Tree Age Research Articles

Allometric equations for estimation of above- and below-ground biomass of Acacia mearnsii in northwestern Ethiopia

Correct estimation of tree biomass is important when calculating uptake or emission of CO2 in relation to land-use and land-use change. The objectives of this study were (1) to estimate the root/shoot ratio for the estimation of root biomass based on the above-ground biomass (AGB) of Acacia mearnsii, and (2) to develop allometric equations for the estimation of the above-and below-ground biomass (BGB) of Acacia mearnsii. To estimate the AGB and BGB, twenty-four trees of varying ages (3, 4, 5, and 6 years) were harvested, with six trees per age group. We measured the dry biomass for different tree parts and developed allometric models using tree height (H) and diameter at breast height (DBH) as independent variables. The results showed that the biomass of the stem accounted for 69% of the total biomass, followed by branches (14%), roots (8.1%), and leaves (7.3%). The recorded mean root/shoot ratio was 0.11. The biomass of the stem and coarse roots increased with increasing tree age, while a contrary trend was observed for the other tree components. Each component has its unique allometric model.

Total-evidence dating and the phylogenetic affinities of early fossil passerines

Passeriformes is the most diverse and globally widespread order of living birds. However, little work has been done on the phylogenetic relationships within their fossil record. Recent advances in total-evidence phylogenetic methods have improved topological and age estimation by using morphological, molecular and temporal data. This provides the opportunity to investigate the phylogenetic affinities of five recently described passerines from the early Oligocene of Europe, including some of the most complete and oldest passerine fossils described to date. We compare maximum parsimony, non-clock Bayesian inference, and total-evidence tip-dating Bayesian analysis to estimate relationships and divergence times of the fossil passerines. We find Wieslochia weissi, Crosnoornis nargizia and NT-LBR-0014 form a clade within Tyranni (suboscines) either in the stem or within Old-World suboscines (Eurylaimides). Jamna szybiaki is recovered as the sister lineage of crown Passeriformes. We confirmed the oscine affinities of Resoviaornis jamrozi. Its precise position within Passeri remains ambiguous, but affinities within Corvides or Passerides may be more likely considering the biogeographic history of the group. We emphasize the importance of an informative tree age prior in total-evidence dating analyses and appeal for the further development of models for phylogenetic inference using morphology.

KONTRIBUSI USAHA NIRA AREN YANG DIJADIKAN SOPI TERHADAP PENDAPATAN PETANI SOPI DI NEGERI HATUSUA KECAMATAN KAIRATU KABUPATEN SERAM BAGIAN BARAT

The aim of the research is to find out the contribution of sopi products to the level of income of sopi farmers and, to find out what factors influence the production and sales of sopi products in Hatusua State, West Kairatu Seram District. From the research results, the contribution of sopi is 66.84% or Rp. 561,497,810 per year. Meanwhile, income outside of beef production contributed 33.16% or Rp. 278,600,000 per year. From the results of the research and calculation of the contribution value to the income value of sopi production and income outside of sopi production. The income from sopi production in Hatusua Country has a very large contribution value, compared to the income contribution value outside of sopi production by sopi farmers. Factors that influence the production and sales of sopi in Hatusua State, Kairatu District, West Seram Regency, namely, factors that influence sopi production include weather, type of palm flower, age of palm trees and, type of mayang production level and, factors that influence sales. sopi is the status of a sopi which is still illegal.

Модель формирования березово-еловых насаждений в условиях южной тайги Русской равнины

The results of 30 years or research on the formation and growth of birch forests from the subcanopy spruce population in the conditions of the Russian Plain southern taiga are presented. The studies have been carried out on 19 permanent sample plots (PSPs). They were laid in regionally representative sorrel-blueberry birch forests aged 15–115 years with high density and productivity. The birch plantations on the PSPs belong to the same natural age series. The majority of spruce trees appeared under the canopy of birch forests up to 40 years old. As the birch trees aged, the age structure of spruce trees changed from even-aged to conditionally even-aged. Based on the study of the dynamics of the number of trees, the vertical structure of stands, the growing stock and the total stem wood stock, the age stages of development of the spruce population in the birch forests up to 120 years old have been determined. They are regeneration, young growth, polewood and maturation. The end of the maturation stage occurs at the birch tree age of 120 years. At the same time, the average spruce tree age in the first and second layers is 90 years. The duration of the stages varies from 10 years (the young growth stage) to 40 years (the regeneration and maturation stages). To determine the time of onset and end of other age stages of the subcanopy spruce population, the studies in birch forests older than 120 years are needed. The work performed has made it possible to propose a model of the joint formation of birch forests and the subcanopy spruce population, in which the main taxation characteristics are given for all elements of the stand: age, number of trees, the sum of the cross-section of the stems, the stock of the growing and dead wood, as well as total productivity. According to the model, by the age of a birch of 120 years, the total productivity of modal plantations will be about 950 m3/ha and the growing stock of the stand will be about 490 m3/ha. The share of spruce wood will be 28 % or about 150 m3/ha. After the birch forest decay, a low-density spruce forest of the 3rd quality class can form in its place.

Insight into the correlation between total ginkgotoxin and tree ages, geographical locations, and climatic factors

Ginkgo biloba L. seeds are used for food and medicinal purposes in China, but excessive consumption of them can cause acute toxicity. Ginkgotoxin (MPN) and its-5’-glucoside (MPNG) are the main toxic substances in ginkgo seeds. Ginkgo biloba L. trees are widely cultivated in China, and there are fewer studies on total ginkgotoxin (TMPN, MPN and MPNG) in ginkgo from different regions, which is the main motivation for this work. We determined the levels of TMPN in ginkgo seed samples from different regions of China (24.44–41.19 °N, 98.68–124.43 °E), which ranged from 140.96 ± 4.19 μg/g to 537.14 ± 10.78 μg/g. We found that all 131 ginkgo seed samples contained TMPN. Pearson's correlation was performed to analyze the correlation between the TMPN, tree age, geographical location, and climatic factors. The study showed that for geographical factors, longitude was significantly positively correlated with TMPN, and altitude was significantly negatively correlated with TMPN. Regarding climatic factors, mean annual temperature (MAT) and mean warmest month temperature (MWMT) were significantly and positively correlated with TMPN. Our results contribute to a better understanding of the distribution of TMPN in ginkgo seeds in China and lay a scientific foundation for improving low toxicity and safe ginkgo food ingredients.

Investigating Forest Cover Change Using Historical GIS Technologies: A Case Study with an Example of Jurbarkas District of the Republic of Lithuania

Effective forest management systems based on comprehensive tools need to be developed for the analysis and assessment of forest cover change. This requires a wide range of data, starting from old maps, which allow the reconstruction of spatially referenced information on past forest areas, to recently collected data. The research methodology proposed in this paper involves a combined analysis of data from different sources, using statistical, comparative, and visual analysis methods. The case study is Jurbarkas District of the Republic of Lithuania characterized by a high land productivity score. The research found that the highest forest cover areas were in the 19th century and the lowest in the 20th century. It can be seen that during the period under research, forest areas ‘migrated’ from an area favorable for agricultural activities to a less favorable area with higher slopes. Permanent forest cover areas and the age of the dominant trees have been identified. The age of the trees in the forest areas has allowed for the identification of the periods when the most intensive logging took place. The rate of forest cover change made it possible to predict the total disappearance of the forest areas provided that the factors influencing forest cover change at that time remained unchanged. If the trends in forest change in Jurbarkas District had been maintained in the period between the 19th and 20th centuries, the forest would have disappeared in 2006.

Alder expansion stimulates nitrogen oxide (NOx) emissions from southern Eurasian permafrost peatlands

AbstractNitrogen oxides (NOx) play an important role for atmospheric chemistry and radiative forcing. However, NOx emissions from the vast northern circumpolar permafrost regions have not been studied in situ due to limitations of measurement techniques. Our goals were to validate the offline analytical technique, and based on this, to widely quantify in situ NOx emissions from peatlands in the southern Eurasian permafrost region. To this end, we conducted a comparison of online and offline flux measurements in 2018 and 2019 using the synthetic air flushing, steady‐state opaque chamber method. With differences in annual average and cumulative fluxes less than 0.1 μg N m−2 h−1 and 0.01 kg N ha−1 year−1, the online and offline fluxes were in good agreement, demonstrating the feasibility of conducting offline measurements in remote regions without power supply. The flux measurements over 2 years showed obvious NOx emissions of 0.05–0.14 and 0.13–0.30 kg N ha−1 year−1 in the hollow and hummock microtopography of permafrost peatlands, respectively. The rapid expansion of alder (Alnus sibirica) in the peatlands induced by permafrost degradation significantly increased soil mineral N contents and NOx emissions depending on the age of alder (0.64–1.74 and 1.44–2.20 kg N ha−1 year−1 from the alder forests with tree ages of 1–10 years and 11–20 years, respectively). Alder expansion also intensively altered the thermal state of permafrost including the sharp increases of soil temperatures during the non‐growing season from October to April and active layer thickness. This study provides the first in situ evidences of NOx emissions from the northern circumpolar permafrost regions and uncovers the well‐documented expansion of alders can substantially stimulate NOx emissions and thus, significantly affect air quality, radiative forcing, and ecosystem productivity in the pristine regions.

Soil Degradation due to Long-term Citrus Cultivation in the Upper Vietnamese Mekong Delta

This study investigated the impact of tree age on soil properties in citrus orchards in the upper Vietnamese Mekong Delta province, examining orchards of four age groups (<10, 10–20, 21–30, and over 30 years) at two soil depths (0–20 cm and 20–50 cm). Findings indicate notable variations in soil physicochemical properties with age and depth. In older orchards (over 20 years), bulk density increased and soil pH decreased, with overall low pH values (3.5–5.0) observed. Electrical conductivity remained consistent across all ages. Key nutrients such as nitrogen (N), phosphorus (P), potassium (K), soil organic carbon (SOC), and cation exchange capacity (CEC) generally decreased with the age of the orchards. These trends were consistent across both soil layers. The study highlights the influence of prolonged cultivation on soil health and provides insights for developing strategies to enhance productivity and sustain agricultural practices in citrus orchards.

Changes in carbon stocks according to stand development stages in oriental beech forests in the Marmara Region of Türkiye.

This study was conducted to determine the changes in carbon stocks of oriental beech (Fagus orientalis) according to stand development stage in the Marmara Region of Türkiye. For this purpose, sample plots were taken from a total of 32 areas encompassing four stand development stages (young, middle age, mature and overmature stand). The diameter at breast height and height of all trees in the sample plots were measured, and only three dominant trees's ages per plot were determined. Aboveground carbon stock was calculated using equations developed for beech forests, while the coefficients in the Agriculture, Forestry and Other Land Use guide were used to determine belowground carbon stocks. A soil pit was dug in each plot and soil samples were taken at different depths (0-10, 10-30, 30-60, 60-100cm). In addition, litters were sampled from four different 25 × 25cm sections in each plot, and then the physical and chemical properties of the soil and litters were analysed. The variations in carbon stocks in above- and below-ground tree mass, litter and soil, and in ecosystem carbon stocks according to development stage were examined by analysis of variance and Duncan test, and the relationships between the carbon stocks were investigated by correlation analysis. Aboveground (AG) and belowground (BG) tree, soil and ecosystem carbon stocks showed significant differences between the four stand development stages (P < 0.05), but not the litter carbon stocks (P > 0.05). AG and BG tree and ecosystem carbon stocks increased with progressive stand development stages, while the soil carbon stock was the highest at the young stage. These findings will contribute to the preparation of forest management plans and the national greenhouse gas inventory.

Ectomycorrhizal communities of adult and young European larch are diverse and dynamics at high altitudinal sites

Abstract Background/Aims The European larch is a pioneer tree and a valuable economic resource in subalpine ecosystems, thus playing crucial roles to ecosystem services and human activities. However, their ectomycorrhizal fungal community remains unknown in high altitudinal natural habitats. Here, we explore the mycobiont diversity of Larix decidua var. decidua between naturally rejuvenated and adult trees, compare ectomycorrhizal colonization patterns in geographically disjunct areas within the Alps of South Tyrol, Italy, characterized by distinct climatic conditions, and explore turnover rates across various seasons. Methods Our approach combines morphotyping of mycorrhized root tips with molecular analysis. Particular effort was given to monitor both ectomycorrhizal host-specialist and -generalist fungi. Results Both adult and young trees show a 100% mycorrhization rate, with a total diversity of 68 ectomycorrhizal species. The ectomycorrhizal composition is dominated by typical host specialists of larch trees (e.g., Lactarius porninsis, Russula laricina, Suillus cavipes, S. grevillei, S. viscidus), which are widely distributed across sites. A rich diversity of host generalists was also detected. The composition of rare species within a habitat was comparatively consistent during one sampling campaign, but exhibited significant differences among individual sampling campaigns. The ectomycorrhizal compositions were only weakly correlated with distinct climatic conditions and tree ages. However, species richness and diversity, particularly of generalist fungi, was consistently higher in warmer, drier sites compared to cooler, more humid ones. Conclusions This study suggests potential mycobiont community shifts across climatic conditions with significant implications for the adaptability and resilience of subalpine forests in the face of climate change.

Self-Healing Properties of Water Tree with Microcapsule/Cross-Linked Polyethylene Composite Material Based on Three-Layer Core-Shell Structure.

To overcome the degradation of insulating properties caused by the water tree aging of cross-linked polyethylene (XLPE), a self-repairing material for XLPE based on a microcapsule system is proposed. Three-layer shell nucleus microcapsules/XLPE composites with different microcapsule doping content are prepared. The water tree aging experiments are carried out using the water-needle electrode method to analyze the ability of microcapsules to repair the damaged areas of water trees. The results show that, compared with the XLPE material without microcapsules, the electrical properties of composites decline significantly when the doping concentration of three-layer shell nucleus microcapsules is large. When the doping concentration is 1.0 wt%, the microcapsule/XLPE composite breakdown strength has no noticeable change, and the dielectric loss factor does not change significantly, the space charge density decreases, and the space charge properties have been improved considerably. When the water tree branch develops to the position where the microcapsules are located, the microcapsules will rupture and release their internal repair materials and catalysts and react with water to produce an organic silicone resin to fill the water tree cavity, which can achieve an excellent self-healing effect. In addition, the nano-SiO2 on the surface microcapsules can make the microcapsules and matrix better integrated, which avoids the microcapsule accumulation that tends to occur when incorporating microcapsules, thus improving the repair rate.

Mechanisms and quality variations of non-volatile and volatile metabolites in black tea from various ages of tea trees: Insights from metabolomics analysis

The sensory quality of black tea (BT) influenced by various factors, among which tree age is particularly significant. People prefer BT produced by fresh leaves from old tea trees, yet the correlation between tree age and tea quality has not been thoroughly investigated. In this study, we analyzed the quality of BT from young trees (H-JYH) and old trees (H-OJYH) using e-tongue technology and sensory evaluation. Our findings revealed that H-OJYH had stronger sweetness and sourness, richer flavor, and diminished bitter-astringency compared to H-JYH. 1231 non-volatile metabolites and 504 volatile metabolites were discovered by ultra-performance liquid chromatography (UPLC) and gas chromatography–mass spectrometry (GC–MS). L-tartaric acid and trans-citridic acid were found to contribute to increase acidity, and 7,8-dihydroxy-6-methoxycoumarin and d-fructose 6-phosphate were associated with enhanced sweetness in H-OJYH. Additionally, lower levels of octyl gallate and vanillic acid in H-OJYH contributed to the diminished bitter-astringency. β-ionone, 2-phenylethanol and phenylacetaldehyde merged as characteristic compounds of older tree BT with stronger floral and sweet aroma. Our study serves as a guideline to explore the relationship between tree age and tea quality.

Age and growth reductions increase the proportion of dark heartwood in sugar maple at the northern limit of its range

Abstract The wood of sugar maple (Acer saccharum Marsh.) in the northernmost part of the species range often exhibits high proportions of discoloured wood at the centre of the stems, which is referred to as dark heartwood. This defect significantly decreases the wood market value of the species, which, in turn, challenges the implementation of state-of-the art silvicultural treatments. The causes of dark heartwood are associated with trauma and the colder climate of the northern regions. In this study, we investigate factors influencing the occurrence of dark heartwood in sugar maple’s northern populations, considering tree age, vigour, stem growth, and local climate. We also aimed to determine whether the proportion of dark heartwood is higher in northern stands compared to more southern ones. We collected samples from 302 sugar maple stems at 16 sites within two bioclimatic domains of Quebec, Canada, i.e. the balsam fir–yellow birch domain (representing the northern limit of the sugar maple range) and the sugar maple–yellow birch domain (representing a more southern location within the range). Our results indicate a positive relationship between dark heartwood proportions and stem age, as well as with the amplitude of the maximum growth reduction throughout the tree’s lifespan and the length of the longest suppression period. We also observed significantly higher dark heartwood proportion for a given tree age in northern stands. The results suggest that silvicultural systems aiming to release suppressed crop trees through group selection using a cut-to-length system could favour the development of high quality timber.

Urban cemeteries: The forgotten but powerful cooling islands

Urban parks play a key role in UHI mitigation. However, the role of other prominent types of urban green infrastructure has not been comprehensively studied. Thus, the main objective of this study was to evaluate the role of cemeteries and allotments as cooling islands compared to the well-studied park areas. We assessed the LST of cemeteries, allotments and parks based on Landsat 8 TM images across the five largest German cities during summertime. Random forest regressions explain the LST spatial variability of the different urban green spaces (UGS) with spectral indices (NDVI, NDMI, NDBaI) as well as with tree characteristics (tree type, tree age, trunk circumferences, trunk height or canopy density). As a result, allotments were identified as the hottest UGS with the city means varying between 23.1 and 26.9 °C, since they contain a relatively high proportion of sealed surfaces. The LST spatial variability of allotment gardens was best explained by the NDVI indicating that fields with a higher percentage of flowering shrubs and trees reveal lower LST values than those covered by annual crops. Interestingly, cemeteries were characterized as the coolest UGS, with city means between 20.4 and 24.7 °C. Despite their high proportion of sealed surfaces, they are dominated by old trees resulting in intensive transpiration processes. Parks show heterogeneous LST patterns which could not be systematically explained by spectral indices due to the variability of park functionality and shape. Compared to parks, the tree-covered areas of cemeteries have a higher cooling potential since cemeteries as cultural heritage sites are well-protected allowing old tree growth with intensive transpiration. These findings underline the relevance of cemeteries as cooling islands and deepen the understanding of the role of tree characteristics in the cooling process.

Cedrelinga catenaeformis (Tornillo) in natural and agroforestry systems: Dendrometry, soil and macrofauna

Agroforestry and protected areas are alternatives to mitigate the adverse impacts generated by human activities in the tropical forests of the Peruvian Amazon. The aim of this study was to determine the influence of natural and agroforestry systems of Cedrilinga catenaeformis (Tornillo) on soil properties. The physical, chemical, and soil macrofauna properties, as well as dendrometric variables of Tornillo aged 140 and 180 years in natural systems and 7, 17 and 37 years in agroforestry systems, were examined. Results revealed variability in soil properties depending on their origin; however, no marked differences were observed due to tree age or natural versus agroforestry condition. Regarding soil macrofauna, greater diversity was noted in the older agroforestry system, while dendrometric variables exhibited a sigmoidal behavior, except for wood volume, which showed a linear increase. Agroforestry systems of Tornillo associated with Centrosema macrocarpum (Centrosema) maintain soil properties similarly compared to natural systems; however, the soil of the oldest agroforestry system showed higher activity of earthworms Rhinodrilus lavellei, Rhinodrilus pashanasii, Diptera orders, and Julidae, compared to soils of more recent agroforestry systems and natural systems. It was estimated that dendrometric variables of Tornillo show stagnation in the increase of total height at 150 years, commercial height at 165 years, and DBH at 70 years. Meanwhile, total height and DBH showed very strong and strong positive correlations (p < 0.05) with soil N content and CEC in agroforestry systems with 17 and 37 years. Estimating dendrometric variables and understanding the nutritional requirements in the growth and development of Tornillo will contribute to its more effective management in natural and agroforestry ecosystems in the Amazon region.

Continental-scale evaluation of downy birch pollen production: Estimating the impacts of global change

The high prevalence of hay fever in Europe has raised concerns about the implications of climate change-induced higher temperatures on pollen production. Our study focuses on downy birch pollen production across Europe by analyzing 456 catkins during 2019–2021 in 37 International Phenological Gardens (IPG) spanning a large geographic gradient. As IPGs rely on genetically identical plants, we were able to reduce the effects of genetic variability. We studied the potential association with masting behavior and three model specifications based on mean and quantile regression to assess the impact of meteorology (e.g., temperature and precipitation) and atmospheric gases (e.g., ozone (O3) and carbon-dioxide (CO2)) on pollen and catkin production, while controlling for tree age approximated by stem circumference. The results revealed a substantial geographic variability in mean pollen production, ranging from 1.9 to 2.5 million pollen grains per catkin. Regression analyses indicated that elevated average temperatures of the previous summer corresponded to increased pollen production, while higher O3 levels led to a reduction. Additionally, catkins number was positively influenced by preceding summer's temperature and precipitation but negatively by O3 levels. The investigation of quantile effects revealed that the impacts of mean temperature and O3 levels from the previous summer varied throughout the conditional response distribution. We found that temperature predominantly affected trees characterized by a high pollen production. We therefore suggest that birches modulate their physiological processes to optimize pollen production under varying temperature regimes. In turn, O3 levels negatively affected trees with pollen production levels exceeding the conditional median. We conclude that future temperature increase might exacerbate pollen production while other factors may modify (decrease in the case of O3 and amplify for precipitation) this effect. Our comprehensive study sheds light on potential impacts of climate change on downy birch pollen production, which is crucial for birch reproduction and human health.

Seasonality Affects Low-Molecular-Weight Organic Acids and Phenolic Compounds' Composition in Scots Pine Litterfall.

Secondary plant metabolites, including organic acids and phenolic compounds, have a significant impact on the properties of organic matter in soil, influencing its structure and function. How the production of these compounds in foliage that falls to the forest floor as litterfall varies across tree age and seasonality are of considerable interest for advancing our understanding of organic matter dynamics. Monthly, we collected fallen needles of Scots pine (Pinus sylvestris L.) across stands of five different age classes (20, 40, 60, 80, and 100 years) for one year and measured the organic acids and phenolic compounds. Seven low-molecular-weight organic acids and thirteen phenolic compounds were detected in the litterfall. No differences were observed across stand age. Significant seasonal differences were detected. Most compounds peaked during litterfall in the growing season. Succinic acid was the most prevalent organic acid in the litterfall, comprising 78% of total organic acids (351.27 ± 34.27 µg g- 1), and was 1.5 to 11.0 times greater in the summer than all other seasons. Sinapic acid was the most prevalent phenolic compound in the litterfall (42.15 µg g- 1), representing 11% of the total phenolic compounds, and was 39.8 times greater in spring and summer compared to autumn and winter. Growing season peaks in needle concentrations were observed for all thirteen phenolic compounds and two organic acids (lactic, succinic). Citric acid exhibited a definitive peak in late winter into early spring. Our results highlight the seasonal dynamics of the composition of secondary plant metabolites in litterfall, which is most different at the onset of the growing season. Fresh inputs of litterfall at this time of emerging biological activity likely have seasonal impacts on soil's organic matter composition as well.

Variation in the timing and duration of autumn leaf phenology among temperate deciduous trees, native shrubs and non-native shrubs.

The timing and duration of autumn leaf phenology marks important transitions in temperate deciduous forests, such as, start of senescence, declining productivity and changing nutrient cycling. Phenological research on temperate deciduous forests typically focuses on upper canopy trees, overlooking the contribution of other plant functional groups like shrubs. Yet shrubs tend to remain green longer than trees, while non-native shrubs, in particular, tend to exhibit an extended growing season that confers a competitive advantage over native shrubs. We monitored leaf senescence and leaf fall (2017-2020) of trees and shrubs (native and non-native) in an urban woodland fragment in Wisconsin, USA. Our findings revealed that, the start of leaf senescence did not differ significantly between vegetation groups, but leaf fall started (DOY 273) two weeks later in shrubs. Non-native shrubs exhibited a considerably delayed start (DOY 262) and end of leaf senescence (DOY 300), with leaf-fall ending (DOY 315) nearly four weeks later than native shrubs and trees. Overall, the duration of the autumn phenological season was longer for non-native shrubs than either native shrubs or trees. Comparison of the timing of spring phenophases with the start and end of leaf senescence revealed that when spring phenology in trees starts later in the season senescence also starts later and ends earlier. The opposite pattern was observed in native shrubs. In conclusion, understanding the contributions of plant functional groups to overall forest phenology requires future investigation to ensure accurate predictions of future ecosystem productivity and help address discrepancies with remote sensing phenometrics.

Local and landscape drivers of natural enemy communities in Indonesian oil palm plantation

Abstract Oil palm plantations are typically managed in a monoculture system over large areas. This system contributes to biodiversity loss and promotes pest outbreaks by reducing natural enemies. However, ecosystem functions in oil palm plantations vary spatially and temporally and can still support biodiversity under certain conditions. We conducted a study on the species richness, abundance and species composition of natural enemies in oil palm plantations and investigated the factors influencing natural enemy communities in oil palm plantations at both local and landscape scales. We selected 12 sites in an oil palm plantation in Central Borneo, Indonesia, which were grouped into 4 sub‐areas based on the presence of natural habitats, which varied in local and landscape characteristics. Arthropods were sampled using canopy knockdown fogging with a pyrethroid insecticide. Different taxa of natural enemies responded differently to changes in habitat characteristics within oil palm plantations. Species richness of spiders was not affected by either local or landscape scale, but their species composition was affected by oil palm tree age (local scale) and the total edge of dominant oil palm tree age (landscape scale). Ant species richness was influenced by the class area of natural habitat (landscape scale), whereas their species composition was not influenced by either local or landscape scale. On the other hand, species richness of parasitoid wasps was influenced by light intensity (local scale) and the variation of oil palm tree age within a landscape (landscape scale). However, their species composition was only affected by light intensity. The results suggest that oil palm management practices need to consider both local and landscape scales to maintain biodiversity and biological control and to achieve sustainable management of oil palm plantations.

Inter-tree Variation in Chemical Components of North Sumatra Benzoin Gum (Styrax sp.)

Benzoin gum, which is known as Sumatra benzoin (Styrax sp), is widely used as an ingredient in the incense. Although these resins are widely used as flavours and fragrances, no studies have been made on inter-tree variation of its chemical composition. Therefore, benzoin gum samples were tapped from the 30 individual trees (age 10 years, 9~35 cm in diameter) grown in the community forest of Polung, Humbang Hasundutan Regency, North Sumatra. The gum chemical components were analyzed by GC-MS and identified by comparing the fragmentation pattern with the standard components and literature studies. It was found that the major compounds detected by GC-MS were cinnamic acid (51.48%), cinnamyl cinnamate (62.56%), benzoic acid (1.94%), chavicol (5.18%), benzyl cinnamic acid (7.8%), atropic acid (9.84%), and vanillin (1.47%). Two main constituents that were always detected from 30 benzoin trees were chavicol and cinnamic acid, followed by cinnamyl cinnamate (28 trees) and benzoic acid (14 trees). By cluster analysis, 30 samples of benzoin gum can be classified into clusters I - III based on the average chemical components. Cluster I consisted of 7 individual trees with a higher percentage of benzoic acid and chavicol but lower concentration of cinnamic acid compared to other clusters. Cluster II consisted of 18 individual trees with a high percentage of cinnamyl cinnamate whereas clusters III consisted of 5 individual trees characterized with a high percentage of cinnamic acid. By Pearson correlation, it was observed that no significant correlation between the values of diameter and the amount of chemical components of benzoin gum.