September 2, 2006, 9:17 PM CT

Fighting Weeds With Plant Pathogens

Eventhough plant pathogens are typically viewed as detrimental, plant pathologists with the American Phytopathological Society (APS) say plant pathogens may be a successful, eco-friendly tool for managing weeds.

"The use of plant pathogens to suppress weeds is considered as one of the alternative weed control options for areas or production systems where the use of chemical herbicides is not permitted or feasible," said Erin Rosskopf, USDA, Agricultural Research Service, Fort Pierce, FL. "Plant pathogens may also be used when the herbicide selection or usage must be rotated with other control methods in order to prevent the development of resistant weeds or lessen the impact of herbicides on the environment," she said.

Weed management is important due to the amount of damage weeds can cause to agricultural productivity. Weeds can reduce crop yields by as much as 12 percent (causing up to $32 billion in losses), based on the potential value of all U.S. crops of approximately $267 billion/year. Weeds also pose serious ecological problems. Invasive weeds are capable of altering ecosystem processes and displacing native plant and animal species. In addition, weeds serve as reservoirs for plant pathogens that impact crops.

As per Rosskopf, there are two approaches used for managing weeds with plant pathogens-the classical biological control approach and the bioherbicides approach. The classical biocontrol approach uses a pathogen imported from a foreign location to control a native or naturalized weed with minimal technological manipulations.........

Posted by: Jessica      Permalink         Source

August 29, 2006, 5:54 PM CT

Cylindropuntia Bigelovii

This isn't my best photograph of Cylindropuntia bigelovii or teddybear cholla, but it is one of the better ones I have from this particular location: the Cholla Cactus Garden in Joshua Tree National Park. This small area has the densest concentration of teddybear chollas within this massive park. While enjoying this tiny natural wonder, a thought did creep into my head: "Why build a road (and then highway) right through it?" I'm sure the decision was made before I was born, but I wonder if any thought has been given to rerouting the highway around this small patch, and then reclaiming the decommissioned road for the cholla.

Despite the common name of teddybear cholla, you do not want to hug this plant. Its needles have barbed ends that pierce and lodge. Tweezers or a comb are recommended to pick the needles out if they become embedded in your skin; attempting to pluck them out with your fingers will merely sink them into your fingertips (as I experienced).

The Living Desert has a good resource page on teddybear cholla, while Brad Biringer has photographs of the Cholla Cactus Garden taken in superior light conditions in this photo essay.

Photography resource link: Photoshop Tips and Tricks from the tips section of the Pacific Northwest Nature Photographers group.........

Posted by: Jessica      Permalink         Source

August 24, 2006, 7:16 PM CT

Trifolium Burchellianum

The International Legume Database and Information Service (ILDIS) notes that Burchell's clover is native to the montane shrublands, grasslands and bamboo thickets of eastern and southern Africa. This species is rarely found in cultivation, despite its attractive, thimble-sized inflorescence. Instead, a trip to Africa would reveal that it is an important perennial legume for livestock grazing at 3000m or higher above sea level.

This (cropped) photograph was taken three years ago, and I've not had the opportunity to verify if these plants remain (it's not something you'd casually notice when not in flower due to its size!).

Photography resource link: "Just Say Yes!", an article by Alain Briot for Nature Photographers Online. After reading this essay, all I can say is "Yes!".........

Posted by: Jessica      Permalink         Source

August 23, 2006, 7:53 PM CT

The Sundew With Dew

Wow! That is the coolest looking flower. You've captured the dew marvelously.

Hmmm.........

Posted by: Jessica      Permalink         Source

August 23, 2006, 7:24 PM CT

Botanical Beach

Hundreds of tidepools can be found at Botanical Beach in Juan de Fuca Provincial Park; a number of of these contain this species of surfgrass shown in the photograph, Phyllospadix scouleri.

I wanted to write about both the adaptations (how does a vascular plant survive in a salt water environment?) and sex lives of these dioecious plants (how does the pollen travel from the male to the female plant?), but entertaining texts for these already exist online, courtesy of the Monterey Bay Aquarium Research Institute: Phyllospadix - the Surfers (about adaptations) and Seagrass Courtship (about reproduction challenges).........

Posted by: Jessica      Permalink         Source

August 9, 2006, 11:55 PM CT

Invasive Species Alter Habitat

When scientists study habitats that alien species have invaded, they usually find predictable patterns. The diversity of native species declines, and changes occur in natural processes such as nutrient cycling, wildfire frequency and the movement of water through the system.

But simply observing such changes doesn't prove that the invaders are responsible.

University of Michigan researchers Emily Farrer and Deborah Goldberg, however, came up with a way to tease out the cause of environmental changes in northern Michigan wetlands where invasive cattails have taken hold. The cattails, they found, alter the environment in ways that hinder native species but benefit the invaders. Farrer and Goldberg will present their results Aug. 9 at a meeting of the Ecological Society of America in Memphis, Tenn.

"When you have an invasion, you typically see three things happening at once: the invasion, the change in environment and the decrease in diversity," said Farrer, a graduate student in Goldberg's laboratory group. "But they're all happening concurrently, so you can't really tell which is causing the other." Other factors may enter in. For example, human activity, such as the use of fertilizers and road salt and the suppression of natural wildfires, also may result in environmental changes that affect species diversity.........

Posted by: Jessica      Permalink         Source

August 9, 2006, 7:01 AM CT

Management Of Climate Change

Arctic nations have the wealth and scientific understanding to alter the course of global climate change, if they choose to do so, writes F.S. (Terry) Chapin III, of the University of Alaska Fairbanks, in a paper would be published August 9, 2006 in the journal Ambio.

Chapin, professor of ecology at the Institute of Arctic Biology, and co-authors offer local-to-global policy recommendations to manage Arctic conditions resulting from thawing permafrost, melting sea ice, and relaxation of thermal thresholds. "Nations that govern Arctic lands account for about 40% of global CO2 emissions and therefore have a substantial capacity to reduce the rates of Arctic change," write the authors.

Among the authors' recommendations are that Arctic nations should designate marine protected areas, designate co-managed reserve networks, foster economic adaptation to global change, and reduce greenhouse gas emissions. "A lot of the recommendations for policy change deal with enhancing the capacity of northern regions to be flexible and adaptable to cope with changes, some of which we can predict, and others of which will be surprises," said Chapin.

An increasingly ice-free Arctic Ocean could be zoned to include marine protected areas, designated shipping lanes, and fishing areas co-managed by local residents and government managers. If reserve networks were implemented, they would likely make important contributions to maintaining biodiversity, providing nursery stocks for adjacent fished areas, and ensuring against mismanagement or unexpected events outside the reserves. Economic adaptation is likely to be most effective if it includes incentives to encourage economic diversity and entrepreneurship rather than subsidies for traditional sectors adversely affected by Arctic change.........

Posted by: Tyler      Permalink         Source

August 8, 2006, 0:25 AM CT

Hard Thoughts On Soft Inheritance

Organisms, including humans, all inherit DNA from generation to generation, what biologists call hard inheritance, because the nucleotide sequence of DNA is constant and only changes by rare random mutation as it is passed down the generations.

But there also is evidence, particularly in plants, that non-genetic factors modifying the DNA can also be inherited. The modifications of the genetic material take the form of small chemical additions to one of the DNA bases and the alternative packaging of the DNA. These so-called epigenetic modifications are known to be important for turning genes on and off during the course of an organism's life, but their importance in controlling inheritance has been debated. A number of biologists are skeptical of any form of soft inheritance, where the genetic material is not constant, believing that it is only genetic information - DNA -- that can be passed onto generations.

Now Eric Richards, Ph.D., professor of biology at Washington University in St. Louis, writing in the recent issue of Nature Reviews Genetics, analyzes recent and past research in epigenetics and the history of evolution and proposes that epigenetics should be considered a form of soft inheritance, citing examples in both the plant and mammalian kingdoms.........

Posted by: Jessica      Permalink         Source

August 7, 2006, 11:51 PM CT

The oxygen balance

Oxygen is one of the most significant keys to deciphering past climates. Oxygen comes in heavy and light varieties, or isotopes, which are useful for paleoclimate research. Like all elements, oxygen is made up of a nucleus of protons and neutrons, surrounded by a cloud of electrons. All oxygen atoms have 8 protons, but the nucleus might contain 8, 9, or 10 neutrons. "Light" oxygen-16, with 8 protons and 8 neutrons, is the most common isotope found in nature, followed by much lesser amounts of "heavy" oxygen-18, with 8 protons and 10 neutrons.

The ratio (relative amount) of these two types of oxygen in water changes with the climate. By determining how the ratio of heavy and light oxygen in marine sediments, ice cores, or fossils is different from a universally accepted standard, scientists can learn something about climate changes that have occurred in the past. The standard scientists use for comparison is based on the ratio of oxygen isotopes in ocean water at a depth of 200-500 meters.

What climate factors influence the ratio of oxygen isotopes in ocean water?

Evaporation and condensation are the two processes that most influence the ratio of heavy oxygen to light oxygen in the oceans. Water molecules are made up of two hydrogen atoms and one oxygen atom. Water molecules containing light oxygen evaporate slightly more readily than water molecules containing a heavy oxygen atom. At the same time, water vapor molecules containing the heavy variety of oxygen condense more readily.........

Posted by: Sarah      Permalink         Source

August 7, 2006, 10:10 PM CT

Mercury in Aquatic Ecosystems

Mercury occurs naturally in the environment and cycles among the atmosphere, water, and sediments. Human activities such as coal burning power plants and waste incineration increase the amount of mercury cycling in the environment. Since the industrial revolution, anthropogenic mercury emissions have increased atmospheric mercury levels about threefold, causing corresponding increases in mercury levels in terrestrial and aquatic ecosystems.

Mercury that is released into the atmosphere can be transported long distances and deposited in aquatic ecosystems, where it is methylated to methylmercury. Mercury is a neurotoxicant, to which the human fetus is very sensitive. Methylmercury is an organic form of mercury, the most toxic form, and the form that bioaccumulates in fish. Wildlife and humans are exposed primarily through consumption of contaminated fish. The factors that make some aquatic ecosystems susceptible to this bioaccumulation, however, are unknown, making protection of human health and the health of fish-eating wildlife a challenge.

Research focuses on the processes of mercury methylation and accumulation in aquatic ecosystems, factors that determine ecosystem susceptibility, and investigation of whether reduced emissions will reduce mercury accumulation in susceptible ecosystems.........

Posted by: Tyler      Permalink         Source

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