%0 Journal Article %J Plant Ecology %D 2015 %T Bud bank dynamics and clonal growth strategy in the rhizomatous grass Pascopyrum smithii %A Ott, J.P. %A D.C. Hartnett %K Bud %K Guerilla %K Phalanx Rhizome %K Vegetative reproduction %K Western wheatgrass %X

Recruitment of rhizomatous perennial grass ramets primarily occurs from the belowground bud bank. Investment in guerilla versus phalanx growth is determined by bud availability, development, and spatial distribution. The tiller and bud bank dynamics of Pascopyrum smithii, a dominant rhizomatous grass of the northern mixed-grass prairie, were examined in South Dakota throughout an annual cycle to assess the investment in guerilla versus phalanx growth and the role of different bud populations in renewal versus regenerative functions and vegetative spread via rhizomes. Pascopyrum smithii invested substantially in both phalanx and guerilla tiller production. However, investment in rhizome production before tiller recruitment prioritized guerilla over phalanx growth. Annual tiller recruitment of P. smithii was capable of flexible timing, occurring in either spring or fall. Renewal buds, from which rhizomes and tillers were recruited, primarily consisted of the youngest generation of buds borne at the base of tillers. Although rhizome axillary buds and older tiller axillary buds were rarely used in annual tiller recruitment, they provided a sizable reserve (regenerative) bud bank. The spatial distribution of bud development produced the mixed guerrilla–phalanx growth pattern and flexible tiller recruitment timing of P. smithii. Therefore, P. smithii is capable of employing both conservative and foraging growth strategies which will facilitate its persistence under local neighborhood variability and changing resource availability associated with environmental change. Understanding the spatial distribution of buds as determined by rhizome architecture is essential to understanding the distribution and composition of species within plant communities dominated by clonal species.

%B Plant Ecology %V 216 %P 395 -405 %G eng %U https://link.springer.com/article/10.1007%2Fs11258-014-0444-6 %M KNZ001692 %R 10.1007/s11258-014-0444-6 %0 Journal Article %J American Midland Naturalist %D 2015 %T Vegetative reproduction and bud Bank dynamics of the perennial grass andropogon gerardii in mixed-grass and tallgrass prairie %A Ott, J.P. %A D.C. Hartnett %X

Plant species with wide distributions may differ in their population dynamics across their range, especially in contrasting habitats. Most tiller recruitment of perennial grasses occurs vegetatively from the belowground bud bank rather than from seed. Seed reproduction often occurs under a narrower range of environmental conditions than vegetative reproduction. As a result flowering and seedling recruitment patterns of a species often differ between contrasting habitats and across its range. How vegetative reproduction and bud bank dynamics of a species vary between contrasting habitats has not been well studied and could explain the differences in its persistence and productivity between habitats. Therefore, the vegetative reproduction and dynamics of Andropogon gerardii, a dominant C4 perennial grass of the Great Plains of North America, were compared between tallgrass and northern mixedgrass prairie habitats. Bud production and tiller recruitment in 10 populations were examined throughout an annual growing cycle in the northern mixedgrass prairie of South Dakota. Bud bank characteristics, and individual and population performance were compared with previous work conducted in Kansas tallgrass prairie. Stage-structured matrix models examined population growth rates. Andropogon gerardii tillers produced lower numbers of buds and had lower flowering rates in mixedgrass prairie populations. The annual phenology of bud and tiller development was also contracted to fit within the shorter growing season in northern mixedgrass prairie. However, bud longevity and bud bank age structure were similar between habitats, both having buds that lived for > 2 y and multi-aged bud banks. Similar population growth rates occurred in both habitats despite lower individual performance of both flowering and vegetative reproductive capacity (i.e., bud production) in mixedgrass prairie populations. Lower regional productivity of A. gerardii in northern mixedgrass prairie than in tallgrass prairie does not appear to be due to differences in bud and tiller population growth. Instead, sparse or patchy suitable habitat and/or reduction in tiller size may explain its reduced productivity. Lower population growth rates may be observed in other habitats or in years with harsher environmental conditions that further lower individual performance.

%B American Midland Naturalist %V 174 %P 14 -34 %G eng %U https://doi.org/10.1674/0003-0031-174.1.14 %M KNZ001693 %R http://dx.doi.org/10.1674/0003-0031-174.1.14 %0 Thesis %D 2014 %T Ecological implications of grass bud bank and tiller dynamics in mixed-grass prairie %A Ott, J.P. %Y D.C. Hartnett %K Bud bank %K Grass; Mixed-grass prairie %K perennial grass %K Tiller dynamics %K Vegetative reproduction %X

Perennial grass populations propagate vegetatively via the belowground bud bank. Climate, photosynthetic pathway, and growth form impact bud production, longevity, and dormancy; leading to alterations in bud bank and tiller dynamics. Previous research in mesic C₄-dominated tallgrass prairie revealed that a C₄ grass had greater bud longevity and differing bud bank dynamics than a C₃ species. This study examined the bud bank dynamics of rhizomatous and caespitose grasses in a more arid C₃ dominated prairie to gain insights into how bud banks differ among grass species, growth forms, and environments, and the relationship between bud bank characteristics and grass architecture and growth patterns. The bud bank and tiller dynamics of four perennial grasses in the C₃-dominated northern mixed grass prairie were examined over 15 months. The C₃ caespitose and rhizomatous grasses produced similar numbers of buds per tiller and their bud longevity was [greater than or equal to] 2 years. Tiller longevity drove the turnover within the bud bank of the dominant C₃ caespitose grasses Hesperostipa comata and Nassella viridula. Their polycyclic tillers (tillers that lived for more than one year) created multi-aged bud banks. The rhizomatous C₃ grass Pascopyrum smithii also had a multi-aged bud bank because buds were able to live longer than its annual tillers. Differences between caespitose and rhizomatous C₃ grass bud banks were driven by differences in tiller and rhizome production and spatial distribution. Responses to water availability fluctuations are likely buffered by the maintenance of polycyclic tillers in the caespitose grasses and flexible timing of annual tiller recruitment in the rhizomatous grass. The C₄ rhizomatous grass Andropogon gerardii had similar phenology to populations in its tallgrass prairie range center. Despite declines in bud production per tiller and lowered flowering probability in mixed-grass prairie, A. gerardii maintained a multi-aged bud bank and a positive population growth rate via vegetative reproduction at both the center and edge of its range. Bud bank dynamics of different growth forms and photosynthetic pathways, as they offer insight into the control of grass population dynamics and production, will enhance understanding of the mechanisms by which management practices and environmental change can alter perennial grasslands.

%I Kansas State University %C Manhattan, KS %V PhD. Dissertation %G eng %U http://hdl.handle.net/2097/17277 %9 Ph.D. Thesis %M KNZ001650 %0 Journal Article %J Austral Ecology %D 2013 %T Variation in root system traits among African semi-arid savanna grasses: implications for drought tolerance %A D.C. Hartnett %A Ott, J.P. %A G.T. Wilson %A Setshogo, M. %K grass %K mycorrhiza %K rhizosheath %K root architecture %K savanna %X

In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Drought-tolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization. These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation.

%B Austral Ecology %V 38 %P 383 -392 %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1442-9993.2012.02422.x %M KNZ001548 %R 10.1111/j.1442-9993.2012.02422.x %0 Journal Article %J Plant Ecology %D 2012 %T Contrasting bud bank dynamics of two co-occurring grasses in tallgrass prairie: implications for grassland dynamics %A Ott, J.P. %A D.C. Hartnett %K Meristem %K Photosynthetic pathway %K Plant demography %K Plant population dynamics %K Tiller recruitment %K Vegetative reproduction %X

Because most shoot recruitment in perennial grasses occurs from belowground axillary buds, bud dynamics determine plant population dynamics and meristem limitation to population growth. Therefore, grassland vegetation responses to environmental change or disturbance may be influenced by interspecific differences in bud banks and the patterns and environmental controls of bud development and demography. We examined bud bank dynamics in Andropogon gerardii and Dichanthelium oligosanthes in tallgrass prairie by enumerating and classifying buds throughout 15 months to determine whether grass buds live for multiple years and accumulate; whether bud natality, dormancy and outgrowth are synchronous or variable; and whether bud bank dynamics differ between these co-occurring species. Andropogon gerardii (a C4 species) maintained a larger dormant bud bank, showed synchrony in bud development and transition to tiller, and its buds lived for multiple years. Thus, multiple previous years’ bud cohorts contributed to recruitment. By contrast, D. oligosanthes (a C3 species) maintained a smaller dormant bud bank, had asynchronous bud development with active buds present year-round, and its buds lived for 1 year. Buds played different roles in the dynamics of each species, allowing A. gerardii to over-winter and recruit new spring tillers and D. oligosanthes to survive and recruit new tillers following summer dormancy. These differences in bud bank age structure, phenology, and dynamics between these species suggest greater demographic buffering and time-lag effects in A. gerardii populations. Interspecific differences in bud bank structure and dynamics may explain and help predict grassland responses to environmental change.

%B Plant Ecology %V 213 %P 1437 -1448 %G eng %U https://link.springer.com/article/10.1007%2Fs11258-012-0102-9 %M KNZ001492 %R 10.1007/s11258-012-0102-9 %0 Journal Article %J Journal of Tropical Ecology %D 2012 %T Coping with herbivory at the juvenile stage: Responses to defoliation and browsing in the African savanna tree Colophospermum mopane %A D.C. Hartnett %A Ott, J.P. %A Sebes, K. %A Ditlhogo, M. %K Botswana %K browsing %K defoliation %K Herbivory %K Plant–herbivore interactions %K savanna %K seedlings %K tree recruitment %X

Responses of plants to herbivory are dependent on the type of damage and the ontogenetic stage of the plant. We compared the effects of stem pruning and defoliation on seedlings of Colophospermum mopane, an ecologically important tree species widely distributed in southern Africa. The growth of 160 greenhouse-grown juveniles were measured for 6-mo after germination and then 6-mo after treatments including 50% defoliation, 100% defoliation, 50% stem pruning and controls. Pruning resulted in 30% reductions in total leaf area, height and biomass. Partial defoliation resulted in 30% reductions in total leaf area and plant biomass. However, complete defoliation resulted in a 30% increase in biomass production, a doubling in leaf and lateral branch number, a 45% reduction in leaf size, and no change in total leaf area. Thus, completely defoliated seedlings showed greater performance than those that were only partially defoliated, indicating that C. mopane has become adapted to the chronic and severe defoliation inflicted by Imbrasia belina caterpillars. Comparison of our results with other studies indicates that C. mopane seedlings are less herbivory-tolerant than adults and that pruning has more negative effects than defoliation. Thus, seedling browsers may constrain recruitment in C. mopane, influencing its population dynamics and abundance.

%B Journal of Tropical Ecology %V 28 %P 161 -169 %G eng %U https://www.cambridge.org/core/journals/journal-of-tropical-ecology/article/coping-with-herbivory-at-the-juvenile-stage-responses-to-defoliation-and-stem-browsing-in-the-african-savanna-tree-colophospermum-mopane/5B519E0F1B9BD889D4905FD311257D9A %M KNZ001549 %R http://dx.doi.org/10.1017/S0266467412000028 %0 Journal Article %J Botany %D 2012 %T Higher-order bud production increases tillering capacity in the perennial caespitose grass Scribner's Panicum (Dichanthelium oligosanthes) %A Ott, J.P. %A D.C. Hartnett %K Bud bank %K bunchgrass %K Dichanthelium oligosanthes %K tillering %X

The persistence and dynamics of perennial grass populations strongly depend on tiller recruitment from the bud bank. Because of the structural organization of grasses as populations of phytomers, bud production and tillering are constrained by morphology. An infrequent trait observed in only a few caespitose grasses is the branching of buds to produce higher-order buds prior to tiller development. We studied bud bank dynamics in Dichanthelium oligosanthes (Schult.) Gould a C3 perennial caespitose grass widely distributed in the eastern Great Plains. A hierarchy of bud development occurred in D. oligosanthes, with primary buds branching to produce secondary, tertiary, and quaternary buds. This higher-order bud production increased the overwintering propagule supply for spring recruitment by 4.5 times, and more than half of successful tiller recruits originated as higher-order buds. The temporal patterns of higher-order bud production and development suggest that growing season length may be an important factor determining the extent of higher-order bud production and subsequent year tiller natality in D. oligosanthes. Higher-order bud production likely has important consequences for the population dynamics of grasses. It may increase bud bank densities and tillering capacity, buffer population dynamics, and increase intraclonal tiller densities and resource consolidation in caespitose grasses.

%B Botany %V 90 %P 884 -890 %G eng %U http://www.nrcresearchpress.com/doi/10.1139/b2012-043 %M KNZ001486 %R 10.1139/b2012-043 %0 Journal Article %J South African Journal of Botany %D 2012 %T Interspecific variation in bud banks and flowering effort among semi-arid African savanna grasses %A Dalgleish, H.J. %A Ott, J.P. %A Setshogo, M. %A Muzilla, M. %A D.C. Hartnett %K Bud bank %K Meristem %K Poaceae %K Reproductive allocation %K Vegetative reproduction %X

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.

%B South African Journal of Botany %V 83 %P 127 -133 %G eng %U https://www.sciencedirect.com/science/article/pii/S0254629912001275?via%3Dihub %M KNZ001550 %R 10.1016/j.sajb.2012.08.010 %0 Journal Article %J American Journal of Botany %D 2011 %T Bud production and dynamics of flowering and vegetative tillers of the perennial grass Andropogon gerardii (Poaceae): the role of developmental constraints %A Ott, J.P. %A D.C. Hartnett %K allocation %K axillary bud %K Bud bank %K Meristem %K ontogeny %K perennial grass %K Tiller recruitment %K tradeoff %K Vegetative reproduction %X

•Premise of the Study: 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. •Methods: Vegetative bud production and dynamics and tiller production were examined biweekly through an annual cycle on vegetative and flowering tillers of Andropogon gerardii. •Key Results: 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. •Conclusions: 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.

%B American Journal of Botany %V 98 %P 1293 -1298 %G eng %U https://bsapubs.onlinelibrary.wiley.com/doi/full/10.3732/ajb.1000264 %M KNZ001415 %R 10.3732/ajb.1000264 %0 Thesis %D 2009 %T Bud bank morphology, dynamics, and production in perennial grasses %A Ott, J.P. %I Kansas State University %C Manhattan, KS %V MS Thesis %P 1 -93 %G eng %U http://krex.k-state.edu/dspace/handle/2097/1807 %9 M.S. Thesis %M KNZ001280