Mean Annual Biomass Research Articles

Five‐year field trial of the biomass productivity and water input response of cactus pear (Opuntia spp.) as a bioenergy feedstock for arid lands

AbstractClimate‐resilient and highly water‐use efficient crops are needed to meet the future food, feed, fiber, and fuel demands of a growing human population. Cactus pear (Opuntia spp.) are highly productive yet have crop water demands that are approximately 20% that of traditional crops due to their ability to perform crassulacean acid metabolism (CAM). In the first long‐term field trial of Opuntia for bioenergy in the United States, the aboveground biomass (cladode and fruit) productivity and response to different water inputs of O. cochenillifera, O. ficus‐indica, and O. streptacantha were evaluated at a planting density of 1418 plants ha−1 under three irrigation levels over a 5‐year period to investigate their response to different water inputs. Mean cladode fresh weight, cladode dry weight, cladode count, fruit fresh weight, and fruit dry weight increased linearly by 1.26‐, 1.88‐, 1.53‐, 1.89‐, and 2.13‐fold, respectively, with increasing irrigation from 300 to 716 mm year−1. Significant differences in irrigation response appeared in years 4 and 5 as the cactus trees grew larger. However, no significant differences were observed among the three Opuntia spp. for all parameters measured. Biomass productivity increased over 5 years by 140.8‐ and 132.5‐fold for cladode fresh and dry weight, respectively. Mean annual total aboveground biomass at 300, 407, and 716 mm year−1 water input resulted in 8.25, 11.16, and 15.52 Mg dry mass ha−1 year−1, respectively, at the sparse planting density used here to separate irrigation blocks, which could have been easily quadrupled. O. ficus‐indica performed better than O. cochenillifera and O. streptacantha in terms of cladode biomass and fruit count and quality. Biomass productivity was consistent with previous studies for Opuntia spp. demonstrating that cactus pear displays very high biomass and food/forage potential using substantially lower rates of supplemental irrigation than conventional crops grown in semi‐arid and arid regions.

Composition, biomass and secondary production of the macrobenthic invertebrate assemblage in a mangrove forest in Nayband Bay, Persian Gulf

Nayband Bay is a unique protected area located on the Iranian coast of the Persian Gulf. The bay supports a diverse macrobenthic assemblage; studying the biomass and secondary production of such a habitat can offer insights into the ecosystem’s patterns and processes. In total, 18 benthic sampling sites were taken from six sites along the bay between May 2016 and February 2017. Macrozoobenthos assemblages comprised 60 taxa; among them, gastropods accounted for much of the overall biomass and secondary production. The mean annual biomass of macrobenthos was found to be 1974.68 mg AFDW m−2, while the secondary production was 8.04 mg m−2 y−1. Secondary production values appeared to increase during winter (14.21 mg m−2 day−1) and decrease in spring (4.59 mg m−2 day−1); such seasonal differences were primarily dependent on the presence of different groups of macrobenthos. The annual mean production-to-biomass (P/B) ratio was 6.93, a value that increased from cold seasons to warm seasons. This means that in summer and spring, polychaetes (with smaller species) were the dominant group of macrobenthos. Conversely, in winter, gastropods and crustaceans (with large species) were the dominant group and increased macrobenthic production. High temperature and drought were the main reasons for the decreased density of macrobenthos during the warm seasons. However, a significant reduction in the abundance of macrobenthos was also observed in areas where road construction prevented direct contact between the mangrove trees and the marine tidal system. This could explain the deficient levels of biomass and secondary production among the macrobenthos groups in the area. The results of this study indicate that human activities, like construction, in mangrove forests can reduce both the density of macrobenthos and their rates of secondary production. Therefore, proper management is essential to sustainable anthropogenic development in mangrove forests.

Meiofauna in stream habitats: temporal dynamics of abundance, biomass and secondary production in different substrate microhabitats in a first-order stream

Meiofaunal abundance, biomass and secondary production were investigated over 13 months in an unpolluted first-order stream. Four microhabitats were considered: sediment and the biofilms on dead wood, macrophytes and leaf litter. The relative contribution of the microhabitats to secondary production and the influence of environmental factors on meiofaunal density distribution were estimated. We expected (1) meiofaunal abundance and biomass to exhibit seasonal patterns, with more pronounced seasonal fluctuations on macrophytes and leaf litter than in the other microhabitats, (2) annual secondary production to be highest in sediment; however, the relative contribution of the microhabitats to monthly secondary production would change during the year, and (3) a bottom-up driven influence on meiofaunal density distribution in the microhabitats. Meiofaunal annual mean abundance, biomass and secondary production were 7–14 times higher in sediment and on dead wood than on macrophytes and leaf litter. Significant seasonal patterns described the meiofaunal abundance in sediment and on leaf litter as well as the biomass in sediment, on macrophytes and leaf litter. Organisms in sediment and on dead wood contributed 48 and 43%, respectively, to secondary production m−2, but in regard to the stream area covered by the microhabitats, sediment had the highest share (80%). Significant determinants of the density distribution were AFDM, protozoans, bacteria and Chl-a, which influenced all meiofaunal groups. Our study clearly indicates that meiofaunal organisms in sediment and on dead wood have a remarkable share on total secondary production of lotic systems which is especially relevant for forested low-order streams.

Shut down of the South American summer monsoon during the penultimate glacial

We analysed changes in mean annual air temperature (MAAT), vegetation and biomass burning on a long and continuous lake-peat sediment record from the Colônia basin, southeastern Brazil, examining the responses of a wet tropical rainforest over the last 180 ka. Stronger southern atmospheric circulation up to the latitude of Colônia was found for the penultimate glacial with lower temperatures than during the last glacial, while strengthening of the South American summer monsoon (SASM) circulation started during the last interglacial and progressively enhanced a longer wet summer season from 95 ka until the present. Past MAAT variations and fire history were possibly modulated by eccentricity, although with signatures which differ in average and in amplitude between the last 180 ka. Vegetation responses were driven by the interplay between the SASM and southern circulation linked to Antarctic ice volume, inferred by the presence of a cool mixed evergreen forest from 180 to 45 ka progressively replaced by a rainforest. We report cooler temperatures during the marine isotope stage 3 (MIS 3: 57-29 ka) than during the Last Glacial Maximum (LGM: 23–19 ka). Our findings show that tropical forest dynamics display different patterns than mid-latitude during the last 180 ka.

Temporal variations in litterfall biomass input and nutrient return under long-term prescribed burning in a wet sclerophyll forest, Queensland, Australia

Litterfall helps maintaining nutrient return in forest ecosystems. However, the influence of long-term prescribed burning on the dynamics of litterfall biomass and carbon (C) and nitrogen (N) cycling is poorly understood. A 39-year old prescribed burning field trial in a wet sclerophyll forest, southeast Queensland, Australia, was used to investigate the interactive effects of prescribed fire regimes and temporal variation on the quantity and quality of litterfall and C and N return. Treatments included no burning (NB) since 1969, 2 yearly burning (2yrB; burned 19 times) and 4 yearly burning (4yrB; burned 9 times) since 1972. Litterfall was collected monthly on 32 occasions between 2011 and 2013. Significant temporal variation was observed in monthly and annual litterfall biomass. Both burning treatments had lower monthly inputs of total litterfall and leaf litter, mean annual cumulative litter biomass, litter C concentrations and C return via leaf litter, compared with the NB treatment. Most significant reductions in litter N concentrations and N return via litter were associated with 2yrB treatment. The 4yrB and the NB treatments did not differ significantly in terms of twig biomass, litterfall C:N ratios and N return via leaf litter. Despite both long-term prescribed burning treatments negatively impacting C return to the soil by reducing the quantity and quality of litter inputs, previous studies at the site suggest no difference in 0–10 cm soil organic carbon levels between the 4yrB treatment and the unburnt treatment. Hence a longer period of prescribed burning at the 4yrB frequency is likely required before lower C return translates to differences in ecosystem productivity in this wet sclerophyll forest ecosystem. The 2yrB can potentially alter forest C and N cycling and net primary productivity, but these alterations are unlikely to be detected through short-term studies.

Planktivorous fish predation masks anthropogenic disturbances on decadal trends in zooplankton biomass and body size structure in Lake Biwa, Japan

AbstractPelagic zooplankton samples from Lake Biwa, Japan, collected monthly since 1971, were analyzed for biomass and body size structure. Our aim was to clarify the relative effects of food availability and global warming vs. top‐down control by fish predation on long‐term trends. Annual mean biomass and density‐weighted body size were calculated and compared with water temperature, total phosphorus (TP), as a proxy of food amount, and catch per unit effort (CPUE) of Ayu (Plecoglossus altivelis altivelis), as a proxy of planktivorous fish predation pressure. Mean water temperature above 20 m increased by 0.94°C. TP increased until 1974 and then decreased until 1985, becoming stable after that. Ayu CPUE increased until 1987 and then declined. The study period can be divided into two nutritional phases: a high TP phase (1971–1985) and a low‐stable TP phase (1986–2010). Five zooplankton taxa, Eodiaptomus japonicus, Cyclopoida spp., Daphnia spp., Bosmina longirostris, and Diaphanosoma orientalis, were continuously dominant. Annual mean total crustacean biomass varied from 0.3 to 3.6 g dry weight m−2, slightly decreasing until 1993 but increasing thereafter. Generalized linear models showed that annual mean body sizes were affected by temperature and CPUE, whereas annual mean biomass was affected by TP and CPUE. These had no effect during the high TP phase, whereas only CPUE affected both traits during the low‐stable TP phase. We concluded that zooplankton biomass and body size long‐term trends were mostly influenced by fish predation and that eutrophication and global warming impacts might be affected by top‐down control.

Designer Biochars Impact on Corn Grain Yields, Biomass Production, and Fertility Properties of a Highly-Weathered Ultisol

There are mixed reports for biochars’ ability to increase corn grain and biomass yields. The objectives of this experiment were to conduct a three-year corn (Zea mays L.) grain and biomass production evaluation to determine soil fertility characteristics after designer biochars were applied to a highly weathered Ultisol. The amendments, which consisted of biochars and compost, were produced from 100% pine chips (PC); 100% poultry litter (PL); PC:PL 2:1 blend; PC mixed 2:1 with raw switchgrass (Panicum virgatum; rSG) compost; and 100% rSG compost. All treatments were applied at 30,000 kg/ha to a Goldsboro loam sandy (Fine-loamy, siliceous, sub-active, thermic Aquic Paleudult). Annual topsoil samples were collected in 5-cm depth increments (0 to 15-cm deep) and pH was measured along with Mehlich 1 phosphorus (M1 P) and potassium (M1 K) contents. After three years of corn production, there was no significant improvement in the annual mean corn grain or biomass yields. Biochar, which was applied from PL and PC:PL 2:1 blend, significantly increased M1 P and M1 K concentrations down to 10-cm deep, while the other biochar and compost treatments showed mixed results when the soil pH was modified. Our results demonstrated that designer biochar additions did not accompany higher corn grain and biomass productivity.

Changes in the phytoplankton community structure of the Backshore Wetland of Expo Garden, Shanghai from 2009 to 2010

Phytoplankton community structure, abundance, and species' spatial and temporal distributions were examined for the Backshore Wetland of Expo Garden in Shanghai from September 2009 to August 2010. A total of 371 phytoplankton species were identified from 109 genera 8 phyla. There were 18 dominant species in total, and Phormidium tenue was dominant during four seasons. The mean annual abundance and biomass were 711.11 × 104 cells/L and 5.70 mg/L, respectively. The seasonal changing trend of existing stocks was bimodal, with main peaks of density and biomass occurring in the winter and a secondary peaks occurring in the summer. The Shannon–Wiener diversity index (H′), the Margalef species richness index (D), and Pielou's species evenness index (J) showed a clear seasonal trend. All of the indices showed a changing pattern, with the highest recorded values from the summer to autumn and the lowest recorded values from the winter to spring. The canonical correspondence analysis (CCA) showed that environmental factors, including water temperature, nitrate nitrogen, and pH were the main influencing factors to the change of phytoplankton community structure in the Backshore Wetland of Expo Garden in Shanghai.

Status of Mysis diluviana in Lake Ontario in 2013: Lower abundance but higher fecundity than in the 1990s

Abstract Mysis diluviana is a major component of prey fish diets in the Great Lakes, so annual production of M. diluviana is important for understanding and modeling energy flow through Great Lakes food webs. However, only three lake-wide measurements of M. diluviana annual production in Lake Ontario are currently available (1971, 1990, 1995). During 2013, lake-wide coverage of Lake Ontario was achieved during four periods from April to November. Annual mean density and biomass of M. diluviana in 2013 were 99 #/m2 (SE: 8) and 318 mg dw/m2 (SE: 28) – approximately half of values observed in 1990s. M. diluviana comprised 13–30% of offshore zooplankton biomass in each period. Reproduction peaked in fall, with mean brood size of 32 embryos (range: 11–49), at least 10% larger than in 1990s. Generation time was two years from embryo to initial reproduction. Growth rates were 0.052 mm/d for the age-0 cohort and 0.027 mm/d for the age-1 cohort. Age-0 growth rate was significantly higher than in 1980s–90s (0.035 mm/d). Annual production in 2013 was 0.85 g dw/m2/yr (SE: 0.03) which was 30–40% of values observed in 1990 and 1995 (2.23 and 2.53 g/m2/yr). Annual production to biomass ratio (P/B) in 2013 was 2.65 /yr which was 80–85% of values observed in 1990 and 1995 (3.24 and 3.11 /yr), but this difference was not statistically significant. Our results suggest that changes in annual production over time can be estimated using changes in biomass over time and a mean P/B ratio.

Intertidal clams exhibit population synchrony across spatial and temporal scales.

Long‐term datasets can be particularly useful for parsing out factors influencing populations, yet few studies have utilized continuous datasets to quantify population dynamics in bivalve molluscs. We used dynamic factor analysis on a clam biomass dataset spanning 28 yr and five distinct regions in the southern Salish Sea to determine (1) if native intertidal clam populations exhibit synchrony and (2) what environmental covariates may be correlated with these population trends. Once covariates were accounted for, the model with the most data support included three predominant trends to describe multidecadal change in clam biomass. Intraspecific synchrony was highest among Saxidomus gigantea and Leukoma staminea populations, with no clear evidence of covariance in Clinocardium nuttallii. Specifically, we quantified a pronounced decadal decline in L. staminea and an increase in S. gigantea biomass on most beaches. No beaches showed synchrony in trends across all three species, indicating that species‐specific trends (regardless of location) were more common than beach‐specific trends (regardless of species). Seven environmental covariates were evaluated in their capacity to explain variability in annual mean biomass. Of these, the North Pacific Gyre Oscillation lagged 4 yr prior to the observation year was most supported by the data in the best fitting model, implying that 4 yr old clam biomass is partially determined by oceanographic processes affecting larval clams. Although results suggest large‐scale density‐independent factors play a role in venerid clam population dynamics, it is also likely local factors account for variability not explained by our model.

Ecological envelope maps and stand production of eucalyptus plantations and naturally regenerated maritime pine stands in the central inland of Portugal

Eucalyptus and maritime pine forests provide most of the wood harvested in Portugal. Due mainly to forest fires maritime pine forest has been converted to eucalyptus plantations. In the central inland of Portugal these species are well represented, and their productivities are quite the same. The objectives of the study were: (1) to assess average wood volume, biomass production and carbon content of eucalyptus plantations and naturally regenerated maritime pine stands; (2) to evaluate biomass nutrients concentration of eucalyptus sprouts selection and maritime pine non-commercial thinning; (3) to analyse these forests cover change in relation to the annual burnt areas; and (4) to produce the species ecological envelope maps to foresee future environmental impacts of these forests current distribution. Simulation models were used to assess wood volume, biomass production and carbon content. Field data was collected to evaluate biomass nutrients concentration and to validated simulated data. Forest inventory data and forest cover maps were used to analyse forest cover change. Biogeographical variables were used to produce species ecological envelope maps. It was found that eucalyptus plantations provide higher mean annual wood volume, biomass production and carbon content. Biomass nutrients concentration in eucalyptus sprouts selection were higher than in maritime pine non-commercial thinning, particularly in calcium and potassium. Overall eucalyptus forests area did not increase substantially but the fires in maritime pine forests gave the opportunity for eucalyptus afforestation. That has precluded the opportunity for introducing native broadleaves to respond to climate changes, improve landscape biodiversity and mitigate fire hazard. Implementing good management practices to prevent losses of soil fertility by nutrients exhaustion, organic matter depletion or erosion were found more relevant in eucalyptus plantations than in naturally maritime pine forest. Species ecological envelope maps and production simulation models are key tools for supporting decision in afforestation planning.

First-rotation growth and stand structure dynamics of tree species in organic and conventional short-rotation agroforestry systems

Short-rotation agroforestry systems can potentially maintain agricultural production and promote conservation of soil and biodiversity, especially if grown organically. Hereby, species-specific stand growth determines woody biomass yield and influences management decisions like planting density and harvest requirements. Studies of longer-term growth dynamics in Southern Germany are scarce and none analyzed differences between conventional and organic systems. In this study, four tree species (black alder, black locust, poplar clone Max 3, and willow clone Inger) were planted in an alley-cropping configuration in Southern Germany, grown under organic and conventional systems, and monitored from 2009 to 2012. Growth was assessed with stem base diameter, height, aboveground woody biomass, sprouting, and survival. The tree species did not show a uniform ranking in biometric variables and biomass over time. Four-year mean annual biomass increment (MAI) ranged from 7 to 10 t ha−1 a−1, with poplar and locust having the highest growth rates. Willow had the lowest MAI, as it had a low diameter growth paired with a low wood density, but it developed the highest number of shoots because of increased sprouting in the last year. Size inequality and skewness of the dominant stems increased for all species throughout the years suggesting asymmetric competition. Size inequality as well as mortality was greatest for black locust. Furthermore this was the only species, which developed a right skewed SBD distribution and the highest diameter size range. Size inequality was smallest for poplar and willow, with no or only minimal mortality. Alder was inbetween. For black locust and alder no difference in growth traits between organic and conventional systems appeared after four years. Organic poplar and willow stands performed better than conventional ones after the second year, leaving unclear whether this can be attributed to management or site effect.

Economic assessment of Eucalyptus globulus short rotation energy crops under contrasting silvicultural intensities on marginal agricultural land

Evolving bioenergy markets requires consideration of marginal lands for woody biomass production worldwide. Growing short rotation woody crops for bioenergy (SRWCs) on marginal land minimizes concerns about using croplands for agricultural production and reinforces sustainability of wood supply. Evaluation of the profitability of marginal land that may have SRWCs potential as sources of biomass for energy production has been rarely reported. This study attempts to account for investments uncertainties on SRWCs production considering Eucalyptus globulus managed under contrasting silvicultural intensities on marginal land by comparing four environments and four levels of initial planting density. Our study consider biomass yields over this gradient of productivity and biomass market prices and costs from local contractors. We estimated mean annual aboveground dry biomass increments (MAIs) and evaluated the economic feasibility of various cycles of harvest (2–6 years) using Monte Carlo simulation to examine how uncertainty over the input variables affects NPV of SRWCs. MAIs that ranged 3.91–18.07 Mg ha−1 yr−1 increased with stand density and harvesting age. Rotation length affected economic outcomes although the returns were poor due to high establishment and maintenance costs, low productivities and low biomass prices. Under an average scenario, current market price of biomass, absence of subsidies and current costs, SRWC are not profitable when productivities are lower than 351 m3 ha−1 of green biomass.

Effects of livestock grazing on key vegetation attributes of a remnant forest reserve: The case of Desa'a Forest in northern Ethiopia

The study was conducted in Desa'a Forest with the objective of investigating livestock-forest interaction. This study also evaluated the grazing pressure on Desa'a Forests from livestock, the potential of forests biomass feed production and current livestock density relation to the sustainable stocking rate. Data on socio-economic and community perception about livestock-forest interaction were collected through structured questionnaire on 90 households. To determine the species composition, abundance, density and diversity of woody plants, using stratified random sampling, four transect lines were laid out in east, west, north and south direction. Accordingly, the results are representative of Desa'a Forest. In the study area, 90% of the respondents (81 households) entered their livestock into Desa'a Forest and only 10% of the respondents (9 households) did not use Desa'a Forest. A total of 63 woody plant species were identified in the study area. According to farmers and pastoralists' opinion, 49.15%, 15.25%, 28.81% and 6.79% of woody species were identified as highly palatable, palatable, less palatable and unpalatable respectively. The mean herbaceous biomass production in Desa'a Forest is 1255.86 kg/ha. The predicted mean annual browse biomass production was 3000.72 kg/ha. The potential stocking rates for Desa'a Forest were 68480.39 TLU/year obtained based on the amount of fodder available to the livestock in the forest. The available potential browsing unit per hectare in the centre, North-West direction and south-east direction was 1432.66 BU/ha, 665.83 BU/ha and 203.66 BU/ha, respectively. Only 5.65% of the total surveyed households practice forage development which are the key to overcome feed shortage and decrease the pressure from the forest.

Novel climates reverse carbon uptake of atmospherically dependent epiphytes: Climatic constraints on the iconic boreal forest lichen Evernia mesomorpha.

Changing climates are expected to affect the abundance and distribution of global vegetation, especially plants and lichens with an epiphytic lifestyle and direct exposure to atmospheric variation. The study of epiphytes could improve understanding of biological responses to climatic changes, but only if the conditions that elicit physiological performance changes are clearly defined. We evaluated individual growth performance of the epiphytic lichen Evernia mesomorpha, an iconic boreal forest indicator species, in the first year of a decade-long experiment featuring whole-ecosystem warming and drying. Field experimental enclosures were located near the southern edge of the species' range. Mean annual biomass growth of Evernia significantly declined 6 percentage points for every +1°C of experimental warming after accounting for interactions with atmospheric drying. Mean annual biomass growth was 14% in ambient treatments, 2% in unheated control treatments, and -9% to -19% (decreases) in energy-added treatments ranging from +2.25 to +9.00°C above ambient temperatures. Warming-induced biomass losses among persistent individuals were suggestive evidence of an extinction debt that could precede further local mortality events. Changing patterns of warming and drying would decrease or reverse Evernia growth at its southern range margins, with potential consequences for the maintenance of local and regional populations. Negative carbon balances among persisting individuals could physiologically commit these epiphytes to local extinction. Our findings illuminate the processes underlying local extinctions of epiphytes and suggest broader consequences for range shrinkage if dispersal and recruitment rates cannot keep pace.

Effects of Warming and Precipitation Manipulation on Fine Root Dynamics of Pinus densiflora Sieb. et Zucc. Seedlings

Air warming (TC: control; TW: +3 °C) and precipitation manipulation (PC: control; PD: −30%; PI: +30%) were established to examine effects of these treatments on fine root production (FRP), fine root mortality (FRM), and total root (coarse and fine root) biomass in 33- to 59-month-old Pinus densiflora Sieb. et Zucc. seedlings for two years. We hypothesized that warming and altered precipitation would affect the growth, death, and biomass of fine roots by changing soil temperature and soil water availability. Mean annual FRP and total root biomass were significantly altered by only precipitation manipulation: they were 29.3% (during the two-year period) and 69.0% (after the entire two years) higher, respectively, in PD plots than in PC plots, respectively. In contrast, only warming had a significant effect on mean annual FRM, being 13.2% lower in TW plots than TC plots during the two-year period. Meanwhile, fine root biomass was affected negatively and simultaneously by both soil temperature and soil moisture. It seemed that fine root dynamics have changed so that they maintain their systems in response to the altered soil temperature and moisture. The current study adds significant knowledge for understanding the fine root dynamics of P. densiflora seedlings under altered temperature and precipitation regimes.

Fine root production and turnover of Pinus massoniana and their influencing factors in the Three Gorges Reservoir Area, China

In this study, the annual production and turnover rate of fine root of Pinus massoniana in Three Gorges Reservoir Area were calculated using sequential soil core,litterbag and compartment flux model methods, and the relationship between fine root production, turnover rate and factors was analyzed. The results showed that the annual mean biomass of <0.5, 0.5-1 and 1-2 mm fine root was 0.29, 0.59 and 0.76 t·hm-2, annual production was 0.13, 0.49, 0.37 t·hm-2, and annual turnover rate was 1.49, 1.01, 0.40 a-1, respectively. The effects of factors on production and turnover of fine roots with different diameters were different. Soil temperature and soil Ca content had significant effects on production and turnover of <0.5 mm fine roots, and soil temperature explained the variation of production and turnover by 32.8% and 25.0%, and soil Ca content explained by 65.6% and 73.1%, respectively. There was a positive relationship between fine root biomass and fine root production, and the biomass of fine root explained 41.0%, 41.1% and 54.5% of variation in fine root production for <0.5, 0.5-1 and 1-2 mm fine roots, respectively. P and K contents of fine roots correlated significantly with <0.5 mm fine root production, and explained 32.2% and 39.2% of the variation of <0.5 mm fine root production, respectively. The fine root with diameter <0.5 mm was most closely associated with soil factors, and soil temperature and soil Ca content were the main factors affecting fine root biomass.

Size-dependent responses of zooplankton to submerged macrophyte restoration in a subtropical shallow lake

To explore the size-dependent responses of zooplankton to submerged macrophyte restoration, we collected macrophyte, zooplankton and water quality samples seasonally from a subtropical shallow lake from 2010 to 2012. Special attention was given to changes in rotifers and crustaceans (cladocerans and copepods). The rotifers were grouped into three size classes ( 400 μm) to explore their size-related responses to macrophyte restoration. The results showed that during the restoration, the annual mean biomass and macrophyte coverage increased significantly from 0 to 637 g/m2 and 0 to 27%, respectively. In response, the density and biomass of crustaceans and the crustacean-to-rotifer ratio increased significantly, while the rotifer density decreased significantly. Moreover, rotifers showed significant sizedependent responses to macrophyte restoration. Specially, rotifers < 400 μm were significantly suppressed, while those ≥ 400 μm were significantly encouraged. Overall, the population of large-sized zooplankton tended to boom, while that of small rotifers was inhibited during macrophyte restoration. Redundancy analysis (RDA) revealed positive correlations between macrophytes and crustaceans, rotifers and COD or Chl-a, but negative correlations between macrophytes and COD or Chl-a, and between crustaceans and Chl-a. Moreover, the results indicate that increased predation on phytoplankton by large-sized zooplankton might be an important mechanism for macrophyte restoration during development of aquatic ecosystems, and that this mechanism played a very important role in promoting the formation of a clear-water state in subtropical shallow lakes.

Population and production parameters of the wedge clam Donax trunculus (Linnaeus, 1758) in intertidal areas on the southwest Spanish coast: Considerations in relation to protected areas

The main objectives of this study were (i) to provide an updated age-length key for D. trunculus from Atlantic waters, and (ii) to evaluate population dynamics, the timing of recruitment and production parameters of the wedge clam Donax trunculus in two moderately exposed sandy beaches (the protected area of Doñana National Park and the tourist destination of Isla Canela) along the littoral of Huelva (SW Spain). First an in-depth analysis of the shell and updated estimation of growth parameters of the intertidal D. trunculus population were performed between January 2014 and July 2015 using two different methods i) thin-layer cross section (TL) (ii) length-frequency distributions (LFD). Von Bertalanffy growth functions provided an asymptotic length of 46mm (LFD) and 46.7mm (TL) and growth constants of 0.48 (LFD) and 0.47yr−1 (TL) in Doñana beach. In addition, several deformities as well as signs of shell repair were observed. Population dynamics analyses through length-frequency distribution clarified the timing of recruitment (February–March and July). The mean annual biomass (B¯) of intertidal populations of D. trunculus ranged between 3.03 (Doñana) and 3.31g ash-free dry mass (AFDW) m−2yr−1 (Isla Canela). Individual production showed the highest value at 27mm length (0.117gAFDWm−2yr−1) and annual production (P) ranged between 3.40 (Doñana) and 4.91g (Isla Canela), resulting in renewal rate (P/B¯) values between 1.03 and 1.61, respectively. The present results, together with information on environmental parameters, revealed clear differences in population dynamics and production between beaches related to the presence or absence of a protection figure.

Estimating the spatial distribution, extent and potential lignocellulosic biomass supply of Trees Outside Forests in Baden-Wuerttemberg using airborne LiDAR and OpenStreetMap data

Trees Outside Forests (TOF) represent a source of lignocellulosic biomass that has received increasing attention in the recent years. While some studies have already investigated the potential of TOF in Germany, a spatial explicit analysis, specifically for Baden-Wuerttemberg, is still lacking. We used a unique wall-to-wall airborne Light Detection and Ranging (LiDAR) dataset combined with OpenStreetMap (OSM) data to map and classify TOF of the federal state of Baden-Wuerttemberg (∼35.000km2) in south-western Germany. Furthermore, from annual biomass potentials of TOF areas collected from available literature, we calculated the mean annual biomass supply for all TOF areas in Baden-Wuerttemberg. This combination of remote sensing-based classification and available literature resulted in a mean annual biomass supply between ∼490,000–730,000t from TOF in Baden-Wuerttemberg. The classification congruence on three reference sites was very high (∼99%) using a simple filter technique applied to the LiDAR data and masking man-made objects using OSM data. In contrast, the available literature revealed a high variability of biomass potentials, supporting the demand for an inventory system. Still, the results demonstrate the applicability of LiDAR based vegetation mapping and the value of OSM data in Baden-Wuerttemberg to detect man-made objects.