The emergy ecological footprint for small fish farm in China

Mariculture, especially cage aquaculture remains a growing, vibrant and important production sector for high protein food in coastal regions in China. A quantitative evaluation of the mariculture system is an essential step to documenting its’ sustainability. The method of emergy ecological footprint is applied to evaluate the environmental sustainability of an offshore small fish farm (Great Marine fish farm, GMFF) in the East China Sea. All input needed to support fish farming were accounted and converted into biological space, to estimate the natural capital demand for the rearing process in terms of global hectares. The emergy ecological footprint of GMFF was 1953.19 ha, meaning that nearly 2000 ha of ecologically productive lands were needed to support the fish framing. The largest component of emergy ecological footprint was forage (1183.64 ha), which took up 60.60% of the total footprint; the second and third largest footprint components were fingerlings and fuel. In a word, emergy ecological footprint can serve as a practical and meaningful tool for comparing and monitoring the environmental impact of fish farming. The strong dependence of external contributions of exploiting the wild fish resources affects strongly the level of environmental sustainability of fish farming.     

Loss of aboveground forest biomass and landscape biomass variability in Missouri,US

Disturbance regimes and forests have changed over time in the eastern United States. We examined effects of historical disturbance (circa 1813 to 1850) compared to current disturbance (circa 2004 to 2008) on aboveground, live tree biomass (for trees with diameters ≥13 cm) and landscape variation of biomass in forests of the Ozarks and Plains landscapes in Missouri, USA. We simulated 10,000 one-hectare plots using random diameters generated from parameters of diameter distributions limited to diameters ≥13 cm and random densities generated from density estimates. Area-weighted mean biomass density (Mg/ha) for historical forests averaged 116 Mg/ha, ranging from 54 Mg/ha to 357 Mg/ha by small scale ecological subsections within Missouri landscapes. Area-weighted mean biomass density for current forests averaged 82 Mg/ha, ranging from 66 Mg/ha to 144 Mg/ha by ecological subsection for currently forested land. Biomass density of current forest was greater than historical biomass density for only 2 of 23 ecological subsections. Current carbon sequestration of 292 TgC on 7 million ha of forested land is less than half of the estimated historical total carbon sequestration of 693 TgC on 12 million ha. Cumulative tree cutting disturbances over time have produced forests that have less aboveground tree biomass and are uniform in biomass compared to estimates of historical biomass, which varied across Missouri landscapes. With continued relatively low rates of forest disturbance, current biomass per ha will likely increase to historical levels as the most competitive trees become larger in size and mean number of trees per ha decreases due to competition and self-thinning. Restoration of large diameter structure and forested extent of upland woodlands and floodplain forests could fulfill multiple conservation objectives, including carbon sequestration.     

Emergy synthesis of a combined food and energy production system compared to a conventional wheat (Triticum aestivum) production system

It is a major challenge to produce food and energy sustainably for the ever increasing world population as today's conventional food production and energy needs are met by the fossil based resources, causing enormous environmental load. A novel, combined food and energy (CFE) agro-ecosystem, was designed for sustainable production of food, fodder and energy without chemical inputs (fertiliser, herbicide and fungicide). The objective was an emergy synthesis of the CFE system compared to a conventional wheat (Triticum aestivum) production system to assess resource use efficiency. The emergy indices, used to assess the environmental performance and sustainability, exhibited contrasting differences between the two production systems in terms of outputs (Y), total emergy use, solar transformity, relative use of local renewable resources, environmental loading ratio (ELR), emergy yield ratio (EYR) and emergy sustainability index (ESI). The Y in the CFE consisted of grain, straw, fodder and woodchip production of 4020, 3580, 6100 and 10,000 kg/ha/yr respectively whereas Y in the conventional wheat consisted of 7250 and 3770 kg grain and straw/ha/yr respectively. The Y in the CFE was 81% (2.80E+11 J/ha/yr) higher with 13.5 times (6.40E+03 seJ/J) lower solar transformity compared to the Y (1.54E+11 J/ha/yr) and solar transformity (8.63E+04 seJ/J) in the conventional wheat, exhibiting highly resource intensive production in conventional wheat. The local renewables constituted 19.2% and 2.6% of the total emergy input in the CFE and the conventional wheat respectively with a corresponding lower ELR (4.21) and 22.5% higher EYR (1.26) in CFE compared to conventional wheat. CFE was more reliant on local renewable emergy flows and compatible with the local environment with higher ESI (0.30) compared to conventional wheat (0.03), where 64.5% of the total emergy input constituted chemical inputs. The study demonstrated that the innovative agro-ecosystem, exemplified by CFE, is considerably less resource demanding and more amenable to sustainable production, whether defined in terms of outputs, solar transformity, relative use of local renewable resources, EYR, ELR or ESI.     

Ecological energy accounting for the gambling sector: A case study in Macao

Macao is a population-dense society that depends heavily on exogenous natural resources. In parallel with an expanding gambling sector, tourism became the most important driving force in Macao's economy. Economic growth in Macao has now benefited from the gambling boom and associated tourism for more than two decades. Although traditional economic theory has been used to deal with the economics of the gambling sector, the materials and energy foundation for this sector has not been previously analyzed. This is an important omission from the literature, since the gambling sector provides gamblers with food, tickets, services, water, electricity, equipment, labor, and other services that consume large quantities of materials and energy. In this paper, emergy synthesis is introduced to analyze Macao's gambling sector in 2004. Macao's casinos provide a dense flow of services that favor gambling tourists, since the emergy/$ ratio (1.42 × 10¹² sej/$) for the sector is much lower than that for Macao as a whole (2.38 × 10¹² sej/$). The emergy imports by this sector totaled 78.1 × 10²⁰ sej, and its exports were 77.1 × 10²⁰ sej. The emergy of services therefore plays an important role in Macao's gambling sector, and the transformity of an employee in this sector (11.2 × 10¹⁶ sej/person) was much higher than that of a typical person in Macao (5.27 × 10¹⁶ sej/person).     

Community structure and seasonal dynamics of planktonic ciliates along salinity gradients

The ciliate community structure and seasonal dynamics in a solar saltern of the Yellow Sea were studied based on 4 sampling dates and 8 stations with salinities from 27.7‰ to 311.0‰. The effects of the type and concentration of the fixative used (Lugol's and Bouin's) were tested at the first sampling date. Fixative type and fixative concentration had significant effects on ciliate abundance and biovolume, with 1% Lugol's giving the best results. A detailed investigation using live observations and protargol staining techniques revealed a total of 98 morphospecies from 8 sampling stations. There was obvious seasonal variation in species composition at most of the stations, but this tended to be less distinct with increasing salinity, as the dominant ciliate group shifted from oligotrichs to heterotrichs. Ciliate abundance varied from 4.40×10¹ to 2.11×10⁵ cells l^?1 and biomass ranged between 2.39 and 9.87×10³ μg C l^?1 (at a salinity of 147.6‰). Both abundance and biomass decreased abruptly when salinity exceeded 100–150‰. Statistical analyses suggested that the dynamics of ciliate abundance and biomass were regulated by both salinity and by season, but those of diversity and species richness were mainly controlled by salinity and both significantly decreased with increasing salinity.     

The emergy of metabolism in different ecosystems under the same environmental conditions in the agro-pastoral ecotone of northern China

The sustainability of ecosystem productivity and rules governing ecosystem development are important topics of scientific research. The emergy approach is an effective method for investigating these topics, especially when used to evaluate systems that have developed under the same environmental conditions, such as climate and soil. In this paper, emergy differences between terrestrial ecosystems were studied in Guyuan County, a region representative of the agro-pastoral ecotone in Hebei Province, China. A combination of field tests and a questionnaire survey were carried out between June and August 2015. The ecosystems studied included natural grassland, artificial grassland, field crops and commercial crops. These four ecosystems were further subdivided into a total of ten ecosystems. Natural grassland was divided into free-grazing and mowed ecosystems; artificial grassland consisted of oat, Chinese leymus and corn silage; field crops included naked oats, flax and wheat; and commercial crops consisted of cabbage and potatoes. The results showed that the rain input of 4.78 × 10¹⁴ seJ/ha/yr constituted the highest renewable natural resource emergy and that the purchased emergy inputs of the ten ecosystems ranged from 3.53 to 147.67 × 10¹⁴ seJ/ha/yr. Natural resource emergy input was the basic power to maintain the ecosystem, and purchased emergy input was the direct cause of the development of the ecosystems. Groundwater was the most important non-renewable purchased energy for the production of economic crops. The emergy investment ratios (EIR) for potatoes (27.81) and cabbage (19.03) were higher than those of the other ecosystems, but mowed and artificial Chinese leymus grassland had the higher emergy self-sufficiency rates (ESR). Natural grassland, artificial Chinese leymus grassland and traditional grain crops had a low environmental load and high sustainability, whereas potatoes and cabbage had a high environmental load and low sustainability. Overall, rain-fed artificial grassland has a high development potential from the perspective of environment and productivity.     

The ecological potential of a restored abandoned quarry ecosystem in Mt. Mufu, Nanjing, China

In order to conserve the remaining rare dolomite rocks and restore Mt. Mufu, a forest restoration program has been implemented over ten years. Emergy analysis was used to evaluate the current status of the restored ecosystem, in addition, the ecological potential of the fully developed system was predicted and analyzed. Four main emergy indices of the two systems, EYR, EIR, ELR, and ESI, were calculated and compared. In addition, a relatively new emergy index, PYR, was used to evaluate the restored forest system's ecological potential. The results revealed that the current restored forest system was still in the initial stage of ecological restoration but it has already resulted in several positive effects, such as richness of plant biodiversity and improving air condition. The value of the predicted system's PYR is as great as 201.53, demonstrating that the restored forest system has a great potential for ecological development in the future.     

Emergy analysis of cassava chips-suitable feedstock for fuel ethanol in China

The theory and indices of Odum's concept of emergy are explained. The environmental and economic inputs and sustainability of cassava chips production system are evaluated by emergy methodology. The emergy indices of cassava chips production system were calculated as follows: Tr (transformity) was 6.85E + 11 sej/kg, EYR (emergy yield ratio) was 1.11, ELR (environmental loading ratio) was 1.75, EIR (emergy investment ratio) was 9.33, and ESI (emergy sustainability indice) was 0.63. The emergy indices of four kinds of feedstock for fuel ethanol—corn, wheat, sugarcane, and cassava chips—were compared. Least solar energy was consumed when taking cassava chips as feedstock for fuel ethanol. According to the emergy indices, using cassava chips as the feedstock of fuel ethanol is helpful for sustainable development in China.     

Expanding ecological appropriation approach: Solar space method and a case study in Yangzhou city,East China

In this paper, the authors made an attempt to measure appropriation of ecosystems more reasonably and effectively based on examining the advantages and disadvantages of emergy analysis and ecological footprint. By combining emergy analysis with ecological footprint (EF) in terms of spatial equivalent of energy productivity, a new method of solar space (SS) and its calculating framework was proposed, and some necessary parameters for this method of analysis were calculated. A case study was followed under this calculating framework for Yangzhou city, Jiangsu province, Eastern China, using the data of the year 2000. The main results are as follows: (1) The ecological space in Yangzhou city includes earth surface space and solar space, and their demands were bigger than their supply. In the year of 2000, the earth surface space had an absolute deficit of 2.3063E?02 Ga-ha per capita (global hectares), and the solar space had an absolute deficit of 1.4944E?04 Sa-ha per capita (solar hectares). (2) There was a relative ecological deficit of 3.68% in earth surface space, and that of 154.86% in solar space. (3) Only freshwater areas and built-up areas were in a state of surplus, and there was a relative ecological surplus of 82.66% for freshwater areas, being greater than that for built-up areas. (4) The ranking of absolute ecological deficit in a descending order was as follows: solar space > arable land > pasture > forest > marine area > garden land, while the relative ecological deficit was the following: solar space > pasture land > forest land > arable land > garden land, except marine areas.A qualitative comparison of methodology was made between solar space method and ecological footprint according to their capability to describe the temporal-spatial characteristics of ecosystems appropriation. Moreover, a quantitative comparison was also conducted to show their differences in applicability to the assessment of ecosystems appropriation. It was shown that the calculating results from solar space method were bigger than that from ecological footprint because the former supplemented additional items of appropriation omitted by the later and included some new items of indirect appropriation that were excluded by the later. It is found that the new measure of solar space operates well as an indicator of the city's appropriation to ecosystems.     

Identifying potential restoration areas of freshwater wetlands in a river delta

Identification of potential restoration areas is significant and important for implementing a sustainable restoration project and maintaining the ecosystem integrity. We established an eco-hydrological approach to identify potential restoration areas of freshwater wetlands that should and can be restored. Our eco-hydrological method identifies potential restoration areas from three dimensions, namely, transverse, longitudinal and vertical directions. Based on transfer matrix analysis between freshwater wetland and other land cover types and bird habitat suitability assessment, we identified the areas that should be restored under the 1989 and 2000 goals were 36,112 ha and 37,230 ha, respectively. Based on hydrological connectivity and balance between ecological water supply (EWS) and ecological water requirements (EWRs), the area can be restored under the 1989 and 2000 goals were 31,165 ha and 33,963 ha, respectively. The approach and results of this study can help in future restoration efforts in the Yellow River Delta and other similar coastal wetlands.     

High carbon storage and oxygen (O2) release potential of Mahagony (Swietenia macrophylla) woodlot plantation in Bangladesh

Woodlot plantation takes our attention nowadays because of having high wood value, biomass and carbon stock. It also has considerable potential for regulating climate change by sinking CO₂. This study investigated the market value of Swietenia macrophylla woodlots concerning the current carbon trade mechanism, local timber and oxygen value. The carbon-di-oxide equivalence (CO_2e) and release oxygen (O_{2 Release}) ranged from 125.5 to 1004.5 Mg/ha (mean 436.3 Mg/ha) and 91.25–730.26 Mg/ha (mean 317.2 Mg/ha), respectively. Form carbon trade, the Swietenia macrophylla woodlots owner will earn 4,285–34,470 BDT/ha (mean 14,900 BDT/ha). It also seemed that the present market value of release oxygen (O_{2 Release}) ranged from 3.2 to 25.5 million BDT/ha (average 11.1 million BDT/ha). However, the study area's average DBH, height, density, and basal area were 18.9 cm, 12.6 m, 1233 stem/ha, and 36.6 m²/ha, respectively. The above-ground biomass, below-ground biomass, and total biomass ranged from 45.9 to 389.7 Mg/ha (mean 166.5 Mg/ha), 22.5–157.7 Mg/ha (mean 71.2 Mg/ha), and 68.4–547.4 Mg/ha (mean 237.7 Mg/ha) correspondingly. Besides, the produced wood volume ranged from 64.95-1225.19 m³/ha (average 481.48 m³/ha). While the price of wood ranged from 0.8 to 15.14 million BDT/ha (mean 5.95 million BDT/ha). However, the above-ground, below-ground, and total carbon ranged 22.97–194.85 Mg/ha (mean 87.27 Mg/ha, 11.23–78.85 Mg/ha (35.61 Mg/ha), and 34.2–273.7 Mg/ha (118.89 Mg/ha) independently. Moreover, our three developed basal area-based allometric models are fit for calculating the carbon stock of Swietenia macrophylla woodlots. This study explores the potentiality of woodlots in Bangladesh. Policymakers should encourage the farmers to create more woodlots that actively participate in climate change mitigation.     

Analysis of the factors that affect the distribution and abundance of three Neobuxbaumia species (Cactaceae) that differ in their degree of rarity

We studied three species of columnar cacti in the genus Neobuxbaumia which differ in their degree of rarity: Neobuxbaumia macrocephala (the rarest), Neobuxbaumia tetetzo (intermediate), and Neobuxbaumia mezcalaensis (the most common). To investigate the ecological factors that limit their distribution and abundance, we surveyed 80 localities within the region of Tehuacan-Cuicatlán, in Central Mexico. At each locality we measured several environmental variables, and the density of the Neobuxbaumia populations present. We used a principal component analysis (PCA) to identify the factors that are associated to the presence/absence of each species. Additionally, we carried out multiple regressions between environmental variables and population density to test whether the variation in these variables was related to changes in abundance. The results show that factors significantly affecting the distribution of these species are mean annual temperature, altitude, rainfall, and soil properties such as texture and organic matter content. N. mezcalaensis reaches maximum population densities of 14,740 plants per ha (average density = 3943 plants per ha) and is associated with localities with relatively abundant rainfall. N. tetetzo shows maximum population densities of 14,060 plants per ha (average = 3070 plants per ha), and is associated with sites located at high latitudes and with high phosphorous content in the soil. The rarest species, N. macrocephala, shows maximum densities of 1180 plants per ha (average = 607 plants per ha) and is associated with localities with high soil calcium content. The distribution of this species is limited to sites with specific values of the environmental variables recorded, conferring it a high habitat specificity which accounts for its rarity.     

Emergy and exergy evaluation of a dike-pond project in the drawdown zone (DDZ) of the Three Gorges Reservoir (TGR)

The dike-pond system was a form of ecological engineering that was a component of successional dikes and ponds along the banks of the Pengxi River in the drawdown zone (DDZ) of the Three Gorges Reservoir (TGR). The application of science-based evaluation system was appropriate for the flows of emergy in this agricultural ecosystem. The Emergy Analysis (EmA) has the ability to transform different types of inputs to a common form to allow meaningful comparisons across different systems. This study made use of the emergy analysis that assessed two different types of farming methods in the DDZ of the TGR. One method was planning crops in a dike-pond system (model I), and the other method was conventional agriculture (model II). In addition, the Exergies of both yields of agriculture methods were calculated, and the Exergy and Emergy Density (ED) were combined to explore the quality of these methods. The results showed that the two models relied on different resources. The ED yield of both models were similar, but the emergy investment of model II was greater than that of model I. Model II also used less renewable energy input to the agricultural systems than model I. The agricultural emergy sustainability index (AESI) of model I system (AESI = 2.4 > 1) was greater than that of model II system (AESI = 0.5 < 1), which indicated that the sustainable development of model I was stronger than that of model II in the DDZ of the TGR. The ratio Exergy/Emergy density (R_ex/em) in the two models of different agricultural system were 121.52 × 10⁻³ J/sej (Model I) and 24.19 × 10⁻³ J/sej (model II). Model I was greater than model II, and the result intimated that the model I agricultural system was a new method in the DDZ, but it was older and closer to the steady state than model II. The Emergy and Exergy analysis certifies that model I has a more acceptable and more sustainable development potential and is more stabilized in the DDZ of the TGR.     

Valuation of the loss of plant-related ecosystem services caused by water stress in the wetland of China’s Yellow River Delta

China’s Yellow River Delta is ecologically important because of its role as an eco-tone between terrestrial and aquatic ecosystems. However, water stress caused by drought or flooding creates ecological risks for this important ecosystem. In this study, we assessed community biodiversity, plant biomass, and the plant total nitrogen, total phosphorus, and potassium contents to quantify the potential loss of ecosystem services value arising from water stress. The annual ecosystem services and function value of the wetlands totaled 3.68 × 10⁸ Yuan, of which biomass production and local climate regulation accounted for 39.4% and 49.5% of the total, respectively. The area with the highest value (>2 Yuan m⁻²) lies along both banks of the downstream reaches of the river, whereas areas with the lowest values (<1.5 Yuan m⁻²) were located on the northern bank, near the Bohai Sea coastline. We defined scenarios based on three levels of water stress: drought, sufficient water, and flooding. The potential annual value loss in the drought scenario was 3.60 × 10⁸ Yuan, versus 2.78 × 10⁸ Yuan in the flooding scenario. The minimum loss (with sufficient water) was 2.06 × 10⁸ Yuan. The wetland’s soil water content should therefore be managed to protect the vegetation and minimize the ecological risks (and associated ecosystem service value losses) caused by water stress. Our approach provides a tool for assessing the potential loss of ecosystem services and functions and for calculating ecological compensation payments for wetland damage.     

Influence of phosphorus nutrition on growth and metabolism of Duo grass (Duo festulolium)

Use of suitable plants that can extract and concentrate excess P from contaminated soil serves as an attractive method of phytoremediation. Plants vary in their potential to assimilate different organic and inorganic P-substrates. In this study, the response of Duo grass (Duo festulolium) to variable rates of soil-applied potassium dihydrogen phosphate (KH₂PO₄) on biomass yield and P uptake were studied. Duo grown for 5 weeks in soil with 2.5, 5 and 7.5 g KH₂PO₄ kg^?1 soil showed a significantly higher biomass and shoot P content of 8.3, 11.4 and 12.3 g P kg^?1 dry weight respectively compared to plants that received no soil added P. Also, the ability of Duo to metabolize different forms of P-substrates was determined by growing them in sterile Hoagland's agar media with different organic and inorganic P-substrates, viz. KH₂PO₄, glucose-1-phosphate (G1P), inositiol hexaphosphate (IHP), adenosine triphosphate (ATP) and adenosine monophosphate (AMP) for 2 weeks. Plants on agar media with different P-substrates also showed enhanced biomass yield and shoot P relative to no P control and the P uptake was in the order of ATP > KH₂PO₄ > G1P > IHP = AMP > no P control. The activities of both phytase (E.C.3.1.3.26) and acid phosphatases (E.C.3.1.3.2) were higher in all the P received plants than the control. Duo grass is capable of extracting P from the soil and also from the agar media and thus it can serve as possible candidate for phytoextraction of high P-soil.     

Macrobenthos functional groups as indicators of ecological restoration in the northern part of China’s Yellow River Delta Wetlands

Freshwater releases to restore degraded wetlands are a globally recognized way to maintain the biodiversity and enhance the health of wetland ecosystems. To better understand the efficacy of freshwater releases in the northern part of China’s Yellow River Delta Wetlands, we used macrobenthos functional groups in spring (before freshwater releases), summer (during), and autumn (after) as indicators of the ecological responses. We also created abundance–biomass comparison curves and analyzed secondary production of each trophic level to evaluate the magnitude of the disturbance of the macrobenthos community. Abundance, biomass, and biodiversity of macrobenthos functional groups generally improved after the freshwater releases. In contrast with an intertidal (reference) area, the macrobenthos community in the ecological restoration area tended to be freshwater species. In the ecological restoration area, strong and moderate ecological disturbance of the macrobenthos community was evident during and after freshwater releases because the abundance curve remained above the biomass curve. Secondary production was in the order trophic level III > II ≅ IV in the summer, which indicates fragility of the macrobenthos community. The ecological restoration area had the highest sediment total organic carbon and moisture contents, but the lowest salinity and median particle size, and these differences were statistically significant. Our results suggest that adaptive freshwater releases, including a long-term freshwater release plan that more closely emulates natural flows and increasing the efficiency of freshwater utilization, will be necessary to achieve sustainable management of the wetland’s ecosystem and reduce the disturbance caused by the freshwater releases.     

Satellite monitoring of cyanobacterial harmful algal bloom frequency in recreational waters and drinking water sources

Cyanobacterial harmful algal blooms (cyanoHAB) cause extensive problems in lakes worldwide, including human and ecological health risks, anoxia and fish kills, and taste and odor problems. CyanoHABs are a particular concern in both recreational waters and drinking water sources because of their dense biomass and the risk of exposure to toxins. Successful cyanoHAB assessment using satellites may provide an indicator for human and ecological health protection. In this study, methods were developed to assess the utility of satellite technology for detecting cyanoHAB frequency of occurrence at locations of potential management interest. The European Space Agency's MEdium Resolution Imaging Spectrometer (MERIS) was evaluated to prepare for the equivalent series of Sentinel-3 Ocean and Land Colour Imagers (OLCI) launched in 2016 as part of the Copernicus program. Based on the 2012 National Lakes Assessment site evaluation guidelines and National Hydrography Dataset, the continental United States contains 275,897 lakes and reservoirs >1 ha in area. Results from this study show that 5.6% of waterbodies were resolvable by satellites with 300 m single-pixel resolution and 0.7% of waterbodies were resolvable when a three by three pixel (3 × 3-pixel) array was applied based on minimum Euclidian distance from shore. Satellite data were spatially joined to U.S. public water surface intake (PWSI) locations, where single-pixel resolution resolved 57% of the PWSI locations and a 3 × 3-pixel array resolved 33% of the PWSI locations. Recreational and drinking water sources in Florida and Ohio were ranked from 2008 through 2011 by cyanoHAB frequency above the World Health Organization’s (WHO) high threshold for risk of 100,000 cells mL⁻¹. The ranking identified waterbodies with values above the WHO high threshold, where Lake Apopka, FL (99.1%) and Grand Lake St. Marys, OH (83%) had the highest observed bloom frequencies per region. The method presented here may indicate locations with high exposure to cyanoHABs and therefore can be used to assist in prioritizing management resources and actions for recreational and drinking water sources.     

Granivory reduces biomass and lignin concentrations of plant tissue during grassland assembly

Small mammals can influence grassland assembly by selecting against palatable plants – the community can become dominated by the plants they avoid. This predation-based selection could have indirect effects on community biomass and tissue quality, especially given how untasty plants may have higher concentrations of recalcitrant carbon compounds including lignin. We tested small mammal effects on biomass and tissue quality of roots and shoots in a two-year-old 18 ha restored tallgrass prairie with established zones of high and low plant predation. We focused on the three dominant herbaceous functional groups of tallgrass prairie (perennial forbs, C₃ and C₄ grasses), and targeted the early stages of assembly given that plant predation by small animals can unfold quickly and is difficult to subsequently quantify. We predicted rodent predation to create communities with reduced biomass but an increased abundance of lignin-rich plants; we only observed the former. Rodents reduced aboveground biomass by 46% but preferentially targeted lignin-rich plants, with the latter result explained by the predominance of granivory over herbivory – there was no opportunity for selection based on tissue palatability. Based strictly on aboveground biomass, we estimated small mammals reduced standing stocks of recalcitrant carbon by 65 kg ha⁻¹, with reductions in belowground stocks almost certainly higher given that root:shoot ratios averaged 21:1. Given that the quantity and quality of plant production can affect ecosystem functions including decomposition and the regulation of soil carbon stocks, our work suggests that non-random plant predation may substantially affect rates of soil carbon accumulation in the early stages of grassland development.     

Herbivory,mowing, and herbicides differently affect production and nutrient allocation of Alternanthera philoxeroides

This glasshouse study examined the effect of three damage types on plant growth and nutrient allocation of the invasive aquatic plant, alligator weed (Alternanthera philoxeroides). The damage included: repeated leaf removal, a single application of herbicide, and one-time shoot removal. Damage types were meant to simulate the effects of insect herbivory, chemical, and mowing/grazing, respectively. Response variables included plant biomass and both the concentration and abundance of nutrients. Complete shoot removal and herbicide treatments caused an initial decline in growth rate, followed by several weeks of increasing rates and finally a second decline during the fourth week. Plants from control and repeated leaf removal treatments showed a steady increase in growth rate from the treatment application to the final harvest, but control plants were accumulating biomass three times faster than repeated defoliation plants by the fifth week (9.7 and 3.5 g week⁻¹, respectively). Not surprisingly, all treatments led to lower total cumulative biomass 5 weeks after treatment application (mean 30.8 g) when compared with controls (49.0 g). However, despite the repeated leaf removal and complete shoot removal treatments removing similar quantities of biomass (mean 8.0 and 7.5 g respectively), repeated removal of leaves produced less total biomass (26.2 g) and led to less cumulative above ground biomass (20.1 g) than the other treatments (mean total = 33.1 g, mean above ground = 25.7 g). Repeated leaf removal also produced less below ground biomass (6.1 g) than the shoot removal treatment (8.5 g) and had the greatest negative effect on nitrogen and potassium abundance in plant tissues after 5 weeks. In addition, it reduced the amount of phosphorous to a lower level than herbicide treated or control plants. These results indicate that repeated leaf removal was the treatment most effective in reducing biomass and depleting nutrients in A. philoxeroides plants.     

Organic matter accumulation in western boreal saline wetlands: A comparison of undisturbed and oil sands wetlands

Reconstructing landscapes after open pit mining of the Canadian oil sands presents enormous challenges. Freshwater peatlands dominate the pre-disturbance landscape; however, elevated salinity in the post-disturbance landscape will exclude the use of many freshwater vegetation species for reclamation. Successful reclamation will require plants to grow and accumulate peat despite elevated salinity. We evaluated the potential of salt-tolerant plants to accumulate peat by integrating plant production and decomposition rates in natural and oil sands wetlands across a salinity gradient. These wetlands were dominated by marsh-like vegetation with relatively rapid decomposition, especially of the belowground plant material. Aboveground production was high enough to compensate for rapid decomposition, resulting in mean annual organic matter accumulation of 307 g m^?2. Thus, both natural wetlands (which despite the elevated salinity had peat deposits >35 cm) and the oil sands wetlands accumulated organic matter during the study. There is potential for peat to accumulate in future oil sands wetlands, although long-term accumulation rates may be slower than in undisturbed freshwater fens and bogs. A reliable water supply and a host of other factors will be required for wetlands to accumulate organic matter, and eventually peat, in the post-mining landscape.