Liana abundance and diversity increase along a successional gradient, even with homogeneous closed canopy

Abstract

One-half of the pantropical forests are regrowth that develop in certain stages along the succession gradient. As lianas can colonize rapidly in disturbed areas, they play a key role in forest succession and carbon sequestration. However, current knowledge remains limited and is from only a few sites in neotropical forests. Here we investigated liana succession in a chronosequence located in a Southeast Asian Forest. We determined liana abundance (stem density, basal area, prevalence) and diversity along the succession gradient with ages in the range 3–100 years. We also analyzed community composition, size structure, and the correlation with host tree size. We found that liana abundance and diversity increased non-linearly along the succession gradient, suggesting that the stem exclusion stage (35–41 years)—homogeneous closed canopy with low light penetration—did not inhibit liana colonization. Assuming the reverse J-shaped distribution, we fitted the size structure of each plot with the exponential distribution. The results demonstrated no differences among the fitted parameters of plots in the stem exclusion and the old-growth stage, suggesting the same capability of recruitment and colonization in both stages. Furthermore, we found a weak correlation between liana and host tree size (R2 ≤ 0.16, which varied among plots, implying that many lianas recruited after the establishment of large host trees in the past. The results regarding community composition perhaps suggested a stochastic process of liana colonization during the early stage (3–20 years) because of high spatial heterogeneity (a mosaic of open area alternating with closed canopy). In the stem exclusion and old-growth stages, we observed a predictable trajectory, with the composition of plots in the same stage being clustered. This implied that forest structure or unpredictable treefall gaps of old-growth forests have a limited impact on community dissimilarity. Collectively, these results suggested that (1) some liana species may be generalists or even shade-tolerant species, or (2) there was no seed dispersal limitation in the landscape. The contrary direction of the succession patterns reported here suggests a need for more studies across tropical forests including investigating life history trade-offs such as light tolerance.