Final answer:
The community practices agropastoralism, combining agriculture with pastoralism, specifically engaging in transhumance to move herds seasonally for optimal grazing.
Step-by-step explanation:
The primary mode of production in the community described, where young men take herds to higher altitudes during the summer while their families grow crops and engage in trade, is agropastoralism. This form of subsistence farming combines agriculture and pastoralism, where the community engages in both raising crops and herding livestock. In the scenario you've witnessed, the movement of herds to different altitudes based on seasonal change is known as transhumance, a pattern that allows for the optimization of resources and benefits from both livestock and agriculture.