Secondary production and diet of an invasive snail in freshwater wetlands: implications for resource utilization and competition

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.     

Carbon stock and cycling in a bambooPhyllostachys bambusoides stand

Gross production and carbon cycling in aPhyllostachys bambusoides stand in Kyoto Prefecture, central Japan, were determined, and then a compartment model showing the carbon stock and cycling within the ecosystem was developed. Aboveground carbon stock was 52.3 tC ha⁻¹, increasing at a rate of 3.6 tC ha⁻¹ year⁻¹. Belowground carbon stock was 20.8 tC ha⁻¹ in the root system and 92.0 tC ha⁻¹ in the soil. Aboveground net production was 11.2 tC ha⁻¹ year⁻¹. Belowground net production was crudely estimated at 4.5 tC ha⁻¹ year⁻¹. The gross production was estimated at 41.8 tC ha⁻¹ year⁻¹ by summing the amount of outflow to the environment and the increment in biomass. Leaves consumed 13.7 tC ha⁻¹ year⁻¹ by respiration; the rest (41.8−13.7=28.1 tC ha⁻¹ year⁻¹) was surplus production of the leaves and flowed into the other compartments. The amounts of construction and maintenance respiration of the aboveground compartments were 3.4 and 18.5 tC ha⁻¹ year⁻¹, respectively. The annual amount of soil respiration was 11.2 tC ha⁻¹ year⁻¹. Soil respiration levels of 4.3 and 3.1 tC ha⁻¹ year⁻¹ were estimated for the flow of root respiration and root detritus. The proportion of net to gross production was 37%, which fell within the range of young and mature forests. A shorter life span of culms, compared to tree trunks, resulted in smaller biomass accumulation ratio (biomass/net production) in the ecosystem, of 4.66.     

Life history and secondary production of Glossosoma nigrior Banks (Trichoptera: Glossosomatidae) in two Alabama streams with different geology

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     

Influence of size and seasonal factors on the growth of the deep-sea coral Flabellum alabastrum in mesocosm

Growth rate (linear skeleton extension) was determined in live specimens of the deep-sea cup coral Flabellum alabastrum (Anthozoa: Flabellidae) collected between 600 and 1,200 m off insular Newfoundland (eastern Canada) and kept under laboratory conditions for over 2 years. Smaller individuals grew faster (~5 mm year⁻¹) than larger ones (~1 mm year⁻¹). Seasonal variations in extension rates and qualitative appearance of the growth bands were recorded, with maximum extension occurring in late summer and early fall during maxima in seawater temperature, zooplankton levels, and deposition of suspended detritus. Estimates from a growth model indicate that the largest individuals of F. alabastrum (~43 mm calyx height) are at least 45 years old.     

Reproduction,population dynamics and production of <Emphasis Type="Italic">Nereis falsa</Emphasis> (Nereididae: Polychaeta) on the rocky coast of El Kala National Park,Algeria

The polychaete Nereis falsa Quatrefages, 1866 is present in the area of El Kala National Park on the East coast of Algeria. Field investigations were carried out from January to December 2007 to characterize the populations’ reproductive cycle, secondary production and dynamics. Reproduction followed the atokous type, and spawning occured from mid-June to the end of August/early September when sea temperature was highest (20–23°C). The diameter of mature oocytes was approximately 180 μm. Mean lifespan was estimated to about one year. In 2007, the mean density was 11.27 ind. m⁻² with a minimum of 7.83 ind. m⁻² in April and a maximum of 14.5 ind. m⁻² in February. The mean annual biomass was 1.36 g m⁻² (fresh weight) with a minimum of 0.86 g m⁻² in December and a maximum of 2.00 g m⁻² in June. The population consisted of two cohorts distinguishable from size frequency distributions. One cohort corresponded to the recruitment of 2006 and the other appeared during the study period in September 2007. The annual production of N. falsa was 1.45 g m⁻² year⁻¹, and the production/biomass ratio was 1.07 year⁻¹.     

Production and prey source of juvenile black rockfish <Emphasis Type="Italic">Sebastes cheni</Emphasis> in a seagrass and macroalgal bed in the Seto Inland Sea,Japan: estimation of the economic value of a nursery

The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the difficulty of quantitative estimation of fish production in the field. In the present study, annual production and economic value of wild juvenile black rockfish, Sebastes cheni, a dominant fish species in seagrass and macroalgal beds in the central Seto Inland Sea were estimated. Juvenile S. cheni migrated into vegetated habitats at about 20 mm total length (TL) and grew up to about 60 mm TL by late May. Juvenile abundance was highest in April (2007) or March (2008). Eight cohorts with the same extrusion period (each cohort covering a 10-day period) were identified using otolith daily increments. The annual estimates of S. cheni juvenile production were 13,080 g ha⁻¹ year⁻¹ in 2007 and 18,360 g ⁻¹ year⁻¹ in 2008. Based on the unit price of artificially raised S. cheni juveniles, the economic value of the annual wild juvenile production was converted to 654,000 JPY (Japanese yen: 100 JPY = ca. 1 USD) ha⁻¹ year⁻¹ for 2007 and 918,000 JPY ha⁻¹ year⁻¹ for 2008. Analyses of stomach contents and stable isotope (δ¹³C or δ¹⁵N) showed that juvenile S. cheni were highly dependent on copepods. The planktonic trophic pathway originating from phytoplankton supports the majority of the juvenile black rockfish production during the post-migration period (20–60 mm TL) in the seagrass and macroalgal beds through the production of copepod zooplankton. The total economic value of the ecosystem services of the vegetated habitat is suggested to be much higher than estimates in previous studies if the provisioning and regulating services which originate from fish production were included in the estimates.     

Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient

Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north–south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m⁻² year⁻¹ in the north, to 1.49 g N m⁻² year⁻¹ in the south. The maximum photosynthetic rate (NP_max) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m⁻² year⁻¹, but for S. balticum it seemed to level out at 1.14 g N m⁻² year⁻¹. The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NP_max was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.     

Spatial and Temporal Pattern of Caddisfly Distribution at a Mesohabitat Scale in two Patagonian Mountain Streams Subjected to Pastoral Use

Substrate, flow type, nutrients, aquatic vegetation, organic matter, and caddisfly community structure were studied at two low order streams (Glyn and Nant y Fall) subjected to pastoral use in the Patagonian mountains. At both sites, we examined the effect of habitat type (boulder‐pebble with and without filamentous algae, cobble‐pebble, gravel‐sand, leaf‐pack, the submerged macrophytes Myriophyllum quitense and Isoetes savatieri) and season (high and low water period) on caddisfly assemblages. Benthic particulate organic matter (BPOM) ranged between 4.6 and 472 g m^–2, all allochtonous detrital fractions were significantly higher at leaf‐packs at Glyn, whereas M. quitense habitats supported more BPOM and macrophytes biomass at Nant y Fall. As expected, boulder‐pebble sustained higher Trichoptera richness than M. quitense and gravel‐sand, moreover all habitats showed higher density than M. quitense at Nant y Fall. According to our results at least nine caddisfly species exhibited some habitat preference with boulder‐pebble and cobble‐pebble the most selected habitat. These particular habitats sustained more than 68% of the total caddisfly species. Multidimensional scaling ordination highlighted differences in composition per habitat for both sites showing a clear distinction among depositional and erosional habitats. Substrate, flow type, detritus biomass were important predictors defining assemblages. Based upon our findings, those anthropogenic actions or stressors that change hydraulic as well substrate attributes in mountain streams such as stock trampling, dredging, clearing of riparian areas, will reduce caddisfly richness. These results are relevant for outline management and conservation biomonitoring and schemes in headwater Patagonian streams as well as other similar environments worldwide (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Biometric-based estimation of net ecosystem production in a mature Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) plantation beneath a flux tower

Quantification of carbon budgets and cycling in Japanese cedar (Cryptomeria japonica D. Don) plantations is essential for understanding forest functions in Japan because these plantations occupy about 20% of the total forested area. We conducted a biometric estimate of net ecosystem production (NEP) in a mature Japanese cedar plantation beneath a flux tower over a 4-year period. Net primary production (NPP) was 7.9 Mg C ha⁻¹ year⁻¹ and consisted mainly of tree biomass increment and aboveground litter production. Respiration was calculated as 6.8 (soil) and 3.3 (root) Mg C ha⁻¹ year⁻¹. Thus, NEP in the plantation was 4.3 Mg C ha⁻¹ year⁻¹. In agreement with the tower-based flux findings, this result suggests that the Japanese cedar plantation was a strong carbon sink. The biometric-based NEP was higher among most other types of Japanese forests studied. Carbon sequestration in the mature plantation was characterized by a larger increment in tree biomass and lower mortality than in natural forests. Land-use change from natural forest to Japanese cedar plantation might, therefore, stimulate carbon sequestration and change the carbon allocation of NPP from an increment in coarse woody debris to an increase in tree biomass.     

Hyporheic Production is Substantially Greater than Benthic Production for a Common New Zealand Caddisfly

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.     

Pollen dispersal and deposition characteristics of Abies alba, Fagus sylvatica and Pinus sylvestris, Roztocze region (SE Poland)

Pinus sylvestris L., Abies alba Mill. and Fagus sylvatica L.—the significant forest forming tree species in Europe are important for palaeoecological interpretations based on the results of pollen analysis of fossil deposits. The potential pollen loading for Pinus sylvestris, Abies alba and Fagus sylvatica was modelled using simulated and actual vegetation maps, measured fall-speed values and pollen productivity estimates from the literature. The influx of fir pollen drops sharply with distance from the pollen source due to the high fall speed and moderate pollen productivity. The vast majority of Abies alba pollen is deposited within less than 50 m of the sampling site and a major proportion within 100 m. For beech the corresponding numbers would be 300 and 1,800 m, and for pine 1,000 and 4,500 m. The observed mean pollen accumulation rate (PAR) values for Pinus and Fagus were ca. 5,800 and 1,100 grains cm⁻² year⁻¹, respectively. In the case of Abies, the mean annual PAR for the whole region is ca. 700 grains cm⁻² year⁻¹. In SE Poland the regional signal is represented by PARs of Abies alba <200 grains cm⁻² year⁻¹ and of Fagus sylvatica <500 grains cm⁻² year⁻¹. The local presence/absence threshold values for Abies alba, Fagus sylvatica and Pinus sylvestris are >1,000 grains cm⁻² year⁻¹, >2,000 grains cm⁻² year⁻¹ and >3,500 grains cm⁻² year⁻¹ respectively.     

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year⁻¹ to ponds (up to 5.5 g AFDM m⁻² year⁻¹). Larval production ranged from 0.4 to 7.4 g AFDM m⁻² year⁻¹ among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m⁻² year⁻¹ produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m⁻² and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year⁻¹ (range=21.0–135.2 g AFDM year⁻¹) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year⁻¹ into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r ² =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Biomass and aboveground net primary production in a subtropical mangrove stand of Kandelia obovata (S., L.) Yong at Manko Wetland, Okinawa, Japan

Biomass and aboveground net primary production (ANPP) in a monospecific pioneer stand of a mangrove Kandelia obovata (S., L.) Yong were quantified. The estimated biomasses in leaves, branches, stems, roots, aboveground and total were 5.61 (3.68%), 28.8 (18.9%), 46.1 (30.2%), 71.8 (47.2%), 80.5 (52.8%) and 152 Mg ha⁻¹ (100%), respectively. Stem phytomass increment per tree was estimated using allometric relationships and stem analysis. Stem volume without bark of harvested trees showed a strong allometric relationship with D _0.1² H (D _0.1, diameter at a height of one-tenth of tree height H) (R ² = 0.924). Annual stem volume increment per tree showed a strong allometric relationship with D _0.1² H (R ² = 0.860). Litterfall rate ranges from 3.87 to 56.1 kg ha⁻¹ day⁻¹ for leaves and 0.177 to 46.2 kg ha⁻¹ day⁻¹ for branches. Seasonal changes of litterfall rate were observed, which showed a peak during wet season (August–September). Total annual litterfall was estimated as 10.6 Mg ha⁻¹ year⁻¹, in which 68.2% was contributed by the leaves. The ANPP in the K. obovata stand was 29.9–32.1 Mg ha⁻¹ year⁻¹, which is ca. 2.8–3.0 times of annual litterfall. The growth efficiency (aboveground biomass increment/LAI) was 5.35–5.98 Mg ha⁻¹ year⁻¹. The low leaf longevity (9.3 months) and high growth efficiency of K. obovata makes it a highly productive mangrove species.     

Catabolic diversity of periphyton and detritus microbial communities in a subtropical wetland

The catabolic diversity of wetland microbial communities may be a sensitive indicator of nutrient loading or changes in environmental conditions. The objectives of this study were to assess the response of periphyton and microbial communities in water conservation area-2a (WCA-2a) of the Everglades to additions of C-substrates and inorganic nutrients. Carbon dioxide and CH₄ production rates were measured using 14 days incubation for periphyton, which typifies oligotrophic areas, and detritus, which is prevalent at P-impacted areas of WCA-2a. The wetland was characterized by decreasing P levels from peripheral to interior, oligotrophic areas. Microbial biomass and N mineralization rates were higher for oligotrophic periphyton than detritus. Methane production rates were also higher for unamended periphyton (80 mg CH₄-C kg⁻¹ d⁻¹) than detritus (22 mg CH₄-C kg⁻¹ d⁻¹), even though the organic matter content was higher for detritus (80%) than periphyton (69%). Carbon dioxide production for unamended periphyton (222 mg CO₂-C kg⁻¹ d⁻¹) was significantly greater than unamended detritus (84 mg CO₂-C kg⁻¹ d⁻¹). The response of the heterotrophic microbial community to added C-substrates was related to the nutrient status of the wetland, as substrate-induced respiration (SIR) was higher for detritus than periphyton. Amides and polysaccharides stimulated SIR more than other C-substrates, and methanogenesis was greater contributor to SIR for periphyton than detritus. Inorganic P addition stimulated CO₂ and CH₄ production for periphyton but not detritus, indicating a P limitation in the interior areas of WCA-2a. Continued nutrient loading into oligotrophic areas of WCA-2a or enhanced internal nutrient cycling may stimulate organic matter decomposition and further contribute to undesirable changes to the Everglades ecosystem caused by nutrient enrichment.     

Watershed nitrogen input and riverine export on the west coast of the US

This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km⁻² year⁻¹, with an overall area-weighted average of 1,870 kg N km⁻² year⁻¹. In 2002, the range of inputs was 490–10,875 kg N km⁻² year⁻¹, averaging 2,158 kg N km⁻² year⁻¹. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km⁻² year⁻¹ (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km⁻² year⁻¹ (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km⁻² year⁻¹ (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated with variations in streamflow (export = 0.94 × streamflow − 5.65, R ² = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 × streamflow + 0.06 × input − 227.78, R ² = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 × streamflow − 2.61, R ² = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes that control watershed N export are not yet completely understood.     

Primary production and nutrient budgets of Sarcocornia perennis ssp. alpini (Lag.) Castroviejo in the salt marsh of the Palmones River estuary (Southern Spain)

Biomass, primary production and nutrient budgets associated to Sarcocornia perennis subspecies (ssp.) alpini were studied in the Palmones River estuary salt marsh (Southern Spain) to evaluate the nutrient sequestration capacity of the low marsh. Above- and belowground living and dead biomass, as well as carbon, nitrogen and phosphorus content were monitored during 1 year. Additionally, the fate of aboveground detritus was evaluated in an experiment on litter decomposition. The detritus production of S. perennis ssp. alpini was almost equivalent to its annual primary production indicating a rapid turnover of biomass. We calculated that only 12% of the aboveground detritus was exported out of the low marsh while the rest was decomposed in the sediment with a rate of 0.8 year⁻¹. Changes in concentrations of total carbon, nitrogen and phosphorus in the sediment showed patterns related to S. perennis ssp. alpini belowground biomass. Our results suggested that the sediment functions as a net sink for nutrients accumulating 550 g C m⁻² year⁻¹, 55 g N m⁻² year⁻¹, and 13 g P m⁻² year⁻¹.     

The development of composite dispersal functions for estimating absolute pollen productivity in the Swiss Alps

Considering the complexity of real-world pollen dispersal, a single set of parameters may be inadequate to model pollen dispersal, especially as dispersal occurs on both local and regional scales. Here we combine more than one dispersal function into a composite dispersal function (CDF). The function incorporates multiple parameters and different modes of pollen transportation, and thus has the potential to better simulate the relationship between deposited pollen and the surrounding vegetation than would otherwise be possible. CDFs based on different dispersal functions and combinations of dispersal functions were evaluated using a pollen-trap dataset from the Swiss Alps. Absolute pollen productivity (APP) was estimated at 7,700 ± 2,000 grains cm⁻² year⁻¹ for Larix decidua, 13,500 ± 1,900 grains cm⁻² year⁻¹ for Picea abies and 95,600 ± 17,700 grains cm⁻² year⁻¹ for Pinus cembra (with 95% confidence level). The results are consistent with previous APP estimates made from the same dataset using different methods.     

Production and retention of biogenic matter in the southeast Beaufort Sea during 2003�C2004: insights from annual vertical particle fluxes of organic carbon and biogenic silica

Regional variability in the annual fluxes of particulate organic carbon (POC) and biogenic silica (Si) at the periphery of the Mackenzie Shelf (Beaufort Sea) was investigated using eight long-term sediment traps moored at ~100-m depth. Relatively high autochthonous POC and Si fluxes were recorded in the Mackenzie Trough (4.1 and 8.9 g m⁻² year⁻¹ respectively) and off Cape Bathurst (6.6 and 79 g m⁻² year⁻¹), two areas where upwelling events are frequently observed. Diatomaceous new production was minimum on the mid-slope of the Mackenzie Shelf (2.8 g C m⁻² year⁻¹), moderate in the Mackenzie Trough (14.5 g C m⁻² year⁻¹), and highest off Cape Bathurst (128.7 g C m⁻² year⁻¹). High annual autochthonous POC flux corresponded to high diatom production. Among sites, the vertical attenuation of the POC flux increased with diatomaceous new production. Hence, the retention of autochthonous POC in the surface layer (<100 m) was highest (95%) at the highly productive site off Cape Bathurst, intermediate (72%) in the moderately productive Mackenzie Trough, and low (4%) at the unproductive mid-slope of the shelf. Our results indicate that, on Arctic shelves, upwelling and the production of diatoms increase the fraction of the POC which is retained in the surface layer and diverted to the pelagic food web. In the relatively unproductive waters of the Arctic Ocean, biological hot spots such as the one identified off Cape Bathurst where the food web promotes retention rather than vertical export could be disproportionately important as feeding grounds for higher trophic levels.     

Photosynthetic property and primary production of phytoplankton in sublittoral sand bank area in the Seto Inland Sea,Japan

We investigated the photosynthesis–light intensity (P–I) relationships of phytoplankton collected from a sublittoral sand bank in the Seto Inland Sea, Japan, under different temperature conditions. In spite of low chlorophyll a concentration (<3 mg m⁻³), phytoplankton had considerably high photosynthetic potential (>10 mg C (mg chl a)⁻¹ h⁻¹) in the study area. Based on the P–I relationships, we conducted numerical simulation of areal primary production using published data on water temperature, chlorophyll a concentration, and irradiance. The areal primary production ranged between 159 and 187 g C m⁻² year⁻¹. This production was within the range of typical values reported previously in deeper areas of the Seto Inland Sea. The productivity in the sand bank area was discussed in relation to water current, allochthonous resource input, and fisheries.     

Altitudinal changes in carbon storage of temperate forests on Mt Changbai, Northeast China

A number of studies have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however, the altitudinal changes in C storage in different components (vegetation, detritus, and soil) of forest ecosystems remain poorly understood. In this study, we measured C stocks of vegetation, detritus, and soil of 22 forest plots along an altitudinal gradient of 700–2,000 m to quantify altitudinal changes in carbon storage of major forest ecosystems (Pinus koraiensis and broadleaf mixed forest, 700–1,100 m; Picea and Abies forest, 1,100–1,800 m; and Betula ermanii forest, 1,800–2,000 m) on Mt Changbai, Northeast China. Total ecosystem C density (carbon stock per hectare) averaged 237 t C ha⁻¹ (ranging from 112 to 338 t C ha⁻¹) across all the forest stands, of which 153 t C ha⁻¹ (52–245 t C ha⁻¹) was stored in vegetation biomass, 14 t C ha⁻¹ (2.2–48 t C ha⁻¹) in forest detritus (including standing dead trees, fallen trees, and floor material), and 70 t C ha⁻¹ (35–113 t C ha⁻¹) in soil organic matter (1-m depth). Among all the forest types, the lowest vegetation and total C density but the highest soil organic carbon (SOC) density occurred in Betula ermanii forest, whereas the highest detritus C density was observed in Picea and Abies forest. The C density of the three ecosystem components showed distinct altitudinal patterns: with increasing altitude, vegetation C density decreased significantly, detritus C density first increased and then decreased, and SOC density exhibited increasing but insignificant trends. The allocation of total ecosystem C to each component exhibited similar but more significant trends along the altitudinal gradient. Our results suggest that carbon storage and partitioning among different components in temperate forests on Mt Changbai vary greatly with forest type and altitude.