Nature and Periodicity of Growth Rings in two Bangladeshi Mangrove Species

Abstract

SUMMARYNature and periodicity of growth rings were investigated in Sonneratia apetala and Heritiera fomes, two Bangladeshi mangrove species. From both species we collected three stem discs in the natural forest reserve of the Sundarbans. In addition, three discs were sampled from plantation-grown S. apetala trees of known age. Sanded stem discs revealed distinct growth rings but no periodic fluctuations in vessel variables (vessel density, vessel diameter, vessel grouping), which were measured at high resolution along a transect from pith to bark. The number of growth rings in plantation-grown S. apetala trees corresponded with the documented tree age, hence strongly suggesting the growth rings to be annual. Within species, the annual nature of the rings was further supported by a good match between the tree-ring series. The similar mean curves of S. apetala and H. fomes, growing at the same site in the Sundarbans, pointed to the presence of an external factor influencing their growth. A combination of precipitation and temperature was suggested influencing substrate salinity and phenological events. It became evident that tree-ring research in combination with the analysis of vessel patterns is a valuable tool to further investigate the complex interactions between tree growth and site ecology in mangrove forests.

Salinity drives growth dynamics of the mangrove tree Sonneratia apetala Buch. -Ham. in the Sundarbans, Bangladesh

“…In the low salinity zone (LSZ), the average radial growth of S. apetala is considerably higher than that those of medium (MSZ) and higher salinity (HSZ) zone (Table 2). The average radial growth rate (3.02 ± 1.20 mm) is within the range of the earlier study of Chowdhury et al (2008), where the ring width ranges from 0.40 to 7.00 mm with an average of 2.00 ± 1.00 mm. The lower growth rate in the higher salinity zone indicates a negative influence on tree physiology (Siddiqi et al, 1989).…”

“…Stem asymmetry can also be related to growth stress during stem development due to inundation, sedimentation, erosion, seasonal storms and anthropogenic disturbances (Ellison et al, 2000;Robert et al, 2011). The possibility to crossdate growth ring within and among the samples of S. apetala provides strong evidence that the growth rings are indeed annual driven by seasonality in climate and environmental factors as suggested in previous studies by Chowdhury et al (2008) and Maxwell et al (2018). When comparing growth ring series of S. apetala from the Sundarbans studied by Maxwell et al (2018) with those of our trees from the low (LSZ) (Fig.…”

“…The higher salinity stress due to lower freshwater input might be reflected as more unfavourable growth conditions for trees (Menezes et al, 2003;Robert et al, 2011). The range of average growth rate of S. apetala corresponds well with Rhizophora mucronata (0.50-4.81 mm year −1 ) from Gazi Bay, Kenya (Verheyden et al, 2004), but higher growth rate exhibited than Avicennia marina (1.00 mm year −1 ) from Kenya (Schmitz et al, 2008), Xylocarpus granatum (0.62-2.51 mm year −1 ), Bruguiera gymnorrhiza (0-2.51 mm year −1 ), Rhizophora mucronata (0.94 mm year −1 ) and Sonneratia alba (0.31-1.25 mm year −1 ) from Micronesia (Devoe and Cole, 1998), Heritiera fomes (0.86 to 1.40 mm year −1 ) from the Sundarbans (Chowdhury et al, 2008(Chowdhury et al, , 2016a(Chowdhury et al, , 2016b and lower than Avicennia marina (4.84 mm year −1 ) from Western Australia (Santini et al, 2013). Overall, the range of radial growth rate in different species from different continents shows that mangroves usually have a low growth rate in comparison to terrestrial tree species.…”

“…Mangrove species have received less attention due to absent or indistinct ring boundaries in many species (Amobi, 1974;Srivastava and Suzuki, 2001;Rozendaal and Zuidema, 2010;Robert et al, 2011). However, several studies confirmed the presence of annual growth rings in Rhizophora mangle, R. mucronata, Sonneratia apetala, S. alba, Heritiera fomes, H. littoralis, Xylocarpus granatum and Lumnitzera racemosa (Menezes et al, 2003;Verheyden et al, 2004;Chowdhury et al, 2008Chowdhury et al, , 2016aRobert et al, 2011). For many mangrove species, the timing of growth ring formation is not known which limits chances for the exact dating of ring-width series and hinders the analyses of driving environmental factors behind tree growth (Menezes et al, 2003;Verheyden et al, 2004).…”

Long-Term Hydraulic Adjustment of Three Tropical Moist Forest Tree Species to Changing Climate

“…Tectona grandis was frequently used to develop vessel chronologies (Pumijumnong and Park, 1999; Bhattacharyya et al, 2007; Venegas-González et al, 2015; Sinha et al, 2017). Besides, some mangrove species such as Heretiera fomes and Rhizophora mucronata were studied to develop wood anatomical time series (Verheyden et al, 2005; Chowdhury et al, 2008). In a preliminary study, we investigated wood anatomical features in 27 tree species from a moist tropical forest in Bangladesh and showed their dendrochronological potential (Islam et al, 2018a).…”