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 dis...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.展开更多
The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversit...The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversity maintenance in forest ecosystems.Unfortunately,our understanding of the effects of gap size and within-gap position on the seed germination and radicle growth of C.kawakamii is still limited.In particular,our knowledge on the relationship between gap size and environmental factors and their influence on seed germination and radicle growth is incomplete.In the present study,we studied the influences of forest gaps and within-gap position on seed regeneration on the germination and radicle growth of an endangered species C.kawakamii in a subtropical natural forest in China.We selected three large gaps(LG,gap size above 200 m^(2)),three medium gaps(MG,gap size 50-100 m^(2)),three small gaps(SG,gap size 30-50 m^(2)),and non-gap(NG),and planted the seeds of C.kawakamii in five positions within each gap.The results showed that(1)the influence of forest gaps on seed germination rate was,from highest to lowest,medium gaps(51%),non-gap(47%),small gaps(40%)and large gaps(17%),and the seed germination rate was the highest in all positions in medium gaps,with the exception of the east position.(2)Radicle length in forest gaps was,from highest to lowest,medium gaps,small gaps,large gaps and non-gap,and it was the highest in the east,south,west and north positions of medium gaps.(3)Canopy openness(gap size)and air temperature were the main factors influencing seed germination and radicle growth of C.kawakamii.We concluded that medium-sized gaps were the most suitable for seed germination and radicle growth of C.kawakamii,and they promote the regeneration of this endangered species in the investigated natural forest.展开更多
中国工业存在较为严重的资源错配问题已经成为学界共识,但资源错配在行业间还是行业内更为严重依旧悬而未决,行业间和行业内错配对总量生产率损失的影响如何也亟需深入了解。文章以Hsieh and Klenow(2009)模型框架为主体,引入Aoki(2008...中国工业存在较为严重的资源错配问题已经成为学界共识,但资源错配在行业间还是行业内更为严重依旧悬而未决,行业间和行业内错配对总量生产率损失的影响如何也亟需深入了解。文章以Hsieh and Klenow(2009)模型框架为主体,引入Aoki(2008)的研究逻辑,建立一个同时分解行业间和行业内资源错配的分析框架,采用1999—2013年中国工业企业数据库为样本,实证分析了行业间和行业内资源错配对行业TFP以及总量生产率的损失。研究发现:(1)资源错配指数和产出、生产率增长潜力在不同的行业部门间差异较大。在资源错配指数和TFP改善潜力上:重工业>轻工业;高技术型行业>低技术型行业>中等技术型行业;技术密集型行业>劳动密集型行业>资本密集型行业;下游行业>上游行业;垄断性行业>竞争性行业。(2)要素错配降低了工业整体产出或TFP,即使不增加投入,通过有效消除行业间以及行业内企业间的资源配置扭曲,可使得工业产出提高21.5%。(3)资源错配使得工业TFP(对数值)损失了3.79,行业间的效率损失要高于行业内企业间的效率损失,行业间效率损失占总效率损失的53.08%,行业内企业间的效率损失占46.92%。研究明确了行业间与行业内的资源错配对工业总产出损失的影响大小,为中国工业界资源错配的论断提供了微观依据,也为中国工业企业供给侧结构性改革提供了经验证据和理论指导。展开更多
基金supported by grants from the Strategic Leading Science&Technology Programme,CAS(XDA23070100)National Natural Science Foundation of China(U1808201,31330016)Liaoning Revitalization Talents Program(XLYC1807102).
文摘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.
基金funded by the National Natural Science Foundation of China,grant numbers 31700550 and 31770678the Nature Science Fund of the Fujian Province Science and Technology of China,grant number 2019J01367+1 种基金the Science and Technology Promotion of Project Forestry Bureau of the Fujian Province,grant number 2018TG14-2the Innovation and Technology Fund of Fujian Agriculture and Forestry University,grant number CXZX2018125.
文摘The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversity maintenance in forest ecosystems.Unfortunately,our understanding of the effects of gap size and within-gap position on the seed germination and radicle growth of C.kawakamii is still limited.In particular,our knowledge on the relationship between gap size and environmental factors and their influence on seed germination and radicle growth is incomplete.In the present study,we studied the influences of forest gaps and within-gap position on seed regeneration on the germination and radicle growth of an endangered species C.kawakamii in a subtropical natural forest in China.We selected three large gaps(LG,gap size above 200 m^(2)),three medium gaps(MG,gap size 50-100 m^(2)),three small gaps(SG,gap size 30-50 m^(2)),and non-gap(NG),and planted the seeds of C.kawakamii in five positions within each gap.The results showed that(1)the influence of forest gaps on seed germination rate was,from highest to lowest,medium gaps(51%),non-gap(47%),small gaps(40%)and large gaps(17%),and the seed germination rate was the highest in all positions in medium gaps,with the exception of the east position.(2)Radicle length in forest gaps was,from highest to lowest,medium gaps,small gaps,large gaps and non-gap,and it was the highest in the east,south,west and north positions of medium gaps.(3)Canopy openness(gap size)and air temperature were the main factors influencing seed germination and radicle growth of C.kawakamii.We concluded that medium-sized gaps were the most suitable for seed germination and radicle growth of C.kawakamii,and they promote the regeneration of this endangered species in the investigated natural forest.
文摘中国工业存在较为严重的资源错配问题已经成为学界共识,但资源错配在行业间还是行业内更为严重依旧悬而未决,行业间和行业内错配对总量生产率损失的影响如何也亟需深入了解。文章以Hsieh and Klenow(2009)模型框架为主体,引入Aoki(2008)的研究逻辑,建立一个同时分解行业间和行业内资源错配的分析框架,采用1999—2013年中国工业企业数据库为样本,实证分析了行业间和行业内资源错配对行业TFP以及总量生产率的损失。研究发现:(1)资源错配指数和产出、生产率增长潜力在不同的行业部门间差异较大。在资源错配指数和TFP改善潜力上:重工业>轻工业;高技术型行业>低技术型行业>中等技术型行业;技术密集型行业>劳动密集型行业>资本密集型行业;下游行业>上游行业;垄断性行业>竞争性行业。(2)要素错配降低了工业整体产出或TFP,即使不增加投入,通过有效消除行业间以及行业内企业间的资源配置扭曲,可使得工业产出提高21.5%。(3)资源错配使得工业TFP(对数值)损失了3.79,行业间的效率损失要高于行业内企业间的效率损失,行业间效率损失占总效率损失的53.08%,行业内企业间的效率损失占46.92%。研究明确了行业间与行业内的资源错配对工业总产出损失的影响大小,为中国工业界资源错配的论断提供了微观依据,也为中国工业企业供给侧结构性改革提供了经验证据和理论指导。
