Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei seedlings.The canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following thin-ning.Thinning improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light environ-ment.Under the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral composition.P.bournei photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light environment.In a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal conductance.As a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of P.bournei seedlings,and a reduction increased light absorption and use capacity and height:diameter ratios.The growth advantage transformed from diameter to height,enabling seedlings to access more light.Our findings suggest that the regeneration of shade-tolerant species such as P.bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Phenotypic variation in Phoebe bournei populations preserved in the primary distribution area

Phoebe bournei（Hemsl.） Yang is a rare and protected plant in China. This study was conducted to determine the phenotypic variation in this species and to document phenotypic variation within and among populations of P. bournei. Nested analysis of variance, coefficient of variation, multiple comparisons, principal component analysis（PCA） and correlation analysis were used to analyze ten phenotypic traits in ten natural populations of P.bournei from both the northeastern and the primary region of the range of this species. Significant differences among and within populations were observed in leaf and seed phenotypic traits. Variation among populations（34.92%）was greater than that within populations（26.19%）. The mean phenotypic differentiation coefficient was 53.77% among populations, indicating that variation among populations comprised the majority of the phenotypic variation of P. bournei. The coefficient of variance（CV） of ten traits varied from 6.44 to 18.45%, with an average of 12.03%.The CV of leaf traits among populations（15.64%） was higher than that of seed traits（8.60%）, indicating that seed traits were more stable. The results from CV and PCA indicated that leaf area, leaf length and thousand seed weight were the main factors accounting for the observed phenotypic variations. Significant or highly significant correlations were observed among most leaf and/or in seed phenotypic traits, whereas no significant correlations were observed between phenotypic traits and geographic factors.Based on cluster analysis, the ten populations can be divided into three clusters. These clusters were not a result of geographic distances.

Study on the Structural Characteristics and Physical and Mechanical Properties of Phoebe bournei Thinning Wood

The artificial afforestation of precious Phoebe bournei has been carried out in China.During the cultivation process,thinning wood will be produced.The properties of thinning wood might vary greatly with matured wood and require evaluation for better utilization.The objective of the present study aims to determine the wood structure,fiber morphology,and physical and mechanical properties of the Phoebe bournei thinning wood to help us understand the wood properties and improve its utility value.Three 14-year-old Phoebe bournei were cut from Jindong Forestry Farm of Hunan Province,China.The wood structure and fiber morphology were observed and analyzed with a light microscope and scanning electron microscope.The physical and mechanical properties were tested according to the Chinese national standards.The results showed as follows:(1)The Phoebe bournei thinning wood has a beautiful wood figure and fine texture,whereas the heartwood has not yet formed.(2)It is a diffuse-porous hardwood with small and less pores as well as fine wood rays.(3)The wood fiber is medium length and extremely thin wall thickness.(4)It is low in density and has excellent dimensionally stability.(5)The wood mechanical properties belong to the low to medium class and the comprehensive strength of wood belongs to the medium-strength class.It is concluded that Phoebe bournei thinning wood is suitable for wood carving,handicraft,high-end furniture,and decorative furniture parts.

The chromosome-scale genome of Phoebe bournei reveals contrasting fates of terpene synthase (TPS)-a and TPS-b subfamilies

Terpenoids,including aromatic volatile monoterpenoids and sesquiterpenoids,function in defense against pathogens and herbivores.Phoebe trees are remarkable for their scented wood and decay resistance.Unlike other Lauraceae species investigated to date,Phoebe species predominantly accumulate sesquiterpenoids instead of monoterpenoids.Limited genomic data restrict the elucidation of terpenoid variation and functions.Here,we present a chromosome-scale genome assembly of a Lauraceae tree,Phoebe bournei,and identify 72 full-length terpene synthase(TPS)genes.Genome-level comparison shows pervasive lineage-specific duplication and contraction of TPS subfamilies,which have contributed to the extreme terpenoid variation within Lauraceae species.Although the TPS-a and TPS-b subfamilies were both expanded via tandem duplication in P.bournei,more TPS-a copies were retained and constitutively expressed,whereas more TPS-b copies were lost.The TPS-a genes on chromosome 8 functionally diverged to synthesize eight highly accumulated sesquiterpenes in P.bournei.The essential oil of P.bournei and its main component,b-caryophyllene,exhibited antifungal activities against the three most widespread canker pathogens of trees.The TPS-a and TPS-b subfamilies have experienced contrasting fates over the evolution of P.bournei.The abundant sesquiterpenoids produced by TPS-a proteins contribute to the excellent pathogen resistance of P.bournei trees.Overall,this study sheds light on the evolution and adaptation of terpenoids in Lauraceae and provides valuable resources for boosting plant immunity against pathogens in various trees and crops.

闽楠幼林黄化植株与正常植株表型特征的差异分析

以福建三明市将乐县闽楠(Phoebe bournei)种质保存林内发现的一株黄化植株为研究对象,并以相邻的3株正常植株为对照,通过野外调查和室内测定,分析了2种植株在形态特征和生理特征的差异,结果表明:在植株形态上,黄化植株相较于正常植株表现矮小,且叶片变小;在主要生理指标上,黄化叶片的叶绿素、花青素、叶黄素以及可溶性糖含量均比正常植株显著降低。通过分析,初步推测闽楠植株黄化是遗传因素起主导作用,后续需进一步观察黄化性状能否稳定表现和探究黄化性状变异的机制,以期为挖掘利用特异种质提供理论参考。

不同基质配方对闽楠、浙江楠容器苗生长的影响

以泥炭、珍珠岩和稻壳3种基质材料按不同体积比配制成10种基质配方,综合评价闽楠(Phoebe bournei)、浙江楠(Phoebe chekiangensis)3年生容器大苗的生长情况,结果表明:不同基质配方对闽楠、浙江楠的生长有不同影响,10种基质配方中,40%泥炭+40%黄泥+20%稻壳的基质配方适宜闽楠容器大苗培育,80%泥炭+10%黄泥+10%稻壳的基质配方适宜浙江楠容器大苗培育。

不同苗木类型和林地管理方式对闽楠幼林生长的影响

研究不同苗木类型和不同林地管理方式对闽楠(Phoebe bournei)幼林生长的影响。以5种典型闽楠苗木类型和3种林地管理方式进行试验,对闽楠幼林的成活率以及苗高、胸径、冠幅等形态指标进行测量与分析。结果表明2年生容器苗在全光照和林冠下的存活率均最高,达94.67%和90.62%,胸径增长量显著大于其余4种苗木类型。闽楠幼林在机械整地管理下的胸径、树高、冠幅和造林成活率均最高,机械整地配合间作西瓜处理的闽楠幼林生长速率最高。因此,在今后的闽楠造林中推荐选择全光照条件+2年生容器苗+机械整地+间作西瓜管理。

41个闽楠家系苗期生长节律及早期选择

对41个闽楠(Phoebe bournei)家系1年生苗木的生长节律进行观测并综合评价,结果表明7-9月为苗高的旺盛生长期,大部分家系苗高生长速率在8月最大,苗高生长量最大值为41.75±6.56 cm,且各家系间差异较大。地径旺盛生长季则出现在10-11月,大部分家系生长峰值出现在10月,地径生长量最大值为4.12±0.51 mm,各家系间差异较小。对不同闽楠家系苗高和地径综合评价和排序,表现最优的家系为13号,其苗高比参试家系平均苗高(30.46 cm)高37.06%,比平均地径(3.77 mm)高4.48%。按10%的入选率,筛选出13号、12号、15号、10号、14号等5个家系为优良家系。