Arbuscular mycorrhizal fungi improve the growth of pioneer tree species of tropical forests on savanna and tropical rainforest soils under nursery conditions

Background: Tropical rainforests and savannas are often spatially distributed at close distances. The combined effects of soil type and arbuscular mycorrhizal fungi (AMF) might contribute to explain the preference of tropical rainforest tree species for forest areas over those of savannas. However, few studies have examined such effects on pioneer tropical tree species. Objective: Evaluate the effects of soil type and inoculation with an AMF consortium on the growth of seedlings of pioneer tree species of tropical rainforest. Methods: A factorial 2 x 2 experiment was conducted to evaluate the role of soil type (rainforest or savanna) and native AMF consortium on growth (height and stem diameter) of four native pioneer tree seedling species under tree nursery conditions. Results and conclusions: The highest growth was detected on rainforest soils inoculated with AMF. Uninoculated plants growing on savanna soils rendered the lowest performance. AMF inoculation could be a valuable procedure in ecological restoration projects of tropical forests.

Consequences of a Reduced Number of Plant Functional Types for the Simulation of Forest Productivity

Tropical forests represent an important pool in the global carbon cycle. Their biomass stocks and carbon fluxes are variable in space and time, which is a challenge for accurate measurements. Forest models are therefore used to investigate these complex forest dynamics. The challenge of considering the high species diversity of tropical forests is often addressed by grouping species into plant functional types (PFTs). We investigated how reduced numbers of PFTs affect the prediction of productivity (GPP, NPP) and other carbon fluxes derived from forest simulations. We therefore parameterized a forest gap model for a specific study site with just one PFT (comparable to global vegetation models) on the one hand, and two versions with a higher amount of PFTs, on the other hand. For an old-growth forest, aboveground biomass and basal area can be reproduced very well with all parameterizations. However, the absence of pioneer tree species in the parameterizations with just one PFT leads to a reduction in estimated gross primary production by 60% and an increase of estimated net ecosystem exchange by 50%. These findings may have consequences for productivity estimates of forests at regional and continental scales. Models with a reduced number of PFTs are limited in simulating forest succession, in particular regarding the forest growth after disturbances or transient dynamics. We conclude that a higher amount of species groups increases the accuracy of forest succession simulations. We suggest using at a minimum three PFTs with at least one species group representing pioneer tree species.

Pioneer tree species as fruit flies parasitoids reservoir in the Brazilian Amazon

The objective of this study was to evaluate the potential of the pioneer plant species Bellucia grossularioides (L.) Triana (Melastomataceae) to act as a reservoir for parasitoids of fruit flies in the Brazilian Amazon. We collected 48 samples of fruits (total of 4,012 fruits, 43.98 kg) during the months of July, August and September of 2013, in 15 of the 16 municipalities of Amapá State, Brazil. All samples showed infestation by fruit flies, with rates varying from 60.6 to 239.1 puparia/kg of fruit (mean of 106.8 puparia/kg of fruit). The percentage of emergence varied 18.6 to 64.3% (mean of 39.9%). Specimens of Anastrepha coronilli Carrejo & González (Diptera: Tephritidae) were obtained from all samples collected. Specimens of Neosilba (Diptera: Lonchaeidae) were obtained from five samples, where they were represented by Neosilba bella Strikis & Prado and Neosilba glaberrima (Wiedemann). The mean percentage of parasitism was 12.8%, varying 4.7 to 26.7%. Four species of parasitoids were obtained: Doryctobracon areolatus (Szépligeti), Doryctobracon sp.2, Opius bellus Gahan (Braconidae) and Aganaspis pelleranoi (Brèthes) (Figitidae). Doryctobracon areolatus, present in all municipalities sampled, was the most abundant species. Considering that B. grossularioides is a plant species that is abundant in the area sampled, its relevance with respect to the maintenance of the population of parasitoids is discussed in the context of the integrated management of fruit flies in the Amazon.