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Seedling Survivorship (seedling + survivorship)
Selected AbstractsRestoring Tree Islands in the Everglades: Experimental Studies of Tree Seedling Survival and GrowthRESTORATION ECOLOGY, Issue 2 2008Arnold G. Van Der Valk Abstract In May 2004, 400 tree seedlings of seven different species found on tree islands in the Florida Everglades were planted at different elevations along five transects on eight newly constructed tree islands, four with and four without limestone cores. Seedlings suffered between 40 and 85% mortality during the first 120 days, the period with the lowest water levels. Ilex cassine L., Salix caroliniana Michx., Chrysobalanus icaco L., and Annona glabra had the highest number of surviving seedlings, whereas Magnolia virginiana L., Myrica cerifera L., and Acer rubrum L. had the fewest. During the remainder of the study, water levels were mostly higher and sometimes covered the entire islands for months at a time. After 220 days, nearly all seedlings of M. virginiana and My. cerifera had died. At the end of the study, seedlings of I. cassine and A. glabra had the highest survivorship rates. Seedling biomass of C. icaco and I. cassine was greatest at the highest elevations, whereas seedlings of A. glabra had similar biomass at all elevations. Seedling survivorship was not statistically different between islands with and without limestone cores; however, when seedlings of all species were combined, island core type was significantly different for aboveground biomass, seedling height, and canopy width. Because of the higher survivorship under both low and high water conditions, A. glabra, I. cassine, and S. caroliniana are the most suitable species for establishing tree species on restored tree islands in the Everglades. [source] Do shade-tolerant tropical tree seedlings depend longer on seed reserves?FUNCTIONAL ECOLOGY, Issue 4 2002Functional growth analysis of three Bignoniaceae species Summary 1.,A functional growth analysis was used to determine the duration of strict dependency on seed reserves for energy and nitrogen in three woody Bignoniaceae species (Tabebuia rosea DC., Challichlamys latifolia K. Schum. and Pithecoctenium crucigerum A. Gentry) which differed in cotyledon function (photosynthetic, semi-photosynthetic and storage) and shade tolerance (probability of seedling establishment and survival in the understorey). 2.,Seedlings were raised from seeds in sand culture under combinations of three nitrogen levels (daily supply of nutrient solution containing 100, 10 and 0% of 2·6 mm N) and two irradiances (27 and 1% full sun). Time course of biomass, non-cotyledonous biomass and leaf area for 40 days post-germination were compared to identify when the external availability of nitrogen or light began to affect seedling growth. 3.,Seedlings of all species became dependent on external energy supply earlier than they did on nitrogen supply. In all species seed nitrogen was sufficient to support positive seedling growth for 40 days in shade, but not in sun. 4.,Tabebuia rosea with photosynthetic cotyledons responded to light availability earlier than more shade-tolerant species with storage cotyledons. Challichlamys latifolia, the most shade-tolerant species, had the highest nitrogen concentration in seeds and was the last to respond to external nitrogen availability. Thus seedlings of the most shade-tolerant species depended on seed reserves for the longest period for both energy and nitrogen. 5.,Relative growth rate after seedlings initiated autotrophic growth was in a trade-off relationship with seedling survivorship in the understorey across the three species. Tabebuia rosea, the least shade-tolerant species, had the highest positive net carbon balance in sun and shade. 6.,Functional morphology of cotyledons and concentration of seed nitrogen deserve as much attention as seed size as correlates of contrasting seedling regeneration strategies. [source] Virus infection and grazing exert counteracting influences on survivorship of native bunchgrass seedlings competing with invasive exoticsJOURNAL OF ECOLOGY, Issue 2 2006C. M. MALMSTROM Summary 1,Invasive annual grasses introduced by European settlers have largely displaced native grassland vegetation in California and now form dense stands that constrain the establishment of native perennial bunchgrass seedlings. Bunchgrass seedlings face additional pressures from both livestock grazing and barley and cereal yellow dwarf viruses (B/CYDVs), which infect both young and established grasses throughout the state. 2,Previous work suggested that B/CYDVs could mediate apparent competition between invasive exotic grasses and native bunchgrasses in California. 3,To investigate the potential significance of virus-mediated mortality for early survivorship of bunchgrass seedlings, we compared the separate and combined effects of virus infection, competition and simulated grazing in a field experiment. We infected two species of young bunchgrasses that show different sensitivity to B/CYDV infection, subjected them to competition with three different densities of exotic annuals crossed with two clipping treatments, and monitored their growth and first-year survivorship. 4,Although virus infection alone did not reduce first-year survivorship, it halved the survivorship of bunchgrasses competing with exotics. Within an environment in which competition strongly reduces seedling survivorship (as in natural grasslands), virus infection therefore has the power to cause additional seedling mortality and alter patterns of establishment. 5,Surprisingly, clipping did not reduce bunchgrass survivorship further, but rather doubled it and disproportionately increased survivorship of infected bunchgrasses. 6,Together with previous work, these findings show that B/CYDVs can be potentially powerful elements influencing species interactions in natural grasslands. 7,More generally, our findings demonstrate the potential significance of multitrophic interactions in virus ecology. Although sometimes treated collectively as plant ,predators', viruses and herbivores may exert influences that are distinctly different, even counteracting. [source] Germination and seedling survivorship characteristics of hybrids between native and alien species of dandelion (Taraxacum)PLANT SPECIES BIOLOGY, Issue 2 2004AKIHIKO HOYA Abstract Spontaneous hybrids between native and invasive species of Taraxacum were studied by means of seed germination characteristics at 4,34°C and seedling survivorship at 6,36°C. At high (28,34°C) and low (4°C) temperatures, the germination percentage was low in 4X hybrids and T. platycarpum, whereas it was high in 3X hybrids, MP (male partheno genesis) hybrids and T. officinale. When the seeds that did not germinate at high or low temperatures were incubated at 16°C for 10 days, most of the 4X hybrid and T. platycarpum seeds germinated. It was suggested that the germination of 4X hybrid and T. platycarpum seeds was suppressed at high and low temperatures. At 6,24°C, seedlings of all lineages that included T. platycarpum, T. officinale and three type hybrids exhibited a high survivorship of approximately 80,100% and no significant difference was observed between lineages. In contrast, at high temperatures survivorship of 4X hybrid seedlings was significantly higher than that of other lineages, approximately 90% at 31°C and 80% at 36°C. These results suggested that if 4X hybrid competes with T. officinale in hot areas during the seedling period, 4X hybrid would have the advantage over T. officinale, whose seedlings could not survive under high temperatures. [source] Riparian Forest Restoration: Increasing Success by Reducing Plant Competition and HerbivoryRESTORATION ECOLOGY, Issue 2 2002Bernard W. Sweeney Abstract The reestablishment of riparian forest is often viewed as "best management practice" for restoring stream ecosystems to a quasi-natural state and preventing non-point source contaminants from entering them. We experimentally assessed seedling survivorship and growth of Quercus palustris (pin oak), Q. rubra (red oak), Q. alba (white oak), Betula nigra (river birch), and Acer rubrum (red maple) in response to root-stock type (bare root vs. containerized), herbivore protection (tree shelters), and weed control (herbicide, mowing, tree mats) over a 4-year period at two riparian sites near the Chester River in Maryland, U.S.A. We started with tree-stocking densities of 988/ha (400/ac) in the experimental plots and considered 50% survivorship (i.e., a density of 494/ha [200/ac] at crown closure) to be an "acceptable or minimum" target for riparian restoration. Results after four growing seasons show no significant difference in survivorship and growth between bare-root and containerized seedlings when averaged across all species and treatments. Overall survivorship and growth was significantly higher for sheltered versus unsheltered seedlings (49% and 77.6 cm vs. 12.1% and 3.6 cm, respectively) when averaged across all species and weed control treatments. Each of the five test species exhibited significantly higher 4-year growth with shelter protection when averaged across all other treatments, and all species but river birch had significantly higher survivorship in shelters during the period. Seedlings protected from weeds by herbicide exhibited significantly higher survivorship and growth than seedlings in all other weed-control treatments when averaged across all species and shelter treatments. The highest 4-year levels of survivorship/growth, when averaged across all species, was associated with seedlings protected by shelters and herbicide (88.8%/125.7cm) and by shelters and weed mats (57.5%/73.5 cm). Thus, only plots where seedlings were assisted by a combination of tree shelters and either herbicide or tree mats exhibited an "acceptable or minimum" rate of survivorship (i.e.,>50%) for riparian forest restoration in the region. Moreover, the combined growth and survivorship data suggest that crown closure over most small streams in need of restoration in the region can be achieved most rapidly (i.e., 15 years or less) by protecting seedlings with tree shelters and controlling competing vegetation with herbicides. [source] Simulated effects of herb competition on planted Quercus faginea seedlings in Mediterranean abandoned croplandAPPLIED VEGETATION SCIENCE, Issue 2 2003Benayas Rey Abstract. We tested simulated effects of herb competition on the performance of planted seedlings of Quercus faginea ssp. faginea in Mediterranean abandoned cropland. We produced three types of environment with respect to herb competition: absence of competition (AC), below-ground competition (BGC), and total competition (TC). We assessed the performance of Q. faginea seedlings in each treatment in five ways: (1) seedling mortality, (2) leaf length and total plant leaf area, (3) water potential, (4) total biomass and biomass allocation, and (5) non-structural carbohydrate storage in different plant organs. We also measured (6) soil moisture at different depths and (7) biomass production of herbs. The TC treatment reduced water availability more than the BGC treatment, in agreement with the most pronounced water stress in seedlings under TC conditions. BGC and TC treatments showed a high and similar seedling mortality, which was one order of magnitude higher than that in the AC treatment. Competition treatments affected glucose concentration in both shoots and roots, and followed the rank TC > BGC > AC. Q. faginea seedlings might compensate a lower water availability through glucose accumulation in leaves to reduce the osmotic potential. There was a maximum starch concentration in the BGC treatment that hints that a moderate resource limitation would limit tissue growth but not carbon assimilation. We conclude that the negative effects of herbs on Q. faginea seedlings are mostly a result of competition for water, and that this competition is noticeable since the earliest stages of the establishment. Complete weed removal is a technique that would strongly improve seedling survivorship. [source] Edge Effects and Seedling Bank Depletion: The Role Played by the Early Successional Palm Attalea oleifera (Arecaceae) in the Atlantic ForestBIOTROPICA, Issue 2 2010Antônio Venceslau Aguiar ABSTRACT In this study, we examined the impacts of Attalea oleifera on the structure of seedling bank and discuss potential mechanisms of palm influence. Seed rain, seedling bank, and palm leaf fall were assessed beneath the canopy and in the vicinity of 16 adult palms across the edges of a large fragment (3500 ha) of the Atlantic forest. Moreover, we examined A. oleifera impacts on seed germination and seedling mortality by experimentally submitting seeds and seedlings to prolonged palm-leaf covering. As expected, seedling bank beneath the adults exhibited reduced abundance and species richness at local and habitat scale. Small to large seeds (3.1,30 mm) were underrepresented in the seed rain below adults palms, while experimental leaf covering drastically reduced both seed germination and seedling survivorship. A. oleifera leaf fall occurred over the whole year (3.6±2.7 leaves/individual/yr), which resulted in deep leaf litter mounds (10.7±9.2 cm). Finally, adult palm density (21.6±11.9 individuals/ha) correlated negatively with seedling density across Attalea clusters. Our results suggest that A. oleifera exerts negative effects on the seedling bank by reducing seedling abundance and richness as a consequence of two complementary mechanisms: impoverished and size-biased seed rain plus reduced seed germination and increased seedling mortality due to prolonged covering by fallen leaves. Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp [source] | ||||||||||