Relating tree growth to rainfall in Bolivian rain forests: a test for six species using tree ring analysis

Abstract

Many tropical regions show one distinct dry season. Often, this seasonality induces cambial dormancy of trees, particularly if these belong to deciduous species. This will often lead to the formation of annual rings. The aim of this study was to determine whether tree species in the Bolivian Amazon region form annual rings and to study the influence of the total amount and seasonal distribution of rainfall on diameter growth. Ring widths were measured on stem discs of a total of 154 trees belonging to six rain forest species. By correlating ring width and monthly rainfall data we proved the annual character of the tree rings for four of our study species. For two other species the annual character was proved by counting rings on trees of known age and by radiocarbon dating. The results of the climate-growth analysis show a positive relationship between tree growth and rainfall in certain periods of the year, indicating that rainfall plays a major role in tree growth. Three species showed a strong relationship with rainfall at the beginning of the rainy season, while one species is most sensitive to the rainfall at the end of the previous growing season. These results clearly demonstrate that tree ring analysis can be successfully applied in the tropics and that it is a promising method for various research disciplines.

Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

“…Generally variation in δ 18 O tr correlated most strongly with δ 18 O in precipitation during the wet season (December-May), which corresponds to the main period of growth for this drought-deciduous species (SI Appendix, Fig. S3) (28).…”

“…1) in October 2002. Tree rings were measured and successfully cross-dated (28). For this study, we selected eight large trees (>60 cm in diameter) and isolated wood from each individual ring along a single radius using sharp knives and razor blades.…”

“…One way of improving our understanding is by expanding the spatial and temporal coverage of δ 18 O in tree rings or other proxies within the Amazon. Although our δ 18 O tr record covered only 100-150 y, Cedrela can become substantially older (i.e., > 300 y old) (28) and has a large geographic distribution (i.e., from 25°N to 25°S). Comparison of long-term trends at different extremes, or across different gradients in the Amazon basin could potentially reveal important insights as to what drives the long-term trends.…”

Fenologia de Chrysophyllum gonocarpum (Mart. & Eichler) Engl. (Sapotaceae) em floresta semidecídua do Sul do Brasil

“…No entanto, Pedroni et al (2002) sugeriram que a precipitação, após período de estresse hídrico, foi o principal fator de estímulo ao brotamento em Copaifera langsdorffii Desf. A retomada de crescimento do caule em quatro espécies da Amazônia Boliviana após o período seco também estava relacionada à precipitação (Brienen & Zuidema 2005). Provavelmente, tanto a abscisão das folhas senescentes quanto as primeiras chuvas contribuíram para a reidratação de C. gonocarpum, resultando na ativação das gemas.…”

“…Em florestas estacionais, a abscisão de folhas geralmente ocorre durante o período seco (Reich & Borchert 1984, Morellato & Leitão Filho 1990, Reich 1995, Justiniano & Fredericksen 2000, Pedroni et al 2002, Singh & Kushwaha 2006, enquanto que a produção de folhas e a floração tanto podem ocorrer durante o período seco, como no período chuvoso (Frankie et al 1974, Reich & Borchert 1984, Reich 1995, Justiniano & Fredericksen 2000, Pedroni et al 2002, Singh & Kushwaha 2006. Entre os fatores abióticos, o fotoperíodo (Borchert 2000, Callado et al 2001, Singh & Kushwaha 2006, a irradiação (van Schaik et al 1993, Wright & van Schaik 1994, a precipitação (Opler et al 1976, Brienen & Zuidema 2005, Singh & Kushwaha 2006 e o estresse hídrico (Reich & Borchert, 1984, Borchert 2000, Singh & Kushwaha 2006) são citados como fatores relacionados à periodização de eventos fenológicos.…”