Plant Interspaces Resulting From Contrasting Grazing Management in Northern Mixed-Grass Prairie: Implications for Ecosystem Function

We assessed plant interspaces in July 2007 using continuous line intercepts in twice-replicated pastures of northern mixed-grass prairie with contrasting grazing treatments: 1) long-term (25 yr) heavily grazed, dominated by the bunchgrass blue grama (Bouteloua gracilis), and 2) ungrazed, dominated by the rhizomatous grass western wheatgrass (Pascopyrum smithii). The number of plant interspaces was 26% higher in pastures heavily grazed, but the amount of soil surface occupied by plant interspaces was 27% greater without grazing. Plant interspaces were larger without grazing (14.8 ±  cm, mean ± 1 SE) than heavily grazed (8.9 ±  cm). Plant interspaces represented 87% and 68% of the total soil surface in the ungrazed and heavily grazed communities, respectively. The percentage of soil surface covered by plant interspaces < 20 cm was higher for the heavily grazed (94%) compared to the ungrazed (79%). Litter cover in the plant interspaces was higher without grazing (80 ± 1%) compared to the heavily grazed (57 ± 3%). Grazing-induced structural changes from a rhizomatous- to a bunchgrass-dominated vegetation community were manifest in the size and distribution of plant interspaces. Ecological consequences for erosion from raindrop impacts in larger plant interspaces in the ungrazed community are likely offset by greater litter cover in these communities; conversely, lower litter cover in heavily grazed pastures may increase erosion potential despite occurrence of smaller plant interspaces and less proportion of the soil surface covered by interspaces. Management practices that increase the cover of litter in plant interspaces should reduce the potential of erosion from water and wind in this semiarid rangeland.     

Comparison of the guaranteed analysis with the measured nutrient composition of commercial pet foods

The purpose of this study was to compare the guaranteed analysis of commercial pet foods to their measured nutrient concentrations. Data were collected regarding the guaranteed and measured concentrations of crude protein, crude fat, crude fibre, moisture and ash of pet foods from annual feed inspection reports from South Dakota (2003–2005), Indiana (2004–2005), Rhode Island, New York and New Jersey (2005–2006). The difference for each nutrient was compared among types of food (dry, canned or treat), intended species, target life‐stages, manufacturers and reporting laboratories. Significant differences between the guaranteed and measured nutrient concentrations were found. For all foods, the mean ± one standard deviation of the difference was 1.5 ± 2.0% for crude protein, 1.0 ± 1.7% for crude fat, ‐0.7 ± 1.3% for crude fibre, ‐4.0 ± 3.3% for moisture, and ‐0.5 ± 1.0% for ash. The difference in crude protein was significantly greater for treats than for other food types. The difference in crude fat was significantly less for dry foods than for other food types. The differences in crude fibre and moisture were significantly less for canned foods than for other food types. Only the differences in crude fibre differed significantly among target species, life‐stages, manufacturers or laboratories. More accurate estimations of the nutrient composition and calculated metabolizable energy content of commercial pet foods can be obtained by making adjustments to the guaranteed analysis. This includes adding 1.5% and 1% to the guaranteed minimums for crude protein and crude fat, respectively, and subtracting 0.7%, 4% and 0.5% from the guaranteed maximums for crude fibre, moisture and ash, respectively.     

Clinical and pathological findings associated with congenital hypovitaminosis A in extensively grazed beef cattle

Objective   To determine the cause of exceptionally high mortality (41.4%) in perinatal calves on a beef cattle property 50 km south-west of Julia Creek in north-western Queensland.
Design   Investigations were based on clinical assessment of affected calves and laboratory analysis of pre- and postmortem specimens taken from 12 calves aged from 6 to 36 h of age.
Methods   Associations between gross and histopathological findings and biochemical analyses conducted on serum and tissue samples were examined in relation to clinical observations.
Results   Clinical signs varied, but commonly included mild to severe ataxia, difficulty finding a teat and sucking, blindness (partial or complete, as judged by avoidance of obstacles) and depression with prominent drooping of the head. Gross and histopathological findings included herniation of the cerebellar vermis through the foramen magnum, squamous metaplasia of interlobular ducts in the parotid salivary glands and Wallerian degeneration of the optic nerves. Biochemical analysis of serum and liver samples available from four of the calves revealed low or undetectable levels of both vitamin A and vitamin E.
Conclusion   Although vitamin E is known to have a sparing effect on vitamin A, the role (if any) played by deficiency of this vitamin was uncertain. The combination of clinical signs, postmortem findings, histopathological features and biochemical findings indicate that gestational vitamin A deficiency was highly likely to have been an important contributor to perinatal calf mortalities in this herd.     

Decoupling of microbial glucose uptake and mineralization in soil

The rate of organic matter turnover in soil is a critical component of the terrestrial carbon cycle and is frequently estimated from measurements of respiration. For estimates to be reliable requires that isotopically labelled substrate uptake into the soil microbial biomass and its subsequent mineralization occurs almost simultaneously (i.e. no time delay). Here we investigated this paradigm using glucose added to an agricultural soil. Immediately after collection from the field, various concentrations of ¹⁴C-labeled glucose (1 μM to 10 mM) were added to soil and the depletion from the soil solution measured at 1–60 min after substrate addition. ¹⁴CO₂ production from the mineralization of glucose was simultaneously measured. The microbial uptake of glucose from soil solution was concentration-dependent and kinetic analysis suggests the operation of at least two distinct glucose transport systems of differing affinity. At glucose concentrations reflecting those naturally present in the soil solution (54±10 μM), the half-time (t_1/2) of exogenous glucose was extremely rapid at ca. 30 s. At higher glucose concentrations (100 μM to 10 mM), the t_1/2 values for the high-affinity carrier were altered little, but increasing proportions of glucose were taken up by the low affinity transport system. Glucose mineralization by the soil microbial community showed a significant delay after its uptake into the microbial biomass suggesting a decoupling of glucose uptake and subsequent respiration, possibly by dilution of glucose in labile metabolite pools. By fitting a double first order kinetic equation to the mineralization results we estimated the t_1/2 for the first rapid phase of respiration at natural soil solution glucose concentrations to be 6–8 min, but at least 87% of the added glucose was retained in the microbial biomass prior to mineralization. Our results suggest that in this soil the soil solution glucose pool turns over 100–1000 times each day, an order of magnitude faster than when determined from measurements of mineralization. These results imply that traditional isotopic based measurements of substrate turnover measured using CO₂ may vastly underestimate their rate of cycling in soil.     

A Comparative Study of Immobilized Nitrifying and Co-Immobilized Nitrifying and Denitrifying Bacteria for Ammonia Removal from Sludge Digester Supernatant

Bench scale kinetic experiments were conducted to examine the use of cell immobilization in calcium alginate to remove ammonia in anaerobic sludge digester supernatant. Two systems, immobilized nitrifiers and co-immobilized nitrifiers and denitrifiers, were studied with and without the addition of methanol. Results indicated that partial nitrification (to nitrite) was achieved in both systems. The co-immobilized reactors did not exhibit the extent of nitrite accumulation observed in the solely nitrifying reactors. The nitrifying reactors were unable to buffer the hydrogen ion production, during the nitrification process, to the level the co-immobilized cell reactors achieved. Both of these differences suggested the occurrence of denitrification in the co-immobilized reactors. Scanning electron microscopic images of bacteria immobilized in the alginate spherical beads support the results of the kinetic experiments. Nitrifiers colonized in the 100–200 μm peripheral layer of the beads. Large voids caused by nitrogen gas due to denitrification were found in a number of co-immobilized bead samples.     

Community economies in Monsoon Asia: Keywords and key reflections

A diversity of place‐based community economic practices that enact ethical interdependence has long enabled livelihoods in Monsoon Asia. Managed either democratically or coercively, these culturally inflected practices have survived the rise of a cash economy, albeit in modified form, sometimes being co‐opted to state projects. In the modern development imaginary, these practices have been positioned as ‘traditional’, ‘rural’ and largely superseded. But if we read against the grain of modernisation, a largely hidden geography of community economic practices emerges. This paper introduces the project of documenting keywords of place‐based community economies in Monsoon Asia. It extends Raymond William’s cultural analysis of keywords into a non‐western context and situates this discursive approach within a material semiotic framing. The paper has been collaboratively written with co‐researchers across Southeast Asia and represents an experimental mode of scholarship that aims to advance a post‐development agenda.     

Combining canopy height and tree species map information for large-scale timber volume estimations under strong heterogeneity of auxiliary data and variable sample plot sizes

A timber volume regression model applicable to the state and communal forest area of the federal German state of Rhineland-Palatinate is identified using a combination of airborne laser scanning (ALS)-derived metrics and information from a satellite-based tree species classification map available on the federal state level. As is common in many forest inventory datasets, strong heterogeneity in the ALS data due to different acquisition dates and misclassifications in the tree species classification map had noticeable effects on the regression model’s performance. This article specifically addresses techniques that improve the performance of ordinary least square regression models under such restricting conditions. We introduce a calibration technique to neutralize the effect of misclassifications in the tree species variable that originally caused a residual inflation of 0.05 in adjusted \(R^2\). Incorporating the calibrated tree species information improved the model accuracy by up to 0.07 in adjusted \(R^2\) and suggests the use of such information in forthcoming inventories. We also found that including ALS quality information as categorical variables within the regression model considerably mitigates issues with time lags between the ALS and terrestrial data acquisition and ALS quality variations (increase of 0.09 in adjusted \(R^2\)). The model achieved an adjusted \(R^2\) of 0.48 and a cross-validated root-mean-square error (RMSE\(_{\mathrm{cv}}\)) of 46.7% under incorporation of the tree species and ALS quality information and was thus improved by 0.12 in adjusted \(R^2\) (5% in RMSE\(_{\mathrm{cv}}\)) compared to the simple model only containing ALS height metrics (adjusted \(R^2=0.36\), RMSE\(_{\mathrm{cv}}=51.7\)%).     

Stoichiometric constraints on the microbial processing of carbon with soil depth along a riparian hillslope

Soil organic matter (SOM) content is a key indicator of riparian soil functioning and in the provision of ecosystem services such as water retention, flood alleviation, pollutant attenuation and carbon (C) sequestration for climate change mitigation. Here, we studied the importance of microbial biomass and nutrient availability in regulating SOM turnover rates. C stabilisation in soil is expected to vary both vertically, down the soil profile and laterally across the riparian zone. In this study, we evaluated the influence of five factors on C mineralisation (C_min): (i) substrate quantity, (ii) substrate quality, (iii) nutrient (C, N and P) stoichiometry, (iv) soil microbial activity with proximity to the river (2 to 75 m) and (v) as a function of soil depth (0–3 m). Substrate quality, quantity and nutrient stoichiometry were evaluated using high and low molecular weight ¹⁴C-labelled dissolved organic (DOC) along with different nutrient additions. Differences in soil microbial activity with proximity to the river and soil depth were assessed by comparing initial (immediate) C_min rates and cumulative C mineralised at the end of the incubation period. Overall, microbial biomass C (MBC), organic matter (OM) and soil moisture content (MC) proved to be the major factors controlling rates of C_min at depth. Differences in the immediate and medium-term response (42 days) of C_min suggested that microbial growth increased and carbon use efficiency (CUE) decreased down the soil profile. Inorganic N and/or P availability had little or no effect on C_min suggesting that microbial community growth and activity is predominantly C limited. Similarly, proximity to the watercourse also had relatively little effect on C_min. This work challenges current theories suggesting that areas adjacent to watercourse process C differently from upslope areas. In contrast, our results suggest that substrate quality and microbial biomass are more important in regulating C processing rates rather than proximity to a river.     

Research Practices and Support Needs of Scholars in the Field of Agriculture at Cornell University

ABSTRACT

This article presents the results of one of numerous and coordinated qualitative studies carried out at land-grant universities across the United States, to improve our understanding of agricultural research practices and identify new avenues for library services to meet the changing needs of agricultural faculty and research staff. We interviewed agricultural researchers across several departments at Cornell University about their research practices including research dissemination methods, data sharing, their use of primary and secondary resources, and current challenges in conducting agricultural research. Emerging themes included stakeholder engagement, collaboration and interdisciplinarity, the impact of technology, and research inputs and outputs.