Table 9.10. Precipitation event data by event category.
Event Categoryand
number of Collections
Windspeed > 2 m/s
(JV=65)
Windspeed < 2 m/s
(N=37)
All events
(AT =102)
Mean Intensity
Mean Length (mm/hr)
(hr/event) BCWP BP Total Hours
33.2 ± 3.4 1.24 ± 0.18 0.83 ± 0.13 19906.6 ± 1.2 2.79 ± 0.58^ 2.79 ± 0.58 4422432Total Depth
(mm/yr)
BCWP
26781399 (a)4077BP
179213993191TF
1054 ± 831014 ± 632068 ± 132Data are mean event length (mean ± 1 SE), mean bulk cloud water and precipitation (BCWP) or bulk precipitation (BP) intensity, total wet
hours, and total depths of BCWP, BP, and throughfall (TF; mean ± 1 SE, n = 20) by event category, (a) = precipitation depth estimated from
BP.
logical tower. Ion fluxes in stemflow were assumed
to be 10% of those in TF, and these values were added
to mean ion fluxes in TF (Ulrich 1983).
Annual BCWP and BP depths were 408 cm and 319
cm, respectively; annual TF depth was 207 cm (Table
9.10). Free acidity and NO 3 ~ concentrations in TF were
less than those in BCWP and BP for all events; NH 4 +
concentrations were intermediate between those in
BCWP and BP, and PO 4 ~ and cation concentrations
were greatest in TF. Free acidity and inorganic nitro-
gen fluxes in TF were 0.004 ± 0.001 kg H+/ha/yr and
1.9 ± 0.3 kg N/ha/yr (Table 9.11). Based on a calcu-
lated mass balance flux of Na, total deposition of the
ions were calculated (Clark 1994). Calculated net re-
tention of H+ and inorganic nitrogen by the canopy
represented 92% and 70% of total deposition, respec-
tively. Net leaching of PO 4 ~ and cations occurred from
the canopy (Table 9.12).
Comparison of precipitation with other forests. Volume-
weighted mean pH in both BCWP and BP was inter-
mediate compared to values from other tropical sitesin Central and South America (Table 9.13). The pro-
portion of wind-driven cloud water and precipitation
depth to precipitation depth at Monteverde is within
the range reported from other tropical montane for-
ests (Table 9.14). Rates of ion deposition in both
BCWP and BP in Monteverde were generally within
the range of deposition rates in BP reported from other
tropical premontane and montane forest sites (Table
9.15). Concentrations of NH 4 + in BCWP and BP in
Monteverde were at the low end of the range of the
concentrations from other sites (Table 9.15). Cation
concentrations in BCWP and BP in Monteverde were
intermediate; deposition of H+ was at the low end of
estimates. Few estimates exist for the net retention of
ions by the canopy in tropical montane forests. The
canopy in Monteverde retained a greater proportion
of NO 3 ~ in atmospheric deposition and a greater pro-
portion of the deposited NH 4 + retained by the canopy
compared to others. Greater proportions of PO 4 ~ and
Ca were removed from the canopy in Monteverde.
Concentrations of inorganic nitrogen, calsium, and
potassium in precipitation declined rapidly throughTable 9.11. Precipitation ionic activity by event category.
Ion Deposition or Flux (kg/ha/yr)
Event Category Collector H+ NO 3 --N NH 4 +-N PO 43 'P K+ Ca2+ Mg2+ Na+
Windspeed >2 m/s (N = 65)Windspeed < 2 m/s (JV= 37)All events (N = 102)BCWP
BP
TFBP
TFBCWP
BP
TF0.37
0.16
0.02
(0.01)
0.16
0.02
(0.01)
0.53
0.32
0.04
(0.01)3.1
1.1
0.2
(0.1)
0.6
0.4
(0.1)
3.7
1.7
0.6
(0.2)3.2
1.1
0.7
(0.1)
0.6
0.6
(0.1)
3.8
1.7
1.3
(0.2)0.05
0.03
0.25
(0.05)
0.02
0.23
(0.06)
0.07
0.05
0.48
(0.10)4.5
2.0
38.4
(4.5)
1.0
25.2
(4.7)
5.5
3.0
63.6
(8.8)7.2
3.9
15.0
(1.3)
1.9
8.7
(1.2)
9.1
5.8
23.7
(2.3)6.0
2.0
4.8
(0.5)
0.4
2.9
(0.5)
6.4
2.4
7.8
(i.o)45.6
17.9
27.9
(3.5)
2.6
13.4
(1.7)
48.2
20.5
41.3
(5.1)
Data are ion deposition (kg/ha/yr) in bulk cloud water and precipitation (BCWP) and bulk precipitation (BP), and ion fluxes in throughfall
(TF). Standard errors for ion fluxes in TF are shown in parentheses (N= 20).326 Ecosystem Ecology and Forest Dynamics