Grassy areas such as playing fields, grass verges and lawns are maintained as grassland by mowing and trampling. Mowing removes the upper portions of grassland plants above a certain height. Many tall growing plants are killed when the upper parts of the plant are removed, either by grazing animals or mowers. Other plants have evolved a range of adaptations which enables them to survive in such conditions.
Students sample species frequency using quadrats in two contrasting areas, then use their results to consider the ways in which some plants are adapted to resist trampling.
Through this activity pupils will:
- consider how the distribution of organisms in different habitats is affected by environmental factors
- describe and explain the responses of plants to trampling
- evaluate the method of data collection
Resources to download
Background information for teachers
The key to a successful plant in closely mowed grassland lies in the position of the meristem. The meristem is a group of actively dividing cells forming the growing point of a shoot or a root. Most plants have an apical meristem: the growing point is located at the tip of the shoot (or root). If they are grazed or mown, plants with an apical meristem lose their growing points, and will probably die. Note that some plants can survive if they are able to produce a new side shoot from an axillary bud (the bud in the axil of a leaf).
The leaf blade of grass is long, narrow, and has its meristem near the point where it joins the stem. Even if the upper part of the leaf is broken off, perhaps by a lawnmower, the grass can continue to grow. The competitive advantage of having a growing point close to the ground is lost in longer vegetation, such as underneath shrubs and trees, where the leaves are in shade.
Some common grassland plants, such as the daisy (Bellis perennis), dandelion (Taraxacum officinale), rough hawkbit (Leontodon hispidus) and greater plantain (Plantago major), grow a rosette of leaves. This is a specific growth-form where the plant has very short leaf internodes, resulting in a circle of leaves lying flat against the ground in a spiral fashion to avoid overlapping. A strong straight root (the tap root) grows vertically down in the soil under the leaves. These adaptations give the plants a competitive advantage in short grassland which is mowed or trampled.
In longer vegetation, the rosette growth-form is less common, as the flat leaves are shaded out by surrounding plants. If rosette-forming plants (such as the dandelion) grow amongst taller plants the leaves tend to grow more upright as a clump rather than as the characteristic flat rosette. Both of the growth forms can survive mowing, as the shoot meristems are very close to the ground, though the plants may lose flowers on taller upright flower stems.
Other plants adopt a trailing, creeping or prostate growth form. White clover (Trifolium repens), silverweed (Potentilla anserina) and creeping buttercup (Ranunculus repens) spread vegetatively by means of stolons. These are stems that grow low against the ground, growing new roots and producing new offshoots of the same plant.