disturbance in the experiment reflect the rapid ability of macroinvertebrates to respond to sediment by drifting out of unsuitable areas. The weekly pulse disturbance events resulted in increased sediment deposition compared to the background levels of sediment deposition (indicative of a press disturbance) in both streams. As pulse disturbance events increased, the number of macroinvertebrate taxa decreased. Horokiri Stream invertebrate communities declined by 33% compared to Ration Creek which declined by 50%.</p>

Assessment of the Potential Natural Status of Riparian Zones in the Czech Republic

Riparian zones represent an important ecosystem providing a range of functions and services important to humans—e.g., biodiversity support, a reduction in erosion risk, or the transport of pollutants from the surrounding landscape to watercourses. At the same time, it is, unfortunately, an environment that has been often subjected to significant pressure during the agricultural cultivation of the landscape or the development of industrial and residential activities of human society. Thus, a large number of riparian ecosystems have disappeared or degraded. The assessment of the overall ecological status of riparian habitats constitutes an important source of information for the needs of watercourse management and landscape planning in the riparian landscape, the aim of which should be to maintain good status or to improve the current unsatisfactory state of these habitats. However, in order to reliably evaluate the current ecological status of the landscape, it is necessary to have information on the reference status, i.e., a potentially natural status that would prevail without human influence. For this purpose, a methodology that can determine the potential natural status of riparian zones in Central European conditions was developed. In this study, it was found that approximately a quarter (26 %) of all river basins in the Czech Republic reach very low environmental values of the potential natural status of riparian zones and, conversely, approximately 29 % of river basins are expected to develop significantly above average riparian zone quality if we neglect human impact.

Artificial Plantation Responses to Periodic Submergence in Massive Dam and Reservoir Riparian Zones: Changes in Soil Properties and Bacterial Community Characteristics

Plant and microbiome interactions are necessary for plant nutrient acquisition. However, relatively little is known about the responses of roots, bulk, and rhizosphere soil microbial communities in different artificial vegetation types (woody and herbaceous) in riparian areas of massive dams and reservoirs. Therefore, this study aims to assess such responses at elevations of 165–170 m a.s.l. in the riparian zones of the Three Gorges Dam Reservoir, China. The samples were collected containing the rhizosphere soil, bulk soil, and roots of herbaceous and woody vegetation at different emergence stages in 2018. Then, all the samples were analyzed to quantify the soil properties, bacterial community characteristics, and their interaction in the early and late emergence phases. In different periods, the weight of dominant soil bacteria, including Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Cyanobacteria, was higher, and their composition was different in the rhizosphere, bulk soil, and endophytes. Moreover, the soil co-occurrence networks indicated that the weight of soil physical properties was higher than chemical properties in the early emergence stage. In contrast, the weight of chemical properties was relatively higher in the late emergence stage. Furthermore, the richness and diversity of the bacterial community were mainly affected by soil organic matter. This study suggests that these herbaceous and woody vegetation are suitable for planting in reservoir areas affected by hydrology and human disturbance in light of soil nutrients and soil microbial communities, respectively. Additionally, these results provide valuable information to inoculate the soil with key microbiota members by applying fertilizers, potentially improving plant health and soil production.

Groundwater, Soil, and Vegetation Interactions at Discrete Riparian Inflow Points (DRIPs) and Implications for Boreal Streams

Hydrological processes at hillslope and catchment scales explain a large part of stream chemistry dynamics through source-transport mechanisms from terrestrial to aquatic ecosystems. Riparian zones play a central role, as they exert a strong influence on the chemical signature of groundwater discharge to streams. Especially important are riparian areas where upslope subsurface flow paths converge, because they connect a large part of the catchment to a narrow section of the stream. Recent research shows that both in terrestrial and aquatic ecosystems, riparian convergence zones fulfill important biogeochemical functions that differ from surrounding riparian zones. Most catchment-scale conceptual frameworks focus on generalized hillslope-riparian-stream transects and do not explicitly consider riparian convergence zones. This study integrates collective work on hydrology, groundwater chemistry, vegetation and soils of discrete riparian inflow points (DRIPs) in a boreal landscape. We show that compared to adjacent riparian forests, DRIPs have groundwater levels that are consistently near the surface, and supply organic-rich water to streams. We suggest that interactions between hydrology, wetland vegetation, and peat soil development that occur in DRIPs leads to their unique groundwater chemistry and runoff dynamics. Stream-based studies show that across flow conditions, groundwater inputs from DRIPs to headwater reaches influence stream temperature, water chemistry and biology. As such, accounting for DRIPs can complement existing hillslope and stream observations, which would allow better representation of chemical and biological interactions associated with convergence of subsurface flow paths in riparian zones.

Global Research on Riparian Zones in the XXI Century: A Bibliometric Analysis

Riparian zones (RZs) are transitional environments at the interface between land and freshwater ecosystems, which are important in terms of socioecological services. In this work, we report a bibliometric-based analysis to unveil the knowledge structure and actors of scientific production on riparian zones for the first 20 years of the 21st century. We performed a literature search, querying for riparian zones publications for the period 2001–2020. The selected 1171 bibliographic records were analyzed by extracting several bibliometric indices of reporting tendencies, location, collaboration dynamics, and top topics. Results show that RZs publications increased considerably from 2001 to 2020, and top journals publishing on the subject are from the water, environmental management, and ecology areas. The US, China, Brazil, and Canada were the most productive countries, while the institutions with higher productivity were the Chinese Academy of Sciences and Oregon University. In terms of impact, the US, Canada, and Australia led in citation number, while the country collaboration network showed that the strongest links occur between China and the US. Our results also show that few studies were produced in low-middle income countries, which suggests a need to funnel international funding to study riparian environments in these geographical contexts. According to analysis of frequency, top topics are related to water quality and focused on lotic environments. We here present the main knowledge structure of RZs studies globally for the first 20 years of the XXI century.