The amelioration of degraded larch(Larix olgensis)soil depends on the proportion of Aralia elata litter in larch-A.elata agroforestry systems

Research has indicated that introducing Aralia elata into larch plantations forms an agroforestry system which could provide economic benefi ts for local farmers and improve degraded soils.However,the impact of litter mixtures on soil chemical and microbial properties in this agroforestry system are unclear,which limits effi cient management of the agroforestry system.A 365-d incubation experiment examined the eff ect of litter mixtures of diff erent proportions of larch(L)and A.elata(A)on soil chemical and microbial properties.The results show that levels of mineral N,available P,microbial biomass carbon and nitrogen,cumulative C mineralization,and activities of hydrolases and oxidases increased with an increase of A.elata in the litter mixtures.Concentration of total soil carbon,nitrogen,and phosphorous did not change(except for total nitrogen).Compared with larch litter alone,levels of mineral N,available P,microbial biomass carbon and nitrogen,cumulative C mineralization,and the activities of hydrolases and oxidases increased by 7.6–433.5%.Most chemical and microbial properties were positively correlated with mixed litter proportions and the initial levels of N,P,K,Ca,Mg,Mn,Zn and Cu in the litter,while negatively correlated with the initial concentrations of C,Fe and lignin,C/N and lignin/N ratios.The results indicate that A.elata litter can improve degraded larch soil and the degree depends on the proportion of A.elata litter in the litter mixtures.

Correction to:The amelioration of degraded larch(Larix olgensis)soil depends on the proportion of Aralia elata litter in larch-A.elata agroforestry systems

Correction to:J.For.Res.https://doi.org/10.1007/s11676-022-01526-w The article“The amelioration of degraded larch(Larix olgensis)soil depends on the proportion of Aralia elata litter in larch-A.elata agroforestry systems”,written by Pingzhen Gao·Jiaojun Zhu·Qiaoling Yan·Kai Yang and Jinxin Zhang was originally published Online First without Open Access.

Response of Pinus koraiensis seedling growth to different light conditions based on the assessment of photosynthesis in current and one-year-old needles

As one of the three major five-leaved pines in the northern hemisphere, Pinus koraiensis is the most important dominant tree species in the natural mixed-broadleaved Korean pine forests. However, the regeneration of P koraiensis under the canopy of secondary forest stands is poor because of the light limitation. This study was conducted to understand how P koraiensis seedlings adapt to different light intensities and what would be the optimum light level for their establishment and growth. Three repetition plots with four light intensities （15%, 30%, 60% and 100% of the natural incident irradiances, achieved by suspending layers of black nylon net above and surrounding the plots） were set up under natural climate conditions in a montane region in eastern Liaoning Province, Northeast China. A total of 80 P koraiensis seedlings with similar height and root collar diameter were transplanted into four plots. After one year of acclimation to the specific light conditions, the seasonal variations of the photosynthetic variables and needle traits of the current and one-year-old needles, and the growth parameters were observed under four light intensities. The results indicated that： （1） The seedling at 60% treatment exhibited the greatest growth, which agreed with the response of the light-saturated photosynthetic rates （Amax） and the dark respiration rate （Rd） in the current and one-year-old needles, i.e., Rd at 60% treatment was significantly lower than that at 100% treatment, but Amax did not differ between the seedlings at 100% and 60% treatments. （2） The P. koraiensis seedlings have a certain photosynthetic plasticity to adapt the light conditions by adjusting their needle traits and regulating the physiological processes, because Amax, Rd, light saturation point and compensation point, the needle mass area, needle nitrogen and chlorophyll contents were significantly （p〈0.05） correlated with the light intensities. Especially, Am,x at 100% and 60% treatments was significantly higher （p〈0.05） than that at 30% and 15% treatments for both current and one-year-old needles. （3） The needles of different ages played a commutative role during the growing season, i.e., the one-year-old needles played a major role for the photosynthesis in the early growing season; the current year needles did in the later growing season. This ensured the effective photosynthesis throughout the growing season. These findings suggest that P. koraiensis is the in-between heliophilous and shade-tolerant tree species at least for the seedlings up to 8 years.

Causal effects of shelter forests and water factors on desertification control during 2000–2010 at the Horqin Sandy Land region, China

The Horqin Sandy Land（HSL）, the largest sandy land in the semi-arid agro-pastoral ecotone of Northeast China, has been subject to desertification during the past century. In response, and to control the desertification,government implemented the Three-North Shelter/Protective Forest Program, world＇s largest ecological reforestation/afforestation restoration program. The program began in1978 and will continue for 75 years until 2050. Understanding the dynamics of desertification and its driving forces is a precondition for controlling desertification.However, there is little evidence to directly link causal effects with desertification process（i.e., on the changing area of sandy land） because desertification is a complex process,that can be affected by vegetation（including vegetation cover and extent of shelter forests） and water factors such as precipitation, surface soil moisture, and evapotranspiration.The objectives of this study were to identify how influencing factors, especially shelter forests, affected desertification in HSL over a recent decade. We used Landsat TM imagery analysis and path analysis to identify the effects of spatiotemporal changes in water and vegetation parameters during2000–2010. Desertification was controlled during the study period, as indicated by a decrease in desert area at a rate of163.3 km2year-1and an increase in the area with reduced intensity or extent of desertification. Total vegetation cover in HSL increased by 10.6 % during the study period and this factor exerted the greatest direct and indirect effects on slowing desertification. The contribution of total vegetation cover to controlling desertification increased with the intensity of desertification. On slightly and extremely severe desertified areas, vegetation cover contributed 5 and 42 % of the desertification reduction, respectively. There were significant correlations between total vegetation cover and water conditions（i.e., evapotranspiration and precipitation）and the area of shelter forests（P ／ 0.0001）, in which water conditions and the existence of shelter forests contributed49.7 and 12.8 % to total vegetation cover, respectively. The area of shelter forests increased sharply due to program efforts, but only shrub forests had significant direct effects on reducing the area of desertification categorized as slightly desertified. The reason for the lack of direct effect of increased arbor forests（accounting for 95.3 % of the total increase in shelter forests） on reducing desertification might be that the selected arbor species were not suited to water conditions（low precipitation, high evapotranspiration） prevailing at HSL. The establishment of shelter forests aided control of desertification in the HSL region, but the effect was less than expected. Effective control of desertification in the HSL region or other similar sandy areas will require greater improvements in vegetation cover. In particular,shrub species should be selected for plantation with reference to their potential to survive and reproduce in the harsh climatic and weather conditions typical of desertified areas.

Roles of abscisic acid and gibberellins in maintaining primary and secondary dormancy of Korean pine seeds

Primary dormancy of seeds of Korean pine(Pinus koraiensis Sieb.et Zucc.)after dispersal in the autumn and the induction of secondary dormancy the fi rst summer following seed dispersal limit the regeneration of mixed broadleaved Korean pine forests in Northeast China.This study was to determine how changes in the levels of abscisic acid(ABA)and gibberellic acid(GA)maintain primary and secondary dormancy of Korean pine seeds under germination conditions.We transferred seeds with one of fi ve primary dormancy states or three secondary dormancy states to germination conditions and measured changes in the levels of ABA,GA 1+3(GA 1 and GA 3)and GA 4+7(GA 4 and GA 7)in the seed coat,megagametophyte and embryo during incubation.Seed coat ABA levels in primary dormant seeds(PDS)and ABA levels in various parts of secondary dormant seeds(SDS)gradually declined during incubation but were still higher than in seeds for which dormancy was progressively released.GA 4+7 and GA 1+3 levels in embryos greatly decreased 35%and 24%,respectively,during incubation of SDS,and thus,the ratio of ABA to GA 4+7 in embryos and megagametophytes signifi cantly increased.The ratio of ABA to GA 1+3 in various parts of SDS increased slightly during incubation.In contrast,in seeds for which secondary dormancy was already released,GA 4+7 and GA 1+3 levels in the embryo,GA 4+7/ABA ratio in the embryo and seed coat,and the GA 1+3/ABA in the embryo and megagametophyte signifi cantly increased during incubation.There was no trend in the changes in the levels of ABA,GA 4+7 or GA 1+3 in embryos and megagametophytes of PDS or the levels of GA 4+7 or GA 1+3 in megagametophytes of SDS during incubation.The results suggest that high ABA levels in the seed coat maintain primary dormancy of Korean pine seeds.Maintenance of secondary dormancy involves a reduction of GA 4+7,GA 1+3,GA 4+7/ABA,and GA 1+3/ABA and the retention of high ABA levels.

Effects of harvest intensity on the marketable organ yield,growth and reproduction of non-timber forest products(NTFPs):implication for conservation and sustainable utilization of NTFPs

Background:Non-timber forest products(NTFPs)are an important part of forest biodiversity,and the subsistence and trade of local people,especially in less developed countries.Because of the high ecological and economic value,NTFPs have faced the problem of over-exploitation,and the key to solve this problem is to determine the feasible way of sustainable utilization of NTFPs.Harvest intensity is one of the most important and easily controlled utilization factors,which can greatly influence the plant individual survival,growth and reproductive performances,and even the population structure and dynamics.Therefore,we chose two common and important NTFPs species with different marketable parts(i.e.,Acanthopanax senticosus with tender leaves and Aralia elata with tender buds)as our study objects.Aiming to determine the optimum harvest intensity for sustainably utilizing both NTFPs species,five levels of harvest intensity treatments(i.e.,control,light,medium,high and severe)were designed to assess the effects of harvest intensity on their marketable organ yield,plant growth and reproductive performances.Results:The biomass growth rates of marketable organ and plant growth of A.senticosus under light harvest intensity treatment were significantly higher than those under other harvest intensities.The plant height growth and 1000-seed weight of A.elata under severe harvest intensity treatment were significantly lower than those under control treatment.Conclusions:The light harvest intensity with 25% leaf removal and the high harvest intensity with all terminal buds harvested are the optimum harvest intensity to maintain the sustainable utilization of A.senticosus and A.elata,respectively.These findings could provide managers with basic but practical guidance for making decisions about the sustainable harvest management plan for the cultivated NTFPs species,and further provide a theoretical basis for managers to establish the harvest regulations for wild NTFPs species.Consequently,the local residents or communities can improve their income while ensure the sustainable development of wild NTFPs.

Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China:a comparison between natural secondary forest and larch plantation

Aims Natural secondary forest(NSF)and larch plantation are two of the predominant forest types in Northeast China.However,how the two types of forests compare in sustaining soil quality is not well understood.This study was conducted to determine how natural secondary forest and larch plantation would differ in soil microbial biomass and soil organic matter quality.Methods Microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),soil organic carbon(SOC)and total nitrogen(TN)in the 0-to 15-cm and 15-to 30-cm soil layers were investigated by making chemical and biological measurements in the montane region of eastern Liaoning Province,Northeast China,during the growing season of 2008 in stands of NSF and Larix olgensis plantation(LOP).Important Findings We found that soil MBC and MBN were significantly lower in the LOP than in the NSF.Both MBC and MBN declined significantly with increasing soil depth in the two types of stands.The ratios of MBC to SOC(MBC/SOC)and MBN to TN(MBN/TN)were also significantly lower in the LOP than in the NSF.Moreover,the values of MBC,MBC/SOC,and MBN/TN significantly varied with time and followed a similar pattern during the growing season,all with an apparent peak in summer.Our results indicate that NSF is better in sustaining soil microbial biomass and nutrients than larch plantation in the temperate Northeast China.This calls for cautions in large-scale conversions of the native forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.

Effects of logging on the trade-off between seed and sprout regeneration of dominant woody species in secondary forests of the Natural Forest Protection Project of China

Background:Promoting natural regeneration(including seed and sprout regeneration)of dominant woody species is essential for restoring secondary forests.However,such restoration processes have been decelerated by the enclosure under Natural Forest Protection Project of China(NFPP).It remains unclear how to implement appropriate management measures(e.g.,whether to apply logging and the suitable intensity)to facilitate natural regeneration according to the responses of two regeneration modes to management measures.We monitored the early stages of seed regeneration(seed rain,soil seed bank,and 1–3-year-old seedlings)and sprout regeneration(stump sprout rate,stump survival rate,probability of sprouting,and number of sprouts per stump)over the first 3 years(2017–2019)after logging under three intensity regimes(control[0%],25%,and 50%logging intensity)in secondary forests.Results:The seed rain density decreased markedly,seedling density increased insignificantly after logging,and logging promoted seedling survival at an increasing conversion rate of 3-year-old seedlings(37.5%under 0%,100%under 25%,and 80.95%under 50%logging)compared to those of the control.The proportion of 3-year-old seedlings increased with logging intensity and was the highest(16.2%)at 50%logging intensity.Sprout density was not affected by logging intensity,however,under 25%and 50%logging,it decreased by 27%and 6%in 2018,and by 37%and 33%in 2019,respectively.Seedling density was 41.65-and 15.31-fold higher than that of sprouts in the 50%and 25%logging treatments,respectively.Based on the relative contributions of the two regeneration modes after logging,three groups of natural regeneration patterns were classified for dominant woody species in temperate secondary forests,i.e.,seed regeneration preference(Betula dahurica,Carpinus cordata and Fraxinus mandshurica),sprout regeneration preference(Acer mono and Acer pseudosieboldianum)and no preference(Quercus mongolica,Fraxinus rhynchophylla,and Juglans mandshurica).Conclusion:In addition to enclosure,appropriate logging can be applied according to the responses of various natural regeneration patterns of dominant woody species to logging in temperate secondary forests under the NFPP.

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.