| Qilian Mountain is located in the western part of Gansu Province and the northeastern edge of Qinghai Province,which is the development of the economic and social development of the Hexi Corridor and the western region.It is the main land security,strategic channel and ecological security barrier,geographical location and ecological location in the northwest China.In the national ecological security construction and ecological barrier construction has a very important strategic position.Qilian Mountain as one of the most sensitive areas of global climate change,compound ecosystem in the overall development and stability of the overall situation.Picea crassifolia Kom.Is one of the most widely distributed fields in the Qilian Mountains,with the largest area and the highest productivity.The natural regeneration of trees has become one of the most active fields in forest research at home and abroad.Based on the investigation of the community structure of Picea crassifolia in the northern slope of Qilian Mountains,the natural regeneration of spruce seedlings under different altitude gradients and the distribution characteristics of natural regeneration seedlings and the response of natural regeneration to forest types and community structure,To provide a scientific basis for the study of the succession of Picea crassifolia community.The main results are as follows:(1)In the Qilian Mountains,the ability of the natural restoration of Picea crassifolia is poor.With the change of altitude,the reason for the poor regeneration under canopy is mainly due to the thickness of litter layer and the limitation of water and heat conditions,from moisture limit to heat limit.The water condition is the limiting factor of the natural regeneration of the low altitude alpine spruce.The high altitude natural regeneration is mainly restricted by the heat condition.Natural updates at different altitudes are the smallest at 2900 m,and as the altitude gradient increases,the natural regeneration also increases.The natural regeneration of Picea crassifolia was 2900m<3000m<3100m<3200m<2800m<2700m<2500m,and the natural regeneration ability of Picea crassifolia at 2500m-3200m above sea level was affected by stand type and canopy density.(2)The number of newly updated seedlings of Picea mongolica increased with the increase of altitude gradient,and then increased the trend.The seedlings were updated at altitudes of 3200-3300m(25~55cm)(>25cm)The results showed that the number of natural regeneration strains of Picea crassifolia was 179,1375,300 plants/hm2,and the number of natural regeneration strains of Pleurotus nebrodensis was2,500/hm2,2700m,2800m and 2900m moss,respectively.2930m,3000m grasses of Picea crassifolia updated strains of 50,275 plants/hm2 for no natural regeneration capacity.2500-2600m natural update 85~105cm height of the lack of seedlings;altitude of 3300m or so the number of natural regeneration of the number of seedlings is not much difference,update the situation is poor,some high distribution of seedlings less.(3)Distributed in the 3300m forest line near the shrubs Qinghai spruce forest,the tree layer is more sparse,seedlings and young trees 2500 plants/hm~2;distributed in the 2600-3000m altitude moss Qinghai spruce forest is the northern slope of Qilian Mountains Qinghai spruce forest distribution Wide,large area,the highest productivity of forest types,natural regeneration seedlings 1500/hm~2,mostly in the age of forest,the number of natural regeneration of the preservation rate is very low.From 2500-3300m above sea level,the distribution pattern of natural regeneration seedlings changed from random distribution to cluster distribution.2900m above sea level were randomly distributed;85~105cm seedlings were evenly distributed;3000m altitude seedlings showed random distribution;3100-3300m three sea sections,the natural update seedlings showed cluster distribution.(4)The height distribution of Picea crassifolia was moderate in the middle(25~55cm)height,which indicated that the number of natural regeneration of Picea crassifolia was higher in the expansion gap,45~105cm height of the seedlings accounted for a high proportion of height,and in the canopy closed small gaps,the natural regeneration of Picea frigida.(5)The natural regeneration of Picea crassifolia was not only related to the forest type,but also had a significant relationship with the canopy density.The fitting equation of Yuba canopy and natural regeneration was Y=-0.0002x+0.8511,R~2=0.62,There was a significant negative correlation between them.Forest canopy closure<0.4,natural regeneration is good,forest canopy closure>0.85 basic no update ability,between them natural update in general.(6)Picea crassifolia Natural regeneration in the ground by the thickness of5-15cm update good,with the increase of the thickness of the ground,the worse the regeneration effect is.The Moss Spruce Woodland is updated well under 25%,the cover degree is$number and the cover degree is more than 50%and the update effect is worse with the cover degree.(7)The natural regeneration seedlings of Picea mongolica population in Picea crassifolia,with the extension of time,the population distribution gradually appears as cluster distribution. |
