جستجوی مقالات مرتبط با کلیدواژه « Canopy » در نشریات گروه « اکولوژی »

The effects of flood spreading according to soil type and climate on vegetation cover of tree and rangeland species show different changes. The aim of this study was to investigate the periodic changes of vegetation including fruitful and non-fruitful cultivated trees and rangeland species in the Bam Abbarik flood spreading station. In this study, in order to perform forest studies, first the operation of locating the plots, selecting and marking the bases and preparing the certificate was carried out and rectangular parts of 350 square meters with random - systematic distribution were used. Also, in rangeland studies, 1×1 plots were used to measure canopy coved percentage and density and were recorded in the relevant tables. For measuring dry forage production, cut-off and weighing method were used. The results showed that Eucalyptus bases in this aquifer with density of 531 bases in hectare have an average height of 3.62 m and trunk diameter mean at collar site of 18 cm and the crown diameter average 3.6 m. In the study of rangeland cover, the effect of vegetative type, vegetative form, and interaction between vegetative type and vegetative form on crown was significant. Also, the effect of vegetative form, interaction of vegetative type in channel, channel interaction in vegetative form and vegetative form and channel interaction in this experiment were significant on plant density.

Estimators of distance sampling methods based on random spatial pattern of trees are bias in non-random spatial pattern. The purpose of this study was to evaluate the effect of spatial pattern of oak trees on the results of quantitative characteristics estimation of three different stands by nearest-individual method estimators in Chaharzabar  forests in Islamabad, west of Kermanshah province. For this purpose, three stands were selected in the area and within each stand half one hectare plot was identified. After full callipering of trees in the stands, according to completely randomized design, 30 samples with  nearest-individual method in each stand carried out. Then, spatial pattern, density, canopy cover and tree height were calculated with nearest-individual sampling method. Results showed that from the three studied stands, two stands had random spatial pattern and one had clumped pattern. Of  five estimators of nearest –individual method based on acceptable accuracy criteria (range ± 10%) for estimate density of trees, the formula proposed by Byth and Ripley in the random spatial pattern and the formula suggested by Batcheler and Bell in aggregate pattern were the most appropriate estimators. In order to estimate trees canopy cover percentage, the formulas suggested by Byth and Ripley, Cottam et al. and Morisita in the random spatial pattern were appropriate. However,  none of them were appropriate to estimate the canopy percentage of trees in clumped spatial pattern. To estimate the height of the trees, since the height was calculated independently of the estimators, it was found that estimation of the tree height by this sampling method yielded good results in both random and clumped patterns. Finally, it can be concluded that the spatial pattern of the trees was effective on the estimators of the nearest-individual distance sampling method.