Growth Of Vascular Plants Research Articles

An arthropod community beyond the dry limit of plant life

Water availability, which enables plant growth and animal activity, regulates dryland ecosystem function. In hyper-arid ecosystems, rain cannot support vascular plant growth. Therefore, hyper-arid vegetation is restricted to the lower topography, where runoff accumulates. Typically, food resources originating from areas of dense vegetation are dispersed across the desert floor, enabling animal life in areas lacking vascular plant growth. However, certain regions, such as the hyper-arid upper topography, may be devoid of plant-derived food resources. The present study examined arthropod activity in the upper topography of a hyper-arid desert, in comparison with arthropod activity in the lower topography. Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel, vegetated riverbeds. Surprisingly, the study revealed dense arthropod communities in the barren upper topography. Arthropods collected in the upper topography represented 26% of total arthropod abundance. In addition, the overlap between arthropod identity in the ridges and wadis (i.e., riverbeds) was low, and certain arthropods were strongly affiliated with the ridges. The upper topographic communities included high numbers of silverfish (Zygentoma: Lepismatidae), malachite beetles (Psiloderes), and predatory mites (Acari: Anystidae), and these arthropods were present at various life stages. It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area. These results raise the possibility that other food sources, independent from vascular plants, may play a significant role in the life history of hyper-arid arthropods.

Overcoming establishment thresholds for peat mosses in human-made bog pools.

Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat‐forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human‐made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later‐successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human‐made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late‐successional species S. palustre. We conclude that open water and floating peat mats in human‐made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat‐forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor‐peat substrate. Correct species selection for restoration is crucial for success.

The Pioneering Role of Bryophytes in Ecological Restoration of Manganese Waste Residue Areas, Southwestern China

The mining of manganese brings excellent wealth to humankind. However, it destroys the ecological environment, mainly manifested as heavy metal pollution and vegetation destruction. The restoration of ecological vegetation in manganese mining areas has become an important work after mineral exploitation. The effect of bryophytes on ecological restoration in mining areas is irreplaceable. The bryophytes diversity and its pioneering role in two types of manganese waste residue areas were investigated in Guizhou province, China. The results showed that there were 24 species of mosses in mine waste slag areas, and all of them belonged to 6 families and 15 genera; the species Gymnostomum subrigidulum, Pohlia gedeana, and Bryum atrovirens were the dominant mosses. There were 6 species of mosses in electrolytic manganese slag areas, and all of them belonged to 5 families and 5 genera. The dominant moss was B. atrovirens. The bryophytes diversity in the electrolytic manganese slag areas with lower pH was poorer than that in mine slag areas. The accumulation of heavy metals in mosses showed that B. atrovirens collected from two types of areas had a strong ability to accumulate Mn with the cumulants 5588.00 μg/g and 4283.41 μg/g, respectively. All mosses had a strong enrichment ability to Cd. It indicated that mosses had strong tolerance to heavy metals. Bryophytes increased the available nutrients and bacterial community diversity of mosses growth substrates in two types of areas. Besides, we studied the relationships between bacterial community structure and soil factors. The main soil factor affecting the bacterial community structure was available nitrogen (AN) in mine waste slag areas, while it was pH in the electrolytic manganese residue areas. The systematic study suggested that bryophytes increased the available nutrients and the microbial community diversity of the growth substrates in manganese waste residue areas, which provided the basic conditions for the growth of vascular plants.

Value of large Quercus robur fallen logs in enhancing the species diversity of vascular plants in an old-growth mesic broad-leaved forest in the Central Russian Upland

Large old trees and decaying logs are key-retained structures for the retention forestry approach, but quantitative estimations of the role of fallen logs in the overall diversity and composition of forest vascular species are few and controversial. Particularly for mesic deciduous forests only a small number of such estimates are known. Our study aimed to partly fill this gap using data collected in the Reserve Kaluzhskie Zaseki where large Quercus robur individuals of more than 300 years old and fallen logs are frequent. We found 44 fallen oak logs supporting vascular plants within a 200-ha forest tract. The vegetation in plots of 1 m2 located on the fallen logs and on the forest floor adjacent to the logs was surveyed together with vegetation in fifteen 10 × 10 m plots randomly placed in patches without large fallen logs. NMDS and PERMANOVA were applied to examine differences in composition between fallen logs and forest floor. Generalized linear models were used to examine the relationships between environmental variables and species richness. Additive diversity partitioning was performed to examine differences in species richness and to estimate the contribution of the fallen logs to the general diversity in vascular species. In total, 71 vascular plant species in 108 1 m2-plots were identified. Twenty-five and 16 species were detected only on fallen logs and on the forest floor, respectively. More than 60% of the studied logs were in early stages of decomposition; their mean diameter was 75.4 ± 25.6 cm. Fallen logs significantly affected species richness and composition in terms of both woody seedlings and herbaceous species. The diameter of logs significantly and positively affected species diversity and composition. Large logs with cracked bark at the first two stages of decay were places of successful vascular plant establishment and growth. The abundance and frequency of tree seedlings were higher on the logs than on the forest floor and seven out of ten tree species appeared to be significant indicator species for the log-plots. Illumination varied over the observed sites and directly influenced the richness of herbaceous species and the overall species composition, but had no effect on woody species richness. We conclude that retention of large fallen logs can be an effective tool for maintaining and restoring the vascular species richness and composition in mesic broad-leaved forests.

A common soil temperature threshold for the upper limit of alpine grasslands in European mountains

While climatic research about treeline has a long history, the climatic conditions corresponding to the upper limit of closed alpine grasslands remain poorly understood. Here, we propose a climatic definition for this limit, the ‘grassline’, in analogy to the treeline, which is based on the growing season length and the soil temperature. Eighty-seven mountain summits across ten European mountain ranges, covering three biomes (boreal, temperate, Mediterranean), were inventoried as part of the GLORIA project. Vascular plant cover was estimated visually in 326 plots of 1 × 1 m. Soil temperatures were measured in situ for 2–7 years, from which the length of the growing season and mean temperature were derived. The climatic conditions corresponding to 40% plant cover were defined as the thresholds for alpine grassland. Closed vegetation was present in locations with a mean growing season soil temperature warmer than 4.9 °C, or a minimal growing season length of 85 days, with the growing season defined as encompassing days with daily mean ≥ 1 °C. Hence, the upper limit of closed grasslands was associated with a mean soil temperature close to that previously observed at the treeline, and in accordance with physiological thresholds to growth in vascular plants. In contrast to trees, whose canopy temperature is coupled with air temperature, small-stature alpine plants benefit from the soil warmed by solar radiation and consequently, they can grow at higher elevations. Since substrate stability is necessary for grasslands to occur at their climatic limit, the grassline rarely appears as a distinct linear feature.

Growth of Grimmia mosses on volcanic tephra: Geoecological processes of biocrust development in Haleakalā crater (Maui, Hawai′i)

This research examines high-elevation biocrusts on volcanic tephra in Haleakalā Crater, Maui, Hawai′i; geomorphic, ecological, and pedological processes are discussed, in order to provide an integrated geoecological view of linkages that have influenced biocrust genesis. The study considers four spatial scales: (i) the landscape scale; (ii) the site scale; (iii) the miniature scale and, (iv) the microscopic scale. (i) Biocrusts grow at ~ 2335 m on a hydrologic basin circumscribed by four cinder cones which contributed tephra materials during eruptions between 11000 and 5000 BP, ~2700 BP, and 970 ± 50 BP. Basin landforms provide multiple clues about past geomorphic processes that have affected crust evolution, including intermittent runoff, which decreased the length of cryptobiosis periods, allowing poikilohydric mosses to gradually expand into dense biocrusts; and widespread frost activity, which caused tephra sorting and extensive slope creep on cinder cones. Ubiquitous signs of current frost disturbance are also found on basin soils. (ii) The study site, located amidst bare volcanic tephra—ash and lapilli—includes mainly two organisms: an acrocarpous moss, Grimmia torquata, and a foliose lichen, Peltigera rufescens. Biocrusts attained 40.23% groundcover;G. torquata was found on 64 undisturbed specimens, and showed 78.3% frequency on 46 sampling plots, whereas P. rufescens grew on 23.4% of specimens. Biocrusts also supported 13 vascular species. The most common were grasses, with 5.6% cover and 67.4% total frequency, including Trisetum glomeratum (47.8%) and Deschampsia nubigena (19.6%); other vascular plants reached just 0.85% combined cover. Tests show 72% of vascular-plant cover was statistically correlated with presence of biocrusts, suggesting these have beneficial—presumably pedological—effects on vascular plant growth. (iii) Biocrust microtopography was characterized by intermingling areas of rolling, 15–35 mm-high, protrusions, and 40–75 mm-high pinnacles. (iv) Soil micromorphology indicated crust growth was probably influenced by a host of genetic processes, including wind abrasion and erosion; aeolian dust deposition; soil desiccation during seasonal wet-dry cycles; rainwash and raindrop impact; diurnal temperature cycles; and bioturbation by burrowing fauna. The interactions among these agents are integrated into an idealized crust developmental sequence during the past few millennia.

Bryophyte diversity is related to vascular plant diversity and microhabitat under disturbance in karst caves

Plant diversity, habitat properties, and their relationships in karst caves remain poorly understood. We surveyed vascular plant and bryophyte diversities and measured the habitat characteristics in six karst caves in south China with different disturbance histories (one had been disturbed by poultry feeding, three had been disturbed by tourism, and two were undisturbed). The plant diversity differences among the six caves were analyzed using cluster analysis, and the relationships of plant diversity and microhabitat were assessed using canonical correspondence analysis. We found a total of 43 angiosperm species from 27 families, 20 lycophyte and fern species from 9 families, and 20 species of bryophytes from 13 families in the six caves. Habitat characteristics including light intensity, air relative humidity, air temperature, and soil properties varied among the caves. The plant diversity in karst caves was not rich, but the species composition was unique. The caves with high disturbance had the lowest species richness, numbers of individuals, and Shannon-Wiener diversity indices but the highest Simpson’s dominance indices. The caves with less disturbance had the highest numbers of species, numbers of individuals, and Shannon-Wiener diversity indices but the lowest Simpson’s dominance indices. The disturbed caves were often dominated by drought-tolerant, tenacious mosses (bryophytes), while the relatively undisturbed caves contained abundant liverworts (bryophytes), which were better adapted to humid environments. Plant diversity in karst caves was closely related to habitat heterogeneity, light and water status, and nutrient availability. Tourism and poultry farming were associated with the degradation of vegetation in some karst caves. Protecting and restoring bryophytes might facilitate the settlement, growth, and succession of vascular plants in karst caves. Bryophytes can be used as indicators of overall plant diversity and restoration status in karst caves.

Not so stressful after all: Epiphytic individuals of accidental epiphytes experience more favourable abiotic conditions than terrestrial conspecifics

Vascular epiphytes are mainly associated with tropical and subtropical forest ecosystems. However, the frequent occurrence of accidental epiphytes in temperate forests proves that epiphytic growth of vascular plants is possible in tree crowns at these latitudes. Comparing the abiotic conditions of epiphytic and terrestrial microhabitats in conjunction with intraspecific differences in functional traits of the inhabiting plants, we identified limitations to vascular epiphytism in the study area in a Central European low mountain range. We determined light availability, winter temperatures, soil moisture, nutrient concentrations, and pH of arboreal soil in crotches of broad-leaved trees and in the immediate vicinity of each tree on the ground. Similarly, we quantified total plant water content, relative foliar chlorophyll content, specific leaf area (SLA), leaf dry matter content (LDMC), root-mass fraction, and aboveground nutrient concentrations of 110 pairs of epiphytic and terrestrial conspecifics. Water and nutrient availability were generally high in crotches filled with arboreal soil, suggesting better growth conditions than on the ground. A trophic advantage of epiphytic individuals over terrestrial conspecifics can be deduced from higher plant nutrient concentrations, higher SLA, and lower LDMC. Advantageous growth conditions might even result in higher growth rates and higher fitness of epiphytic individuals. Our findings highlight that vascular epiphytism in the study area is not necessarily limited by abiotic conditions but at least partly by the availability of old and structurally diverse trees providing suitable microhabitats. Accordingly, management actions in these secondary forest ecosystems should incorporate the preservation of old and large deciduous trees in order to sustain arboreal microhabitats and the associated biota.

Maize ANT1 modulates vascular development, chloroplast development, photosynthesis, and plant growth

Arabidopsis AINTEGUMENTA (ANT), an AP2 transcription factor, is known to control plant growth and floral organogenesis. In this study, our transcriptome analysis and in situ hybridization assays of maize embryonic leaves suggested that maize ANT1 (ZmANT1) regulates vascular development. To better understand ANT1 functions, we determined the binding motif of ZmANT1 and then showed that ZmANT1 binds the promoters of millet SCR1, GNC, and AN3, which are key regulators of Kranz anatomy, chloroplast development, and plant growth, respectively. We generated a mutant with a single-codon deletion and two frameshift mutants of the ANT1 ortholog in the C4 millet Setaria viridis by the CRISPR/Cas9 technique. The two frameshift mutants displayed reduced photosynthesis efficiency and growth rate, smaller leaves, and lower grain yields than wild-type (WT) plants. Moreover, their leaves sporadically exhibited distorted Kranz anatomy and vein spacing. Conducting transcriptomic analysis of developing leaves in the WT and the three mutants we identified differentially expressed genes (DEGs) in the two frameshift mutant lines and found many down-regulated DEGs enriched in photosynthesis, heme, tetrapyrrole binding, and antioxidant activity. In addition, we predicted many target genes of ZmANT1 and chose 13 of them to confirm binding of ZmANT1 to their promoters. Based on the above observations, we proposed a model for ANT1 regulation of cell proliferation and leaf growth, vascular and vein development, chloroplast development, and photosynthesis through its target genes. Our study revealed biological roles of ANT1 in several developmental processes beyond its known roles in plant growth and floral organogenesis.

In-situ assessment of the effects of periphyton on the growth of Vallisneria americana

Proliferation of nuisance algae in aquatic ecosystems is an increasingly common, global problem that can be attributed to a broad suite of anthropogenic activities. One particular concern is that algae can shade rooted vascular plants, decrease their productivity, and, in extreme cases, cause mortality and a loss of the ecological services they provide. The loss of macrophytes in Florida’s iconic spring-fed systems is especially alarming. In the Chassahowitzka River, for example, increases in epiphytic algae correlated with reductions in the abundance of important macrophytes such as Vallisneria americana. However, the relationships between loads of epiphytic algae and associated periphyton and the growth of vascular plants have not been characterized adequately. Here, we quantified the effect of epiphytic algae and associated periphyton using direct, in-situ measurements of growth rates for V. americana. Periphytic loads ranged from 11 to 15,211 mg DM per shoot (0.08 to 32.37 mg DM cm−2 of leaf), and weekly growth rates ranged from 0 to 197 mg DM or 0 to 87 cm2 per shoot (0 to 94 mg DM or 0 to 39 cm2 per leaf). Data indicated that changes in the growth rates of V. americana were the consequences of combined stresses from environmental factors (e.g., light at the water’s surface and periphytic loads) and physiological factors (e.g., leaf age). Life spans were shorter and turnover rates were faster only when shoots were exposed to higher periphytic loads throughout their lives. Boundary analyses of data for growth of leaves identified a threshold of 4–5 mg DM cm−2 of leaf in full sunlight, with heavier periphytic loads considered detrimental, and that threshold indicated that 20%–26% of incident, full sunlight was the minimum light requirement for V. americana in the Chassahowitzka River. A threshold for periphytic loads represents a valuable indicator that complements data on water quality, and the method to calculate a threshold provides a valuable tool that can improve management of all aquatic systems where the effects of periphyton on macrophytes are of concern.

Root endophytic Penicillium promotes growth of Antarctic vascular plants by enhancing nitrogen mineralization.

Fungal endophyte associations have been suggested as a possible strategy of Antarctic vascular plants for surviving the extreme environmental conditions of Antarctica. However, the mechanisms by which this occurs are still poorly understood. The role of root fungal endophytes in nitrogen mineralization and nutrient uptake, as well as their impact on the performance of Antarctic plants, were studied. We tested root endophytes, isolated from Colobanthus quitensis and Deschampsia antarctica, for lignocellulolytic enzyme production, nitrogen mineralization, and growth enhancement of their host plants. Penicillium chrysogenum and Penicillium brevicompactum were identified using a molecular approach as the main root endophytes inhabiting C. quitensis and D. antarctica, respectively. Both root endophytes were characterized as psychrophilic fungi displaying amylase, esterase, protease, cellulase, hemicellulase, phosphatase and urease enzymatic activities, mainly at 4°C. Moreover, the rates and percentages of nitrogen mineralization, as well as the final total biomass, were significantly higher in symbiotic C. quitensis and D. antarctica individuals. Our findings suggest that root endophytes exert a pivotal ecological role based not only to breakdown different nutrient sources but also on accelerating nitrogen mineralization, improving nutrient acquisition, and therefore promoting plant growth in Antarctic terrestrial ecosystems.

Will rising atmospheric CO2 concentration inhibit nitrate assimilation in shoots but enhance it in roots of C3 plants?

Bloom et al. proposed that rising atmospheric CO2 concentrations 'inhibit malate production in chloroplasts and thus impede assimilation of nitrate into protein of C3 plants, a phenomenon that will strongly influence primary productivity and food security under the environmental conditions anticipated during the next few decades'. Previously we argued that the weight of evidence in the literature indicated that elevated atmospheric [CO2 ] does not inhibit NO3 - assimilation in C3 plants. New data for common bean (Phaseolus vulgaris) and wheat (Triticum aestivum) were presented that supported this view and indicated that the effects of elevated atmospheric [CO2 ] on nitrogen (N) assimilation and growth of C3 vascular plants were similar regardless of the form of N assimilated. Bloom et al. strongly criticised the arguments presented in Andrews et al. Here we respond to these criticisms and again conclude that the available data indicate that elevated atmospheric [CO2 ] does not inhibit NO3 - assimilation of C3 plants. Measurement of the partitioning of NO3 - assimilation between root and shoot of C3 species under different NO3 - supply, at ambient and elevated CO2 would determine if their NO3 - assimilation is inhibited in shoots but enhanced in roots at elevated atmospheric CO2 .

Data variability or paradigm shift? Slow versus fast recovery of biological soil crusts-a review

Biological soil crusts, known also as biocrusts, provide valuable ecosystem services, especially in arid and semiarid regions. They may affect geomorphological (stability), hydrological (infiltration, evaporation), biochemical (carbon and nitrogen fixation) and ecological (germination and growth of vascular plants) processes, and their disturbance may have important ecological consequences. The common view, as reflected in hundreds of papers, regards biocrusts as having extremely slow recovery with characteristic time of up to hundreds and even thousands of years. Long recovery time implies that disturbance or climate change may have severe long-lasting consequences even once the conditions return to their initial state, triggering ample efforts to hasten biocrust recovery by inoculation. We critically analyze available estimates of the crust recovery time and present systematic measurements and theoretical considerations that attest to relatively rapid recovery of the crusts. We conclude that the likely recovery time of cyanobacterial crusts is 5–10 years, while that of lichen- and moss-dominated crusts is 10–20 years. Subsequently, costly and potentially negative effects to the ecosystem during inoculation should be weighed against the fast natural recovery of the biocrusts.

Axenic growth of the arbuscular mycorrhizal fungus Rhizophagus irregularis and growth stimulation by coculture with plant growth-promoting rhizobacteria.

Arbuscular mycorrhizal (AM) fungi are ecologically important for the growth and survival of most vascular plants. These fungi are known as obligate biotrophs that acquire carbon solely from host plants. A 13C-labeling experiment revealed the ability of axenically grown Rhizophagus irregularis DAOM 197198 to derive carbon from axenic culture on a relatively novel medium containing two sources of palmitic acid developed by Ishii (designated IH medium). In a separate experiment, this model fungus grew larger mycelia and produced more daughter spores on the IH medium in the presence of two Variovorax paradoxus strains than in axenic culture. In contrast, a strain of Mycobacterium sp. did not influence the growth of the AM fungus. Rhizophagus irregularis produced branched absorbing structures on the IH medium and, in monoxenic culture with V. paradoxus, sometimes formed densely packed hyphal coils. In this study, we report for the first time the formation of coarse terminal pelotons and of terminal and intercalary very fine (≈ 1 μm diameter) hyphal elongations, which could form daughter spores in the presence of V. paradoxus. This study shows the value of IH medium and certain rhizobacteria in the culture of R. irregularis DAOM 197198 in vitro.

Untargeted metabolomic profiling of Sphagnum fallax reveals novel antimicrobial metabolites.

Sphagnum mosses dominate peatlands by employing harsh ecosystem tactics to prevent vascular plant growth and microbial degradation of these large carbon stores. Knowledge about Sphagnum‐produced metabolites, their structure and their function, is important to better understand the mechanisms, underlying this carbon sequestration phenomenon in the face of climate variability. It is currently unclear which compounds are responsible for inhibition of organic matter decomposition and the mechanisms by which this inhibition occurs. Metabolite profiling of Sphagnum fallax was performed using two types of mass spectrometry (MS) systems and 1H nuclear magnetic resonance spectroscopy (1H NMR). Lipidome profiling was performed using LC‐MS/MS. A total of 655 metabolites, including one hundred fifty‐two lipids, were detected by NMR and LC‐MS/MS—329 of which were novel metabolites (31 unknown lipids). Sphagum fallax metabolite profile was composed mainly of acid‐like and flavonoid glycoside compounds, that could be acting as potent antimicrobial compounds, allowing Sphagnum to control its environment. Sphagnum fallax metabolite composition comparison against previously known antimicrobial plant metabolites confirmed this trend, with seventeen antimicrobial compounds discovered to be present in Sphagnum fallax, the majority of which were acids and glycosides. Biological activity of these compounds needs to be further tested to confirm antimicrobial qualities. Three fungal metabolites were identified providing insights into fungal colonization that may benefit Sphagnum. Characterizing the metabolite profile of Sphagnum fallax provided a baseline to understand the mechanisms in which Sphagnum fallax acts on its environment, its relation to carbon sequestration in peatlands, and provide key biomarkers to predict peatland C store changes (sequestration, emissions) as climate shifts.

2000 years of variability in hydroclimate and carbon accumulation in western Siberia and the relationship with large-scale atmospheric circulation: A multi-proxy peat record

The climate of Siberia is primarily influenced by the Siberian High (SH), although other large-scale atmospheric circulation systems, in particular North Atlantic Oscillation (NAO) storm tracks, play an important role. How variability in the relative strength and trajectory of these climatic systems has affected local to regional palaeoclimatic conditions remains little known. Here, we employ multi-proxy peat core analysis (δ13C, δ15N in Sphagnum, plant macrofossil, pollen, charcoal) from Plotnikovo Mire, part of the Great Vasyugan Mire in western Siberia (Tomsk province, Russia). We provide a high-resolution record of variations in climatic conditions and the biogeochemical fluxes of carbon and nitrogen over the past 2000 years and then discus the link between local climatic conditions and larger scale atmospheric circulation patterns. Our record shows that generally warm and dry conditions prevailed from BC 500 to 500 CE. Warm and wet episodes occurred during the early (800–950 CE) and later (1150–1300 CE) part of the Mediaeval Climate Anomaly (MCA), and were interrupted by a warm and dry mid-MCA phase (1000–1200 CE). Progressively cooler and wetter conditions established from 1400 CE, which became most marked between 1600 and 1850 CE, coincident with the Little Ice Age (LIA). Finally, drying of the mire surface reflects the warming trend of recent decades. We found that C accumulation was greater (90 g C m−2 yr−1) at times of wetter conditions and when Sphagnum was dominant, and lowest (35 g C m−2 yr−1) during periods of mixed vascular plant growth and Sphagnum under drier/unstable hydrological conditions. This peatland has been an active C sink over the past 1500 years, however, its ability to sequester carbon has decreased with recent warming and may continue to decrease with ongoing climatic warming and drying. We hypothesise that generally warm and moist conditions at the study site and over wider Siberia during the MCA could have been linked to a weakening of the Siberian High, which in turn enhanced the ingress of Atlantic moisture-carrying air masses across Siberia. Conversely, a strengthened SH overlapping negative North Atlantic Oscillation (NAO) modes during the LIA, resulted in a longer cold season with a delayed snowmelt and diminished evapotranspiration. This study shows that the interplay of moisture bearing air masses from different origins led to complex local hydroclimate and biogeochemical patterns. However, to resolve the spatio-temporal coherency of such climate variability due to the interaction of different air masses, and therefore better predict future climate changes, a denser network of palaeo-records is needed.

Species‐specific clonality in east Asian island flora: Phylogenetic and environmental constraints

AbstractPlant clonality is a ubiquitous trait observed in many phylogenetic clades and vegetations across tropical to arctic biomes. However, there is no consensus regarding determinant factors of species clonality; especially in the context of species assembly processes, ecological/evolutionary drivers of clonal growth remain largely unknown. To elucidate macroecological drivers of clonality, we examined phylogenetic conservatism/convergence of clonal growth in Japanese vascular plants and explored the ecological role of clonality. We created a dataset of clonal plants that were classified into phalanx, guerrilla and detachable clonal forms for 3,179 species, along with data regarding species geographical distributions and phylogenies. Then, we tested the association of phylogenetic and environmental factors with species clonality for three life‐form groups (fern, herb and woody species), and identified explanatory factors of clonal growth along large‐scale environmental gradients. Species clonality was phylogenetically constrained; specifically, for herb and woody species, phylogenetic signals across all the clonal growth forms, or especially the detachable form in ferns, were significant. Moreover, clonal growth of Japanese vascular plants was largely explained by taxonomic levels, and also partly by temperature, soil fertility, and species diversity in the distribution range, suggesting both processes; taxon‐dependent evolution of vascular plant clonality and evolutionary convergence of clonality across multiple clades of vascular plants relative to environmental constraints. Our findings demonstrated that species‐specific clonal growth, which acts as a trait related to abiotic/biotic niche, contributes to shaping large‐scale plant diversity patterns through species sorting along abiotic gradients.

Jasmonate-Related MYC Transcription Factors Are Functionally Conserved in Marchantia polymorpha.

The lipid-derived phytohormone jasmonoyl-isoleucine regulates plant immunity, growth and development in vascular plants by activating genome-wide transcriptional reprogramming. In Arabidopsis (Arabidopsis thaliana), this process is largely orchestrated by the master regulator MYC2 and related transcription factors (TFs). However, the TFs activating this pathway in basal plant lineages are currently unknown. We report the functional conservation of MYC-related TFs between the eudicot Arabidopsis and the liverwort Marchantia polymorpha, a plant belonging to an early diverging lineage of land plants. Phylogenetic analysis suggests that MYC function first appeared in charophycean algae and therefore predates the evolutionary appearance of any other jasmonate pathway component. M. polymorpha possesses two functionally interchangeable MYC genes, one in females and one in males. Similar to AtMYC2, MpMYCs showed nuclear localization, interaction with JASMONATE-ZIM-DOMAIN PROTEIN repressors, and regulation by light. Phenotypic and molecular characterization of loss- and gain-of-function mutants demonstrated that MpMYCs are necessary and sufficient for activating the jasmonate pathway in M. polymorpha, but unlike their Arabidopsis orthologs, do not regulate fertility. Therefore, despite 450 million years of independent evolution, MYCs are functionally conserved between bryophytes and eudicots. Genetic conservation in an early diverging lineage suggests that MYC function existed in the common ancestor of land plants and evolved from a preexisting MYC function in charophycean algae.

Population dynamics of Echinops gmelinii Turcz. at different successional stages of biological soil crusts in a temperate desert in China.

The effects of biological soil crusts (BSC) on vascular plant growth can be positive, neutral or negative, and little information is available on the impacts of different BSC successional stages on vascular plant population dynamics. We analysed seedling emergence, survival, plant growth and reproduction in response to different BSC successional stages (i.e. habitats: bare soil, cyanobacteria, lichen and moss crusts) in natural populations of Echinops gmelinii Turcz. in the Tengger Desert of northwest China. The winter annual E. gmelinii is a dominant pioneer herb after sand stabilisation. During the early stages of BSC succession, the studied populations of E. gmelinii were characterised by high density, plant growth and fecundity. As the BSC succession proceeded beyond moss crusts, the fecundity decreased sharply, which limited seedling recruitment. Differences in seedling survival among the successional stages were not evident, indicating that BSC have little effect on survival in arid desert regions. Moreover, E. gmelinii biomass allocation exhibited low plasticity, and only reproductive allocation was sensitive to the various habitats. Our results further suggest that the negative effects of BSC succession on population dynamics are primarily driven by increasing topsoil water-holding capacity and decreasing rain water infiltration into deeper soil. We conclude that BSC succession drives population dynamics of E. gmelinii, primarily via its effect on soil moisture. The primary cause for E. gmelinii population decline during the moss-dominated stage of BSC succession is decreased fecundity of individual plants, with declining seed mass possibly reducing the success of seedling establishment.

Weakening of the ‘enzymatic latch’ mechanism following long-term fertilization in a minerotrophic peatland

Despite the global importance of understanding the effects of nitrogen (N) and phosphorus (P) deposition on carbon (C) cycling in northern peatlands, the control of N and P interactions through the ‘enzymatic latch’ mechanism has been largely overlooked. A long-term fertilization experiment in a moderate-rich fen in northeast China was conducted to evaluate the underlying mechanisms of how continuous N and P addition regulate key extracellular enzymes and their interactions, and the subsequent influences on organic C storage in peatlands. The results demonstrated that the growth of Sphagnum moss and vascular plants were both reduced by N addition but enhanced by P addition. Phenolic concentrations were higher in P addition treatments, as were phenol oxidase activities. In general, N addition played a critical role in regulating the stoichiometry of β-D-glucosidase, N-acetyl-β-glucosaminidase and phosphatase, while P addition was more important in regulating their activities. The direct and indirect effects due to fertilization and shifts in vegetational composition, respectively, weakened the ‘enzymatic latch’ mechanism that controls the decomposition of organic matter after long-term fertilization. Our results indicate that P likely plays a more important role than N in controlling microbial extracellular enzymatic activities and organic matter decomposition in northern minerotrophic peatlands. Consequently, the interactions between N and P is likely of primary significance in regulating the biogeochemical cycling of peatlands.