If you attended the 2008 Master Gardener Mini-College, perhaps you heard Doug Tallamy speak about the importance of native plants to the conservation of bird and insect species. A seminal paper, which provides data in support of Tallamy's arguments, was recently published in Conservation Biology (Burghardt, Tallamy and Shriver. 2009. Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conserv Biol. 1:219-24).
Burghardt and colleagues measured the diversity of birds and caterpillars (which are, of course, the larval or juvenille form of butterflies) in 12 suburban yards in Pennsylvania. Six yards were landscaped almost exclusively with native plants (43% native and 6% exotic plant cover), and the other six were landscaped with exotic shrubs and groundcovers (although, native trees were present on these properties; 18% native and 26% exotic plant cover).
The abundance of caterpillars (the larvae of butterflies and moths) was 4 times greater on the 'native sites', relative to the 'exotic' sites. In addition, the number of different species represented by these caterpillars was 3 times greater on the 'native' sites, relative to the 'exotic' sites. Approximately 19 species of bird were found at the native sites, compared to 11 species at the 'exotic' sites. Mean abundance of birds at the 'native' sites was 17, compared to 11 birds at the 'exotic' sites.
Why do yards landscaped with native plants contain a greater abundance and diversity of birds and butterfly larvae? Burghardt and colleagues hypothesize that greater food availability for caterpillars at 'native' sites creates greater food availability for birds at such sites. Because many plant feeding insects can not feed exotic plants, and because many birds rely upon insect protein (rather than seed protein) to rear their young, planting native plants seems to cascade up the food chain - fostering an increase in abundance and diversity of plant feeding insects, which in turn fosters an increase in abundance and diversity of insect-feeding birds.
What does this mean for the home gardener? A yard landscaped with native plants can be beautiful, may reduce your fertilizer and water use (if you zone your plants accordingly, and if the natives are adapted to your soils), and can help to conserve biodiversity in your area.
For more on native plant gardening, please visit the Eco-Gardening website created by OSU Extension's Linda McMahan.
Wednesday, February 18, 2009
Monday, February 16, 2009
Happy President's Day
In honor of President's Day, I thought I would take a few moments to honor some of our past presidents, who were also prolific gardeners.
Topping this last has to be the first President of the United States of America (one of my personal heros, for the way that he so selflessly stepped away from power, despite the protests of many compatriots). George Washington farmed at his Mount Vernon estate, where he overcame the poor soils by practicing a relatively novel plan of crop rotations. When he abandoned tobacco farming in about 1765, he switched to wheat and at least 60 other field crops.
Of course, we can not forget Thomas Jefferson, who grew more than 170 varieties of fruit and 330 varieties of vegetables in the gardens at his Monticello estate, and had a special interest in the pea plant. In fact, Jefferson cultivated over 22 varieties of pea. Following the expedition of Lewis and Clark, Jefferson developed a curiosity about the plants of North America, and how they could be used for practical purposes.
In 1825 John Quincy Adams developed the first flower garden at the White House. Adams also planted herbs and vegetables at the White House, as well as ornamental trees.
In 1835, Andrew Jackson established a White House orangery (a type of greenhouse) where tropical trees and flowers could be grown. Jackson also added the Jackson magnolia to the White House grounds. The orangery was demolished in 1857. In 1878, Rutherford B. Hayes started the tradition of planting commemorative trees for Presidential Inaugurations - a tradition that persists today.
As for First Ladies - Eleanor Roosevelt famously began the Victory Garden movement in 1943, when she planted a vegetable garden on the lawn of the White House and Lady Bird Johnson has long been associated with efforts to conserve native plants.
Today, Roger Doiron of Kitchen Gardeners International is helping to lead a campaign to re-establish a Victory Garden on the lawn of the White House.
Happy President's Day!
Topping this last has to be the first President of the United States of America (one of my personal heros, for the way that he so selflessly stepped away from power, despite the protests of many compatriots). George Washington farmed at his Mount Vernon estate, where he overcame the poor soils by practicing a relatively novel plan of crop rotations. When he abandoned tobacco farming in about 1765, he switched to wheat and at least 60 other field crops.
Of course, we can not forget Thomas Jefferson, who grew more than 170 varieties of fruit and 330 varieties of vegetables in the gardens at his Monticello estate, and had a special interest in the pea plant. In fact, Jefferson cultivated over 22 varieties of pea. Following the expedition of Lewis and Clark, Jefferson developed a curiosity about the plants of North America, and how they could be used for practical purposes.
In 1825 John Quincy Adams developed the first flower garden at the White House. Adams also planted herbs and vegetables at the White House, as well as ornamental trees.
In 1835, Andrew Jackson established a White House orangery (a type of greenhouse) where tropical trees and flowers could be grown. Jackson also added the Jackson magnolia to the White House grounds. The orangery was demolished in 1857. In 1878, Rutherford B. Hayes started the tradition of planting commemorative trees for Presidential Inaugurations - a tradition that persists today.
As for First Ladies - Eleanor Roosevelt famously began the Victory Garden movement in 1943, when she planted a vegetable garden on the lawn of the White House and Lady Bird Johnson has long been associated with efforts to conserve native plants.
Today, Roger Doiron of Kitchen Gardeners International is helping to lead a campaign to re-establish a Victory Garden on the lawn of the White House.
Happy President's Day!
Thursday, January 1, 2009
Lawns and Turf - Helpful or Hurtful to Global Climate Change
It is perhaps appropriate that my thoughts turn to climate change and the amount of carbon that I personally emit into the atmosphere, as I drive around the state for Master Gardener and other trainings. From January to March, I am scheduled to deliver 17 talks, that will require that I drive approximately 2612 round trip miles. Together, these trips will emit approximately 2023 pounds of carbon dioxide if I take my own vehicle (a 2006 Ford Escape, that gets 25 miles per gallon) and 1011 pounds of carbon dioxide if I rent a Hybrid sedan from OSU Motor Pool (50 miles per gallon). Because I am often asked to talk about integrated pest management, alternatives to pesticide or some other facet of sustainable gardening, I often feel hypocritical for driving around the state to teach and promote sustainable choices. But, I enjoy meeting the many Master Gardeners from across the state, learning more about Master Gardener Programs in individual counties, and always enjoy the scenary.
Given that my thoughts have turned to how much carbon I emit when I drive to teach, I thought I would blog about how much carbon we can sequester or emit via our lawn care practices.
In 2002, an article in Agronomy Journal (94:930-935) by Qian and Follett attracted much attention from scientists and industry professsionals, alike. Briefly, Qian and Follett measured the soil organic matter (abbreviated, hereafter, as SOM) in 15 golf courses that ranged in age from 1.5 to 45 years old (as of the year 2000). Because carbon is a key component of SOM (approximately 57% of soil organic matter is carbon, by weight), scientists have long used measures of SOM as a proxy for the amount of carbon sequestered by soils. Qian and Follett found that SOM increased with the age of the golf course, and that SOM continued to increase until about 31 years in fairways and 45 years in putting greens. Furthermore, Qian and Follet found that previous land use influenced total SOM. Agricultural fields that were converted into golf courses had lower SOM than golf courses that were converted from native grasslands. This last finding can potentially be explained by another study, conducted by Khan and colleagues (see below).
However, a paper presented at a recent meeting of the American Geophysical Union questions the overall utility of turf to moderate the emission of greenhouse gasses. Amy Townsend Small measured SOM in 4 parks in Irvine, California. The parks were established between 4 and 34 years ago. While Townsend Small found that older parks had more SOM, she also found that older parks emitted more nitrous oxide, which is a potent greenhouse gas. Although the precise cause of this relationship is not known, Townsend Small hypothesizes that a build up of nitrogen in the soils, as a result of repeated fertilizer applications, may contribute to increased nitrous oxide emissions.
In addition, a recent paper published in the Journal of Environmental Quality by Khan and colleagues reports that long term application of nitrogen fertilizers to corn fields decreases SOM. Khan and colleagues suggest that excessive nitrogen applications increases the decomposition of dead organic matter and SOM by soil bacteria. This is perhaps why Qian and Follet found that golf courses converted from agricultural fields had less SOM than golf courses convereted from native grasslands - the native grasslands were not subject to repeated fertilizer applications.
Taken together, what does all of this mean for you, the gardener? Here are the take home points:
1) Plants in general, including turf grasses in lawns, sequester carbon and may help mitigate carbon emissions and global climate change.
2) The benefits we all may gain, from increased SOM and carbon sequestration, can be nullified if we use fertilizers excessively. Excess fertilizer may volatize into nitrous oxide (a greenhouse gas) or may accelerate the decomposition of organic matter in the soil. Neither of these is good for helping to slow global climate change.
3) Khan and colleagues suggest that farmers should get a soil test before applying fertilizers to their fields. Doing so will lessen the likelihood that fertilizers are applied excessively. I suggest the same for you and I, dear gardener. Having your soil tested prior to applying fertilizers will help to ensure that we apply only what is needed, and only when soil nutrients are truly depleted.
Given that my thoughts have turned to how much carbon I emit when I drive to teach, I thought I would blog about how much carbon we can sequester or emit via our lawn care practices.
In 2002, an article in Agronomy Journal (94:930-935) by Qian and Follett attracted much attention from scientists and industry professsionals, alike. Briefly, Qian and Follett measured the soil organic matter (abbreviated, hereafter, as SOM) in 15 golf courses that ranged in age from 1.5 to 45 years old (as of the year 2000). Because carbon is a key component of SOM (approximately 57% of soil organic matter is carbon, by weight), scientists have long used measures of SOM as a proxy for the amount of carbon sequestered by soils. Qian and Follett found that SOM increased with the age of the golf course, and that SOM continued to increase until about 31 years in fairways and 45 years in putting greens. Furthermore, Qian and Follet found that previous land use influenced total SOM. Agricultural fields that were converted into golf courses had lower SOM than golf courses that were converted from native grasslands. This last finding can potentially be explained by another study, conducted by Khan and colleagues (see below).
However, a paper presented at a recent meeting of the American Geophysical Union questions the overall utility of turf to moderate the emission of greenhouse gasses. Amy Townsend Small measured SOM in 4 parks in Irvine, California. The parks were established between 4 and 34 years ago. While Townsend Small found that older parks had more SOM, she also found that older parks emitted more nitrous oxide, which is a potent greenhouse gas. Although the precise cause of this relationship is not known, Townsend Small hypothesizes that a build up of nitrogen in the soils, as a result of repeated fertilizer applications, may contribute to increased nitrous oxide emissions.
In addition, a recent paper published in the Journal of Environmental Quality by Khan and colleagues reports that long term application of nitrogen fertilizers to corn fields decreases SOM. Khan and colleagues suggest that excessive nitrogen applications increases the decomposition of dead organic matter and SOM by soil bacteria. This is perhaps why Qian and Follet found that golf courses converted from agricultural fields had less SOM than golf courses convereted from native grasslands - the native grasslands were not subject to repeated fertilizer applications.
Taken together, what does all of this mean for you, the gardener? Here are the take home points:
1) Plants in general, including turf grasses in lawns, sequester carbon and may help mitigate carbon emissions and global climate change.
2) The benefits we all may gain, from increased SOM and carbon sequestration, can be nullified if we use fertilizers excessively. Excess fertilizer may volatize into nitrous oxide (a greenhouse gas) or may accelerate the decomposition of organic matter in the soil. Neither of these is good for helping to slow global climate change.
3) Khan and colleagues suggest that farmers should get a soil test before applying fertilizers to their fields. Doing so will lessen the likelihood that fertilizers are applied excessively. I suggest the same for you and I, dear gardener. Having your soil tested prior to applying fertilizers will help to ensure that we apply only what is needed, and only when soil nutrients are truly depleted.
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