Hendersonia acicola on pine needles infected by Lophodermella sulcigena     

C. P. Mitchell  B. Williamson  C. S. Millar 《Forest Pathology》1976,6(2):92-102

Hendersonia acicola normally infects only needles already infected, in July-August of their first year, by Lophodermella sulcigena. Secondary infection, by H. acicola, occurs at the base of the L. sulcigena lesion either in August-October of the first year (early secondary infection) or after fruiting of L. sulcigena in June-July of the second year (late secondary infection). Early secondary infection prevents fruiting of L. sulcigena. An intercellular matrix forms at the base of the L. sulcigena lesion in response to both early and late secondary infection and rapid tissue disorganisation and disintegration ensues. Secondary infection decreases with increase in height up the tree and often results in needle breakage.  相似文献   

Classifying tree planters and non planters in a subsistence farming system using a discriminant analytical approach   总被引：1，自引：0，他引：1  

A. K. Mahapatra  C. P. Mitchell 《Agroforestry Systems》2001,52(1):41-52

Since the 1970s tree planting has been promoted to meet the multipurpose needs of subsistence farmers and to arrest deforestation in many developing countries. Financial support and extension systems were developed as tree growing outside the forest became more important. The limited success of the forest extension approaches used in the 1980s has been attributed to the failure to ascertain householders' priorities and attitudes to tree growing. Although the broader theoretical paradigm of factors influencing householders' planting of trees has been discussed household and regional level analyses are rare. This study used discriminant analysis to assess the extent to which social and economic factors affect smallholder farmer tree planting in Orissa, eastern India. The validity of the predictive model to define the different groups was tested by assessing the accuracy of classification. The significance of the factors was probed using the identified variables in the discriminant functions developed for smallholder farmers in the coastal and inland zones of Orissa. The results contradicted some common assumptions that only large landowners with a substantial income are innovators. The likelihood of adopting agroforestry is dependent on the progressive attitude of farmers, membership of village organisations, their wealth status and, more importantly, their perceived risk concerning agricultural production. This approach enables tree planters and non-planters to be characterised and hence give better targetting of planning and social forestry programmes.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

Potential long-term growth gains from early clump thinning of coppice-regenerated oak stands     

Kim E. Lowell  Harold E. Garrett  Robert J. Mitchell 《New Forests》1989,3(1):11-19

A study was established in the Missouri Ozarks to evaluate coppice regeneration of oak. Five years after a 32-year-old stand was clearcut and regenerated naturally through stump sprouts, the dominant sprout on each stump was identified based upon height. Treated plots were thinned to the single dominant sprout on each stump whereas control plots were not thinned. Twenty-five years later the largest 247, 371, 494, and 618 stems per ha were examined and height of the dominant sprout at age 5 was found to be strongly related to dbh at age 30 in both thinned and unthinned plots. However, in the thinned plots, the largest 494 stems per ha were on average 11%, 28%, and 58% greater, respectively, in height, dbh, and volume compared to similar dominant sprouts in unthinned plots. Logistic regression analysis was used to develop curves for the evaluation of potential gains from clump thinning. In this analysis, the average height of a stand at age 5 was used to estimate thinning gains at age 30.  相似文献   

The effect of short day treatments on containerized Douglas-fir morphology,physiology and phenology     

Turner  Jennifer  Mitchell  Stephen J. 《New Forests》2003,26(3):279-295

The effect of short day treatments (blackout) on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) container seedlings at the time of lift and following cold storage was investigated. Variables measured included height, root collar diameter (RCD), root growth capacity (RGC), photosynthetic efficiency after –18 °C freezing (PEF), and days to terminal bud break (DBB). From one to four blackout dormancy induction treatments were started on three dates (July 12, July 26, and August 10) with 10 or 20 d between multiple blackouts. Increasing the number of blackout treatments resulted in lower RCD, lower DBB in the late winter/early spring, and higher PEF in the early fall. Later blackout start dates decreased PEF in the early fall, and increased overall height and late fall RGC as compared to earlier blackout start dates. Nurseries growing Douglas-fir seedlings from coastal Pacific Northwest provenances should be aware that blackout regimes can decrease RGC in the late fall, and cause quicker dormancy release in the early spring. Coastal Douglas-fir can be lifted and planted in the early fall, when RGC and DBB are relatively high. If planting between February and April is necessary, seedlings given blackout should be cold stored in January to maintain an adequate level of dormancy, RGC and PEF.  相似文献   

Boron and ectomycorrhizal influences on indole-3-acetic acid levels and indole-3-acetic acid oxidase and peroxidase activities of Pinus echinata Mill. roots     

Mitchell RJ  Garrett HE  Cox GS  Atalay A 《Tree physiology》1986,1(1):1-8

The level of indole-3-acetic acid (IAA) in shortleaf pine (Pinus echinata Mill.) roots was increased by inoculation with the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch. Indole-3-acetic acid oxidase activity was also increased suggesting that the increased level of IAA was the result of increased synthesis. Boron fertilization reduced IAA levels in roots inoculated with P. tinctorius but not in noninoculated roots.  相似文献   

Boron fertilization and carbohydrate relations in mycorrhizal and nonmycorrhizal shortleaf pine     

Atalay A  Garrett HE  Mawhinney TP  Mitchell RJ 《Tree physiology》1988,4(3):275-280

Eight-week-old shortleaf pine seedlings (Pinus echinata Mill.) with and without ectomycorrhizae formed by Pisolithus tinctorius were treated for two to eight weeks with 25 microg borate ml(-1) solution applied either to the soil, or as a foliar spray, or in both ways. Control seedlings were fertilized only with modified Hoagland's solution containing 0.03 microg ml(-1) borate. Five sugars (pinitol, fructose, glucose, myoinositol and sucrose) were quantitated in both mycorrhizal and nonmycorrhizal roots by gas-liquid chromatography. Fertilization with boron increased the total carbohydrate content of mycorrhizal roots except in seedlings receiving foliar applications of boron. Foliar + soil fertilization yielded a 24% increase in total carbohydrates in mycorrhizal roots, whereas foliar fertilization alone decreased the total carbohydrate content. Carbohydrate content of nonmycorrhizal roots was significantly increased only by soil fertilization with boron. Individual sugars were affected less by boron fertilization in nonmycorrhizal roots than in ectomycorrhizal roots. However, significant increases in sugars in response to boron fertilization were observed in both ectomycorrhizal and nonmycorrhizal plants.  相似文献   

Time series analysis of forest carbon dynamics: recovery of Pinus palustris physiology following a prescribed fire     

G. Starr  C. L. Staudhammer  H. W. Loescher  R. Mitchell  A. Whelan  J. K. Hiers  J. J. O’Brien 《New Forests》2015,46(1):63-90

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Disposition,behavioural and physiological effects of escalating doses of intravenously administered fentanyl to young foals          下载免费PDF全文

H. K. Knych  E. P. Steffey  H. C. Casbeer  M. M. Mitchell 《Equine veterinary journal》2015,47(5):592-598

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Longitudinal data collection of Mycobacterium avium subspecies Paratuberculosis infections in dairy herds: the value of precise field data     

Ynte H Schukken  Robert H Whitlock  Dave Wolfgang  Yrjo Grohn  Annabelle Beaver  JoAnn VanKessel  Mike Zurakowski  Rebecca Mitchell 《Veterinary research》2015,46(1)

Longitudinal infection data on Mycobacterium avium subspecies paratuberculosis (MAP) was collected on three dairy farms in Northeastern United States during approximately 10 years. Precise data on animal characteristics and animal location within farm were collected on these farms. Cows were followed over time with regard to MAP status during biannual fecal and serum sampling and quarterly serum sampling. Approximately 13 000 serum samples, 6500 fecal samples and 2000 tissue samples were collected during these years. Prevalence of positive samples was 1.4% for serological samples, 2.2% in fecal samples and 16.7% in tissue samples. Infection dynamics of MAP was studied and resulted in a number of potential changes in our understanding of MAP infection dynamics. First, a high prevalence of MAP infection was observed in these herds due to lifetime follow up of cows, including slaughter. Second, two distinctly different infection patterns were observed, so called non-progressors and progressors. Non-progressors were characterized by intermittent and low shedding of MAP bacteria and a virtual absence of a humoral immune response. Progressors were characterized by continuous and progressive shedding and a clearly detectable and progressive humoral immune response. Strain typing of MAP isolates on the three farms identified on two of three farms a dominant strain type, indicating that some strains are more successful in terms of transmission and infection progression. Continuous high quality longitudinal data collection turned out to be an essential tool in our understanding of pathobiology and epidemiology of MAP infections in dairy herds.  相似文献   

Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes     

Mitchell AE  Hong YJ  Koh E  Barrett DM  Bryant DE  Denison RF  Kaffka S 《Journal of agricultural and food chemistry》2007,55(15):6154-6159

Understanding how environment, crop management, and other factors, particularly soil fertility, influence the composition and quality of food crops is necessary for the production of high-quality nutritious foods. The flavonoid aglycones quercetin and kaempferol were measured in dried tomato samples (Lycopersicon esculentum L. cv. Halley 3155) that had been archived over the period from 1994 to 2004 from the Long-Term Research on Agricultural Systems project (LTRAS) at the University of California-Davis, which began in 1993. Conventional and organic processing tomato production systems are part of the set of systems compared at LTRAS. Comparisons of analyses of archived samples from conventional and organic production systems demonstrated statistically higher levels (P < 0.05) of quercetin and kaempferol aglycones in organic tomatoes. Ten-year mean levels of quercetin and kaempferol in organic tomatoes [115.5 and 63.3 mg g(-1) of dry matter (DM)] were 79 and 97% higher than those in conventional tomatoes (64.6 and 32.06 mg g(-1) of DM), respectively. The levels of flavonoids increased over time in samples from organic treatments, whereas the levels of flavonoids did not vary significantly in conventional treatments. This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter. Well-quantified changes in tomato nutrients over years in organic farming systems have not been reported previously.  相似文献