Estimating and mapping forest biomass using regression models and Spot-6 images (case study: Hyrcanian forests of north of Iran) Mohadeseh Ghanbari Motlagh & Sasan Babaie Kafaky & Asadollah Mataji & Reza Akhavan Received: 16 January 2018 /Accepted: 11 May 2018 # Springer International Publishing AG, part of Springer Nature 2018 Abstract Hyrcanian forests of North of Iran are of great importance in terms of various economic and environmental aspects. In this study, Spot-6 satellite images and regression models were applied to esti- mate above-ground biomass in these forests. This research was carried out in six compartments in three climatic (semi-arid to humid) types and two altitude classes. In the first step, ground sampling methods at the compartment level were used to estimate aboveground biomass (Mg/ha). Then, by reviewing the results of other studies, the most ap- propriate vegetation indices were selected. In this study, three indices of NDVI, RVI, and TVI were calculated. We investigated the relationship between the vegetation indices and aboveground biomass measured at sample-plot level. Based on the results, the relationship between aboveground biomass values and vegetation indices was a linear regression with the highest level of significance for NDVI in all compartments. Since at the compartment level the correlation coefficient between NDVI and aboveground biomass was the highest, NDVI was used for mapping aboveground biomass. According to the results of this study, biomass values were highly different in various climatic and altitudinal classes with the highest biomass value observed in humid climate and high-altitude class. Keywords Aboveground biomass . Spot images . Vegetation indices . Hyrcany Introduction Nowadays, among the most important global concerns is the increasing trend in atmospheric carbon dioxide, global warming, and its potential for global climate change. As the largest surfaces covering the non- glacial lands of the earth, forest ecosystems absorb large amounts of atmospheric carbon dioxide via photosyn- thesis (Lorenz and Lal 2010) and by storing 86% of carbon dioxide in terrestrial lands and 73% of soil carbon (Sedjo 1993) forest ecosystems are considered to be the most important carbon sink or sponge in Environ Monit Assess (2018) 190:352 https://doi.org/10.1007/s10661-018-6725-0 M. G. Motlagh Student of Forestry, Faculty of Natural resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: mohadeseh.motlagh@gmail.com S. B. Kafaky (*) : A. Mataji Department of Forestry, Faculty of Natural resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: s.babaiek@yahoo.com A. Mataji e-mail: amataji@srbiau.ac.ir R. Akhavan Research Institute of Forests and Ranglands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran e-mail: akhavan@rifr-ac.ir