Effects of drought on non-structural carbohydrates and C,N,and P stoichiometric characteristics of Pinus yunnanensis seedlings

To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.

The Identification of Phenylalanine Ammonia-Lyase(PAL)Genes from Pinus yunnanensis and an Analysis of Enzyme Activity in vitro

Phenylalanine ammonia lyase(PAL)is the rate-limiting and pivotal enzyme of the general phenylpropanoid path-way,but few reports have been found on PAL genes in Pinus yunnanensis.In the present study,three PAL genes were cloned and identified from P.yunnanensis seedlings for thefirst time,namely,PyPAL-1,PyPAL-2,and PyPAL-3.Our results indicated that the open-reading frames of PyPAL genes were 2184,2157,and 2385 bp.Phylogenetic tree analysis revealed that PyPALs have high homology with other known PAL genes in other plants.In vitro enzymatic analysis showed that all three PyPAL recombinant proteins could catalyze the deamination of L-phenylalanine to form trans-cinnamic acid,but only PAL1 and PAL2 can catalyze the conversion of L-tyrosine toρ-coumaric acid.Three PyPAL genes were expressed in different tissues in 1-year-old P.yunnanensis,and such genes had different expression patterns.This study lays a foundation for further understanding of the biosynthesis of secondary metabolites in P.yunnanensis.

Variation in seed and seedling traits and their relations to geo-climatic factors among populations in Yunnan Pine(Pinus yunnanensis)

Differences in seed germination and seedling growth among populations of Pinus yunnanensis Franch. were quantified to provide information for use in the regeneration, reforestation, and improvement of this species. Seed germination and seedling growth traits at the nursery stage were investigated at the population level. We evaluated relationships between pairs of measured traits as well as the association between measured traits and geo- climatic variables including longitude, latitude, elevation, temperature and precipitation. Seedling growth showed significant differences although a low magnitude of variation was found in the seed germination traits among the populations. Some populations with strong and stable growth （e.g., the Baoshan population） may be selected as superior seed sources for regeneration and reforestation. Germination percentage was negatively correlated with elevation, and positively with precipitation. In addition, germination index, vigor index and seedling height were positively correlated with precipitation. Seed germination index, cotyledon number and length, and seedling diameter were significantly and positively correlated with seed weight. Strong correlations between pairs of traits will be helpful in early evaluations for the selection of certain prominent traits.

Selective logging enhances ecosystem multifunctionality via increase of functional diversity in a Pinus yunnanensis forest in Southwest China

Background:The impacts of selective logging on ecosystem multifunctionality(EMF)remain largely unexplored.In this study,we analyzed the response of nine variables related to four ecosystem functions(i.e.nutrient cycling,soil carbon stocks,decomposition,and wood production)to five selective logging intensities in a Pinus yunnanensisdominated forest.We included a control group with no harvest to evaluate the potential shifts in EMF of the P.yunnanensis forests.We also assessed the relationship between above-and belowground biodiversity and EMF under these different selective logging intensities.Additionally,we evaluated the effects of biotic and abiotic factors on EMF using a structural equation modeling(SEM)approach.Results:Individual ecosystem functions(EFs)all had a significant positive correlation with selective logging intensity.Different EFs showed different patterns with the increase of selective logging intensity.We found that EMF tended to increase with logging intensity,and that EMF significantly improved when the stand was harvested at least twice.Both functional diversity and soil moisture had a significant positive correlation with EMF,but soil fungal operational taxonomic units(OTUs)had a significant negative correlation with EMF.Based on SEM,we found that selective logging improved EMF mainly by increasing functional diversity.Conclusion:Our study demonstrates that selective logging is a good management technique from an EMF perspective,and thus provide us with potential guidelines to improve forest management in P.yunnanensis forests in this region.The functional diversity is maximized through reasonable selective logging measures,so as to enhance EMF.

Capacitance Characteristics of Pinus densata,Pinus tabuliformis,Pinus yunnanensis and the hybrids Pinus tabuliformis×Pinus Yunnanensis

We employed capacitance to evaluate the kinship and interspecific variation of homoploid hybrid conifer Pinus densata,P.tabuliformis,P.yunnanensis and artificial hybrids of P.tabuliformis(maternal parent)and P.yunnanensis(paternal parent)which were cultivated and selected in the common garden experiment.By measuring capacitance spectra under different voltage frequencies,we could differentiate different germplasms based on the electrical response.We aims to demonstrate that P.densata as the hybrid of P.tabuliformis and P.yunnanensis based on the capacitance values of the species,and to provide new evidence to the previously known biological evidence,as well as and the parental effect on the hybrids.Our results revealed that capacitance values between the species are significantly different in the spectra where P.yunnanensis positioned at the lowest and P.densata was much higher than all other species,indicating that P.densata had possessed a great capacity to store electrical energy.The capacitance spectra of P.densata and the artificial hybrid are not similar,which rejected our hypothesis.Both of the capacitance values of P.densata and the hybrids were closer to P.tabuliformis than to P.yunnanensis,which shows that the maternal influence was stronger than the paternal influence.Correlation analysis on the relationship between capacitance and fitnessrelated characteristics showed that capacitance is negatively correlated to mortality rate,and positively correlated with second-year survival rate.High capacitance values of P.densata and some of the hybrids reveal their superior adaptability to harsh environment in the Tibet Plateau.We concluded that capacitance as a new indicator for plant fitness and evolution evidence of homoploid hybrid conifers.

Variations in electrical impedance and phase angle among seedlings of Pinus densata and parental species in Pinus tabuliformis habitat environment

Electrical impedance （El） and phase angle （PHI） parameters in AC impedance spectroscopy are important electrical parameters in the study of medical pathology. However, little is known about their application in variation and genetic relationship studies of forest trees. In order to test whether impedance parameters could be used in genetic relationship analysis among conifer species, E1 and PHI were measured in a seedling experiment test composed of Pinus tabuliformis, Pinus yunnanensis, and Pinus densata in a habitat of Pinus tabuliformis. The results showed that variations in both EI and PHI among species were sig- nificant in different electric frequencies, and the EI and PHI values measured in the two populations of P. densata were between the two parental species, P. yunnanensis and P. tabuliformis. These results show that these two impedance parameters could reflect the genetic relationship among pine species. This was the first time using the two AC impedance spectroscopy parameters to test the genetic relationship analysis between tree species, and would be a hopeful novelreference methodology for future studies in evolution and genetic variation of tree species.

Ophiostomatales (Ascomycota) associated with Tomicus species in southwestern China with an emphasis on Ophiostoma canum

Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction.In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan,China,six ophiostomatalean fungi(Ophiostoma canum,O.ips,O.tingens,Leptographium yunnanense,Leptographium sp.1 and Leptographium sp.2)were isolated from the beetles or their galleries;O.canum was the most common fungal species.The distribution of O.canum was associated with stands heavily damaged by Tomicus species and a higher percentage of valid galleries of Tomicus yunnanensis and T.minor in Yunnan pine(Pinus yunnanensis).After inoculation of Yunnan pine with the fungus,a phloem reaction zone formed and monoterpenes accumulated in the phloem.These results suggested that O.canum was pathogenic to Yunnan pine and that the wide distribution of the fungus might be benefi cial to reproduction of pine shoot beetles in Yunnan pine.However,because the reaction zone and monoterpene accumulation were mild,fungal damage of Yunnan pine might be limited.A more integrated study considering all the fungal species should be done to better understand the interactions among bark beetles,blue-stain fungi,and the tree hosts in the region.

Influence of Human Pressure on Forest Resources and Productivity at Stand and Tree Scales: The Case Study of Yunnan Pine in SW China

This paper examines human impact on stands and individual trees of Pinus yunnanensis growing near the small mountain villages of Pianshui and Yangjuan in southwestern Sichuan Province,China.In an effort to assess whether use of these forests was sustainable,we examined the effects of human use in two ways.First,we directly measured the effect of cutting branches,for fuel and fodder,on tree growth.We hypothesized that branch cutting would negatively impact tree growth.We established 12 plots on four hills and compared 14 pairs of trees,one tree in each pair with an apparently full crown and the other with a considerable portion of the crown removed.Second,we assessed stand and tree properties over a 500 m elevation gradient above the villages where we hypothesized that as elevation increases,stand and tree properties should show fewer human impacts.Although extensive branch cutting reduced the live crown,tree height and diameter,compensatory processes likely enabled trees to recover and to add basal area increments(BAIs) similar to those added by trees with full crowns.Trees and stands close to villages showed less growth and lower basal areas,respectively,than stands and trees at intermediate or distant elevations from villages.Areas relatively close to the villages showed considerable effects of human-related disturbances such as branch cutting,grazing,tree and shrub removal,losses of litter,and human and animal trails.Such areas had increased soil erosion and often loss of the ‘A' horizon.Stands close to villages had younger trees,lower stand basal areas,smaller basal area increments,and more stumps.Our results suggest an increasingly vulnerable interface between occupants of these two villages and their surrounding forests.

云南松幼苗生物量特征对外源氮磷叶面喷施的响应

培育壮苗造林可以促进林分生长、缩短林木的培育年限,为了促进云南松(Pinus yunnanensis)壮苗的培育,本试验对云南松幼苗进行2因素3水平的氮磷组合叶面喷施,测定云南松幼苗生物量的变化规律。结果表明:叶面喷施氮、磷肥能够促进幼苗生物量的增长,效果为单施氮肥>氮磷配施>单施磷肥。4 g/L尿素能够有效促进干质量、鲜质量累积,通过对不同处理的观测发现,在幼苗的鲜质量、干质量、含水率、分配比均出现了高浓度抑制的现象。

外源赤霉素对去顶后云南松生物量分配的影响及异速生长分析

为了探究不同浓度赤霉素对去顶后云南松(Pinus yunnanensis)生长及生物量积累、分配的影响,揭示云南松生物量分配特征及各器官间相对生长关系,为去顶后云南松激素促萌提供理论依据,以1年生去顶云南松苗木为试验对象,设置不同的赤霉素浓度进行处理。分析不同处理下云南松生长及生物量积累、分配的影响和云南松各个器官的异速生长关系。结果表明,不同处理对去顶后云南松地径生长有显著影响,对生物量积累与投资同样存在显著差异。叶与侧根生物量呈不显著的正相关,萌条和叶生物量呈显著负相关,此外其余器官两两之间呈正相关关系,各个器官之间存在等速或异速生长关系。赤霉素浓度300 mg/L有利于去顶后云南松地径的生长,同时萌条生物量和地上生物量积累为最高,萌条生物量分配比为最高。去顶后云南松各器官生物量分配积累存在着相关性,共同促进或者抵抗,与器官相对生长关系共同响应赤霉素的添加。

2年生云南松苗木分级标准

为了对2年生云南松(Pinus yunnanensis)进行苗木质量分级,采用目前苗木分级研究应用较为广泛的聚类分析及标准差法对苗木质量分级进行研究对比分析,结果表明,采用聚类分析方法得到的苗木分级结果为:Ⅰ级苗苗高H_(Ⅰ)≥11.76 cm,地径D_(Ⅰ)≥15.09 mm;Ⅱ级苗苗高7.93 cm≤H_(Ⅱ)<11.76 cm,地径13.82 mm≤D_(Ⅱ)<15.09 mm;Ⅲ级苗苗高H_(Ⅲ)<7.93 cm,地径D_(Ⅲ)<13.82 mm;采用标准差法分析结果为:Ⅰ级苗苗高H_(Ⅰ)≥15.42 cm,地径D_(Ⅰ)≥18.19 mm;Ⅱ级苗苗高8.64 cm≤H_(Ⅱ)<15.42 cm,地径12.65 mm≤D_(Ⅱ)<18.19 mm;Ⅲ级苗苗高HⅢ<8.64 cm,地径D_(Ⅲ)<12.65 mm。经过Ⅰ、Ⅱ级苗木占比比例确定最佳苗木分级方法为标准差法,以此为云南松苗木分级奠定理论基础。

森林火灾后云南高原森林真菌群落响应的物种特异性

森林地下部分包含了丰富的真菌多样性。森林火灾产生的高温和对地上植被的破坏,会改变真菌的群落组成并影响后期森林的恢复。云南是我国重要的林区,也是森林火灾的频发区。本文旨在研究以云南松(Pinus yunnanensis)和柠檬桉(Eucalyptus citriodora)为主要树种的混交林在林冠火发生后地下真菌的响应。实验采集了两种树种下的矿质土、根际土和细根3个位点的样品,通过高通量测序手段,分析了真菌的多样性、群落组成、网络结构和生态营养型等信息。结果发现,3个采样点之间的群落组成具有显著性差异,矿质土壤中的alpha多样性高于根际土壤和细根中的alpha多样性。对于树种而言,柠檬桉的真菌网络复杂程度高于云南松。两种树种的前10个优势属以腐生真菌为主,其中云南松的毛霉菌门相对丰度高于柠檬桉。在生物标志物的比较中,云南松的根和根际土壤中均以外生菌根真菌为主,而柠檬桉的根和根际土壤则表现为以腐生真菌和共生真菌为主。我们的研究结果表明森林火灾后云南高原典型森林中真菌群落的响应具有物种特异性。