摘要:

The moose,Alces americana, in British Columbia reaches its greatest populations in the young second growth forest areas. Numbers decrease as the forest approaches its climax stage. The decline in population is known to be mainly the result of malnutrition.The present study of three stages in forest succession growing under virtually identical conditions of soil and climate has concerned itself with quantity of available palatable browse; carotene and ascorbic acid content of available palatable and unpalatable trees and shrubs; and with determination of values for moisture, protein, carbohydrate, ether extractives, and total mineral content. Most of the analyses are confined to the winter dormant period.It is determined that the forest changes studied involve a reduction in quantity of palatable browse to about one-third; that there is an increase of carotene values and possibly of total mineral content in the vegetation on more advanced forest areas, but that in ascorbic acid content, ether extractives, total carbohydrates, and proteins the vegetation upon the younger forest areas is superior to that on the older areas.It is concluded, therefore, that the declining carrying capacity noted in a forest approaching its climax stage results from decreases in both the quantity and quality of food produced.It is further concluded that the most desirable winter range for moose is one upon which there is a variety of palatable species, predominantly in an early stage of growth, but with an intermixture of older forest stands bearing palatable coniferous trees.

ISSN:1923-4287    

DOI:10.1139/cjr50d-016

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Thiouracil depressed the increases of serum calcium, serum riboflavin, and serum vitamin A evoked by estrogen in the sexually immature pullet. In these respects the effects of thiouracil resembled the effects of thyroxine. In contrast to thyroxine, however, thiouracil increased the hypertrophy of the liver and oviduct induced by estrogen. Estrogen did not significantly increase total liver riboflavin, whereas estrogen plus thiouracil produced a significant increase.

ISSN:1923-4287    

DOI:10.1139/cjr50d-017

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The carbon dioxide production of deer mice at 1° to 18 °C. was not affected by humidity, but increasing the temperature decreased the carbon dioxide production of the mice. Heat transmission of mouse fur was also independent of humidity.

ISSN:1923-4287    

DOI:10.1139/cjr50d-018

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Undercooling points are shown to be unreliable as a measure of insect cold-hardiness. Insects held in an undercooled state freeze at irregular intervals, often over long periods of time. Freezing, which is fatal to most insects, is initiated by the formation of an ice-crystal nucleus, and the probability of such formation is dependent upon the extent of undercooling (temperature), cold-hardiness (a complex resulting from previous treatment), and time. For a specified degree of cold-hardiness, the probability of freezing is dependent upon temperature and time. If the temperature is fixed, the probability of freezing can be expressed in units of time. Freezing can take place on a rising temperature gradient as well as on a falling one.Unless an overwintering population is adequately protected by its environment and a high degree of cold-hardiness, losses from freezing will take place by degrees during the entire winter.

ISSN:1923-4287    

DOI:10.1139/cjr50d-019

出版商:NRC Research Press    

年代:1950

数据来源: NRC