Linking breeding and wintering ranges of a migratory songbird using stable isotopes

We used the natural abundance of stable isotopes (carbon and hydrogen) in the feathers of a neotropical migrant songbird to determine where birds from particular breeding areas spend the winter and the extent to which breeding populations mix in winter quarters. We show that most birds wintering on western Caribbean islands come from the northern portion of the species' North American breeding range, whereas those on more easterly islands are primarily from southern breeding areas. Although segregated by breeding latitude, birds within local wintering areas derive from a wide range of breeding longitudes, indicating considerable population mixing with respect to breeding longitude. These results are useful for assessing the effects of wintering habitat loss on breeding population abundances and for predicting whether the demographic consequences will be concentrated or diffuse.     

Belrus: A new russet skin potato variety,combining high quality,pest resistance,and adaptation to the Northeastern United States and Florida

BelRus, a new russet potato variety, is medium late in maturity and adapted primarily for the Northeastern United States and northern Florida. Tubers are long, smooth and moderately flat with a heavy russet skin. Eyes are shallow and immediately adjacent skin is, for the most part, nonrussetted in the Northeastern U.S. Industry speaks of the BelRus there as the “white eyed russet.” BelRus is slightly higher in specific gravity than ‘Russet Burbank’, has a superior flavor when baked, and yields excellent french fries and flakes. Glycoalkaloid content of BelRus is quite low, being about 2 mg/100 g fresh tissue. BelRus is immune to virus A and tuber net necrosis; highly resistant to tuber heat necrosis, northern root knot nematode (Meloidogyne hapla), and the pinkeye bacterial disease; moderately resistant to scab, Verticillium wilt, leaf roll and potato virus Y. It is not resistant to either late blight or early blight, or viruses M, S, and X. Necrotic spotting of the foliage occurs following periods of high temperature and extended drought. BelRus has demonstrated high tolerance to bruising and storage rots incurred during harvest and handling. Shrinkage in bulk storage has been minimal. BelRus is recommended to be planted at about 25 cm (10 inches) in-the-row on 90 cm (36) rows with about 215 kg (180–200 lbs/acre), N₂/ha in-the-row.     

Cover Crops for Saline Soils

A 3-year study was conducted in the Central Valley of California to evaluate 125 prospective winter-growing cover crops for growth and nitrogen productivity in saline soils. Soil saturation paste electrical conductivities (ECes) in the surface 15 cm averaged 7 dS  m⁻¹ at fall planting and 5.3 dS m⁻¹ at spring harvest dates of each experiment. Species evaluated varied substantially in plant height. In general, the tallest plants were the Brassica species, which consistently grew to over 1.4 m. Annual grasses (barley, rye, triticale and wheat) averaged about 1.0–1.3 m in each year. Of the legume species screened, heights were greatest for Hedysarum coronarium , Trifolium alexandrium , Vicia spp., and Medicago polymorpha and truncatula , averaging 59, 47, 39, 38 and 37 cm, respectively, over all experiments. About one third of the species screened produced crop cover in excess of 90 % in each year. Groups of plants with consistently high crop cover percentages included various species/accessions of Brassica , Hedysarum , annual grasses, cool-season annual medics, Medicago polymorpha and Medicago truncatula , and two annual clovers, Trifolium alexandrium cv 'Multicut' and rose clover, Trifolium hirtum cv 'Hykon.' Total above-ground plant dry weights were highest for Brassica spp., which produced twice as much biomass as the annual grass species, and roughly four times as much dry matter as any of the legume species. Hedysarum , Lana and Namoi woolypod vetch, purple vetch, berseem clover, and several of the annual medic species consistently had the highest biomass among the legumes.     

Nitrogen Fixation by Irrigated Berseem Clover versus Soil Nitrogen Supply

Nitrogen fixation was estimated by the difference method for two cultivars of berseem clover ( Trifohum alexandrinum L.), using annual ryegrass ( Lolium multiflorum Lam.) as the control in field trials from 1983 to 1988. Five or six cuttings were obtained each year under supplemental irrigation, and dry matter production and uptake of nitrogen into harvested forage were measured.
Estimates of nitrogen fixation by berseem clover ranged from 272 to 400 kg N/ha depending on year and cultivar, while plant N derived from soil (based on N uptake by the ryegrass) ranged from 50 to 235 kg N/ha. Graphs of nitrogen fixed versus available soil nitrogen had a reverse linear-plateau shape with a plateau at lower soil nitrogen levels that broke sharply in a linear decline as available soil N surpassed a minimum threshold. Such a two-phase response suggests that nitrogen fixation by the clover was limited by soil N supply above this threshold and by other limiting factors at low soil N levels, perhaps genetic traits controlling carbon assimilation or environmental limitations other than nitrogen. Seasonal nitrogen process patterns showed abundant nitrogen fixation by the clover after it had depleted most of the soil nitrogen supply.