Lianas in a subtropical Atlantic Forest: Host preference and tree growth

Determinants of liana abundance on several canopy tree species and the impact of liana abundance on host tree growth were studied in a subtropical Atlantic Forest in northeastern Argentina. Six permanent 1 ha plots were located in a native forest stand. In three of those plots all lianas were cut and allowed to decompose in situ, while the other three plots were used as a control treatment. Liana richness, abundance and climbing mechanisms were studied in seventeen 20 in x 20 in subplots inside the 1 ha control plots. A total of 841 liana stems larger than I cm diameter were registered in the 0.68 ha sample area, representing 47 species. Lianas belonging to the Bignoniaceae and Fabaceae families were the most abundant, corresponding to 49.4 and 16.6% of all individuals, respectively. The most common climbing mechanism observed was coiling tendrils, representing the 61.1% of all individuals. Lianas scrambling and twining were represented by 19.6 and 15.6% of the individuals, respectively. The number of lianas climbing a tree was inversely correlated with host tree trunk length. Bark characteristics also played a role on the degree of liana infestation. Some tree species hosted several lianas and the larger the diameter of the largest liana in a host tree the greater was the number of climbing lianas. Facilitation was hypothesized to explain this pattern meaning that many lianas used other lianas climbing a tree for reaching the upper canopy. Tree stem diameter growth was more than 100% lower in two out of the four species studied for liana-laden than for liana-free trees. Results lend support to the hypothesis that cutting of lianas from selected host trees can be used as a forest management technique to enhance tree growth and decrease the length of cutting cycles in native forest stands. (C) 2007 Elsevier B.V. All rights reserved.