THE CANADA- U.S. TRADE DISPUTES ON DAIRY AND POULTRY: A GOOD EXAMPLE

International Relations/Trade,

Zonation, Competitive Displacement and Standing Crop of Northwest Iowa Fen Communities

Well developed Iowa fens contain three distinct vegetation zones (border zone, sedge mat zone and discharge zone). On the average, the above ground standing crop of these zones is 425, 197 and 528 g/m2 respectively. Species growing on these fens show three basic distributional patterns: (1) they grow in the border and discharge zones; (2) they grow primarily in the sedge mat zone or (3) they grow in all three zones. Individual plants of species growing in the border and/or discharge zone are on the average 1.6 to 2.7 times taller and weigh 1.8 to 5.4 times more than when they grow on the sedge mat zone. Species with primarily bimodal or ubiquitous distributions show the greatest decline in height and weight when found in the discharge zone. The three Iowa fen zones are a result of differences in environmental conditions, plus competitive displacement of the dominant sedge mat species from the border and discharge zones

The History of Plant Ecology in Iowa as Reflected in the Proceedings of the Iowa Academy of Science

All plant ecology papers published in the Proceedings from 1887 to 1973 were identified. On the average only 1.4 papers were published per year. An examination of the number of papers published in successive five-year intervals indicates that there were three distinct periods in the history of plant ecology in Iowa with three individuals dominating each period: 1887-1931 - L. H. Pammel, B. Shimek, and Ada Hayden; 1932-1951 - H. S. Conard, J. M. Aikman, and Ada Hayden; 1952-1971 - J. M. Aikman, R. F. Thorne, and R. Q. Landers. There have been very few active plant ecologists in Iowa, and more than 50 percent of all the papers published in the Proceedings were authored or co-authored by only 10 people. All the papers identified are also classified according to subject matter

Floristic Composition and Structure of Fen Communities in Northwest Iowa

Iowa fens have three distinct, concentric vegetation zones: a border zone, a sedge mat zone, and a discharge zone where ground water supplying the fens comes to the surface. Calamagrostis inexpansa Gray, Viola nephrophylla Greene, Scirpus americanus Pers. and Carex spp. are the dominants in the border zone. The composition of this zone is quite variable both within and between fens. The sedge mat is composed primarily of Rhynchospora capillacea Torr. Other species normally found in this zone are Lobelia kalmii L., Muhlenbergia racemosa (Michx.) BSP, Parnassia glauca Raf., Triglochin maritima L. and Scirpus americanus. Although all of the species in this zone are also found in the other zones, this zone is readily distinguishable because of the low stature of the vegetation. The discharge zone is dominated usually by Carex spp. or Calamagrostis inexpansa, except at one fen where Phragmites communis Trin. and Helianthus grosseserratus Martens are the dominants. The sedge mat zone on the average has fewer species per quadrat (5.8 versus 6.0 and 8.6), lower Shannon-Weaver index (0.8 versus 1.15 and 1.40) and higher Simpson\u27s index (0.58 versus 0.42 and 0.32) than the discharge and border zones, respectively