Johnson, Arthur H

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  • Publication
    Foraminiferal biostratigraphy of Late Oligocene-Miocene reefal carbonates in southwestern Puerto Rico
    (2000-12-01) Banerjee, Amit; Yemane, Keddy; Johnson, Arthur H
    Recently exposed Oligocene-Miocene (O-M) strata in Santa Elena, Guyanilla and the section at Playa de Jaboncilla, southwestern Puerto Rico show variations in lithology and in the occurence and relative abundance of planktonic and benthic foraminifers. The planktonic foraminifers are interspersed in the relatively deeper, open marine shelf segments, wheras the intervening shallower segments are characterized by an abundance of benthic foraminifers. Although shallow marine, smaller benthic foraminifers are generally of limited use for biostratigraphy, they are used in conjunction with planktonic taxa to develop a high-resolution biostratigraphy for the Oligocene-Miocene reefel carbonates of southwestern Puerto Rico. Upper Oligocene mudstone and packstone and overlying Miocene argillaceous limestone and chalk yielded a diverse foraminiferal fauna comprising both planktonic (Catapsydrax, Chiloguembelina, Dentoglobigerina, Globigerina, Globigerinoides) and benthic (Anomalinoides, Arcaias, Cancris, Elphidum, Eorupertia, Hanzawaia, Heterostegina, Lepidocyclina, Miogypsina, Miosorites, Neorotalia, Rosalina, Siphonina, Stilostomella and Yaucorotalia) taxa. This assemblage indicates a late Oligocene-Miocene (P21 - M14 Zone)age for the Santa Elena and Playa de Jaboncilla sections, with a break in sedimentation at the top of the upper Oligocene. Significant shallowing occurred between the upper Oligocene and Miocene resulting in a hiatus, comparing well with the global seal-level regression at that time. This hiatus lasted for 3.3 million years as shown by the absence of planktonic foram Zone P22 (27.1 Ma - 23.8 Ma).
  • Publication
    A Dendroctonus Bark Engraving (Coleoptera: Scolytidae) From A Middle Eocene Larix (Coniferales: Pinaceae): Early Or Delayed Colonization?
    (2001-11-01) Labandeira, Conrad C; LePage, Ben A; Johnson, Arthur H
    An engraving made by a scolytid bark beetle, assigned to the genus Dendroctonus of the tribe Tomicini, has been identified on a mummified, middle Eocene (45 Ma) specimen of Larix altoborealis wood from the Canadian High Arctic. Larix altoborealis is the earliest known species of Larix, a distinctive lineage of pinaceous conifers that is taxonomically identifiable by the middle Eocene and achieved a broad continental distribution in northern North America and Eurasia during the late Cenozoic. Dendroctonus currently consists of three highly host-specific lineages that have pinaceous hosts: a basal monospecific clade on Pinoideae (Pinus) and two sister clades that consist of a speciose clade associated exclusively with Pinoideae and six species that breed overwhelmingly in Piceoideae (Picea) and Laricoideae (Pseudotsuga and Larix). The middle Eocene engraving in L. altoborealis represents an early member of Dendroctonus that is ancestral to other congeneric species that colonized a short-bracted species of Larix. This fossil occurrence, buttressed by recent data on the phylogeny of Pinaceae subfamilies and Dendroctonus species, indicates that there was phylogenetically congruent colonization by these bark-beetle lineages of a Pinoideae + (Piceoideae + Laricoideae) host-plant sequence. Based on all available evidence, an hypothesis of a geochronologically early invasion during the Early Cretaceous is supported over an alternative view of late Cenozoic cladogenesis by bark beetles onto the Pinaceae. These data also suggest that host-plant chemistry may be an effective species barrier to colonization by some bark-beetle taxa over geologically long time scales.
  • Publication
    Community and population dynamics of spruce-fir forests on Whiteface Mountain, New York: recent trends, 1985-2000
    (2003-01-01) Battles, John J; Fahey, Timothy J; Siccama, Thomas G; Johnson, Arthur H
    We remeasured two sets of permanent plots in old-growth, spruce–fir forests on Whiteface Mountain to quantify ongoing vegetation dynamics at sites impacted by spruce decline. One set of plots was a stratified random sample of the vegetation in a subalpine watershed (Baldwin site). The other was selected to represent forest conditions in a high-elevation subset of the spruce–fir forest (Esther site). Between 1987 and 1997, there was a significant increase in aboveground tree biomass at Baldwin with the majority of the increment due to the growth of canopy-sized trees. This growth occurred with little change in either species composition or size structure. The annual mortality rate of 1.2%·year–1 for canopy-sized red spruce (Picea rubens Sarg.) in Baldwin almost matched the recruitment rate of 1.4 stems/ha per year. In addition, the relative growth rate of spruce was significantly faster than associated species. In contrast, spruce trees in Esther died at a rate of the 3.6%·year–1 (1985–1995), and survivors grew more slowly than other species. The most obvious community-level trend at Esther (1985–2000) was an increase in overall tree density with most of this increase due to ingrowth of small trees. The demography of the spruce population at Baldwin suggests that the decline is over for at least this population.
  • Publication
    Nitrogen availability and forest productivity along a climosequence on Whiteface Mountain, New York
    (2003-10-01) Vann, David R; Joshi, Amishi B; Johnson, Arthur H; Miller, Eric K
    We studied broadleaf and needle-leaf forests along an elevation gradient (600–1200 m) at Whiteface Mountain, New York, to determine relationships among temperature, mineral N availability, and aboveground net primary productivity (ANPP) and controls on the latter two variables. We measured net N mineralization during the growing season, annual litterfall quantity and quality, aboveground woody biomass accumulation, and soil organic matter quality. Inorganic N deposition from cloudwater markedly increases mineral N availability above 1000 m in this region. Consequently, mineral N availability across the climosequence remains relatively constant because N mineralization decreases with increasing elevation. Across this climosequence, air temperature (as growing season degree-days) exerted the most control on ANPP. Nitrogen mineralization was most strongly related to soil growing season degree-days and less so to lignin to N ratios in litter. ANPP was correlated with N mineralization but not with mineral N availability. Combining our data with those from similar studies in other boreal and cool temperate forests shows that N mineralization and ANPP are correlated at local, regional, and interbiome scales. Regarding the persistent question concerning cause and effect in the N mineralization – forest productivity relationship, our data provide evidence that at least in this case, forest productivity is a control on N mineralization.
  • Publication
    A biogeochemical analysis of the Pocono till barrens and adjacent hardwood forest underlain by Wisconsinan and Illinoian till in northeastern Pennsylvania
    (2004-09-01) Wibiralske, Anne W; Latham, Roger Earl; Johnson, Arthur H
    We assessed soil and vegetation nutrient capital in the landscape mosaic of till barrens and hardwood forests on the Pocono Plateau in northeastern Pennsylvania. These shrublands, which contain an unusual abundance of rare species, occur primarily on Illinoian-aged glacial till, though some patches grow on Wisconsinan till. We hypothesized that barrens soil and vegetation contain smaller quantities of nutrients than forest soil and vegetation, and under the same vegetation, Illinoian till soils have a smaller nutrient content than Wisconsinan till soils. We measured pH, total C and N, and exchangeable Ca, Mg, K, and Al content of the soils and determined C, N, Ca, Mg, K, and P content of the vegetation. Litter and soil organic matter in the barrens have a higher C/N ratio than the forest. The Illinoian barrens Oa horizon is thicker and contains a greater quantity of exchangeable mineral nutrients than the other Oa horizons. Differences in vegetation nutrient capital strongly mirror differences in biomass. Our results show no strong association of parent material with soil or vegetation nutrient capital. Instead, they suggest that plant community characteristics, not soil nutrient availability, shape the landscape pattern of barrens and forest, particularly plant-driven positive feedbacks primarily involving fire frequency.
  • Publication
    Site factors determining epiphytic lichen distribution in a dieback-affected spruce-fir forest on Whiteface Mountain, New York: stemflow chemistry
    (2002-11-01) Schmull, Michaela; Vann, David R; Hauck, Markus; Johnson, Arthur H; Runge, Michael
    Epiphytic lichen diversity in a dieback-affected forest of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) on Whiteface Mountain, New York, U.S.A., was higher on dead compared with living trees and on fir compared with spruce. Diversity differed more between living and dead spruce than between living and dead fir. Cover of all lichen species that occurred on more than 50% of the sample trees, except for two species, decreased with increasing mean concentration of NO3– in stemflow. Concentrations of NO3– were higher on living spruce compared with dead spruce and with living and dead fir. The negative correlations between lichen cover and NO3– concentration may reflect either a decrease of lichen abundance caused by toxic effects of higher NO3– concentrations or a removal of NO3– from stemflow by epiphytic lichens. Experimental exposure of Hypogymnia physodes to NaNO3 reduced chlorophyll concentrations. This result, together with estimations of lichen and needle biomass, indicates that a dependence of lichen cover on NO3– concentrations in stemflow may be the cause for the negative correlations. The sulphur concentration in stemflow did not affect lichen abundance on Whiteface Mountain. The manganese concentration in stemflow may have an effect on single species.
  • Publication
    The value of paleoecology as an aid to monitoring ecosystems and landscapes, chiefly with reference to North America
    (2001-06-01) Gorham, Eville; Brush, Grace S; Graumlich, Lisa J; Rosenzweig, Michael L; Johnson, Arthur H
    Paleoecological indicators are examined as to their accuracy in reconstructing past biotic communities and environmental conditions, their utility in answering important questions about such communities and conditions, and the temporal and spatial scales over which they are effective. Next, environmental problems susceptible of paleoecological analysis are considered, as are the ecosystem and landscape properties that can be inferred from such an analysis. The usefulness of paleoecology in anticipating ecological "surprises" is then discussed. Finally, a set of conclusions and recommendations is presented.