Latex Harvesting Technologies Adapted to Hevea brasiliensis Muell Clones GT 1; RRIC 100 and BPM 24 Arg. (Euphorbiaceae) belonging to the Moderate Metabolism Class in the Socio-economic Context of Côte d'Ivoire

Improving the productivity of rubber trees has always been a major concern for rubber farmers. The majority of growers opt for overexploitation of the trees. This disturbs the physiological balance of the rubber trees, which leads to the recrudescence of tapping panel dryness and rather to a drop in production. To solve this problem, the present study proposes to define a latex harvesting technology (or technologies) for the moderate metabolism clone class that will allow the improvement of plantation yield and the increase of the economic life of the trees. To achieve this, the GT 1, RRIC 100 and BPM 24 clones of the moderate metabolism class were used as plant material. The results showed that the reduction in tapping frequency had no negative effect on the vegetative state of the trees. This reduction was compensated by a high number of annual stimulations, which resulted in high dry rubber production. Analysis of dry rubber production, radial rubber growth and tapping panel dryness rate indicates that the moderate metabolic class clones performed better with the latex harvesting technologies S/2 d3 6d/7 ET2.5% Pa1(1) 6/y; S/2 d4 6d/7 ET2.5% Pa1(1) 6/y and S/2 d5 6d/7 ET2.5% Pa1(1) 1.

Climate change and the complex dynamics of green spruce aphid--spruce plantation interactions

Aphids can have a significant impact on the growth and commercial yield of spruce plantations. Here we develop a mechanistic deterministic mathematical model for the dynamics of the green spruce aphid (Elatobium abietum Walker) growing on Sitka spruce (Picea sitchensis (Bong.) Carr.). These grow in a northern British climate in managed plantations, with planting, thinning and a 60-year rotation. Aphid infestation rarely kills the tree but can reduce growth by up to 55%. We used the Edinburgh Forest Model (efm) to simulate spruce tree growth. The aphid sub-model is described in detail in an appendix. The only environmental variable which impacts immediately on aphid dynamics is air temperature which varies diurnally and seasonally. The efm variables that are directly significant for the aphid are leaf area and phloem nitrogen and carbon. Aphid population predictions include dying out, annual, biennual and other complex patterns, including chaos. Predicted impacts on plantation yield of managed forests can be large and variable, as has been observed; they are also much affected by temperature, CO 2 concentration and other climate variables. However increased CO 2 concentration appears to ameliorate the severity of the effects of increasing temperatures coupled to worsening aphid infestations on plantation yield.

Modelling the Effect of Microsite Influences on the Growth and Survival of Juvenile Eucalyptus globoidea (Blakely) and Eucalyptus bosistoana (F. Muell) in New Zealand

The effect of microsite on juvenile forest plantation yield is rarely explored. This is because juvenile plantation growth is considered to be reasonably homogenous due to a lack of resource competition between trees prior to canopy closure. However, models of juvenile plantation height growth and survival that are sensitive to microsite variation could aid decisions relating to site preparation, plantation establishment and early silvicultural treatments. In this study, juvenile Eucalyptus bosistoana and E. globoidea height growth and survival proportion were modelled against topographic and environmental microsite characteristics as independent variables. The experiment included three different sites situated in a sub-humid region of New Zealand. A total of 540 plots were planted with 18,540 trees in regular rows and columns. Micro-topographical variables significantly influenced height growth and survival proportion of both E. bosistoana and E. globoidea, but species differed in their responses. More sheltered microsites yielded greater height growth and survival for both species. The height of both species was influenced by wind exposure, morphometric protection, and distance from the nearest ridge. E. bosistoana height was also influenced by topographic position and surface plan curvature. Survival was affected by surface profile curvature for both species, while E. globoidea survival was also impacted by surface plan curvature and distance from the top ridge. This study identified microsite factors influencing juvenile height and survival of two Eucalyptus species.

The Effects of Material’s Transport on Various Steps of Production System on Energetic Efficiency of Biodiesel Production

Rapeseed plantation biodiesel production systems require the transportation of goods, like raw materials, machines and tools, and products between various conversion stages of agricultural as well as industrial subsystems. Each transportation step requires the consumption of some energy. This consumption decreases the net amount of energy delivered out of the biofuel production system, and consequently decreases the energetic efficiency of the system. The majority of studies on biofuel sustainability are done by means of the LCA method with the use of a data average for some region and period of time. Such analyses do not reveal the possible causes of the conclusions determined. The present work deals with computer modelling of the influence of the energy consumed on those transport routes on the energetic efficiency of the production system. The model enables determination of the effects caused by changes introduced to technological parameters. The effects caused by variation of fuel consumption, the load capacity of transportation means, size of plantation, distribution and sizes of individual fields, distances between fields, plantation yield, and finally the distance between the plantation and the industrial facility are studied using the numerical model developed earlier. This approach is aimed towards identifying the reasons for the behavior of a system controlled by many somewhat coupled variables.

The Effects of Material’s Transport on Various Steps of Production System on Energetic Efficiency of Biodiesel Production

Based on rapeseed plantation biodiesel production system requires transportation of goods, like raw materials, machines and tools, and products between various conversion stages of agricultural as well as industrial subsystems. Each transportation step requires consumption of some energy. This consumption, decreases the net amount of energy delivered out of the biofuel production system, and consequently decreases energetic efficiency of the system. The present work deals with computer modelling of the influence of energy consumed on those transport routes on the energetic efficiency of production system. The effects caused by variation of several parameters like fuel consumption and load capacity of transportation means, size of plantation, distribution and sizes of individual fields, distances between fields, as well as plantation yield, and finally the distance between plantation and the industrial facility are studied using the numerical model developed

Predicting site index from climatic, edaphic, and stand structural properties for seven plantation-grown conifer species in Quebec

Models were built to relate site index to biophysical variables and stand structure for seven conifer species grown in plantation. Reduced models without stand structure were also derived to allow the prediction of site index even when information on the stand is unavailable. Biophysical variables tested were degree-days, aridity, summer precipitation, vapour pressure deficit, and soil water-holding capacity. The stand structure was accounted for using a Shannon evenness index of diameter at breast height distribution. Both full and reduced models had low to moderate R2 values and were slightly biased for most of the species. The results indicate that while correlations between phytometric and biophysical site indices are rather weak, those between plantation yield predicted using both indices and volume observed in the field are reasonably high (above 0.80). The biophysical site index models derived in this study could be used for strategic planning to estimate plantation yield or allowable cut for each of the seven conifer species.

Adaptation to climate change: Genetic variation is both a short- and a long-term solution

We propose a methodology combining a biophysical site index model and a seed source transfer model based on both temperature and precipitation to estimate white spruce plantation yield under present and future global warming conditions. The biophysical site index model predicts dominant height at 25 years, which is further used to estimate plantation yield using yield tables. The transfer model shows that, on average, seed sources are best adapted to the temperature conditions where they presently grow, and give maximum yield under these conditions. However, this model also shows that transfer of seed sources to drier sites could improve plantation yield. To predict site index values under climate change conditions, values obtained from the biophysical site index model are corrected by a factor estimated using the seed source transfer model. Our simulation results predict that global warming should favour a slight increase in white spruce plantation yield in southern Québec. However, one cannot expect to obtain similar yields from a seed source rapidly exposed to warmer conditions compared with a seed source that is presently growing under climatic conditions to which it has become adapted. It would take several generations (adaptation lag) for a seed source to adapt to warmer conditions. We believe that the method we propose will be helpful in identifying the most productive seed source to be used at any given location in the province, and in revising seed source transfer rules. Key words: climate change, white spruce, provenance test, transfer model, site index, adaptation, plantation, GIS