Approaches to interdisciplinary mixed methods research in land change science and environmental management

Combining qualitative and quantitative methods and data is crucial to understanding the complex dynamics and often interdisciplinary nature of conservation. Many conservation scientists use mixed methods, but there are a variety of mixed methods approaches, a lack of shared vocabulary, and few methodological frameworks. We reviewed articles from 2 conservation-related fields that often incorporate qualitative and quantitative methods: land-change science (n= 16) and environmental management (n= 16). We examined how authors of these studies approached mixed-methods research by coding key methodological characteristics, including relationships between method objectives, extent of integration, iterative interactions between methods, and justification for use of mixed methods. Using these characteristics, we created a typology with the goal of improving understanding of how researchers studying land-change science and environmental management approach interdisciplinary mixed methods research. We found 5 types of mixed methods approaches, which we termed simple nested, informed nested, simple parallel, unidirectional synthesis, and bidirectional synthesis. Methods and data sources were often used to address different research questions within a project, and only around half of the reviewed papers methodologically integrated different forms of data. Most authors used one method to inform the other rather than both informing one another. Very few articles used methodological iteration. Each methodological type has certain epistemological implications, such as the disciplinary reach of the research and the capacity for knowledge creation through the exchange of information between distinct methodologies. To exemplify a research design that can lead to multi-dimensional knowledge production, we provide a methodological framework that bidirectionally integrates and iterates qualitative and quantitative methods

Differing short-term impacts of agricultural tarping on soil-dwelling and surface-active arthropods

Agricultural tarping, the practice of placing impermeable plastic tarps over crop beds before planting to suppress weeds, is rising in popularity. However, the use of tarps has uncertain effects on soil arthropod communities. We studied the impact of silage (black plastic) tarps and clear plastic tarps on surface-active and soil-dwelling arthropods by tracking immediate impacts and arthropod recovery for 5 weeks after tarps were removed. We also assessed how well environmental and experimental variables explained arthropod diversity and composition. During tarp application, we found that both silage and clear plastic tarps had significant negative impacts on surface-active arthropod diversity, while only clear plastic tarps impacted soil-dwelling arthropods. Surface-active arthropod diversity recovered by 1-3 weeks after tarping, but at 5 weeks after tarping soil-dwelling arthropod diversity was significantly lower in silage tarp and clear plastic plots than control plots. Tarps also led to compositional changes in the arthropod communities, though these changes were only significant during tarp cover. The variables that best explained arthropod diversity and community composition were treatment (i.e., silage tarp, clear plastic tarp, or control) during tarping and farm site after tarps were removed. Other variables, such as soil moisture and weed coverage, were not strong model predictors. These results imply that tarps may have temporary impacts on surface-active arthropods but potentially longer-lasting impacts on soil-dwelling arthropods. Continuing to monitor impacts on tarps on soil arthropods will better inform the sustainability of this practice

Detritivores and Carbon Cycling in Agroecosystems: Assessing the Potential of an Understudied Ecosystem Service

Detritivores, including earthworms, beetles, ants, springtails, and mites, are an ecological group that live in the soil and consume litter. Detritivores are often used as indicators of healthy soil, but there is a paucity of work investigating their role in ecosystem functioning. While it is recognized that they play a part in litter fragmentation, the extent to which detritivores mineralize carbon and perform other important carbon-related functions is often misunderstood or uncertain. The implications for detritivores and carbon cycling are particularly important to understand in the context of agriculture. Healthy, organic-matter rich soil is integral to crop success and can also act as a sink for carbon, which can help offset climate change. In this sense, detritivore communities in agricultural fields could potentially serve two major ecosystem services: the regulation of soil health and carbon storage. We carried out a systematic literature review with the objective of determining what is known and unknown about the role of detritivores in mediating carbon cycling. Specifically, we used a series of search terms in Web of Science to collect and assess studies that looked at the impact of individual species or whole communities on the physical and chemical properties of litter and soil. Our initial analyses demonstrate that detritivores’ impacts stretch much farther than litter fragmentation, and that they can play important roles in carbon mineralization, soil structure creation, and soil aggregation, though these impacts may be specific to certain species or functional groups. We additionally found that the literature is heavily weighted towards certain taxonomic groups, like earthworms and nematodes, and that there is a paucity of and need for research for groups like ground beetles, springtails, and mites. These results indicate that detritivores play a much more important role in soil health and agricultural productivity than previously believed and that agricultural management plans should prioritize detritivore conservation

Soil Invertebrates In Agriculture: Assessing Ecosystem Services, Biodiversity Impacts, And Farmer Perceptions

Harmonizing biological diversity and crop production is a major goal towards building more sustainable food systems. Soil invertebrates are diverse and abundant organisms in agriculture, but relatively little is known about their benefits or how agricultural management impacts them. In this dissertation, I dig into the complex interactions between agricultural land use and soil invertebrate biodiversity to better inform farmer decision-making. I find that soil invertebrate communities have major potential contributions to agroecosystems (Chapter 2) and are shaped heavily by agricultural land use (Chapters 3, 4), but remain too uncertain to contribute to farmers’ management choices (Chapter 5). First, I identified four main mechanisms by which soil invertebrates contribute to carbon cycling through a review of over 600 articles. I linked these mechanisms to agriculturally-relevant ecosystem services such as climate regulation, pest control, and crop and livestock production (Chapter 2). I then studied the novel perennial crop, milkweed, in comparison to other common New England land uses and found that milkweed hosts taxonomically and functionally diverse arthropod communities (Chapter 3). Testing an emerging agricultural practice for weed suppression, tarping (placing plastic sheets over crop beds), I found that tarps caused an immediate negative effect on arthropods. Recovery of arthropods varied after tarp removal, though many groups recovered within 3-5 weeks (Chapter 4). Finally, I sought to more broadly understand the complex tradeoffs of tarping using mixed methods and participatory action research. In interviews, farmers expressed that they valued soil biodiversity, but, apart from pest species and earthworms, had limited knowledge of these communities on their farms (Chapter 5). This dissertation expands knowledge on soil invertebrate diversity in agriculture, but highlights that considerable work is needed to raise awareness of this group and promote their inclusion in decision-making

Biases and limitations of Global Forest Change and author-generated land cover maps in detecting deforestation in the Amazon.

Studying land use change in protected areas (PAs) located in tropical forests is a major conservation priority due to high conservation value (e.g., species richness and carbon storage) here, coupled with generally high deforestation rates. Land use change researchers use a variety of land cover products to track deforestation trends, including maps they produce themselves and readily available products, such as the Global Forest Change (GFC) dataset. However, all land cover maps should be critically assessed for limitations and biases to accurately communicate and interpret results. In this study, we assess deforestation in PA complexes located in agricultural frontiers in the Amazon Basin. We studied three specific sites: Amboró and Carrasco National Parks in Bolivia, Jamanxim National Forest in Brazil, and Tambopata National Reserve and Bahuaja-Sonene National Park in Peru. Within and in 20km buffer areas around each complex, we generated land cover maps using composites of Landsat imagery and supervised classification, and compared deforestation trends to data from the GFC dataset. We then performed a dissimilarity analysis to explore the discrepancies between the two remote sensing products. Both the GFC and our supervised classification showed that deforestation rates were higher in the 20km buffer than inside the PAs and that Jamanxim National Forest had the highest deforestation rate of the PAs we studied. However, GFC maps showed consistently higher rates of deforestation than our maps. Through a dissimilarity analysis, we found that many of the inconsistencies between these datasets arise from different treatment of mixed pixels or different parameters in map creation (for example, GFC does not detect reforestation after 2012). We found that our maps underestimated deforestation while GFC overestimated deforestation, and that true deforestation rates likely fall between our two estimates. We encourage users to consider limitations and biases when using or interpreting our maps, which we make publicly available, and GFC's maps

Projected losses of ecosystem services in the US disproportionately affect non-white and lower-income populations

Social inequalities may be reflected in how ecosystem services are distributed among groups of people. Here the authors estimate the distribution of three ecosystem services across demographic and socioeconomic groups in the US between 2020 and 2100, finding that non-white and lower-income groups disproportionately bear the loss of ecosystem service benefits

Tradeoffs of a rising agroecological practice: addressing uncertainty around tarping with participatory action research and mixed methods

Transitioning to more sustainable agricultural practices is a key goal in agroecology. Before practices are adopted, however, farmers must weigh a complex set of biophysical and socioeconomic tradeoffs. Tarping is a weed control practice gaining popularity in New England, but many of its biophysical impacts remain unclear to farmers. Here, we used participatory action research to engage in mutual learning with farmers around the tradeoffs of tarping for weed control. We collected quantitative biophysical data with a field study and qualitative data on biophysical and socioeconomic factors by interviewing farmers. We found tarping has a number of benefits, challenges, and uncertainties, though most farmers had positive overall perceptions of the practice. Many of our biophysical results matched farmers’ experiences, including that tarping dramatically heated soils, suppressed weeds, and increased crop yields. However, our mixed results for the effects of tarping on soil nitrate contrasted farmers’ perception that tarping increases soil nitrate availability. Engaging in participatory and mixed methods research was an effective approach to unveil complex tradeoffs around tarping and ensure our research was relevant to farmer interests. Future research on long-term effects of tarps will be valuable to inform the sustainability of this practice.</p