pH dominates variation in tropical soil archaeal diversity and community structure

Little is known of the factors influencing soil archaeal community diversity and composition in the tropics. We sampled soils across a range of forest and nonforest environments in the equatorial tropics of Malaysia, covering a wide range of pH values. DNA was PCR-amplified for the V1-V3 region of the 16S rRNA gene, and 454-pyrosequenced. Soil pH was the best predictor of diversity and community composition of Archaea, being a stronger predictor than land use. Archaeal OTU richness was highest in the most acidic soils. Overall archaeal abundance in tropical soils (determined by qPCR) also decreased at higher pH. This contrasts with the opposite trend previously found in temperate soils. Thaumarcheota group 1.1b was more abundant in alkaline soils, whereas group 1.1c was only detected in acidic soils. These results parallel those found in previous studies in cooler climates, emphasizing niche conservatism among broad archaeal groups. Among the most abundant operational taxonomic units (OTUs), there was clear evidence of niche partitioning by pH. No individual OTU occurred across the entire range of pH values. Overall, the results of this study show that pH plays a major role in structuring tropical soil archaeal communities

Distinctive Phyllosphere bacterial communities in tropical trees.

Recent work has suggested that in temperate and subtropical trees, leaf surface bacterial communities are distinctive to each individual tree species and dominated by Alpha and Gammaproteobacteria. In order to understand how general this pattern is, we studied the phyllosphere bacterial community on leaves of six species of tropical trees at a rainforest arboretum in Malaysia. This represents the first detailed study of 'true' tropical lowland tree phyllosphere communities. Leaf surface DNA was extracted and pyrosequenced targeting the V1-V3 region of 16S rRNA gene. As was previously found in temperate and subtropical trees, each tree species had a distinctive bacterial community on its leaves, clustering separately from other tree species in an ordination analysis. Bacterial communities in the phyllosphere were unique to plant leaves in that very few operational taxonomic units (0.5%) co-occurred in the surrounding soil environment. A novel and distinctive aspect of tropical phyllosphere communities is that Acidobacteria were one of the most abundant phyla across all samples (on average, 17%), a pattern not previously recognized. Sequences belonging to Acidobacteria were classified into subgroups 1-6 among known 24 subdivisions, and subgroup 1 (84%) was the most abundant group, followed by subgroup 3 (15%). The high abundance of Acidobacteria on leaves of tropical trees indicates that there is a strong relationship between host plants and Acidobacteria in tropical rain forest, which needs to be investigated further. The similarity of phyllosphere bacterial communities amongst the tree species sampled shows a significant tendency to follow host plant phylogeny, with more similar communities on more closely related hosts

Soil pH and biome are both key determinants of soil archaeal community structure

The mechanisms underlying community composition and diversity of soil archaea are poorly understood. We compared both total archaea and ammonia oxidizing archaea (AOA) using 16S rRNA and amoA genes pyrosequencing respectively, in two different biomes: tropics (Malaysia), and temperate (Korea and Japan). Despite differences in characteristics of these biomes, we found that at the broad taxonomic level the dominant archaeal lineages are the same, except in certain instances (16S rRNA gene: group 1.1a Thaumarchaeota; amoA gene: Nitrososphaera and Nitrosotalea lineages). However, at the OTU level, both total archaea and AOA communities showed biome-specific patterns, indicating that at lower taxonomic levels biome differences are also important. In both biomes, total archaeal diversity showed a negative correlation with pH, but a hump-shaped curve for AOA diversity, peaking at ∼pH 6.0. Within each biome, pH also emerged as the delimiting factor determining variation in community composition of both total archaea and AOA. Communities from each biome clustered separately, even at analogous pH levels. At the OTU level, certain shared OTUs did occur at approximately the same pH range in both biomes. We found that closely related OTUs of both total archaea and AOA respectively tended to co-occur, suggesting that in evolutionary terms these closely related lineages have conserved very similar ecological requirements. This predictability also strongly suggests that soil archaeal community assembly has strongly deterministic aspect. Overall, our findings emphasize that soil archaeal communities are to large extent predictable and structured by both biome and by soil chemical environment, especially pH

Final report on agroforestry Malaysia (study 4) for the period of Dec. 18, 1991 to Dec. 18, 1994

A recent survey showed that 90% of 113700 ha of tin tailings remain barren and unproductive. Realising the importance and development of rehabilitating degraded lands for agroforestry practices, the lnternatio11al Research Center (IDRC) together with Forest Research Institute Malaysia (FRIM) and the Universiti Pertanian Malaysia (UPM) have jointly embarked on a agroforestry project for the rehabilitation of tin tailings. The study conducted by FRIM was specifically aimed at developing a cost effective silvicultural technique for rehabilitation of sand tailing. Four selected multipurpose tree species, namely Melia indica, Acacia auriculiformis, A. mangium and Casuarina equisetifolia were planted at low and high sites of sand tailings, at 1.5 m and 7.5 m above standing water level (a.s.w.l.). respectively, in Malim Nawar, Perak. In addition, A. auriculiformis and A. mangium were also planted at low and high sites of sand tailings, at 1 and 3 m a.s.w.l. respectively, at Satang Berjuntai, Selangor. The effect of soil conditioner was also examined for A. aurlculiformis on sand tailings in Satang Berjuntai. Soil composition, soil temperature, soil moisture, soil chemical properties were also examined for both study sites. Survival and growth parameters such as collar diameter increment and top height increment were also assessed and analysed. At one year after planting, data on physiological parameters involving transpiration and photosynthesis were also collected and analysed, but only from the plots at Malim Nawar. Both study sites at Malim Nawar and Satang Berjuntai are typical sand tailings with more than 95% sand. Sand dunes higher than 3 m a.s.w.l. experienced water deficits in dry day at 15 em depth. Acute water deficits were observed on sand dune with higher percentage of coarse sand. Higher maximum temperature was also recorded at the high sites of sand dunes. Sand tailings has lowered nutrient contents compared to natural forest. Freshly mined-over sand tailings at Satang Berjuntai was observed to be very poor in nutrient contents. At 12 and 30 months after planting, A. auriculiformis has significantly the best survival, collar diameter increment and top height increment at low and high sites of Malim Nawar, Perak and Batang Berjuntai, Selangor. The potential of A. auriculiformis is further supported by having significantly higher water use efficiency (net photosynthesis rate/transpiration rate) compared to A. mangium at all sites. A. mangium when it was freed from defoliators showed prominent growth at low site of sand dune. Though without statistically evidence, individuals of A. hybrid found amongst the A. auriculiformis has better growth than A. auriculiformis at all sites. It was necessary to add soil conditioner for tree planting on sand tailing and the sand dune height no higher than 1.5 m a.s.w.l was recommended. At freshly mined-over site, application of soil conditioner was necessary even after crown closure. Outputs from this study were two scientific publications. Based on the study, a cost effective technique has been developed for tree planting on sand tailing

Tropical Soil Bacterial Communities in Malaysia: pH Dominates in the Equatorial Tropics Too

The dominant factors controlling soil bacterial community variation within the tropics are poorly known. We sampled soils across a range of land use types-primary (unlogged) and logged forests and crop and pasture lands in Malaysia. PCR-amplified soil DNA for the bacterial 16S rRNA gene targeting the V1-V3 region was pyrosequenced using the 454 Roche machine. We found that land use in itself has a weak but significant effect on the bacterial community composition. However, bacterial community composition and diversity was strongly correlated with soil properties, especially soil pH, total carbon, and C/N ratio. Soil pH was the best predictor of bacterial community composition and diversity across the various land use types, with the highest diversity close to neutral pH values. In addition, variation in phylogenetic structure of dominant lineages (Alphaproteobacteria, Beta/Gammaproteobacteria, Acidobacteria, and Actinobacteria) is also significantly correlated with soil pH. Together, these results confirm the importance of soil pH in structuring soil bacterial communities in Southeast Asia. Our results also suggest that unlike the general diversity pattern found for larger organisms, primary tropical forest is no richer in operational taxonomic units of soil bacteria than logged forest, and agricultural land (crop and pasture) is actually richer than primary forest, partly due to selection of more fertile soils that have higher pH for agriculture and the effects of soil liming raising pH.

Nickel-silicide: Carbon contact technology for N-channel MOSFETs with silicon-carbon source/drain

10.1109/LED.2007.910793IEEE Electron Device Letters29189-92EDLE

Global haemostatic tests demonstrate the absence of parameters of hypercoagulability in non-hypoxic mild COVID-19 patients: a prospective matched study

10.1007/s11239-021-02575-4JOURNAL OF THROMBOSIS AND THROMBOLYSI