Effect of temporal variation in precipitation on the demography of four herbaceous populations in a tropical dry forest area in Northeastern Brazil

Abstract

Abstract:In tropical dry forests, the dynamics of herbaceous populations is strongly influenced by seasonal and annual variation in total rainfall. Moreover, the present and past events of climatic anomalies (e.g. severe drought years and erratic rain before the growth season) may cause drastic reductions in population size, leading to the temporal disappearance of some species. Therefore, this three-year study aimed to assess the dynamics of Delilia biflora (Asteraceae), Commelina obliqua (Commelinaceae), Phaseolus peduncularis (Fabaceae) and Euphorbia heterophylla (Euphorbiaceae). The study was conducted in an area of tropical dry forest known as Caatinga, situated in the experimental station of the Pernambuco Agronomic Institute (IPA), in Caruaru, Pernambuco, Brazil. The Caatinga has a semiarid climate with strong seasonal and annual variation in total precipitation. During this study, there was a climatic anomaly event called the 2006 drought, and also erratic rains in the dry season. The birth, death and survival of plants were evaluated monthly using 105 plots (1 × 1 m). Differences in density between years and seasons were evaluated using the Kruskal-Wallis test. The explanatory power of present and past precipitation on density was evaluated using the General Linear Model. In this study, we present the first record of Euphorbia heterophylla in the studied area. The studied populations were larger during the rainy seasons and in wet years, and were drastically reduced in the driest year and dry seasons. Commelina obliqua was the least sensitive to variation in total rainfall. Regarding the variation in density, all four species were present during all three years. Birth rates were higher during the rainy season, and death rates were higher in the dry season. Sporadic rain in the dry season caused pronounced seedling recruitment followed by death, and had a strong impact on the dynamics of D. biflora, E. heterophylla and P. peduncularis. The precipitation of the current year explained between 3 % -18 % of the inter-annual density variation, and the explanatory power of the previous year precipitation on the density of populations ranged from 32 % to 67 %. Therefore, climatic events of the past also have a significant consequence over the four populations. In conclusion, drastic reduction in total precipitation between years may be considered as a predictive parameter for herbaceous plants population size (in the present and future time) in a Northeastern Brazilian tropical dry forest area. Rev. Biol. Trop. 63 (4): 903-914. Epub 2015 December 01.

Effect of simulated extreme rainfall on the vegetative phenology of perennial and annual herbaceous plants from a Brazilian dry forest

“…2007; Silva et al . 2015; Souza et al . 2020) to a greater or lesser extent, depending on the characteristics of the species under consideration and their adaptation strategies to mitigate water stress injuries (Webster & Grey, 2008; Nogueira et al .…”

“…In the Caatinga, consecutive days with no rain (dry spells) are common within the rainy season period, and the opposite is also true, i.e., the occurrence of short periods of rain within the dry season (erratic rainfall) (Santos et al 2013;Silva et al 2015;Santos et al 2016;Marengo et al 2017). Therefore, the treatments adopted in this study simulated the volume of rainfall in previous years, taking into account the occurrence of dry spells or erratic rainfall.…”

“…1a). In this type of vegetation, sporadic droughts (called "veranico" or dry spells) can occur within the rainy season, as well as sporadic rainfall within the dry season (Santos et al 2013;Silva et al 2015;Santos et al 2016;Marengo et al 2017;Aguiar et al 2020). Furthermore, annual precipitation of drier years can be concentrated in just two consecutive months (Silva et al 2016;Fig.…”

“…Furthermore, such methodology can provide insights into the behaviour of plant species in natural environments (Wu et al 2011;Kooyers 2015;Copeland et al 2016;Estiarte et al 2016;Knapp et al 2018). This is relevant for the populations of herbaceous species that, in this type of forest, characteristic of the Brazilian Caatinga, are highly sensitive to seasonal and interannual variation in rainfall behaviour, with an increase or decrease in the size of their populations or even a reduction in biodiversity between years (Lima et al 2007;Reis et al 2006;Silva et al 2015;Santos et al 2013;Aguiar et al 2020;Souza et al 2020).…”

Canals as invasion pathways in tropical dry forest and the need for monitoring and management

“…At this phase, herbaceous plants showed the greatest variation in area occupancy (Figure 3). In dry forests, climatic fluctuations are commonly associated with drastic oscillations in the population size of herbaceous species (Sala & Lauenroth, 1982;Sun et al, 2019;Vega & Montaña, 2004), including the Caatinga (Reis et al, 2006;Silva et al, 2015).…”