The effect of annual variation in precipitation on growth and litter production in a tropical dry forest in the Yucatan of Mexico.

We describe the responses of a tropical dry forest to variations in rainfall over a four year period. Long-term study plots (1600 m) were established in 1984 and DBH measurements of trees were made annually. Leaf litter and litter of flowers, fruits, and other reproductive parts were measured regularly over the same time period. There were significant annual differences in tree growth and leaf litter production and the differences were correlated with differences in precipitation. Annual precipitation totals varied by almost 600 rom during the four years and the number of months with no precipitation during the dry season ranged from 5.5 to O. Annual rates of tree growth were most closely related to the sum of precipitation in the current and previous year. Annual k.af litter production was correlated with the amount ofprecipitation in the current year. There were no annual differences in the biomass of reproductive materials collected in litter traps. Resume: Les auteurs ont decrit les reponses d'une foret seche tropicale aux variations des precipitations au cours de quatre ans. Les parcelles experimentales (1600 m~ pour une etude along terme, ont ete etablies en 1984 et les mesures de DBH (DBH>lO em) ont ere effectuees chaque annee. Les litieres de feuilles, fleurs, fruits et autres organes de reproduction ont ere mesurees regulierement pendant la meme periode. On a observe des differences annuelles significatives en ce qui concerne la croissance des arbres et la production de la litiere de feuille; ces differences sont liees aux variations des precipitations. Les precipitations totales annuelles ont varie de presque 600 mm pendant les 4 ans et Ie nombre de mois sans prcScipitation pendant la saison seche a varie de 0 a 5.5. Les taux allnuels de la croissance des arbres montrent une relation etroite avec la somme des precipitations de I'annee en cours et celles de I'annee precedente tandis que la production annuelle de la litiac de feuilles est lire a la precipitation de l'annee en eours. On n'a pas releve de differences annuelles dans la biomasse des organes reproducteurs recoltes dans les piages e litiere. Resumo: Os autores descrevem as respostas de uma floresta tropical seca as vana~es aa precipita~odurante urn periodo de quatro anos. Em 1984 foram establecidas parcelas premanentes de -1 600 m2 tendo-se procedido a medida anual do DAP. A biomassa caida respeitante as folhas, flores, frutos e outros orgaos reprodutivos foi regularmente medida para os mesmos intervalos de tempo. Varificou-se existirem diferen~as anuais significativas no crescimento arb6reo e na produ~ de folhada na dependencia da precipita~ilo. As precipi~s anuais totais variaram quase 600 rom dllrante. os quatro anos, e 0 numero de meses sem precipita~o'durante a esta~ilo seca variou entre os 5,5 e os O. As taxas anuais de crescimento das arvores mosti3riUn-se muito estreitamente relacionadas com com a soma da precipita~o'00' ano cOrrente e no anterior. A pfodii~ anual da folhada esteve igualmente correlacionada com 0 quantitativo da precipita~do ano corrente: Nilo se verificaram diferen~ anuais na biomassa do material reprodutivo colectado ~os colectores de folhada. ,. ~. ,"'. •.