Microbial Population Dynamics under Tropical Trees in an Arboretum

We evaluated carbon stock accumulation on potential of tree species in five forest-types in Omo Forest Reserve of western Nigeria. This included four forest plantations and a natural forest of mixed species. The reserve was stratified into Gmelina arborea, Tectona grandis, Pinus carebeae and Nauclea diderrichii plantations as well as natural forest. Each forest-type was assessed using circular plot method. Plot points were pre-determined using remote sensing. For each point, two circular plots were established, the main plot with a radius of 12.61 m (500 m2 ) and the subplot with a radius of 5.64 m (100 m2 ). In each plot, tree Dbh and height were measured for trees with Dbh ≥10 cm, while only trees with Dbh <10 cm but >2 cm (i.e. 2 cm ≤ Dbh < 10 cm) were considered in the sub-plot. Soil samples were also collected at 10 locations with 2 each in the north, south, east, west and at the plot centre, in each forest-type. The samples were analysed to obtain soil organic carbon. Above- and belowground biomass and carbon stocks were estimated using the appropriate allometries formulated for the tropics. All empirical relationships were included in the existing allometries with Dbh and height as predictors. Landsat images of the reserve in 1991, 2000, 2014 and 2019 were processed and analysed to assess forest degradation. The results revealed that 23-year-old Pinus caribaea plantation sequestered more carbon (35.78±2.73 tons/ha) than 35-year-old Gmelina arborea (18.96±1.82 tons/ha), 43-year-old Tectona grandis (17.75±2.13 tons/ha) and 43-year-old Nauclea diderrichii (17.36±1.87 tons/ha) plantations and natural forest (21.98±2.38 tons/ha). The study showed that stand density influences carbon stock accumulation of forest. It was observed that individual stems of Pinus caribaea were better carbon accumulators than Gmelina arborea, Tectona gransdis and Nauclea diderrichii. The same trend was observed for CO2 captures as Pinus caribaea captured 131.31±10.02 tons/ha with Nauclea diderrichii the least, having a value of 63.71±6.9 tons/ha.
 Keywords: Biomass, Carbon stock, Degradation, Forest-type, Stand density

Stem volume models play an important role in forest management, evaluating the economic value of a forest stand and assisting forest managers and other interested parties in determining the optimal strategies for the utilization and conservation of forest resources. Little attention is given to the use of multivariate regression models for plantation species in the study area. This study involved the development of a multivariate regression equation with continuous and categorical independent variables for simultaneous prediction of merchantable volume for <i>Gmelina arborea</i> and <i>Tectona grandis</i> in Dogo-Ketou Forest Reserve. Simple random sampling technique was adopted for plot location from the selected two plantations. Thirty-one temporary plots of dimension 25m by 25m were selected for complete enumeration in all the two plantations of the same age. Tree growth variables measured included diameter at breast height (Dbh) and merchantable height. All data obtained were analyzed using descriptive statistics and multivariate regression analysis. The predictors for the equation were Dbh, merchantable height and tree species type. The results of the analysis revealed that <i>Gmelina arborea</i> exhibited higher average Dbh and height, wider Dbh and height range, more pronounced positive skewness in Dbh distribution, and more negative skewness in height distribution compared to <i>Tectona grandis</i>. Kurtosis values indicated relatively flatter Dbh and height distributions for both species, with <i>Gmelina arborea</i> showing a more peaked height distribution. Gmelina arborea also showed higher mean volume than <i>Tectona grandis</i>. The multivariate regression model developed is: Volume (m³) = -0.467 + 0.024*(Height) + 2.683*(Dbh) + 0.016 (Tree species) with R² of 91.3%. The diameter at breast height (Dbh), height, and tree species were found to be statistically significant predictors for stem volume estimation. The developed model for both plantation species will provide useful basis for yield prediction in the study area.

In this investigation the extent to which sediment salinity gradients can be used to predict the sensitivity of microbial populations in mangrove ecosystem was investigated. The microbial groups monitored were heterotrophic bacteria, coliform bacteria, actinomycetes, fungi and yeasts. Pearson's Product-Moment Correlation (r) analyses were done on Log10-transformed estimates of population densities. The values obtained from the intertidal (epipellic) and subtidal (benthic) sediments were less than the critical value of 0.707 (n=8, p=0.05). This indicates that salinity was less closely related to the microbial population densities. A positive but insignificant relationship was found for fungi (r=0.03) in intertidal sediment. The total heterotrophic bacteria (r=-0.69), coliforms (r=-0.54), actinomycetes (r=-0.43) and yeasts (r=-0.56) were negatively affected by salinity in epipellic sediment. But in the benthic sediment, total heterotrophic bacteria (r=0.55) and unexpectedly, the fungi (r=0.58) and actinomycetes (r=0.29) exhibited positive but insignificant correlations while coliform and yeast counts in the benthic sediments were negatively influenced by salinity. However the coefficient of determinations (R2) revealed that total heterotrophic bacteria (48.06%) and yeasts (31.18%) were more extensively distributed in the intertidal sediments than coliforms. (29.38%,actinomycetes (18.68%) and fungi (0.09%). In contrast, the fungi (33.48%) demonstrated a wider distribution in benthic sediment. This may be ascribed to their existence, mostly as dormant, but culturable spores in the anoxic bottom sediment. The weak relationship exhibited by coliforms further confirms their usefulness as indicator of faecal contamination in estuarine ecosystem.

Physical and flame characteristics of fifteen tree species in South-East Nigeria were investigated. The tree species Daniellia oliveri, Anacadium occidentale, Vitex doniana, Lonchocarpus griffonianus, Gmelina arborea, Nauclea latifolia, Tectona grandis, Mangifera indica, Delonix regia, Newbouldia laevis, Azadirachta indica, Dialium guineense, Terminalia superba, Manilkara obovata and Irvingia gabonensis were identified and named by taxonomists. The aim was to investigate the effects of oven and sun dried densities of timbers on major flame characteristics (ignition time, flame propagation rate, after glow time, flame duration and ash formation) and to establish timber density relationship with the flame properties. Physical properties (density and moisture content) and flame characteristics of all the timbers were carried out using their respective standard methods. Oven and sun dried densities of timbers ranged from 0.39 to 0.97 and 0.45 to 1.16 g/cm3 respectively. Moisture content of oven and sun dried timbers ranged from 8.02 to 11.56% and 8.15 to 11.65 % respectively. The range of values for ignition time were (3.00-10.00) seconds for oven dried timbers and (5.00-10.00) seconds for sun dried timbers. Flame propagation rate ranged between 0.15 and 0.27 cm/s and from 0.09 to 0.25 cm/s for oven and sun dried timbers respectively. The values for flame duration ranged from 12.00 to 56.00 seconds for oven dried timbers and 7.00 to 45.00 seconds for sun dried timbers. Afterglow times of oven and sun dried timbers ranged from 70.00 to 267.00 and 19.00 to 188.00 seconds respectively. Ash formation values ranged from 0.19 to 2.38 and 0.25 to 2.46 % for oven and sun dried timbers respectively. Combustion/pyrolysis pattern of oven and sun dried timbers on exposure to fire was similar. Density related to flame propagation rate, although, for the denser hard woods above 0.60g/cm3 and 0.70g/cm3 for oven and sun dried timbers respectively, this dependence was less straight forward. The flame characteristics of the oven dried timbers compared favourably with sun dried timbers and showed that ignition time, flame duration, afterglow time and ash formation have no clear relationship with timber density.

Soil properties, such as carbon stock, nitrogen stock, cation exchange capacity (CEC), bulk density (BD), and pH, may have a different status when the forest type changes. We were interested in how tree species identity and diversity affect soil properties. Forest soil profiles were sampled at a fixed depth (0–10, 10–20, 20–40, and 40–60 cm). The abovementioned soil properties were compared by species to demonstrate the influence of tree species identity. We calculated the true Shannon diversity index and evaluated tree species diversity effects on soil properties. We found that the soil BD, CEC, and pH were all influenced by tree species identity. Tree species diversity only showed a negative effect on soil carbon stock; in contrast, a positive effect on soil nitrogen stock in the 0‐ to 10‐cm soil layer was found. High diversity could lead to a change in the soil nutrient conditions in the form of C/N ratio decreases. In contrast, tree species diversity had a marginal effect on the soil BD, pH, and CEC. We concluded that tree species identity was a strong driver of soil properties in the study area, especially in the 0‐ to 10‐cm layer, and that tree species diversity only altered the soil nutrient condition to some extent.

Abstract. Hossen S, Hossain MK, Hossain MA, Uddin MF. 2020. Quantitative assessment of tree species diversity of Himchari National Park (HNP) in Cox’s Bazar, Bangladesh. Asian J For 5: 1-7. The aim of the study was to assess the tree species composition, dominance, and quantitative distribution of tree species of Himchari National Park, Cox’s Bazar in Bangladesh through stratified random sampling method using sample plots (51) of 20 m x 20 m in size during the period of January 2017 to May 2018. A total of 961 stems (dbh ≥ 5 cm) of 88 tree species belonging to 64 genera and 37 families were enumerated where the stem density and basal area were 457.39 stem ha-1 and 10.979 m2 ha-1 respectively. On the other hand, the species diversity index, Shannon-Wiener’s diversity index, Shannon’s maximum diversity index, species evenness index, Margalef’s diversity index, and Simpson’s diversity index were 0.092, 3.733 ± 0.0071, 4.477, 0.834, 12.667 and 0.039 ± 0.0003 respectively. The highest Importance Value Index (IVI) was found for Acacia auriculiformis (23.23) followed by Tectona grandis (13.05), Gmelina arborea (12.66), Syzygium fruticosum (12.34), Casuarina equisetifolia (10.57), and Dipterocarpus turbinatus (10.55). The IVI value represents that Acacia auriculiformis possess highest dominance that is followed by Tectona grandis and Gmelina arborea. Percentage distribution of tree individuals into different height classes found in quadrats showed that height range 3 - &lt;8 m had the highest (59.83%) percentage of tree individuals. On the other hand, different dbh (having dbh ≥5 cm) classes showed that most of the trees (65.97%) belonged to dbh range 5 - &lt;15 cm. The outcome of present study suggests for the protection, sustainable management, and conservation of the tree resources of HNP, Cox’s Bazar, Bangladesh.

Agricultural practices linked to shifts in groundwater microbial structure and denitrifying bacteria

This study was aimed at identifying indigenous microorganisms from palm oil mill effluent (POME) and to ascertain the microbial load. Isolation and identification of indigenous microorganisms was subjected to standard microbiological methods and sequencing of the 16S rRNA and 18S rRNA genes. Sequencing of the 16S rRNA and 18S rRNA genes for the microbial strains signifies that they were known as Micrococcus luteus 101PB, Stenotrophomonas maltophilia 102PB, Bacillus cereus 103PB, Providencia vermicola 104PB, Klebsiella pneumoniae 105PB, Bacillus subtilis 106PB, Aspergillus fumigatus 107PF, Aspergillus nomius 108PF, Aspergillus niger 109PF and Meyerozyma guilliermondii 110PF. Results revealed that the population of total heterotrophic bacteria (THB) ranged from 9.5 × 105 – 7.9 × 106 cfu/mL. The total heterotrophic fungi (THF) ranged from 2.1 × 104 – 6.4 × 104 cfu/mL. Total viable heterotrophic indigenous microbial population on CMC agar ranged from 8.2 × 105 – 9.1 × 106 cfu/mL and 1.4 × 103 – 3.4 × 103 cfu/mL for bacteria and fungi respectively. The microbial population of oil degrading bacteria (ODB) ranged from 6.4 × 105 – 4.8 × 106 cfu/mL and the oil degrading fungi (ODF) ranged from 2.8 × 103 – 4.7 × 104 cfu/mL. The findings revealed that microorganisms flourish well in POME. Therefore, this denotes that isolating native microorganisms from POME is imperative for effectual bioremediation, biotreatment and biodegradation of industrial wastewaters.

China is currently the only country that has commercialized genetically engineered tree species, and this has attracted worldwide attention. As a perennial tree species, transgenic poplar has a long growth cycle and needs to be tested for long-term ecological risks. The main purpose of this study was to explore the ecological safety of perennial transgenic poplars in arthropod community, physical and chemical properties of soil, gene flow, and soil microbial diversity. The study found transgenic poplars could effectively inhibit the number of pests. Moreover, transgenic poplar 741 did not affect the stability of the arthropod community. Studies on the microbial diversity of poplar showed that transgenic poplars did not affect the physical and chemical properties of the soil and the soil microbial community structure. Furthermore, the microbial community structure was obviously affected by location and season. The results showed that a 5-year-old transgenic 741 poplar did not pose an ecological risk, and did not affect the microbial community structure or functional diversity. This study provides a reference for the ecological security evaluation of transgenic poplars, and provides a theoretical basis for promoting the commercialization of transgenic poplars.

In summer 2018, Central Europe was hit by an extreme drought event that widely impacted ecosystems and markedly increased tree mortality in forest ecosystems across the continent. As climate models predict an increase in frequency and severity of such events, there is an urgent need to adapt forests in order to maintain the diverse benefits they provide. Soil processes play an essential role in this context and are key for a plethora of terrestrial ecosystem functions, but they are strongly dependent on water availability. Here, we investigated how tree species richness (TSR), composition, and identity in a 13‐year‐old temperate tree diversity experiment influenced selected ecosystem functions (as important representatives of different ecosystem processes) during the 2018 summer drought. We focused on the stability of soil microbial biomass and standard litter decomposition, as well as tree species‐specific mortality rates. Contrary to our expectations, TSR did not generally increase the resistance of soil functions or decrease tree mortality rates. However, the resistance of these functions was determined by tree species identity and community composition. For the resistance of both soil functions (microbial biomass and litter decomposition), we found that TSR effects depended on the presence of certain tree species. Moreover, we found that the performance of a specific tree species in monoculture, Norway spruce, was a poor predictor of its response to drought in tree species mixtures. Taken together, the results of our study demonstrate that the species composition of tree stands determines tree mortality and the resistance of soil functions under drought. This indicates that enhancing multiple ecosystem functions under environmental disturbance requires maintaining diverse forests.

Microbial communities composed of bacteria, archaea and fungi play a pivotal role in driving the biogeochemical cycles in the marine ecosystem. Despite the vastness of the South Indian Ocean, only a few studies reported the simultaneous analysis of bacterial, archaeal and fungal diversity therein, particularly archaeal and fungal communities in deep-sea environments received less attention previously. In this study, microbial diversity, community composition and dynamics in microbial community structure in eight deep-sea sediment samples collected from different sites at varying depths of the South Indian Ocean were explored using Next-Generation Sequencing. In total, 21 bacterial phyla representing 541 OTUs were identified from the eight samples, where phylum Proteobacteria was found as the most abundant bacterial phylum in five out of eight samples. Firmicutes and Chloroflexi were the dominant phyla in the rest of the three samples. In the case of archaea, uncultured species belonging to the phyla Thaumarchaeota and Euryarchaeota were the abundant taxa in all the samples. Similarly, Ascomycota and Basidiomycota were the most abundant fungal phyla present therein. In all the eight samples studied here, about 10-58% and 19-26% OTUs in archaeal and fungal communities were mapped to unclassified taxa respectively, suggesting the lack of representation in databases. Co-occurrence network analysis further revealed that bacterial communities tend to be more dynamic than archaeal and fungal communities. This study provides interesting insights into the microbial diversity, community composition and dynamics in microbial community structure in the deep-sea sediments of the South Indian Ocean.

The dynamics of individual microbial populations and their gene functions in agricultural soils, especially after major activities such as nitrogen (N) fertilization, remain elusive but are important for a better understanding of nutrient cycling. Here, we analyzed 20 short-read metagenomes collected at four time points during 1 year from two depths (0 to 5 and 20 to 30 cm) in two Midwestern agricultural sites representing contrasting soil textures (sandy versus silty loam) with similar cropping histories. Although the microbial community taxonomic and functional compositions differed between the two locations and depths, they were more stable within a depth/site throughout the year than communities in natural aquatic ecosystems. For example, among the 69 population genomes assembled from the metagenomes, 75% showed a less than 2-fold change in abundance between any two sampling points. Interestingly, six deep-branching Thaumarchaeota and three complete ammonia oxidizer (comammox) Nitrospira populations increased up to 5-fold in abundance upon the addition of N fertilizer. These results indicated that indigenous archaeal ammonia oxidizers may respond faster (are more copiotrophic) to N fertilization than previously thought. None of 29 recovered putative denitrifier genomes encoded the complete denitrification pathway, suggesting that denitrification is carried out by a collection of different populations. Altogether, our study identified novel microbial populations and genes responding to seasonal and human-induced perturbations in agricultural soils that should facilitate future monitoring efforts and N-related studies.IMPORTANCE Even though the impact of agricultural management on the microbial community structure has been recognized, an understanding of the dynamics of individual microbial populations and what functions each population carries are limited. Yet, this information is important for a better understanding of nutrient cycling, with potentially important implications for preserving nitrogen in soils and sustainability. Here, we show that reconstructed metagenome-assembled genomes (MAGs) are relatively stable in their abundance and functional gene content year round, and seasonal nitrogen fertilization has selected for novel Thaumarchaeota and comammox Nitrospira nitrifiers that are potentially less oligotrophic than their marine counterparts previously studied.

Soil salinization is one main environmental factor restricting plant growth and agricultural productivity. However, phytoremediation is one of the important means to improve saline-alkali soil by planting halophytes or salt-tolerant plants. In order to study whether there are differences among soil microorganisms in different phytoremediation, the effects of four plants, including alfalfa (MX), oil sunflower (YK), maize (YM) and ryegrass (HMC) on soil physicochemical properties, enzyme activity and microbial community diversity and composition were investigated in this study and the relationships between microbial community structure and soil physicochemical properties, enzyme activity were analyzed. The results showed that all plants treatments significantly decreased pH, TS (total saltinity) and BD (bulk density), while increased OM (organic matter), TN (total nitrogen), AN (available nitrogen), TP (total phosphorus), AP (available phosphorus), TK (total potassium) and TPOR (total porosity), and the number of nitrite bacteria reduced by planting at the same time. Except for YM, other treatments significantly increased the number of nitrifying and denitrifying bacteria compared with CK, while only YK increased that of fungi. Additionally, all plants increased the activity of nitrite reductase and decreased that of urease. More interestingly, plants treatments shifted microbial community compositions, and only YM significantly decreased the bacterial diversity and increased the fungal diversity. Redundancy analysis suggested that TK, pH, BD, TS, AN, OM and nitrite reductase, lignin peroxidase were the key environmental factors that shaped the bacterial community structure, while that of fungi was mainly driven by OM, nitrite reductase, urease and lignin peroxidase. The results indicated that MX and YM are the best choice for remediation of saline-alkali soil. These data can provide certain theoretical basis for the further restoration of saline-alkali land. HIGHLIGHTS The effects of different phytoremediation on microbial diversity and community structure were different. Phytoremediation can significantly decreased pH, TS and BD, while increased OM, TN, AN, TP, AP, TK and TPOR in saline-alkali soil. All plants increased the activity of nitrite reductase and decreased the activity of urease.

Background & aim : In general, biodiversity has positive effects on ecosystem functioning. In forests, understorey vegetation is influenced by both the composition and species richness of the overstorey through species-specific effects on environmental conditions at the forest floor. Forest fragmentation is also known to influence understorey vegetation composition and richness. However, the combined effects of tree species diversity and forest fragmentation have not been studied yet. With the TREEWEB research platform, consisting of 53 forest plots along a tree species diversity and forest fragmentation gradient, we aim to unravel the combined effects of tree species diversity, tree species identity and forest fragmentation on the understorey composition and diversity. Methods : The TREEWEB platform includes forest plots of three tree species richness levels, containing all possible species combinations of Quercus robur, Quercus rubra and Fagus sylvatica. Complete dilution is avoided in the design, allowing separation between tree species identity and diversity effects. Vegetation surveys were conducted in all plots to investigate the species richness, species diversity, compositional turnover and cover of the herb layer as well as the shrub layer cover. Key results : Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects. No clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found. Conclusion : Tree species identity effects were most important in explaining the observed patterns in the understorey vegetation. Further in-depth research will allow us to disentangle which mechanisms underlie these patterns and whether effects of fragmentation are more pronounced at higher trophic levels.

Lonar Lake is a hypersaline and hyperalkaline soda lake and the only meteorite impact crater in the world situated in basalt rocks. Although culture-dependent studies have been reported, a comprehensive understanding of microbial community composition and structure in Lonar Lake remains elusive. In the present study, microbial community structure associated with Lonar Lake sediment and water samples was investigated using high-throughput sequencing. Microbial diversity analysis revealed the existence of diverse, yet largely consistent communities. Proteobacteria (30%), Actinobacteria (24%), Firmicutes (11%), and Cyanobacteria (5%) predominated in the sequencing survey, whereas Bacteroidetes (1.12%), BD1-5 (0.5%), Nitrospirae (0.41%), and Verrucomicrobia (0.28%) were detected in relatively minor abundances in the Lonar Lake ecosystem. Within the Proteobacteria phylum, the Gammaproteobacteria represented the most abundantly detected class (21–47%) within sediment samples, but only a minor population in the water samples. Proteobacteria and Firmicutes were found at significantly higher abundance (p ≥ 0.05) in sediment samples, whereas members of Actinobacteria, Candidate division TM7 and Cyanobacteria (p ≥ 0.05) were significantly abundant in water samples. Compared to the microbial communities of other hypersaline soda lakes, those of Lonar Lake formed a distinct cluster, suggesting a different microbial community composition and structure. Here we report for the first time, the difference in composition of indigenous microbial communities between the sediment and water samples of Lonar Lake. An improved census of microbial community structure in this Lake ecosystem provides a foundation for exploring microbial biogeochemical cycling and microbial function in hypersaline lake environments.