Live Grass Research Articles

Ortho-Vanillin based multifunctional scaffold for selective detection of Al3+ and Zn2+ employing molecular logic with DFT study and cell imaging with live Grass pea

Ligand (E)-N’-(2-hydroxy-3-methoxybenzylidene) acetohydrazide (HL) has been designed and synthesized from o-vanillin and acetohydrazide for selective sensing of Al3+ and Zn2+ ions. In the photoluminescence studies, the receptor HL itself shows very poor fluorescence but on incremental addition of Al3+ and Zn2+ ions in solution of the probe HL individually leads to a sharp increase in emission intensities at wavelengths 468 nm (∼15 fold) and 504 nm (∼8 fold) respectively. Due to excited state intramolecular proton transfer (ESIPT), HL exhibits weak emission in absence of any analytes but in presence of Al3+ and Zn2+, chelation-enhanced fluorescence (CHEF) with coordination of Al3+ and Zn2+ inhibits ESIPT, which results large increase of fluorescence enhancement. The ligand HL shows high selectivity and sensitivity to detect Al3+ and Zn2+ among various metal ions with LOD (Limit of Detection) 0.836 × 10−6 M and 1.01 × 10−6 M respectively. DFT calculation has been performed to study the binding phenomenon of ligand HL with metal ions. A molecular logic gate has been build-up with Al3+ and Zn2+ and EDTA as three chemical input. Simultaneously, cytotoxicity and cell biology for the probe and corresponding Al3+ sensing were observed.

A phenology-driven fire danger index for northern grasslands

Background Directly after snowmelt, northern grasslands typically have highly flammable fuel-beds consisting of 100% grass litter. With green-up, the addition of high-moisture foliage leads to progressively decreasing fire hazard. Aims Our aim was to create a fire-danger index for northern grasslands that incorporated grass phenology. Methods We made use of 25 years of Swedish wildfire data and 56 experimental fires conducted during one full fire-season, merged with established models for moisture content and flame spread rates. Refined data on equilibrium moisture content of grass litter were obtained through laboratory tests. Key results The RING (Rate of spread In Northern Grasslands) model uses cumulative air temperature as a proxy for growing season progression. Three independent functions account for impact of wind, moisture content and the damping effect of live grass, respectively. The latter results in exponentially decaying rate of spread (ROS) with the progressing season. Following the field experiments, green grass proportion as low as 10–20% (live/dead dry-mass) resulted in model-ROS so reduced that the grassland fire season could effectively be considered over. Conclusions The model, calculated from standard meteorological data only, matches the experimental results and separately performed validation tests, as well as wildfire dispatch data. Implications RING has been used in Sweden since 2021 and is likely applicable to other northern regions as well.

Post‐fire recovery of soil microbial functions is promoted by plant growth

AbstractForest fires can alter the biological properties of soils. There is increasing evidence that fires cause a shift in soil microbial communities, which play a central role in forest carbon and nutrient cycling. In this study, we evaluate the effect of soil heating on soil microbial functions. We hypothesised that fire reduces the catabolic functional diversity of soil, and that post‐fire plant growth enhances its recovery. To test this, we experimentally heated a forest soil at 200°C (T200) or 450°C (T450). Heated and unheated soils were then incubated in tubs with or without live grass (Lolium perenne L.). We determined the functional profiles by measuring the substrate‐induced respiration (SIR) using the Microresp™ technique and analysed nutrient availability at the end of the incubation. At both temperatures, soil heating altered the respiration responses to substrate additions and the catabolic functional diversity of soils. Functional diversity was initially reduced in T200 soils but recovered at the end of the incubation. In contrast, T450 soils initially maintained the catabolic functional diversity, but decreased at the end of the incubation. Heating‐induced nutrient availability stimulated the growth of grass, which in turn increased the response to several substrates and increased the functional diversity to values similar to the unheated controls. Our results suggest that fire‐driven alteration of soil microbial communities has consequences at a functional level, and that the recovery of plant communities enhances the recovery of soil microbial functions.Highlights Soil experimental heating altered microbial functions and reduced soil functional diversity. Soil heating also increased nutrient availability, enhancing plant growth. Growth of plants promoted the recovery of soil functional diversity. Post‐fire recovery of functional diversity may be related to the recovery of photosynthetic tissues.

Oscillation and dispersion of live grass carp egg settlement in static water: Laboratory experiments and theoretical models

AbstractFull understanding of the settling process of drifting fish eggs in static water is crucial for improving predictions of fish egg drift in rivers, which can inform reservoir operations by incorporating the ecological requirements of fish. However, current understanding of the settling process remains limited. Observations and analysis of live grass carp egg settlement in static water, with a video capture technology and wavelet analysis, have improved understanding. Results reveal that microscale oscillation and dispersion occur during the settling process. The oscillating velocities of eggs had periods of 0.113 s in longitudinal and 0.135 s in vertical, with oscillating angles around 1.13°. The maximum position differences among eggs after stably settling for 14 s were 25.0 mm in vertical and 4.2 mm in longitudinal. Mechanical models were then established and employed to elucidate two settling phenomena. Simulated results revealed that microscale oscillation was related to biological attributes (the egg specific gravity and diameters of the egg and embryo), special inner structure of the live egg and random hydraulic disturbance of the surroundings. Dispersion was mainly caused by the difference between eggs (diameter and specific gravity). This work furthers understanding and forecasts of fish egg drift in rivers, from which river engineers and managers can better estimate the locations of fish spawning sites, calculate ecological water requirement, and designate ecological conservation areas.

COMPOSICIÓN BOTÁNICA Y EVALUACIÓN NUTRICIONAL IN VITRO DE PASTO KIKUYO COMPARADO CON GRAMÍNEAS DE CLIMA TEMPL

<p><strong>Background: </strong>Intensive continuous grazing of temperate grass and legume pastures has been a feeding strategy adopted in small-scale dairy systems (SSDS) in the highlands of central Mexico that reduces costs and increases profitability of farms. However, temperate grasses have low persistency due to agroclimatic and management conditions, so that pastures are invaded by kikuyu grass (<em>Cenchrus clandestinus</em>), a sub-tropical grass that may be a valuable forage resource in these systems. There are not many studies in Mexico on kikuyu grass pastures and on the relationship between botanical composition, nutritional value and ruminal fermentation parameters, important aspects for their inclusion in feeding strategies for dairy cattle. <strong>Objective: </strong> The objective was to determine the botanical composition and to assess the <em>in vitro </em>digestibility of dry matter (DM), organic matter (OM), and neutral detergent fibre (NDF), and to characterize the kinetics of <em>in vitro </em>ruminal fermentation of a pasture based on with kikuyu grass (KY) in comparison to pastures based on festulolium cv. Spring Green (FL), tall fescue cv. TF-33 (TF), and perennial ryegrass cv. Pay Day (RG), all associated with white clover. <strong>Methodology: </strong> There were four sampling periods every 14 days. On the last day of each period, five random samples in each pasture were cut to ground level to determine botanical composition by manual separation, and 200g samples from each pasture taken by simulated grazing to determine digestibilities and the <em>in vitro </em>fermentation dynamics. Statistical analyses were following a split-plot model. <strong>Results: </strong>There was a higher proportion of grasses in KY and a better <em>in vitro </em>nutritional value for RG, related to a higher content of structural carbohydrates in KY, being a subptropical grass compared to temperate pastures with lower content of cell walls. <strong>Results: </strong>There was a higher proportion (P<0.05) of live grass in KY. There were no differences (P>0.05) among pastures for <em>in vitro </em>nutritional value. There were differences (P<0.05) among pastures and periods for the insoluble fraction fermentation rate (C<sub>B</sub>) and for the interaction between pastures and periods for gas production in 4.0 h of the soluble fraction (A) and the soluble carbohydrate fermentation rate (C<sub>A</sub>), but no differences between pastures, periods or the interaction (P>0.05) for other parameters of ruminal fermentation (lag time and total gas production). <strong>Implications: </strong> Pastures of kikuyu grass associated with white clover have a similar <em>in vitro </em>nutritional value as pastures of temperate grasses representing a valuable forage resource for SSDS. <strong>Conclusion: </strong>In spite of differences in some <em>in vitro </em>ruminal fermentation parameters, the <em>in vitro </em>nutritional value of kikuyu grass pastures associated with white clover is similar to pastures based on temperate grasses with white clover.</p>

Impacts of Land Surface Conditions and Land Use on Dust Events in the Inner Mongolian Grasslands, China

Aeolian processes in temperate grasslands (TGs) are unique because the plant growth–decay cycle, soil water, and land-use interactions affect the seasonal and inter-annual changes in dust events. Land-use types in Inner Mongolian TGs are unique (settled grazing and grass mowing) compared with those in Mongolian TGs. Since 2003, land use has been controlled by grassland protection legislation, which is intended to prevent desertification and dust storms. In this study, we used process-based ecosystem (DAYCENT) and statistical modeling, along with dust event observations from March to June of 1981–2015, to (1) identify critical land surface factors controlling dust emissions (vegetation components, live grass, standing dead grass, litter, and soil moisture) at typical and desert steppe sites in Inner Mongolia and (2) estimate the impact of controlled land-use legislation on dust events. The DAYCENT model realistically simulated the dynamics of the observed vegetation components and soil moisture in 2005–2015. At both sites, similar significant correlations were obtained between spring dust events and wind speed or a combination of all surface factors that retained anomalies (memory) from the preceding year. Among the surface factors, vegetation was a critical factor that suppressed dust in Inner Mongolian TGs, similar to that in Mongolian TGs. In the desert steppe, standing dead grass had the strongest memory and was significantly correlated with dust events, whereas no significant correlations were observed in the typical steppe. This suggests that, in a typical steppe region, heavy grazing and mowing result in few dead grasses, thereby inhibiting the prevention of dust events. Moreover, the simulations of dust events under controlled (light grazing) and uncontrolled (heavy grazing) land-use conditions demonstrated that the grassland protection legislation reduced the occurrence of dust events in typical and desert steppe sites by 25 and 40%, respectively, since 2003.

Impacts of invasive annual grasses and their litter vary by native functional strategy

Invasive species may act as a functional filter on native communities by differentially affecting species with different trait values. Across environments, invasive plants typically display traits associated with high resource acquisition and fast growth. Conversely, native plants, especially those in water-limited environments, tend to adopt one of two functional strategies: fast growth during high resource availability to avoid stress (resource-acquisitive), or slow growth during resource-poor conditions to tolerate stress (resource-conservative). While invasive competition can be a strong filter on these groups, many invaders also alter the structure of native communities through their accumulation of litter. How fast-growing invaders with litter shift native functional communities remains unknown. To elucidate these functional shifts, I manipulated invasive annual grasses and their litter in an annual grassland and followed the demographic rates of six native annual forb species that varied in their functional strategy. Live grass competition alone decreased per capita growth rates of resource-acquisitive natives and had no effect on resource-conservative natives. The presence of litter, however, decreased growth rates in both functional types of natives, with stronger declines in resource-acquisitive species through differential effects on seed set and germination. Invaders in this system thus create an unfavorable environment for natives through litter, limiting the capacity of both resource-acquisitive and resource-conservative native forbs to maintain high population growth. These findings suggest that grass invasions have the potential to dramatically shift the functional composition of native communities through the time-lagged effects of their litter.

Instantaneous Pre-Fire Biomass and Fuel Load Measurements from Multi-Spectral UAS Mapping in Southern African Savannas

Landscape fires are substantial sources of (greenhouse) gases and aerosols. Fires in savanna landscapes represent more than half of global fire carbon emissions. Quantifying emissions from fires relies on accurate burned area, fuel load and burning efficiency data. Of these, fuel load remains the source of the largest uncertainty. In this study, we used high spatial resolution images from an Unmanned Aircraft System (UAS) mounted multispectral camera, in combination with meteorological data from the ERA-5 land dataset, to model instantaneous pre-fire above-ground biomass. We constrained our model with ground measurements taken in two locations in savanna-dominated regions in Southern Africa, one low-rainfall region (660 mm year−1) in the North-West District (Ngamiland), Botswana, and one high-rainfall region (940 mm year−1) in Niassa Province (northern Mozambique). We found that for fine surface fuel classes (live grass and dead plant litter), the model was able to reproduce measured Above-Ground Biomass (AGB) (R2 of 0.91 and 0.77 for live grass and total fine fuel, respectively) across both low and high rainfall areas. The model was less successful in representing other classes, e.g., woody debris, but in the regions considered, these are less relevant to biomass burning and make smaller contributions to total AGB.

Increasing grazer density leads to linear decreases in Spartina alterniflora biomass and exponential increases in grazing pressure across a barrier island

Researchers now recognize that top-down as well as bottom-up forces regulate salt marsh primary production. However, how top-down forces vary with grazer density is still poorly resolved. To begin to address this void, we (1) surveyed grazing intensity in short-form Spartina alterniflora across Sapelo Island, Georgia (USA), and (2) removed varying densities of grazers from 13 sites over 2 yr. Our survey revealed a non-linear relationship between snail abundance and grazing intensity, with grazing scars per stem increasing exponentially with snail density. Further, there appeared to be a threshold at ~80 snails m-2, below which increasing snail density did not significantly increase grazing scars—potentially because snails target dead grass rather than live grass when competition with other snails is low. Increasing snail densities also exponentially reduced stem density within a plot, but only over 80 snails m-2. Our removal experiment showed that snails linearly decreased S. alterniflora biomass across a naturally representative range of snails (0-586 snails m-2) and that top-down control of short-form S. alterniflora was important at multiple sites across an island, with snail removal on average increasing primary production by 164%. Our results reveal that top-down control of short-form S. alterniflora is a common process across this intensively studied island, and that grazing scars increase non-linearly with snail density, while consumer effects on biomass increase linearly. Future models based on marsh plant growth (e.g. geomorphic evolution, primary production) should incorporate both the importance and functional form of grazer control to create more accurate carbon budgets and to better understand marsh network dynamics.

Identifying turbulence features hindering swimming capabilities of grass carp larvae (Ctenopharyngodon idella) through submerged vegetation

Aquatic vegetation can provide habitat and refuge for a variety of species in streams. However, the flow features generated by submerged patches of vegetation can also pose a challenge for fish larvae. We conducted a series of experiments with live grass carp larvae (starting ∼50 h post hatch) in a laboratory racetrack flume, using a submerged array of rigid cylinders to mimic vegetation. We used particle image velocimetry to characterize the flow field, and particle tracking velocimetry to obtain position and displacement of the fish. Four speeds and two submergence ratios were investigated. In contrast with previous studies with grass carp eggs, our data showed an active response from larvae to determine their position. Our study shows that: (1) mean velocity by itself is not a reliable predictor, as some larvae will seemingly prefer to be in areas of higher speeds with lower shear and turbulence, (2) turbulence characteristics can be used to identify areas avoided by larvae, (3) turbulence length scales are relevant to determine spatial distribution of larvae and their swimming capabilities within and above vegetated patches and similar roughness elements in streams. These findings can inform the design of monitoring and control strategies in rivers based on turbulence and turbulence scales generated by natural and man-made instream structures.

Semi‐arid savanna herbaceous production and diversity responses to interactive effects of drought, nitrogen deposition, and fire

AbstractQuestionSavannas are globally widespread and furnish a variety of ecological services through their structural heterogeneity. Unfortunately, those essential ecosystem services are threatened by climate changes including expected increases in duration of drought and nitrogen deposition. The objective of this study was to determine how overall herbaceous production, functional group production and diversity respond in the short‐term to interactions between forecasted environmental conditions and prescribed fires.LocationWestern Edwards Plateau, Texas (latitude 31°N, longitude 100°W).MethodsWe randomly assigned full‐factorial treatment combinations of rainout shelters, simulated nitrogen deposition and prescribed fires to field plots in an herbaceous‐dominated area of a semi‐arid savanna. Aboveground net primary productivity (assessed via destructive harvest) and diversity (using Shannon’s index) were assessed as indicators of ecosystem functioning.ResultsTotal aboveground net primary production was reduced by fire in the short‐term (4 months), and reduced by drought at 8 months, but drought reductions were later overridden by lagged responses to large precipitation events (12 months). Forb production increased in response to nitrogen addition (8 months) and drought (12 months), but decreased as a result of fire (12 months). Live grass production was consistently reduced by drought. Plant species diversity was positively responsive to nitrogen addition, particularly in the absence of drought.ConclusionsOur findings suggest that the concentrated precipitation events that are forecasted to follow extended droughts may aid rapid recovery of drought‐induced production decreases. In addition, the small‐scale diversity of this semi‐arid savanna may be driven more by resource availability than light‐competition in the short‐term. Managers and ecologists can use these results to help disentangle the ecosystem functioning that may be observed in the presence of future droughts, nitrogen deposition and prescribed fire. Understanding these processes will be key to protecting the integrity of savannas.

Influence of turbulence and in-stream structures on the transport and survival of grass carp eggs and larvae at various developmental stages

Understanding the response of grass carp to flow and turbulence regimes during early life stages is fundamental to monitoring and controlling their spread. A comprehensive set of hydrodynamic experiments was conducted with live grass carp eggs and larvae, to better understand their drifting and swimming patterns with 3 different in-stream obstructions: (1) a gravel bump, (2) a single cylinder, and (3) submerged vegetation. The hydrodynamic behavior of eggs and larvae with each obstruction was continuously monitored for about 85 consecutive hours. Transient spatial distributions of the locations of eggs and larvae throughout the water column were generated for each flow scenario. Results show that the active swimming capabilities of larvae allow them to seek areas of low turbulence and low shear stresses, and that eggs are susceptible to damage by high levels of turbulence, which was further corroborated with tests in an oscillating grid-stirred turbulence tank. Our study seeks to better inform field collection of grass carp during early life stages, and to guide the design of alternative approaches to control the dispersal of this invasive species in North America.

Maladaptive nest-site selection by a sagebrush dependent species in a grazing-modified landscape

Animals are expected to select habitats that maximize their fitness over evolutionary time scales. Yet in human-modified landscapes, habitat selection might not always lead to increased fitness because animals undervalue high-quality resources that appear less attractive than those of lower quality. In the American West, agriculture has modified landscapes, yet little is known about whether agricultural changes alter the reliability of the cues animals use to identify habitat quality; ultimately forming maladaptive breeding strategies where behavioral cues are mismatched with survival outcomes.Using the greater sage-grouse, a species highly dependent upon sagebrush landscapes, we (1) evaluated how females select nesting habitats based on sagebrush type, along with livestock grazing related linear and point features, and other biotic, abiotic characteristics, given hypothesized influences on hiding cover, microclimate and predator travel routes and perches, (2) compared habitat selection information with results for nest survival estimates to evaluate if selection appears to be adaptive or not, and (3) used our results to evaluate the most appropriate strategies for this species in a grazing-modified landscape. Nest-site selection for sagebrush type appears to be maladaptive: in the most-preferred sagebrush type, nest survival rate was one-fourth the rate realized by females nesting in the sagebrush type avoided. Nest survival was four times higher for nests placed away from (>100 m), rather than next to (1 m), the nearest fence, and survival was lower within sites with higher cow pie density (a proxy for previous grazing intensity). Live and dead grasses influenced selection and survival in opposing ways such that dead grass was selected for but resulted in reduced survival while live grass was avoided but resulted in increased survival. Results collectively provide the first empirical evidence that a specific type of sagebrush acts as an ecological trap while another sagebrush type is undervalued. These results also suggest that adding more fences to control livestock grazing systems will likely reduce sage-grouse nest survival.

Grazing Systems Do Not Affect Bird Habitat on a Sandhills Landscape

Grassland birds are declining faster than any other guild of birds in North America, in part because of degradation of their breeding habitat. Rangeland managers recommend increasing heterogeneity to improve biodiversity; however, on privately owned rangelands, beef production likely decreases heterogeneity on the landscape. One suggestion has been to use multiple grazing systems across a landscape to increase heterogeneity and provide benefits for avian biodiversity, but there is little research to support this recommendation. Thus, our goal was to examine heterogeneity and songbird abundance in relation to grazing systems used by private producers in a large, intact rangeland region. We measured vegetation structure and conducted avian surveys in the Nebraska Sandhills on 11 management units with five different grazing systems, including season-long continuous, deferred rotation, management intensive, dormant season only, and a fixed rotation. On each management unit we assessed the relationship between vegetation structure or songbird abundance and potential management effects, such as grazing system, stocking rate, and management intensity. Season of use and stocking rate were the most common sources of variation in vegetation structure and songbird abundance. Grazing system did not explain variation in vegetation structure or bird abundance, except for heterogeneity in live grass cover, litter cover, shrub cover, and abundance of field sparrows. Vegetation structure varied across the landscape we sampled, but the range of heterogeneity was narrow. Thus, managers should not assume that using a variety of grazing systems across a landscape will inevitably result in heterogeneity of vegetation structure. Rather, managers should focus on creating contrasting vegetation structure in large areas to increase large-scale heterogeneity. This may be achieved through the application of more extreme management practices (e.g., long-term heavy grazing and long-term rest or patch-burn grazing) so that a wider variety of vegetation composition and structure is available to support biodiversity.

Mapping fractional landscape soils and vegetation components from Hyperion satellite imagery using an unsupervised machine-learning workflow

ABSTRACTAn unsupervised machine-learning workflow is proposed for estimating fractional landscape soils and vegetation components from remotely sensed hyperspectral imagery. The workflow is applied to EO-1 Hyperion satellite imagery collected near Ibirací, Minas Gerais, Brazil. The proposed workflow includes subset feature selection, learning, and estimation algorithms. Network training with landscape feature class realizations provide a hypersurface from which to estimate mixtures of soil (e.g. 0.5 exceedance for pixels: 75% clay-rich Nitisols, 15% iron-rich Latosols, and 1% quartz-rich Arenosols) and vegetation (e.g. 0.5 exceedance for pixels: 4% Aspen-like trees, 7% Blackberry-like trees, 0% live grass, and 2% dead grass). The process correctly maps forests and iron-rich Latosols as being coincident with existing drainages, and correctly classifies the clay-rich Nitisols and grasses on the intervening hills. These classifications are independently corroborated visually (Google Earth) and quantitatively (random soil samples and crossplots of field spectra). Some mapping challenges are the underestimation of forest fractions and overestimation of soil fractions where steep valley shadows exist, and the under representation of classified grass in some dry areas of the Hyperion image. These preliminary results provide impetus for future hyperspectral studies involving airborne and satellite sensors with higher signal-to-noise and smaller footprints.

Correction: Dynamic Changes of Soil Surface Organic Carbon under Different Mulching Practices in Citrus Orchards on Sloping Land.

[This corrects the article DOI: 10.1371/journal.pone.0168384.].

Dynamic Changes of Soil Surface Organic Carbon under Different Mulching Practices in Citrus Orchards on Sloping Land.

Mulching management has been used in many places all over the world to improve agricultural sustainability. However, the cycling of carbon in the soil under applications of mulch on sloping arable land is not yet fully understood. A four-year field experiment was carried out in Xiaofuling watershed of Danjiangkou reservoir in China. The object was to evaluate the effects of the application of straw mulch (ST) and grass mulch (GT) on dynamic changes in soil organic carbon and its fractions. Results showed that mulch applied on the soil surface increased the contents of SOC and its active fractions in the soil. Compared to the control without cover (CK), ST and GT treatments increased the contents of SOC, LOC, DOC, POC and EOC by 14.73%, 16.5%, 22.5%, 41.5% and 21%, respectively, in the 0–40 cm soil layer, and by 17%, 14%, 19%, and 30%, respectively, in the 0–100 cm soil layer. The contents of organic carbon and its active fractions decreased with increasing soil depth in all of the treatments. SOC was accumulated in the period of December to the following March. The contents of soil DOC and LOC were high in January to March, while the contents of soil POC and EOC were high in June to September. The relative contents of soil organic carbon fractions were POC > EOC > LOC > DOC over the four years. Straw mulching had no significant effect on the changes in soil organic carbon active fractions during the different periods. Based on this long-term field experiment in Danjiangkou reservoir, we found that straw mulching had a significant effect on soil, increasing SOC content and stock in slopping arable land, and that live grass mulching was more effective than rice straw mulching. We discuss possible optimal periods for the implementation of mulching practices on sloping land.

All My Sons

All My Sons

Coyote (Canis latrans) mammalian prey diet shifts in response to seasonal vegetation change

Drylands typically have strong seasonal variation in rainfall and primary productivity. This study examines the effects of seasonal change in grass-derived resource availability on the base of the food chain of a mammalian predator. Seasonal changes in live grass cover were measured in two vegetation types at the Sevilleta National Wildlife Refuge in central New Mexico, USA. Non-invasive genetic sampling of scat was used to identify individuals in the local coyote (Canis latrans) population. Stable carbon and nitrogen isotope analysis of hair removed from scats of 45 different coyotes was used to assess seasonal variation in the diet of mammalian coyote prey that came from C4 grasses. Live grass cover increased from the spring to the summer and fall; contribution of C4 grasses to the diet of mammalian coyote prey increased from the summer to the fall and was higher in grassland areas. There were significant differences in the seasonal patterns in the prey diet between grassland and shrubland areas.

Acoustical characterization of grass-covered ground

An investigation of acoustical properties of soil covered with live grass is presented. Measurements of normal surface impedance of such samples have been performed over a 200–2000 Hz frequency band using a vertical impedance tube. A phenomenological model is used to predict acoustic properties of the samples. In this work, the samples are considered as a three-component system: soil, grass roots, and foliage. Acoustic impedance of this composite material has components resulting from the different constituent elements. In order to differentiate the acoustic absorption contribution of each element, grass that was controlled for both water content and grass blade height was grown. The acoustic contribution of the soil was determined by performing measurements on unseeded ground with an equivalent watering protocol. Contributions of the roots and foliage were determined by making impedance measurements before and after shearing the mature foliage near the soil surface. The effect of water content in the soil was estimated by making measurements of the samples before and after oven desiccation. We show the effects of roots and foliage on acoustic absorption of grass-covered ground and the acoustic parameters of these complex media estimated using an equivalent fluid model.