Ordosica Community Research Articles

Soil Moisture Dynamics and the Response to Precipitation in Fixed Sand Dunes of Artemisia Ordosica Community in Mu Us Sandy Land

Soil Moisture Dynamics and the Response to Precipitation in Fixed Sand Dunes of Artemisia Ordosica Community in Mu Us Sandy Land

Precipitation amount and event intervals interact to change plant diversity during dry years in a desert shrubland

Variations in species diversity and soil properties in response to future climate change is a key focus area in ecological research. The influence of precipitation amount on plant community diversity and soil properties, in sandy desert ecosystems, is poorly studied. We chose the Artemisia ordosica community to examine how diversity, and the physical and chemical properties of soil vary in response to changes in precipitation. An in situ experimental platform was used to simulate total monthly precipitation at specific intervals in a desert-grassland region of northern China. The influence of precipitation on the community was investigated using three precipitation amount levels and two intervals. The relative density, coverage, and frequency of species in each experimental quadrat was analyzed for evaluating the community structure. Results showed that variability in precipitation amounts and intervals altered the species diversity in the A. ordosica communities. Increased precipitation amount enhanced whole community’s species diversity via improving the richness of perennial forbs. Lengthening the precipitation intervals enhanced whole community’s species diversity in the context of low precipitation amount but reduced species diversity in high precipitation amount condition. The precipitation patterns affected community species composition and diversity mainly by controlling soil moisture, secondly by changing the nitrogen and organic matter content of the surficial soils. This study revealed that effects of precipitation interval on the species diversity depended on annual precipitation amount and offer an innovative insight to evaluating the succession of desert ecosystems in the context of precipitation change in the future.

Water-use characteristics of two dominant plant species in different community types in the Mu Us Desert

Shrubs are pioneer species for ecological restoration in drylands and can promote the growth of herbaceous plants. Knowledge of the water-use characteristics of these revegetated species in different community types is crucial for understanding interspecific and intraspecific interactions and guiding ecological restoration; however, few studies have focused on this process. In this study, we explored the water sources and root distribution of plants in three community types in the Mu Us Desert: a mixed community including a shrub species Artemisia ordosica and a grass species Leymus secalinus, a pure A. ordosica community, and a pure L. secalinus community. We measured the δ18O of the plant xylem and soil water within 100 cm of the soil surface and surveyed the root biomass distribution. The main water source for both A. ordosica and L. secalinus in mixed communities was from the shallow soil layer (0–20 cm) and it overlapped most of the time. When soil moisture in the shallow soil layer was low, L. secalinus still used water from the shallow soil layer, whereas A. ordosica mainly used water from the dry deep soil layer (60–100 cm). The water sources for A. ordosica were significantly different among different communities. In contrast, L. secalinus had similar water sources in different communities. We also found that the root biomass of shrubs was significantly lower in mixed communities than in pure communities. Moreover, when available soil water increased, the root biomass of grasses increased significantly, whereas that of shrubs did not significantly change. These results suggest grasses have an advantage over shrubs in competing for water and this may lead to the exclusion of shrubs from the community, and grasses dominated community. Our study can be used as a reference for assessing the persistence of shrub species to guide future ecological restoration.

The branching architecture of artemisia ordosica and its resistance to wind erosion

Different branching architectures reflect the adaptation strategies of different plants and affect their resistance to wind erosion. This study presents field-based observations that demonstrate the relationship between the branching architecture of Artemisia ordosica and its resistance to wind erosion. This species is the dominant plant species in the semi-fixed and fixed dunes of the Mu Us Sandy land. The overall bifurcation ratio (OBR) of semi-fixed sandy land is higher than the fixed sandy land 0.27; Similarly, the total stepwise bifurcation ratio (SBR) is higher than the fixed sandy land about 0.74; The length of first levels of total branches is also higher than 8.07. The aerodynamic roughness was greater than the A. ordosica community in the fixed and semi-fixed sandy land than in the bare sandy land. The airflow fields in the cross-wind direction were strongly affected by the windward shape of the plants, which became gradually narrower from the base to the top, while in the leeward direction, the wind speed at different heights behind the plant returned to the incoming airflow velocity. The result confirms that the influence of the windward shape of the plant on the surrounding airflow field is much larger than the influence of plant thickness, porosity or other factors.

Soil water use sources and patterns in shrub encroachment in semiarid grasslands of Inner Mongolia

Soil water sources for shrub encroachment in arid and semiarid regions have not been fully understood. This study used stable δ2H and δ18O isotope ratios of plants, soil water and precipitation, coupled with proportional similarity index of species to identify relations between shrub encroachment and water sources for four shrub and grass species at various shrub encroachment stages in a semiarid grassland of Inner Mongolia. We found that shallow rooted grasses (Agriophyllum squarrosum and Stipa bungeana) predominantly used shallow soil water (0–20 cm) during growing season. In contrast, deeply-rooted semi-shrubs (Artemisia ordosica and Artemisia sphaerocephala) used middle and deep soil water in July but shallow and middle soil depth water in May and September. Plants competition for soil water in different shrub encroachment stages were different depending on plant water use sources. The highest plant competition existed in the A. ordosica community in semi-fixed sandy land, followed by A. squarrosum community in shifting sandy land, A. ordosica community in fixed sandy land, and S. bungeana community in fixed sandy land. Competition for soil water and differences of water use sources of grass and shrub species were crucial in driving shrub encroachment in semiarid grasslands. Communities dominated by A. ordosica were not stable, with an increase in surface soil water availability, the dominance was replaced by S. bungeana. Our findings on the linkage between plant water use sources and patterns and shrub encroachment shall help future arid and semiarid grassland management under changing climate conditions.

Soil microbial interactions modulate the effect of Artemisia ordosica on herbaceous species in a desert ecosystem, northern China

Soil microbes are essential for enhancing the performance (i.e., recruitment and growth) of individual plants, thereby influencing the structure and diversity of plant communities. However, how soil microbes drive the plant interspecific interactions remains largely unexplored, particularly in harsh desert ecosystems. To address this knowledge gap, we examined the community composition and species interaction networks of soil bacteria using high-throughput 16S rRNA gene sequencing along a successional gradient of an Artemisia ordosica community in the Mu Us Desert, northern China. We also explored how A. ordosica affects the soil bacteria, especially keystone species, and herbaceous plants with community succession. Our main goal is to determine how soil bacteria regulate the interactions of A. ordosica with herbaceous plants. The results showed that soil bacterial community composition and main taxonomic groups were primarily influenced by the presence of A. ordosica along the successional gradient. The phylogenetic molecular ecological network analysis identified nine keystone species, with five species categorised as module hubs and four species as connectors. We found that the effects of A. ordosica on module hubs were highly correlated with its effects on soil nitrogen content and biomass of specific herbaceous plants, resulting in an increase of soil fertility and herbaceous under the shrub. These results indicated that soil bacterial interactions might be a crucial driver affecting plant interspecific interactions. Although our results highlighted the importance of bidirectional interactions between plants and soil microbes from the perspective of biotic interactions, their contribution to plant community succession still needs further confirmation through more robust evidence from future studies. However, overall our findings advanced the current understanding of plant-soil interactions on the processes of ecological restoration and desertification reversion, especially in stressful desert ecosystems.

Responses of shallow soil water content in Artemisia ordosica community to different rainfall patterns

The shrub species, Artemisia ordosica, commonly occurs in the eastern Hobq desert. Here, we used a micrometeorological observation system to continuously monitor the rainfall and soil water content in 0-10, 10-30, and 30-50 cm soil layers during the growing season from 2016 to 2018. The dynamic spatial and temporal changes in soil water content under different rainfall patterns were examined, and the replenishing effects of rainfall events on soil water content and water infiltration characteristics were analyzed. The results showed that soil water content of the surface layer in the A. ordosica community had significant seasonal and vertical variation under rainfall fluctuation. Rainfall amount and soil water content before rain were the main factors controlling soil water replenishment and infiltration. The soil surface layer (0-10 cm) was sensitive to rainfall, and the rainfall of 3.8 mm began to replenish this layer. The responses of 10-30 cm soil layer to rainfall was slower, more than 8.6 mm rainfall being needed for effective replenishment. The response of the 30-50 cm soil layer to rainfall was even more delayed, and replenishment at this depth could not be achieved until the rainfall exceeded 11.8 mm. The water infiltration rate increased with rainfall amount and decreased with soil depth, while water infiltration depth was positively correlated with the rainfall amount and soil water content before rainfall. During the study period, rainfall of <10 mm occurred predominantly, accounting for 78.4% of the total rainfall events. The rainfall mainly replenished soil layer above 30 cm, and the replenishment of deep soil was very limited, which was not conducive to the growth of deep-rooted species. Therefore, rainfall patterns directly affected the composition, distribution, and succession of plant communities in this area.

Enzyme and osmotic adjustment compounds of key species can help explain shrub encroachment in a semiarid sandy grassland

RationaleIn arid and semiarid grasslands where shrub encroachment usually occurs, water plays an important role and might control the process of shrub encroachment. Understanding how species adapt to different sandy environments can help explain the shrub encroachment process. Central methodsFour different grades of shrub encroached grasslands were selected as follows: the Agriophyllum squarrosum community in shifting sandy land (SA), the Artemisia ordosica community in semifixed sandy land (SFA), the A. ordosica community in fixed sandy land (FA) and the Stipa bungeana community in fixed sandy land (FS), which are located on the Ordos Plateau (China) and were selected to analyze the dynamics of enzyme and osmotic adjustment compounds of species in different stages of shrub encroachment. Key resultsThe results showed that from the community in shifting sandy land to the community in fixed sandy land, the average enzyme activities of species decreased and then increased; the malondialdehyde content increased, and the osmotic adjustment compounds increased (or increased and then decreased). The enzyme activities of grasses were significantly higher than those of shrubs. However, there were no significant differences in the malondialdehyde contents of grasses and shrubs. The proline and soluble protein contents of shrubs were significantly higher than those of grasses. The soluble sugar content of grasses was significantly higher than those of shrubs. The D values indicated that the drought resistance of the five species decreased as follows: S. bungeana in FS > S. bungeana in FA > Caragana korshinskii in FA > C. korshinskii in FS > A. ordosica in FS > A. squarrosum in SA > Artemisia sphaerocephala in SFA > A. sphaerocephala in SA > A. ordosica in FA > A. ordosica in SFA. Main conclusionsThe results suggest that the five dominant species in different shrub encroachment stages could enhance their drought resistance by upregulating the antioxidant system and osmotic adjustment in response to drought stress. S. bungeana had a higher drought resistance. For different plant functions, grass had a higher drought resistance than shrubs. It is concluded that S. bungeana can adapt to a drier environment; when the surface soil layer becomes dry, S. bungeana communities developed well due to its high drought ability. Compared to A. ordosica, the S. bungeana community can be a dominant community when human disturbance decreased in the Ordos Plateau.

Relationship between vegetation C, N, P stoichiometry and species diversity in sand land.

Vegetation stoichiometry represents plant nutrition limitation status. Whether it can affect the species diversity of plant community remains to be explored. In this study, we examined plant carbon (C), nitrogen (N), phosphorus (P) concentrations and stoichiometry, and further analyzed the relationship between stoichiometry and species diversity in Artemisia ordosica community and Salix psammophila community in sand land of the Ningxia Habahu National Nature Reserve. The results showed that, for the S. psammophila community growing in mobile and semi-fixed sand dunes, there was a significant negative correlation between Simpson index and vegetation C/N ratio, but no significant correlation between Simpson index and vegetation N/P ratio. For A. ordosica community distributed in semi-fixed and fixed dunes, the Shannon index had a significant positive correlation with vegetation N/P ratio and a significant negative correlation with vegetation C/N ratio. Combined the vegetation stoichiometry with the results of regression analysis (RDA), P concentration and thus N/P ratio had different influences on the species diversity for A. ordosica community and S. psammophila community. Our results showed that vegetation stoichiometry has an important influence on species diversity of plant community in sand land.

Vegetation succession of abandoned croplands in Ruanliang and Yingliang in the Ordos Plateau

Shrub encroachment has been a key phenomenon in arid and semi-arid grasslands over the last century. However, little research has been dedicated to vegetation dynamics in the abandoned croplands, which are surrounded by shrub-encroached grasslands. In this study, several abandoned croplands in Ruanliang and Yingliang in the Ordos Plateau were selected, and the biomass, coverage, density, root pattern, and plant litter dynamics were studied. The results showed that: (1) The abandoned croplands in Ruanliang experienced three community types, including weeds community, the subshrub Artemisia ordosica community, and the perennial grass community, while the abandoned croplands in Yingliang experienced three community types, including weeds community, perennial Stipa bungeana with Artemisia frigida community, and S. bungeana community. (2) The important value for the annual or biennial grass in abandoned croplands in Ruanliang declined during the restoration process, for the perennial grass it increased, and for the subshrub it first increased and then went down to zero. In Yingliang abandoned croplands, however, the perennial grass remained dominant during the succession process. (3) The root of A. ordosica in Ruanliang abandoned croplands was mainly distributed in soil depths of 0–30 cm; the root of the perennial grass was mainly in the 0–20 cm range, and S. bungeana was found at soil depths of 0–5 cm. To restore to a natural vegetation state, about 20 years would be needed to recover the total biomass, and 10 years would be needed to restore the vegetation coverage in Ruanliang abandoned croplands. For Yingliang abandoned croplands, about 15 and 20 years would be needed to restore the total biomass and vegetation coverage, respectively, to a state of natural vegetation.

Dynamics of soil physical properties and biological soil crust during the vegetation restoration process of abandoned croplands in the Ordos Plateau, China

A series of typical abandoned croplands in the regions of Ruanliang and Yingliang in the Ordos Plateau, China, were selected, and dynamics of the surface litter, biological soil crust and soil bulk density, soil texture, and soil moisture in different soil layers were investigated. The results showed that in the abandoned cropland in Ruanliang, the clay particle content and surface litter of the surface soil layer (0-10 cm) increased during the restoration process, while that of soil bulk density substantially decreased and soil water content slightly increased in the surface soil. In the medium soil layer (10-30 cm), the clay particle content increased and the soil water content slightly decreased. In the deep soil layer (30-50 cm), there was a relatively large variation in the physical properties. In the abandoned cropland in Yingliang, the coverage of litter and the coverage and thickness of the biological soil crust increased during the abandonment process. The surface soil bulk density, soil clay particle content and soil water content remained constant in 0-10 cm soil layer, while the physical properties varied substantially in 10-40 cm soil layer. The shallow distribution of the soil water content caused by the accumulation of the litter and clay particles on the soil surface might be the key reason of the replacement of the semi-shrub Artemisia ordosica community with a perennial grass community over the last 20 years of the abandoned cropland in Ruanliang. The relatively high soil water content in the shallow layer and the development of the biological soil crust might explain why the abandoned cropland in Yingliang was not invaded by the semi-shrub A. ordosica during the restoration process.

Relationships between Artemisia ordosica communities and environmental factors following sand-dune stabilization in the Mu Us desert, northwest China

Artemisia ordosica is an excellent sand-fixing shrub for sand stabilization in northwestern China. Sand dune stabilization, a critically important process, leads changes in abiotic factors, such as soil structure and nutrient contents. However, the effects of factors on an A. ordosica community following sand stabilization remain unclear. In this study, we used canonical correspondence analysis (CCA) to examine the relationships between A. ordosica communities and environmental factors at three habitats: semi-fixed dune (SF), fixed dune with low-coverage biological soil crust (F), and fixed dune with high-coverage biological soil crust (FC) in Mu Us desert. The mean height and coverage of plants increased with sand stabilization, while species diversity and richness increased initially and then reduced significantly. Correlation analysis and CCA revealed that slope, soil organic carbon, and nutrient contents, proportion of fine soil particles, soil moisture, and thickness of biological soil crust were all highly correlated with vegetation characteristics. These environmental factors could explain 40.42 % of the vegetation–environment relationships at the three habitats. The distribution of plant species was positively related to soil moisture in the SF dune. Soil moisture, soil nutrient, and fine-particle contents mainly affected plants distribution in the F dune. In the FC dune, distribution of plant species was positively and negatively correlated with the thickness of biological soil crust and soil moisture at a depth 0–20 cm, respectively. The dominance value of typical steppe species increased significantly following sand-dune stabilization and relations between species and samples in CCA ordination bi-plots showed that perennial grasses could invade the A. ordosica community on FC, indicating A. ordosica communities had a tendency to change into typical steppe vegetation with the further fixation. We conclude that the significant differentiation not only occurred in community characteristics, but also in the relationships between vegetation and environmental factors among the three stages of dune fixation. So, restoration of degraded dune ecosystems should be based on habitat conditions and ecological needs.

Spatial heterogeneity of soil and vegetation characteristics and soil-vegetation relationships along an ecotone in Southern Mu Us Sandy Land, China

This study aims to examine the changes in the spatial heterogeneity of soil properties at different soil layers, the spatial heterogeneity of soil and vegetation characteristics along an ecotone, and soil-vegetation relationships along the ecotone in a critical area of desertification. A study site was established across a Lespedeza potaninii (dominant) community (LPC) and an Artemisia ordosica (dominant) community (AOC), with the ecotone between these two communities. In this study, “along the ecotone” means from LPC, via the ecotone, and then to AOC. Three parallel transects (300-m long) were arranged at 50-m intervals along the site. Along each transect, at 10-m spacings, 1 m × 1-m quadrats were marked for the vegetation survey and soil sampling. Soil samples were analyzed in the laboratory after natural air-drying. Data analyses were conducted with a combination of classical and geostatistical methods. In most cases, species importance values and soil properties changed significantly (P < 0.05) along the ecotone. Most soil and vegetation variables were moderately spatially autocorrelated. Kriging interpolated maps showed patch patterns of soil chemical properties. The C/(Co + C) values of soil properties were larger at 5–10-cm than those at 0–5-cm. Vegetation characteristics were mainly positively correlated with soil organic carbon (SOC), total nitrogen (TN), and electrical conductivity (EC). TN at 0–5-cm (TN1), EC at 0–5-cm (EC1), and available potassium at 5–10-cm (AK2) were selected as the predictors for plant species richness and diversity in the stepwise regression analysis between vegetation characteristics and soil properties. Soil nutrients decreased significantly (P < 0.05) along the ecotone. Soil and vegetation properties had moderate spatial heterogeneity. Soil properties had a stronger spatial heterogeneity at subsurface layers compared to surface layers. TN1, EC1, and AK2 were the predominant factors for the plant community structure along the ecotone in the critical area of desertification.

Research on the Succession of &lt;i&gt;Artemisia ordosica &lt;/i&gt;Community in Mu Us Sandy Land

Mu Us sandy land is an important ecological barrier in Northern China. Artemisia ordosica is the dominant species in Mu Us sandy land, the development of biological soil crust in Artemisia ordosica community seriously impediment precipitations, which result in the deterioration of soil water within 40cm, where most of Artemisia ordosica roots distribution. That led to the recession of Artemisia ordosica in the fixed sand dunes in a long time.

Dynamic relationship between parabolic dunes and &amp;lt;italic&amp;gt;Artemisia ordosica&amp;lt;/italic&amp;gt;

Parabolic dunes arising from the interaction between Artemisia ordosica shrubs and aeolian activities are distributed widely in the southern part of the Hobq desert. On the dunes, the shrubs sequentially experience a process of invasion, germination, development and decline. Results of topographical investigations of a parabolic dune combined with satellite images from 2005, 2007 and 2010 show that the dune moved toward the east while its two arms expanded outward. Shrubs were distributed at the crests of both arms, on the flat area between the arms and outside the slopes of the arms. Their growth and deterioration were closely related to the dynamic changes brought about by the eastward movement of the body of the dune in conjunction with the expansion of the arms. The eastward movement of the parabolic dune body created space for the growth of shrubs between the arms which lead to a zonal distribution of the Artemisia ordosica community based on age, size, coverage and the like. The nebkas that derive from deposits trapped by shrubs on the arms of the dune play a crucial role in maintaining the parabolic shape of the dune. However, as the arms expand outward, the shrubs that were previously on the crest move to the inside slopes of the dune, which leads to their deterioration. The shrubs on the outside slopes of the parabolic dune maintain the stability of the slopes, whereas sand deposition on the body of the dune leads to the deterioration of the shrubs.

Pedogenic Carbonate and Soil Dehydrogenase Activity in Response to Soil Organic Matter in Artemisia ordosica Community

Little attention has been paid to the role of soil organic matter (OM) in the formation of pedogenic carbonate in desert soils. The relationships among soil OM, soil dehydrogenase activity (DHA), and soil CaCO3 inaplantcommunity dominated by Artemisia ordosica, located on the eastern boundary of Tengger Desert in the Alxa League, Inner Mongolia, China, were studied to understand whether OM was directly involved in the formation of pedogenic carbonate. The results showed that DHA and CaCO3 positively correlated with OM content, and DHA, OM, and CaCO3 were correlated with each other in their spatial distribution, indicating that abundant OM content contributed to the formation of CaCO3. Therefore, the formation of pedogenic CaCO3 was a biotic process in the plant community dominated by A. ordosica.

Storage of biomass and net primary productivity in desert shrubland of Artemisia ordosica on Ordos Plateau of Inner Mongolia, China

Biomass and net primary productivity (NPP) are two important parameters in determining ecosystem carbon pool and carbon sequestration. The biomass storage and NPP in desert shrubland of Artemisia ordosica on Ordos Plateau were investigated with method of harvesting standard size shrub in the growing season (June–October) of 2006. Results indicated that above-and belowground biomass of the same size shrubs showed no significant variation in the growing season (p>0.1), but annual biomass varied significantly (p<0.01). In the A. ordosica community, shrub biomass storage was 699.76-1246.40 g·m−2 and annual aboveground NPP was 224.09 g·m−2·a−1. Moreover, shrub biomass and NPP were closely related with shrub dimensions (cover and height) and could be well predicted by shrub volume using power regression.

Measurement of rainfall interception by xerophytic shrubs in re-vegetated sand dunes / Mesure de l'interception de la pluie par des arbustes xérophiles sur des dunes de sable replantées

More than 40 years of re-vegetation using mainly xerophytic shrubs Artemisia ordosica Krasch. and Caragana korshinskii Kom. at Shapotou Desert Experimental Research Station near Lanzhou, China has resulted in established dwarf-shrub and herbaceous cover on sand dunes. Precipitation, as the sole source of water replenishment in the semiarid area, plays a pertinent role in sustaining the desert ecosystem. A field study was conducted to (a) measure interception loss on shrub canopies during individual rainfall events, (b) determine the canopy storage capacity of individual plants, and (c) explore the relationship between interception and rainfall parameters. The total rainfall and its respective partitions as throughfall were determined and the interception losses in the studied ecosystem were quantified. Interception loss was shown to differ among the xerophyte taxa studied. During the growing seasons, the average shrub community interception loss is 6.9% and 11.7% of the simultaneous overall precipitation, for A. ordosica and C. korshinskii, respectively. Taking into account the observed rainfall conditions and vegetation cover characteristics, it was concluded that the interception loss was 2.7% of the total annual precipitation verified in the period for the A. ordosica community with an average cover of 30%, canopy projection area of 0.8 m2 and canopy storage capacity of 0.75 mm. In contrast, interception loss for the C. korshinskii community was 3.8% with an average cover of 46%, canopy projection area of 3.8 m2 and canopy storage capacity of 0.71 mm. For individual plants of both shrubs, the proportion of interception loss to gross rainfall decreased notably as the rainfall intensity increased between 0 and 2 mm h−1, while it tended to remain constant at about 0.1–0.2 for A. ordosica and 0.1–0.3 for C. korshinskii when the rainfall intensity was >2 mm h−1.

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.