Isolation of 15 polymorphic microsatellite loci in Acacia hybrid (Acacia mangium×Acacia auriculiformis)

This study reports the isolation of 15 microsatellites in Acacia hybrid (Acacia mangium×Acacia auriculiformis) based on the 5′ anchored polymerase chain reaction technique. Polymorphism of these loci was evaluated in a sample of 24 hybrid individuals. The level of polymorphism ranged from two to eight alleles with an observed heterozygosity ranging from 0.083 to 0.875. These loci were also characterized in both the parental species. The number of alleles ranged from two to six for both A. mangium and A. auriculiformis with the observed heterozygosity values ranging from 0.167 to 0.625 and 0.042 to 0.458 respectively. Five of these loci demonstrated Mendelian inheritance in a segregating F₁ population; four presented a distorted ratio and the remaining six did not segregate in progenies as they were homozygous in both parents.     

5种相思树和尾巨桉人工林土壤养分和酶活性特征

为揭示固氮树种土壤养分转化的酶学机制,对固氮树种[厚荚相思(Acacia crassicarpa)、黑木相思(A. melanoxylon)、卷荚相思(A.cincinnata)、大叶相思(A.auriculiformis)和马占相思(A.mangium)]及非固氮树种尾巨桉(Eucalyptusurophylla×E.grandis)人工林的土壤养分含量、酶活性及其相关性进行研究。结果表明,相思林40～60cm土层的pH均高于尾巨桉林;5种相思林土壤各土层的TP、TK含量均低于尾巨桉林,而20～40 cm土层的TC、TN含量均高于尾巨桉林,黑木相思林和马占相思林各土层的有效养分均显著高于尾巨桉林(P0.05)。0～10 cm土层中,相思林的土壤酸性磷酸酶和纤维素酶活性均高于尾巨桉林,大叶相思林的土壤脲酶、蔗糖酶、纤维素酶和芳基硫酸酯酶活性显著高于尾巨桉林(P0.05),卷荚相思林的土壤脲酶、纤维素酶、几丁质酶和淀粉酶活性显著高于尾巨桉林(P0.05)。相关分析结果表明,土壤脲酶、蔗糖酶和几丁质酶活性与AP显著负相关(P0.05),蔗糖酶和纤维素酶活性与NH4+-N显著负相关(P 0.05),脲酶、纤维素酶、芳基硫酸酯酶与土壤TK显著负相关(P0.05),几丁质酶活性与TN含量呈显著正相关(P0.05),土壤淀粉酶活性与NH4+-N呈显著正相关(P 0.05),过氧化氢酶活性与土壤TK含量呈显著正相关。可见,与尾巨桉人工林相比,在我国南方退化山地引种相思树可提高土壤关键酶的活性,对土壤有效养分具有明显改良作用,有利于退化地土壤的生态修复及人工林长期生产力的维持。     

Nucleotide sequence analysis of two lignin genes in Acacia auriculiformis × Acacia mangium hybrid for enhancement of wood pulp quality

There is large potential in the establishment of Acacia auriculiformis × Acacia mangium hybrid plantations through selection of high quality parents especially with characteristics favourable for some end products like pulp and fibre. Trees altered in their lignin profile with reduced amounts of lignin or increased extractable syringyl are desirable in the pulp and paper industry. Cinnamoyl-CoA reductase (CCR) and caffeic acid O-methyltransferase (COMT) are two enzymes likely to regulate lignin content and composition in the syringyl (S)- and guaiacyl (G)-related monolignols at specific branches of the lignin biosynthetic pathway. A goal of this study was to discover the genetic variation in CCR and COMT genes in Acacia species using single nucleotide polymorphisms (SNPs). In this study, two lignin genes, CCR (3,317 bp) and COMT (2,764 bp), were isolated from the Acacia hybrid, sequenced and analysed in silico. Southern blot analysis suggested that there are one to two copies of genes encoding CCR and COMT in the Acacia hybrid. Upon genotyping 480 individuals from natural populations of A. auriculiformis and A. mangium, six CCR SNPs were found in A. auriculiformis and five CCR SNPs in A. mangium. Three COMT SNPs were found in A. auriculiformis and one COMT SNP in A. mangium. A pair of CCR SNPs showed high linkage disequlibrium (LD) with r ² value of 0.870 in an A. mangium population from Papua New Guinea. The SNPs will be further exploited through the candidate gene-based LD mapping to identify QTLs for the Acacia marker-assisted breeding. This is the first documentation of the isolation, cloning and re-sequencing of CCR and COMT genes in the Acacia hybrid and the natural populations of A. auriculiformis and A. mangium.     

Recovery of species diversity and composition of braconid parasitic wasps after reforestation of degraded grasslands in lowland East Kalimantan

Human-induced disturbances and wildfires can transform areas of tropical rainforest into Imperata-dominated grassland, but it may be possible that recovery of biodiversity is facilitated by reforestation with fast-growing trees. We compared the assemblages of braconid wasps as parasitoids of taxonomically diverse groups of insects among Imperata grasslands, young and mature plantations of Acacia mangium, young secondary forests after wildfires, and old secondary forests in the lowland of East Kalimantan. The abundance and species richness of braconids, which had declined in Imperata grasslands, somewhat increased in Acacia plantations, and also the species composition of braconids in Acacia plantations was transitional between Imperata grasslands and old secondary forests. Parasitoids of detritivores and wood borers increased markedly after plantation, while those of herbivores showed a distinct turnover of species all over the range from grasslands to old secondary forests. The plantation of A. mangium had most likely facilitated the recovery of the diversity of host forest and their parasitoids, but the recovery was just at the rudimentary stage even in mature plantations. Monitoring of parasitic wasps would be useful to test the continuous recovery of forest biodiversity in plantation stands.     

The population of Acacia tree species producing gum arabic in the Karamoja region, Uganda

The study aimed at determining the population status of the different Acacia tree species producing gum arabic in the undisturbed, grazed and cultivated habitats in the Karamoja region, Uganda. A total of 135 sample plots each measuring 20 × 20 m² (0.04 ha) with each habitat having 45 plots were selected and established in the seven counties using a simple random sampling technique. The tree species present, their abundances and sizes were recorded. Twelve Acacia species were identified and a total of 5535 recorded in the sampled area. Out of these, five were gum‐producing acacias. Acacia senegal dominated the acacias in all the seven counties and in all habitats of Karamoja with Acacia nilotica (72.3%), Acacia seyal (13.4%), Acacia sieberiana (4%) and Acacia gerrardii (2.6%). Non‐gum‐producing acacias constituted 7.19% of the total abundance. The tree densities increased with increase in tree size in the undisturbed and grazed habitats but decreased in the cultivated habitat. Most Acacia trees were of large size, an indication of old age and poor regeneration that could affect their future population status. It is recommended that further investigations be carried out into the causes of poor regeneration of Acacia species.     

Development, inheritance and cross-species amplification of microsatellite markers from Acacia mangium

Microsatellite markers were developed in Acacia mangium Willd. to provide highly variable co-dominant markers for linkage mapping and studies of the breeding system. After an enrichment procedure 40% of colonies contained microsatellites in contrast with less than 1% from a non-enriched library. The majority of microsatellite sequences were AC repeats. Co-dominant segregation of alleles in two full-sib crosses of A. mangium was demonstrated at 33 microsatellite loci. The markers were highly variable relative to restriction fragment lengths polymorphisms (RFLPs). In the two pedigrees 53% of microsatellite loci were fully informative compared with 15% of RFLPs. Based on alleles detected among four parental genotypes, the microsatellites consisting of dinucleotide repeats were more polymorphic than those with tri- and tetra-nucleotide repeats. The microsatellite markers were not as transferable across species in the genus Acacia as RFLPs. Two thirds of the primers developed in A. mangium (subgenus Phyllodineae, section Juliflorae) amplified DNA from other species within the same section but failed to amplify in species from the subgenus Acacia. The availability of multiallelic, PCR-based, co-dominant microsatellite loci makes possible efficient studies of gene flow and breeding systems in A. mangium, a species with low allozyme variation. Received: 30 December 1999 / Accepted: 10 May 2000     

The influence of savanna trees on nutrient,water and light availability and the understorey vegetation

In an East African savanna herbaceous layer productivity and species composition were studied around Acacia tortilis trees of three different age classes, as well as around dead trees and in open grassland patches. The effects of trees on nutrient, light and water availability were measured to obtain an insight into which resources determine changes in productivity and composition of the herbaceous layer. Soil nutrient availability increased with tree age and size and was lowest in open grassland and highest under dead trees. The lower N:P ratios of grasses from open grassland compared to grasses from under trees suggested that productivity in open grassland was limited by nitrogen, while under trees the limiting nutrient was probably P. N:P ratios of grasses growing under bushes and small trees were intermediate between large trees and open grassland indicating that the understorey of Acacia trees seemed to change gradually from a N-limited to a P-limited vegetation. Soil moisture contents were lower under than those outside of canopies of large Acacia trees suggesting that water competition between trees and grasses was important. Species composition of the herbaceous layer under Acacia trees was completely different from the vegetation in open grassland. Also the vegetation under bushes of Acacia tortilis was different from both open grassland and the understorey of large trees. The main factor causing differences in species composition was probably nutrient availability because species compositions were similar for stands of similar soil nutrient concentrations even when light and water availability was different. Changes in species composition did not result in differences in above-ground biomass, which was remarkably similar under different sized trees and in open grassland. The only exception was around dead trees where herbaceous plant production was 60% higher than under living trees. The results suggest that herbaceous layer productivity did not increase under trees by a higher soil nutrient availability, probably because grass production was limited by competition for water. This was consistent with the high plant production around dead trees because when trees die, water competition disappears but the high soil nutrient availability remains. Hence, in addition to tree soil nutrient enrichment, below-ground competition for water appears to be an important process regulating tree-grass interactions in semi-arid savanna.     

Restoration of natural vegetation in degraded Imperata cylindrica grassland: understorey development in forest plantations

Abstract. Reclamation of former, degraded forest lands occupied by Imperata cylindrica is one of the crucial environmental and forestry issues in the humid tropics, notably Southeast Asia. We suggest that it is possible to gradually restore the original natural forest cover with the help of a sacrifice fallow crop of fast-growing exotic tree species. Recently, a set of suitable fast-growing plantation tree species has been identified and stand establishment methods developed for this purpose. We assessed the regeneration of natural vegetation in stands of different plantation tree species and evaluated the ecological impact of species composition in the plantation understorey. PCA ordination, regression analysis and analysis of covariance were applied at different stages of the study. We found a marked vegetational resemblance between stands dominated by Acacia mangium: they had the highest number of indigenous trees in their understorey, whereas stands of other plantation trees supported more diverse grass and herb vegetation. A high proportion of evergreen woody vegetation reduces the risk of fire and grass competition and enhances secondary succession towards natural forest.     

The sugar and nitrogen content of the gums of Acacia species in the Mountain Ash and Alpine Ash forests of central Victoria and its potential implications for exudivorous arboreal marsupials

Abstract Chemical analysis of the total sugar and total nitrogen content of Acacia dealbata, Acacia obliquinervia and Acacia frigescens gum exudate was completed. These trees were located within stands of 53 year old Mountain Ash, Eucalyptus regnans and Alpine Ash, Eucalyptus delegatensis forest in the Central Highlands of Victoria, southeastern Australia. Values for sugar content ranged from 24 to 68% per sample. Gum samples that were collected in E. regnans forests had a significantly lower (P<0.05) sugar content than those from stands dominated by E. delegatensis. Statistical analyses using Scheffe's S-test indicated that there was a significant difference in the sugar content of gums between A. dealbata and A. frigescens but not between A. dealbata and A. obliquinervia or A. obliquinervia and A. frigescens. Values for the nitrogen content of Acacia gum varied from 0.2 to 0.7% per sample. Statistical analyses revealed that nitrogen content was significantly influenced (P<0.05) by a combination of three interacting factors: (i) Acacia species; (ii) tree diameter; and (iii) forest type. Therefore, the findings of this study indicate that the sugar and nitrogen content of Acacia gum may vary between forest types and tree species. The gum of Acacia species is an important source of food for several species of arboreal marsupials, and differences in sugar and nitrogen content could be a factor potentially influencing the distribution and abundance of these animals.     

Genetic linkage mapping in Acacia mangium 1. Evaluation of restriction endonucleases, inheritance of RFLP loci and their conservation across species

Random genomic probes were used to assess levels of restriction fragment length polymorphism (RFLP) in two 2-generation outbred pedigrees of Acacia mangium Willd. Probes were evaluated for their ability to detect polymorphic loci in each pedigree and to determine the relative efficiency of different restriction enzymes in revealing polymorphisms. Sixty two percent of the probes which detected single- or low-copy number sequences revealed polymorphisms with at least one restriction enyzme. HpaII was the most efficient in detecting polymorphism among first-generation individuals. The recognition sequence of HpaII contains a CpG dimer, suggesting that cytosines in the CpG sequence may be hotspots for mutation in plant genomes, as previously reported in bacterial and mammalian genomes. Mendelian inheritance of 230 loci was demonstrated based on single-locus segregation in second-generation individuals. Less than 5% of loci showed evidence of segregation distortion. The proportion of fully informative loci (15%) was lower than previously reported in eucalypts reflecting the lower level of genetic diversity in A. mangium. The RFLP probes are suitable for the construction of a high-density genetic linkage map in A. mangium. Cross-hybridisation of the A.mangium RFLPs to DNA from species representing the three subgenera of the genus Acacia indicates that these markers could be used in breeding programs of other diploid acacias, for comparative studies of genome organisation, and for phylogenetic studies. Received: 5. June 1999 / Accepted: 30 July 1999     

Chemotaxonomic aspects of some Acacia gum exudates from series Juliflorae*

Data for the chemical composition of the gum exudates from Acacia acradenia, A. aneura, A. acuminata, A. beauverdiana, A. coolgardiensis, A. kempeana, A. microneura, A. resinomarginea, A. stereophylla and A. torulosa are presented. Comparisons with the data reported previously for other species of the series Juliflorae, viz. A. auriculiformis, A. holosericea, A. leptostachya, A. mangium and A. pubifolia confirm that the gums from this series have interesting combinations of chemical properties that are unusual in Acacia. The data do not offer much chemotaxonomic support for the groupings of the Juliflorae suggested by Bentham (1864). On the basis of their gross morphological features, the species under consideration are re-grouped in a way that is also better supported chemically.     

广州红锥-马占相思林物种组成与多样性研究

为了解广州市龙眼洞林场红锥(Castanopsis hystrix)-马占相思(Acacia mangium)阔叶混交林的群落结构,对其物种多样性进行了分析.结果表明,红锥-马占相思阔叶混交林的物种丰富度依次为乔木层>灌木层>草本层>层间植物层.乔木层的Simpson和Shannon-Wiener指数分别为0.945和...     

The composition of acacia gum exudates from species of the subseries Juliflorae

An analytical study has been made of gum specimens from Acacia auriculiformis (two specimens), A.holosericea, A.mangium, A.leptostachya and A.pubifolia, which belong to subseries Juliflorae of the Series Phyllodineae. These gums appear to be more proteinaccous, more acidic and more viscous, with higher methoxyl contents and higher molecular weights but with lower proportions of rhamnose and arabinose, than the majority of Acacia gums studied so far.     

Contrasting Cloud Forest Restoration Potential Between Plantations of Different Exotic Tree Species

The role of exotic tree plantations for biodiversity conservation is contested. Such plantations nevertheless offer various ecosystem service benefits, which include carbon storage and facilitation of indigenous tree species regeneration. To assess forest restoration potential in tropical exotic tree plantations, we assessed native cloud forest tree regeneration in 166 plots in ca. 50‐year‐old plantations of five timber species that are widely used in tropical plantations (Pinus patula, Eucalyptus saligna, Cupressus lusitanica, Grevillea robusta and Acacia mearnsii). Differences in species abundance, diversity and composition were compared among plantations, and between plantations and disturbed and undisturbed indigenous Afromontane cloud forest (southeast Kenya) relicts after controlling for environmental variation between plots (i.e. altitude, distance to indigenous forest, soil depth, slope, aspect) and for environmental and stand structural variation (i.e. dominant tree height and basal area). Regenerating trees were mostly early‐successional species. Indigenous tree species regeneration was significantly higher in Grevillea plantations, where the seedling community also included late‐successional tree species. Regeneration under Eucalyptus was particularly poor. Acacia had a strong invasive nature, reducing its potential role and usefulness in indigenous forest restoration. Our study underlined that exotic tree plantations have differential effects on native tree species regeneration, with high potential for Grevillea plantations and low potential for invasive exotic species.     

Cross-amplification of nonnative Acacia species in the Hawaiian Islands using microsatellite markers from Acacia koa

Thirty-one microsatellite markers, developed from Acacia koa, were evaluated for cross-amplification of seven nonnative species of Acacia in the Hawaiian Islands. The number of alleles per locus ranged from one to seven, with 16 of the 31 markers showing polymorphism in at least two of the nonnative Acacia species. Of the Acacia species examined, A. melanoxylon showed the highest percentage of amplified loci.     

干热河谷印楝和大叶相思人工林根系生物量及其分布特征

以元谋干热河谷10年生印楝和大叶相思为研究对象,采用分层挖掘法对印楝纯林、大叶相思纯林及印楝×大叶相思混交林根系生物量及其分布特征进行研究.结果表明:印楝×大叶相思混交林根系总生物量为2.707 t/hm2,介于印楝纯林(2.264t/hm2)和大叶相思纯林(3.405 t/hm2)之间.混交林内主根总生物量为1.057 t/hm2,为印楝纯林和大叶相思纯林的69.9％和69.7％,而除粗根外,混交林内其它径级的侧根(中根、小根和细根)生物量均介于印楝纯林和大叶相思纯林之间,分别为印楝纯林的228.7％、120.1％、450.0％,为大叶相思纯林的71.3％、65.8％和48.8％.干热河谷印楝和大叶相思人工林根系在土壤表层分布比例大,尤其足0-0.2 m土层内,其根系生物量占根系总生物量的63.6％-76.3％.根系垂直累积生物量与土壤深度可用二次方程拟合,拟合方程的二阶导数表明,垂直方向上,印楝纯林根系分布较混交林均匀,而混交林较大叶相思纯林均匀.     

木麻黄纯林及其混交林对土壤剖面理化性质的影响

为明确混交林对木麻黄林地土壤肥力的改善作用,该文选取海南岛北部滨海沙地木麻黄纯林、木麻黄-琼崖海棠混交林、木麻黄-大叶相思混交林3种林分类型,通过采集土壤剖面样品,分析腐殖质层、0～100 cm土壤各层次的理化性质、分布特征及其林分间差异。结果表明：(1)与纯林相比,木麻黄-琼崖海棠混交林可显著提高腐殖质层以及20～40 cm土壤层pH,增幅分别为6.11%和5.97%。(2)与纯林相比,木麻黄-琼崖海棠混交林和木麻黄-大叶相思混交林均可显著提高各层土壤的有机碳和全氮含量,有机碳含量增幅分别为69.8%～358.3%和90.2%～908.3%,全氮含量增幅分别为44.1%～160.7%和31.4%～210.7%;另外,木麻黄-琼崖海棠混交林还可显著提高0～100 cm各土层的全磷含量,增幅为20.8%～39.6%,而木麻黄-大叶相思混交林可显著提高20～100 cm各土层的全磷含量,增幅为25.0%～39.6%;木麻黄-大叶相思混交林对腐殖质层速效养分的改善效果较好,而两种混交林均可显著提高各土层的速效钾含量。(3)方差分析表明,林分类型和土层深度对林下有机碳、全氮、全磷、有效磷、硝态...     

马占相思树干液流特征及其与环境因子的关系

运用Granier热消散式探针法对华南丘陵退化荒坡植被恢复先锋树种马占相思(Acaciamangium)树干液流密度进行长期连续观测,并对其周围环境因子如空气温度、空气相对湿度、土壤相对湿度、光合有效辐射和总辐射进行同步观测。通过分析发现马占相思边材厚度与胸径存在显著线性相关关系;马占相思树干液流密度最大值与边材面积具显著相关关系;马占相思树干东、南、西、北4个方位测得的液流密度具显著差异,且各方位相互之间均有显著相关关系;马占相思树干液流每天到达峰值与光合有效辐射和水蒸气压亏缺到达峰值存在一定的时滞,这两个时滞与树高无关,个体间时滞差异在湿季较小,干季较大;干湿季液流平均值和最大值具显著差异,湿季蒸腾水量大于相同时间内干季蒸腾水量;液流的变化与空气温度、空气相对湿度、光合有效辐射、总辐射、水蒸气压亏缺等环境因子的变化具显著相关关系,按相关程度排序为:光合有效辐射>总辐射>水蒸气压亏缺>空气相对湿度>空气温度。