The multiple functions of alder in the social-economy and ecology widely recognised by local people make the alder based rotation and inter-cropping system popular in the Himalaya region from North Pakistan to South-west China and Burma. Alder (Alnus nepalensis) is a native tree species wildly grown in the Himalaya and Hengduan region. Alder trees grow rapidly and are symbiotically nitrogen-fixing, they produce huge quantities of high quality leaf litter which promotes soil enrichment. The patterns of this alder based system are diverse and flexible in different ethnic areas. Crop choice differs at household level. Traditionally, local people apply the leaves of alder as an organic substitute of livestock manure. The fertility of 1,000kg dry leaves of alder is equal to 14.3kg of nitrogen, 2.4kg of phosphorus and of 2.2kg potassium without any pollution of the soil and natural environment compared to the application of chemical fertilizers. This is a most important ecological benefit from alder based agricultural systems.

In recent years people have developed several alternatives to the traditional alder system, these are, however, often not sustainable. It is, therefore, important to preserve the traditional system and its associated indigenous knowledge for the future.