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931.
A comparison of agrisilvicultural systems with plantation forestry in the Atlantic Lowlands of Costa Rica 总被引:1,自引:0,他引:1
Survival and growth data (ages 0–5 years) are presented for two timber species (Acacia mangium, Cordia alliodora) planted in monocultures or in association with a sequence of agricultural cropsZea mays, Zingiber officinale andEugenia stipitata (a fruit shrub) in the tropical humid Caribbean lowlands of Costa Rica. Average annual height and diameter growth rates were 3.2 m and 4.0 cm (C. alliodora), 3.5 m and 3.8 cm (A. mangium).C. alliodora associated with crops gave the greatest productivity with an average total stem volume increment of 19 m3 ha–1 yr–1. Root rot ofA. mangium (mainlyRosellinia sp.), leading to tree mortality, was greater in pure plots compared to associated plots.A. mangium can not be recommended for similar sites because of this problem. 相似文献
932.
杉木苗根系打泥浆后造林不仅能提高造林成活率,而且与当年生幼树的根系地径和树高的生长关系密切,在不同的造林时间或造林后的不同时间,其影响程度是不同的。 相似文献
933.
ABSTRACT Growth Simulation, an analytical modeling technique, has been increasingly used in ecological studies and practical forestry applications where dendrochronology is not applicable. The technique uses randomly sampled diameter increments from tagged trees over a known time interval to assemble a statistical sample of lifetime growth trajectories. We carried out a validation of Growth Simulation using a temperate species in order to compare indirect model outputs with direct tree ring analysis. Rings were measured on sample disks cut from 55 pine branches ranging in age from 8–36 years. Assessments included lifetime growth rates, growth rate with respect to diameter and age, periodic annual increment (PAI), cross-referencing of rings by date, and autocorrelation of growth over successive periods. Tree ring analysis and Growth Simulation showed close correspondence for all parameters tested (maximum, median, and minimum growth rates; longevity estimates). Growth Simulation is found to be a robust and informative technique for studies of tropical tree growth, and is especially useful where analysis of tree rings is not feasible or when bootstrapping analysis of ring data is of interest. 相似文献
934.
Classifying tree planters and non planters in a subsistence farming system using a discriminant analytical approach 总被引:1,自引:0,他引:1
Since the 1970s tree planting has been promoted to meet the multipurpose needs of subsistence farmers and to arrest deforestation in many developing countries. Financial support and extension systems were developed as tree growing outside the forest became more important. The limited success of the forest extension approaches used in the 1980s has been attributed to the failure to ascertain householders' priorities and attitudes to tree growing. Although the broader theoretical paradigm of factors influencing householders' planting of trees has been discussed household and regional level analyses are rare. This study used discriminant analysis to assess the extent to which social and economic factors affect smallholder farmer tree planting in Orissa, eastern India. The validity of the predictive model to define the different groups was tested by assessing the accuracy of classification. The significance of the factors was probed using the identified variables in the discriminant functions developed for smallholder farmers in the coastal and inland zones of Orissa. The results contradicted some common assumptions that only large landowners with a substantial income are innovators. The likelihood of adopting agroforestry is dependent on the progressive attitude of farmers, membership of village organisations, their wealth status and, more importantly, their perceived risk concerning agricultural production. This approach enables tree planters and non-planters to be characterised and hence give better targetting of planning and social forestry programmes.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
935.
曲靖市营造生物防火林带研究与应用 总被引:1,自引:0,他引:1
按照不同海拔区域,不同立地条件,选择生长迅速、郁闭快、适应性强、萌发率强、枝叶茂密、含水量高、耐火性强、含油脂少、不易燃烧的耐火树种,草种进行立体配置营造林带,并对不同配置的林带进行阻火抗火试验。筛选出最佳的防火树种和草种,按最佳配置营造防火林带,在云南省曲靖市推广应用。 相似文献
936.
937.
Seeds of Juniperus procera collected from five provenances across its geographic range in Ethiopia were subjected to cold-moist stratification at 5°C
or 10°C for 6–12 weeks. The effect of aqueous smoke solution in overcoming the light requirement for germination, and the
potential of visible (VIS) and near infrared reflectance (NIR) spectroscopy for sorting sound and insect-damaged seeds were
also investigated. Highly significant differences in germination were detected among provenances (P < 0.0001) and stratification periods (P < 0.0001), but not between temperature regimes (P=0.111). Seeds from the south and southeast distribution ranges had higher percentage germination after 6 weeks of stratification
than seeds collected from north, northwest and central ranges of distribution. The smoke treatment did not affect germination
regardless of whether the seeds were exposed to light. Exposure to light increased germination capacity three fold. Sound
and damaged seeds were distinguished with 90% accuracy using VIS + NIR spectroscopy. It can be concluded that dormancy in
juniper seeds varies with provenances, and cold stratification for 6 weeks alleviates dormancy in some seed lots. Tentatively,
smoke treatment seems ineffective in overcoming photo-dormancy in juniper seeds. VIS + NIR spectroscopy has demonstrated a
great potential for sorting damaged seeds, thereby upgrading seed lot purity. 相似文献
938.
This paper examines the first-best instruments for biodiversity maintenance in commercial boreal forests when landowners behave either in Faustmannian or Hartmanian way. Using an extended Hartman model, we show that biodiversity conservation requires both prolonged rotation age and leaving retention trees. While the former promotes some old growth species, the latter create new structural elements of decaying and dead wood, which can sustain a variety of saprolyxic species. A fully synchronized combination of retention tree subsidy and tax instrument is needed both to lengthen the privately optimal rotation period and to provide an incentive to leave retention trees. Using Finnish data we illustrate empirically the sizes of instruments. When combined with a harvest tax, the retention tree subsidy is 1000 and 750 € in the Faustmann and in the Hartman model, respectively. When used with a timber subsidy or a site value tax, the retention tree subsidy is 1700 €/ha in both models. The harvest tax rate varies over the range 40–65% in the Faustmann model and 20–40% in the Hartman model, while timber subsidy is between 0.5–1.0% and site value tax is about 1.75%. 相似文献
939.
Height–diameter equations for boreal tree species in Ontario using a mixed-effects modeling approach
Height–diameter relationships based on stand characteristics (trees/ha, basal area, and dominant stand height) were investigated for balsam fir, balsam poplar, black spruce, jack pine, red pine, trembling aspen, white birch, and white spruce using data from permanent growth study plots in northern Ontario, Canada. Approximately half the data were used to estimate model parameters with the rest used for model evaluation. Multiple Chapman–Richards functions with parameters expressed in terms of various stand characteristics were fit to determine the best models for predicting height. 相似文献
940.
I. Verinumbe 《Agroforestry Systems》1993,21(3):287-292
In order to obtain data which will facilitate the scientific development of multiple intercropping of trees in agroforestry systems, the effects ofFaidherbia albida Del. orZiziphus spina-christi L. Desf. on soil quality and on yield of interplantedLeucaena leucocephala L. were investigated. The distance to which bothFaidherbia albida andZiziphus spinachristi trees improved soil quality as well asLeucaena leucocephala andSorghum vulgare L. production around them was about two times the radius of the tree crown. Higher yields of plants underZiziphus spina-christi thanFaidherbia albida were explained by similarly higher concentrations of available phosphorus (P). Other soil parameters, including total nitrogen (N), were similar under both species; being higher under the tree canopies than away from them. The study identified optimum tree spacing for agroforestry to be twice the tree crown radius. It also demonstrated the advantages of multiple tree mixtures over pure stands in improving soil quality and productivity. 相似文献