| The Loess Plateau is the largest accumulative loess area in the world,but the climate is arid,the vegetation is sparse,and the loss of water and soil is serious in this area.This situation is closely related to human activity,especially estrepement and deforestation,except natural factors.So it is imperative under the situation to accelerate the recovery and restoration.Ziwuling Mountain,which is located in the hinterland of the Loess Plateau,the forest coverage rate is 88.3%,and the vegetation is the best preserved,the most typical,the most valuable natural secondary forest ecosystems on the ecologically fragile areas of the Loess Plateau. Ziwuling Mountain forest region has crucial effect on adjusting regional climate,maintaining ecological balance and promoting ecologically sustainable economic development on the Loess Plateau.So the research of forest community regeneration has significant ecological meaning for recovery and restoration of degenerative ecosystem.Based on field survey to Ziwuling Mountain,adopting Levins index and Pianka index,the generational(seedling,sapling and adult) niche breadth and overlap of Quercus liaotungensis,Pinus tabulaeformis and other arbor tree species were studied in different community types,which was Q. liaotungensis forest,P.tabulaeformis+Q.liaotungensis mixed forest and artificial P.tabulaeformis forest on sunny and shady slope.The relationship between arbor tree seedlings and soil nutrient,and the relationship among arbor tree seedlings were also studied.(1) The results showed that the generational niche breadth of Q.liaotungensis and P. tabulaeformis was different in these community types.The niche breadth of adult was the same as community.The niche breadths of Q.liaotungensis' seedling and sapling were the highest in artificial P.tabulaeformis forest on sunny slope and shady slope,which are 0.91,0.95,0.98 and 0.94. There was significant difference among other community.It indicated the growth of Q. liaotungensis' seedling and sapling was inclined to the environmental condition of artificial P. tabulaeformis forest.The niche breadth of Q.liaotungensis' seedling was the highest in Q. liaotungensis forest on sunny slope and artificial P.tabulaeformis forest on shady slope,which are 0.79 and 0.63.There was significant difference among other community.The niche breadth of Q. liaotungensis' sapling was the highest in artificial P.tabulaeformis forest on suuny slope and in P. tabulaeformis+Q.liaotungensis mixed forest on shady slope,which are 1.00 and 0.83.There was significant difference among other community.The growth of P.tabulaeformis' seedling was adaptable not only to the environment condition of Q.liaotungensis forest on sunny slope but to that of artificial P.tabulaeformis forest on shady slope.The growth of P.tabulaeformis' sapling was adaptable not only to the environment condition of artificial P.tabulaeformis forest but to that of Q. liaotungensis forest on sunny slope.As a whole,artificial P.tabulaeformis forest had an important effect on the restoration of natural vegetation in this region.Artificial P.tabulaeformis forest and P. tabulaeformis+Q.liaotungensis mixed forest would have existed over a long period of time,while P.tabulaeformis+Q.liaotungensis mixed forest on sunny slope would have even more.(2) The niche overlap of Q.liaotungensis' seedling and sapling niche breadth is consistent in most cases,but some times is not consisten.The niche overlap of Q.liaotungensis' seedling were higher in artificial P.tabulaeformis forest on sunny slope and shady slope,which are 0.68 and 0.70. There was significant difference among other community on sunny slope,but there was significant difference between Q.liaotungensis' forest shady slope.On sunny slope,the niche overlap of P. tabulaeformis' seedling and sapling were higher in artificial P.tabulaeformis forest,which are 0.56 and 0.65.There was significant difference among other community,but there was significant difference between Q.liaotungensis' forest shady slope.On shady slope,the niche overlap of P. tabulaeformis' seedling and sapling were higher in P.tabulaeformis+Q.liaotungensis mixed forest, which are 0.64 and 0.61.(3) The niche breadth of Acer grosseri,A.ginnala,Carpinus turczaninowii and Toxicodendron vernicifluum's seedling,sapling and adult were higher than other trees in different community types on sunny slope and shady slope.They are the common companion species and have a wide distribution.The niche breadth of A.ginnala's seedling,which the sunny slope niche breadth was higher than shady slope in different community types,was contrary to Q.liaotungensis' seedling in different community.Because both A.ginnala's and Q.liaotungensis' seedling have a wide distribution,so the niche overlap between two was more higher than the niche overlap between P. tabulaeformi and A.ginnala's.But the he niche overlap between P.tabulaeformi and Q. liaotungensis' seedling was higher.(4) The analysis between tree seedlings and soil nutrient showed that the factor of influence on different trees seedling were difference.The factor of soil nutrient influence on Q.liaotungensis' seedling was organic matter.Along with the content of organic matter in soil increased its density decreases slowly,when the content of organic matter was 10g/kg,Q.liaotungensis' seedling density was to keep in a stable leve.And Q.liaotungensis' seedling density mainly concentrated in the organic matter for the 5～8 g/kg.The factor of soil nutrient influence on P.tabulaeformis seedling was available potassium.The content of available potassium in natural P.tabulaeformis forest was higher than that of artificial P.tabulaeformis forest,so when P.tabulaeformis as a restoration should be paid attention to investigating the available potassium content of cultivation.(5) Q.liaotungensis' seedlings were significantly positive correlated with Crataegus pinnatifid seedling,Pyrus betulaefolia seedlings and Toxicodendron vernicifluum seedlings(r=0.65,P＜0.01; r=0.43,P＜0.01;r=0.42,P＜0.01).They were all negatively associated with the organic matter(r =-0.39,P＜0.01;r=-0.42,P＜0.05;r=-0.38,P＜0.05).This shows that the soil nutrients were very important to tree regeneration,but also play a important role in the community composition and structure.P.tabulaeformis seedlings were negative correlated with correlation with A.ginnala seedlings(r=-0.54,P＜0.01).At the same time,P.tabulaeformis seedlings and A.ginnala seedlings were statistically significantly correlated with available potassium content(r=0.42,P＜0.01;r=-0.48,P＜0.01).(6) The number of Q.liaotungensis' seedlings and P.tabulaeformis seedlings were gradually decreased as the age increasing,which respectively at the age of nine and eight to achieve a stability state.The mortality rate and killing valuable of Q.liaotungensisa seedling was higher at the age of six and eight,while the mortality rate and killing valuable of P.tabulaeformis seedling was higher at the age of three and seven.But the cause of their death needs further research. |
PDF Full Text Request