United States Geological Survey

About: United States Geological Survey is a government organization based out in Reston, Virginia, United States. It is known for research contribution in the topics: Population & Groundwater. The organization has 17899 authors who have published 51097 publications receiving 2479125 citations. The organization is also known as: USGS & US Geological Survey.

Ecology for a Crowded Planet

Abstract: Within the next 50 to 100 years, the support and maintenance of an extended human family of 8 to 11 billion people will be difficult at best. The authors of this Policy Forum describe changes that are required if we hope to meet the needs and aspirations of humans while improving the health of our planet9s ecosystems. Problems as diverse as disease transmission and global climate change have benefited substantially from advances in ecology. Such advances have set the stage for emergence of a proactive ecological science in which social and political realities are acknowledged and attention is turned decisively toward the future. The ecological sciences must chart an understanding of how ecosystem services can persist given their extensive human use. Innovative research on the sciences of ecosystem services, ecological restoration, and ecological design must be massively accelerated and must be accompanied by more effective communication of ecological knowledge to society.

The Cenozoic palaeoenvironment of the Arctic Ocean.

Abstract: The history of the Arctic Ocean during the Cenozoic era (0–65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm ‘greenhouse’ world, during the late Palaeocene and early Eocene epochs, to a colder ‘icehouse’ world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ~14 Myr, we find sedimentation rates of 1–2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (~3.2 Myr ago) and East Antarctic ice (~14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (~45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ~49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (~55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.

Allocation of extracellular enzymatic activity in relation to litter composition, N deposition, and mass loss

Abstract: Decomposition of plant material is a complex process that requiresinteraction among a diversity of microorganisms whose presence and activity issubject to regulation by a wide range of environmental factors. Analysis ofextracellular enzyme activity (EEA) provides a way to relate the functionalorganization of microdecomposer communities to environmental variables. In thisstudy, we examined EEA in relation to litter composition and nitrogendeposition. Mesh bags containing senescent leaves of Quercusborealis (red oak), Acer rubrum (red maple) andCornus florida (flowering dogwood) were placed on forestfloor plots in southeastern New York. One-third of the plots were sprayedmonthly with distilled water. The other plots were sprayed monthly withNH4NO3 solution at dose rates equivalent to 2 or 8 g N m−2 y−1. Mass loss, litter composition, fungal mass, and the activities ofeight enzymes were measured on 13 dates for each litter type. Dogwood wasfollowed for one year, maple for two, oak for three. For each litter type andtreatment, enzymatic turnover activities were calculated from regressions of LN(%mass remaining) vs. cumulative activity. The decomposition of dogwood litterwas more efficient than that of maple and oak. Maple litter had the lowestfungal mass and required the most enzymatic work to decompose, even though itsmass loss rate was twice that of oak. Across litter types, N amendment reducedapparent enzymatic efficiencies and shifted EEA away from N acquisition andtoward P acquisition, and away from polyphenol oxidation and towardpolysaccharide hydrolysis. The effect of these shifts on decomposition ratevaried with litter composition: dogwood was stimulated, oak was inhibited andmaple showed mixed effects. The results show that relatively small shifts intheactivity of one or two critical enzymes can significantly alter decompositionrates.