浑善达克沙地三种生境中不同植物的水分生理生态特征

Hydrological characteristics of different species in three habitats of Hunshandak Sandland

对浑善达克沙地固定沙丘、丘间低地和湿地 3种生境中 83种植物的叶片渗透势 (Ψs)和含水量 (L WC)进行了对比研究 ,结果表明 :各生境下植物Ψs之间差异显著 (P<0 .0 1 )。固定沙丘的小叶锦鸡儿 (Caragana microphylla)Ψs最低 ,为 - 6 .5 4 MPa;湿地的湿车前 (Plantago cornuti)最高 ,为 - 0 .6 3MPa。 4 3%的植物 Ψs变化于 - 1 .0 0至 - 1 .99MPa之间 ,33%的植物变化范围为 - 2 .0 0至 - 2 .99MPa。 L WC变化也很大 ,小叶锦鸡儿最低 ,为 2 6 % ;而碱蓬 (Suaeda glauca)和钝叶瓦松 (Orostachysmalacophyllus)的则很高 ,分别为 98%和 97%。统计表明 ,85 %植物 L WC变化于 6 0 %至 89%之间。就生活型而言 ,灌木 Ψs最低 ,乔木次之 ,草本植物最高。在不同生境中 ,植物Ψs随生境土壤水势 (Ψsoil)升高而增加 ,其中乔木和灌木Ψs变化趋势为 :固定沙丘 <丘间低地 (P<0 .0 1 ) ;草本植物为 :固定沙丘 <丘间低地 <湿地 (P<0 .0 1 )。叶片含水量随生活型及生境的变化与渗透势相似。植物叶片渗透势与根系分布深度呈极显著负相关 (P<0 .0 0 1 ) ,而叶片渗透势与含水量呈显著正相关 (P<0 .0 1 )。

Hunshandak Sandland in Inner Mongolia of China distributes in typical grassland. It is often sensitive to environmental changes, also lack of precipitation that restricts to the native plants to develop regularly. However, over grazing has induced serious grassland degradation in the past few decades here. For the serious sandstorm occurred frequently in north China, Hunshandak Sandland has been widely blamed as one of sandstorm centers. Therefore, it is urgent to take imperative measures for the restoration of degraded land there. For this purpose, the natural plant species should be the first selection rather than introducing merely exotic species. As far as natural vegetation is concerned, water is the most restrictive factor in controlling the growth and distribution of plant species in an arid or semi-arid region. So it is necessary to explore the hydrological and other relative features characteristics of the natural in order to fully understand how the native plants response to their habitats. Also such findings will offer the scientific basis for the restoration of the degraded sandlands. Hence, in this paper, the leaf osmotic potential (Ψ s) and leaf water content (LWC) of 83 species have been investigated in the three main habitats of Hunshandak sandland, i.e. fixed sand dune, lowland and wetland. The relationships between Ψ s of individual plant and its rooting depth, LWC, as well as growth forms and habitats were also examined. The Ψ s values of the 83 species varied from -6.54 MPa (Caragana microphylla) to -0.63MPa (Plantago cornuti) (P<0.01). Among all species measured, 43% had the value of Ψ s from -1.00 MPa to -1.99 MPa, 33% between -2.99 and -2.00MPa, 18% above (-1.00MPa) and 6% below -3.00MPa. LWC varied from 26% of Caragana microphylla in fixed sand dune to 98% of Suaeda glauca at lowland. Orostachys malacophyllus with CAM photosynthetic pathway also had a high LWC of 97%. LWC values of 85% species were between 60% and 89%. For different growth forms, shrubs usually had the lowest Ψ s, while grasses showed the highest values. In fixed sand dune and lowland, the Ψ s values of different growth forms were ordered as follows: shrubs<trees<grasses(P<0.01). Accordingly, similar trends were noted in LWC of different growth forms. Ψ s increased when the soil water potential (Ψ (soil)) elevated from fixed sand dune, via lowland to wetland. For grasses, the order appeared, fixed sand dune<lowland<wetland(P<0.01). However, both trees and shrubs had higher Ψ s in fixed sand dune than in lowland. Moreover, analogous trends of LWC to those of Ψ s were recorded among three growth forms along different habitats. We also found in this study that the leaf osmotic potential decreased with the increase of rooting depth, a negative correlation existing between rooting depths and Ψ s for all species (P<0.001). Nevertheless, a positive relationship between Ψ s and LWC was found in all habitats (P<0.01). Such findings may explain the long-term adaptation strategies of various plants to frequent drought in sandland areas.