bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of wildfire ash on water chemistry and biota in South‐Western U.S.A. streams
Authors: Earl Stevan R. , Blinn Dean W.
Published: May 2003

1. We monitored streams within the Gila River drainage in south‐western New Mexico, U.S.A., over a 5‐year period, to investigate the influence of ash input on water quality and stream biota following forest wildfires.

2. Nutrients [ammonium, nitrate, soluble reactive phosphate (SRP)], potassium and alkalinity were most affected by fires; all were increased in stream water following ash input. Concentrations of each returned to prefire conditions within 4 months. Ammonium and nitrate also increased in stream water as a result of atmospheric fallout (e.g. smoke) from fires outside the catchment.

3. Periphyton biomass was not affected significantly by wildfires, although there was a shift in diatom assemblage to smaller more adnate taxa. Cocconeis placentula was frequently the dominant postfire species.

4. The influence of wildfires on macroinvertebrates ranged from minimal to dramatic reductions in density depending upon the duration of ash flows and the characteristics of the ash material that entered each system. Macroinvertebrate densities returned to prefire conditions within 1 year.

5. An in‐situ ashing experiment was conducted on a first‐order stream in the Gila River drainage to monitor on‐site physiochemical and biotic responses during and after fire ash addition, for comparison with ash delivery from real wildfires on monitored streams. Physical–chemical parameters and algae and macroinvertebrates were monitored in an ashed and upstream reference reach for 13 months. Results generally substantiated findings from monitored streams.

6. Concentrations of major ions and nutrients, as well as turbidity, conductivity and pH, increased immediately in stream water below the point of ashing, while dissolved oxygen decreased. Changes in water chemistry were short‐lived (=24 h) except for SRP. The concentration of SRP in stream water was significantly higher in the ashed reach than the control reach for at least 1 month after ash input.

7. Periphyton biomass and diatom assemblages were not significantly altered in the ashing study, whereas macroinvertebrate density was measurably lower in the ashed reach for nearly a year. Macroinvertebrate drift was over 10‐fold greater in the ashed reach compared with the reference reach during ashing. Dissimilarity between macroinvertebrate communities in the reference and ashed reaches was significantly greater than variation within reaches for nearly a year.
Nutrient limitation of epilithic and epixylic biofilms in ten North American streams
Authors: Tank Jennifer L. , Dodds Walter K.
Published: May 2003

1. Nutrient diffusing substrata were used to determine the effect of added inorganic nitrogen (N) and phosphorus (P) on the development of epilithic and epixylic biofilms in 10 North American streams. Four treatments of diffusing substrata were used: Control (agar only), N addition (0.5 m NaNO3), P addition (0.5 m KH2PO4), and N + P combined (0.5 m NaNO3 + 0.5 m KH2PO4). Agar surfaces were covered with glass fibre filters (for epilithon) or discs of untreated white oak wood veneer (for epixylon).

2. We found that if algae showed significant response to nutrient addition, N limitation (either N alone or N with P) was the most frequent response both on GF/F filters and on wood. Despite the low dissolved nutrient concentrations in our study streams, more than a third of the streams did not show any response to N or P addition. In fact, P was never the sole limiting nutrient for algal biofilms in this study.

3. Nutrient addition influenced algal colonisation of inorganic versus organic substrata in different ways. The presence of other biofilm constituents (e.g. fungi or bacteria) may influence whether algal biomass on wood increased in response to nutrient addition. Algae on organic and inorganic substrata responded similarly to nutrient addition in only one stream.

4. Fungal biomass on wood was nutrient limited in six of 10 study streams. N limitation of fungal biomass (with or without secondary P limitation) was most frequent, but P limitation did occur in two streams.

5. Our results show that biomass responses to nutrient addition by the heterotrophic and autotrophic components of the epixylic biofilm were different, though both experienced the same stream nutrient conditions. For algae and fungi growing on wood, limiting nutrients were rarely similar. Only three of nine streams showed the same biomass response to nutrient addition, including two that showed no significant change in biomass despite added nutrients.
Predicting the impacts of an introduced species from its invasion history: an empirical approach applied to zebra mussel invasions
Authors: Ricciardi Anthony
Published: May 2003

1. Quantitative models of impact are lacking for the vast majority of known invasive species, particularly in aquatic ecosystems. Consequently, managers lack predictive tools to help them prioritise invasion threats and decide where they can most effectively allocate limited resources. Predictive tools would also enhance the accuracy of water quality assessments, so that impacts caused by an invader are not erroneously attributed to other anthropogenic stressors.

2. The invasion history of a species is a valuable guide for predicting the consequences of its introduction into a new environment. Regression analysis of data from multiple invaded sites can generate empirical models of impact, as is shown here for the zebra musselDreissena polymorpha.Dreissena's impacts on benthic invertebrate abundance and diversity follow predictable patterns that are robust across a range of habitat types and geographic regions. Similar empirical models could be developed for other invaders with a documented invasion history.

3. Because an invader's impact is correlated with its abundance, a surrogate model may be generated (when impact data are unavailable) by relating the invader's abundance to environmental variables. Such a model could help anticipate which habitats will be most affected by invasion. Lack of precision should not be a deterrent to developing predictive models where none exist. Crude predictions can be refined as additional data become available. Empirical modelling is a highly informative and inexpensive, but underused, approach in the management of aquatic invasive species.
Seasonal and diel patterns of invertebrate drift in different alpine stream types
Authors: Hieber Mäggi , Robinson Christopher T. , Uehlinger Urs
Published: May 2003

1. We examined the seasonal and diel patterns of invertebrate drift in relation to seston and various habitat characteristics in two each of four different kinds of alpine streams [rhithral (snow‐fed) lake outlets, rhithral streams, kryal (glacial‐fed) lake outlets and kryal streams]. Samples were collected at four times of the day (dawn, midday, dusk and midnight) during three seasons (spring, summer and autumn).

2. Habitat characteristics differed mainly between rhithral and kryal sites, with the latter having higher discharge and turbidity, lower water temperature, and higher concentrations of ammonium, and particulate and soluble reactive phosphorus. Seasonality in habitat characteristics was most pronounced for kryal streams with autumn samples being more similar to rhithral sites.

3. The concentration of seston was lowest in the glacial‐influenced lake outlets and slightly higher in the stream sites; no seasonal or diel patterns were evident.

4. The density of drifting invertebrates averaged less than 100 m−3 and was lowest (<10 m−3) at three of the four kryal sites. Taxon richness and diversity were lowest at rhithral lake outlets. Chironomidae dominated the drift as well as benthic communities and <30% of benthic taxa identified were found in the drift.

5. Drifting invertebrates showed no consistent seasonal pattern. However, density tended to be highest in spring at rhithral sites and in autumn at kryal sites. No diel periodicity in drift density was found at any site and the lack of diel pattern may be a general feature of high altitude streams.

6. Glacially influenced habitat parameters were a major factor affecting drift in these alpine streams, whereas no clear differences were observed between streams and lake outlets. Our findings indicate that invertebrate drift in alpine streams is primarily influenced by abiotic factors, and therefore, substantially differs from patterns observed at lower altitude.
Oviposition in three species of limnephiloid caddisflies (Trichoptera): hierarchical influences on site selection
Authors: Hoffmann A. , Resh V.H.
Published: May 2003

1. Oviposition site selection was studied in three trichopteran species; an undescribed species of Hydatophylax (Limnephilidae), Onocosmoecus unicolor (Limnephilidae) and Neophylax rickeri (Uenoidae), in two Coastal Range streams in California, U.S.A.

2. Hydatophylax sp. egg masses were generally found at or above the water surface on substrata near the bank in pools, where undercut banks, overhanging vegetation and rocks shaded attachment sites and provided wind protection. Onocosmoecus unicolor females deposited their egg masses exclusively above the water on moist emergent wood. The egg masses of N. rickeri were almost exclusively found in high velocity areas of riffles, where females oviposited under water and attached their egg masses to the submersed undersides of unembedded, protruding stones with large emergent surfaces.

3. For Hydatophylax sp. and N. rickeri, a hierarchical selection scheme is proposed in which females use cues at three different spatial levels (stream, stream subunit, substratum) to choose oviposition sites. Females of O. unicolor seemed to choose at only two different levels of spatial resolution (stream, substratum).

4. The formation of large aggregations of egg masses in N. rickeri and O. unicolor suggests that females actively choose oviposition sites where conspecific egg masses are already attached. The clustering of egg masses may minimise the risk of predation through the dilution effect, because egg masses of N. rickeri and O. unicolor are both attacked by dipteran predators.

5. Females of the three Trichoptera species studied are able to make a clear choice of oviposition site in the heterogeneous stream environment. In comparison with other stream microhabitats, these are characterised by stable and relatively predictable environmental conditions during the time of egg development, which is seen as the main selective pressure leading to the observed egg‐laying behaviour.
Can C4 plants contribute to aquatic food webs of subtropical streams?
Authors: Clapcott Joanne E. , Bunn Stuart E.
Published: May 2003

1. Recent stable isotope studies have revealed that C4 plants play a minor role in aquatic food webs, despite their often widespread distribution and production. We compared the breakdown of C3 (Eucalyptus) and C4 (Saccharum and Urochloa) plant litter in a small rain forest stream and used laboratory feeding experiments to determine their potential contribution to the aquatic food web.

2. All species of litter broke down at a fast rate in the stream, although Urochloa was significantly faster than Eucalyptus and Saccharum. This was consistent with the observed higher total organic nitrogen of Urochloa compared with the other two species.

3. The breakdown of Urochloa and Saccharum was, however, not associated with shredding invertebrates, which were poorly represented in leaf packs compared with the native Eucalyptus. The composition of the invertebrate fauna in packs of Urochloa quickly diverged from that of the other two species.

4. Feeding experiments using a common shredding aquatic insect Anisocentropus kirramus showed a distinct preference for Eucalyptus over both C4 species. Anisocentropus was observed to ingest C4 plant litter, particularly in the absence of other choices, and faecal material collected was clearly of C4 origin, as determined by stable isotope analysis. However, the stable carbon isotope values of the larvae did not shift away from their C3 signature in any of the feeding trials.

5. These data suggest that shredders avoid the consumption of C4 plants, in favour of native C3 species that appear to be of lower food quality (based on C : N ratios). Lower rates of consumption and lack of assimilation of C4 carbon also suggest that shredders may have a limited ability to process this material, even in the absence of alternative litter sources. Large scale clearing of forest and vegetation for C4 crops such as sugarcane will undoubtedly have important consequences for stream ecosystem function.
Effect of packaging cycle on the colour stability of six beef muscles stored in a modified atmosphere mother pack system with oxygen scavengers
Authors: Isdell Emer , Allen Paul , Doherty Alice , Butler Francis
Published: May 2003

The effect of two packaging cycles (double flush, 28 s; triple flush, 55 s) on the colour stability of beef in retail trays with oxygen scavengers within a mother pack (50% CO2/50% N2) was assessed. Steaks from six muscles, M. longissimus dorsi, M. psoas major, M. semimembranosus, M. gluteus medius, M. semitendinosus and M. biceps femoris, were examined. The residual oxygen in mother packs was unaffected by the packaging cycle and was below 0.1% in trays for both treatments for up to 6 weeks storage. After storage for 2, 4 or 6 weeks, the packaging cycle had no effect on colour stability (HunterLab a and hue) during 96 h of display. Panel scores for visual and odour acceptability of packaged steaks were generally as high as for fresh controls. Based on reflectance measurements (R630 –R580), M. longissimus dorsi and M. semitendinosus steaks had a display life of 4 days after storage for up to 6 weeks. M. psoas major and M. semimembranosus steaks had a display life as long as fresh controls after 4 weeks, whereas M. gluteus medius and M. biceps femoris steaks had a shorter display life than fresh steaks. It was concluded that the double‐flush cycle could be used without affecting the colour or acceptability of beefsteaks.
Effect of ethanol concentration on the efficiency of extraction of ginseng saponins when using a microwave‐assisted process (MAP™)
Authors: Kwon Joong‐Ho , Lee Gee‐Dong , Bélanger Jacqueline M. R. , Jocelyn Paré J. R.
Published: May 2003

Summary This research determined the effect of ethanol concentration (vol.%) on the extraction of saponins from ginseng using a microwave‐assisted process (MAPTM) at different powers under atmospheric pressure conditions. The optimized particle size of ginseng roots and mass‐to‐solvent volume ratio were 60 mesh and 1 : 10 (g mL−1), respectively. The yields of total solids and crude saponins were influenced by ethanol concentration, with the highest value at 45–60% for the former and 60–75% for the latter, at microwave power levels of 88 and 162 W. Their respective yield per unit time (60 s) was higher at 162 W than at 88 W; however, the extraction efficiency was lower for the former than for the latter. Extraction properties of ginsenosides were similar to those of crude saponins. The results show that the ethanol concentration was influential in MAP extraction of ginseng saponins and that total imparted energy and level of applied power should be considered in terms of extraction efficiency.
Changes in carotenoid, physicochemical and sensory values of deep‐fried carrot chips during storage
Authors: Sulaeman Ahmad , Keeler Laurie , Giraud David W. , Taylor Steve L. , Driskell Judy A.
Published: May 2003

Deep‐fried carrot chips were packaged in layered film (metallized polyester and linear low‐density polyethylene) pouches under a partial vacuum of <1% O2 concentration. Packages containing chips were stored in dark chambers at three conditions: 0–1 °C, 94–98% relative humidity (r.h.) (A); 22–23 °C, 31–45% r.h. (B); and 29–31 °C, 89–93% r.h. (C) for 0–5 months. Retention of α‐ and β‐carotene content and vitamin A activity were >82% over 5 months for all conditions. Colour values (L, a, b) were unchanged over 5 months for A and B, but decreased gradually (P < 0.05) for C. No changes in moisture content, fat content, water activity, texture values and sensory values were observed over time for A and B, but changed (P < 0.05) for C. No sensory differences were observed by condition or time in colour. Carrot chips, packaged in partially vacuumed opaque pouches, can be stored for at least 5 months at 0–1 °C, 94–98% r.h. or 22–23 °C, 31–45% r.h.
An analysis of water vapour diffusion in whey protein films
Authors: Yoshida Cristiana M. P. , Antunes Antonio C. B. , Antunes Leila J. , Antunes Aloísio J.
Published: May 2003

The macroscopic aspects of moisture transmission in whey protein films were determined by measuring water vapour adsorption. A theoretical model was constructed in which two kinds of water vapour fluxes were considered: one originating from diffusion, whilst the other was a flux due to the gravitation drift of moisture. The comparison of theoretical and experimental results showed that only the diffusion process was present.
Flavour components of orange wine made from a Turkish cv. Kozan
Authors: Selli Serkan , Cabaroglu Turgut , Canbas Ahmet
Published: May 2003

Volatile flavour components of a wine made from orange variety Kozan were isolated by adsorption on Amberlite XAD‐2 resin followed by extraction with pentane–dichloromethane (2 : 1, v/v), identification by GC‐MS and quantification by GC‐FID using an internal standard method. In the Kozan wine, seventy‐five volatile components, including terpenes (twenty), alcohols (sixteen), esters (eighteen), volatile phenols (eleven), acids (five), ketones (two), aldehyde (one), lactone (one) and C13‐norisoprenoid (one) were identified. Isoamyl alcohol, 2‐phenylethanol, linalool, terpinene‐4‐ol and ethyl‐4‐hydroxy butanoate were the main components. Considering their threshold values and the concentrations they are present in, the most potent aroma compounds of the orange wine were ethyl hexanoate, ethyl octanoate, linalool, citronellol, 2‐phenylethanol and eugenol.
The kinetic evaluation of the use of high hydrostatic pressure to destroy Lactobacillus plantarum and Lactobacillus brevis
Authors: Mallidis C. , Galiatsatou P. , Taoukis P. S. , Tassou C.
Published: May 2003

The kinetics (D and zp values) of the high‐pressure destruction of Lactobacillus plantarum and Lactobacillus brevis, isolated from traditional Greek salads, were determined. These two strains exhibited the highest pressure resistance of all bacteria and yeasts isolated from these products. Model suspensions of phosphate buffer (pH 7.0) or citrate buffer (pH 4.2) were used for high‐pressure inactivation. The D values ranged from 11 to 1160 s in a neutral environment and a pressure range of 530–400 MPa, and from 1.5 to 560 s in an acidic environment with a pressure range of 530–270 MPa. A significant reduction in the pressure resistance was observed by lowering the pH of the suspension medium, especially as the pressure became greater. The effect of pressure change on D values was pH dependent. Values of zp of 70 and 80 MPa for L. plantarum and 71 and 100 MPa for L. brevis were obtained in neutral and acidic environments, respectively.
Ethics in food and agriculture: views from FAO‡
Authors: Bhardwaj Minakshi , Maekawa Fumi , Niimura Yuki , Macer Darryl R. J.
Published: May 2003

This paper presents analysis of interviews conducted at the United Nations Food and Agricultural Organization (FAO) during June to August 1999, which reveal the concerns behind the development of the Ethics in Food and Agriculture Program at FAO. Formal interviews with 103 staff members of all positions and across all divisions of FAO, revealed that although ethics as a word was not widely and openly discussed at FAO until the end of the 1990s, as indicated by the nature of the programmes and policies, the members had deep ethical motivation for their work. The results of the keyword analysis of the interviews are presented under the general issues of food, rural development, information, genetic modification, private sector and funding, environment, animal issues and personnel matters. Most of the interviewed staff saw ethics as the basis of the constitutional mandate, with the role of FAO being to promote global food security, balanced conservation, management and utilization of natural resources, and sustainable rural development. Information dissemination, and the need for a participatory approach were also raised as major issues by a third of the people interviewed.
Cryoprotection of protein by highly concentrated branched oligosaccharides
Authors: Auh J. H. , Kim Y. R. , Cornillon P. , Yoon J. , Yoo S. H. , Park K. H.
Published: May 2003

Cryoprotection of protein by highly concentrated branched oligosaccharides (HBOS) was investigated by using a model solution containing bovine serum albumin (BSA). The glass transition temperature of the BSA solution with HBOS, determined by modulated differential scanning calorimetry, was −16.1 °C, which is higher than that of sucrose at either 4 or 8% concentration by weight (−27.2 °C). Also, changes in the unfrozen water fraction and their mobilities, determined by nuclear magnetic resonance, were used as indices of protein stabilization. The results revealed that the amount of unfrozen water increased whereas the mobility was decreased by addition of HBOS. Thus we propose that the cryoprotection effect can occur by preserving the protein in a rigid structure formed by the water and the cryoprotectant HBOS.
Shelf‐life modelling of ready‐to‐eat coconut
Authors: Sinigaglia Milena , Corbo Maria R. , D'Amato Daniela , Campaniello Daniela , Altieri Clelia
Published: May 2003

In this research the possible use of coconut as raw material to produce ready‐to‐eat fruit was investigated. The development of spoilage micro‐organisms in packaged cut coconut stored at 4, 12, 21 and 24 °C was monitored. Spoilage of minimally processed coconut was correlated with high levels of mesophilic bacteria and was strongly dependent on temperature; however the modified atmosphere, created by respiration of the fruit when contained under a film barrier, could be fundamental to the determination of the product's shelf‐life. The shelf‐life of the product was kinetically modelled in order to check the effects of storage temperature and to assess the microbial indices most relevant for hygiene and quality of the product. Our results suggest that mathematical modelling could allow manufactures to rely on more objective parameters to determine the shelf‐life of their products.
Technological characterization of lactic acid bacteria from Tenerife cheese
Authors: Pérez Graciela , Cardell Evaristo , Zárate Victoria
Published: May 2003

Summary One hundred and thirty lactic acid bacteria (Lactococcus, Lactobacillus and Leuconostoc), isolated from Tenerife cheese, were technologically characterized. Interesting differences within genera, species and strains were found. None of the strains showed lipolytic activity on tributyrin agar while the majority exhibited proteolytic activity on calcium caseinate agar. Citrate was metabolized exclusively by 98.3% of the lactobacilli isolates. Lactococcus lactis ssp. lactis showed the highest acidifying and proteolytic activities in milk, although considerable inter‐strain variations were found. Lactobacilli had the highest aminopeptidolytic activity. Dipeptidase activity was displayed by most lactic acid bacteria isolates with the higher specific activity exhibited by Lc. lactis ssp. lactis strains. Leuconostoc isolates had the highest esterolytic and β‐galactosidase activity.
The extension of the shelf‐life of sardine which were packaged in a vacuum stored under refrigeration, and treated by δ‐irradiation
Authors: Kasımoğlu Aylin , Denli Emine , İç Erhan
Published: May 2003

Sardines (Sardina pichardus) were vacuum packaged in polyethylene bags, and irradiated at 1, 2 and 3 kGy doses in a Co‐60 δ‐irradiator. The unirradiated and irradiated samples were stored at 2 ± 1 °C. Microbiological analyses were done for total aerobic mesophiles, micrococci and staphylococci, coagulase positive staphylococci,Enterobacteriaceae, coliform bacteria,Escherichia coli, and psychrophilic bacteria. Trimethylamine‐nitrogen (TMA‐N), thiobarbituric acid (TBA) and pH values were determined. Sensory attributes were also evaluated. In the unirradiated samples, TMA‐N and pH values showed good correlations with sensory scores. There were no differences in TBA values between the irradiated samples. Based on microbiological criteria, the shelf‐life increased two to threefold compared with the control samples. These experiments demonstrate that irradiation extends the storage life of pre‐packaged sardines and that, for practical purposes, the different treatments make very little difference to the extension of shelf‐life of acceptable product.
Evaluation of nutrients and some anti‐nutrients in lesser‐known, underutilized oilseeds
Authors: Enujiugha Victor N. , Ayodele‐Oni Olubunmi
Published: May 2003

The levels of anti‐nutritional factors and the chemical composition of five underutilized and not well known commercial oilseeds – castor bean, conophor nut, ‘egusi’ melon, African oil bean and locust bean – were determined. The crude protein values for the respective oilseeds were 201.8, 227.5, 314.1, 206.3 and 290.6 g kg−1 DM, whereas the crude fat values were 449.6, 491.8, 439.3, 522.8 and 261.9 g kg−1 DM respectively. The results show that oilseeds may be a good source of vegetable oils, whereas defatted cakes might be useful in food fortification or as animal feed ingredients. The crude fibre contents of oilseeds were found to be significant (31.4–90.6 g kg−1 DM), which suggests that consumption of oilseeds and their products would aid bowel functioning.

The seeds were found to contain high concentrations of phosphorus and potassium (2.6–4.6 and 3.9–6.5 g kg−1 DM, respectively); the low sodium content observed is in agreement with the generally low sodium encountered in unprocessed foods. The energy values of the seeds range from 4.1 Mcal kg−1 DM in locust bean to 5.9 Mcal kg−1 DM in conophor nut, which could be considered adequate for supplying useful amounts of calories.

Oxalates, phytates and tannins occurred in varying concentrations in the oilseeds. Whereas castor bean contained the highest level of oxalates (6.5 g kg−1 DM), the same seed was relatively low in its content of the other anti‐nutritional factors analysed. Phytic acid, phytate phosphorus and tannins had their highest values in African oil bean seed (4.1, 1.2 and 0.8 g kg−1 DM, respectively), which may be considered a major barrier to the use of the seed. However, it is expected that traditional methods employed in processing the seeds, namely hydrothermal treatment, soaking and fermentation, would considerably reduce the levels of the anti‐nutritional factors.
Effects of CO2 absorbent and high‐pressure treatment on the shelf‐life of packaged Kimchi products
Authors: Lee Joo W. , Cha Dong S. , Hwang Keum T. , Park Hyun J.
Published: May 2003

Summary The effects on extending the shelf‐life of commercial Kimchi products and preventing pouch inflation by absorbing CO2 with calcium hydroxide, were compared with a treatment using high‐hydrostatic pressure. The changes in the quality factors of Kimchi, such as CO2 accumulation in the headspace of the pouch, pH, total acidity and the microbial population of both total viable cells and lactic acid bacteria were measured during storage for 24 days at 10 °C. Pressurization at 400 and 600 MPa for 5 min at 20 °C were both effective in preventing inflation of the Kimchi pouches during storage at 10 °C, as was CO2 absorption at the level of 0.5 g CO2 absorbent per 80 g Kimchi.
Effects of extrusion conditions on quality of cassava bran/cassava starch extrudates
Authors: Hashimoto Jorge Minoru , Grossmann Maria Victoria E.
Published: May 2003

Blends of cassava bran and cassava starch were processed in a single‐screw extruder. Response surface methodology was used to determine the effect of the concentration of cassava bran (10–50%), barrel temperature (150–210 °C), feed moisture (16–20%) and screw speed (120–180 r.p.m.) on the characteristics of the dried extrudates. All the independent variables were significant (P < 0.05) for radial expansion. The water absorption index (WAI) and water solubility index (WSI) were affected by bran level, screw speed and temperature, while only moisture and temperature influenced specific volume. The maximum radial expansion was found when all the independent variables were at their lowest levels. Lowest‐density extrudates (highest specific volume) were obtained at 16–18% moisture and 180–200 °C. An increase in bran level increased the WAI but decreased the WSI when the temperature was higher than 170 °C . Screw speed had a slight effect on those responses, decreasing water absorption and increasing water solubility when changed from 120 to 180 r.p.m.
Influence of natural fermentation on physico‐chemical characteristics of rice noodles
Authors: Lu Zhan‐Hui , Li Li‐Te , Cao Wei , Li Zai‐Gui , Tatsumi Eizo
Published: May 2003

Summary The influence of fermentation of whole milled rice granules on the physico‐chemical characteristics of rice starch and the rheological properties of rice noodles was investigated. The rice granule samples were fermented at 35 °C for 27 h. The results indicated that fermentation did not have a significant effect on the starch and amylose content of rice granules. Protein, lipid and ash content decreased whereas free fatty acid increased during fermentation. The rice noodles made from fermented samples had a lower maximum stress, 54 kPa, and higher maximum strain, 10.8%, and had a white, transparent appearance and favourable chewy mouth‐feel compared with the control sample.
Root competition can cause a decline in diversity with increased productivity
Authors: Rajaniemi Tara K. , Allison Victoria J. , Goldberg Deborah E.
Published: May 2003

1 Plant community theory often invokes competition to explain why species diversity declines as productivity increases. Competition for all resources might become more intense and lead to greater competitive exclusion or, alternatively, competition for light only could become more intense and exclude poor light competitors.

2 To test these hypotheses, we constructed communities of seven old‐field species using combined monocultures. Constructs experienced no interspecific competition, only shoot competition or only root competition, with and without fertilizer. Diversity in these limited interaction communities was compared to diversity in unfertilized and fertilized mixtures of the seven species.

3 Diversity decreased with fertilization in mixtures and in communities with only root competition. Shoot competition had small effects on the community and did not contribute to changes in diversity with fertilization.

4 Root competition may strongly impact plant community structure in unproductive communities where light never becomes limiting, or under non‐equilibrium conditions following human disturbances.
Resprouting of the Mediterranean‐type shrub Erica australis with modified lignotuber carbohydrate content
Authors: Cruz Alberto , Pérez Beatriz , Moreno José M.
Published: May 2003

The vigour of plant resprouting after fire may be driven by the amount of stored non‐structural carbohydrates (NC). However, the extent to which NC reserves limit this response in woody plants has not been established.

This study analyses the effects of modifying NC concentrations in the lignotuberous Mediterranean‐type shrub Erica australis, on resprouting after experimental burning. A factorial experiment with two treatments (shade and burn) was carried out, with three levels per treatment. Plants were shaded (exposure to 100%, 50% or 20% of incident radiation for 1 year), following which they were clipped (control, no fire), or clipped and burned at one of two levels of severity. After this, they were allowed to resprout and grow for 2 years.

Shading modified NC concentrations in the lignotuber, but not in the roots. Two years after burning, plants subjected to the greatest shading, which reduced their NC concentrations to 44% (sum of NC) or 19% (starch) of that of control plants, had suffered higher mortality after resprouting, had a significantly lower number of resprouts, of shorter length, and had produced lower biomass per plant than less shaded or unshaded plants. However, plants subjected to intermediate shade, which suffered a reduction in NC concentrations to 70% of that of control plants, did not differ in resprouting response from control plants.

Burning caused more direct mortality, and a severe reduction in both number or biomass of resprouts, than just clipping. There were no significant shade × burning interaction effects.

While reductions in NC may limit resprouting, such limitation may only occur when NC is reduced to much lower concentrations than caused by commonly experienced conditions. The role of NC reserves in limiting resprouting of lignotuberous, woody plants such as E. australis might therefore not be as important as is commonly assumed.
Stimulated growth of Betula pubescens and Molinia caerulea on ombrotrophic bogs: role of high levels of atmospheric nitrogen deposition
Authors: Tomassen Hilde B. M. , Smolders Alfons J. P. , Lamers Leon P. M. , Roelofs Jan G. M.
Published: May 2003

1 In order to test whether the observed invasion of ombrotrophic bogs in the Netherlands by Molinia caerulea and Betula pubescens is the result of long‐term high nitrogen (N) loads, we conducted a 3‐year fertilization experiment with Sphagnum fallax turfs. Six different N treatments were applied ranging from 0 (control) to 4 g N m−2 year−1.

2 During the experimental period, ammonium concentrations in the peat moisture remained very low due to high uptake rates by Sphagnum. Tissue N concentrations in S. fallax showed a linear response to the experimental N addition. Excess N was accumulated as N‐rich free amino acids such as arginine, asparagine and glutamine, especially at N addition rates of 0.25 g m−2 year−1 or higher, indicating N‐saturation.

3 Despite the high tissue N : P ratio (above 35), above‐ground biomass production by Molinia was still stimulated at N addition rates of 4 g m−2 year−1, and foliar nutrient concentrations were unaffected compared to the control. In contrast to Molinia, Betula was unable to increase its above‐ground biomass. Foliar N concentrations in Betula were significantly higher at N addition rates of 4 g m−2 year−1 and excess N was stored in foliar arginine, making up 27% of the total N concentration. Evapotranspiration was increased at higher N addition rates due to stimulated total above‐ground biomass production of the vegetation.

4 N addition at the actual Dutch deposition rate of 4 g m−2 year−1 stimulated the growth of Molinia in this experiment, providing evidence that the observed dominance of Molinia on ombrotrophic bogs in the Netherlands is caused by high N deposition levels. Based on the observed changes in biomass production and tissue nutrient concentrations, we assume that a long‐term deposition of 0.5 g N m−2 year−1, or higher, leads to undesirable changes in species composition and increased risk of desiccation.
Dispersal and gene flow of Populus nigra (Salicaceae) along a dynamic river system
Authors: Imbert Eric , Lefèvre François
Published: May 2003

1 We used genetic markers to study gene flow of the riparian pioneer tree species Populus nigra along the Drôme river (France). This dioecious species is supposed to have more efficient dispersal mechanisms for pollen (wind) and seeds (wind and water) than other trees.

2 Seedlings belonging to the same reproduction/migration event were sampled in 22 riparian forest fragments along the river and their genetic diversity assessed through six nuclear microsatellites.

3 We found a high level of diversity and significant differentiation among populations. The significant isolation by distance allowed us to reject the infinite island model of migration.

4 Gene flow parameters were higher in the upper, mountainous part than in the alluvial plain downstream. There was no accumulation of diversity downstream, indicating migration rates were symmetrical upstream and downstream. This was confirmed by computing individual migration parameters between adjacent populations.

5 The results are discussed with regard to the dispersal mechanisms of seeds and pollen. The discrepancy between potential gene flow and effective gene flow is interpreted as an effect of fragmentation, due to the alteration of the natural dynamics of the riparian ecosystem rather than to physical barriers.
Effects of mineral and nutrient input on mire bio‐geochemistry in two geographical regions
Authors: Bragazza Luca , Gerdol Renato , Rydin Håkan
Published: May 2003

1 We assessed the role of climatic conditions and the effects of different, long‐term atmospheric depositions in controlling the mineral and nutrient contents in pore‐water, surface peat and in living Sphagna at a boreo‐nemoral mire in Sweden and an alpine mire in Italy.

2 The terrestrial contribution of Ca2+, Mg2+ and in bulk precipitation was much greater at the Italian mire, in accordance with the different bedrock in the region and the higher level of atmospheric pollution.

3 At both mires, the contribution of bulk precipitation to the concentration of major ions in mire pore‐water was much greater in the ombrotrophic than in the minerotrophic part, because of the raised morphology of the mires, which limited the inflow of mineral soil water to the margins. The only ions strongly depleted in mire pore‐water compared with precipitation were K+, and and these were therefore limiting to plant growth.

4 Higher concentration in pore‐water at the Swedish mire, which experienced lower atmospheric inputs of sulphate, was probably caused by oxidative processes during a long dry period in the summer before sampling.

5 Higher rates of , , as well as atmospheric inputs at the Italian mire were reflected in significantly higher N and, partly, S concentrations in ombrotrophic Sphagna. Higher concentration in pore‐water at the Italian mire was associated with a lower N retention coefficient of the ombrotrophic Sphagnum plants, suggesting a reduced nitrogen filtering ability of the moss layer.
High hybrid fitness at seed and seedling life history stages in Louisiana irises
Authors: Johnston Jill A. , Arnold Michael L. , Donovan Lisa A.
Published: May 2003

1 Relative fitness of hybrid genotypes will determine the role that hybrids can play in the evolution of a plant species complex. To realistically evaluate hybrid fitness and how environmental variation affects fitness in a long‐lived species, all life stages must be considered.

2 We evaluated germination, seedling survival and growth of two Louisiana iris species and their early generation hybrids in several experimental environments created by manipulating light and water levels.

3 Species and hybrids all required similar moist conditions for germination. The proportion of germinated seeds was highest in shade and seedling survival highest in sun.

4 Iris brevicaulisexhibited the lowest germination and seedling survival overall, yet those individuals that survived grew vigorously.Iris fulvahad high levels of germination and seedling survival, but yielded the smallest plants at the end of one season of growth.

5 Germination rates, seedling survival and seedling growth of hybrids equalled or exceeded one or both parent species, indicating that hybrids in this system have high relative fitness at seed and seedling stages in several environmental conditions.

6 We conclude thatIris fulvaandI. brevicaulisshare a common regeneration niche and similar early stage relative fitness with their hybrids. Thus, environment‐dependent fitness in this system is due primarily to selection at adult stages.
Diversity effects on production in different light and fertility environments: an experiment with communities of annual plants
Authors: Fridley Jason D.
Published: May 2003

1 Small‐scale plant species richness may enhance local production if the local environment promotes resource partitioning (a form of complementarity) or causes some species to perform better next to interspecific neighbours (facilitation) than when grown in monoculture. Little is known, however, about how species richness and environmental factors such as soil fertility and light levels interact to affect ecosystem production.

2 To determine whether some environments promote a positive richness‐production relationship, I performed an experiment using artificial plant communities, selected from a pool of six annuals and one perennial species, with different levels of species richness and composition. Each community was grown in either high or low soil fertility and either full sun or 50% shade.

3 Higher species richness significantly enhanced above‐ground production. This effect did not depend on environmental treatment due to consistent sampling effects for a particularly productive and competitive species. However, overyielding, which measures the combined effect of complementarity and facilitation, did depend on environmental conditions and was enhanced by increased soil fertility in plots in full sunlight.

4 Relative yield analyses of species of different height and growth form, coupled with data on the performance of each species in monoculture, support the hypothesis that mixtures overyielded by means of light partitioning (rather than facilitation), an effect that was precluded under shaded conditions.

5 The results therefore suggest that higher annual plant species richness may enhance production when environmental conditions allow for resource partitioning.
Plasticity of growth characteristics in wild barley (Hordeum spontaneum) in response to nutrient limitation
Authors: Elberse I. A. M. , Van Damme J. M. M. , Van Tienderen P. H.
Published: May 2003

1 The genetic basis of phenotypic plasticity in relative growth rate (RGR) and its components was studied in Hordeum spontaneum (wild barley). Four accessions from each of nine natural populations from Israel and Iran were grown at four nutrient levels. Genetic variation in RGR and its components, differences in phenotypic plasticity, and interactions among growth and relevant morphological characteristics were studied.

2 RGR was reduced by up to 60% at decreased nutrient levels, with contributions from all components (net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and leaf mass fraction (LMF)). NAR and LAR (due mainly to LMF) were both reduced by 35% at the lowest nutrient level.

3 For growth‐related traits, most genetic variation was found in LMF and LAR. Differences in RGR among populations could be largely explained by smaller seeds resulting in faster growing plants. Although mean population seed weight correlated negatively with humidity at the sampling site, multivariate analyses showed that differences in growth and morphology among populations were not significantly correlated with differences in environmental conditions in their natural habitats.

4 The level of plasticity in RGR did not differ among populations or accessions‐within‐populations. By contrast, the RGR components LMF and LAR differed in plasticity, both among populations and among accessions‐within‐populations. RGR seems to be buffered from changes in plasticity by a trade‐off in degree of plasticity between the underlying components (NAR and LAR).

5 Path analysis based on accession means showed that some of the interrelationships among RGR components changed with nutrient level. NAR had the highest influence on RGR. LMF was the connecting factor among morphological and growth traits. At the two lowest nutrient levels trade‐offs appeared between LAR (mainly via LMF) and NAR. A trade‐off between LMF and SLA appeared at the two intermediate nutrient levels.
Comparative growth analysis of tropical forest and savanna woody plants using phylogenetically independent contrasts
Authors: Hoffmann William A. , Franco Augusto C.
Published: May 2003

1 The savanna–forest boundary in the tropics is marked by a discontinuity not only in tree density, but also in species composition, with few tree species regularly occurring in both savanna and forest environments.

2 We performed comparative growth analysis for nine congeneric pairs, each containing one savanna species and one forest species, grown in a factorial design involving two light and two nutrient levels.

3 Contrary to predictions, there was no difference in relative growth rates (RGR) between savanna and forest species. However, there were clear differences in allocation patterns and in phenotypic responses to light intensity. Savanna species allocated more biomass to roots and maintained lower leaf area per unit plant mass (LAR), and lower leaf area per unit leaf mass (SLA).

4 Savanna species also exhibited greater phenotypic plasticity in specific leaf area, leaf area ratio and net assimilation rate in response to light intensity. An increase in LAR in response to shading of savanna species offset a decrease in net assimilation rate per unit leaf area (NAR), such that RGR was largely unaffected.

5 For most plant traits measured, more of the interspecific variation could be attributed to differences among genera than to differences between the two functional types, indicating that these seedling traits are highly conserved within the congeneric species pairs. Many of these traits were correlated to seed mass, which is itself highly conserved within genera.
Microhabitat dependent responses to resource pulses in the aridland perennial, Cryptantha flava
Authors: Peek Michael S. , Forseth Irwin N.
Published: May 2003

1 A 3‐year field study examined the physiological and demographic consequences of resource pulse use by an herbaceous, aridland perennial, Cryptantha flava, as well as potential competitive and facilitative interactions with larger shrubs.

2 We applied a pulse of urea and faecal pellets, simulating Mule deer excretions, to plants growing between and under Sagebrush and Rabbitbrush canopies.

3 We hypothesized that C. flava would show strong positive responses to N pulses in open microhabitats, and such plants had approximately 50% increases in leaf N concentrations within days of pulse application, accompanied by increased photosynthetic rates. Over the next year, higher rates of growth and reproduction were found in the plants receiving supplemental N.

4 We predicted that due to shading, plants would not respond to N pulses when growing under shrubs but supplemental N caused increases in leaf N similar to that in open growing plants. However, the response of both growth and reproduction was less than in the open, suggesting at least partial light limitation.

5 In 2000, a year of below average precipitation, all plants decreased in size, but survival was facilitated under shrubs (93%) relative to that of open plants (84%).

6 In the open, there was a trade‐off between rapid growth in favourable years and survival in dry years. Supplemental N in years of average precipitation increased RGR from 0.42 to 1.16 rosettes rosette−1 year−1, but reduced from −0.02 to −0.2 in dry years.

7 Plant performance in aridlands thus results from complex interactions between microhabitat, nutrient pulses and yearly precipitation patterns.