| Chinese fir (Cunninghamia lanceolata), which is widely distributed in southern provinces as one of the important commercial tree species, is the most important one of locally cultivated species in subtropical regions of southern China. Firs can not only provide with raw materials for economic construction, but also produce ecological benefits, especially forest hydrological functions. Therefore the exploration of the effect of fir forests on the rainfall distribution process and the revelation of the hydrological function of the forest ecosystem are of great significance to the regional study as well as the entire southern area.In the dissertation I select the artificial fir forests of different densities in Dagangshan, Jiangxi Province, and use the location-observation methods to study the fir forest hydrological effects according to different densities.I take the atmosphere precipitation from National Field Research Station in Dagangshan as the reference, and study the canopy (interception, the throughfall, stemflow and meteorological factors resulted from different densities of fir forests.The purpose of this dissertation is to understand the regular pattern of redistribution of rainfall interception resulted from different densities of Chinese fir. The results showed as the followings:In the29rainfall observations, the total precipitation is501.4mm. Rainfalls during the observation are primarily light rains with a total number of13, together with9moderate rains,5heavy rains, and2rainstorms. Those Rain lasted for between50min-460min, with rainfall intensity ranging from1.3mm/h～22.9mm/h.In spite of different densities, the throughfall in the firs presented an increasing trend against the ascending of the precipitation. This positively linear correlationship is similar to the one between the canopy interception and the precipitation. The fraction of throughfall to precipitiation is great in two differently aged firs only if the precipitation is more than40mm. If the precipitation is at smaller level, the throughfall in the younger firs (with lower density) is greater than the one in the older firs. The relationship of throughfall against precipitation in those firs regardless of the forest density can be fitted by the simple linear regression model, respectively. However, each model is significantly different from another and they are not substituted for each other in terms of the two-Way ANOVA of single dependent variable.Given the same forest age, the stemflow of Chinese firs increases as the forest density increases. Furthermore, the stemflows of6different densities mainly emerge when rainfall intensity is less than10mm per1h, and the stemflows decline when rainfall intensity is greater than20mm per1h. Especially, the amount of stemflow in6density firs is different from each other according to one-way ANONA. In the study, there is a positive correlation between canopy interception and rainfall, at the same time a negative correlation exists between the canopy interception rate and rainfall although it is not at a significant level, and is apparently subject to rainfall duration and rainfall being continuous or not. Under the same precipitation, all the canopy interception volumes of all the firs planted in1993(N970, N1220, N1750) are greater than those ones of three firs planted in1981. Besides, there is significant difference among the six density in terms of the canopy interception.The19-year-old fir forest is more sensitive to rainfall duration than the31-year-old Chinese fir does. In the case of similar rainfall amount, the impact of rainfall intensity on the interception is very obvious, and at the moderate level, the greater the rainfall intensity is, the smaller the interception will beand at the light level,, however, the greater the intensity of the rainfall is, the more the interception will be. Meanwhile, when the rainfall intensities are similar, canopy interception of rainfall show distinct differences due to different duration of rainfalls.All in all, in the same precipitation, canopy interception capabilities of six different-density artificial fir forests present in the order:N1750> N1220> N97o> N47oo> N3500> N2700.i-e., the higher density implies the greater interception ability given that the forest stands have the same age. The effects of meteorological factors on canopy interception capabilities is different in terms of forest density by gray correlation analysis. The gray correlation between canopy interception and meteorological factors for N970presents in the order:rainfall duration> rainfall intensity> rainfall outside the forest> wind> humidity> temperature; and for N1220the order is in rainfall outside the forest> rainfall intensity> rainfall duration> wind> temperature> humidity, for N1750the order is in rainfall intensity> rainfall duration> rainfall> wind> temperature> humidity; and the N2700have anorder of rainfall intensity> rainfall duration> rainfall outside the forest> wind> humidity> temperature,the N3500havingan order:rainfall outside the forest> rainfall duration> rainfall intensity> wind> temperature> humidity; the N4700have an order of rainfall duration> rainfall outside the forest> rainfall intensity> wind> temperature> humidity. |
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