Data for: Abundance, condition and size of a foundation species vary with altered soil conditions, remnant type and potential competitors

Native biodiversity often depends on remnant vegetation for
survival in agricultural landscapes. However, the size and shape of remnant patches
can affect their conservation values through edge effects and isolation of ecologically
important species such as foundation species. Foundation species interact with
and profoundly affect other species, leading to cascading community effects if
they are lost from an ecosystem. We used spinifex grass (Triodia scariosa)
to investigate the patterns, processes and consequences of remnant shape and habitat
degradation, including nutrient enrichment and soil compaction, for a
foundation plant species in agricultural landscapes. First, we quantified differences
in biotic and soil variables between narrow linear remnants and larger, more equilateral
nature reserves. We then assessed whether these differences explained variation
in spinifex abundance and condition. Finally, we tested whether edge effects influenced
spinifex abundance. We surveyed 4,230 quadrats across 282 sites in south-eastern
Australia and measured the size and condition of 11,514 spinifex clumps. Linear
remnants were characterized by different plant communities, elevated nutrient
levels, more compact soil and higher abundance of non-spinifex grasses compared
to nature reserves. Spinifex was twice as abundant in reserves than linear remnants
and was negatively associated with soil compaction and soil nutrients. Spinifex
condition was negatively associated with soil nitrogen and non-spinifex
grasses. Linear remnants had proportionally fewer small spinifex clumps compared
to reserves, suggesting lower recruitment in linear remnants. We found minimal
evidence of edge effects on environmental variables, and no clear edge effect
on spinifex abundance. Given the large contribution of linear remnants to
native vegetation cover, measures to minimise nutrient enrichment and disturbance
in these areas may help arrest potential ongoing declines in this foundation plant
species in agricultural landscapes.