Pioneer Tree Species Research Articles

Morphological and Physiological Changes of Broussonetia papyrifera Seedlings in Cadmium Contaminated Soil.

Broussonetia papyrifera is a widely distributed economic tree species, and it is also a pioneer species in adverse environments. In order to investigate the growth and adaptation mechanism of B. papyrifera under cadmium (Cd) contaminated soil, potted experiments were used with six-month treatments to study Cd enrichment and the transportation, morphological and physiological characteristics of B. papyrifera tissues. The results showed that Cd mainly accumulated in the root when the Cd concentration was high (14.71 mg/kg), and the root biomass was significantly reduced by Cd stress although Cd promoted the growth of seedlings. The bioconcentration factors (BCF) increased with the increase in Cd concentration, and reached the maximum value of 0.21 at 14.71 mg/kg. On the contrary, translocation factor (TF) decreased significantly at 8.28–14.71 mg/kg Cd concentration. Cd not only led to the loose arrangement of the xylem vessels of leaves, but also changed the chlorophyll content. However, B. papyrifera could synthesize organic solutes such as soluble protein, soluble sugar and proline to reduce the intracellular osmotic potential. Our study proved that B. papyrifera has good tolerance to Cd stress and is a pioneer tree species for soil and ecological environment restoration.

Plant Genotype Influences Physicochemical Properties of Substrate as Well as Bacterial and Fungal Assemblages in the Rhizosphere of Balsam Poplar.

Abandoned unrestored mines are an important environmental concern as they typically remain unvegetated for decades, exposing vast amounts of mine waste to erosion. Several factors limit the revegetation of these sites, including extreme abiotic and unfavorable biotic conditions. However, some pioneer tree species having high levels of genetic diversity, such as balsam poplar (Populus balsamifera), can naturally colonize these sites and initiate plant succession. This suggests that some tree genotypes are likely more suited for acclimation to the conditions of mine wastes. In this study, we selected two contrasting mine waste storage facilities (waste rock from a gold mine and tailings from a molybdenum mine) from the Abitibi region of Quebec (Canada), on which poplars were found to have grown naturally. First, we assessed in situ the impact of vegetation presence on each mine waste type. The presence of balsam poplars improved soil health locally by modifying the physicochemical properties (e.g., higher nutrient content and pH) of the mine wastes and causing an important shift in their bacterial and fungal community compositions, going from lithotrophic communities that dominate mine waste environments to heterotrophic communities involved in nutrient cycling. Next, in a greenhouse experiment we assessed the impact of plant genotype when grown in these mine wastes. Ten genotypes of P. balsamifera were collected locally, found growing either at the mine sites or in the surrounding natural forest. Tree growth was monitored over two growing seasons, after which the effects of genotype-by-environment interactions were assessed by measuring the physicochemical properties of the substrates and the changes in microbial community assembly. Although substrate type was identified as the main driver of rhizosphere microbiome diversity and community structure, a significant effect due to tree genotype was also detected, particularly for bacterial communities. Plant genotype also influenced aboveground tree growth and the physicochemical properties of the substrates. These results highlight the influence of balsam poplar genotype on the soil environment and the potential importance of tree genotype selection in the context of mine waste revegetation.

Agricultural land-use change alters the structure and diversity of Amazon riparian forests

Riparian forests play key roles in protecting biodiversity and water resources, making them priorities for conservation in human-dominated landscapes, but fragmentation associated with expanding tropical croplands threatens their ecological integrity. We compared the structure of tropical riparian forests within intact and cropland catchments in a region of intensive soybean production in the southeastern Brazilian Amazon. We studied forest plots (varying from 120 to 210 m long) that bisected riparian zone forests and headwater streams in ten catchments. Four plots were within large areas of intact primary forest and six were in bands of protected riparian forest along streams within croplands as required by the Brazilian Forest Code. We found that riparian forests in croplands harbored fewer species of trees and seedlings/saplings, and had higher proportions of opportunistic, pioneer tree species. We also found greater variation in tree species composition, and higher internal dissimilarity in croplands compared with forests. The observed patterns in tree species composition were driven mainly by differences between riparian forest-cropland edges and those bordering intact upland forests. Forests nearest to streams in cropland and forested catchments were more similar to one another. Results suggest that wider buffers are needed at the edges of croplands to maintain riparian forest structure. The minimum 30-m riparian buffers now required by the Brazilian Forest Code may thus be insufficient to prevent long-term shifts in riparian forest species composition and structure.

Impact of fires on an open bamboo forest in years of extreme drought in southwestern Amazonia

In Brazil’s state of Acre, in southwestern Amazonia, wildfires mediated by extreme droughts in 2005 and 2010 affected more than 500,000 ha of forest, causing changes in their structure, species diversity, and aboveground biomass (AGB), and the expansion of bamboo. Our objective was to analyze these changes in an open bamboo forest in Acre after forest fires occurred either in one of the extreme drought years (2005 or 2010) or in both years (2005 + 2010). We sampled 9.75 ha (in 2016 and 2017), distributed in 18 0.5 ha (100 m × 50 m) plots and three 0.25-ha (50 m × 50 m) plots. We identified a strong fire effect on the number of tree individuals per hectare, which declined by 50% if the forest was burned in only one year (2005 or 2010) and by 74% if burned in both years. This was inversely related to the expansion of bamboo stems, which increased in number by 7 to 9 times. Changes in forest structure and species composition after the fire were characterized by a high importance value for pioneer tree species; reductions in the number of trees with logging potential, in the basal area of trees, and in the number of lianas; and an increase in the density of bamboo stems. AGB in the burned forests was 51–73% that of the unburned forest. With the expansion of bamboo, its contribution to AGB increased from 1% in the unburned forest to 27% in the twice-burned forest. These forms of degradation represent serious threats to Amazon forests.

Silver birch aboveground biomass allocation pattern, stem and foliage traits with regard to intraspecific crown competition

Abstract In the conditions of Central Europe, silver birch (Betula pendula Roth) has so far not been an important species for commercial purposes but might be relevant from ecological point of view. For instance, prompt succession by birch and other pioneer tree species at large-scale post-disturbance areas is necessary to compensate for previous carbon losses by natural disasters. Therefore, our attention was focused on 14-year-old birch trees growing at the wind-thrown area in the High Tatra Mts. (northern Slovakia). We sampled aboveground biomass of 20 silver birch trees representing four classes of crown competition: 0 – competition free crowns, 1 – crowns under mild competition, 2 – crowns under moderate competition, 3 – crowns under severe competition. We studied biomass allocated to stems, branches and foliage, and basic properties of stems and foliage. The crown-competition free birches were nearly 13 m high, and their aboveground tree biomass was 150 kg. The biomass of birches under severe competition was five times lower. Crown competition modified biomass ratios of foliage to branch as well as of branch to stem. Our results showed that birches under severe competition stress invest more in height than in diameter. At the same time, crown competition modified foliage weight and specific leaf area (SLA), which was clear mostly in the upper part of the crowns. However, foliage area was influenced by crown competition only to a negligible extent. Our main finding is that foliage position (upper, middle or lower third of crown) affected foliage properties more than intraspecific crown competition. Finally, we pointed out that silver birch is a rather productive species that is not ecologically demanding. Therefore, it might be a prospective tree species under the ongoing climate change and the present period of intensification in renewable resources utilisation.

Climate Change and Invasive Species: Challenges and Opportunities for Forest Establishment on Appalachian Surface Mines

ABSTRACT Climate change and harsh environmental conditions present significant barriers to the reforestation of surface-mined sites in Appalachia. An experimental site was established on a reclaimed surface mine in eastern Kentucky to investigate the impacts of soil amendments (fertilizer additions and mycorrhizal inoculations) on the growth and survival of northern red oak and loblolly pine, and the effects of amendments and species planted on soil development. While early effects of soil fertility and mycorrhizae treatments were apparent, these did not affect the growth or survival of either species after 10 growing seasons. Overall, loblolly pine exhibited greater growth (7.6 m) and survival (58%) than northern red oak (1.8 m height growth and 39% survival). While the poor growth and survival of northern red oak were attributed to heavy vegetative competition from nonnative species, loblolly pine rapidly achieved canopy closure and shaded out competitive understory vegetation. This study documents that non-native loblolly pine may serve as an important pioneering tree species in reforestation of reclaimed mine sites by potentially outcompeting invasive exotic understory plant species. We speculate that, by suppressing invasive species, loblolly pine may have the potential to serve as a “nurse tree” for more economically and ecologically desirable hardwood species.

Salinity Tolerance and Occurrence of Salix nigra Marshall (Black Willow) in Tidal Wetlands of Chesapeake Bay Tributaries

Salix nigra Marshall (Black Willow) is a pioneer tree species that establishes in North American river floodplains and is widely used for bank stabilization. However, its salinity tolerance and occurrence in tidal wetlands of estuarine systems along the North American Atlantic coast is largely unknown. Climate change accompanied by land subsidence and changes in precipitation pattern induce increases in salinity that may affect coastal vegetation. Alteration of hydromorphology of coastal plain estuaries causes additional increases in salinity that affects forested tidal freshwater wetlands. We investigated the salinity tolerance and occurrence of Black Willow in tidal wetlands of 2 Chesapeake Bay tributaries and in a greenhouse hydroponic experiment. A salinity of more than 1 part per thousand (ppt) salt limited the willows' occurrence in the field and the cuttings' performance in the experiment. Dry mass was significantly lower in salinity of 2 and 3 ppt compared to the control and salinity of 1 ppt. Cuttings originating from tidal freshwater wetlands developed more belowground biomass and leaves than cuttings from brackish wetlands. The better performance of cuttings originating from tidal freshwater wetlands may indicate a higher resilience to short-term increases in salinity in tidal freshwater wetland forests with implications for tidal forest restoration in eastern North America.

The reclaimed coal mine ecosystem diverges from the surrounding ecosystem and reaches a new self-sustaining state after 20–23 years of succession in the Loess Plateau area, China

Whether or not the completely destroyed ecosystem would follow a succession trajectory towards the surrounding forest ecosystem after restoration remains debatable. Here, a comprehensive dataset of thirty-five ecosystem functions were measured on five reclaimed opencast coal mine forest plots (two Robinia pseudoacacia - Pinus tabuliformis mixed forests with different technosol conditions: RPT and RPM; one R. pseudoacacia - Ulmus pumila - Ailanthus altissima mixed forest: RUA; one Picea meyeri - Picea wilsonii - Hippophae rhamnoides mixed forest: PPH; one R. pseudoacacia monoculture forest: RM) and one natural forest plot (Populus simonii monoculture forest: PM) in Pingshuo opencast coal mine, Shanxi Province, China. These functions were employed to examine the reclamation effects among plots in terms of four management scenarios (i.e., biomass productivity, carbon sequestration, general biodiversity conservation and nutrient accumulation) and to determine the affinities between reclaimed ecosystem and its native counterpart according to Bray Curtis Distance Algorithm. The results showed that after 20–23 years of succession, thirty-five ecosystem functions differed among plots and eight highest ecosystem functions were found in RPT and RPM (P < 0.05). In scenarios of biomass productivity, carbon sequestration, general biodiversity conservation and nutrient accumulation scenarios, RPM scored 0.645, 0.470, 0.467 and 0.578, respectively. Accordingly, RPT scored 0.458, 0.447, 0.405 and 0.515, respectively. Consequently, RPT and RPM had the highest scores in the four management objectives compared to other plots. With regard to the ecosystem affinities, RPT was analogous to RPM. Similarly, RUA and PPH resembled PM and RM, respectively. Overall, the pioneer tree species determined the reclamation quality in the dump in the long term, which could be referred as the “trigger effect” in the succession trajectory in reclaimed ecosystem, and the reclaimed coal mine ecosystem diverged from the surrounding ecosystem and reached a new self-sustaining state after 20–23 years of succession.

Spontaneous plant recolonization on reclaimed post-coal mining sites in East Kalimantan, Indonesia: Native versus alien and succession progress

Abstract. Hapsari L, Trimanto, Budiharta S. 2020. Spontaneous plant recolonization on reclaimed post-coal mining sites in East Kalimantan, Indonesia: Native versus alien and succession progress. Biodiversitas 21: 2003-2017. Comparative vegetation analyses subjected to recolonization of spontaneous plants were carried out in two post-coal mining reclamation sites, with different ages of reclamation, specifically 9 years old and 17 years old, in Bontang, East Kalimantan. This study aims to determine the spontaneous plant diversity and composition, identify the spontaneous alien plant species invasion (IAS), analyze the underlying micro-climates and soil factors and their association to the spontaneous plant recolonization, also to evaluate the succession progress. Results showed that both reclamation sites have undergone some vegetation and environmental improvements. The plant succession stage of both sites was identified at the same stage, as establishment phase of early-succession stage in transition to mid-succession stage. The spontaneous plants were comprised of two layers, i.e. (i) understories include grasses, ferns, lianas, herbs, shrubs and tree seedlings; and (ii) saplings include some of trees and small trees. Plant diversity indices on both sites were in moderate category. At understory layer, the 9-y.o. site was mostly dominated by grass Polytrias indica, whereas the 17-y.o. site was dominated by shrub Asystasia gangetica. At sapling layer, the 9-y.o. site was mostly dominated by Glochidion obscurum, whereas the 17-y.o. site was dominated by Macaranga tanarius. Dominant pioneer tree and shrub species in two reclamation sites mostly from general species component of secondary tropical forests from the families Euphorbiaceae, Phyllantaceae, Melastomaceae, Leguminosae, and Lamiaceae. It was recorded seven IAS in the 9-y.o. site, which six out of seven species were dominant. Meanwhile, in the 17-y.o. site was recorded eight IAS but only four species were dominant. Two dominant noxious weed species were also identified. Each IAS and noxious weed species has invasiveness traits that make them well-grown, successfully recolonized and invaded the reclamation site. Environmental factors include air temperature, air moisture, and light intensity; and soil conditions include pH, C/N ratio and physicochemical properties affected the variation of spontaneous plant establishment on each reclamation site. These comparative study findings may become inputs for coal mining operations management to evaluate and improve their reclamation program; such as by soil reconditions, controlling the populations of IAS, and planting more intensively of native tree species.

Status of Arbuscular mycorrhiza (AM) in nurseries of willow, poplar and pine seedlings in Himachal Pradesh

Poplar and willow are economically-important, fast-growing tree species with the ability to colonize nutrient-poor environments. Willow ( Salix sp .) offers a great potential as a source of renewable energy and for bioremediation and polluted environments. To initiate a study on the possible contribution of arbuscular mycorrhiza to this ability, we isolated mycorrhial fungi from in and around the rhizosphere of native poplar ( Populus sp.), willow ( Salix sp .) and pine ( Pinus sp .) seedlings grown in research nurseries at Dr. Y.S. Parmar University of Horticulture and Forestry, Solan (H.P.). Several species of mycorrhizal fungi grew well in the rhizosphere of these trees, were characterized based on morphological studies. The number of spores per 50 g of rhizosphere soil from pinus, willow and poplar were found to be 1380, 1290, 1300 and 540, 490, 530 spores at 106 µ and 250 µ mesh sieves, respectively. The presence of these AM fungi may help explain the ability of these pioneering tree species to grow under nitrogen limitation. Their presence will be helpful in mitigating the losses due to soil borne diseases as well as enhancing the plant vigor.

Introducing the Potential Medicinal and Ecological Value of a Pioneer Tree Species as a Justification to Conserve and Sustainably Manage Tropical Secondary Forests: Vismia macrophylla as a Case Study

Increasingly, secondary forests in Costa Rica are cleared before having the decades needed to reach maturity. This paper investigates the medicinal and ecological value that a small community in Costa Rica's Northern Zone receives from regenerating secondary forests by presenting a case study of pioneer tree species Vismia macrophylla. Two expert healers within this community described V. macrophylla's antifungal properties; one further demonstrated its harvest, preparation, and application. To supplement local medicinal knowledge, we completed a gas chromatography and mass spectrometry analysis of V. macrophylla tissue. We found potential antibiotic efficacy, which we suggest is primarily linked to acetic acid, and identified hexanal, which is recognized as antifungal. We surveyed V. macrophylla demography and surrounding plant diversity in 20-50 m2 plots in the primary and secondary forests to better understand the ecological context in which it occurs. We found V. macrophylla grew taller and wider in secondary forests. Furthermore, plant diversity was similar between primary and secondary forest plots with V. macrophylla. Our findings highlight the value of secondary forests in providing medicinally important species, like V. macrophylla, to their neighboring communities as they undergo succession. Our study illustrates how interdisciplinary ethnographic, chemical, and ecological research can be used to promote the sustainable use and preservation of recovering secondary forests for the benefit of the communities they surround.

Mapping Atlantic rainforest degradation and regeneration history with indicator species using convolutional network.

The Atlantic rainforest of Brazil is one of the global terrestrial hotspots of biodiversity. Despite having undergone large scale deforestation, forest cover has shown signs of increases in the last decades. Here, to understand the degradation and regeneration history of Atlantic rainforest remnants near São Paulo, we combine a unique dataset of very high resolution images from Worldview-2 and Worldview-3 (0.5 and 0.3m spatial resolution, respectively), georeferenced aerial photographs from 1962 and use a deep learning method called U-net to map (i) the forest cover and changes and (ii) two pioneer tree species, Cecropia hololeuca and Tibouchina pulchra. For Tibouchina pulchra, all the individuals were mapped in February, when the trees undergo mass-flowering with purple and pink blossoms. Additionally, elevation data at 30m spatial resolution from NASA Shuttle Radar Topography Mission (SRTM) and annual mean climate variables (Terraclimate datasets at ∼ 4km of spatial resolution) were used to analyse the forest and species distributions. We found that natural forests are currently more frequently found on south-facing slopes, likely because of geomorphology and past land use, and that Tibouchina is restricted to the wetter part of the region (southern part), which annually receives at least 1600 mm of precipitation. Tibouchina pulchra was found to clearly indicate forest regeneration as almost all individuals were found within or adjacent to forests regrown after 1962. By contrast, Cecropia hololeuca was found to indicate older disturbed forests, with all individuals almost exclusively found in forest fragments already present in 1962. At the regional scale, using the dominance maps of both species, we show that at least 4.3% of the current region's natural forests have regrown after 1962 (Tibouchina dominated, ∼ 4757 ha) and that ∼ 9% of the old natural forests have experienced significant disturbance (Cecropia dominated).

Organic matter transformation in post-agrogenic soils of the Middle Taiga zone

Objective. The purpose is to study the organic matter transformation in Podzols from the middle taiga zone.Methods. The study materials are arable lands from the central regions of the Komi Republic. These lands are not agriculturally used since the early 90-ies of the former century. The soil analyses are done according to the common methods.Results. The study allows for the humus profile structure of Podzols along with the following successive stages as meadow idle land young forest dwarf shrub-green moss spruce forest. It also describes the mechanisms of post-agrogenic humus transformation in agricultural sod Podzols due to the self­ restoring succession.Conclusion. Initially, the post-agrogenic soils normally repeat agrozems by characteristics. The upper soil part forms a thin grey-humus (sod) horizon. It contains large amounts of humus, exchangeable cations, and nutrition elements. The specific synthesis and destruction processes of humic substances at the meadow idle land stage change the qualitative humus composition. In contrast with arable lands, the humus composition is dominated with fulvic acids as being best appropriate to the concerned bioclimatic zone. The humuc-fulvic humus composition holds only in the upper old-arable soil part of the meadow idle land. The appearance of pioneer tree species increases the dominating position of FAs and the Cha/Cfa ratio resembles that for forest soil. The organic matter is poor in nitrogen compounds, especially at the young forest stage. By the C/N ratio, the post-agrogenic soils also gradually get close to naturally formed soils under virgin forest.

Root Traits and Biomechanical Properties of Three Tropical Pioneer Tree Species for Forest Restoration in Landslide Areas

Frequent earthquakes, monsoon torrential rains and typhoons cause severe landslides and soil erosion in Taiwan. Hibiscus taiwanensis, Macaranga tanarius, and Mallotus paniculatus are major pioneer tree species appearing on landslide-scarred areas. Thus, these species can be used to restore the self-sustaining native vegetation on forest landslides, to control erosion, and to stabilize slope. However, their growth performance, root traits and biomechanical properties have not been well characterized. In this study, root system and root traits were investigated using the excavation method, and biomechanical tests were performed to determine the uprooting resistance, root tensile strength and Young’s modulus of 1-year-old Hibiscus taiwanensis, Macaranga tanarius, and Mallotus paniculatus seedlings. The results reveal that relative to H. taiwanensis, M. tanarius and M. paniculatus seedlings had significantly larger root collar diameter, longer taproot length, higher root biomass, higher root density, higher root length density, heavier root mass, larger external root surface area, higher root tissue density, larger root volume, longer total root length, and a higher root tip number. Additionally, the height of M. paniculatus seedlings was significantly higher than those of H. taiwanensis and M. tanarius. Furthermore, the uprooting resistance and root tensile strength of M. paniculatus seedlings was significantly higher than those of H. taiwanensis and M. tanarius. Young’s modulus of M. paniculatus and M. tanarius seedlings was also significantly higher than that of H. taiwanensis. These growth characteristics and biomechanical properties demonstrate M. paniculatus and M. tanarius are superior than H. taiwanensis, considering growth performance, root anchorage capability, tensile strength and Young’s modulus. Taken as a whole, the rank order for species selection of these pioneer species for reforestation comes as: M. paniculatus M. tanarius H. taiwanensis. These results, along with knowledge on vegetation dynamics following landslides, allow us to better evaluate the effect of selective removal management of pioneer species on the resilience and sustainability of landslides.

COMPARATIVE VESSEL TRAITS OF MACARANGA GIGANTEA AND VATICA DULITENSIS FROM MALAYSIAN BORNEO

Trade-offs in wood anatomical characteristics reflect different strategies used by trees to deal with water transport in response to variation in environmental conditions. To study vascular strategies for Bornean rainforest trees, we compared water transport-related anatomical characteristics in branch wood between the common tree species Vatica dulitensis (Dipterocarpaceae) from old-growth forest and the common pioneer tree species Macaranga gigantea (Euphorbiaceae) from selectively logged forest. We hypothesised that the vessel traits of the pioneer species would reflect the need to capture and transport resources to support its fast growth rate (resource-acquisitive strategy), while the species of the old-growth forest would display more conservative vessel traits (resource-conservative strategy). We found that M. gigantea had significantly greater vessel area, hydraulically weighted diameter, vessel area to number ratio, and potential hydraulic conductivity than V. dulitensis. These results suggest that vessel traits of the common old-growth species would ensure high hydraulic safety during occasional drought when soil moisture is limited, while the common species of selectively logged forest possesses an efficient water transport system but its vessels would confer lower hydraulic safety during drought conditions. These contrasting vascular strategies highlight the potential for divergent responses of species of Bornean forest trees to future climatic extremes.

Adaptation of Pioneer Plant at the Coal Mining Area in East Kalimantan Indonesia

Environment quality decrease is one of the impact of coal mining activities in East Kalimantan. The land becomes barren and critical, making it difficult for plants to grow and adapt, therefore post-mining area needs to be rehabilitated to restore the soil of the land as an important factor in crop cultivation. Before being planted with local trees, the environmental conditions must be suitable for seedlings to be planted. One of the pioneer plants functions is to stabilize the post-mining environmental conditions. The objective of this study was to determine a pioneer species that have a well adapt to the post-coal mining environment in East Kalimantan. This study using completely randomized block design. The plot used a rectangular 30×25 meter plot of 15 plots for five pioneer tree species. Data collected were the plant life percentage, plant height, stem diameter and crown diameter. The study result showed that from the five species of pioneer plants there were three species has an optimal growth they are Alstonia scholaris, Homalanthus populneus and Croton argyratus. Based on the List Significance Difference test 5% level results shows the Alstonia scholaris and Croton argyratus life percentage is not significantly different with Homalanthus populneus, but it is very different from Macaranga gigantea and Trema tomentosa. Homalanthus populneus is the most adaptable pioneer species in the open area, its growing in the open post-mining area and from the forest with has intact condition. The genetic factors really affect the adaptation and growth of pioneer plants in post-mining areas.

Spatial distribution and interspecific association patterns between Mansonia altissima A. Chev., Ceiba pentandra (L.) Gaertn and Triplochiton scleroxylon K. Schum. in a moist semi-deciduous forest

Mansonia altissima A. Chev. has an aggregated distribution at the juvenile life stage that becomes random at the mature life stage. Ceiba pentandra (L.) Gaertn could play the role of nurse plant in the management of M. altissima populations providing them a moderate forest shade in large gaps for early growth. M. altissima and Triplochiton scleroxylon K. Schum. displayed independent distribution patterns. M. altissima is a species with economic value found in moist semi-deciduous forests of tropical Africa. The analysis of spatial distribution patterns can help to understand the ecology of this species in forest stands dominated by emergent pioneer tree species like C. pentandra and T. scleroxylon. To assess the spatial distribution patterns of M. altissima and spatial relationships with C. pentandra and T. scleroxylon in their natural habitat. We investigated the spatial patterns of the three species during three life stages; juvenile (immature trees), premature (trees with minimum flowering diameter) and mature (trees with minimum fruiting diameter). Diameter at breast height (DBH) was measured and geographical coordinates of trees were recorded within ten one-ha plots, divided into sixteen subplots (625 m2). We computed the L(r) function, normalized from Ripley’s K(r) function to detect aggregated, random or regular distribution patterns. Aggregations were detected in juvenile and premature M. altissima. Size and scales of spatial aggregation were inversely proportional to the DBH size. M. altissima and C. pentandra displayed interspecific association patterns at the similar life stages. Both species were positively associated within a radius ≥ 3 m. No positive association was detected between M. altissima and T. scleroxylon. Interspecific association patterns between M. altissima and C. pentandra suggest that C. pentandra could be used as a nurse tree in reforestation and management practices of M. altissima populations.

The effect of different anthropogenic disturbances on litterfall of a dominant pioneer rain forest tree in Gabon

AbstractTropical rain forests worldwide are affected by anthropogenic disturbances, and secondary forests that develop afterwards are often dominated by pioneer tree species, but the consequences of different anthropogenic disturbances on nutrient cycling are poorly understood. Because most nutrient cycling in tropical rain forests occurs through litterfall and in the soil organic layer, we measured litterfall of a widespread and dominant pioneer tree, okoume (Aucoumea klaineana, Burseraceae) in Gabon, in one forest previously disturbed by logging and in another by agriculture. Litterfall of okoume trees, measured over 14 months, was 18.2 Mg ha−1 year−1 in the formerly logged forest, which was 72.6% greater than in the forest more recently disturbed by agriculture (10.6 Mg ha−1 year−1). Litter decomposition rates were more rapid in the formerly logged forest, and this may explain why litter thickness was 32% lower in the formerly logged forest, despite the greater litterfall within it. Our results highlight that two widespread anthropogenic disturbances in Gabonese rain forests have significantly different consequences on litterfall of a dominant tree and therefore are likely to have different effects on nutrient cycling and forest ecosystem function.

Efek Timbal (Pb) Terhadap Pertumbuhan dan Adaptabilitas Acacia mangium Pada Tailing Emas

Gold mining is a human activity with high environmental risk through its tailing, due to the heavy metals content. Lead (Pb) is one of dangerous heavy metals in the world, because its toxicity to organism and environment. Phytoremediation is a method to remove hazard pollutant from environment by using plant. Acacia mangium is fast growing and pioneer tree species which mostly grow on the secondary forest as well as marginal land. Usually, this species is used for revegetation on postmining land. Study on Pb effect to A. mangium is an important issue to support phytoremediation advancement as well as for forest restoration. This study aimed to analyze the effect of Pb with several levels toward the growth and adptability of A. mangium on the gold tailing. The results showed that Pb increment on tailing were significantly effect on the growth and adaptability of the plants. A. mangium showed a well performance even on 900 mg Pb/kg tailing with high tolerance index (TI &gt; 100%). Moreover, this species had ability to accumulate Pb in the root higher than shoot tissue. A. mangium had a good potency as phitoremediant plant, also as revegetation plant on the marginal land, such as on the gold mining tailing. Key words: Acacia mangium, heavy metal, lead, phytoremediation, Pb

Biomass estimation model for small diameter Auri tree (Acacia auriculiformis A. Cunn. ex Benth.)

Auri (Acacia auriculiformis A. Cunn. ex Benth.) is one of pioneer tree species developed in forest and land rehabilitation. This species can be used as a short-rotation plantation forest for biomass energy source that produces small diameter stem. The potential use of small diameter auri needs to be supported by accurate biomass estimation. This study aims at developing biomass estimation model for young, small diameter auri tree and comparing the local model to generic model. Measurements were carried out on 92 samples of 2-years old auri tree planted with stand densities of 1850-2500 trees/ha. Data was analysed using 8 local models and compared to 5 generic models. Result of the study shows that the best model for estimating small diameter auri biomass is B1 model (B = 0.016(D20)2.78). The comparison of local and generic models suggested that the local model is better in predicting the auri biomass. This model is valid for small diameter auri species in West Nusa Tenggara Province. This model also seems reliable to apply in similar climatic region, but need a local data validation.