Water-holding Characteristics Of Litter In Spruce-fir Mixed Forest

Spruce-fir mixed forest is the main forest type in Northeast China.Litter plays an important role in hydrological ecology.In this study,60 litter samples?fresh,semi-decomposed,complete decomposed?were selected from four 1-hm²plots of natural spruce-fir mixed forest under four cutting intensities?0.00%,6.29%,11.22%and 21.21%?in Jingouling Forest Farm,Yanji,Jilin Province.The maximum water holding capacity,maximum water holding rate,effective water holding capacity and the water holding process?water holding capacity,water holding rate and water absorption rate?of litter samples were measured using indoor immersion method.The effects of cutting intensity and decomposition stage on the water holding characteristics of litter were analysed using one-way and two-way ANOVA and multiple comparisons.The water holding process model was fitted,and the correlation analysis was applied to explore other factors that may affect the water holding capacity of litter.The results will help to deepen the understanding of the hydrological regulation process of forest ecosystem and provide a scientific reference for the selection of natural forest management measures.In addition,18 litter samples in different decomposition stages were randomly selected for water immersion test and leakage test in order to design a more time-saving and efficient apparatus for measuring the water holding process of litter by using indoor immersion method.The main results and conclusions were showed as follows:?1?In this study,a device for measuring the water holding capacity of litter was designed.When used to study the water holding process of litter,it can obviously shorten the experimental period and reduce the labor cost.?2?There were significant differences in the maximum water holding capacity,maximum water holding capacity and effective storage capacity of litter in different decomposition stages of spruce-fir mixed forest?P<0.05?.The maximum water holding capacity of litter in the three decomposition stages was significantly different with the highest in the semi-decomposed horizon of 49.41 t/hm²;As for the maximum water holding capacity,no significant difference was found between fresh litter and semi-decomposed horizon,but they were both significantly different from the complete decomposed horizon,which was the highest of 325.32%;As for the effective storage capacity,litter in the three decomposition stages was significantly different from each other,and the semi-decomposed horizon was the highest,which was 29.92 t/hm².This indicated that the decomposition stage was an important factor affecting the water holding capacity of litter.?3?There were no significant differences in the maximum water holding capacity,the maximum water holding rate and the effective retention of litter in spruce-fir mixed forest under the four cutting intensities?P>0.05?,indicating that cutting with a small range of intensity may not have a significant impact on the water holding capacity of litter.Among them,the control?0.00%?plot had the highest maximum water holding capacity?98.94 t/hm²?,the highest water holding rate?303.40%?and the largest effective storage capacity?51.30 t/hm²?.?4?Before the litter of the spruce-fir mixed forest reached the saturation state,there was a significant logarithmic function relation of the water holding capacity and soaking time,i.e.Q=alnt+b;a significant logarithmic function relation of the water holding rate and soaking time,i.e.L=alnt+b;and a significant power function relationship between water absorption rate and soaking time,i.e.V=at^-b.In the expression,t means soaking time.The above models provide a scientific reference for the study of water holding law of forest litter under natural conditions.?5?The water holding capacity of litter in the semi-decomposed horizon of spruce-fir mixed forest was the best;under the four cutting intensities,the control group had the best water holding capacity of litter,but the difference between the moderate cutting and the control was very small.This indicated that moderate cutting did not have a significant negative impact on the water holding capacity of spruce-fir mixed forest litter.A two-way ANOVA showed that the interaction between decomposition stage and cutting intensity significantly affected the water-holding capacity of litter.?6?The standing crop of litter in spruce-fir mixed forest had a significant impact on the maximum water holding capacity and effective storage capacity,and there were very significant positive correlations between the standing crop and these two indicators?P<0.01?.This indicated that the standing crop was also one of the factors affecting the water holding capacity of litter.