Ramet Density Research Articles

Impacts of ramet density and herbivory on floral volatile emissions and seed production in Solidago altissima.

Plants produce an array of floral olfactory and visual cues to attract pollinators, including volatile organic compounds (VOC), which mediate plant-pollinator interactions and may be influenced by herbivory and neighboring plants. Consequently, these factors may affect plant fitness by disrupting pollination. However, most evidence comes from controlled experiments, limiting our understanding of how VOCs function in natural populations. This study investigated how herbivory and conspecific ramet density influence floral VOC profile, pollination, and seed production in a naturally occurring population of Solidago altissima. We recorded leaf herbivory and ramet density surrounding one focal ramet in 1-m2 plots. We collected VOCs from the floral headspace and measured ovary fertilization as a proxy for pollination success and the number of seeds produced by the focal ramet. Our findings revealed interactive effects between ramet density and herbivory on floral VOC emission, richness, and diversity. Specifically, at lower ramet densities, herbivory did not affect floral volatile emissions. However, in highly dense stands, herbivory suppressed floral volatile emissions. Despite these changes, floral volatiles did not affect pollination and the number of seeds in S. altissima. Our field-based findings underscore the importance of understanding the complex responses of floral VOCs to environmental stressors and their contributions to plant reproduction within natural communities. Our results suggest that while herbivory and ramet density influence floral scent, these changes do not affect reproduction in our study. Ultimately, generalist-pollinated plants like S. altissima might not rely heavily on chemical signaling during pollination.

The Population of the Glacial Relict Betula nana Surviving Anthropogenic Pressure (the Case of Šepeta Peatland in Northeastern Lithuania)

The main objective of the study was to evaluate the population characteristics of Betula nana under different anthropogenic influences. The study was conducted in the vicinity of the exploited Šepeta peatland (northeastern Lithuania). The population status of B. nana was determined by comparing the ramet density and morphology (height, branching, and leaf size), the age structure, the number of generative ramets, and their flowering characteristics in four study areas at different distances from the exploited peatlands and in different habitats. Around 20 environmental factors were included in the analysis, covering water levels, peat, and vegetation characteristics. Shading, drainage and increased amounts of nitrogen in the habitats are the main factors contributing to the differences and structure of B. nana cenopopulations. Although taller ramets with larger leaves are observed under the changed conditions as an adaptation to shading, the negative anthropogenic effects in the most affected habitats are reflected in a reduction in the number of flowering ramets, lower vegetative regeneration, and an increase in the number of dead twigs on mature ramets.

Bioturbating megafauna limits the expansion of Cymodocea nodosa seagrass meadows

In seagrass systems, there is a realization that biotic interactions affecting sediment stability might be as important as abiotic stressors in shaping the growth and distribution patterns of seagrass vegetation. However, few studies have looked at the interaction between seagrass and large (mega) bioturbating species, although through sediment reworking activity they may have the capacity to cause large scale impact on seagrass establishment. We assessed the effect of bioturbation by mobile megabioturbators (species lager than 5 cm) on subtidal seagrass (Cymodocea nodosa) using a manipulative field experiment where access by megabioturbators was restricted for 4 months during the growth season. There was a negative effect of megabioturbators on both the biomass and density of young seagrass ramets extending outwards from a mature seagrass meadow, but megabioturbators did not have a notable effect on seagrass growth in the meadows. Interestingly, the exclusion of megabioturbators in all tested habitats significantly modified the infaunal community composition, indicating the presence of complexity in biotic interactions and the possibility of indirect effects caused by the megabioturbators. Overall, megabioturbators have direct and indirect impact in seagrass habitats, playing a significant role in seagrass distribution patterns.

Crop rotation and cultivation effects on Convolvulus arvensis population dynamics in small grain organic cropping systems

Convolvulus arvensis L. Scop. (field bindweed) is a difficult weed to manage in organic cropping systems. Convolvulus arvensis suppression often requires intensive tillage and cultivation practices that have negative impacts on soil quality. To improve C. arvensis management in organic, small grain cropping systems, we compared ten cropping system treatments in a field trial from the autumn of 2017 until harvest of 2020 in Corvallis, MT, USA. Cropping system treatments varied along a gradient of tillage and crop competition, with tillage intensity and competition inversely related. High soil disturbance and no competition occurred in two treatments that remained in tilled fallow for two consecutive years. Six cropping system treatments had different combinations of tillage and annual or biennial crops, including wheat and forages. Two treatments had minimal soil disturbance and maximum competition from two consecutive years of perennial alfalfa. Convolvulus arvensis ramet density was counted annually to estimate changes in treatments over time. Differences in soil chemical and physical properties between treatments were also assessed in the final years of the study. In the first two years, there was no difference in C. arvensis ramet density among cropping system treatments. In the final two years of the study, C. arvensis density remained below one ramet per m2 in intensively tilled fallow treatments and perennial alfalfa treatments, but was much more variable in treatments with more diverse annual and biennial crop rotations with minimal to moderate tillage. The only differences between treatments in soil physical and chemical properties was aggregate stability. Soil from the most intensively tilled fallow treatments had lower soil aggregate stability than six other treatments, indicating higher erosion potential. Our results suggest that annual cropping systems can lead to increased C. arvensis density. Incorporating a perennial forage or an intensively tilled fallow period can prevent C. arvensis expansion in small grain organic cropping systems, but the perennial forage can protect and enhance soil quality.

Динаміка рівнинних популяцій Symphytum cordatum Waldst. et Kit. ex Willd. у різних умовах росту

Dynamics of isolated lowland populations of the Carpathian subendemic species Symphytum cordatum Waldst. et Kit. ex Willd. at the edge of its range is investigated. They were analyzed as a case study on the prospects of the lowland populations of S. cordatum under different growth conditions. Changes in the individual and group parameters of this species during the 17-year period are studied. Characteristic-markers of endangered state of S. cordatum populations in the mountain and lowland parts of its range are established. They include: low percentage of generative group or its absence, decrease in size and numbers of clones, significant reduction of the population area, considerable decrease in density of ramets and their low biometrical parameters as well as inhibition of vegetative propagation. It was established that population near Brodky village (Stryisky region, Lviv Oblast) exhibited high individual and group parameters during a long period and is capable of expansion, which ensures survival in the long-term perspective. Negative effects of anthropogenous impact on the population of S. cordatum in the city of Lviv are revealed. During the past period the area of the population decreased 3-folds, density of generative ramets, their hight and mass – 2-folds and considerable reduction in the area and number of clones were established as well. During the last years the population has been increasingly affected intensive mowing, trampling and raking which makes it endangered. It was established that small in their area and numbers lowland populations of S. cordatum growing in unfavorable ecological and coenotic conditions are most sensitive to anthropopression. The importance of protection of S. cordatum at the edge of its range is emphasized to provide conservation of regional biodiversity and gene pool of this species. Biotope conservation must be applied for such lowland populations of montane species like S. cordatum, it would prevent disturbance to sensitive small species habitats. This may be provided by creation of local reserves.

Structure of Equisetum variegatum (Equisetaceae) populations in natural and anthropogenic habitats

Many native plant species colonise anthropogenic habitats, but relatively little information is available on the status and development of their populations under unusual conditions. The most reliable information on the status and performance of plants in particular habitats is obtained through population studies. The study aimed to determine the characteristics of Equisetum variegatum populations occurring in natural and anthropogenic habitats. Nine coenopopulations of Equisetum variegatum occurring in natural and anthropogenic habitats were studied in four administrative districts (Kelmė, Lazdijai, Trakai and Varėna) of Lithuania. The ramet density, shoot height, total number of shoots and the number of fertile and sterile shoots and buds in a ramet were assessed. The density of Equisetum variegatum ramets was significantly higher in natural habitats than in anthropogenic habitats. The largest mean height of shoots was found in shrubland and shallow water habitats, whereas the largest mean number of all shoots, fertile shoots and buds in a ramet was recorded in dry sands. Old shoots in natural habitats comprised a significantly smaller portion (18.1%) of all shoots than in anthropogenic habitats (42.8%). Thus, all the studied traits can be used to evaluate the status of the populations. Long-term studies of Equisetum variegatum populations should be performed to determine how they change in response to the succession of natural and anthropogenic habitats. As the natural habitats of Equisetum variegatum decline, anthropogenic habitats may be considered the refugia for their populations.

Life-history traits and density dependence in metapopulations of a tropical moss: a monoicous species that is almost dioicous.

Life-history traits, such as reproductive allocation, sexual expression, sex ratio, and reproductive success, are central aspects of a species' ecology and evolution. For example, bias in male and female sex expression may play a large role in determining the viability of populations in the face of environmental pressures, such as population fragmentation, climate change and habitat occupancy. Thus, in this study, we investigated reproductive traits in 10 meta-populations of Fissidens flaccidus Mitt. From each meta-population, 30 patches were randomly selected, and 1 cm2 samples were collected form each patch. A total of 20,173 ramets were analyzed and classified into male, non-sporophytic female, sporophytic female, and non-sex expressing. In addition, population density in each patch was quantified. Our results showed that relative reproductive allocation in perigonia and sporophytes is greater than perichaetia. Trade-off between sexual relative reproductive allocation and asexual gemma production was observed, suggesting an important role of female ramets in asexual reproduction. The number of male ramets does not influence the reproductive success observed in each patch, and ramet density may induce male sex expression. Thus, we concluded that reproductive allocation in male function is efficient, since fewer male ramets can assure a considerable reproductive success. Furthermore, our results suggest that there may be a habitat preference between the sexes, since male ramets are found in patches with high density and mostly below female ramets, suggesting an avoidance of direct sunlight by male ramets.

Clonal integration systemically regulates leaf microstructure of Bouteloua dactyloides interconnected ramets to better adapt to different levels of simulated insect herbivory.

Stolon connection of clonal plants can translocate resources and signalling molecules between interconnected ramets to enhance resistance. Plants are well known to enhance leaf anatomical structure and vein density to respond to insect herbivory. Herbivory signalling molecules are transferred through vascular system to alert distant undamaged leaves, which is called systemic defence induction. Here, we investigated how clonal integration modulates leaf vasculature and anatomical structure of Bouteloua dactyloides ramets to cope with different levels of simulated herbivory. Ramet pairs were subject to six treatments, daughter ramets were exposed to three defoliation levels (0 %, 40 % or 80 % leaf removal) and their stolon connections to mother ramets were either severed or kept intact. Local 40 % defoliation increased vein density and adaxial/abaxial cuticle thickness, decreased leaf width and areolar area of daughter ramets. However, such effects of 80 % defoliation were much smaller. Compared with remote 40 % defoliation, remote 80 % defoliation increased leaf width and areolar area and decreased vein density of interconnected undefoliated mother ramets. Without simulated herbivory, stolon connection negatively affected most leaf microstructural traits of both ramets except from denser veins of mother ramets and more bundle sheath cells of daughter ramets. The negative effect of stolon connection on leaf mechanical structures of daughter ramets was ameliorated in the 40 % defoliation treatment, but not in the 80 % defoliation treatment. Stolon connection increased vein density and decreased areolar area of daughter ramets in the 40 % defoliation treatment. In contrast, stolon connection increased areolar area and decreased bundle sheath cell number of 80 % defoliated daughter ramets. Defoliation signals were transmitted from younger ramets to older ramets to change their leaf biomechanical structure. Clonal integration can adjust leaf microstructure of younger ramets according to the degree of herbivory stress, especially leaf vasculature.

Evaluation of acetolactate synthase (ALS)-inhibiting herbicides for red sorrel (Rumex acetosellaL.) management in lowbush blueberry (Vaccinium angustifoliumAiton)

Red sorrel is a common herbaceous perennial weed species in lowbush blueberry fields that may be managed with acetolactate synthase (ALS)-inhibiting herbicides. Greenhouse and field experiments were established to determine the crop tolerance and potential efficacy on red sorrel of tribenuron-methyl, nicosulfuron + rimsulfuron, foramsulfuron, flazasulfuron, pyroxsulam, and halosulfuron-methyl. Ramet density of greenhouse-grown red sorrel plants established from root fragments was reduced by tribenuron-methyl, flazasulfuron, and pyroxsulam, though tribenuron-methyl and flazasulfuron were the most consistently effective herbicides under field conditions. Spring non-bearing year tribenuron-methyl and flazasulfuron applications reduced both non-bearing and bearing year total red sorrel ramet density and reduced non-bearing year red sorrel flowering ramet and seedling density without injuring lowbush blueberry. Fall non-bearing year tribenuron-methyl and flazasulfuron applications reduced bearing year red sorrel total and flowering ramet density, and this application timing should be evaluated further to improve understanding of crop injury risks. Fall bearing year tribenuron-methyl and flazasulfuron applications reduced non-bearing year red sorrel total and flowering ramet density but did not reduce seedling density. Nicosulfuron + rimsulfuron, foramsulfuron, pyroxsulam, and halosulfuron-methyl efficacy on red sorrel were inconsistent or limited, and these herbicides are not recommended for red sorrel management in lowbush blueberry.

The selective advantage of mast flowering in Veratrum album subsp. oxysepalum: Implications of the predator satiation hypothesis.

Synchronous, highly variable flower or seed production among years within a population (i.e., masting) has been reported in numerous perennial plants. Although masting provides ecological advantages such as enhancing pollination efficiency and/or escape from predator attack, little is known about the degree of these advantages and variations in masting behavior among populations of conspecific plants. We determined flowering ramet density and reproductive success (fruit-set success and herbivorous damage) of a perennial herb, Veratrum album subsp. oxysepalum, across six lowland and six alpine populations in northern Japan during 2-3 years. We then analyzed the relationship between floral density and reproductive success to assess the ecological significance of mast flowering. Flowering intervals of individual plants were estimated by counting annual scars on rhizomes. Most populations had mast flowering, but the intervals between flowering for individual plants were shorter in the alpine populations than in the lowland populations. Floral damage by stem borers (dipteran larvae) and seed predation by lepidopteran larvae were intense in the lowland populations. Seed production of individual ramets increased with higher floral density owing to the effective avoidance of floral-stem damage and seed predation. Although stem borers were absent in the alpine habitat, seed predation decreased with higher floral density also in the alpine populations. Pollination success was independent of floral density in both of the alpine and lowland populations. These results strongly support the predator satiation hypothesis for mast flowering by this species.

Effects of Restoration Years on Vegetation and Soil Characteristics under Different Artificial Measures in Alpine Mining Areas, West China

In view of the problem of sustainable restoration of vegetation in alpine mining areas, vegetation communities and physical and chemical properties of soil under different artificial restoration measures (i.e., grass monoculture, sowing quantity and topsoil replacement) were investigated for five consecutive years (2016–2020) in the sloped eastern area of a northern slag mound in the Jiangcang mining area of the Muli coalfield in Qinghai, China. The results showed that the vegetation characteristics of different sowing treatments with different kinds of grass species, such as Elymus nutans, Poa pratensis cv. Qinghai and Poa crymophila cv. Qinghai, were significantly different (p < 0.05). The content of soil available nitrogen and phosphorus was significantly different among different grass species (p < 0.05). Vegetation coverage and ramet density of sowing treatment five were significantly higher than those of a lower sowing quantity (p < 0.05). There was no significant difference in the vegetation characteristics among different grass species treatments five years after the restoration (p > 0.05). There was no significant difference in vegetation height of different soil covering treatments (p > 0.05). In the early stage of restoration, vegetation coverage and ramet density in TR2 (resurfacing soil 10 cm) and TR3 (resurfacing soil 15 cm) were significantly higher than those without treatment. Soil N, P and organic matter under the treatments of TR1 (resurfacing soil 5 cm), TR2 and TR3 were significantly higher than those in CK (p < 0.05) in the early stage of restoration, but there was no significant difference in soil N, P and organic matter after five years of restoration. Overall, the vegetation and soil characteristics showed a trend of increase first and then decrease during the 5-year restoration period under different artificial measures. There were significant differences in the vegetation and soil characteristics among different treatments in the second year of restoration (p < 0.05), but there was no significant difference between the first year and the fifth year of restoration, which indicated that vegetation and soil began to degrade after five years of restoration, and substrate nutrients in the mining waste soil could only support the short-term restoration of vegetation. Therefore, it is necessary to target matrix nutrients in future vegetation restoration in alpine mining areas.

Spatial Aggregation and Biometric Variability of the Grass Calamagrostis epigejos (L.) Roth during Different Expansion Stages in Mesic Mountain Meadows

Calamagrostis epigejos (L.) Roth is one of the most expansive clonal grass species. Despite many publications about its biology, the expansive mechanism of C. epigejos is relatively unknown. Therefore, the aim of this study was to determine: I. the dependency between Calamagrostis epigejos ramet density, habitat properties, and the biometric variability of the species; II. the relation between clone architecture and the diversity parameters and the productivity of grassland biocoenoses; III. the expansion strategy of Calamagrostis epigejos within mesic meadows, representing three stages of degradation. The research was conducted in the Central Sudetes (SW Poland). Ten transects were selected for the study, each representing Arrhenatheretalia-type meadows with patches degraded as a result of Calamagrostis epigejos expansion:initial, intermediate, and advanced. The phalanx strategy was observed within the studied range of the Calamagrostis epigejos expansion in the mesic mountain meadows. The study showed no relation between the Calamagrostis epigejos expansion and the phenomenon of ramet self-thinning, though it noted the influence of the habitat on the variability of its biometric features.

Optimal foraging strategies in varying nutrient heterogeneity: responses of a stoloniferous clonal plant to patch pattern, size and quality

ABSTRACT Contrast and aggregation are two components of spatial heterogeneity. To precisely determine the influence of varying nutrient heterogeneity on the foraging behavior of clonal plants, we selected Potentilla anserina L. as the material and designed different patch patterns, sizes and qualities. In Experiment 1, compared with random and uniform patch patterns, aggregation increased ramet density and biomass accumulation at the patch scale, but not at the plot scale. This implies that the adaptive responses of clonal plants to nutrient heterogeneity depend on spatial scale. We further designed three levels of patch size with the same fertilizer concentration at the patch scale in Experiment 2, and four levels of patch quality with the same total amount of fertilizer at the plot scale in Experiment 3. Increased ramet density and stolon growth rate within small patches in Experiment 2 demonstrated effects of heterogeneity on plant foraging responses at the patch scale, while no difference was found in Experiment 3. This means that the influence of patch size on ramet establishment and residence time was alleviated by patch contrast at larger spatial scales. Hence, spatial scale is a key factor determining the interactions between heterogeneous ecosystem components.

Clonal Growth Characteristic of Epiphytic Orchid <i>Dendrobium sinense</i>

Dendrobium sinense  is a perennial epiphytic orchid, which belongs to the genus of  Dendrobium  and the family of Orchidaceae. Under natural conditions,  D. sinense  has a low seed setting rate and the environmental requirements for its seed germination a very stringent. Besides sexual propagation, asexual ways like clonal propagation is also found in  D. sinense.  In this study, five transects were set up in Bawang Ridge of Hainan Province to monitor the dynamic change of  D. sinense  population and study the influence of clonal propagation on population ecology of  D. sinense . The main results are as follows:  D. sinense  belongs to a bulbous clonal plant, Spacer between pseudobulbs is only 0.35 cm around. Buds are tillered on the base of the one-year pseudobulb and deveiopment through the energy transfer between the ramets to continuation the genet life. Branching intensity enhanced as genet grow up. And different ramet from the genet have big difference in growth situation. The scale of genet cannot expansion infinitely,  D. sinense  can adjust expend speed according to the density of ramets. Clonal growth provides material and energy reserves to sexual reproduction and create more sites for flowering by increasing the growth axis.

Evaluation of currently registered herbicides for fall bearing year red sorrel (Rumex acetosella L.) management in lowbush blueberry (Vaccinium angustifolium Aiton)

Red sorrel is a common creeping herbaceous, perennial weed species in lowbush blueberry fields and reproduces asexually via ramets from creeping roots. Ramets emerge throughout the season but remain vegetative due to a vernalisation requirement for flowering. This weed may therefore be managed with fall herbicide applications, but few currently registered herbicides have been evaluated for fall red sorrel management in lowbush blueberry. The objectives of this research were to (i) determine the effect of various herbicide treatments on red sorrel shoot and root biomass in the greenhouse, (ii) determine the effect of fall bearing year herbicide applications on overwintered red sorrel ramet density in the field, (iii) determine if reduced overwintered ramet density reduces flowering ramet density in the field, and (iv) estimate the potential for red sorrel to recover from fall bearing year herbicide applications. Dicamba, tribenuron-methyl, and glufosinate reduced red sorrel shoot and root biomass in the greenhouse and reduced overwintered ramet density in the field. Clopyralid, sulfentrazone, and flumioxazin reduced shoot and root biomass in the greenhouse but exhibited limited efficacy in the field. Nicosulfuron + rimsulfuron and glyphosate were ineffective in both the greenhouse and field. Dichlobenil and pronamide reduced overwintered ramet density in the field. Reduction of overwintered ramet density did not consistently reduce flowering ramet density. Dichlobenil reduced seedling density at two sites, but no herbicide consistently reduced summer non-bearing year ramet density. Fall herbicide applications alone, therefore, do not appear to maintain red sorrel suppression in lowbush blueberry fields.

Estimates of common milkweed (Asclepias syriaca) utilization by monarch larvae (Danaus plexippus) and the significance of larval movement

The population of monarch butterflies east of the Rocky Mountains has noticeably declined over the past two decades. The decline is due, in part, to loss of breeding and forage habitat in the Southern and Midwestern USA. To support a resilient overwintering population of six hectares of occupied forest canopy, approximately 1.6–1.8 billion additional ramets of milkweed are needed in the summer breeding range. Milkweed establishment that facilitates natural behavior of monarchs is necessary for effective conservation restoration. This study explored the effect of milkweed ramet density on larval search behavior, milkweed utilization, and survival without predation, parasitism, or competition. Under our experimental greenhouse conditions, monarch larvae abandoned their natal ramet, and subsequent ramets, prior to the pre-pupal wandering stage and before all available leaf biomass on a ramet was consumed. This is consistent with previous field observations. Larvae consumed biomass from three or four milkweed ramets that totaled the approximate biomass of single 10–35 cm ramet. Movement behavior suggests that isolated ramets may not support development through pupation, even though an isolated ramet could provide enough biomass. Our results suggest milkweed patches containing at least two to four ramets of closely-spaced common milkweed would provide sufficient biomass for development and increase the likelihood that larvae moving in random directions would encounter non-natal ramets to support development. Larval movement behavior and biomass requirements are critical aspects of monarch larval biology that should be considered in habitat restoration and maintenance plans, monitoring survey designs and protocols, and population modeling.

Different community crown layer environment under purple ear arrow bamboo shoots of growth development research

<p>The Jinfo Mountain National Nature Reserve in 3A different type community (deciduous broad-leaved forest, Evergreen deciduous broad-leaved mixed forest, Evergreen broad-leaved forest) under purple ear fargesia (<em>Fargesia decurvata</em> J.L.Lu) Young are of Growth Development Research. Results display: (1) Deciduous broad-leaved forest and evergreen deciduous broad-leaved mixed forest under the purple ear fargesia shooting of early and long duration 110 d Shooting large shooting rate is high; evergreen broad-leaved forest under the shooting of late and short duration 88 D Shooting less shooting rate low; evergreen deciduous broad-leaved mixed forest in the shooting of maximum. (2) Shooting period is divided 3A stage: early stage and the end the community in purple ear fargesia into each period of time have difference evergreen deciduous broad-leaved mixed forest in the first to enter the shooting stage deciduous broad-leaved forest followed by evergreen broad-leaved forest. Shooting stage is also back are the peak back are rate of size for: evergreen deciduous broad-leaved mixed forest > Deciduous broad-leaved forest>Evergreen broad-leaved forest. (3) The same community crown layer environment under purple ear fargesia Different Period Unearthed of young are ground diameter no significant difference. In deciduous broad-leaved forest and evergreen deciduous broad-leaved mixed forest canopy environment in the Period Unearthed of young are ground diameter between no significant difference but were significantly greater than the evergreen broad-leaved forest (<em>P</em> < 0.05). (4) Purple ear fargesia young are unearthed after 80 d About complete high growth process and in line Logistic Equation was Slow-Fast-Slow Of growth trend. High growth rate for: evergreen deciduous broad-leaved mixed forest > Deciduous broad-leaved forest > Evergreen broad-leaved forest and difference significant (<em>P</em> < 0.05). (5) Purple ear understory of bamboo cloning reproduction and ramet density between have close relationship. With the ramets density of increase shooting quantity increase bamboo quantity reduce. This study show that different Community crown layer environment under purple ear bamboo growth development significant difference in evergreen deciduous broad-leaved mixed forest in development best evergreen broad-leaved forest in development worst, population density of bamboo of update development the important regulation role.</p>

Browsing and fire decreases dominance of a resprouting shrub in woody encroached grassland

North American grasslands have experienced increased relative abundance of shrubs and trees over the last 150yr. Alterations in herbivore composition, abundance, and grazing pressure along with changes in fire frequency are drivers that can regulate the transition from grassland to shrubland or woodland (a process known as woody encroachment). Historically, North American grasslands had a suite of large herbivores that grazed and/or browsed (i.e., bison, elk, pronghorn, deer), as well as frequent and intense fires. In the tallgrass prairie, many large native ungulates were extirpated by the 1860s, corresponding with increased homesteading (which led to decreased fire frequencies and intensities). Changes in the frequency and intensity of these two drivers (browsing and fire) have coincided with woody encroachment in tallgrass prairie. Within tallgrass prairie, woody encroachment can be categorized in to two groups: non-resprouting species that can be killed with fire and resprouting species that cannot be killed with fire. Resprouting species require additional active management strategies to decrease abundance and eventually be removed from the ecosystem. In this study, we investigated plant cover, ramet density, and physiological effects of continuous simulated browsing and prescribed fire on Cornus drummondii C.A. Mey, a resprouting clonal native shrub species. Browsing reduced C.drummondii canopy cover and increased grass cover. We also observed decreased ramet density, which allowed for more infilling of grasses. Photosynthetic rates between browsed and unbrowsed control shrubs did not increase in 2015 or 2016. In 2017, photosynthetic rates for browsed shrubs were higher in the unburned site than the unbrowsed control shrubs at the end of the growing season. Additionally, after the prescribed fire, browsed shrubs had ~90% decreased cover, ~50% reduced ramet density, and grass cover increased by ~80%. In the roots of browsed shrubs after the prescribed fire, nonstructural carbohydrates (NSC) experienced a twofold reduction in glucose and a threefold reduction in both sucrose and starch. The combined effects of browsing and fire show strong potential as a successful management tool to decrease the abundance of clonal-resprouting woody plants in mesic grasslands and illustrate the potential significance of browsers as a key driver in this ecosystem.

Is there a maximum length of strap-like leaves for submerged angiosperms?

Leaves are critical plant organs for photosynthesis. In addition, leaf length is an important indicator of leaf size. Although previous studies have revealed the maximum length of leaves from terrestrial plants, as well as their limiting factors, these issues remain relatively unexplored for leaves of submerged macrophytes. Based on meta-analysis of 48 species of aquatic plants, we found that the strap-shaped leaves of submerged macrophytes were particularly long, with a maximum length among studied species of 300 cm (e.g., Vallisneria australis). To explore the role of light in regulating maximum leaf length, we first calculated the suitable growth zone (SGZ) for submerged macrophytes according to light conditions. Results showed that the vertical range of the SGZ was approximately twice that of the maximum leaf length mentioned above. This suggests that light was not the only factor limiting maximum leaf length. In addition to hydraulic conditions and water depth, the short lifespan and slow leaf growth rate also contributed to the limitation of maximum leaf length. Correlation analysis between maximum leaf length and ramet density also revealed a potential trade-off between the two traits in submerged macrophytes. Thus, in addition to light conditions, various other factors limited leaf elongation and thus regulated the maximum length of submerged strap-like leaves.

The success of rock translocation for populations of the chasmophytic Aeollanthus saxatilis (Lamiaceae)

To ensure the rescue, temporary conservation and further restoration of plant populations and communities threatened by exploitation, translocation appears to be an appropriate method in the context of mining. Little is known, however, on its effect on mutualistic interactions, such as pollination, and on the resulting plant population dynamics. Whole-rock translocations were performed as a conservation strategy for the endemic metallophyte flora of Katanga, Democratic Republic of the Congo. The aim of this study was to quantify the flower visitation, sexual reproduction and ramet demographic structure in such a translocated population, and to compare the data with those from natural populations of Aeollanthus saxatilis, one of the threatened species of the chasmophytic community. The study also documented the plant’s flower visitor guild. The ramet density, demographic structure, pollination success and seed abortion rate were assessed in 10 quadrats per population, in the translocated population and in two subsisting natural populations. The flower visitation rate was quantified during three observation periods (20 min each) in six quadrats per population.Small differences were observed in the visitor guild between the translocated and natural populations, but the flower visitation rate was equivalent. No clear difference in the reproductive performance or ramet demographic structure of the populations was found. The flower visitor guild was mainly composed of generalist pollinators, which probably helped in establishing a functional visitor guild at the receptor site.Rock translocation therefore appears to be an encouraging approach, allowing the conservation of functional mutualistic interactions and the maintenance of a population structure comparable to that of natural chasmophytic plant populations.