Riparian Vegetation Width Research Articles

Assessing riparian zone changes under the influence of stress factors in higher-order streams and tributaries: Implications for the management of massive dams and reservoirs.

Riparian ecosystem services along higher-order streams and connected tributaries may change over time as disturbances continuously increase, resulting in diverse deterioration of buffer zones. How habitat, plant cover, regeneration, erosion, and exotic parameters (riparian health conditions) change within huge dams and reservoirs worldwide is an unanswered question. We used multivariate statistical techniques to assess changes in riparian health parameters affected by disturbances identified in 304 transects within the Three Gorges Dam Reservoir, China, and associated tributaries. Kruskal-Wallis tests (p<0.01) revealed high diversity in habitat, plant cover, regeneration, erosion, and overall stream condition. There was also notable variance relating to exotic and pressure parameters. The critical variables of riparian health indicators and stress factors identified by principal component analysis explained 58.40% and 74.6% (in the main waterway) and 53.23% and 71.0% (in the tributaries) of the total variance. Among riparian health indicators, one habitat parameter (riparian vegetation width) in the main waterway and one regeneration parameter (tree size classes) in tributaries contributed greatly, along with other specified parameters. Furthermore, stress factors such as farming systems, land-use types, and pollutant activity variables had the highest impact on these water bodies. In comparison, counting stress factors alone showed more deterioration in the main waterway with a range of (r=-0.527-0.493), as determined using Pearson correlation (p<0.05). Furthermore, after indexing, the parameters exhibited weaker coefficient values in tributaries, where exotic correlated negatively with other indexed values. These findings are relevant for managers of massive dam and reservoir ecosystems seeking to mitigate environmental and socioeconomic losses.

Influence of different riparian vegetation widths and substrate types on the communities of larval Odonata (Insecta) in southern Brazilian streams

Abstract: Aim We assessed the influence of substrate type and categories of riparian vegetation widths on the community structure of Odonata (Insecta) in southern Brazilian streams. Methods Sampling took place in twelve stream reaches differing in their riparian vegetation widths (from more than 40 m up to less than 5 m). Larval odonates were collected in inorganic (stone and gravel) and organic (leaf litter) substrates at each stream reach. Differences in Odonata composition among substrates and categories of riparian vegetation width were tested using PERMANOVA and visualized with ordination diagrams. In addition, we assessed the influence of riparian vegetation width taking into account two levels of resolutions: fine (four categories: &gt; 40 m, 30-15 m, 15-5 m and &lt; 5 m) and coarse (narrower and broader than 15 m). Results Odonata composition differed more strongly according to substrate type regardless of the level of resolution. Organic substrate (litter) had different composition and higher richness than inorganic ones. Odonata composition significantly differed between riparian vegetation widths at the coarser level of resolution (narrower and broader than 15 m); at the coarser level, the interaction between substrate and riparian widths was significant, with the composition from litter substrate in broader widths differing from stone and gravel in narrower widths. Conclusions The composition of odonate larvae responded to the major reductions in riparian widths (above &gt; 15 m), indicating that reductions above this level are enough to affect the community structure of Odonata. Additionally, the different composition of Odonata in organic substrates in broader riparian vegetation widths compared to inorganic substrates in narrower widths indicate a complex relationship between riparian vegetation and substrate in the assembly of insect communities in southern Brazilian forest streams. The interaction between riparian vegetation widths and substrate suggests that the effects of reductions in riparian widths on Odonata composition are not similar across substrate types.

Effects of riparian vegetation width and substrate type on riffle beetle community structure

AbstractRiffle beetle community structure is influenced by the preservation condition of stream riparian vegetation. Though, the width of riparian vegetation required to ensure conservation of stream insect communities is still controversial. Effects of alterations in riparian vegetation widths on stream insect community structure can be overcame by other environmental variables, like substrate type, hindering accurate assessments. We tested the effects of different riparian vegetation widths (&gt;40, 30–15, 15–5 and &lt;5 m) along with different substrate types (inorganic and organic) on riffle beetle community structure in southern Brazilian 4th‐ to 5th‐order streams. Riparian buffer widths and substrate types influenced riffle beetle community structure, but no interaction between them was observed. Reduced riparian vegetation widths downstream were associated with changes in riffle beetle dominant genera (Macrelmis predominated only in streams with narrowest riparian widths). Additionally, communities in organic substrates had lower equitability and different dominant genera (Hexacylloepus and Heterelmis) than inorganic ones. Our results showed that reductions in riparian vegetation were associated with water pollution and changes in riffle beetle community structure, suggesting that buffer strips narrower than 5 m are not adequate to maintain environmental integrity of southern Brazilian streams. These results have special importance for the conservation of stream insects in Brazil, as reductions up to less than 5 m in stream banks of small properties are allowed by the new Brazilian Forest Code, independently of stream order.

Structure of potamoplankton along a gradient of preservation of riparian vegetation in subtropical streams

Water quality in lotic and lentic systems is greatly influenced by the land use in the adjacent areas. This study was conducted in order to assess whether different degrees of preservation of riparian forest (from well preserved with 30m wide up to degraded with < 5 m wide) influence potamoplankton community structure. The study was conducted in three streams in the upper region of the Rio dos Sinos basin, at four sampling sites, with different width of the forest. Samplings were gathered for abiotic and biological analysis in winter (August 2010) and summer (January/February 2011). The analysis of environmental and biotic variables indicated that seasonality was the main determinant of biomass patterns, regardless of the width of riparian vegetation. The potamoplankton community of the studied streams responded to environmental conditions, although lack of significant difference among the different degrees of riparian vegetation preservation has been observed. Increasing trends on biomass, richness and diversity of species, and higher concentrations of total phosphorus and nitrogen in the non-preserved areas might indicate that the different gradients of preservation of riparian vegetation are related with the water quality in subtropical streams and consequently with the potamoplankton structure.

The influence of connectivity in forest patches, and riparian vegetation width on stream macroinvertebrate fauna

We assessed two dimensions of stream connectivity: longitudinal (between forest patches along the stream) and lateral (riparian vegetation), using macroinvertebrate assemblages as bioindicators. Sites representing different land-uses were sampled in a lowland basin that holds a mosaic of protected areas. Land-use analysis, forest successional stages and riparian zone widths were calculated by the GIS analysis. Macroinvertebrate fauna was strongly affected by land-use. We observed a continuous decrease in the number of sensitive species, %Shredders and IBE-IOC biotic index from the upstream protected area to highly deforested sites, increasing again where the stream crosses a Biological Reserve. When analysing buffer strips, we found aquatic fauna responding to land-use alterations beyond the 30 m riparian corridor (60 m and 100 m wide). We discussed the longitudinal connectivity between forest patches and the riparian vegetation buffer strips necessary to hold high macroinvertebrate diversity. We recommend actions for the increase/maintenance of biodiversity in this and other lowland basins.

Riparian vegetation change on the Clarence River floodplain

The natural streamside levees on the floodplain of the Clarence River in subtropical eastern Australia were occupied by riparian rainforest prior to European settlement. They were almost completely cleared for agriculture over a ten-year period from 1857 as a direct consequence of changes to land ownership laws. The floodplain is now a highly developed landscape, with the riverside levees occupied by roads, houses and agriculture, with minimal remnant vegetation. Comparison of 343 sites from 1942 and 2001 aerial photographs using GIS show that there has been an increase in overstorey riparian vegetation density and riparian width, both from very low bases. Ground surveys record that the overstorey riparian vegetation is predominately native with a weedy mid-stratum. Species diversity is low and targeted plantings may be required to provide a pool of rainforest species to start the slow process of recreating this important area of biodiversity. The majority of the increase in the width of riparian vegetation is due to the streams in the floodplain becoming narrower. This is caused by a combination of stream meander and infrastructure protection works. This study highlights the interaction of erosion, stream meander, infrastructure protection and riparian vegetation, and the implications for those managing floodplain streams.

Habitat use of remnant forest habitats by the threatened arboreal marsupial Dromiciops gliroides (Microbiotheria) in a rural landscape of southern Chile

Context. Remnant forest patches in rural landscapes may be important sites for maintaining viable populations of restricted forest species, especially when these remnant habitats maintain some connectivity, for instance through riparian vegetation strips and other forest patches. Aims. We assessed the use of remnant forest habitats in a rural landscape of southern Chile (40°S) by the ‘near threatened’ arboreal marsupial Dromiciops gliroides (Microbiotheria), in relation to habitat type (riparian strips, forest fragments and continuous forests), width of the riparian forests, and the presence and abundance of the hemiparasite Tristerix corymbosus, whose fruits are readily eaten by D. gliroides. Methods. In two summers, 2004 and 2008, we set up grids of 96 live traps for three consecutive nights at each of 16 sites along two riparian forest strips, four additional sites in remnant, non-riparian forest patches, and four more within continuous pre-Andean forest. We counted hemiparasites on trees in the trapping grid area, and estimated their individual volumes. Key results . In total, 48 individuals of D. gliroides were captured at all sites during the 2 years. We documented a significant positive relationship between the width of riparian vegetation and the number of individuals captured (r s = 0.78, P = 0.02, n = 8) for one riparian strip, but not for the second one. Neither habitat type nor the frequency of hemiparasites related statistically to D. gliroides abundance. Key conclusions. We conclude that in the rural landscape of the Chilean Lake District, narrow riparian forest strips, in a highly inter-connected mosaic of remnant forest patches may be as important as large patches and continuous Andean forests to sustain viable populations of this threatened, strictly arboreal, marsupial. Implications. The present study reports, for the first time, the presence in narrow riparian forests immersed in a pasture-dominated agricultural matrix of this forest-specialist marsupial, which was previously known only from continuous pre-Andean forests.

EFFECTS OF MULTI‐SCALE ENVIRONMENTAL CHARACTERISTICS ON AGRICULTURAL STREAM BIOTA IN EASTERN WISCONSIN1

ABSTRACT: The U.S. Geological Survey examined 25 agricultural streams in eastern Wisconsin the determine relations between fish, invertebrate, and algal metrics and multiple spatial scales of land cover, geologic setting, hydrologic, aquatic habitat, and water chemistry data. Spearman correlation and redundancy analyses were used to examine relations among biotic metrics and environmental characteristics. Riparian vegetation, geologic, and hydrologic conditions affected the response of biotic metrics to watershed agricultural land cover but the relations were aquatic assemblage dependent. It was difficult to separate the interrelated effects of geologic setting, watershed and buffer land cover, and base flow. Watershed and buffer land cover, geologic setting, reach riparian vegetation width, and stream size affected the fish IBI, invertebrate diversity, diatom IBI, and number of algal taxa; however, the invertebrate FBI, percentage of EPT, and the diatom pollution index were more influenced by nutrient concentrations and flow variability. Fish IBI scores seemed most sensitive to land cover in the entire stream network buffer, more so than watershed‐scale land cover and segment or reach riparian vegetation width. All but one stream with more than approximately 10 percent buffer agriculture had fish IBI scores of fair or poor. In general, the invertebrate and algal metrics used in this study were not as sensitive to land cover effects as fish metrics. Some of the reach‐scale characteristics, such as width/depth ratios, velocity, and bank stability, could be related to watershed influences of both land cover and geologic setting. The Wisconsin habitat index was related to watershed geologic setting, watershed and buffer land cover, riparian vegetation width, and base flow, and appeared to be a good indicator of stream quality Results from this study emphasize the value of using more than one or two biotic metrics to assess water quality and the importance of environmental characteristics at multiple scales.

Charcoal accumulation following a recent fire in the Cascade Range, northwestern USA, and its relevance for fire-history studies

Stratigraphic records of macroscopic charcoal particles (&gt;125 μm in diameter) are widely used as a means of reconstructing past fire events, yet fire-history studies rest on assumptions about the processes by which charcoal is transported and deposited in lake sediments. In order to clarify the interpretation of charcoal data, charcoal abundance in sediment cores was examined from 36 lakes within and near the 1996 Charlton Burn, a large stand-replacing fire in the central Cascade Range of Oregon. Stratigraphic variations in charcoal abundance provided strong evidence that macroscopic charcoal recorded a signal of local fire and that prevailing winds affected charcoal transportation, increasing charcoal abundance in lakes downwind of the fire. Charcoal abundance in the uppermost sediments (0–2 cm depth) was related primarily to whether or not a site had burned and secondarily to the surface area of the lake. At the Charlton Burn area, other variables that may influence the transportation of charcoal after a fire, such as relative position of unburned lakes, distance of the lake from the centre of the fire, maximum adjacent slope, and width of riparian vegetation, were not statistically significant. These results support the assumption in charcoal analysis that there is a relationship between the occurrence of local fire and peaks in macroscopic charcoal. Confirming this relationship strengthens the interpretation of long-term fire-history records.