In Tibetan Buddhism, the Refuge Tree, (alternate English renderings: Refuge Field, Merit Field, Field of Merit: 'field' is a rendering of the Sanskrit "kshetra"), may be represented on a thangka as a mnemonic device and precursor to being fully visualized by the sadhaka during advanced Refuge Formula or evocation, the lineage of gurus and transmission of teachings is depicted in visual form as a visual mind map. Refuge tree and merit fields, as mandala, are Pure lands.
Each denomination or sect, and even each lineage or disciplic succession or Parampara has a "genealogical" chart that has come to be rendered into English under a number of names, principally Refuge Tree or Refuge Field. In this Refuge Tree are represented the founders and teachers in a tree diagram or fractal arrangement that symbolizes the interconnectedness of the various groups and constituents and as it takes a branching form is iconic of a tree and growth patterning.
The Field of Merit (Tibetan: ཚོགས་ཞིང་།, Wylie: tshogs zhing) is a pictorial representation in tree form of the "Three Jewels" (skt. Triratna) and the Lama (skt. Guru), employed in Tibetan Buddhism as an object of veneration when taking Refuge. Each school or sect has its own distinctive form of the tree in which the numerous lineage-holders or vidyadhara and Dharma Protectors or dharmapāla are represented.
The merit field (tshogs zhing, that is the source of all the accumulation of merit, designates the manifestation of the Three Jewels (Buddha, Dharma, Sangha) and of the Three Roots (Guru, Deva, Dakini) visualised by the practitioner.
Santina (1997: p.227) states that:
Within the context of Tibetan Buddhism, the importance of lineage extends far beyond the ordinary sense of a particular line of inheritance or descent. Lineage is a sacred trust through which the integrity of Buddha's teachings is preserved intact as it is transmitted from one generation to the next. The vital link through which the spiritual tradition is nourished and maintained is the profound connection between an enlightened master and perfectly devoted disciple. The master-disciple relationship is considered extremely sacred by all the major schools of Tibetan Buddhism.