多枝柽柳水分利用策略对沙堆堆积过程的响应

Response of water use strategies of Tamarix ramosissima to nebkhas accumulation process

多枝柽柳(Tamarix ramosissima)作为干旱荒漠区的优势树种,其与风沙长期作用过程中形成了柽柳沙堆,研究沙堆上多枝柽柳水分利用来源及其对各水源的利用比例,可为干旱荒漠区原生植被的保护及恢复提供科学依据。该研究以空间序列代替时间序列的方法,通过野外调查及室内模型分析,解析了不同发育阶段沙堆上多枝柽柳的水分来源及其对各水源的利用比例,揭示了沙堆堆积过程中多枝柽柳的水分利用策略。结果表明:(1)多枝柽柳沙堆土壤水分含量随沙堆堆积增高而存在较大差异,且0-500 cm层土壤平均水分含量依次为雏形阶段(4.57%)>增长阶段(4.46%)>衰退阶段(3.62%)>稳定阶段(3.48%);(2)雏形及增长阶段沙堆土壤含水率在40-180cm层显著升高,稳定及衰退阶段沙堆土壤含水率分别在180-360cm和360-500cm层显著升高。(3)各发育阶段沙堆上,0-40 cm层土壤含水率及稳定氧同位素比值(δ^(18)O)波动较大,季节变化明显,且随土层深度的增加δ^(18)O趋于稳定,表明表层土壤受外界环境影响较大。(4)春季,多枝柽柳在雏形阶段沙堆上主要利用360-500 cm层土壤水,其次利用0-40cm层土壤水,利用比例分别为53.1%和21.4%;增长阶段沙堆上主要利用0-40和360-500cm层土壤水,利用比例分别为53.1%和23.0%;稳定阶段沙堆上主要利用0-40和180-360cm层土壤水,利用比例分别为49.8%和29.3%;衰退阶段沙堆上主要利用360-500 cm层土壤水,利用比例为60.9%。夏季,多枝柽柳在雏形和增长阶段沙堆上主要利用360-500cm层土壤水,利用比例分别为61.1%和42.8%,且在增长阶段沙堆上还利用40-180和180-360cm层土壤水;稳定阶段沙堆上其对各层土壤水的利用较为均匀,而衰退阶段沙堆上主要吸收180-360和360-500cm层土壤水,利用比例分别为29.0%和44.1%。秋季,雏形阶段沙堆上以360-500 cm层土壤水为主要水源,增长和稳定阶段沙堆上均以180-360和360-500 cm层土壤水为主要水源,衰退阶段沙堆上主要利用360-500cm深层土壤水,利用比例高达92.3%,反映出多枝柽柳在不同发育阶段沙堆上呈现出不同的水分利用策略。

Aims Tamarix ramosissima,as the main dominant plant species in arid deserts,has formed Tamarisk nebkhas during its long-term interaction with wind-sand.The study on water sources of T.ramosissima at nebkhas and its ratio to each water source can provide scientific basis for the conservation,restoration of native vegetation in arid desert areas.Methods This study employed“space for time”methodology to clarify the water sources of T.ramosissima at nebkhas,with the ratio of each water source quantified for T.ramosissima at different developmental stages of nebkhas,through field investigation and indoor model analysis.Important findings(1)The soil moisture of T.ramosissima nebkhas varied with the nebkhas accumulation process.The average soil moisture in the 0-500 cm soil depth ranked in the order of:the embryonic stage(4.57%)>growth stage(4.46%)>decline stage(3.62%)>stable stage(3.48%).(2)The soil water content of the dunes increased significantly in the 40-180 cm layer during the embryonic and growth stages,and in the 180-360 and 360-500 cm layers during the stable and decline stages,respectively.(3)The soil water content and stable oxygen isotope ratio(δ^(18)O)in the 0-40 cm layer of the nebkhas at each stage of development fluctuated significantly with seasonal changes,and theδ^(18)O stabilized with increasing depth of the soil layer,indicating that the surface soil was influenced more by the external environment.(4)In spring,T.ramosissima mainly used the soil water in the 360-500 cm layer in the embryonic stage nebkhas,followed by the soil water in the 0-40 cm layer,with proportions of 53.1%and 21.4%,respectively;in the growth stage nebkhas,T.ramosissima mainly used soil water in 0-40 and 360-500 cm layers,with ratios of 53.1%and 23.0%,respectively;in the stable stage nebkhas,T.ramosissima mainly used soil water in 0-40 and 180-360 cm layers,with ratios of 49.8%and 29.3%,respectively;in the decline stage nebkhas,T.ramosissima mainly used soil water in the 360-500 cm layer,with a ratio of 60.9%.In summer,T.ramosissima mainly used soil water in the 360-500 cm layer in the embryonic and growth stage nebkhas,and the ratio was 61.1%and 42.8%,respectively.Tamarix ramosissima also used soil water in the 40-180 and 180-360 cm layers in the growing stage nebkhas;the use of soil water in each layer by T.ramosissima was uniform in the stable stage nebkhas;T.ramosissima mainly absorbed soil water in 180-360 and 360-500 cm layers in the decline stage nebkhas,with ratios of 29.0%and 44.1%,respectively.In autumn,the main water source of T.ramosissima on embryonic stage nebkhas was 360-500 cm soil water;soil water in 180-360 cm layer and 360-500 cm layer was the main water source for T.ramosissima in the grow and stable stage nebkhas;in the decline stage nebkhas,T.ramosissima mainly used soil water in 360-500 cm depth,and the ratio was as high as 92.3%,indicating that T.ramosissima showed different water use strategies in different development stages of nebkhas.