Bridging the Research-Implementation Gap in Weed Management on California Rangelands

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Abstract

Substantial gaps exist between weed management researchers and practitioners with respect to prompt exchange of knowledge between the two groups, hindering the implementation of effective management to solve weed problems. We conducted a survey between 2016 and 2018 among weed management practitioners (n = 259) across diverse ecoregions on California rangelands and collected essential information from practitioners for bridging the research-implementation gap. The information included management costs, high-priority weeds, and spatial scales and temporal changes in weed management. The management cost had a mean of $5.12 ha−1yr−1 with a large variance implying the uncertainty of this information. The percentage of annual budget dedicated to weed management explained about 30% of the variation in this cost. Moreover, this annual per-unit area cost decreased with increasing management area. The average size of rangeland managed by survey respondents was 1 256 ha. The top three high-priority weeds statewide were yellow starthistle (Centaurea solstitialis), medusahead (Taeniatherum caput-medusae), and all thistles combined. Medusahead and some thistle species remained on the top list in each ecoregion. Respondents overwhelmingly (80.9%) noted changes in weed problems in the past 5−10 yr, specifically citing greater weed pressure and changes in weed species. A significantly higher proportion of respondents from agencies and private businesses reported changes in weed problems than those from universities and nongovernmental organizations (NGOs), further underscoring the gap between practitioners and researchers. A majority of the respondents (75.3%) indicated the record-setting California drought had a negative effect on weed management, reducing treatment efficacy and favoring weeds over desirable species. Overall, our findings illustrate increasing challenges in weed management on California rangeland. These challenges call for adaptive management-research programs to increase cost-effectiveness of weed management and to swiftly and effectively respond to dynamic weed problems on large spatial and long temporal scales.

Introduction

Weedy and invasive plants have large negative impacts on conservation of biodiversity and essential human activities relying on natural resources such as farming and livestock grazing (DiTomaso, 2000, Pimentel et al., 2005, Olson, 2006, Gilbert and Levine, 2013). Effective weed management requires translating insights from scientific evidence to management practices adaptable to the variable ecological and evolutionary conditions in plant invasions (Memmott et al., 2010, Anderson, 2014). Extensive research studies have been carried out in academic institutions to understand the ecological and evolutionary processes of plant invasions and to provide solutions for weed management (Shea and Chesson, 2002, Sax et al., 2005, Kettenring and Adams, 2011, Gilbert and Levine, 2013, Kuebbing et al., 2013). Nevertheless, there remains a disconnect between what research programs have produced and what weed management practitioners need (Esler et al., 2010, Bayliss et al., 2013, Matzek et al., 2014, Matzek et al., 2015).

This is often referred to as the “knowing-doing gap” (Esler et al. 2010); however, the term may be misinterpreted as if the doers do not necessarily possess critical knowledge. In fact, experienced field practitioners hold one of the most voluminous caches of weed management knowledge (Anderson, 2014, Matzek et al., 2014). Therefore, this disconnect between science and management is more appropriately characterized here as the “research-implementation gap.” Bridging this gap ensures that science is addressing the most pressing and relevant issues for practitioners and to create a beneficial feedback between research and management. With this feedback, scientific predictions can be tested in large-scale, long-term field applications, and informed management practices can be more effective and adaptive to changing ecological conditions (Dietze et al. 2018).

The barrier for knowledge flow exists on both ends. Applied research is substantially underrepresented in the scientific literature of biological invasions (Esler et al., 2010, Matzek et al., 2015), and the published results from many applied research studies are not readily accessible to practitioners (Esler et al., 2010, Bayliss et al., 2012). Alternatively, practitioners largely rely on field observations to make management decisions (Bayliss et al. 2012). Practitioners accumulate large amounts of field evidence, experience, and multiyear data, which are mostly shared informally among practitioners or archived internally (Matzek et al. 2014). Not knowing what the practitioners know, researchers might produce studies with limited relevance to management, especially with regard to spatial and temporal scales at which practitioners make decisions (Esler et al., 2010, Kettenring and Adams, 2011, Bayliss et al., 2013, Matzek et al., 2015, Roche et al., 2015a).

Here we analyzed results from a survey of weed management practitioners on California rangelands. The state of California is largely characterized by a floristic province that is a biodiversity hotspot in a Mediterranean climate. This floristic province is especially vulnerable to plant invasions (Seabloom et al. 2006). The direct annual cost to monitor and control invasive plants in California is about $82 million (Brusati 2009), and the indirect economic cost is even greater. Despite substantial control efforts that have been implemented, California’s weeds continue to invade working landscapes, highlighting the need for more effective approaches of weed management. Bridging the research-implementation gap is one of the keys to more successful weed management. The goal of this study was to synthesize practitioner knowledge to narrow the existing gap in the following subjects: 1) weed management costs; 2) high-priority weeds; and 3) spatial scales and temporal dynamics of weed management.

We collected survey responses on weed management costs because few studies address implementation costs, an essential factor in management decision making (Kettenring and Adams, 2011, Bayliss et al., 2013, Matzek et al., 2015, Roche et al., 2015b, Gornish et al., 2018). We used the survey results to understand implementation costs of weed management and whether these costs change with spatial scales. We addressed high-priority weeds in our survey because the invasive species most commonly studied mismatch the species of greatest concern for land managers (Matzek et al. 2015). We used the survey responses to determine high-priority weeds on rangelands throughout California and in each of its ecoregions. Finally, many research studies are limited in their temporal and spatial scales and cannot provide predictions or solutions required for large-scale, long-term adaptive management in response to a variable environment (Kettenring and Adams, 2011, Bayliss et al., 2013, Anderson, 2014, Matzek et al., 2015, Roche et al., 2015a). We used the survey results to determine spatial scales of weed management on California rangelands and to understand how weed management changed over time. The timing of our survey (2016−2018) coincided with the record-setting drought that California experienced between 2011 and 2019 (NIDIS 2019, and especially between 2012 and 2014; see Diffenbaugh et al. 2015). We asked survey respondents how the drought affected weed management. Our intention was to use this baseline information to understand solutions necessary for weed management to adapt to intensifying drought predicted under climate change (Diffenbaugh et al., 2015, Williams et al., 2015).

By analyzing practitioner knowledge, we aim to present findings that can help research programs adjust their priorities and approaches in order to match the budget, priority, and spatial and temporal scales of interest in weed management. In the discussion section, we further discuss the need and ways of creating adaptive research-management programs through which practitioners may also become more responsive to research recommendations and provide scientific evidences acquired through weed management practices to enhance scientific research.

Section snippets

Practitioner Survey

We developed a survey for weed practitioners in California in collaboration with management professionals. Survey questions were pilot tested with six California Cooperative Extension advisors and specialists. Questions were divided into sections on respondents’ professional background, weed management perspectives and priorities, and management practices. We distributed the final survey between 2016 and 2018 at a series of seven University of California Cooperative Extension education

Costs of Weed Management

Estimating annual per-unit area cost of weed management requires survey responses reporting both management area and annual management cost, which were only reported by 77 respondents. The median and mean of the cost, after back-transformed from a log10 transformation, was $2.22 ha−1yr−1 and $5.12 ha−1yr−1, respectively. The lower and upper bound of one standard deviation of this variable, after the back-transformation, was $0.19 ha−1yr−1 and $95.40 ha−1yr−1, respectively. The median-mean

Weed Management Costs

Various studies have suggested that understanding management costs is one major knowledge gap between researchers and practitioners (Bayliss et al., 2013, Matzek et al., 2015). Few weed management studies have indicated the costs of their methods (Kettenring and Adams, 2011, Matzek et al., 2015, Gornish et al., 2018). Thus, practitioners have little information about the affordability of implementing certain methods suggested as effective by research studies. However, weed management cost is

Implications

Our survey of weed management practitioners on California rangeland indicated that the worst weeds had either increased or changed their identity within the past decade and the record-setting California drought had negatively impacted weed management. These worrisome changes suggested that the spending in weed management, which averaged about $5 ha−1yr−1, might not be adequate to solve the weed problem. Yet spending on weed management was limited by the percentage of annual budget that could be

Acknowledgments

We thank two anonymous reviewers for their constructive comments that improved this article.

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    This study was funded by the California Department of Pesticide Regulation’s Pest Management Alliance Grant Program (15-PML-G002).

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