16.5 Uniqueness of Organic Matter
One of the unique characteristics of organic matter is that it can swell and shrink,
following rainy and dry seasons. Gravimetric water content in the organic matter
ranges from 3 to 15 times of its constant dry-mass. The water content <300% is
critical and becomes flammable. High thermal water removal causes organic matter
to change hydrophobic, staying permanently dry and undissolved in water.
Bulk density of peat soil is commonly not >0.1 g cm
À3 (Soil Survey Staff 2014).
The range of undisturbed bulk density is 0.02–0.25 g cm
À3 . Low bulk densities
ranging from 0.02 to 0.15 g cm
À3 indicate fibric peats. Bulk densities of hemic and
sapric peats range from 0.15 to 0.20 and 0.20 to 0.35 g cm
À3 . The average value of
bulk density in the less disturbed site is 0.08 g cm
À3 (Sinclair et al. 2020). Bulk
density of disturbed peats increases, in particular, in the upper section of peat profile
near canals, and also in deforested sites. An increase of 20 and 30% of bulk density
values of the intact peat forest in the acrotelm layer was recorded. This occurs
because of consolidation, compaction, and biological decomposition, resulting
from drainage to lowering groundwater table and land-use change. An increase of
bulk density in degraded peats would lead to an inaccurate estimate of carbon stocks.
Further, drainage canals cause peat subsidence, with an average rate of 4.3 cm per
year (Evans et al. 2019). About 70% of peat subsidence resulted from biological
oxidation (Ishikura et al. 2019).
Peat accumulates when the rates of biological decomposition are lower than the
rates of organic matter intakes. Under complex chemical and biological processes,
organic matter slowly decays. Low C/N ratio and the abundance of phenol-oxidase
indicate rapid rates of peat decomposition. A drawdown of the groundwater table
causes a decrease of C/N ratio (Anshari et al. 2010; Tonks et al. 2017) and the release
of the phenol-oxidase enzyme to decompose peats (Freeman et al. 2004). Organic
materials of degraded peats are not stable and become sources of carbon (Itoh et al.
2017; Sangok et al. 2017; Könönen et al. 2018; Cooper et al. 2019).
16.6 Circularity of Organic Carbon and Singularity
of Native Vegetation
In addition to the importance of peat as water storage, tropical peat swamp forest also
stores enormous amounts of organic carbon. This carbon is stored in five compartments (Table 16.2). These consist of above-ground biomass (ABG), below-ground
biomass (BGB), woody debris (W), litter (L), and peat soil (S). It is important to note
that the ample carbon storage in this ecosystem is stored in the undrained peat soil.
The more thickness, the more carbon is preserved.
Table 16.2 presents the values of carbon storage in a tropical peat ecosystem.
Ample carbon storage in peats indicates that the protection of temperate peat and
tropical peat swamp forests is vital to mitigate climate change.
468
G. Anshari
One of the unique characteristics of organic matter is that it can swell and shrink,
following rainy and dry seasons. Gravimetric water content in the organic matter
ranges from 3 to 15 times of its constant dry-mass. The water content <300% is
critical and becomes flammable. High thermal water removal causes organic matter
to change hydrophobic, staying permanently dry and undissolved in water.
Bulk density of peat soil is commonly not >0.1 g cm
À3 (Soil Survey Staff 2014).
The range of undisturbed bulk density is 0.02–0.25 g cm
À3 . Low bulk densities
ranging from 0.02 to 0.15 g cm
À3 indicate fibric peats. Bulk densities of hemic and
sapric peats range from 0.15 to 0.20 and 0.20 to 0.35 g cm
À3 . The average value of
bulk density in the less disturbed site is 0.08 g cm
À3 (Sinclair et al. 2020). Bulk
density of disturbed peats increases, in particular, in the upper section of peat profile
near canals, and also in deforested sites. An increase of 20 and 30% of bulk density
values of the intact peat forest in the acrotelm layer was recorded. This occurs
because of consolidation, compaction, and biological decomposition, resulting
from drainage to lowering groundwater table and land-use change. An increase of
bulk density in degraded peats would lead to an inaccurate estimate of carbon stocks.
Further, drainage canals cause peat subsidence, with an average rate of 4.3 cm per
year (Evans et al. 2019). About 70% of peat subsidence resulted from biological
oxidation (Ishikura et al. 2019).
Peat accumulates when the rates of biological decomposition are lower than the
rates of organic matter intakes. Under complex chemical and biological processes,
organic matter slowly decays. Low C/N ratio and the abundance of phenol-oxidase
indicate rapid rates of peat decomposition. A drawdown of the groundwater table
causes a decrease of C/N ratio (Anshari et al. 2010; Tonks et al. 2017) and the release
of the phenol-oxidase enzyme to decompose peats (Freeman et al. 2004). Organic
materials of degraded peats are not stable and become sources of carbon (Itoh et al.
2017; Sangok et al. 2017; Könönen et al. 2018; Cooper et al. 2019).
16.6 Circularity of Organic Carbon and Singularity
of Native Vegetation
In addition to the importance of peat as water storage, tropical peat swamp forest also
stores enormous amounts of organic carbon. This carbon is stored in five compartments (Table 16.2). These consist of above-ground biomass (ABG), below-ground
biomass (BGB), woody debris (W), litter (L), and peat soil (S). It is important to note
that the ample carbon storage in this ecosystem is stored in the undrained peat soil.
The more thickness, the more carbon is preserved.
Table 16.2 presents the values of carbon storage in a tropical peat ecosystem.
Ample carbon storage in peats indicates that the protection of temperate peat and
tropical peat swamp forests is vital to mitigate climate change.
468
G. Anshari