Spontaneous chromosome instability and tissue culture-induced karyotypic alteration in wheat-Thinopyrum intermedium alien addition lines.

MAIN CONCLUSION: Wheat lines harboring wild-relative chromosomes can be karyotypically unstable during long-term maintenance. Tissue culture exacerbates chromosomal instability but appears inefficient to induce somatic homoeologous exchange between alien and wheat chromosomes. We assessed if long-term refrigerator storage with regular renewal via self-fertilization, a widely used practice for crop germplasm maintenance, would ensure genetic fidelity of alien addition lines, and explored the possibility of inducing somatic homoeologues exchange by tissue culture. We cytogenetically characterized sampled stock seeds of originally confirmed 12 distinct wheat-Thinopyrum intermedium alien addition lines (dubbed TAI lines), and subjected immature embryos of the TAI lines to tissue culture. We find eight of the 12 TAI lines were karyotypically departed from their original identity as bona fide disomic alien addition lines due to extensive loss of whole-chromosomes of both Th. intermedium and wheat origins during the ca. 3-decade storage. Rampant numerical chromosome variations (NCVs) involving both alien and wheat chromosomes were detected in regenerated plants of all 12 studied TAI lines, but at variable rates among the wheat sub-genomes and chromosomes. Compared with NCVs, structural chromosome variations (SCVs) occurred at substantially lower rates, and no SCV involving the added alien chromosomes was observed. The NCVs manifested only moderate effects on phenotypes of the regenerated plants under field conditions.

Implications of germination tolerances on invasion potential of Arthraxon hispidus.

Arthraxon hispidus is an introduced, rapidly spreading, and newly invasive grass in the eastern United States, yet little is known about the foundational biology of this aggressive invader. Germination responses to environmental factors including salinity, pH, osmotic potential, temperature, and burial depth were investigated to better understand its germination niche. Seeds from six populations in the Mid-Atlantic US germinated 95% with an average mean time to germination of 3.42 days of imbibition in the dark at 23°C. Germination occurred across a temperature range of 8-37°C and a pH range of 5-10 (≥83%), suggesting that neither pH nor temperature will limit germination in many environments. Arthraxon hispidus germination occurred in high salinity (342 mM NaCl) and osmotic potentials as low as -0.83MPa. The NaCl concentration required to reduce germination by 50% exceeded salinity concentrations found in soil and some brackish water saltmarsh systems. While drought adversely affects A. hispidus, 50% germination occurred at osmotic potentials ranging from -0.25 to -0.67 MPa. Given the climatic conditions of North America, drought stress is unlikely to restrict germination in large regions. Finally, emergence greatly decreased with burial depth. Emergence was reduced to 45% at 1-2 cm burial depths, and 0% at 8 cm. Emergence depths in concert with adequate moisture, germination across a range of temperatures, and rapid germination suggests A. hispidus' seed bank may be short-lived in moist environments, but further investigation is warranted. Given the broad abiotic tolerances of A. hispidus and a widespread native range, A. hispidus has the potential to germinate in novel territories beyond its currently observed invaded range.

Grazing herbivores reduce herbaceous biomass and fire activity across African savannas.

Fire and herbivory interact to alter ecosystems and carbon cycling. In savannas, herbivores can reduce fire activity by removing grass biomass, but the size of these effects and what regulates them remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density. We show that, broadly across African savannas, grazing herbivores substantially reduce both herbaceous biomass and fire activity. The size of these effects was strongly associated with grazing herbivore densities, and surprisingly, was mostly consistent across different environments. A one-zebra increase in herbivore biomass density (~100 kg/km2 of metabolic biomass) resulted in a ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage point reduction in burned area. Our results indicate that fire models can be improved by incorporating grazing effects on grass biomass.

Variations and trade-offs in leaf and culm functional traits among 77 woody bamboo species.

BACKGROUND: Woody bamboos are the only diverse large perennial grasses in mesic-wet forests and are widely distributed in the understory and canopy. The functional trait variations and trade-offs in this taxon remain unclear due to woody bamboo syndromes (represented by lignified culm of composed internodes and nodes). Here, we examined the effects of heritable legacy and occurrence site climates on functional trait variations in leaf and culm across 77 woody bamboo species in a common garden. We explored the trade-offs among leaf functional traits, the connection between leaf nitrogen (N), phosphorus (P) concentrations and functional niche traits, and the correlation of functional traits between leaves and culms. RESULTS: The Bayesian mixed models reveal that the combined effects of heritable legacy (phylogenetic distances and other evolutionary processes) and occurrence site climates accounted for 55.10-90.89% of the total variation among species for each studied trait. The standardized major axis analysis identified trade-offs among leaf functional traits in woody bamboo consistent with the global leaf economics spectrum; however, compared to non-bamboo species, the woody bamboo exhibited lower leaf mass per area but higher N, P concentrations and assimilation, dark respiration rates. The canonical correlation analysis demonstrated a positive correlation (ρ = 0.57, P-value < 0.001) between leaf N, P concentrations and morphophysiology traits. The phylogenetic principal components and trait network analyses indicated that leaf and culm traits were clustered separately, with leaf assimilation and respiration rates associated with culm ground diameter. CONCLUSION: Our study confirms the applicability of the leaf economics spectrum and the biogeochemical niche in woody bamboo taxa, improves the understanding of woody bamboo leaf and culm functional trait variations and trade-offs, and broadens the taxonomic units considered in plant functional trait studies, which contributes to our comprehensive understanding of terrestrial forest ecosystems.

Seed germination demonstrates inter-annual variations in alkaline tolerance: a case study in perennial Leymus chinensis.

BACKGROUND AND AIMS: The escalating issue of soil saline-alkalization poses a growing global challenge. Leymus chinensis is a perennial grass species commonly used in the establishment and renewal of artificial grasslands that is relatively tolerant of saline, alkaline, and drought conditions. Nonetheless, reduced seed setting rates limit its propagation, especially on alkali-degraded grassland. Inter-annual variations have an important effect on seed yield and germination under abiotic stress, and we therefore examined the effect of planting year on seed yield components of L. chinensis. METHODS: We grew transplanted L. chinensis seedlings in pots for two (Y2), three (Y3), or four (Y4) years and collected spikes for measurement of seed yield components, including spike length, seed setting rate, grain number per spike, and thousand seed weight. We then collected seeds produced by plants from different planting years and subjected them to alkaline stress (25 mM Na2CO3) for measurement of germination percentage and seedling growth. RESULTS: The seed setting rate of L. chinensis decreased with an increasing number of years in pot cultivation, but seed weight increased. Y2 plants had a higher seed setting rate and more grains per spike, whereas Y4 plants had a higher thousand seed weight. The effects of alkaline stress (25 mM Na2CO3) on seed germination were less pronounced for the heavier seeds produced by Y4 plants. Na2CO3 caused a 9.2% reduction in shoot length for seedlings derived from Y4 seeds but a 22.3% increase in shoot length for seedlings derived from Y3 seeds. CONCLUSIONS: Our findings demonstrate significant differences in seed yield components among three planting years of L. chinensis under pot cultivation in a finite space. Inter-annual variation in seed set may provide advantages to plants. Increased alkalinity tolerance of seed germination was observed for seeds produced in successive planting years.

Environmental and seed-position effects on viability and germination of buried seeds of an invasive diaspore-heteromorphic annual grass.

Environmental factors, such as temperature and moisture, and plant factors, such as seed position on the mother plant, can affect seed viability and germination. However, little is known about the viability and germination of seeds in different positions on the mother plant after burial in soil under natural environmental conditions. Here, diaspores from three positions on a compound spike and seeds from two/three positions in a diaspore of the invasive diaspore-heteromorphic annual grass Aegilops tauschii were buried at four depths for more than 2 years (1-26 months) under natural conditions and viability and germination monitored monthly. Viability of seeds in each diaspore/seed position decreased as burial depth and duration increased and was associated with changes in soil temperature and moisture. Germination was highest at 2 cm and lowest at 10 cm soil depths, with peaks and valleys in autumn/spring and winter/summer, respectively. Overall, seeds in distal diaspore and distal seed positions had higher germination percentages than those in basal diaspore and basal seed positions, but basal ones lived longer than distal ones. Chemical content of fresh diaspores/seeds was related to diaspore/seed position effects on seed germination and viability during burial. We conclude that seeds in distal diaspores/seed positions have a 'high risk' strategy and those in basal positions a 'low risk' strategy. The two risk strategies may act as a bet-hedging strategy that spreads risks of germination failure in the soil seed bank over time, thereby facilitating the survival and invasiveness of A. tauschii.

Microbial symbionts buffer hosts from the demographic costs of environmental stochasticity.

Species' persistence in increasingly variable climates will depend on resilience against the fitness costs of environmental stochasticity. Most organisms host microbiota that shield against stressors. Here, we test the hypothesis that, by limiting exposure to temporally variable stressors, microbial symbionts reduce hosts' demographic variance. We parameterized stochastic population models using data from a 14-year symbiont-removal experiment including seven grass species that host Epichloë fungal endophytes. Results provide novel evidence that symbiotic benefits arise not only through improved mean fitness, but also through dampened inter-annual variance. Hosts with "fast" life-history traits benefited most from symbiont-mediated demographic buffering. Under current climate conditions, contributions of demographic buffering were modest compared to benefits to mean fitness. However, simulations of increased stochasticity amplified benefits of demographic buffering and made it the more important pathway of host-symbiont mutualism. Microbial-mediated variance buffering is likely an important, yet cryptic, mechanism of resilience in an increasingly variable world.

A bamboo 'PeSAPK4-PeMYB99-PeTIP4-3' regulatory model involved in water transport.

Water plays crucial roles in expeditious growth and osmotic stress of bamboo. Nevertheless, the molecular mechanism of water transport remains unclear. In this study, an aquaporin gene, PeTIP4-3, was identified through a joint analysis of root pressure and transcriptomic data in moso bamboo (Phyllostachys edulis). PeTIP4-3 was highly expressed in shoots, especially in the vascular bundle sheath cells. Overexpression of PeTIP4-3 could increase drought and salt tolerance in transgenic yeast and rice. A co-expression pattern of PeSAPK4, PeMYB99 and PeTIP4-3 was revealed by WGCNA. PeMYB99 exhibited an ability to independently bind to and activate PeTIP4-3, which augmented tolerance to drought and salt stress. PeSAPK4 could interact with and phosphorylate PeMYB99 in vivo and in vitro, wherein they synergistically accelerated PeTIP4-3 transcription. Overexpression of PeMYB99 and PeSAPK4 also conferred drought and salt tolerance in transgenic rice. Further ABA treatment analysis indicated that PeSAPK4 enhanced water transport in response to stress via ABA signaling. Collectively, an ABA-mediated cascade of PeSAPK4-PeMYB99-PeTIP4-3 is proposed, which governs water transport in moso bamboo.

Context-dependent benefits of forest soil addition on Aleppo pine seedling performance under drought and grass competition.

Seedling establishment under natural conditions is limited by numerous interacting factors. Here, we tested the combined effects of drought, herbaceous competition, and ectomycorrhizal inoculation on the performance of Aleppo pine seedlings grown in a net-house. The roots of all pine seedlings were strongly dominated by Geopora, a fungal genus known to colonize seedlings in dry habitats. Ectomycorrhizal fungi (EMF) inoculum significantly increased seedling height, biomass, and the number of side branches. However, under either competition or drought, the positive effect of EMF on seedling biomass and height was greatly reduced, while the effect on shoot branching was maintained. Further, under a combination of drought and competition, EMF had no influence on either plant growth or shape. The discrepancy in pine performance across treatments highlights the complexity of benefits provided to seedlings by EMF under ecologically relevant settings.

Diversity inhibits foliar fungal diseases in grasslands: Potential mechanisms and temperature dependence.

A long-standing debate exists among ecologists as to how diversity regulates infectious diseases (i.e., the nature of diversity-disease relationships); a dilution effect refers to when increasing host diversity inhibits infectious diseases (i.e., negative diversity-disease relationships). However, the generality, strength, and potential mechanisms underlying negative diversity-disease relationships in natural ecosystems remain unclear. To this end, we conducted a large-scale survey of 63 grassland sites across China to explore diversity-disease relationships. We found widespread negative diversity-disease relationships that were temperature-dependent; non-random diversity loss played a fundamental role in driving these patterns. Our study provides field evidence for the generality and temperature dependence of negative diversity-disease relationships in grasslands, becoming stronger in colder regions, while also highlighting the role of non-random diversity loss as a mechanism. These findings have important implications for community ecology, disease ecology, and epidemic control.

Nitrogen addition alleviates water loss of Moso bamboo (Phyllostachys edulis) under drought by affecting light-induced stomatal responses.

The combined climate-change-evoked drought and nitrogen (N) deposition have severely affected plant carbon and water relations governed by stomata. However, the interplay between steady-state and dynamic stomatal behavior responses to light remains unclear regarding its impact on plant water and carbon relations. The objective here was to investigate whether light-induced stomatal dynamics could mitigate the adverse effects of steady-state gas exchange on water conservation or photosynthesis under drought and N addition conditions. We conducted a manipulative experiment to investigate the impacts of throughfall reduction, N addition, and their combination on light-induced stomatal and photosynthetic dynamics in a Moso bamboo (Phyllostachys edulis) forest. We determined the influence of stomal response rate on water loss and photosynthesis, and further assessed whether it mitigated the effects of steady-state gas exchange (gs). We found that Moso bamboo decreased gs under throughfall reduction, while accelerated stomatal opening and biochemical activation when irradiance increased, which reduced the lag in photosynthesis during the induction period. In contrast, under the combined throughfall reduction and N addition condition, Moso bamboo increased gs but showed faster stomatal closure, which decreased the percentage of transpiration following a decrease in light intensity. Our findings indicate that stomatal dynamic behavior may depend on the effects of steady-state gas exchange on water conservation and carbon uptake under different soil water and N conditions. These discoveries contribute to our understanding of the coupling mechanisms of plant water use and carbon uptake in the context of global changes.

Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands.

Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional-scale and local-scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one-season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional-scale and local-scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot-level variation was contingent on pasture-level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture-level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture-level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot-level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture-level and plot-level favorability interacted: perennial grasses had a higher plot-level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross-scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.

Allometric relationships and trade-offs in 11 common Mediterranean-climate grasses.

Biomass allocation in plants is the foundation for understanding dynamics in ecosystem carbon balance, species competition, and plant-environment interactions. However, existing work on plant allometry has mainly focused on trees, with fewer studies having developed allometric equations for grasses. Grasses with different life histories can vary in their carbon investment by prioritizing the growth of specific organs to survive, outcompete co-occurring plants, and ensure population persistence. Further, because grasses are important fuels for wildfire, the lack of grass allocation data adds uncertainty to process-based models that relate plant physiology to wildfire dynamics. To fill this gap, we conducted a greenhouse experiment with 11 common California grasses varying in photosynthetic pathway and growth form. We measured plant sizes and harvested above- and belowground biomass throughout the life cycle of annual species, while for the establishment stage of perennial grasses to quantify allometric relationships for leaf, stem, and root biomass, as well as plant height and canopy area. We used basal diameter as a reference measure of plant size. Overall, basal diameter is the best predictor for leaf and stem biomass, height, and canopy area. Including height as another predictor can improve model accuracy in predicting leaf and stem biomass and canopy area. Fine root biomass is a function of leaf biomass alone. Species vary in their allometric relationships, with most variation occurring for plant height, canopy area, and stem biomass. We further explored potential trade-offs in biomass allocation across species between leaf and fine root, leaf and stem, and allocation to reproduction. Consistent with our expectation, we found that fast-growing plants allocated a greater fraction to reproduction. Additionally, plant height and specific leaf area negatively influenced the leaf-to-stem ratio. However, contrary to our hypothesis, there were no differences in root-to-leaf ratio between perennial and annual or C4 and C3 plants. Our study provides species-specific and functional-type-specific allometry equations for both above- and belowground organs of 11 common California grass species, enabling nondestructive biomass assessment in California grasslands. These allometric relationships and trade-offs in carbon allocation across species can improve ecosystem model predictions of grassland species interactions and environmental responses through differences in morphology.

Assessing vulnerability to embolism and hydraulic safety margins in reed-like Restionaceae.

The African Restionaceae (Poales), the dominant graminoid layer in the megadiverse Cape Floristic Region of South Africa, are distributed across a wide range of moisture availability, yet currently there is very little known about the underlying hydraulics of this group. We tested two methods for measuring culm vulnerability to embolism, the optical and pneumatic methods, in three species of Cannomois ranging in habitat from semi-riparian (Cannomois virgata) to dryland (Cannomois parviflora and C. congesta). Estimates of culm xylem vulnerability were coupled with measures of turgor loss point (ΨTLP) and minimum field water potential (ΨMD) to assess hydraulic safety margins. The optical and pneumatic methods produced similar estimates of P50, but differed for P12 and P88. All three species were quite vulnerable to embolism, with P50 of -1.9 MPa (C. virgata), -2.3 MPa (C. congesta), and -2.4 MPa (C. parviflora). Estimates of P50, ΨTLP and ΨMD aligned with habitat moisture stress, with highest values found in the semi-riparian C. virgata. Consistent differences in P50, ΨMD and ΨTLP between species resulted in consistent hydraulic safety margins across species of 0.96 ± 0.1 MPa between ΨMD and P50, with onset of embolism occurring 0.43 ± 0.04 MPa after ΨTLP for all three species. Our study demonstrates that restio occupancy of dry environments involves more than the evolution of highly resistant xylem, suggesting that other aspects of water relations are key to understanding trait-environment relationships in this group.

Plant development: Laying the foundation for high-performance photosynthesis.

A new study shows that TOO MANY LATERALS/WIP6 acts as a key regulator of vein specification and development across C3 and C4 photosynthetic grasses.

Effects of increasing atmospheric CO2 on leaf water δ18O values are small and are attenuated in grasses and amplified in dicotyledonous herbs and legumes when transferred to cellulose δ18O values.

The oxygen isotope composition of cellulose (δ18O values) has been suggested to contain information on stomatal conductance (gs) responses to rising pCO2. The extent by which pCO2 affects leaf water and cellulose δ18O values (δ18OLW and δ18OC) and the isotope processes that determine pCO2 effects on δ18OLW and δ18OC are, however, unknown. We tested the effects of pCO2 on gs, δ18OLW and δ18OC in a glasshouse experiment, where six plant species were grown under pCO2 ranging from 200 to 500 ppm. Increasing pCO2 caused a decline in gs and an increase in δ18OLW, as expected. Importantly, the effects of pCO2 on gs and δ18OLW were small and pCO2 effects on δ18OLW were not directly transferred to δ18OC but were attenuated in grasses and amplified in dicotyledonous herbs and legumes. This is likely because of functional group-specific pCO2 effects on the model parameter pxpex. Our study highlights important uncertainties when using δ18OC as a proxy for gs. Specifically, pCO2-triggered gs effects on δ18OLW and δ18OC are possibly too small to be detected in natural settings and a pCO2 effect on pxpex may render the commonly assumed negative linkage between δ18OC and gs to be incorrect, potentially confounding δ18OC based gs reconstructions.

How does exotic Spartina alterniflora affect the contribution of iron-bound organic carbon to soil organic carbon in salt marshes?

Iron-bound organic carbon (OC-FeR) is important for the stability of soil organic carbon (SOC) in salt marshes, and the Spartina alterniflora invasion reshaped local salt marshes and changed the SOC pool. To evaluate the effects of S. alterniflora invasion on the contribution of OC-FeR to SOC, we determined the OC-FeR content and soil characteristics in the 0-50 cm soil profile along the vegetation sequence, including mudflats (MF), S. alterniflora marshes established in 2003 (SA03) and 1989 (SA89), the ecotone of S. alterniflora and Phragmites australis (SE), S. salsa marsh (SS), and P. australis marsh (PA). The SOC content was 6.55-17.5 mg g-1 in the S. alterniflora marshes. Reactive iron oxides (Fed, Feo, Fep) accumulated significantly in the S. alterniflora and P. australis salt marshes. PA and S. alterniflora marshes had higher DOC contents of 0.28-0.77 mg g-1. The OC-FeR content in the 0-50 cm soil profile in these ecosystems ranged from 0.3 to 3.29 mg g-1, with a contribution to the SOC content (fOC-FeR) of approximately 11 %, which was highest in SA03 (16.3 % ~ 18.8 %), followed by SA89, SE, and PA. In addition, the molar ratios of OC-FeR to Fed were <1, indicating that the iron oxides were associated with SOC through sorption more than coprecipitation. According to the structural equation model, SOC, DOC and iron oxides were the direct driving factors of OC-FeR formation, while the vegetation zone indirectly functioned by regulating organic C inputs, iron oxide formation, and pH. This study suggested that S. alterniflora invasion promotes iron-bound organic carbon accumulation by increasing organic C inputs and regulating iron oxide formation in salt marshes, but such promotion will degenerate with development duration.

Anthropogenic nitrogen pollution impacts saltmarsh resilience with inhibition of seedling establishment and population dispersal.

Saltmarsh, a prominent buffer ecosystem, has been identified as an important sink for nitrogen (N) pollutants from marine- and land-based anthropogenic activities. However, how the enriched anthropogenic N impacts saltmarsh sustainability has been neglected due to limited understanding of marsh resilience based on seedling establishment and population dispersal under anthropogenic N inputs. This study combined mesocosm experiments and model simulations to quantify the effects of increased anthropogenic N on the seedling-based vegetation expansion of Spartina alterniflora. The results indicated that seedling survivals, growth rates, and morphological indicators were inhibited by 20.08 %, 37.14 %, and > 35.56 %, respectively, under 1.5 gN/kg anthropogenic N. The sensitivity rate of vegetation expansion was increased by 70 % with 1 gN/kg increased N concentration under the scenario of low seedling density (< 15 m/yr). These findings revealed an important unidentified weakness of the marsh development process to anthropogenic N inputs. Finally, we highlighted the importance of appropriate protection measures to control nutrient pollution in salt marshes. Our study provides new insights for enhancing the resilience and sustainability of saltmarsh ecosystems.

Higher order polyploids exhibit enhanced desiccation tolerance in the grass Microchloa caffra.

Desiccation tolerance evolved recurrently across diverse plant lineages to enable survival in water-limited conditions. Many resurrection plants are polyploid, and several groups have hypothesized that polyploidy contributed to the evolution of desiccation tolerance. However, due to the vast phylogenetic distance between resurrection plant lineages, the rarity of desiccation tolerance, and the prevalence of polyploidy in plants, this hypothesis has been difficult to test. Here, we surveyed natural variation in morphological, reproductive, and desiccation tolerance traits across several cytotypes of a single species to test for links between polyploidy and increased resilience. We sampled multiple natural populations of the resurrection grass Microchloa caffra across an environmental gradient ranging from mesic to xeric in South Africa. We describe two distinct ecotypes of M. caffra that occupy different extremes of the environmental gradient and exhibit consistent differences in ploidy, morphological, reproductive, and desiccation tolerance traits in both field and common growth conditions. Interestingly, plants with more polyploid genomes exhibited consistently higher recovery from desiccation, were less reproductive, and were larger than plants with smaller genomes and lower ploidy. These data indicate that selective pressures in increasingly xeric sites may play a role in maintaining and increasing desiccation tolerance and are mediated by changes in ploidy.

Spartina alterniflora invasion decouples multiple elements in coastal wetland soils.

Deciphering the biogeochemical coupling of multiple elements in soils could better mechanistic understanding of ecosystem stability response to the alien invasion. The coupling of 45 elements in soils from wetlands covered by Spartina alterniflora (Sa) was compared with that in soils covered by native Phragmites australis (Pa) in coastal regions of China. Results showed that S. alterniflora invasion not only significantly reshaped geochemical enrichment and dispersion states, but also decoupled the coupling of multiple elements in soils compared with Pa. Atomic mass emerged as the primary factor governing the coupling of multiple elements, of which a significantly positive correlation exhibited between atomic mass with elemental coupling in Pa, but no such relation was observed in SaThe coupling of lighter elements was more susceptible to and generally enhanced by the invasion of S. alterniflora compared to the heavier, of which carbon, iron (Fe), and cadmium (Cd) had the highest susceptibility. Besides atomic mass, biological processes (represented by soil organic carbon, nitrogen, phosphorus, and sulfur), interactions between sea and land (represented by salinity and pH), and their combination explained 17 %, 10 %, and 13 % variation in the coupling of multiple elements, respectively. The present work confirmed that S. alterniflora invasion was the important factor driving soil multi-element cycling and covariation in coastal wetlands.