Population Dynamics Of Quercus Acutissima In Qiaoshan Forest Area

In order to investigate the dynamic changes of Q.acutissima populations in Qiaoshan forest area,the natural secondary forests of Q.acutissima in Shuanglong Forest Farm of Qiaoshan Forests in the southern Loess Plateau were selected as the research object.It was studied that the quantity structure and dynamics,and the flowering and solidification of the Q.acutissima populations under the different habitat conditions(including sunny slope,semi-sunny slope,semi-shade slope and shade slope),and that the interspecific associations of the main tree populations in the Q.acutissima community.This explains the law of the dynamic changes of Q.acutissima populations under natural conditions,and also provides the basis for the management,renewal and maintenance of the natural secondary forests of Q.acutissima in the region.There are the main conclusions:1.The analysis of the age structure of the Q.acutissima population in different habitats shows that t Q.acutissima seedlings(age class I)has the largest number of individuals,which decreases dramatically at age class II;The number of populations decreases significantly at age class III and IV,which is the most fragile stage of the life history of Q.acutissima populations;The number of individuals increases at first and then decreases at age class V to XII.At age class II and IV,there is no significant reduction in semi-sunny slope,while the most obvious decrease in shade slope.The survival curve of Q.acutissima populations belongs to Deevy III type,and the mortality during seedling stage is the largest.The survival curve and death curve of the Q.acutissima population has the smallest fluctuation amplitude in semi-sunny slope,while the largest amplitude in sunny slope,semi-shade slope and shade slope.These results can be explained by the survival function that the survival rate and cumulative mortality of the populations in the four habitats are complementary;At age class II,the risk rate reaches the highest;After the age grade II,the semi-sunny slope becames stable,and the sunny slope,semi-sunny slope,and shady slope fluctuate comparatively large and the shade slope reaches-0.46 at age class III particularly,whose function value is significantly lower than other habitats.2.There are no significant negative correlations among these 17 tree populations in the Qiaoshan forest area,as the species tended to be distributed independently and the community was unstable.The~2test results showed that among the 136 species pairs of the 17dominant populations,the vast majority of these associations was not significant.Analysis of the AC and PC results revealed that the 17 main populations had different habitat demands,and the probability of simultaneous emergence of each species pair was small.Based on the cluster analysis and interspecific association results,the habitats of the 17 main populations were divided into three ecological groups.3.In different habitats,the minimum reproductive age of the Q.acutissima populations was sunny slope(7a)<semi-sunny slope(9a)<semi-shade slope(11a)<shade slope(12a),and the maximum reproductive age,average reproductive age and reproductive age were semi-sunny slope>semi-shade slope>sunny slope>shade slope.The onset of the Q.acutissima population on the sunny slope was the earliest.The time interval was similar in all habitats from the onset to the peak flowering date and then to the end date.The duration of the flowering period on the shade slope was the shortest,and there were significant differences with the other three slope directions.The seed number of single tree of Q.acutissima population on the semi-sunny slope was the largest,expressed as that semi-sunny slope>sunny slope>semi-shade slope>shade slope.The fruiting of Q.acutissima was concentrated in the upper and the sun of the canopy,and it was smaller when it on the upper and the sun of the canopy in sunny and semi-sunny slopes than semi-shade slope and shade slope.The age structure,interspecific relationship,reproductive age,and sexual reproduction of Q.acutissima populations are all related to environmental factors,most of which are light conditions.In the future management of the Q.acutissima forest,We can adjust the population structure,interspecies relationships,and improve the sexual reproduction environment of the population through reasonable thinning,and promote the sustained and stable growth of the paralyzed population under different habitat conditions.