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

A Checklist of the Aquatic and Wetland Vascular Plants of Iowa: I. Ferns, Fern Allies, and Dicotyledons

This paper is an annotated checklist of the aquatic and wetland ferns, fern allies, and dicotyledons of Iowa and is based primarily on published floristic surveys. For each species, information about its habitat, distribution, synonomy, and frequency of occurrence is provided, plus a distribution map. A total of 9 ferns, 6 fern allies, and 262 dicotyledons are considered aquatic or wetland species in Iowa

Ideal ages for family formation among immigrants in Europe

This paper investigates ideal ages for marriage and parenthood among immigrants from over 160 countries origins living in 25 European countries. Ideals regarding the timing of family formation are indicative of how individuals perceive the family life course and provide insight into family-life aspirations and the meaning attached to these transitions. Using data from the European Social Survey (Round 3, 2006; N = 6,330) and a cross-classified multilevel modeling approach, we investigate associations between the influences of the dominant family formation timing patterns in countries of origin and settlement, individual-level characteristics, and ideal ages. We make innovative use of a standard demographic measure, the singulate mean age of marriage, to measure family formation patterns. Results suggests that residential context influences are associated with the timing ideals of all migrants, but origin influences seem to be associated with the ideals of only the most recent migrant

Intergenerational support among migrant families in Europe

Intergenerational support is important throughout the individual life course and a major mechanism of cultural continuity. In this study, we analyse support between older parents and their adult children among international migrant and non-migrant populations in North, Centre and Southern Europe. Data from the Survey of Health, Ageing and Retirement in Europe are used to compare upward and downward practical support, grandparenting, and frequency of contact among 62,213 parent–child dyads. Findings indicate limited differences in support between migrants and non-migrants as well as between migrants of various origins. However, persistent differences in intergenerational support across Europe along a north–south gradient are found irrespective of migrant status