Table 9.7. Biomass (kg/ha) of epiphytic material (EM) components on seven
substrates in the Monteverde leeward cloud forest study area.
EM Component
Substrate
TrunkBranch crotchesInner branchesBranch matsBranch tipsUnderstoryGroundcoverTotalBryo
482
[16]
086
[8]
3149
[51]
200
[100]
120
[100]
21
[92]
4058
[12]DOM
498
[17]
18,600
[83]
698
[65]
948
[15]
001
[4]
20,745
[63]Stems
1590
[53]
00465
[8]
0002055
[6]Ferns
43
[1]
00198
[3]
000241
[1]Fol
155
[5]
0140
[13]
366
[6]
001
[4]
662
[2]Roots
222
[8]
3800
[17]
150
[14]
1072
[17]
0005244
[16]Rep
3 t 0 0 0 0 0 0 3[t]Total
299322400107461982001202333,008Data are based on destructive sampling in 17 trees, understory, and groundcover plots. Proportion (%) of
each EM component for a given substrate is in brackets. Bryo = bryophytes and lichens; DOM = dead organic
matter (crown humus, dead leaves and stems); Fol = foliage; Rep = reproductive parts (flowers and fruits).
t = trace (<0.01%).(Nadkarni 1981), or from neighboring plants with
roots that grow apogeotropically (Sanford 1987).
We excavated four 1-m^2 pits. Living roots were
sieved, sorted, dried, and weighed. To encompass
horizontal variation in the upper horizon in the for-
est floor, we sampled 15 randomly located points
within the study area to a depth of 20 cm. Biomass
estimates were comparable between pit and core
samples. Total belowground root biomass ranged be-
tween 1500 g/m^2 and 7220 g/m^2 , which is similar to
root biomass for other tropical montane forests (Vitou-
sek and Stanford 1986). Fine root biomass (<2 mm)
ranged from 300 g/m^2 to 1300 g/m^2 ; it made up 20-
40% of total belowground root biomass. Although we
noted the presence of a thick root mat in the highly
organic H and Aa horizons, more than 30% of the fine
root biomass occurred below this depth (ca. 0-20 cm).
The substantial biomass of fine roots at lower soil
depths suggests a potential mode of nutrient conserva-
tion thatons/has not been widely documented (Vance
and Nadkarni 1992).
Mycorrhizae, a fungal-root relationship that appear
to enhance water and nutrient uptake for the host
plants, have been little investigated at this site. One
survey was carried out in the canopy and forest floor
of the Monteverde leeward cloud forest study area
(Maffia et al. 1993; Maffia et al., "Vesicular-Arbuscular
Mychorrhizae," pp. 338-339).
Root biomass in the canopy was assessed as de-
scribed above. On inner branch surfaces, total root
biomass averaged 150 g/m^2 of branch area. The deep
humus pockets located at branch junctions of mature
trees contained around 80% of the total root biomass
and five times more fine root biomass than inner
branch surfaces.
The substantial biomass of fine roots at lower soil
depths suggests a potential avenue for nutrient conser-
vation. Although the biomass of canopy roots is smaller
than that of their belowground counterparts, they ap-
pear to occupy an important niche in this forest due to
their access to potentially large fluxes of nutrients pass-
ing through the canopy in mist and rain and mineral-
ized from canopy humus. High concentrations of roots
at branch junctions could be particularly effective in
exploiting nutrients in stemflow. Canopy roots could
thus act as an important nutrient-conserving mecha-
nisms in the montane rain forest ecosystem by trapping
nutrients before they reach the forest floor, and trees
capable of creating them may be favored in cloud for-
est environments (see Nadkarni, "Factors Affecting
Initiation and Growth," pp. 339-341).9.2.2. Nutrient Inputs
Nutrient inputs can take many forms and are difficult
to quantify. Potential sources of nutrients include an
array of "autochthonous" (originating within the sys-
tem) and "allochthonous sources" (originating from
outside the system; see Nadkarni and Matelson, "Fine
Litter Dynamics," pp. 341-343, and Table 9.24). The323 Ecosystem Ecology and Forest Dynamics