4.2. Soil Conservation Parameters
Soil conservation parameter measurements at each plot were made over the study period between November 2010 and January 2011. Throughfall, stemflow,
runoff, and soil erosion measurements from Castanopsis argentea, Michelia montana, and Control plots are presented in Table 2.
Table 2 Throughfall, stemflow, runoff, and soil erosion from Castanopsis argentea, Michelia montana, and Control plots at Gunung Halimun
Rainfall Events
Throughfall mm
Stemflow
mm
Runoff
mm Soil erosion
g
X
1
X
2
X
1
X
2
X
1
X
2
X
3
X
1
X
2
X
3
1 18.10
10.21 0.14
0.14 0.30
0.30 1.18
5.44 4.01
16.05 2
25.30 25.30
0.18 0.18
0.54 0.46
1.64 9.80
10.01 18.32
3 19.99
20.06 0.17
0.23 0.62
0.35 1.42
4.03 7.91
16.93 4
27.99 28.00
0.16 0.16
0.69 0.52
1.82 12.45
11.08 21.50
5 29.59
29.51 0.25
0.26 0.73
0.35 2.45
13.14 11.71
17.18 6
18.74 18.74
0.10 0.19
0.46 0.31
0.93 8.34
7.38 5.41
7 12.29
12.36 0.15
0.14 0.28
0.18 0.70
5.06 4.86
4.20 8
8.80 9.06
0.02 0.03
0.13 0.10
0.72 2.26
3.54 24.99
9 28.70
23.25 0.18
0.18 0.58
0.42 2.25
10.35 9.20
18.45 10
25.80 21.89
0.20 0.16
0.56 0.39
1.61 8.29
8.64 10.20
11 62.34
62.34 0.37
1.20 1.54
1.28 3.81
27.75 24.68
35.97 12
5.30 5.40
0.07 0.04
0.29 0.02
0.67 3.74
2.09 26.10
13 19.81
19.90 0.09
0.09 0.49
0.34 1.38
8.86 7.84
18.98 14
17.89 17.99
0.07 0.07
0.62 0.30
1.15 11.13
7.08 6.50
15 8.70
12.15 0.14
0.15 0.30
0.17 1.01
5.41 4.78
22.61 16
18.60 18.69
0.10 0.16
0.46 0.31
1.21 8.32
7.36 4.85
17 26.38
26.28 0.27
0.38 0.65
0.48 1.91
11.70 10.44
9.67 18
19.10 19.17
0.17 0.17
0.23 0.33
1.78 4.08
7.56 15.56
19 31.30
25.49 0.07
0.37 0.63
0.46 2.03
11.35 10.05
9.70 20
15.06 15.13
0.15 0.08
0.27 0.24
1.43 4.95
5.96 39.75
21 13.75
13.84 0.13
0.07 0.34
0.21 1.12
6.16 5.44
20.26 22
25.19 25.29
0.07 0.07
0.63 0.46
1.63 11.26
9.97 26.72
23 16.77
16.77 0.18
0.12 0.56
0.27 1.14
10.14 6.64
11.87 24
15.09 15.17
0.12 0.07
0.38 0.24
0.99 6.76
5.97 11.62
25 11.00
12.08 0.14
0.13 0.30
0.17 0.89
5.38 4.75
26.11 26
14.36 14.44
0.13 0.06
0.36 0.22
1.29 6.43
5.68 29.88
27 33.75
33.84 0.10
0.10 0.47
0.65 2.33
8.39 13.36
50.36 28
16.61 16.70
0.11 0.45
0.41 0.27
1.64 7.44
6.57 28.34
29 6.82
6.90 0.14
0.05 0.31
0.05 0.66
5.57 2.70
21.18 30
17.12 17.21
0.11 0.16
0.43 0.28
1.43 7.66
6.78 35.98
31 12.32
12.40 0.14
0.14 0.31
0.18 2.25
5.52 4.87
26.55 32
22.56 22.56
0.18 0.26
0.56 0.40
1.64 10.05
8.93 12.36
33 12.70
12.79 0.14
0.14 0.32
0.18 1.22
5.70 5.03
18.09 Total
657.8 640.9
4.73 6.20
15.7 10.8 49.32
272.9 253
662.2 Estimated erosion rate tonhayear
0.81 0.75
1.98 Note: X
1
= Castanopsis argentea Stone model; X
2
= Michelia montana Petit model; X
3
= Control plot
4.2.1. Rainfall
Fifty total rainfall events were registered during the study period starting from 23 November 2010 to 20 January 2011, accounting for a total rainfall
amount of 952.77 mm. Thirty three runoff-producing events, accounting for a total amount 822 mm were evaluated. More than 87 of the raindays had gross
rainfall totals of more than 8 mm day
-1
, ranging from 8.22 to 63.51 mm day
-1
. This large water yield illustrates that the climate, as Gunung Halimun National Park in
general, belong to type A of Schmidt and Ferguson 1951 classification with the annual rainfall of 4000-6000 mm. Similarly high yields have been reported for
other montane forests. For instance, the tropical forests on Barro Colorado Island, Panama, receive on average 2612 mm of rainfall annually Windsor 1990.
Rainforests are one of the most efficient systems for retaining and recirculating freshwater on the planet. In general, tropical rainforests usually receive
considerably more rainfall compared to other biomes. However, such forests are potentially under threat from climate change,
which could result in reduced cloud water interception and improved conditions for evaporation.The net effect of these changes is reduced yield, which is
important hydrologically, and altered moisture conditions,which could also be disastrous for plant and animal species dependent on wet and humid conditions.
4.2.2. Throughfall and stemflow for the different plots
Stemflow and throughfall values were respectively 4.73 and 640.91 mm for Castanopsis argentea, 6.20 and 657.82 mm for Michelia montana. Stemflow
and throughfall were found to represent 0.5 and 77.96 for Castanopsis argentea w
ith Stone‟s model, 0.7 and 80.02 for Michelia Montana with Petit‟s model, respectively of the cumulative precipitation input. Measurements of both
throughfall and stemflowfor the two species are within the range of values found in other rainforest ecosystems. At the Educational Forest Mountain Gunung
Walat, Sukabumi, Aththorick 2000 reported 3.850 and 427.421 mm for throughfall and stemflow respectively for Trema orientalis
tree with Rauh‟s model. Stemflow value of Massart‟s model 6.455 mm found by the same author
was nearly to value of stemflow of Michelia montana 6.20 mm. The cumulative throughfall value for our study falls within the upper range of cumulative
throughfall values reported by Navar et al. 1999 for six study plots within the Northern Gulf of Mexico Coastal Plain 73.4-83.7. Cumulative stemflow
generated, although not significantly different, is similarr to the average values observed by Navar et al.1999 0.4-6.5. Other observations have been
made for other montane rainforests. At the Australian tropical rainforest, McJannet et al. 2007 reported 65 3739 mm and 7 418 mm of gross
precipitation for throughfall and stemflow respectively. The significant discrepancy between these findings warrants further attention. Throughfall and
stemflow importance varie from the total incident precipitation, depending on branch and stand morphology and on bark roughness.
In this study, comparison of the two species of tree indicated the importance of crown form. Michelia Montana was found in site with more direct
overhead rainfall interception on average than Castanopsis argentea, generallysmall leaves in the canopy. Michelia Montana was more highly branched
with a shell of drooping leaves on the outside of the crown. Castanopsis argentea had whorle branches in tiers with planar foliage arrays. Michelia montana
appeared moreefficient at intercepting the larger amounts of rainfall available in rain forest understorey sites.
4.2.3. Erosion and runoff for the different plots
Measured runoff and soil loss data from the vegetation patches showed that Castanopsis argentea and Michelia Montana produced significantly less runoff
and erosion than the Control. The maximum values of runoff were approximately 2.45, 1.54 and 1.28 mm for the Control, Castanopsis argentea and Michelia
montana, respectively. Total runoff measured was 49.32, 15.74 and 10.87 mm, for plots. Runoff values were similar among Castanopsis argentea and Michelia
montana, and they differ from the Control. The plots of Castanopsis argentea and Michelia montana reduced runoff by 31.33 and 45.37 , respectively, as
compared to the control surface. Runoff coefficients estimated from the observed data were 0.06, 0.019, and 0.013 for the Control, Castanopsis argentea, and
Michelia montana, respectively. The values for Castanopsis argentea, and Michelia montana are similar to those reported by Vásquez-Méndez et al. 2010
for Acacia farnesiana and Opuntia sp 0.01 in a semiarid area in Central
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