Effects Of Phylogenetic Diversity On Productivity Of A Mixed Broadleaved-Korean Pine Forest

Forests are the most important reservoir of terrestrial biodiversity,and as the largest terrestrial ecosystem on the earth,forests play a vital role in regulating the global carbon cycle and also can mitigate climate change.In recent years,the relationship between biodiversity and ecosystem function is one of the hot spot in ecological research.The driving effect of plant diversity on forest productivity has been widely focused,but its underlying mechanisms are still controversial.We explored the impacts of phylogenetic diversity and other biotic and abiotic factors on forest productivity at different successions and spatial scales based on a 9 ha typical mixed broadleaved-Korean pine(Pinus koraiensis)forest dynamic monitoring plot of and1 ha secondary birch(Betula platyphylla)forest dynamic monitoring plot in Liangshui National Nature Reserve,Heilongjiang Province,with the censuses data in 2005 and 2018,using boosted regression tree analysis?structural equation models and linear regression.The results of the study are as follows:(1)In the broadleaved-Korean pine forest,species diversity and phylogenetic diversity were both positively correlated with productivity.At the spatial scale of 10m×10m,species diversity indirectly promotes productivity only through the mediation of the initial biomass.The strength of species diversity on productivity gradually enhanced as spatial scales increased,while the effects of phylogenetic diversity on productivity showed opposite trend.On small scales,the effects of phylogenetic diversity on productivity was stronger than species diversity.And on large scales,the effects of phylogenetic diversity on productivity was lower than species diversity.(2)Productivity was affected by abiotic factors.Soil factors were significantly positively correlated with productivity at different scales,which was gradually dominated as spatial scales increased.Organic carbon and total phosphorus are the most relevant factors.The effect of initial biomass on productivity gradually decreased with the increase of space scales.(3)The productivity of the secondary forest is less than that of the broadleaved-Korean pine forest,indicating that the productivity increases gradually with the development of forest succession.(4)Moreover,among the secondary birch forest and the broadleaved-Korean pine forest,phylogenetic diversity had the strongest ability to explain productivity,followed by species diversity,soil nutrients and stand density.Compared with the secondary birch forest,the diversity of broadleaved-Korean pine forest had a stronger relationship with productivity,and the contribution of stand density to productivity was reduced.Moreover,the contribution of soil nutrients to productivity remained relatively constant in two succession stages.Our results indicated that evolutionary information should be considered in future ecosystem function studies,which might provide additional explanatory power for other diversity metrics.Meanwhile,the effects of different succession stages,spatial scales and abiotic factors should also be considered,which could provide a scientific basis for further understanding the mechanisms underlying the changes of forest productivity.