Master's Theses

Document Type

Thesis - campus only access

Date of Award

Spring 1961

Degree Name

Master of Science (MS)

Department

Biology

Advisor

F. W. Albertson

Abstract

This investigation was an attempt to determine the effects of a change of habitat factors on the responses of big bluestem which dominates favorable site in the mixed prairie association. Responses of big bluestem on five habitats were determined with reference to the following factors: (1) soil composition; (2) temperature; (3) relative humidity; (4) evaporation; (5) wind; (6) light; and (7) mulch cover. The five habitats for studying big bluestem were selected on the basis of range site and exposure. Four were located on an east-facing slope and the fifth was located on a west-facing slope. During the growing season of 1960, when this study was conducted, a mid-season drought occurred, greatly affecting vegetative growth. One hundred square-foot quadrats were established in order to make weekly measurements of big bluestem. Responses of big bluestem to habitat factors were grouped into four main categories as follows: (1) weekly and cumulative height of plants and number of leaves of each marked plant; (2) basal cover and composition; (3) plant population; and (4) total production. Climatic and edaphic factors of each habitat were measured weekly. Findings were as follows: (1) In spite of considerable difference in depth of soil among habitats, the texture of soils was the same for all habitats. (2) Average maximum air temperature was higher on the west-facing slope than on the east-facing slope for the season. (3) Air temperatures were consistently higher inside the vegetation than outside. (4) Surface-soil was consistently warmer during the day than sub-soil. (5) Soil temperatures were highest in the afternoon in surface soil and in the evening in sub-soil. (6) Average weekly relative humidity was consistently higher inside the vegetation than above. (7) Relative humidity inside the vegetation was lower on the west-facing slope than that on any habitat on the east-facing slope. (8) Rate of evaporation was higher from the habitat on the west-facing slope than that on any habitat on the east-facing slope. (9) Wind velocity was higher at the top of vegetation than inside. (10) The velocity was higher in the evening than that of noon or morning. (11) Light intensity was lower inside the vegetation than outside and was the lowest at the mulch level. (12) Average height and number of leaves per plant was greatest on habitat D favored by more mesic conditions. (13) Though big bluestem plants did not increase in height after July 15, new basal leaves were produced by many plants until September 13. (14) Only one per cent of the plants of big bluestem produced inflorescences. (15) Basal cover was lowest on the west-facing slope having more xeric conditions. (16) Exposure and depth of soil were primarily the determining factors for variations in species occurrence. (17) Percent survival of big bluestem plants was proportional to variations in intensity of habitat factors. (18) A linear increase in amount of mulch was found with increased height of plants. (19) The highest yield of big bluestem was harvested on habitat D favored by more mesic conditions while the lowest production was associated with more xeric condition of habitat E.

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Rights

© 1961 K.R. Patel

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