Vegetation Measurement





Vegetation Measurement

Vegetation measurement is the measure of vegetation in a specific area. It helps people understand the vegetation structure and its composition. The methods implemented in measuring vegetation include cover, frequency, density, biomass and structure. This report seeks to explore only two methods; cover and density showing how they are used to measure vegetation.

The methods used in measuring density differ from the other. These methods vary depending on the different parameters. These parameters are vital in ecology and forestry. The different methods include:

Point frame method

This method was an original proposal of Madden and Levy in 1993. The horizontal point frame method entails of a frame. The frame has three parallel transverse rails with punched holes at regular intervals. Estimation of vegetation was achieved through pushing pins at each hole then the hits corresponding to the vegetation recorded. The calculation of the vegetation density was achieved through;

Dv = (1/ Lp) x (Nhits/ Nholes)

Lp is the length of the pin in meters while is Nholes the overall number of holes. This method, according to Dudley is the one of the most objective measuring methods of vegetation density. Previous methods have shown that this method is efficient, reliable and accurate.

Cover board method

In this method, a white board with grid is horizontally moved away from the observer and the distance, L, is then recorded. The grid has half of its points covered with vegetation from the observer’s location. On a random distribution of vegetation, the density is calculated through;

e˄ (-Dv_l) = 0:5

Dv = (-1/L) ln 0:5

The advantages of this method were that it required little equipment, it was rapid and that it provided approximates over great distances in scant vegetation. However, this method relies on subjective approximates of fractional coverage from the observer, which is prone to differ with another causing substantial error.

Plant cover is the percentage of ground surface that is under vegetation or other coverage like the rocks, moss, litter or bare-ground. Different types of measurement are used in measuring the plant cover.

Basal cover

This is the measure of the proportion of the plant extending into the soil. It is usually more stable from one year to another and changes minimally due to the fluctuation of climate or usage by grazers. It is commonly used for trend evaluations or calculations of species structure.

Foliar cover

This is the measure of a leaf’s exposed area in vertical projection. The cover equals the size of the shadow with the sun at noon. The small openings in a leaf are excluded. This method is highly vulnerable to perennial fluctuations due to biotic or climatic factors. It may be very difficult to measure apart for some form of growths like shrubs, cactus and forbs.

Canopy cover

This is the estimate of the area of influence of a particular plant. The total canopy may over exceed 100% due to overlapping of shadows from overlapping plants. These methods of evaluation of the vegetation measurement are important because they help the users of the land particularly the farmers to know which areas are good for farming. It also helps understand the climate area of certain plants and boost their growth by providing a conducive environment.

Works cited

Basic Problems and Techniques in Range Research: A Report of a Joint Committee of the American Society of Range Management and the Agricultural Board. Washington: National Academy of Sciences- National Research Council, 1962. Print.

Wirth, Troy A, and David A. Pyke. Monitoring Post-Fire Vegetation Rehabilitation Projects: A Common Approach for Non-Forested Ecosystems. Reston, Va: U.S. Geological Survey, 2007. Print.