Effects of Sand Burial on the Survival, Growth, and Biomass Allocation in Semi-shrub Hedysarum laeve Seedlings

Hedysarum laeve Maxim. (Leguminosae) is one of the major species used frequently in revegetation of dune_field in the sandlands of the northern part of China by means of aerial sowing. Seedlings of the species after emergence above the sand surface may be buried in sand to various depths during its establishment in late spring and early summer. A study was made to examine the effects of sand burial at different levels of 0 (control), 33%, 67%, 100% and 133% of their shoot height, on the survivorship, growth, and biomass allocation pattern of H. laeve seedlings (one and two weeks old after emergence). When burial depth was up to 100% of their shoot height, about 70% seedlings died; and the burial at depth of 133% of their shoot height led to death of all seedlings. When seedlings was buried at depth of 33% and 67% of their shoot height, respectively, after six_week growth, their biomass of whole plant, blade, and root and relative growth rate were higher than the unburied counterparts. The seedlings in both 33% and 67% sand burial treatments did not significantly change their biomass allocation pattern comparing with the unburied ones. Furthermore, the number of leaves and shoot height of the seedlings in both 33% and 67% sand burial treatments were not significantly different from those of unburied individuals, respectively. The newly born leaves of the surviving seedlings, in 33%, 67%, and 100% burial treatments, during the period of experiment, were significantly more than those in control.

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.

Relation of Wind-induced Sand Displacement to Plant Biomass and Plant Sand-binding Capacity

Desertification is a process in which vegetation cover degrades followed by increased wind and water erosion. Plants adapted to moving sand conditions are able to reverse this process. They can stabilize die substrate. Not much data is available on the soil stabilization capacity of plants. This study was conducted to investigate the wind-induced sand displacement around plants in relation to their biomass. Sand displacement is examined in relation to the biomass allocation pattern of three different plant species. A new method was developed to experimentally investigate plant sand-binding capacity. The relationship between sand displacement and plant biomass was not linear. Apart from the amount of biomass, species-specific plant characters like the biomass allocation pattern and plant structure may be very important in determining the sand-binding capacity.