毛乌素沙地主要固沙灌(乔)木林地水分平衡研究

以定位观测资料为基础,对毛乌素沙地流动风沙土、天然油蒿和鼻柏灌丛及沙柳和樟子松人工林下0cm-100cm风沙,1997上4月-1998年10月水量平衡进行了研究。结果表明,在0cm-100cm的土层内,土壤贮水量没有明显的贮水稳定层。流动沙丘各土层之间贮水量的变率,1997年差异较小,年平均为5.5%;1998年明显增大,年平均值为17.0%,并且最大值与最小值之间相差10%.油蒿群落土壤贮水量的变化主要发生在0cm-80cm的土层内,尤其是0cm-20cm土层变动明显,0cm-100cm土层内年均变率为16.2%;樟子松和沙柳人工林地两年贮水量变率各层次之间差异最小,年均变率分别为18.7%和14.7%;臭柏群落土壤贮水量的变化主要集中在0cm-60cm或0cm-80cm的土层内,并且以0cm-20cm和40cm-60cm土层变化较明显.土壤贮水量的变幅大小,同时受降雨量及降雨时空分布的影响,1998年度的变率明显高于1997年度。各样地土壤贮水量季节变化一般出现两个高峰.第1个高峰出现在4月,第2个贮水高峰值一般出现在7月或8月,此期间是该地区的雨季,其降雨量约占全年降雨量的46.7%,成为土壤水分的恢复补给时期。5月－7月上旬，植物进入生长盛期，耗水量增加，加之降雨补给较少，形成第1个主要失水时期；8月－10月，降雨量逐渐减少，气温和地温较高，植物枝叶茂盛，土壤蒸散量大，形成第2个失水时期，生长期内土壤总贮水量，有植被的沙地较流动沙丘低约100mm-200mm。沙地水量平衡研究结果表明：流沙的年蒸散量最小，两年平均为191.38mm，并且1997年的蒸散量大于1998年约32mm。油蒿、沙柳、樟子松、臭柏样地的蒸散量均大于流沙，而且表现出1998年度大于1997年度的特征（除樟子松外）。4种植物中，以臭柏群落蒸散量最高，年均255.25mm，其次是沙柳，年均值为277.624mm，油蒿和樟子松年均蒸散量分别为263.28mm和246.225mm。4种植物的年均蒸散量均小于同期降雨量334.3mm（均值），基本能够维持土壤水量平衡。

A STUDY ON WATER BALANCE OF MAIN FIXED-DUNE SHRUBS(ARBORS)IN MU US

On the base of located observations,soil moisture variation and water balance of shifting sandy soil and 0cm-100cm sandy soil under the shrubs of Artemisia ordosica and Sabina vulgalis, and artificial woods of Salix psammophila and Pinus syvistrisvar.mongolica had been studied from April 1997 to October 1998 in Mu Us sandy area.The results showed that there was no obvious stable water storage layer in 0cm-100cm soil.The rate of water reservation vairous in different soil layers ,varied slightly in shifting sandy dune and the year average rate was 5.5%in 1997.The rate turned obviously,the yearly average rate was 17.0%,and the difference between the maximum and minimum was 10% in 1998.The variation of soil water reservation of Artemisia ordosica population occurred mainly in 0cm-80cm soil layer,especially in 0cm-20cm soil layer,and the year average rate in 0cm-100cm soil layer was 16.2%.The year average rate of the soil water reservation of Pinus syvistris var.mongolica and Salix psammophila were 18.7% and 14.7% individually and the variations of the soil water reservation of different soil layers are the lowest.The variations of soil water reservation of Sabina vulgalis population concentrate mainly on 0cm-60cm or 0cm-80cm soil layers,especially 0cm-20cm and 40cm-60cm soil layers varied obviously.The range of soil water reservation variation was influenced by the precipitation and its distribution.The variation rate was higher in 1998 than that in 1997.There are two summits of seasonal variation of soil water reservation.One was April,another was in July or August,which was locally rainy season and it's precipitation was about 46.7% of the year's.It was the main period of the soil water resuming and compensation,from May to the first ten-day of July, plants begin growing quickly,the water consumption became larger,and the precipitation compensation was less.So this period became the first water loss period.From August to October,the precipitation became less,the air and soil temperature are higher,the leaves and branches of plants are luxuriant,the soil evaporation is larger,so this period was the second water losing period.The total soil water reservation of the sands covered with plants in growth period was 100mm-200mm lower than the one of the shifting dune.The results of water balance study showed that the year evaporation is the lowest in shifting sandy dune,and the average was 191.382mm in two years,and the one in 1997 is 32mm larger than the one in 1998.The soil evaporations under Artemisia ordosica,Sabina vulgalis,Salix psammophila and Pinus syvistris var.mongolica are larger than the one of the shifting sandy dune,and these are larger in 1998 than in 1997,except Pinus syvistris var.mongolica.Among the four plants,the evaporation of Sabina vulgalis was the highest and the year average was 285.25mm.The year average evaporation of Salix psammophila was 277.624mm,and the year average evaporation of Artemisia ordosica and Pinus syvistris var. mongolica were 263.28mm and 246.225mm individually.The year average evaporation of the four plants are smaller than year average precipitation.So the soil water reservation can maintain balance.