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The benthic community was analyzed to evaluate pollution-induced changes for the polychlorinated biphenyl (PCB)-contaminated site at Hunters Point (HP) relative to 30 reference sites in San Francisco Bay, California, USA. An analysis based on functional traits of feeding, reproduction, and position in the sediment shows that HP is depauperate in deposit feeders, subsurface carnivores, and species with no protective barrier. Sediment chemistry analysis shows that PCBs are the major risk drivers at HP (1,570 ppb) and that the reference sites contain very low levels of PCB contamination (9 ppb). Different feeding traits support the existence of direct pathways of exposure, which can be mechanistically linked to PCB...
1. At the heart of the body of research on biodiversity effects on ecosystem function is the debate over whether different species tend to be functionally singular or redundant. When we consider ecosystem multi-function, the provision of multiple ecosystem functions simultaneously, we may find that seemingly redundant species may in fact play unique roles in ecosystems. 2. Over the last few decades, the significance of biological soil crusts (BSCs) as ecological boundaries and ecosystem engineers, and their multi-functional nature, has become increasingly well documented. We compiled ‘functional profiles’ of the organisms in this understudied community, to determine whether functional singularity emerges when...
1. Soil microbes are fed primarily by root-derived substrates, fulfil functions such as mineralization, immobilization, decomposition, pathogeneity and improvement of plant nutrition, and form the basis of the below-ground food web. Hitherto, below-ground processes have generally been monitored using a `black-box' approach, thereby ignoring effects of global change at a finer level of resolution. We describe shifts in the activity between microbial functional groups associated with roots of Artemisia tridentata, and the influence of this change on higher trophic levels. 2. We tested the hypothesis that elevated atmospheric CO2 causes the soil community to change qualitatively. We measured the responses of several...
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This dataset includes two series of data. The first series contains growth model coefficients for >90 fish species in the Upper Mississippi River System (UMRS). These models were fit form empirical length and weight data observed from 1993-2007 during routine annual scientific monitoring of the UMRS fish community under a federal/state partnership program known as the Upper Mississippi River Restoration (UMRR) program (see: https://umesc.usgs.gov/ltrm-home.html, accessed 3/18/2020). To achieve growth model coefficients for each fish species, length and weight data were log10 transformed and fit using statistical regression techniques (Proc GLM in SAS v 9.4). Model coefficients representing the regression y-intercept,...
Bromus tectorum (cheatgrass), an alien annual grass, has become naturalized in a variety of habitats ranging from arid steppe to mesic forest communities within the intermountain region of western North America. To examine the contribution of genetic differentiation to the success of cheatgrass, we measured photosynthesis, growth, phenology and biomass allocation in populations collected as seed from contrasting habitats and grown in a glasshouse. In addition, we examined the effects of drought and population seed source on characteristics of photosynthesis and growth. In general, leaf-level photosynthetic response to variation in light, temperature and soil moisture did not vary significantly among the different...
1. Hydraulic redistribution may have important consequences for ecosystem water balance where plant root systems span large gradients in soil water potential. To assess seasonal patterns of hydraulic redistribution, we measured the direction and rate of sap flow in tap-roots, lateral roots and main stems of three mature Prosopis velutina Woot. trees occurring on a floodplain terrace in semiarid south-eastern Arizona, USA. Sap-flow measurements on two of the trees were initiated before the end of the winter dormancy period, prior to leaf flush. 2 Despite the absence of crown transpiration during the dormant season, sap flow was detected in lateral roots and tap-roots of P. velutina. Reverse flow (away from the stem)...
1 The ability of drought-stressed Bouteloua gracilis H.B.K. Lag. ex Steud. to respond rapidly to a small rainfall event with increases in leaf water potential and leaf conductance directed our attention to the role of the roots in these responses. Our first objective was to determine whether new root growth was required to restore the water status to that of a non-stressed plant, following a small rainfall event. The results indicated that surviving roots were able to absorb water at approximately 40% of the rate of new roots, which was sufficient to restore non-stressed leaf water potentials within one day of watering. 2 The second objective was to estimate the rate and amount of new root growth following simulated...
1. It has been suggested that much of the elevated CO2 effect on plant productivity and N cycling in semi-arid grasslands is related to a CO2-induced increase in soil moisture, but the relative importance of moisture-mediated and direct effects of CO2 remain unclear. 2. We grew five grassland species common to the semi-arid grasslands of northern Colorado, USA, as monocultures and as mixtures of all five species in pots. We examined the effects of atmospheric CO2 concentration (ambient vs. 780 p.p.m.) and soil moisture (15 vs. 20% m/m) on plant biomass and plant N uptake. Our objective was to separate CO2 effects not related to water from water-mediated CO2 effects by frequently watering the pots, thereby eliminating...
1. Soil characteristics influence plant communities in part through water relations. Hypothetically, finer textured soils in arid climates should be associated with more negative plant and soil water potentials during drought, greater resistance of xylem to cavitation, and shallower root systems than coarse soils. 2. These hypotheses were tested by comparing the water relations of Great Basin shrubs growing in sand versus loam soils. The eight study species (Chrysothamnus nauseosus, Chrysothamnus viscidiflorus, Chrysothamnus parryi, Tetradymia glabrata, Atriplex canescens, Atriplex confertifolia, Grayia spinosa and Sarcobatus vermiculatus) varied in typical rooting depth and vegetative phenology. 3. Xylem pressures...
1. The gelatinous cyanobacterial Collema tenax is a dominant lichen in biotic soil crusts in the western United States. In laboratory experiments, we studied CO2 exchange of this species as dependent on water content (WC), light and temperature. Results were compared with performance of green-algal lichens of the same site investigated earlier. 2. As compared with published data, photosynthetic capacity of C. tenax is higher than that of other cyanobacterial and green-algal soil-crust species studied. At all temperatures and photon flux densities of ecological relevance, net photosynthesis (NP) shows a strong depression at high degrees of hydration; maximal apparent quantum-use efficiency of CO2 fixation is also...
1. An air-injection method was used to study loss of water transport capacity caused by xylem cavitation in roots and branches of Pinus edulis (Colorado Pinyon) and Juniperus osteosperma (Utah Juniper). These two species characterize the Pinyon?Juniper communities of the high deserts of the western United States. Juniperus osteosperma can grow in drier sites than P. edulis and is considered the more drought tolerant. 2.Juniperus osteosperma was more resistant to xylem cavitation than P. edulis in both branches and roots. Within a species, branches were more resistant to cavitation than roots for P. edulis but no difference was seen between the two organs for J. osteosperma. There was also no difference between juveniles...
Artemisia tridentata Nutt, is a drought-tolerant shrub that expands inflorescences during summer and autumn, even though xylem pressure potentials may be less than -5.0 MPa. Supplemental watering increased total inflorescence biomass and the biomass of floral heads over 450 and 550%, respectively. Inflorescences displayed positive net photosynthesis until xylem pressure potentials decreased below -5.0 MPa. Growth of inflorescences was not dependent on carbon imported from vegetative leaves; removal of all leaves on vegetative branches did not change inflorescence biomass, and 14CO2 fixed by adjacent vegetative branches was not transferred into inflorescences. Expanding inflorescences during summer may enhance competitive...
Plants of four Great Basin grass species were grown from seed in two greenhouses at low (340 ? l l-1) and high (680 ? l l-1) CO2 concentration. In all four species, high CO2 promoted mean increases in the number of basal stems, leaf area, specific leaf weight and above-ground dry weight. High CO2 resulted in an increase in CO2 assimilation in two C3 grasses but not in a C4 grass, while all three species showed decreases in stomatal conductance. Mean increases of 60% in aboveground dry weight and 80% in water-use-efficiency are consistent with previously reported high CO2 effects on grasses. No consistent differential effects of high CO2 were observed when comparing annual vs perennial species. Global CO2 enrichment...
* 1 Soils are one of the last great frontiers for biodiversity research and are home to an extraordinary range of microbial and animal groups. Biological activities in soils drive many of the key ecosystem processes that govern the global system, especially in the cycling of elements such as carbon, nitrogen and phosphorus. * 2 We cannot currently make firm statements about the scale of biodiversity in soils, or about the roles played by soil organisms in the transformations of organic materials that underlie those cycles. The recent UK Soil Biodiversity Programme (SBP) has brought a unique concentration of researchers to bear on a single soil in Scotland, and has generated a large amount of data concerning biodiversity,...
Photosynthesis, Growth, and Biomass Allocation in Habitat Ecotypes of Cheatgrass (Bromus tectorum), credited to Rice, Kevin J, published in 1992. Published in Functional Ecology, volume 6, issue 1, on pages 32 - 40, in 1992.
1. Microclimate was measured and photosynthetic responses to a climate warming manipulation were compared for the evergreen shrub Artemisia tridentata and the herbaceous forb Erigeron speciosus in the Rocky Mountains, Colorado, USA. 2. Soil was warmer and drier under infra-red heaters compared with control plots. 3. Midday xylem pressure potential did not differ for A. tridentata on heated vs control plots but was lower for E. speciosus on heated plots compared with controls. Leaf temperatures did not vary for the two species on heated or control plots. 4. There were no significant treatment or species differences in the diurnal patterns of CO2 assimilation or stomatal conductance to water vapour. Also, there were...
* 1 Productivity of dryland communities is often co-limited by water and nutrients. Since atmospheric CO2 enrichment induces water savings by plants, elevated CO2 and nutrients could interact to reduce growth limitation, irrespective of the direct influence of CO2 on photosynthesis. We studied CO2 effects in model communities from the semi-arid Negev of Israel with 17 mostly annual C3 species at three CO2 concentrations and three nutrient treatments. * 2 Community biomass increased at elevated (440 and 600 �L L?1) compared to pre-industrial CO2 (280 �L L?1) by 34% on average in the low-nutrient control, by 45% in the high P and by 50% in the high NPK treatment. Less evapotranspiration at elevated CO2 increased soil...
    map background search result map search result map Fish growth model coefficients and functional guild categories for Upper Mississippi River System fishes data Fish growth model coefficients and functional guild categories for Upper Mississippi River System fishes data