Tree Weights of Avicennia germinans in Mangrove Ecosystems Along the Guyana Coastline

Abstract

Mangroves are known as highly functional and productive ecosystems despite the numerous human and environmental disturbances they face continuously. These disturbances are known to affect their ecosystem states as well as their biomass allocation in their roots, trunks, stems, and leaves. We utilized a combination of plotless sampling methods and established common allometric equations to examine and compare the aboveground, trunk, and root weights of over 600 Avicennia germinans trees found along the Guyana coastline in natural, degraded, and restored ecosystems. Our results highlighted that while the restored ecosystems possessed taller trees with greater densities, the natural ecosystems possessed trees with greater aboveground (54396.24 kg/ha), trunk (19127.08 kg/ha), and root weights (20984.44 kg/ha) due to greater diameter at breast height values (> 30-40 cm). Furthermore, positive correlation coefficients (0.97 < r _s < 1.00) and regression values (p < 0.05) yielded compelling evidence in favor of the relationship between biomass allocation through tree organ weights and ecosystem types. Our findings support the notion that the composition and magnitude of disturbances within an ecosystem may affect mangrove tree biomass, hence influencing the net primary productivity of mangrove forests over time. This may have implications for their ability to accumulate and allocate biomass, as well as store carbon in the future. As such, the proactive conservation of existing mangrove forests is crucial for sustaining their productivity and viability, as well as augmenting their significance in biogeochemical cycles and their role in mitigating climate change.

Keywords: Avicennia germinans; Guyana; biomass allocation; climate change; disturbances; ecosystems; mangroves; trees.

FIGURE 1

Map of Guyana showing the nine study sites along the coastline.

FIGURE 2

Sampling of A. germinans trees using the point centered quarter method (PCQM). NB: DBH, diameter at breast height.

FIGURE 3

General representation of the mean canopy heights of A. germinans trees found within each ecosystem type.

FIGURE 4

Overall mangrove tree organ weights per ecosystem type in (a) kg (mean ± SE) and (b) total per hectare (kg/ha). NB: WAG, aboveground weight; WR, root weight; WT, trunk weight.