Long-term revegetation success of severely degraded chenopod shrublands

Abstract

The restoration of severely degraded vegetation communities is often said to require mechanical intervention. However, the degree of intervention required, and its capacity to successfully restore areas of bare (scalded) soil and high weed cover into functioning chenopod shrubland, is unknown. Ten years on from mechanical intervention and direct seeding using a Contour Seeder and Camel Pitter, the abundance and cover of species was compared across disturbed and undisturbed microtopographic zones using one-way repeated-measures ANOVA and pairwise t-tests. Along Contour Seeder rip lines, recruitment of perennial species was greatest in the furrow (e.g. direct seeded: F2,78 = 27.15, P < 0.001; wild-sourced: F2,78 = 13.19, P < 0.001), and annual (and short-lived perennial) species equal to, or greater, on the undisturbed flat (wild-sourced: F2,98 = 43.91, P < 0.001). At the species-level, these trends often coincided with the species’ life-history strategy, but not always (e.g. the perennial Atriplex stipitata illustrated the annual trend; F2,78 = 7.71, P < 0.001). It is also important to note that a trend in recruitment could be driven by recruitment patterns in any one demographic phase. For example, the perennial trend in Atriplex vesicaria and Sida fibulifera abundance was driven by the recruitment of reproductive plants (F2,48 = 15.57, P < 0.001), or seedlings (F2,36 = 5.24, P = 0.010), respectively. These results indicate the functional benefits of mechanical intervention vary between species. The perennial and annual trends detected along Contour Seeder rip lines were less apparent along Camel Pitter rip lines where both perennial and annual species benefited from the initial disturbance. Overall, mechanical intervention facilitated the patchy recruitment of a Maireana pyramidata over A. vesicaria low shrubland, including several perennial and annual chenopods, indicating an early stage of recovery.