Artemisia Ordosica Research Articles

Long-term effects of revegetation on soil water content of sand dunes in arid region of Northern China

Desert is a challenging environment for organisms largely controlled by extreme abiotic factors including soil water content. The objectives of this study were to: (1) determine the effect of vegetative water utilization on soil water content; and (2) monitor the long-term vegetative response to the change of soil water content after establishing the revegetation of sand dunes of the Shapotou Region in the Tengger Desert, Northern China. The permanent revegetation plots were established in different sites in 1956, 1964, 1976 and 1982. Soil water content was monitored at 20 cm intervals of 10–300 cm in depth. Water content in sand dunes, was measured gravimetrically after 24-h desiccation at 105°C during the entire period of revegetation through the year to 2000. Our data show that soil water contents rapidly decreased at 9–10 years after revegetation, and similarly the vertical profile of soil water contents also decreased by depth. Annual precipitation is positively correlated with the water contents at depths 0–40 cm, although no clear-cut relationship was shown between precipitation and soil water at the deeper soil layers (from 40 to 300 cm). It is therefore concluded that water utilization of different plant species: shrub with deep-rooting system and annual plants with shallow-rooting system influences the spatial distribution of water inside the soil profile. Temporal and spatial variances of soil water also affected the changes in composition, coverage and biomass of vegetation. Vegetation composition of dominant species has successively changed from all shrub species, such as Caragana korshinskii and Hedysarum scoparaium to annual plants and shrub with shallow-rooting system ( Artemisia ordosica). The shrub biomass also changed along with soil water content, although the biomass of herb species increased over time. After 45 years, the shrub coverage decreased from the highest average 30.21% to the current level of 6%, whereas herb coverage increased over time. The soil water content was, however, kept relatively constant at lower level (1.23%) despite shrub coverage was reduced to about 6%. These results provide important baseline information for establishing vegetation and utilization of limited water resource in arid desert regions.

WATER UTILIZATION OF NATURAL AND PLANTED TREES IN THE SEMIARID DESERT OF INNER MONGOLIA, CHINA

We used stable isotope techniques to investigate water utilization of two native trees, Sabina vulgaris Ant. and Artemisia ordosica Krasch., and one introduced tree, Salix matsudana Koidz., in the semiarid Mu-Us desert, Inner Mongolia, China. The study site was in a region where there has been a decline in agricultural productivity, caused by severe desertification over the past several decades. S. matsudana is used extensively for reforestation to protect farms and cultivated lands from shifting sand dunes. We identified water sources for each tree species by comparing the stable isotopes δD and δ18O in water in stems, soil, and groundwater. We also measured δ13C levels in leaves to evaluate the intrinsic water-use efficiency (WUE) of each plant. Comparison of isotopes showed that S. vulgaris and S. matsudana consume relatively deep soil water as well as groundwater, whereas A. ordosica uses only shallow soil water. The δ13C measurements indicated that S. vulgaris has exclusively high WUE, whereas that of the other species was typical of temperate-region C3 plants. The water source data plus WUE data suggest that planted S. matsudana uses groundwater freely, whereas native plants conserve water. Thus, reforestation with S. matsudana might cause irreversible groundwater shortages. Corresponding Editor: E. A. Holland.

Alleviatory effects of calcium on the toxicity of sodium, potassium and magnesium chlorides to seed germination in three non-halophytes

AbstractSaline soils contain numerous salts with varying impact on seed germination. Seeds of three non-halophytic species found in Chinese sandy deserts (Artemisia ordosica, Aristida adscensionis and Bassia dasyphylla) were incubated in salt solutions (NaCl, KCl or MgCl2, each with or without CaCl2) at 20°C in the dark. The effects of each salt on the percentage of seeds from which visibly detectable radicles emerged, and the percentage of seeds with emerging radicles surviving to a length of at least 4 mm, were examined. NaCl, KCl and MgCl2 were toxic to emerging radicles in all three species, but before radicle emergence these salts reduced seed germinability only in A. ordosica. The toxic effects of each salt on the radicles were alleviated in all three species by the addition of low concentrations of CaCl2. MgCl2 was more toxic than NaCl and KCl, and the concentration of CaCl2 needed to alleviate the toxicity of MgCl2 was several times higher than that required for alleviation of NaCl or KCl toxicity. These results suggest that Ca2+ present in saline soils alleviates the toxic effects of other salt components on seed germination, and that the results of germination experiments with a single salt are not always applicable to field conditions.

Analysis of water consumption of artificial sand-fixing plants and simulation of ecological moisture fitness

The theory and simulation of niche fitness of plant species has led to a quantitative study of the niche on the distribution regularity following limited spatial-temporal precipitation. The theory examines the constraints to plants in arid regions and the relationship between precipitation and water consumption of sand-fixing plants. The degree of ecological moisture fitness of sand-fixing plants was analyzed quantitatively and the method of simulating moisture fitness degree was established. The relative computation analysis and numerical simulation were completed on the basis of experimental data. The results showed that the values of ecological moisture fitness in different experimental conditions change as a parabola, and the maximum value appears at the annual precipitation peak stage. With increasing plant densities in Caragana korshiskii (CK) or Artemisia ordosica (AO) monoculture, the value of the degree of ecological fitness decreased. The ecological fitness degree is greater in monoculture when ...

Effect of different microhabitats and stand age on survival of introduced sand-fixing plants

Survival of 24 cultivated, non-native sand-fixing plant species in the shifting sand dunes was studied. The effect of stand age on survival of Caragana korshinskii and Hedysarum scoparium did not show any significance, but the survival of Artemisia ordosica differed significantly among different stand ages. The results of variance analyses suggested that 21 species performed significant difference among the three microhabitats. Twelve plant species performed higher survival rate and survival frequency on the dune crest, five species on the dune plinth and 11 species in the dune valley. These results are meaningful for establishing artificial sand-fixing vegetation on the mobile sand land.

Plant species effect on the spatial patterns of soil properties in the Mu-us desert ecosystem, Inner Mongolia, China

Although Artemisia ordosica Krasch. and Sabina vulgaris Ant. are the dominant shrub species in the Mu-us desert ecosystem, they differ in their botanical traits. We investigated the spatial patterns of soil properties using geostatistical analysis to examine the effect of plant species on these spatial patterns. Comparison among three microsite types (under A. ordosica, under S. vulgaris, and the opening between vegetation) showed that A. ordosica generally had less effect than S. vulgaris on local soil properties. The long life-span, prostrate life-form, and evergreen leaf-habit of S. vulgaris may lead to a higher accumulation of organic and fine materials under S. vulgaris. The range of spatial autocorrelation found in the mass of organic matter on the soil surface was smaller than that of the coverage of S. vulgaris (11.5 m) which corresponded to the canopy patch size of this species, and was longer than the canopy patch size of A. ordosica. The ranges of total C and N, and pH (11.7–15.6 m) were similar to that of S. vulgaris. The range of available P (106.3 m) was comparable to that of the coverage of A. ordosica (86.2 m) considered to be the scale of the distribution of this species. The ranges of silt+clay and exchangeable K, Ca, and Mg (31.0–46.7 m) were not related to plant presence, and were similar to that of topography (43.1 m).

Seed Germination of Chinese Desert Plants

To investigate the effects of global warming on the germination behavior of Chinese desert plants, responses of seed germination to temperature, light illumination and water and salt stresses were examined on Artemisia ordosica and Lespedeza davurica. The optimal temperature for germination was 20°C for both species. In the dark condition, the final germination rates were higher than 50% under temperature regimes in the range of 15-30°C for A. ordosica and 10-30°C for L. davurica. This result shows that seed germination of both tested species are relatively insensitive to changes in temperature. Both water and salt stresses resulted in decreases in final germination rates and retardation of germination in both species. Seed germination of L. davurica was less affected by both stresses than that of A. ordosica. Although some A. ordosica seeds germinated when they were wetted with NaCl solutions having water potentials of -0.3--0.6MPa, most of the radicles subsequently died in these media. This result suggests that salinization of the soil is critical for the survival of this species. It was concluded that although a temperature rise by itself does not much affect the germination behavior of these species, changes in seasonal distribution of rainfall events and salinization of the soil caused by climate change can have crucial effects on their distribution.

Ecophysiological behavior of Artemisia ordosica on the process of sand dune fixation

AbstractThe population structure and water relations of Artemisia ordosica were studied at different stages of the sand dune fixation process. Vegetation coverage and biomass increased as the sand dune fixation process progressed. In contrast, individual growth rate decreased in the late fixation stage. On fixed sand dunes the modal age of A. ordosica plants was higher and seedlings or saplings were rearely observed. On active sand dunes, settlement of seedlings was regulated by sand mobility; that is, seedlings were observed only when sand mobility was below 10 cm per year. Leaf transpiration was highest in active sand dunes. Stand transpiration in fixed sand dunes was lower than in semi‐fixed sand dunes. These differences in transpiration were related to a decrease in soil water availability, which was affected by the increase in the aeolian fine soil component during the course of sand dune fixation. The reduction in soil water status and the cessation of sand movement were considered to be important factors in the decline of the Artemisia ordosica community.