摘要:

AbstractA mathematical model for simulating the penetration, propagation and absorption of radiation within crop canopies of random leaf distribution is presented. Although the treatment of radiation penetration is based on well known theory, a new approach is developed for tracing the quantity and direction of reflected and transmitted radiation. This approach allows for multiple reflection and transmission up to any required level of accuracy, reflection from the soil, upward as well as downward flux and provides an explicit account of the quantities and direction of scattered radiation. These features will be of most significance at wavelengths where absorption is lowest such as the near‐infrared wavebands which are important in remote sensing applications. The approach taken also allows for more flexible consideration of foliage angle which will be most relevant in the photosynthetically active waveband where absorption is high.The predictions of the downward and upward travelling flux densities are compared under ideal conditions with measurements made in canopies of known architecture with three different species, under both clear and overcast skies. Good agreement was obtained in all cases. The expected model deviation in the case of non‐random foliage distribution is demonstrated, and the implications for further model development indica

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01143.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractTwo studies of arid zone plant communities are described. In the first, the perennial grass Eragrostis eriopoda was sampled over 8 months for dry weight and water stress of tops, and water content and tension of soil to a depth of 150 cm. In the second, lasting 2 years, pure Eragrostis and pure Aristida con‐torta (annual) communities were sampled for dry weight of tops and roots and soil water content. Plots of naturally occurring mixtures of Eragrostis and Aristida were also studied.During periods of prolonged high soil water content, perennial communities greatly out‐yielded annuals (1200 and 260gm‐2respectively). During prolonged droughts all communities yielded less than 100 gm‐2.Perennial root systems were larger than for annuals. The weight of annual roots varied little with season as distinct from perennials which varied greatly. Maximum weight of annual roots occurred in the top 10 cm of soil; the zone of maximum rooting by perennials was 10–30 cm. Water loss from annual, perennial and bare plots was similar and extended throughout the measured profile. Two gradients of soil water tension of opposite signs developed during prolonged drought. The greater was due to evapo‐transpiration and the lesser developed below the zone of recharge.On average. Eragrostis grew 4.6 times faster than the annuals which enjoyed a marginally more favourable water regime. In a mixture which had received one heavy simulated grazing the presence of annuals reduced the growth of Eragrostis by 68%, suggesting that the invasion of Eragrostis by annuals would seriously reduce p

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01144.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractRock outcrops on spurs and summits on Wilson's Promontory tend to be more prevalent on hot dry slopes than cool moist ones. In this comparatively moist climate, the rock outcrop vegetation can be grouped into high altitude, low altitude and coastal types. The surrounding rock‐heath is characterized below 400–500 m by Kunzea ambigua and above this altitude by Callistemon pallidus. Moss aprons of Campylopus bicolor on rock faces are often held in place by roots of surrounding shrubs on slopes up to 20°. Bryophyte and lichen communities vary with altitude, and annuals and geophytes are common. Fire may result in retrogression if forests and shrub zones are destroyed and humic top soil burnt or eroded away. Fossil root‐grooves occur in granite on the summit of Mt Latrobe and are the legacy of a cloud forest of Nothofagus cunninghamii. The rock‐heath species are more drought resistant than the‘climax’tree species and may develop very low water potentials. The rate of succession may be correlated with the highly variable rate of decay of each individual block of granite.The soils of the early successional stages are veneers of humic sands enriched with hill‐wash, whilst the soils of the forest stages vary from duplex podzols to gradational podzolic soils of much greater moisture storage. Woody plant establishment is mostly initiated along rock joints: the rock surfaces and boulders so by‐passed are colonized by more mesic species. Many zonations appear to be static since advances are cancelled by retreats.The rate of succession on bare granite is controlled by local climate, altitude, slope, fire and macro‐and micro‐jointing patterns. In general, the early stages bear strong similarities over a relatively wide range of climate. The so‐called climaxes which have developed represent a continuum in response to the complex environments found

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01145.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractBenthic macrofauna was sampled from Naval Reserve Bank, Moreton Bay, Queensland, using an 0.05 m2van Veen grab, and data were used to investigate spatial micropatterning. Samples were taken within a 5 × 6 square sampling grid (total area 730 in2) with an intersampling distance of 6 m. Samples were taken in duplicate on each occasion at 2‐inonth intervals. Particle size of sediments and depth data were also collected. Data on other abiotic factors such as temperature, salinity and currents were inferred.Sampling gave data for 131 species. Hierarchical numerical classificatory techniques were employed to obtain (a) spatial patterns (site‐groups) based on biotic data, and (b) species‐groups which characterize the above site groups. Species diversity (SH) species richness (S), species evenness (J’) and individual species diversity (I) indices were computed for the total data set for each site with the species summated over the sampling times.A selected number of species were used in the classification. The spatial patterns were well defined but the species‐groups categorizing them were somewhat confused. Species diversity indices were found to be of little aid in the interpretation of the site patterns or in generating alternative

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01146.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe ability ofSitophilus oryzae(L.) andS. granarius(L.) to acclimate when transferred from 27°C, a near optimal temperature, to 15° C, a marginal temperature, was examined in terms of chill‐coma temperature, dispersal, oxygen consumption and rate of oviposition.The chill‐coma temperature ofS. oryzaewas higher and the increment of acclimation less than that ofS. granarius.Acclimation, although well advanced after 2 weeks after transfer, took more than 4 weeks to complete. Re‐acclimation after the reciprocal transfer took only 2 weeks.The dispersal of S. oryzae held at 15 and 27° C prior to testing differed when the weevils were released in wheat at 27°C but not when released at 15°C. Cold‐acclimatedS. granariusdispersed less than warm‐acclimated weevils when released in wheat at both 15 and 27°C.The activity oxygen consumption of cold‐acclimated weevils was less than that of warm‐acclimated weevils. Inverse‐shifts of acutely determined R‐T relationships appeared more significant than changes in temperature sensitivity. Acclimation to 15° C took 8–10 days and re‐acclimation to 27°C about 6–8 days.S. oryzaeconsumed less oxygen per unit of weight thanS. granariusbut was more temperature sensitive. Resting oxygen consumption, which was less temperature sensitive than activity consumption, also exhibited inverse acclimation in both species.S. granariusshowed evidence of inverse acclimation of oviposition

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01147.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe sequence and relative injuriousness of insect pests was studied for three successive years in unsprayed cotton of the Namoi Valley. Heliothis punctigera Wallengren, the native budworm, and to a lesser extent H. armigera (Hübner), the cotton bollworm, prevented the setting of full crops by destroying buds and bolls. After setting, high proportions of bolls were injured by Earias huegeli Rogenhofer, the rough bollworm. Incidental damage was caused to seedlings by Thrips imaginis Bagnall, the plague thrips, and lo leaves by Anomis flava Fabricius, the cotton looper, and byAustracris guttulosa (Walker), the spur‐throated locust. In commercial crops, pest control must rely on the use of broad‐spectrum insecticides: H. armigera iscurrently resistant to several of these, and has become the principal species in the local population of cotton pests.A number of enviromental features impede the natural control of pests in the southerly areas where cotton is now produced. In comparison to the older dryland cropping practised in central Queensland, a higher yield is necessary to cover the production costs of irrigated cotton; a shorter growing season prevents the plants from compensating effectively for insect damage and the natural enemies of cotton pests are less abundant and less ac

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01148.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractRabbit warrens are distributed in a clumped manner in three areas totalling 1696 ha in the Southern Tablelands of New South Wales.While the discontinuous distribution may be partly related to original patterns of colonization, the present distribution is closely related to agricultural practices and the rabbits’biological requirements. The highest densities of warrens are in the agriculturally less valuable areas. The number of burrows in use in a warren is related to the number of rabbits living in the warren, although at the time of the study, large warrens contained fewer rabbits than expecte

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01149.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe Japanese snipe Gallinago hardwickii breeds in Japan and migrates south, through New Guinea, to spend the southern summer in Australia. There is no acceptable evidence yet that it reaches the continent other than in north Queensland. Its movement in Australia is mainly coastal Most of the population spends the summer south of the Richmond River, New South Wales: elsewhere it is a passage migrant. Little is known of the movements of individual birds as few have been banded. The distribution of the species and that of G. megala in Australia is discussed.There is no evidence of sexual activity whilst the birds are in Australia. Pre‐migratory fattening begins in February and in birds that had spent the summer in the highlands most fattening takes place at lower altitudes. There is a complete moult while the birds are in Australia. The food consists of animal and plant material, including seeds. The principal animals eaten are the larvae of insects and earthworms.In Japan the bird breeds away from water in grassland, often in elevated dry situations. In Australia it frequents highland and lowland freshwater and occasionally saline habitats. In Japan much habitat has been destroyed but areas cleared for re‐afforestation provide suitable breeding places and the continued production of these disclimax communities results in regeneration of suitable breeding habitat. In Australia most habitat alteration is detrimental to the species and hence its population is not sec

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01150.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractAbove and below ground biomass of Avicennia marina (Forsk.) Vierh. was studied in a mangrove community near Sydney, Australia. Data were obtained for seedlings (0–80 cm) and established trees (≥ 200 cm) growing in two nearby sites. Estimates were made of total mangrove biomass and its components: roots and pneumatophores; trunks and branches: leaves and petioles. The sites studied differed in average tree size (277 kg v. 97 kg) and in seedling biomass (0.12 km m‐2v. 0.02 kg m‐2) but not in total biomass (29.2 kg m‐2v. 27.3 kg m‐2).The partitioning of biomass of Avicennia marina in this temperate mangrove community was similar to that of Rhizophora mangle in a tropical mangrov

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01151.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Books are reviewed in this article:Biogeography: an ecological and evolutionary approach C. D. Cox, I. N. Healey&P. D. Moore

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1977.tb01152.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY