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1.
Plant and soil carbon accumulation following fire in Mediterranean woodlands in Spain 总被引:1,自引:0,他引:1
We measured plant and soil carbon (C) storage following canopy-replacing wildfires in woodlands of northeastern Spain that
include an understory of shrubs dominated by Quercus coccifera and an overstory of Pinus halepensis trees. Established plant succession models predict rapid shrub recovery in these ecosystems, and we build on this model by
contrasting shrub succession with long-term C storage in soils, trees, and the whole ecosystem. We used chronosequence and
repeated sampling approaches to detect change over time. Aboveground plant C increased from <100 to ~3,000 g C m−2 over 30 years following fire, which is substantially less than the 5,942 ± 487 g C m−2 (mean ±1 standard error) in unburned sites. As expected, shrubs accumulated C rapidly, but the capacity for C storage in
shrubs was <600 g C m−2. Pines were the largest plant C pool in sites >20 years post fire, and accounted for all of the difference in plant C between
older burned sites and unburned sites. In contrast, soil C was initially higher in burned sites (~4,500 g C m−2) than in unburned sites (3,264 ± 261 g C m−2) but burned site C declined to unburned levels within 10 years after fire. Combining these results with prior research suggests
two states for C storage. When pine regeneration is successful, ~9,200 g C m−2 accumulate in woodlands but when tree regeneration fails (due to microclimatic stress or short fire return intervals), ecosystem
C storage of ~4,000 g C m−2 will occur in the resulting shrublands. 相似文献
2.
Survival, growth, aboveground biomass accumulation, sediment surface elevation dynamics and nitrogen accumulation in sediments
were studied in experimental treatments planted with four different densities (6.96, 3.26, 1.93 and 0.95 seedlings m−2) of the mangrove Rhizophora mucronata in Puttalam Lagoon, Sri Lanka. Measurements were taken over a period of 1,171 days and were compared with those from unplanted
controls. Trees at the lowest density showed significantly reduced survival, whilst measures of individual tree growth did
not differ among treatments. Rates of surface sediment accretion (means ± SE) were 13.0 (±1.3), 10.5 (±0.9), 8.4 (±0.3), 6.9
(±0.5) and 5.7 (±0.3) mm year−1 at planting densities of 6.96, 3.26, 1.93, 0.95, and 0 (unplanted control) seedlings m−2, respectively, showing highly significant differences among treatments. Mean (±SE) rates of surface elevation change were
much lower than rates of accretion at 2.8 (±0.2), 1.6 (±0.1), 1.1 (±0.2), 0.6 (±0.2) and −0.3 (±0.1) mm year−1 for 6.96, 3.26, 1.93, 0.95, and 0 seedlings m−2, respectively. All planted treatments accumulated greater nitrogen concentrations in the sediment compared to the unplanted
control. Sediment %N was significantly different among densities which suggests one potential causal mechanism for the facilitatory
effects observed: high densities of plants potentially contribute to the accretion of greater amounts of nutrient rich sediment.
While this potential process needs further research, this study demonstrated how higher densities of mangroves enhance rates
of sediment accretion and surface elevation processes that may be crucial in mangrove ecosystem adaptation to sea-level rise.
There was no evidence that increasing plant density evoked a trade-off with growth and survival of the planted trees. Rather,
facilitatory effects enhanced survival at high densities, suggesting that managers may be able to take advantage of high plantation
densities to help mitigate sea-level rise effects by encouraging positive sediment surface elevation. 相似文献
3.
Questions: What influence does mechanical mastication and other fuel treatments have on: (1) canopy and forest floor response variables that influence understory plant development; (2) initial understory vegetation cover, diversity, and composition; and (3) shrub and non‐native species density in a second‐growth ponderosa pine forest. Location: Challenge Experimental Forest, northern Sierra Nevada, California, USA. Methods: We compared the effects of mastication only, mastication with supplemental treatments (tilling and prescribed fire), hand removal, and a control on initial understory vegetation response using a randomized complete block experimental design. Each block (n=4) contained all five treatments and understory vegetation was surveyed within 0.04‐ha plots for each treatment. Results: While mastication alone and hand removal dramatically reduced the midstory vegetation, these treatments had little effect on understory richness compared with control. Prescribed fire after mastication increased native species richness by 150% (+6.0 species m2) compared with control. However, this also increased non‐native species richness (+0.8 species m2) and shrub seedling density (+24.7 stems m2). Mastication followed by tilling resulted in increased non‐native forb density (+0.7 stems m2). Conclusions: Mechanical mastication and hand removal treatments aided in reducing midstory fuels but did not increase understory plant diversity. The subsequent treatment of prescribed burning not only further reduced fire hazard, but also exposed mineral soil, which likely promoted native plant diversity. Some potential drawbacks to this treatment include an increase of non‐native species and stimulation of shrub seed germination, which could alter ecosystem functions and compromise fire hazard reduction in the long‐term. 相似文献
4.
Increase in isoprene and monoterpene emissions after re-watering of droughted Quercus ilex seedlings
We followed the diurnal cycles of isoprenoid emissions from Quercus ilex seedlings under drought and after re-watering. We found that Quercus ilex, generally considered a non-isoprene emitter, also emitted isoprene although at low rates. The emission rates of isoprene
reached 0.37 ± 0.02 nmol m−2 s−1 in controls, 0.15 ± 0.03 nmol m−2 s−1 under drought and 0.35 ± 0.04 nmol m−2 s−1 after re-watering, while emission rates of monoterpenes reached 11.0 ± 3.0, 7.0 ± 1.0 and 23.0 ± 5.0 nmol m−2 s−1, respectively. Emission rates recovered faster after re-watering than photosynthetic rate and followed diurnal changes in
irradiance in controls and under drought, but in leaf temperature after re-watering. 相似文献
5.
Akio Takenaka 《Ecological Research》1986,1(2):129-140
Ecophysiological comparisons were made of the growth and photosynthetic characteristics between seedlings of deciduousQuercus serrata and evergreenQuercus myrsinaefolia. Q. myrsinaefolia seedlings naturally occurring in secondary coppice forests showed exponential-like growth in height with age, while sympatricQ. serrata seedlings were considerably smaller in height, their growth being limited by shortage of light. The photosynthetic characteristics
measured under laboratory conditions showed no bases for the differences in growth between the two species on the forest floor:
Light compensation points of the seedlings raised under 5% daylight were almost identical for the two species, being about
6.0 μE·m−2·s−1. Growth analysis of seedlings planted in a coppice forest showed that bothQ. serrata andQ. myrsinaefolia could hardly grow during the summer under the shrub layer, when relative photon flux density (RPFD) was 0.9±0.5%. In the
winter, when RPFD under the leafless canopy increased to 29.3±2.7%, the dry matter production of the evergreen seedlings ofQ. myrsinaefolia was much improved. Current-year seedlings of the species showed NAR of 0.102±0.021 g·dm−2·mo−1 during the winter. Temperature dependency of photosynthesis and increment of leaf temperature by direct solar beam also indicated
active photosynthesis ofQ. myrsinaefolia on the forest floor during the winter. 相似文献
6.
Erika S. Zavaleta 《Plant Ecology》2006,184(1):53-63
Accelerating invasion of grasslands by woody species is a widespread global phenomenon. The native shrub Baccharis pilularis has recently increased in abundance in some California grasslands, with large local community and ecosystem effects. I investigated potential contributions of (1) future global climate and atmospheric changes and (2) variation in moisture and nutrient availability to increased Baccharis germination and early establishment rates. I examined responses of Baccharis seeds and seedlings to simulated warming (+ 1−2 °C) and elevated CO2 (+ 300 ppm) in a 2-year field experiment. Warming and CO2 treatments were applied at ambient and increased water and nitrogen levels chosen to simulate future increases in precipitation (+ 50%) and N deposition (+ 7 gN m−2 y−1). Elevated CO2 and water addition each increased or accelerated germination. Herbivory strongly reduced seedling populations during the winter wet season; drought further reduced seedling survival in the spring. Overall Baccharis survivorship was extremely low (<0.1%) across all treatments, complicating the interpretation of global change effects. 相似文献
7.
Rodrigo S. P. de Skowronski Paula F. Gheller Sandra Bromberg Carlos J. David Mônica A. V. Petti Thaïs N. Corbisier 《Polar Biology》2009,32(6):839-851
The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island,
Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005).
The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m−2, 261.7 ± 455.9 mg Phaeo m−2), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m−2, 108.8 ± 73.0 mg Phaeo m−2) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m−2, 58.3 ± 38.9 mg Phaeo m−2). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton
and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found
in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment
characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass
apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material. 相似文献
8.
Short-term soil inorganic N pulse after experimental fire alters invasive and native annual plant production in a Mojave Desert shrubland 总被引:1,自引:0,他引:1
Todd C. Esque Jason P. Kaye Sara E. Eckert Lesley A. DeFalco C. Richard Tracy 《Oecologia》2010,164(1):253-263
Post-fire changes in desert vegetation patterns are known, but the mechanisms are poorly understood. Theory suggests that
pulse dynamics of resource availability confer advantages to invasive annual species, and that pulse timing can influence
survival and competition among species. Precipitation patterns in the American Southwest are predicted to shift toward a drier
climate, potentially altering post-fire resource availability and consequent vegetation dynamics. We quantified post-fire
inorganic N dynamics and determined how annual plants respond to soil inorganic nitrogen variability following experimental
fires in a Mojave Desert shrub community. Soil inorganic N, soil net N mineralization, and production of annual plants were
measured beneath shrubs and in interspaces during 6 months following fire. Soil inorganic N pools in burned plots were up
to 1 g m−2 greater than unburned plots for several weeks and increased under shrubs (0.5–1.0 g m−2) more than interspaces (0.1–0.2 g m−2). Soil NO3
−−N (nitrate−N) increased more and persisted longer than soil NH4
+−N (ammonium−N). Laboratory incubations simulating low soil moisture conditions, and consistent with field moisture during
the study, suggest that soil net ammonification and net nitrification were low and mostly unaffected by shrub canopy or burning.
After late season rains, and where soil inorganic N pools were elevated after fire, productivity of the predominant invasive
Schismus spp. increased and native annuals declined. Results suggest that increased N availability following wildfire can favor invasive
annuals over natives. Whether the short-term success of invasive species following fire will direct long-term species composition
changes remains to be seen, yet predicted changes in precipitation variability will likely interact with N cycling to affect
invasive annual plant dominance following wildfire. 相似文献
9.
Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM),
southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29,
0.62 ± 0.33 and 0.46 ± 0.19 (× 108 cells l−1), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged
∼0.35 ± 0.14 × 108 cells l−1 in SWM and 0.39 ± 0.16 × 108 cells l−1 in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m−2 d−1 during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region
are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in
SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m−2 d−1) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m−2), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and
mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions
including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further,
rapid mineralization by bacteria will make essential nutrients available to autotrophs. 相似文献
10.
To identify the importance of arbuscular mycorrhizal fungi (AMF) colonizing wetland seedlings following flooding, we assessed
the effects of AMF on seedling establishment of two pioneer species, Bidens frondosa and Eclipta prostrata grown under three levels of water availability and ask: (1) Do inoculated seedlings differ in growth and development from
non-inoculated plants? (2) Are the effects of inoculation and degree of colonization dependent on water availability? (3)
Do plant responses to inoculation differ between two closely related species? Inoculation had no detectable effects on shoot
height, or plant biomass but did affect biomass partitioning and root morphology in a species-specific manner. Shoot/root
ratios were significantly lower in non-inoculated E. prostrata plants compared with inoculated plants (0.381 ± 0.066 vs. 0.683 ± 0.132). Root length and surface area were greater in non-inoculated
E. prostrata (259.55 ± 33.78 cm vs. 194.64 ± 27.45 cm and 54.91 ± 7.628 cm2 vs. 46.26 ± 6.8 cm2, respectively). Inoculation had no detectable effect on B. frondosa root length, volume, or surface area. AMF associations formed at all levels of water availability. Hyphal, arbuscular, and
vesicular colonization levels were greater in dry compared with intermediate and flooded treatments. Measures of mycorrhizal
responsiveness were significantly depressed in E. prostrata compared with B. frondosa for total fresh weight (−0.3 ± 0.18 g vs. 0.06 ± 0.06 g), root length (−0.78 ± 0.28 cm vs.−0.11 ± 0.07 cm), root volume (−0.49 ± 0.22 cm3 vs. 0.06 ± 0.07 cm3), and surface area (−0.59 ± 0.23 cm2 vs.−0.03 ± 0.08 cm2). Given the disparity in species response to AMF inoculation, events that alter AMF prevalence in wetlands could significantly
alter plant community structure by directly affecting seedling growth and development. 相似文献
11.
Zivanai Tsvuura Megan E. Griffiths Richard M. Gunton Peter J. Franks Michael J. Lawes 《Oecologia》2010,164(4):861-870
The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain
plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to
determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb (Isoglossa woodii) selects for species at either end of the light response continuum during the herb’s vegetative and reproductive phases.
Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in
the greenhouse at 12–14% irradiance, and their light compensation points measured using an open-flow gas exchange system.
The light compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m−2 s−1 in Celtis africana to 6.4 ± 0.7 μmol m−2 s−1 in Allophylus natalensis, indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol
CO2 mol−1 photon). Rates of dark respiration were significantly lower in a generalist pioneer species (Acacia karroo) than in a forest pioneer (C. africana), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade
tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing
low light levels beneath the I. woodii understorey, which excludes most light-demanding species from the seedling community. 相似文献
12.
Nelso P. Navarro Andrés Mansilla Estela M. Plastino 《Journal of applied phycology》2010,22(4):385-394
The effects of UVB radiation on the different developmental stages of the carrageenan-producing red alga Iridaea cordata were evaluated considering: (1) carpospore and discoid germling mortality; (2) growth rates and morphology of young tetrasporophytes;
and (3) growth rates and pigment content of field-collected plant fragments. Unialgal cultures were submitted to 0.17, 0.5,
or 0.83 W m−2 of UVB radiation for 3 h per day. The general culture conditions were as follows: 12 h light/12 h dark cycles; irradiance
of 55 μmol photon.per square meter per second; temperature of 9 ± 1°C; and seawater enriched with Provasoli solution. All UVB irradiation treatments
were harmful to carpospores (
0.17 \textW \textm - 2 = 40.9 ±6.9% 0.17\;{\text{W}}\,{{\text{m}}^{ - 2}} = 40.9 \pm 6.9\% ,
0.5 \textW \textm - 2 = 59.8 ±13.4% 0.5\;{\text{W}}\,{{\text{m}}^{ - 2}} = 59.8 \pm 13.4\% ,
0.83 \textW \textm - 2 = 49 ±17.4% 0.83\;{\text{W}}\,{{\text{m}}^{ - 2}} = 49 \pm 17.4\% mortality in 3 days). Even though the mortality of all discoid germlings exposed to UVB radiation was unchanged when compared
to the control, those germlings exposed to 0.5 and 0.83 W m−2 treatments became paler and had smaller diameters than those cultivated under control treatment. Decreases in growth rates
were observed in young tetrasporophytes, mainly in 0.5 and 0.83 W m−2 treatments. Similar effects were only observed in fragments of adult plants cultivated at 0.83 W m−2. Additionally, UVB radiation caused morphological changes in fragments of adult plants in the first week, while the young
individuals only displayed this pattern during the third week. The verified morphological alterations in I. cordata could be interpreted as a defense against UVB by reducing the area exposed to radiation. However, a high level of radiation
appears to produce irreparable damage, especially under long-term exposure. Our results suggest that the sensitivity to ultraviolet
radiation decreases with increased algal age and that the various developmental stages have different responses when exposed
to the same doses of UVB radiation. 相似文献
13.
Responses of Vegetation and Ecosystem CO2 Exchange to 9 Years of Nutrient Addition at Mer Bleue Bog 总被引:1,自引:0,他引:1
Anthropogenic nitrogen (N) loading has the potential to affect plant community structure and function, and the carbon dioxide
(CO2) sink of peatlands. Our aim is to study how vegetation changes, induced by nutrient input, affect the CO2 exchange of a nutrient-limited bog. We conducted 9- and 4-year fertilization experiments at Mer Bleue bog, where we applied
N addition levels of 1.6, 3.2, and 6.4 g N m−2 a−1, upon a background deposition of about 0.8 g N m−2 a−1, with or without phosphorus and potassium (PK). Only the treatments 3.2 and 6.4 g N m−2 a−1 with PK significantly affected CO2 fluxes. These treatments shifted the Sphagnum moss and dwarf shrub community to taller dwarf shrub thickets without moss, and the CO2 responses depended on the phase of vegetation transition. Overall, compared to the large observed changes in the vegetation,
the changes in CO2 fluxes were small. Following Sphagnum loss after 5 years, maximum ecosystem photosynthesis (Pgmax) and net CO2 exchange (NEEmax) were lowered (−19 and −46%, respectively) in the highest NPK treatment. In the following years, while shrub height increased,
the vascular foliar biomass did not fully compensate for the loss of moss biomass; yet, by year 8 there were no significant
differences in Pgmax and NEEmax between the nutrient and the control treatments. At the same time, an increase (24–32%) in ecosystem respiration (ER) became
evident. Trends in the N-only experiment resembled those in the older NPK experiment by the fourth year. The increasing ER
with increasing vascular plant and decreasing Sphagnum moss biomass across the experimental plots suggest that high N deposition may lessen the CO2 sink of a bog. 相似文献
14.
Raúl Muñoz María Hernández Ana Segura Joao Gouveia Antonia Rojas Juan Luis Ramos Santiago Villaverde 《Applied microbiology and biotechnology》2009,83(1):189-198
The long-term performance and stability of Pseudomonas putida mt-2 cultures, a toluene-sensitive strain harboring the genes responsible for toluene biodegradation in the archetypal plasmid
pWW0, was investigated in a chemostat bioreactor functioning under real case operating conditions. The process was operated
at a dilution rate of 0.1 h−1 under toluene loading rates of 259 ± 23 and 801 ± 78 g m−3 h−1 (inlet toluene concentrations of 3.5 and 10.9 g m−3, respectively). Despite the deleterious effects of toluene and its degradation intermediates, the phenotype of this sensitive
P. putida culture rapidly recovered from a 95% Tol− population at day 4 to approx. 100% Tol+ cells from day 13 onward, sustaining elimination capacities of 232 ± 10 g m−3 h−1 at 3.5 g Tol m−3 and 377 ± 13 g m−3 h−1 at 10.9 g Tol m−3, which were comparable to those achieved by highly tolerant strains such as P. putida DOT T1E and P. putida F1 under identical experimental conditions. Only one type of Tol− variant, harboring a TOL-like plasmid with a 38.5 kb deletion (containing the upper and meta operons for toluene biodegradation), was identified. 相似文献
15.
Recovery of Aboveground Plant Biomass and Productivity After Fire in Mesic and Dry Black Spruce Forests of Interior Alaska 总被引:1,自引:0,他引:1
Michelle C. Mack Kathleen K. Treseder Kristen L. Manies Jennifer W. Harden Edward A. G. Schuur Jason G. Vogel James T. Randerson F. Stuart Chapin III 《Ecosystems》2008,11(2):209-225
Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession.
In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years
after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence
of sites that varied in time since fire (2 to ∼116 years). Four years after fire, total biomass at the 1999 burn site had
increased exponentially to 160 ± 21 g m−2 (mean ± 1SE) and vascular ANPP had recovered to 138 ± 32 g m−2 y−1, which was not different than that of a nearby unburned stand (160 ± 48 g m−2 y−1) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting
graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total
biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically
(dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ± 180 (dry) and 4008 ± 233 g m−2 (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per
tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence
to 335 ± 68 g m−2 y−1 in the mature site, but in the dry chronosequence it peaked at 410 ± 43 g m−2 y−1 in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production
in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance
of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better
understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the
carbon balance of Interior Alaska.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
S. Deudero A. Blanco A. Box G. Mateu-Vicens M. Cabanellas-Reboredo A. Sureda 《Biological invasions》2010,12(1):41-52
Invasive epiphyte Lophocladia lallemandii macroalga induces changes in the erect bryozoan Reteporella grimaldii at shallow Posidonia oceanica meadows at a Mediterranean pristine location. Bryozoan densities at noninvaded seagrass plots (88.32 ± 3.11 colonies m−2) are higher than those at invaded plots (13.39 ± 1.09 colonies m−2) with a fourfold decrease in number of colonies. Activation of enzymatic pathways (catalase, superoxide dismutase, glutathione
peroxidase) and increase in lipid peroxidation malondialdehyde (MDA) [0.80 ± 0.06 nmol/mg prot at Posidonia oceanica plots to 1.08 ± 0.04 nmol/mg prot at L. lallemandii (P < 0.05)] is observed on sessile bryozoans as response to anoxia caused by L. lallemandii. δ13C of bryozoan isotopic composition differed among treatments, covering a broad range (−19.30‰ invaded to −2.84‰ at noninvaded
plots), suggesting modification of food sources. Induced shifts of a filter-feeding erect bryozoan by dense algal turfs at
invaded seagrasses are demonstrated, highlighting the need to further address interaction across natural communities and alien
species invaded systems before further cascade effects are driven. 相似文献
17.
Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles
and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of
C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance
were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate
was greatest at 0.5 m depth (0.055 ± 0.032 mm day−1), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m−2 s−1. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day−1) with an average irradiance of 248 ± 116 μmol photons m−2 s−1. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg
fresh wt m−1). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope. 相似文献
18.
Witjaksono Bruce A. Schaffer Angel M. Colls Richard E. Litz Pamela A. Moon 《In vitro cellular & developmental biology. Plant》1999,35(3):238-244
Summary The proliferation and survival of avocado nodal cultures of juvenile origin were affected by the form and concentration of
nitrogen. Optimum growth was achieved on modified Murashige and Skoog medium containing 67% KNO3 and 33% NH4NO3 with total N of 40 mM supplemented with 100 mg l−1
myo-inositol, 1 mg l−1 thiamine HCl, 30 g l−1 sucrose, and 4.44 μM BA with a 16-h photoperiod (120–150 μmol m−2 s−1). Proliferating shoots and plantlets were photosynthetically active. Better shoot growth and accumulation of higher biomass
occurred in a CO2-enriched environment than under ambient CO2 conditions. CO2 assimilation efficiency, however, was higher under the latter conditions than in a CO2-enhanced environment, e.g., 31±7 and 17±2 μmol CO2 m−2 s−1, respectively. The net CO2 assimilation rates of in vitro grown plantlets were comparable to those of seedlings ex vitro. 相似文献
19.
M. Angélica Casanova-Katny Gustavo E. Zúñiga Luis J. Corcuera Leon Bravo Miren Alberdi 《Polar Biology》2010,33(4):477-483
Primary photochemistry of photosystem II (F
v/F
m) of the Antarctic hair grass Deschampsia antarctica growing in the field (Robert Island, Maritime Antarctic) and in the laboratory was studied. Laboratory plants were grown
at a photosynthetic photon flux density (PPFD) of 180 μmol m−2 s−1 and an optimal temperature (13 ± 1.5°C) for net photosynthesis. Subsequently, two groups of plants were exposed to low temperature
(4 ± 1.5°C day/night) under two levels of PPFD (180 and 800 μmol m−2 s−1) and a control group was kept at 13 ± 1.5°C and PPFD of 800 μmol m−2 s−1. Chlorophyll fluorescence was measured during several days in field plants and weekly in the laboratory plants. Statistically
significant differences were found in F
v/F
m (=0.75–0.83), F
0 and F
m values of field plants over the measurement period between days with contrasting irradiances and temperature levels, suggesting
that plants in the field show high photosynthetic efficiency. Laboratory plants under controlled conditions and exposed to
low temperature under two light conditions showed significantly lower F
v/F
m and F
m. Moreover, they presented significantly less chlorophyll and carotenoid content than field plants. The differences in the
performance of the photosynthetic apparatus between field- and laboratory-grown plants indicate that measurements performed
in ex situ plants should be interpreted with caution. 相似文献
20.
Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China 总被引:2,自引:0,他引:2
Yuze Mao Hongsheng Yang Yi Zhou Naihao Ye Jianguang Fang 《Journal of applied phycology》2009,21(6):649-656
In this study the red alga, Gracilaria lemaneiformis, was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 3 weeks at the Marine Aquaculture Laboratory of the Institute
of Oceanology, Chinese Academy of Sciences (IOCAS) in Qingdao, Shandong Province, North China. The nutrient uptake rate and
nutrient reduction efficiency of ammonium and phosphorus from scallop excretion were determined. The experiment included four
treatments each with three replicates, and three scallop monoculture systems served as the control. Scallop density (407.9 ± 2.84 g
m−3) remained the same in all treatments while seaweed density differed. The seaweed density was set at four levels (treatments
1, 2, 3, 4) with thallus wet weight of 69.3 ± 3.21, 139.1 ± 3.80, 263.5 ± 6.83, and 347.6 ± 6.30 g m−3, respectively. There were no significant differences in the initial nitrogen and phosphorus concentration between each treatment
and the control group (ANOVA, p > 0.05). The results showed that at the end of the experiment, the nitrogen concentration in the control group and treatment
1 was significantly higher than in the other treatments. There was also a significant difference in phosphorus concentration
between the control group and the IMTA treatments (ANOVA, p < 0.05). Growth rate, C and N content of the thallus, and mortality of scallop was different between the IMTA treatments.
The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus changed with different cultivation density
and time. The maximum reduction efficiency of ammonium and phosphorus was 83.7% and 70.4%, respectively. The maximum uptake
rate of ammonium and phosphorus was 6.3 and 3.3 μmol g−1 DW h−1. A bivalve/seaweed biomass ratio from 1:0.33 to 1:0.80 (treatments 2, 3, and 4) was preferable for efficient nutrient uptake
and for maintaining lower nutrient levels. Results indicate that G. lemaneiformis can efficiently absorb the ammonium and phosphorus from scallop excretion and is a suitable candidate for IMTA. 相似文献