Read the extract given below and answer the question that follows:

Drought affects the life of pastoralists everywhere. When rains fail and pastures are dry, cattle are likely to starve unless they can be moved to areas where forage is available. That is why, traditionally, pastoralists are nomadic; they move from place to place. This nomadism allows them to survive bad times and avoid crises. But from the colonial period, the Maasai were bound down to a fixed area, confined within a reserve, and prohibited from moving in search of pastures. They were cut off from the best grazing lands and forced to live within a semi-arid tract prone to frequent droughts. Since they could not shift their cattle to places where pastures were available, large numbers of Maasai cattle died of starvation and disease in these years of drought. An enquiry in 1930 showed that the Maasai in Kenya possessed 720,000 cattle, 820,000 sheep and 171,000 donkeys. In just two years of severe drought, 1933 and 1934, over half the cattle in the Maasai Reserve died. As the area of grazing lands shrank, the adverse effect of the droughts increased in intensity. The frequent bad years led to a steady decline in the animal stock of the pastoralists.

The Maasai were cut off from the best grazing lands and forced to live within what kind of land tract?