The potential of Azadirachta excelsa characteristics as urban trees in residential areas

Residential areas have the potential to conserve economically and ecologically important local tree species. However, local species to be planted in residential areas, including business and office districts, have to meet certain criteria in accordance mainly with the significant tree functions and services. This study was aimed at investigating the potential of Kayu bawang (Azadirachta excelsa) based on the desired characteristics for urban trees. The analysis of tree characteristics was based on their morphometrics which has been conducted in two planting systems, namely monoculture and polyculture, found on the private forests in Bengkulu Province. The two planting systems of Kayu bawang were reflected in the target location (e.g., roadside, park, and yard). Variables used for assessment included total height, the diameter of breast height, clear stem height, live crown height, the diameter of the crown, live crown ratio, crown projection area, and slenderness ratio. The results showed that the tree crown architecture is classified as decurrent, while the average live crown ratio (LCR) was moderate, which had an average live crown ratio (LCR) of 51-64 %, meaning not too dense appearance. The average slenderness ratio (SR) is generally moderate, where SR of Kayu bawang in monoculture system was 76, polyculture was 54 to 81. It can be concluded that this species does not really meet the criteria as urban trees on roadside because they have moderate LCR and SR values, but they can be used to enrich parks and other sites for promoting local tree identity.

Distinct effects of host and neighbour tree identity on arbuscular and ectomycorrhizal fungi along a tree diversity gradient

Plant diversity and plant-related ecosystem functions have been in focus in biodiversity-ecosystem functioning studies. However, in this context, biotic interactions with mycorrhizal fungi have been understudied although they are crucial for plant-resource acquisition. We investigated the effects of tree species richness, tree mycorrhizal type on arbuscular (AMF) and ectomycorrhizal fungal (EMF) communities. We aimed to understand how dissimilarities in taxa composition and beta-diversity are related to target trees and neighbours of the same/different mycorrhizal type. We sampled a tree experiment with saplings (~7 years old), where tree species richness (monocultures, 2-species, and 4-species mixtures) and mycorrhizal type were manipulated. AMF and EMF richness significantly increased with increasing tree species richness. AMF richness of mixture plots resembled that of the sum of the respective monocultures, whereas EMF richness of mixture plots was lower compared to the sum of the respective monocultures. Specialisation scores revealed significantly more specialised AMF than EMF suggesting that, in contrast to previous studies, AMF were more specialised, whereas EMF were not. We further found that AMF communities were little driven by the surrounding trees, whereas EMF communities were. Our study revealed the drivers of mycorrhizal fungal communities and further highlights the distinct strategies of AMF and EMF.

A new Vegetation-Plot Database for the Coastal Forests of Kenya

Biodiversity data based on standardised sampling designs are key to ecosystem conservation. Data of this sort have been lacking for the Kenyan coastal forests despite being biodiversity hotspots. Here, we introduce the Kenyan Coastal Forests Vegetation-Plot Database (GIVD ID: AF-KE-001), consisting of data from 158 plots, subdivided into 3,160 subplots, across 25 forests. All plots include data on tree identity, diameter and height. Abundance of shrubs is presented for 316 subplots. We recorded 600 taxa belonging to 80 families, 549 of which identified to species and 51 to genus level. Species richness per forest site varied between 43 and 195 species; mean diameter between 13.0 ± 9.8 and 30.7 ± 20.7 cm; and mean tree height between 5.49 ± 3.99 and 12.29 ± 10.61 m. This is the first plot-level database of plant communities across Kenyan coastal forests. It will be highly valuable for analysing biodiversity patterns and assessing future changes in this ecosystem. Taxonomic reference: African Plant Database (African Plant Database version 3.4.0). Abbreviations: DBH = diameter at breast height; GIVD = Global Index of Vegetation-Plot Databases; KECF-VPD = Kenyan Coastal Forests Vegetation Plot Database.