28117(2): 281-9, 2002

1,3) 2) 2) 2)

20 00 1 20 011 2 m

5 c m 2 .31

1 9 6 1 2 0 0 0

2 0 0 2 1 7(2):281-9

Research paper

A Study of the Influence of Slopeland Betel-nut Plantationson Microclimate

Shiang-Yue Lu,1,3) Chiung-Pin Liu,2) Liang-Shin Hwang,2) Kai-Jung Tang2)

Summary

Rapid increases in betel-nut plantations in the 1980s and 1990s have significantly affectedthe environment and biological conditions of slopeland in Taiwan. Impacts of converting from1) 844 198 Liukuei Station, Taiwan Forestry

Research Institute. 198 Chung-Shin Village, Liukuei, Kaohsung 844, Taiwan.2) 100 53 Division of Watershed Management,

Taiwan Forestry Research Institute. 53 Nanhai Rd., Taipei 100, Taiwan.3) Corresponding author.

2002 1 2002 3 Received January 2002, Accepted March 2002.

霦

282

forested land to betel-nut plantations on the environment are serious enough to have attractedmuch concern from government and environmental groups. A series of research on this topichas already been carried out. However, most of these researches were focused on problems ofsoil and water conservation associated with slopeland betel-nut plantations. In order to exam-ine differences in microclimatic conditions between betel-nut plantations and natural hard-wood forests, the average air temperature, relative humidity, earth temperature, solar radiation,and rainfall above and below the canopies of these 2 stands were continuously monitored. Theavailable continuous records from January 2000 to January 2001 indicate that there are nodifferences between these 2 study areas in temperatures above and below the canopy. However,the yearly average earth temperature (at 5-cm depth) of the betel-nut plantation was 2.3higher than that of natural hardwood forest, which was significant at the 1% level. The multi-layered and denser canopy of natural hardwood forest stands consumes much solar energy byevapotranspiration and photosynthesis than does that of betel-nut stands. Therefore less en-ergy is available for heating the soil which results in lower earth temperatures than found inbetel-nut plantations. However, the difference is less significant during rainy days and at night.Relative humidity is strongly influenced by canopy cover. The transportation of moisture canbe hindered under a heavy forest canopy which results in higher relative humidity. Statisticalresults indicate that relative humidity was significantly under-canopy conditions of naturalhardwood stands, whereas above the canopy, it was not as high. In addition, the long-term weatherrecords at Lienhuachih meteorological station of Taiwan Forest Research Institute also revealthat the annual average air temperature, especially for summer seasons, shows a tendency ofincrease after 1980. Further studies are needed to clarify the effects of the rapid increase inbetel-nut cultivation on climate changes in the Lienhuachih area.Key words: betel nut, microclimate, Lienhuachih.Lu SY, Liu CP, Hwang LS, Tang KJ. 2002. A Study of the Influence of Slopeland Betel-nut

Plantations on Microclimate. Taiwan J For Sci 17(2):281-9.

1960

1990

(Lu et al. 1999)

(Hwang and Wu 1992, Liang and Cheng 1992, Hu

1993, Chen 1997)

( )

28317(2): 281-9, 2002

7 6 0 m

20 13.5 m

2 2 m 70%

1 0 0%

17 m

Fig. 1

1 9 6 1

2000

2,181.3 mm 20.8

1,032.9 mm 86%

3 9

89.3% 735.0 mm

3 7 . 0

-0.7 (Lu 1997, Lu et al. 2000)

1 5

1 8 m

(Young 05103 Wind Monitor) (E20

Silicon Pyranometer) (MP 101A temp./

RH probe) 2 m

5 cm

(111 temperature probe)

1 0 min

Campbell CR10 data-logger (Campbell Sci-

entific Ltd.) CR10 data-log-

ger

2 0 0 0 1 1 9

1 18 1

2000 5 12

1 0 7

3 4 8

( )

( )

t- test

( )

Fig. 1. Location of the experimental area.

284

1961 - 2000

( )

(Ce l l ie r e t a l .

1996, McCaughey and Saxton 1988, Ogee et al.

2001):

Rn

= H + E + G, (1)

Rn

(net radiation MJ/m2)

H (atmospheric sensible heat

flux MJ/m2)

E (latent heat or evapora-

tion flux MJ/m2)

G (net en-

ergy storage within the canopy MJ/m2)

G

G = Gs+ G

a+ G

w+ G

v+ G

p(2)

Gs

(soil heat storage)

Ga

(sensible heat stor-

age in the canopy)

Gw

(latent heat stor-

age in canopy air)

Gv

( b i o m a s s h e a t

storage)

Gp

(photosynthetic en-

ergy storage)

Ta b le 1

Ta b le 2

Table 1

1%

Table 1. Comparison of air temperature and relative humidity between natural hardwoodforest and betel-nut plantation for different conditions

Averaget-value

Betel-nut Natural hardwood

Canopy temp. ( ) 20.4 20.2 0.654Canopy R.H. (% ) 92.4 89.8 5.716**Under-canopy temp. ( ) 20.5 19.6 3.254**Under-canopy R.H. (% ) 92 93 -2.820**Ground temp. ( ) 22.0 19.5 9.103**1)** Significant at 1% significance level.

28517(2): 281-9, 2002

2%

1 0 0%

4%

(albedo) (Reifsnyder and Lull 1965)

(Reifsnyder and

Lull 1965, Lu 1996)

1%

(soil heat flux)

0700

1 90 0

2000 0600

Ta b le 3

1%

Table 2. Monthly average temperature, relative humidity,total solar radiation and rainfallfor a betel-nut plantations(Betel)and a natural hardwood forest(Hard.)

Above the canopy Below the canopy GroundSolar

Temperature R.H. Temperature R.H. Temp.Radiation

Rainfall

Betel Hard. Betel Hard. Betel Hard. Betel Hard. Betel Hard. mm

% % % %MJ/m2

Jan 14.5 14.2 91 88 16.8 13.7 91 90 16.1 15.5 57.09 25.5

Feb 15.2 15.3 90 89 15.0 14.8 90 93 16.7 15.6 38.01 139.5

Mar 17.8 17.8 89 87 17.6 17.2 88 91 19.0 17.6 91.30 31.5

Apr 20.4 20.3 92 90 20.2 19.7 91 93 21.2 19.1 84.08 222.5

May1) 22.1 21.8 95 89 21.8 21.2 96 94 23.2 19.3 43.91 105.0

Jun 23.4 23.2 93 91 23.3 22.4 93 94 25.3 21.8 100.00 1319.5

Jul 24.3 24.0 92 89 24.1 23.2 91 93 26.2 22.7 114.28 223.5

Aug 23.5 23.1 94 92 23.3 22.4 94 95 25.2 22.5 97.95 455.5

Sep 22.9 23.0 92 88 22.8 22.2 90 91 24.8 22.2 88.06 52.0

Oct 22.8 22.7 94 90 22.7 22.1 92 93 24.5 23.1 84.06 27.5

Nov 19.9 19.7 97 93 19.8 19.3 95 95 22.1 20.6 68.33 89.0

Dec1) 17.4 17.3 93 92 18.8 16.8 92 91 19.5 17.0 63.25 58.0

Avg. 20.4 20.2 93 90 20.5 19.6 92 93 22.0 19.7

Total 930.31 1749.01) Some records were lost during these months.

286

(

2.0 mm )

8 9 2 5 9

T a b l e 4

1% 5 %

10mm

4 4

( 1 )

( H )

( G) ( E )

( GS)

(Reifsnyder and Lull 1965, McCaughey and Saxton

1988, Xia et al. 2001) (2)

Table 3. Comparison of air and earth temperatures between betel-nut plantations and naturalhardwood forests for daytime and nighttime

Avg. of daytime Avg. of nighttime

Betel Hardwood t-value Betel Hardwood t-valueCanopy temp. ( ) 22.2 22.0 0.720 19.0 18.6 0.452Under-Canopy temp.( ) 22.2 21.4 4.231** 19.0 18.6 1.141Earth Temp. ( ) 22.9 20.0 11.168** 21.8 19.7 7.662**

** Significant at the 1% significance level.

Table 4. Comparison of air temperatures and relative humidities between natural hardwoodforests and betel-nut plantations under rainy days and sunny days

Avg. of sunny days Avg. of rainy days

Betel Hardwood t-value Betel Hardwood t-valueCanopy temp. ( ) 20.2 20.0 0.431 21.1 20.8 0.600Canopy R.H. (%) 91 88 6.001** 96 95 2.181**Under Canopy Temp. ( ) 20.4 19.5 2.741** 21.1 20.2 1.823*Under Canopy R.H. (%) 90 91 -2.773** 96 97 -1.655*Earth temp. ( ) 21.8 19.5 7.275** 23.2 20.4 6.093**

** Significant at the 1% significance level * Significant at the 5% significance level.

28717(2): 281-9, 2002

T (E cal/cm3)

E = T,

(hea t capacity

cal/(cm3 )) T

0.4 cal/(cm3 ) (Petterssen 1980)

2 . 3 (1 m2) 5 cm

( 8 h r )

45,400 cal (6.595 watts/m2)

(Reifsnyder and Lull 1965, Hsia et al. 1992)

1

9 .0 8 1 0 8 c a l

T a b l e 5

Table 5. Monthly average minimum daily ground temperatures (�) for betel-nut plantationsand natural hardwood forests (�)

Jan Feb Mar Apr May Jun Jul Aug Set Oct Nov Dec

Betel-nut 15.9 16.3 18.4 19.8 22.4 23.7 24.7 24.4 23.0 23.4 21.4 18.4Hardwood 15.2 15.3 17.1 18.3 19.1 21.1 21.8 21.1 21.8 22.4 20.2 16.2

Fig. 2. Average daily air temperature for different seasons in the Lienhuachih area andthe cultivated area of betel-nut in Taiwan.

288

(soil

heat flux)

(Xia et al. 2001, Lu et al. 2000)

1961 2000

( 3 - 5 6 - 8

9 - 11 12 2 )

(Fig. 2) 1980

( )

1 9 6 1

Table 6

1 9 8 0

(Fig. 2, Agriculture and Forest Depart-

ment 1991)

2 .3

- -03-2

Agriculture and Forest Department. 1991.

Table 6. Yearly average air temperature in the Lienhuachih area

Average daily Average maximum Average minimumRange

temperature daily temperature daily temperature

1961-1965 20.5 27.5 15.41966-1970 20.5 26.0 15.81971-1975 20.2 26.0 16.01976-1980 20.3 26.4 15.71981-1985 21.2 25.3 16.31986-1990 21.4 25.2 16.91991-1995 21.6 25.0 17.31996-2000 21.2 25.1 17.31) The yearly average is the average of all daily records in each year.

28917(2): 281-9, 2002

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