Early development of marine catfishes (Ariidae): from mouth brooding to the release of juveniles in nursery habitats

The development and allometric growth patterns of the ariid catfishes Cathorops spixii and Cathorops agassizii were studied from neurula embryos to juveniles. The ontogenetic sequence revealed that prior to hatching, embryos of both species are well developed, and their axial and appendicular skeletons are well ossified. Embryos of both species grow slowly longitudinally, but positively allometric growth (growth coefficient, β₁ > 1) was observed in head width and eye diameter. It is hypothesized that these growth patterns might be related to functional priorities for the development of sensory organs, such as the inner ears (otoliths), the Weberian apparatus, eyes and nostrils, during the embryonic period. The first appearance of vertebrae and otoliths, as well as the ossification of otoliths and the Weberian apparatus, occur earlier in embryos of C. agassizii than in embryos of C. spixii. After hatching, mouth‐brooded free embryos of both species grow isometrically. Negatively allometric growth was observed in head width and eye diameter during the yolk‐sac period, which is expected given that the sensory organs are already formed. Free embryos of C. agassizii are distinguishable from those of C. spixii by their larger eyes, longer snouts, longer heads and heavier yolk sacs. The end of the yolk‐sac period is characterized by a direct change from free embryo to juvenile, without a true larval period. The juveniles of the two species can also be distinguished from each other by the larger eyes of C. agassizii compared with C. spixii, as in adult fishes.     

Factors affecting seasonal variations in demersal fish assemblages at an ecocline in a tropical–subtropical estuary

Seasonal changes of fish species composition in terms of biomass, density and number of species in three areas of the main channel of the Paranaguá Estuary (axis east–west) are described in relation to seasonal fluctuations in salinity, water temperature and dissolved oxygen in the main channel. Two hundred and thirty‐four samples were collected monthly, between July 2000 and June 2001, in the main channel. Seventy‐nine species of 29 families were captured with a total estimated mean density and biomass of 1513 individuals ha^?1 and 34 kg ha^?1, respectively. The number of species and total mean density differed significantly among areas and seasons, but the total mean biomass differed only significantly throughout the ecocline (areas) of the Paranaguá Estuary. For the most abundant species, the mean densities of Stellifer rastrifer, Aspistor luniscutis, Menticirrhus americanus, Sphoeroides testudineus, Cynoscion leiarchus and Symphurus tesselatus (with the exception of Cathorops spixii and Genidens genidens) differed significantly among seasons. The mean biomass of these species, with the exception of G. genidens, S. rastrifer, A. luniscutis and S. testudineus, also differed significantly for the factor seasons. Area was a significant factor for the eight most abundant species (density and biomass), except S. testudineus (density), G. genidens, C. leiarchus and S. tesselatus (biomass). The season v. area interaction term was significant for C. leiarchus (density). Most of these differences occurred during the rainy season when fishes concentrated principally in the middle of the estuary, where the salinity remained stable. It is suggested that the salinity stability in the middle of the estuary is the main reason why the most estuarine resident fish species move downstream and remain there, regardless of the increased freshwater runoff. Moreover, canonical correspondent analysis output detected that during the late rainy season, the variable dissolved oxygen (P < 0·01) was the most important environmental variable, responsible for structuring patterns of fishes assemblages in the west–east axis of Paranaguá Estuary. During the end of the dry season, both salinity (P < 0·01) and dissolved oxygen (P < 0·05) were responsible for this ecological feature in the estuary. Finally, it was possible to detect that juveniles and adults of some important species respond differently to seasonal fluctuations of the ecocline‐determining environmental factors. This behaviour is suggested as a strategy to avoid competition and predation during the rainy season in the middle estuary. The Paranaguá Estuary did not fit with the pre‐existing models described in the tropical and subtropical estuarine fish literature since its main channel fish assemblages remained within its bounds even during the rainy season.     

Population Dynamics and Diet of the Madamango Sea Catfish Cathorops spixii (Agassiz, 1829) (Siluriformes: Ariidae) in a Tropical Bight in Southeastern Brazil

The madamango sea catfish, Cathorops spixii (Siluriformes: Ariidae), is often among the most abundant fishes on the South American Atlantic coast. In the present study, conducted in shallow, non-estuarine coastal areas of Caraguatatuba Bight in southeastern Brazil, collections of this species, the most abundant member of the ichthyofauna, included primarily medium-sized individuals, indicating that the area may play a specific role in their development. Although studies of the local ichthyofauna have been much neglected, the area is economically important and its ecological significance is undervalued. This study primarily treats habitat use by C. spixii, assessing certain population parameters and the dietary composition. Monthly samples were taken from August 2003 through October 2004, with three trawls in two areas, corresponding to depths of about 1 to 4 m. The catfish showed two main peaks of abundance in the area, in April/May and July 2004. A mode around 9 cm SL persisted through time, and the entrance of younger recruits peaked from January to April. The low estimate for body-growth parameters (K = 0.16) corroborates some K-strategist characteristics of the species. The asymptotic length was 27.3 cm SL and total mortality (Z) was 1.01 yr⁻¹. Cathorops spixii showed an omnivorous feeding habit, preying mainly upon polychaetes, copepods and bivalves, with considerable seasonality in its diet.     

PRODUCTIVITY OF THE FILAMENTOUS ALGA PITHOPHORA OEDOGONIA (CHLOROPHYTA) IN SURREY LAKE,INDIANA1

Biomass, akinete numbers, net photosynthesis, and respiration of Pithophora oedogonia were monitored over two growing seasons in shallow Surrey Lake, Indiana. Low rates of photosynthesis occurred from late fall to early spring and increased to maximum levels in late spring to summer (29–39 mgO₂·g^?1 dry wt·h^?1). Areal biomass increased following the rise in photosynthesis and peaked in autumn (163–206g dry wt·m^?2). Photosynthetic rates were directly correlated with temperature, nitrogen, and phosphorus over the entire annual cycle and during the growing season. Differences in photosynthetic activity and biomass between the two growing seasons (1980 and 1981) were apparently related to higher, early spring temperatures and higher levels of NO₃-N and PO₄-P in 1981. Laboratory investigations of temperature and light effects on Pithophora photosynthesis and respiration indicated that these processes were severely inhibited below 15°C. The highest P_max value occurred at 35°C (0.602 μmol O₂·mg^?1 chl a·min^?1). Rates of dark respiration did not increase above 25°C thus contributing to a favorable balance of photosynthetic production to respiratory utilization at high temperatures. Light was most efficiently utilized at 15°C as indicated by minimum values of I_k(47 μE·m^?2·s^?1) and I_c (6 μE·m^?2·s^?1). Comparison of P. oedogonia and Cladophora glomerata indicated that the former was more tolerant of temperatures above 30°C. Pithophora's tolerance of high temperature and efficient use of low light intensity appear to be adaptive to conditions found within the dense, floating algal mats and the shallow littoral areas inhabited by this filamentous alga.     

Herbage response to tree thinning in a Eucalyptus crebra woodland

The effects of a range of tree densities on native herbage (mainly Aristida ramosa, Bothriochloa decipiens and Themeda australis biomass in a Eucalyptus crebra woodland near Kingaroy, Queensland, were investigated between March 1977 and July 1981. Rainfall in this area averages 750 mm year^?1. Initial tree density was 640 trees ha^?1 and this was manipulated using arboricide chemicals to leave plots containing 640, 320, 160, 80 and nil live trees ha^?1. Fires were excluded from the whole area, and half the plots were grazed by cattle. The largest increase in herbage biomass was recorded in the ‘all trees killed’ treatment (nil trees ha^?1), closely followed by the ‘scattered tree’ treatment (80 trees ha^?1). The relationship between tree density and herbage biomass was linear. Recruitment of grass and forb plants, as reflected by changes in density, varied according to treatment. Increased grass recruitment was correlated with cattle grazing, whilst forb recruitment was influenced mainly by tree density.     

Density-dependent growth performance of Indian major carps in rainwater reservoirs

The study was carried out to evaluate growth performance of Indian major carps at different stocking densities in rainwater reservoirs. In this experiment, the absolute growth performance of Catla catla, Labeo rohita and Cirrhinus mrigala at stocking densities of 5000, 8000 and 11 000 fingerlings per hectare was 377.7, 215.4 and 241.9; 370.2, 186.7 and 219.1; and 306.7, 163.4 and 180.6 g, respectively. The recorded biomass yield at 5000, 8000 and 11 000 fingerlings per hectare was 1035, 1572 and 1573 kg ha^?1 per 180 days of culture. The effect of stocking density on production performance (performance index, PI) was highly significant (P < 0.05) at the higher stocking density of 11 000 ha^?1, while there was no significant variation between PI at stocking densities of 5000 and 8000 ha^?1. This indicates optimum production performance at 8000 ha^?1, where yield is significantly higher (P < 0.05) than yield at 5000 ha^?1 and almost equal to the yield at 11 000 ha^?1. An increase in stocking density from 8000 to 11 000 ha^?1, however, showed a sharp decline in average mean body weight of each species, even with supplemental feeding. With an increase in stocking density, the biomass yield increased to an optimum (1572 kg ha^?1), with no substantial increase thereafter. Reductions in growth, which occurred at high density, did not appear to be due to poor water quality as the water quality did not differ significantly among various treatments. Thus, the reduced survival and growth at high density appears to be a behavioural interaction or physiological response to density itself.     

Plant and frond dynamics of the giant kelp,Macrocystis pyrifera,forming a fringing zone in the Falkland Islands

Fluctuations in plant and frond characteristics are described for Macrocystis pyrifera (L.) C. Agardh (Laminariales, Phaeophyta) forming a fringing zone in the Falkland Islands. Giant kelp plants were sampled along a transect in the austral autumn (May 1986) and late spring (December 1986) which, according to previous frond weight analysis, were the times when extremes in population parameters were expected. Plant density and holdfast wet weights were similar for both seasons, but plants had more fronds and the fronds weighed more in spring than in autumn. Consequently, in autumn the frond biomass (1·1 wet kg m^?2) and productivity (34·1 wet g m^?2 d^?1) were lower than in spring, when a biomass of 5·0 wet kg m^?2 and a productivity of 72·4 wet g m^?2 d^?1 were recorded. Production of new fronds and loss of old fronds were determined at monthly intervals between April 1986 and March 1987. New frond production rates followed fluctuations in the quantity of light and varied between 0·08 and 0·48 fronds per plant per day. Frond loss rates did not show a seasonal pattern and fluctuated between 0·05 and 0·42 fronds per plant per day. It is suggested that the Falkland Islands Macrocystis population is more stable than most other giant kelp beds at high latitudes, because of the absence of winter storms.     

Germination, field establishment patterns and nitrogen fixation of indigenous legumes on nutrient-depleted soils

Integrating N₂-fixing indigenous legumes in smallholder farming systems has potential to alleviate some of the major soil fertility constraints associated with lack of nitrogen (N) inputs in many parts of Sub-SaharanAfrica. Studies were conducted under low (450–650 mm yr^?1) and high (>800 mm yr^?1) rainfall areas in Zimbabwe to investigate the establishment and nitrogen fixation patterns of fifteen indigenous legume species. The legume seeds were broadcast in mixtures at 120 seeds m^?2 species^?1 during 2004/05 and 2005/06 rainfall seasons.Eriosema ellipticum, Crotalaria ochroleuca andC. pallida had emergence rates above 15% compared with <10% forTephrosia radicans andIndigofera astragalina. Seed hardness accounted for >50% germination failure, while low viability explained 10–30%.Crotalaria ochroleuca andC. pallida attained a maximum biomass of 5–9 t ha^?1 (dry weight) over six months, while species that reached peak biomass over three months (e.g.C. cylindrostachys andC. glauca) gave lowest yields of ≈0.5 t ha^?1. Biennials,Neonotonia wightii, E. ellipticum and Tephrosia radicans, exhibited slow growth rates and only attained their maximum biomass of ≈2 t ha^?1 in the second season. The legumes derived 60–99% of their N from the atmosphere, fixing 5–120 kg N ha^?1 under low rainfall and 78–267 kg N ha^?1 under high rainfall. These findings suggest that the legumes could contribute in restoring productivity of soils continuously cultivated with little or no nutrient inputs in most of Zimbabwe and similar agro-ecologies in SubSaharan Africa.     

Seasonal dynamics of above‐ and below‐ground biomass and nitrogen partitioning in Miscanthus × giganteus and Panicum virgatum across three growing seasons

The first replicated productivity trials of the C4 perennial grass Miscanthus × giganteus in the United States showed this emerging ligno‐cellulosic bioenergy feedstock to provide remarkably high annual yields. This covered the 5 years after planting, leaving it uncertain if this high productivity could be maintained in the absence of N fertilization. An expected, but until now unsubstantiated, benefit of both species was investment in roots and perennating rhizomes. This study examines for years 5–7 yields, biomass, C and N in shoots, roots, and rhizomes. The mean peak shoot biomass for M. × giganteus in years 5–7 was 46.5 t ha^?1 in October, declining to 38.1 t ha^?1 on completion of senescence and at harvest in December, and 20.7 t ha^?1 declining to 11.3 t ha^?1 for Panicum virgatum. There was no evidence of decline in annual yield with age. Mean rhizome biomass was significantly higher in M. × giganteus at 21.5 t ha^?1 compared to 7.2 t ha^?1 for P. virgatum, whereas root biomass was similar at 5.6–5.9 t ha^?1. M. × giganteus shoots contained 339 kg ha^?1 N in August, declining to 193 kg ha^?1 in December, compared to 168 and 58 kg ha^?1 for P. virgatum. The results suggest substantial remobilization of N to roots and rhizomes, yet still a substantial loss with December harvests. The shoot and rhizome biomass increase of 33.6 t ha^?1 during the 2‐month period between June and August for M. × giganteus corresponds to a solar energy conversion of 4.4% of solar energy into biomass, one of the highest recorded and confirming the remarkable productivity potential of this plant.     

Miscanthus × giganteus productivity: the effects of management in different environments

Miscanthus × giganteus is a C₄ perennial grass that shows great potential as a high‐yielding biomass crop. Scant research has been published that reports M. × giganteus growth and biomass yields in different environments in the United States. This study investigated the establishment success, plant growth, and dry biomass yield of M. × giganteus during its first three seasons at four locations (Urbana, IL; Lexington, KY; Mead, NE; Adelphia, NJ) in the United States. Three nitrogen rates (0, 60, and 120 kg ha^?1) were applied at each location each year. Good survival of M. × giganteus during its first winter was observed at KY, NE, and NJ (79–100%), and poor survival at IL (25%), due to late planting and cold winter temperatures. Site soil conditions, and growing‐season precipitation and temperature had the greatest impact on dry biomass yield between season 2 (2009) and season 3 (2010). Ideal 2010 weather conditions at NE resulted in significant yield increases (P < 0.0001) of 15.6–27.4 Mg ha^?1 from 2009 to 2010. Small yield increases in KY of 17.1 Mg ha^?1 in 2009 to 19.0 Mg ha^?1 in 2010 could be attributed to excessive spring rain and hot dry conditions late in the growing season. Average M. ×giganteus biomass yields in NJ decreased from 16.9 to 9.7 Mg ha^?1 between 2009 and 2010 and were related to hot dry weather, and poor soil conditions. Season 3 yields were positively correlated with end‐of‐season plant height () and tiller density (). Nitrogen fertilization had no significant effect on plant height, tiller density, or dry biomass yield at any of the sites during 2009 or 2010.     

Carbon allocation in a Bornean tropical rainforest without dry seasons

To clarify characteristics of carbon (C) allocation in a Bornean tropical rainforest without dry seasons, gross primary production (GPP) and C allocation, i.e., above-ground net primary production (ANPP), aboveground plant respiration (APR), and total below-ground carbon flux (TBCF) for the forest were examined and compared with those from Amazonian tropical rainforests with dry seasons. GPP (30.61 MgC ha^?1 year^?1, eddy covariance measurements; 34.40 MgC ha^?1 year^?1, biometric measurements) was comparable to those for Amazonian rainforests. ANPP (6.76 MgC ha^?1 year^?1) was comparable to, and APR (8.01 MgC ha^?1 year^?1) was slightly lower than, their respective values for Amazonian rainforests, even though aboveground biomass was greater at our site. TBCF (19.63 MgC ha^?1 year^?1) was higher than those for Amazonian forests. The comparable ANPP and higher TBCF were unexpected, since higher water availability would suggest less fine root competition for water, giving higher ANPP and lower TBCF to GPP. Low nutrient availability may explain the comparable ANPP and higher TBCF. These data show that there are variations in C allocation patterns among mature tropical rainforests, and the variations cannot be explained solely by differences in soil water availability.     

Carbon budget and methane and nitrous oxide emissions over the growing season in a Miscanthus sinensis grassland in Tomakomai,Hokkaido, Japan

Species in the Miscanthus genus have been proposed as biofuel crops that have potential to mitigate elevated atmospheric carbon dioxide (CO₂) levels and nitrous oxide (N₂O) and methane (CH₄) emissions. Miscanthus sinensis is widespread throughout Japan and has been used for biomass production for centuries. We assessed the carbon (C) budget and N₂O and CH₄ emissions over the growing season for 2 years in a M. sinensis‐dominated grassland that was naturally established around 1972 in Tomakomai, Hokkaido, Japan, which is near the northern limit for M. sinensis grassland establishment on Andisols. Average C budget was ?0.31 Mg C ha^?1, which indicates C was released from the grassland ecosystem to the atmosphere. Dominant components in the C budget appeared to be aboveground net primary production of plants (1.94–2.80 Mg C ha^?1) and heterotrophic respiration (2.27–3.11 Mg C ha^?1). The measurement of belowground net primary production (BNPP) of plants in the M. sinensis grassland was extremely variable, thus only an approximate value could be calculated. Mean C budget calculated with the approximated BNPP value was 1.47 and ?0.23 Mg C ha^?1 for 2008 and 2009, respectively. Given belowground biomass (9.46–9.86 Mg C ha^?1) was 3.1–6.5 times higher than that of aboveground biomass may provide additional evidence suggesting this grassland represents a C sink. Average CH₄ emissions across years of ?1.34 kg C ha^?1 would indicate this grassland acts as an atmospheric CH₄ sink. Furthermore, average N₂O emissions across years were 0.22 kg N ha^?1. While the site may contribute N₂O to the atmosphere, this value is lower compared with other grassland types. Global warming potential calculated with the approximated BNPP value was ?5.40 and 0.95 Mg CO₂ Eq ha^?1 for 2008 and 2009, respectively, and indicates this grassland could contribute to mitigation of global warming.     

Effects of goat pastoralism on ecosystem carbon storage in semiarid thicket,Eastern Cape,South Africa

Abstract Intensive pastoralism with goats transforms semiarid thicket in the Eastern Cape, South Africa from a dense vegetation of tall shrubs to an open landscape dominated by ephemeral grasses and forbs. Approx. 800 000 ha of thicket (which prior to the introduction of goats had a closed canopy and a Portulacaria afra Jacq. component) have been transformed in this manner. Ecosystem C storage in intact thicket and loss of C due to transformation were quantified. Carbon storage in intact thicket was surprisingly high for a semiarid region, with an average of 76 t C ha^?1 in living biomass and surface litter and 133 t C ha^?1 in soils to a depth of 30 cm. Exceptional C accumulation in thicket may be a result of P. afra dominance. This succulent shrub switches between C₃ and CAM photosynthesis, produces large quantities of leaf litter (approx. 450 g m^?2 year^?1) and shades the soil densely. Transformed thicket had approx. 35% less soil C to a depth of 10 cm and approx. 75% less biomass C than intact thicket. Restoration of transformed thicket landscapes could consequently recoup more than 80 t C ha^?1.     

Continental fire density patterns in South America

Aims Quantification of the effects and interactions of natural and anthropogenic factors, including climate, canopy structure, land use and management conditions, on vegetation burning. The study of these relationships is fundamental to predict regional fire patterns and develop sound management and regulation policies for biomass burning at national and global levels. Location Southern South America, including Argentina, Brazil, Paraguay, Uruguay, Bolivia and Chile. Methods Based on National Oceanic and Atmosphere Administration–Advance Very High Resolution Radiometer (NOAA–AVHRR) satellite images, we identified fires in southern South America with a daily frequency for two periods (1999/2000 and 2000/01) using a contextual fire detection algorithm and integrating the density of these fires at a monthly scale into a 0.5 × 0.5° grid. We combined vegetation and climate global databases and land use information from national census data to explore the relationship of these factors with fires across the region. Results The whole study region had a mean fire density of 0.10 and 0.05 fires km^?2 year^?1 in 1999/2000 and 2000/01, respectively, with extreme values as high as 1.37 in fires km^?2 year^?1 in Para State, Brazil. Water deficit estimates, derived from a climatic water balance, showed the better correlation with fire density (r = 0.28; P < 0.001; n = 4467), interacting strongly with land use. In areas with low agricultural use fire density increased with water deficit, whereas in highly agricultural areas this relationship was not observed. Agriculture significantly reduced fire density in prairies and savannas but increased its frequency in rain forests. Main conclusions These results suggest that agriculture prevents biomass burning in semiarid areas but enhances it in humid environments, where biomass accumulates at faster rates.     

Variation in biomass and carbon storage by stand age in pine (Pinus tabulaeformis) planted ecosystem in Mt. Taiyue,Shanxi, China

Forest ecosystems play dominant roles in global carbon budget because of the large quantities stored in live biomass, detritus, and soil organic matter. Researchers in various countries have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however, the relationship between stand age in different components (vegetation, forest floor detritus, and mineral soil) and C storage and sequestration remains poorly understood. In this paper, we assessed an age sequence of 18-, 20-, 25-, 38-, and 42-year-old Pinus tabulaeformis planted by analyzing the vertical distribution of different components biomass with similar site conditions on Mt. Taiyue, Shanxi, China. The results showed that biomass of P. tabulaeformis planted stands was ranged from 88.59 Mg ha^?1 for the 25-year-old stand to 231.05 Mg ha^?1 for the 42-year-old stand and the major biomass was in the stems. Biomass of the ground vegetation varied from 0.51 to 1.35 Mg C ha^?1 between the five stands. The forest floor biomass increased with increasing stand age. The mean C concentration of total tree was 49.94%, which was higher than C concentrations of ground vegetation and forest floor. Different organs of trees C concentration were between 54.14% and 47.74%. C concentrations stored in the mineral soil for each stand experienced decline with increasing soil depth, but were age-independent. Total C storage of five planted forests ranged from 122.15 to 229.85 Mg C ha^?1, of which 51.44–68.38% of C storage was in the soil and 28.46–45.21% in vegetation. The study provided not only with an estimation biomass of P. tabulaeformis planted forest in Mt. Taiyue, Shanxi, China, but also with accurately estimating forest C storage at ecosystem scale.     

Improving the Agronomy of Alyssum murale for Extensive Phytomining: A Five-Year Field Study

Large ultramafic areas exist in Albania, which could be suitable for phytomining with native Alyssum murale. We undertook a five-year field experiment on an ultramafic Vertisol, aimed at optimizing a low-cost Ni-phytoextraction crop of A. murale which is adapted to the Balkans. The following aspects were studied on 18-m² plots in natural conditions: the effect of (i) plant phenology and element distribution, (ii) plant nutrition and fertilization, (iii) plant cover and weed control and (iv), planting technique (natural cover vs. sown crop). The optimal harvest time was set at the mid-flowering stage when Ni concentration and biomass yield were highest. The application of N, P, and K fertilizers, and especially a split 100-kg ha^?1 N application, increased the density of A. murale against all other species. It significantly increased shoot yield, without reducing Ni concentration. In natural stands, the control of graminaceous weeds required the use of an anti-monocots herbicide. However, after the optimization of fertilization and harvest time, weed control procured little benefit. Finally, cropping sown A. murale was more efficient than enhancing native stands and gave higher biomass and phytoextraction yields; biomass yields progressively improved from 0.3 to 9.0 t ha^?1 and phytoextracted Ni increased from 1.7 to 105 kg ha^?1.     

Enhanced decomposition of selenium hyperaccumulator litter in a seleniferous habitat��evidence for specialist decomposers?

Grassland canopy management (spring burn, mowing and residue removal in late-summer, or no management) and native tallgrass species composition (cool season mixture, warm season mixture, or combined cool and warm mixture) effects on C and N in aboveground biomass and soil were investigated at Brookings SD on a previously-plowed Barnes clay loam (fine-loamy, superactive, frigid Calcic Hapludoll). During the last 2 yr of the 9-yr experiment, shoot biomass was affected by canopy management with the burn (2,730 kg ha^?1) and mow (3,421 kg ha^?1) treatments containing less than no management (4,655 kg ha^?1). Burn treatment biomass contained 1,189 kg ha^?1 and 25 kg ha^?1 of C and N, mow contained 1,433 kg ha^?1 and 33 kg ha^?1 of C and N, while no management contained 2,014 kg ha^?1 and 39 kg ha^?1 of C and N, respectively. Soil C accumulation was independent of grass species composition. Soil C accumulation rates, which increased in strong linear fashion (r ² of 0.89 to 0.92) after initial grass establishment, were 387 kg C ha^?1 yr^?1, 503 kg C ha^?1 yr^?1, and 711 kg C ha^?1 yr^?1 for burn, mow, and no management treatments, respectively. Thus, grassland management methods used after conversion of cropland to grassland have important effects on grass biomass and soil C accumulation.     

Biomass dynamics in a logged forest: the role of wood density

Wood density (WD) is believed to be a key trait in driving growth strategies of tropical forest species, and as it entails the amount of mass per volume of wood, it also tends to correlate with forest carbon stocks. Yet there is relatively little information on how interspecific variation in WD correlates with biomass dynamics at the species and population level. We determined changes in biomass in permanent plots in a logged forest in Vietnam from 2004 to 2012, a period representing the last 8 years of a 30 years logging cycle. We measured diameter at breast height (DBH) and estimated aboveground biomass (AGB) growth, mortality, and net AGB increment (the difference between AGB gains and losses through growth and mortality) per species at the individual and population (i.e. corrected for species abundance) level, and correlated these with WD. At the population level, mean net AGB increment rates were 6.47 Mg ha^?1 year^?1 resulting from a mean AGB growth of 8.30 Mg ha^?1 year^?1, AGB recruitment of 0.67 Mg ha^?1 year^?1 and AGB losses through mortality of 2.50 Mg ha^?1 year^?1. Across species there was a negative relationship between WD and mortality rate, WD and DBH growth rate, and a positive relationship between WD and tree standing biomass. Standing biomass in turn was positively related to AGB growth, and net AGB increment both at the individual and population level. Our findings support the view that high wood density species contribute more to total biomass and indirectly to biomass increment than low wood density species in tropical forests. Maintaining high wood density species thus has potential to increase biomass recovery and carbon sequestration after logging.     

Morphology and biomass production of prairie cordgrass on marginal lands

Prairie cordgrass (Spartina pectinata Link.) is indigenous throughout most of the continental United States and Canada to 60°N latitude and is well suited to marginal land too wet for maize (Zea mays L.) and switchgrass (Panicum virgatum L.). Evaluations of prairie cordgrass in Europe and North America indicated it has high potential for biomass production, relative to switchgrass, in short‐season areas. Our objective was to describe morphology and biomass production and partitioning in mature stands of ‘Red River’ prairie cordgrass and determine biomass production of natural populations on marginal land. This study was conducted from 2000 to 2008 in eastern South Dakota. Mean biomass production of mature stands of Red River was 12.7 Mg ha^?1. Leaves composed >88% of the biomass, and 60% of the tillers had no internodes. Belowground biomass to a depth of approximately 25 cm, not including roots, was 21 Mg ha^?1. Tiller density ranged from 683 tillers m^?2 for a 10‐year‐old stand to 1140 tillers m^?2 for a 4‐year‐old stand. The proaxis was composed of about eight phytomers, with rhizomes originating at proximal nodes and erect tillers at distal nodes. Vegetative propagation was achieved by both phalanx and guerilla growth. Differences among natural populations for biomass were expressed on gravelly marginal land. However, production, averaged across populations, was low (1.37 Mg ha^?1) and comparable to ‘Cave‐In‐Rock’ switchgrass (1.67 Mg ha^?1) over a 4‐year period. The large carbon storage capacity of prairie cordgrass in proaxes and rhizomes makes it useful for carbon sequestration purposes. Prairie cordgrass should be compared with switchgrass and other C₄ perennial grasses along environmental gradients to determine optimum landscape positions for each and to maximize bioenergy production and minimize inputs.     

Carbon dynamics in successional and afforested spruce stands in Thuringia and the Alps

Changes in the carbon stocks of stem biomass, organic layers and the upper 50 cm of the mineral soil during succession and afforestation of spruce (Picea abies) on former grassland were examined along six chronosequences in Thuringia and the Alps. Three chronosequences were established on calcareous and three on acidic bedrocks. Stand elevation and mean annual precipitation of the chronosequences were different. Maximum stand age was 93 years on acid and 112 years on calcareous bedrocks. Stem biomass increased with stand age and reached values of 250–400 t C ha^?1 in the oldest successional stands. On acidic bedrocks, the organic layers accumulated linearly during forest succession at a rate of 0.34 t C ha^?1 yr^?1. On calcareous bedrocks, a maximum carbon stock in the humus layers was reached at an age of 60 years. Total carbon stocks in stem biomass, organic layers and the mineral soil increased during forest development from 75 t C ha^?1 in the meadows to 350 t C ha^?1 in the oldest successional forest stands (2.75 t C ha^?1 yr^?1). Carbon sequestration occurred in stem biomass and in the organic layers (0.34 t C ha^?1 yr^?1on acid bedrock), while mineral soil carbon stocks declined. Mineral soil carbon stocks were larger in areas with higher precipitation. During forest succession, mineral soil carbon stocks of the upper 50 cm decreased until they reached approximately 80% of the meadow level and increased slightly thereafter. Carbon dynamics in soil layers were examined by a process model. Results showed that sustained input of meadow fine roots is the factor, which most likely reduces carbon losses in the upper 10 cm. Carbon losses in 10–20 cm depth were lower on acidic than on calcareous bedrocks. In this depth, continuous dissolved organic carbon inputs and low soil respiration rates could promote carbon sequestration following initial carbon loss. At least 80 years are necessary to regain former stock levels in the mineral soil. Despite the comparatively larger amount of carbon stored in the regrowing vegetation, afforestation projects under the Kyoto protocol should also aim at the preservation or increase of carbon in the mineral soil regarding its greater stability of compared with stocks in biomass and humus layers. If grassland afforestation is planned, suitable management options and a sufficient rotation length should be chosen to achieve these objectives. Maintenance of grass cover reduces the initial loss.