80
Daniel Sis cart, Victoria Diego and Francisco Lloret
The same abiotic factors that determine primary production will also influence to some extent acorn production. An experiment to evaluate the effect of nitrogen, phosphorus and water on primary production was carried
out in Prades. The experiment was based on a factorial combination of irrigation, nitrogen fertilization, and phosphorus fertilization (see Chap. 13).
Acorn production was estimated by litterfall traps sampled monthly from
April 1989 to March 1994.
N
E
-
·s
u:
N
E
350
300
250
200
150
100
50
Nitrogen
o no nitrogen
~ nitrogen
$
$
38%
3% 3%
o ~--------~~
1989-901990-91
1991-921992-931993-94
350
Irrigation
300
250
200
150
100
50
o no irrigation
~ irrigation
24%
38% • •
30%
0....1..------'-1989-901990-91
1991-921992-931993-94
Fig. 6.2. Fruit fall (mean + SE) during 5 years for holm oak in plots receiving nitrogen vs. no
nitrogen fertilizer (top) and irrigation vs. no irrigation (bottom) at Prades. Percentages of fruit
fall over totallitterfall are indicated. For each bar n=12 plots. ANOVA signification: $ P< 0.1;
.. P < 0.05; .. * P < 0.01; ...... P < 0.001