The storage and utilization of carbohydrates in response to elevation mediated by tree organs in subtropical evergreen broad-leaved forests

Global climate change can affect tree growth and carbon sink function by influencing plant carbohydrate synthesis and utilization,while elevation can be used as an ideal setting under natural conditions to simulate climate change effects.The effect of elevation on tree growth may depend on organ type.However,the allocation patterns of nonstructural and structural carbohydrates(NSCs and SCs,respectively)in different tree organs and their response to elevation remain unclear.We selected four dominant tree species,Schima superba,Castanopsis eyrei,Castanopsis fargesii and Michelia maudiae,along an elevation gradient from 609 to 1,207 m in subtropical evergreen broad-leaved forests and analyzed leaf,trunk,and fine root NSCs,carbon(C),nitrogen(N)and phosphorus(P)concentrations and the relative abundance of SCs.Leaf NSCs increased initially and then decreased,and trunk NSCs increased with increasing elevation.However,root NSCs decreased with increasing elevation.The relative abundance of SCs in leaves and trunks decreased,while the relative abundance of root SCs increased with increasing elevation.No significant correlations between SCs and NSCs in leaves were detected,while there were negative correlations between SCs and NSCs in trunks,roots,and all organs.Hierarchical partitioning analysis indicated that plant C/N and C/P were the main predictors of changes in SCs and NSCs.Our results suggest that tree organs have divergent responses to elevation and that increasing elevation will inhibit the aboveground part growth and enhance the root growth of trees.A tradeoff between the C distribution used for growth and storage was confirmed along the elevation gradient,which is mainly manifested in the"sink"organs of NSCs.Our results provide insight into tree growth in the context of global climate change scenarios in subtropical forest ecosystems.

Arbuscular mycorrhizal fungi communities associated with wild plants in a coastal ecosystem

Arbuscular mycorrhizal fungi(AMF)form a near-ubiquitous mutualistic association with roots to help plants withstand harsh environments,and play a key role in the establishment of coastal beach plant communities.Yet little is known about the structure and composition of AMF communities on coastal beaches of eastern China.In this study,we investigated the occurrence,community composition and diversity of AMF associated with common wild plants on a coastal beach of North Jiangsu,China.Almost all of the local wild species were colonized by AMF except for Chenopodium album L.Thirty-seven AMF species were isolated from the rhizosphere belonging to 12 genera in seven families.Glomus was the dominant genus and Funneliformis mosseae the dominant species.The colonization,spore composition and diversity of AMF were strongly related to edaphic factors.Sodium(Na^(+))ions in the soil significantly and negatively affected the colonization rate by AMF and both soil Na^(+)levels and pH had a significant negative effect on AMF spore density and evenness.However,there was a significant positive correlation between species richness and total organic carbon.The results provide insights into soil factors affecting native AMF communities in coastal beach habitats which could benefit vegetation recovery and soil reclamation efforts.

Dendroclimatic response of Picea jezoensis along an altitudinal gradient in Changbai Mountains

We investigated the effects of climate on Yeddo spruce (Picea jezoensis)radial growth along altitudinal gradients in the subalpine forests of Changbai Mountains using dendroclimatic analyses. Yeddo spruce at its lower and upper distribution limits was more sensitive to the climate. Despite precipitation being generally considered sufficient, we found that precipitation significantly affected Yeddo spruce radial growth. Yeddo spruce at its lower distribution limit was much more affected by precipitation while Yeddo spruce at its upper distribution limit was much more affected by minimum temperature. Yeddo spruce at its medial altitude was affected by sunshine ratio. These results demonstrated that climate affected Yeddo spruce growth differently depending on its altitudinal distributions in the Changbai Mountains. Both temperature and precipitation in the annualization period significantly correlated with Yeddo spruce radial growth. However, warmer signals were not reflected in radial growth trend during the past 20 years because annual total precipitation declined during the same period. It appeared that the climate affected tree rings growth by altering soil moisture availability.

A large carbon sink induced by the implementation of the largest afforestation program on Earth

Background Three-North Afforestation Program(TNAP)in China is the largest ecological restoration project on Earth(ongoing from 1978 to 2050),harboring a huge area of newly planted forests,which provides a wealth of goods and ecosystem services that benefit society at levels ranging from region to East Asia.This project-induced carbon(C)sink has been expected to be large,but its size and location remain uncertain.Results In this study,we investigated the changes in the C stocks of biomass,soil C and the C accumulation ben-efited from the ecological effects in the project areas from 1978 to 2017 within the Three-North regions(4.069×10^(6)km^(2)),and evaluated its project-induced C sequestration.Using a combination of remote sensing images,field obser-vations and national forest inventory data,we estimated a total ecosystem sink of 47.06 Tg C per year(1 Tg=10^(12)g)increased by the TNAP implementation.Importantly,we first found that the C sink via the ecological effects of this project could contribute to a high proportion up to 15.94%,indicating a critical role of ecological effects in shaping the distribution of C stocks in the protective forests.This finding suggests that it is necessary to explicitly consider carbon sequestration benefited from the ecological effects when estimating C sink and parameterizing C models of the restoration projects in China and globally.Conclusions Our results update the estimates of C pools in the world’s largest ecological restoration project area,demonstrating that this project has substantially contributed to mitigating the climate change.

The effects of stump size and within-gap position on sprout non-structural carbohydrates concentrations and regeneration in forest gaps vary among species with different shade tolerances

Background:To restore secondary forests(major forest resources worldwide),it is essential to accelerate the natural regeneration of dominant trees by altering micro-environments.Forest gaps are products of various disturbances,ranging from natural storms or wildfires to anthropogenic events like logging and slashing-andburning,and sprouts of most tree species with non-structural carbohydrates(NSCs)storage can regenerate from stumps after gap formation.However,how the stump sprouts with diverse NSCs storages and stump sizes(i.e.,diameters)adapt to various micro-environments of within-gap positions remains unclear.Therefore in this study,we monitored the stump sprout regeneration(density,survival,and growth)and NSCs concentrations of three dominant tree species with different shade tolerances and varying stump diameters at five within-gap positions for the first two consecutive years after gap formation.Results:Stump diameter was positively correlated with sprout density,growth,and survival of all three tree species,but insignificantly related with sprout NSCs concentrations at the early stage after gap formation.The effect of within-gap position on sprout NSCs concentrations was different among species.After an environmental adaptation of two growing seasons,the north of gap(higher light availability and lower soil moisture habitat)was the least conducive for shade-intolerant Quercus mongolica to accumulate leaf NSCs,and the east of gap(shadier and drier habitat)was conducive to increasing the leaf NSCs concentrations of shade-tolerant Tilia mandshurica.Conclusions:Within-gap position significantly affected leaf NSCs concentrations of all three tree species,but most of the sprout growth,survival,and stem NSCs concentrations were independent of the various within-gap positions.Besides stump diameter,the NSCs stored in stump and root systems and the interspecific differences in shade tolerance also contributed more in sprout regeneration at the early stage(2 years)of gap formation.A prolonged monitoring(>10 years)is needed to further examine the long-term effects of stump diameter and within-gap position on sprout regeneration.All of these findings could be applied to gap-based silviculture by promoting sprout regeneration of dominant tree species with different shade tolerances,which would help accelerate the restoration of temperate secondary forests.

Cascading effect of source limitation on the granivore-mediated seed dispersal of Korean pine(Pinus koraiensis)in secondary forest ecosystems

Background:Granivore-mediated seed dispersal is susceptible to changes in seed availability and silvicultural management,which alters synzoochorous interactions in the antagonism-mutualism continuum and affects the seed dispersal effectiveness(SDE),and eventually,the plant recruitment.We conducted a whole-year study of seed addi-tion to quantify the granivores-Korean pine(Pinus koraiensis)synzoochorous interactions and the SDE in the same sec-ondary forests with two treatments.Both treatments had seed source limitations:one was caused by the disappear-ance of Korean pine due to the historical disturbance,the other by pinecone harvesting in Korean pine plantations adjacent to the secondary forests.Thinning with different intensities(control,25%,and 50%)were also performed to further explore the synzoochorous interactions and SDE in response to silvicultural management in the second type of forests.Results:Source limitation increased the proportion of pre-and post-dispersal seed predation,and made the granivores-Korean pine interaction shift more towards antagonism,with the estimated SDE of 2.31 and 3.60,respec-tively,for the secondary forests without and with Korean pine.Thinning with different intensities did not alleviate the reactions towards antagonism but altered SDE;granivores occurrence decreased,but the proportion of pre-and post-dispersal seed predation increased,resulting in a fivefold decreased seedling recruitment in 25%thinning(the lowest SDE of 0.26).Conclusion:The source limitation coupling thinning biased the synzoochorous interactions more towards antago-nism and significantly lowered granivore-mediated SDE,which limited the successful recruitment of Korean pine in secondary forests.Forest managers should control pinecone harvesting,protect the synzoochorous interaction,and take into account masting event for Korean pine regeneration in the future.