Abstract
The interception of rainfall by vegetation canopies plays an important role in the hydrologic process of ecosystems. Most estimates of canopy rainfall interception in present studies are mainly through field observations at the plot region. However, it is difficult, yet important, to map the regional rainfall interception by vegetation canopy at a larger scale, especially in the southern rainy areas of China. To obtain a better understanding of the spatiotemporal variation of vegetation canopy rainfall interception with regard to the basin scale in this region, we extended a rainfall interception model by combining the observed rainfall data and moderate resolution imaging spectroradiometer leaf area index (MODIS_LAI) data to quantitatively estimate the vegetation canopy rainfall interception rate (CRIR) at small/medium basin scales in Guangdong Province, which is undergoing large changes in vegetation cover due to rapid urban expansion in the area. The results showed that the CRIR in Guangdong declined continuously during 2004–2012, but increased slightly in 2016, and the spatial variability of CRIR showed a diminishing yearly trend. The CRIR also exhibited a distinctive spatial pattern, with a higher rate to the east and west of the mountainous areas and a lower rate in the central mountainous and coastal areas. This pattern was more closely related to the spatial variation of the LAI than that of rainfall due to frequent extreme rainfall events saturating vegetation leaves. Further analysis demonstrated that forest coverage, instead of background climate, has a certain impact on the canopy rainfall interception, especially the proportion of broad-leaved forests in the basin, but more in-depth study is warranted in the future. In conclusion, the results of this study provide insights into the spatiotemporal variation of canopy rainfall interception at the basin scale of the Guangdong Province, and suggest that forest cover should be increased by adjusting the species composition to increase the proportion of native broad-leaved species based on the local condition within the basin. In addition, these results would be helpful in accurately assessing the impacts of forest ecosystems on regional water cycling, and provide scientific and practical implications for water resources management.
Highlights
Canopy rainfall interception is the amount of rainwater that is intercepted, stored, and subsequently lost by evaporation from the canopy [1,2]
Considering that canopy rainfall interception is an important component of the water balance in a terrestrial ecosystem, an accurate estimation of rainfall interception by the vegetation canopy is of great value in the study of hydrological processes [5]
We found that the canopy rainfall interception rate (CRIR) at the basin scale in Guangdong ranged from 0.33% and 11.67%, which is similar to results in other studies in China that ranged from 0% and 12% [58]
Summary
Canopy rainfall interception is the amount of rainwater that is intercepted, stored, and subsequently lost by evaporation from the canopy [1,2]. Considering that canopy rainfall interception is an important component of the water balance in a terrestrial ecosystem, an accurate estimation of rainfall interception by the vegetation canopy is of great value in the study of hydrological processes [5]. Since canopy rainfall interception cannot be measured directly, it is usually estimated by determining the difference between gross rainfall and the sum of throughfall and stemflow [7,8,9], which are commonly assessed through the study of individual leaves or whole plants and extrapolated to entire plant communities This means that an average value is generally obtained by using a large number of collectors and a large collection area [10,11]. Canopy storage capacity is a key factor in controlling rainfall interception by vegetation canopy [7,26,27]
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