| The Greater Khingan Range is a sensitive area of global climate change in China.The impact of the reduced native Larix gmelinii forest on the function and biodiversity of underground ecosystems due to external disturbances has become one of the important ecological problems.This study was conducted in June(spring)and August(autumn)2017,with natural secondary mixed forests(referred to as control)that were not affected by harvesting,15 years after severe logging disturbance(referred to as harvesting for 15 years),and 30 years after severe logging disturbance(referred to as harvesting for 30 years),pitfall traps were used to investigate the community characteristics and seasonal changes of ground-dwelling soil arthropods under heavy harvesting.And the effects of environmental filtering,dispersal limitation and biotic interactions on community assembly of typical ground-dwelling soil arthropods were analyzed in 20m×20m scale based on niche and neutral theory.The main results are as follows:1.Composition and diversity of ground-dwelling soil arthropodsA total of 78924 ground-dwelling soil arthropods were collected during the study period,belonging to 111 groups of 70 families.Among them,29169 are macro soil arthropods,belonging to 4 classes,14 orders,52 families,83 groups,the dominant group is Tetramorium;49755 are meso/micro soil arthropods,belonging to 2 classes,2 orders,18 families,29 groups,with Onychiurus,Hypogastrura and Sminthurinus dominant.The main nutritional function groups of them are phytophagy.The distribution of ground-dwelling soil arthropods wass related to harvesting disturbance and sampling period.the total number sort of soil arthropods is: plots after harvesting 15 years > controls > plots after harvesting 30 years;the groups sort is: controls > plots after harvesting 15 years > plots after harvesting 30 years.And the number of soil arthropods collected in spring was lower than that in autumn,but the groups was higher than that in autumn.Shannon-Wiener index(H'),Pielou index(E)of macro soil arthropods in harvested plots were significantly higher than control plots,Simpson index(C)was significantly lower than the control plots;the groups and Margalef index(D)of meso/micro soil arthropods were significantly lower than the control plots.The LSD test indicated that there was no significant difference in the diversity index of macro soil arthropods between the 15-year and the 30-year harvesting plots.Besides,there was a significant difference in the Margalef index of the meso/micro soil arthropods.Furthermore,only the groups,H',E and D of meso/micro soil arthropods in spring were significantly higher than that in autumn,while C was lower.The Jaccard analysis showed that the similarity of soil arthropods community in the 15,30-year plots and the control plots were 0.74 and 0.72,respectively.And the similarity of soil arthropods in spring and autumn was 0.77,the similarity between harvesting for 15 and harvesting 30-year plots was 0.89,which indicated that the ground-dwelling soil arthropods community changed certainly.This result is the same as the typical discriminant analysis,that is,the ground-dwelling soil arthropods in the harvesting plots is different from controls,and there are certain seasonal changes.After harvesting disturbances,ground-dwelling soil arthropods changed due to changes in available resources of the study area.The niche breadth of soil arthropods in harvested plots was significantly higher than that in the control plots,while from spring to autumn,the niche breadth of soil arthropods was significantly lower.However,the niche overlap index of surface soil arthropods is around 0.050.2.Effects of environmental filtering,dispersal limitation and biotic interactions on the assembly of ground-dwelling soil arthropods communityBased on the dominant and common species of soil arthropods in the study area,the effects of environmental filtering,dispersal limitation and biotic interactions on soil arthropods community assembly were analyzed on the scale of 20m×20m.On account of the environmental principal component and Moran eigenvalues,variation partitioning was applied to explore the relative regulation of environmental filtering and dispersal limitation.Null model and species coexistence pattern analysis of niche overlap were used to identify the regulation of biotic interactions.We found that the construction of macro soil arthropods was mainly controlled by dispersal limitation and environmental filtering,and the regulation of biotic interactions was not obvious.Furthermore,the relative importance of environmental filtering and dispersal limitation has little to do with harvesting disturbances,but it is related to the seasons.In spring,dispersal limitation was the main regulator,environmental filtering was secondary,however,they were both the main regulators;For meso/micro soil arthropods community,dispersal limitation was the main regulator,and environmental filtering was secondary.The relative extent of them was not related to harvesting disturbance and seasonal variation.Whereas the regulation of biotic interactions had seasonal changes,which was not obvious in spring,but had a certain effect in autumn.RDA indicated that soil nitrogen,phosphorus and organic carbon had a highly significant impact on macro soil arthropods.Moreover,soil p H had the most significant effect on meso/micro soil arthropods.It shows that environmental factors have a vital influence on soil arthropods.In the view of the above results,we can conclude that: The community composition and diversity of ground-dwelling soil arthropods are related to harvesting disturbance and sampling period.At the spatial scale of 20 m×20 m,the construction of ground-dwelling soil arthropods community was regulated by dispersal limitation and environmental filtering.The biotic interactions had a certain effect,but it is not the main driving force.In addition,the relative regulation of environmental filtering,dispersal limitation and biotic interactions was influenced by the season. |
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