Grouping of regions on the basis of grasslans vegetation

Abstract

This article gives an example of the classification of regions into groups based on the results of grassland-vegetation maps. The classification is done in such a way as to bring out the agronomic problems of each group.During the last 12 years detailed vegetation surveys have been made in the Nether lands of c. 150,000 ha and rough surveys of c. 22,000 ha. The results were mapped and are used in planning improvement schemes for entire regions. These grassland-vegetation maps show the present situation of the productivity and quality of grassland. Information is also given on such habitat factors as water supply and management status that determine the agronomic value of grassland. Every vegetation unit (DE BOER, 1963 a) has an average "use value", viz. a relative figure which is closely correlated to the starch-equivalent production per ha. By measuring the area covered by the various vegetation units and multiplying by the relative figures, the total improvement possibilities can be calculated and com pared with the cost. The influence of the improvement of the water supply or the sward can be separately valuated (DE BOER, 1963 b). At the moment data is available on more than 50 regions and it will be interesting to compare them. Each region comprises a number of entire farms. As there are only slight differences in climate in the Netherlands, the soil in situ is the regulator of the water supply. The soil factors regulating the water supply are: a. average trend of the ground-water table, b. permeability, c. water capacity, d. capil larity. This group of factors together determines the agricultural value of the grass land. Water excess will be discussed as the first grouping principle, because under Dutch climate and soil conditions water excess is a very important factor and expensive to improve. For the sake of simplicity the different classes of "wet grassland" of the detailed map are combined in one class of "too wet" grassland. All grassland with 5 % or more of plant species indicating wet conditions belongs to this class (KRULTNE and DE VRIES, 1963). For further details on the classification of vegetation units readers are referred to an earlier publication (DE BOER, 1956). As the percentage of "wet indicators" increases, the following disadvantages also increase in severity; de pression of grass growth in spring or at other times of the season with low tem peratures (DE BOER, 1963 C) and treading or poaching by cattle in rainy periods. These properties are great obstacles to the intensification of grassland use.

Extensification of dairy farming and floristic richness of peat grassland.

“…Due to the hydrological differences across the fields, differences in the botanical composition within the fields might be expected. To examine this, we compared the abundances of some species that are known to indicate moist or drought circum stances (according to the list of de Boer, 1965) in the two sampling plots at the out side of the fields with those in the two plots near the middle of the fields. There were indeed differences within the fields: the moisture-indicating species Alopecurus ge niculates and Glyceria fluitans had a significantly, but slightly, higher abundance in the middle of the fields, whereas the drought indicators Dactylis glomerata and Poa pratensis did not differ significantly (Table 1).…”

Effects of drainage on the botanical richness of peat grassland.

“…To check whether the botanical composition differs at different moisture levels we also examined the occurrence of some typical moisture-and drought-indicating spe cies. To this end we chose the moisture indicators Alopecurus geniculatus, Glyceria fluitans and Phalaris arundinacea and the drought indicators Dactylis glomerata and Poapratense (de Boer, 1965).…”