Quantifying the extent of niche areas in the global fleet of commercial ships: the potential for “super-hot spots” of biofouling

Niche areas of ships, such as lateral thruster tunnels, sea chests, and propellers, are often hot spots for the accumulation of biofouling organisms, a potential source of aquatic invasive species. Yet, the relative importance of different niche areas is poorly resolved, in terms of both total surface area and the associated biota (i.e., the species of organisms and their abundances). To address this information gap, a method was developed to estimate the extent of various niche areas in the global fleet of 120,252 commercial ships active between 1999 and 2013. The total niche area for these vessels was estimated to be 32,996 × 10³ m², representing approximately 10% of the total wetted surface area (WSA) available for colonization by biota. Considering the portion of niche areas relative to the total WSA, it was highest for passenger vessels (27%), followed by tugs (25%), and fishing vessels (21%), with niche areas representing a small portion of the WSA for bulk carriers and tankers (7–8%). Examining the different types of niche areas, thruster tunnels had the greatest total extent (10,189 × 10³ m²), representing a disproportionately large contribution (>50%) of the total niche area for passenger vessels and tugs compared to other vessel types. This result, combined with the use and cleaning of thrusters, may render them “super-hot spots” of biofouling. The uneven distribution and extent of niche areas across vessels has implications for transfers of organisms and management strategies to reduce invasions associated with the surfaces of ships.     

Antifouling chromanols isolated from brown alga Sargassum horneri

Biofouling in aquatic environments have a wide range of detrimental effects on man-made structures and cause economic loss. Current antifouling compounds including Diuron, dichlorofluanid, and Irgarol are toxic and can accumulate in marine environments. Thus, effective and environmentally friendly antifoulants are needed. Six structurally similar compounds were isolated from the brown alga, Sargassum horneri, based on bioactivity-guided isolation by reversed-phased liquid flash chromatography and high-performance liquid chromatography. Six chemical constituents possessing antifouling activities were identified as chromanols consisting of polyprenyl chain by nuclear magnetic resonance and mass spectroscopy. Antifouling activities of these six compounds were determined against representative fouling organisms including a hard fouling organism the mussel Mytilus edulis, a soft fouling macroalga Ulva pertusa, the biofouling diatom Navicula annexa, and the biofouling bacteria Pseudomonas aeruginosa KNP-3 and Alteromonas sp. KNS-8. The compounds could inhibit larvae settlement of mussel M. edulis with an EC₅₀ of 0.11–3.34 μg mL^?1, spore settlement of U. pertusa zoospores (EC₅₀ of 0.01–0.43 μg mL^?1), and the diatom N. annexa (EC₅₀ of 0.008–0.19 μg mL^?1). The two biofouling bacteria were sensitive to the tested compounds (minimum inhibitory concentration of 1.68–36.8 and 1.02–30.4 μg mL^?1, respectively). From toxicity tests on juvenile Sebastes schlegelii fish, brine shrimp Artemia salina, and microalga Tetraselmis suecica, S3 had the lowest LC₅₀ values of 60.2, 108, and 6.7 μg mL^?1 and exhibited no observed effect concentration at 24.5, 41.6, and 3.1 μg mL^?1 for these three tested marine organisms, respectively.     

Fluxes of nitrogen and phosphorus in a gallery forest in the Cerrado of central Brazil

The Gallery forests of the Cerrado biome play a critical role in controlling stream chemistry but little information about biogeochemical processes in these ecosystems is available. This work describes the fluxes of N and P in solutions along a topographic gradient in a gallery forest. Three distinct floristic communities were identified along the gradient: a wet community nearest the stream, an upland dry community adjacent to the woodland savanna and an intermediate community between the two. Transects were marked in the three communities for sampling. Fluxes of N from bulk precipitation to these forests resulted in deposition of 12.6 kg ha^?1 y^?1 of total N of which 8.8 kg ha^?1 was as inorganic N. The throughfall flux of total N was generally <8.4 kg ha^?1 year^?1. Throughfall NO₃?CN fluxes were higher (7?C32%) while NH₄?CN and organic N fluxes were lower (54?C69% and 5?C46%) than those in bulk precipitation. The throughfall flux was slightly lower for the wet forest community compared to other communities. Litter leachate fluxes differed among floristic communities with higher NH₄?CN in the wet community. The total N flux was greater in the wet forest than in the dry forest (13.5 vs. 9.4 kg ha^?1 year^?1, respectively). The stream water had total N flux of 0.3 kg ha^?1 year^?1. The flux of total P through bulk precipitation was 0.7 kg ha^?1 year^?1 while the mean fluxes of total P in throughfall (0.6 kg ha^?1 year^?1) and litter leachate (0.5 kg ha^?1 year^?1) declined but did not differ between communities. The low concentrations presented in soil solution and low fluxes in stream water (0.3 and 0.1 kg ha^?1 year^?1 for N and P, respectively) relative to other flowpaths emphasize the conservative nutrient cycling of these forests and the importance of internal recycling processes for the maintenance and conservation of riparian and stream ecosystems in the Cerrado.     

Nutrient export to an Eastern Atlantic coastal zone: first modeling and nitrogen mass balance

We have studied 15 catchments supplying freshwater to a French Atlantic coastal lagoon, where increase in nitrogen loads due to agriculture is supposed to have destabilized the ecosystem in the last decades. The catchment is a lowland composed of Pleistocene sands with an average slope of 0.25%. To study the nutrient export in relation to land-use surface waters were sampled bi-weekly between October 2006 and January 2009 and land-use was established by plane photographs and Geographic Information System (GIS). Cultivated pine forests represent more than 80% of the total surface and 7% of the catchment area has been deforested recently. Significant areas of some catchments are used for maize crop. Housing is confined to the coastal zone. Maize and forest crop give a robust signature in terms of nitrate export. In view of modeling the nutrient fluxes, we have established the mean export rate for every land-use: forested parcels, deforested parcels, cultivated surfaces, and housing areas export 45, 93, 2850, and 61 kg N-nitrate km^?2 year^?1, respectively. Exports of ammonium, dissolved organic N (DON), and dissolved inorganic P (DIP) could not be related to land use. The mean export is 13, 100, and 0.57 kg km^?2 year^?1 for N-ammonium, DON, and DIP, respectively. The modeling of nitrogen flux is in good agreement with our measures for the largest catchment, which supplies about 90% of the total continental DIN flux. However, small catchments are more dynamic due to hydrological conditions and the model is less accurate. This work has permitted to complete and unify scattered studies about nutrient cycling in this area. Thus we have established and compared the nitrogen budget of cornfields and cultivated pine forest. We have emphasized that (i) fertilizer use should be reduced in cornfields because they stock between 200 and 6400 kg DIN km^?2 year^?1, and (ii) the nitrogen budget in pine forest mostly depends on tree harvesting and symbiotic N-fixation, which is poorly constrained. Export of N by rivers represents a small contribution to the N budget of soils.     

Geographic distribution of livestock-associated Staphylococcus aureus in the United States

Sampling for livestock-associated Staphylococcus aureus (LA-SA) in the United States is haphazard. The diversity of LA-S. aureus in the U.S. appears to be greater than in other countries. We review the epidemiology of LA-S. aureus in U.S. pigs, occupationally-exposed individuals, and environmental samples to assess the diversity and abundance of U.S. LA-S. aureus.     

Carbon cycling and sequestration in a Japanese red pine (Pinus densiflora) forest on lava flow of Mt. Fuji

Biometric-based carbon flux measurements were conducted in a pine forest on lava flow of Mt. Fuji, Japan, in order to estimate carbon cycling and sequestration. The forest consists mainly of Japanese red pine (Pinus densiflora) in a canopy layer and Japanese holly (Ilex pedunculosa) in a subtree layer. The lava remains exposed on the ground surface, and the soil on the lava flow is still immature with no mineral soil layer. The results showed that the net primary production (NPP) of the forest was 7.3 ± 0.7 t C ha^?1 year^?1, of which 1.4 ± 0.4 t C ha^?1 year^?1 was partitioned to biomass increment, 3.2 ± 0.5 t C ha^?1 year^?1 to above-ground fine litter production, 1.9 t C ha^?1 year^?1 to fine root production, and 0.8 ± 0.2 t C ha^?1 year^?1 to coarse woody debris. The total amount of annual soil surface CO₂ efflux was estimated as 6.1 ± 2.9 t C ha^?1 year^?1, using a closed chamber method. The estimated decomposition rate of soil organic matter, which subtracted annual root respiration from soil respiration, was 4.2 ± 3.1 t C ha^?1 year^?1. Biometric-based net ecosystem production (NEP) in the pine forest was estimated at 2.9 ± 3.2 t C ha^?1 year^?1, with high uncertainty due mainly to the model estimation error of annual soil respiration and root respiration. The sequestered carbon being allocated in roughly equal amounts to living biomass (1.4 t C ha^?1 year^?1) and the non-living C pool (1.5 t C ha^?1 year^?1). Our estimate of biometric-based NEP was 25 % lower than the eddy covariance-based NEP in this pine forest, due partly to the underestimation of NPP and difficulty of estimation of soil and root respiration in the pine forest on lava flows that have large heterogeneity of soil depth. However, our results indicate that the mature pine forest acted as a significant carbon sink even when established on lava flow with low nutrient content in immature soils, and that sequestration strength, both in biomass and in soil organic matter, is large.     

Gross precipitation and throughfall chemistry in legume species planted in Northeastern México

Plant cover modifies throughfall chemistry, and the solute concentration is dependent on the plant species at any given site. The chemistry of gross rainfall and throughfall of four endemic species planted in northeastern Mexico was evaluated from March 1996 to March 1997. Chemical solutes measured included Ca, K, Mg, Na, Fe, Mn, Cu, and Zn. Dry deposition and canopy leaching fluxes were estimated following the canopy budget model. Variance analyses tested the statistical dependence of the total and net fluxes on the species and seasons. Regression analysis tested the dependence of chemical concentrations on rainfall depth and lag time between rains. A total of 52 rainfall events were recorded during the study period summing 523 mm. Significant differences were noted on the total and net fluxes between the plant species. For total flux, average throughfall (37.8 kg ha^?1 year^?1) almost doubled the flux of solutes compared to rainfall (24.1 kg ha^?1 year^?1). Pithecellobium ebano (Berland.) C.H. Mull. (43.3 kg ha^?1 year^?1), Acacia berlandieri Benth. (38.7 kg ha^?1 year^?1), and Pithecellobium pallens (Bent.) Standl. (38.4 kg ha^?1 year^?1) recorded the highest total flux of solutes, and Acacia rigidula Benth. (30.9 kg ha^?1 year^?1) the smallest. Chemical solutes showed significant differences for total and net fluxes. Ca was the dominant cation with 48% and 52% of the total constituent flux for rainfall and throughfall, respectively. However, K, Mg and Cu approximately doubled in throughfall in contrast to gross rainfall. Species with the largest aboveground biomass had lower throughfall volumes (i.e., higher interception rates) but higher chemical solute inputs to the forest floor. Rainfall depth and lag time between rains explained part of the variation for most species, stressing the partial dependence of the washing effect and the amount of dry deposition on canopies. This research discusses the importance and the sources of incoming solutes on the studied plant species.     

Modeling denitrification in a tile-drained, corn and soybean agroecosystem of Illinois, USA

Denitrification is known as an important pathway for nitrate loss in agroecosystems. It is important to estimate denitrification fluxes to close field and watershed N mass balances, determine greenhouse gas emissions (N₂O), and help constrain estimates of other major N fluxes (e.g., nitrate leaching, mineralization, nitrification). We compared predicted denitrification estimates for a typical corn and soybean agroecosystem on a tile drained Mollisol from five models (DAYCENT, SWAT, EPIC, DRAINMOD-N II and two versions of DNDC, 82a and 82h), after first calibrating each model to crop yields, water flux, and nitrate leaching. Known annual crop yields and daily flux values (water, nitrate-N) for 1993–2006 were provided, along with daily environmental variables (air temperature, precipitation) and soil characteristics. Measured denitrification fluxes were not available. Model output for 1997–2006 was then compared for a range of annual, monthly and daily fluxes. Each model was able to estimate corn and soybean yields accurately, and most did well in estimating riverine water and nitrate-N fluxes (1997–2006 mean measured nitrate-N loss 28 kg N ha^?1 year^?1, model range 21–28 kg N ha^?1 year^?1). Monthly patterns in observed riverine nitrate-N flux were generally reflected in model output (r ² values ranged from 0.51 to 0.76). Nitrogen fluxes that did not have corresponding measurements were quite variable across the models, including 10-year average denitrification estimates, ranging from 3.8 to 21 kg N ha^?1 year^?1 and substantial variability in simulated soybean N₂ fixation, N harvest, and the change in soil organic N pools. DNDC82a and DAYCENT gave comparatively low estimates of total denitrification flux (3.8 and 5.6 kg N ha^?1 year^?1, respectively) with similar patterns controlled primarily by moisture. DNDC82h predicted similar fluxes until 2003, when estimates were abruptly much greater. SWAT and DRAINMOD predicted larger denitrification fluxes (about 17–18 kg N ha^?1 year^?1) with monthly values that were similar. EPIC denitrification was intermediate between all models (11 kg N ha^?1 year^?1). Predicted daily fluxes during a high precipitation year (2002) varied considerably among models regardless of whether the models had comparable annual fluxes for the years. Some models predicted large denitrification fluxes for a few days, whereas others predicted large fluxes persisting for several weeks to months. Modeled denitrification fluxes were controlled mainly by soil moisture status and nitrate available to be denitrified, and the way denitrification in each model responded to moisture status greatly determined the flux. Because denitrification is dependent on the amount of nitrate available at any given time, modeled differences in other components of the N cycle (e.g., N₂ fixation, N harvest, change in soil N storage) no doubt led to differences in predicted denitrification. Model comparisons suggest our ability to accurately predict denitrification fluxes (without known values) from the dominant agroecosystem in the midwestern Illinois is quite uncertain at this time.     

Engineered antifouling microtopographies: the role of Reynolds number in a model that predicts attachment of zoospores of Ulva and cells of Cobetia marina

A correlation between the attachment density of cells from two phylogenetic groups (prokaryotic Bacteria and eukaryotic Plantae), with surface roughness is reported for the first time. The results represent a paradigm shift in the understanding of cell attachment, which is a critical step in the biofouling process. The model predicts that the attachment densities of zoospores of the green alga, Ulva, and cells of the marine bacterium, Cobetia marina, scale inversely with surface roughness. The size and motility of the bacterial cells and algal spores were incorporated into the attachment model by multiplying the engineered roughness index (ERI_II), which is a representation of surface energy, by the Reynolds number (Re) of the cells. The results showed a negative linear correlation of normalized, transformed attachment density for both organisms with ERI_II · Re (R ² = 0.77). These studies demonstrate for the first time that organisms respond in a uniform manner to a model, which incorporates surface energy and the Reynolds number of the organism.     

Carbon dioxide and methane emissions from interfluvial wetlands in the upper Negro River basin, Brazil

Extensive interfluvial wetlands occur in the upper Negro River basin (Brazil) and contain a mosaic of vegetation dominated by emergent grasses and sedges with patches of shrubs and palms. To characterize the release of carbon dioxide and methane from these habitats, diffusive and ebullitive emissions and transport through plant aerenchyma were measured monthly during 2005 in permanently and seasonally flooded areas. CO₂ emissions averaged 2193 mg C m^?2 day^?1. Methane was consumed in unflooded environments and emitted in flooded environments with average values of ?4.8 and 60 mg C m^?2 day^?1, respectively. Bubbles were emitted primarily during falling water periods when hydrostatic pressure at the sediment?Cwater interface declined. CO₂ and CH₄ emissions increased when dissolved O₂ decreased and vegetation was more abundant. Total area and seasonally varying flooded areas for two wetlands, located north and south of the Negro River, were determined through analysis of synthetic aperture radar and optical remotely sensed data. The combined areas of these two wetlands (3000 km²) emitted 1147 Gg C year^?1 as CO₂ and 31 Gg C year^?1 as CH₄. If these rates are extrapolated to the area occupied by hydromorphic soils in the upper Negro basin, 63 Tg C year^?1 of CO₂ and 1.7 Tg C year^?1 as CH₄ are estimated as the regional evasion to the atmosphere.     

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.     

Effect of nitrogen and phosphorus fertilization on the composition of rhizobacterial communities of two Chilean Andisol pastures

The effect of nitrogen (N) and phosphorus (P) fertilization on composition of rhizobacterial communities of volcanic soils (Andisols) from southern Chile at molecular level is poorly understood. This paper investigates the composition of rhizobacterial communities of two Andisols under pasture after 1- and 6-year applications of N (urea) and P (triple superphosphate). Soil samples were collected from two previously established sites and the composition of rhizobacterial communities was determined by denaturing gradient gel electrophoresis (PCR–DGGE). The difference in the composition and diversity between rhizobacterial communities was assessed by nonmetric multidimensional scaling (MDS) analysis and the Shannon–Wiener index. In Site 1 (fertilized for 1 year), PCR–DGGE targeting 16S rRNA genes and MDS analysis showed that moderate N application (270 kg N ha^?1 year^?1) without P significantly changed the composition of rhizobacterial communities. However, no significant community changes were observed with P (240 kg P ha^?1 year^?1) and N–P application (270 kg N ha^?1 year^?1 plus 240 kg P ha^?1 year^?1). In Site 2 (fertilized for 6 years with P; 400 kg P ha^?1 year^?1), PCR–DGGE targeting rpoB, nifH, amoA and alkaline phosphatase genes and MDS analysis showed changes in rhizobacterial communities only at the highest rate of N application (600 kg N ha^?1 year^?1). Quantitative PCR targeting 16S rRNA genes also showed higher abundance of bacteria at higher N application. In samples from both sites, the Shannon–Wiener index did not show significant difference in the diversity of rhizobacterial communities. The changes observed in rhizobacterial communities coincide in N fertilized pastures with lower soil pH and higher pasture yields. This study indicates that N–P application affects the soil bacterial populations at molecular level and needs to be considered when developing fertilizer practices for Chilean pastoral Andisols.     

The influence of plants on atmospheric methane in an agriculture-dominated landscape

The primary objective of this study was to clarify the influence of crop plants on atmospheric methane (CH₄) in an agriculture-dominated landscape in the Upper Midwest of the United States. Measurements were carried out at two contrasting scales. At the plant scale, CH₄ fluxes from soybean and corn plants were measured with a laser-based plant chamber system. At the landscape scale, the land surface flux was estimated with a modified Bowen ratio technique using measurements made on a tall tower. The chamber data revealed a diurnal pattern for the plant CH₄ flux: it was positive (an emission rate of 0.4?±?0.1 nmol m^?2 s^?1, average of soybean and corn, in reference to the unit ground area) during the day, and negative (an uptake rate of ?0.8?±?0.8 nmol m^?2 s^?1) during the night. At the landscape scale, the flux was estimated to be 14.8 nmol m^?2 s^?1 at night and highly uncertain during the day, but the available references and the flux estimates from the equilibrium methods suggested that the CH₄ flux during the entire observation period was similar to the estimated nighttime flux. Thus, soybean and corn plants have a negligible role in the landscape-scale CH₄ budget.     

Emissions of CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O from undisturbed,drained and mined peatlands in Estonia

The aim of this study is to estimate emissions of greenhouse gases CO₂, CH₄ and N₂O, and the effects of drainage and peat extraction on these processes, in Estonian transitional fens and ombrotrophic bogs. Closed-chamber-based sampling lasted from January to December 2009 in nine peatlands in Estonia, covering areas with different land-use practices: natural (four study sites), drained (six sites), abandoned peat mining (five sites) and active peat mining areas (five sites). Median values of soil CO₂ efflux were 1,509, 1,921, 2,845 and 1,741 kg CO₂-C ha^?1 year^?1 from natural, drained, abandoned and active mining areas, respectively. Emission of CH₄-C (median values) was 85.2, 23.7, 0.07 and 0.12 kg ha^?1 year^?1, and N₂O-N ?0.05, ?0.01, 0.18 and 0.19 kg ha^?1 year^?1, respectively. There were significantly higher emissions of CO₂ and N₂O from abandoned and active peat mining areas, whereas CH₄ emissions were significantly higher in natural and drained areas. Significant Spearman rank correlation was found between soil temperature and CO₂ flux at all sites, and CH₄ flux with high water level at natural and drained areas. Significant increase in CH₄ flux was detected for groundwater levels above 30 cm.     

A passive apparatus for controlled-flux delivery of biocides: hydrogen peroxide as an example

A new test method has been developed to estimate the required release rate of hydrogen peroxide (H₂O₂) to prevent marine biofouling. The technique exploits a well-defined concentration gradient of biocide across a cellulose acetate membrane. A controlled flux of H₂O₂, an environmentally friendly biocide, was obtained. Larvae of the barnacle, Balanus improvisus, were subjected to known release rates of H₂O₂ from a surface, under laboratory conditions. It was found that the distribution of settled larvae was not significantly different from the controls when H₂O₂ fluxes of 5–8 μg cm^?2 day^?1 were applied. However, release rates of 40 μg cm^?2 day^?1 significantly displaced the distribution of settled larvae towards the area of the chamber farthest away from the membrane. Membrane tests in seawater (Jyllinge Harbour, Denmark) for over 16 weeks showed that release rates of H₂O₂ of approximately 2800 μg cm^?2 day^?1 deterred biofouling efficiently. A H₂O₂ release rate of about 224 μg cm^?2 day^?1 resulted in some slime formation, but it was less than that on the H₂O₂-free control. It appears that to obtain efficient resistance to biofouling in natural seawater requires much higher membrane release rates of H₂O₂ (factor of between 5 and 50) than laboratory membrane exposure assays using barnacle larvae.     

Nitrogen biogeochemistry of a mature Scots pine forest subjected to high nitrogen loads

Nitrogen (N) biogeochemistry of a mature Scots pine (Pinus sylvestris L.) stand subjected to an average total atmospheric N deposition of 48 kg ha^?1 year^?1 was studied during the period 1992–2007. The annual amount of dissolved inorganic nitrogen (DIN) in throughfall (TF) averaged 34 kg ha^?1 year^?1 over the 16-year monitoring period. The throughfall fluxes contained also considerable amounts of dissolved organic nitrogen (DON) (5–8.5 kg N ha^?1 year^?1), which should be incorporated in the estimate of N flux using throughfall collectors. Throughfall DIN fluxes declined at a rate of ?0.9 kg N ha^?1 year^?1, mainly due to the decreasing TF fluxes of ammonium (NH₄), which accounted for 70% to TF DIN. The decrease in TF DIN was accompanied by a decrease in DIN leaching in the seepage water (?1.6 kg N ha^?1 year^?1), which occurred exclusively as nitrate (NO₃ ^?). Nitrate losses in the leachate of the forest floor (LFH) equalled the TF NO₃ ^? delivered to the LFH-layer. On the contrary, about half of the TF NH₄ ⁺ was retained within the LFH-layer. Approximately 60% of the TF DIN fluxes were leached indicating that N inputs were far in excess of the N requirements of the forest. For DON, losses were only substantial from the LFH-layer, but no DON was leached in the seepage water. Despite the high N losses through nitrate leaching and NO _x emission, the forest was still accumulating N, especially in the aggrading LFH-layer. The forest stand, on the contrary, was found to be a poor N sink.     

Carbon cycling and net ecosystem production at an early stage of secondary succession in an abandoned coppice forest

Secondary mixed forests are one of the dominant forest cover types in human-dominated temperate regions. However, our understanding of how secondary succession affects carbon cycling and carbon sequestration in these ecosystems is limited. We studied carbon cycling and net ecosystem production (NEP) over 4 years (2004–2008) in a cool-temperate deciduous forest at an early stage of secondary succession (18 years after clear-cutting). Net primary production of the 18-year-old forest in this study was 5.2 tC ha^?1 year^?1, including below-ground coarse roots; this was partitioned into 2.5 tC ha^?1 year^?1 biomass increment, 1.6 tC ha^?1 year^?1 foliage litter, and 1.0 tC ha^?1 year^?1 other woody detritus. The total amount of annual soil surface CO₂ efflux was 6.8 tC ha^?1 year^?1, which included root respiration (1.9 tC ha^?1 year^?1) and heterotrophic respiration (RH) from soils (4.9 tC ha^?1 year^?1). The 18-year forest at this study site exhibited a great increase in biomass pool as a result of considerable total tree growth and low mortality of tree stems. In contrast, the soil organic matter (SOM) pool decreased markedly (?1.6 tC ha^?1 year^?1), although further study of below-ground detritus production and RH of SOM decomposition is needed. This young 18-year forest was a weak carbon sink (0.9 tC ha^?1 year^?1) at this stage of secondary succession. The NEP of this 18-year forest is likely to increase gradually because biomass increases with tree growth and with the improvement of the SOM pool through increasing litter and dead wood production with stand development.     

Regional assessment of emerald ash borer, <Emphasis Type="Italic">Agrilus planipennis</Emphasis>, impacts in forests of the Eastern United States

Native to Asia, the emerald ash borer (Agrilus planipennis Fairmaire) has caused extensive mortality of ash tree species (Fraxinus spp.) in the eastern United States. As of 2013, the pest was documented in 18 % of counties within the natural range of ash in the eastern United States. Regional forest inventory data from the U.S. Forest Service Forest Inventory and Analysis program were used to quantify trends in ash mortality rate and volume per hectare relative to the year of initial emerald ash borer detection. Results indicate that the annual ash mortality rate increases by as much as 2.7 % per year after initial detection of the pest in a county. Corresponding decreases in ash volume (as much as 1.8 m³ per hectare per year) continue for several more years until most live ash is killed. These results, while not necessarily representative of the effects on ash in urban ecosystems, document the severe impact this invading herbivore is having on forests as it expands its range in North America.     

The potential for hull-mediated species transfers by obsolete ships on their final voyages

Shipping has contributed strongly to biological invasions in coastal ecosystems, transferring species in ballast tanks and on exposed underwater surfaces (hulls). A long history exists that documents biota associated with ships’ hulls, including some recent analyses of modern ships, but relatively little is known about the associated risks of invasion. In general, the likelihood of invasion is expected to increase with increasing propagule supply, which suggests that high‐density transfers on hulls may pose a relatively high invasion risk. Obsolete vessels are expected to be at an extreme end of the spectrum for biofouling, since they sit at anchorage for long periods and are towed at relatively slow speeds when moved, but this remains largely unexplored. In this paper, we quantified the biofouling communities of two obsolete vessels, one stationary for one decade and the other for two decades, before and after their final transit from California to Texas. Pre‐departure biofouling surveys across both vessels detected 22 species of macroinvertebrates. The biomass was dominated by the introduced bryozoan Conopeum chesapeakensis, which occurred in 98% of samples and created a three‐dimensional structure (2–5 cm thick). Mobile species, inhabiting the vertical biofouling matrix, were more numerous than sessile ones. Interestingly, the non‐native Asian clam Corbula amurensis, not previously associated with hull fouling assemblages, was recorded in 9% of samples. During the 43‐day voyage, organisms encountered salinity variation that ranged between zero (Panama Canal) and at least 37 parts per thousand (Brownsville, Texas) and temperatures that varied between 9.9 °C and 31.6 °C. Upon arrival in Texas, we measured an expected decrease in biofouling extent across both vessels but also a surprising increase in species richness (57 species were recorded), with small compositional differences between ships that did not exist prior to departure. Several species were recorded alive upon arrival, including non‐natives that are not known to be established in Texas waters. The physiological tolerance and associated risk of colonization have not yet been evaluated for these organisms, or for the broader species pool associated with a standing fleet (n > 200 ships) that may undergo similar movements. Nonetheless, a compelling case exists for vector management based on organism flux alone, to reduce the risk of coastwise and inter‐oceanic invasions.