Abstract
This paper describes the method to estimate air and soil temperatures in the natural plant communites at different stages of succession in Sugadaira, Central Japan.
Data for the estimation were obtained at the instrument screen and in following four plant communities including bare ground:
1) Bare ground
2) Convex stand dominated by Miscanthus sinensis (M. sinensis A)
3) Concave stand dominated by M sinensis (M. sinensis B)
4) Mixed stand of M sinensis and young Pinus densiflora trees (M sinensis C)
5) P, densiflora forest
The observation was carried out once a month from May to October, 1983. Air temperature of stands was measured at hourly interval for 24 hours at 6cm, 15cm, 26cm, 56cm, 106cm and 156cm height using a thermister thermometer.
Soil temperature was measured at 2cm, 5cm, 10cm and 20cm depth at the above mentioned stands with thermister thermometer from April to October, 1983. Measurements were made at 6:00 a, m. and 2:00 p. m. about 10 days a month.
A close relationship between the air temperature at the instrument screen and those of stands was found. The relationships were described as Y=αX+β for each stand (X: air temperature at the instrument screen, Y : air temperature in stands). The correlation coefficient of the relationship was more than 0. 9 for most of the stands. Using this equation, we are able to estimate the daily mean temperature of plant communities if we have a and β in the equation. The a in the equation changes according to phytomass of the stand as Fig. 3(a):
α=1.66 exp(-2.85×104B) (B: biomass of the stand (kg/m2))
The β in the equation also changes according to phytomass of the stand as Fig. 3(b):
β=2.23ln B-2.5
The plant biomass effect for air temperature in plant communities may be as follows:
1) Leaf temperature rises by absorption of solar radiation and makes surrouding air warm, but at the same time latent heat is lost by transpiration.
2) The existence of leaves weakens the wind speed and prevents air within the stand from mixing with environment.
3) Heat flux to above and below ground changes by varing of soil moisture inside communities.
The relationship between air temperature at the instrument screen and soil temperature also described as Y=αX+β (X: air temperature at the instrument screen, Y: soil temperature in stands). We can obtain a good estimation for mean values during the period more than 5-days but not for daily mean values from this equation. Using these equations, we obtain good estimations for measured air and soil temperatures in M. sinensis stand A for a period from May to September in 1981 (Fig. 5) and from April to September in 1978 (Fig. 7) respectively.
