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Bank Dynamics (bank + dynamics)
Kinds of Bank Dynamics Selected AbstractsFlooding, soil seed bank dynamics and vegetation resilience of a hydrologically variable desert floodplainFRESHWATER BIOLOGY, Issue 2 2006SAMANTHA J. CAPON Summary 1. This paper explores soil seed bank composition and its contribution to the vegetation dynamics of a hydrologically variable desert floodplain in central Australia: the Cooper Creek floodplain. We investigated patterns in soil seed bank composition both temporally, in response to flooding (and drying), and spatially, with relation to flood frequency. Correlations between extant vegetation and soil seed bank composition are explored with respect to flooding. 2. A large and diverse germinable soil seed bank was detected comprising predominantly annual monocot and annual forb species. Soil seed bank composition did not change significantly in response to a major flood event but some spatial patterns were detected along a broad flood frequency gradient. Soil seed bank samples from frequently flooded sites had higher total germinable seed abundance and a greater abundance of annual monocots than less frequently flooded sites. In contrast, germinable seeds of perennial species belonging to the Poaceae family were most abundant in soil seed bank samples from rarely flooded sites. 3. Similarity between the composition of the soil seed bank and extant vegetation increased following flooding and was greatest in more frequently flooded areas of the floodplain, reflecting the establishment of annual species. The results indicate that persistent soil seed banks enable vegetation in this arid floodplain to respond to unpredictable patterns of flooding and drying. [source] Differences in seed mass between hydric and xeric plants influence seed bank dynamics in a dryland riparian ecosystemFUNCTIONAL ECOLOGY, Issue 2 2008J. C. Stromberg Summary 1Dryland riparian zones have steep spatial gradients of soil moisture and flood disturbance, and the component hydrogeomorphic surfaces support hydric to xeric plant species. These systems undergo extremes of flood and drought, a dynamic that may select for persistent soil seed banks. We asked if reliance on this strategy differed among plants in three moisture groups (hydric, mesic and xeric), and if patterns were related to diaspore traits. 2We assessed the composition of soil and litter seed banks (emergence method) and extant vegetation along a riparian hydrogradient, and measured seed persistence (using an indirect method) and diaspore mass and shape variance of the component species. 3Hydroriparian species had smaller diaspores than xeroriparian species, corresponding to differences in selective pressures on seedlings in their respective habitats, but the two groups formed persistent seed banks at approximately equal percentages. Persistent seeds were smaller than transient seeds, but within the persistent seed group there was separation between the smaller-diaspored hydrophytes and larger-diaspored xerophytes. 4Distribution patterns of extant vegetation, in concert with diaspore trait differences among moisture-affinity groups, gave rise to divergent spatial patterns of diaspores within the soil: hydroriparian diaspores were abundant not only along wet channel bars but also in deep soils under floodplain forests and shrublands, presumably owing to dispersal by flood waters. Xeroriparian diaspores were largely restricted to the litter and upper soil layers of their drier, higher, floodplain habitats. With increasing depth in the soil of floodplain forests and shrublands, viable diaspores became smaller and rounder, and plant composition shifted from xeroriparian to hydroriparian species. 5The wide distribution of hydroriparian diaspores in floodplain soils influences disturbance dynamics, increasing the probability that ephemeral wetland communities will develop wherever suitable conditions are stochastically created by floods. Persistent seed banks also allow many xeric annuals to be maintained in dryland riparian zones throughout extended drought, similar to processes that occur in desert uplands. [source] Population dynamics in Digitalis purpurea: the interaction of disturbance and seed bank dynamicsJOURNAL OF ECOLOGY, Issue 6 2007NINA SLETVOLD Summary 1Plant ecologists have long since realized that the persistence of many facultative biennial plants depends upon disturbance. However, we still have a limited knowledge of the population-level effects of disturbance, and the connection between adult and seed bank dynamics. 2Using data from a 3-year demographic study combined with experimental gap-opening in a large population of Digitalis purpurea, we parameterized stochastic transition matrix models in ,disturbed' vs. ,undisturbed' areas. We simulated different gap sizes (fraction of population that was disturbed) and temporal disturbance patterns (constant, random, regular and irregular return intervals) and evaluated the effects on population growth rate and seed bank dynamics. To explore seed bank importance we used two alternatives for seed bank survival rate (0.75/0.35) and three alternatives for seed bank recruitment fraction (0.9/0.5/0.1). 3Observed background recruitment levels were insufficient to ensure a positive population growth rate. Increased amounts of gap-opening led to higher growth rates, and population persistence was predicted at moderate disturbance levels if seed bank survival was high (0.75). 4Temporal disturbance pattern affected model results; random and interval scenarios resulted in lower population growth rates and higher extinction risks than constant scenarios of the same average disturbance level. Small and frequent disturbances led to considerably higher growth rates than large and rare disturbances. 5Stochastic elasticity analyses identified the seed bank as the most important life cycle stage with respect to population growth and persistence in most scenarios, and its relative impact was positively related to seed bank survival rate and negatively related to disturbance level. Variation in the recruitment fraction from seed bank vs. seed rain affected both population growth rate and elasticity patterns, indicating the large impact of spatial variation in seed bank density. 6Synthesis: Despite the existence of a large seed bank, our data suggest that recruitment may be locally seed-limited due to a patchy seed bank structure. Local population development may consequently differ widely from gap to gap. These results illustrate how spatial structures in both seed bank, adult population and gap formation interact to shape plant population dynamics, as well as the occurrence of microsite- vs. seed-limitation. [source] Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China: (II) Seed BankJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2008Run-Guo Zang Abstract Spatial and temporal patterns of seed bank dynamics in relation to gaps in an old growth tropical montane rainforest of Hainan Island, South China, were studied over two consecutive years. From June 2001 to June 2003, soil seed bank sampling blocks were taken near each of the four sides of each seed trap and immediately put into a nursery for observation of seedling emergence dynamics in four seasons (each experiment in each season). The abundances of seedlings that emerged from seed banks showed the trend of vine functional group (VFG) > shrub functional group (SFG) > tree functional group (TFG) > herb functional group (HFG), but the trend in species richness of seedlings that emerged from the soil seed banks was TFG > VFG > SFG > HFG. The abundances of seedlings that emerged from seed banks in the three gap zones showed no significant differences, but significant differences did exist for the species richness. The time of sampling or seasons of experiments had significant influences on both the species richness and seedling abundances. The seedling emergence processes of each experiment all revealed the unimodal patterns. Few emergences occurred 1 year after each experiment. Compared with those under closed canopies, the recruitment rates from seed to seedlings and from seedlings to saplings in gaps were higher, but the mortality rates from saplings to big trees were also higher in the gaps. [source] Aerial seed bank dynamics and seedling emergence patterns in two annual Mediterranean AsteraceaeJOURNAL OF VEGETATION SCIENCE, Issue 3 2010F. Bastida Abstract Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non-dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within-season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph-specific patterns of between-year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between-year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within-year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within-season, risk-reducing traits in ruderal Mediterranean habitats characteristic of the study species. [source] Seed bank dynamics in tall-tussock grasslands along an altitudinal gradientJOURNAL OF VEGETATION SCIENCE, Issue 2 2003Guillermo Funes Zuloaga et al. (1994); Zuloaga & Morrone (1996, 1999) Abstract. We studied the germinable soil seed bank of tall-tussock grasslands along an altitudinal gradient in the mountains of central Argentina. We selected 10 sampling plots at three altitudinal levels (1200 m, 1600 m and 2200 m). We assessed the composition of the established vegetation and took ten compound soil samples (0 - 5 cm depth) at each plot in autumn and spring. The soil samples were sieved, chilled, and incubated in a glasshouse to assess the composition of the seed bank. The similarity between the composition of the seed bank flora and that of the established vegetation was low throughout the gradient. Most species did not change their seed bank strategy along the gradient. Seed bank richness and density increased with altitude. Most species had a persistent seed bank at all altitudinal levels, and the proportion of such species increased with altitude. These results suggest that a cold climate directly and/or indirectly favours the formation of seed banks and seed persistence in the soil. [source] Temporal patterns of genetic variation across a 9-year-old aerial seed bank of the shrub Banksia hookeriana (Proteaceae)MOLECULAR ECOLOGY, Issue 13 2005LUKE G. BARRETT Abstract The pattern of accumulation of genetic variation over time in seed banks is poorly understood. We examined the genetic structure of the aerial seed bank of Banksia hookeriana within a single 15-year-old population in fire-prone southwestern Australia, and compared genetic variation between adults and each year of a 9-year-old seed bank using amplified fragment length polymorphism (AFLP). B. hookeriana is well suited to the study of seed bank dynamics due to the canopy storage of its seeds, and because each annual crop can be identified. A total of 304 seeds from nine crop years and five maternal plants were genotyped, along with 113 plants from the adult population. Genetic variation, as assessed by the proportion of polymorphic markers (Pp) and Shannon's index (I), increased slightly within the seed bank over time, while gene diversity (Hj), did not change. Pp, I, and Hj all indicated that genetic variation within the seed bank quickly approached the maximal level detected. Analysis of molecular variance revealed that less than 4% of variation could be accounted for by variation among seeds produced in different years, whereas there was greater differentiation among maternal plants (12.7%), and among individual seeds produced by different maternal plants (83.4%). With increasing population age, offspring generated each year were slightly more outbred, as indicated by an increase in the mean number of nonmaternal markers per offspring. There were no significant differences for Hj or I between adults and the seed bank. Viability of seeds decreased with age, such that the viability of 9-year-old seeds was half that of 2-year-old seeds. These results suggest that variable fire frequencies have only limited potential to influence the amount of genetic variation stored within the seed bank of B. hookeriana. [source] Can atmospheric input of nitrogen affect seed bank dynamics in habitats of conservation interest?APPLIED VEGETATION SCIENCE, Issue 3 2008The case of dune slacks Abstract. Questions: Does the increased atmospheric deposition of nitrogen, which can have major effects on the established vegetation of nutrient-poor habitats, also impact germination from the soil seed bank? Location: Coastal dune slacks at Newborough Warren, Wales, UK. Methods: The effects of nitrogen addition (15 kg.ha -1.a -1) on seed germination from the soil seed bank were investigated using the seedling emergence method between September 2004 and February 2005. Results: More seedlings emerged from fertilised samples than unfertilised controls. Most species showed enhanced germination after fertilisation with nitrogen, with seedling numbers statistically significantly greater in nitrogen addition samples in a quarter of species abundant enough for analysis. Species that responded positively to fertilisation were species with low Ellenberg indicator values indicative of infertile sites. Conclusions: Most species showed increased germination after fertilisation with nitrogen, including early successional species normally growing in nutrient-poor conditions. This suggests that the increased atmospheric deposition of nitrogen probably not only impacts on established vegetation, but also has the potential to alter seed bank dynamics. [source] | |||||||||||||