Key;
Laboratory;
of;
Desert;
and;
Desertification,;
Cold;
and;
Arid;
Regions;
Environmental;
and;
Engineering;
Research;
Institute,;
Chinese;
Academy;
of;
Sciences,;
Lanzhou,;
Gansu;
730000,;
China;
疏勒河流域; 沙质荒漠化; 评估; 三北防护林工程; 沙化土地; 农业生产方式; 人类活动; SDL;