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1.
《Southern Forests》2013,75(4):277-285
Field establishment of South Africa’s most important commercial pine species, Pinus patula, is severely hampered by the pitch canker fungus, Fusarium circinatum. Importantly, hybrids between P. patula and other pine species tolerant to the pitch canker fungus, such as P. tecunumanii and P. oocarpa, have been identified as an alternative planting stock. In this study, variation in tree volume and dynamic modulus of elasticity (MOEdym) of the P. patula × P. tecunumanii (low- and high-elevation [LE and HE] ecotypes) hybrid was compared with the P. elliottii × P. caribaea hybrid, and the pure species P. tecunumanii (LE) and P. patula. The MOEdym was assessed using the Fakkop TreeSonic microsecond instrument across three sites. The results of the study showed that P. patula × P. tecunumanii LE performed significantly better than P. patula × P. tecunumanii HE for volume and MOEdym, which in turn was significantly better than P. patula. The MOEdym and tree growth decreased with an increase in elevation. There was significant taxon × site interaction for volume and MOEdym. The results of these trials suggested that P. patula × P. tecunumanii LE is a suitable alternative to P. patula in the Sabie region of Mpumalanga in South Africa on frost-free sites, in terms of the traits that were assessed. 相似文献
2.
R. G. Mitchell M. J. Wingfield G. R. Hodge E. T. Steenkamp T. A. Coutinho 《New Forests》2013,44(3):443-456
The field survival of Pinus patula seedlings in South Africa is frequently below acceptable standards. From numerous studies it has been determined that this is largely due to the pitch canker fungus, Fusarium circinatum. Other commercial pines, such as P. elliottii and P. taeda, show good tolerance to this pathogen and better survival, but have inferior wood properties and do not grow as well as P. patula on many sites in the summer rainfall regions of South Africa. There is, thus, an urgent need to improve the tolerance of P. patula to F. circinatum. Operational experience indicates that when P. patula is hybridized with tolerant species, such as P. tecunumanii and P. oocarpa, survival is greatly improved on the warmer sites of South Africa. Field studies on young trees suggest that this is due to the improved tolerance of these hybrids to F. circinatum. In order to test the tolerance of a number of pine hybrids, the pure species representing the hybrid parents, as well as individual families of P. patula × P. tecunumanii, a series of greenhouse screening trials were conducted during 2008 and 2009. The results indicated that species range in tolerance and hybrids, between P. patula and these species, are intermediate in tolerance to F. circinatum. Within P. patula × P. tecunumanii, large family variation exists when pollen from the high elevation source of P. tecunumanii is used. The results of these studies illustrate the importance of developing pine hybrid breeding programs to overcome the susceptibility of our pure species to pathogens such as F. circinatum. 相似文献
3.
J. Roux B. Eisenberg A. Kanzler A. Nel V. Coetzee E. Kietzka M. J. Wingfield 《New Forests》2007,33(2):109-123
Plantations of Pinus spp. constitute approximately 50% of the South African forestry industry. The first aim of this study was to develop a reliable
inoculation technique to screen Pinus spp., for tolerance to infection by F. circinatum, which threatens pine forestry in South Africa. Inoculation of branches was compared with stem inoculations and we considered
the number of branches or trees required to obtain statistically significant results. Furthermore, variation in the susceptibility
of some Pinus families, clones and hybrids was considered. Results showed that branch inoculations were closely correlated with those from
stem inoculations, and that it is important to consider branch and stem diameters when assessing susceptibility of trees.
Subsequent trials using branch inoculations showed significant differences in F. circinatum tolerance amongst a range of pine species and hybrids of potential interest to forestry in South Africa. Significant differences
in susceptibility were also found among clones of two P. radiata families. The most tolerant trees were P. elliottii × caribaea and P. patula × oocarpa hybrids, while the most susceptible species were P. patula, P. greggii and hybrids of these two. This is the first trial considering the susceptibility of Pinus hybrids, Pinus clones and some P. patula provenances, and the results indicate excellent potential for breeding for tolerance to pitch canker in South Africa.
Application The accurate selection of disease tolerant planting stock for the South African forestry industry is crucially important
for the continued sustainability of this important industry. The work described here provides valuable information on an artificial
inoculation technique that will assist the industry in screening trees for tolerance to the pitch canker fungus, F. circinatum. It also provides some indication of the relative susceptibility of a number of Pinus spp., hybrids and families currently being evaluated in the country. 相似文献
4.
During the last 20 years a program to develop and commercialize the Pinus patula × Pinus tecunumanii hybrid, as a replacement for P. patula, has been successfully implemented. The first crosses were initiated during the early 1990s and lead to establishment of field trials across a wide variety of sites. This work gained further impetus when it became apparent that Fusarium circinatum, was causing poor post-planting survival of newly established stands of P. patula. P. tecunumanii, has been shown to be tolerant to this disease and thus a second, more comprehensive hybrid testing phase was implemented. Improvements in controlled pollination techniques and propagation methods, as well as access to genetically improved parent-stock and the use of molecular marker technology for fingerprinting was effectively utilized to greatly improve the process during this second phase. The use of artificial inoculation trials have demonstrated that the hybrid, in particular when using the low elevation (LE) provenances of P. tecunumanii, had substantially greater tolerance to F. circinatum than P. patula and survival figures from field trials support these results. Four-year volumes also indicate large growth improvements, although frost damage on certain sites presents a challenge for deployment on colder sites; and this is being tackled through breeding and accurate mapping of frost risk. Large-scale controlled pollinations and vegetative multiplication are now utilized commercially to produce the P. patula × P. tecunumanii (LE) hybrid as an alternative to P. patula. 相似文献
5.
《Southern Forests》2013,75(4):301-310
Through the collaborative efforts of companies affiliated with the International Program for Tree Improvement and Conservation (Camcore), a number of pine hybrids have been produced over the last decade. Many of these have been planted in trials across southern Africa that broadly represent winter and summer rainfall areas, with the latter ranging from warm to cold temperate sites. The five-year survival and growth of the hybrids and other pines in 12 of these trials were compared with Pinus radiata in the winter rainfall, and P. patula in the summer rainfall, regions where these species have been planted extensively. Except for the highest altitude site, where freezing conditions are common, the survival of most hybrids and tropical pines was better than P. patula or P. radiata. This was, in part, attributed to their improved tolerance to the pitch canker fungus, Fusarium circinatum, which was present in the nursery at the time of planting. In the winter rainfall area, the P. elliottii × P. caribaea hybrid, P. maximinoi and, surprisingly, the P. patula hybrids performed well. In the summer rainfall regions, hybrids with tropical parents such as P. caribaea, P. oocarpa and P. tecunumanii were more productive in the subtropical/warm temperate zone and, with increasing elevation, those hybrids crossed with P. patula performed relatively better. The P. patula × P. tecunumanii hybrid, particularly when crossed with low-elevation P. tecunumanii, performed exceptionally across most sites. 相似文献
6.
R. G. Mitchell M. J. Wingfield G. R. Hodge E. T. Steenkamp T. A. Coutinho 《New Forests》2012,43(4):473-489
The increasing threats from pests and diseases demand that the South African forest industry explores options to deploy alternative pine species in plantation development. This is especially true for species, such as Pinus patula Schiede and Deppe ex Schltdl. and Cham., which are highly susceptible to the pitch canker fungus Fusarium circinatum. Losses due to F. circinatum have been confined mostly to nurseries and at field establishment resulting in a significant cost to the industry. Although, the fungus has not as yet resulted in stem and branch infections on established P. patula in South Africa, it has caused pitch canker on other, more susceptible species such as P. radiata D. Don., and P. greggii Engelm. ex Parl. As alternatives to P. patula, on the warmer and cooler sites in South Africa, families of P. elliottii Engelm var. elliottii, P. tecunumanii (Schw.) Eguiluz and Perry, P. maximinoi H. E. Moore and P. pseudostrobus Lindl. were screened for tolerance to infection by F. circinatum in greenhouse studies. Seedlings were wounded and inoculated with spores of F. circinatum. Lesion development following inoculation was used to differentiate the levels of tolerance between families. The results showed that P. maximinoi, P. pseudostrobus, and the low elevation variety of P. tecunumanii are highly tolerant to infection with very little family variation. The narrow sense heritability estimates for these species were less than 0.06. In contrast, P. elliottii showed good tolerance with some family variation and a heritability of 0.22, while the high elevation source of P. tecunumanii showed a high degree of family variation and a heritability of 0.59. These results provide the industry with valuable information on pine species tolerant to F. circinatum that could be used as alternatives to P. patula in South Africa. 相似文献
7.
Pinus patula and high-elevation (HE) sources of P. tecunumanii exhibit intermediate levels of resistance to pitch canker (Fusarium circinatum), compared to extremely resistant species such as P. oocarpa, and extremely susceptible species such as P. radiata. Seedlings from 20 P. patula provenances and 15 HE P. tecunumanii provenances were artificially inoculated with the pitch canker fungus at 21 and 12 weeks of age, respectively, and assessed
for resistance 12–20 weeks later. There was important provenance variation in pitch canker resistance for both species. The
20-week LiveStem percentage ranged from 70.3% to 43.6% among the P. patula provenances and 59.6% to 11.7% among HE P. tecunumanii provenances. There was a geographic pattern to the provenance variation, and in both species, low altitude sources demonstrated
more resistance than those from high elevation. Provenance variation in pitch canker resistance could be useful when making
selection and breeding decisions with these species. 相似文献
8.
《Southern Forests》2013,75(4):247-252
The pitch canker fungus, Fusarium circinatum, has caused large-scale mortality of young Pinus patula Schiede and Deppe ex Schltdl. and Cham. seedlings in nurseries in South Africa since 1990. Diseased seedlings have been inadvertently carried to the field, which in turn have died and has reduced stocking below an acceptable level. Tree breeders have suggested that the only long-term solution to limit infection by this pathogen is to identify and deploy tolerant P. patula families. A commonly used technique to identify tolerant clones is to artificially inoculate open-pollinated progeny from orchard clones with F. circinatum under greenhouse conditions. In these trials, large variation in tolerance to the pathogen among seedlings within open-pollinated families was observed and this could be influenced by the pollen parent. Therefore, identifying individual full-sib families, where both parents are known, should improve the identification of tolerant families, which can then be repeated. In this study, cuttings from control-pollinated P. patula seedling hedges were inoculated with F. circinatum in a greenhouse. The results showed large family variation where some of the full-sib families were similar in tolerance to P. elliottii Engelm. var. elliottii seedlings. Therefore, it is recommended that breeders focus on identifying specific family combinations that are more tolerant to F. circinatum. 相似文献
9.
《Southern Forests》2013,75(4):203-210
Approximately 50% of the area planted to softwood trees in South Africa has been established with Pinus patula, making it the most important pine species in the country. More effort has gone into developing this species for improved growth, tree form and wood properties than with any other species. This substantial investment has been threatened in the last 10 years by the pitch canker fungus, Fusarium circinatum. The fungus infects and contaminates nursery plants and, once transferred to the field, causes severe mortality of young trees in the first year after establishment. Although nurserymen have some control of the disease, it is recognised that the best long-term solution to mitigate damage because of F. circinatum infection is to identify tolerant species, clones and hybrids for deployment in plantations in the future. Research has shown that alternative species such as P. tecunumanii, P. maximinoi and P. elliottii are suitable for warm sites. Pine hybrids, particularly between P. patula and the high-elevation sources of P. tecunumanii, appear to be a suitable replacement on subtemperate and temperate sites. Although these alternative species and hybrids are more sensitive to subfreezing temperatures than P. patula, their planting range can be increased by including cold tolerance as a selection criterion. Future breeding efforts will most certainly focus on improving the tolerance of pure P. patula to F. circinatum, which can be achieved by identifying specific family crosses and tolerant clones. The commercial deployment of disease-tolerant control-pollinated P. patula and hybrid families will most likely be established as rooted cuttings, which requires more advanced propagation technology. In the long term, new seed orchards comprised of P. patula clones tolerant to F. circinatum could be used to produce seed for seedling production. 相似文献
10.
R. G. Mitchell M. J. Wingfield G. R. Hodge W. S. Dvorak T. A. Coutinho 《New Forests》2013,44(1):135-146
The future of South Africa’s most important pine species, Pinus patula, is threatened by the pitch canker fungus, Fusarium circinatum. Pinus maximinoi and P. tecunumanii represent two subtropical species that provide an alternative to planting P. patula on the warmer sites of South Africa. Extending the planting range of P. tecunumanii and P. maximinoi to include higher and colder altitude sites will reduce the area planted to P. patula and the risk of F. circinatum. During 2007 progeny trials of P. tecunumanii and P. maximinoi were planted on a sub-tropical and sub-temperate site. Shortly after the establishment of these trials, unusually cold weather conditions were experienced across South Africa (?3°C at the sub-temperate site) resulting in severe mortality. This provided the opportunity to assess the variation in survival as a measure of frost tolerance within these two species to determine whether it could be improved upon through selection. Results indicated that the variation in survival was under genetic control in P. tecunumanii (h (0,1) 2 = 0.16, h L 2 = 0.27) and P. maximinoi (h (0,1) 2 = 0.11, h L 2 = 0.23) at the sub-temperate site. Correlations in provenance ranking for survival across sites were high for both species. Moderate correlations in family survival for P. tecunumanii (r = 0.52) were found at the two sites. Improvements in cold tolerance can thus be made in both species extending their planting range to include greater areas planted to P. patula thereby limiting the risk of F. circinatum. 相似文献
11.
A taxonomic study on 14 cone and needle traits of 281 trees from 33 provenances of Pinus oocarpa, P. oocarpa var. ochoterenae, P. patula var. longipedunculata, P. patula var. patula and P. tecunumanii in Central America and Mexico was conducted to quantify the affinity between closely related species. A second objective was to determine the geographic range of P. tecunumanii in Mexico. Cluster analysis placed 52% of all provenances in taxa different from those assigned by field foresters. Trees from 15 provenances of what was locally known as Pinus oocarpa var. ochoterenae from Chiapas were statistically indistinguishable from high elevation Central American sources of P. tecuncumanii when assessed for cone and needle characteristics. However, trees from two provenances known locally as P. oocarpa var. ochoterenae from southwestern Oaxaca, Juquila and Tlacuache, were found to be distinct from P. tecunumanii and may be a variant of P. patula. Canonical discriminant analysis was used to determine the taxonomic affinity among newly formed clusters. The spatial (Mahalanobis) distance between P. tecunumanii and P. patula var. patula, P. patula var. longipedunculata, and P. oocarpa was 42.0, 44.4, and 109.4 respectively, and highly significant. The geographic range of Pinus tecunumanii in Mexico appears to be confined to the state of Chiapas. 相似文献
12.
A species introduction experiment including several tropical pines and eucalypts was established in 1966/1967 in the Tchianga research station in Angolan Highlands. Despite 27 years of political conflict (1975-2002) and lack of management, the research experiment has remained relatively well conserved. We measured the best conserved plots that were 41 years old in 2007 to obtain information on the growth of different pine species. We calculated stand characteristics including basal area, dominant height, mean diameter, and stand volume for Pinus patula Schiede ex Schiltdl. Et Cham., Pinus pseudostrobus Lindl., Pinus kesiya Royle ex Gordon, Pinus devoniana Lindl., Pinus chiapensis (Martinez) Andresen, Pinus elliottii Engelm., Pinus greggii Engelm. Ex Parl., Pinus montezumae Lamb. and Pinus oocarpa Schiede ex Schltdl. The growing stock volume at 41 years was the highest in P. pseudostrobus, 1,325 m3·ha-1, followed by P. kesiya with 1,200 m3·ha-1. The widely planted P. patula had a growing stock volume of 892 m3·ha-1. P. oocarpa and P. pseudostrobus had the highest stand basal area, over 80 m2·ha-1. Using increment core analyses we studied the temporal development of stand characteristics. Analysis of the mean annual increment (MAI) showed that rotation lengths of 20-30 years would maximize wood production. With these rotation lengths, the MAI of P. pseudostrobus would be 35 m3·ha-1. Other productive species were P. kesiya, P. oocarpa and P. chiapensis. P. patula had a maximum MAI of 20 m3·ha-1. P. greggii had the lowest mean annual volume production, only about 13 m3·ha-1. 相似文献
13.
The disease known as pitch canker results from infection of Pinus species by the fungus Fusarium circinatum. This fungus also causes a serious root disease of Pinus seedlings and cuttings in forestry nurseries. Pinus radiata and P. patula are especially susceptible to the pathogen, but there are no records of pitch canker on P. patula in established plantations. To date, only planting material of this tree species in nurseries or in plantations at the time of establishment have been infected by F. circinatum. Symptoms of pitch canker have recently emerged in an established P. patula plantation in South Africa and this study sought to determine whether the symptoms were caused by F. circinatum. Isolates from cankers were identified as F. circinatum using morphology and DNA-based diagnostic markers. Microsatellite markers were then used to determine the genetic diversity of a collection of 52 isolates. The entire population included 17 genotypes representing 30 alleles, with a greater number of genotypes collected from younger (three- to six-year-old) than older (12- to 19-year-old) trees. Both mating types of F. circinatum were present, but no evidence of sexual recombination was inferred from population genetic analyses. This is the first record globally of pitch canker on P. patula trees in managed plantations. It is of significant concern to South Africa, where P. patula is the most important Pinus species utilised for plantation forestry. 相似文献
14.
Carlos A Rodas Rubén Serna Maria D Bolaños Ginna M Granados Michael J Wingfield 《Southern Forests》2015,77(3):165-171
Adelgids (Hemiptera) in the genus Pineus have been reported as introduced insect pests causing serious losses to Pinus plantations worldwide. In 2008, Pineus boerneri was recorded for the first time in Colombia, with infestations noted on Pinus kesiya, P. tecunumanii, P. maximinoi and P. oocarpa. The lack of information on this insect in Colombia prompted investigations of its life cycle and infestation levels as well as host susceptibility of the main Pinus species planted in Colombia. In addition, the possibility of using a Ceraeochrysa species, an already established predator of adelgids in Colombia, for biological control was considered. Results showed that Pineus boerneri in Colombia has an anholocyclic life cycle comprised of four instars with a complete duration of between 49 and 97 d. Infestations were higher in the middle and upper part of trees. Pinus kesiya and P. maximinoi had the highest levels of susceptibility in field as well as in greenhouse trials. A survey of naturally infested trees showed P. tecunumanii to be moderately susceptible, whereas P. patula and P. oocarpa had low levels of susceptibility in a greenhouse trial but were not susceptible in the field. Investigations considering the impact of predation of Ceraeochrysa species showed a high predation rate of up to 140 P. boerneri consumed per day by a single Ceraeochrysa individual. Other predators of P. boerneri were recorded but were not sufficiently common to warrant detailed study. 相似文献
15.
Francois S Malan 《Southern Forests》2015,77(4):269-276
This paper discusses family differences in the stiffness of young Pinus elliottii×P. caribaea wood and how these differences relate to differences in growth rate and altitude. Trees for measurement were obtained from three 5?year?old progeny trials established at three diverse sites on the estate of Komatiland Forests (Pty) Ltd. The trials included the following controls: P. elliottii, P. patula, P. taeda, P. patula×P. tecunumanii and P. tecunumanii. Diameter at breast height and sound velocity (which has a direct relationship with wood stiffness) were measured on all healthy trees. Virtually all of the species and hybrids exhibited marked decreases in growth rate and velocity (stiffness) with increasing altitude; the effect on velocity was most likely partly due to the inverse relationship that normally exists between wood density and altitude in most pines. Differences in growth rate explained only a small proportion of the total variation in velocity. The average sound velocities of P. patula, P. patula×P. tecunumanii and P. tecunumanii surpassed the velocity values of most of the P. elliottii×P. caribaea crosses at all three sites. Results of Spearman rank correlations of average treatment velocity between sites suggested only some similarity in the ranking orders among sites. The inverse effect of altitude on wood stiffness suggests that trees grown at increased altitudes are likely to yield wood with higher proportions of wood not meeting the minimum stiffness requirement for structural lumber at final harvest. The wood of some P. elliottii×P. caribaea crosses would be particularly vulnerable. Considering the large variation found, presumably largely genetic, there can be little doubt that a good opportunity exists for the development of genotypes more suitable for planting at higher altitudes. 相似文献
16.
The susceptibility of Pinus oocarpa to freezing temperatures limits the commercial deployment of the highly productive Pinus patula × P. oocarpa hybrid in South Africa. Identifying P. oocarpa germplasm with increased frost tolerance is important. Twenty-three P. oocarpa provenances, originating from Mexico, Honduras, Guatemala and Nicaragua, were therefore assessed for their tolerance to freezing conditions by analysing field survival after frost events, subjecting needles to freezing temperatures and assessing damage using the electrolyte leakage test, and exposing young plants to freezing temperatures in a semi-controlled environment and scoring tissue damage based on a visual assessment. The performance of many of the provenances represented in the field and artificial freezing studies were similar and there was a strong correlation between provenance ranking in the whole plant freezing and electrolyte leakage test. We therefore support the use of these techniques as a means to assess cold tolerance in P. oocarpa at the provenance level. Provenances from north-western Mexico demonstrated more frost tolerance than those from southern Mexico. Provenances representing Honduras and Guatemala appear to be highly susceptible to frost. 相似文献
17.
Juan L. Lopez Robert C. Abt William S. Dvorak Gary R. Hodge Richard Phillips 《New Forests》2018,49(1):123-142
Financial performance of the P. patula × P. tecunumanii, P. greggii × P. tecunumanii, P. taeda × P. tecunumanii hybrids and their parental species was studied for South Africa. A model was developed for use in determining the profitability of a tree-breeding program (TBP) with pine hybrids in commercial plantations. Growth measurement data were collected in four, 12-year-old genetic trials on Mondi and Sappi land holdings in South Africa. Growth models developed for P. patula and P. taeda in South Africa were used to infer models for the other taxa and to calculate the optimal financial rotation age at discount rates of 6 and 8%. Financial data on pine plantations were collected from different sources in South Africa. Optimal rotation lengths in this study were found to be between 12 and 16 years for pulpwood and 17 years for sawtimber. The model output shows the net present value (NPV), the internal rate of return, and the minimum area that a tree grower has to plant every year in order to justify the investment in a TBP. A stochastic approach with Monte Carlo simulation showed that the sensitivity of NPV to uncertainty in the wood price was greater than that for the planting, harvesting, and transport costs. 相似文献
18.
《Scandinavian Journal of Forest Research》2012,27(6):483-493
Abstract Pinus patula and Pinus tecunumanii, two pines native to Mexico and Central America, are important plantation species for the forestry sector in the tropics and subtropics. In recent decades, members of the International Tree Conservation & Domestication Program (CAMCORE), North Carolina State University, have established large, multisite provenance trials for these pine species. The data provide valuable information about species and provenance choice for plantation establishment in many regions with different climates. However, since climate is changing rapidly, it may become increasingly difficult to choose the right species and provenance to plant. The aim of this study is to test the suitability of seed material under changing climate of two P. patula varieties (P. patula var. patula and P. patula var. longipedunculata) and two P. tecunumanii ecotypes (highland and lowland). For each variety and ecotype, a site quality model was developed that statistically relates growth to environmental factors and couples the predictions to the average 2020 climate prediction of four general circulation models. Three developed models were significant and robust. Provenances of P. tecunumanii from lowland areas in Central America are expected to be most productive in 2020 because of their promising performance under rather hot and wet climates. 相似文献
19.
André Nel Francois S Malan Ron Braunstein C Brand Wessels Arnulf Kanzler 《Southern Forests》2018,80(2):159-168
A study was undertaken to evaluate the quality of the timber produced by Pinus elliottii × Pinus caribaea var. hondurensis (PECH) and the Pinus patula × Pinus tecunumanii low elevation (PPTL) and high elevation (PPTH) hybrids and their parent species for both kraft pulp and sawn-timber production. Trees were taken from unthinned tree improvement trials managed for pulpwood, ranging in age between 15 and 19 years. All sawn boards produced by study trees met the minimum wood density requirement for S5-grade structural timber (360 kg m?3), but approximately 17% of the boards failed to meet the other requirements for the grade, largely due to knot-related defects. Results of dynamic modulus of elasticity assessments performed on all of the boards suggested that a large percentage of boards would not meet the specified average stiffness (7 800 MPa). This was confirmed by the results of static bending tests performed on a subsample of boards. All boards tested for all species and hybrids met the required fifth percentile bending strength value for grade S7 (15.8 MPa) according to SANS 6122 (2008) specifications. The kraft pulping results indicated that the samples taken from the upper part of the stem yielded slightly better results on average than the samples representing the whole tree with respect to uniformity in the kappa vs charge and temperature, and yield vs kappa traits, with slight improvement of pulp yield (52% vs 50%) and some strength properties compared with whole tree pulping. Samples from the upper part of the stem had a close delignification rate in the 60–80 kappa range. The delignification rate for PPTL in the 60–80 kappa range was slower and the yield was slightly lower than P. patula (53.17% vs 52.72%) despite a higher kappa number. The pulp strengths short-span compressive test, breaking length and tearing strength of PECH were similar to those of P. elliottii, which were in turn generally lower than those of P. patula. The pulp strengths of PPTL and PPTH were similar to those of P. patula, whereas P. caribaea strengths were intermediate between those of P. patula and P. elliottii. With the exception of a slightly lower pulp yield, PPTL emerged as the best all-round hybrid for both pulp and sawn-timber properties. 相似文献
20.
《Southern Forests》2013,75(3-4):153-161
This study developed growth models for Pinus patula Schiede ex Schltdl. et Cham. for the Central Highlands of Angola for simulating the development of stand characteristics. The model set included dominant height, individual-tree diameter increment, individual-tree height and self-thinning models. The study was based on 7 656 radial increment observations obtained from increment cores from eight plots located in five sites in the Angolan Highlands. The model set enables the simulation of stand development on an individual tree basis. Despite the fact that site variation among the plots was small, a traditional site category index based on slope catena correlated logically with the observed diameter growth rate of the plots. The developed models showed a high level of accuracy when the simulated stand development was compared to observed development. The shape of the dominant height model is similar to earlier models developed in southern Africa. 相似文献