毛乌素沙地油蒿(Artemisia ordosica)群落土壤水分动态特征

Soil Moisture Dynamics of Artemisia ordosica Communities in the Mu Us Sandy Land

以流动沙地作对照,在毛乌素沙地选择半固定沙地油蒿(Artemisia ordosica)群落、具生物结皮的油蒿群落和油蒿+本氏针茅(Stipa capillata)群落设置样地,以10min间隔获取5、15、30、50、70cm深度土壤水分实时监测数据,分析生长季不同植被覆盖下沙地土壤水分动态变化特征。结果表明:(1)4个样地均为秋季储水量最大,油蒿+本氏针茅群落0~80cm层土壤储水能力最强,平均增加了30mm。(2)受土壤蒸发影响的同时,得不到春季小降水事件的补给,流动沙地20~60cm层春季土壤含水量只有4%,生长季波动明显,呈双峰型,0~20cm层和60~80cm层土壤含水量较稳定;半固定沙地油蒿群落0~60cm层土壤含水量长期处于6%左右,60~80cm层春季最低、夏季和秋季得到较好的补给,呈双峰型;具生物结皮的油蒿群落0~10cm平均土壤含水量大于10~20cm层,0~10cm层土壤水分受生物结皮影响呈双峰型,而10~60cm土壤水分较稳定,呈单峰型,60~80cm层土壤含水量在春季最低,呈双峰型;油蒿+本氏针茅群落土壤持水性有明显增加,夏季和秋季土壤含水量可长期处于12%~14%,呈明显的双峰型,而60~80cm土层得不到充分的降水补给,长期处于4%左右,呈单峰型。(3)不同植被覆盖的沙地土壤水分对30mm左右降水的响应深度不同,流动沙地可到70cm,半固定沙地油蒿群落到50cm,具生物结皮的油蒿群落到30cm,油蒿+本氏针茅群落到40cm;极端降水能够影响所有样地0~70cm土壤含水量。

Soil moisture content of the 5,15,30,50 and 70cm soil layers was continuously measured at 10-min intervals for four sites:shifting dune(I),Artemisia ordosica community in semi-fixed dune(II),A.ordosicacommunity with biological soil crusts(III),and A.ordosica +Stipa bungeanacommunity(IV),in the Mu Us Sandy land of Inner Mongolia,to determine soil moisture dynamics during the growing season under different land coverage.The results indicated that:(1)Soil moisture storage capacity was largest for all sites in autumn,while the capacity of the A.ordosica+ Stipa bungeana community was the largest of all the sites,at least 30 mm larger than that of the other sites.(2)Influenced by soil evaporation and lacking the replenishment of small rainfall in spring,soil moisture content of the 20-60 cm soil layer in the shifting dune was only 4%and showed substantial variation during the whole growing season,while the soil moisture contents of the 0-20 cm and 60-80 cm layers were much more stable.Soil moisture content of the 0-60 cm soil layer in the A.ordosicacommunity in semi-fixed dune was about 6%for the majority of the study period and was unimodal.Soil moisture content of the 60-80 cm layer was bimodal,showing minimum moisture content in spring and replenishment of moisture content in summer and autumn.Average soil moisture content of the 0-10 cm layer in A.ordosicacommunity with biological soil crusts was more than for the 10-20 cm soil layer.With the influence of the biological soil crusts,soil moisture content of the 0-10 cm layer was bimodal,while the moisture content in the 10-60 cm layer was stable and unimodal.Soil moisture content of the 60-80 cm soil layer was bimodal and lowest in spring.Water holding capacity of A.ordosica+S.bungeanacommunity was significantly increased compared with the other sites.Soil moisture content of the 0-60 cm soil layer was 12% to 14%for most of the summer and autumn,and showed a distinct bimodal pattern during the growing season.Because of a lack of adequate replenishment from precipitation,soil moisture content of the 60-80 cm soil layer was unimodal and steady at about 4%.(3)Soil moisture content after individual precipitation was different by about 30 mm in sites of different land coverage.Precipitation could influence soil water down to 70,50,30,and 40 cm for shifting dune,A.ordosicacommunity in semi-fixed dune,A.ordosicacommunity with biological crusts,and A.ordosica+S.bungeanacommunity,respectively.Extreme precipitation could rapidly affect the soil layer down to 70 cm in all sites.