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.

Effects of Sand Burial Depth on Xanthium Spinosum Seed Germination and Seedling Growth

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 had significant effects at different 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, and the 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.

Climate Change 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 sand burial-dependent growth responses of two Tragopogon species from different habitats

Wind-driven sand movement leading to sand burial is an essential environmental factor in coastal sand dunes; therefore, plants native to sand dunes need to possess specific adaptations. The present study aimed to compare responses to variable sand burial intensity of Tragopogon heterospermus, rare plant species native to coastal dunes, and Tragopogon pratensis taxonomically related grassland species. Plants in culture were established from seeds collected in natural habitats, cultivated in an automated greenhouse, and individuals of different age were buried by sand in the different depths. Both plants had basic sand burial tolerance, seen as an elongation of adult plants’ leaf bases under moderate sand burial conditions. However, only dune-adapted T. heterospermus plants exhibited efficient resource allocation from roots to shoots with increased sand accretion intensity. T. heterospermus plants had pronounced age dependence of burial tolerance, with higher sensitivity to sand burial at an earlier stage due to small shoot height and, possibly, certain physiological factors.

Variation in Growth Response of Coastal Dune-Building Grass Species Ammophila Arenaria and Leymus Arenarius to Sand Burial

Ammophila arenaria and Leymus arenarius are dune-building grass species native to European seacoasts. The present study aimed to compare growth responses to the sand burial of A. arenaria and L. arenarius from coastal habitats of the Baltic Sea, when the intensity of sand accretion was relatively low under controlled conditions. Plants were grown from seeds collected from natural coastal habitats, transplanted into individual containers, buried in the sand at different depths in the rapid shoot elongation stage, and further cultivated (11 or 9 weeks) in an automated greenhouse. Burial in sand significantly stimulated the growth of shoots of A. arenaria, the effect was earlier at high burial intensities (46 and 60%) and was evident ten days after the start of treatment. Both shoot and root dry mass increased for plants buried at 13%; however, increased burial depth (37, 46 and 60%) resulted in a significant increase in root biomass. In comparison, shoot biomass decreased significantly at the highest burial intensity (60%). For L. arenarius, there was no direct dependence of shoot elongation rate on burial depth. There was a tendency for increased elongation growth and biomass allocation to leaf sheaths despite a decrease in total shoot mass. Most strikingly, root biomass decreased with sand burial in parallel with increased burial depth up to 21% intensity. In conclusion, although both grass species showed a positive shoot growth response to moderate sand burial intensity, differences in individual responses at the morphological and physiological level indicate the existence of different genetically based adaptation strategies.

Effect of sand burial on the subcritical water repellency of a dominant moss crust in a revegetated area of the Tengger Desert, Northern China

Sand burial is a ubiquitous disturbance that influences the ecological and hydrological properties of moss crusts in many sandy desert areas. There is little available information regarding the effect of sand burial on the water repellency (WR) of moss crusts in desert areas. Therefore, this study evaluated the effects of sand burial (sand depths of 0 (control), 0.5, 1, 2, 4 and 10 mm) followed by three simulated precipitation regimes (through applying 4 and 6 mm, 2 and 3 mm, and 1 and 1.5 mm of distilled water at 8-day intervals in spring and autumn, respectively) on the WR of a widespread moss crust dominated by Bryum argenteum Hedw. in a revegetated area of the Tengger Desert, China. The results showed moss crust WR remained subcritical during the whole experiment, and that it considerably decreased immediately after sand burial, even though the values of WR were significantly higher in autumn than those in spring under the same treatment (p < 0.05). Furthermore, the depth threshold (TD) values for sand burials that reduced WR to zero were 1 and 2 mm in spring and autumn, respectively. After a recovery period of nearly one-season (72 days), the WR of the moss crust significantly increased (p < 0.05). In addition, sand burial had two separate effects on moss crust WR. Specifically, shallower sand burial (burial depth less than 0.5 mm) increased moss crust WR, whereas deeper sand burial (burial depth exceeds 0.5 mm) decreased it. The TD values also significantly increased to 2 and 4 mm in spring and autumn, respectively. These findings about the effects of sand burial on moss crust WR provide additional information that can be used to better understand the influence of sand burial on moss crust colonization and maintenance in arid sand-burial-stressed ecosystems, and to help explain why there are some contrasting viewpoints on biocrust WR.