Living Architecture Monitor - Green Roofs for Healthy Cities

More documents

Recommendations

Info

NATIVEPLANTRESEARCH IMPACTOFGROWINGMEDIA ON PRAIRIEGRASSES RESEARCHFROMLINCOLNNEBRASKAPROVIDESINSIGHTONTHEPERFORMANCEOF GROWINGMEDIAINTHEESTABLISHMENTOFTALLNATIVEGRASSESONEXTENSIVEROOFS By Richard K. Sutton American conservationist, Aldo Leopold asked us to “Think like a mountain.” When it comes to extensive green roofs in drier climates, however, we need to think like a prairie. Selected research on tall grass prairie species questions their use, but sedum now used on too many extensive green roofs is a monoculture inherited from Northwest European countries including Germany — and nature rewards diversity. In the Great Plains’ climate, short- and mid-grass prairies have evolved diverse communities of grasses, forbs and sedges in shallow soil with hot summers, cold winters, high winds, low humidity and little rainfall. While sedum grows well in Germany’s effective 15 to 18 inches of net precipitation (accounting for potential evapotranspiration), the Great Plains prairie can flourish on net precipitation that has a 0- to 15-inch deficit. Thinking like a prairie in 2006, Architectural Partnership, an architectural firm in Lincoln, Nebraska, designed the state’s first public building, the Pioneers Park Nature Center (PPNC) Prairie Building addition, to incorporate a 900-square-foot extensive green roof. The green roof uses Hydro-tek Gardendrain system covered by three and one-half inches of Rooflite’s 95 per cent heat expanded shale and five per cent compost by volume. Given where the building was situated, it was only logical to take note of the mission of the Pioneers Park Nature Center (PPNC) — that is, to teach the public about the importance of native plants and animals — and use prairie plants on the green roof. As a landscape architect doing research at UN-Lincoln, I worked with the PPNC staff to design an assemblage of green roof prairie plants that included grasses, sedges and forbs. Plantings were placed to be ongoing three- to five-year (or longer) experimental plots and a roof-top prairie. Our first studies look at the establishment of the selected prairie plants especially their growth under two simple treatment additions to the Rooflite media. Though the first treatment (supplementing available moisture with super-absorbent polymer gels such as Horta-sorb) has been around the horticulture industry for years it has not, to my knowledge, yet found its’ way onto green roofs. The second treatment (adding soil microbes gleaned from prairie soils) has gained use in landscape plantings on low-nutrients soils and hypothesized to help activate the compost fraction in the media, thus making nutrients and water more readily available to plants. A dozen six-by-six foot plots were randomly planted eight inches on center to a mixture of native species consisting of six grasses, one sedge and five forbs as # 72 plugs. Three plots each were randomly assigned to: “American conservationist, Aldo Leopold asked us to ‘Think like a mountain.’ When it comes to extensive green roofs in drier climates, however, we need to think like a prairie.” LEFTBecky Seth, a Pioneers Park Nature Center naturalist, assists Dr. Richard Sutton in recording prairie plant growth ratings on the nature center’s new extensive green roof.
FIRSTGROWINGSEASONPLOTGROWTHRATINGSFOR TREATMENTSWITHMICROBESHORTA-SORBHEIR INTERACTIONANDROOFLITECONTROL GROWTHRATINGSANDAVERAGEFORTREATMENTS TREATMENTS TOTALPERBLOCK AVERAGETREATMENT AVERAGEPERPLANT GROWTHRATING GROWTHRATING GROWTHRATING Blk 4 A Control 169 Blk 7 A Control 153 Blk 20 A Control 152 474 158 2.63 Blk 1 B Microbes 168 Blk 3 B Microbes 167 Blk 5 B Microbes 168 503 168 2.80 Blk 6 C Horta-Sorb 183 Blk 10 C Horta-Sorb 182 Blk 11 C Horta-Sorb 176 541 180 3.00 Blk 2 D Microbes + Horta-Sorb 202 Blk 8 D Microbes + Horta-Sorb 192 Blk 9 D Microbes + Horta-Sorb 188 582 194 3.23 1) A treatment of: Horta-sorb; 2) A slurry of prairie microbes; 3) A combination of Horta-sorb and microbes; and 4) A control consisting of straight Rooflite. 6 = Roots well established and exceptional growth and vigor and establishment of plant crown greater than 6 cm but less than 10 cm; 7 = Plant expanding beyond 10 cm but less than 16 cm; and 8 = Plant expanding to greater than 16 cm. In addition, 95-hundredths of an inch of water was applied by irrigation per week from June to September. The plants were examined monthly from July to October and rated for growth and establishment, using the following system: PLANTGROWTHRATINGSYSTEM 0 =Dead or missing plant; 1= Live plant in poor condition; less crown or stem growth than when planted plant loose; no rooting beyond initial plug; 2 = Plant established but crown not expanding or top growth stagnant, beyond areas of plug; 3 = Plant with roots established and crown expanding up to 1 cm beyond; or vigorous top growth; 4 = Plant roots established and plant crown expanded up to 2 cm beyond; additional stems; 5 = Roots well established and vigorous; plant crown expanded beyond original plug area by greater than 2 cm but less than 6 cm; Data from the end of the first growing season (October) is just being analyzed. Raw plot totals for plant growth ratings are greatest (above) for the interaction of Horta-Sorb and the slurry of microbes, next for the Horta-Sorb alone, then next for the slurry of microbes alone and finally lowest for the Rooflite media alone. This data has not been checked for homogeneity of variance or significant differences, however the visual difference between the treatments and the control are readily apparent when one sees the green roof plots for the plants in treatments are greener and appear more robust. The implications are that media manipulation may make short and mid-grass prairie plantings a viable alternative to sedum for extensive green roofs in the Great Plains. Richard K. Sutton, ASLA, Ph.D, is a Lincoln, Nebraska-based associate professor of Agronomy and Horticulture and Horticulture and Landscape Architecture at the University of Nebraska-Lincoln. He is a featured presenter at Green Roofs For Healthy Cities’ upcoming annual conference — www.greenroofs.org/baltimore. LIVING ARCHITECTURE MONITOR WINTER
Page 1 and 2: GREEN ROOFS FOR HEALTHY CITIES WINT
Page 3 and 4: COLD What can we learn from the cli
Page 5 and 6: THEGROWINGMEDIA&PLANTISSUE Welcome
Page 7 and 8: THEGROWINGMEDIA&PLANTISSUE ALIVINGL
Page 9 and 10: GREENROOFSGO EXTREME—ANDPRIMETIME
Page 11 and 12: Photos courtesy Elisabeth Whitelaw
Page 13 and 14: THEGROWINGMEDIA&PLANTISSUE Q: Looki
Page 15 and 16: THEGROWINGMEDIA&PLANTISSUE PROJECTS
Page 17 and 18: THEGROWINGMEDIA&PLANTISSUE transfor
Page 19 and 20: THEGROWINGMEDIA&PLANTISSUE “DON
Page 21 and 22: THEGROWINGMEDIA&PLANTISSUE “Organ
Page 23: THEGROWINGMEDIA&PLANTISSUE of dead
Page 27 and 28: THEGROWINGMEDIA&PLANTISSUE Ron Wik
Page 29 and 30: THRIVINGCONDITIONS Tips for sustain
Page 31 and 32: THEGROWINGMEDIA&PLANTISSUE DROUGHT
Page 33 and 34: THEGROWINGMEDIA&PLANTISSUE LEFTFIGU
Page 35 and 36: “The design process is organized
Page 37 and 38: seeing is that green walls are beco
Page 39 and 40: THEGROWINGMEDIA&PLANTISSUE Fifth Cr
Page 41 and 42: THEGROWINGMEDIA&PLANTISSUE profile
Page 43 and 44: SCIENTIFIC INTEREST GREENROOFSDEBUT
Page 45 and 46: THEGROWINGMEDIA&PLANTISSUE FROMTHE

Living Architecture Monitor - Green Roofs for Healthy Cities

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?