**Abstract**

Spatial and temporal variability in forest has become a topic attracting great attention regarding the role of the forest ecosystems in biogeochemical cycles, climate change and biological diversity and in human society. Advances in the natural sciences have brought insights into and a better understanding about the patterns and processes at different spatial and temporal scales. At the same time, this supports a better management of the forest ecosystems and landscapes. Variability from the tree level to the landscape is addressed. Tree characteristics and functions, forest stand dynamics and ecological succession to forest landscape ecology are put together, considering their interrelations and dependencies. Managing forest stands and variability at different scales is described and discussed, including the scope of sustainability. An evaluation of forest and landscape characteristics in Portugal is performed with propositions considering these different elements.

**Keywords:** forest ecosystems, forest management, landscape
