Institute;
of;
Geographic;
Sciences;
and;
Natural;
Resources;
Research,;
CAS,;
Beijing;
100101,;
China;
Institute;
of;
Tibetan;
Plateau;
Research,;
CAS,;
Beijing;
100085,;
China;
Graduate;
School;
of;
the;
Chinese;
Academy;
of;
Sciences,;
CAS,;
Beijing;
100039,;
China;
NDVI; 西藏高原; 青藏铁路; 青藏公路; 土壤覆盖层;