Time filter

Source Type

Letcher S.G.,Purchase College, State University of New York | Chazdon R.L.,University of Connecticut | Andrade A.C.S.,National Institute of Amazonian Research | Bongers F.,Wageningen University | And 7 more authors.
Perspectives in Plant Ecology, Evolution and Systematics

The phylogenetic structure of communities can reveal forces shaping community assembly, but the vast majority of work on phylogenetic community structure has been conducted in mature ecosystems. Here, we present an analysis of the phylogenetic structure of three Neotropical rain forest communities undergoing succession. In each site, the net relatedness of the community is initially high and consistently declines during succession. This pattern is evident both when comparing plots of different age classes and when comparing stem size classes within each plot: the oldest plots and the youngest stem cohorts, representing the most advanced stages of succession, have the lowest relatedness. Our results suggest that succession leaves a distinct signature in the phylogenetic structure of communities, which may reflect an increasing role of biotic interactions in community assembly during succession. We discuss theoretical explanations for the decline in community phylogenetic relatedness during succession, and suggest directions for future study. © 2011 Perspectives in Plant Ecology, Evolution and Systematics. Source

Kim J.K.,University of Connecticut | Kraemer G.P.,Purchase College, State University of New York | Yarish C.,University of Connecticut
Marine Ecology Progress Series

We previously demonstrated the suitability of seaweed aquaculture as a nutrient management tool, using the warm temperate rhodophyte Gracilaria tikvahiae McLachlan. The present follow-up study revealed an even higher nutrient bioextraction capacity in the cold-water species Saccharina latissima at 3 sites-the mouth of the Bronx River Estuary (Bronx, NY; BRE), western Long Island Sound (Fairfield, CT; WLIS) and central Long Island Sound (Branford, CT; CLIS), during winter and spring of the 2012-2013 growing season. These sites differ in temperature (BRE > CLIS > WIS), salinity (BRE < WLIS = CLIS) and nutrients (BRE WLIS = CLIS). We estimated that S. latissima could remove up to 180, 67 and 38 kg N ha-1 at BRE, WLIS and CLIS respectively, in a hypothetical kelp farm system with 1.5 m spacing between longlines. In the same hypothetical kelp farm system, the estimated carbon sequestration values are 1350 (BRE), 1800 (WLIS) and 1100 (CLIS) kg C ha-1. The potential monetary values of N sequestration by the sugar kelp are up to $1600 (BRE), $760 (WLIS) and $430 (CLIS) ha-1, if incorporated in the State of Connecticut Nitrogen Credit Trading Program and a carbon-pricing scheme. The potential economic values of C sequestration are $30-300 (BRE), $40-400 WLIS), and $24-240 (CLIS) ha-1. These results suggest that seaweed aquaculture is a useful technique for nutrient bioextraction in urbanized coastal waters, such as LIS and BRE. Alternation of the warm-and cold-water species would maximize nutrient bioextraction and augment other ecosystem services, producing economic benefits for the region while helping to manage non-source eutrophication. © 2015 Inter-Research. Source

Kim J.K.,University of Connecticut | Kraemer G.P.,Purchase College, State University of New York | Yarish C.,University of Connecticut

We investigated emersion-induced nitrogen (N) release from Porphyra umbilicalis Kütz. Thallus N concentration decreased during 4 h of emersion. Tissue N and soluble protein contents of P. umbilicalis were positively correlated and decreased during emersion. Growth of P. umbilicalis did not simply dilute the pre-emersion tissue N concentration. Rather, N was lost from tissues during emersion. We hypothesize that emersion-induced N release occurs when proteins are catabolized. While the δ15N value of tissues exposed to emersion was higher than that of continuously submerged tissues, further discrimination of stable N isotopes did not occur during the 4 h emersion. We conclude that N release from Porphyra during emersion did not result from bacterial denitrification, but possibly as a consequence of photorespiration. The release of N by P. umbilicalis into the environment during emersion suggests a novel role of intertidal seaweeds in the global N cycle. Emersion also altered the physiological function (nitrate uptake, nitrate reductase and glutamine synthetase activity, growth rate) of P. umbilicalis and the co-occurring upper intertidal species P. linearis Grev., though in a seasonally influenced manner. Individuals of the year round perennial species P. umbilicalis were more tolerant of emersion than ephemeral, cold temperate P. linearis in early winter. However, the mid-winter populations of both P. linearis and P. umbilicalis, had similar temporal physiological patterns during emersion. © 2013 Kim et al. Source

Siegel P.,Purchase College, State University of New York | Demorest A.,Amherst College
Psychotherapy Research

This article presents a systematic case study of maladaptive interpersonal schemas. These schemas are conceived of as affective scripts, or sequences of behaviors that regulate emotion in interpersonal relationships. Part I presents a test of the method for identifying affective scripts. Independent raters applied FRAMES (Fundamental Repetitive and Maladaptive Emotion Structures; Hoelzer & Dahl, 1996) to a representative sample of transcripts of a long-term psychotherapy. Empirical checks of each assessment procedure verified the identification of five maladaptive scripts in hundreds of narratives and enactments with the therapist. In Part II, these scripts were tracked across treatment to identify adaptive changes. Statistical analyses indicated a reduction in maladaptive scripts and an increase in adaptive changes. The evolution of the most pervasive script is described in detail. Strengths and weaknesses of the method are discussed. © 2010 Society for Psychotherapy Research. Source

Bedard A.-C.V.,Mount Sinai School of Medicine | Newcorn J.H.,Mount Sinai School of Medicine | Clerkin S.M.,Mount Sinai School of Medicine | Clerkin S.M.,Purchase College, State University of New York | And 6 more authors.
Journal of the American Academy of Child and Adolescent Psychiatry

Objective Visuospatial working memory impairments have been implicated in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). However, most ADHD research has focused on the neural correlates of nonspatial mnemonic processes. This study examined brain activation and functional connectivity for visuospatial working memory in youth with and without ADHD. Method Twenty-four youth with ADHD and 21 age- and sex-matched healthy controls were scanned with functional magnetic resonance imaging while performing an N-back test of working memory for spatial position. Block-design analyses contrasted activation and functional connectivity separately for high (2-back) and low (1-back) working memory load conditions versus the control condition (0-back). The effect of working memory load was modeled with linear contrasts. Results The 2 groups performed comparably on the task and demonstrated similar patterns of frontoparietal activation, with no differences in linear gains in activation as working memory load increased. However, youth with ADHD showed greater activation in the left dorsolateral prefrontal cortex (DLPFC) and left posterior cingulate cortex (PCC), greater functional connectivity between the left DLPFC and left intraparietal sulcus, and reduced left DLPFC connectivity with left midcingulate cortex and PCC for the high load contrast compared to controls (p <.01; k > 100 voxels). Reanalysis using a more conservative statistical approach (p <.001; k > 100 voxels) yielded group differences in PCC activation and DLPFC-midcingulate connectivity. Conclusion Youth with ADHD show decreased efficiency of DLPFC for high-load visuospatial working memory and greater reliance on posterior spatial attention circuits to store and update spatial position than healthy control youth. Findings should be replicated in larger samples. Source

Discover hidden collaborations