Amazonian deforestation and global warming: carbon stocks in vegetation replacing Brazil''s Amazon forest

Carbon stocks in vegetation replacing forest in Brazilian Amazonia affect net emissions of greenhouse gases from land-use change. A Markov matrix of annual transition probabilities was constructed to estimate landscape composition in 1990 and to project future changes, assuming behavior of farmers and ranchers remains unchanged. The estimated 1990 landscape was 5.4% farmland, 44.8% productive pasture, 2.2% degraded pasture, 2.1% ‘young’ (1970 or later) secondary forest derived from agriculture, 28.1% ‘young’ secondary forest derived from pasture, and 17.4% ‘old’ (pre-1970) secondary forest. The landscape would eventually approach an equilibrium of 4.0% farmland, 43.8% productive pasture, 5.2% degraded pasture, 2.0% secondary forest derived from agriculture, and 44.9% secondary forest derived from pasture. An insignificant amount is regenerated ‘forest’ (defined as secondary forest over 100 years old). Average total biomass (dry matter, including below-ground and dead components) was 43.5 t ha⁻¹ in 1990 in the 410 × 10³ km² deforested by that year for uses other than hydroelectric dams. At equilibrium, average biomass would be 28.5 t ha⁻¹ over all deforested areas (excluding dams). These biomass values are more than double those forming the basis of deforestation emission estimates currently used by the Intergovernmental Panel on Climate Change (IPCC). Although higher replacement landscape biomass decreases net emissions from deforestation, these estimates still imply large net releases.     

Effects of forest floor planting and stock type on growth and root emergence of Pinus contorta seedlings in a cold northern cutblock

A two-year field trial was conducted to determine the growth response, and root emergence pattern of interior lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings in response to container type and forest floor removal. Seedlings were grown in Styroblocks^TM, Copperblocks^TM, or AirBlocks^TM, and were planted directly into the undisturbed forest floor or into manually prepared planting spots where the forest floor had been scraped away to expose the mineral soil. Seedlings planted into scalped planting spots exhibited marginally but significantly (7%) greater above-ground growth rates (seedling stem volume); whereas seedlings planted into the forest floor produced significantly more (11%) new roots. There were no differences in above- or below-ground biomass. Seedlings grown in Copperblock^TM containers produced a higher proportion of roots near the top of the plug when tested at lifting, however this pattern was not observed in the field. Given that scalping is more costly than forest floor planting, and that the increased shoot growth was relatively small, we recommend that forest floor planting be considered as an alternative to manual spot scalping for sites, such as the site tested here: those with cold, but well-drained soils and where competition from other plants is not a serious problem.     

The effects of within-species and between-species variation in wood density on the photodegradation depth profiles of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa)

Low density wood is more rapidly eroded than denser wood when exposed to the weather, possibly because it is more susceptible to photodegradation. Fourier transform infrared microscopy was used to examine: (1) the depth of photodegradation in earlywood and latewood of sugi (Japanese cedar) and earlywood of hinoki (Japanese cypress) exposed for up to 1500 h to artificial sunlight emitted by a xenon lamp (375 W/m² within the 300 to 700 nm spectral range); and (2) the relationship between the density of wood tissues and depth of photodegradation. The depth of photodegradation varied between species (sugi and hinoki) as well as within a growth ring (sugi earlywood and latewood), and there was an inversely proportional relationship between depth of photodegradation and wood density. These findings may explain why low density earlywood is more rapidly eroded than latewood during weathering, and more generally, why there is an inverse relationship between the density of wood species and their rate of erosion during artificial and natural weathering. Part of this work was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004     

Variances of tracheid lengths in tropical pines from central Africa

Summary Individual tracheid lengths were measured in macerated tissue samples of Pinus merkussii Jungh. and de Vries, P. kesiya Royle ex Gordon (syn. P. khasya Royle) and P. patula Schiede and Deppe. The sample trees were selected from stands of different ages, treatments and sites in central Africa.A sampling unit of 50 tracheids, measured for convenience on two microscope slides, was chosen on the basis of an earlier study. The variation in individual tracheid length and the variation of within-slide variance was studied by means of analysis of variance and variance components. This indicated the nunber of samples required in the different sampling categories to give maximum sampling efficiency. Sampling categories included both random factors (individual tracheids, number of slides, radii in discs) and fixed factors (annual rings, tree classes, thinning treatments, etc.).While large effects were attributable to fixed factors more than half the total variation was explained by random factors. The effect of the number of slides was rarely important and two slides need be used only to facilitate the location of the required number of tracheids and to provide a check on operator consistency. The sample unit of 50 tracheids can detect differences in tracheid length of 0.20 ... 0.34 mm thus confirming the routine used in this laboratory as a practical and meaningful procedure.Laboratory work was carried out in Kitwe, computing at Oxford. Paper published with permission of Professor of Forest Science, Oxford and Director, Agricultural Research Council of Zambia.     

Anatomy of the primary-secondary transition zone in stems of Populus deltoides

Summary The transition from primary to secondary stem tissues occurs as a continuum, and a precise anatomical definition of the transition does not exist. A definition was derived for Populus deltoides based on the birefringent properties of the fiber wall. This definition was quantitatively reproducible in the 9 plants tested, and the secondary transition was found to occur in the internode associated with the first mature leaf from the apex. The primary-secondary transition did not occur uniformly around the periphery. It was first observed in the vascular bundles opposite the incoming trace, and from there it progressed in a counter-clockwise direction. Within the transition internode, each vascular bundle and each tissue comprising the bundle differentiated in accord with the physiological age and the phyllotactic disposition of the developing leaf to which it led. Within any one vascular bundle, differentiation occurred first in the metaxylem vessels and associated fibers, followed closely by extension of fibers into the interfascicular regions and centripetal differentiation of the phloem fibers. The ontogenetic sequence of differentiation for each of the principal tissues of the secondary transition zone is described.The technical assistance of Mr. Gary Buchschacher with the ultramicrotomy and photomicrography is gratefully acknowledged.     

Planted conifer seedling growth under two soil thermal regimes in high-elevation forest openings in interior British Columbia

A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons.     

Use of pyrethroid analogues to identify key structural features for enhanced esterase resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

It has been reported previously that the major resistance mechanism to pyrethroid insecticides by the cotton bollworm Helicoverpa armigera (Hübner) in Australia is a consequence of overproduction of esterase isoenzymes. This paper reports structure-activity relationships that support such a view, based on in vivo bioassays conducted with a range of pyrethroid structures containing a variety of acid and alcohol moieties and the correlation with in vitro esterase inhibition assays against the same structures, and identifies the critical regions of the molecule with regard to esterase inhibition, and hence resistance. The implications of this work in terms of possible resistance management are evaluated and discussed.     

Vascular-Streak Dieback: A New Encounter Disease of Cacao in Papua New Guinea and Southeast Asia Caused by the Obligate Basidiomycete Oncobasidium theobromae

ABSTRACT The basidiomycete Oncobasidium theobromae was identified as the cause of a devastating disease of cacao named vascular-streak dieback (VSD) in Papua New Guinea in the 1960s. VSD now causes losses among cacao seedlings and kills branches in mature cacao trees throughout Southeast Asia and parts of Melanesia. The characteristic symptoms include a green-spotted chlorosis and fall of leaves beginning on the second or third flush behind the stem apex, raised lenticels, and darkening of vascular traces at the leaf scars and infected xylem. Eventually complete defoliation occurs and, if the fungus spreads to the trunk, the tree will die. O. theobromae is a highly specialized, near-obligate parasite of cocoa. It is a windborne, leaf-penetrating, vascular pathogen, and may have evolved as an endophyte on an as yet unidentified indigenous host. The rate of disease spread on cocoa is limited because basidiocarps develop only on fresh leaf scars during wet weather, and basidiospores remain viable for a few hours on the night they are shed. Consequently, very few new infections occur beyond 80-m from diseased trees. Transmission of the disease through seed or infected cuttings has not been demonstrated. Strict quarantine measures applied to the movement of intact plants are crucial in reducing spread of the disease. Integrated management, including the planting of less susceptible genotypes, nursery construction and management, canopy pruning and shade management, provides effective control.     

Timing and order of different insecticide classes drive control of Drosophila suzukii; a modeling approach

The spotted-wing drosophila, Drosophila suzukii Matsumura, is an invasive pest causing significant damage to soft skinned fruits. Control of D. suzukii is critical since there is no tolerance for infested fruit in the market. While most insecticides control one or more D. suzukii life-stages (e.g., egg, larvae, and adult), the impact of insecticides that are toxic to immature stages  is unclear on the subsequent generation of a field population. Insecticides were applied at field recommended rates on cherries and blueberries in the laboratory to determine immature D. suzukii mortality. Spinetoram, cyantraniliprole, malathion, methomyl, spinosad, and phosmet resulted in relatively high mortality of all immature life stages. Zeta-cypermethrin, cyclaniliprole, and fenpropathrin resulted in lower mortality of egg and all larval instars. Malathion was also applied to lowbush blueberries with different fruit sizes (small, medium, and large) in the laboratory and there was no statistical difference in mortality rates depending on fruit sizes. Mortality data from the laboratory experiments were used to parameterize a refined D. suzukii population model. The model revealed that the timing and order of different insecticide classes are important to control D. suzukii population. Model runs that included early applications of more effective insecticides resulted in high immature mortality and greater reduction of D. suzukii populations compared to treatments applied later.