The Influences of Grazers in Biodiversity of Insects

Essay 2012 14 Pages

Biology - Miscellaneous


Table of Content


1. Introduction

2. Description

3. Method of the concrete example

4. Discussion

5. Conclusion

6. Sources


Grassland in Europe and other parts of our world offers many animals an appreciable biotope. Not only insects also spiders adopt this specific vegetation influenced by dry and poor soil as their habitat. In Europe the grassland disappears more and more. Many of these areas were under farmers hands and are left fallow nowadays. After a certain period it will happen that bigger herbals such as trees and bushes obtain the fallow area.

In this essay a certain study case made from the Swedish University of Agricultural Science will show how grazers influence the diversity of insects. Grazers such as cattle, sheep and horses are introduced as mowing animals with the goal to avoid the growth of larger plants as trees and bushes.

1. Introduction

All over the world the nature is featured with different biotopes. High Biodiversity within plant species and animals can be provided in all those variation amount of biotopes. European grassland, as one of the category of these areas, offers indeed good conditions for a high diversity of species and their habitat. The good condition for breeding leads particularly birds and invertebrates to live in this area. Over the last year’s most European grassland was regulated by grazers or maintained through cutting. Due to agricultural changes in its practice and land use grassland more and more disappeared significantly. Nowadays Europe showed an enormous decline of grassland area which declined 12, 8 %. [6]. Caused by agricultural land using many fields are used intensively and so the physical condition of soil changed completely. [7] Wind erosion influenced more and more the grassland area. Caused by the wind the sheet erosion increased very fast, so the area of grassland is forced to be changed all the time. This fact is highly interested for insects which have to adapt the quality of the biotope in every moment of their life. Not all species are able to move quickly from one place to another if the biotope is on the way to change its collocation. So grassland with its high level living quality is an eminent biotope for all insect species. Flowers, grasses, plants and the so plant covered soil provide nutrition, hiding places and reproduction area. Grassland areas can be characterized by different kinds of their using such as grazed areas or non-grazed areas. The different areas of grassland all over Europe can be also separated in dry locations in middle Europe such as so called primary grasslands. This form of grassland is found naturally by erosion of wind and water. Primary grasslands often are located on rocks and consequently they do not have a high significant under layer or a high amount of soil layer. Secondary grasslands arise as a consequence of human. In the earlier times our ancestors maid their fields and cut trees in forest without controlling the risk of the decline of natural grassland area or even erosion. Cutting trees and farming the land conducted that areas become dry. Wind bowed threw the areas, the soil became sandy. As a consequence of disturbing the natural way of the existing biotope changed into grassland areas. At least the various types of grassland differ mainly in their size: while natural expanded grassland so called primary grassland is mostly found in small covered areas secondary grasslands are characteristic in their wide expansion and hence big areas. Both named vegetation types tend to be as forest if they are unused as grazing area or not influenced anymore by erosion of wind and water. As far as the vegetation type of grassland decreases more and more the number of endangered insect species can be influenced of this fact one day. Especially the diverse group of arthropods reveals enormous variations in their behavior in different seasons, size, their possibility of moving or not, the trophic level or even their strategy of life history. Arthropods also have requirements for habitats of particular successional phases or the vegetation in their different structural characteristics. [1] The effects of influencing grassland areas by agricultural methods are for Arthropods therefore very significant. This paper will treat the management of characteristic grassland focusing on the habit of insects.Fehler! Verweisquelle konnte nicht gefunden werden. [4] In general Agricultural and forest management by human plays a big role of their habitat. Different benefit types of natural resources such in forestry and agriculture changed the landscape dramatically. The way of using grassland as meadows for cattle, sheep and horses provoke that the affected vegetation type changed. Shortcutting of grazers induced an adjustment in grass length and density. Different types of grazing such as intensively grazing by cows or less grazing influence have a determined effect on the basic components of insect species. [1] But grassland is not only an area where grazing animals are searching for nutrition. Grazed areas without human influence appear in forest areas or such as isolated biotopes. As a place of high biodiversity in species of animals and insects the characteristic grassland takes an important role in the network of nature. In the concrete example below grazed areas by cattle will be compared with non-grazed areas without cattle with a view to the amount of insects. The hypothesis that species richness is depending on the abundance of plants will be tested in the following disposal. This essay will also point out the requirements of the insect biodiversity of beetles, butterflies and grasshoppers [11] towards the vegetation area in grassland.[8]

2. Description

In the beginning of the description some definition should be clarified. So the term of characteristic grassland is often used. This specific area is mostly covered by grasses as the dominant vegetation. Trees and large shrubs don´t exist in this vegetation type. Climate as an important factor influences this area with a high differential of temperature during wintertime and summertime. Typically it consists of warm and wet summers followed by cold and dry winters with heavy frosts. Species such as many bulbous plants are dominating this vegetation type. Grasslands are often characterized the presence of many wetlands.

However offers a high diversity of insects’ species and plants a convenient place for living. Due to the specific and characteristic conditions it has a multivariate flora and fauna which will be told in following paragraphs.

Characteristic grasslands are defined as dried areas inhabited by grasses and dry plants which don´t need much water. [6] Such plants and grass species are Bromus erectus and Tor-grass (Brachipodium pinnatum), Anemone silvestris, Euphorbia cyparissias and Trifolium pratense (et cetera). Trees species are rather rare in this area because of the soil condition. Most times trees are not able to grow because of grazers. Sandy soil causes also a drought area and the water abundance is decreasing. At least strong weather conditions such as in summer or winter with gelid winters complicate most plant species to grow in this vegetation area. Different grass species are in this case the dominant species because they are able to adapt to the ruff conditions in a strong way. [7] Flowers also exist in grassland. As already mentioned Trifolium pretense and Annemone silvestris settle also down in this vegetation type. Last mentioned plants are very important for insects species like honey bee.

Old grassland used as active agricultural field by human has a very good physical condition. Field capacity is on a good level and the relationship of water amount in this area also is in a good shape. Due to the good network of grass roots in the soil old grasslands are also highly protected against wind and water erosion. [6] The soil of grassland mostly tends to be calciferous. A feature of calciferous soil is the high amount of calcium carbonate. The percentage of lime can be up to 40 percent. This condition causes a high level of species richness in plants because the plants need a balanced PH-value in the range of five up to seven point five. This volume is very important for their gathering of nutrition. Calciferous soils are soils such as black cotton soil, mixed rendzina in Aeolian silt deposit areas, rendzina on lime stone, arid sol and soils on clay, calciferous brick earth or also glacial drift.

Different experiments in different areas showed that number of specific orders of insects always occur in the same way.



ISBN (eBook)
ISBN (Book)
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Wageningen University – Fundamental and Applied Biology of Insects
insects grassland management grazers essay Wageningen university




Title: The Influences of Grazers in Biodiversity of Insects