CO_2浓度倍增与干旱胁迫对油松(Pinus tabulaeformis)相对分枝级水力结构的影响

在密闭式生长箱内经过13个月高CO2浓度培养的5年生油松(Pinus tabulaeformis)为实验对象,采用改良冲洗法研究了CO2浓度倍增(720μmolmol-1)与干旱胁迫交互作用对油松相对分枝级水力结构参数的影响。通过测定油松不同分枝级的水力结构参数分别在720μmolmol-1CO2和380μmolmol-1CO2(大气现有CO2浓度)浓度下随着干旱胁迫的变化,得出不同分枝级的导水率(Kh)、比导率(Ks)和胡伯尔值(Hv)在2个CO2浓度下均随着干旱胁迫的增加而逐渐下降,叶比导率(Lsc)在720μmolmol-1CO2浓度下随着干旱胁迫的增加非线性变化(0级>2级>1级)不同于380μmolmol-1CO2(0级>1级>2级)。同期干旱胁迫条件下,720μmolmol-1CO2浓度下的Kh、Ks、Lsc和Hv均大于380μmolmol-1CO2且差异显著。根据整株苗木的水势将苗木的水分状况分为4个梯度,在正常水分(-0.45^-0.65MPa)、轻度干旱(-1.15^-0.75MPa)和中度干旱(-1.95^-1.35MPa)胁迫时,3个分枝级均在720μmolmol-1CO2条件下的Kh和Ks较380μmolmol-1CO2增加,说明交互作用能提高导水能力,同时加快水分运输效率。在重度干旱(<-2.80MPa)胁迫时Kh比380μmolmol-1CO2增加,而Ks比380μmolmol-1CO2减小,即交互作用提高了水分运输的安全性,却减少了有效性。

油松(Pinus tabulaeformis)人工林林下植被发育对油松生长节律的响应

林下植被作为森林生态系统的一个重要组成部分,对维持林分结构和土壤质量起着重要作用。不同年龄树种对林下植被发育的影响已有所涉及,但这些为数不多的研究往往割裂了林木种群的生长规律与其林下植被间的相互作用,以林龄为尺度探讨林下植被发育的差异必然掩盖了林分种群对林下植被作用的异质性。采用时序研究法,按照油松(Pinus tabulaeformis)高速生期、径速生期、材积慢生期和材积速生期等不同发育时期,探讨林下植被组成、多样性、生物量和元素积累量的差异性。结果表明,高速生期阶段油松与林下植被竞争最为激烈,林下植被物种丰富度、多样性、生物量、元素积累量均最低。因此,高速生期阶段应及时对油松采取较大强度的抚育间伐以缓和油松种群与林下植被剧烈竞争的关系。径速生阶段林下植被与油松竞争最为缓和,草本层Gleason、Shannon-Wiener、Pielow指数由高生长阶段的7.817、2.222和0.769剧增到19.978、3.470和0.907,灌木层、草本层地上部分生物量、元素积累量也均达到最大。径速生阶段对油松林分的管理可相对粗放一些。进入材积阶段,油松与林下植被的关系日趋紧张。材积慢生阶段灌木层、草本层生物量由径速生期的2262.61、461.92kg/hm2分别下降至1549.85、220.84kg/hm2,而灌木层Gleason、Shannon-Wiener指数均达到峰值。相对于材积慢生期,材积速生期灌木层、草本层物种多样性指数、元素积累量进一步下降,而生物量略有上升,材积速生期阶段应对油松林分适度间伐或主伐。可见,林下植被可作为人工纯林乔木生长规律的指示剂,根据林下植被发育状况选择林分经营方式具有一定的参考价值。

不同生态条件下油松(Pinus tabulaeformis)菌根根际土壤微生物群落

利用BIOLOG代谢指纹方法分析了陕南商南和陕北安塞不同生态条件下油松菌根根际土壤微生物群落。结果表明,安塞油松和商南油松菌根根际微生物对糖类和氨基酸类碳源较易利用,商南油松菌根根际微生物总体上代谢碳源的种类和活性远大于安塞油松,而且对同类碳源的代谢商南油松的AWCD比安塞油松均高出2倍多。安塞油松菌根根际微生物以氨基酸类代谢群为优势类群,商南油松以糖类代谢群为优势类群。微生物群落多样性指数和微生物群落主成分分析(PCA)指标均表明商南油松和安塞油松菌根根际土壤微生物群落有明显不同,起分异作用的碳源主要为糖类,其次是羧酸类和氨基酸类。商南油松菌根根际土壤微生物群落AWCD极显著高于安塞油松(P<0.01),细菌数量显著高于安塞油松(P<0.05),Shannon指数和丰富度指数达极显著性差异(P<0.01),商南油松和安塞油松菌根侵染率差异不显著,但菌根生物量差异达极显著水平(P<0.01)。相关性分析表明,菌根生物量与丰富度指数、AWCD呈极显著正相关,与Shannon指数呈显著正相关,但是与菌根侵染率相关性不显著。在商南温暖潮湿丘陵区油松菌根根际微生物活性、群落大小和多样性高于安塞油松,在安塞黄土高原干旱区微生物群落稳定性强于商南油松。

公路绿化植物油松(Pinus tabulaeformis)和小叶杨(Populus simonii)对重金属元素的吸收与积累

对内蒙古西部公路绿化植物油松(Pinustabulaeformis)、小叶杨(Populussimonii)及其根际土壤中重金属元素(Cd、Hg、Pb、Cu、Zn、Ni、Cr)和类金属元素(As和Se)含量以及根际土壤重金属(Cu、Zn、Pb、Ni和Cr)形态、土壤pH值进行了测定。对比分析了公路沿线不同绿化植物及其不同器官对重金属元素的吸收与积累特征。结果表明:绿化植物根际土壤对重金属元素的吸附及污染程度以Cd为最高。随原子序数的递增,小叶杨和油松两种植物的根部和茎叶两种营养器官中重金属的含量均表现出“N”字形变动趋势。而且重金属元素在不同植物不同器官中的含量具有Zn>Cu>Ni,Cr,As,Pb>Cd>Hg的基本规律。小叶杨茎叶对重金属元素Cr、Ni和Pb的富集能力较根部为强,油松茎叶对重金属元素Cr、Ni、Cu和Pb的富集能力较根部为强。绿化植物根际土壤重金属元素有效态占总量百分比的大小序列为Zn>Pb>Ni、Cr>Cu,与重金属元素在不同植物不同器官中的含量大小序列Zn>Cu>Ni、Cr、As、Pb>Cd>Hg并非趋于一致。公路绿化植物对根际土壤中重金属元素的吸收和积累与重金属元素有效态所占的比例有关。

油松(Pinus tabulaeformis)树轮宽度与气候因子统计相关的生理机制——以贺兰山地区为例

通过分析贺兰山地区气候因子的变化特征,并且参考北美、俄罗斯的研究结果,确定了Vaganov-Shashkin生理响应模型的参数,并根据研究区的实际情况对参数作了相应修正,得出两组不同的参数,两组参数拟合出相同的结果,说明模型内在的机理是稳定的,更能反映出它的生理学特性.对树轮宽度序列和气候因子进行相关分析,发现比较明显的相关有与5～8月份降水的正相关,与5～8月份温度的负相关,与9、10月份温度的正相关.模型分析结果认为,从5月中旬到8月底,降水不能满足树木生长的需要,故形成树轮宽度与该时段降水的正相关,而在这个时段,由于温度和降水呈负相关,表现为树轮宽度与温度的负相关,其实这在很大程度上是一种间接的相关.到9月份,由于温度下降比较明显,这时树木生长的主要控制因素已转化为温度,所以形成了与9、10月份温度的正相关.模型分析还发现,树轮宽度的形成与生长结束时间相关性强,而与生长开始时间的关系不明显.

秦岭火地塘林区油松(Pinus tabulaeformis)林休眠期的土壤呼吸

林木休眠期林地土壤CO2释放是森林生态系统碳平衡关键组成部分之一。由于绝大多数森林生态系统林木休眠期土壤CO2释放过程测定困难,国内有关林木休眠期CO2释放,量化方面的研究开展较少。采用动态开路气室法对秦岭火地塘林区天然次生油松(Pinus tabulaeformis)林土壤呼吸的日变化进行了测定,分析了土壤呼吸速率(mgCO2m-2h-1)与土壤温度和体积含水率的关系,基于土壤日均呼吸速率和土壤日均温度指数方程与观测季的总天数,估算了林木休眠期林地土壤CO2释放量。结果表明:(1)研究区林地土壤呼吸速率存在较大的时、空变异。不同观测部位土壤呼吸速率的峰值出现时间各异,呼吸作用较弱的时段也不一致。同一观测部位不同观测月中,土壤日均呼吸速率变异系数分别为48.38%,82.51%和81.88%;(2)当土温>8.5℃时,0~5 cm和5~10 cm土层,土壤日均温与土壤日均呼吸速率间存在极显著(p<0.001)的指数关系,Q10分别为1.297和1.323;(3)0~5 cm和5~10 cm土层,土壤体积含水率与土壤呼吸速率间关系复杂;(4)林木休眠期研究区林地土壤CO2释放量变化于(977.37±88.43)^(997.19±80.73)gCm-2(p=0.005)间。

土壤温度对油松(Pinus tabulaeformis)树干液流活动的影响

为了弄清土壤温度对油松树干边材液流活动的影响作用,利用热扩散式边材液流测定系统(TDP-30)和自动气象站对油松边材液流速率和土壤温度等环境因子进行了为期一年的同步测定。结果表明,土壤温度对树干液流活动的影响,一方面与靠近植物最适吸水温度的土层有关,另一方面,与树种的根系分布特征有关。春季表层土壤温度对液流速率的影响最为显著,夏季深层土壤最大,秋季的最大影响土层间于春夏之间。10.0～14.9℃的土壤温度对油松树干边材液流活动的作用最为明显。土壤温度开始对油松液流活动起显著作用的温度阈值约为10℃左右。

子午岭林区人工与天然油松林(Pinus tabulaeformis)养分库和碳库特征

为了揭示黄土高原地区人工油松林自然化发育过程中的植物叶片与土壤养分库和碳库的变化规律,采用典型样地法,以子午岭林区天然油松群落为参照,选择了不同立地条件的人工油松林,分别对其土壤的氮库、碳库及植物叶片养分库和碳库进行了分析。结果表明,该区油松针叶C、N、P的含量平均值分别为(499.5±63.75)mg/g、(8.53±0.50)mg/g和(0.94±0.64)mg/g,叶片C含量大小依次为阳坡天然林>阴坡天然林>阴坡人工林>阳坡人工林,阳坡人工林叶片N、P含量显著高于阳坡天然林。不同立地条件下油松林叶片C/N、C/P差异显著,叶片N、P和N/P均达到极显著水平,但是叶片C含量差异不显著。油松叶片C含量与N、P含量均呈极显著负相关,N和P之间的呈显著正相关。不同立地的油松林除40～60cm土层土壤C、N含量无显著差异外,0～20cm和20～40cm两个土层的人工林土壤C、N含量显著高于天然林,同时阳坡人工林土壤C、N含量显著高于阴坡人工林。0～20cm、20～40cm两个土层土壤C含量与N含量均呈极显著正相关,与植物N、P均呈显著正相关。子午岭林区阳坡的人工油松林不仅叶片养分含量较高,而且林地土壤是该区土壤的最大养分库和碳库。

Climate-growth relationships of Pinus tabuliformis along an altitudinal gradient on Baiyunshan Mountain,Central China

A set of standard chronologies for tree-ring width(TRW),earlywood width(EWW)and latewood width(LWW)in Pinus tabuliformis Carr.along an altitudi-nal gradient(1450,1400,and 1350 m a.s.l.)on Baiyunshan Mountain,Central China to analyze the effect of varying temperature and precipitation on growth along the gradi-ent.Correlation analyses showed that at all three altitudes and the TRW and EWW chronologies generally had signifi-cant negative correlations with mean and maximum tem-peratures in the current April and May and with minimum temperatures in the prior July and August,but significant positive correlations with precipitation in the current May.Correlations were generally significantly negative between LWW chronologies and all temperatures in the prior July and August,indicating that the prior summer temperature had a strong lag effect on the growth of P.tabuliformis that increased with altitude.The correlation with the standard-ized precipitation evapotranspiration index(SPEI)confirmed that wet conditions in the current May promoted growth of TR and EW at all altitudes.Significant altitudinal differences were also found;at 1400 m,there were significant positive correlations between EWW chronologies and SPEI in the current April and significant negative correlations between LWW chronologies and SPEI in the current September,but these correlations were not significant at 1450 m.At 1350 m,there were also significant negative correlations between the TRW and the EWW chronologies and SPEI in the prior October and the current July and between LWW chronology and SPEI in the current August,but these cor-relations were not significant at 1400 m.Moving correlation results showed a stable response of EWW in relation to the SPEI in the current May at all three altitudes and of LWW to maximum temperature in the prior July-August at 1400 m from 2002 to 2018.The EWW chronology at 1400 m and the LWW chronology at 1450 m were identified as more suitable for climate reconstruction.These results provide a strong scientific basis for forest management decisions and climate reconstructions in Central China.

Potential reduction in carbon fixation capacity under climate change in a Pinus koraiensis forest

There has been an increasing recognition of the crucial role of forests, responsible for sequestering atmospheric CO_(2), as a moral imperative for mitigating the pace of climate change. The complexity of evaluating climate change impacts on forest carbon and water dynamics lies in the diverse acclimations of forests to changing environments. In this study, we assessed two of the most common acclimation traits, namely leaf area index and the maximum rate of carboxylation(V_(cmax)), to explore the potential acclimation pathways of Pinus koraiensis under climate change. We used a mechanistic and process-based ecohydrological model applied to a P. koraiensis forest in Mt. Taehwa, South Korea. We conducted numerical investigations into the impacts of(i) Shared Socioeconomic Pathways 2–4.5(SSP2-4.5) and 5–8.5(SSP5-8.5),(ii) elevated atmospheric CO_(2) and temperature, and(iii) acclimations of leaf area index and V_(cmax)on the carbon and water dynamics of P. koraiensis. We found that there was a reduction in net primary productivity(NPP) under the SSP2-4.5 scenario, but not under SSP5-8.5, compared to the baseline, due to an imbalance between increases in atmospheric CO_(2) and temperature. A decrease in leaf area index and an increase in V_(cmax)of P. koraiensis were expected if acclimations were made to reduce its leaf temperature. Under such acclimation pathways, it would be expected that the well-known CO_(2) fertilizer effects on NPP would be attenuated.

Microenvironmental effects on growth response of Pinus massoniana to climate at its northern boundary in the Tongbai Mountains,Central China

The Tongbai Mountains is an ecologically sensi-tive region and the northern boundary of Pinus massoniana Lamb.To analyze the effect of different microenvironments on tree growth response to climate factors,we developed standard chronologies for earlywood width(EWW),late-wood width(LWW),and total ring width(TRW)of P.massoniana at two sampling sites on slopes with different orientations,then analyzed characteristics of the chronolo-gies and their correlations with climate variables from five stations in the region and with a regional normalized differ-ence vegetation index(NDVI).Statistical results showed that the TRW/EWW/LWW chronology consistency and charac-teristics(mean sensitivity,signal to noise ratio,expressed population signal)for trees growing on the southeastern slope were much higher than for trees on the northeastern slope.Correlations indicated that temperature in current March and August has a significant positive effect on TRW/EWW/LWW formation,and the effect on the northeastern slope was weaker than on the southeastern slope.Compared to temperature,precipitation has more complicated effects on tree growth,but the effect on the northeastern slope was also generally weaker than on the southeastern slope.Step-wise linear regression analyses showed that temperature in August was the main limiting factor at the two sampling sites.Similarly,the response of tree growth on the southeast-ern slope as determined by the NDVI is better than on the northeastern slope,and the TRW/EWW/LWW chronologies for the southeastern slope explained over 50%of the total NDVI variances in June.Overall,the results indicate that the difference in the climate response of P.massoniana at two sampling sites is clearly caused by differences in the microenvironment,and such differences should be properly considered in future studies of forest dynamics and climate reconstructions.

Stability assessment of tree ring growth of Pinus armandii Franch in response to climate change based on slope directions at the Lubanling in the Funiu Mountains,China

Global warming will affect growth strategies and how trees will adapt.To compare the response of tree radial growth to climate warming in different slope directions,samples of Pinus armandii Franch were collected and treering chronologies developed on northern and western slopes from the Lubanling in the Funiu Mountains.Correlation analyses showed that two chronologies were mainly limited by temperatures in the previous June–August and the combination of temperatures and moisture in the current May–July.The difference of the climate response to slopes was small but not negligible.Radial growth of the LBL01 site on the northern slope was affected by the combined maximum and minimum temperatures,while that of the LBL02 site was affected by maximum temperatures.With regards to moisture,radial growth of the trees on the north slope was influenced by the relative humidity in the current May–July,while on the western slope,it was affected by the relative humidity in the previous June–August,the current May–July and the precipitation in the current May–July.With the change in climate,the effects of the main limiting factors on growth on different slopes were visible to a certain extent,but the differences in response of trees on different slopes gradually decreased,which might be caused by factors such as different slope directions and the change in diurnal temperature range.These results may provide information for forest protection and ecological construction in this region,and a scientific reference for future climate reconstruction.

Stability assessment of tree ring growth of Pinus armandii Franch in response to climate change based on slope directions at the Lubanling in the Funiu Mountains,China

Global warming will affect growth strategies and how trees will adapt.To compare the response of tree radial growth to climate warming in different slope directions,samples of Pinus armandii Franch were collected and tree-ring chronologies developed on northern and western slopes from the Lubanling in the Funiu Mountains.Correlation analyses showed that two chronologies were mainly limited by temperatures in the previous June-August and the com-bination of temperatures and moisture in the current May-July.The difference of the climate response to slopes was small but not negligible.Radial growth of the LBLO1 site on the northern slope was affected by the combined maximum and minimum temperatures,while that of the LBLO2 site was affected by maximum temperatures.With regards to moisture,radial growth of the trees on the north slope was influenced by the relative humidity in the current May-July,while on the western slope,it was affected by the relative humidity in the previous June-August,the current May-July and the precipitation in the current May-July.With the change in climate,the effects of the main limiting factors on growth on different slopes were visible to a certain extent,but the differences in response of trees on different slopes gradually decreased,which might be caused by factors such as different slope directions and the change in diurnal temperature range.These results may provide information for forest protection and ecological construction in this region,and a scientific reference for future climate reconstruction.

Advances in Research of Drought Stress in Major Pinus spp.: A Bibliometric Analysis and Narrative Review

Climate change has caused fluctuations in the frequency and severity of droughts,favoring extended periods of drought associated with anthropic actions and triggering other stressful abiotic effects that threaten terrestrial ecosystems.As climate warming intensifies,drought is a major challenge for forest growth.Pine(Pinus Linn.)is an important genus of forest in the Northern Hemisphere and has a certain tolerance to drought.This article analyzes and reviews the advances in research about drought stress of major Pinus spp.plants in recent years and discusses understanding and future core problems.To adapt to water-deficient environments,pine plants adapt to drought by changing growth traits,closing some stomata on leaves,changing the growth and structure of roots,and adjusting their physiological activities.Moreover,the expression of specific genes is altered,causing changes in the expression of several signaling molecules and metabolites to counteract drought stress.

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.

Effects of tree size and organ age on variations in carbon,nitrogen,and phosphorus stoichiometry in Pinus koraiensis

Carbon(C),nitrogen(N),and phosphorus(P)are of fundamental importance for growth and nutrient dynamics within plant organs and deserve more attention at regional to global scales.However,our knowledge of how these nutrients vary with tree size,organ age,or root order at the individual level remains limited.We determined C,N,and P contents and their stoichiometric ratios(i.e.,nutrient traits)in needles,branches,and fine roots at different organ ages(0-3-year-old needles and branches)and root orders(1st-4th order roots)from 64 Pinus koraiensis of varying size(Diameter at breast height ranged from 0.3 to 100 cm)in northeast China.Soil factors were also measured.The results show that nutrient traits were regulated by tree size,organ age,or root order rather than soil factors.At a whole-plant level,nutrient traits decreased in needles and fine roots but increased in branches with tree size.At the organ level,age or root order had a negative effect on C,N,and P and a positive effect on stoichiometric ratios.Our results demonstrate that nutrient variations are closely related to organ-specific functions and ecophysiological processes at an individual level.It is suggested that the nutrient acquisition strategy by younger trees and organ fractions with higher nutrient content is for survival.Conversely,nutrient storage strategy in older trees and organ fractions are mainly for steady growth.Our results clarified the nutrient utilization strategies during tree and organ ontogeny and suggest that tree size and organ age or root order should be simultaneously considered to understand the complexities of nutrient variations.

Carbon,nitrogen and phosphorus stoichiometry in Pinus tabulaeformis forest ecosystems in warm temperate Shanxi Province,north China

Although carbon(C), nitrogen(N), and phosphorous(P) stoichiometric ratios are considered good indicators of nutrient excess/limitation and thus of ecosystem health, few reports have discussed the trends and the reciprocal effects of C:N:P stoichiometry in plant–litter–soil systems. The present study analyzed C:N:P ratios in four age groups of Chinese pine, Pinus tabulaeformis Carr., forests in Shanxi Province, China: plantation young forests(AY,<20 year-old); plantation middle-aged forests(AM, 21–30 year-old); natural young forests(NY,<30 year-old); and natural middle-aged forests(NM,31–50 year-old). The average C:N:P ratios calculated for tree, shrub, and herbaceous leaves, litter, and soil(0–100 cm) were generally higher in NY followed by NM,AM, and AY. C:N and C:P ratios were higher in litter than in leaves and soils, and reached higher values in the litter and leaves of young forests than in middle-aged forests;however, C:N and C:P ratios were higher in soils of middle-aged forests than in young forests. N:P ratios were higher in leaves than in litter and soils regardless of stand age; the consistent N:P<14 values found in all forests indicated N limitations. With plant leaves, C:P ratios were highest in trees, followed by herbs and shrubs, indicating a higher efficiency in tree leaf formation. C:N ratios decreased with increasing soil depth, whereas there was no trend for C:P and N:P ratios. C:N:P stoichiometry of forest foliage did not exhibit a consistent variation according to stand age. Research on the relationships between N:P, and P, N nutrient limits and the characteristics of vegetation nutrient adaptation need to be continued.

不同林龄油松(Pinus tabulaeformis)人工林植物、凋落物与土壤C、N、P化学计量特征

在陕西省北部延安市境内子午岭林区,采用时空互代的方法选取9、23、33、47年生油松(Pinus tabuliformis)人工林为研究对象,比较油松不同器官(叶、枝、干、根)、凋落物及土壤C、N、P含量及其比值的差异,探讨它们随林龄的变化及其相互间的关系,以期为油松人工林的生产、改善和林木生长环境的调节提供参考。结果表明:除根中C含量在林龄间差异不显著外,其它器官C、N、P含量及其比值在林龄间均差异显著且随林龄增加变化趋势不尽相同。9、23、33、47年生油松林C、N、P含量及N∶P比值均在叶中最高;C∶N比值均在干中最高,根中次之;C∶P比值均在干中最高,其它器官大小次序不一。除33年生油松林叶中N∶P比值大于14外,其它各器官各林龄N∶P比值均小于14,且N∶P比值随林龄先增加后减少,故可判断油松在该区域受N限制较为严重,且随林龄的增加受N限制的情况有所缓解。不同林龄土壤和凋落物C、N、P含量及其比值差异显著,且后者均大于前者。土壤与凋落物C、P含量及C∶N、C∶P、N∶P比值随林龄增加变化趋势完全一致,表明土壤与凋落物之间有着密切的关系。叶片与凋落物N、P含量及C∶N、C∶P、N∶P比值之间显著相关,表明凋落物的养分承自植物叶片,二者之间关系紧密;植物和土壤的C、N、P含量之间均不存在显著相关性,说明土壤C、N、P供应量对乔木叶片C、N、P含量影响不大。

Anatomic Study of Female Sterility of Pinus tabulaeformis Carr.

The anatomic research on the mutant clone of Pinus tabulaeformis Carr. in the seed orchard in Xingcheng, Liaoning Province was carried out. The female cone of the mutant clone looked like normal, but its ovules degenerated in the early stage. This paper tries to find out the reason and time of ovule abortion. It seems that the ovule abortion is probably caused by female sterility because the microspores of this mutant clone were normal. Through the serial observations on the one-year-old macrosporangiates and the ovules of two-year-old female cones of mutant and normal clone, it is found that the reason of ovule abortion in mutant clone is the failure of the mitosis of free nuclei in the female gametophyte, and the time is about in the early April.