Productivity of high and low density populations ofJaponaria laminata armigera (Diplopoda) in a warm-temperate forest ecosystem

Summary

The productivity of the final larval and adult populations of a large sized diplopod,Japonaria laminata armigera were studied at a warm temperate ever-green broad leaf forest in Chiba Japan. The population density was about 200/m² in May 1962, and 7/m² in May 1966, the former being about 30 times as much as the latter. A remarkable growth of animals was seen from June to November, and the growth pattern of individuals in both populations was very similar. The growth and mortality were calculated by the following formulae,

$$\begin{gathered} G = (N_t + \frac{{\Delta {\rm N}}}{2})\Delta W, \hfill \\ M = (W_{t - 1} + \frac{{\Delta W}}{2})\Delta N \hfill \\ \end{gathered} $$

whereG is growth,M mortality,N _t number at the timet,W _t −1 mean body weight of animals at the timet−1, ΔN decrease in number during the period of time fromt−1 tot, ΔW growth in mean body weight during the time fromt−1 tot. The constantb in the formulaR=aW ^b representing the relation between body weight and oxygen consumption ofJaponaria laminata was determined at 0.81, andQ ₁₀ was estimated at about 2. The amounts of growth and assimilation were calculated. The pattern of dynamics in terms of productivity of the population in the two periods were very similar. But, the amounts of assimilation were computed at 57.8 kcal/m²/from May 1962 to April 1963, and 3.01 kcal from May 1966 to April 1967. The former is 20 times as much as the latter. The growth or ecological efficiencies for the populations were similar.