Dynamics of fallow successions and introduction of robusta coffee in shifting cultivation areas in the lowlands of Papua New Guinea

The traditional shifting cultivation system in the lowlands of Papua New Guinea consists of mixed food crop gardens in which yams (Dioscorea spp.), bananas, taro (Colocasia esculenta) and sugarcane predominate. The cropping cycle is usually for 18 months, followed by a fallow cycle of up to 30 years. During the cropping cycle, two species of fruit trees, Pometia pinnata and Artocarpus altilis are also planted, the leaves of the former also being used as a mulch and green manure in yam cultivation. Fallow succession follows rather systematic patterns about which farmers have a thorough understanding. Robusta coffee, a cash-crop component, has been added to the system in some areas since the late 1950s. It is usually grown in permanent blocks, but is interplanted with Leucaena as shade. Food crops are planted in the establishment stage, bananas and Xantohosoma being retained even in mature coffee gardens. The system seems to be a potentially promising one. But very little quantitative information is available on the production and performance of the system and practically no systematic research has been undertaken. Since the Papua New Guinea fallow gardeners are willing to accept innovations, it will be appropriate and timely to undertake serious studies so that the system can be improved. A few items that merit immediate research attention are indicated.     

Structural health assessment of in situ timber: An interface between service life planning and timber engineering

Abstract

The in situ assessment of timber structures has gained considerable attention in recent years due to some unexpected failures of public buildings. The assessment of timber, however, has been used in the evaluation of historic structures for a number of years, and the methods employed have evolved from visual observation (which is still one of the most effective ways of evaluating in situ timber) to more sophisticated methods that use various physical phenomena such as stress-wave or X-ray energy attenuation. In the health assessment of timber, effects of biotic elements such as insects and fungi are of interest, which, of course, is always connected with the presence of water in wood. The structural assessment encompasses questions related to the structural integrity of in situ members and the performance of components and the system. The structural health assessment not only focuses on biotic elements but also attempts to quantify engineering properties of the material such as strength degradation, modulus of elasticity, loss of cross-section, extent of checks, and other quantitative parameters needed for subsequent evaluation of the structural system, frequently expressed as load-bearing capacity. Service life planning of a structure is a complex issue that is related not only to the materials but also the environment and the use of the structure. Assessment of the health and properties of existing timber elements yields a piece of information that is necessary but not sufficient for the service life estimate. In the evaluation of structural timber, a mere use of various assessment techniques is not sufficient and usually an involvement of disciplines such as wood anatomy, wood physics, and statistics is needed. A reliable estimate of the parameters of in situ timber requires careful planning of measurements (experiments) since the material is highly variable and any statement about the properties of an element or even the entire system must reflect the random character of the wood properties. This paper will summarize the state-of-the art methods used in the assessment of in situ timber and analyze the strengths and the weaknesses of selected methods. An attempt will be made to outline future directions in the development of in situ assessment methods.     

Initial agronomic evaluation of Parkia biglobosa in the humid zone of Nigeria

Parkia biglobosa is an important traditional economic tree legume of considerable multipurpose potentials that has not been well researched. It is used for fodder, human food, fuel wood, timber, green manure, medicine, provides shade for forage grasses and livestock and protects soil from heat and it is important in soil nutrient cycling.The objective of this study was to determine the effect of management regimes (cutting frequency and height) on the coppicing ability, fodder production, and nutritive value potentials of cultivated Parkia trees. This initial study has shown that the tree has a potential as fodder for livestock as well as human food and should be further studiedto fully understand its biology, agronomy and feeding value under various agroforestry or silvopastoral systems of humid tropics in West Africa.     

Die Rolle der Fliegen in der Epidemiologie der Poliomyelitis

Summary By summing up the scattered evidence from the literature it is to note that it exists a complete chain of evidence to prove that flies have the capacity to transmit poliomyelitis virus. For it has been observed that the faecal material of infected persons contains the virus, that the flies visit the faeces and are able to pick up the virus, that flies caught in natural conditions harbour the virus, that the virus maintains for three weeks in the fly, that the fly is capable of supporting the multiplication of the virus, that the excrement of the flies contains the virus, that flies visit human food and deposit their excrement in it and that such food eaten by apes results in infection. Some facts support the hypothesis that besides faecal material, carcasses may also play a role as a source of viruses for flies. It is also possible that flies can infect man not only by the oral route but also via wounds. It has been stated that infection via wounds causes paralysis more readily than oral infection. Some facts support the idea that the higher incidence of paralyses in poliomyelitis occurring in the temperate climates should depend on the frequent infection of wounds of susceptible persons by blowflies, which are predominating in the fly fauna of more northern areas. In warmer climates, where houseflies are predominating, the virus is transmitted effectively by flies to foodstuffs. The infection reaches thus the man by the oral route and results most often in a nonparalytic disease.There has been accumulated some evidence for the wiev that fly transmission of poliomyelitis occurs to such a degree that it is of epidemiological significance. It has been observed four times thatLucilia illustris and some other blowflies of this genus has shown a much greater abundance during epidemic years for poliomyelitis than during nonepidemic years. It has also been shown that poliomyelitis occurs significantly later in the southern coastal area of Finland, where the very late flyingLucilia sericata (the species from which poliomyelitis viruses have most often been isolated) occurs, than outside this area. In Finland the outbreak of poliomyelitis epidemics is preceded for about 1–2 weeks by an increase of the abundance of this blowfly and by the ovipositional periods of most other blowflies of the genusLucilia. The occurrence of cloudy days, which are unfavourable for the activity of blowflies, shows a weak positive correlation with the incidence of poliomyelitis. This fact is possibly an indication of the invalidity of the hypothesis of fly transmission of poliomyelitis, but it is also possible that the inhibition of normal ovipositional activity may drive the blowflies to the surface of homoiothermic animals or to human dwellings. Statistics on the changes of theLucilia fauna during the 20th century in Finland show that an increase in their dominance coincided, with the increase in the incidence of paralytic poliomyelitis and the rise in the summer temperatures. Especially the expansion ofLucilia sericata to south Finland coincided clearly with the increase in the incidence of paralytic poliomyelitis. Some facts speak for the comprehension that this highly synanthropic species should be responsible for the fact that the incidence of poliomyelitis is in Finland higher in great cities than in small cities or rural districts. Studies on the effect of fly abatement in poliomyelitis control have remained inconclusive.     

Food intake and utilization of <Emphasis Type="Italic">Alabama argillacea</Emphasis> (Hübner) (Lepidoptera: Noctuidae) fed on cotton cultivars with colored fibers

The study investigated the development, survivorship, and food intake of cotton leafworm Alabama argillacea (Hübner) fed on three cotton cultivars with colored fibers. Significantly shorter larval life-span and higher pupal weight as well as higher survival rates were observed in A. argillacea fed on leaves of BRS Safira and BRS Rubí cotton cultivars compared with the BRS 200 cultivar (BRS = Brazil). Weight gain, feces, and food intake were higher in A. argillacea fed on leaves of BRS Safira compared with the BRS 200 cultivar. The cotton cultivar significantly affected all larval food intake and utilization indices for A. argillacea. The larvae of A. argillacea were more efficient (higher efficiency in converting ingested (ECI) and digested (ECD) food) when fed on leaves of the BRS Safira cultivar in comparison to the BRS 200 cultivar, since the larval phase was shortened and food intake was higher, resulting in a higher growth rate (RGR). However, A. argillacea larvae fed on the leaves of the BRS 200 cultivar, with lower ECI and ECD, exhibited a compensatory response, extending the duration of the larval phase and increasing food intake, resulting in a higher relative metabolic rate. We conclude that BRS Safira provides the best food quality for A. argillacea, BRS 200 the worst, and BRS Rubi plants of intermediate quality.     

The homegarden agroforestry system of Bukoba district,North-Western Tanzania. 3. An economic appraisal of possible solutions to falling productivity

Homegardens of Bukoba are a traditional multi-storey agroforestry farming system based on mixed cropping and livestock keeping. Major crops are banana (Musa spp.) grown for food and coffee (Coffea canephora var.robusta) for cash. Livestock keeping is dominated by cattle. Over the last few decades the farming system in Bukoba has been pervaded by a host of constraints ranging from biological to socio-economic. Consequently farm productivity has declined and so has the economic welfare of the people in the area. A questionnaire survey was conducted in 1991 to 72 households in Bukoba district to compare three potential farming systems: the rehabilitation of the homegardens, the cultivation of two annual crops namely maize and beans as intercrops and the continuation of the current non-rehabilitated homegardens. Results strongly support the rehabilitation of homegardens by use of cattle manure and proper crop and livestock husbandry practices. Rehabilitated homegarden has the highest net present value and is not very sensitive to changes in prices of inputs and outputs.     

Weitere Beobachtungen an Speckkäfern (Dermestidae)

Summary Additional observations on Dermestidae (Coleoptera) Additional observations have been described on some life patterns ofDermestes maculatus andDermestes lardarius, two species of the familyDermestidae (Bacon or Skin Beetles). The pupation of the larvae in the wood and the form of their cavities are dealt with; only fungal infected wood is attacked byDermestes. The present observations have also shown thatDermestes do not digest wood. Beetles and larvae consume mainly pure fats or food substances with fatty components. Anatomically certain elements of the mouthparts of the beetles seem to be typical constructed for the fatty nutrition. The hairlike sense organs in the antennae for the reception of smell are most important in locating the food.     

Smallholder Cacao (Theobroma cacao Linn.) cultivation in agroforestry systems of West and Central Africa: challenges and opportunities

The cultural features, management practice, environmental sustainability, and economic profitability of smallholder cacao (Theobroma cacao)production in West and Central Africa are reviewed. The aim is tohighlight factors affecting the cacao production and marketing sectorand to propose appropriate strategies to ensure sustainable and profitable cacao production in the region. The cacao cultivation system causes minimum damage to soil resources. In terms of carbon sequestration and below- and above-ground bio-diversity, the cacao agroforest is superior to the alternative food crop production land use. The food crop production system is based on the practice of slash-and-burn farming, which, due to population pressure and reduced fallow cycle, is no longer sustainable. Economic profitability analysis of this system in Cameroon showed that, at current prices, even with no value assigned to the tree species, the sector could still be profitable. Based on the current review and our knowledge of West and Central Africa, there is an urgent need to: (a) rationalize and optimize arrangement of the various components in cacao agroforest, (b) domesticate high value and shade tolerant indigenous species such as Gnetum africanum and integrate into the system in order to enhance the system's diversity and profitability, (c) develop shade-tolerant and disease-resistant cacao varieties, (d) integrate small-stock production into the system, and (e) develop an enabling policy environment addressing cacao marketing, plant protection, land tenure and transformation of non-cacao primary products from the cacao agroforests. This revised version was published online in June 2006 with corrections to the Cover Date.     

Deterioration of a sustainable agro-silvo-pastoral system in the Sudan: the gum gardens of Kordofan

The development and establishment of agroforestry systems is often suggested as a way to stabilize rural economies in developing countries [King, 1979]. At the same time, some traditional systems are being lost, due to an inability to protect the perennial or tree crop components of the system. These traditional systems and the forces that reinforce or destroy them should be carefully studied by those in the process of encouraging adoption of agroforestry systems in the developing world. The gum gardens of Western Sudan are a case in point.Acacia senegal (hashab) andAcacia seyal (talh) are the two major marketable gum-producing trees found in the western region of Sudan. TheAcacias are grown as part of an agro-silvo-pastoral system that has persisted for more than a hundred years in Kordofan Province, where 70% of Sudan's gum Arabic was once produced, as well as most of its grain and livestock products. After a lengthy drought lasting from 1979 to 1985 gum production in Sudan drastically decreased. It was reported that pest attacks and drought were major causal agents in the decline of gum production [Awouda, 1989; Sungar, 1986]. A survey executed in Northern Kordofan Province, starting in August of 1986, did uncover a great number of deadAcacias due to drought and pest attack, but from interviews with gum farmers we conclude that the decline in gum production is largely due to unfavorable socioeconomic relationships exacerbated by the drought, leading to the deterioration of the agroforestry system of production. An inability to get a fair price for gum at the local level and increasing emphasis on a cash economy led to the neglect of the tree components of the system. The gum gardens have long flourished with the intensive husbandry of small-scale farmers. Once these farmers were no longer able to care for them, the gum trees disappeared from the system, indicating that a lack of community stability can be fatal to even a well-developed agroforestry system.     

Competitive interactions of a new invader (Spodoptera frugiperda) and indigenous species (Ostrinia furnacalis) on maize in China

Spodoptera frugiperda has been reported in China since the beginning of 2019, threatening maize production and raising questions about interactions with indigenous pests on maize. Spodoptera frugiperda is in the same feeding guild as the indigenous species Ostrinia furnacalis, with both pests attacking maize plant tissues such as whorls and tassels. In this study, the interaction of these species was assessed under laboratory and field conditions by examining the survival and predation rate of larvae in maize whorls and tassels. Intraspecific and interspecific interactions of larvae were assessed to characterize movements in arenas in the presence and absence of food. When S. frugiperda and O. furnacalis were present at an equal ratio, S. frugiperda prevailed over O. furnacalis with a high survival rate (over 90%) and predation rate of O. furnacalis (over 40%) under most scenarios in both laboratory and field conditions. When both species occurred at different ratios in the field, S. frugiperda had on average almost 16 times the number of survivors as O. furnacalis on whorls, and 8.3 times the number on tassels, highlighting a substantial advantage in these environments. Spodoptera frugiperda larvae undertook a low frequency of lethal attacks (strikes) and showed a higher incidence of defensive movements compared to O. furnacalis. A field survey showed that S. frugiperda larvae can colonize vegetative plant stages in maize, but it remains to be seen if competitive interactions can be linked to population dynamics of both species though they are expected to favor S. frugiperda.

     

Log sawing position optimization using computed tomography scanning

When disjoining a log, several factors affect the value of the sawn timber. There are log features, such as outer shape, knots, rot, and so on. There are also sawing parameters, such as sawing pattern, log position, and so on. If full information about log features is available, sawing parameters can be adapted in order to maximize product value in sawmills. This is soon possible, since computed tomography (CT) scanners for the sawmill industry are being realized. This study aimed at investigating how CT data can be used to choose rotational position, parallel displacement, and skew of sawlogs, to maximize the value of the sawn products. The study was made by sawing simulation of 269 CT scanned logs of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] H. Karst.). The results showed that value recovery could be improved by 13% in average, compared to a sawing position based on log outer shape, and 21% compared to sawing logs centered and horns down. It can be concluded that a CT scanner, used in a sawline to optimize sawing parameters, has a large potential for increasing value recovery and thus profit.     

Separating the effects of trees on crops: the case of Faidherbia albida and millet in Niger

Faidherbia albida (Del.) A. Chev. is an important tree species of the scattered tree or parkland systems in the Sahel. The improved crop growth under its canopy is well known, and has been attributed to various components notably: higher soil fertility, improved microclimate and better soil physical properties. The relative contributions of each of these components are not known, but knowledge about this is essential for making proper decisions concerning management options. The overall tree effect on crop production (expressed as fraction of the sole crop production) is analysed here as a weighted sum of (positive and negative) relative net tree effects on the resources for crop growth. In this sum, the weights reflect the degree of limitation of the resources in the environment at the tree-crop interface. The paper shows how the relative net tree effects and the accompanying weights can be estimated from field experiments. In an on-farm field experiment in Niger, millet production under the F. albida canopy was about 36% higher than in the open field. The nitrogen availability under trees was estimated to be more than 200% higher than in the open causing a 26% production increase. The phosphorus availability was estimated to be almost 30% higher and because of its high limitation causing a production increase of 13%. The net effect via other resources (notably light and water) was negligible (3% production reduction) and not significant.This revised version was published online in November 2005 with corrections to the Cover Date.     

The banana (Musa spp.) — Coffee robusta: traditional agroforestry system of Uganda

Banana (Musa spp.) — with Coffee robusta a traditional agroforestry system in Uganda is a purely mixed cropping system managed on a sustained production basis. The basic primary production is banana as a main food crop and Coffee robusta as the main cash crop. The variety of trees deliberately retained, managed and planted, animals and crops in the system are managed by the farmers to maximize production by supplying timber, fruits, fuelwood, fodder, food, medicinal and other miscellaneous uses.     

Modelling incidence of root rot in picea abies plantations in Southern Sweden

An empirical model is presented to forecast the incidence of root rot at stand level. In addition, the impact of different thinning programmes on the incidence of root rot is evaluated. The model is based on data from 152 permanent forest research plots of pure Picea abies in southern Sweden, within which the incidence of root rot at stump height in thinned trees has been recorded after each thinning since 1950. In total, about 20 000 stumps have been studied. According to simulations with the model, areas previously used as fields or for grazing are particularly susceptible to root rot, while old hardwood sites are less susceptible. Furthermore, simulations with the model imply that the earlier, the harder or more often a stand is thinned, the faster will be the development of root rot.     

Human impacts drive forest structure and diversity. Insights from Mediterranean mountain forest dominated by <Emphasis Type="Italic">Abies pinsapo</Emphasis> (Boiss.)

Environmental factors and land-use are likely interacting to drive forest structure and species diversity, making it difficult to disentangle their separate impacts. Both components influence the resilience and stability of mountain forests in the Mediterranean Basin, since secular land-use has shaped stands structure and forests dynamics are constrained to the environment. Approaches covering environmental factors and contrasting land-uses are still needed to understand their implications on forest dynamics. We investigated patterns of environmental variables, stand structure and biodiversity in forest dominated by Abies pinsapo for 61 stands over their whole range. In addition, since land-use by local inhabitant could be a key factor, logging intensity was quantified by stumps basal area and recent land-use history was investigated. Partial redundancy analysis (pRDA) was conducted to assess to which degree the structural attributes are related to environmental characteristics and/or the land-use in the main A. pinsapo forests. Environmental characteristics accounted for 13% of the total variance, while the contrasting land-use (Spain vs. Morocco) and the stumps basal area, as indicator of human logging, accounted for 23% of the total variance. Trees species diversity was near 5 times higher in Moroccan stands than in stands from south Spain. According to recent human logging, Spanish stands have been strictly protected, but Moroccan stands showed widespread axe-logging by local inhabitant over the smaller tree sizes. Our results suggest that the preservation of a minor perturbation regimen by local populations enhance and help to preserve the whole biodiversity of this relict habitat.     

Long term effects of fire on ectomycorrhizas and soil properties in Nothofagus pumilio forests in Argentina

The forests of Nothofagus pumilio have historically been affected by forest fires. The effects of fire on certain above and belowground, biotic and abiotic components of these ecosystems have been previously documented, albeit belowground components have received much less attention. It has been suggested that the effects observed in the short-term after a fire usually differ from the longer-term effects. The long-term effects of fire (i.e. >5 years after burning) on belowground components in Nothofagus forests are currently unknown. In the present study we evaluated the long-term effect of fire on ectomycorrhiza (ECM) colonization and morphotype composition in N. pumilio roots, as well as soil chemical properties in temperate forests in Patagonia. Sampling was conducted in three mature monospecific forests. In each, nearby burned and unburned sites were selected. The time since the occurrence of fires differed between areas (i.e. 6-10 years). Within each site, 3 transects of 40 m were established randomly along which 5 samples of roots and soil were collected in spring and autumn. The main results were: (1) in comparison with the unburned site, ECM colonization was lower in the burned site in the area with the shorter time length since fire occurrence and no effects in the other two areas were observed; (2) richness and diversity were not significantly affected by fire but there was a significant effect of season for both parameters, being higher in spring; (3) ECM dominance was significantly higher in the unburned than in the burned site in Tronador, while in Challhuaco the opposite was observed, mainly in autumn; (4) in general carbon, nitrogen and phosphorous decreased while pH increased in the burned sites; (5) ECM colonization positively correlated with NH⁴⁺ and phosphorus and negatively with pH but was not significantly correlated with organic matter or any other soil variable. Altogether the results suggest that effects of fire on ectomycorrhiza and soil properties in N. pumilio forests are probably related to the time elapsed since fire occurrence combined with site characteristics. In addition, the direct and indirect effects of fire in these forest systems may persist for more than 10 years.     

Lacquer-based agroforestry system in western Yunnan, China

The lacquer tree (Toxicodendron vernicifiuum) based agroforestry system is a very important farming system with development potential in western Yunnan, southwest China. It is, however, less understood in scientific fields. The Lemo people (a branch of the Bai minority nationality) traditionally grow lacquer trees interplanted with upland food crops in swidden fields. During a 10–15 year fallow period, farmers can harvest various products from lacquer trees, including resin for selling or trading, leafy shoots for vegetable, pericarps for making wax, roots and leaves for pesticide, dry resin for medicine, and seeds for vegetable oil extraction. The Lemo people believe the lacquer tree is the most important crop in their community. The lacquer agroforestry system provides the Lemo people with food, cash income and environmental benefits. Further studies on the lacquer agroforestry system will be indispensable to improve this system so as to disseminate it to other communities.This revised version was published online in November 2005 with corrections to the Cover Date.     

Large cardamom (Amomum subulatum Roxb.) plantation — An age old agroforestry system in Eastern Himalayas

Large cardamom (Amomum subulatum Roxb.) is a shade loving plant grown in the Indian hill states of Sikkim and Dargeeling district of West Bengal. About 30 important tree species are used to provide shade to the cardamom plants. Alnus nepalensis, a deciduous, nitrogen fixing and fast growing tree, is the species most commonly underplanted with cardamom. In addition to providing shade, it is also used for fuelwood. The old trees are cut and young plants coming up are allowed to grow in cyclic order. The quick decomposing leaf litter of A. nepalensis also fertilises the cardamom plants. The nitrogen added to the soil in this way has been found to be as high as 249 kg/ha. Large cardamom thrives well in a moist soil, which is maintained by water diverted from seasonal springs on the upper slopes. The system is well suited to conserving soil, water and tree cover of the characteristically steep slopes of the region. Moreover, the management inputs required for growing cardamom are low but the crop gives a higher financial return than rice or maize. The shade trees used in the system are also a major source of fuel, fodder and timber, especially as access to state owned forests is restricted by legislation. However, increasing incidence of viral chirkey and foorkey disease, panicle rot and capsule borer are reducing the cardamom productivity. It has been observed that integrating dairying and apiculture will further augment profitability from large cardamom agroforestry system.     

Introducing the <Emphasis Type="Italic">montado</Emphasis>, the cork and holm oak agroforestry system of Southern Portugal

The Portuguese montado is an agro-silvo pastoral system quite similar to the dehesa in Spain, and covering in Portugal most of the Southern region of the country, Alentejo. The trees in the montado are cork oh holm oak, and the system is mostly acknowledged due to the cork production, but also due to its singular savanna like land cover pattern, its multiple and complementary productions, the support of a diversity of ecosystems services and its biodiversity. The present special issue covers the diversity of components of the montado and of perspectives required to understand and assess the functioning of the system. This Editorial introduces the montado system, describes its extension and similarities to the dehesa in Spain, and addresses the multiple productions and externalities of the montado. It also refers to the several components of the system. It focus on the uniqueness and values of this system, stressing its potential and threats, and the requirements for integrated knowledge production. In the end of the Editorial, each one of the papers that compose the special issue are presented.