黄土高原樟子松和落叶松与其他树种枯落叶混合分解对土壤的影响

通过采集树木枯落叶与土壤进行室内混合分解培养试验,研究了黄土高原常见的樟子松和落叶松与其他树种枯落叶混合分解对土壤性质的影响及存在的相互作用,从而为不同树木种间关系的探索和该地区人工纯林的混交改造提供科学指导。结果表明:12种枯落叶单一分解均明显提高了土壤脲酶(54%—110%)、脱氢酶(85%—288%)和磷酸酶(81%—301%)活性以及有机质(29%—55%)和碱解N(12%—49%)含量,但对土壤速效P含量和CEC的影响存在较大差异。综合而言,樟子松分别与白桦、刺槐、白榆、柠条和落叶松枯落叶混合分解在对土壤性质的影响中存在相互促进作用,而分别与小叶杨、沙棘、紫穗槐、侧柏和辽东栎枯落叶混合分解在对土壤性质的影响中存在相互抑制作用;落叶松分别与刺槐、白桦、小叶杨和紫穗槐枯落叶混合分解在对土壤性质的影响中存在相互促进作用,而分别与柠条、侧柏、辽东栎、沙棘、油松和白榆枯落叶混合分解在对土壤性质的影响中存在相互抑制作用。     

Sustained effects of atmospheric [CO2] and nitrogen availability on forest soil CO2 efflux

Soil CO₂ efflux (F_soil) is the largest source of carbon from forests and reflects primary productivity as well as how carbon is allocated within forest ecosystems. Through early stages of stand development, both elevated [CO₂] and availability of soil nitrogen (N; sum of mineralization, deposition, and fixation) have been shown to increase gross primary productivity, but the long‐term effects of these factors on F_soil are less clear. Expanding on previous studies at the Duke Free‐Air CO₂ Enrichment (FACE) site, we quantified the effects of elevated [CO₂] and N fertilization on F_soil using daily measurements from automated chambers over 10 years. Consistent with previous results, compared to ambient unfertilized plots, annual F_soil increased under elevated [CO₂] (ca. 17%) and decreased with N (ca. 21%). N fertilization under elevated [CO₂] reduced F_soil to values similar to untreated plots. Over the study period, base respiration rates increased with leaf productivity, but declined after productivity saturated. Despite treatment‐induced differences in aboveground biomass, soil temperature and water content were similar among treatments. Interannually, low soil water content decreased annual F_soil from potential values – estimated based on temperature alone assuming nonlimiting soil water content – by ca. 0.7% per 1.0% reduction in relative extractable water. This effect was only slightly ameliorated by elevated [CO₂]. Variability in soil N availability among plots accounted for the spatial variability in F_soil, showing a decrease of ca. 114 g C m^?2 yr^?1 per 1 g m^?2 increase in soil N availability, with consistently higher F_soil in elevated [CO₂] plots ca. 127 g C per 100 ppm [CO₂] over the +200 ppm enrichment. Altogether, reflecting increased belowground carbon partitioning in response to greater plant nutritional needs, the effects of elevated [CO₂] and N fertilization on F_soil in this stand are sustained beyond the early stages of stand development and through stabilization of annual foliage production.     

气候变化对我国红松林地理分布影响的研究

在红松林地理分布规律研究的基础上,应用地理信息系统ＩＤＲＩＳＩ和专门计算机软件——生态信息系统ＧＲＥＥＮ,找出适宜红松林分布的地理气候参数区间,并以此确定了红松林适宜分布区,在此基础上,根据全球气候预测模型ＧＣＭｓ预测的２０３０年的气候变化结果,就气候变化对我国红松林地理分布的可能影响进行了预测。结果表明：到２０３０年,因气候变化的影响,我国适宜红松分布的面积将有所增加,但增加幅度不大,仅占当前气候条件下适宜红松分布面积的３．４％,局部地区变化的情况是：在黑龙江省的西北部适宜红松分布的面积将有所增加;在辽宁省的西南部适宜红松分布的面积将有所减少。红松林现实分布区的南界将向北移动０．１～０．６个纬度,北界将向北扩展０．３～０．５个纬度,黑龙江省境内的红松林分布区的西界将向西扩展０．１～０．５个经度。我国适宜红松分布的面积将由当前气候条件下的２．９×１０７ｈｍ２,增加到３．０×１０７ｈｍ２。就当前气候变化影响预测中存在的问题及未来研究的方向进行了讨论。     

Increases in cytokinin levels in Scots pine in relation to chilling and bud burst

Levels of isopentenyladenosine and zeatin riboside were monitored in buds and needles of Scots pine ( Pinus sylvestris L.) seedlings grown under controlled climatic conditions and in field-grown trees. Extracts were purified by immunoaffinity chromatography and high-performance liquid chromatography. Cytokinin levels were quantified with an enzyme-linked immunosorbent assay. The cytokinin content was low in buds and needles of dormant seedlings but increased during dormancy release, reaching peak values in buds just before resumption of shoot growth. Samples collected in the field also showed a marked increase in the levels of cytokinins just prior to bud burst. Further, the biological activity of applied cytokinins in activating the dormant buds of Scots pine is shown. The results indicate a probable role of cytokinins in seedlings during dormancy release.     

黄龙山林区封育油松种群动态研究

对不同封育年限油松种群的高度、径级、年龄结构进行分析,运用马尔可夫转移矩阵预测种群密度动态。结果表明,不同封育年限种群的生长发育明显不同。种群个体高度以2～4m和6～8。占优势,胸径以0～2cm的小径阶和〉20cm的大径阶占较大比重;在各封育系列中,种群的密度中、大级出现几率较大。在封育45年前,种群的年龄结构中大树所占比例最大;45年后,小树和幼苗则较多,但种群弱小个体大量死亡。本区天然林保护年限最短应确定为45年。     

Four cytosolic-type CuZn-superoxide dismutases in germinating seeds of Pinus sylvestris

A differential analysis of CuZn-superoxide dismutase (SOD. EC 1.15.1.1) isozymes after native-polyacry lamide gel elecrrophoresis (PAGE) and isoelectric focusing (IEF) indicated that germinating seeds of Scots pine (Pinus sylvestris L.) 3 days after the start of imbibition (3 DAI) contain five CuZn-SOD isozymes. Two isozymes co-migrated on native–PAGE but were separated after IEF. CuZn-SODs of Scots pine were purified from germinating seeds (3 DAI) by anion-exchange chromatography, hydrophobic interaction chromatography and chromatofocusing. The final separation of CuZn-SOD isozymes was accomplished by native-PAGE. CuZn-SOD isozymes were electroblotted and their NH₂-terminal amino acid sequence was determined. Comparisons of the amino acid sequences with sequences of CuZn-SOD isozymes from other plant sources indicated that one CuZn-SOD isozyme was of the chloroplastic type whereas the other four isozymes belonged to the cytosolic-type CuZn-SODs, The NH₂-terminal amino acid sequence of the chloroplastic CuZn-SOD and of one cytosolic-type CuZn-SOD were identical to those of two previously isolated, sequenced and localized CuZn-SOD isozymes from Scots pine needles. Two cytosolic-type CuZn-SOD isozymes showed a homology at 20 out of 21 NH₂-terminal amino acids. Mitochondria and glyoxysomes were isolated by differential and Percoll density-gradient centrifugation from germinating seeds (3 DAI). The cell fractionation experiments did not suggest that a major part of the CuZn-SOD activity in germinating seeds was derived from glyoxysomes or mitochondria.     

福建万木林天然马尾松林分特征

福建万木林天然马尾松林为以马尾松占绝对优势的松阀混交林,物种多样性与四周的天然阔叶林相近,林分蓄积量高达９８４．２ｍ３ｈｍ－２,是罕见的、典型的天然马尾松丰产林,为珍贵的自然资源。     

Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature

Abstract. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day⁻¹ at 8°C to 0.30 °C day⁻¹ at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening.     

Discrepancies between water potential isotherm measurements on Pinus ponderosa seedling shoots: xylem hysteresis and apoplasmic osmotic potentials *

Abstract. Sap expression, air drying and a combined technique were used to measure the water potential isotherm of Pinus ponderosa Laws, seedling shoots with the pressure chamber. Discrepancies between water relations parameters derived from these techniques can be partially explained by air entry into air drying tissues, hysteresis in the xylem water potential isotherm and dilution of apoplasmic solutes during sap expression.     

Different effects of supplied ammonium on glutamine synthetase activity in mustard (Sinapis alba) and pine (Pinus sylvestris) seedlings

The activity of glutamine synthetase (GS) in mustard ( Sinapis alba L.) and Scots pine ( Pinus sylvestris L.) seedlings was used as an index to evaluate the capacity to cope with excessive ammonium supply. In these 2 species GS activity was differently affected by the application of nitrogen compounds (NH₄⁺ or NO₃⁻). Mustard seedlings older than 5 days showed a considerable increase in GS activity after NH₄⁺ or NO₃⁻ application. This response was independent of the energy flux, but GS activity in general was positively affected by light. Endogenous NH₄⁺ did not accumulate greatly after nitrogen supply. In contrast, seedlings of Scots pine accumulated NH₄⁺ in cotyledons and roots and showed no stimulation of GS activity after the application of ammonium. In addition, root growth was drastically reduced. Thus, the pine seedlings seem to have insufficient capacity to assimilate exogenously supplied ammonium. NO₃⁻, however, did not lead to any harmful effects.