Changes in plant debris and carbon stocks across a subalpine forest successional series

Background:As a structurally and functionally important component in forest ecosystems,plant debris plays a crucial role in the global carbon cycle.Although it is well known that plant debris stocks vary greatly with tree species composition,forest type,forest origin,and stand age,simultaneous investigation on the changes in woody and non-woody debris biomass and their carbon stock with forest succession has not been reported.Therefore,woody and non-woody debris and carbon stocks were investigated across a subalpine forest successional gradient in Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau.Results:Plant debris ranged from 25.19 to 82.89 Mg∙ha−1 and showed a global increasing tendency across the subalpine forest successional series except for decreasing at the S4 successional stage.Accordingly,the ratios of woody to non-woody debris stocks ranged from 26.58 to 208.89,and the highest and lowest ratios of woody to non-woody debris stocks were respectively observed in mid-successional coniferous forest and shrub forest,implying that woody debris dominates the plant debris.In particular,the ratios of coarse to fine woody debris stocks varied greatly with the successional stage,and the highest and lowest ratios were found in later and earlier successional subalpine forests,respectively.Furthermore,the woody debris stock varied greatly with diameter size,and larger diameter woody debris dominated the plant debris.Correspondingly,the carbon stock of plant debris ranged from 10.30 to 38.87 Mg∙ha−1 across the successional series,and the highest and lowest values were observed in the mid-coniferous stage and shrub forest stage,respectively.Most importantly,the carbon stored in coarse woody debris in later successional forests was four times higher than in earlier successional forests.Conclusions:The stock and role of woody debris,particularly coarse woody debris,varied greatly with the forest successional stage and dominated the carbon cycle in the subalpine forest ecosystem.Thus,preserving coarse woody debris is a critical strategy for sustainable forest management.

Effects of forest canopy density and epixylic vegetation on nutrient concentrations in decaying logs of a subalpine fir forest

Background:Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems.Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs.However,it is unclear how the forest canopy density and epixylic vegetation growth affect the nutrient concentrations in deadwood.Methods:We measured the concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),sodium(Na),magnesium(Mg),and manganese(Mn)in experimentally exposed decaying logs placed in gaps,at the edge of gaps,and under the closed canopy during a four-year decomposition experiment in a Subalpine Faxon fir forest(Abies fargesii var.faxoniana)on the eastern Qinghai-Tibetan Plateau,China.To assess the effect of the epixylic vegetation,we experimentally removed it from half of the logs used in the study.Results:Under open canopy conditions in the gap and at the edge,the concentrations for most of the nutrients in the bark and the highly decayed wood were lower than under the closed canopy.The effect of the epixylic treatment on nutrient concentrations for all but K and Na in barks varied with the decay classes.Significantly lower concentrations of N,P,Ca,and Mn following the removal of epixylic vegetation were observed in the wood of decay class IV.Epixylic vegetation significantly increased most nutrient concentrations for decaying barks and wood under open canopy conditions.In contrast,epixylic vegetation had no or minimal effects under the closed canopy.Conclusions:Forest canopy density and epixylic vegetation significantly alter the nutrient concentrations in decaying logs.Open canopies likely accelerate the rate of nutrient cycling between the epixylic vegetation and decaying logs in subalpine forests.

Molecular glue triggers degradation of PHGDH by enhancing the interaction between DDB1 and PHGDH

Cancer stem cells(CSCs)play a pivotal role in tumor initiation,proliferation,metastasis,drug resistance,and recurrence.Consequently,targeting CSCs has emerged as a promising avenue for cancer therapy.Recently,3-phosphoglycerate dehydrogenase(PHGDH)has been identified as being intricately associated with the regulation of numerous cancer stem cells.Yet,reports detailing the functional regulators of PHGDH that can mitigate the stemness across cancer types are limited.In this study,the novel“molecular glue”LXH-3-71 was identified,and it robustly induced degradation of PHGDH,thereby modulating the stemness of colorectal cancer cells(CRCs)both in vitro and in vivo.Remarkably,LXH-3-71 was observed to form a dynamic chimera,between PHGDH and the DDB1-CRL E3 ligase.These insights not only elucidate the anti-CSCs mechanism of the lead compound but also suggest that degradation of PHGDH may be a more viable therapeutic strategy than the development of PHGDH inhibitors.Additionally,compound LXH-3-71 was leveraged as a novel ligand for the DDB1-CRL E3 ligase,facilitating the development of new PROTAC molecules targeting EGFR and CDK4 degradation.