Can aerial herbicide application control Grey Willow (Salix cinerea L.) and stimulate native plant recovery in New Zealand wetlands?

Grey Willow (Salix cinerea L.) poses a significant threat to wetland ecosystems in New Zealand. To manage the ecological impacts and to control further spread, cost‐effective large‐scale control methods are needed. We investigated the response of Grey Willow and dominant wetland plant groups to the aerial boom‐spray application of glyphosate at 9 L/ha and triclopyr (amine) at 18 L/ha at three New Zealand wetlands. We found glyphosate substantially reduced the dominance of tall (>2 m) Grey Willow with commensurate increases in the dominance of most native plant groups. Triclopyr (amine) application resulted in poor Grey Willow control, was not associated with increased native plant group dominance, and some native plant groups declined where triclopyr (amine) was applied. We conclude that the aerial application of glyphosate is an effective large‐scale Grey Willow control tool and could be used to initiate the restoration of native plant communities in wetlands dominated by Grey Willow. But, evidence of Grey Willow recovery after control suggests that increases in native plant dominance will be reversed as Grey Willow re‐establish. Further research is needed to determine how to maintain and enhance native plant dominance after control, and to determine how to manage Grey Willow in fen areas where the Grey Willow canopy is discontinuous and nontarget herbicide impacts can occur. The aerial boom‐spray application of triclopyr (amine) for large‐scale Grey Willow control should be discontinued as it does not provide effective control and results in negative ecological outcomes.     

Mapping Grey Willow (Salix cinerea) stand architecture using airborne laser scanning: implications for large‐scale tree weed control

We investigated the potential of airborne laser scanning (ALS) for mapping the stand architecture of Grey Willow (Salix cinerea), an invasive wetland weed in New Zealand. In particular, we focused on two metrics, tree height and canopy density, both of which influence the efficacy and nontarget impacts of herbicides aerially broadcast by helicopter to control tree weeds. We compared ground‐based measures of Grey Willow height and canopy density with ALS‐derived data, and the relationship between canopy density as estimated by each method and aerial herbicide deposition at three wetland sites in New Zealand. Analysis revealed strong linear relationships between ground‐based and ALS metrics, indicating that ALS data could be used to generate accurate, high‐resolution digital maps of Grey Willow height and canopy density. These maps coupled with computer‐guided variable flow rate technologies, which enable optimal placement of herbicide, could maximise Grey Willow mortality while reducing the mortality of nontarget indigenous plants. We recommend the application of ALS‐derived maps and computer‐guided variable flow rate technology is investigated for more targeted large‐scale tree weed control.     

Impacts on invertebrate fungivores: a predictable consequence of ground-cover weed invasion?

Empirical impact evidence exists for few of New Zealand’s environmental weeds. Financial constraints prevent managers examining all impacts of all weeds. Therefore it is useful to seek generalisable rules which allow managers to predict impacts of new invasions. Invasive weeds may indirectly affect fungivorous invertebrates through mechanisms such as altered litter-fall, decomposition rates, and microclimate, all of which may alter fungal activity. I tested the hypothesis that fungivorous invertebrates would be consistently affected by three invasive weeds, and that this effect would be more pronounced than for other invertebrate functional groups. Using pitfall traps, I compared invertebrates beneath climbing asparagus, tradescantia and ginger with invertebrates of uninvaded lowland forest. Five out of six Coleoptera taxa which differed in abundance between invaded and uninvaded sites were fungivores; the remaining taxon was a saprophage. At least two taxa of fungivorous Coleoptera responded to each of the three weed species. Acari (mainly Oribatids, some of which are fungivores), Isopoda and Amphipoda (decomposers) were the only taxa to respond to the presence of all three weed species. These results provide some support for the hypothesis that fungivores are particularly responsive to ground-cover weed invasion, but suggest this could be extended to include decomposers as well. However, the direction of effect differed among weed species. Therefore, while changes in fungivore and decomposer abundance may be predicted as one of the more likely consequences of ground-cover weed invasion in New Zealand low-land forest, site- and taxa-specific effects make it difficult to predict the direction of effect.     

Herbicide treatment alters the effects of water hyacinth on larval mosquito abundance

Invasive aquatic weeds are managed with herbicides to reduce their negative impacts on waterways in many areas, including the California Delta Region. Herbicides create a dynamic environment of living and decomposing plant matter that could affect larval mosquitoes and other invertebrates, such as their predators and competitors. Our objective was to compare the number of larval mosquitoes in water or water hyacinth, before and after an herbicide treatment. We created replicated pond mesocosms with water hyacinth, water hyacinth treated with glyphosate and an oil adjuvant, open water, and water with glyphosate plus adjuvant. We sampled for larval mosquitoes and other aquatic invertebrates. Before herbicide addition, there was a trend for more larval mosquitoes in open water tanks than in tanks with water hyacinth. Herbicide application resulted in an immediate decrease of larval mosquitoes. As decay progressed, larval mosquitoes became most abundant in mesocosms with herbicide‐treated hyacinth and very few larval mosquitoes were found in other habitat treatments. Although the numbers of predatory and competitor insects had some variation between treatments, no clear pattern emerged. This information on how invasive weed management with herbicides affects larval mosquitoes will allow control practices for larval mosquitoes and invasive weeds to be better integrated.     

Invertebrate community response to fire and rodent activity in the Mojave and Great Basin Deserts

Recent increases in the frequency and size of desert wildfires bring into question the impacts of fire on desert invertebrate communities. Furthermore, consumer communities can strongly impact invertebrates through predation and top‐down effects on plant community assembly. We experimentally applied burn and rodent exclusion treatments in a full factorial design at sites in both the Mojave and Great Basin deserts to examine the impact that fire and rodent consumers have on invertebrate communities. Pitfall traps were used to survey invertebrates from April through September 2016 to determine changes in abundance, richness, and diversity of invertebrate communities in response to fire and rodent treatments. Generally speaking, rodent exclusion had very little effect on invertebrate abundance or ant abundance, richness or diversity. The one exception was ant abundance, which was higher in rodent access plots than in rodent exclusion plots in June 2016, but only at the Great Basin site. Fire had little effect on the abundances of invertebrate groups at either desert site, with the exception of a negative effect on flying‐forager abundance at our Great Basin site. However, fire reduced ant species richness and Shannon's diversity at both desert sites. Fire did appear to indirectly affect ant community composition by altering plant community composition. Structural equation models suggest that fire increased invasive plant cover, which negatively impacted ant species richness and Shannon's diversity, a pattern that was consistent at both desert sites. These results suggest that invertebrate communities demonstrate some resilience to fire and invasions but increasing fire and spread of invasive due to invasive grass fire cycles may put increasing pressure on the stability of invertebrate communities.     

Dynamics of canopy-dwelling arthropods under different weed management options,including glyphosate,in conventional and genetically modified insect-resistant maize

The use of genetically modified varieties tolerant to herbicides (HT varieties) and resistant to insects (Bt varieties) in combination with application of a broad-spectrum herbicide such as glyphosate could be an effective option for the simultaneous control of weeds and pests in maize. Nevertheless, the possible impact of these tools on nontarget arthropods still needs to be evaluated. In a field study in central Spain, potential changes in populations of canopy-dwelling arthropods in Bt maize under different weed management options, including glyphosate application, were investigated. Canopy-dwelling arthropods were sampled by visual inspection and yellow sticky traps. The Bt variety had no effect on any group of studied arthropods, except for the expected case of corn borers—the target pests of Bt maize. Regarding the effects of herbicide regimes, the only observed difference was a lower abundance of Cicadellidae and Mymaridae on yellow sticky traps in plots not treated with pre-emergence herbicides. This effect was especially pronounced in a treatment involving two glyphosate applications. The decrease in Cicadellidae and Mymaridae populations was associated with a higher density of weeds in plots, which may have hindered colonization of the crop by leafhoppers. These differences, however, were only significant in the last year of the study. The low likelihood of the use of glyphosate- and herbicide-tolerant varieties for weed control triggering important effects on the nontarget arthropod fauna of the maize canopy is discussed.     

Individual and combined effects of fine sediment and the herbicide glyphosate on benthic macroinvertebrates and stream ecosystem function

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The Impact of Hydrological Restoration on Benthic Aquatic Invertebrate Communities in a New Zealand Wetland

Drainage is a major disturbance affecting wetlands, as drains lower water tables and convert lentic habitats to lotic ones. Consequently, invertebrate communities in drained wetlands are likely to differ from those in unimpacted wetlands. This study investigated the effect of hydrological restoration on invertebrate communities in small drains in a New Zealand fen. Invertebrates were collected over 4 summers from 10 drains within the wetland, one of which was blocked as part of a restoration program. The sampling protocol thus represented a Before‐After Control‐Impact experiment. Invertebrate community composition varied over the 4 years, but variability was greatest in the manipulated drain before and after it was blocked. Relative abundance of the amphipod Paraleptamphopus decreased after blockage, whereas those of the midges Chironomus zelandicus and Tanypodinae increased. Relative abundances of these taxa in control sites were unchanged. Hydraulic restoration thus had a demonstrable impact on the invertebrate communities. The invertebrate community of the blocked drain was compared to that of natural wetlands in undisturbed catchments. Similarity was very low prior to drain blockage, but increased following drain blockage. Invertebrate communities in the restored drain were more similar to those of low pH wetlands than high pH wetlands. Given the goal of restoring the communities to those similar to natural conditions, this was a beneficial result. These results, coupled with studies that showed a decline in the cover of alien pasture grasses around the blocked drain, suggest that drain blockage represents a cost‐effective way of restoring wetland plant and aquatic invertebrate communities, especially where connectivity allows for the natural recruitment of these organisms into restored areas.     

Terrestrial Invertebrate Community Structure as an Indicator of the Success of a Tropical Rainforest Restoration Project

Rainforest restoration is a relatively new endeavor, and few attempts have been made to assess the success of such restoration efforts in terms of the reestablishment of an ecosystem. Small plantings of rainforest tree species have been carried out adjacent to mature rainforest at Lake Barrine National Park in North Queensland, Australia, since 1988. The aim of this project was to assess the leaf litter invertebrate fauna of these plantings as indicators of the success of the restoration process. Plots planted in 1988, 1989, and 1990, as well as adjacent mature rainforest, were sampled in the wet and dry seasons of 1994. Invertebrates were extracted from leaf litter samples with Berlese Funnels and sorted to order. Diversity, the abundance of different size classes and orders of invertebrates, and the abundance of different functional groups were examined. In most respects the 1988 plot was found to differ little from the mature rainforest plots, whereas the 1990 plot lacked small and predatory invertebrates, especially in the dry season. The 1989 plot was intermediate in invertebrate abundance and diversity. The use of partially deciduous trees in the 1989 and 1990 plots, resulting in lower canopy cover at the driest time of the year, may have contributed significantly to the differences found between the early and later plantings. It is recommended that trees that provide good canopy cover year-round be used as dominant species in plantings to facilitate the development of a leaf litter ecosystem that can be sustained throughout the year.     

Controlling perennial pepperweed (<Emphasis Type="Italic">Lepidium latifolium</Emphasis>) in a brackish tidal marsh

Perennial pepperweed (Lepidium latifolium) is an aggressively invasive species that spreads by vegetative growth and seeds. Common methods for removal such as hand-pulling and mowing are impractical in brackish marsh environments. We evaluated the effects of two herbicide treatments (imazapyr and imazapyr + glyphosate) against a non-herbicide control (flower head removal) on invasive pepperweed and native vegetation in three habitats (bay edge, channel edge, and levee) in brackish marshes. Both herbicide treatments produced significantly better control of pepperweed than the control, but imazapyr alone took 2 years of treatment to produce levels of control that were similar to one year of the imazpyr + glyphosate treatment. Both herbicide treatments also reduced native cover, but the effects were more severe in plots treated with imazapyr + glyphosate than in plots treated with imazapyr alone. Effects on pepperweed were similar across the three habitats, but impacts on native vegetation were less severe in bay edge environments. Managers should consider the tradeoffs when choosing a treatment plan for pepperweed: the quick reduction of pepperweed achieved by the combination of imazapyr and glyphosate may come at the expense of creating opportunities for reinvasion by causing bare ground and/or patches of litter that are slowly recolonized by native species.     

Aquatic macroinvertebrate community responses to wetland mitigation in the Greater Yellowstone Ecosystem

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Canopy manipulations of exotic Bitter Willow (Salix elaeagnos) forest for indigenous seedling recruitment: A pilot study

The invasive exotic tree species Bitter Willow (Salix elaeagnos; Salicaceae) has colonised areas of rank exotic grassland and has been found to contain indigenous seed, dispersed by frugivorous birds into the monospecific stands. This small pilot study examined whether indigenous seedlings that have germinated in the understorey of exotic Bitter Willow stands could be stimulated to establish through the creation of small‐scale canopy gaps. In Bitter Willow forest, four single Bitter Willow trees were poisoned to create canopy gaps. Light transmission and seedling regeneration of tree and shrub species were assessed beneath both the four manipulated and three comparable intact Bitter Willow canopies. Over 3 years, seedling height and density increased more beneath opened compared to intact Bitter Willow canopies. These results suggest that Bitter Willow can fill the roles of both a facilitative nurse and a perch tree. Larger‐scale canopy manipulation experiments of both Bitter Willow and other Salix species are needed to determine the full potential of canopy manipulations for forest restoration.     

Effects of Initial Site Treatments on Early Growth and Three-Year Survival of Idaho Fescue

Prairies in the Pacific Northwest have been actively restored for over a decade. Competition from non‐native woody and herbaceous species has been presumed to be a major cause for the failure of restoration projects. In this research, plugs of the native prairie bunchgrass, Festuca idahoensis Elmer var. roemeri (Pavlick), were grown from seed in a nursery and transplanted into a grassland site dominated by non‐native pasture grasses. The growth of the plants was followed for three years, and biomass of all volunteer plants was measured. Before planting, five treatments were applied to the plots: removal of vegetation by burning, removal of vegetation by an herbicide‐and‐till procedure, soil impoverishment by removal of organic matter, fertilizer application, and compost mulch application. Initial growth of Idaho fescue plugs was greatest with fertilizer and compost mulch. Plants grown in mulched plots were also able to photosynthesize later into the dry summer season. After the first year, plots initially fertilized or composted had the lowest survival rate of Idaho fescue. Impoverished and herbicide‐and‐till plots had the greatest 3‐year survival. Mulched plots supported the greatest weed growth after three years. Stressful environments give a competitive advantage to Idaho fescue in prairie restoration projects. As weedy species increase, growth and survival of Idaho fescue decreases.     

Effects of glyphosate herbicide on soil and litter macro-arthropods in rainforest: Implications for forest restoration

Summary    Ecological restoration activities, including reforestation, often involve the use of herbicides for the removal of weedy plant cover. Little is known, however, about the effects of herbicides on assemblages of non-target organisms that colonize restored patches. We describe a field experiment to investigate effects of glyphosate herbicide (Roundup® Biactive™) on rainforest-associated soil- and litter-dwelling macro-arthropods. Our experimental protocol differed in two ways from other ecotoxicological studies of herbicides. First, we applied herbicide at a rate considerably greater than the manufacturer's recommended maximum in order to simulate worst-case scenarios that may occur in the practice of forest restoration. Second, our field experiment was carried out under dense canopy cover with sparse understorey vegetation, so that indirect impacts caused by the loss of existing vegetation were eliminated. Paired herbicide-treated and control plots were created within five rainforest remnants on the Maleny plateau of subtropical eastern Australia. Macro-arthropods were collected using litter extraction before, approximately 3 days after, and 3 months after herbicide application. Responses of arthropods were analysed at two levels of taxonomic resolution: 'coarse' arthropods (arthropods sorted to Order/Class), and ant species. Our results suggest that the use of glyphosate herbicide formulated as Roundup® Biactive™ is suitable for the control of unwanted plants in rainforest restoration sites as it appears to have minimal impact on assemblages of soil and litter macro-arthropods or at least those typical of intact rainforest.     

Enhancing the diversity of breeding invertebrates within field margins of intensively managed grassland: Effects of alternative management practices

Severe declines in biodiversity have been well documented for many taxonomic groups due to intensification of agricultural practices. Establishment and appropriate management of arable field margins can improve the diversity and abundance of invertebrate groups; however, there is much less research on field margins within grassland systems. Three grassland field margin treatments (fencing off the existing vegetation “fenced”; fencing with rotavation and natural regeneration “rotavated” and; fencing with rotavation and seeding “seeded”) were compared to a grazed control in the adjacent intensively managed pasture. Invertebrates were sampled using emergence traps to investigate species breeding and overwintering within the margins. Using a manipulation experiment, we tested whether the removal of grazing pressure and nutrient inputs would increase the abundance and richness of breeding invertebrates within grassland field margins. We also tested whether field margin establishment treatments, with their different vegetation communities, would change the abundance and richness of breeding invertebrates in the field margins. Exclusion of grazing and nutrient inputs led to increased abundance and richness in nearly all invertebrate groups that we sampled. However, there were more complex effects of field margin establishment treatment on the abundance and richness of invertebrate taxa. Each of the three establishment treatments supported a distinct invertebrate community. The removal of grazing from grassland field margins provided a greater range of overwintering/breeding habitat for invertebrates. We demonstrate the capacity of field margin establishment to increase the abundance and richness in nearly all invertebrate groups in study plots that were located on previously more depauperate areas of intensively managed grassland. These results from grassland field margins provide evidence to support practical actions that can inform Greening (Pillar 1) and agri‐environment measures (Pillar 2) of the Common Agricultural Policy (CAP). Before implementing specific management regimes, the conservation aims of agri‐environment measures should be clarified by defining the target species or taxonomic groups.     

Impacts of introduced brown and rainbow trout on benthic invertebrate communities in shallow New Zealand lakes

1. Brown and rainbow trout have been introduced to many inland waters in New Zealand, but research on the impacts on native communities has focused mainly on streams. The purpose of this study was to compare the benthic communities of trout and troutless lakes. Based on previous studies in North America and Europe, we predicted that the benthic biomass, and especially the abundance of large invertebrates, would be lower in lakes with trout as compared to those without. We surveyed the invertebrate fauna of 43 shallow, high‐elevation lakes (26 with and 17 without trout) in four geographic clusters on the central South Island and then conducted a detailed quantitative study of invertebrate biomass and community structure in 12 of these lakes. 2. Benthic community composition and diversity of lakes with and without trout were nearly identical and biomass was as high or higher in the lakes with as without trout. There was no evidence that trout have caused local extinctions of benthic invertebrates. Although the proportional abundance of large‐bodied aquatic was slightly lower in lakes with than without trout, the abundance of several groups of large‐bodied benthic taxa (dragonflies, caddisflies and water bugs) did not differ. 3. Our findings are in contrast to those in North American and Europe where trout introductions into previously troutless lakes have led to declines in the abundance of benthic invertebrates, especially large‐bodied taxa. We propose that the modest effects of trout in New Zealand could be explained by (i) the high areal extent of submergent vegetation that acts as a benthic refuge, (ii) low intensity of trout predation on benthic communities and/or (iii) characteristics of the benthic invertebrates that make them relatively invulnerable to fish predation. 4. Regardless of the relative importance of these hypotheses, our results emphasise that the same invertebrates occurred in all of the lakes, regardless of size, elevation and presence of trout, suggesting habitat generalists dominate the benthic fauna in shallow New Zealand lakes.     

Relationships between Methylobacteria and Glyphosate with Native and Invasive Plant Species: Implications for Restoration

After removing invasive plants, whether by herbicides or other means, typical restoration design focuses on rebuilding native plant communities while disregarding soil microbial communities. However, microbial–plant interactions are known to influence the relative success of native versus invasive plants. Therefore, the abundance and composition of soil microorganisms may affect restoration efforts. We assessed the effect of herbicide treatment on phytosymbiotic pink‐pigmented facultative methylotrophic (PPFM) bacteria and the potential consequences of native and invasive species establishment post‐herbicide treatment in the lab and in a coastal sage scrub (CSS)/grassland restoration site. Lab tests showed that 4% glyphosate reduced PPFM abundance. PPFM addition to seeds increased seedling length of a native plant (Artemisia californica) but not an invasive plant (Hirschfeldia incana). At the restoration site, methanol addition (a PPFM substrate) improved native bunchgrass (Nassella pulchra) germination and size by 35% over controls. In a separate multispecies field experiment, PPFM addition stimulated the germination of N. pulchra, but not that of three invasive species. Neither PPFM nor methanol addition strongly affected the growth of any plant species. Overall, these results are consistent with the hypothesis that PPFMs have a greater benefit to native than invasive species. Together, these experiments suggest that methanol or PPFM addition could be useful in improving CSS/grassland restorations. Future work should test PPFM effects on additional species and determine how these results vary under different environmental conditions.     

Weed and invertebrate community compositions in arable farmland

A large proportion of the land surface area of Great Britain (GB) is used for arable agriculture. Due to changes in farm management practices over the last 50 years, there have been marked declines in the abundance of arable wildlife groups of conservation importance, including weeds, invertebrates and birds. Here we ask whether changes in weed species composition, driven by changes in management, such as a change in crop or a modification in herbicide regime, might be expected to lead to changes in the species compositions of other wildlife groups, including invertebrates. Using multivariate analyses, on data from eight crop and herbicide management groups sampled across 266 arable fields, we show that the weed composition changes with the crop and herbicide management adopted and the invertebrate composition changes with the crop grown. We conclude that each conventional crop sampled had a unique composition of weeds and invertebrates, and expect this to be true for all conventional arable crops. Changes in weed species composition, driven by changes in crop or herbicide management, will lead to changes in the compositions of invertebrates, and possibly other wildlife groups. However, these changes will probably be buffered by the effect of functional redundancy, the crop and dispersal. Handling editor: Gimme Walter.     

Seasonal variation in foraging conditions for Ring Ouzels Turdus torquatus in upland habitats and their effects on juvenile habitat selection

Recent studies indicate that variation in juvenile survival may be particularly important in driving avian population dynamics. The quality of habitats available to inexperienced juveniles of migrant species is critical to their survival because they must obtain enough food to build up fat reserves for migration, while avoiding predation. We radiotracked 110 juvenile Ring Ouzels Turdus torquatus, a species of high conservation concern in the UK, to quantify for the first time seasonal patterns in foraging habitat and food abundance during this potentially key life‐history period. Key attributes of foraging plots were compared with those on control plots (representing the broad habitat types selected by foraging juveniles) during 2007–08. Birds foraged on invertebrates in grass‐rich plots during June to mid‐July and then shifted to foraging mainly on moorland berries in higher‐altitude, heather‐rich plots during mid‐July to early‐September. Juveniles selected invertebrate foraging plots with low soil acidity, and increasingly selected plots with high earthworm (an important food) biomass and grass cover, but low grass and all vegetation height as the season progressed. In contrast, earthworm biomass and grass cover remained constant, and grass and all vegetation height increased, on control plots. Juveniles selected berry foraging plots with higher abundance of ripe Bilberries Vaccinium myrtillus and Crowberries Empetrum nigrum than found on control plots. Juvenile Ring Ouzels thus appear to require access to short, grass‐ and invertebrate‐rich habitat during early summer, and taller, heather‐dominated and berry‐rich areas in late summer. The use of two distinct habitat types during the pre‐migratory period illustrates the need for a detailed understanding of the requirements of juvenile birds.     

Variation in wetland invertebrate communities in lowland acidic fens and swamps

1. Invertebrates were collected semi‐quantitatively from four relatively undisturbed wetlands in the west coast of New Zealand’s South Island: two acidic fens and two swamps. Samples were collected from up to four discrete habitats within each wetland: large open‐water channels, small leads (small, ill‐defined channels with emergent vegetation in them) and large (>10 m diameter) or small (<10 m diameter) ponds. Samples were also collected from different plant species within each wetland, each with different morphology, and from areas without vegetation. This was done to determine whether invertebrate communities varied more between‐wetlands than within‐wetlands, as the results had implications for future wetland monitoring programmes. 2. Principal components analysis of water chemistry data revealed striking differences in pH, conductivity and nutrients between the four wetlands. Not surprisingly, pH was lowest in one of the acidic fens, and highest in one of the swamps, where conductivity was also high. Midges (Tanytarsus, Tanypodinae, Orthocladiinae and Ceratopogonidae), nematodes, harpactacoid copepods and the damselfly Xanthocnemis dominated the invertebrate fauna. Orthoclad midges and mites were the most widespread taxa, found in 91 of 94 samples. Diptera were the most diverse invertebrate group, followed by Trichoptera and Crustacea. 3. Ordination analysis of the invertebrate data showed that the four wetlands supported different invertebrate communities. However, species composition did not change completely along the ordination axes, suggesting that a relatively species‐poor invertebrate fauna was found in the wetlands. Taxa such as molluscs were restricted to wetlands with high pH. Multi‐response permutation procedures (MRPP) was used to analyse resultant ordination scores to see how they differed according to five terms: ‘Wetland’, ‘Habitat’, ‘Growth Form’, ‘Morphology’ and ‘Plant’. Most of the sample separation along ordination axes reflected differences between wetland, although the ‘Habitat’ and ‘Plant’ terms also explained some of the variation. The ‘Growth Form’ and ‘Morphology’ terms had only minor effects on community composition. 4. A multivariate regression tree modelled invertebrate assemblages according to the five predictor terms. The resultant model explained 54.8% of the species variance. The ‘Wetland’ term contributed most to the explanatory power, followed by ‘Habitat’. ‘Growth type’ and ‘Morphology’ explained only a small amount of variance to the regression tree, while the different plant species explained none of the variation. 5. Variation in these New Zealand wetland invertebrate communities appears to be controlled most by large‐scale factors operating at the level of individual wetlands, although different habitats within individual wetlands contributed slightly to this variation. Based on these results, sampling programmes to describe wetland invertebrate communities do not need to sample specific habitats or plant types within a wetland. Instead, samples can be collected from a wide range of habitats within individual wetlands, and pooled. Within each habitat, it is unnecessary to collect individual samples from different macrophytes or un‐vegetated areas. Our results suggest that collecting replicate pooled samples from different habitats within each wetland will be sufficient to characterize the invertebrate assemblage of each wetland.