Method for determining forest gap area lower limit

Abstract

The invention discloses a method for determining a forest gap area lower limit. The method comprises the steps of: performing treading in the target area forest, and selecting a typical sample plot ora sample line capable of representing the area forest to perform crown gap quantity statistics; shooting a hemispherical image, wherein the principle is that: the area of the crown gap is measured according to the projection principle of a fisheye lens on the basis of a hemispherical image which is vertically and upwards shot in a forest gap; calculating the total area of crown gaps in the sampleplot or on the sample line; according to the total area of the crown gaps and the total number of the crown gaps, calculating an average crown gap area; calculating a crown gap area standard deviation; and representing the upper limit of the confidence interval of the crown void area, namely the lower limit of the forest gap area, by using the sum of the average crown void area and the standard deviation of the canopy void area. The method can be used for accurately representing the characteristic parameters of the forest gap area, so that the lower limit of the forest gap size can be objective and quantitative, a unified standard is provided for different forest gap researches, and the disordered situation of determining the lower limit of the forest gap area in the forest gap research field is changed.

Description

technical field [0001] The invention relates to a method for determining the lower limit of area, in particular to a method for determining the lower limit of gap area. Background technique [0002] Forest gaps are common small-to-medium-scale disturbances in forests. They are special canopy gaps that can significantly increase the light intensity in the forest, thereby changing the composition of different light-demanding plants in the forest, and play an important role in forest regeneration and succession. , while ordinary canopy gaps have no significant effect on this. Gap size, shape, edge tree height, etc. are considered to be the main characteristic factors affecting gap regeneration; among them, gap size is the most important index to evaluate the environmental heterogeneity and resource allocation of gaps. The earliest term "forest gap" appeared in the term "Storm gapstructure" in Secrader's 1936 Norwegian spruce paper; Disturbance (small-scale such as tree lodgin...

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Problems solved by technology

However, since the concept of forest gaps has not been quantified, how to distinguish the difference between forest gaps and ordinary forest canopy gaps has become a difficult point in field research on forest gaps

This also leads to different setting of the lower limit of gap size in different studies. For example, Brokaw (1982) set the lower limit of gap size to an area of ​​20m2, Veblen (1985) set it to an area of ​​25m2, Nakashizuka et al. (1995 ) and Schliemann&Bockheim (2011) set the area as 10m2. Runkle (1992) believed that the lower limit of the gap size is the size of a circle with a diameter of 1 / 2 canopy tree. Some scholars also use the smallest pixel of remote sensing images as the lower limit of the gap size (Betts et al., 2005; Kellner et al., 2009; Vepakomma et al., 2008); although the above-mentioned lower limit of forest gap size is quantitative, it lacks scientific basis and uniform standards

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