Temporal shifts in the explanatory power and relative importance of litter traits in regulating litter decomposition

Background:Litter traits critically affect litter decomposition from local to global scales.However,our understanding of the temporal dynamics of litter trait-decomposition linkages,especially their dependence on plant functional type remains limited.Methods:We decomposed the leaf litter of 203 tree species that belong to two different functional types(deciduous and evergreen)for 2 years in a subtropical forest in China.The Weibull residence model was used to describe the different stages of litter decomposition by calculating the time to 10%,25%and 50%mass loss(Weibull t_(1/10),t_(1/4),and t_(1/2)respectively)and litter mean residence time(Weibull MRT).The resulting model parameters were used to explore the control of litter traits(e.g.,N,P,condensed tannins and tensile strength)over leaf litter decomposition across different decomposition stages.Results:The litter traits we measured had lower explanatory power for the early stages(Weibull t_(1/10)and t_(1/4))than for the later stages(Weibull t_(1/2)and MRT)of decomposition.The relative importance of different types of litter traits in influencing decomposition changed dramatically during decomposition,with physical traits exerting predominant control for the stages of Weibull t_(1/10)and MRT and nutrient-related traits for the stages of Weibull t_(1/4),and t_(1/2).Moreover,we found that litter decomposition of the early three stages(Weibull t_(1/10),t_(1/4),and t_(1/2))of the two functional types was controlled by different types of litter traits;that is,the litter decomposition rates of deciduous species were predominately controlled by nutrient-related traits,while the litter decomposition rates of evergreen species were mainly controlled by carbon-related traits.Conclusions:This study suggests that litter trait-decomposition linkages vary with decomposition stages and are strongly mediated by plant functional type,highlighting the necessity to consider their temporal dynamics and plant functional types for improving predictions of litter decomposition.

Cathepsin D knockdown regulates biological behaviors of granulosa cells and affects litter size traits in goats

Cathepsin D(CTSD),the major lysosomal aspartic protease that is widely expressed in different tissues,potentially regulates the biological behaviors of various cells.Follicular granulosa cells are responsive to the increase of ovulation number,hence indirectly influencing litter size.However,the mechanism underlying the effect of CTSD on the behaviors of goat granulosa cells has not been fully elucidated.This study used immunohistochemistry to analyze CTSD localization in goat ovarian tissues.Moreover,western blotting was applied to examine the differential expression of CTSD in the ovarian tissues of monotocous and polytocous goats.Subsequently,the effects of CTSD knockdown on cell proliferation,apoptosis,cell cycle,and the expression of candidate genes of the prolific traits,including bone morphogenetic protein receptor IB(BMPR-IB),follicle-stimulating hormone(FSHR),and inhibinα(INHA),were determined in granulosa cells.Results showed that CTSD was expressed in corpus luteum,follicle,and granulosa cells.Notably,CTSD expression in the monotocous group was significantly higher than that in the polytocous group.In addition,CTSD knockdown could improve granulosa cell proliferation,inhibit cell apoptosis,and significantly elevate the expression of proliferating cell nuclear antigen(PCNA)and B cell lymphoma 2(Bcl-2),but it lowered the expression of Bcl-2-associated X(Bax)and caspase-3.Furthermore,CTSD knockdown significantly reduced the ratios of cells in the G0/G1 and G2/M phases but substantially increased the ratio of cells in the S phase.The expression levels of cyclin D2 and cyclin E were elevated followed by the obvious decline of cyclin A1 expression.However,the expression levels of BMPR-IB,FSHR,and INHA clearly increased as a result of CTSD knockdown.Hence,our findings demonstrate that CTSD is an important factor affecting the litter size trait in goats by regulating the granulosa cell proliferation,apoptosis,cell cycle,and the expression of candidate genes of the prolific trait.

Soil burial has a greater effect on litter decomposition rate than nitrogen enrichment in alpine grasslands

Aims Litter is frequently buried in the soil in alpine grasslands due to grassland degradation,serious rodent infestation and frequent strong winds.However,the effects of various litter positions on litter decomposition rates and nutrient dynamics under nitrogen(N)enrichment in such areas remain unknown.Methods A field experiment was performed in the alpine grasslands of northwest China to investigate the influence of litter position(surface,buried in the soil and standing)and N enrichment on litter decomposition,using data from two dominant grass species(Festuca ovina and Leymus tianschanicus)in control and N-enriched plots.Important Findings Litter decomposition rates were much faster in buried litter and slower in standing litter than in surface litter.N enrichment significantly affected litter quality and then influenced decomposition.But no significant differences in litter mass remaining were observed between control and N-enriched soil burial.These results indicated that N enrichment significantly affected litter decomposition by changes in litter quality.In addition,all litter exhibited net carbon(C)and phosphorus(P)release regardless of treatments.Litter exhibited net N accumulation for litter from the control plots but showed N release for litter from N enrichment plots.These suggested that litter decomposition can be limited by N and N enrichment influenced N cycling of litter.Current study presented direct evidence that soil buried litter exhibited faster mass loss and C release,and that soil burial can be a candidate explanation why litter decomposes faster than expected in dryland.