| Mohe County is located in the Greater Xing’an Mountains, Located in China’s northernmost territory, It is a cold temperate regions, the typical zonal vegetation is Larix gmelinii forest.Early Days,to satisfy the needs of national development,a large number of high-quality trees were felled,A sharp increase in mineral extraction, leading to the forest coverage rate dropped in this area,a sharp decline in the ability of Forest Water Conservation,soil erosion,since the implementation of the Natural Forest Protection Project,forest ecosystems were better protection and restoration,the strong advantage in growth of Larix gmelinii forest were radually showing, accumulation amount of larch was rich in the region.Restoration of the ecological regions, soil and water holding, optimize resources and water quality and improve the quality of environment and climate have an extremely important role.In this paper for the study select natural larch forest, locating observations in natural larch forest.It revealed the natural larch Interception and lag effects of the throughfall,at the same time simulated the canopy interception.The results showed:1)Relatively little rain in May and June,accounting for 15% of the total annual rainfall,a larger proportion of rainfall in 7-8 months,up to 60%.A significant reduction in rainfall in September,only 10%.Study area rainfall concentrated in July and August,consistent with the type of climate in the region over the same period of rain and heat:Rainfall level<5.0mm rainfall events occur most frequently,accounting for 75% of the total rainfall observation period screenings,but rainfall in the same period the proportion of the total rainfall is low,only 21.01%.The frequency of rainfall> 20.0mm rainfall events was the lowest,only 7.14%,but the rainfall accounted for 43.26% of the total observation period of rainfall.2)Rainfall penetration stemflow and canopy interception respectively accounted for 76.5%,2.6%,and 20.9% of the total rainfall over the same period.At the same time it showed some spatial and temporal characteristics,rainfall week, throughfall week and throughfall rate week reached the maximum in the fourth week of observation,while the minimum is showed inconsistency,throughfall rate week of interannual variability volatile,and with no significant change in rainfall week variation.In period of 5-9 months,the throughfall rate showed a fluctuating change, which, the throughfall rate was the highest in May,followed in September the lowest; since spring (May) to autumn (September) were with the month passage the seasonal throughfall showed a gradual downward trend, respectively 35.4mm,126.45mm,60.35mm, respectively accounting for 80.05%77.39%, and 73.96%.Stemflow of different months in observation period,except in August due to a single rainfall was a large led to large external stem-flow rate, average stemflow rate of 2.82% in May,higher than in other months.Rainfall and stemflow rate showed a good linear relationship,the equation:SFδ=0.0004P2+0.0173P-0.0063, R2=0.9323.Between the canopy interception(Ⅰ) and the rainfall (P) showed a linear relationship,the equation:Ⅰ=0.0035P2+0.2094P+0.2252 (n=56,R2=0.8473); The average canopy interception rates’monthly variation were volatile,which was in May, July, August respectively 17.14%, 18.88%,18.53%,change is not obvious,however, in June and September has shown a more substantial change,respectively 27.32% and 31.36% The seasona lrainfall variation showed.relatively small in spring and autumn,while its canopy interception rate is relatively large,respectively 28.85% and 33.04%,summer rainfall is larger,however,the canopy interception rate was the lowest,its 19.89%.The extreme of Week rainfall and week canopy interception rate were inconsistencies at time of occurrence.Canopy interception (rate) not only by the impact of the rainfall,but also rainfall characteristics change with a certain degree of response,its broadly consistent rainfall, canopy interception (rate) of the main constraints to the rainfall intensity,namely, the greater the intensity of rainfall, canopy interception (rate) less,Constraints of canopy interception (rate) size was the length of dried before rain,but before rain drying period is long enough, its control effect decreased significantly, the main constraints and turned rainfall characteristics.3)The timing of throughfall, stemflow and rainfall events after precipitation were not synchronous, and lag periods ranged from67.8±7.8 min to17.2±3.9min and 112.0±38.8 min to 48.3±10.6 min following precipitation for throughfall and stemflow,respectively.Under the same level of rainfall, time lag of throughfall and stemflow rainfall intensity increases with decreasing,when rainfall intensity is 2mm/h,lag time was significantly shortened.Throughfall and stemflow lag time increased with drying period before rain and growth,when before rain during the dry period≥48h,rainfall is the dominant factor of the lag time.Rainfall termination,when the rainfall is greater than 5.0mm,the termination of throughfall also lagged,and with the increase in rainfall intensity increases,but no significant relationship with drying period before rain.However,with regard to stemflow prior to termination of rainfall,primarily concerned with the level of rainfall, rainfall level smaller terminated sooner.4)Simulated value for canopy interception was 65.17mm and the measured value was 63.53mm, with a relative error of 2.58%; which is 2.59% when comparing the measured value of weekly cumulative canopy interception and its simulated value. The simulation results of the canopy interception in different seasons were 12.81mm(spring), 43.28mm(summer),9.08mm(autumn) and their measured values were accordingly 12.72mm(spring),41.77mm(summer),9.04mm(autumn), with the relative errors of 0.71%, 3.62% and 0.44%, respectively. The simulation results of single rainfall showed that precision of Gash model was higher under the low rainfall condition (PG<2.0mm), with a variation range of relative standard error being 4.76%-9.52%; but the simulation precision obviously decreased with the increase of rainfall. Once PG is greater than 12.23 mm, the relative error could rise to 60%.Overall, the Gash model can be applicable to simulate canopy interception in the Larix gmelinii forest and provide a scientific and simplified method for hydrological cycle of this forest and further application in Da Hingan Mountains. |
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