Site Quality Evaluation-importance- STAND DENSITY

Site Quality Evaluation-importance-stand density : 

Site Quality Evaluation-importance-stand density N.KANAGARAJ 1ST MSC [FORESTRY] FOREST COLLEGE AND RESEARCH INSTITUTE METTUPALAM-641301 TAMILNADU INDIA

Site quality : 

Site quality Site quality is the inherent biological capacity of an area to be productive.

Site quality can influence: : 

Site quality can influence: Species composition (through competition), Response to disturbances, The ease or difficulty of getting desired regeneration cultural practices The growth and yield of a stand.

Slide 4: 

Therefore, the success or failure of forest management depends, to a large extent, on correct evaluation of forest sites or sound judgment in fitting species to sites (Smith 1962).  For these reasons, foresters need to understand the relationships between forests and their physiographic environment Soil Topography Climate Biotic factors interact to produce a multitude of forest sites.

site index : 

site index Site index - which uses tree growth as a measure of site quality Mean height of upper crown class trees that have been free to grow in an even-aged stand at a specified index age . Difficult or impossible to accurately assess site index in stands that are uneven aged, mixed species

Soil survey maps : 

Soil survey maps Soil survey maps to delineate sites of different quality. This approach proved unsuccessful Because site index varied widely within mapping (Van Lear 1991).

Guide requires the user to evaluate- soil-site properties : 

Guide requires the user to evaluate- soil-site properties The guide requires the user to evaluate soil-site properties that are grouped into three general factors: (1) geographic and topographic position, (2) soil moisture and aeration during the growing season (3)soil fertility and physical condition.

Common methods use : 

Common methods use (1)measured soil and site characteristics in a mathematical equation (2) soil mapping units (3) the presence or growth of other plant species Prediction of site index by use of soil and topographic characteristics in a multiple regression equation

New method of site quality evaluation : 

New method of site quality evaluation New method of site quality evaluation that combined both subjective and objective approaches. They first evaluated the relative importance of four major soil factors on growth of a particular species. The soil factors were: (1) Physical condition (2) Moisture availability during the growing season (3) Nutrient availability, and (4) Aeration

IMPORTANCE : 

IMPORTANCE Forest managers need site-specific information on site quality to make intelligent decisions regarding species selection and management practices.

Stand density : 

Stand density A quantitative measure of tree cover on an area The amount of tree material per unit area or space. Stands are described as Over stocked, 50% stocked, Under stocked

Measurement of stand density : 

Measurement of stand density Measures of stand density are more accurate and more useful in analysis and estimation of forest growth and yield than stocking. Stand density is a quantitative measure of density that can be expressed in absolute or relative units

Slide 13: 

Absolute measures of stand density include Basal area per acre and Trees per acre Relative measures of stand density express site occupancy as a percentage of a predetermined standard

Slide 14: 

An important role of the forester is to regulate stand density through initial planting spacing, thinning and other silvicultural practices.

Slide 15: 

1.Number of trees - which is readily determined by counting. 2.Tree size - which involves a number of factors Stem - characterised by diameter, height and taper Crown - characterised by spread and depth Root - characterised by spread and depth (both difficult to measure). 3.Spatial distribution on the ground - which is not readily determined. Generally, a square or triangular spacing is assumed. Stand density is a function of three elements:

Define maximum density : 

Define maximum density The density at which a stand undergoes substantial and continuing mortality induced by competition Changes in density may affect both the timber yield from a site and the sizes of the individual trees on it.

Stand Density Index : 

Stand Density Index This type of relative measure describes the relationship between basal area per acre (BA/A), trees per acre (TPA), and the quadratic mean diameter (QMD).

Stand density versus stocking : 

Stand density versus stocking Stand density Stand density is a absolute measurement based on basal area, number of trees per acre or volume per acre. Stand density reflects the degree of crowding of stems within a stand . Stocking Stocking is a relative term that relates a given stand density to a management objective Out of two stands with equal stand density one may be overstocked and the other under stocked

Simple measures of stand density : 

Simple measures of stand density Basal area per acre Basal area per acres is a combined measure of both, number of trees and their size Widely used because it is simple to measure via point sampling and it is highly correlated with volume and growth of forest stands

Stand density index : 

Stand density index A density measurement based on the number of trees per acre and the diameter of the average tree In 1933, Dr. Reineke examined a large number of fully stocked stands (i.e., stands without mortality due to self-thinning) He plotted the logarithm of trees/acre against the logarithm of the average stand diameter

Stand density index : 

Stand density index He found that fully stocked stands result in a straight line defined by the equation: log(Num Tree/Acre) = SpeciesConst.-1.605log (Average StandDBH) Average stand diameter is the diameter of a tree with average basal area (also referred to as the ‘quadratic mean diameter’) This is NOT the same as the average dbh

REFERENCE : 

REFERENCE Gingrich, S.F. 1967. Measuring and evaluating stocking and stand density in upland hardwood forests in the Central States. Forest Science 13:38 – 53. Krajicek, J.E., Brinkman, K.A., and Gingrich, S.F. 1961. Crown competition – A measure of density. Forest Science 7:35 – 42. Reineke, L.H. 1933. Perfecting a stand-density index for even-aged forests. Journal of Agricultural Research 46:627 – 638.

Stand density index : 

Stand density index Reineke quatified this in his stand density index (SDI) log(SDI) = log(NumTreePerAcre) +1.605log(AverageStandDBH)-1.605 SDI can be calculated for any dbh SDI is also the optimal number of trees/acre for a 10” average stand diameter Mortality (self-thinning) occurs when the SDI of a given stand is higher than the SDI of fully stocked stand for those site conditions