This study investigates responses in the leaf anatomy of Black Locust (Robinia pseudoacacia L.) to the atmospheric pollutants, SO 2 , NO 2 and O 3 and climate in Tehran. The anatomical variables studied include thickness of the leaf lamina and of its main constituent tissues and the length and density of stomata. We present evidence that, in response to urban air pollution, the spongy mesophyll layer is thinner, the upper cuticle of the leaf thicker and stomatal density and the ratio of palisade parenchyma to spongy parenchyma are increased. Similar responses were also detected in relation to a climatic gradient. Stomatal density and thickness of the leaf lamina and of its mesophyll layer were all higher under warmer drier conditions. This overlap in anatomical response to two very different suites of environmental variables may reflect a functional overlap between mechanisms designed to restrict water loss in dry climates and those that minimize the uptake of toxic gases in polluted habitats.

Problem statement: Leaf phenology describes the seasonal cycle of leaf functioning and is essential for understanding the interactions between the biosphere, the climate and biogeochemical cycles. This study aimed to quantify changes in plant phenology of deciduous broadleaf forests between the years 1982-1999 and investigate the relationships between the onset dates of phenology and climatic factors. Approach: We studied the climate changes effected on the growing season duration in vegetation of Iran, using the AVHRR/NDVI biweekly time-series data collected from 1982-1999 and concurrent mean temperature and precipitation data. The first estimated fastest changes of NDVI corresponded to the vegetation green-up and dormancy from the seasonal cycle of NDVI during 1982-1999. The onset dates of vegetation green-up and dormancy were determined based on the estimated rates and the NDVI seasonal cycles. Results: The results showed that over the study period, the growing season duration has lengthened by 0.94 days year

Physiographic factors along with edaphic conditions play a crucial role in establishment of plant species throughout a region. Identification of the most effective factors is of high importance in sustainable management of a forest ecosystem. This study aims to investigate the relationships between understory vegetation and some environmental factors in natural forest ecosystems. This study has been carried out among the Fagetum orientalis communities of Ramsar Region, located in the north of Iran. For this purpose, 105 releves were sampled by a randomizedsystematic method throughout the study area, using the Braun-Blanquet scale. Physiographic parameters such as elevation, as well as slope and orientation were measured. By identification of the herb-layer vegetation contained in each sampling, vegetation composition and cover abundance of species were separately identified. Then, the aforementioned properties of soil were entirely measured in the taken samples. Cluster analysis and detrended correspondence analysis have been applied to classify the site. Moreover, in order to determine the relation between species composition and environmental factors, canonical correspondence analysis was used. Results showed a significant relation between distribution of plant types and environmental factors. Eventually, environmental factors including slope, orientation, silt percent, pH, organic matter and soluble phosphorous were among the most effective factors in establishment of Hedera pastuchowii, Solanum kieseritzkii, Oplismenus undulatifolius, Sedum stoloniferum, Rubus hyrcanus and Saxifraga cymbalaria species.

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