The legacy of harvest and fire on ecosystem carbon storage in a north temperate forest

Forest harvesting and wildfire were widespread in the upper Great Lakes region of North America during the early 20th century. We examined how long this legacy of disturbance constrains forest carbon (C) storage rates by quantifying C pools and fluxes after harvest and fire in a mixed deciduous forest chronosequence in northern lower Michigan, USA. Study plots ranged in age from 6 to 68 years and were created following experimental clear‐cut harvesting and fire disturbance. Annual C storage was estimated biometrically from measurements of wood, leaf, fine root, and woody debris mass, mass losses to herbivory, soil C content, and soil respiration. Maximum annual C storage in stands that were disturbed by harvest and fire twice was 26% less than a reference stand receiving the same disturbance only once. The mechanism for this reduction in annual C storage was a long‐lasting decrease in site quality that endured over the 62‐year timeframe examined. However, during regrowth the harvested and burned forest rapidly became a net C sink, storing 0.53 Mg C ha⁻¹ yr⁻¹ after 6 years. Maximum net ecosystem production (1.35 Mg C ha⁻¹ yr⁻¹) and annual C increment (0.95 Mg C ha⁻¹ yr⁻¹) were recorded in the 24‐ and 50‐year‐old stands, respectively. Net primary production averaged 5.19 Mg C ha⁻¹ yr⁻¹ in experimental stands, increasing by < 10% from 6 to 50 years. Soil heterotrophic respiration was more variable across stand ages, ranging from 3.85 Mg C ha⁻¹ yr⁻¹ in the 6‐year‐old stand to 4.56 Mg C ha⁻¹ yr⁻¹ in the 68‐year‐old stand. These results suggest that harvesting and fire disturbances broadly distributed across the region decades ago caused changes in site quality and successional status that continue to limit forest C storage rates.     

Geographic variation in size and sexual dimorphism of North American weasels

Geographic variation in size (skull length) and sexual dimorphism in Mustela erminea, Mustela frenata and Mustela nivalis in North America is described and analysed in relation to latitude, longitude, climatic variables, and sympatry or allopatry of these species. Only erminea increases in size with latitude; it does so regardless of the presence or absence of frenata or nivalis. Latitude is a better predictor of size in erminea than available measures of climate, seasonality or prey size. There is no evidence for character displacement between any pair of species. The sexes covary in size in frenata and erminea , and probably in nivalis , although geographic variation in sexual dimorphism occurs in frenata and erminea. The principal cause of sexual dimorphism appears to be sexual selection for large size in males rather than the high energetic requirements resulting from an elongate body shape. However, prey size may constrain female size (and possibly also male size). Regional differences in the abundance of prey during the growth of young weasels may affect adult size much more in males than in females and contribute to geographic variation in sexual dimorphism.     

INVESTIGATIONS REGARDING THE NATURE OF THE INTERACTION BETWEEN IRON AND MOLYBDENUM OR VANADIUM IN NUTRIENT SOLUTIONS WITH AND WITHOUT A GROWING PLANT

Iron offset the toxicity of molybdenum or vanadium in nutrient solutions more effectively when it was supplied at the same time as the molybdenum or vanadium than when it was given separately in alternate 3-day periods.
Allowing nutrient solutions of pH 4.6 containing high concentrations of iron, with or without vanadium, to stand for 4 days before use did not delay the restoration of colour to chlorotic plants, but even z days' standing reduced the iron content of their roots and the vanadium content of both shoot and root. The presence of vanadium had little effect on iron uptake.
In parallel experiments with molybdenum, standing the solutions for 7–9 days before use delayed colour recovery, but shorter periods had no effect. Standing for z days or longer greatly reduced the iron content of the root, but the molybdenum content was unaffected or increased. High molybdenum greatly increased the iron in the root, but had little effect on that in the shoot.
Precipitation of iron in the nutrient solution was delayed by high concentrations of either ammonium or sodium molybdate if the initial pH was 4.6, but not if it was 6.6. Vanadium had no influence on the precipitation of iron at pH 4.6.
At least part of the compensating action of iron on molybdenum or vanadium toxicity would appear to take place outside the plant.     

COMPARATIVE ASPECTS OF THE ONTOGENY OF TASTE

Pigs are proposed as a useful laboratory model for the investigationof taste preferences and other controls of ingestive behaviorin the newborn. Suckling pigs can be easily trained to feedthemselves from an artificial feeding apparatus so that intakecan be measured directly. In this manner preferences for glucose,sucrose, fructose and lactose were found in pigs 3 wk of age.The preference threshold for glucose is considerably higherthan that reported for more mature pigs. Taste aversion wasdemonstrated in suckling pigs 2 wk of age. After the taste ofglucose had been paired with LiCl injection, poisoned pigs didnot show the strong glucose preference shown by control pigs.In addition to oropharyngeal controls of intake, gastrointestinalcontrols of intake in the newborn pig were investigated.Loadsof milk or 5% glucose, but not 0.9% NaCl, given by gavage depressedsubsequent intake in piglets 1 wk of age. Caloric or glucostaticmechanisms, but not volume alone, appear to be involved in satietyin the newborn pig. ^*Supported by USPHS Special Fellowship 5F03 AM55321-02 to K.A.H.Request for reprints should be sent to Dr. K. A. Houpt, Dept.of Physiology, N.Y.S. College of Veterinary Medicine, Ithaca,New York 14853, U.S.A.     

Gametogenesis,brooding and planulation in laboratory populations of a temperate scleractinian coral Balanophyllia elegans maintained under contrasting photoperiod regimes

Summary

Males of Balanophyllia elegans Verrill, 1864 in Monterey Bay, California, spawn in the fall. Fertilization occurs within the females and the internally brooded embryos develop into large benthic planulae that are released mainly in the late winter. Field-collected corals were held in the laboratory under contrasting photoperiod regimes (ambient or in-phase, and 6 months out-of-phase) for 6.5 years. After two years in the laboratory corals planulated at the same time, independent of photoperiod. Corals show a cyclic pattern of later winter and early spring planulation that coincides with declining sea temperatures in Monterey Bay. Gametes appeared in the first laboratory generation at IS months and brooded embryos were found in females at 31 months under both light regimes. Planulae production by laboratory-reared corals peaked at the same time as that of the parents. These findings suggest that the temporal pattern of planulation is regulated by both endogenous and exogenous components that can be modified in some way by disturbance caused to the corals when collected or by the time of collection.     

THE INFLUENCE OF THE pH OF THE NUTRIENT SOLUTION AND THE FORM OF IRON SUPPLY ON THE COUNTERACTION OF IRON DEFICIENCY IN PEAS, SOYBEAN AND FLAX BY HIGH CONCENTRATIONS OF MOLYBDENUM

The prevention of chlorosis in flax by high concentrations of molybdenum in a nutrient solution was associated with a delay in the precipitation of iron from ferric citrate, a slower drift of pH towards alkalinity and an increase in the iron content of the root. These effects were greater with ammonium than with sodium molybdate and occurred with solutions started at pH 4.6 but not at pH 6.6.
When FeEDTA was the source of iron, a similar delay in pH drift in the solution and accumulation of iron in the root occurred, but there was no chlorosis or precipitation of iron in the control treatment, so the effect of high molybdenum could not be fully determined.
When ferric chloride was used, high molybdenum did not prevent chlorosis nor delay iron precipitation or cause accumulation of iron in the root, though the rate of pH drift resembled that of solutions containing the organic forms of iron.
Similar results were obtained with peas and soybeans receiving high molybdenum treatment, but suppression of chlorosis was only temporary.
It is suggested that the capacity of molybdenum to offset chlorosis is due to the formation, in acid solution, of a complex with phosphorus which renders iron more available by delaying the formation of ferric phosphate. This seems to occur only when iron is supplied in the organic form.     

The effect of bacterially‐dense environments on the development and immune defences of the blowfly Lucilia sericata

Competitive interactions between insects and microbes and the associated cost of development in bacterially‐dense environments are investigated using the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) as a model. The effects of developing in a bacterially‐dense environment are measured by assessing the fitness consequences of competition using the pathogen Staphylococcus aureus. Fitness is quantified in terms of larval survival, puparial development and adult emergence.The influence of bacteria on larval immune defences is investigated using optical density to assess whether antibacterial potency of the larval excretion/secretion changes in response to the degree of contamination of the larval environment. The results obtained demonstrate that bacterial presence has no detrimental effect on survival of L. sericata from egg to adult eclosion, or on puparial size. Additionally, the level of microbial contamination of larvae has no effect on the antibacterial potency of the larval excretion/secretion. These findings confirm that larval antibacterial activity is not induced by the presence of environmental bacteria but is produced constitutively.     

SOME INTERRELATIONSHIPS BETWEEN MANGANESE, MOLYBDENUM AND VANADIUM IN THE NUTRITION OF SOYBEAN, FLAX AND OATS

Soybean and flax were grown in nutrient solutions containing high and low levels of molybdenum and vanadium, in combination with toxic (10–25 p.p.m.) and non-toxic (1 p.p.m.) manganese. Molybdenum (20 and to a less extent 10 p.p.m.) intensified the chlorosis induced by manganese excess, though these concentrations were harmless in the presence of 1 p.p.m. Mn. Vanadium (= 1.0, 5 and 10 p.p.m. Mo) counteracted some of the symptoms of manganese toxicity, but the two higher rates were harmful to growth irrespective of the manganese supply. Toxic concentrations of vanadium at first deepened the green colour of the shoot, though apical iron-deficiency chlorosis was generally induced later. Low molybdenum (0.1 p.p.m.) or equivalent vanadium had no influence on growth or iron nutrition at either level of manganese. Visual differences were corroborated by changes in the nitrogen, phosphorus and iron contents of the plants. There was no evidence of replaceability of molybdenum by vanadium.
Oats were grown in nutrient solutions containing various combinations of manganese (nil–400 p.p.m.) and molybdenum (nil–20 p.p.m.). The appearance of manganese-deficiency symptoms was not affected by the quantity of molybdenum provided, and the manganese and molybdenum contents of the leaves were mutually independent of the quantity of each element supplied.