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1.
Secondary production and diet of an invasive snail in freshwater wetlands: implications for resource utilization and competition 总被引:1,自引:0,他引:1
Invasive species can monopolize resources and thus dominate ecosystem production. In this study we estimated secondary production
and diet of four populations of Pomacea canaliculata, a freshwater invasive snail, in wetlands (abandoned paddy, oxbow pond, drainage channel, and river meander) in monsoonal
Hong Kong (lat. 22°N). Apple snail secondary production (ash-free dry mass [AFDM]) ranged from 165.9 to 233.3 g m−2 year−1, and varied between seasons. Production was lower during the cool dry northeast monsoon, when water temperatures might have
limited growth, but fast growth and recruitment of multiple cohorts were possible throughout much (7–10 months) of the year
and especially during the warm, wet southwest monsoon. The diet, as revealed by stomach-content analysis, consisted mainly
of detritus and macrophytes, and was broadly consistent among habitats despite considerable variation in the composition and
cover of aquatic plants. Apple snail annual production was >10 times greater than production estimates for other benthic macroinvertebrates
in Hong Kong (range 0.004–15 g AFDM m−2 year−1, n = 29). Furthermore, annual production estimates for three apple snail populations (i.e. >230 g AFDM m−2 year−1) were greater than published estimates for any other freshwater snails (range 0.002–194 g AFDM m−2 year−1, n = 33), regardless of climatic regime or habitat type. High production by P. canaliculata in Hong Kong was attributable to the topical climate (annual mean ~24°C), permitting rapid growth and repeated reproduction,
together with dietary flexibility including an ability to consume a range of macrophytes. If invasive P. canaliculata can monopolize food resources, its high productivity indicates potential for competition with other macroinvertebrate primary
consumers. Manipulative experiments will be needed to quantify these impacts on biodiversity and ecosystem function in wetlands,
combined with management strategies to prevent further range extension by P. canaliculata. 相似文献
2.
Sharon M. L. Ewe Evelyn E. Gaiser Daniel L. Childers David Iwaniec Victor H. Rivera-Monroy Robert R. Twilley 《Hydrobiologia》2006,569(1):459-474
We present here a 4-year dataset (2001–2004) on the spatial and temporal patterns of aboveground net primary production (ANPP)
by dominant primary producers (sawgrass, periphyton, mangroves, and seagrasses) along two transects in the oligotrophic Florida
Everglades coastal landscape. The 17 sites of the Florida Coastal Everglades Long Term Ecological Research (FCE LTER) program
are located along fresh-estuarine gradients in Shark River Slough (SRS) and Taylor River/C-111/Florida Bay (TS/Ph) basins
that drain the western and southern Everglades, respectively. Within the SRS basin, sawgrass and periphyton ANPP did not differ
significantly among sites but mangrove ANPP was highest at the site nearest the Gulf of Mexico. In the southern Everglades
transect, there was a productivity peak in sawgrass and periphyton at the upper estuarine ecotone within Taylor River but
no trends were observed in the C-111 Basin for either primary producer. Over the 4 years, average sawgrass ANPP in both basins
ranged from 255 to 606 g m−2 year−1. Average periphyton productivity at SRS and TS/Ph was 17–68 g C m−2 year−1 and 342–10371 g C m−2 year−1, respectively. Mangrove productivity ranged from 340 g m−2 year−1 at Taylor River to 2208 g m−2 year−1 at the lower estuarine Shark River site. Average Thalassia testudinum productivity ranged from 91 to 396 g m−2 year−1 and was 4-fold greater at the site nearest the Gulf of Mexico than in eastern Florida Bay. There were no differences in periphyton
productivity at Florida Bay. Interannual comparisons revealed no significant differences within each primary producer at either
SRS or TS/Ph with the exception of sawgrass at SRS and the C−111 Basin. Future research will address difficulties in assessing
and comparing ANPP of different primary producers along gradients as well as the significance of belowground production to
the total productivity of this ecosystem. 相似文献
3.
BROCK M. HUNTSMAN MICHAEL P. VENARSKY JONATHAN P. BENSTEAD ALEXANDER D. HURYN 《Freshwater Biology》2011,56(9):1746-1760
1. Surface ecosystems provide the primary source of organic matter to many cave communities. Variation in the strength of connectivity to the surface suggests that some caves may be more resource‐limited than others. To test this, we examined diet, prey availability and production of an obligate cave salamander Gyrinophilus palleucus (Plethodontidae), a top predator, in two south‐eastern U.S.A. caves with different levels of organic matter (Tony Sinks cave, 165 g AFDM m?2; Bluff River cave, 62 g AFDM m?2). 2. We quantified density, biomass, growth rate, production and diet of G. palleucus monthly for 21 months. Diet composition, differences in prey communities and seasonal patterns in prey consumption were also analysed. 3. Salamander density, biomass and secondary production were significantly greater in the high organic matter cave (0.10 m?2, 0.18 g AFDM m?2, 0.12 g AFDM m?2 year?1) than in the low organic matter cave (0.03 m?2, 0.03 g AFDM m?2, 0.01 g AFDM m?2 year?1). Although growth rates were not statistically different between the two cave salamander populations, low recaptures probably influenced this result. 4. Isopoda prey were the major contributor to salamander production in the high organic matter cave (69%). In the low organic matter cave, production was provided by isopods (41%) and oligochaetes (20%). The lower number of prey taxa contributing to salamander production in the high organic matter cave suggests the ability to forage more selectively. 5. The differences in foraging strategy, density, biomass and secondary production were probably related to differences in the strength of surface connectivity, which controls organic matter supply. Links between basal resource level and top predator performance show the importance of bottom‐up limitation in the food webs of caves and other detritus‐based ecosystems. 相似文献
4.
We studied life history and secondary production of a caddisfly scraper, Glossosoma nigrior, in two Alabama streams. Collier Creek, located within the Appalachian Plateau physiographic province, is underlain by sandstone
bedrock, while Hendrick Mill Branch is located in the Valley and Ridge physiographic province with limestone bedrock. G. nigrior populations in both streams exhibited trivoltine life histories, which were attributed to the higher water temperature regimes
than those found in more northern streams. Mean larval density (556 m−2) and biomass (B) (49.2 mg AFDM m−2) were much higher in Hendrick Mill Branch than Collier Creek (78 m−2 and 6.7 mg AFDM m−2). G. nigrior in Hendrick Mill Branch maintained continuous larval growth and higher larval density than Collier Creek throughout the year
mainly due to a greater availability of optimal habitat, a more stable hydrology, and warmer winter water temperature. These
factors also resulted in the much higher annual secondary production (P) in Hendrick Mill Branch (965 mg AFDM m−2; P/B = 18.3) than Collier Creek (115 mg AFDM m−2; P/B = 17.9). Gut content analysis revealed that algae (>50%) and detritus (>40%) were the major diet items for G. nigrior, and the majority of secondary production (>80%) was contributed by the consumption of algae. Glossosoma populations play an important role in trophic linkage in these streams with their high production and grazing activities.
Handling editor: D. Dudgeon 相似文献
5.
Martin Emil Blicher Lars Maltha Rasmussen Mikael Kristian Sejr Flemming Ravn Merkel S?ren Rysgaard 《Polar Biology》2011,34(8):1105-1116
The number of common eiders (Somateria
mollissima borealis) in west Greenland declined dramatically during the twentieth century, supposedly because of human activities. However, their
sensitivity to alternative drivers of variation, such as climate conditions, diseases or food availability, remains unstudied.
In this study, we describe prey availability and assess the trophic coupling between eiders and their macrobenthic prey in
a shallow inlet, Nipisat Sound; a key wintering habitat in the south-west Greenland Open Water Area. Macrobenthic species
abundance and biomass were studied, and annual production was estimated by an empirical model, including environmental characteristics,
fauna composition and individual biomass. In spring 2008, average macrozoobenthic abundance and biomass were 6,912 ind m−2 and 28.4 g ash-free dry mass (AFDM) m−2 (647 kJ m−2), respectively. Annual production was estimated at 13.9 g AFDM m−2 year−1 (317 kJ m−2 year−1). During the winters of 2008–2010, we monitored the number of common eiders (S. mollissima borealis) and king eiders (Somateria spectabilis) and observed a distinct peak in abundance during winter with up to 15.000 birds in Nipisat Sound. Based on physiological
costs of different activities in combination with the observed behavioural pattern, we obtained an estimate of the energy
required for eiders to balance their costs of living, which amounted to 58% of the estimated total annual production of macrobenthos
in Nipisat Sound. This result suggests that eider predation affects macrobenthic species composition and biomass and demonstrates
the potential importance of variations in prey availability for the population dynamics of eiders in Greenland. 相似文献
6.
Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic
pond. The gross primary production of phytoplankton was 290 gC m−2 per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident
solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m−3), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60
g dry weight m−2, of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m−2 and 0.61 g dry weight m−2, respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m−2.Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The
maximum density, the mean biomass, and the production were 19,100 m−2, 0.81 g dry weight m−2, and 11.7 g dry weight m−2yr−1, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production
ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only
on zooplankton but also algae. 相似文献
7.
Natalia P. Kosykh Natalia G. Koronatova Natalia B. Naumova Argenta A. Titlyanova 《Wetlands Ecology and Management》2008,16(2):139-153
We measured phytomass stock and production in Western Siberian mire ecosystems (palsa, ridge, oligotrophic and mesotrophic
hollows, fen). To determine the contribution of different phytomass fractions into total production, we developed a method
to estimate below-ground production (BNP). Standing crop of living above-ground phytomass on treeless plots varied from 300
to 660 g m−2, reaching maximum on palsa, where 81% of phytomass consisted of Sphagnum mosses and lichens. In the hollows and the fen, Sphagnum percentage varied from 70 to 95%. Standing crop of living below-ground phytomass varied from 325 to 1,210 g m−2. It consisted of woody stems, stem bases, rhizomes and roots, with the latter contributing from 30 to 60%. Total production
of mire ecosystems in northern taiga of Western Siberia ranged from 350 to 960 g m−2 year−1 and depended on microtopography of the ecosystem (the presence of permafrost and water table depth). Production of treeless
plant communities located on the elevated sites depended on the presence of permafrost: in comparison with the ridge, palsa
production was lower. Production on the low sites increased with increase pH and reached maximum (960 g m−2 year−1) in poor fens. Bryophytes were the major producers above ground. Their production varied from 100 to 272 g m−2 year−1 and reached maximum on ridges. BNP contributed 37–66%, increasing due to increased contribution of sedges. 相似文献
8.
Earthworm secondary production and N flux in agroecosystems: a comparison of two approaches 总被引:1,自引:0,他引:1
Production was estimated for Aporrectodea spp. and Lumbricus spp. populations in corn agroecosystems with a 5-year history of manure or inorganic fertilizer applications during 1994–1995
and 1995–1996. Earthworm biomass and production were greater in manure than inorganic fertilizer plots, although biomass and
production declined by about 50% between 1994–1995 and 1995–1996 due to unfavorable climatic conditions. Production was highest
during the spring and autumn when soil temperatures were between 4 and 22°C. Production was higher in Lumbricus spp. than Aporrectodea spp. populations due to greater Lumbricus spp. biomass. Aporrectodea spp. production was 3.47–16.14 g ash-free dry weight (AFDW) m–2 year–1, while Lumbricus spp. production was 6.09–18.11 g AFDW m–2 year–1, depending on the fertilizer treatment and the method used to estimate production. However, production estimates from the
instantaneous growth rate method were within 27% of the values calculated using the size-frequency method. Nitrogen flux through
earthworms was used to estimate efficiency quotients. Net production efficiency (P/A) ranged from 0.64 to 0.76, assimilation efficiency (A/C) ranged from 0.1 to 0.3, and gross production efficiency (P/C) ranged from 0.06 to 0.22. Annual N flux through earthworm populations was higher in manure than inorganic fertilizer plots,
and ranged from 2.95 to 5.47 g N m–2 year–1 in 1994–1995 and 1.76 to 2.92 g N m–2 year–1 in 1995–1996. The N flux through earthworms represented an amount equivalent to 16–30% of crop N uptake during 1994–1995
and 11–18% of crop N uptake during 1995–1996. We concluded that the effects of earthworms on N cycling in corn agroecosystems
were substantial, and that N flux through earthworms was influenced significantly by fertilizer amendments.
Received: 20 September 1999 / Accepted: 24 March 2000 相似文献
9.
Life-history and production of Olinga feredayi in both benthic and hyporheic stream habitats were investigated in a pristine Waikato, New Zealand, forest stream over two
years to investigate the contribution of hyporheic habitat to total secondary production. O. feredayi had a univoltine life-history with adult emergence occurring from November to March. Larvae with case lengths < 2 mm were
present on most dates suggesting delayed egg hatching. Benthic densities were inversely related to maximum peak daily flow
in the month prior to sampling, and positively related to the dry mass of particulate organic matter present in samples. Reach-average
benthic production calculated by the size-frequency method was 0.024 g DM m−2 year−1. Hyporheic production was 4.276 g DM m−3 year−1 and 6.462 g DM m−3 year−1 in colonisation baskets set at 15–30 cm and 30–45 cm within the substratum, respectively, 2.3–3.4 times greater than production
in surface baskets (0–15 cm). Averaged out over the reach scale, it was estimated that 96% of annual secondary production
of O. feredayi occurred in hyporheic habitats >10 cm below the streambed surface. Our study clearly demonstrates that only sampling benthic
habitats can lead to gross under-estimation of population-level annual production, and provides evidence for the role of the
hyporheos as a source of secondary production that may partly account for the Allen Paradox. 相似文献
10.
Population dynamics and production of the freshwater snail Chilina gibbosa Sowerby 1841 (Chilinidae,Pulmonata) in a North-Patagonian reservoir 总被引:1,自引:1,他引:0
Chilina gibbosa is an endemic snail widely distributed in Patagonia, Argentina. Due to its importance in the benthic fauna and in the diet
of some fish in the oligo-mesotrophic reservoir Ezequiel Ramos Mexía (39° 30′ S, 69° 00′ W), special attention has been given
to its life cycle, growth patterns and annual production. Samples were taken monthly at five littoral stations between June
1983 and July 1984.
Mean abundance and biomass of C. gibbosa were much higher in vegetated stations dominated by Potamogeton berteroanus (Station 1 : 583 ind. m−2, 5.95 g AFDM m−2) or by Nitella clavata (Station 5 : 275 ind. m−2, 4.18 g AFDM m−2) than bare stations with low transparency or stations with other macrophytes. The snails presented a clustered spatial pattern
and their abundance was significantly correlated with macrophyte wet biomass only when this was above 250 g m−2. Analysis of size distributions showed an annual life cycle with a reproductive period in the summer. However, differences
in recruitment and growth occurred probably due to differences in water temperature and food availability. Growth was maximum
in summer and almost absent during winter. Hence, shell growth data fit a sigmoid curve well, and growth was somewhat higher
at Station 1. Annual production at Stations 1 and 5, estimated by the ‘growth increment summation’ method (28.8 g AFDM m−2 and 14.18 g AFDM m−2 respectively), was among the highest recorded for pulmonate gastropods, possibly due to a low interspecific competition.
The P : B ratio values were within the range for univoltine gastropods (4.84 and 3.39).
The high productivity and turnover rate of these snails grant a high availability of food for the abundant molluscivore, the
silverside Patagonina hatcheri. 相似文献
11.
The Western Australian termite,Drepanotermes tamminensis (Hill), harvests various plant materials according to biomass availability. The main litter components harvested by this
termite in a woodland dominated byEucalyptus capillosa are bark and leaves of the major tree species, while in shrubland dominated byAllocasuarina campestris, shoots of this species are taken. Harvesting mainly occurs during the autumn (April–May) and spring (September–October)
seasons. The commencement and duration of harvesting appears to depend partly on weather conditions, with harvesting taking
place at temperatures between 15 and 25°C after periods of rain. This species of termite harvests approximately 15.6 g m−2 year−1 and 3.2 g m2 year−1 (dry weight of plant material) in the woodland and shrubland, respectively. 相似文献
12.
Responses of sawgrass and spikerush to variation in hydrologic drivers and salinity in Southern Everglades marshes 总被引:3,自引:3,他引:0
Daniel L. Childers David Iwaniec Damon Rondeau Gustavo Rubio Emilie Verdon Christopher J. Madden 《Hydrobiologia》2006,569(1):273-292
Aboveground net primary production (ANPP) by the dominant macrophyte and plant community composition are related to the changing
hydrologic environment and to salinity in the southern Everglades, FL, USA. We present a new non-destructive ANPP technique
that is applicable to any continuously growing herbaceous system. Data from 16 sites, collected from 1998 to 2004, were used
to investigate how hydrology and salinity controlled sawgrass (Cladium jamaicense Crantz.) ANPP. Sawgrass live biomass showed little seasonal variation and annual means ranged from 89 to 639 gdw m−2. Mortality rates were 20–35% of live biomass per 2 month sampling interval, for biomass turnover rates of 1.3–2.5 per year.
Production by C. jamaicense was manifest primarily as biomass turnover, not as biomass accumulation. Rates typically ranged from 300 to 750 gdw m−2 year−1, but exceeded 1000 gdw m−2 year−1 at one site and were as high as 750 gdw m−2 year−1 at estuarine ecotone sites. Production was negatively related to mean annual water depth, hydroperiod, and to a variable
combining the two (depth-days). As water depths and hydroperiods increased in our southern Everglades study area, sawgrass
ANPP declined. Because a primary restoration goal is to increase water depths and hydroperiods for some regions of the Everglades,
we investigated how the plant community responded to this decline in sawgrass ANPP. Spikerush (Eleocharis sp.) was the next most prominent component of this community at our sites, and 39% of the variability in sawgrass ANPP was
explained by a negative relationship with mean annual water depth, hydroperiod, and Eleocharis sp. density the following year. Sawgrass ANPP at estuarine ecotone sites responded negatively to salinity, and rates of production
were slow to recover after high salinity years. Our results suggest that ecologists, managers, and the public should not necessarily
interpret a decline in sawgrass that may result from hydrologic restoration as a negative phenomenon. 相似文献
13.
McCormick Paul V. Shuford III Robert B. E. Backus John G. Kennedy William C. 《Hydrobiologia》1997,362(1-3):185-210
We sampled periphyton in dominant habitats at oligotrophic and eutrophic sites in the northern Everglades during the wet and
the dryseasons to determine the effects of nutrient enrichment on periphytonbiomass, taxonomic composition, productivity,
and phosphorus storage. Arealbiomass was high (100–1600 g ash-free dry mass [AFDM]m−2) in oligotrophic sloughs and in stands of the emergentmacrophyte Eleocharis cellulosa, but was low in adjacent stands of
sawgrass,Cladium jamaicense (7–52 g AFDM m−2). Epipelon biomasswas high throughout the year at oligotrophic sites whereas epiphyton andmetaphyton biomass varied seasonally
and peaked during the wet season.Periphyton biomass was low (3–68 g AFDM m−2) and limitedto epiphyton and metaphyton in open-water habitats at eutrophic sites andwas undetectable in cattail stands (Typha
domingensis) that covered morethan 90% of the marsh in these areas. Oligotrophic periphytonassemblages exhibited strong seasonal
shifts in species composition and weredominated by cyanobacteria (e.g., Chroococcus turgidus, Scytonema hofmannii)during the
wet season and diatoms (e.g. Amphora lineolata, Mastogloiasmithii) during the dry season. Eutrophic assemblages were dominated
byCyanobacteria (e.g., Oscillatoria princeps) and green algae (e.g., Spirogyraspp.) and exhibited comparatively little seasonality.
Biomass-specific grossprimary productivity (GPP) of periphyton assemblages in eutrophic openwaters was higher than for comparable
slough assemblages, but areal GPP wassimilar in these eutrophic (0.9–9.1 g C m−2d−1) and oligotrophic (1.75–11.49 g C m−2d−1) habitats. On a habitat-weighted basis, areal periphytonGPP was 6- to 30-fold lower in eutrophic areas of the marsh due to
extensiveTypha stands that were devoid of periphyton. Periphyton at eutrophic siteshad higher P content and uptake rates than
the oligotrophic assemblage, butstored only 5% as much P because of the lower areal biomass.Eutrophication in the Everglades
has resulted in a decrease in periphytonbiomass and its contribution to marsh primary productivity. These changesmay have
important implications for efforts to manage this wetland in asustainable manner.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Karibu Fukuzawa Hideaki Shibata Kentaro Takagi Fuyuki Satoh Takayoshi Koike Kaichiro Sasa 《Ecological Research》2007,22(3):485-495
We measured the vertical distribution and seasonal patterns of fine-root production and mortality using minirhizotrons in
a cool–temperate forest in northern Japan mainly dominated by Mongolian oak (Quercus crispula) and covered with a dense understory of dwarf bamboo (Sasa senanensis). We also investigated the vertical distribution of the fine-root biomass using soil coring. We also measured environmental
factors such as air and soil temperature, soil moisture and leaf area indices (LAI) of trees and the understory Sasa canopy for comparison with the fine-root dynamics. Fine-root biomass to a depth of 60 cm in September 2003 totaled 774 g m−2, of which 71% was accounted for by Sasa and 60% was concentrated in the surface soil layer (0–15 cm), indicating that understory Sasa was an important component of the fine-root biomass in this ecosystem. Fine-root production increased in late summer (August)
when soil temperatures were high, suggesting that temperature partially controls the seasonality of fine-root production.
In addition, monthly fine-root production was significantly related to Sasa LAI (P<0.001), suggesting that fine-root production was also affected by the specific phenology of Sasa. Fine-root mortality was relatively constant throughout the year. Fine-root production, mortality, and turnover rates were
highest in the surface soil (0–15 cm) and decreased with increasing soil depth. Turnover rates of production and mortality
in the surface soil were 1.7 year−1 and 1.1 year−1, respectively. 相似文献
15.
Hiroshi Koizumi 《Journal of plant research》1989,102(4):521-532
Photosynthetic and respiratory activities and gross production in relation to temperature conditions were investigated in
the population of an evergreen herb,Pyrola japonica, growing on the floor of a deciduous forest in the warm temperate region of central Japan.
Analysis of the temperature-photosynthesis relationship ofP. japonica leaves during the growing season indicated distinct seasonal changes in the temperature optimum for photosynthesis. This
population was found to be acclimatable to ambient air temperatures exceeding 15C, but this acclimation became less pronounced
under thermal conditions below 15 C. This plant possessed narrow photosynthetic optima in the warm season but wide optima
in the cold season. The shape of the temperature-respiration curve did not vary significantly with the months except for April.
The Q10 for respiration between 10 C and 20 C was calculated to be 1.93–2.65. Annual dry matter loss associated with respiration
was estimated to amount to 159.1 g d.w.m−2 based on the measurements of the seasonal changes in the respiratory activity of each organ. Gross production of this population
was estimated to be 219.3 g d.w.m−2 year−1 as the sum total of the net production (60.2 g d.w.m−2year−1) and the respiration. Monthly gross production was high in the early growing season, and low and stable in winter. 相似文献
16.
1. We investigated the impacts of saltcedar invasion on organic matter dynamics in a spring‐fed stream (Jackrabbit Spring) in the Mojave Desert of southern Nevada, U.S.A., by experimentally manipulating saltcedar abundance. 2. Saltcedar heavily shaded Jackrabbit Spring and shifted the dominant organic matter inputs from autochthonous production that was available throughout the year to allochthonous saltcedar leaf litter that was strongly pulsed in the autumn. Specifically, reaches dominated by saltcedar had allochthonous litter inputs of 299 g ash free dry mass (AFDM) m?2 year?1, macrophyte production of 15 g AFDM m?2 year?1 and algal production of 400 g AFDM m?2 year?1, while reaches dominated by native riparian vegetation or where saltcedar had been experimentally removed had allochthonous litter inputs of 7–34 g AFDM m?2 year?1, macrophyte production of 118–425 g AFDM m?2 year?1 and algal production of 640–900 g AFDM m?2 year?1. 3. A leaf litter breakdown study indicated that saltcedar also altered decomposition in Jackrabbit Spring, mainly through its influence on litter quality rather than by altering the environment for decomposition. Decomposition rates for saltcedar were lower than for ash (Fraxinus velutina), the dominant native allochthonous litter type, but faster than for bulrush (Scirpus americanus), the dominant macrophyte in this system. 相似文献
17.
James E. Kaldy 《Hydrobiologia》2006,560(1):433-217
The non-indigenous seagrass Zostera japonica Ascher. & Graeb. (dwarf eelgrass) was first identified in central Oregon (USA) estuaries about 30 years ago. The autecology
of this species is poorly described at the southern end of its non-native range although several process oriented studies
have been conducted. I examined the production ecology of Z. japonica in the Yaquina Bay estuary. Strong seasonal patterns in light and temperature appeared to control the seasonal variations
in biomass and growth. Above- and below-ground biomass ranged between 40–100 and 70–170 gdw m−2 respectively and seasonal changes in the root:shoot ratio were controlled by above-ground biomass dynamics. Shoot density
ranged between 4000 and 11 000 shts m−2. Areal leaf growth ranged between 0.1 and 1.7 gdw m−2 d−1 and annual production was about 314 ± 60 gdw m−2 y−1 (mean ± SD). Nutrients were not limiting in this system as a result of coastal upwelling and watershed inputs. The Z. japonica population studied in Oregon exhibited different patterns of persistence, phenology and flowering intensity relative to other
populations along its native and non-native range. These differences suggest that management policies developed for one site
may not be appropriate for other sites. The data presented here greatly expands our knowledge base on Z. japonica and provides insight to the processes controlling the dynamics and spread of this non-indigenous seagrass.
An erratum to this article is available at . 相似文献
18.
To understand the background of the strong variation and recent decline of stocks and production of mussels (Mytilus edulis) on tidal flats of the Wadden Sea, we analysed long-term (twice-annual for 26 years) and multi-station (15 sites) estimates
of numbers, mean individual weights, biomass, and annual production on Balgzand, a 50-km2 tidal-flat area in the westernmost part of the Wadden Sea (The Netherlands). Somatic production was estimated from summed
growth increments of soft tissues per half-year period and expressed in ash-free dry mass (AFDM). In adults, positive values
in spring/summer regularly alternated with negative values in autumn/winter, when up to ∼25% (mean: 14%) of individual weight
gains in the preceding season were lost. No weight losses were observed during the first winter of the life of mussels. The
26-year mean of net somatic tissue production P amounted to 5.5 g AFDM m−2 a−1 at a mean biomass B of 3.2 g AFDM m−2; the ratio P/B varied strongly with age composition of the mussel population and ranged between 0.5 and 3.0 a−1 (mean: 1.7). Within the restricted areas of mussel beds, mean biomass and annual production values were two orders of magnitude
higher. In the Wadden Sea, mussel beds cover a typical 1% of extensive tidal flat areas. Numerical densities of recruits showed
straight-line relationships with subsequent life-time year-class production. Once recruits had reached an age of ∼10 months,
their numbers predicted subsequent production within narrow limits. Production per recruit averaged 0.21 g AFDM for 10-mo
recruits and was not related to recruit density. Local variation in annual production varied strongly, with maximal values
between mid-tide and low-tide level, where recruitment was also maximal. Production per recruit was higher at low than at
high intertidal levels. Frequently failing recruitment is indicated as the main cause of declining mussel stocks in the Wadden
Sea. As in other bivalve species, a declining frequency of the occurrence of cold winters appears to govern declining recruitment
success and consequently declining production. 相似文献
19.
Van Geest GJ Hessen DO Spierenburg P Dahl-Hansen GA Christensen G Faerovig PJ Brehm M Loonen MJ Van Donk E 《Oecologia》2007,153(3):653-662
A dramatic increase in the breeding population of geese has occurred over the past few decades at Svalbard. This may strongly
impact the fragile ecosystems of the Arctic tundra because many of the ultra-oligotrophic freshwater systems experience enrichment
from goose feces. We surveyed 21 shallow tundra ponds along a gradient of nutrient enrichment based on exposure to geese.
Concentrations of total phosphorus (P) and dissolved inorganic nitrogen (DIN) in the tundra ponds ranged from 2–76 to 2–23 μg l−1 respectively, yet there was no significant increase in phytoplankton biomass (measured as chlorophyll a; range: 0.6–7.3 μg l−1) along the nutrient gradient. This lack of response may be the result of the trophic structure of these ecosystems, which
consists of only a two-trophic level food chain with high biomasses of the efficient zooplankton grazer Daphnia in the absence of fish and scarcity of invertebrate predators. Our results indicate that this may cause a highly efficient
grazing control of phytoplankton in all ponds, supported by the fact that large fractions of the nutrient pools were bound
in zooplankton biomass. The median percentage of Daphnia–N and Daphnia–P content to particulate (sestonic) N and P was 338 and 3009%, respectively, which is extremely high compared to temperate
lakes. Our data suggest that Daphnia in shallow arctic ponds is heavily subsidized by major inputs of energy from other food sources (bacteria, benthic biofilm),
which may be crucial to the persistence of strong top–down control of pelagic algae by Daphnia. 相似文献
20.
Takayoshi Tsuchiya 《Ecological Research》1989,4(2):157-166
Growth of a floating-leaved plant,Hydrocharis dubia L., was examined under varying nutrient conditions between 0.3 and 30 mgN l−1 total inorganic nitrogen.H. dubia plants cultured under the most nutrient-rich condition showed the highest maximum ramet density (736 m−2), the highest maximum biomass (80.4 g dry weight m−2), and the highest total net production (185 g dry weight m−2 in 82 days). Plants under nutrient-poor conditions had a relatively large proportion of root biomass and a small proportion
of leaves with a long life span.
Compared with other floating-leaved and terrestrial plants, the maximum biomass ofH. dubia was relatively small. This, and the rapid biomass turnover, was related to the short life span of leaves (13.2–18.7 days)
and large biomass distribution to leaves. 相似文献