The golf ball method for rapid assessment of grassland structure

Abstract

Summary A key task for native grassland managers is to assess when biomass reduction is necessary to maintain plant and animal diversity. This requires managers to monitor grassland structure. Parks Victoria and La Trobe University developed a method for rapid assessment of grassland structure using golf balls. Baker‐Gabb et al. (Ecological Management & Restoration, 17, 2016, p235) provide an example of where the method has been used to manage grassland structure to favour an endangered bird, the Plains‐wanderer (Pedionomus torquatus). In this study, we provide further critical analysis of the method using three data sets collected across different parts of Victoria that relate golf ball scores to various habitat attributes. We demonstrate how the golf ball score provides a good surrogate for key aspects of grassland structure. We show that the method does not provide a reliable surrogate for above‐ground biomass or vegetation cover, although we discuss how biomass and cover are not particularly good indicators of grassland structure. We argue that elements of grassland structure may be better correlated with desired conservation outcomes (e.g. plant species diversity or the presence of a particular species) than biomass or cover alone. We discuss examples of how the golf ball method has been used, and how it can be improved. The method will be particularly useful where a link can be demonstrated between golf ball scores and desired conservation outcomes, such as in the case of the Plains‐wanderer.

Habitat requirements of Tetanocera elata (Diptera: Sciomyzidae): case study of a dry meadow in western Ireland

“…Unlike plant community analysis, structural features were measured only at the start and end of the adult flight season to track the seasonal growth of plants in survey plots. Finally, vegetation "openness" (i.e., thickness or thinness of plant coverage) at each plot was measured at the beginning (16 June) and end (10 August) of the sampling period using the golf-ball method for rangeland assessment described by Schultz et al (2017) to compare changes in plant structure over the peak growing period. Ten golf balls (fluorescent orange for easier visual detection [Links Choice, VA, USA]) were dropped perpendicularly into each plot from a height of approximately 2 m and each was assigned a score based on visibility of the golf balls.…”

“…Lower scores (e.g., fewer golf balls visible) correspond to a "closed" vegetation structure suggesting more dense growth, while plots with high scores (e.g., higher visibility of golf balls) indicate a more "open" structure. The exception to this was where vegetation had such a closed structure that the balls could not penetrate; in these cases, golf balls were assigned a score of 0 associated with extremely dense vegetation (Schultz et al, 2017).…”

“…For these co-occurring plots, the associated plot is listed. min/max), mean depth of detritus layer, median vegetation thickness score (Schultz et al 2017), and mean calculated Ellenberg values (Hill et al 1999). Statistically significant differences between plot categories per variable are indicated by the same superscript letter.…”

Multivariate drivers of diversity in temperate Australian native grasslands

“…Measures of grassland structure that include multiple variables, such as grass height and cover (or grass volume, Howland et al 2014;Schultz et al 2017), likely provide a better estimate of the vegetation profile than biomass, and might capture attributes of grass swards that plants and animals respond to (e.g. habitat complexity, light availability).…”

“…habitat complexity, light availability). There are other approaches for measuring grassland structure and heterogeneity, including variance in biomass (Dorrough and Ash 1999), point quadrats to capture height and canopy distribution (Lunt 1997b), the 'golf ball method' to provide an integrative measure of vegetation density, height and heterogeneity (Schultz et al 2017), and horizontal photography to measure vertical arrangement of vegetation (Zehm et al 2003). Measuring the amount of bare ground, cryptogamic crust, and soil cracks is also important as these attributes affect seed germination of native (Briggs and Morgan 2011) and exotic species (Morgan 2006), provide important refuges for fauna (Hadden 1995;Bourke et al 2017), and are responsive to management interventions (Morgan 2004;Wong and Morgan 2012).…”