Introduction

Most mosses are poikilohydric and ectohydric, with limited ability to regulate water loss, acquiring moisture and nutrients via external conduction from surface water or dry deposition (rainfall, mist droplets and airborne dust) (Proctor et al. 2007). In arctic, boreal and arid ecosystems, prolific ground cover has enabled mosses to exert influence on soil temperature and nitrogen availability, evapotranspiration and vascular plant interactions (Belnap 2006; Betts et al. 1999; Bonan and Shugart 1989; During and Tooren 1990; Gornall et al. 2007). It has been suggested that mosses can be a potential source of nutrients and moisture to vascular plants, supplying leaked nutrients from their cells upon rehydration (Wilson and Coxson 1999), or possibly through associations with mycorrhiza networks (Davey and Currah 2006). The moss layer can also assist germinating seeds and seedlings, buffering harsh abiotic conditions and providing camouflage against seed predation (During and Tooren 1990; Rayburn et al. 2012). Conversely, mosses may limit available resources to surrounding vascular plants by sequestering nutrient precipitation inputs and accumulating organic matter (Cornelissen et al. 2007). An association with cyanobacteria fixes nitrogen which is retained by the moss rather than releasing it into the soil (Rousk et al. 2016). In the arctic, alteration of soil temperature and moisture have been shown to influence microbe activity and rates of mineralisation and nitrification (Gornall et al. 2007).
The role of mosses in ecosystem function is complex and are often poorly understood (Bond‐Lamberty et al. 2011; Chamizo et al. 2016) and research surrounding the topic in New Zealand is almost entirely lacking (DeLucia et al. 2003; Michel et al. 2013) in spite of mosses accounting for >90% ground cover in many habitats (Pfeiffer 2003). Even in some of the driest habitats mosses, and particularly Hypnum cupressiforme , forms an almost continuous carpet, for example under stands of the canopy shrub kānuka (Kunzea serotina , Myrtaceae) of lowland New Zealand (Beever 1986; Macmillan 1976; Molloy and Ives 1972).
This research aimed to explore the role of the moss carpet within the kānuka stands associated with ecological restoration of a dryland habitat that has virtually disappeared from the contemporary irrigated intensively-farmed landscapes of the lowland plains of eastern South Island in New Zealand (Bowie et al. 2016). In view of their natural ground cover prominence, it is likely that mosses have a functional role in the restoration of these ecosystems. It is also possible that these highly modified landscapes are unsuitable for the establishment of mosses. This has perspectives both in terms of the possible juxtaposition of these two land uses, and also whether restoration of dryland habitat has a role in provision of ecosystem services.