Coupling Remote Sensing With a Process Model for the Simulation of Rangeland Carbon Dynamics

Rangelands provide significant environmental benefits through many ecosystem services, which may include soil organic carbon (SOC) sequestration. However, quantifying SOC stocks and monitoring carbon (C) fluxes in rangelands are challenging due to the considerable spatial and temporal variability tied to rangeland C dynamics as well as limited data availability. We developed the Rangeland Carbon Tracking and Management (RCTM) system to track long-term changes in SOC and ecosystem C fluxes by leveraging remote sensing inputs and environmental variable data sets with algorithms representing terrestrial C-cycle processes. Bayesian calibration was conducted using quality-controlled C flux data sets obtained from 61 Ameriflux and NEON flux tower sites from Western and Midwestern US rangelands to parameterize the model according to dominant vegetation classes (perennial and/or annual grass, grass-shrub mixture, and grass-tree mixture). The resulting RCTM system produced higher model accuracy for estimating annual cumulative gross primary productivity (GPP) (R2 > 0.6, RMSE <390 g C m−2) relative to net ecosystem exchange of CO2 (NEE) (R2 > 0.4, RMSE <180 g C m−2). Model performance in estimating rangeland C fluxes varied by season and vegetation type. The RCTM captured the spatial variability of SOC stocks with R2 = 0.6 when validated against SOC measurements across 13 NEON sites. Model simulations indicated slightly enhanced SOC stocks for the flux tower sites during the past decade, which is mainly driven by an increase in precipitation. Future efforts to refine the RCTM system will benefit from long-term network-based monitoring of vegetation biomass, C fluxes, and SOC stocks

An interlaboratory comparison of mid-infrared spectra acquisition: Instruments and procedures matter

Diffuse reflectance spectroscopy has been extensively employed to deliver timely and cost-effective predictions of a number of soil properties. However, although several soil spectral laboratories have been established worldwide, the distinct characteristics of instruments and operations still hamper further integration and interoperability across mid-infrared (MIR) soil spectral libraries. In this study, we conducted a large-scale ring trial experiment to understand the lab-to-lab variability of multiple MIR instruments. By developing a systematic evaluation of different mathematical treatments with modeling algorithms, including regular preprocessing and spectral standardization, we quantified and evaluated instruments' dissimilarity and how this impacts internal and shared model performance. We found that all instruments delivered good predictions when calibrated internally using the same instruments' characteristics and standard operating procedures by solely relying on regular spectral preprocessing that accounts for light scattering and multiplicative/additive effects, e.g., using standard normal variate (SNV). When performing model transfer from a large public library (the USDA NSSC-KSSL MIR library) to secondary instruments, good performance was also achieved by regular preprocessing (e.g., SNV) if both instruments shared the same manufacturer. However, significant differences between the KSSL MIR library and contrasting ring trial instruments responses were evident and confirmed by a semi-unsupervised spectral clustering. For heavily contrasting setups, spectral standardization was necessary before transferring prediction models. Non-linear model types like Cubist and memory-based learning delivered more precise estimates because they seemed to be less sensitive to spectral variations than global partial least square regression. In summary, the results from this study can assist new laboratories in building spectroscopy capacity utilizing existing MIR spectral libraries and support the recent global efforts to make soil spectroscopy universally accessible with centralized or shared operating procedures

Alternative tracer gases for the ERUCT technique to estimate methane emission from grazing animals

The methane emission of grazing ruminants can be estimated using the Emissions from Ruminants Using a Calibrated Tracer (ERUCT) technique by applying sulphur hexafluoride (SF6) in low-release permeation tubes. The low background concentration of SF6 coupled with its low detection limits and solubility similar to methane made SF6 a good tracer. However, discovery of alternative tracer gases is desirable since SF6 itself is a greenhouse gas. The development of high-release permeation tubes has given new opportunities to use tracer gases with higher detection limits than SF6. An extended literature search for alternative tracer gases was undertaken screening approximately 300 potential gases. The suitability of stable isotope tracers was also screened. A large number of candidate gases were eliminated due to potential health risks, differences in their chemical properties relative to methane, being unsuited to delivery by permeation tubes or requiring high purchase or analytical costs. Laboratory evaluations of leading candidate gases (ethane, propane, butane) were conducted. It is concluded that ethane and stable isotopes of methane have the potential as alternative tracers for the ERUCT technique but optimisation of the permeation tube is required before validation in animal studies

Effects of different fibre sources and fat addition on cholesterol and cholesterol-related lipids in blood serum, bile and body tissues of growing pigs

Knowledge is limited on the efficacy of hindgut-fermentable dietary fibre to reduce blood, bile and body tissue cholesterol levels. In three experiments with growing pigs the effects of different kinds and levels of bacterially fermentable fibre (BFS) on cholesterol metabolism were examined. Various diets calculated to have similar contents of metabolizable energy were supplied for complete fattening periods. In the first experiment, a stepwise increase from 12 to 20% BFS was per-formed by supplementing diets with fermentable fibre from sugar beet pulp (modelling hemicelluloses and pectin). Beet pulp, rye bran (modelling cellulose) and citrus pulp (pectin) were offered either independently or in a mixture in the second experiment. These diets were opposed to rations characterized in carbohydrate type by starch either mostly non-resistant (cassava) or partly resistant (maize) to small intestinal digestion. The third experiment was planned to explore the interactions of BFS from citrus pulp with fat either through additional coconut oil/palm kernel oil blend or full-fat soybeans. In all experiments the increase of the BFS content was associated with a constant (cellulose) or decreasing (hemicelluloses, pectin) dietary proportion of non-digestible fibre. In experiment I an inverse dose-response relationship between BFS content and cholesterol in blood serum and adipose tissue as well as bile acid concentration in bile was noted while muscle cholesterol did not respond. In experiment 2 the ingredients characterized by cellulose and hemicelluloses/pectin reduced cholesterol-related traits relative to the low-BFS-high-starch controls whereas, except in adipose tissue cholesterol content, the pectinous ingredient had the opposite effect. However, the changes in serum cholesterol mainly affected HDL and not LDL cholesterol. Adipose tissue cholesterol also was slightly lower with partly resistant starch compared to non-resistant starch in the diet. Experiment 3 showed that the use of citrus pulp increased serum cholesterol concentrations when levels were low in the corresponding low-BFS diets (low-fat and soy bean diets), but caused no further increase in the coconut-oil/palm kernel oil blend diet. From the present results it seems that fermentable hemicelluloses have a more favourable effect of decreasing metabolic cholesterol and related traits than hardly digestible fibre, fermentable cellulose or, particularly, pectin. Furthermore, some types of fibre expressed a certain potential to reduce cholesterol content of fat pork and pork products by up to 10% (experiment 1) and 25% (experiment 2)

Saponin rich tropical fruits affect fermentation and methanogenesis in faunated and defaunated rumen fluid

A comparison of the effects on rumen fermentation of three saponin rich tropical fruits supplemented to forage-based diets was completed using a rumen simulation technique (Rusitec). The diets contained either no tropical fruit or 100?mg/g of Sapindus saponaria (crude saponins, 120?mg/g), 200?mg/g of Enterolobium cyclocarpum (crude saponins, 19?mg/g) or 200?mg/g of Pithecellobium saman (crude saponins, 17?mg/g). The four diets were evaluated with faunated and defaunated rumen fluid obtained from a single donor cow. Compared to the control diet, P. saman decreased (P<0.05) ammonia concentration of rumen fluid, and E. cyclocarpum and P. saman increased (P<0.05) n-butyrate proportion of total volatile fatty acids. Defaunation enhanced (P<0.05) propionate proportion with corresponding reductions of acetate and n-butyrate. Organic matter degradation of the S. saponaria diet did not differ from that of the control diet but was higher (P<0.05) with P. saman and E. cyclocarpum. Only one of the saponin rich fruits evaluated, S. saponaria, decreased (P<0.05) protozoal count (by 54%) and daily methane release (by 20%) relative to control, but without affecting the methanogen count. Defaunation suppressed methanogenesis by 43% over all diets (P<0.05), and the effect of S. saponaria on methane was more pronounced in defaunated (29%) versus faunated rumen fluid (14%). When related to organic matter apparently fermented, differences relative to the control diet persisted (P<0.05), but methane release per unit of fibre degraded did not differ between the S. saponaria diet and the control diet. This study demonstrated that supplementation with S. saponaria is effective against ruminal methanogenesis, but that this was not exclusively an effect of the associated depression in protozoal count

Ruminal fermentation, methanogenesis and nitrogen utilization of sheep receiving tropical grass hay-concentrate diets offered with Sapindus saponaria fruits and Cratylia argentea foliage

The effects of supplementing a tropical, low-quality grass hay (Brachiaria dictyoneura) with legume foliage (Cratylia argentea) or fruits of the multipurpose tree Sapindus saponaria on ruminal fermentation, methane release and nitrogen (N) utilization were evaluated. Six Swiss White Hill lambs were used in a 6 ? 6 Latin-square design with a 3 ? 2 factorial arrangement of treatments with measurements of energy metabolism being conducted using open-circuit respiratory chambers. Treatments consisted of three basal diets, either grass alone or legume : grass ratios of 1 : 2 or 2 : 1. These basal diets were supplemented (1 : 3) with a control concentrate or with a concentrate containing 250 g/kg dry matter of S. saponaria fruits. The apparent total tract digestibilities of organic matter (OM) and neutral-detergent fibre (NDF) were reduced and the proportionate crude protein (CP) losses through faeces were increased (P 0·1) by the inclusion of S. saponaria in the concentrate, but increased linearly (P 0·05) indicates that supplementation with S. saponaria fruits is a useful means to reduce methane emission from sheep given both tropical grass-based and grass-legume-based diets. Likewise, including legumes in N-limited tropical diets seems to represent an environmentally friendly way to improve animal productivity

Comparing the Soil Management Assessment Framework to the Haney Soil Health Test Across Managed Agroecosystems

Soil health assessments within managed agroecosystems help to further understand conservation practice efficacy when management practices are altered. In this study, soil health was quantified via the Soil Management Assessment Framework (SMAF) and the Haney Soil Health Test (HSHT) within eight fields (a dryland pasture and seven dryland fields under no-till conditions for various time lengths, cropping system diversity differences, and (in)organic fertilizer use) in Northeastern Colorado. The results across cropping systems were variable when comparing the two frameworks, yet the pasture site received the greatest soil health score (SHS) from both frameworks. Management differences were present for soil physical, chemical, and biological indicators in SMAF, yet the HSHT outcomes show high variability between each field, and the SHS did not align with the understanding of management practices. The HSHT SHSs greatly relied on the single indicator Solvita CO2-C burst (r = 0.82). The HSHT mineralizable N overestimated N availability and was not correlated to the SMAF 28-day N mineralization (R2 &lt; 0.01), and via a pathway analysis, only two SMAF biological indicators (&beta;-glucosidase (BG) and microbial biomass carbon (MBC)) along with bulk density (Bd) correlated to the HSHT. The overall soil health scores between the two frameworks were only moderately correlated (r = 0.48), which was ascribed to the lack of HSHT soil physical and chemical indicators. While the HSHT can still be useful for tracking general trends in soil biological health over time, the SMAF remains the more comprehensive and robust tool for assessing soil health in the studied agroecosystems