Responses of Hedysarum Laeve,a guerrilla clonal semi-shrub in the Mu Us Sandland,to local sand burial

In arid and semi-arid inland deserts,one of the environmental stresses for plants is recurrent sand burial,which can influence the physical and biotic microenviron-ments of the plants and soil.Previous studies have shown that different levels of sand burial have different effects on plants.Slight sand burial could increase the height increment,leaf biomass and the number of new ramets of the plants while heavy sand burial could impair the growth of the plants and even decrease their chances of survival.In other words,below a certain threshold level of burial,the growth of plants is stimulated probably because of multiple factors.However,as the level of burial increases,the positive response starts to decline until it becomes a negative value.Arid and semi-arid inland deserts are frequently colonized and stabilized by many rhizomatous clonal plants.Clonal physiological integration often helps clonal plants buffer local environmen-tal stress encountered by ramets.A rhizomatous clonal semi-shrub,Hedysarum laeve(H.laeve),is the dominant plant species and important for vegetation restoration in the Mu Us sandland.To investigate whether clonal integration can increase the threshold of sand burial and help rhizomatous H.laeve tolerate heavy sand burial,we conducted a field experiment.The results showed that slight sand burial could accelerate ramet growth and enhance leaf biomass,stem bio-mass and shoot biomass,while heavy sand burial reducesed the biomass of the plant and impairs survival and growth of the ramets.Clonal integration increased the threshold of sand burial.Under heavy sand burial,ramets connected to other ramets not buried in sand were more in terms of height increment,stem biomass,leaf biomass and shoot biomass compared to the ramets encountering sand burial but disconnected from other ramets.It suggested that clonal physiological integration could help H.laeve ramets tolerate relatively heavy sand burial.We also discussed that clonal integration plays a role in H.laeve presence in the Mu Us sandland.

毛乌素沙地游击型克隆半灌木羊柴对局部沙埋的反应

不同程度的沙埋是生长在于旱和半干旱区内陆沙丘的植物经常遭遇的事件，沙埋可以改变植物所处的生物和非生物环境条件。已有研究表明不同程度的沙埋对于植物的影响不同。轻微程度的沙埋可以增加植物高度、促进生物量的积累和新生分株的产生。如果沙埋强度不断增加，对植物的影响由正效应逐渐转变为负效应。即超过一定沙埋阈值后，沙埋会削弱植物的生长，甚至影响植物的存活。干旱和半干旱区内陆沙丘中常常生长着许多克隆植物，克隆整合常常可以缓解克隆植物分株所遭受的局部环境胁迫。根茎型克隆植物羊柴（Hedysarum laeve）是毛乌素沙地的优势半灌木之一，也是当地重要的固沙植物。为了探讨克隆整合的作用是否可以提高沙埋阈值，并有助于羊柴忍受高强度的沙埋，以其为研究对象开展了野外实验。结果表明：轻微程度的沙埋（例如沙埋深度是原始羊柴分株高的10％-20％）可以加速羊柴分株的高生长，提高叶片生物量、茎生物量以及整个地上部分的生物量。高强度的沙埋（例如沙埋深度是原始羊柴分株高的80％-100％）会削弱羊柴分株的存活和生长。在与不遭受沙埋分株相连的情况下，羊柴分株遭受沙埋的阈值高于没有分株相连的，而且在高强度的沙埋下，前者（有分株相连的遭受沙埋的分株）比后者（没有分株相连的遭受沙埋的分株）在株高增量、茎生物量、叶片生物量以及地上分株生物量上都要显著高。这暗示着克隆整合提高了羊柴遭受沙埋的阈值并有助于羊柴分株忍受高强度的沙埋。