| Forests are a major component of Earth’s ecosystem,and canopy interception plays a key role in forest hydrological processes and forest ecosystem services.Canopy interception changes the hydrological process of forests by intercepting a part of the precipitation and slowing down the impact of rainfall when it falls directly on the soil,thus,reducing nutrient loss in soil.Pinus sylvestris var.mongolica.is one of the tree species found in China that exhibits strong stress resistance.As an evergreen tree with drought,cold,and desert resistance,it is the main tree species used for afforestation in China.However,with global climate change,the effects of increasing temperature and decreasing rainfall have intensified,which tends to dry out the soil in these areas.Moreover,forest canopy interception strengthens the evaporation rate,and the water supply to soil in this area is further reduced,which can lead to drought.Therefore,understanding the utilization of rainwater by Pinus sylvestris and its significance to the hydrological cycle is necessary to study the interception process of rainfall by artificial forest canopy in temperate humid regions.Additionally,it is beneficial to the restoration and reconstruction of vegetation in this region.The main results are as follows:1.A total of 64 individual rainfall events were documented during the experiment period from June 2（DOY153）to September 30（DOY273）,2019 in Magu forest farm,Fushun city,Liaoning Province.Total amount of rain was 491mm.The rainfall was mainly moderate to light rain（0-5mm and 5-10mm）,with few heavy rainfall events(1-4mm.h-1and 4-6mm.h-1)in the rainy season.2.The canopy interception,stemflow and throughfall accumulations were 84.3 mm,29.6mm,and 377.1 mm,respectively,accounting for 17.2%,6.0%,and 77%of the total rainfall outside the forest,respectively.3.Rainfall is affected by the nature of forest canopy during forest redistribution.The results showed a linear correlation between rainfall and throughfall,and the fitting results are the best,the canopy interception is the second,and the stemflow is the worst.The threshold of stemflow was 5 mm of precipitation outside the forest.The canopy interception,stemflow and rainfall penetration increased with increasing rainfall grade,but the stemflow and rainfall penetration decreased.The relationship between throughfall and the leaf area index was significant.However,there was no significant relationship between leaf area index and monthly mean canopy interception rate,stemflow rate,and throughfall rate,so the fitting effect was not ideal.4.The mean values of atmospheric pressure,temperature,wind speed,relative humidity,and solar radiation flux during the rainfall period was 862.7 KPa,0.80 ms-1,17.0℃,71.2%,and 77.97 Wm-2,respectively.The canopy density c,stemflow coefficient,and trunk water holding capacity was 0.6,0.402,and 0.124 mm,respectively.Other major parameters were compared and calculated.Transpiration rate of saturated forest canopy in the rainfall period was calculated using regression method and Penman-Monteith equation,and the calculation method of forest canopy water-holding capacity was also improved based on Leyton constraint method and according to the distance from point to straight line mathematical laws.Then,other parameters were extended to the canopy layer and substituted into the revised Gash model to analyze the output canopy rainfall redistribution and obtain the transpiration rate of saturated forest canopy during the rainfall period.The fitting coefficients of canopy interception,stemflow,and throughfall were higher,and the fitting effect was the highest（R2equals to 0.82,0.74,and 0.91）.5.The canopy interception simulated by the revised Gash model was lower than the actual value,and the sensitivity ranking of each parameter change to the canopy interception output of the revised Gash model can be seen as follows:canopy water holding capacity>average evaporation rate of saturated canopy>ratio of canopy water holding capacity to average evaporation rate of saturated canopy>trunk water holding capacity>rainfall intensity>canopy density>stemflow coefficient. |
