Tree growth is correlated with hydraulic efficiency and safety across 22 tree species in a subtropical karst forest.

Karst forests are habitats in which access to soil water can be challenging for plants. Therefore, safe and efficient xylem water transport and large internal water storage may benefit tree growth. In this study, we selected 22 tree species from a primary subtropical karst forest in southern China and measured their xylem anatomical traits, saturated water content (SWC), hydraulic conductivity (Ks) and embolism resistance (P50). Additionally, we monitored growth of diameter at breast height (DBH) in 440 individual trees of various sizes over three consecutive years. Our objective was to analyze the relationships between xylem structure, hydraulic efficiency, safety, water storage and growth of karst tree species. The results showed significant differences in structure but not in hydraulic traits between deciduous and evergreen species. Larger vessel diameter, paratracheal parenchyma and higher SWC were correlated with higher Ks. Embolism resistance was not correlated with the studied anatomical traits, and no tradeoff with Ks was observed. In small trees (5-15 cm DBH), diameter growth rate (DGR) was independent of hydraulic traits. In large trees (>15 cm DBH), higher Ks and more negative P50 accounted for higher DGR. From lower to greater embolism resistance, the size-growth relationship shifted from growth deceleration to acceleration with increasing tree size in eight of the 22 species. Our study highlights the vital contributions of xylem hydraulic efficiency and safety to growth rate and dynamics in karst tree species; therefore, we strongly recommend their integration into trait-based forest dynamic models.

Complete chloroplast sequence of Fenerivia ghesquiereana (Annonaceae): a rare and endemic tree from Madagascar.

Fenerivia ghesquiereana (Cavaco & Keraudren) R.M.K. Saunders (Annaonaceae) is a rare and endemic tree restricted to the warm tropical forests of Madagascar, a major global hotspot for biodiversity. Species in the genus are mostly restricted to a thin belt along the eastern edge of the island and remain under intense pressure due to deforestation for logging, mining and slash-and-burn agriculture ('tavy'), despite national pledges to curb biodiversity losses and increase park protection to combat illegal logging and poaching. Here we report the complete chloroplast genome sequence of this species to support ongoing efforts to complete the (sub-)tribal classification of the family. The chloroplast sequence of F. ghesquiereana was 160,194 bp in length, including two inverted repeat regions of 26,093 bp, a large single-copy region of 89,041 bp and a small single-copy region of 18,967 bp. A total of 160 genes were annotated, of which 115 are coding, 37 are tRNA genes, and eight are rRNA genes. The overall GC content was 39%; this was higher in the IRs (43.4%) when compared to the LSC (30.7%) and the SSC (33.9%) regions. A Maximum Likelihood phylogenetic analysis with a selection of other plastomes in Annonaceae placed F. ghesquiereana as sister to Meiogyne hainanensis (Merr.) in subfamily Malmeoideae.