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Nitorgen and Phosphorus Fertilization Effects on Venezuelan Montane Forest Trunk Growth and Litterfall
Author(s) -
Tanner E. V. J.,
Kapos V.,
Franco W.
Publication year - 1992
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1938722
Subject(s) - plant litter , human fertilization , phosphorus , zoology , montane ecology , litter , biology , ecology , agronomy , chemistry , nutrient , organic chemistry
In a montane rain forest a °2500 m in Venezuela we fertilized plots with N, with P, or N and P for 4.5 yr. We measured trunk growth in circumference in control plots and in those fertilized with N and P, and measured litterfall in all four treatments. There were five 12 x 12 m plots per treatment. N was applied at 225 kg°ha — 1 °yr — 1 and P at 75 kg°ha — 1 °yr — 1 for the first 2 yr, and subsequently N was applied at 150 kg°ha — 1 °yr — 1 and P at 50 kg°ha — 1 °yr — 1 . Rates of trunk growth in N and P fertilized plots were roughly doubled those in control plots (1.4 vs. 0.6 mm/yr). Total litterfall averaged 4.3 Mg°ha — 1 °yr 1 1 in the control plots. In the 4th yr after fertilization litterfall was significantly higher in plots fertilized with N + P (1.50 g°m — 2 °d — 1 ) than in control plots (1.00 g°m — 2 °d — 1 ). There were no significant differences in rates of litterfall between treatments during the first 3 yr after the first fertilization. The changes of rates of litterfall with time were significantly different between treatments. Litterfall in control plots fell by 9% per year, that in P—fertilized plots fell by 5% per year, and litterfall in N— and in N + P—fertilized plots remained approximately constant. Nitrogen concentrations in litterfall were unaffected by fertilization with N or with P. Phosphorus concentrations were significantly increased by P fertilization. We conclude that N is more limiting that P in this forest.