Microsite and litter cover effects on soil conditions and seedling recruitment in a saline agricultural system

Abstract

Successful revegetation of saline land is dependent on seedling recruitment to maintain vegetative cover for lowering of saline water tables and agricultural production. This paper examines seasonal effects of tree/shrub microsites and leaf-litter on soil conditions and seedling recruitment in a saline grazing system planted with Eucalyptus sargentii Maiden tree rows (15 years old) and saltbush (Atriplex spp.) inter-rows (8 years old). Salt bush rows were also slightly mounded. As litter accumulation decreases with increased distance from tree rows, soil conditions and seedling recruitment were compared between paired bare and litter-covered zones within three microsites: tree row, saltbush row 1 (saltbush row closest, viz. 3–4 m, to tree row) and saltbush mid-row (middle row of saltbush between adjacent tree rows, viz. 7–9 m from trees). Microsite facilitation in winter was negligible due to moderate temperatures and high water availability. However, in warmer months, saltbush mid-row microsites were most favourable for recruitment. Tree microsites inhibited recruitment through increased salinity, water repellency and potential root competition. Despite negative interactions within the tree row, trees indirectly facilitated recruitment through litter provision in saltbush rows. Overall, litter increased seedling densities through amelioration of soil temperatures and salinity. Litter reduced salinity (top 2 cm) in warmer months, from ‘severe’ where only halophytes survive, to ‘moderate’ where growth of non-halophytic species is possible, but at reduced rates. Recruitment was influenced by microsite characteristics including, litter quantities, mounding and row position.