Spatio-temporal patterns of rangeland forage nutritive value and grazer selection with patch-burning in the US northern Great Plains.

Understanding how management influences forage nutritive value and grazer selection within grazing seasons is an ongoing effort for researchers and land managers globally. We used six, 65 ha pastures managed with patch-burn grazing and stocked with either cow-calf pairs (0.45-0.5 ha • AUM-1) or gestating ewes (0.4-0.48 ha • AUM-1) to explore how patterns in rangeland forage drive grazer selection in semi-arid rangeland over four summer grazing seasons at monthly intervals. We used near-infrared spectroscopy to determine nutritive value parameters from monthly forage clippings. We evaluated livestock performance as the average daily weight gains of each animal. We used mixed-effect models and ordination to compare patch and grazer types across the time-since-fire gradient and found that time-since-fire was significant for all measured variables. Cattle and sheep consistently preferred recently burned patches throughout grazing seasons. These recently burned patches typically contained available forage with higher crude protein and moisture content, lower biomass, and lower acid detergent fiber, acid detergent lignin, and neutral detergent fiber compared to intermediate time since fire patches and patches burned three years ago. Differences between patch-burn grazing with cattle and sheep were observed as additional patch contrasts for available biomass and crude protein, but grazer type and ecological site were not statistically significant factors for the nutritive value ordination. Our study indicates that patch-burn grazing is capable of imposing and maintaining heterogeneous, grazer selection, forage biomass, and nutritive value patterns desirable for heterogeneity focused land management, regardless of grazer type. These findings are especially relevant to the northern Great Plains where introduced grasses are homogenizing the structural environment of remaining rangelands. With prescribed fire currently an uncommon practice throughout the region, these findings provide a baseline of expectations for practitioners and land managers implementing patch-burn grazing and illustrate how grazing livestock can benefit from the patch contrast in forage nutritive value and biomass.

Weather and Fuel as Modulators of Grassland Fire Behavior in the Northern Great Plains.

Fuel and weather interact to affect wildland fire behavior, but little is known about associations between these variables in the northern Great Plains of North America. Few studies consider rate of spread or statistically test the influence of fuel and weather. We measured overall fuel load and moisture ahead of prescribed fires in North Dakota, USA, and used a thermocouple array to measure two-dimensional rate of spread, soil surface temperature, and aboveground flame temperature, to compare with fire weather data. Flame temperatures averaged 225 °C during spring burns and 250 °C during fall burns, and were generally higher with greater fuel loads and lower overall fuelbed moisture. Surface temperatures averaged ≈100 °C, although 50% of observations were ≤60 °C. Fires spread at an average of 2.5 m min-1, increasing with wind speed. As such, prescribed fire in northern Great Plains working rangeland appear to spread slowly and effect low soil surface temperatures, often limited by high fuelbed moisture. Fire behavior measurements respond differently to variability in fuel and weather. Belowground heating is likely minimal. We suggest ecologists ought to consider which fire behavior measurements best relate to fire effects, and managers consider weather and ignition pattern mitigations when fuels constrain desired fire behavior to ensure effective burns.

Fuel Properties of Effective Greenstrips in Simulated Cheatgrass Fires.

Invasive annual grasses alter fire regime in steppe ecosystems, and subsequent trends toward larger, more frequent wildfires impacts iconic biodiversity. A common solution is to disrupt novel fuel beds comprising continuous swaths of invasive annual grasses with greenstrips-linear, human-maintained stands of less-flammable vegetation. But selecting effective native species is challenged by the fact that identifying the optimal combination of plant traits that interrupt wildfire spread is logistically difficult. We employed fire behavior simulation modeling to determine plant traits with high potential to slow fire spread in annual Bromus-dominated fuelbeds. We found species with low leaf:stem (fine:coarse) ratios and high live:dead fuel ratios to be most effective. Our approach helps isolate fuelbed characteristics that slow fire spread, providing a geographically-agnostic framework to scale plant traits to greenstrip effectiveness. This framework helps managers assess potential native species for greenstrips without needing logistically-difficult experimental assessments to determine how a species might affect fire behavior.

Bird and invertebrate communities appear unaffected by fracking traffic along rural roads despite dust emissions.

The development of shale petroleum resources has industrialized rural landscapes. We investigated how traffic from energy development expands and intensifies the road-effect zone through increased dust exposure, and how birds and invertebrates inhabiting the road-effect zone in agricultural areas of the Bakken region might be affected by dust exposure. We used dust collectors, trail cameras, and sweep-netting at increasing distances from unpaved roads to determine dust deposition, relative bird abundance, and invertebrate abundance, respectively. We found that traffic associated with fracking along unpaved roads emitted substantial dust 180 m into adjacent crop fields. But neither bird abundance or behavior, nor invertebrate abundance or community composition, appeared to be affected by dust or traffic. These findings suggest that wildlife in previously intensified agricultural landscapes like crop fields are resilient to intensification from energy development, but the same might not be true for wildlife in previously undisturbed habitat.

Local Perceptions of Hydraulic Fracturing Ahead of Exploratory Drilling in Eastern South Africa.

Applications for exploratory shale gas development via hydraulic fracturing (fracking) have raised concern about energy development impacts in South Africa. Initially, focus was on the arid Karoo, but interest now includes KwaZulu-Natal, a populous, agricultural province with high cultural, ecological, and economic diversity. We conducted focus groups and an online survey to determine how some South Africans perceive fracking. Focus group participants were unanimous in their opposition, primarily citing concerns over water quality and rural way-of-life. The survey confirmed broad consistency with focus group responses. When asked which provinces might be affected by fracking, KwaZulu-Natal ranked behind provinces in the Karoo, suggesting an awareness bias towards Karoo projects. Frequently-identified concerns regarding Agriculture and Natural Resources were Reduced quality of water, Negative impacts to ecosystems and natural biodiversity, Reduced quantity of water, and Pollution hazards. Frequent concerns regarding Social, Cultural, and Local Community issues were Impacts to human health, Visual/aesthetic degradation of tourism areas, Degradation of local infrastructure, and Physical degradation of tourism sites. Most survey respondents were pessimistic about potential benefits of fracking to South Africa's domestic energy supply, and did not agree fracking would reduce negative impacts of coal mining or create jobs. Survey respondents were pessimistic about government's preparedness for fracking and agreed fracking created opportunity for corruption. Many respondents agreed they would consider fracking when voting, and identified needs for more research on fracking in South Africa, which focused heavily on environmental impacts, especially water, in addition to the welfare of local citizens and their communities.

Moderate patchiness optimizes heterogeneity, stability, and beta diversity in mesic grassland.

Heterogeneous disturbance patterns are fundamental to rangeland conservation and management because heterogeneity creates patchy vegetation, broadens niche availability, increases compositional dissimilarity, and enhances temporal stability of aboveground biomass production. Pyrodiversity is a popular concept for how variability in fire as an ecological disturbance can enhance heterogeneity, but mechanistic understanding of factors that drive heterogeneity is lacking. Mesic grasslands are examples of ecosystems in which pyrodiversity is linked strongly to broad ecological processes such as trophic interactions because grazers are attracted to recently burned areas, creating a unique ecological disturbance referred to as the fire-grazing interaction, or pyric herbivory. But several questions about the application of pyric herbivory remain: What proportion of a grazed landscape must burn, or how many patches are required, to create sufficient spatial heterogeneity and reduce temporal variability? How frequently should patches burn? Does season of fire matter? To bring theory into applied practice, we studied a gradient of grazed tallgrass prairie landscapes created by different sizes, seasons, and frequencies of fire, and used analyses sensitive to nonlinear trends. The greatest spatial heterogeneity and lowest temporal variability in aboveground plant biomass, and greatest plant functional group beta diversity, occurred in landscapes with three to four patches (25%-33% of area burned) and three- to four-year fire return intervals. Beta diversity had a positive association with spatial heterogeneity and negative relationship with temporal variability. Rather than prescribing that these results constitute best management practices, we emphasize the flexibility offered by interactions between patch number and fire frequency for matching rangeland productivity and offtake to specific management goals. As we observed no differences across season of fire, we recommend future research focus on fire frequency within a moderate proportion of the landscape burned, and consider a wider seasonal burn window.

Assessment of a livestock GPS collar based on an open-source datalogger informs best practices for logging intensity.

Ecologists have used Global Positioning Systems (GPS) to track animals for 30 years. Issues today include logging frequency and precision in estimating space use and travel distances, as well as battery life and cost. We developed a low-cost (~US$125), open-source GPS datalogger based on Arduino. To test the system, we collected positions at 20-s intervals for several 1-week durations from cattle and sheep on rangeland in North Dakota. We tested two questions of broad interest to ecologists who use GPS collars to track animal movements: (1) How closely do collared animals cluster in their herd? (2) How well do different logging patterns estimate patch occupancy and total daily distance traveled? Tested logging patterns included regular logging (one position every 5 or 10 min), and burst logging (positions recorded at 20-s intervals for 5 or 10 min per hour followed by a sleep period). Collared sheep within the same pasture spent 75% of daytime periods within 51 m of each other (mean = 42 m); collared cattle were within 111 m (mean = 76 m). In our comparison of how well different logging patterns estimate space use versus constant logging, the proportion of positions recorded in 1- and 16-ha patches differed by 2%-3% for burst logging and 1% for regular logging. Although all logging patterns underestimated total daily distance traveled, underestimations were corrected by multiplying estimations by regression coefficients estimated by maximum likelihood. Burst logging can extend battery life by a factor of 7. We conclude that a minimum of two collars programmed with burst logging robustly estimate patch use and spatial distribution of grazing livestock herds. Research questions that require accurately estimating travel of individual animals, however, are probably best addressed with regular logging intervals and will thus have greater battery demands than spatial occupancy questions across all GPS datalogger systems.

Reflections on a boom: Perceptions of energy development impacts in the Bakken oil patch inform environmental science & policy priorities.

Ecosystems worldwide have been subject to new or intensified energy development facilitated by technologies such as horizontal drilling and hydraulic fracturing, activity that has generated concern for air, water, biotic, and social resources. Application of these technologies in the development of the Bakken oil patch has made it one of the most productive petroleum plays in North America, causing unprecedented landscape industrialization of otherwise rural, agricultural counties in western North Dakota. The region is isolated, and development impacts have not been well-studied. To identify concerns of citizens of the Bakken and determine how research and policy might support them, we conducted a two-part study: First, we held focus groups with resource management and community leaders in three major oil-producing counties. Second, we used an outline of the major concerns expressed by focus group members as a survey for landowners and farm/ranch operators. We found little relationship between survey respondents' reported categorization of energy impacts and actual land area impacted, suggesting factors such as attitude towards development, degree of compensation, and level of disturbance are relevant. Landowners agreed with focus groups on the nature of relationships between energy companies and locals and development impacts on infrastructure and communities; those reporting greater impacts tended to agree more strongly. But many specific problems described in focus groups were not widely reported in the survey, suggesting energy-community relationships can be improved through state-level public policy and respect from energy companies for locals and their way of life. Consideration of these concerns in future energy policy-both in the Bakken and worldwide-could reduce social tension, lessen environmental impact, and increase overall social, economic, and environmental efficiency in energy development.

Temporal variability in aboveground plant biomass decreases as spatial variability increases.

Ecological theory predicts that diversity decreases variability in ecosystem function. We predict that, at the landscape scale, spatial variability created by a mosaic of contrasting patches that differ in time since disturbance will decrease temporal variability in aboveground plant biomass. Using data from a multi-year study of seven grazed tallgrass prairie landscapes, each experimentally managed for one to eight patches, we show that increased spatial variability driven by spatially patchy fire and herbivory reduces temporal variability in aboveground plant biomass. This pattern is associated with statistical evidence for the portfolio effect and a positive relationship between temporal variability and functional group synchrony as predicted by metacommunity variability theory. As disturbance from fire and grazing interact to create a shifting mosaic of spatially heterogeneous patches within a landscape, temporal variability in aboveground plant biomass can be dampened. These results suggest that spatially heterogeneous disturbance regimes contribute to a portfolio of ecosystem functions provided by biodiversity, including wildlife habitat, fuel, and forage. We discuss how spatial patterns of disturbance drive variability within and among patches.

Connecting soil organic carbon and root biomass with land-use and vegetation in temperate grassland.

Soils contain much of Earth's terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass--sampled from 0-170 cm and 0-100 cm, respectively--in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested. We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration.