Previous attempts to identify nationally important wetlands for biodiversity in NewZealand were based on expert panel opinions because quantitative approaches were hampered by a lack of data. We apply principles of systematic conservation planning to remote sensing data within a geographical information system (GIS) to identify nationally important palustrine and inland saline wetlands. 2. A catchment-based classification was used to divide New Zealand into 29 biogeographic units. To meet representation goals, all wetland classes need to be protected within each unit. 3. We mapped current and historic wetlands down to a minimum size of 0.5 ha. Over 7000 current wetlands were mapped using standardised satellite imagery and a collection of point or polygon data. Historical extent was estimated from soil information refined using a digital elevation model. The current extent of wetlands is 10% of the historic extent, which is consistent with previous estimates. 4. A classification was produced using fuzzy expert rules within a GIS to identify seven wetland classes: bog, fen, swamp, marsh, pakihi ⁄ gumland, seepage and inland saline. Swamps and pakihi ⁄ gumland are the most common, but the former has sustained the greatest reduction in area with only 6% of its historical extent remaining. A preliminary field assessment of classification accuracy in the Otago region found only 60% agreement, mainly because of the misclassification of marshes into swamps. 5. Wetland condition was estimated using six measures of human disturbance (natural cover, human-made impervious cover, introduced fish, woody weeds, artificial drainage and nitrate leaching risk) applied at three spatial scales: the wetland's catchment, a 30-m buffer around the wetland and the wetland itself. Measures were transformed and combined into a single condition index. More than 60% of remaining wetlands had condition indices <0.5, probably indicating moderate to severe degradation and loss of native biodiversity. 6. Sites were ranked within each biogeographic unit using the wetland classification to ensure a representative set of wetland diversity. Rankings were determined by combining condition and complementarity to calculate conservation effectiveness that was then weighted by irreplaceability. Highest ranked sites in each biogeographic unit were usually the largest remaining wetlands that contained multiple wetland classes. This reflects their potential to protect a diverse range of wetland classes and a high proportion of the remaining habitat.

Periphyton communities were sampled every 4 weeks for a year at five sites in the Motueka River and at one site in the adjacent Riwaka River, New Zealand. This was in an attempt to distinguish the relative importance of large-scale catchment variables (geology/land use) from small-scale local variables (velocity) in determining the development of periphyton in the rivers. Cellular nitrogen correlated positively with the proportion of the sub-catchments in marble (r = 0.938, P < 0.01). Growth appeared to be N-limited during the year, thus average chlorophyll biomass also correlated strongly with marble (r = 0.983, P < 0.001). However, the maximum low-flow chorophyll a level at each site was strongly and negatively correlated with water velocity (r = -0.981, P < 0.001). This indicated that the macro-scale factors of the catchment are probably more important in determining longer-term (> 1 year) average production, but the micro-scale factors are more important in determining short-term (monthly) temporal biomass dynamics. This supports current ecological theory on the spatial and temporal effects of primary versus secondary regulators of stream ecosystem dynamics. M92035

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Anthropogenic drainage causes loss of natural character in herbaceous wetlands due to increased soil oxygen penetration. We related vegetation gradients in a New Zealand polje fen to long-term effects of drains by using hydrological, edaphic and vegetation data, and a before-aftercontrol-impact (BACI) design to test responses to experimental drain closure. Soil profiles and continuous water level records revealed a site subject to frequent disturbance by intense but brief floods, followed by long drying periods during which areas close to drains experienced lower water tables and more variable water levels. Classification of vegetation data identified 12 groups along a moisture gradient, from dry areas dominated by pastoral alien species, to wet communities dominated by native wetland sedges. Lower total species diversity and native representation in pastoral communities were related to the high proportion of alien competitor and competitor-disturbance species, compared with the stress tolerator-dominated flora of other groups. Species-environment relationships revealed highly significant correlations with soil water content and aeration as measured by redox potential (E H ) and steel rod oxidation depth, as well as soil nutrient content and bulk density. Comparison of root anatomy confirmed greater development of floodtolerant traits in native species than in pastoral aliens, and vegetation N:P ratios indicated that most communities were probably nitrogen-limited. Flooding rapidly re-established wetland hydrology in dried sites in the impact area, and lowered E H and soil oxidation depth, but had no effect on N and P availability. Presence and cover of pastoral alien species decreased in these areas. This study supports the use of hydrological manipulation as a tool for reducing soil oxidation and thus the impact of alien plant species at restoration sites with minimal intervention, but suggests the need for detailed information on species flooding tolerances and hydrological preferences to underpin this approach.