Background:Studies on optimal stand management often make simplifications or restrict the choice of treatments,Examples of simplifications are neglecting natural regeneration that appears on a plantation site,omitting...Background:Studies on optimal stand management often make simplifications or restrict the choice of treatments,Examples of simplifications are neglecting natural regeneration that appears on a plantation site,omitting advance regeneration in simulations,or restricting thinning treatments to low thinning(thinning from below).Methods:This study analyzed the imparts of simplifications on the optimization results for Fennoscandian boreal forests.Management of pine and spruce plantations was optimized by gradually reducing the number of simplifying assumptions.Results:Forced low thinning,cleaning the plantation from the natural regeneration of mixed species and ignoring advance regeneration all had a major impact on optimization results.High thinning(thinning from above) resulted in higher NPV and longer rotation length than thinning from below.It was profitable to leave a mixed stand in the tending treatment of young plantation.When advance regeneration was taken into account,it was profitable to increase the number of thinnings and postpone final felling.In the optimal management,both pine and spruce plantation was gradually converted into uneven-aged mixture of spruce and birch.Conclusions:The results suggest that,with the current management costs and timber price level,it may be profitable to switch to continuous cover management on medium growing sites of Fennoscandian boreal forests.展开更多
本文基于2017—2021年Web of Science(WoS)和中国知网(CNKI)数据库中以澳洲坚果为主题发表的相关文献,利用WoS自带分析工具和文献计量学软件CiteSpace,分析澳洲坚果研究现状、研究热点和发展趋势,以期为我国澳洲坚果产业发展提供参考。...本文基于2017—2021年Web of Science(WoS)和中国知网(CNKI)数据库中以澳洲坚果为主题发表的相关文献,利用WoS自带分析工具和文献计量学软件CiteSpace,分析澳洲坚果研究现状、研究热点和发展趋势,以期为我国澳洲坚果产业发展提供参考。结果显示:2017—2021年澳洲坚果领域发文量国际发文量呈增长趋势,但增幅变化不大,澳大利亚在WoS占总体发文量的36.86%。Food Science Technology是WoS收录期刊中发文量占比最多(16.99%),其次是Environmental Sciences(11.86%)和Plant Science(10.58%)。国际研究方向主要集中在澳洲坚果的基因组和宏基因组、种仁及油料、栽培种质和杂交种植、种壳剩余物加工利用和种植园管护5个方面。国内期刊发文量在2021年增速显著,此前则逐年下降,研究热点与国际联系紧密,包括澳洲坚果种仁油料和蛋白、品种选育、土壤磷利用、虫害防治和种仁干燥加工等方向。文献计量分析表明澳洲坚果的花枯病是坐果率偏低的主要原因之一,而真菌分离株的腐生或共生能力还未确定,应深入研究,为提高澳洲坚果产量及产业发展提供科学依据和理论支撑。展开更多
Kenya’s public forest sector plantations have been the main source of roundwood for wood-based industries but several factors have reduced its capacity to meet increasing demands, resulting in huge deficits. The grow...Kenya’s public forest sector plantations have been the main source of roundwood for wood-based industries but several factors have reduced its capacity to meet increasing demands, resulting in huge deficits. The growth of small-holder forestry over the last three decades has demonstrated the potential to supplement the deficits. The imposed logging moratorium in public and community forests in 2002-2012 and 2018 not only opened markets for small-holder tree growers but also increased demand pressure from various wood consumers. This paper presents an assessment of the status of farm-based wood resources three years within the latest moratorium period and the potential of farm tree resources to complement wood from public forest plantations. Data were collected from 56 households using semi-structured interviews, key informants interviews, and a rapid assessment of standing and harvested trees from 146 on-farm plots. The main commercial tree species found on the farms were;Cupressus lusitanica, Eucalyptus sp., Grevillea robusta, Pinus patula, and Acacia mearnsii. Eucalypts were the most planted trees with an average land size of 1.08 ha. The farm tree resources have sustained some level of wood demand since the moratorium, as indicated by the high volume of wood harvested. The study found that about 40% of current wood resources consisted of trees less than 5 years, and most harvests were of small diameter classes which are essentially juvenile wood and are unsuitable for structural and furniture use. Furthermore, most small-scale farmers lack appropriate silvicultural and management knowledge, preferring smaller growing spacing as shown by the high planting density of 1659 stems·ha<sup>-1</sup> and also use of inferior germ-plasm, with implications on the quality of wood from farms. It is recommended that rigorous capacity building on tree growing and management techniques be undertaken and a progressive and supportive policy framework on harvesting and trade of trees on-farm be developed.展开更多
文摘Background:Studies on optimal stand management often make simplifications or restrict the choice of treatments,Examples of simplifications are neglecting natural regeneration that appears on a plantation site,omitting advance regeneration in simulations,or restricting thinning treatments to low thinning(thinning from below).Methods:This study analyzed the imparts of simplifications on the optimization results for Fennoscandian boreal forests.Management of pine and spruce plantations was optimized by gradually reducing the number of simplifying assumptions.Results:Forced low thinning,cleaning the plantation from the natural regeneration of mixed species and ignoring advance regeneration all had a major impact on optimization results.High thinning(thinning from above) resulted in higher NPV and longer rotation length than thinning from below.It was profitable to leave a mixed stand in the tending treatment of young plantation.When advance regeneration was taken into account,it was profitable to increase the number of thinnings and postpone final felling.In the optimal management,both pine and spruce plantation was gradually converted into uneven-aged mixture of spruce and birch.Conclusions:The results suggest that,with the current management costs and timber price level,it may be profitable to switch to continuous cover management on medium growing sites of Fennoscandian boreal forests.
文摘Kenya’s public forest sector plantations have been the main source of roundwood for wood-based industries but several factors have reduced its capacity to meet increasing demands, resulting in huge deficits. The growth of small-holder forestry over the last three decades has demonstrated the potential to supplement the deficits. The imposed logging moratorium in public and community forests in 2002-2012 and 2018 not only opened markets for small-holder tree growers but also increased demand pressure from various wood consumers. This paper presents an assessment of the status of farm-based wood resources three years within the latest moratorium period and the potential of farm tree resources to complement wood from public forest plantations. Data were collected from 56 households using semi-structured interviews, key informants interviews, and a rapid assessment of standing and harvested trees from 146 on-farm plots. The main commercial tree species found on the farms were;Cupressus lusitanica, Eucalyptus sp., Grevillea robusta, Pinus patula, and Acacia mearnsii. Eucalypts were the most planted trees with an average land size of 1.08 ha. The farm tree resources have sustained some level of wood demand since the moratorium, as indicated by the high volume of wood harvested. The study found that about 40% of current wood resources consisted of trees less than 5 years, and most harvests were of small diameter classes which are essentially juvenile wood and are unsuitable for structural and furniture use. Furthermore, most small-scale farmers lack appropriate silvicultural and management knowledge, preferring smaller growing spacing as shown by the high planting density of 1659 stems·ha<sup>-1</sup> and also use of inferior germ-plasm, with implications on the quality of wood from farms. It is recommended that rigorous capacity building on tree growing and management techniques be undertaken and a progressive and supportive policy framework on harvesting and trade of trees on-farm be developed.
