Short Rotation Intensive Culture Plantations Research Articles

Evaluating sampling designs and deriving biomass equations for young plantations of poplar and willow clones

Short-rotation intensive culture (SRIC) for bioenergy production is at its pre-commercial stage in Canada. To be economically viable, these types of plantations need an accurate examination of actual yields, which requires precise and efficient estimation methods (i.e., specific allometric equations and sampling methods). At six SRIC plantations from three Canadian provinces (Quebec, Ontario and Alberta), 6 willow and 10 poplar clones were sampled and clone allometric equations were developed to estimate plant biomass. A stem selection approach was successfully used to develop plant allometric equations, reducing the number of stems to be measured by up to 81% in coppiced plantations relative to traditional stem equations. Clone-specific equations were more accurate than equations for groups of clones, but the difference in terms of RMSE% was generally small (less than 5%). Using extensive measurements of all the plants inside a plantation and a simulation approach, we also compared five sampling methods (simple random sampling, stratified sampling, systematic sampling, random and systematic cluster sampling) to estimate total biomass inside the plantation. Simple random sampling and stratified random sampling were the most efficient methods (i.e., increased precision for equal sample size) for the estimation of average plant biomass, survival and total plantation biomass. Stratified random sampling (based on the position inside the plantation) made it possible to reduce the sample size as compared to simple random sampling, but only at higher levels of precision (e.g., 25 less plants at 5% precision). Applications of sampling using remote sensing techniques and GIS are briefly discussed.

Absence of association between heterozygosity and biomass production in Salix exigua Nutt

The relations between heterozygosity derived from a total of 12 variable isoenzyme loci and total above-ground leafless biomass production were examined in four full-sib families of Salix exigua, a willow species important in breeding efforts for short-rotation intensive-culture plantations. Relations were investigated by comparing the performance of heterozygotes with that of corresponding homozygotes in locus by locus comparisons, by investigating multiple regression models with individual loci as independent variables, and by employing the adaptive distance model. All these analytical approaches resulted in the manifestation of the absence of any relations between isoenzyme loci and biomass production. Possible reasons that may account for these results are discussed.

Geneti|c diversity of superior Salix clones selected for intensive forestry plantations

A number of willow clones are today in use in short rotation intensive culture plantations. The clonal nature of this crop makes it an easy target for pests and pathogens when grown in monocultures. This is a major concern as plantations of coppice must remain viable for up to 20 years to be profitable. In this paper the genetic diversity of 114 selected willow clones was examined and the possible solution of growing willows in multiclonal plantations is discussed. Forty five Salix eriocephala clones, 53 S. exigua clones and 16 clones of their inter-specific hybrid (12 S. eriocephala× exigua clones and 4 S. exigua× eriocephala clones), were evaluated. Starch gel electrophoresis was employed and 12 enzyme systems were used for the assessment of the genetic variation in the clonal material. A total of 29 loci and 57 alleles were revealed. Three measures of genetic diversity were used in order to evaluate the genetic base of the clonal set: average number of alleles per locus, percentage of polymorphic loci and mean heterozygosity. Results indicated that the genetic diversity within a species, is generally lower than the genetic diversity observed in natural populations or full-sib families of the same species. These results, however, are within the limits obtained from natural populations of the Salicaceae family. Heterozygosity values were found to be greater than similar values from poplar clonal material. In contrast to the results within species, inter-specific hybrid clones presented relatively high amounts of genetic diversity. The significance of these results in the management of clonal plantations is discussed from both the operational and conservation points of view.

Single rotation vs coppice systems for short-rotation intensive culture plantations—optimality conditions for volume production

Short rotation intensive culture plantations can be managed under a single rotation or coppice system. This paper shows the optimality conditions that must exist in order to maximize volume production of short rotation coppice stands. The results indicate the importance of equating the current annual increment of the stand to its mean annual increment whether managing with a single rotation or a series of coppice rotations over a cycle of time. The mathematical conditions for having the coppice system rather than the single rotation for volume production are also derived. These conditions indicate the average of the mean annual increments for the coppice harvests must be greater than the maximum mean annual increment of the single rotation. Finally, an example illustrates an application of the optimality conditions to a set of hypothetical data.

Hybrid poplar spacing/productivity relations in short rotation intensive culture plantations

It is often argued that in short rotation intensive culture plantations, biomass productivity increases with narrower tree spacings. Biomass productivity and tree spacing relations were studied for up to 16 years in northern Wisconsin hybrid poplar plantations. Maximum mean annual biomass increment was 12.8 Mg ha −1 yr −1 for Populus clone NE-41 planted at a l m 2 spacing. Productivity differences related to spacing were found to be minor. Productivity was influenced mainly by clone, irrigation and disease. A hypothesis is proposed that time to canopy closure is linearly related to time to maximum mean annual biomass productivity. Wide spacing and wide-crown trees that permit wider tree spacing allow longer rotations, which can lower costs and increase flexibility in management.

Coppicing success of young Eucalyptus saligna in Hawaii

Coppicing characteristics of felled 3-year-old E. saligna trees growing in Hawaii were evaluated for four DBH classes and two stump-height segments. About 40% of all the stumps had at least one living shoot > 2 cm at the end of the 20-week study period. Tree size before felling had no effect on number of dormant buds available to develop into shoots, sprouting success or length of the longest sprout per stump, but all of these variables were affected by stump-height segment. Standardized 20-cm stump segments above the lowest branch scars (about 34–60 cm above ground) had about double the number of dormant buds, sprouting success and length of the longest shoot per stump than stump segments below the lowest branch scars. Ambrosia-beetle attacks on the stumps were coincidental with coppice development (2–8 weeks after felling), and were less severe on the stumps from the smaller trees and on the upper stump segments. Reasons for the low coppicing success of E. saligna in Hawaii are unknown. The opportunity for coppice (frequency of dormant buds) and the disturbance of coppicing by ambrosia beetles need to be more fully understood before coppicing can be a dependable method of regenerating this species in short-rotation intensive culture plantations in Hawaii.