摘要：Remote sensing and aerial photography are means of exploring, studying and estimating vegetation variables such as species frequency and density in forests and rangelands. Common remote sensing images usually offer general information about vegetation parameters. For detailed information about vegetation (e.g. estimation of vegetation density and/or frequency), larger scale images are needed. The present research was conducted to estimate the density of rangeland vegetation in Inche Boroon area, north of Gorgan city. Using aerial photographs acquired from digital camera mounted on a tittered balloon in different flight altitudes, density and frequency of the main shrub species of the studied region, Halocnemum strobilaceum , were estimated on photographs at different scales (from 1:50 – to 1:1000) and were compared with field measurements. Results showed no significant difference between the field and image estimation of density below 1:600 (heights lower than 75 m) but at lower scales the difference was significant. No significant difference between field and image estimation of shrub frequency was also observed up to the scale of 1:1000. Due to the wider field of view of photographs at smaller scales, flight heights of 75 m and 130 m are thus suggested as the appropriate heights to estimate Halocnemum strobilaceum density and frequency respectively in the study area.
