Soil Bacterial Community Shifts Are Driven by Soil Nutrient Availability along a Teak Plantation Chronosequence in Tropical Forests in China

Soil bacterial communities play crucial roles in ecosystem functions and biogeochemical cycles of fundamental elements and are sensitive to environmental changes. However, the response of soil bacterial communities to chronosequence in tropical ecosystems is still poorly understood. This study characterized the structures and co-occurrence patterns of soil bacterial communities in rhizosphere and bulk soils along a chronosequence of teak plantations and adjacent native grassland as control. Stand ages significantly shifted the structure of soil bacterial communities but had no significant impact on bacterial community diversity. Bacterial community diversity in bulk soils was significantly higher than that in rhizosphere soils. The number of nodes and edges in the bacterial co-occurrence network first increased and then decreased with the chronosequence. The number of strongly positive correlations per network was much higher than negative correlations. Available potassium, total potassium, and available phosphorus were significant factors influencing the structure of the bacterial community in bulk soils. In contrast, urease, total potassium, pH, and total phosphorus were significant factors affecting the structure of the bacterial community in the rhizosphere soils. These results indicate that available nutrients in the soil are the main drivers regulating soil bacterial community variation along a teak plantation chronosequence.

Impact of Human Activities on the Distribution of Termite Communities in Teak Plantations (Tectona grandis L. F., Verbenaceae) in the Korhogo Communal Area (North Côte d'Ivoire)

Aims: This study aimed to assess the impact of human activities on termites in teak plantations in the Korhogo communal area. Methodology: Termites were sampled from October to November 2020 using the transect method recommended by Jones and Eggleton (2000). The study was carried out in three teak plantations undergoing different levels of human activities, with a forest fragment as reference area. Five types of human activity were assessed and the overall proportion of human pressure on each habitat was calculated. The species richness (S), Shannon index (H'), Evenness (E) and the relative abundance were calculated of termites for each habitat type. Analyses of variance (ANOVA) were used to compare the species richness and abundance of termites. Results: The results showed that the village plantation of teak (PVT) had the highest degree of human pressure (50.94%), followed by the teak plantation of the forest of Mount Korhogo (TFMK) (29.24%). The teak plantation of Botanical Garden (TJB) was under low pressure (6.60%). A total of 30 species grouped in 19 genera and 8 sub-families of termites were identified in all plots. Termite diversity was high in the forest fragment (19.67 ± 1.15) and in the teak plantation of Botanical Garden (21.33 ± 2.08), but low in the village teak plantation (11 ± 1). The abundance of termites evolves in the same direction as the species richness. Conclusion: Anthropogenic activities affect the trophic composition of termites, particularly the humivore group. Reconstruction of the fauna and flora of the teak forests would be beneficial for the conservation of termite species. In this region, teak forests would thus play a role as a refuge for termite communities, which are recognised as the main soil fertilising organisms in the tropics.

Space Planting, Competition, and Productivity of a Seven-Year-Old Clonal Teak Plantation in the East Java Monsoon Forest Area

Tree breeding of teak results in selected clones with high growth. Intensive silviculture is required to support a large-scale clonal teak plantation. Appropriate spacing is one of the methods to increase forest plantation productivity. Research of teak clone spacing was conducted on a seven-year-old clonal teak plantation with randomized completely block design. The treatments tested in this study were four plant spacing distances, namely, 3 m × 3 m, 6 m × 2 m, 8 m × 2 m, and 10 m × 2 m. Results show that spacing had significantly different effects on diameter, height, bole height, branch angle, crown area, crown projections, volume, and competition index. However, the height growth did not exhibit any significant differences. The 10 m × 2 m spacing produced the best diameter growth, crown area, and competition index, but has a low volume per hectare and the lowest height of free branch and branch angle. Meanwhile, the 3 m × 3 m spacing will increase bole height and stand volume per hectare. This result suggests that spacing could improve the growth of teak clone but must be followed by intensification of proper maintenance to reduce branch angle and increase bole height.

A Comparative Study of Carbon Storage in Two Cocoa (Theobroma cacao) Shade-Types and a Teak Plantation in the Moist Semi-deciduous Forest Zone of Ghana.

on life, it is important that steps are taken to mitigate its effects. With the intensification of cocoa production, there has been a shift in traditional cocoa farming over the years leading to the removal of shade trees, hence, removal of carbon sinks. This study was carried out to compare the amount of carbon stored in cocoa ecosystems to that of a 20 years teak plantation and to calculate the trade-off of carbon between the two systems. Cocoa farms of similar ages (20 years) were selected in which three-subplots were demarcated on each farm at Piase in the Bosomtwe District. Tree Diameter at Breast Height (DBH) was measured and soils samples were collected and analyzed for organic carbon percentage and bulk density. One-way Analysis of Variance was used to analyze above and belowground tree carbon and two-way analysis of variance was used to analyze soil organic carbon stored. Teak plantation recorded higher carbon stock (739.33±2.24 Mg C.ha-1) compared to full sun cocoa (9.36±2.24 Mg C.ha-1). Soil organic carbon across the three farms showed significant (p = 0.0010) variations with depths. The 0-20 cm soil depth stored significantly more (p = 0.0000) organic carbon compared to 20-40 cm soil depth. Total soil carbon stored revealed significant differences amongst the various farms with the full sun (40.857±0.52 Mg C.ha-1) being the least whilst the teak plantation stored the highest (72.42±0.52 Mg C.ha-1). Total carbon (above-ground tree carbon + below-ground tree carbon + soil organic carbon) showed significant difference (p= 0.0000) between land use types with shaded cocoa farm (74.3±0.89 Mg C.ha-1), full sun cocoa farm (32.02±0.89Mg C.ha-1) and that of the teak plantation (950.91±0.89 Mg C.ha-1) respectively. Traditional cocoa ecosystem (shaded cocoa farms) has the potential to store carbon significantly higher than that of the full sun systems.

Variability of throughfall erosivity among crown positions in a teak plantation based on raindrop measurements and throughfall partitioning

<p>Knowledge of throughfall erosivity is necessary for the accurate prediction of soil erosion in some forests with little protective ground cover. This study compared throughfall drops and erosivity between open rainfall and for four different crown positions in a teak plantation in Thailand. Throughfall was partitioned into free throughfall, splash throughfall, and canopy drip using drop size distributions of both open rainfall and throughfall. Relative to open rainfall, we found the following: (1) throughfall drops were lower in number but larger in size due to the coalescence of raindrops on canopies; (2) throughfall drops, especially canopy drip, had lower velocity due to insufficient fall distance from the canopy to the forest floor to reach terminal velocity, which partly depends on crown base height and the vertical distribution of foliage; and (3) throughfall usually had higher kinetic energy due to larger drop size, which depends on the amount of canopy drip and the crown base height. Mid-crown positions were subjected to higher throughfall kinetic energy than in the canopy gap or near-stem positions. Compared to mid-crown positions, the gap position had smaller drops and less canopy drip, while the near-stem position had lower drop fall velocity. The erosivity of throughfall with respect to crown position is useful in the development of high-resolution soil erosion risk maps that can help maintain forest productivity in teak plantations.</p><p>The work was funded by JSPS KAKENHI Grant numbers JP17780119, JP15H05626, and JP17KK0159 and the CREST Program of JST (Japan Science and Technology Agency). A part of the study is published in Nanko et al. (2020) doi:10.1007/978-3-030-26086-6_12. </p>

Early-Season Effects of Wildfire on Soil Nutrients and Weed Diversity in Two Plantations

This study assessed early-season effects of spontaneous wildfires on soil fertility and weed diversity in two managed plantations – cashew and teak – in Ilorin, Nigeria. Soil pH and nutrients in the topsoils and subsoils of burned and unburned plantations plots after a spontaneous wildfire were analysed. Species diversity and similarity were determined based on the composition and abundances of weed flora two months post-fire. The fire effects on soil nutrients and weed composition in the plantations were evaluated using the canonical correspondence analysis. Burns incidence significantly improved the organic carbon, organic matter, and Ca contents while reducing total N and Mg in both plantations. Twenty-eight weed species were distributed in 9 angiosperm families. Fire differently affected weed composition, abundance and diversity in the plantations. Burning improved soil organic carbon and organic matter contents and restricted Tephrosia bracteolata, Desmodium tortuosum, Daniellia oliveri, Senna obtusifolia and Zornia latifolia to the burned cashew plantation. The occurrence of Euphorbia heterophylla, Eriosema psoraleoides and Crotalaria retusa in the burned teak plantation was associated with a direct fire effect on soil Na and Ca contents. Burning influenced soil nutrients in the studied plantations, but weed diversity increased in the teak plantation and was reduced in the cashew plantation.

KERENTANAN KEBAKARAN HUTAN BERDASARKAN KARAKTER UMUR TANAMAN JATI

Forest management in Java dominated with Teak plantation that organize with community. One threats of forest damages is forest fires. Forest fires caused by susceptible fuel, oxygen rate, and fires resource. Teak plantation closed with community activities that using fires within purpose or not. This research aim to identify the effect of plant age towards forest fires susceptibility by combustion rate. This research conducted in Wanagama I EduForest. The effects of plant age towards forest fires susceptibility analysed by bark thickness and water content of bark. Teak bark samples taken on various age of 5th, 15th, and 40th. Foresf fires suceptibility observed by combustion test. The effects of teak age towards on bark thickness and water content, combustion rate analysed using anova with 10% of confident level. The results showed that 1) plant age affecting thickness and water content of teak bark; 2) bark thickness affect fire susceptibility rate of teak on various age, bark thickness has growth along age increase which more tolerant towards of combustion; and 3) Surface forest fires in Wanagama I caused by multiple sources of fire ignition that closed to road accesibility, and the damage mostly occurred until 100 cm of height from forest ground.