Why were the Kalangs of Java known as a community of skilled forest cutters?

Why were the Kalangs of Java known as a community of skilled forest cutters?

The Kalangs of Java used shifting cultivation. They harvested teak. They were also skilled forest cutters. Without their expertise it was difficult for the king of Java to build their palaces.
They were so valuable to the king that in 1755 when the Mataram kingdom of Java split, the 6000 Kalang families were equally divided among the two kingdoms. Thus, the 7 Kalangs were regarded as the skilled forest cutter community.