司马迁规划的农牧地区分界线在黄土高原上的推移及其影响

司马迁规划的由碣石至于龙门的农牧分界线，是适合于生态环境的。当时如此，后世亦然。在农耕操作尚稽留在粗放经营的时期，为农为牧都不能过分超越这条分界线。过分超越就会促成这条分界线的移动，从而影响到生态环境的平衡发展，引起不良的后果。这条分界线绝大段落经过黄土高原，黄土高原沟壑纵横，甚至于黄河的溃决泛滥，都与这条分界线的移动有关，是不应稍事忽视的。

The Boundary between the Farming and Pasturing Areas on the Loess Highlands

The boundary marked out by Sima Qian between the farming and pasturing areas was in accordance with the physical environment of the Loess Highland. Not only the farming but also the ha-pasturing areas should not spread excessively and unreasonably, when the extensive agricultural techniques were adopted as the primary farming means, in order to avoid some ecological problems. The-development of ravines and gullies on the Loess Highland and even the floods were related with the change of this dividing line in history.