Are toe fringes important for lizard burying in highly mobile sand?

Toe fringes are a key innovation for sand dwelling lizards, and the relationship between toe fringe function and substrate properties is helpful in understanding the adaptation of lizards to sand dune environments. We tested the sand burial performance of Phrynocephalus mystaceus on different sand substrates with toe fringe manipulation, with the aim of assessing whether the function of the toe fringes shifts under different substrate properties, especially in highly mobile substrates. The sand burial performance of P. mystaceus was influenced by substrate properties in relation to the toe fringe states of the lizard. After removal of the bilateral toe fringes, the sand burial ability score of P. mystaceus was significantly higher on sand substrates below 100 mesh than on native sand substrates. As the angle of stability of the substrate properties decreased, the sand burial performance of the lizard was even better after the bilateral toe fringes were removed. The results of the LASSO model and the path analysis model showed that the stability angle provided the opposite effect on sand burial performance in different toe fringe states. These results further suggest that the sand burial function of toe fringes may not be suitable for highly mobile sand substrates. It remains to be tested further whether the function of toe fringes is more important for running on sand.

Shrub Growth Improves Morphological Features of Nebkhas: A Case Study of Nitraria tangutorum in the Tengger Desert.

To understand the role of shrubs in nebkha development, a comparative analysis of nebkha morphology and shrub features was conducted in two different habitats at the southeast margin of the Tengger Desert, Northern China. Morphometric variables of 184 Nitraria tangutorum nebkhas were measured in a semi-fixed lake-basin lowland site (site 1, n = 102) and a salinized fixed sand site (site 2, n = 82). Mean length, width, projected area, and accumulated sand volume were all greater in nebkhas in site 1 than in site 2 (p < 0.05); however, mean height (i.e., sand burial depth) did not differ significantly in nebkhas between the two sites (p > 0.05). The larger nebkha volume in site 1 relative to site 2 (mean, 88.19 m3 vs. 33.16 m3) implied that the projected area influenced the accumulated sand volume. Nebkhas in site 1 tended to have large areas, low densities, and high spatial autocorrelation, while nebkhas in site 2 exhibited opposite trends with stochastic distribution. Mean vegetation density was significantly higher in site 1 than in site 2 (p < 0.05), while mean vegetation height exhibited an opposite trend (p < 0.05). In addition, there was higher vegetation coverage in site 1 than in site 2 (p > 0.05). According to the results, plant species (i.e., N. tangutorum) limited nebkha height under similar wind regimes regardless of the transport distance of aeolian material, while aeolian deposition and its effect on shrub growth jointly increased nebkha size.

[Discussing the basic ecological relations of sand dune vegetation process]. / è®ºæ²™ä¸˜æ¤è¢«è¿‡ç¨‹çš„åŸºæœ¬ç”Ÿæ€å ³ç³».

Dune is often considered as a degraded ecosystem. Natural vegetation restoration and stable artificial vegetation construction are the basic means restoring dune ecosystem. Based on long-term study of dune ecosystem, by taking into consideration both the philosophical principles of unity of opposites and dynamic change, and related ecological theories, we put forward some ecological relations that should be paid attention to in the study of vegetation assembly from the perspective of the uniqueness of dune ecosystem. We discussed the necessity of coupling relationships of scale-pattern-process and the transformation of synergy-tradeoff relationships, interpreted the importance of distinguishing sand dune stabilized and shifting phases, disturbance and stress, wind erosion and sand burial in the study of vegetation process. We further explored the applied value of niche law or neutral law in the study of dune vegetation process. Finally, we discussed the issues that should be paid attention to in the study of dune vegetation process from the aspects of adaptability to aeolian activities and drought tolerance, physiological and reproductive process, sexual and asexual reproduction of plants. This study would provide theoretical supports for vegetation restoration and stable vegetation construction of dune ecosystem.

Sand Burial, Rather than Salinity or Drought, Is the Main Stress That Limits the Germination Ability of Sophora alopecuroides L. Seed in the Desert Steppe of Yanchi, Ningxia, China.

Global change and environmental pollution have reawakened ecologists to the great threat of multi-stress interactions to different growth stages of plants. Sophora alopecuroides L., a dune plant, has been widely studied for its medicinal components and strong salinity tolerance. S. alopecuroides seeds, obtained from the desert steppe of Yanchi, Ningxia, China, were used to analyze the effects of sand burial, salinity, drought, and their interactions on seed germination (germination percentage, germination energy, and germination index). The results showed that sand burial and salinity stress had significant effects on the seed germination ability of S. alopecuroides, and drought stress had no significant effect, but the interaction of the three stresses had a significant effect. Under different drought-stress treatments, the interaction of no sand burial and a certain degree of salinity stress significantly improved the germination ability of S. alopecuroides, and the overall intensity of the effects of the three stresses showed that sand burial > salinity > drought. Considering the germination percentage, germination energy, and germination index of S. alopecuroides under various stress interactions, the treatment of no sand burial × 1% soil saline-alkali content × 18-20% soil water content was adopted to maximize the germination ability of S. alopecuroides. In the desert steppe area of Yanchi, Ningxia, sand burial stress was still the most limiting factor for seed germination of S. alopecuroides, and soil saline-alkali content should be increased moderately, and soil moisture should be ensured to obtain the best germination ability.

Plastic litter in coastal sand dunes: Degradation behavior and impact on native and non-native invasive plants.

Pollution associated to marine plastic litter is raising increasing concerns due to its potential harmful effects on human health, biota, and coastal ecosystems. However, limited information is available on the degradation behavior of plastics, especially biodegradable ones, in dune habitats. Moreover, the effects of plastics on dune plant growth and ability to withstand environmental stresses and invasion by non-native plants have been largely neglected. This is a particularly relevant issue since biological invasions are major threats to dune ecosystems. In this 18-month study, we examined the degradation behavior of two plastic bags, non-biodegradable (NBP) or biodegradable/compostable (BP), in the dune environment by visual observations and analytical techniques. Concomitantly, we investigated the individual and combined effects of bag type and sand burial (no burial vs. partial burial) on the performance of a native dune plant (Thinopyrum junceum) and an invasive plant (Carpobrotus sp.) and on their interaction. NBP did not show relevant degradation signs over the experimental period as expected. BP exhibited gradual surface modifications and changes in chemical functionality and were almost disintegrated after 18 months. Bags and burial reduced independently T. junceum survival and growth, and most plants died within 8 months of plastic exposure. Bags and burial did not affect Carpobrotus survival. However, burial decreased Carpobrotus growth while NBP increased it. Both plastics increased Carpobrotus competitive ability, and no T. junceum plants survived to co-occurrent Carpobrotus, BP, and burial. These findings indicate that removing all littered plastics from beach-dune systems not only is critical to reduce plastic pollution but also to prevent further spread of invasive species in coastal dunes.

Functional Trait Responses of Sophora alopecuroides L. Seedlings to Diverse Environmental Stresses in the Desert Steppe of Ningxia, China.

The seedling stage of plants is a crucial and vulnerable period in population and community dynamics. Despite this, studies on how plant traits respond to different environmental stresses often tend to overlook this early stage. Our study focused on Sophora alopecuroides L. seedlings in Ningxia Yanchi desert steppe, analyzing the effects of sand burial, salinity, and drought on their key aboveground and belowground traits. The results showed that sand burial significantly negatively affected stem biomass (SB), leaf biomass (LB), stem diameter (SD), leaf length (LL), leaf width (LW), leaf area (LA), and total root volume (RV), but positively influenced total root length (RL). As sand burial depth increased, SB, LB, SD, LL, LW, LA, RV, root biomass (RB), RV, and lateral root numbers (LRN) significantly decreased. Salinity stress negatively affected SB, LB, SD, LL, LW, LA, RB, RL, and RV, with these traits declining as the stress concentration increased. Drought stress had a positive effect on SD and LL, with both traits showing an increase as the intensity of the drought stress intensified; however, it adversely affected RL. In Ningxia Yanchi desert steppe, salinity stress had the most significant effect on the traits of S. alopecuroides seedlings, followed by sand burial, with drought having the least significant effect. This study provides essential theoretical support for understanding how S. alopecuroides seedlings cope with environmental stresses in their early life stages.

Effect of Rhizome Severing on Survival and Growth of Rhizomatous Herb Phragmites communis Is Regulated by Sand Burial Depth.

Rhizome fragmentation and sand burial are common phenomena in rhizomatous clonal plants. These traits serve as an adaptive strategy for survival in stressful environments. Thus far, some studies have been carried out on the effects of rhizome fragmentation and sand burial, but how the interaction between rhizome fragmentation and sand burial affects the growth and reproduction of rhizomatous clonal plants is unclear. We investigated the effect of the burial depth and rhizome fragment size on the survival and growth of the rhizomatous herb Phragmites communis using 288 clonal fragments (6 burial depths × 8 clonal fragment sizes × 6 replicates) in a field rhizome severing experiment. The ramet survival of the rhizomatous species significantly increased with the sand burial depth and clonal fragment size (p < 0.01), and the effects of the clonal fragment size on ramet survival depended on the sand burial depth. Sand burial enhanced both the vertical and horizontal biomass (p < 0.05), while the clonal fragment size affected the vertical biomass rather than the horizontal biomass. Sand burial facilitated the vertical growth of ramets (p < 0.05) while the number of newly produced ramets firstly increased and then decreased with the increasing clonal fragment size, and the maximal value appeared in four clonal fragments under a heavy sand burial depth. There is an interaction between the burial depth and rhizome fragment size in the growth of rhizome herbaceous plants. The population growth increases in the increase of sand burial depth, and reaches the maximum under severe sand burial and moderate rhizome fragmentation.

Differential Influences of Wind-Blown Sand Burial on Bacterial and Fungal Communities Inhabiting Biological Soil Crusts in a Temperate Desert, China.

Biological soil crusts (BSCs) are an integration of external photoautotrophs and internal heterotrophic communities. Sand burial is a ubiquitous disturbance that affects the biodiversity and ecological function of BSCs, but little is known about the influence of sand burial on microbial communities in arid sandy deserts. Here, based on a long-term field experiment and utilizing high-throughput sequencing, we assessed the influence of sand burial on bacterial and fungal communities inhabiting two typical successional stages of BSCs (cyanobacterial crusts for early successional stage and mixed crusts for late successional stage) at the three-sand buried depth (0, 0.5, and 10 mm) in the Tengger Desert, Northern China. We found that the diversity, abundance, and composition of the bacterial and fungal communities were all altered by the sand burial treatment. Different indicator taxa were identified in unburied and buried (shallow and deep) BSCs. Changes in soil properties caused by sand burial have been suggested as a possible cause of changes in the bacterial and fungal community composition in BSCs.

Effects of sand burial depth on Xanthium spinosum seed germination and seedling growth.

In desert habitats, sand burial is an important factor affecting germination of plant seeds and seedling growth. Xanthium spinosum has strong adaptability in arid desert areas, and is a common malignant invasive plant in Xinjiang, China. The effects of different sand burial depths on seed germination, seedling emergence, growth and biomass allocation were studied to provide a scientific basis for further control of X. spinosum. Six sand burial depths (1, 2, 3, 5, 7 and 9 cm) were established to explore the response of X. spinosum seed germination and seedling growth to sand burial. The first emergence time, peak emergence time, emergence rate, seedling growth height, biomass and biomass distribution of X. spinosum seeds was significantly different at sand burial depths (P < 0.05). The X. spinosum seeds had the highest emergence rate (71.5%) at 1 cm sand burial and the maximum seedling height (7.1 cm). As sand burial depth increased, the emergence rate and seedling height gradually decreased. Emergence rate (12.25%) and seedling height (2.9 cm) were lowest at 9 cm sand burial. The root length at 9 cm depth (13.6 cm) was significantly higher than that at other sand depths (P < 0.05). The sand burial depth affected the biomass accumulation and distribution of X. spinosum. As sand burial depth increased, the root biomass and rhizome ratio increased, and the most deeply buried seedlings allocated more biomass for root growth. The optimal sand burial depth for seed germination and seedling growth of X. spinosum was 1-3 cm, and high burial depth (5-9 cm) was not conducive to the germination and growth of X. spinosum seedlings. For prevention and control of X. spinosum, we suggest deeply ploughing crops before sowing to ensure X. spinosum seeds are ploughed into a deep soil layer.

Modification of Growth and Physiological Response of Coastal Dune Species Anthyllis maritima to Sand Burial by Rhizobial Symbiosis and Salinity.

The aim of the present study was to establish an experimental system in controlled conditions to study the physiological effect of abiotic/biotic interaction using a rare wild leguminous plant species from coastal sand dunes, Anthyllis maritima. The particular hypothesis tested was that there is an interaction between sand burial, rhizobial symbiosis and salt treatment at the level of physiological responses. Experiment in controlled conditions included 18 treatment combinations of experimental factors, with two intensities of sand burial, rhizobial inoculation and two types of NaCl treatment (soil irrigation and foliar spray). Shoot biomass was significantly affected both by burial and by inoculation, and by interaction between burial and NaCl in the case of shoot dry mass. For plants sprayed with NaCl, burial had a strong significant positive effect on shoot growth irrespective of inoculation. General effect of inoculation with rhizobia on shoot growth of plants without NaCl treatment was negative except for the plants buried 2 cm with sand, where significant stimulation of shoot dry mass by inoculant was found. The positive effect of burial on shoot growth was mainly associated with an increase in leaf petiole height and number of leaves. Performance index significantly increased in buried plants in all treatment combinations, and leaf chlorophyll concentration increased in buried plants independently on burial depth, and only in plants not treated with NaCl. Inoculation led to significant increase of leaf peroxidase activity in all treatment combinations except NaCl-irrigated plants buried for 2 cm by sand. Sand burial stimulated peroxidase activity, mostly in non-inoculated plants, as inoculation itself led to increased enzyme activity. In conclusion, strong interaction between sand burial and NaCl treatment was evident, as the latter significantly affected the effect of burial on growth and physiological indices. Moreover, rhizobial symbiosis had a significant effect on physiological processes through interaction with both sand burial and NaCl treatment, but the effect was rather controversial; it was positive for photosynthesis-related parameters but negative for growth and tissue integrity indices.

Warming alters the interaction of two invasive beachgrasses with implications for range shifts and coastal dune functions.

Forecasting the effects of climate change on the distribution of invasive species can be difficult, because invaders often thrive under novel physical conditions and biotic interactions that differ from those in their native range. In this study, we experimentally examined how rising temperatures and sand burial could alter the abundance and biotic interactions of two invasive beachgrasses, Ammophila arenaria and A. breviligulata, along the U.S. Pacific Northwest coast. We asked whether the current geographic ranges of the two congeners, and thus their effects on dune morphology and coastal ecosystem services, might shift as a consequence of climate driven changes in warming and sand supply. Our results show that A. breviligulata had lower biomass and tiller production when exposed to warming and high rates of sand burial, while A. arenaria showed neutral or positive responses to those treatments. Nevertheless, under all experimental combinations, A. breviligulata had strong negative effects on A. arenaria, while A. arenaria had weaker effects on A. breviligulata. Our models predict that although A. breviligulata mostly excludes A. arenaria, elevated temperatures and high rates of sand burial also increase the likelihood of species coexistence. We suggest that under climate change, the differences in physiological tolerance and the mediation of species interactions could expand the northern distributional limit of A. arenaria but restrict the southern limit of A. breviligulata. Moreover, because beachgrass abundance has direct effects on biophysical functions of dunes, reductions in vigor from warming could alter coastal protection, biodiversity, and carbon sequestration.

Comparison of biodegradable polyesters degradation behavior in sand.

Sandy beaches represent environmental compartments particularly vulnerable to litter pollution, and they reflect the magnitude of pollution of adjacent compartments: water and coastal areas. The substitution of conventional polymers by biodegradable materials is generally considered as an alternative for reducing environmental accumulation of plastic debris. The present study is aimed to investigate the degradation of poly(lactic acid), poly(ε-caprolactone), poly(butylenesuccinate adipate) and poly(3-hydroxybutyrate) buried in sand for 267 days, simulating them as beach litter. The analysed polyesters showed different degradation mechanisms and kinetics. PLA is mainly subjected to weathering by physical aging; after an initial faster degradation of the amorphous phase, PCL showed a decrease of its degradation rate; similarly to PCL, the degradation of PBSA started from the amorphous phase; PHB is clearly subjected to biological degradation. The degradation trend of the investigated materials in sand decreased in the order PHB > PBSA > PCL > PLA. PLA, PCL and PBSA did not undergo complete degradation in sand during the testing time.

Sand burial helps regulate timing of seed germination of a dominant herb in an inland dune ecosystem with a semiarid temperate climate.

Sand burial plays important role in the life history of species in sandy areas of arid and semi-arid temperate regions, by affecting seed germination, seedling growth and survival and plant community. However, few studies have focused on the effects of sand burial on the dynamics of seed dormancy in such areas. In this study, seed germination characteristics of Allium tenuissimum, a dominant perennial herb in the dune ecosystem in Ordos Plateau in northern China, was investigated. Dormancy dynamics were monitored for seeds buried at sand depths of 0, 2 and 5 cm in the natural habitats for 13 months. Freshly matured seeds of A. tenuissimum were conditionally dormant and germinated to high percentages at high but not low temperatures. Germination percentages were increased by incubation at summer temperature (15/25 °C) and dry storage, but GA3 and cold stratification had no significant effects. These results suggested that seeds of A. tenuissimum were conditionally dormant, and incubation under warm, wet (but not cold, wet) conditions and dry after-ripening resulted in complete dormancy releasing. Seeds buried at 2 and 5 cm in the field for 13 months exhibited seasonal changes in germination, with an increase in spring and summer followed by decrease in autumn and winter. However, seeds on the soil surface (0 cm) gradually came out of dormancy beginning in January, and germinated percentage was highest in July, after which remained high. The peak of nondormancy for seeds buried in the field was in the summer, which corresponds to the period of highest annual precipitation. Sand burial helped mediate seeds dormancy dynamics of A. tenuissimum via seasonal dormancy cycling. Our finding contributes to a better understanding of how timing of seedling establishment is controlled in a semiarid dune ecosystem in temperate climate.

Experimental sand burial and precipitation enhancement alter plant and soil carbon allocation in a semi-arid steppe in north China.

Sand burial is a common phenomenon in inland semi-arid and arid areas, affecting plant growth and even plant community structure. Precipitation regime, including the variation of precipitation intensity and frequency, also drives community structure and functions in such areas. However, few studies have focused on the combined effect of sand burial and changed precipitation regime on community function, specifically its role in carbon storage. A 2-yr field experiment with factorial treatments of precipitation (control, slight enhancement and strong enhancement) and sand addition (control and 5 cm sand addition) was conducted to test the responses of plant and soil carbon content in a semi-arid typical steppe in N China. Results showed that sand burial had no significant effect on plant carbon density, but significantly changed the allocation of plant carbon from aboveground to belowground; these responses differed among species and life forms in the community. Precipitation enhancement had no significant effects on plant carbon and its allocation, perhaps because effects of precipitation on plants are due more to precipitation frequency than to precipitation intensity per event. Sand burial and precipitation enhancement decreased soil carbon, especially soil organic carbon, and promoted soil carbon to be distributed deeper down the soil profile. These findings will help to understand how sand deposition affects plant and soil carbon storage and their allocation in plant communities under a changing precipitation regime, and more generally, to understand carbon storage dynamics in early-successional sandy ecosystems in the context of global change.

Impacts of Sand Burial and Wind Erosion on Regeneration and Growth of a Desert Clonal Shrub.

Sand burial and wind erosion caused by sand movement are common phenomena in desert environments, but the effects on clonal shrub have rarely been investigated. Here, we assessed how sand movements affect the population regeneration capacity of juvenile clonal fragments of the shrub Calligonum mongolicum growing in mobile desert sand dunes. We investigated the population status and natural regeneration capacity in three types of mobile dunes (heavy wind erosion, heavy sand burial and moderate sand burial). Clonal propagation of C. mongolicum was markedly different across sites. Moderate sand burial sites had the largest ramet density and bud number per unit length of rhizome, and the overwinter survival rate was significantly higher at sand burial sites than at wind erosion sites, suggesting that C. mongolicum may have well adapted to the moderate sand burial environment. We further examined the effects of clonal integration on clonal regeneration of this species. Physiological, biochemical and morphological characteristics of parent and daughter ramets growing in heterogeneous sandy habitats (sand burial or wind erosion) were measured. The results showed that being connected or severed from the maternal plant critically determined survival of daughter ramets on wind eroded rhizomes. When eroded rhizomes remained connected, the mother ramets had the highest chlorophyll a, b and a + b contents. However, both the mother plant and the daughter ramets undergoing erosion had higher proline and soluble protein levels than sand buried ramets. Meanwhile, the daughter ramets undergoing sand burial had higher photosynthetic rates (P n), chlorophyll fluorescence parameters (F m and F o), and phenotypic traits of assimilating shoots, i.e., node number, length and volume than wind-eroded ramets. However, significant differences with mother plants, whether connected or severed, were very limited. It was concluded that moderate sand burial environments promoted clonal reproduction and growth of C. mongolicum. Additionally, physiological integration with mother raments in favorable conditions can alleviate stress on daughter ramets exposed to wind erosion. This physiological effect may do not occur for sand buried daughter ramets. These survival strategies and phenotypic responses should be carefully considered in shrub and sand dune management in sand fixation plantations of C. mongolicum.

Effects of sand burial on the survival and growth of two shrubs dominant in different habitats of northern China.

Plants that grow in dune ecosystems always suffer from sand burial. Shrubs play implications on the healthy functioning of dune ecosystems due to control blowing sand. However, the survival and growth responses of shrubs to sand burial remain poorly understood. The survival rate and seedling height of two shrubs (Artemisia halodendron and Lespedeza davurica) along with the soil properties under different burial depths were examined in order to reveal the causing ecophysiological attributes of sand burial on shrubs in the desertified region. It was found that A. halodendron can survive a burial depth of 6 cm greater than its seedling height, which is a dominant shrub in mobile dunes with intense burial, whereas a burial depth equivalent to three fourths of its seedling height is detrimental to L. davurica, which is dominant in fixed dunes with less burial. The reasons for the shrub death under sand burial were associated with the physical barrier to vertical growth and the reduction in photosynthetic area. In conclusion, A. halodendron can facilitate the stabilization of mobile dunes because of their high tolerance to the frequent and intensive sand burial, while L. davurica can be beneficial for the recovery process because of their higher survival rates under shallow burial following restoration of mobile dunes.

[Effects of sand burial on fluxes of greenhouse gases from the soil covered by biocrust in an arid desert region.] / 沙埋对干旱沙区生物结皮覆盖土壤温室气体通量的影响.

Based on the measurements of the fluxes of CO2, CH4 and N2O from the soil covered by two types of biocrusts dominated separately by moss and algae-lichen, followed by 0 (control), 1 (shallow) and 10 (deep) mm depths of sand burial treatments, we studied the effects of sand burial on greenhouse gases fluxes and their relationships with soil temperature and moisture at Shapotou, southeastern edge of the Tengger Desert. The results showed that sand burial had significantly positive effects on CO2 emission fluxes and CH4 uptake fluxes of the soil covered by the two types of biocrusts, but imposed differential effects on N2O fluxes depending on the type of biocrust and the depth of burial. Deep burial (10 mm) dramatically increased the N2O uptake fluxes of the soil co-vered by the two types of biocrusts, while shallow burial (1 mm) decreased the N2O uptake flux of the soil co-vered by moss crust only and had no significant effects on N2O uptake flux of the soil covered by algae-lichen crust. In addition, CO2 fluxes of the two biocrusts were closely related to the soil temperature and soil moisture, thereby increasing with the raised soil surface temperature and soil moisture caused by sand burial. However, the relationships of burial-induced changes of soil temperature and moisture with the changes in the other two greenhouse gases fluxes were not evident, indicating that the variations of soil temperature and moisture caused by sand burial were not the key factors affecting the fluxes of CH4 and N2O of the soil covered by the two types of biocrusts.

Distribution of three congeneric shrub species along an aridity gradient is related to seed germination and seedling emergence.

Environmental tolerance of a species has been shown to correlate positively with its geographical range. On the Ordos Plateau, three Caragana species are distributed sequentially along the precipitation gradient. We hypothesized that this geographical distribution pattern is related to environmental tolerances of the three Caragana species during seed germination and seedling emergence stages. To test this hypothesis, we examined seed germination under different temperature, light and water potentials, and monitored seedling emergence for seeds buried at eight sand depths and given different amounts of water. Seeds of C. korshinskii germinated to high percentages at 5 : 15 to 25 : 35 °C in both light and darkness, while those of C. intermedia and C. microphylla did so only at 15 : 25 and 25 : 35 °C, respectively. Nearly 30 % of the C. korshinskii seeds germinated at -1.4 MPa at 20 and 25 °C, while no seeds of the other two species did so. Under the same treatments, seedling emergence percentages of C. korshinskii were higher than those of the other two species. The rank order of tolerance to drought and sand burial of the three species is C. korshinskii > C. intermedia > C. microphylla. The amount of precipitation and sand burial depth appear to be the main selective forces responsible for the geographical distribution of these species.

Intraspecific variation of a desert shrub species in phenotypic plasticity in response to sand burial.

Shoot elongation is one of the main plastic responses of plants to burial, a ubiquitous stress factor in dry ecosystems. Yet, intraspecific variation in this response to burial and the extent to which this variation is functionally coordinated with variation in other trait responses are largely unknown. We subjected seedlings of the shrub Caragana intermedia from 18 maternal parents (i.e. different half-sib families) to repeated partial burial to investigate how burial affects shoot growth, stem mechanical traits and associated plasticity. Burial increased both stem elongation and diameter growth of plants, but decreased biomass production. Half-sib families had different rates of shoot elongation, and differed in their response to burial with respect to biomechanical stem properties. Across half-sib families, the magnitude of these responses in mechanical traits was positively correlated with the magnitude of the stem elongation response. These results indicate that plasticity in different stem traits in response to sand burial and intraspecific variation therein are functionally coordinated with respect to mechanical stability. The results emphasize the importance of considering functionally coordinated traits when analyzing phenotypic plasticity in plants.

Clonal integration helps Psammochloa villosa survive sand burial in an inland dune.

• Rhizomatous clonal plants frequently colonize and stabilize dunes on sea and lake shores, and in inland deserts and desertified areas, where sand burial is common. To date, little attention has been paid to how clonal integration affects their ability to withstand sand burial. • In an inland dune Psammochloa villosa ramets were buried under 0, 20, 40 and 60 cm of sand, and the rhizomes at the edges of the 50 × 50 cm2 treatment quadrats were either severed or left connected. • With increasing burial depth the surviving ramets of P. villosa decreased markedly both in number and in size (number of leaves and above-ground biomass). In the connected quadrats, however, sand burial resulted in significantly smaller decreases than in the severed quadrats of the number, but not in size, of the surviving P. villosa ramets. • We conclude that clonal integration increased the ability of P. villosa to withstand sand burial, and that P. villosa could emerge from deep burial probably by elongating vertical structures with the help of the energy imported from the connected, unburied ramets.