Planted Riparian Buffer Zones in New Zealand: Do They Live Up to Expectations?

Abstract River and stream rehabilitation projects are increasing in number, but the success or failure of these projects has rarely been evaluated, and the extent to which buffers can restore riparian and stream function and species composition is not well understood. In New Zealand the widespread conversion of forest to agricultural land has caused degradation of streams and riparian ecosystems. We assessed nine riparian buffer zone schemes in North Island, New Zealand that had been fenced and planted (age range from 2 to 24 years) and compared them with unbuffered control reaches upstream or nearby. Macroinvertebrate community composition was our prime indicator of water and habitat quality and ecological functioning, but we also assessed a range of physical and water quality variables within the stream and in the riparian zone. Generally, streams within buffer zones showed rapid improvements in visual water clarity and channel stability, but nutrient and fecal contamination responses were variable. Significant changes in macroinvertebrate communities toward “clean water” or native forest communities did not occur at most of the study sites. Improvement in invertebrate communities appeared to be most strongly linked to decreases in water temperature, suggesting that restoration of in‐stream communities would only be achieved after canopy closure, with long buffer lengths, and protection of headwater tributaries. Expectations of riparian restoration efforts should be tempered by (1) time scales and (2) spatial arrangement of planted reaches, either within a catchment or with consideration of their proximity to source areas of recolonists.     

挠力河流域河流生境质量评价

选择挠力河流域6个河段21个样点进行河流生境质量调查和评价。采用包括河水、河道和人类干扰等3大项目共11项评价指标,涵盖河流水量、水质和速度与深度组合,河道形状、结构、侵蚀程度和植被状况,河岸人类活动、周围土地利用以及水工设施等河流生境质量评价指标系统,进行河流生境质量评价。结果显示,全流域47.6%的样点河流生境质量处于优等或良好等级,33.3%的样点为一般等级,约19.1%的样点为较差等级,没有最差等级的样点。研究表明,挠力河流域河流生境质量整体状况良好,个别样点生境质量较差;河流生境质量受到周围土地利用的重要影响;河流生境质量与河流水质及河流生物完整性密切相关。有关河流生境评价的指标与标准以及参照系等研究有待深入。     

Effects of forestry on the thermal habitat of Dolly Varden (<Emphasis Type="Italic">Salvelinus malma</Emphasis>)

Forestry activities in riparian areas are known to affect stream communities considerably. Not only do riparian deforestation resulting from agriculture or urbanization developments affect stream communities but extensive commercial plantation and forestry practices can alter stream environments adjacent to remaining, intact or secondary forests. Because forestry often includes the construction of logging roads through the riparian zone, this can directly degrade stream environments. Twelve streams in the Shiretoko Peninsula, Hokkaido were investigated so as to determine the effects of forestry practices on stream temperature, periphyton biomass, grazer (benthic invertebrates) biomass and Dolly Varden (Salvelinus malma Walbaum) biomass. The greater the proportion of planted area in the catchment, the higher the stream temperature. Stream temperature directly affects periphyton biomass and Dolly Varden biomass negatively. Neither stream temperature nor periphyton biomass predicted grazer biomass, whereas a positive correlation was found between grazer biomass and Dolly Varden biomass that forage on invertebrates. The overall results indicated that Dolly Varden in the Shiretoko streams were negatively affected by forestry practices and the resultant stream temperature increases. Without effective future riparian forest management, the complex effects of both riparian disturbance and ongoing global warming could further reduce Dolly Varden populations in the region.     

In situ measurements of net primary production in a Colorado mountain stream

Six stations were established on a Colorado mountain stream, and net primary productivity was measured in situ during all seasons. For 24-hour periods the dissolved oxygen and temperature of the water were electronically monitored over an undisturbed 1 x 1 m section of rubble bottom enclosed by a large plastic dome tightly fitted to the substrate. A submerged pump maintained a current within the dome, and the whole apparatus was submerged below the stream level. The bottom community net metabolism varied between heterotrophy and autotrophy with no correlations with altitude, season, light, water chemistry, and temperature. Readings were all very low and ranged from -27.38 to 35.59 grams of carbon fixed per square meter per year. There were no correlations between biomass of the bottom fauna and net community productivity.Contribution No. 71, University of Colorado Limnology Laboratory     

Fish abundance and habitat relationships in forest and grassland streams, northern Hokkaido, Japan

The relationships between habitat variables and population densities of masu salmon (Oncorhynchus masou), rosyface dace (Leuciscus ezoe), Siberian stone loach (Noemacheilus barbatulus) and wrinklehead sculpin (Cottus nozawae) were examined by data collected at 55 reaches in forest and grassland streams in northern Hokkaido, Japan. Regression analysis suggested that salmon and dace densities were affected by water temperature (negative for salmon, positive for dace) and structural habitat factors (woody debris for salmon, pools for dace). Salmon density was higher in forest reaches than in grassland reaches, whereas dace density was higher in grassland reaches, suggesting that the removal of riparian forest had raised water temperature and allowed upstream invasions by dace. In contrast to salmon and dace, neither the density of loach nor sculpin differed between the forest and grassland reaches. For their densities, a negative effect of each on the other was most important, suggesting a strong effect of interspecific competition between loach and sculpin on their distributions. However, regression models also suggested that substrate heterogeneity mediated the outcome of their interspecific competition. On the basis of the results, a scenario is predicted for a fish-assemblage change with a typical land-development process in Hokkaido, and the importance of leaving or restoring riparian buffer for conservation and restoration of stream habitat is emphasized.     

An exploration of factors influencing lotic insect species richness

An understanding of factors that influence species richness of lotic insects is generally lacking. We present comparative data on aquatic insect species richness from several North American and other streams. Factors such as large sample numbers and drainage area (species area relationships) are not significant predictors of species richness across the streams we examined. We explore several hypotheses regarding the origins and maintenance of species richness using Upper Three Runs Creek (UTR), South Carolina, USA, as a reference stream. UTR has the highest species richness of any stream in the Western Hemisphere. Hypotheses examined included historical, regional and local processes such as: (1) Evolutionary time, (2) disturbance regime/environmental variability, (3) temperature/evolutionary-speed, (4) productivity, and (5) habitat heterogeneity. Of these hypotheses, we suggest that productivity and habitat heterogeneity appear to contribute most to the high species richness found in UTR. We believe that multidisciplinary analysis of other streams is necessary because without this crucial information our knowledge of, and desire to protect biodiversity in streams will be wanting.     

Effects of experimental acidification on a lotic macroinvertebrate community

A three month experimental acidification was carried out on lotic bottom communities. Experiments were conducted under semi-natural conditions in plasticized wooden channels. Acidified communities (pH 4.0), with or without added aluminum, were compared with a reference community (pH 6.3–6.9). Added aluminum concentrations were respectively 0.2 and 0.4 mg 1^–1 in experiments performed in 1982 and 1983. Water chemistry and taxonomic composition of the macroinvertebrate communities were monitored. Under acidified conditions, results were similar, with or without added aluminum. Mean abundances of all groups of organisms were lowered. Mayflies nearly completely disappeared from the acidified channels. The only organism not affected by the acidification was Microtendipes sp. Differences in the organism response were observed: Orthocladiinae (Rheocricotopus, Parametriocnemus, Corynoneura, Thienemanniella, Nanocladius, Cricotopus) and Ephemeroptera (Baetis, Habrophlebia, Habrophlebiodes, Paraleptophlebia, Ephemerella), especially early instars, were very sensitive to low pH, Chironomini and Tanypodinae were much less sensitive, while Tanytarsini were intermediate; Oligochaeta and Nematoda were difficult to classify, their response being different from one year to another. Organisms inhabiting the surface of artificial substrates disappeared very rapidly from the system, while those buried inside had a delayed reaction to acidification. Aluminum which was mainly in the monomeric form was not responsible for community modifications. Direct action of hydrogen ions through a physiological stress seems a more credible explanation. These results, induced by a continuous experimental acidification, suggest that if this small headwater stream undergoes acidification, the resulting invertebrate community will be very simplified, with only resistant species able to cope with the acid conditions.