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Although we know that rainfall interception (the rain caught, stored, and evaporated from aboveground vegetative surfaces and ground litter) is affected by rain and throughfall drop size, what was unknown until now is the relative proportion of each throughfall type (free throughfall, splash throughfall, canopy drip) beneath coniferous and broadleaved trees. Based on a multinational data set of >120 million throughfall drops, we found that the type, number, and volume of throughfall drops are different between coniferous and broadleaved tree species, leaf states, and timing within rain events. Compared with leafed broadleaved trees, conifers had a lower percentage of canopy drip (51% vs. 69% with respect to total throughfall volume) and slightly smaller diameter splash throughfall and canopy drip. Canopy drip from leafless broadleaved trees consisted of fewer and smaller diameter drops (D50_DR, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D50_DR of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D50_DR of 5.92 mm) than leafed broadleaved trees. Based on throughfall volume, the percentage of canopy drip was significantly different between conifers, leafed broadleaved trees, leafless broadleaved trees, and woody surface drip points (p ranged from <0.001 to 0.005). These findings are partly attributable to differences in canopy structure and plant surface characteristics between plant functional types and canopy state (leaf, leafless), among other factors. Hence, our results demonstrating the importance of drop‐size‐dependent partitioning between coniferous and broadleaved tree species could be useful to those requiring more detailed information on throughfall fluxes to the forest floor.

The raindrop size distribution of throughfall and open rainfall was monitored continuously during a rainfall event using laser raindrop-sizing instruments (LD gauges), in order to calculate the raindrop impact energy in a plantation of mature Japanese cypress (Chamaecyparis obtusa), where surface erosion at the forest floor had been a problem. Data from two rainfall events were analyzed. The LD gauges recorded qualitative raindrop size distribution, and the capture rate during each rainfall event was used to manipulate raindrop data quantitatively. Throughfall and open rainfall comparisons revealed several important differences. First, throughfall raindrops were fewer in number and larger in size than open rainfall drops. In one rainfall event, for example, throughfall raindrops were less than one-fifth as frequent as open rainfall raindrops; in addition, the maximum throughfall raindrop diameter was 6.35 mm compared to 3.31 mm for open rainfall raindrops. Second, throughfall raindrops that were larger than the largest open rainfall raindrops comprised 63.8% of the throughfall precipitation by volume. Third, total raindrop impact energy from throughfall was over twice that of open rainfall. Moreover, comparison of throughfall events implied that throughfall raindrops did not always have a uniform distribution between different events or among different periods of time in one rainfall event, in contrast to findings in previous studies which showed that throughfall raindrops had a uniform size distribution independent of rainfall intensity. It is possible that an abrupt transition of throughfall intensity from low to high changes the distribution of throughfall raindrops.