中文摘要：

为了揭示青藏高原三江源区草地退化对生态系统地表反照率的影响，利用2006年12月至2007年11月一整年的观测数据，分析了地表反照率的季和日变化特征及其影响因子。退化草地生态系统的年均地表反照率为0．22，生长季（5～9月）的平均地表反照率为0．18，非生长季为0．25。在植物生长初期的5月，地表反照率主要受土壤水分影响，5月末至6月初出现全年最低值；植物生长旺季的7～8月，受植被的影响地表反照率相对较稳定，并略高于生长季中其它各月。地表反照率的日变化呈“U”型，阴天的地表反照率高于晴天。全年地表反照率出现的最大频率集中在0．20附近，非生长季在0．22附近，生长季在0．18附近。退化草地生态系统生长季地表反照率的变化受土壤水分和植被的的影响，而非生长季受积雪的影响较大。

英文摘要：

To examine the albedo characteristics of degraded grassland ecosystem in the source region of the three rivers in the Qinghai-Tibetan Plateau, the seasonal and diurnal variations of albedo and its affecting factors were studied using the data measured from December 2006 to November 2007. The annual average albedo of degraded grassland ecosystem was 0.25, with the average value of 0.18 in growing season （from May to September） and 0.25 in non-growing season. In the early of growth season, the albedo was dominated by soil water content, and minimum value appeared in the end of May or early of June; the albedo in the July and August for strong growing season was conservative, and little higher than in other months of growing season. The diurnal albedo showed ＂U＂ pattern, and the albedo in cloudy skies was higher than in clear skies. The highest frequency of albedo distribution was in about 0.20 for whole year, and was 0.22 in non-growing season and 0.18 in growing season. The results indicate that the albedo in growing season was strongly affected by soil water content and vegetation conditions, and the snow cover is the main factor affecting the albedo in non-growing season.