Planting spacing affects canopy structure,biomass production and stem roundness in poplar plantations

To improve the productivity and wood quality of poplar plantations, effects of four planting spacing on canopy characteristics, biomass production and stem roundness in poplar plantations were evaluated over 8 years. Planting spacing influenced canopy characteristics of the plantations, and further affected the understory vegetation and plantation productivity. Understory vegetation biomass and Shannon-Wiener index were negatively correlated with leaf area index, but both diversity indexes and aboveground biomass of understory vegetation were higher in stands with a wider spacing. Tree diameter growth increased with increasing planting spacing, while the increment in plantations of square configurations (5?×?5 m and 6?×?6 m) was higher than those with rectangular configurations (3?×?8 m, 4.5?×?8 m). The highest poplar biomass production was achieved in the plantation with 5?×?5 m spacing at age 8. Moreover, poplar trees showed a tendency with better stem roundness in a square configuration. The results suggest that planting spacing not only affect canopy characteristics, understory vegetation and tree growth but also wood quality, and square configurations (5?×?5 m and 6?×?6 m) could be a better option for poplar plywood timber production at similar sites.     

Increasing rubber planting density to shade Imperata: a bioeconomic modelling approach

The profitability to smallholders of rubber production in Imperata infested areas of Indonesia was assessed using an existing bioeconomic model. An Imperata groundcover component was incorporated within the model as follows: tree girth = f(Imperata groundcover) = f(relative shading) = f(crown height, canopy width, tree spacing) = f(tree girth). The first two relationships represent extensions to the original model.Cumulative tree girth was predicted for rubber planting densities from 400 to 1000 stems/ha. At low tree planting rates, competition from Imperata restricts tree growth. At high tree planting rates, Imperata is controlled, but there are negative consequences from inter-tree competition. These two effects of higher planting rates counterbalanced, such that tree girth was approximately constant across the range of tree densities.Tree girth is a driving force in determining latex yield. Latex yield was translated into present value net economic returns within the model, by reference to prices and costs associated with rubber production in South Sumatra, Indonesia in 1995. Economic returns from planting 400 to 1000 trees/ha were calculated. Rubber growing by smallholders on Imperata infested land, was found to be profitable. Maximum profitability was obtained at 600 trees/ha. However, the sensitivity of net economic returns, with respect to tree density, was not great. This was due to the counterbalancing effects of changes in tree density.     

两类不同营养状态橡胶园的产量和死皮病情的调查研究

对甲等宜林地二代胶园和丙等宜林地一代胶园GT1品种橡胶树产量和死皮病率的调查结果:甲等宜林地二代胶园的干胶产量极显著(P<0.01)地低于丙等宜林地一代胶园;而死皮病率极显著(P<0.01)地高于后者,分析认为主要原因是二代胶园土壤营养不足。     

On-farm evaluation of the establishment of clonal rubber in multistrata agroforests in Jambi,Indonesia

Perennial tree crops are often grown in complex multistrata systems that incorporate natural vegetation. These systems contribute simultaneously to sustaining rural livelihoods and to the conservation of biodiversity, but their productivity is usually low. Introduction of high yielding germplasm, usually selected in monocultural plantations, is a potential way to increase productivity, but a critical requirement is that such plants can be established in a competitive multispecies environment. The establishment of clonal planting stock in the jungle rubber agroforests of Indonesia was explored through participatory on-farm research. The trial involved four farmers who grew clonal rubber trees in a total of 20 plots, constituting five replicate experimental blocks spread across four farms. Unexpectedly, vertebrate pest damage by monkeys (Presbytis melalophos nobilis) and wild pigs (Sus scrofa) was the most important influence on establishment, explaining almost 70% of the variation in rubber tree growth. The amount of labour invested in weeding was also positively correlated with rubber tree growth. Farmers generally decided to completely cut back vegetation between rows of rubber trees, including potentially valuable trees, rather than weeding within the rows and selectively pruning trees in the inter-row. Farmers thought that the inter-row vegetation would harbour vertebrate pests and compete with the clonal rubber, and they had access to fruits, firewood and other non-timber forest products from other land. Thus, contrary to expectations, when offered clonal germplasm, farmers opted to use plantation monoculture methods to protect what they considered a valuable asset, rather than maintain the traditional multispecies strategy they use with local germplasm. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecular identification of the powdery mildew fungus infecting rubber trees in China

Powdery mildew is a foliar disease of rubber trees. It is one of the most important leaf diseases in rubber plantations worldwide. The causal agent of this powdery mildew, previously known as Oidium heveae, has been identified under various names. To precisely identify the causal agents of this disease, 57 conidial samples were collected from 2013 to 2017 in Hainan, Yunnan and Guangdong provinces, the main rubber tree planting regions in China. Based on morphological observations using light and scanning electron microscopy, pathogenicity testing, and nrDNA ITS and 28S sequences, Erysiphe quercicola is suggested as the only causal agent of rubber tree powdery mildew in China.     

Comparison of diameter-distribution-prediction,stand-table-projection,and individual-tree-growth modeling approaches for young red alder plantations

A red alder planting spacing study was used to compare three modeling approaches that have been successfully used for other tree species. These three approaches predict stand structure and dynamics in plantations that are 7 to 16 years old, with planting densities of 976 to 13 899 trees/ha. The diameter-distribution-prediction approach tended to over-predict the diameter at breast height (dbh) for larger trees in stands planted at low density and to under-predict dbh for smaller trees in stands planted at high density. This approach may be useful for comparing planting densities when a tree list is not available. The stand-table-projection approach tended to under-predict dbh for smaller trees in young stands planted at low density and to over-predict dbh for smaller trees in young stands planted at high density. This approach, however, provided consistency between stand- and tree-level growth projections, and should be useful for comparing planting densities when a tree list is available. The individual-tree-growth approach provided the best representations of observed diameter distributions at all planting densities, stand ages, and growth intervals. This approach may be best suited for stands that have been thinned, stands with mixtures of species, and stands with heterogeneous size classes.     

Growth of widely spaced trees. A case study from young agroforestry plantations in France

Pessimistic forecasts often suggest that widely spaced trees enjoying free growth (no competition with other trees) will fail to provide high quality timber. This challenges the temperate agroforestry practice of planting widely spaced trees to produce high quality timber. We analyse tree growth data from recent temperate agroforestry plantations aged three to eight years, featuring low tree plantation densities (50 to 400 stems ha−1), the association of trees with intercrops (silvoarable systems) or animals (silvopastoral systems), and the use of plastic shelter tubes to protect trees (1.2 to 2.5 m high) and avoid damage by cattle or sheep in pastures or facilitate maintenance in silvoarable systems. The plantations are located in climates ranging from Mediterranean, dry central temperate plains, cold and wet central uplands to mild oceanic areas. Some plantations included a forestry control (high density of plantation, no tree shelter, no intercropping nor grazing). Trees were evaluated for height and diameter growth and stem form (straightness and absence of knots). Trees in most agroforestry plots grew satisfactorily, often faster than in forestry control plots. In some experimental plots, average annual height increments as high as 1 m and diameter increments as high as 1.5 cm were observed. Few agroforestry plantations were unsuccessful, and the reasons for the failures are discussed: animal damage in silvopastoral plots, but also a wrong choice of tree species unsuitable for local soil and climate characteristics. From these early results we can formulate some guidelines for designing future agroforestry plantations in temperate climates, concerning tree density, use of tree shelters and care required for widely spaced trees. This revised version was published online in June 2006 with corrections to the Cover Date.     

Variations in productivity and wood properties of Amazonian tachi-branco trees planted at different spacings for bioenergy purposes

Tachi-branco(Tachigali vulgaris,L.F.Gomes da Silva H.C.Lima) is a leguminous tree species native to the Amazon rainforest that has drawn attention for its remarkably fast growth,a required trait for biomass/bioenergy plantations.In evaluations of biomass production and wood properties of T.vulgaris planted in homogeneous plantations at different spacings in the Amazonian state of Para,Brazil,biomass of 7-year-old trees was quantified for individual trees and the entire population.Wood was also sampled to assess properties relevant to bioenergy applications.The choice for spacing dimension for planting nonclonal T.vulgaris should consider whether the priority is greater productivity per tree,achieved with greater spacings(9.0 m~2 and 12.0 m~2),or productivity per area,achieved with closer spacings(6.0 m~2 and 7.5 m~2).Genetic variability of the T.vulgaris seed stand and/or high heritability of wood traits overcame the effect of different spacing on all morphological,physical,chemical and energetic properties of T.vulgaris wood.This species has moderate basic density when cultivated at spacings larger than 6 m~2 and net heating value above 7.95 MJ/kg,which is suitable for bioenergy purposes.The high variation in wood properties within tree spacing is strongly indicative of great potential for genetic breeding.The fast growth and the suitable moderate wood basic density confirm the outstanding potential of homogeneous plantations of T.vulgaris for providing wood for bioenergy.     

橡胶优良品种海垦2在云南的适应性

橡胶树优良品种海垦 2在云南省热带作物科学研究所、勐捧农场、孟定农场的适应性试验研究表明 ,1～ 11割年平均单株年产干胶 5.2 7kg ,是对照RRIM6 0 0的 12 2 .8% ;单位面积产量为 2 0 96kg/hm2 ,是对照RRIM6 0 0的138.5%。海垦 2干胶含量高 ,产胶潜力大 ,可以在云南省一类型植胶区大规模种植     

造林密度对毛红椿等阔叶用材树种早期生长的影响

开展了毛红椿(Toona ciliata var. pubescens)、光皮桦(Betula luminifera)、乳源木莲(Manglietia yuyuanensis)、杂交马褂木(Liriodendron chinense.× L.tulipifera)、桤木(Alnus cremastogyne)和南酸枣(Choerospondias axillaria)6种优良阔叶用材树1 666、2 500、3 333株/hm~23种造林密度试验,对4年生林分的观测结果显示:造林密度为1 666株/hm~2桤木林分胸径显著高于造林密度为3 333株/hm~2和2 500株/hm~2的桤木林分;造林密度对其它各树种各生长指标的影响不显著.光皮桦和桤木的生长较快,乳源木莲生长最慢.研究认为,以培育中、大径材为目的的用材林,光皮桦、桤木初植密度宜定在1 666株/hm~2;毛红椿、杂交马褂木、南酸枣初植密度以1 666株/hm~2和2 500株/hm~2为宜,乳源木莲则以2 500株/hm~2和3 333株/hm~2为宜.     

多代连栽对不同发育阶段杉木人工林生产力的影响

在全国杉木中心产区的闽北林区,选择不同栽植代数、不同立地及不同发育阶段杉木人工林,进行多代连栽对不同发育阶段杉木人工林生长力影响的系统研究,结果表明:多代连栽对不同发育阶段杉木人工林生产力有较大影响。随栽植代数增加,不同发育阶段杉木林平均木生物量、林分生物量及林分净生产力均呈逐代下降趋势,表现为1代>2代>3代,其中2代16地位指数不同发育阶段杉木林林分生物量比1代下降1 45%～11 68%;3代杉木比1代下降17 44%～60 53%,比2代下降16 23%～55 31%,多代连栽导致了杉木人工林生产力的明显衰退。     

3种初植密度桉树林分生长、材种出材量及经济效益动态分析

目的 通过监测3种初植密度桉树人工林16 a的生长情况,分析其材种出材量及经济效益,为培育桉树中、大径材提供理论参考。 方法 收集和分析桉树人工林3种初植密度1 250、883、667株·hm−2 16 a的生长数据,计算材种出材量,同时分析平均生长量、内部收益率和净现值。 结果 密度1 250株·hm −2与密度883、667株·hm −2的胸径生长均差异显著（p < 0.05）;不同密度间林分蓄积量差异不显著（p > 0.05）。中径材出材量及其年均出材量在7～12 a和第16 年以密度883株·hm−2的林分最大,7～12 a密度667株·hm−2 > 1 250株·hm−2,第16年密度1 250株·hm−2超过密度667株·hm−2。密度883株·hm−2在第16年开始出现大径材。密度1 250 株·hm−2的轮伐期为7 a, 密度883、667株·hm−2均为9 a。9 a时密度1 250、883株·hm−2的净现值达到峰值,密度667株·hm−2在8 a时达到峰值,密度1 250、883、667株·hm−2的最大净现值分别为30 994、40 193、31 288元·hm−2,对应的内部收益率分别为37%、41%、42%。 结论 初植密度883株·hm−2有最高的净现值、内部收益率以及较高的生长潜力,667株·hm−2次之,1 250株·hm−2最低。     

关于我国人工林长期生产力的保持

为了保持我国人工林的长期生产力和提高森林质量,达到可持续经营的目的。作者在以往研究工作的基础上,广泛收集了国内外有关成果与资料,概括论述了我国人工林森林生产力的现状、不能保持生产力的原因与机理以及长期保持人工林生产力的技术对策。按第八次清查的全国森林资源数据,每公顷蓄积量为89.79 m3,其中天然林为104.6 m3,人工林为52.76 m3,人工林森林生产力明显低于天然林;我国优势树种人工林每公顷蓄积量也不高,如杉木为69.8 m3,马尾松为56.2 m3,落叶松为58.6 m3,这些数据比日本2002年3月公布的人工林相似树种的数据低很多,如日本针叶树蓄积量为227.97 m3· hm-2,柳杉为295.83 m3 ·hm-2,落叶松为189.88 m3 ·hm-2。关于年生长量,按全国第七次资源清查的中龄林与近熟林的数据做统计：杉木人工林5.2~4.2 m3 ·hm-2,马尾松为3.2~1.8 m3· hm-2,柏木为3.4~3.2 m3 ·hm-2;但按作者掌握的我国重点或示范性、试验性小面积人工林生长量看,却很高,按我国编制的速生丰产林标准的生长量数据看比较高。我国大面积人工林生产力不高,短周期经营的杨树、桉树人工林也不高,主要原因是：（1）纯林化与针叶化严重。按第八次全国森林资源统计,纯林占人工林的85%,而且针叶化明显,人工乔木林10个优势树种中针叶林比例高达56.9%。人工纯林结构简单,生物多样性低,生物学上缺乏稳定性。人工纯林特别是针叶纯林,抗性低,抗自然灾害和大气污染能力均差,人工纯林维护地力的能力也弱。（2）集约育林的技术措施：立地控制技术未得到推广,适地适树适品种原则在育林中未能认真贯彻;密度、植被、地力控制技术也执行不力,大面积上的人工林仍属于粗放经营;连作引起林地土壤理、化、生物特性恶化,土壤质量衰退,导致林木生长不良,林分生产力逐代下降;造林作业造成水土流失,如杉木造林,传统的育林技术未得到明显改进,福建尤溪炼山后进行的3年观测结果表明,炼山和水土流失损失的有机质高达989.35 kg·hm-2,养分586.26 kg·hm-2。桉树在砖红壤进行的机耕整地,水土流失也很严重,不合理的造林作业,最终导致土壤质量与森林生产力下降。短周期培育人工林带来了2个重要问题,一是对林地肥力要求高,二是如何利用无性系才能保持长期生产力。短周期经营采用的无性系,生长速度快,生长量大,轮伐期短,养分需求量大,如刚果12号W5无性系,通常利用地上部分,以5~7 a的轮伐期计,消耗的养分达571.75 kg·hm-2,我国培养短周期人工林的土壤质量本底原本普遍不高,如果采取连作,土壤有机质养分会明显下降,土壤质量衰退,并对其功能产生危害。我国杨树、桉树等人工林要达到短周期持续经营,还需要实行多无性系造林。我国人工林长期生产力保持的技术对策,应采取先进的集约育林措施,包括遗传控制、立地控制、密度控制、植被控制与地力控制。     

无性系和株行距对杨树人工林生长和树冠结构的影响

【目的】探索无性系、株行距及两者交互作用对杨树人工林的林木生长和树冠结构的影响。【方法】采用双因素随机试验设计,通过调查36块13年生杨树样地胸径、树高、活枝下高和冠幅等指标,以综合指数法构建3个林分综合指数(生长指数、冠形指数、干冠协调指数)。【结果】南林95杨和南林895杨的胸径、树高和生长指数显著高于南林797杨(P <0.05)。南林797杨的冠幅、树冠体积和树冠圆满度显著高于南林895杨,与南林95杨差异不显著(P> 0.05)。株行距为6 m×6 m和4.5 m×8 m的林分胸径、冠形指数和生长指数均显著高于5 m×5 m和3 m×8 m林分,不同密度林分对树高影响不显著(P> 0.05)。在相同密度条件下,正方形和长方形配置对东西和南北冠幅有显著影响,较大株行距促进树冠生长,但对胸径、树高和平均冠幅等影响不显著(P> 0.05)。无性系和株行距对冠长、活冠比、树冠表面积和干冠协调指数影响均不显著,且无性系和株行距对林木生长和树冠结构均无显著交互作用(P> 0.05)。【结论】杨树无性系对林木胸径、树高和树冠结构的影响大于株行距。综合考虑林木生长和树冠结构等两个方面,在类似的立地条件上,相比于其它无性系和配置方式,以南林95杨在种植株行距为6 m×6 m(278株/hm^2)时具有培育大胸径林木的潜力,适于培育速生、优质大径材。     

东风橡胶分公司橡胶芽接树新割制生产情况调查

通过对橡胶树割胶树位调查,低于20割龄胶树实施新割制,一般表现干胶产量增产和年度间产量变化平稳,累计死皮病率低,而高于20割龄胶树实行新割制、老龄割制和强割制,虽然提高刺激剂使用浓度,仍不能表现干胶增产,同时4～5级死皮率明显增高;品系GT1表现比RRIM更耐刺激,增产幅度大,死皮率更低。     

The potential for increasing rubber production by matching tapping intensity to leaf area index

Understanding resource capture can help design appropriate species combinations, planting designs and management. Leaf area index (LAI) and its longevity are the most important factors defining dry matter production and thus growth and productivity. The ecophysiological modifications and yield of rubber (Hevea spp.) in an agroforestry system (AFS) with beans (Phaseolus vulgaris L.) were studied. The experiment was established in Southeast-Brazil, with three rubber cultivars: IAN 3087, RRIM 600 and RRIM 527. The AFS comprised double rows of rubber trees along with beans sown in autumn and winter seasons in 1999. There was about 50% higher rubber yield per tree in the AFS than the rubber monoculture. Trees within the AFS responded to higher solar radiation availability with higher LAI and total foliage area, allowing its greater interception. All three cultivars had higher LAI in the AFS than monoculture, reaching maximum values in the AFS between April and May of 3.17 for RRIM 527; 2.83 for RRIM 600 and 2.28 for IAN 3087. The maximum LAI values for monocrop rubber trees were: 2.65, 2.62 and 1.99, respectively, for each cultivar. Rubber production and LAI were positively correlated in both the AFS and monoculture but leaf fall of rubber trees in the AFS was delayed and total phytomass was larger. It is suggested that trees in the AFS were under exploited and could yield more without compromising their life cycle if the tapping system was intensified. This shows how knowledge of LAI can be used to manage tapping intensity in the field, leading to higher rubber yield.     

Nutrient Management for Eucalypt Plantations in South China

Eucalypts are very popular for revegetation in many parts of south China because of their capacity to tolerate degraded sites and unfertile soils,and their fast growth potential to coppice. This paper reviews a decade of field trials in china, undertaken as part of several bilateral researchprograms in plantation forestry, concerning the use of fertilizers, harvest residue management and inoculation with ectomycorrhizal fungi. One of the key questions addressed is whether the productivity of plantation eucalypts in south China can be increased to the world average by nutrient management across a rotation.     

Possibilities of diverse rubber based agroforestry systems for smallholdings in India

Rubber growers in South East Asian countries are facing acute crisis due to the price volatility, sharp increase in cost of cultivation, increasing drought and declining soil fertility. With an objective to generate additional income and improve small-holder welfare by integrating diverse crops in rubber ecosystem, three experiments were conducted in Rubber Research Institute of India during 2001–2014 period. In one experiment, coffee, vanilla on Glyricidia standards, Garcinia and nutmeg were cultivated along with rubber without altering the planting design and density of rubber trees. Growth of rubber was significantly higher under mixed planting and yield was not influenced. Soil moisture status during summer and microbial population were higher in mixed planting system and soil nutrient status was maintained. Yield of all the intercrops was good during initial years. As the shade from rubber canopy intensified, Garcinia perished but vanilla and coffee continued to yield reasonably well. In another experiment, nine shade tolerant medicinal plants were evaluated in mature rubber plantation. All the medicinal plants established well and produced reasonable biomass, but the performance of Strobilanthes cuspida and Alpinia calcarata were comparatively better. In another study, it was observed that short duration vegetables like amaranthus and salad cucumber can be cultivated during the annual leaf shedding period in mature rubber plantations to meet part of the household requirement. The results showed that diverse crops can be integrated with rubber without any adverse effect on growth and yield of rubber. Crop diversification generated additional income, mitigated drought and sustained soil fertility.     

Spatial distribution of Hevea brasiliensis trunk phloem necrosis within a plot: aggregation but no evidence of constraint on cumulated growth

Trunk phloem necrosis (TPN) is a major constraint in rubber (Hevea brasiliensis) plantations. Current knowledge supports a scenario of a multi‐factor physiological ‘disease’ caused by an accumulation of endogenous and exogenous stresses. Without evidence of a pathogen, the apparent spread of the syndrome from tree to tree along the planting line, strongly suggested the implication of a major local soil constraint. The objectives of the study were to address, within a plot, three points of the above scenario: the short‐distance aggregation of affected trees; their correspondence with local micro‐areas facing the highest environmental constraints; and the relative weakness of TPN trees that had accumulated several stresses since planting. The study was conducted in a young rubber tree stand (clone RRIM 600) of Northeast Thailand, where the number of TPN affected individuals was 8% after 3 years of tapping. Trunk girth and trunk basal area were used as indicators of local environmental constraints. Spatial patterns were analysed using the framework of marked point processes and K functions. The results confirmed the short‐distance aggregation of TPN affected trees. But, TPN trees were not located within micro‐areas where trees had a lower trunk basal area than average. Hence, the clusters of TPN do not occur in the most constraining environmental micro‐areas of the plot in terms of growth since planting. Moreover, from comparison of girth, current girth increment and height of bark consumption, we infer that TPN trees were not smaller and less vigorous than other trees before the syndrome outbreak. Finally, our conclusions mean the previous scenario driven by major soil constraints becomes a ‘more complex scenario’ in which specific soil conditions (not the most constraining in term of cumulated growth), possibly in interaction with inter‐individual competition, induce a late and subtle stress favouring a necrotic reaction against tapping stress.