Implications of landscape configuration on understory forage productivity: a remote sensing assessment of native forests openings

Agroforestry Systems - Sound management of native forests used for cattle grazing requires understanding the dynamics of forage productivity in the openings. Despite their importance, forage...     

Understanding patterns of tree adoption on farms in semi-arid and sub-humid Ethiopia

Trees on farms are a widespread feature of landscapes across a large part of Ethiopia with an important role in enhancing the resilience of smallholder livelihoods through the provision of ecosystem services. Despite their importance, little is known about what trees are planted or retained from natural regeneration by different types of farmers that results in the pattern of tree cover found in the region. We address this knowledge gap through analysis of household survey data from semi-arid and sub humid areas of Oromia regional state. A set of composite variables that represent distinctive patterns of tree cover on farms were derived from principal component analysis and Pearson correlation analysis. This revealed two major tree adoption strategies: farmer managed natural regeneration (FMNR) of trees to meet subsistence needs as well as contributing to other ecosystem services; and, high value agroforestry (HVAF) involving planted trees used largely to produce fruits, timber and fodder. Regression analysis further identified fine-scale variation in ecological and socio-economic factors that affect which of these two broad strategies are adopted by farmers. Favorable climatic conditions coupled with institutional arrangements to control free grazing were pre-conditions for HVAF, whereas poor biophysical potential and sloping land provided a positive incentive for farmers to adopt FMNR. Farmers with preferences for tree species with multiple utilities and locational flexibility favored FMNR while adoption of HVAF was more asset-driven. Our findings reveal that farmers integrate many native and exotic tree species on their farms to meet their variable farm conditions, needs and asset profiles in stark contrast to most tree promotion efforts that focus on a few, usually exotic, tree species. We recommend that future agroforestry promotion should embrace a diversity of tree species appropriate to matching the fine scale variation in ecological conditions and farmer circumstances encountered in the field.     

Water use by whitebark pine and subalpine fir: potential consequences of fire exclusion in the northern Rocky Mountains

In subalpine forests of the northern Rocky Mountains, fire exclusion has contributed to large-scale shifts from early-successional whitebark pine (Pinus albicaulis Engelm.) to late-successional subalpine fir (Abies lasiocarpa (Hook.) Nutt.), a species assumed to be more shade tolerant than whitebark pine and with leaf to sapwood area ratios (A(L):A(S)) over twice as high. Potential consequences of high A(L):A(S) for subalpine fir include reduced light availability and, if hydraulic sufficiency is maintained, increased whole-tree water use. We measured instantaneous gas exchange, carbon isotope ratios and sap flow of whitebark pine and subalpine fir trees of different sizes in the Sapphire Mountains of western Montana to determine: (1) whether species-specific differences in gas exchange are related to their assumed relative shade tolerance and (2) how differences in A(L):A(S) affect leaf- and whole-tree water use. Whitebark pine exhibited higher photosynthetic rates (A = 10.9 micromol x m(-2) x s(-1) +/- 1.1 SE), transpiration rates (E = 3.8 mmol x m(-2) x s(-1) +/- 0.7 SE), stomatal conductance (g(s) = 166.4 mmol x m(-2) x s(-1) +/- 5.3 SE) and carbon isotope ratios (delta13C = -25.5 per thousand +/- 0.2 SE) than subalpine fir (A = 5.7 micromol x m(-2) x s(-1) +/- 0.9 SE; E = 1.4 mmol x m(-2) x s(-1) +/- 0.3 SE; g(s) = 63.4 mmol x m(-2) x s(-1) +/- 1.2 SE, delta13C = -26.2 per thousand +/- 0.2 SE; P < 0.01 in all cases). Because subalpine fir had lower leaf-area-based sap flow than whitebark pine (QL = 0.33 kgx m(-2) x day(-1) +/- 0.03 SE and 0.76 kg x m(-2) x day(-1) +/- 0.06 SE, respectively; P < 0.001), the higher A(L):A(S) in subalpine fir did not result in direct proportional increases in whole-tree water use, although large subalpine firs used more water than large whitebark pines. The linear relationships between tree size and daily water use (r2 = 0.94 and 0.97 for whitebark pine and subalpine fir, respectively) developed at the Sapphire Mountains site were applied to trees of known size classes measured in 12 natural subalpine stands in the Bob Marshall Wilderness Complex (western Montana) ranging from 67 to 458 years old. Results indicated that the potential for subalpine forests to lose water by transpiration increases as succession proceeds and subalpine fir recruits into whitebark pine stands.     

Rapid,non-destructive carbon analysis of forest soils using neutron-induced gamma-ray spectroscopy

Forest soils are pivotal to understanding global carbon (C) cycling and evaluating policies for mitigating global change. However, they are very difficult to monitor because of the heterogeneity of soil characteristics, the difficulty of representative sampling, and the slow time scale of response to environmental change. Here we demonstrate that use of gamma-ray spectroscopy facilitates in situ non-destructive analysis of C and other elements in forest soils. In this approach the element-specific gamma-rays are induced by fast and thermal neutrons interacting with the nuclei of the elements present in the soil. Background gamma-rays emanating from naturally occurring radionuclides in the forest are recorded as well. We applied this approach in a mature northern hardwood forest on glacial till soils at the Bartlett Experimental Forest in New Hampshire, USA. The inelastic neutron scattering (INS) system yielded strong signals in gamma-ray counts/h, from C and other elements present in the soil matrix that included silicon, oxygen, hydrogen, iron, aluminum, manganese and potassium. The INS sensitivity for carbon was 20.656 counts h⁻¹ kg⁻¹ C m⁻² based on current net C gamma-ray counts and the data for the O horizon and mineral soil to a depth of 30 cm obtained from a nearby quantitative soil pit (7.35 kg C m⁻²). We estimate the minimum detectable change to be ∼0.34 kg C m⁻², which is ∼5% of the current soil C content, and the minimum detectable limit to be ∼0.23 kg C m⁻². Eight % reproducibility from 11 measurements was limited, in part, by the large variability in the system counting geometry due to the uneven forest microtopography. The INS approach has the potential to revolutionize belowground monitoring of C and other elements, because the possibility of detecting a 5% change in forest soils has not been possible with destructive sampling methods.     

Animal health: foundation of a safe, secure, and abundant food supply

During the past century, reductions in animal diseases have resulted in a safer, more uniform, and more economical food supply. In the United States, the passage of the 1906 Federal Meat Inspection Act mandated better sanitary conditions for slaughter and processing, as well as inspection of live animals and their processed products. Following World War II, Congress passed the Poultry Products Inspection Act. Both acts are regulated by the Food Safety and Inspection Service (FSIS) of the US Department of Agriculture (USDA). The USDA's Animal and Plant Health Inspection Service (APHIS) is responsible for regulations governing the health of live animals prior to slaughter. This article is a brief overview of the ways in which the current predominance of zoonotics among emerging diseases underscores the importance of veterinary health professionals and the need for continued coordination between animal-health and public-health officials. Examples of intersections between animal- and public-health concerns include bovine spongiform encephalopathy (BSE) and Johne's disease, as well as extending beyond food safety to diseases such as avian influenza (AI). In the United States, we have in place an extensive public and private infrastructure to address animal-health issues, including the necessary expertise and resources to address animal-health emergencies. However, many challenges remain, including a critical shortage of food-animal veterinarians. These challenges can be met by recruiting and training a cadre of additional food-supply veterinarians, pursuing new technologies, collaborating with public-health officials to create solutions, and sending a clear and consistent message to the public about important animal-health issues.     

Guest Editor’s Introduction to the Special Issue on “Animal Movement Modeling”

In this introduction, we provide a brief overview to statistical models for animal trajectories and then summarize the set of invited articles that comprise the issue.     

Humic products in agriculture: potential benefits and research challenges—a review

Journal of Soils and Sediments - Humic products have been used in cropland agriculture for several decades, but lack of widespread credibility has restricted their use to small proportions of...     

Economic valuation of acidic deposition damages: Preliminary results from the 1985 NAPAP assessment

This paper presents estimates of the monetary value of the biophysical damages caused by acid deposition for the National Acid Precipitation Assessment Program's 1985 Assessment. Economic damages are estimated for four effect areas: commercial agriculture, forests, recreational fishing and selected types of materials. The preliminary nature of the value of the estimated damages in each area is emphasized. The estimated values should be interpreted with appropriate regard for the uncertainties about the physical effects of acid deposition and the assumptions in the economic analysis.