Effects of density, shrub-herb coverage and trunk shape on the in-forest patch index of planted Pinus tabuliformis forests

ObjectiveStand density, shrub-herb coverage and trunk shape are important factors affecting the in-forest landscape quality. It is expected that the formation mechanism of the landscape quality in artificial forest of Pinus tabuliformis in Beijing could be discussed from the perspective of changing landscape index of the color patch.

MethodBy analyzing the structure characteristics of forest landscape patches of color images, the effects of stand density, shrub-herb coverage and trunk shape changes on the in-forest patch index were studied.

ResultThe stand density had a significant influence on splitting index (SPI), and SPI decreased with the increase of density; shrub-herb coverage had significant influence on aggregation index (AI) and landscape shape index (LSI), and both indexes increased with the increase of shrub-herb coverage. Trunk shape had a very significant effect on Simpson's evenness index (SIEI) and a significant influence on LSI. LSI was higher when the trunk shape was both bend and straight, SIEI was higher when the trunk shape was straight. The interaction of stand density and shrub-herb coverage had significant effect on LSI, SPI, SIEI, the three indexes all decreased with the increase of stand density, and increased with the increase of shrub-herb coverage. The interaction of stand density and trunk shape had significant influence on LSI, SIEI, two indexes decreased with the increase of stand density, the value of LSI was larger when the trunk was both bend and straight, the value of SIEI was larger when the trunk was straight. The interaction of shrub-grass coverage and trunk shape had a significant influence on SIEI, SIEI increased with the increase of shrub-herb coverage, and the value of SIEI was larger when the trunk was both bend and straight.

ConclusionStand density, shrub-herb coverage, trunk shape and their interactions all had significant influence on forest landscape index. The main reason was that the change of structural elements caused the change of the number and the shape of the patches in the visual field, and then caused the change of plaque index.