| The Chinese cork oak(Quercus variabilis)is a common deciduous broadleaf tree in East Asia(24° to 42° N and 96° to 140° E)and plays a key role in the development of economy and ecosystem in China.To determine the effect of forest cutting on the growth of fine roots,the annual productivity and turnover rate of fine roots were measured in a cork oak forest,in Louguantai forests,the north slope of Qinling Mountains,and the architecture,morphological characteristics and biomass of fine roots were investigated in Foping,the south slope of Qinling Mountains.The fine root carbon and nitrogen compounds were analyzed in the juvenile oak trees after stem removal with the other physiological indices,including root vigor activity and anti-oxidant enzymes.To detect the relationship of sprouts growth with climate factors and soil conditions,the sprouts number,height and dry weight were investigated in following 3 years after stem removal in both regions.The main results are as follows:(1)The reserves,production and turnover rate of fine roots decreased in the stands after stem removal,and the architecture and morphological characteristics of fine roots were altered.In the Louguantai forests,more necromass of fine roots were observed after stem cutting.The ratio between necromass and biomass of fine roots increased after cutting compared with the control and was the highest in June.The root mass with diameter<1 mm was affected proportionately more than that of diameter 1-2 mm root.The effect of cutting on roots was observed more significantly in the deeper soil.The annual fine root production and the average turnover rate in the stands after cutting for three years were 60.3%and 80.3%of the control stands,respectively.With principle components analysis(PCA),aboveground stand structure,including canopy cover,sprout height,and basal area,influenced fine root growth primarily after cutting.In Foping forests,the number of the first-,second-,and third-order roots were lower in the management plots than the control.The branching ratios(Rb)decreased after cutting without significance.The management in the forest reduced the root length density,surface area,specific root length and biomass of fine roots,with the increasing trend of root tissue density.No significant difference was observed on root mean diameter.The effect was observed significantly in the first-order roots.The average of fine root biomass in the plots of 3 years after stem removal recovered to 83%of control plots,and the root length density recovered to 71%.(2)The alteration of nonstructural carbohydrate,nitrogen reserves,root vigor(TTC reduction),lipid peroxidation(MDA)and antioxidant enzymes in different positions of roots branch were investigated on the condition of the removal of stem and canopy.The soluble sugar and starch reduced significantly after stem cutting.The ratios between soluble sugar and starch increased in the fine roots of stumps,particularly at the latter stage(150d)after stem removal.Total N contents in the fine roots after stem cutting declined more proportionally than total C contents,which caused the increasing C/N ratios for the stumps.The shortage of photosynthesis production after stem removal produced superoxide anion and dropped TTC reduction in the fine roots.The highest value of MDA content and CAT activity in the fine roots of stumps was observed at the medial stage(90 d)and then decreased.The SOD activity increased during the experiment with the declining POD activity.The change of physiological indices in the first-order roots were affected by stems cutting more significantly than the third-order roots.(3)The effect of different level of neighborhood interference on the morphological character of stump sprouts was studied in 72 clumps of stump of Q.variabilis in Foping forests.The BAL/BA method with the ration of basal area of trees larger than the subject tree to the total base area of sprouts was used to represent the level of neighborhood interference.The 84.7 percentage of the total stumps were low and middle level of neighborhood interference.The base diameter and length of the dominate sprout,crown area,amount of leaf,amount of lateral branch,average length and base diameter of lateral branch were significantly different under the different neighborhood interference.The base area,with the biomass of sprout,lateral branch and the leaf were increased by the increased level of neighborhood interference.The current-year sprouts grew better under the middle neighborhood interference than other interference.The power function y=a·xb represented the relationship between the morphological character and competition index.The ability of photosynthesis contributed more significantly to the regeneration of stump sprout than the ability of water and mineral intake and transport.The light intensity has the more relationship to the growth of sprouts than other environment factors.(4)In Louguantai cork oak forests,the stump sprouts length increased to 87.6±35.7 cm in the 3rd year after cutting with the number of sprouts per stump of 3.9 and the sprouts biomass of 0.17 t·ha-1,whereas the length,number and biomass of sprouts in Foping cork oak forests were 177.3 ±37.2 cm,8.9 individual and 3.46 t·ha-1.The annual growth rate of sprouts in Foping was greater than that in Lougantai.The length,number and dry weight of sprouts per stump increased with the increasing basal diameter and height of stumps,whereas higher linear relationship was found between the sprouts length and stump diameter.The mean month temperature and precipitation during July and October affected the augment of sprout length more seriously than those during April and June.The more rainfall and lower temperatures in May promote sprout growth.The inverse function fitted better to the relationship between the lengths of domination sprouts and the number of sprouts per stump.The self-thinning is helpful and effective for sprouts to allocate and utilize the source,and'Sprouts Substitute Stem' is the main way for forest regeneration.The model of sprout productivity was established through the principle components and stepwise regression method.The precision of the model was approximately 80%,indicating that it is useful to predict the biomass of sprout in both forests.(5)Suggestion:The sprouts in the stump should be thinned to relieve the competition for light and nutrition,suggesting that one sprout in the stump with<10 cm diameter,two sprouts in the stump with 10-20 cm diameter and three or four sprouts in the stump with>30:cm diameter.The nitrogen contents in the soil should be fertilized to improve the root growth and sprouts regeneration.The rotation duration of coppice was suggested to be above 6 years.The stem should be seleced to harvest based on the aim and the optimization peried of harvest between current November and next March.The management of cork oak forests should be conducted according the scientific and sustainable method. |
PDF Full Text Request