Presented by Richard A. MacKenzie, Aquatic ecologist, US Forest Service at Mangrove Research in Indian sub-continent: Recent Advances, Knowledge Gaps and Future Perspectives on 8 - 10 December 2021

1. The importance of permanent mangrove plots for
understanding coastal ecosystems: Why do we need them?
Richard A. MacKenzie

2. (Donato et al. 2012, Donato et al. 2014, Murdiyarso et al. 2016, Nam et al 2016, MacKenzie et al. 2016, Sharma et al, 2021)
• Mangroves and tropical wetlands
store 3-5x more carbon than any
other tropical or temperate
ecosystem
• Waterlogged sediments lack the
oxygen needed for processes that
breakdown carbon.

3. -40
-20
0
20
40
D1 D2 D3 U1 U2 U3
Aboveground
carbon
accumulation
rate
(Mg
C
ha
-1
yr
-1
)
Site
MacKenzie and Sharma, unpublished

4. NEP = NPP - NER

5. Rodda et al, 2016

6. 61.3 Mg CO2e ha-1 y-1 18.3 Mg CO2e ha-1 y-1 29.7 Mg CO2e ha-1 y-1
NEP = NPP – Rh
71.9 – 61.3 = 10.6 Mg C ha-1 yr-1
NEP = NPP – Rh
0 – 18.3 = - 18.3 Mg C ha-1 yr-1
NEP = NPP – Rh
42.4 – 29.7 = 12.7 Mg C ha-1 yr-1
Intact mangrove Deforested mangrove Restored mangrove
Sharma et al, unpublished

7. 1) Current mean sea-level rise (3.2 mm/yr) is 2x greater than the rate in the 20th century (1.5 mm/yr)
2) Sea-level is predicted to increase by 37-250 cm by 2100
Sea-level rise greatest future threat to mangroves

8. THINKING beyond the canopy
+ +
+
-
-
-/+
Active
root zone
Basement layer
Peat
SURFACE
PROCESSES
SUB-SURFACE
PROCESSES
DEEP TECTONIC
Maintain vertical elevation
Ocean/River
Root growth

9. PACMAN – PACific Island MANgrove monitoring network

10. 210PB
1. Sediment cores sectioned into 2-cm (0-20 cm) and 4-cm
intervals (20-60 cm)
2. 210Pb extracted using hot acid digestion and analyzed with
alpha spectrometry.
3. Elevation change (mm/yr) determined w/
constant rate of supply or rapid steady state mixing models.
D1B0
210
Pb Activity (pCi/g)
0.0 0.4 0.8 1.2 1.6 2.0
Cumulative
mass
(g/cm
2
)
0
2
4
6
8
10
12
14
16

11. Krauss et al 2010
Rod Surface Elevation Tables (rSETs)
1. SET pipes driven into the mud
until refusal and capped with
an SET receiver.

12. 1. rSET pipes driven into the mud
until refusal and capped with
an SET receiver.
2. rSET arm attached to receiver,
nine pins slid through holes
in the arm to the forest floor,
and the heights of exposed
pins above the rSET arm
measured over time to
determine elevation changes.
3. Measurements made in four
different directions for a total
of 36 measurements per plot.
Elevation change calculated
from changes in pin heights
over time relative to an initial
starting point.
Rod Surface Elevation Tables (rSETs)

13. Sapwalap
Sea
level
(mm)
-500
-400
-300
-200
-100
0
100
200
300
sea level (mm)
Interior
Riverine
Fringe
1996 2000 2004 2008 2012 2016 2020
Rod Surface Elevation Tables (rSETs)

14. COMPACT BIOMASS LIDAR (CBL)
1. CBL attached to rSET receiver and scanned plot in
45o increments for a total of 8 different directions.
2. CBL samples 30,000-100,000 points with each scan.
3. Elevation change measured by comparing elevations of
each point over time.

15. High sea level rise
• Higher sea-level rise results
• Extensive transition to low
elevation mangrove species
after 2060
• Loss of current low
elevation mangrove area by
2100.
Pohnpei species
Bruguiera gymnorrhiza
Rhizophora apiculata
Rhizophora stylosa
Xylocarpus granatum
Sonneratia alba
(High Elev.)
(Low Elev.)
(Generalist)

16. Permanent mangrove
monitoring plots can provide the
information needed for better
management of mangroves and the
continued provision of goods and services
that so many people rely on. They also
provide valuable education experiences
for students, scientists, conservationist,
and most important, decision and
policy makers.

17. Rich MacKenzie
richard.mackenzie@usda.gov