nsdó ttir, I. S. 2006. Impact of warming and timing of snow melt on soil microarthropod assemblages associated with Dryas-dominated plant communities on Svalbard. Á/ Ecography 29: 111 Á/119.Open Top Chambers (OTCs) were used to measure impacts of predicted global warming on the structure of the invertebrate community of a Dryas octopetala heath in West Spitsbergen. Results from the OTC experiment were compared with natural variation in invertebrate community structure along a snowmelt transect through similar vegetation up the adjacent hillside. Changes along this transect represent the natural response of the invertebrate community to progressively longer and potentially warmer and drier growing seasons. Using MANOVA, ANOVA, Linear Discriminant Analysis and x 2 tests, significant differences in community composition were found between OTCs and controls and among stations along the transect. Numbers of cryptostigmatic and predatory mites tended to be higher in the warmer OTC treatment but numbers of the aphid Acyrthosiphon svalbardicum , hymenopterous parasitoids, Symphyta larvae, and weevils were higher in control plots. Most Collembola, including Hypogastrura tullbergi , Lepidocyrtus lignorum and Isotoma anglicana , followed a similar trend to the aphid, but Folsomia bisetosa was more abundant in the OTC treatment. Trends along the transect showed clear parallels with the OTC experiment. However, mite species, particularly Diapterobates notatus, tended to increase in numbers under warming, with several species collectively increasing at the earlier exposed transect stations. Overall, the results suggest that the composition and structure of Arctic invertebrate communities associated with Dryas will change significantly under global warming.

1. Kānuka (Kunzea serotina, Myrtaceae) dryland shrubland communities of the lowland plains of South Island (Te Wai Pounamu), New Zealand (Aoteoroa), contain a ground cover largely consisting of mosses, predominantly Hypnum cupressiforme. There has been no previous study of the role of mosses in this threatened habitat which is currently being restored within a contemporary irrigated and intensively farmed landscape that may be incompatible with this component of the ecosystem.2. The aim of the present study was to investigate the influence of moss ground cover on hydrology, nitrogen (N) availability and vascular plant interactions, and in relation to nutrient spillover from adjacent farmland. Experimental work was a combination of glasshouse experiments and field-based studies.3. Extremes of soil temperature and moisture were found to be mediated by the moss carpet, which also influenced N speciation; available N declined with moss depth. The moss layer decreased the amount of germination and establishment of vascular plants but, in some cases, enhanced their growth. Spillover of mineral nitrogen and phosphate from farmland enhanced invasion of exotic grasses which may have benefited from conditions provided by the moss carpet. Synthesis:We found the moss layer to be crucial to ecosystem functioning in these dry habitats with low nutrient substrate. However, when the moss layer is accompanied by nutrient spillover, it has the potential to increase exotic weed encroachment. Our results not only emphasize the importance of non-vascular plant inclusion in restoration schemes but also highlights the importance of mitigating for nutrient spillover.

Summary Associated with restoration of 150 ha of native plant communities within a highly exposed low rainfall landscape, we evaluated whether the benefits of tree guards and weed mats justified a doubling of planting costs. One‐year‐old nursery‐grown specimens of Kānuka (Kunzea serotina) and Pomaderris (Pomaderris amoena) were planted with and without polythene and rigid plastic tree guards, and weed mats, then monitored for 12 months. Herbivory was reduced with both types of tree guard by 10–35%, but mortality was largely caused by desiccation. Polythene tree guards provided the best protection, buffering extremes of ambient and soil temperature in summer but with no effect on soil temperature in winter. Weed mat addition reduced soil temperature fluctuation further in winter; a moss turf mat was best. Both mulch and moss weed mats reduced soil temperature in summer and raised soil moisture in winter. We showed that tree guards could save at least NZ$ 70 k/ha, but this is likely to vary with plant species traits and site conditions.

Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha−1), lime (6000 kg CaCO3 ha−1), and superphosphate (470 kg ha−1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha−1 y−1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.

1. Kānuka (Kunzea serotina, Myrtaceae) dryland shrubland communities of the lowland plains of South Island (Te Wai Pounamu) New Zealand (Aoteoroa) contain a ground cover largely consisting of mosses, predominantly Hypnum cupressiforme. There has been no previous study of the role of mosses in this threatened habitat which is currently being restored within a contemporary irrigated and intensively-farmed landscape that may be incompatible with this component of the ecosystem. 2. The aim of the present study was to investigate the influence of moss ground cover on hydrology, nitrogen (N) availability and vascular plant interactions, and in relation to nutrient spillover from adjacent farmland. Experimental work was a combination of glasshouse experiments and field-based studies. 3. Extremes of soil temperature and moisture were found to be mediated by the moss carpet, which also influenced N speciation; available N declined with moss depth. The moss layer decreased the amount of germination and establishment of vascular plants but, in some cases, enhanced their growth. Spillover of mineral nitrogen and phosphate from farmland enhanced invasion of exotic grasses which may have benefited from conditions provided by the moss carpet. 4. Synthesis: We found the moss layer to be crucial to ecosystem functioning in these dry habitats with low nutrient substrate. However, when the moss layer is accompanied by nutrient spillover it has the potential to increase exotic weed encroachment. Our results emphasise the importance of non-vascular plant inclusion in restoration schemes but also highlights the importance of mitigating for nutrient spillover.