Genetic Variation of Six Azadirachta excelsa (Jacks) Jacobs Populations

The study of the extent and pattern of genetic variation of six populations of Azadirachta excelsa (Jacks) Jacobs, i.e. Manong (Perak), Pokok Sena (Kedah), Sik (Kedah), FRIM (Selangor), Merchang (Terengganu) and Sg. Caru (Pahang) was carried out using starch gel electrophoresis. The analysis on eleven enzyme systems was found to be coded by 25 and 26 loci. The mean of observed heterozygosity ranged from 0.08 to 0.11 and the percentage of proportion of polymorphic loci varied from 61.54% to 73.08%. The extents of genetic identities ranged from 0.81 to 0.98

Growth, Morphological and Genetic Variation of Azadlrachta Excelsa (Jack) Jacobs Genotypes

A study was made on six seed sources of Azadirachta excelsa Jack) Jacobs at ages one and two years at two different locations, i.e. Rantau Panjang (Selangor) and Merchang (Terengganu) to determine the patterns of interand intra-specific variation in growth, genetic and morphological characteristics of this species. Measurements of survival, height, basal diameter (BD) and diameter breast height (DBH) were made on all trees at ages one and two years after planting in the field. Five characteristics of leaf morphology, i.e. leaf shape, leaf margin, leaf base, leaf angle and internode were also analysed for seed source variation. In addition, 19 enzyme systems were used to determine the genetic variation among seed sources using isozyme analysis. All the seed sources survived well during the first year with 91.25% in Rantau Panjang and 70.00% in Merchang but the survival reduced to 86.45% and 41.33% respectively during the second year. The mean height values ranged from 126.85 cm to 209.38 cm in Rantau Panjang and 49.76 cm to 72.19 cm in Merchang during the first year, and 212.83 cm to 367.07 cm in Rantau Panjang and 85.40 cm to 156.16 cm in Merchang during the second year. Whereas, the mean values of BD ranged from 2.04 em to 3.40 em in Rantau Panjang and 0.64 em to 0.87 em in Merchang during the first year, and 3.33 cm to 5.65 em in Rantau Panjang and 0.97 em to 1.54 em in Merchang during the second year. Meanwhile, the mean values of DBH for the first and second years ranged from 0.85 cm to 2.23 cm and 1.94 cm to 3.98 cm in Rantau Panjang respectively while in Merchang, the mean values of DBH ranged from 0.53 to 0.93 for second year

Age- and size-related changes in physiological characteristics and chemical composition of Acer pseudoplatanus and Fraxinus excelsior trees

Forest growth is an important factor both economically and ecologically, and it follows a predictable trend with age. Generally, growth accelerates as canopies develop in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline are multiple and may be linked to age- or size-related processes, or both. Our objective was to determine the relative effects of tree age and tree size on the physiological attributes of two broadleaf species. As age and size are normally coupled during growth, an approach based on grafting techniques to separate the effects of size from those of age was adopted. Genetically identical grafted seedlings were produced from scions taken from trees of four age classes, ranging from 4 to 162 years. We found that leaf-level net photosynthetic rate per unit of leaf mass and some other leaf structural and biochemical characteristics had decreased substantially with increasing size of the donor trees in the field, whereas other gas exchange parameters expressed on a leaf area basis did not. In contrast, these parameters remained almost constant in grafted seedlings, i.e., scions taken from donor trees with different meristematic ages show no age-related trend after they were grafted onto young rootstocks. In general, the results suggested that size-related limitations triggered the declines in photosynthate production and tree growth, whereas less evidence was found to support a role of meristematic age

Net primary productivity of forest trees: A review of current issue

Forest growth is important both economically and ecologically and it follows a predictable general trend with age. Generally, the growth of all forests accelerates as canopies develop in young forests and declines substantially soon after the maximum leaf area is attained. The causes of this decline trend are multiple. Initially, age- and size-related declines were attributed to photosynthesis-respiration imbalance. Subsequently, several competing hypotheses have been proposed over the years, although nutrient and hydraulic limitation hypotheses appear to be the most likely to have caused it. In this paper, the authors attempt to review these hypotheses and concentrate on one related aspect, as this can set the scene for further examining the issues of age-related versus size-related processes

Wood density and carbon estimates of mangrove species in Kuala Sepetang, Perak, Malaysia

Mangrove forests provide a broad array of ecosystem services including fisheries production, sediment regulation, wood production and protection from storms and waves. Mangroves also may have an important role as a pool in global carbon budgets and in mitigating climate change. Here we investigated the wood density and carbon content of the mangrove species in Kuala Sepetang, Perak. Using data from 13 mangrove species, the value for wood density and carbon were estimated. Wood density ranged from 0.33 gcm-³ to 0.64 gcm-³, where the lowest and highest values were given by Sonneratia caseolaris and Ceriops tagal, respectively. The carbon content was 42.48% on average, where Bruguiera cylindrical gave the lowest value at 45.13 % while Lumnitzera racemosa was the highest at 45%. These values suggest that Kuala Sepetang mangrove forest has the potential to sequester and store substantial amounts of atmospheric carbon

Variations in wood density, annual ring width and vessel properties of quercus brantii affected by crown dieback

Funding: This research received no external funding. Acknowledgments: We would like to thank A. Hawasi and S. Soltani for their kind help during this work.Peer reviewedPublisher PD

Soil CO2 efflux of oil palm and rubber plantation in 6-year-old and 22-year-old chronosequence

Soil CO2 efflux, in relation with chronosequence at oil palm and rubber plantations, was measured monthly, each with both 6- and 22-year-old stands. Other environmental factors such as soil temperature and relative humidity (RH), as well as soil properties, were also measured at 0–30 cm depth. Soil CO2 efflux was found to be highly affected by forest types and chronosequence factor. The 22-year-old age stand (M = 0.91; SD = 0.17 g CO2 m−2 h−1) had significantly higher soil CO2 efflux than the 6-year-old stand (M = 0.54; SD = 0.18 g CO2 m−2 h−1). Soil RH plays a significant role controlling soil CO2 efflux compared with soil temperature, especially at younger stands of tropical oil palm and rubber plantations spatially. Lower Q10 values were found to be caused by higher temperature that had reduced enzymatic and substrates activities for soil respiration. Non-discernible trends of temporal soil CO2 efflux, soil temperature, and RH indicated that other significant factors could be the catalyst, and thus further research is required to explain the relations between soil CO2 efflux and environmental factors. Research findings indicated that older stand age of oil palm and rubber plantations in Malaysia released higher soil CO2 efflux, but with no degrading effects towards the environment

Growth, photosynthesis, chlorophyll content and nutrient partitioning of kenaf as influenced by different levels of carbon

The effects of carbon (C) levels on growth, photosynthesis, chlorophyll content, and nutrient partitioning on five kenaf varieties were investigated. Kenaf plants were grown in pots containing sandy beach ridges interspersed with swales (BRIS) soil. Organic carbon at levels of 0, 10, 20, 30, and 40 t ha−1, were applied to the pots. The results showed that plant height, stem diameter, leaf number, leaf area, chlorophyll content and photosynthesis rate increased with an increase in carbon levels up to 20 t ha−1but decreased with additional increase in carbon levels. The proportion of nitrogen in leaves was minimum at 0 and maximum at 20 t ha−1carbon levels. In stem and roots, proportion of nitrogen (N) decreased after 10 t ha−1carbon, while in leaves phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) increased after 20 t ha−1. Variety HC2 showed maximum N, P, and K in leaves and total nutrient content