A. Bryce Cooper

Land use effects on habitat, water quality, periphyton, and benthic invertebrates in Waikato, New Zealand, hill‐country streams

Abstract Water quality, habitat, and biota were compared during spring amongst c. 100 m reaches on 11 streams draining pasture, native (podocarp‐broadleaf) forest, and exotic pine forest established on pasture 15 years previously. Differences were greatest between the pasture and native forest streams. Only 1–3% of incident light reached native and pine forest streams whereas 30% reached pasture streams. Pasture streams had 2.2°C higher mean temperature than the native streams, and 5‐fold higher nitrate, 30‐fold higher algal biomass, and 11‐fold higher gross photosynthesis. Native streams were 60% wider than pasture, with pine streams intermediate. Pine and pasture streams had 3‐fold higher suspended solids and fine sediment stored in the streambed than native streams. Woody debris volume was 17‐fold greater in pine than pasture streams, with native streams intermediate. Invertebrate taxa richness did not differ between land uses. Community composition differed most between pasture and native forest, with...

Effects of riparian set-aside on soil characteristics in an agricultural landscape: Implications for nutrient transport and retention

Physical, chemical, biochemical and microbial properties of riparian soils beneath native scrub (Leptospermum scoparium), grazed pasture, and set-aside pasture along the edge of a third order stream near Taupo, New Zealand were compared. In the 12 years since retirement from grazing, dominant vegetation in the set-aside areas changed from pasture grasses to native tussock (Poa cita). Riparian set-aside soils had an extremely high hydraulic conductivity in the surface horizon (6340 mm h−1) compared with that in the riparian grazed pasture (15 mm h−1) indicating that surface runoff water transported into the zone would infiltrate, fill soil pores and emerge as subsurface flow at the stream edge. Phosphorus available for transport was highest in riparian set-aside soils, indicating P saturation of the zone. Nitrate pool size was strongly correlated to nitrifying potential (Spearmans ϱ = 0.897), with both being extremely low in riparian set-aside. Microbial biomass was greater in riparian set-aside (1900 mg C g−1) than riparian native (1460 mg C g−1) or riparian pasture (1080 mg C g−1). The results imply that riparian set-aside has led to the development of a zone likely to supply runoff to the adjacent stream that is depleted in sediment-bound nutrients and dissolved N but enriched in dissolved P.

Shade effects on stream periphyton and invertebrates: An experiment in streamside channels

Abstract The effects of shade on periphyton and invertebrates were investigated by comparisons in 12 replicate channels beside a pasture stream where shade cloth reduced the photosynthetically available radiation (PAR) by 0, 60, 90, and 98%. Periphytic productivity decreased with increasing shade. Periphyton chlorophyll a was consistently low (< 30 mg m−2) under 98 and 90% shade and usually low at 60% shade, whereas blooms were common during summer in the unshaded channels. More periphytic taxa occurred in the open than shaded channels and the relative concentration of the photo‐protective pigment beta‐carotene decreased with increasing shade. Nitrate uptake rates by periphyton, measured in separate chamber studies, decreased progressively as shade increased from 60% through 90% to 98%, and were more strongly correlated with gross primary productivity than periphyton chlorophyll a and particulate carbon levels. Total invertebrate and chironomid densities declined significantly as shade increased from 60 t...

Nitrogen and phosphorus in streamwaters from adjacent pasture, pine, and native forest catchments

Abstract Measurements were made of nitrogen (N) and phosphorus (P) concentrations in streams draining three adjacent catchments of different land use. Generally, the pasture catchment stream showed highest concentrations of N and P, compared to the streams draining the pine and native catchments. Total N export coefficients (kg km‐2 year‐1) were estimated as 1195, 131, and 367 for the pasture, pine, and native catchments, respectively. Total P export coefficients (kg km‐2 year‐1) were estimated as 167, 9.5, and 12.0 for the pasture, pine, and native catchments, respectively. Exports of N and P from the pasture catchment were unevenly distributed through the year, with most export occurring as particulate forms during storm events. By comparison, export from the two forested catchments was more evenly distributed and baseflow dissolved forms of N and P formed a higher proportion of total export. The influences of land use were attributable to differences in hydrology, source materials of N and P available ...

Nitrate loss and transformation in 2 vegetated headwater streams

Abstract The processes of nitrate removal from the stream waters of 2 headwater catchments were studied. In study stretches where the stream channels were vegetated with thick mats of grass (Gly‐ceria fluitans), nitrate removal processes were particularly active. In such grassed stream channels, c. 75% of the nitrate removal was attributable to plant uptake and the remainder to denitrifica‐tion. Both of these nitrate removal processes were linearly dependent on nitrate concentration, resulting in an exponential decline of nitrate level from the springs along the streams length. Regeneration of nitrogen, by plant decay within the stream channel, results in export of dissolved organic nitrogen and paniculate nitrogen from the catchments. The overall impact of vegetated stream channels in modifying nitrogen exports from catchments is discussed.

Land‐water interactions at Whatawhata, New Zealand: Introduction and synthesis

Abstract A programme of research is introduced on the effects on stream ecosystems of land‐use change from native forest to pasture, and subsequent re‐afforestation with exotic pine plantations. The results detailed in the 11 accompanying papers conclude that land‐use change has had strong effects on many key physical, chemical, and biological aspects of stream ecosystems in and adjacent to Whatawhata Research Centre, near Hamilton, New Zealand. Six of these papers compare streams, draining catchments with similar topography, geology, and soils, to investigate land‐use effects on stream lighting, water quality, channel morphology, benthic and hyporheic habitat and faunas, fish, and food webs. Two papers investigate hypotheses on the influence of shade and crayfish using streamside mesocosms. Finally, three papers use the experimental sites to evaluate methods for studying crayfish populations, stream carbon pathways, and a stream temperature model. These studies provide a comprehensive description of land...