Tsukuba Geoenvironmental Sciences, Vol. 1, pp. 27-31, Dec. 26, 2005.

“Litter marks” indicating infiltration area of stemflow-induced water
Shin’ichi IIDA*, Jun’ichi KAKUBARI** and Tadashi TANAKA*

Abstract
We found out “litter marks” around the tree bases,
which have the shape like circle. These litter marks
seem to be caused by the infiltration excess overland
flow due to higher intensity of stemflow than theinfiltration capacity of surface soil. It is suggested thatthe litter marks can be a useful indicator to estimate theinfiltration area of stemflow-induced water.
Key words: groundwater recharge, infiltration excess,litter mark and stemflow
1. Introduction
Forest canopy intercepts rainfall and the intercepted
rainfall is partitioned into throughfall and stemflow.
These two components have different infiltration
patterns significantly. Throughfall, which drips fromthe canopy wetted by rainfall or reaches the forest floor
directly without contact with the canopy, is highly spatial
diffused inputs on the forest floor. Stemflow is yieldedby the intercepted rainfall and funnels down along thestem, meaning concentrated point inputs around the treebase.
This concentrated inputs of stemflow has been
considered as an important source for the groundwater
recharge (e.g. Durocher, 1990; Tanaka et al., 1991).
However, there are few studies clarifying the contribution of stemflow-induced water on the groundwater
recharge except for Tanaka et al. (1996) and Taniguchi
et al. (1996). The main reason is the difficulty toevaluate the infiltration area of the stemflow-inducedwater (Ai), which is needed to calculate the groundwater
recharge amount as a unit of water column, Rs (i.e. Rs =amount of stemflow/Ai). Although Tanaka et al. (1991)
evaluated Ai based on the data of “infiltration area mark”,
this phenomenon is rarely observed because theinfiltration area mark of stemflow-induced water is often
difficult to distinguish from the infiltration area ofthroughfall. Therefore, it is necessary to find the simple
and facile methods for the evaluation of Ai to evaluate
the recharge amount by the stemflow-induced water.
*Graduate School of Life and Environmental Sciences, Universityof Tsukuba, Japan** Graduate Student, Graduate School of Life and Environmental
Sciences, University of Tsukuba, Japan

We looked around the tree bases and found out “littermarks” which have the shape like circle. It seems thatlitter marks result from the movement of the litter due
to higher intensity of stemflow than the infiltration
capacity of surface soil, that is the infiltration excess
overland flow. Assuming that the stemflow-induced
water percolates in the vertical direction, the infiltration
area of stemflow (Ai) can be estimated by the area of
the infiltration excess overland flow (Ao) (i.e. Ai = Ao).
Herwitz (1986) also evaluated Ai from the observed dataof stemflow intensity and infiltration capacity of surface
soil in a tropical rain forest (A i = A o = intensity ofstemflow / infiltration capacity). The purpose of thispaper is to describe the phenomenon of litter marks andto compare the extent of litter marks with the infiltration
area marks by Tanaka et al. (1991) for evaluating theavailability of litter marks to estimate Ai.
2. Method
In March 2005, we observed the litter marks ofFormosa sweet gum (Liquidambar formosana Hance)
and two species of evergreen oak (Quercus myrsinaefolia Blume and Quercus phillyraeoides A. Gray) within
the campus of Univ. Tsukuba. Figures 1–3 show thelitter mark found around the tree base of Formosa sweet
gum and evergreen oaks, respectively. It is obvious fromthese figures that the shape of the litter marks shows analmost circle. The radius of litter mark and the diametersat breast height (DBH) and at the tree base (DTB) weredetermined by tape measures. Hourly amounts of gross
rainfall were obtained from the routine observation dataof the Terrestrial Environment Research Center (TERC),Univ. Tsukuba.
3. Results and discussion
3.1 Possible formation process of litter marks
The observed shape of the litter marks was an almost
circle (Figs. 1–3), and corresponded with the shape ofinfiltration area marks of stemflow reported by Tanakaet al. (1991). During the rainfall event on 23 March2005, the infiltration excess overland flow was observed
around the tree base of Formosa sweet gum as shown inFig. 4. From onset of the rainfall (22 March 2005) tothe time when Fig. 4 was taken, 18 mm of gross rainfall
was recorded, and the rainfall intensity was 1.5 mm/h27

Iida, S., Kakubari, J. and Tanaka, T.

Fig. 1 Litter mark around the tree base of Formosa sweet gum (Liquidambar formosana
Hance). Photo was taken on 10 March 2005.

Fig. 2 Litter mark around the tree base of evergreen oak (Quercus myrsinaefolia Blume).
Photo was taken on 9 March 2005.

28

“Litter marks” indicating infiltration area of stemflow

Fig. 3 Litter mark around the tree base of evergreen oak (Quercus phillyraeoides A.
Gray). Photo was taken on 10 March 2005.

at this time. The total amount of rainfall of this event
was 38 mm, and the maximum and mean rainfall
intensities were 6.5 and 1.1 mm/h, respectively (Table1). Iida et al. (2005) reported that the annual mean
rainfall intensity ranged from 1.2 to 1.4 mm/h for thetwo common years at TERC. There is little difference
between the annual mean rainfall intensities and therainfall intensity of 1.5 mm/h on 23 March 2005. This
fact implies that the infiltration excess overland flow
could occur so often in this study site. Another possible
important factor affecting the area of infiltration excess
overland flow is the impact of raindrop energy on theforest floor. Nanko et al. (2004) pointed out that totalenergy of raindrop impact of throughfall was over twicethat of gross rainfall, and suggested that such large
energy of raindrop impact of throughfall could increase
the occurrence of surface erosion on a bare groundsurface. In the case of this study, however, groundsurface was covered entirely by litter fall before
appearing the litter marks. Therefore, it is consideredthat the impact of raindrop energy on the extension of
the litter marks may not be so large in this site.
The observed litter marks could correspond to thelargest rainfall event after the end of fall in 2004, when
Formosa sweet gum had defoliated and the material oflitter has been provided on the forest floor. The largest
rainfall event was recorded from 15 to 16 January 2005,

Table 1 Characteristics of rainfall for the events inJanuary and March, 2005. The former is thelargest event after the defoliation of Formosa
sweet gum, and the latter is the event when
Fig. 4 was taken.

and the total amount of gross rainfall and the mean
rainfall intensity were 88.5 mm and 2.3 mm/h, respectively (Table 1). This mean rainfall intensity was 1.5
times larger than 1.5 mm/h, when the infiltration excess
overland flow was observed on 23 March, 2005 (Fig.
4). It is appropriate to consider that the observed littermarks occurred during the maximum rainfall event after
the defoliation.
3.2 Relationship between diameter at tree base and radiusof litter markTanaka et al. (1991) clarified that there was a logarithmic
relationship between DTB and the infiltration area markof stemflow inputs. The observed litter marks also have
similar relationship with DTB as shown in Fig. 5.
29

Iida, S., Kakubari, J. and Tanaka, T.

Fig. 4 Occurrence of the infiltration excess overland flow by stemflow-induced waterfor Formosa sweet gum. Photo was taken on 23 March 2005 when the rainfall
intensity was 1.5 mm/h.

Fig. 5 Relationships between the diameter at the tree base and the radius of litter markor infiltration area mark from the center of the stem.

30

“Litter marks” indicating infiltration area of stemflow

Including the data cited from Tanaka et al. (1991), weobtained the following relationship:y = 23.361n(x) –31.53
R 2 = 0.753(1)where x is DTB (cm) and y the radius of infiltration areaof stemflow inputs and litter marks from the center ofthe stem (cm). The essentially similar relationship as
Tanaka et al. (1991) suggests that litter mark is a usefulindicator of Ai.
4. Concluding remarks
It can be suggested that the infiltration area of
stemflow-induced water (Ai) is estimated by the littermarks. Litter marks result from the infiltration excess
overland flow caused by stemflow-induced water, andthe extent of the litter mark depends on the intensity ofstemflow and the magnitude of infiltration capacity. The
observed litter marks are attributed to the rainfall eventwith the maximum stemflow yielded after thedefoliation. Although the relationship between thediameter at the tree base and the radius of litter markalmost corresponds to that reported by Tanaka et al.
(1991), the rainfall amount and intensity are different
each other. Therefore, it is necessary to clarify therelationship between the intensity of stemflow and theinfiltration capacity in a future study, to use the littermark for the estimation of Ai.

References
Durocher, M.G.. (1990): Monitoring spatial variabilityof forest interception. Hydrol. Process., 4, 215-229.
Herwitz, S.R. (1986): Infiltration-excess caused bystemflow in a cyclone-prone tropical rainforest.
Earth Surf. Process. Landf., 11, 401-412.
Iida, S., Tanaka, T. and Sugita, M. (2005): Change ofinterception process due to the succession fromJapanese red pine to evergreen oak. J. Hydrol., 315,
154-166.
Nanko, K. Hotta, N. and Suzuki, M. (2004): Assessing
raindrop impact energy at the forest floor in a mature
Japanese cypress plantation using continuous
raindrop-sizing instruments. J. For. Res., 9, 157164.
Tanaka, T., Tsujimura, M. and Taniguchi, M. (1991):
Infiltration area of stemflow-induced water. Ann.
Rep., Inst. Geosci., Univ. Tsukuba, 17, 30-32.
Tanaka, T., Tsujimura, M. and Taniguchi, M. (1996):
Significance of stemflow in groundwater recharge.
2: A cylindrical infiltration model for evaluating thestemflow contribution to groundwater recharge.
Hydrol. Process., 10, 81-88.
Taniguchi, M., Tsujimura, M. and Tanaka, T. (1996):
Significance of stemflow in groundwater recharge.
1: Evaluation of the stemflow contribution torecharge using a mass balance approach. Hydrol.
Process., 10, 71-80.
Received 8 September 2005
Accepted 4 October 2005

31