Persistence of biodiversity in a dryland remnant within an intensified dairy farm landscape

Abstract

Abstract:The lowland Canterbury Plains of New Zealand have been extensively modified since human occupation, but with recent conversions to irrigated dairy farming very few remnants of native dryland vegetation remain in the region. We investigated soil chemistry, plant distribution and soil invertebrates along transects in Bankside Scientific Reserve, a small (2.6 ha) remnant. The vegetation is a mosaic of native woody shrubs, predominantly Kunzea serotina (kanuka, Myrtaceae) and Discaria toumatou (matagouri, Rhamnaceae), and dry grassland. Changed soil conditions appear to have made the reserve less conducive for native species, but better suited to invasion by exotic plants. Compared with detailed surveys before the dairy conversion, only 31% of the original 65 native vascular plant species were recorded in the present study and 27 new exotic species had arrived since the original survey. Soil nutrient concentrations and pH were lower in the reserve than in surrounding farmland; peaks of nitrate and ammonium were recorded at the boundary. Soil phosphate was elevated in lower-lying areas within the reserve, an effect associated with natural drainage channels and evident up to 20 m into the reserve. Four species of native megascolecid earthworms were found in the reserve but not in neighbouring pasture, whereas the diversity and abundance of beetles and spiders in the reserve was similar to that observed at least 10 m into surrounding farmland. This study highlights the importance of the soil environment in sustaining biodiversity. We conclude that this remnant retains valuable communities of native species, but is apparently being impacted by phosphate encroachment and habitat fragmentation. This does not appear to be an intractable management issue for the interface between agricultural systems and conservation sites within a dairy landscape mosaic. We suggest that attention is required to maintain buffer zones adjacent to small, isolated and vulnerable remnants of original biota that are surrounded by intensive agriculture.

Molecular identification and distribution of native and exotic earthworms in New Zealand human-modified soils

“…Native species in the Megascolecidae family are often restricted to protected habitats and remnants of native vegetation, but they are also found on the borders of agricultural land (Kim et al 2015). Coexistence of native and exotic species has recently been reported where patches of native vegetation borders agricultural land (Kim et al 2015;Bowie et al 2016) or when native vegetation is restored on agricultural land .…”

Interactions of native and introduced earthworms with soils and plant rhizospheres in production landscapes of New Zealand

“…Human colonization and introduction of mammalian pests to these islands has been relatively recent, but native biodiversity has been impacted particularly severely (Lee, 1961;Sparling and Schipper, 2002;MacLeod and Moller, 2006). Agricultural modification of landscapes, vegetation and soils has certainly been to the detriment of native earthworms (Lee, 1959a;Molloy, 1988;Bowie et al, 2016).…”

Response of endemic and exotic earthworm communities to ecological restoration

“…The apparent inability of endemics to survive in agricultural land has encouraged efforts to increase the dispersion of exotic earthworms in New Zealand agricultural land in recent years. At the same time, the ability of exotic earthworms to encroach under New Zealand native vegetation has only very recently been investigated (Bowie et al ). The introduction of similar European species in Australia has led to concerns regarding their potential impact on native Australian soil fauna (Baker et al ).…”

“…However, there is very little information about the potential of exotic earthworms to colonize soil under native vegetation or the potential for endemic species to recover from land conversion. In a recent study, we reported the ability of exotic earthworms to move from pasture into adjacent native vegetation particularly into areas affected by leaching of soil nutrients from agricultural land (Bowie et al ).…”