LITTER PRODUCTION I N FORESTS O F THE WORLD
133
3. Effect of Thinning
If a closed-canopy forest is thinned there is a decrease in litter production which is roughly proportional to the degree of thinning. Data
in Table IV demonstrate this relationship for Pseudotszqa menziesii
(Dimock, 1958), Picea abies (Wright, 1957) and Fraxinus excelsior
(Boysen-Jensen, 1930). In all cases the control stand has the highest
litter-fall and the most heavily thinned stand the lowest. Moller (1945)
has shown the effect of thinning upon the standing crop of Fagus silvatica leaves. With no thinning, leaf crop was 2.0 tiha, with Bregentved
thinning 1.9 t/ha and with Vemmetofte thinning 1.7 t/ha.
4.' Effect of Litter Removal
Rights to utilize forest litter still existed in Germany in 1954, particularly in Bavaria, where it sometimes caused extreme reduction of
forest growth (Mayer-Krapoll, 1956). By comparing areas with and
without rights to litter utilization, it has been estimated that annual
forest output may require forty years to recover from long-continued
litter removal. The loss of nitrogen in the litter is believed to be of
especial significance in lessening forest productivity. Wiedemann ( 195 1)
presented data from study plots (Hermeskeil143,146, Table 363, p. 260)
indicating that twenty-five years of litter utilization reduced basal
area increase by about two-thirds. Thirty years were then required for
recovery.
D. THE TIME FACTOR
1. Seasonal Variation
If forest litter is ever to be utilized economically, it will be of importance to know the pattern of litter-fall, whether distinctly seasonal, or
more or less continuous. Such knowledge is also of the utmost importance to students of population dynamics in organisms responsible for
litter breakdown, and may be of interest to persons concerned with the
role of organic matter in soil development.
The pattern of litter-fall varies greatly, as demonstrated by Figs. 2-5.
In the Equatorial forests of Ghana, Colombia and Malaya litter-fall is
continuous throughout the year, but with a tendency for slightly
greater deposition during the first half of the year. I n Ghana a, short dry
season in January and February was noted as leading to increased leaffall (Nye, 1961). Laudelot and Meyer (1954) state that at Yangambi in
the Congo there are two minima in the wet seasons and two maxima at
the ends of the dry seasons. According to Deville (private communication) seven-year plantation of Acacia decurrens showed highs in
133
3. Effect of Thinning
If a closed-canopy forest is thinned there is a decrease in litter production which is roughly proportional to the degree of thinning. Data
in Table IV demonstrate this relationship for Pseudotszqa menziesii
(Dimock, 1958), Picea abies (Wright, 1957) and Fraxinus excelsior
(Boysen-Jensen, 1930). In all cases the control stand has the highest
litter-fall and the most heavily thinned stand the lowest. Moller (1945)
has shown the effect of thinning upon the standing crop of Fagus silvatica leaves. With no thinning, leaf crop was 2.0 tiha, with Bregentved
thinning 1.9 t/ha and with Vemmetofte thinning 1.7 t/ha.
4.' Effect of Litter Removal
Rights to utilize forest litter still existed in Germany in 1954, particularly in Bavaria, where it sometimes caused extreme reduction of
forest growth (Mayer-Krapoll, 1956). By comparing areas with and
without rights to litter utilization, it has been estimated that annual
forest output may require forty years to recover from long-continued
litter removal. The loss of nitrogen in the litter is believed to be of
especial significance in lessening forest productivity. Wiedemann ( 195 1)
presented data from study plots (Hermeskeil143,146, Table 363, p. 260)
indicating that twenty-five years of litter utilization reduced basal
area increase by about two-thirds. Thirty years were then required for
recovery.
D. THE TIME FACTOR
1. Seasonal Variation
If forest litter is ever to be utilized economically, it will be of importance to know the pattern of litter-fall, whether distinctly seasonal, or
more or less continuous. Such knowledge is also of the utmost importance to students of population dynamics in organisms responsible for
litter breakdown, and may be of interest to persons concerned with the
role of organic matter in soil development.
The pattern of litter-fall varies greatly, as demonstrated by Figs. 2-5.
In the Equatorial forests of Ghana, Colombia and Malaya litter-fall is
continuous throughout the year, but with a tendency for slightly
greater deposition during the first half of the year. I n Ghana a, short dry
season in January and February was noted as leading to increased leaffall (Nye, 1961). Laudelot and Meyer (1954) state that at Yangambi in
the Congo there are two minima in the wet seasons and two maxima at
the ends of the dry seasons. According to Deville (private communication) seven-year plantation of Acacia decurrens showed highs in