Short-term responses of decomposers to flow restoration in Fossil Creek,Arizona, USA

Dam decommissioning projects, although numerous, rarely include complete sets of data before and after restoration for evaluating the ecological consequences of such projects. In this study, we used a before-after control-impact (BACI) design to assess changes in leaf litter decomposition and associated macroinvertebrate and fungal decomposers following dam decommissioning in Fossil Creek, Arizona, USA. Leaf litterbags were deployed in a relatively pristine site above the dam and a highly disturbed site below the dam where over 95% of the flow was previously diverted for hydropower generation. Leaf litter decomposition was significantly slower below the dam both measurement years (pre- and post-restoration) with no site-year interaction, indicating that decomposition in this stream section was not affected by increased flow. In contrast, both macroinvertebrates and fungi differed significantly above and below the dam prior to restoration but were similar post-restoration, supporting the concept that decomposer communities can quickly rebound following reintroduction of full flow. Our results indicate that some aquatic ecosystem variables can return to a more natural state following ecological restoration activities such as water flow restoration. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: S. Stendera     

Influences of travertine dam formation on leaf litter decomposition and algal accrual

At the time of this study Fossil Creek was being considered as a site for the restoration of a native fish assemblage, however there was concern amongst fisheries managers about the stream being food limited due to calcium carbonate (travertine) deposition. To evaluate the effects of travertine deposition on the aquatic food base we used leaf litterbags to compare decomposition rates and nutrient diffusing artificial substrates to compare algal accrual rates and nutrient limitation between two distinct reaches in Fossil creek: a travertine dam forming reach and a reach without travertine dam formation (riffle-pool reach). Decomposition was significantly faster in the travertine dam forming reach than in the riffle-pool reach. Macroinvertebrates in the leaf packs were more diverse in the travertine reach but more abundant in the riffle-pool reach. Algae accrued more quickly in the travertine reach than in the riffle-pool reach and only responded to nutrient enrichment in the travertine reach. This study was conducted prior to a hydroelectric dam decommissioning project in Fossil Creek where full flows were reintroduced back into the stream after a century of diversion. Our results suggest concurrent increases in algal productivity, decomposition, and macroinvertebrate diversity in the next decade as travertine dams rebuild, providing a richer food base for fish and other aquatic organisms. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. Handling editor: K. Martens     

Effects of leaf longevity and retranslocation efficiency on the retention time of nutrients in the leaf biomass of different woody species

Summary A study was made of the retention times of N and P in the leaf biomass and their relationship with the retranslocation percentages and the leaf longevities in some woody species in Central Spain. The retention times of both nutrients were strongly related to the nutrient status of each species. These results suggest that a prolonged retention time is a way of increasing nutrient use efficiency in conditions of low nutrient availability. Plants can increase the retention time of nutrients in their leaf biomass by means of an increase in leaf longevity and/or by means of an increase in retranslocation efficiency. However, the effect of the retranslocation efficiency on retention times was almost negligible compared with the effect of leaf longevity. This suggests that an increase in leaf longevity is probably the best adaptation for increasing efficiency in the use of nutrients.     

Effects of augmentation of coarse particulate organic matter on metabolism and nutrient retention in hyporheic sediments

SUMMARY 1. Metabolic and biogeochemical processes in hyporheic zones may depend on inputs of coarse particulate organic matter. Our research focused on how differing quantity and quality of organic matter affects metabolism and nutrient retention in the hyporheic zone of a first-order Appalachian stream.
2. Sixteen plots were established on a tributary of Hugh White Creek, NC, U.S.A. Sediment was extracted and treated with leaves, wood, plastic strips or remained unamended. Following treatment, sediment was returned to the stream and, approximately 3 months later, samples were removed from each plot.
3. Aerobic and anaerobic metabolism were measured as the change in O₂ and CO₂ in recirculating microcosms. At the same time, we monitored other possible terminal electron accepting processes and changes in nutrient concentrations. Aerobic metabolism was low in all treatments and respiratory quotients calculated for all treatments indicated that metabolism was dominated by anaerobic processes.
4. Rates of anaerobic respiration and total (combined aerobic and anaerobic) respiration were significantly greater ( P  < 0.05) in plots treated with leaf organic matter compared to controls.
5. Addition of leaves, which had a low C:N ratio, stimulated respiration in hyporheic sediments. Anaerobic processes dominated metabolism in both control and amended sediments. Enhanced metabolic rates increased retention of many solutes, indicating that energy flow and nutrient dynamics in the subsurface of streams may depend upon the quantity and quality of imported carbon.     

Effects of growth temperature and winter duration on leaf phenology of Erythronium japonicum,a forest spring geophyte

The effects of growth temperature and winter duration on the leaf phenology of Erythronium japonicum were examined in two experiments. Bulbs wintered in the field were cultivated at 10 and 20° C and the bulbs were cultivated at 15° C after chilling treatment at 3° C for 60 and 120 days and without chilling in winter. The plants cultivated at 20° C showed significantly earlier leaf emergence, a more rapid rate of leaf extension and shorter leaf longevity than those cultivated at 10° C. The decrease in the leaf longevity at 20° C resulted from the decreases in the durations of all of the developmental, mature, and senescent phases. The bulbs without chilling treatment did not sprout leaves and those with chilling treatment sprouted leaves. The increase in the length of chilling treatment from 60 to 120 days affected leaf phenology in same manner as the increase in the growth temperature from 10 to 20° C.     

中国浙江新昌化石木研究

本文介绍了发现于中国东南沿海地区浙江省新昌县中生代地层中的一种化石木新种———新昌南洋杉型木 (AraucarioxylonxinchangenseDuansp .nov .)。这种化石木保存在早白垩世馆头组中、下部的紫红色泥砂岩中 ,分布在新昌县城西部 ,南北绵延 2 5公里、东西宽约 2公里的狭长地区。由于在化石木产区曾发现过多种植物化石 ,因而确定了该区在早白垩世时期处于我国的欧洲 中国植物区内 ,属亚热带 热带气候区 ,种种迹象表明此时气候有些干旱。同区发现的松柏目叶化石 ,其气孔构造与南洋杉科有一定的亲缘关系 ,这一点似乎与化石木之属可以对应。     

The role of timing, duration, and frequency of inundation in controlling leaf litter decomposition in a river-floodplain ecosystem (Tagliamento, northeastern Italy)

Despite growing recognition of the importance of a natural flow regime in river-floodplain systems, researchers struggle to quantify ecosystem responses to altered hydrological regimes. How do frequency, timing, and duration of inundation affect fundamental ecosystem processes such as leaf litter decomposition? Along the semi-natural Tagliamento River corridor, located in northeastern Italy, we employed in situ experiments to separate effects of different inundation components on breakdown rates of black poplar (Populus nigra). We used a litter-bag method with two different mesh sizes to investigate how fungi and macroinvertebrates influence leaf breakdown rates. Ten treatments, each representing a specific combination of duration and frequency of inundation, were deployed in two seasons (summer, winter) to mimic complex inundation patterns. After 30 days of exposure, mean percentage of remaining leaf litter (ash free dry mass) ranged between 51% (permanent wet) and 88% (permanent dry). Leaf breakdown was significantly faster in winter than in summer. Duration of inundation was the main inundation component that controlled leaf breakdown rates. Leaf-shredding macroinvertebrates played only a role in the permanent wet treatment. Fungal parameters explained the faster leaf breakdown in winter. Our study suggests that modifications of the inundation regime will directly modify established decomposition processes. Factors reducing duration of inundation will decelerate leaf breakdown rates, whereas a decrease in flow variation will reduce leaf breakdown heterogeneity.     

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation,North Dakota (USA)

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).     

Microdynamics and seasonal changes in manganese oxide epiprecipitation in Pinal Creek, Arizona

In Pinal Creek, Arizona, Mn oxyhydroxides (MnO_x) collect as thick precipitates on surface sediment, within the streambed, beneath algal mats, and on submerged and emergent plants and mosses. The proximate source of Mn is a thick, alluvial alkaline aquifer that was contaminated by past acid mine waste disposal practices associated with copper mines located upstream in the Globe–Miami area. Almost every organism in Pinal Creek is coated with MnO_x. Some are actively precipitating manganese, and others are doing it passively. The variety and seasonality of epilithic biological processes resulting in Mn oxidation (epiprecipitation) was studied for more than a year by analyzing artificial substrates placed in surface water having different flows and different vegetation types and densities. Most epiprecipitation took place on the holdfasts of the green alga, Ulothrix sp., and the iron bacterium, Leptothrix discophora. Extensive patches of MnO_x also coated extracellular polymeric substances of fungal hyphae and bacterial filaments. The dominant macroscopic precipitation was in the form of MnO_x clumps on mosses, green algae, and cyanobacterial mats, consistent with precipitation by pH elevation during photosynthesis. Most oxidation occurred in the spring and summer, in agreement with thermal, biological, and chemical activity models. More biological oxidation occurred in swifter water, consistent with oxygen elevation models. The efficiency of this naturally occurring, diverse ecosystem suggests that remediation efforts to remove metal contaminants such as Mn should focus on creation of habitats that raise biodiversity.US Geological Survey, retired     

氮钙对香石竹多酚氧化酶、过氧化物酶和叶斑病的影响

1　引　　言近几年安徽省香石竹鲜切花生产得到迅速发展 ,但每年6月至 10月间叶斑病均有较严重发生 ,药物也很难从根本上防止叶斑病的发生和蔓延 ,影响香石竹的生产 .由于多数香石竹生产基地长期只注重用销铵、尿素等Ｎ肥 ,而忽视施用含Ｃａ2 + 肥料和Ｃａ2 + 的生理作用 ,导致栽培基质Ｎ(ＮＯ-3 )、Ｃａ2 + 失去平衡 ,植株对病害抵抗能力降低 .本试验着重研究Ｎ(ＮＯ-3 )、Ｃａ2 + 营养浓度对与抗病性有关的多酚氧化酶、过氧化物酶活性和植株发生叶斑病程度的关系 ,为合理施肥减轻叶斑病对香石竹危害程度提供理论依据 .2　材料与方法2 1　…     

Colonization of leaf patches at topographically different locations by insect shredders in a small mountain stream

We examined physical constraints on the colonization of leaf patches by shredder individuals by comparing the colonizations of artificially standardized leaf patches placed at different locations within a stream reach (i.e., riffles, middles and edges of pools). Stonefly taxa (Nemoura, Protonemura) colonized riffle patches 2–10 times more often than pool (middle, edge) patches, whereas caddisfly taxa (two species of Lepidostoma, Nothopsyche) almost exclusively colonized pool patches. Colonization also differed between the middle and edge patches in pools for most taxa; it was 2–5 times greater in edge patches for Nemoura and in middle patches for Lepidostoma. The abilities of species to cope with low oxygen circulation and high shear stress appear to determine differences in colonization between riffle and pool patches, whereas species-specific dispersion behavior (e.g., return time from drift) may differentiate colonization between middle and edge patches in pools. Our results suggest that changes in leaf distribution within a reach can affect the suitability of stream reaches in terms of food acquisition for shredder individuals.     

Effects of leaf quality and microhabitat on the survival of a leaf-rolling weevil (Attelabidae)

Female Cycnotrachelus roelofsi (Coleoptera: Attelabidae) construct two types of leaf roll, i.e., cut-off cradles (CCs) and suspended cradles (SCs), in which to lay eggs; these cradles are generally constructed using older and younger leaves, respectively. We conducted two experiments to determine whether the quality of cradle leaves affects egg and larval survival. In the first experiment, we severed all SCs from a tree and placed them on the ground with unmanipulated CCs in the early breeding season. In the second experiment, we resuspended all CCs in a tree with unmanipulated SCs in the late breeding season. We also compared leaf mass per area (LMA), polyphenol content, and nitrogen content between the two cradle types to determine whether there were any differences in leaf quality. Larval mortality, probably caused by cradle herbivory, was significantly greater in severed SCs than in intact CCs in the early season, suggesting that leaf quality had a profound effect on larval mortality in the terrestrial microhabitat. In contrast, larval mortality did not differ between resuspended CCs and intact SCs in the late season, suggesting that leaf quality had little effect on larval mortality in the arboreal microhabitat. LMA was higher in CCs than in SCs, but there were no differences in the nitrogen and polyphenol contents. These results suggest that cradles constructed using mature, tough leaves were more effective against terrestrial cradle herbivores than those constructed using new, soft leaves.     

Flow velocity retardation and sediment retention in two constructed wetland–ponds

Hydraulic properties of two constructed wetland–ponds in agricultural watersheds in southern Finland were examined by simulations with two-dimensional hydrodynamic and water quality transport models. Hydraulic efficiency was determined for the existing and hypothetical layouts of both wetlands to find out the effects of different design options. Suspended sediment retention in the wetlands was simulated with a two-dimensional model for sediment transport. Hydraulic efficiency was found to be highly improved by baffles that direct the main flow to optimally exploit the wetland acreage. Also, an elongated shape of wetland appeared beneficial; hydraulic efficiency was high regardless of the size or position of the inlet. As for suspended sediment retention, the wetland area in relation to its watershed proved to be an essential factor. According to water quality observations, the wetland which occupied 5% of its watershed area was capable of reducing the inflow of total suspended solids (TSS) concentrations during flood events by 43–72%, whereas the reduction varied between −7 and 5% in the other wetland with a corresponding ratio of 0.5%. Model simulations of the same flood events plausibly predicted the output TSS concentrations, even though with wider ranges of the reductions (26 to 74 and −13 to 43%, respectively).     

Fossil spores and pollen grains of cretaceous (Upper campanian) from Sakhalin, Russia

This paper shows fossil spores and pollen grains from Cretaceous (Upper Campanian) of Sakhalin, Russia, with scanning electron microscopy. A total of 520 palynomorph assemblages consisting of 25% spores of pteridophytes and bryophytes, 4.5% of ephedroid pollen grains, 6.5% of coniferous pollen grains, and 64% of angiospermous pollen grains were recovered in the present study. 5 genera of pteridophytes, 4 genera of gymnosperms, and 18 genera of angiosperms are described in the present study. The frequent and representative genera from the stratum areEphedripites, Liliacidites, Clavatipollenites, Tricolpites, Aquilapollenites, andAzonia. A new genus,Sciadopitipollenites, that is comparable with extantSciadopitys is proposed in the present study. Polycolpate pollen with the same exine sculpture ofClavatipollenites suggests a generic differentiation in the Chloranthaceae during the Cretaceous age. The diverse spores and pollen paleoflora shown in the present study suggests a wide diversification of angiosperms in the Upper Campanian at the eastern side of Laurasia (Aquilapollenites province).     

A long-term perspective of dissolved organic carbon transport in Sycamore Creek, Arizona, USA

Dissolved organic carbon (DOC) dynamics were examined over five years (1989–1993) in Sycamore Creek, a Sonoran Desert stream, specifically focusing on DOC concentration in surface and hyporheic waters, and rates of export. In 1989 and 1990, the years of lowest stream discharge (0.08 and 0.04 m³ s^–1 annual mean of daily discharge, respectively), DOC was high, averaging 7.37 and 6.22 mgC l^–1 (weighted annual means). In contrast, from 1991 through 1993, a period of increased flow (1.1, 1.2 and 4.3 m³ s^–1), concentration was significantly lower (P<0.001) with annual mean concentrations of 3.54, 3.49 and 3.39 mgC l^–1. Concentration exhibited little spatial variation between two sampling stations located 6 km apart along the mainstem or between surface and hyporheic waters. Annual export of DOC from Sycamore Creek varied 100-fold over the five-year period from a mean rate of only 24 kgC d^–1 in 1990 to 2100 kgC d^–1 in 1993. Ninety percent of DOC was exported by flows greater than 2.8 m³ s^–1, and 50% during flows greater than 27 m³ s^–1; flows of 2.8 and 24 m³ s^–1 occurred only 9 and 1% of the time. The export of organic matter in Sycamore Creek appears to be coupled to El Niño-Southern Oscillation phenomena. The years of highest export, 1991–1993, had El Niño conditions while 1989 and 1990 had medial conditions.     

Fossil Flowers and Associated Plant Fossils from the Kamikitaba Locality (Ashizawa Formation, Futaba Group, Lower Coniacian, Upper Cretaceous) of Northeast Japan

in situ spores, and megaspores also document the presence of Selaginellaceae and Schizaeaceae. Received 8 February 1999/ Accepted in revised form 7 April 1999     

TDZ, auxin and genotype effects on leaf organogenesis in Fragaria

The different types of organogenic (roots and adventitious shoots) and callus formation responses of leaves from 30-day-old proliferating shoots of different Fragaria spp. genotypes were studied in response to MS medium supplemented with 4.54 μM 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea (thidiazuron; TDZ) alone and in combination with 0.98 μM indole-3-butyric acid (IBA), 0.84 μM3-benzo[b]selenienyl acetic acid (BSAA) or 0.90 μM2,4-dichlorophenoxy acetic acid (2,4-D). The study included: nine octoploid Fragaria x ananassa cultivars and breeding selections; two octoploid breeding selections from F. virginiana glauca inter-species crosses; two diploid F. vesca cultivars; and one diploid clone of F. nubicola Lindl. TDZ plus IBA promoted the highest shoot regeneration efficiencies from leaves of nearly all of the genotypes, while the TDZ/BSAA and TDZ/2,4-D combinations promoted high regeneration efficiencies for only some of the genotypes (Alpina W.O., Sveva, AN 91.371.53, Onda, Paros and FO93.143.5). For the more efficient regenerating genotypes, IBA induced the highest frequency of regenerating leaves, while BSAA induced the highest number of regenerated shoots from leaves and more callus production for most of the genotypes.     

Influence of solar radiation and leaf angle on leaf xanthophyll concentrations in mangroves

Summary Mangroves have similar xanthophyll cycle components/chlorophyll ratios [i.e. (V+A+Z)/chl] to other plant species. (V+A+Z)/chl ratios were sensitive to the light environment in which leaves grew, decreasing as light levels decreased over a vertical transect through a forest canopy. The (V+A+Z)/chl ratio also varied among species. However, in sun leaves over all species, the (V+A+Z)/chl ratios correlate with the proportion of leaf area displayed on a horizontal plane, which is determined by leaf angle. Thus, leaf angle and the xanthophyll cycle may both be important in providing protection from high light levels in mangrove species. A canopy survey assessed whether (V+A+Z)/chl ratios could be correlated with species dominance of exposed positions in forest canopies.Rhizophora mangroves, with near-vertical leaf angles, andBruguiera parviflora, with small, horizontal, xanthophyllrich leaves, dominated the canopy, whileB. gymnorrhiza, a species with large, horizontally arranged leaves, was less abundant at the top of the canopy. Thus, two different strategies for adapting to high solar radiation levels may exist in these species. The first strategy is avoidance through near vertical leaf angles, and the second is a large capacity to dissipate energy through zeaxanthin. The (V+A+Z)/chl ratio was also negatively correlated with the epoxidation state of the xanthophyll cycle pool (the proportion present as violaxanthin and half that present as antheraxanthin) at midday. This suggested that the requirement for dissipation of excess light (represented by the midday epoxidation state) may influence the (V+A+Z)/chl ratio.     

Effects of elevated CO2 and O3 on leaf damage and insect abundance in a soybean agroecosystem

By altering myriad aspects of leaf chemistry, increasing concentrations of CO₂ and O₃ in the atmosphere derived from human activities may fundamentally alter the relationships between insect herbivores and plants. Because exposure to elevated CO₂ can alter the nutritional value of leaves, some herbivores may increase consumption rates to compensate. The effects of O₃ on leaf nutritional quality are less clear; however, increased senescence may also reduce leaf quality for insect herbivores. Additionally, changes in secondary chemistry and the microclimate of leaves may render plants more susceptible to herbivory in elevated CO₂ and O₃. Damage to soybean (Glycine max L.) leaves and the size and composition of the insect community in the plant canopy were examined in large intact plots exposed to elevated CO₂ (~550 μmol mol⁻¹) and elevated O₃ (1.2*ambient) in a fully factorial design with a Soybean Free Air Concentration Enrichment system (SoyFACE). Leaf area removed by folivorous insects was estimated by digital photography and insect surveys were conducted during two consecutive growing seasons, 2003 and 2004. Elevated CO₂ alone and in combination with O₃ increased the number of insects and the amount of leaf area removed by insect herbivores across feeding guilds. Exposure to elevated CO₂ significantly increased the number of western corn rootworm (Diabrotica virgifera) adults (foliage chewer) and soybean aphids (Aphis glycines; phloem feeder). No consistent effect of elevated O₃ on herbivory or insect population size was detected. Increased loss of leaf area to herbivores was associated with increased carbon-to-nitrogen ratio and leaf surface temperature. Soybean aphids are invasive pests in North America and new to this ecosystem. Higher concentrations of CO₂ in the atmosphere may increase herbivory in the soybean agroecosystem, particularly by recently introduced insect herbivores. Handling editor: Gary Felton.