闽南麻竹人工林地上部分现存生物量的研究

对闽南地区麻竹人工林地上部分生物量模型及现存生物量结构进行了研究。结果表明:以模型m=a·(D2H)b对麻竹地上部分总生物量和秆生物量进行估计较为可靠,而对枝、叶生物量的估计需引进枝下高因子h及模型m=a·Db·(H-h)C或m=a·Db·[(H-h)/h]C.闽南地区麻竹人工林地上部分平均现存生物量为39.518t·hm-2,按年龄分配为:3年生生物量最高,占59.17%,其次为2年生、4年生、5年生;按器官分配为:秆生物量最高,占62.81%,其次为枝、叶。地上部分总生物量与秆生物量随竹秆高度增加而递减,枝、叶生物量自6～8m区分段分别向秆基及秆梢递减。     

麻竹枝叶生长对钩梢的响应

为了解冠层生物量积累、分配及枝叶大小对麻竹立竹受营林措施干扰(钩梢)后的响应,对不同竹龄全梢、钩梢麻竹地上构件生物量、生物量比、单叶特征、大小枝生物量分配比例及商品竹叶数量进行了调查.结果表明:麻竹立竹地上现存生物量分配格局为秆＞枝＞叶.叶生物量、叶/枝和叶/秆生物量比为2年生＞3年生＞1年生.随着竹龄的增加,枝、秆生物量、地上生物量和枝/秆生物量比总体上呈增加的趋势.2年生和3年生立竹枝、叶生物量分配比例显著高于1年生立竹,秆生物量分配比例显著小于1年生立竹.此外,随着竹龄的增加,立竹减少了对0 ～8 mm枝生物量的分配,增加了对8～16 mm、16 mm以上枝生物量的投入,以提高空间拓展能力,截获更多光资源.钩梢强烈影响了生物量分配格局,显著减小了麻竹立竹枝、叶、秆、地上生物量.钩梢后麻竹立竹增加了枝、叶生物量分配比例,减少了秆生物量的分配比例,同时提高了单叶叶面积和单叶干质量,增加了8～16 mm、16 mm以上枝生物量分配比例,减小0～8 mm枝生物量分配比例,以权衡枝叶的生长,提高立竹对环境的适合度.钩梢后立竹叶/枝、叶/秆、枝/秆生物量比升高,表明生物量分配更多地向叶和枝倾斜.钩梢麻竹商品竹叶数量较全梢麻竹增加29.68％,且发生部位明显降低,钩梢后冠层下部商品竹叶数量增加79.73％,中部商品竹叶数量增加25.81％,降低了采摘高度.在钩梢后的一个生长季内,钩梢影响了麻竹立竹资源利用策略,表现为枝与叶之间关系的变化,但随钩梢年限的增加其变化规律如何尚需进一步研究.     

华北沙地小黑杨林生物量及其与树冠关系的研究

应用相对生长法和典型样方调查法对华北沙地不同密度、不同年龄的小黑杨人工林生物量和生产力进行了估算,同时对树冠与生物量的关系进行了研究。结果表明:密度为1 000株· hm^-2、500株· hm^-2、250株· hm^-2的小黑杨林分(27年生)的生物量分别为85.31 t·hm^-2、102.60 t·hm^-2、86.74 t·hm^-2;生产力分别为3.16 t·hm^-2·a^-1、3.80 t·hm^-2·a^-1、3.21 t·hm^-2·a^-1,密度500株· hm^-2为华北沙地小黑杨的合理密度。不同密度小黑杨不同器官生物量所占的比例差异不明显,地上部分生物量在83% - 86%之间,其中干57% - 62%,枝11% - 16%,叶2% - 3%,皮8% - 10%;地下部分生物量在14% - 17%之间。对不同年龄小黑杨的生物量和生产力研究表明,27年生的比23年生的分别高59.74%和36.20%。同时,23年生小黑杨的根、叶所占比例明显高于27年生的根、叶比例,但是干生物量所占比例低于27年生小黑杨,反映了23年生小黑杨的生物量和生产力处在快速生长期,小黑杨的轮伐期应在27年以后。小黑杨生物量与树冠之间存在极显著的相关关系,其中树干生物量与树冠指数之间可以用线性模型y=ax+b描述,利用遥感技术可以反映小黑杨林树干生物量,为进一步利用遥感预测小黑杨木材材性提供了重要的基础数据。     

胁迫条件下毛竹miR164b及其靶基因PeNAC1表达研究

MicroRNAs(miRNAs)在植物生长发育以及抗逆等过程中起着重要的调控作用。miR164 作为植物特有的miRNA,其主要的靶基因是植物NAC转录因子。为揭示毛竹 miR164 对其靶基因的调控机制,通过茎环引物法和RT-PCR技术,从毛竹(Phyllostachys edulis)中克隆出miR164b成熟序列及其靶基因PeNAC1。序列分析表明miR164b的靶点位于PeNAC1 编码区,RLM-5'RACE PCR产物测序结果证实切割位点位于靶点的第10-11位碱基之间。组织特异性表达分析表明,毛竹 miR164b和PeNAC1在根、茎、叶及鞘中均表达,其中miR164b在根中表达丰度最高,在茎中表达丰度最低;而PeNAC1的表达丰度恰好与miR164b 相反。实时定量PCR结果显示,NaCl(250 mmol·L^-1)、低温(4℃)和强光(1 500 μmol·m^-2·s^-1)处理后毛竹叶片中 miR164b 的表达均明显下调,GA₃(100 μmol·L^-1)处理后 miR164b表达量明显上调;而在同样处理条件下,PeNAC1的表达恰好呈现出与其完全相反的趋势。由此表明,miR164b对靶基因PeNAC1 具有表达调控作用,可能与毛竹响应非生物胁迫的抗逆过程密切相关,这为利用miRNA开展竹子抗逆分子育种提供了参考。     

宁夏六盘山香水河小流域华北落叶松人工林乔木层生物量的坡面变化和尺度效应

生物量受坡面环境条件变化影响而有坡面变化与尺度效应。本文在六盘山半湿润区的香水河小流域选择了33 a生华北落叶松人工林的一个斜坡长480 m,水平长398 m的典型坡面,在整个坡面上建立了宽30 m的调查样带,均匀分为空间连续的16个样地,在2014年生长季中期调查不同坡位的样地生物量,分析其坡面变化规律。结果表明:生物量存在明显的坡位差异。坡面生物量t·hm^-2平均值为118.59,其变化范围为96.19 139.18,变幅为42.99,变异系数为0.12;随着离坡顶距离的增加,生物量总体上呈现先升高后降低的变化趋势,在坡面的中上部(水平坡长为87.71 m)达到最大。生物量存在坡面空间尺度效应,即随着相对坡长(X₁)的增加,生物量的顺坡滑动平均值(Y₁)先增大后减小,其回归关系式为:Y₁=23.004X₁³-60.834X₁²+31.786X₁+123.43(R²=0.84),坡面尺度效应表现为每100 m水平坡长生物量变化的数值为6.12 t·hm^-2;各样地生物量与整个坡面平均值的比值(Y₂,小数)随相对坡长有很好的非线性关系,基本上呈先增加后下降、后趋于稳定的变化趋势,其关系式为Y₂=1.722 6X₁³-2.844 5X₁²+1.033 8X₁+1.000 1(R²=0.57),可基于此将特定坡位样地的生物量换算成整个坡面的估算值。造成生物量坡面变化的主要原因是太阳辐射和光照时间随海拔的变化等多种因素造成的。     

不同径级云南松各部位生物量及其分布规律

利用标准木法测定了不同径级云南松人工林生物量及生物量在垂直方向上的分布规律。结果表明:云南松生物量随径级的增大而增大,5~7.5 cm径级云南松生物量为(6.642±1.129)×10³ g·株^-1;7.6~12.5 cm径级为(2.533±0.387)×10⁴ g·株^-1;12.6~17.5 cm径级为(5.897±1.331)×10⁴ g·株^-1;17.6~22.5 cm径级为(1.063±0.211)×10⁵ g·株^-1;≥22.6 cm径级为(2.208±0.409)×10⁵ g·株^-1。在不同径级组成中云南松各器官生物量的分配比例存在一定的变化:随着径级的增大,主干和根部生物量呈现先下降后上升的趋势,枝和叶生物量占总生物量的比例为先升高后降低,而树皮的比例则一直下降。主干生物量在0~2 m高度层最大,占总生物量的27.62%。6~8 m高度层枝、叶生物量最大,分别占各自总生物量的35.85%、38.34%。云南松根系生物量主要分布在0~30 cm土层深度内,占总根系生物量的65.49%。     

不同防治措施对皖南春季马尾松林节肢动物和虫生真菌群落的影响

在皖南春季越冬代马尾松毛虫防治时期,于安徽长江以南采用不同治虫策略的5个林场,选立地条件和林分状况类似的马尾松纯林,对节肢动物和虫生真菌群落的调查表明,常年释放白僵菌的林场和长期监测虫情、准确挑治虫源地的林场害虫种数约占群落总种数的50%,个体数约占70%,益害物种数比(Ns/Ps)为0.72～0.83,个体数比(Nn/Pn)为0.44～0.45,多样性指数(H′)波动小,松毛虫虫口≤2.0条·株^-1.交替放菌和施药的林场,滥用农药、尤其不治虫的林场,害虫种数约占群落总种数的60%左右,个体数>74%,Ns/Ps0.46～0.54,Nn/Pn0.23～0.34,H′波动大,松毛虫虫口6.0～10.0条·株^-1,超过防治指标(5条·株^-1).长期的放菌或及时施药挑治利于优化群落结构,增大多样性指数,强化生态控制的力度     

峨热竹无性系种群地上部分生物量结构与模型研究

通过对四川省石棉县栗子坪自然保护区峨热竹分株地上部分基径、枝下高、全高及分株各构件生物量进行调查和测量,研究了其地上部分生物量分配结构和形态可塑性,构建了地上部分生物量模型。研究表明：峨热竹各分株含水率随年龄增长呈下降趋势,同一龄级分株构件含水率高低表现为叶〉枝〉秆;峨热竹分株总生物量表现出多年生〉2年生〉1年生的分配特征,而同一分株各构件间则表现出秆〉枝〉叶的生物量分配格局;基径分别与各龄级秆生物量和总生物量具有显著相关性,而全高与2年生及多年生枝叶生物量具有显著相关性;以基径和全高为自变量分别建立的线性模型可为相似区域峨热竹不同龄级分株秆和枝叶构件生物量的估测提供借鉴。     

苏麻竹地上部分生物量分配及竹笋成分分析

对苏麻竹地上各部分生物量分配及竹笋成分进行了分析研究。结果表明:苏麻竹地上部分各构件间含水率存在极显著差异,不同年龄的立竹地上部分构件间的含水率亦存在极显著差异;立竹地上各部位生物量分配表现为秆 > 枝条 > 叶片,相同部位不同年龄立竹生物量以2年生竹为最低,1年生竹最高;立竹秆生物量及立竹总生物量与胸径、株高之间模型拟合效果最好,可以用于估计苏麻竹的地上生物量;苏麻竹笋中的游离氨基酸种类丰富,并含有7种人体必需的氨基酸;蛋白质、可溶性糖和淀粉含量能够满足食用需要。研究结果可为苏麻竹的推广种植和开发利用提供数据支撑。     

沿海山地柳杉人工林生物量研究

对福清灵石山国有林场26年生柳杉人工林生物量及其分配的研究结果表明:26年生柳杉人工林平均树高、平均胸径和林分单位面积蓄积量分别为15.7 m、20.2 cm和668.55 m3.hm-2;林分单位面积总生物量为364.55 t.hm-2,地上部分总生物量为313.86 t.hm-2,其中树干、叶、皮及枝等器官生物量分别占地上部分总生物量的84.79%、6.25%、6.24%及2.72%;地下部分总生物量为50.69 t.hm-2,其中根桩和骨骼根、中根及吸收根生物量分别占根系总生物量的89.21%、9.71%和1.08%。从标准木不同层次生物量分布情况上看,不同层次总生物量、树干及皮生物量随着树高的增加基本呈现出逐渐递减的规律;枝与叶生物量随着树体的升高,其生物量出现先增加后减少的趋势。     

<Emphasis Type="Italic">Ophiostoma</Emphasis> species associated with bark beetles infesting three <Emphasis Type="Italic">Abies</Emphasis> species in Nikko,Japan

Ophiostoma species were isolated from bark beetles and Abies mariesii, A. veitchii and A. homolepis attacked by the beetles in Nikko, Tochigi, central Honshu, Japan. One to two Ophiostoma species were frequently isolated from each species of bark beetle. Ophiostoma subalpinum was the most common associate of Cryphalus montanus. Ophiostoma sp. B as well as O. subalpinum was a common fungus associated with Polygraphus proximus. Ophiostoma europhioides was isolated from Dryocoetes hectographus and D. autographus as one of the common associates. Ophiostoma sp. J and Ophiostoma sp. S were frequently isolated from D. autographus and D. striatus, respectively. These fungi seem to have specific relationships with particular bark beetles. Ophiostoma sp. B, Ophiostoma sp. J and Ophiostoma sp. S have unique morphological characteristics and appear to be new species. Five trees of A. veitchii, approximately 43 years old, were inoculated with five Ophiostoma species to assess the relative virulence of the fungi. Ophiostoma subalpinum, Ophiostoma sp. B, and O. europhioides had relatively higher virulence than the other species studied.     

Improving the evaluation of multiple-dowel-type connection strength

Our study focuses on predicting the ultimate short-term load carrying capacity of timber-to-timber connections with dowel-type fasteners. The wide range of possible configurations in practice makes the resolution of these values by tests unrealistic. Moreover, different current regulations do not consider some specific failure mechanisms. In many countries, the reduction of resistance involved by this phenomenon is taken into account by considering an effective number of dowels (n_ef) smaller than the actual number of dowels (n) in the connection. However, these different regulations disagree on the values of n_ef and on other points (spacing, partial coefficient of security, formulas). These discrepancies in design rules invite the fundamental research on this topic and, therefore, new methods are sought in order to estimate the load carrying capacities of the connections. In the light of these, our approach consists of predicting the load carrying capacity with the neural network numerical tool. The results obtained by this analysis tool are satisfactory, although the model remains complex. Subsequently, we focus on the simplification of this numerical model with classical regression techniques in order to implement it in a design code.     

Parasitic Ichneumonoidea on the horse chestnut leaf miner, Cameraria ohridella (Lepidoptera: Gracillariidae) in Slovakia

Parasitic Hymenoptera from the suprafamily Ichneumonoidea attacking the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) were studied in southwest Slovakia during 2000 and 2001. The search for such species resulted in the determination of eight ichneumonid species, Gelis agilis (Fabricius), Itoplectis alternans (Gravenhorst), I. clavicornis (Thompson), I. maculator (Fabricius), Scambus annulatus (Kiss), S. brevicornis (Gravenhorst), Zatypota percontatoria (Müller), Adelognathus sp. and a braconid Colastes braconius Haliday. The most abundant species was S. annulatus. All these species recorded are polyphagous and often facultative hyperparasitoids, except C. braconius, which departs from this norm in not being hyperparasitic. The presence of more diversified native parasitoids and hyperparasitoids from the Ichneumonoidea predicate a slow successive adaptation of the parasitoid fauna to the invasive host, Cameraria ohridella.     

Insecticidal activity of certain medicinal plants

The methanol extracts of eight species of medicinal plants were tested for insecticidal activity in third instar larvae of Egyptian cottonworm (Spodoptera littoralis). All extracts showed a certain degree of larval toxicity. The extracts of Ocimum basilicum, Origanum majorana and Salvia officinalis appeared to be highly toxic. The extracts significantly affected the growth indexes [relative growth rate (RGR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD)].     

A new norlignan from Taxodium ascendens

A new norlignan, (2R,3R,4S,5S)-2,4-bis(4-hydroxyphenyl)-3,5-dihydroxy-tetrahydropyran (1), together with 9 known compounds were isolated from the branches and leaves of Taxodium ascendens. Their structures were mainly determined on the basis of MS, IR, 1D and 2D NMR spectral evidences. Methanol extract showed inhibitory activity on carbonic anhydrase II with an IC₅₀ value of 4.27 µg/ml, acetone extract and methanol extract inhibited activity of cathepsin B with IC₅₀ values of 2.12 and 3.71 µg/ml, respectively.     

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.     

<Emphasis Type="Italic">Bursaphelenchus mucronatus</Emphasis> (Nematoda: Aphelenchoididae) vectored by <Emphasis Type="Italic">Monochamus </Emphasis><Emphasis Type="Italic">urussovi</Emphasis> (Coleoptera: Cerambycidae) in Hokkaido,Japan

Bursaphelenchus mucronatus Mamiya et Enda has been recovered for the first time from adults of the cerambycid beetle, Monochamus urussovi (Fischer), in Hokkaido, Japan. The nematode was also recovered from the inner bark of Picea jezoensis (Siebold et Zuccarini) Carrière and Abies sachalinensis (Fr Schmidt) Masters infested with M. urussovi larvae. PCR–RFLP analysis indicated that B. mucronatus in Hokkaido is the European type.     

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.     

Trees and shrubs as sources of fodder in Australia

Experience with browse plants in Australia is briefly reviewed in terms of their forage value to animals, their economic value to the landholder and their ecological contribution to landscape stability. Of the cultivated species only two have achieved any degree of commercial acceptance (Leucaena leucocephala and Chamaecytisus palmensis). Both of these are of sufficiently high forage value to be used as the sole source of feed during seasonal periods of nutritional shortage. Both are also leguminous shrubs that establish readily from seed. It is suggested that a limitation in their present use is the reliance on stands of single species which leaves these grazing systems vulnerable to disease and insects. Grazing systems so far developed for high production and persistence of cultivated species involve short periods of intense grazing followed by long periods of recovery. Similar management may be necessary in the arid and semi-arid rangelands where palatable browse species are in decline.     

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.