大兴安岭南段华北落叶松人工林径向生长对气候变化的响应

【目的】华北落叶松是内蒙古大兴安岭南段主要的人工林树种,分析华北落叶松年轮宽度指数的变化以及与气象因子的相关性,以此判断华北落叶松人工林在大兴安岭南段地区的适应性,为可持续经营管理提供理论依据。【方法】赛罕乌拉是大兴安岭南段次生林的典型地段,并且是内蒙古最大的次生林区。在1986年种植的华北落叶松人工林区域内,按国际树木年轮库(ITRDB)的要求,2013年随机采集54棵华北落叶松108根树芯,其中死树14棵。运用树木年轮气候学方法,建立华北落叶松年轮宽度年表,利用相关函数分析1986-2013年的气温和降水气象因子与年表的相关性,揭示华北落叶松径向生长对气候响应规律。【结果】(1)华北落叶松径向生长与上一年5、7月的平均最高温和平均气温呈显著性负相关(P <0.05),与当年冬季11月的降水量具有显著性正相关(P <0.05),和其它月份也均成正相关但显著性不明显,表明华北落叶松主要受到冬季降水量的影响。(2)通过年轮与气象因子的响应分析得出,华北落叶松对气候的响应具有明显的"滞后性",具体表现为,干旱胁迫对当年树木的径向生长量影响不显著,对第2年树木的径向生长量影响显著。2006年发生极端干旱年,发生后的4年内华北落叶松发生死亡现象。【结论】大兴安岭南段华北落叶松人工林的径向生长主要受到当年冬季11月降水量的显著性影响。华北落叶松受到干旱胁迫时有明显的"滞后性",影响体现在第2年即形成窄轮。这可能意味着,随着未来干旱的加剧,冬季降水对华北落叶松的生长变得更加重要。     

天然华北落叶松径向生长对气候变化的响应

在气候暖干化趋势下,进行森林经营树种对气候变化的响应研究,有助于适宜的经营技术构建以及森林经营对气候变化的应对。选取围场县龙头山林场天然华北落叶松,建立年轮宽度年表,应用相关分析、Mann-Kendall检验、逐步回归等方法,研究华北落叶松径向生长对气候变化的响应。结果表明:1)近60年来,本地区气温显著升高,在1980年发生升高突变;降水量有减少趋势,但变化趋势不明显。2)华北落叶松径向生长受气温与降水的双重影响,与多数气温因子呈显著负相关,与多数降水因子呈显著正相关,当年3,4月份降水是树木径向生长的重要限制因素。3)生长季极端高温与径向生长呈显著负相关,湿润指数与径向生长呈极显著正相关。4)利用当年生长季平均温度及3,4月份降水量和湿润指数模拟华北落叶松径向生长,发现在暖干化趋势下,研究区华北落叶松的生长将呈现减缓趋势。     

利用杉木年轮进行生长与气候关系的分析

通过回归模型分析了杉木的平均年轮指数与平均月降水量及各月平均气温的关系。结果表明,月平均降水量对杉木的直径生长有重要的作用,９月份降水量与直径生长呈极显著的正相关关系,１２月份平均降水量与直径生长呈极显著的负相关关系,直径生长量受前１年生长影响最大。     

川西亚高山岷江冷杉和铁杉年轮对气候因子的响应

研究四川卧龙亚高山森林岷江冷杉和铁杉树木年轮与气候因子的关系.结果表明:川西亚高山针叶林树木径向生长主要受气温的制约,卧龙地区岷江冷杉树轮宽度序列与当年2和4月月平均气温显著正相关(P≤0.05),而与多数月平均降水量和月平均相对湿度负相关;铁杉树轮宽度序列与上一年7月和当年2--4月月平均气温显著正相关(P≤0.05),与上一年10月和当年5月月平均降雨量显著正相关(P≤0.05),而与上一年7月及当年4和9月月平均相对湿度显著负相关(P≤0.05).     

祁连山地区青海云杉年轮宽度对气候变化的响应

以祁连山区青海云杉(Picea crassifolia)为样本,建立了青海云杉树木年轮宽度年表,应用相关分析和响应函数分析等年轮气候学方法,研究了青海云杉径向生长对气候变化的响应。结果表明:青海云杉年轮宽度与当年3-8月的平均气温呈正相关关系,特别是与3月平均气温的相关性最为显著(P<0.05);与当年3、5月的降水量呈显著的正相关关系(P<0.05);与当年4月日照时数呈显著的正相关关系。响应函数分析表明:青海云杉年轮宽度与上年10月和当年3、5月平均气温、上年12月和当年5、8月降水量、当年4、7月的日照时数存在显著的相关性(P<0.01)。综合来看,祁连山区青海云杉生长同时受春季温度、夏季降水和春季日照的影响明显。     

冀北山地油松、落叶松径向生长对气象因子的响应

为探索冀北山地油松与落叶松径向生长与气象因子的关系,选取承德围场地区立地条件相似的油松与落叶松2个样本作为研究对象,研究二者的生长规律,并结合该地区降水与气温2个主要气象因子,研究气象因子对油松、落叶松径向生长的影响。结果表明:1)冀北山地油松、落叶松2个树种生长与气温和降水都有较为显著的相关性,其中2、3月份的气温与油松径向生长呈显著正相关,而6月份则呈显著负相关;2)上年12月份的降水与其显著负相关,当年6月的降水与其显著正相关;3)落叶松方面,2、5、6月这3个月份的气温与落叶松径向生长呈显著负相关,上一年11月、当年的3、8、9月的气温与落叶松径向生长呈正相关,但不显著;4)该地区降水与落叶松径向生长总体呈正相关,其中3、5、6、7月份的降水与落叶松径向生长呈显著正相关;5)松径向生长与上一年12月份至当年4月份的气温总体呈正相关,与5—10月份的气温整体呈负相关,与上一年10—12月份的降水呈负相关,与当年4—10月份降水呈正相关;6)落叶松对气象因子响应程度略大于油松,落叶松与降水因子整体呈正相关,与气温呈负相关,说明该区域内气温是落叶松径向生长的限制因素。     

西藏色季拉山西藏红杉径向生长对气温和降水波动的响应

[目的]基于色季拉山地区特有树种西藏红杉年轮样芯,研究西藏红杉径向生长对气温和降水量的波动响应。[方法]利用树木年代学的方法,结合TASP-Win及ARSTAN程序建立标准年表,采用Pearson及bootstrap的计算方式将年轮宽度指数与1961—2020年气温及降水分别进行相关分析。[结果]径向生长在气温波动前后存在较大的差异。在气温波动前西藏红杉与前一年8月,当年1月及6月平均气温呈正相关（P<0.05）,与前一年9—10月及12月平均降水呈正相关,与前一年8月降水呈负相关,与1月至12月的相对湿度呈显著正相关（P<0.01）。在气温发生波动后,与当年3—12月平均气温呈负相关,与前一年8月及当年6月降水为显著正相关。[结论]藏东南地区的气候条件极为特殊,气候的波动导致水热条件发生变化是限制西藏红杉径向生长的主要原因,在非生长季,气温短暂的变化对树木径向生长同样有着显著的影响。     

江苏农博园湿地松径向生长对气候变化的响应

依据树木年代学方法，以江苏农博园湿地松人工林作为研究对象，获取年轮宽度资料，建立年轮宽度年表，探讨影响该树种径向生长的主要气候限制因子。结果表明：湿地松径向生长对气候因子的响应比较敏感，适合用于年轮气候学研究；相关函数分析表明，湿地松径向生长与上年和当年5月平均气温呈显著负相关，与上年5月降水量呈显著正相关。滑动相关进一步表明，升温导致的干旱胁迫是限制湿地松生长的主要原因，如果未来全球气温进一步升高，将对湿地松生长产生不利的影响。     

侧柏年轮宽度和年轮密度对气候变化的响应

通过响应函数分析和多元回归分析等年轮气候学方法,研究北京地区侧柏年轮宽度和年轮密度对气候变化的响应.结果表明:侧柏年轮宽度序列和年轮密度序列对气候变化相当敏感.前一年10月到当年9月的月平均气温和月降水量的响应函数模型可解释年轮宽度变化的58.45%,年轮密度变化的77.81%.夏季降水对侧柏年轮宽度有显著的正效应,而对年轮密度则表现出负效应.与降水的影响相反,夏季气温对侧柏年轮宽度表现出显著的负效应,对年轮密度表现出显著的正效应.其中,当年7月的气温和降水对侧柏年轮宽度和年轮密度的作用尤为显著.说明侧柏的年轮宽度和年轮密度均可用于年轮气候学研究,且年轮密度包含的信息量高于年轮宽度.     

云阳县柏木生长与气候变化和虫害发生的关系

应用树木年轮生态学方法研究三峡库区云阳县柏木生长动态,通过交叉定年并滤除遗传因子对生长的影响,建立柏木标准年表和残差年表,并进行年表与气候因子相关性分析。结果表明:云阳县柏木年轮生长与当年春季平均温度之间存在极显著负相关关系,与1,2月的月平均温度之间存在显著负相关关系;月降雨量和湿度指数对柏木生长没有显著影响。柏木鞭角华扁叶蜂的发生与标准年表的相关分析表明柏木叶蜂的发生总面积、柏木感虫率与柏木生长存在显著相关关系。通过多元回归得出云阳柏木年轮指数与气候因子的关系模型,用于柏木生长的预测模拟。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.