Belowground Bud Research Articles

Contribution of different bud types to community regeneration on a typical steppe under various enclosure durations in Inner Mongolia, China

Understanding the changes in the total bud bank, and its contribution to community regeneration, in response to grassland enclosure to livestock grazing, is crucial for grassland management. Despite its importance, the contribution of the total bud bank and that of different bud types to community regeneration as a whole have been rarely explored. The vegetative offspring recruited from different bud types was investigated in grasslands having different enclosure durations to livestock grazing on a typical steppe of Inner Mongolia, China. Total vegetative offspring density was significantly higher (p<0.05) under continuous grazing than in fenced grasslands, but no significant changes were found among plots with different enclosure durations to livestock grazing. The percentage and density of tiller-ramets were significantly higher (p<0.05) under continuous grazing than in fenced grasslands. However, rhizome-ramets followed an opposite pattern (p<0.05). Bulb-ramets showed negligible differences in percentage and density among grasslands with different enclosure durations to livestock grazing and those exposed to continuous grazing. Root-derived ramets only occurred in fenced plots. Our results indicate that (1) grassland enclosure to domestic livestock reduce vegetative regeneration from belowground bud banks; (2) enclosure duration to livestock grazing showed no evident effect on the whole contribution of the belowground bud bank to vegetative regeneration, but changed the relative contribution of the different bud types, and (3) while grassland enclosure to livestock grazing reduced density of tiller-ramets, rhizome- and root-derived sapling densities were increased. Therefore, changes in the regenerative contribution of different bud types might be used to (1) predict community dynamic under disturbances and climatic changes, and (2) delineate adequate policies for grassland management and utilization.

Temporal dynamics of plant community regeneration sources during tallgrass prairie restoration

Ecological restoration aims to augment and steer the composition and contribution of propagules for community regeneration in degraded environments. We quantified patterns in the abundance, richness, and diversity of seed and bud banks across an 11-year chronosequence of restored prairies and in prairie remnants to elucidate the degree to which the germinable seed bank, emerged seedlings, belowground buds, and emerged ramets were related to community regeneration. There were no directional patterns in the abundance, richness, or diversity of the germinable seed bank across the chronosequence. Emerged seedling abundance of sown species decreased during restoration. Richness and diversity of all emerged seedlings and non-sown emerged seedling species decreased across the chronosequence. Conversely, abundance and richness of belowground buds increased with restoration age and belowground bud diversity of sown species increased across the chronosequence. Numbers of emerged ramets also increased across the chronosequence and was driven primarily by the number of graminoid ramets. There were no temporal changes in abundance and richness of sown and non-sown emerged ramets, but diversity of sown emerged ramets increased across the chronosequence. This study demonstrates that after initial seeding, plant community structure in restored prairies increasingly reflects the composition of the bud bank.

Controls on bud activation and tiller initiation in C3and C4tallgrass prairie grasses: the role of light and nitrogen

Population dynamics of perennial grasses in tallgrass prairie ecosystems are strongly influenced by vegetative outgrowth from their belowground bud banks. We examined the role of light and nitrogen in regulating tiller initiation and tested an integrated model of controls on bud dormancy and activation in several C3and C4grasses. In addition, we assessed the interaction of nitrogen and light quantity and red – far red spectral composition on tiller initiation. Belowground perennating organs of three C3and three C4species were grown under full light or dark conditions, amended with one of four nitrogen concentrations (0 to 350 ppm N). Dormant buds were also subjected to full light under different spectral compositions or to continuous darkness. Our results among C3grasses support the integrated model as light and nitrogen played important and interacting roles in the regulation of bud banks. However, differences in responses among C4grasses and a lack of light × nitrogen interactions suggest that an alternative model may be necessary for this functional group. Our results provide predictions of responses to nitrogen enrichment or light imitations in prairie ecosystems due to interacting disturbances such as reduction in fire frequencies, alterations in grazing intensities, or climate change.

Inter-specific variation in bud banks and flowering effort among semi-arid African savanna grasses

Population viability and productivity of grasses in southern African savannas are dependent upon both successful seed production and tiller recruitment from the belowground bud bank. Relative recruitment rates from buds versus seeds influence population dynamics, genetic diversity, and patterns of vegetation productivity. We assessed patterns in bud bank size and flowering effort in fourteen semi-arid savanna grass species in the Kalahari region of Botswana. There was high inter-specific variability and between-year variability in flowering effort (percentage of tillers flowering). Bud production (number of buds per tiller) exhibited high inter-specific variability, but was more consistent between-years than flowering effort. Relative allocation to flowering versus bud production varied with life history, with longer-lived perennial grasses showing higher bud production and lower flowering effort relative to shorter-lived grasses. Several species showed higher bud production and lower flowering effort in a wet year compared to a dry year, and grass species that are regularly grazed maintained significantly larger bud banks than non-grazed species. These differential demographic responses among co-occurring species suggest that environmental change in semi-arid savannas may alter the composition, relative abundances and diversity of grasses, and that the maintenance of a belowground bud bank is an important factor influencing their resiliency, their capacity to recover from grazing and/or drought, and their persistence and sustainability under changing environmental conditions. Meristem-limitation in species that maintain few viable buds may constrain their population viability under changing conditions in semi-arid savannas.

Bud production and dynamics of flowering and vegetative tillers in Andropogon gerardii (Poaceae): the role of developmental constraints

Perennial grasses maintain aboveground tiller populations through vegetative reproduction via belowground buds and sexual reproduction via seed. The maintenance of a bud bank has important demographic consequences for perennial grasses. A tradeoff between these reproductive modes would be expected for a plant with limited resource availability. However, the ontogeny of the tiller could affect its ability to allocate between these two modes of reproduction. Vegetative bud production and dynamics and tiller production were examined biweekly through an annual cycle on vegetative and flowering tillers of Andropogon gerardii. Andropogon gerardii maintains a large reserve of dormant buds. Although vegetative and flowering tillers had similar bud phenology, flowering tillers produced larger numbers of buds of larger size, and transitioned a larger proportion of their buds to tiller, than did vegetative tillers. Therefore, a negative consequence of sexual reproduction on vegetative reproduction was not evident at the tiller level. A size threshold for floral induction likely exists that results in flowering tillers having more buds per tiller than vegetative tillers. The increased bud outgrowth of flowering tillers could be a result of their larger bud size or weaker apical dominance as compared to vegetative tillers. Plant development can place significant constraints on tradeoffs between the reproductive modes in perennial grasses and could affect their plasticity in plant reproductive allocation. Differences in developmental phenology and bud production between flowering and vegetative tillers may influence grass responses to environmental changes such as altered precipitation regimes or resource availability.

Rhus glabra response to season and intensity of fire in tallgrass prairie

Altered fire regimes play a key role in shrub expansion in grasslands worldwide. We assessed how season and type or intensity of fire affected the growth and demography of Rhus glabra, a common woody invader in North American mesic grasslands. Fire during any season killed 99% of ramets but stimulated new ramet recruitment from belowground buds, resulting in a near-complete turnover of ramet populations. During the first 2 years following fire, populations on spring-burned sites had the greatest post-fire ramet densities and population growth rates, and winter- and spring-burned populations showed the highest resprouting rates. However, after 10 years, R. glabra cover on summer-burned sites was 3.5 times greater than on autumn- or winter-burned treatments. Thus, short-term post-fire responses may not be good predictors of long-term changes in abundance. Low-intensity spring backfires resulted in the highest ramet population growth rates, whereas high-intensity headfires in any season resulted in slower growth, and populations burned with low-intensity winter fires declined. In addition, season of fire influenced browsing pressure, suggesting that plant responses may be partially a result of indirect effects of fire on rates of herbivory. Overall, our results demonstrate that the application of frequent autumn or winter backfires is an effective management tool for limiting R. glabra expansion in grasslands, and that long-term data are critical for management decision-making, particularly in systems characterised by high interannual climate variability.

The Association of Dispersal and Persistence Traits of Plants with Different Stages of Succession in Central European Man-Made Habitats

Traits related to seed dispersal, clonality and bud bank affect the success or failure of plant species. Using data from 13 successional seres in various human-made habitats the spectra of traits associated with dispersal and persistence were compared to determine the traits that can be used to predict the occurrence of particular plant species at each stage in a succession and how the importance of these traits changes over time. Differences in the traits of species associated with primary and secondary successions were also studied. Species with seeds that are dispersed by water (hydrochory) decreased in abundance during the course of succession. Species with a splitting main root, monocyclic and dicyclic shoots also decreased in abundance. Species capable of forming a potential below-ground bud bank, hypogeogenous rhizome and retaining a long-term connection with clonal offspring increased in abundance. The results indicate that seed dispersal is more important in determining the species composition in the early stages of succession whereas bud banks and clonal traits are more important in the later stages and for colonizing a locality. Primary and secondary seres did not remarkably differ in the trait spectra of the species present indicating that these trends occur in both types of succession.

Summer warming effects on biomass production and clonal growth of Leymus chinensis

Understanding how the biomass production and clone growth of perennial grasses respond to summer warming is crucial for understanding how grassland productivity responds to global warming. Here, we experimentally investigated the effects of summer warming on the biomass production and clonal growth of potted Leymus chinensis in a phytotron. Summer warming significantly decreased the biomass of both parent and daughter shoots, slightly increased the belowground biomass, and lead to a significant increase in root : shoot ratio. Warming significantly increased the total belowground bud number and decreased the daughter shoot number. Importantly, the proportions of each type of bud changed; vertical apical rhizome buds decreased, while horizontal rhizome buds increased in number. The change in proportions of each type of bud is closely related to the decrease in daughter shoot number, rhizome number and length, as well as the decrease in aboveground biomass and increase in belowground biomass. These results indicate that, as a rhizomatous, perennial grass, L. chinensis adopts a selective growth strategy that reduces the energy allocated to aboveground growth and emphasises the development of belowground organs. The implication is that continued summer warming, will further reduce the aboveground biomass production of temperate grasslands dominated by rhizomatous, perennial grasses. Inevitably, species that depend on these grasses for forage will suffer should global climate warming continue.

A soil heat and water transfer model to predict belowground grass rhizome bud death in a grass fire

AbstractQuestion:Grasses often resprout from surviving belowground buds following a fire in which aboveground matter is consumed. We used a soil heat and water transport model to present a general method for determining the potential mortality of rhizome buds due to fire for three tallgrass species (Andropogon gerardii, Sorghastrum nutans, andPanicum virgatum).Methods:Soil heating was described by physical processes that include heat conduction through the soil and heating and evaporation of soil water. We considered the following factors: soil moisture, texture, mineral thermal conductivity, maximum surface temperature, and fire residence time. Simulated soil temperature profiles were combined with measured belowground bud distributions to determine the proportion of buds expected to be heated to lethal temperatures under various conditions.Location:Wisconsin, USA.Results:Lethal temperatures for buds do not occur below ∼2 cm, and at least 30% of rhizome buds remain below lethal temperatures, even under extreme conditions.Conclusions:The model explains the possible mechanisms for grass belowground rhizome bud survival in fires. Changes in fire and soil conditions do not notably impact soil temperatures and rhizome bud survival.

The effects of fire frequency and grazing on tallgrass prairie productivity and plant composition are mediated through bud bank demography

Periodic fire, grazing, and a variable climate are considered the most important drivers of tallgrass prairie ecosystems, having large impacts on the component species and on ecosystem structure and function. We used long-term experiments at Konza Prairie Biological Station to explore the underlying demographic mechanisms responsible for tallgrass prairie responses to two key ecological drivers: fire and grazing. Our data indicate that belowground bud banks (populations of meristems associated with rhizomes or other perennating organs) mediate tallgrass prairie plant response. Fire and grazing altered rates of belowground bud natality, tiller emergence from the bud bank, and both short-term (fire cycle) and long-term (>15 year) changes in bud bank density. Annual burning increased grass bud banks by 25% and decreased forb bud banks by 125% compared to burning every 4 years. Grazing increased the rate of emergence from the grass bud bank resulting in increased grass stem densities while decreasing grass bud banks compared to ungrazed prairie. By contrast, grazing increased both bud and stem density of forbs in annually burned prairie but grazing had no effect on forb bud or stem density in the 4-year burn frequency treatment. Lastly, the size of the reserve grass bud bank is an excellent predictor of long-term ANPP in tallgrass prairie and also of short-term interannual variation in ANPP associated with fire cycles, supporting our hypothesis that ANPP is strongly regulated by belowground demographic processes. Meristem limitation due to management practices such as different fire frequencies or grazing regimes may constrain tallgrass prairie responses to interannual changes in resource availability. An important consequence is that grasslands with a large bud bank may be the most responsive to future climatic change or other global change phenomena such as nutrient enrichment, and may be most resistant to exotic species invasions.

Underground systems of Asteraceae species from the Brazilian Cerrado1

Abstract Underground systems of Asteraceae species from the Brazilian Cerrado. The aim of this study was to describe the underground systems structure, the origin of the shoot buds, and to identify the storage reserve of seven Asteraceae species in order to understand the adaptive strategies of these species in burned Cerrado areas and their higher frequency in the floristic surveys for herbaceous and undershrub layers of this biome. The subterranean systems types—diffuse underground system, rhizophore, tuberous roots, and xylopodium—varied among the studied species, but all of them have high shoot bud-forming potential. Fructans of the inulin type were detected as storage substances. The presence of these characteristics on the underground systems could explain the frequency of these species in the floristic surveys from the Brazilian Cerrado, in which fire and seasonal drought are frequent. It is possible that the belowground bud banks in the Cerrado biome are as important as demonstrated in North Ameri...

Bud banks of perennial savanna grasses in Botswana

AbstractThree semi‐arid savanna grasses in Botswana (Stipagrostis uniplumis,Eragrostis lehmanniana, andAristida stipitata) were sampled to quantify their belowground bud banks during the dormant season and to estimate their relative allocation to vegetative and sexual reproduction. Bud banks of these African perennial caespitose grasses were also compared with four perennial caespitose grasses of semi‐arid North American grasslands. The three African grasses each maintained approximately two buds per tiller and showed a high percentage (88–99%) of tillers producing seed. OnlyE. lehmannianaproduced new aerial tillers from axillary buds at elevated nodes on the stem as well as from the belowground bud bank. Compared with species of North American grasslands, these African grasses produced fewer belowground buds but showed a much higher percentage of tillers producing seed. These patterns indicate relatively greater belowground meristem limitation, lower allocation to vegetative reproduction (tillering) and higher allocation to seed reproduction in these African grasses, although studies of more species are needed to assess the generality of this pattern. The management of savannas in ways that favour the maintenance of a reserve population of belowground buds may increase the ability of grasses to respond to pulses of resource availability, increase their compensatory growth capacity following grazing or drought, and decrease the invasibility of these plant communities by exotic species, whereas maintaining allocation to sexual reproduction may be important for conserving genetic variation and enhancing their capacity to adapt to environmental change.

Belowground bud banks and meristem limitation in tallgrass prairieplant populations

Rhizome meristem populations were sampled in tallgrass prairie to quantify the size, grass : forb composition, and temporal and spatial variability of the soil bud bank and to compare fire effects on bud bank and seed bank composition. Soil cores (10.5 cm diameter, 15 cm deep) were collected from replicate annually and infrequently burned tallgrass prairie sites, and intact rhizomes and rhizome buds were censused. Bud bank densities ranged from approximately 600 to 1800 meristems/m(2) among sites and had high spatial and seasonal variability. In annually burned prairie, the total bud bank density was two-fold greater and the grass : forb meristem ratio was more than 30-fold greater than that of infrequently burned prairie. These patterns are opposite those observed in soil seed banks at this site. The rhizome population in annually burned prairie was 34% larger than the established aboveground tiller population. By contrast, the bud bank density in unburned prairie was significantly lower than aboveground stem densities, indicating possible belowground meristem limitation of stem density and net primary production on infrequently burned prairie. The patterns observed in this study suggest that the densities and dynamics of tallgrass prairie plant populations, as well as their response to disturbance (e.g., fire and grazing) and climatic variability, may be mediated principally through effects on the demography of belowground bud populations. Patterns of seed reproduction and seed bank populations have little influence on short-term aboveground population dynamics of tallgrass prairie perennials.

The Formation and Development of Adventitious Buds on Potato Sprouts

Potato tubers were pre-sprouted in trays at 10 °C for 28 d. The scale leaves at the base of the sprouts were marked and tubers then planted in field soil. Twenty-eight days after planting an average of three adventitious buds were present per sprout compared with an average of six below-ground axillary buds. Ten per cent of adventitious buds formed stolons compared with almost 100 per cent of axillary buds. Similar responses were seen with tubers pre-sprouted either in the light or dark.

Shoot regeneration after fire or freezing temperatures and its relation to plant life-form for some heathland species

Shoot regeneration after prescribed burning or following the freezing temperatures of winter was monitored for nineteen heathland species present in an Arctostaphyleto-Callunetum community in northeast Scotland. Species whose renewal buds were near the surface of the ground started to grow earlier in the spring than species with renewal buds above the surface, but grouping species according to the position of their renewal bud (i.e. their life-form) did not account for all of the interspecific variation apparent. In the case of shoot regeneration after fire, species whose renewal buds were destroyed by fire because they were above-ground started to regenerate about the same time as species with belowground buds, protected from fire, but reached their maximum frequency of occurrence later. Grouping species by life-form was of limited value as a means of interpreting this interspecific variation in the timing of shoot regeneration after fire. It would be unwise to use plant life-form as the sole basis for interpreting or predicting a species' response to temperature stress when extreme temperatures occur regularly, as they do in heathland. The possible use of other plant traits to interpret and predict interspecific variation in the regeneration rate of heathland plants is discussed.