Limited native plant regeneration in novel, exotic-dominated forests on Hawai’i

Ecological invasions are a major driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exotic-dominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native trees smaller than 10 cm in diameter were absent in 28 of the 46 sites and rare in the others. Natives were never the dominant understory species; in fact, they accounted for less than 10% of understory basal area at all but six sites, and less than 4% on average. Sites with native species in the understory tended to be on young lava substrate lacking human disturbance, and were mostly located close to intact, native-dominated forest stands. Even where we found some native species, however, most were survivors of past exotic encroachment into native forest, rather than products of active recolonization by native species. In contrast with successional trajectories in Puerto Rico, Hawaii\u27s exotic-dominated forests can emerge, via invasion, without human disturbance and native Hawaiian plants are largely unable to colonize them once they appear. We suggest that a wide diversity of growth strategies among the exotic species on Hawai’i may limit the opportunities for native plants to colonize exotic-dominated forests

Status of the European Green Crab in Oregon Estuaries, Fall 2003

Prepared for the Pacific States Marine Fisheries Commission and the Alaska Department of Fish of Game.The invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, caused much initial alarm. Following the strong El Niño of 1997-98, young green crabs appeared in estuaries along the coasts of Oregon, Washington, and as far north as Port Eliza on the west coast of Vancouver Island, British Columbia. Unusually strong northward-moving coastal currents (up to 50 km/day from September 1997 to April 1998) must have transported green crab larvae from more established source populations in California to the Northwest. Coastal transport events have been much weaker in recent years. Crabs from the 1997/98 colonizing year class were still in the population during the early summer of 2003. Males from that year class ranged from 86-98 mm in carapace width. By the fall we did not trap any crabs over 80 mm, suggesting that these older crabs were dying. Estimates for green crab longevity range from 4 years in Europe to 6 years in Maine. We thus predict that most of the colonizing year class will die of senescence over the 2003/2004 winter. The loss of the 97/98-year class of green crabs, however, does not mean that green crabs are becoming extinct in Northwest estuaries. Recruitment in 2003 in Yaquina, Netarts, Tillamook and Willapa Bay have has been much stronger than in previous years. Circumstantial evidence indicates that these estuaries harbor a small self-sustaining population that is not dependent on a larval source from California. Even though green crab abundance in the Northwest is low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons: 1) to elucidate the process of range expansion of a model non-indigenous marine species with planktonic larvae and 2) to serve as an early warning system for the next strong recruitment event of green crabs

Pengebelønning og anerkjennelse - hånd i hånd? - En kvalitativ studie innen salgsbransjen

I innledningen av oppgaven vil vi presentere problemstilling sammen med studiens avgrensning og struktur. I den andre delen fremlegger vi vårt teoretiske rammeverk, hvor vi har tatt utgangspunkt i en hovedmodell og en støttemodell. Denne oppgaven har tatt utgangspunkt i hvordan pengebelønning og anerkjennelse oppleves forskjellig hos hver enkelt selger, men også hvordan disse virkemidlene påvirker en selgers motivasjon. I den tredje delen av studien gjør vi rede for de valg som vi har tatt i henhold til det metodiske fundamentet. Her vil også fremgangsmåten for datainnsamlingen bli presentert sammen med refleksjonen. Det er gjennomført dybdeintervjuer, hvor de åtte selgerne som vi har intervjuet også har dannet grunnlaget for vår primærdata. Alle åtte er aktive innen salgsbransjen i dag, og har i tillegg erfaring med begge belønningsformene. I den fjerde og avsluttende delen av studien, vil vi presentere våre funn separat, hvor vi videre drøfter empirifunnene opp mot vårt teoretiske rammeverk. Vi søker her å finne forståelse rundt temaet, i likhet med å frembringe opplevelser mot vår kjernemodell, men også støttemodell. Konklusjonen har vært avhengig av de empirifunn som har fremkommet i analysen, hvor det helt til slutt vil bli gjort refleksjoner rundt egen oppgave og videre forskning

Special Publication No. 1, Checklist Of The Internal And External Parasites of Deer, Odocoileus Hemionus And O. Virginianus, In The United States And Canada

United States Department of Agriculture, Bureau of Animal Industr

The impact of lianas on 10 years of tree growth and mortality on Barro Colorado Island, Panama

1. Lianas compete intensely with trees, but few studies have examined long‐term effects of liana infestation on tree growth and mortality. We quantified the effects of lianas in tree crowns (n = 2907) and rooted within 2 m of trees (n = 1086) on growth and mortality of 30 tree species from 1995 to 2005 on Barro Colorado Island (BCI), Panama, documented liana infestation in tree crowns in 1996 and 2007 to determine the dynamics of liana infestation, and quantified liana infestation in the crowns of 3231 additional canopy trees (d.b.h. ≥20 cm) in 2007 to compare with the same metric determined by previous studies in 1967 and 1980. 2. Severe liana infestation increased tree mortality: 21% of liana‐free trees in 1996 had died by 2007, whereas 42% of trees with more than 75% of the crown infested by lianas in 1996 had died by 2007. 3. Liana infestation of tree crowns significantly reduced tree growth, particularly on sun‐exposed trees. The proximity of rooted lianas significantly reduced the growth of shaded trees. 4. Liana infestation was dynamic: 10.9% of trees with severe liana infestation in their crowns in 1996 had shed all of their lianas by 2007 and 5.3% of trees with no lianas in their crown in 1996 had severe liana infestation in 2007. 5. Liana infestation was common: lianas were present in 53% of trees of the 30 focal species. Including lianas rooted within 2 m of the tree increased this percentage to 78%. Using both above‐ and below‐ground measures may provide a better estimate of liana competition than either measure alone. 6. Liana infestation is increasing on BCI. Lianas were present in the crowns of 73.6% of canopy trees (d.b.h. ≥20 cm). Liana canopy infestation was 57% higher than in 1980 and 65% higher than in 1967, which is consistent with reported increases in liana abundance, biomass, and leaf and flower production. 7. Synthesis. We used one of the largest studies ever conducted on lianas to confirm the negative effects of lianas on tree growth and survival over 10 years. Liana infestation of trees was widespread, dynamic and increasing on BCI

Status of the European Green Crab in Oregon Estuaries in 2004

Prepared for the Pacific States Marine Fisheries Commission and the Alaska Department of Fish of Game.The recent invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, caused much initial alarm. Following the last El Niño of 1997-98, a strong cohort of young green crabs appeared in estuaries along the coasts of Oregon, Washington, and as far north as Port Eliza on the west coast of Vancouver Island, British Columbia. Unusually strong northward-moving coastal currents (up to 50 km/day from September 1997 to April 1998) must have transported green crab larvae from more established source populations in California to the Northwest. Coastal transport events and recruitment of young green crabs have been much weaker in recent years. It was hoped that green crabs would go extinct in the Pacific Northwest estuaries once the original colonists reached the end of their life span of 4-6 years. This has not happened. Some recruitment has occurred every year since 1998. Recruitment strength appears to be linked to winter temperatures: cold winters (2002) result in poor recruitment while warm winters (2003), in good recruitment. Circumstantial evidence suggests that Coos, Yaquina, Netarts and Tillamook estuaries in Oregon and Willapa Bay, Washington harbor a small self-sustaining population of green crabs that is not dependent on a larval source from California. There can be a substantial time lag between the discovery of an exotic species and its impact on the native community. For example, green crabs were documented to exist in New England in 1817, but it was not until the 1950’s when this species expanded its range and increased in abundance sufficiently to impact the soft-shelled clam populations in Massachusetts, Maine and Nova Scotia. Even though green crab abundance in the Pacific Northwest is low when compared to Europe, eastern North America, Tasmania and California, it is imperative to continue monitoring efforts for two reasons: 1) to elucidate the process of range expansion of this model non-indigenous marine species with planktonic larvae and 2) to understand the role of ocean conditions on recruitment in order to predict the next strong recruitment event of green crabs

Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales.

Humans have more than doubled inputs of reactive nitrogen globally and greatly accelerated the biogeochemical cycles of phosphorus and metals. However, the impacts of increased element mobility on tropical ecosystems remain poorly quantified, particularly for the vast tropical dry forest biome. Tropical dry forests are characterized by marked seasonality, relatively little precipitation, and high heterogeneity in plant functional diversity and soil chemistry. For these reasons, increased nutrient deposition may affect tropical dry forests differently than wet tropical or temperate forests. Here, we review studies that investigated how nutrient availability affects ecosystem and community processes from the microsite to ecosystem scales in tropical dry forests. The effects of N and P addition on ecosystem carbon cycling and plant and microbial dynamics depend on forest successional stage, soil parent material, and rainfall regime. Responses may depend on whether overall productivity is N- vs. P-limited, although data to test this hypothesis are limited. These results highlight the many important gaps in our understanding of tropical dry forest responses to global change. Large-scale experiments are required to resolve these uncertainties

The aged lymphoid tissue environment fails to support naive T cell homeostasis.

Aging is associated with a gradual loss of naive T cells and a reciprocal increase in the proportion of memory T cells. While reduced thymic output is important, age-dependent changes in factors supporting naive T cells homeostasis may also be involved. Indeed, we noted a dramatic decrease in the ability of aged mice to support survival and homeostatic proliferation of naive T cells. The defect was not due to a reduction in IL-7 expression, but from a combination of changes in the secondary lymphoid environment that impaired naive T cell entry and access to key survival factors. We observed an age-related shift in the expression of homing chemokines and structural deterioration of the stromal network in T cell zones. Treatment with IL-7/mAb complexes can restore naive T cell homeostatic proliferation in aged mice. Our data suggests that homeostatic mechanisms that support the naive T cell pool deteriorate with age.11128Ysciescopu

Pervasive and strong effects of plants on soil chemistry: a meta-analysis of individual plant ‘Zinke’ effects

Plant species leave a chemical signature in the soils below them, generating fine-scale spatial variation that drives ecological processes. Since the publication of a seminal paper on plant-mediated soil heterogeneity by Paul Zinke in 1962, a robust literature has developed examining effects of individual plants on their local environments (individual plant effects). Here, we synthesize this work using meta-analysis to show that plant effects are strong and pervasive across ecosystems on six continents. Overall, soil properties beneath individual plants differ from those of neighbours by an average of 41%. Although the magnitudes of individual plant effects exhibit weak relationships with climate and latitude, they are significantly stronger in deserts and tundra than forests, and weaker in intensively managed ecosystems. The ubiquitous effects of plant individuals and species on local soil properties imply that individual plant effects have a role in plant–soil feedbacks, linking individual plants with biogeochemical processes at the ecosystem scale

The aged lymphoid tissue environment fails to support naive T cell homeostasis

Aging is associated with a gradual loss of naive T cells and a reciprocal increase in the proportion of memory T cells. While reduced thymic output is important, age-dependent changes in factors supporting naive T cells homeostasis may also be involved. Indeed, we noted a dramatic decrease in the ability of aged mice to support survival and homeostatic proliferation of naive T cells. The defect was not due to a reduction in IL-7 expression, but from a combination of changes in the secondary lymphoid environment that impaired naive T cell entry and access to key survival factors. We observed an age-related shift in the expression of homing chemokines and structural deterioration of the stromal network in T cell zones. Treatment with IL-7/mAb complexes can restore naive T cell homeostatic proliferation in aged mice. Our data suggests that homeostatic mechanisms that support the naive T cell pool deteriorate with age © The Author(s) 2016111101sciescopu