Shade-based control of Imperata cylindrica: tree fallows and cover crops

Imperata is shade-intolerant, although little is known of the relative roles of competition for light, water and nutrients in suppressing its growth. Shading of Imperata results in reduced carbohydrate storage, reduced rhizome and tuber-bulb production, reduced shoot dry weight, increased susceptibility to competition, increased susceptibility to herbicides and decreased vigor/regeneration. Herbaceous cover crops in the genera Calapogonium, Crotoleria, Mucuna and Pueraria have been shown to effectively suppress Imperata growth and can be used to prevent and in some cases eradicate Imperata. Tree fallows with fast-growing species such as Sesbania sesban, Acacia nilotica and Leucaena leucocephala can improve soil physical and chemical properties and suppress weed growth. Forest plantations have been successfully used, particularly with the use of moderate to high tillage, weeding and fertilizer inputs to suppress Imperata growth. These plantations produce marketable wood and reclaim the site for other uses. Additional research is needed to evaluate the specific nature of competition and allelopathic effects from Imperata. Continued evaluation of tree species and provenances for Imperata suppression, forms of tillage after woody fallow crops and the constraints to adoption of cover crops and trees as Imperata control measures are also needed.     

闽南山地卷荚相思施肥试验初报

在福建省长泰岩溪国有林场,采用L9(34)正交设计,探讨P肥(钙镁磷)、N肥(尿素)、K肥(氯化钾)对卷荚相思生长的影响。结果表明:不同施肥处理对卷荚相思胸径、树高、单株材积和蓄积量有显著影响,其中P肥影响最大,N肥次之,K肥影响最小。综合林木生长量及经济效益(产出投入比)分析,选择尿素50 g·株-1、钙镁磷750 g·株-1、氯化钾50 g·株-1效果最好。     

活性肥促进桉树幼龄林肥效利用的研究

含微量元素、镧系元素(稀土)、植物酶活性剂等植物营养的活性肥与桉树专用肥同时施用,可促进按树幼林对营养元素的吸收利用,提高施肥的肥效,促进树高和材积的显著增长.与单施500g复混肥相比较,施放30 g活性肥/株 375 g复混肥/株的单株材积比单施复混肥的提高35.5%,经济效益非常显著.     

桉树人工林中期施肥试验研究

对尾巨桉2.5 a生间伐后的林分进行施肥试验.结果表明,间伐后施用适量的N、P、K肥有明显的增产效果.以每株施用磷酸二铵(N、P)750 g、氯化钾(K肥)90~270 g、硼砂(B肥)0~30 g,即每株施N135 g、P2O5338 g、K2O50~100 g、B 0~5 g的增产效果最好,优化配比为N:P2O5:K2O:B=1∶2.5∶0.37~1.11∶0~0.04.在肥料元素合理配比下,磷酸二铵、氯化钾和硼砂的总施肥量控制在850~950 g/株,以单质肥料测算,则N、P2O5、K2O、B有效养分总量应控制在520~575 g/株范围.以该施肥组合方案进行实施,施肥后2.5 a林分平均胸径、树高和材积年均生长量分别达3 cm、3.2 m和0.10 m3以上,比未施肥的林分分别提高190%~200%、268%~273%和400%~465%,可净增加收入7~8万元/hm2.中期施肥对提高林分生长量和经营经济效益显著.     

Changes in Amount and Distribution of Stem Growth in Pole-Stage Corsican Pine Following Application of Nitrogen Fertilizer

Ring-width measurements on trees felled in a nitrogen-deficientpole-stage crop of Corsican pine on the sand dunes of Culbinforest (Morayshire) showed that, in addition to a growth checkascribed to the low nitrogen content of the soil, there wasevidence for decreasing site quality, tree growth decliningprogressively with time. This feature is ascribed to the continuingimmobilization of the limited nitrogen capital in the newlydeveloping mor humus layer. Ammonium sulphate, at rates equivalentto 84, 168, 336, and 504 kg elemental nitrogen ha^–1, wasapplied to this crop when it was 36 years old, and the treatmentsrepeated for a further 2 years. Nitrogen levels in the foliagerose from 0.9 per cent to as high as 20 per cent in the firstyear, increasing to 2.6 per cent after the third year of application.Response in terms of basal area appeared in the year after firstapplication but was not accompanied by any changes in the patternof growth throughout the season, nor was there a significanteffect of tree size on the proportional change in relative basalarea growth induced by the fertilizer, except for a slightlyreduced response by the smallest trees to the lower rates ofapplication. A similar low response by the smallest trees wasfound for height, but, in addition, height growth after treatmentwas greatest for the middle-sized trees, despite the fact thatthese had been growing significantly more slowly than the largesttrees prior to application of the fertilizer. Form factor remainedunaltered by the treatments but taper changed slightly. Heightand basal area showed very different response patterns to thetreatments. Thus, whereas maximum height growth occurred atthe 168 kg N ha^–1 treatment rate (2.41 m over 7 years,1.4 times the control growth) maximum basal area growth occurredat the 504 kg N ha^–1 rate, the highest rate used (13.0m² ha^–1 over seven years, 2.4 times the control growth);volume growth was maximum at the 336 kg N ha^–1 rate (126m³ ha^–1 over 7 years, 2.6 times the control growth). Whenrelated to levels of foliar nitrogen in the previous year, annualheight growth was maximum at 1.6 per cent with maximum basalarea growth occurring nearer 2.2 per cent. It is estimated thatvolume growth would be maximised at just over 20 per cent nitrogen.     

The effects of some extrinsic and intrinsic factors on the proportion of vessels in Gmelina arborea Roxb.

Summary Wood samples of Gmelina arborea were collected from four different localities (sites) in Nigeria. The proportion of vessels was determined by a modification of Ladell's (1959) randomized dot technique. The site and plot effects on vessel proportion were not significant. The tree effect was very highly significant with a variance component of up to 25.4 per cent. The tree mean values of vessel proportion ranged from 9 to 21.3 per cent. There was no close correlation between tree mean values of vessel proportion and tree growth parameters (tree height, diameter at breast height and crown diameter). The effect of stem height was not significant. The effects of radii (the variation around the stem's circumference) and age were very highly significant with variance components of up to 21 and 11.7 per cent respectively. The differences in the values of vessel proportion for earlywood and latewood were very highly significant; the variance component was 22.9 per cent. Earlywood had a lower proportion of vessels than latewood (12 and 16 per cent respectively). Vessel proportion was not correlated with ring width. The effects of factor interactions were not practically important.     

刚果12号桉优化栽培效果分析

以刚果１２号桉元性系组培苗为材料，进行４种不同密度和４种不同施肥处理双因素试验，３年生结果表明：不同密度和施肥措施对刚果１２号桉生长有极显著影响，密度效应和施肥效应互作用显著；密度效应较施肥效应大，其方差分量前者约为后者的９倍；密度越大，单株材积越小，但单位面积蓄积越大；不同施肥处理以添加钾肥的明显有利于林木生长。     

Fomes annosus Butt Rot of Sitka Spruce: III. Losses in Yield and Value of Timber in Diseased Trees and Stands

Direct losses in yield and value sustained through the rejectionof butt-rotted wood either in the forest or at the sawmill werecalculated for 484 butt-rotted Sitka spruce trees, 23 to 50-years-old,from 27 stands in Britain. Losses were calculated followingthe rejection of either decayed or incipiently-decayed wood. The results suggest that approximate losses in a stand may notbe difficult to estimate since the average loss per tree (percent of tree volume or value) did not vary widely in standsof trees of different age or size and overall losses were closelyassociated with the numbers of affected trees. The mean lossper tree following rejection of butt lengths containing incipiently-decayedwood was 33 per cent of volume, and 43 per cent of value, comparedwith 22 per cent and 27.5 per cent respectively for losses followingrejection of butts containing decayed wood. These value losseswere estimated using the Forestry Commission 1977 price/sizecurve and depended on notional changes in the breast-heightdiameter of affected trees following rejection of rotted buttlengths in the forest. A computer-simulated sawmilling study of 202 trees of sawlogsize from the main study suggested that losses in value sustainedthrough the rejection of decayed or incipiently-decayed buttlengths might be reduced by about 10 per cent if such lengthswere converted into pallet boards instead. The consequences of these various methods for estimating directlosses due to F. annosus butt rot are considered in relationto their use in standard forest management financial appraisals.Aspects of indirect losses, i.e., the increased susceptibilityto windblow and possible reductions in increment of butt-rottedtrees, not considered in detail in this paper, are also discussed.     

马尾松近熟林施肥技术研究

通过对17a生马尾松近熟林施肥试验4年的生长效应分析表明:在南方红壤地区施适量的P,K肥对马尾松近熟林生长有显著的促进作用,但施用过量却有负作用;施N肥短期内对林木生长不利;施肥效果显著时可掩盖林地本身质量对林木生长的影响。根据对各肥种水平效应值的分析可知,最佳施肥处理为每株混施P2O590g,K2O 90g,其4年蓄积定期生长量比对照高13.4%。施肥措施对促进小径阶木生长有利。在肥效期内施肥措施与马尾松近熟林的生长效应呈显著相关性。     

几种施肥处理对桉树生长的影响

本文以桉树无性系DH32-29和GL9为试验对象，通过设置不同肥种及用量施肥处理研究其对这2种无性系生长的影响。结果表明：在本文设置的肥料有效养分梯度下，DH32-29胸径生长对肥料有效养分含量高低无显著差异，而GL9胸径生长、DH32-29树高生长和单株材积生长表现出明显的高有效养分促进作用；GL9树高和单株材积前期生长较快，后期生长潜力不足；DH32-29生长量较GL9大。     

The role of vegetation management for enhancing productivity of the world's forests

The management of competing vegetation has evolved with forestmanagement over the past half century and is now an integralpart of modern forestry practice in many parts of the world.Vegetation management, primarily using herbicides, has provenespecially important in the establishment of high-yield forestplantations. There has been a substantial amount of researchquantifying the wood yield gains from the management of competingvegetation over the past few decades. We reviewed results from60 of the longest-term studies in North America (Canada andUS), South Africa, South America (Brazil) and New Zealand/Australia.About three-quarters of the studies reported 30–500 percent increases in wood volume from the most effective vegetationtreatments. In North America, where the longest-term studiesfor a variety of tree species were between 10 and 35 years old(or from 20–100 per cent of rotation age), gains in woodvolume ranged from 4–11 800 per cent in Pacific north-westernforests, 14–5840 per cent in the south-eastern forests,and 49–5478 per cent in northern forests. In South Africaand South America (Brazil), several full-rotation (6–8years) studies with eucalyptus indicate 29–122 per centand 10–179 per cent increases in wood volume yield, respectively,from effective vegetation management. In New Zealand, time gainsof 1 to 4 years from early vegetation control in radiata pineplantations translated into 7–27 per cent increases inwood volume yield over a 25- to 30-year rotation.     

施肥对油茶春梢生长及叶片矿质元素含量的影响

为了实现对油茶的高效精准施肥,以普通油茶良种‘长林4号’盆栽大苗为试材,研究了不同施肥策略及复合肥不同氮、磷、钾配比对春梢生长及叶片主要矿质元素氮磷钾元素含量的影响。研究结果表明:复合肥和有机肥的施用量对春梢长度影响显著,而复合肥不同氮磷钾配比对春梢长度无显著影响;冬季有机肥的施用对春梢叶片氮磷钾矿质元素含量无显著影响,而不同复合肥施用量、氮磷钾配比和施用频次显著影响春梢叶片氮钾元素含量,对叶片磷元素的含量影响则不显著;冬季施用25 g/株有机肥、5月份施用N∶P2O5∶K2O配比为5∶1∶5的复合肥15 g/株,对促进油茶春梢生长、改善春梢叶片氮钾营养效果最佳。     

Wood ash use in forestry - a review of the environmental impacts

The use of wood fuel for energy production in the UK is setto increase in the near future as part of a government commitmentto increase renewable sources to 10 per cent by 2010. The ashgenerated as a by-product of combustion, whether for heat orpower generation, has potential use as a fertilizer in forestsystems. This review assesses the available information on factorsaffecting the quality of the ash and environmental implicationsarising from its application. The key determinants of wood ashchemistry are the tree species combusted, the nature of theburn process and the conditions at the application site. Woodash from hardwood species produces higher levels of macronutrientsin their ash than conifers, and the silica content is frequentlylower. A furnace temperature between 500 and 900°C is criticalto the retention of nutrients, particularly potassium, and determinesthe concentrations of potentially toxic metals including aluminiumin the ash. Fly ash, the lightest component that accumulatesin the flue system, can contain high concentrations of cadmium,copper, chromium, lead and arsenic and this ash should not beused as fertilizer. The form of the ash at application is important,with loose ash releasing Ca, K and Na more rapidly than granulatedash. Heavy metal, radionuclide and dioxin contamination of woodash-based fertilizers is minimal and unlikely to affect ecosystemfunction. The effects of wood ash are primarily governed byapplication rate and soil type. The benefits are maximized atlow dose rates, with possible toxicity from applications inexcess of 10 t ha^–1. For most forest sites, a single woodash application per rotation could replace all the nutrientslost after whole-tree harvesting (excepting N). Long-lastingpositive effects on tree growth have been observed on shallowpeats, in which the humus is slowly mineralized in responseto elevated pH and increased nutrient availability. In contrast,wood ash application to podzols is only effective in enhancingtree growth when nitrogen availability is non-limiting. To date,published research of wood ash effects on trees growing in claysand loams is minimal. A lag time for positive tree responsesto wood ash application is often observed, and may be the resultof phosphorous limitation at higher soil pH. The greatest reportedadverse ecological effects are to acidophilic ecosystems, particularlythe constituent bryophyte, soil bacteria and ectomycorrhizalcommunities.     

The Interaction of Green Spruce Aphid and Fertilizer Applications on the Growth of Sitka Spruce

In an 11-year-old stand of Sitka spruce (Picea sitchensis [Bong.]Carr.) application of nitrogen fertilizers, at a rate of 10kgN ha^–1 month^–1, increased mean diameter incrementby 12 per cent, while the further addition of phosphorus, at5 kg ha^–1 month^–1, resulted in a 23 per cent increase.An attack by the green spruce aphid (Elatobium albietinum Walker)occurred during the period of fertilizer addition. The mostseverely affected trees showed a reduction in diameter growthof 50 to 56 per cent but the severity of the attack betweentrees was unrelated to the treatments applied. However, fertilizerapplication did hasten the recovery of diameter growth afterdefoliation.     

Growth and nutrition of Pinus radiata in response to fertilizer applied after thinning and interaction with defoliation associated with Essigella californica

Infestations of Essigella californica following the installation of post-thinning fertilizer trials in Pinus radiata plantations provided an opportunity to examine the impact of repeated defoliation over a period of 8 years (1997–2005). Replicated treatments (n = 4) of nil fertilizer (control), N (300 kg ha⁻¹) as urea, P (80 kg ha⁻¹) and S (45 kg ha⁻¹) as superphosphates were applied immediately after thinning at three sites and this was followed by a second application of NPS fertilizers 6 years later with N applied at 300 kg ha⁻¹ as urea and ammonium sulphate and P at 80 or 120 kg ha⁻¹. Defoliation of untreated P. radiata gradually increased to 50% over a period of 8 years. Basal area growth was negatively correlated with average defoliation for two consecutive post-fertilizer periods of 6 and 2 years. Growth responses to fertilizer varied considerably between sites but the largest improvement in growth was due to NPS fertilizer, this increased basal area by 30–80%. Application of N fertilizer raised total N levels in foliage and increased defoliation with a commensurate loss in growth under conditions of deficiencies of S or P. Repeated infestations gradually increased the percentage of trees with severe defoliation (>80% loss of foliage) indicating that nutrient-deficient trees have a reduced capacity for foliage recovery between episodes of peak infestation. In contrast, treatment with N fertilizer in combination with S- and P-corrected deficiencies of these nutrients, raised levels of total N in foliage and reduced defoliation to approximately 20%. Basal area growth responses to NPS fertilizers reflected improved nutrition as well as reduced insect damage. The reduction in defoliation under conditions of balanced tree nutrition was most likely due to enhanced needle retention following correction of P deficiency as well as greater availability of nutrients enabling a more vigorous recovery of P. radiata after an episode of E. californica activity. Treatment with fertilizer therefore reduced the long-term impact of aphid damage and improved growth of P. radiata.     

Responses of carbon gain and growth of Pinus radiata stands to thinning and fertilizing

Thinning of forest stands is widely carried out to minimize the slowing of growth of individual stems that follows from increasing competition among trees as they become bigger. After thinning, there is an increase in the growth rate of remaining trees because of an increase in the availability of resources per tree. Often, there is also an increase in foliar efficiency (biomass increase/foliage amount). On sites where mineral nutrient supply is limiting, fertilizers may be applied, often in association with thinning, to boost productivity. Growth responses to fertilizer application depend on an adequate supply of other resources, but also involve nonlinear interactions among mineral nutrients and between nutrients and other growth-limiting environmental factors. The effects of thinning and fertilizing on the carbon gain and growth responses of Pinus radiata D. Don to availability of resources (light, mineral nutrients and water) and to changes in the canopy are discussed.     

Effects of thinning and fertilization on wood properties and economic returns for Norway spruce

The effects of silviculture on wood and tracheid properties, and economic returns of Norway spruce (Picea abies (L.) Karst.) were investigated in two case studies, one comparing different thinning intensity in southeastern Finland and the other considering the effects of optimal nutrient addition in northern Sweden. Models for predicting the wood and tracheid properties of Norway spruce were integrated into a distance-independent process-based growth and yield model. Increasing the thinning intensity resulted in a lower mean wood density, tracheid length, and latewood proportion in harvested wood. Wood density and tracheid length of harvested pulpwood slightly decreased in later thinnings and final cuts. Thinning regimes with high early growing stock and decreasing later growing stock were most profitable. Nutrient addition accelerated volume growth and increased the value growth. The increase in volume growth due to nutrient addition more than offset the economic influence of the loss in wood density and tracheid length.     

山地苹果园穴贮肥水技术研究

为了解决洮南市北部半山区在山地发展苹果树水资源缺乏的矛盾,以洮南市北部半山区果树试验场20年生的123苹果树为试材,研究山地苹果园采用穴贮肥水技术措施对苹果树生长发育的影响。结果表明：穴贮肥水技术可提高新梢生长量21.6%,提高叶绿素含量14.7%;平均单果质量比清耕提高22.3%。特等果率较对照提高27.3%。穴贮肥水可使苹果树增产2161.64 kg.hm-2,纯增收1689.07元.hm-2。     

大岛樱引种和扦插繁殖生产试验研究

都江堰市1993年8月首次从日本引种大岛樱后,经5a引种栽培试验,其年均高1．6～2.0cm,每株产符合规格的叶片达100片以上。采用嫩枝扦插可扩大苗木数量。在生产上,合理施肥,防止积水,预防病虫害,能促进大岛樱叶的生长。