Coarse pine bark mulch as open surface cover fails to improve establishment of sown native grasslands

Abstract

Summary This study was conducted across twelve agricultural locations in south‐western Victoria, Australia, encompassing a range of soil types and climatic conditions. It investigated the addition of an open layer of coarse organic pine wood chip mulch (~70% surface cover) directly following direct seeding of native grassland species. The intent was to mimic positive effects of naturally occurring organic surface litter (which are typically depleted in such settings) on seedling emergence and establishment. Findings revealed negative results in that the use of an open layer of coarse pine chip mulch failed to improve native establishment at 12‐months or to moderate soil temperature and moisture extremes in comparison to non‐mulched plots. This outcome suggests the effectiveness of open surface mulches under the scenario of direct seeding may be highly site context, mulch‐type, and application approach dependent. In situations where such mulch applications are not likely to be beneficial, significant costs relating to their purchase and application could be avoided.

Native establishment improved and weed competition reduced by topsoil removal in direct‐sown native grasslands

“…Another broad aim of restoration is to establish suitable plant numbers (per unit area) to create functional and resilient vegetation that is reflective of reference densities (Coor 2003;Gibson-Roy et al 2021c). Our study found that topsoil removed plots had significantly higher native plant numbers over all 3 years compared to cultivated and herbicide-treated plots.…”

“…In agricultural landscapes barriers to their recovery include (i) land management practices such as cultivation and over grazing, (ii) a lack of source populations and propagules, limiting seed supply for restoration or spontaneous recovery, (iii) high soil nutrient levels favouring the growth of exotic pasture and other non-native species (referred to here as weeds), (iv) high standing weed biomass creating fierce aboveground competition, and (v) rich weed seed and bud banks providing dense emergent seedling competition. Given these challenges, the return of grasslands to arable landscapes through restoration must rely on overcoming these agricultural legacies, ideally by reducing soil nutrients, depleting weed loads and overcoming poor native propagule availability (Prober et al 2002;Cole et al 2004;Torok et al 2011;Broadhurst et al 2015;Robinson 2015;Wong & Dorrough 2015;Pedrini et al 2022;Gibson-Roy & Carland 2023;Gibson-Roy et al 2023a, 2023b.…”