Barrier island forest ecosystem: role of meteorologic nutrient inputs

The Sunken Forest, located on Fire Island, a barrier island in the Atlantic Ocean off Long Island, New York, is an ecosystem in which most of the basic cation input is in the form of salt spray. This meteorologic input is sufficient to compensate for the lack of certain nutrients in the highly weathered sandy soils. In other ecosystems these nutrients are generally supplied by weathering of soil particles. The compensatory effect of meteorologic input allows for primary production rates in the Sunken Forest similar to those of inland temperate forests.     

Nutrient cycling

The small-watershed approach to problems of nutrient cycling has these advantages. (i) The small watershed is a natural unit of suitable size for intensive study of nutrient cycling at the ecosystem level. (ii) It provides a means of reducing to a minimum, or virtually eliminating, the effect of the difficult-to-measure variables of geologic input and nutrient losses in deep seepage. Control of these variables makes possible accurate measurement of nutrient input and output (erosion) and therefore establishes the relationship of the smaller ecosystem to the larger biospheric cycles. (iii) The small-watershed approach provides a method whereby such important parameters as nutrient release from minerals (weathering) and annual nutrient budgets may be calculated. (iv) It provides a means of studying the interrelationships between the biota and the hydrologic cycle, various nutrient cycles, and energy flow in a single system. (v) Finally, with the small-watershed system we can test the effect of various land-management practices or environmental pollutants on nutrient cycling in natural systems.     

Role of Erythronium americanum Ker. in Energy Flow and Nutrient Dynamics of a Northern Hardwood Forest Ecosystem

The aboveground activity of the spring herb, Erythronium americanum, is restricted to the period between snowmelt and forest canopy development. Its phenology and production capacity closely adapt the species to this temporal niche in northern deciduous forests. While E. americanum has a minor effect on energy flow, it may reduce losses of potassium and nitrogen from the ecosystem during the period of maximum removal by incorporating these elements in accumulating biomass. Later, during the summer, these nutrients are made available when the above-ground, nonperennating tissues decay.     

Hydrogen ion input to the hubbard brook experimental forest,New Hampshire,during the last decade

Being downwind of eastern and midwestern industrial centers, the Hubbard Brook Experimental Forest offers a prime location to monitor long-term trends in atmospheric chemistry. Continuous measurements of precipitation chemistry during the last 10 yr provide a measure of recent changes in precipitation inputs of H ion. The weighted average pH of precipitation during 1964–65 to 1973–74 was 4.14, with a minimum annual value of 4.03 in 1970–71 and a maximum annual value of 4.21 in 1973–74. The sum of all cations except H ion decreased from 51 μeq 1^?1 in 1964–65 to 23 μeq 1^?1 in 1973–74 providing a significant drop in neutralizing capacity during this period. Based upon regression analysis, the input in equivalents of H ion and nitrate increased by 1.4-fold and 2.3-fold respectively, from 1964–65 to 1973–74. Input of all other ions either decreased or showed no trend. Based upon a stoichiometric formation process in which a sea-salt, anionic component is subtracted from the total anions in precipitation, SO₄ ⁼, contribution to acidity dropped from 83% to 66%, whereas NO₃ ^? increased from 15% to 30% during 1964–65 to 1973–74. The increased annual input of H ion at Hubbard Brook during the past 10 yr is highly correlated with the increased input of nitrate in precipitation.     

Pregnancy rate and first-service conception rate in Angus heifers

The objective of this project was to determine the genetic control of conception rate, or pregnancy percentage in Angus beef heifers. Producers from 6 herds in 5 states provided 3,144 heifer records that included breeding dates, breeding contemporary groups, service sires, and pregnancy check information. Two hundred fourteen sires of the heifers were represented; with 104 sires having less than 5 progeny, and 14 sires having greater than 50 progeny. These data were combined with performance and pedigree information, including actual and adjusted birth weights, weaning weights, and yearling weights, from the American Angus Association database. Heifer pregnancy rate varied from 75 to 95% between herds, and from 65 to 100% between sires, with an overall pregnancy rate of 93%, measured as the percentage of heifers pregnant at pregnancy check after the breeding season. Pregnancy was analyzed as a threshold trait with an underlying continuous distribution. A generalized linear animal model, using a relationship matrix, was fitted. This model included the fixed effects of contemporary group, age of dam, and first AI service sire, and the covariates of heifer age at the beginning of breeding, adjusted birth weight, adjusted weaning weight, and adjusted yearling weight. The relationship matrix included 4 generations of pedigree. The heritability of pregnancy and first-service conception rates on the underlying scale was 0.13 +/- 0.07 and 0.03 +/- 0.03, respectively. Estimated breeding values for pregnancy rate on the observed scale ranged from -0.02 to 0.05 for sires of heifers. Including growth traits with pregnancy rate as 2-trait analyses did not change the heritability of pregnancy rate. As expected for a reproductive trait, the heritability of pregnancy rate was low. Because of its low heritability, genetic improvement in fertility by selection on heifer pregnancy rate would be expected to be slow.     

The impact of endophyte-infected fescue consumption on digital circulation and lameness in the distal thoracic limb of the horse

This experiment was conducted to evaluate if consumption of endophyte-infected fescue alters digital circulation in the distal thoracic limb of the horse and to assess if soundness of the hooves of horses is affected by consumption of endophyte-infected fescue. Twelve American Quarter Horses (mean initial BW 459 ± 31 kg), 6 mares and 6 geldings, were used in this 90-d study that comprised high-endophyte (E+) and low-endophyte (E-) treatment groups. Fescue seed was integrated into the E+ diet at a rate sufficient to bring total ergovaline to 200 μg/kg, and endophyte-free fescue seed was incorporated into the E- diet from d 0 to 90. From d 30 to 60, native prairie hay was replaced with high- or low-endophyte fescue hay, bringing total dietary ergovaline to 280 μg/kg (E+) and 18 μg/kg (E-). From d 61 to 90, fescue seed was ground to decrease particle size. On d 0, 30, 60, and 90, Doppler ultrasonography and thermographic imaging were used to measure the diam. of the medial palmar artery, velocity of blood flow, and surface temperature of the hoof as indicators of digital circulation. Lameness examinations were conducted on the same days. There were no consistent treatment differences observed when evaluating measurements of digital circulation. On d 60, horses in the E+ treatment group showed increased hoof sensitivity in the left limb (P = 0.02). These horses tended to have increased hoof sensitivity when both thoracic limbs were averaged (P = 0.06), and they demonstrated increased lameness during longeing (P = 0.08). Data indicated that mares may have increased digital circulation, regardless of treatment, compared with geldings (P ≤ 0.05). Heavier horses also had greater arterial diam., velocity of blood flow, and hoof temperature than lighter BW horses (P ≤ 0.05) on d 30, 60, and 90 at time points that ranged from 90 to 180 min after feeding. Although horses consuming the E+ diet demonstrated increased lameness, especially on d 60, compared with horses consuming the E- diet, the measures of digital circulation did not support the hypothesis that digital circulation was reduced. Because of observed lameness issues, limiting the access of horses to endophyte-infected fescue may be prudent.     

Evidence against hydrogen-based microbial ecosystems in basalt aquifers

It has been proposed that hydrogen produced from basalt-ground-water interactions may serve as an energy source that supports the existence of microorganisms in the deep subsurface on Earth and possibly on other planets. However, experiments demonstrated that hydrogen is not produced from basalt at an environmentally relevant, alkaline pH. Small amounts of hydrogen were produced at a lower pH in laboratory incubations, but even this hydrogen production was transitory. Furthermore, geochemical considerations suggest that previously reported rates of hydrogen production cannot be sustained over geologically significant time frames. These findings indicate that hydrogen production from basalt-ground-water interactions may not support microbial metabolism in the subsurface.     

Transport and loss of nitrous oxide in soil water after forest clear-cutting

Whole-tree harvesting increased the concentration of nitrous oxide dissolved in soil water by two orders of magnitude over the concentration expected in equilibrium with the atmosphere. In contrast, the nitrous oxide content of soil water in an intact, second-growth forest was close to the expected theoretical value. Nitrous oxide, produced at active sites in the soil, dissolves in soil water and is transported to seeps and streams where it rapidly degasses from the solution and is released into the atmosphere. This loss of nitrous oxide after clear-cutting is not important to the nitrogen economy of the site; however, it may be important to the global atmospheric budget of nitrous oxide. Sources of nitrous oxide may have been overlooked because nitrous oxide emissions can be separated in time and space from the sites of the most intense production of nitrous oxide.