Correlation and Pathway Analysis of the Carbon,Nitrogen,and Phosphorus in Soil-Microorganism-Plant with Main Quality Components of Tea(Camellia sinensis)

The contents of carbon(C),nitrogen(N),and phosphorus(P)in soil-microorganisms-plant significantly affect tea quality by altering the main quality components of tea,such as tea polyphenols,amino acids,and caffeine.However,few studies have quantified the effects of these factors on the main quality components of tea.The study aimed to explore the interactions of C,N,and P in soil-microorganisms-plants and the effects of these factors on the main quality components of tea by using the path analysis method.The results indicated that(1)The contents of C,N,and P in soil,microorganisms,and tea plants were highly correlated and collinear,and showed significant correlations with the main quality components of tea.(2)Optimal regression equations were established to esti-mate tea polyphenol,amino acid,catechin,caffeine,and water extract content based on C,N,and P contents in soil,microorganisms,and tea plants(R^(2)=0.923,0.726,0.954,0.848,and 0.883,respectively).(3)Pathway analysis showed that microbial biomass phosphorus(MBP),root phosphorus,branch nitrogen,and microbial biomass carbon(MBC)were the largest direct impact factors on tea polyphenol,catechin,water extracts,amino acid,and caffeine content,respectively.Leaf carbon,root phosphorus,and leaf nitrogen were the largest indirect impact factors on tea polyphenol,catechin,and water extract content,respectively.Leaf carbon indirectly affected tea polyphenol content mainly by altering MBP content.Root phosphorus indirectly affected catechin content mainly by altering soil organic carbon content.Leaf nitrogen indirectly affected water extract content mainly by altering branch nitrogen content.The research results provide the scientific basis for reasonable fertilization in tea gardens and tea quality improvement.

A meta-analysis of the impacts of forest logging on soil CO2 efflux

Soil CO2 efflux,the second largest flux in a forest carbon budget,plays an important role in global carbon cycling.Forest logging is expected to have large effects on soil CO2 efflux and carbon sequestration in forest ecosystems.However,a comprehensive understanding of soil CO2 efflux dynamics in response to forest logging remains elusive due to large variability in results obtained across individual studies.Here,we used a meta-analysis approach to synthesize the results of 77 individual field studies to determine the impacts of forest logging on soil CO2 efflux.Our results reveal that forest logging significantly stimulated soil CO2 efflux of the growing season by 5.02%.However,averaged across all studies,nonsignificant effect was detected following forest logging.The large variation among forest logging impacts was best explained by forest type,logging type,and time since logging.Soil CO2 efflux in coniferous forests exhibited a significant increase(4.38%)due to forest logging,while mixed and hardwood forests showed no significant change.Logging type also had a significant effect on soil CO2 efflux,with thinning increasing soil CO2 efflux by 12.05%,while clear-cutting decreasing soil CO2 efflux by 8.63%.The time since logging also had variable effects,with higher soil CO2 efflux for 2 years after logging,and lower for 3-6 years after logging;when exceeded 6 years,soil CO2 efflux increased.As significantly negative impacts of forest logging were detected on fine root biomass,the general positive effects on soil CO2 efflux can be explained by the accelerated decomposition of organic matter as a result of elevated soil temperature and organic substrate quality.Our results demonstrate that forest logging had potentially negative effects on carbon sequestration in forest ecosystems.

Impact of living mulch on soil C:N:P stoichiometry in orchards across China:A meta-analysis examining climatic,edaphic,and biotic dependency

The use of living mulch in orchards is a widely accepted management strategy for improving soil quality and enhancing tree productivity.Although the effects of living mulch on soil organic carbon(C)and nutrients have been previously investigated,changes in the stoichiometric ratios of C,soil total nitrogen(N),and soil total phosphorous(P)under different climatic,edaphic,and biotic conditions are currently unknown.These factors are important indicators of elemental balance associated with ecological interactions.In order to examine the effects of living mulch in orchards on soil C:N:P stoichiometry under different conditions,a meta-analysis was undertaken.The results showed that in general,living mulch significantly(P<0.05)increased C:P and N:P ratio,while the impact on C:N ratio was not significant,a result that was related to the coupled increase of C and N.Phosphorous limitation occurred shortly after the addition of living mulch;after four years this effect receded.In contrast,an increase in C occurred simultaneously with N increase at all stages.Specifically,the treatment effect was context-dependent.The living mulch did not change soil stoichiometry in orchards with old trees(>10 years),an occurrence which may be related to changes in the amount of fungi.Grass life history also had a significant influence on the treatment effect on soil stoichiometry,while N-fixing characteristics did not.The treatment effect was significant in areas with moderate mean annual temperature and mean annual precipitation,which might be related to the litter ratio of grass and trees.Effects on stoichiometric ratios were significant in the top soil layer(0–20 cm),in contrast to the deep soil layers.Therefore,grass species and management practices,such as fertilization,should be selected according to the specific soil and climatic conditions of the management area.