Soil properties under a Pinus radiata – ryegrass silvopastoral system in New Zealand. Part I. Soil N and moisture availability, soil C, and tree growth     

S. X. Chang  G. Amatya  M. H. Beare  D. J. Mead 《Agroforestry Systems》2002,54(2):137-147

Understanding the changes in soil properties in silvopastoral systems is important in regulating the interactions between tree and understorey pastures. In this study, the effects of understorey management on soil mineral N and moisture availability, soil temperature, soil C, and tree growth were investigated in a seven-year-old silvopastoral agroforestry experiment in Canterbury, New Zealand. The systems included understorey treatments of bare ground and ryegrass (Lolium perenne) pasture. Soil mineral N, moisture content, and temperature were monitored from July 1997 to July 1998 in two positions (0.9 and 3.5 m north of tree rows) and two soil depths (0–10 and 10–20 cm). Soil C and N in the 0–10 cm depth were higher in the ryegrass than in the bare ground plots, reflecting the organic C and N input in the ryegrass plots, as well as greater N loss from the bare ground plots in the form of nitrate leaching and/or denitrification. Soil C was higher in the position 0.9 m than 3.5 m away from the tree rows, possibly caused by the greater C input from decomposing fine tree roots and needle litterfall at the 0.9 m position. Soil moisture availability was greater in the bare ground than in the ryegrass plots in the summer. No effect of understorey management on soil temperature was found. Soil nitrate levels were lower in the ryegrass plots and may be limiting when soil moisture supply was adequate. Tree volume growth from winter 1997 to 1998 was significantly greater in the bare ground treatment, reflecting better soil moisture and N supply conditions. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

Yield and foliar injury responses of mature plum trees to salinity     

G. J. Hoffman  P. B. Catlin  R. M. Mead  R. S. Johnson  L. E. Francois  D. Goldhamer 《Irrigation Science》1989,10(3):215-229

Summary The salt tolerance of mature Santa Rosa plum trees was assessed on 20-year-old trees grown in the San Joaquin Valley of California. The experimental design consisted of six levels of irrigation water salinity (electrical conductivities of 0.3 to 8 dS/m) replicated five times with each replication consisting of ten trees. Salinity treatments imposed in March 1984 did not influence tree yields harvested in June 1984. In 1985, the second year of treatments, yield from the highest salt treatment (electrical conductivity of irrigation water, EC _i , of 8 dS/m) was reduced by half; the number of fruit harvested was reduced 40%, and fruit size was reduced significantly. Foliar damage was so severe by the end of 1985 that nonsaline water was applied to the two highest salt treatments (EC _i = 6 and 8 dS/m) in an attempt to restore tree vigor. In 1986 salt effects had become progressively worse on the continuing saline treatments. A linear piece-wise salt tolerance curve is presented for soil salinity values, expressed as the electrical conductivity of saturated extracts (EC _e ) integrated to a soil depth of 1.2 m over a 2-year period. The salt tolerance threshold for relative yield (Y _r ) based on 3 years of data was 2.6 dS/m and yield reduction at salinity levels beyond the threshold was 31% per dS/m (Y _ir=100 – 31 [EC _e – 2.6]j). Significant foliar damage occurred when leaf chloride concentrations surpassed 200 mmol/kg of leaf dry weight (0.7%). Sodium concentrations in the leaves remained below 10 mmol/kg (0.02%) until foliar damage became severe. This suggests that chloride was the dominant ion causing foliar damage.  相似文献   

Long-term response of mature plum trees to salinity     

P. B. Catlin  G. J. Hoffman  R. M. Mead  R. S. Johnson 《Irrigation Science》1993,13(4):171-176

Deciduous fruit trees are known to be salt sensitive but the degradation may be delayed for a number of years depending on salinity level and tree size. A field experiment was conducted in the San Joaquin Valley of California on mature plum trees. The objectives were to quantify salt tolerance with time and to document the development and impact of salt stress over a 6-year period. After three years, the salt tolerance threshold, measured as the electrical conductivity of saturated soil extracts, for fruit yield was 2.6 dS/m. At salinity levels in excess of the threshold, yield was reduced at the rate of 31% for each 1 dS/m increase in soil salinity. The continuation of this experiment for an additional three years did not alter the salt tolerance as measured by fruit yield. Attempts to revive trees that had been severely damaged by excess salinity were successful but recovery, depending on the severity of damage, requires several years.  相似文献   

Protracted spawning of St Lawrence River northern pike (Esox lucius): simulated effects on survival, growth, and production     

J. M. Farrell  J. V. Mead  B. A. Murry 《Ecology of Freshwater Fish》2006,15(2):169-179

Abstract –  An individual-based early life history model demonstrated that the timing and distribution of St Lawrence River northern pike ( Esox lucius ) spawning could affect subsequent young-of-year (YOY) production during nursery and influence year-class formation. Three different spawning patterns have emerged from empirical studies, where egg deposition occurred along the entire littoral gradient beginning in seasonally flooded emergent habitats in tributaries, progressing to submerged aquatic vegetation in shallow bays, and ending in deep water littoral habitats (up to 6 m). The spawning period is protracted, and typically lasts 6–8 weeks due to the presence of a strong thermal gradient. The model used temperature as the driving variable to predict egg abundance, stage-specific development, growth, survival, and ultimately relative production of YOY northern pike within 1-ha plots representative of the three habitats. Earlier spawning (mean 21 days) and higher mean daily survival and growth yielded higher YOY net production for tributaries (mean = 3095.4 g ha⁻¹, SD = 2028.6) relative to the shallow bay habitat (202.5 g ha⁻¹, SD = 125.7). In contrast, deep littoral habitat represented an ecological sink with little production (<0.9 g ha⁻¹). The results demonstrate the importance of the linkage between spawning and nursery processes in determining reproductive success.  相似文献   

HUMMINGBIRD AND HORNET     

Mead CW 《Science (New York, N.Y.)》1908,28(717):408

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THE MANAGEMENT OF LONG GRASS AS A BIRD REPELLENT ON AIRFIELDS     

H. Mead  A. W. Carter  † 《Grass and Forage Science》1973,28(4):219-222

Authorities responsible for the safety of aircraft have for a number of years been very concerned with the dangers and the damage caused by aircraft striking birds while in flight, particular since the introduction of the jet engine. Methods of reducing this risk have been sought, which have brought about the method of grass management described in this paper.  相似文献   

THE BREEDING OF ANIMALS AT WOODS HOLL DURING THE MONTH OF APRIL, 1898     

Mead AD 《Science (New York, N.Y.)》1898,7(177):702-704

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THE EPIDIASCOPE     

Mead AD 《Science (New York, N.Y.)》1905,21(526):152-153

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Salmonella enteritidis PT4: broiler breeder flock breakdowns.     

N G Fowler  G C Mead 《The Veterinary record》1992,130(19):431-432

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A soluble recombinant fusion protein of the transmembrane envelope protein of equine infectious anaemia virus for ELISA.     

L M Thomas  P J Huntington  L J Mead  D L Wingate  B A Rogerson  A M Lew 《Veterinary microbiology》1992,31(2-3):127-137

The use of the bacterial expression vector, pGex, to produce an abundant, soluble fusion protein of gp45 from equine infectious anaemia virus is described. Purification of the recombinant protein was achieved by one step affinity chromatography on immobilized glutathione using competitive elution so no harsh conditions were required. This provides a readily available antigen that is defined, plentiful and cheap. Yields of 3.5 mg of purified soluble protein/litre of bacterial culture were obtained. This antigen was found to be suitable for ELISA. Background reactivity to either the glutathione-S-transferase (GST) fusion partner by immune sera or the EIA-GST fusion protein by normal sera were negligible.  相似文献