Relating the survival and growth of planted longleaf pine seedlings to microsite conditions altered by site preparation treatments     

Benjamin O. Knapp  G. Geoff Wang  Joan L. Walker 《Forest Ecology and Management》2008,255(11):3768-3777

Pine plantations in the southeastern United States are often created using site preparation treatments to alleviate site conditions that may limit survival or growth of planted seedlings. However, little is understood about how site preparations affect longleaf pine (Pinus palustris P. Miller) seedlings planted on wet sites. In a 2-year study (2004 and 2005) on poorly drained, sandy soils of Onslow County, North Carolina, we examined the effects of common site preparation treatments on microsite conditions and quantified relationships between microsite conditions and longleaf pine seedling survival and growth. Treatments used in the study included site preparations designed to control competing vegetation (chopping and herbicide) combined with those that alter soil conditions (mounding and bedding). During both years, mounding and bedding treatments reduced the amount of moisture within the top 6 cm of soil and increased soil temperatures when compared to flat planting (p < 0.001). Soil moisture was inversely related to seedling mortality in 2004 (r² = 0.405) and inversely related to root collar diameter in 2005 (r² = 0.334), while light was positively related to root collar diameter in 2005 (r² = 0.262). Light availability at the seedling level was highest on treatments that effectively reduced surrounding vegetation. Herbicides were more effective than chopping at controlling vegetation in 2004 (p < 0.001) and 2005 (p = 0.036). Controlling competing vegetation, especially shrubs, was critical for increasing early longleaf pine seedling growth.  相似文献   

A stand density index for complex mixed species forests in the northeastern United States   总被引：2，自引：0，他引：2  

Mark J. Ducey  Rachel A. Knapp 《Forest Ecology and Management》2010

Quantifying stand density is important for accurate prediction of net biomass and carbon accumulation, for estimating growth and mortality risks of trees, stands, and regions, and for the management of forests for multiple goods and services. Building on previous work relating maximum stand density to wood specific gravity, we develop a stand density equation for the mixed species forests of the northeastern United States using data from the US Forest Service, Forest Inventory and Analysis program. We used quantile regression, in concert with a quantile selection and evaluation procedure, to ensure conformity between our density measure and previously developed guidance for well-studied stand types. The resulting strictly additive relative density measure appears to provide reasonable prediction of maximum density even for plantations of exotic conifers in the region. The results suggest that maximum stand densities after accounting for wood specific gravity may be lower in northeastern North America than in the south or west.  相似文献   

Phase I Clinical Trial and Pharmacokinetics of Intravesical Mitomycin C in Dogs with Localized Transitional Cell Carcinoma of the Urinary Bladder     

A.H. Abbo  D.R. Jones  A.R. Masters  J.C. Stewart  L. Fourez  D.W. Knapp 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2010,24(5):1124-1130

Background: Transitional cell carcinoma (TCC) is the most common cancer of the urinary tract in dogs. The most frequent cause of death is urinary obstruction from the primary tumor. Standard medical therapy for TCC is only partially effective. Hypothesis/Objectives: Intravesical administration of mitomycin C (MMC) in dogs with invasive TCC will result in antitumor activity against the primary tumor and minimal systemic drug absorption. Animals: Thirteen privately owned dogs with naturally occurring, histopathologically diagnosed TCC of the urinary bladder. Methods: A prospective phase I trial was performed. MMC was given intravesically (600 μg/mL initial concentration) for 1 h/d for 2 consecutive days each month. The MMC concentration was escalated to a maximum of 800 μg/mL in groups of 3 dogs until the maximum tolerated dose (MTD) was determined. Serum assays for MMC were performed to determine the extent of systemic absorption of the MMC. Results: The MTD of MMC based on local toxicoses was 700 μg/mL (1‐h dwell time, 2 consecutive days). In addition, 2 dogs had severe myelosuppression and appeared to have systemic absorption of MMC. Five dogs had partial remission, and 7 dogs had stable disease. Conclusions: Intravesical MMC has antitumor activity in dogs with invasive TCC. Further study is needed to determine the cause of the myelosuppression associated with MMC administration, and to develop strategies to minimize this risk.  相似文献   

Modulation of diversity by grazing and mowing in native tallgrass prairie   总被引：4，自引：0，他引：4  

SL Collins  AK Knapp  JMB riggs  JM Blair  EM Steinauer 《Science (New York, N.Y.)》1998,280(5364):745-747

Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.  相似文献   

Introgressiomics: a new approach for using crop wild relatives in breeding for adaptation to climate change     

Jaime Prohens  Pietro Gramazio  Mariola Plazas  Hannes Dempewolf  Benjamin Kilian  María J. Díez  Ana Fita  Francisco J. Herraiz  Adrián Rodríguez-Burruezo  Salvador Soler  Sandra Knapp  Santiago Vilanova 《Euphytica》2017,213(7):158

The need to boost agricultural production in the coming decades in a climate change scenario requires new approaches for the development of new crop varieties that are more resilient and more efficient in the use of resources. Crop wild relatives (CWRs) are a source of variation for many traits of interest in breeding, in particular tolerance to abiotic and biotic stresses. However, their potential in plant breeding has largely remained unexploited. CWRs can make an effective contribution to broadening the genetic base of crops and to introgressing traits of interest, but their direct use by breeders in breeding programs is usually not feasible due to the presence of undesirable traits in CWRs (linkage drag) and frequent breeding barriers with the crop. Here we call for a new approach, which we tentatively call ‘introgressiomics’, which consists of mass scale development of plant materials and populations with introgressions from CWRs into the genetic background of crops. Introgressiomics is a form of pre-emptive breeding and can be focused, when looking for specific phenotypes, or un-focused, when it is aimed at creating highly diverse introgressed populations. Exploring germplasm collections and identifying adequate species and accessions from different genepools encompassing a high diversity, using different strategies like the creation of germplasm diversity sets, Focused identification of germplasm strategy (FIGS) or gap analysis, is a first step in introgressiomics. Interspecific hybridization and backcrossing is often a major barrier for introgressiomics, but a number of techniques can be used to potentially overcome these and produce introgression populations. The generation of chromosome substitution lines (CSLs), introgression lines (ILs), or multi-parent advanced inter-cross (MAGIC) populations by means of marker-assisted selection allows not only the genetic analysis of traits present in CWRs, but also developing genetically characterized elite materials that can be easily incorporated in breeding programs. Genomic tools, in particular high-throughput molecular markers, facilitate the characterization and development of introgressiomics populations, while new plant breeding techniques (NPBTs) can enhance the introgression and use of genes from CWRs in the genetic background of crops. An efficient use of introgressiomics populations requires moving the materials into breeding pipelines. In this respect public–private partnerships (PPPs) can contribute to an increased use of introgressed materials by breeders. We hope that the introgressiomics approach will contribute to the development of a new generation of cultivars with dramatically improved yield and performance that may allow coping with the environmental changes caused by climate change while at the same time contributing to a more efficient and sustainable agriculture.  相似文献   

Nachweis von Yersinia enterocolitica und Yersinia pseudotuberculosis in Kotproben gesunder Schlachtschweine in Abhängigkeit von der Jahreszeit     

A. Weber  W. Knapp 《Zoonoses and public health》1981,28(5):407-413

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Outcrossing Rates of Experimental Populations of Cuphea lanceolate     

S. J. Knapp    L. A. Tagliani  B.-H. Liu 《Plant Breeding》1991,106(4):334-337

Outcrossing rates of Cuphea lanceolata Ait., a new Dilseed crop, have not been estimated; however, this species is known to be insect-pollinated, self-compatible, and autosterile. We used five allozyme loci and the mixed mating model to estimate the outcrossing rates of experimental populations of Cuphea lanceolata Ait. grown at Corvallis, Oregon in 1987 and 1988. Populations were grown using densities of one and 27 plants m^?2. Multilocus out-crossing rate estimates of populations grown at low and high density ranged from 0.61 to 0.85 and 0.93 to 0.94, respectively. Density caused differences may be caused by differences in pollinator movement. In open plantings, e.g., space-plant nurseries, selfing rates are increased by increased within plant pollination by bumblebees, the primary pollinators of C. lanceolata in temperate zones. The movement of pollinators between plants is enforced in dense plantings. We found C. lanceolata is predominantly al-logamous, but selfing rates as great as 39.0 % were observed among space-plants; thus, the progeny of an open-pollinated individual plant grown in this type of nursery is a mixed half-sib and S₁ family. Maximum outcrossing can be achieved by using dense plantings.  相似文献   

Maternal breed of sire effects on postweaning performance of first-cross heifers and production characteristics of 2-year-old heifers.     

W L Reynolds  J J Urick  B W Knapp  M D MacNeil 《Journal of animal science》1991,69(11):4368-4376

Postweaning growth rates from weaning to 18 mo, fall condition score, pregnancy rates, and production to 2 yr of age were evaluated in a study of Angus (A)-, Pinzgauer (P)-, Red Poll (R)-, Simmental (S)-, and Tarentaise (T)-sired females from Hereford dams. First-cross heifers from the different sire breeds did not differ (P greater than .10) in initial weight. During a 140-d feed test, S gained 98.6 kg, exceeding (P less than .05) gains of P, 92.3; A, 91.4; and R, 87.3 kg but not T, 94.1 kg. Red Poll-sired heifers weighed less at the end of the 140-d test (P less than .05) than the other crosses, which did not significantly differ from each other. No breed of sire differences were found in gain from 140 d to fall weight. Simmental-sired heifers weighed more (P less than .05) than A- and R-sired heifers at 18 mo. Breed of sire and year interacted to affect pregnancy rate of the yearling heifers when mated to Shorthorn sires for 45 d. Percentage of dystocia varied from a low of 26.3 and 28.9% for T- and A-sired heifers, respectively, to 54.4 and 60.8% for P- and S-sired heifers, respectively (P less than .05). Age of dam of heifers affected (P less than .05) weight at the different period end points but not gains after weaning. Age of dam also affected incidence of dystocia. Two-year-old heifers from young dams had more dystocia than heifers from older dams. Shorthorn-sired calves from 2-yr-old heifers with different sire breeds differed in birth weight (P less than .05) but not survival from birth to weaning, ADG from birth to weaning, weaning age, or weaning condition score. Average 200-d weight of calves from P-, S- and T-sired heifers exceeded those from A- and R-sired heifers by 10.7 kg, or 5.7%.  相似文献   

Epizootiologic factors of Fascioloides magna (trematoda) in Oregon and Southern Washington   总被引：2，自引：0，他引：2  

V J Dutson  J N Shaw  S E Knapp 《American journal of veterinary research》1967,28(124):853-860

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Effect of collection time and exercise restriction on the prediction of urine protein excretion, using urine protein/creatinine ratio in dogs   总被引：1，自引：0，他引：1  

D L McCaw  D W Knapp  J E Hewett 《American journal of veterinary research》1985,46(8):1665-1669

Nonproteinuric and proteinuric dogs were studied to determine whether the urine protein/creatinine ratio from a 24-hour urine sample could be used to predict urine protein excretion. Urine protein/creatinine ratios estimated from urine produced during daylight hours and from that produced during nighttime hours were compared to determine whether time of sample collection influenced the prediction of the urine protein excretion value. Urine protein/creatinine ratios in urine from male dogs were compared with those from female dogs to determine whether sex had an influence on the value. Hospitalized and nonhospitalized dogs were used to determine the effect of exercise restriction. The urine protein/creatinine ratio varied significantly between healthy and proteinuric dogs (P = 0.0001). It was not influenced by collection period or sex. Animals not confined to hospital cages had a significantly lower urine protein/creatinine ratio than did hospitalized animals confined to a cage (P = 0.003).  相似文献