Implication of community-level ecophysiological parameterization to modelling ecosystem productivity:a case study across nine contrasting forest sites in eastern China

Parameterization is a critical step in modelling ecosystem dynamics.However,assigning parameter values can be a technical challenge for structurally complex natural plant communities;uncertainties in model simulations often arise from inappropriate model parameterization.Here we compared five methods for defining community-level specific leaf area(SLA)and leaf C:N across nine contrasting forest sites along the North-South Transect of Eastern China,including biomass-weighted average for the entire plant community(AP_BW)and four simplified selective sampling(biomass-weighted average over five dominant tree species[5DT_BW],basal area weighted average over five dominant tree species[5DT_AW],biomass-weighted average over all tree species[AT_BW]and basal area weighted average over all tree species[AT_AW]).We found that the default values for SLA and leaf C:N embedded in the Biome-BGC v4.2 were higher than the five computational methods produced across the nine sites,with deviations ranging from 28.0 to 73.3%.In addition,there were only slight deviations(<10%)between the whole plant community sampling(AP_BW)predicted NPP and the four simplified selective sampling methods,and no significant difference between the predictions of AT_BW and AP_BW except the Shennongjia site.The findings in this study highlights the critical importance of computational strategies for community-level parameterization in ecosystem process modelling,and will support the choice of parameterization methods.

Plant community and soil properties drive arbuscular mycorrhizal fungal diversity:A case study in tropical forests

The mutual interdependence of plants and arbuscular mycorrhizal fungi(AMF)is important in carbon and mineral nutrient exchange.However,an understanding of how AMF community assemblies vary in different forests and the underlying factors regulating AMF diversity in native tropical forests is largely unknown.We explored the AMF community assembly and the underlying factors regulating AMF diversity in a young(YF)and an old-growth forest(OF)in a tropical area.The results showed that a total of 53 AMF phylogroups(virtual taxa,VTs)were detected,38±1 in the OF and 34±1 in the YF through high-throughput sequencing of 18S rDNA,and AMF community composition was significantly different between the two forests.A structural equation model showed that the forest traits indirectly influenced AMF diversity via the plant community,soil properties and microbes,which explained 44.2%of the total observed variation in AMF diversity.Plant diversity and biomass were the strongest predictors of AMF diversity,indicating that AMF diversity was dominantly regulated by biotic factors at our study sites.Our study indicated that forest community traits have a predictable effect on the AMF community;plant community traits and soil properties are particularly important for determining AMF diversity in tropical forests.

Plant diversity and community history shift colonization success from early- to mid-successional species

Aims Functional traits are supposed to play an important role in deter-mining the colonization success of new species into established communities.short-term experimental studies have documented higher resistance of more diverse grasslands against coloni-zation by new species.However,little is known about which traits colonizers should have to successfully invade diverse plant communities in the longer term and how community his-tory may modify the resistance of diverse communities against colonization.Methods In a grassland biodiversity experiment(Jena Experiment)established with different species richness(s;1,2,4,8 and 16)and functional group(Fg)number and composition(1 to 4;legumes,grasses,small herbs,tall herbs),we studied colonization of naturally dispersed species in split-plots(i)with different duration of weeding(never weeded,weeded for 3 or 6 years and then un-weeded for 1 year)and(ii)with different duration of colonization(7 years,4 years and 1 year after cessation of weeding).Important Findingsresistance against colonization by new species declined with increased duration of weeding(on average 13,17 and 22 col-onizer species in 1-,4-and 7-year-old communities,respec-tively).Communities established at low diversity accumulated more colonizer species with a longer duration of weeding than more diverse communities.Duration of colonization had only small effects on the number of colonizer species.Colonizers with early successional traits,i.e.annual life cycle,reproduction by seeds,small seeds,long-lived seeds and an earlier start of a longer flowering period,were favoured in species-poor newly established experimental plant communities(short duration of weeding)and early after cessation of weeding(short duration of colonization).a change from early-to mid-successional traits,i.e.taller growth,perennial life cycle,vegetative reproduction,characterized colonization at increased plant diversity and in communities with legumes or without grasses.legume absence/grass presence and increased duration of weeding led to a shift in colonizer strategies from rapid nutrient uptake and cycling(higher specific leaf area)to nutrient retention and symbiotic N2 fixation.our study shows that non-random trait spectra of naturally dispersed colonizers encompass trade-offs between different functions(reproduction,persistence,growth)reflected in a change from early-to mid-successional traits at increasing plant diversity,with a longer duration of weeding and a longer time of colonization.