Final report for GW22-237
Project Information
Montana producers are in a constant balance of managing non-native annual weeds and producing quality forage in high quantities. Ventenata is a non-native annual grass first identified in the United States in 1952 and identified in Montana in the 1990s. As a species with high drought tolerance and low forage quality, it is imperative we find integrated weed management strategies to control this species, while improving forage quality. Our goals are to improve our understanding of ventenata ecology, evaluate integrated weed management practices to control ventenata, increase desired forage and grassland sustainability. We intend to address these goals through two field studies: 1) ventenata and forage response to different growth conditions (current, warmer, warmer + drier) with and without herbicide treatment; and 2) ventenata and forage response to integrated management strategies with herbicides (Axiom, Rejuvra, Rejuvra + Plateau) and fertilizers (N, micronutrient, no fertilizer). Our approach is unique and will add to existing knowledge of how to manage this invasive species. We will share the outcomes of this research with producers, managers, and Montana State University students through several different outreach strategies. We will publish locally and in peer reviewed publications. The findings of this project will provide producers and managers with vital information for controlling ventenata while simultaneously increasing forage quantity and quality using integrated strategies under differing climatic conditions.
The research goals of this project are to evaluate integrated weed management approaches to suppress ventenata and improve quality and quantity of forage by increasing desired grasses. To assess our goals we have three objectives, each with sub-objectives.
The main objectives are:
Objective 1) Quantify ventenata’s competitive ability with other vegetation under different growth conditions (current, warmer, and warmer + drier conditions). These data will allow me to quantify:
1a) the response of ventenata to herbicide (Rejuvra, no spray) under different growth conditions,
1b) if forage and other vegetation are impacted by ventenata and herbicide (Rejuvra, no spray) under different growth conditions, and
1c) if ventenata cycles N more rapidly than cheatgrass and forage species under current conditions.
Objective 2) Evaluate effectiveness of integrated management approaches with herbicides (Axiom, Rejuvra, Rejuvra + Plateau, no spray) and fertilizer (N, micronutrient, no-fertilizer) to control ventenata and improve abundance and quality of desired species. These data will allow me to quantify:
2a) the response of ventenata under different treatment combinations,
2b) if forage and native vegetation are impacted by the treatment combinations, and
2c) if forage quality is impacted by the different treatments.
The educational goals of this project are to further educate Montana producers and managers, the public, and students about the non-native grass ventenata and share outcomes of integrated weed management approaches to suppress ventenata and improve quality and quantity of forage. To assess our goals, we have three objectives.
The main objectives are:
Objective 1) Share our results on the ecology and management of ventenata with producers and managers.
1a) Educate individuals on integrated management strategies effective on ventenata so that they may make informed management decisions for their own properties.
1b) Educate individuals on the identification of ventenata and its ecology under different climates.
Objective 2) Share our results about the quality and quantity of forage following integrated management strategies with producers and managers.
2a) Educate individuals on the outcomes of forage quality tests on ventenata and desired species following management so that they make informed management decisions.
2b) Educate individuals on the changes to forage quantity following management so they may make informed management decisions.
Objective 3) Present research to students at Montana State University enrolled in introductory, intermediate, and advanced plant ecology related courses.
Cooperators
- - Producer
Research
The goals of this project are to evaluate integrated weed management approaches to suppress ventenata and improve quality and quantity of forage by increasing desired grasses. To assess our goals we have three objectives, each with subobjectives.
The main objectives are:
Objective 1) Quantify ventenata’s competitive ability with other vegetation under different growth conditions (Normal, Hot, and Hot + Dry). These data will allow me to quantify:
1a) the response of ventenata to herbicide (No spray, Rejuvra) under different growth conditions,
1b) if forage and other vegetation are impacted by ventenata and herbicide
(No spray, Rejuvra) under different growth conditions, and
1c) if ventenata cycles N more rapidly than cheatgrass and forage species under current conditions.
Objective 2) Evaluate effectiveness of integrated management approaches with herbicides (Axiom, Rejuvra, Rejuvra + Plateau, no spray) and fertilizer (macronutrient, micronutrient, no-fertilizer) to control ventenata and improve abundance and quality of desired species. These data will allow me to quantify:
2a) the response of ventenata under different treatment combinations,
2b) if forage and native vegetation are impacted by the treatment combinations, and
2c) if forage quality is impacted by the different treatments.
Methods
Objective 1) was performed on a single site that has a considerable infestation of ventenata. The site has a mix of forage and native grasses (e.g., smooth brome, Kentucky bluegrass, western wheatgrass, and bluebunch wheatgrass) and has not had treatment prior to our own treatments. There was some cheatgrass at the site that was present prior to ventenata invasion. The site is at Amy Cox’s in Gallatin County – see letter of support.
We evaluated ventenata’s and other species’ response under different climate conditions (Normal, Hot, and Hot + Dry) to an herbicide (Rejuvra at 5 oz/acre and no-spray) treatment (Table 1-1). These six treatments, 3 climate x 2 herbicides (Figure 1-1), have been replicated six times totaling 36 plots (applied fall of 2022). We modified current temperatures using open top warming chambers that act as mini greenhouses warming the temperature by ~3.6F (2C), and by adding warming chambers and rainout shelters to partially shield plots (50%) from precipitation to a third of the plots (Figure 1-2). We established the different climates treatments over the summer of 2022 to create the different climate conditions prior to ventenata germinating in the fall. Herbicide was applied on August 10th, 2022, prior to ventenata germination. We assessed the central 1 m2 of each plot, recording cover of each species at the peak of the growing season (July) in 2022-2024, and additionally assessed per plot biomass of functional groups (perennial grasses and forbs) and ventenata in 2024. These treatments were novel due to their accounting for different climate treatments simultaneously with herbicide treatments, allowing us to make informed recommendations based on changing climate.
To answer subobjective 1c we collected soil samples from the control plots at the three sites used in Objective 2. The samples provided information on a myriad of soil components, including Nitrate (lbs/ac), however we were unable to access nutrient cycling.
Objective 2) was addressed at three locations, west (Sanders County (2)) and east (Cascade County (1)) of the Continental Divide in Montana. The sites in Sanders County were near Hot Springs, MT on collaborating producer Evan Melton’s property, and near Trout Creek, MT on collaborating producer John Josepho’s property, and our site in Cascade County was on collaborating producer Kendra Lane’s property. At each site we established a complete split-plot random block design with herbicide as the main treatment (Rejuvra (5 oz/acre), Rejuvra (5 oz/acre) + Plateau (6 oz/acre), Axiom (flufenacet 4 oz/acre and metribuzin 1 oz/acre), and non-sprayed control) (Table 2-1) and fertilizer as a three-way split treatment (macronutrient (NPK; 40 lb/acre), micronutrient (Nutrafix ®; 25 lbs/acre), none) (Table 2-2). Herbicides were applied using a CO2 backpack sprayer at 16 mL /acre at 290 kPa. Thus, within each block of four herbicide treatments there are three split plots for the fertilizer, totaling 12 plots per block, and there are 4 blocks (48 plots) (Figure 2-1). Plots were established August 1-5 of 2022, where fertilizers, Rejuvra and Axiom were applied pre-emergent on this trip. Plateau was applied when the ventenata emerged in the fall on October 19-21, 2022. The herbicide treatment Rejuvra was only approved for use in Montana rangelands in 2020, leaving its impacts on Montana range understudied especially when used on native dominated sites and in combination with fertilizers. Our micronutrient fertilizer, Nutrafix ®, is new to the market and is proposed to provide a novel strategy because the fertilizer mix is designed for the slower growth of perennial grasses rather than the rapid growth of undesired annuals. By combining the new herbicide and micronutrient products, along with more traditional herbicide treatments (Axiom and Plateau) and N fertilizer, we are evaluating new integrated weed management strategies that may prove to be useful for Montana producers and managers.
After the establishment of study sites in August 2022, cover of ventenata was recorded in two 0.75 m2 frames per plot, prior to treatment application to provide baseline information. In the following two years (2023 and 2024) cover of all species was sampled at peak vegetation growth at the end of July, with a sub-set of species sampled and clipped for biomass in 2024, to assess the control of the ventenata and abundance of other vegetation (Objective 2). Biomass was collected by clipping plants at their base and separating into bags by functional group (ventenata, other annual grass, perennial grass, and forbs). They were then dried for 48 hours at 98°F (37°C). Biomass was weighed to the nearest 0.001 g. Due to increased costs associated with nitrate strips, we decided it was more economical to conduct soil sampling. Soil cores were extracted from each treatment within three blocks at each site in May 2023 and sent to Agvise Laboratories for analysis of soil nitrates, phosphorus, and micronutrients. These samples were lost by the postal service and thus the process was repeated in May 2024, this time without loss of samples. This allowed us to extract more samples, answer our questions about soil nitrates, and stay within our proposed budget. Biomass samples of ventenata and dominant grass species were taken to assess forage quality by determining crude protein content (Objective 2c). The samples were analyzed for crude protein content (assessed from N content).
Analysis
Objective 1) Cover and biomass of ventenata, combined perennial grasses, and forbs, as well as species richness and diversity (response variables) were evaluated to determine how each was affected by climate and herbicide treatments (fixed variables). We used generalized linear models with Poisson (richness) and Gaussian (diversity, cover, and biomass) distributions, and analysis of variance to determine statistical differences. A post-hoc Tukey HSD test examined pairwise differences between the treatments. Data were checked for model assumptions of heteroscedasticity, normality, and constant variance, where all models required log transformation.
Objective 2) Cover and biomass of ventenata, combined perennial grasses, species richness, and diversity were evaluated (response variables) to determine how each were affected by herbicide and fertilizer treatment, and year (fixed variables). We used generalized linear models with Poisson (richness) and Gaussian (cover, diversity, biomass) distributions, and analysis of variance to determine statistical differences. In the perennial grass model, due to site level differences, site was used as a random effect. We determined this was not necessary for other models due to little difference among sites. A post-hoc Tukey HSD test was used to examine pairwise differences between the treatments. We analyzed soil samples via linear mixed-effects models of the soil component (Nitrate and Boron) given the fixed effects of herbicide and fertilizer, with the random effect of site. Analysis of variance was used to assess differences and a post-hoc Tukey HSD test examined pairwise differences. Forage quality among ventenata and the dominant species was assessed using a Student’s T-test. Data were evaluated for model assumptions of heteroscedasticity, normality, and constant variance, where all models required log transformation.
Objective 1)
Ventenata cover and biomass
As we would expect prior to treatment effects in 2022, there were no differences in ventenata cover among treatments (p = 0.07; Figure 1-3). In the first season after treatments were imposed (2023) ventenata cover was lower in the two climate treatments relative to the Normal climate (Hot p = 0.02, Hot + Dry p < 0.01; Figure 1-3 b & c). Cover was also lower following treatment with Rejuvra relative to non-sprayed in the Normal and Hot climate treatments (Normal p <0.01, Hot p < 0.01), but not the Hot + Dry treatment (p = 0.20; Figure 1-3 c). In 2024, in the Normal climate treatment, there was less ventenata in the Rejuvra sprayed (p = 0.02), but no difference in the Hot and Hot + Dry treatments when Rejuvra sprayed (p = 0.19, p = 0.43). There was year-to-year variation in ventenata cover regardless of climate or herbicide treatment, as in 2023 cover was 86% lower than in 2022 (p < 0.01), but 2022 and 2024 did not differ (p > 0.44).
Ventenata biomass did not differ given climate treatment (p = 0.97) but was 3% lower in the Rejuvra treatment than non-sprayed (p < 0.01; Figure 1-4).
Perennial grass cover and biomass
There was no effect of year on perennial grass cover (p = 0.66). Cover did not differ within the Normal and Hot climate treatments when comparing herbicide treatments (p > 0.96, all; Figure 1-5 a & b). However, within the Hot + Dry climate treatment in 2022 and 2023, the non-sprayed had greater cover than the Rejuvra treatment (p = 0.03, both), but not in 2024 (p = 0.09; Figure 1-5 c). Biomass did not differ given climate treatment (p = 0.50) or herbicide treatment (p = 0.62).
Forb cover and biomass
Forb cover did not differ following climate (p = 0.51) or herbicide (p = 0.87) treatments, though there is moderate evidence of a difference over time (p = 0.05; Figure 1-7). However, forb biomass did not differ given herbicide treatment (p = 0.32), but forb biomass was greater in the Hot + Dry climate treatment relative to the Hot treatment (p = 0.03), where there was no difference between the Hot + Dry and Control treatments (p = 0.08) or Hot and Control (p = 0.86; Figure 1-8).
Species richness and alpha diversity
Total species richness was 65 species (not counting ventenata), where plots had a mean richness of 8. Richness was not impacted by climate (p = 0.49) or herbicide treatment (p = 0.15) but did vary over the years (p < 0.01) due to natural variation (Figure 1-9). Alpha diversity, via the Inverse Simpson’s index, demonstrated the same pattern, where it was not impacted by climate (p = 0.23) nor herbicide (p = 0.51), but was impacted by year (p = 0.02) due to natural variation (Figure 1-10).
Objective 2)
Ventenata cover and biomass
The cover of ventenata in the non-sprayed control treatment did not change over time (p > 0.10). Ventenata cover decreased from before treatment (2022) to first year post-treatment (2023) for all herbicides (p < 0.01) and within 2023 all herbicides had lower cover than the control (p < 0.01 all; Figure 2-2a&b). However, in the second season (2024), Axiom did not differ from the Control (p = 0.99), while the Rejuvra and Rejuvra + Plateau treatments were lower (p < 0.01; Figure 2-2c). The fertilizer treatments had no effect on ventenata cover (p = 0.19) and did not demonstrate an interaction with year (p = 0.24) or with herbicide (p = 0.40). In the second-year post treatment (2024) ventenata biomass was not impacted by any fertilizer treatment (p = 0.51) nor an interaction between fertilizer and herbicide (p = 0.13).
Biomass did not differ between the Control and Axiom treatments (p = 0.07) but was lower in the Rejuvra (p < 0.01) and Rejuvra + Plateau (p < 0.01) treatments relative to the Control (Figure 2-3).
Perennial grass cover and biomass
Perennial grass cover was not impacted by fertilizer treatment (p = 0.11), herbicide treatment (p = 0.92), nor year post treatment (p = 0.90; Figure 2-4). Similarly, perennial grass biomass did not differ from fertilizer treatment (p = 0.47) nor herbicide treatment (p = 0.96; Figure 2-5).
Forb cover and biomass
Forb percent cover was impacted by herbicide (p = 0.06), as well as the interaction between fertilizer and year (p = 0.02), though there were no pairwise differences in fertilizer and year detected (p > 0.56). Within 2023, when controlling for fertilizer treatment, forb percent cover was highest in the Axiom treatment (mean cover 11%) though it did not differ statistically from the control (mean cover 6%; p = 0.99) or Rejuvra (mean cover 2%; p = 0.36), however there was strong evidence that forb cover was greater than in the Rejuvra + Plateau treatment (mean cover <1%; p < 0.01). All treatments increased in forb cover from 2023-2034 (p = 0.01, all), where increases averaged 38% (Figure 2-6).
There was no evidence of a change in forb biomass given fertilizer treatment (p = 0.65) nor herbicide (p = 0.09; Figure 2-7).
Species richness and alpha diversity
Total species richness across the three sites was 87 species (not counting ventenata), where plots had a mean richness of 5. Richness was not impacted by herbicide treatment (p = 0.73) or fertilizer treatment (p = 0.32), but it was impacted by the interaction between herbicide treatment and year (p = 0.02; Figure 2-8), though no pairwise differences were detected (p > 0.37). Alpha diversity, via the Inverse Simpson’s index, was impacted by herbicide treatment (p = 0.01), but not fertilizer treatment (p = 0.56), year (p = 0.17), nor any interactions (p > 0.13). Alpha diversity was greater in the Axiom treatment relative to the Rejuvra treatment (p = 0.04), but there were no other pairwise differences between herbicides (p > 0.11; Figure 2-9).
Soil analysis
Soil nitrates were not impacted by herbicide treatment (p = 0.09), but were impacted by fertilizer treatment (p < 0.01) in 2024 (2 years post application), where nitrates were higher in the micronutrient fertilizer treatment (3.91 lb/ac) relative to the macronutrient NPK treatment (2.75 lb/ac; p = 0.04), however there was no evidence of greater nitrates in the NPK relative to the no fertilizer treatment (2.75 lb/ac; p = 0.54; Table 2-3). Boron, a primary component of micronutrient treatment, was not impacted by herbicide (p = 0.31), but was by fertilizer (p < 0.01). Boron was greatest in the micronutrient treatment (0.81 ppm), where boron was significantly higher relative to the control (0.21 ppm) and NPK (0.19 ppm) treatments (p < 0.01, both; Table 2-3).
Crude protein
There was no significant difference in crude protein between V. dubia and native perennial grass samples (p = 0.18). Samples were taken in early August when all species were starting to senesce.
Research Outcomes
The goal of this project was to evaluate integrated management strategies to suppress ventenata and increase forage quality and quantity in desired grasses.
In Objective 1 we did this by quantifying ventenata and desired species under simulated climate change conditions (Normal, Hot, Hot + Dry) and following use of a common herbicide (no spray, Rejuvra). We found that the herbicide treatment was effective in suppressing ventenata under all climate treatments, indicating it may be a useful management tool now and in the future. We also found that the climate treatments corresponded to lower ventenata cover, indicating that the conditions we created with the OTCs and rain-out shelters are not conducive to ventenata growth. Perennial grass and forb cover and biomass did not demonstrate clear patterns based on climate and herbicide treatment.
Objective 2 addressed our goal by evaluating the effectiveness of combining herbicides (no spray, Axiom, Rejuvra, Rejuvra + Plateau) and fertilizer (no fertilizer, macronutrient, micronutrient) to manage ventenata and impacts on desired plant species. We found that ventenata was effectively controlled over time by Rejuvra and Rejuvra + Plateau treatments, where Axiom was only effective for one year post treatment. Fertilizer treatments had no effect on ventenata cover. Perennial grass cover and biomass were not impacted by fertilizer treatment nor herbicide. Forb cover was impacted by herbicide one year post treatment, but these effects were no longer detectable two years post treatment, and fertilizer treatment had no effect. Species richness was not impacted by the herbicide or fertilizer treatments. Alpha diversity showed a trend of being lower in the Rejuvra + Plateau treatment relative to the Axiom. Overall, these results demonstrated that Rejuvra and Rejuvra + Plateau were adequate treatments to decrease cover of ventenata without causing detrimental impacts on desired species. Unfortunately, no fertilizer treatment led to increases in desired species.
Ultimately, these projects highlighted the need for research into integrated strategies that consider the impacts of treatments on desired species. While we did not detect the increases in forage cover or crude protein following treatments, this study followed one application over two field seasons. This work adds to a growing body of literature that seeks to estimate the way invasive annual grasses may change following climate change, as well as how these species may be managed in a rangeland context.
Education and Outreach
Participation Summary:
The educational goals of this project are to further educate Montana producers and managers, the public, and students about the non-native grass ventenata and share outcomes of integrated weed management approaches to suppress ventenata and improve quality and quantity of forage. To assess our goals, we have three objectives.
The main objectives are:
Objective 1) Share our results on the ecology and management of ventenata with producers and managers.
1a) Educate individuals on integrated management strategies effective on ventenata so that they may make informed management decisions for their own properties.
1b) Educate individuals on the identification of ventenata and its ecology under different climates.
Objective 2) Share our results about the quality and quantity of forage following integrated management strategies with producers and managers.
2a) Educate individuals on the outcomes of forage quality tests on ventenata and desired species following management so that they make informed management decisions.
2b) Educate individuals on the changes to forage quantity following management so they may make informed management decisions.
Objective 3) Present research to students at Montana State University enrolled in introductory, intermediate, and advanced plant ecology related courses.
Methods
Objectives 1 & 2 were addressed through interactions with cooperating producers and managers along with the public, which included other impacted landowners. Interactions that cooperators have with other landowners and land managers are a critical means to circulate the information gained through this project to the most relevant end-users. Advising professor, Dr. Jane Mangold, is an Extension specialist from Montana State University, and she guided me through these objectives. We disseminated our results through a field day, shared results at established outreach events such as those sponsored by Montana State University Extension or the Montana Weed Control Association, and though digital media such as Dr. Mangold’s Monthly Weed Post. Finally, results of this research will be appropriate for publication in journals such as Invasive Plant Science and Management or Journal of Range Ecology and Management. We will plan for one to two peer reviewed publications. We will also utilize digital media to share our project to a wider audience.
Analysis
We determined the effectiveness of the educational outreach through discussions with landowners post-outreach activity. There was concern among most every landowner and manager in respect to the continued spread of ventenata, and a strong desire to prevent their patches from moving into natural areas or neighboring properties. Rejuvra was a product that was already known to the audience, though many had not used it previously. The micronutrient fertilizer (Nutrafix) was not known to most audience members. In general, the attitudes were positive toward the Rejuvra treatment, as it was highly effective at reducing ventenata cover without impacting perennial grass species. Their attitudes were hesitant toward the micronutrient treatment, as in some instances there was visible damage to native species, and in the non-sprayed and treated with micronutrient plots there was still high ventenata cover. The other herbicides and macronutrient fertilizer received some interest as well, but not to the same degree as the Rejuvra treatment.
The classroom presentations were evaluated through discussion with the classes during and following my presentations. I offered prepared questions at the beginning of the lesson and discussion-oriented questions at the end of the lecture. The discussion engaged students in questions about invasive species, management practices, and ecological implications of management practices. Classes also discussed study design, and how they would conduct a similar study (Would they make any changes? Are there different considerations they would make?). These discussions allow me to gauge if the students understood the presentation but also allowed them the opportunity to think through the concepts they’d learned and combine them with previous concepts taught in those courses. Students tended to be interested in the use of OTCs to manipulate climate and the advantages and disadvantages of that kind of strategy. They wondered if that is the best (or only) strategy to simulate climate change in the field, and if one could construct different types of OTCs for different research questions (bigger, smaller, different type of plastic, etc.). In the field, they were interested in applying the same management techniques in different environments (forest, wetlands, prairie, row-cropping systems etc.) or in areas with different degrees of invasion. There was extensive discussion on how one decides the number of replications necessary for a high-quality experiment and how adding different sites can be beneficial to the research. We were able to relate these projects to their own research projects with respect to design and statistical interpretation. Overall, students came across as interested in the research questions, design, and execution, as well as enthusiastic about conducting their own research into climate change, management, and invasion ecology.
Results
To address Education Objectives 1 & 2, on July 26, 2023, we had a field day with representatives from the Sanders County Weed Board, Montana NRCS, Montana State University Extension, and local landowners, where they visited our research site at Evan Melton’s property. At this field day I presented our research goals, study design, and anticipated results (informational document presented attached). We toured the site and made field observations of treatment effects. We assisted landowners in identifying ventenata and discussed their options for their own property needs. We were able to discuss as a group the needs of Sanders County with respect to ventenata and display our first year’s results to individuals who are invested in the results of our study. Further, both Drs. Rew and Mangold have presented this and other research, along with how to identify annual grasses (Objective 1b) at several extension meetings throughout the state in the last two years. We are scheduled to share details about our project in research Objective 2 on April 4, 2025 in Dr. Mangold’s Monthly Weed Post (http://msuinvasiveplants.org/extension/monthly_weed_post.html). Further details about publications will be shared on our group website (https://www.montana.edu/plantinvasions/) once published.
To address Education Objective 3, I have presented aspects of my research to two Montana State University classes ENSC 410 and LRES 510 (Biodiversity Survey methods). ENSC 410/LRES 510 is a co-convened undergraduate and graduate level course that teaches students strategies used for measuring biodiversity, analysis of biological data, and the importance of studying biodiversity. These projects were used as examples of experimental design strategies within a lecture on imposing treatments on to a landscape. This lecture delved into why I designed the experiments the way I did, how we would sample from our treatment plots, and how one could do a basic statistical analysis on these types of data. This class also requires students to conduct a project where they collect their own biodiversity sampling and write a report. In August of 2022 and 2024 graduate students from the course visited the Amy Cox site (Research Objective 1) to look at the treatments and design. Discussions were held on the objectives and methods of the study, and students were able to examine the study up close. Students conducted independent projects at the same site with an emphasis on the same species of interest (ventenata) in 2022, however their projects focused on the treatment effect of the Nutrafix micronutrient fertilizer from Research Objective 2, that was applied on the same property in a different area from my experiment (but not as part of my project). Students were able to discuss the effects of the product and analyze the richness and diversity following treatment. We were able to compare their results with the product to my results and discuss why we might see differences between our studies (site effects, species present, rates applied, etc.). Then, in August 2024 when graduate students from the class visited the same site, we again discussed experimental design, and they practiced field sampling techniques on the plots (visual % canopy cover). Data from this site were used for homework and reports they wrote on different biodiversity metrics. They were able to describe how the climate treatments impacted plant diversity and ventenata cover, and pontificate on why they thought that was. It provided an opportunity for students to discuss data they collected themselves.