Eucalypt plantation management in regions with water stress     

José LM Gonçalves  Clayton A Alvares  José HT Rocha  Carolina B Brandani  Rodrigo Hakamada 《Southern Forests》2017,79(3):169-183

Most eucalypt plantations are managed in short rotations (6–8 years) and are established in regions with water and nutritional stresses of varying degrees. The mean annual increment in these regions ranges from 20 to 45 m³ ha^?1 y^?1 depending on the level of environmental stress. Improving natural resource use efficiency by breeding and matching genotypes to sites and using appropriate site management practices is a key challenge to sustain or increase productivity. Climate change is emerging as a driving force behind many of the current issues facing natural resources, and is likely to intensify the water constraint. The Intergovernmental Panel on Climate Change has predicted significant increases in surface air temperatures and decreases in rainfall (with more erratic rainfall patterns) over the tropics and subtropics, affecting drier regions in particular. To be truly sustainable, forest management practices must be environmentally friendly, prevent or reduce land degradation, improve biodiversity and increase resilience to climate variation and change. The main efforts should address the problems of water scarcity, low soil fertility and reduced biodiversity. Forest growers should take into account the inherent risks of different forest management systems on the regional water availability and consider reducing forest productivity in order to maintain both ecological and social equilibrium. The design and implementation of management techniques should be adapted to the specific production and protection objectives, which depend on the regional and local edaphoclimatic circumstances, water resources management, protection against soil erosion, diseases, pests, bushfires, strong winds and alien species. This paper addresses the basic requirements for integrating genetic and silvicultural strategies to minimise the water constraints in eucalypt plantations and surrounding water and native vegetation resources. We show several examples of effective forest management actions on the scale of forest stand and watershed in use in Brazil.  相似文献   

Dieldrin residues in soybeans in Illinois, 1965, 1966, 1967, 1971, and 1974     

S Moore  H B Petty  W N Bruce  R Randell  D E Kuhlman 《Pesticides monitoring journal》1977,11(2):94-98

The Illinois soybean crop was monitored in 1965, 1966, 1967, 1971, and 1974 for dieldrin residues resulting from aldrin applied to corn in the years before soybean cultivation. Residue levels of dieldrin in soybeans increased between 1965 and 1974. The percent of fields which had soybeans with a dieldrin level above 0.03 ppm increased between 1965 and 1974. Dieldrin residue levels in soybeans grown in Illinois are expected to decline now that the use of aldrin has diminished and will soon cease. No significant correlation was evident between the dieldrin levels in soybeans and the area of the State where they had grown, the date of planting, or the variety.  相似文献   

The effects of drying on the structure and permeability of the wood of Abies grandis     

J. A. Petty  G. S. Puritch 《Wood Science and Technology》1970,4(2):140-154

Summary The effects of air-drying and solvent-drying on the sapwood of Abies grandis have been investigated by a new method for the determination of the size and number of conducting tracheid lumina and pit membrane pores which involves the measurement of gaseous permeability at various mean pressures. Both earlywood and latewood tracheids (83% of the total) were found to be conducting in solvent-dried wood, but in air-dried wood only latewood tracheids (32% of the total) were conducting. In solvent-dried wood there were on average 27,000 pit membrane pores per conducting tracheid compared with only 600 in air-dried wood. In both, the average pit membrane pore radius was about 0.1 m.Liquid permeabilities have been predicted from the calculated radii and numbers. The liquid permeability of solvent-dried wood was 31 times greater than that of air-dried wood in which the lumina were responsible for 13% of the total resistance to flow. The lumina were responsible for 39% of the resistance in solvent-dried wood and it is suggested that in first-formed earlywood the lumina may cause more than half the total resistance.A new method is described for the cleaning of direct carbon replicas of wood. In this the cellulose is removed by cellulase instead of sulphuric acid, and no wax backing is required. This provides much cleaner replicas. Electron micrographs have been obtained of both earlywood and latewood dried by the two methods.The authors wish to thank Mr. A. R. Sayers for preparing the computer programme used in this work, Dr. R. Ph. C. Johnson for his help and advice regarding the electron microscopy and Professors Matthews and Weatherley for their advice and encouragement.  相似文献   

Potato spraying experiments in louisiana during 1936–1937     

Milton A. Petty 《American Journal of Potato Research》1938,15(7):188-191

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烟草黑胫病菌厚垣孢子和菌丝体在土壤中的存活状态   总被引：12，自引：0，他引：12  

王革  李天飞 《南京农业大学学报》1998,21(1):41-45

将实验条件下制备、提取的黑胫病菌厚垣孢子、菌丝体悬浮液定量加入含水量分别为４０％和７０％的灭菌土壤中,分别于４℃、２５℃和室温下保存,定期检测。结果表明：厚垣孢子在各处理土壤中至少可存活８个月,主要以细胞壁加厚、原生质浓缩的休眠状态存活,而菌丝体只能单独在土壤中存活２个月。在土壤中存活３个月内的厚垣孢子可用选择性培养基直接检测,３个月需用诱捕的方法才能检测出来。温度对厚垣孢子、菌丝体的存活影响明显  相似文献   

Effects of fish heme protein structure and lipid substrate composition on hemoglobin-mediated lipid oxidation     

Richards MP  Nelson NM  Kristinsson HG  Mony SS  Petty HT  Oliveira AC 《Journal of agricultural and food chemistry》2007,55(9):3643-3654

Hemoglobin (Hb) promoted lipid oxidation more effectively in washed tilapia as compared to washed cod in spite of a 2.8-fold higher polyenoic index in the washed cod. This suggested that increasing the fatty acid unsaturation of the substrate did not accelerate the onset of lipid oxidation. Substantial phospholipid hydrolysis in the washed cod was observed, which has the potential to inhibit lipid oxidation. MetHb formation and lipid oxidation occurred more rapidly at pH 6.3 as compared to pH 7.4. Trout Hb autoxidized faster and was a better promoter of lipid oxidation as compared to tilapia Hb. The greater ability of trout Hb to promote lipid oxidation was attributed in part to its lower conformational and structural stability based on secondary and tertiary structure, acid-induced unfolding, and thermal aggregation measurements. It is suggested that the structural instability and lipid oxidation capacity of trout Hb were at least partly due to low hemin affinity. Trout and tilapia Hb were equivalent in their ability to cause lipid oxidation in washed cod muscle heated to 80 degrees C. Apparently, these high temperatures denature both trout and tilapia Hb to such an extent that any differences in conformational stability observed at lower temperatures were negated.  相似文献   

Predation of red squirrels by northern goshawks in a conifer forest in northern England: can this limit squirrel numbers and create a conservation dilemma?     

Steve J Petty  Peter W.W Lurz 《Biological conservation》2003,111(1):105-114

Red squirrels (Sciurus vulgaris) have been lost from most broadleaved habitats in England due to the range expansion of grey squirrels (S. carolinensis). Currently, the main refugia for red squirrels in England are the extensive exotic conifer forests in the north. These forests are also home to an expanding population of northern goshawks (Accipiter gentilis) that were re-established in the 1970s. During the breeding season (March - August), goshawks feed mainly on birds, with species of Columbidae, Corvidae and Phasianidae/Tetraonidae comprising 79% of 5445 prey items collected during 1973-1996. Only 97 red squirrels were recorded in this sample. We estimated that ca. 79 red squirrels were removed by goshawks each breeding season in Kielder Forest, but there was much annual variation (8-261 squirrels predated) that appeared to be related to the masting frequency of Norway spruce (Picea abies). Goshawks were likely to remove fewer squirrels outside the breeding season (September-February) because only adult males overwintered in the study area. Based on the area of conifers of a cone-bearing age and known densities of squirrels, we estimated that 1294-5556 adult squirrels produced 2135-9167 offspring annually in Kielder. For goshawks to reduce the population growth rate of squirrels to zero, predation would have to exceed 50% of the population. Clearly, this does not appear to be the case. This conclusion is in broad agreement with other studies indicating that food availability (conifer seed) is the main factor limiting numbers of tree squirrels, not predation. Thus, existing conservation management for sympatric populations of red squirrels and goshawks are compatible.  相似文献   

Corrections for capillaries used in permeability measurements of wood     

J. F. Siau  J. A. Petty 《Wood Science and Technology》1979,13(3):179-185

Summary Owing principally to kinetic energy losses, flow in which the flow rate is not linearly proportional to the applied pressure difference occurs to a considerable extent when the Reynolds number exeeds the length-to radius ratio of the capillary. When capillaries are used for flow or viscosity measurements corrections must be made for kinetic energy losses, end-effects and gas expansion. The results obtained for air flow through straight circular capillaries imply that non-linear flow may occur in wood and other heterogeneous porous media at Reynolds numbers in the region of 0.1 to 10.This work was carried out at the University of Aberdeen while J. F. Siau was on sabbatical leave and was partially supported by the NATO Senior Scientists Programme. The authors thank Professor J. D. Matthews for providing facilities for this work.  相似文献   

Wettability of Sitka spruce timber stored in a Scottish sawmill yard     

C. J. Payne  S. Woodward  J. A. Petty 《Wood Science and Technology》2001,35(1-2):107-115

Kiln-dried and air-dried Sitka spruce battens were exposed to outdoor weathering within stickered, close packed and wrapped packs and at the upper surface of these packs. A four-week exposure period was used in James Jones and Sons Ltd. sawmill yard near Aboyne, NE Scotland. The wettability of batten samples removed from the packs of timber was determined by a drop contact angle method using a video tape technique. Timber exposed to air drying before weathering in the experimental packs generally had a greater wettability than kiln-dried timber at the end of the exposure period. However, kiln-dried timber stored in stickered packs developed a greater wettability than similarly stored air-dried timber, suggesting that the kiln drying process increased the susceptibility of timber to developing increased wettability. Close-packed timber protected from sunlight and rain water, by covering the upper surface of the pack with microporous plastic sheeting, maintained a lower wettability than unprotected close-packed or stickered timber. Fungal spoilage was unlikely to develop on timber stored in pack types which developed high timber wettability, the storage conditions leading to an increase in wettability were adverse to fungal development. Kiln-dried timber stored in stickered packs in the sawmill yard may become particularly vulnerable to fungal attack if subsequently exposed to damp conditions in service. Received 15 October 1998  相似文献   

Stabilized Liquid Membrane Device (SLMD) for the Passive, Integrative Sampling of Labile Metals in Water     

W. G. Brumbaugh  J. D. Petty  J. N. Huckins  S. E. Manahan 《Water, air, and soil pollution》2002,133(1-4):109-119

A stabilized liquid membrane device (SLMD) is described forpotential use as an in situ, passive, integrative samplerfor cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead(Pb), and zinc (Zn) in natural waters. The SLMD (patent pending)consists of a 2.5-cm-wide by 15-cm-long strip of low-density polyethylene (LDPE) layflat tubing containing 1 mL of an equalmixture (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-[4-ethyl-1-methyloctyl]-8-quinolinol). The reagentmixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of several divalent metals for up to several weeks. Depending on samplerconfiguration, concentration factors of several thousand canbe realized for these metal ions after just a few days. In addition to in situ deployment, the SLMD may be useful for laboratory determination of labile metal species in grab samples. Methods for minimizing the effects of water flow onthe sampling rate are currently under investigation.  相似文献