Secondary forests are rapidly expanding in tropical regions. Yet, despitethe importance of understanding the hydrological consequences of land-coverdynamics, the relationship between forest succession and canopy interceptionis poorly understood. This lack of knowledge is unfortunate because rainfallinterception plays an important role in regional water cycles and needs tobe quantified for many modeling purposes. To help close this knowledge gap,we designed a throughfall monitoring study along a secondary successiongradient in a tropical forest region of Panama. The investigated gradientcomprised 20 forest patches 3 to 130 yr old. We sampled each patch with aminimum of 20 funnel-type throughfall collectors over a continuous 2-monthperiod that had nearly 900 mm of rain. During the same period, we acquiredforest inventory data and derived several forest structural attributes. Wethen applied simple and multiple regression models (Bayesian modelaveraging, BMA) and identified those vegetation parameters that had thestrongest influence on the variation of canopy interception. Our analysesyielded three main findings. First, canopy interception changed rapidlyduring forest succession. After only a decade, throughfall volumesapproached levels that are typical for mature forests. Second, aparsimonious (simple linear regression) model based on the ratio of thebasal area of small stems to the total basal area outperformed more complexmultivariate models (BMA approach). Third, based on complementary forestinventory data, we show that the influence of young secondary forests oninterception in real-world fragmented landscapes might be detectable only inregions with a substantial fraction of young forests. Our results suggestthat where entire catchments undergo forest regrowth, initial stages ofsuccession may be associated with a substantial decrease of streamflowgeneration. Our results further highlight the need to study hydrologicalprocesses in all forest succession stages, including early ones.
展开▼
