The Influence Of Urbanization On Tree Phylogenetic Diversity And Its Relationship With Landscape Characteristics In Typical Areas Of Northeast China

The research on the coupling relationship between forest landscape characteristics and tree phylogenetic diversity is helpful to reveal the indicative effect of landscape dynamic changes on plant diversity,and realize the protection of tree diversity through the adjustment and optimization of landscape level.This study took 420 quadrats in low urbanization regions and heavy urbanization regions as research objects.Using threshold model and redundancy analysis to study the relationships between phylogenetic diversity and landscape characteristics in northeast China.To provide reasonable suggestions for the conservation of tree diversity in northeast China.The results showed that:1.The differences in different urbanized regions and influencing factors of phylogenetic diversity:(1)In 50 km × 50 km grid cell level,compared with the low-urbanization regions,the high-urbanization regions had higher tree phylogenetic diversity,more distant relationship between tree.species and more divergent phylogenetic structure.FPD(Faith phylogenetic diversity)was 1.4 times of that in low urbanization region,MPD(Mean pairwise distance)and MNTD(Mean nearest taxon distance)were 30.03%and 38.85%higher than that in low urbanization region,respectively.The mean values of SesPD(standardized Faith phylogenetic diversity),SesMPD(standardized mean pairwise distance)and SesMNTD(standardized the mean nearest taxon distance)of trees in heavy urbanization region were all greater than 0,while those in low urbanization region were all less than 0.(2)The tree phylogenetic diversity in northeast China was less affected by latitude and altitude(P>0.05),but more affected by longitude,number of sampling points and tree species(P<0.05).2.The differences in different urbanized regions and the influencing factors of forest landscape characteristics:(1)The forest landscape area of the low urbanization area was larger than that of the high urbanization area,which CA(Total forest patch area)was 4.18 times that of heavy urbanization region,and PLAND(Percentage of forest landscape area)and LPI(Percentage of forest maximum patch area)were 72.51%and 74.71%higher than that of heavy urbanization region,respectively.In addition,compared with the heavy urbanization region,the patch shape of forest landscape in low urbanization region was more irregular.The degree of fragmentation and heterogeneity of forest landscape in low urbanization region was less than that in heavy urbanization region.(2)The forest area and aggregation index were significantly affected by the longitude,latitude,altitude,sampling number and species number,while the shape index was mainly affected by longitude and species number(P<0.05 or P<0.01).3.The relationship between phylogenetic diversity and forest landscape characteristics:(1)Forest landscape shape characteristics had an obvious threshold effect on tree phylogenetic diversity.When SHAPE_MN(Mean Shape Index)reached 1.2,1.14 and 1.2,it results in significantly decreased of MPD,SesPD and SesMPD(P<0.01);FRAC_MN(Mean Fractal Dimension Index)reacheed 1.02,1.02,and 1.01,resulting in significantly decreased in MPD,SesPD,and SesMPD(P<0.01).(2)There was a good coupling relationship between tree phylogenetic diversity and forest landscape area,shape and aggregation characteristics in northeast China,among which landscape shape and aggregation characteristics had a significant impact on tree phylogenetic diversity.SHAPE_MN had the largest interpretation of tree pedigree diversity(31.5%),followed by PD(Forest patch density)and NP(Number of forest patches),with maximum interpretation of 29.8%and 29.1%,respectively.Both FPD and SesMNTD had the best coupling relationship with PD and were positively correlated with PD.MPD,SesPD and SesMPD all had the best coupling relationship with SHAPE_MN,and showed a significant negative correlation with SHAPE_MN(p<0.01).The coupling relationship between MNTD and NP was the best,and the correlation between MNTD and NP was very significant(p<0.01).(3)The interpretation of FPD,MPD and MNTD by sampling method(sampling site and quadrat numbers)was greater than that of landscape features,while the interpretation of SesPD,SesMPD and SesMNTD by landscape features was greater than that of sampling method.In summary,urbanization could largely improve tree species phylogenetic diversity,with the risk of alien tree species invasion.Future protection of native plant ecosystems requires repeated consideration of the degree of urbanization.Regulating the regularization of forest landscape shape and controlling the number and density of patches will be beneficial to the protection of forest tree phylogenetic diversity at the regional level,and there are threshold changes in this process.