Estimation of fine root production, mortality and turnover with Minirhizotron in Larix gmelinii and Fraxinus mandshurica plantations

Fine root turnover is a major pathway for car-bon and nutrient cycling in forest ecosystems. However, to estimate fine root turnover, it is important to first understand the fine root dynamic processes associated with soil resource availability and climate factors. The objectives of this study were: (1) to examine patterns of fine root production and mortality in different seasons and soil depths in the Larix gmelinii and Fraxinus man-dshurica plantations, (2) to analyze the correlation of fine root production and mortality with environmental factors such as air temperature, precipitation, soil temperature and available nitrogen, and (3) to estimate fine root turn-over. We installed 36 Minirhizotron tubes in six mono-specific plots of each species in September 2003 in the Mao'ershan Experimental Forest Station. Minirhizotron sampling was conducted every two weeks from April 2004 to April 2005. We calculated the average fine root length, annual fine root length production and mortality using image data of Minirhizotrons, and estimated fine root turnover using three approaches. Results show that the average growth rate and mortality rate in L. melinii were markedly smaller than in F. mandshurica, and were high-est in the surface soil and lowest at the bottom among all the four soil layers. The annual fine root production and mortality in F. mandshurica were significantly higher than in L. gmelinii. The fine root production in spring and summer accounted for 41.7% and 39.7% of the total annual production in F. mandshurica and 24.0% and 51.2% in L. gmelinii. The majority of fine root mortality occurred in spring and summer for F. mandshurica and in summer and autumn for L. gmelinii. The turnover rate was 3.1 a-1 for L. gmelinii and 2.7 a-1 for F. mandshurica. Multiple regression analysis indicates that climate and soil resource factors together could explain 80% of the varia-tions of the fine root seasonal growth and 95% of the seasonal mortality. In conclusion, fine root production and mortality in L. gmelinii and F. mandshurica have dif-ferent patterns in different seasons and at different soil depths. Air temperature, precipitation, soil temperature and soil available nitrogen integratively control the dynamics of fine root production, mortality and turnover in both species.     

太白红杉种群邻体范围与邻体竞争强度的研究

采用逐步扩大范围的方法探讨了不同径级基株所受的邻体竞争强度 平均竞争强度和总竞争强度 与影响范围的关系 ,结果发现 : 1 邻体的平均竞争强度随影响范围的增加而降低 ,在一定的范围内下降较快 ,而超出该范围后下降的幅度变小 ,可以此为依据来确定邻体范围 ; 2 不同径级的基株 ,邻体范围有一定的差异 ; 3 邻体总的竞争强度和影响范围的关系服从对数函数关系 CI=Aln C+B .结果表明采用逐步扩大范围的方法能有效地确定邻体范围 ,提出了确定邻体范围的新方法     

太白红杉生殖年龄及其影响因素分析

研究了太白红杉的平均生殖年龄、最高生殖年龄和最小生殖年龄以及与环境之间的关系。结果表明太白红杉的平均生殖年龄为78．59a,最小生殖年龄为26a,最大生殖年龄为208a;其中南坡太白山最小生殖年龄26a、最高生殖年龄153a、平均生殖年龄72．97a;北坡最小生殖年龄29a、最高生殖年龄208a、平均生殖年龄92a。海拔和年降水与平均生殖年龄呈正相关,坡度与最高生殖年龄呈正相关,最高生殖年龄与最小生殖年龄呈正相关,表明提早生殖会减少太白红杉的生殖寿命。     

菌丝桥在日本落叶松幼苗间磷传递和植株生长中的作用

 应用四室隔网系统研究了菌丝桥在日本落叶松(Larix kaempferi)幼苗间传递磷的作用。结果表明,供体接种卷缘桩菇(Paxillus involutus)和彩色豆马勃（Pisolithus tinctorius）后,其外延菌丝可以穿过隔离层侵染受体落叶松,在供体和受体落叶松间形成了菌丝桥。供体植株接种菌根真菌后生物量明显增加,但是对受体植株没有显著的影响。菌根真菌侵染的供体和受体植株的根、地上部吸磷量均分别显著高于对照,而且供体植株根、地上部吸磷量增加的程度明显高于受体。被卷缘桩菇和彩色豆马勃侵染的受体植株体内32P的放射性强度分别是对照的10倍和6倍,两者形成菌丝桥后传递到受体植株的32P分别为供体植株体内32P的1.10%和0.22%。供体植株吸收的32P可以通过菌丝桥传递给受体,但是绝对数量十分有限,对受体植株磷营养没有产生显著的影响,但P. involutus和P. tinctorius侵染受体植株后,促进了受体落叶松对磷的吸收,这是菌丝桥形成后,真菌帮助受体植株吸收磷引起的。     

Spatial analysis of structural and tree‐ring related parameters in a timberline forest in the Italian Alps

Abstract. We investigated the variability in spatial pattern of some structural, dendrochronological and dendroclimatological features of a mixed Larix decidua‐Pinus cembra forest at the timberline in the eastern Italian Alps at fine geographical and temporal scales. Forest structure variables such as stem diameter, tree height, age and tree‐ring related parameters (yearly growth index, mean sensitivity, first order autocorrelation and some dendroclimatic variables) have been compared at various scale levels. We observed that most of the variables show positive autocorrelated structures due to both forest dynamics and fine‐scale driving forces, probably related to microrelief. Spatial structure of yearly indexed radial growth appears sensitive to extreme climatic events. Secondary succession after past disturbances drives the forest towards a structure governed by a gap regeneration dynamics that seems to ensure the different requirements of the two main tree species present. Small spatial scale studies of forest structures, especially if integrated to dendro‐ecological data, seem an efficient tool to assess the disturbance regime and species sensitivity to environmental change.     

太白红杉（Larix chinensis）叶的形态解剖学特征与环境因子的关系

根据生态气候学方法推断出不同海拔高度气候指标,应用多元统计方法,对分布于秦岭太白山地区海拔3000－3400m的太白红杉（Larix chinensis)叶特征进行了生态解剖学研究,分析了影响其变化的主导生态因子。观察指标包括叶形态指标（叶片总厚度、每束叶中的叶数和叶长宽比）、叶解剖学特征（叶表皮角质膜厚度、上、下表皮厚度,近上、下表皮叶肉厚度,内皮层厚度,管胞直径,叶传输组织和维管束厚度及其与叶片总厚度之比）。结果表明：（1）水热综合因子是影响太白叶长宽比和叶表皮角质膜厚度的主导因子,随着水热综合因子的增大,叶长宽比呈增加趋势,而角质膜厚度则逐渐变薄。（2）年降水量是影响其它形态解剖学指标的主导因子,随着年降水量的增加,每束叶中的叶数、叶厚度、管胞直径、叶传输组织和维管束厚度、内皮层厚度、传输组织和维管束厚度及其与叶总厚度之比呈减少和变薄的趋势,而上、下表皮厚度则逐渐增加。（3）近上、下表皮叶肉厚度与环境因子无明显相关,可能属于比较保守的性状。     

落叶松根际土壤磷的有效性研究

野外用剥落法采集落叶松(Larixgmelini)根际土与非根际土,分析P浓度的变化,结果表明,落叶松根际土与非根际土全P浓度无明显差异,但根际土有效P却明显高于非根际土.12年生时根际土有效P增加12.6%,40年生时增加23.4%,表明落叶松根际对土壤中的P具有活化作用.落叶松根际土无机P各组分与非根际土亦有差异,表现出根际土OP低于非根际土,AlP、FeP、CaP和NH4ClP则高于非根际土的趋势.落叶松根际土的pH低于非根际土,但落叶松根际并未发生明显酸化.落叶松根际有效P与pH变化相关不显著.     

Non‐parametric habitat models with automatic interactions

Questions: Can a statistical model be designed to represent more directly the nature of organismal response to multiple interacting factors? Can multiplicative kernel smoothers be used for this purpose? What advantages does this approach have over more traditional habitat modelling methods? Methods: Non‐parametric multiplicative regression (NPMR) was developed from the premises that: the response variable has a minimum of zero and a physiologically‐determined maximum, species respond simultaneously to multiple ecological factors, the response to any one factor is conditioned by the values of other factors, and that if any of the factors is intolerable then the response is zero. Key features of NPMR are interactive effects of predictors, no need to specify an overall model form in advance, and built‐in controls on overfitting. The effectiveness of the method is demonstrated with simulated and real data sets. Results: Empirical and theoretical relationships of species response to multiple interacting predictors can be represented effectively by multiplicative kernel smoothers. NPMR allows us to abandon simplistic assumptions about overall model form, while embracing the ecological truism that habitat factors interact.     

Aneuploidy and polyploidization in haploid tissue cultures of Larix decidua

Haploid embryogenic lines of Larix decidua which had been maintained on medium free of plant growth regulatiors were screened for chromosomal abnormalities. Chromosome squashes were prepared from fast-growing suspension culture. alternatively, a method using burst protoplasts was devised for improving chromosome spreads. One line showed polyploidization with chromosome mumbers ranging from haploid to tetraploid. This line is presently predominantly diploid. Aneuploidization also occurred. The most effective method for counting chromosomes was from burst protoplasts. It is recommended that long-term cultures of conifer tissues be checked for genetic stability.