Diversity of root-associated fungi of Vaccinium mandarinorum along a human disturbance gradient in subtropical forests,China

Aims Ericaceous plant species can host diverse fungi in their roots,including ericoid mycorrhizal fungi(ERMF),endophytes,pathogens and some species with unknown functions.However,how this diversity of fungi responds to different human disturbances is not well understood.Methods In this study,we examined the effects of different human disturbance on fungal diversity in hair roots of Vaccinium mandarinorum,an ericaceous plant.Fungal DNA was extracted from hair roots of V.mandarinorum and high-throughput sequencing was applied to detect the diversity of root-associated fungi along a human disturbance gradient in subtropical forests in Gutianshan National Nature Reserve(GNNR)in East China.The four forest types with different disturbance regime were:old growth forest(OGF),secondary forest with once cut(SEC I),secondary forest with twice cut(SEC II)and Cunninghamia lanceolata plantation(PLF).Important Findings The results showed that:(i)diverse fungal operational units(OTUs)were detected in hair roots of V.mandarinorum in the four types of forests,covering fungal phyla of Ascomycota,Basidiomycota,Chytridiomycota,Glomeromycota and Zygomycota;(ii)Community composition of root-associated fungi of V.mandarinorum in PLF was distinct from those in the other three forest types,and two types of secondary forests had similar fungal community composition;(iii)Different fungal families respond differently to human disturbances:fungal families with significant preference to OGF were ectomycorrhizal or saprophytic fungi while fungal families with higher relative abundance in PLF were plant pathogenic or saprophytic fungi;(iv)The first principal component(PC1)of plant community had a significant effect on composition of root-associated fungal community,while edaphic parameters showed no significant effect on fungal community composition in roots of V.mandarinorum.Our results help to better understand the responses of both ericaceous plants and their fungal partners to human disturbances and forest managements.

Relative contributions of biotic and abiotic factors to the spatial variation of litter stock in a mature subtropical forest

Aims Dead plant material(i.e.litter)is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems.The storage of litter is jointly determined by its production from plants and decomposition in a given environment.However,only few studies have explored the relative importance of en-vironmental(i.e.abiotic)and plant(i.e.biotic)factors in driving the spa-tial variation of litter mass.The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest.Methods The aboveground litter mass was sampled in 187 grids of a 20-hm forest dynamics plot in a subtropical broad-leave forest in eastern China.The contributions of environmental variables,topographical and species variables on litter stocks were quantified by the boosted regression tree analysis.Important Findings The mean aboveground litter stock was 367.5 g m^(−2) in the Tiantong dynamics forest plot across all the 187 grids.The litter stock ranged from 109.2 to 831.3 g m^(−2) and showed a large spatial variation with the coefficient of variance as 40.8%.The boosted regression tree analysis showed that slope elevation and soil moisture were the most influential variables on the spatial variation of litter stock.The relatively influence of abiotic factors(environmental and topographical factors)was 71.4%,which is larger than biotic factors(28.6%).Overall,these findings sug-gest that abiotic factors play a more important role than plants in driving the spatial variation of aboveground litter stock in the subtropical forest.Given that the global carbon-cycle models have been aiming to refine from the hundred kilometers to sub-kilometer scale,this study highlights the urgency of a better understanding of the spatial variation of litter stock on the fine scale.

Country-level land carbon sink and its causing components by the middle of the twenty-first century

Background:Countries have long been making efforts by reducing greenhouse-gas emissions to mitigate climate change.In the agreements of the United Nations Framework Convention on Climate Change,involved countries have committed to reduction targets.However,carbon(C)sink and its involving processes by natural ecosystems remain difficult to quantify.Methods:Using a transient traceability framework,we estimated country-level land C sink and its causing components by 2050 simulated by 12 Earth System Models involved in the Coupled Model Intercomparison Project Phase 5(CMIP5)under RCP8.5.Results:The top 20 countries with highest C sink have the potential to sequester 62 Pg C in total,among which,Russia,Canada,USA,China,and Brazil sequester the most.This C sink consists of four components:productiondriven change,turnover-driven change,change in instantaneous C storage potential,and interaction between production-driven change and turnover-driven change.The four components account for 49.5%,28.1%,14.5%,and 7.9%of the land C sink,respectively.Conclusion:The model-based estimates highlight that land C sink potentially offsets a substantial proportion of greenhouse-gas emissions,especially for countries where net primary production(NPP)likely increases substantially and inherent residence time elongates.

Thermal acclimation of leaf respiration varies between legume and non-legume herbaceous

Aims Ubiquitous thermal acclimation of leaf respiration could mitigate the respiration increase.However,whether species of different plant functional groups showing distinct or similar acclimation justifies the simple prediction of respiratory carbon(C)loss to a warming climate.Methods In this study,leaf dark respiration(Rd)of illinois bundleflower(IB,legume),stiff goldenrod(GR,C_(3) forbs),indian grass,little bluestem and king ranch bluestem(IG,LB and KB,C_(4) grass)were measured with detached leaves sampled in a 17-year warming experiment.Important Findings The results showed that Rd at 20℃ and 22℃(R_(20) and R_(22))were significantly lower in the warming treatment for all the five species.Lower R_(22) in warmed than R_(20) in control in GR,KB,LB and IG imply acclimation homeostasis,but not in IB.The significant decline in temperature sensitivity of respiration(Q_(10))of GR resulted in the marginal reduction of Q_(10) across species.No significant changes in Q_(10) of C_(4) grasses suggest different acclimation types for C_(3) forbs and C_(4) grass.The magnitude of acclimation positively correlated with leaf C/N.Our results suggest that non-legume species had a rela-tive high acclimation,although the acclimation type was different between C_(3) forbs and C_(4) grasses,and the legume species displayed no acclimation in Rd.Thus,the plant functional types should be taken into account in the grassland ecosystem C models.