Print PageThe Araucaria forest, located at the southern distribution of the Atlantic Forest in southern Brazil and a global “hot-spot” of biological diversity has been intensively degraded. Araucaria angustifolia (Araucariaceae), hereafter Araucaria, is the dominant species associated with this forest. Control of pine currently represents a significant hurdle for restoration of Araucaria forests.
We integrate analyses of spatial association with empirical measures of juvenile performance indices to assess regeneration of Araucaria forests in abandoned pine plantations. The study site, lcoated in the São Francisco de Paula National Forest of Rio Grande do Sul, Brazil, is characterized by two common pioneer species, Baccharis uncinella and Vernonia discolor, in addition to some remnant pine (Pinus taeda). We analyze the responses of Araucaria and P. taeda to these early-successional species.
Target species were mapped and measured January through June 2006, and were re-measured after 23 months for growth. We used the program SADIE to quantify spatial dispersion. We used three of the indices generated by SADIE: the aggregation index (Ia) the cluster index, (v), and the association index (C). We also measured the light environment of each pioneer species. Araucaria and Pinus juvenile performance was analyzed in response to pioneer association using ANCOVA.
Results/Conclusions
Pinus taeda showed significantly patchy distribution in the study area and this species showed significantly positive spatial association wtih B. uncinella and negative spatial associations with V. discolor. Pinus growth was greater than that of Araucaria in all treatments, and was also greatest in canopy gaps and least under conspecific canopies. P. taeda growth did not differ under V. discolor or B. uncinella canopies. Araucaria colonization and early growth is not strongly facilitated by these early pioneers, but pine colonization and early growth is facilitated by B. uncinella. Pioneer effects were important with V. discolor supporting a higher diversity of native species under its canopy than B. uncinella and with B. uncinella promoting pine invasion.
Our results suggest Pinus taeda presents a significant barrier to Araucaria forest restoration. Spatial analyses integrated with growth measurements show that the pioneer B. uncinella improves Pinus colonization while jeopardizing Araucaria colonization. In contrast, the pioneer V. discolor decreases Pinus colonization with no effect on Araucaria colonization.
