Comparing ecological restoration alternatives: Grand Canyon, Arizona     

Peter Z. Ful  W. Wallace Covington  H. B. Smith  Judith D. Springer  Thomas A. Heinlein  Kristin D. Huisinga  Margaret M. Moore 《Forest Ecology and Management》2002,170(1-3):19-41

Three treatments designed to initiate the process of restoring the surface fire regime and open forest structure of a southwestern ponderosa pine forest were compared on the Kaibab National Forest along the Grand Canyon’s South Rim. The treatments were: (1) full restoration (FULL)—thinning trees to emulate stand structure prior to fire regime disruption ca. 1887, forest floor fuel treatment, and prescribed burning, (2) minimal thinning (MIN)—removing young trees only around living old-growth (pre-1887) trees, fuel treatment, and prescribed burning, (3) burn-only (BURN)—representing the current management policy in Grand Canyon National Park (GCNP), and (4) CONTROL. Each treatment was applied to a 12 ha unit. Compared to reconstructed 1887 conditions, all study sites were much more dense prior to treatment (94–176 trees/ha in 1887, compared to 783–3693 trees/ha in 1997). However, basal area increases were less striking (12.6–20.3 in 1887, 17.5–27.0 m²/ha in 1997), reflecting past harvest and dwarf mistletoe reduction treatments that removed many large pines. In 2000, 1 year after treatment, tree densities were reduced to 11, 23, and 37 of pre-treatment levels in the FULL, MIN, and BURN treatments, respectively. Understory plant communities showed significant declines in richness and plant frequency across years, probably due to a severe drought in 2000 (60% of average precipitation). No differences in plant communities were observed across treatments, despite the mechanized disturbance associated with tree removal in the FULL treatment. Prescribed fire behavior (flame length, flaming zone depth) and effects (bole char, crown scorch) were similar across all three burned treatments. Simulated fire behavior under dry, windy conditions was reduced in all three treatments compared to the control. The FULL treatment was much less susceptible to crownfire due to reduced crown bulk density and crown fuel load and increased crown base height. Crownfire susceptibility of the BURN treatment was only slightly reduced, while the MIN treatment was intermediate. Compared to the reference conditions of forest structure, the FULL treatment represented the most rapid and comprehensive restoration treatment, although the residual stand was at the low end of historical density. The BURN treatment thinned many small trees but had minor effects on crownfire susceptibility. Effects of the MIN treatment fell between FULL and BURN. The experimental treatments may be useful for the creation of defensible firebreaks near developments, roads, and boundaries with the FULL treatment, supplemented by MIN and BURN treatments over larger areas.  相似文献   

Identification of parents suitable for molecular mapping of immunity and resistance genes in solanum species     

Carol A. Ishimaru  Nora L. V. Lapitan  Anne VanBuren  Ann Fenwick  Kristin Pedas 《American Journal of Potato Research》1994,71(8):517-533

A survey of DNA polymorphisms and bacterial ring rot reactions inSolanum species was conducted to identify parents that when crossed would produce an F₁ mapping population useful for identifying DNA markers tightly linked to genes for immunity or resistance to bacterial ring rot.Solanum tuberosum, S. acaule, diploidSolanum species, doubled monoploid lines ofS. phureja, and somatic fusion hybrids betweenS. tuberosum andS. brevidens were established in tissue culture from single true potato seeds or tubers and evaluated for bacterial ring rot reactions in greenhouse studies with root-inoculated tissue cultured plantlets. Establishment of tissue culture stocks insured the availability of homogeneous genetic material for use in bacterial ring rot assays and genetic analyses. Presence ofClavibacter michiganense subsp.sepedonicum was assessed in stems by an immunofluorescence antibody assay (IFAS). Two accessions were found to be immune to bacterial ring rot. DNA polymorphisms were detected within and among 24 accessions evaluated with 24 RFLP markers and 10 arbitrary oligonucleotide primers (RAPDs). These results identify parents suitable for future mapping of gene (s) for immunity or resistance to bacterial ring rot.  相似文献   

Climate and land change impacts on future managed wetland habitat: a case study from California’s Central Valley     

Wilson  Tamara S.  Matchett  Elliott  Byrd  Kristin B.  Conlisk  Erin  Reiter  Matthew E.  Wallace  Cynthia  Flint  Lorraine E.  Flint  Alan L.  Joyce  Brian  Moritsch  Monica M. 《Landscape Ecology》2022,37(3):861-881

Landscape Ecology - California’s Central Valley provides critical habitat for migratory waterbirds, yet only 10% of naturally occurring wetlands remain. Competition for limited water supplies...  相似文献   

Hierarchical action and inhibition of plant Dicer-like proteins in antiviral defense     

Deleris A  Gallego-Bartolome J  Bao J  Kasschau KD  Carrington JC  Voinnet O 《Science (New York, N.Y.)》2006,313(5783):68-71

The mechanisms underlying induction and suppression of RNA silencing in the ongoing plant-virus arms race are poorly understood. We show here that virus-derived small RNAs produced by Arabidopsis Dicer-like 4 (DCL4) program an effector complex conferring antiviral immunity. Inhibition of DCL4 by a viral-encoded suppressor revealed the subordinate antiviral activity of DCL2. Accordingly, inactivating both DCL2 and DCL4 was necessary and sufficient to restore systemic infection of a suppressor-deficient virus. The effects of DCL2 were overcome by increasing viral dosage in inoculated leaves, but this could not surmount additional, non-cell autonomous effects of DCL4 specifically preventing viral unloading from the vasculature. These findings define a molecular framework for studying antiviral silencing and defense in plants.  相似文献   

Effects of oral 3% hydrogen peroxide used as an emetic on the gastroduodenal mucosa of healthy dogs          下载免费PDF全文

Alicia H. Niedzwecki DVM  Bradley P. Book DVM  DABVP  DACVECC  Kristin M. Lewis DVM  MS  DACVIM  J. Scot Estep DVM  DACVP  Joseph Hagan ScD 《Journal of Veterinary Emergency and Critical Care》2017,27(2):178-184

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Sleep Characterization at High Altitude     

Nicholas Kanaan  Caleb Phillips  Becky Higbee  David Pomeranz  Michael Shaheen  Kristin Fontes  Patrick Cain  Sean Wentworth  Carolyn Meyer  Grant Lipman 《The Forestry Chronicle》2017,28(4):366

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