A typical task in wireless sensor network is to collect a data from sensor nodes towards sink. This paper shows various tree formation techniques used in the data gathering. In wireless sensor network, various data gathering techniques used that are hierarchical data gathering, chain based data gathering, tree based data gathering etc. This paper shows study on various tree formation techniques that can assist in data gathering. The data are collected from different sensors and is forwarded towards the sink node; for this purpose various tree formation techniques are used. The purpose of these techniques is to improve factors like a network lifetime, reduce an energy consumption and delay etc. Keywords: Data gathering, tree formation, network lifetime, energy consumption
