Impact factors on fine root seasonal dynamics in Fraxinus mandshurica plantations

Fine root turnover plays important roles in carbon allocation and nutrient cycling in forest ecosystems. Seasonal dynamics of fine roots is critical for understanding the processes of fine root turnover. From May to October 2002, soil core method was used for estimating the seasonal pattern of fine root (diameter < 1 mm) parameters (biomass, specific root length (SRL) and root length density (RLD)) in a Manchurian ash (Fraxinus mandshurica) plantation located at the Maoershan Experiment Station, Heilongjiang Province, northeast of China. The relationships of fine root biomass, SRL and RLD with available nitrogen in soil, average soil temperature per month in 10 cm depth and soil moisture content were analyzed. Seasonal variation of fine root biomass was significant (P < 0.05). The peak values of fine root biomass were observed both in spring and in autumn, but SRL and RLD were the highest in spring and lowest in autumn. Specific root length and root length density were higher in spring and summer, which means that fine root diameter was thinner. In autumn, both parameters decreased significantly due to secondary incrassation of fine root diameter or the increase of tissue density. Seasonal dynamics of fine roots was associated with available nitrogen in soil, soil temperature in 10 cm depth and moisture content. Fine root biomass has a significant relationship with available NH₄ ⁺-N in soil. Available NO₃ ⁻-N in soil, soil temperature in 10-cm depth and moisture content have a positive correlation with fine root biomass, SRL and RLD, although these correlations are not significant (P > 0.05). But the compound effects of soil available N, soil temperature and soil moisture content are significant to every root parameter. The variations of these three root parameters in different seasons show different physiological and ecological functions in different growing periods. Translated from Scientia Silvae Sinicae, 2006, 42(9): 7–12 [译自: 林业科学]     

水曲柳落叶松混交林中细根空间分布

采用根钻取样方法对年生水曲柳落叶松混交林中细根空间分布状况进行了研究。结果表明,水曲柳落叶松地下生物量的空间分配差异显著。在林分水平上,水曲柳的根生物量密度高于落叶松(分别为4442.3和2234.9g/m3)。两树种在相邻区域中分配的细根生物量较高,表明种间根系竞争较弱。落叶松行间的水曲柳细根生物量密度和根长密度均高于水曲柳行间的落叶松细根,表明水曲柳地下部分具有较强能力。根系的空间分布有利于混交林中水曲柳的生长。图1表4参19。     

林分密度对侧柏人工林细根形态的影响

以徐州林场50年生侧柏人工林为研究对象,采用挖掘法获取土壤根系样品,探究林分密度对侧柏人工林不同根序细根形态的影响。结果表明:细根的直径和根长随着根序上升而显著增大,而比根长则随着根序的上升而显著减小。低林分密度(1 679株/hm2)与中林分密度(2 250株/hm2)相比显著减小了表层土壤1、2级细根的平均直径和平均根长,亚表层土壤3级细根的根长,显著增大了亚表层土壤2级细根的平均比根长;高林分密度(3074株/hm2)比中林分密度显著增大了2级根的平均比根长。与高林分密度相比,低林分密度显著减小了表层土壤1、2级细根的平均直径,增大了亚表层土壤5级细根的平均直径。     

Relationships between larch growth and forest site factors

Dahurian larch (Larix gmelinii Rupr.) Rupr is one of the dominant species in both natural and man-made forests in northeast China. Effects of site factors, including topography, soil properties and nutrient elements (P, Ca, K, Mg, Mn, Zn, Cu, Ag, Co and Ni) on the growth of larch were analyzed in detail, qualitatively and quantitatively. The ordination technique was used to group the site factors and to classify sites for larch. Analysis indicated that height growth, diameter (DBH) and volume of the larch varied among site types and this will be of theoretical and practical significance in developing larch plantations.     

胡桃楸落叶松纯林与混交林中根际土壤的养分特征(英文)

与非根际土壤相比较,研究了胡桃楸落叶松纯林与混交林中根际土壤pH值、有机质及氮 、磷、钾等养分元素的特征。结果表明：各林分中,除胡桃楸纯林外,根际土壤的pH值均不 同程度低于非根际土壤;除混交林中落叶松根际土有机质含量略低于非根际土外,根际土壤 有机质含量均高于非根际土壤;根际土壤存在氮的相对累积,磷和钾在根际则具有一定的亏 缺趋势,其程度与树种相关;各林分下,氮、磷、钾在根际中均得以活化,表现为根际土壤 速效氮、磷、钾含量偏高;混交林中落叶松根际速效氮含量明显高于其纯林,而混交林中胡 桃楸根际速效磷、钾含量明显高于其纯林。     

Dynamic feature of flavonoids content in different organs of larch （Larix gmelinii）

Flavonoids in plants is very important in its ecological role and economic value. The dynamic features of flavonoids content in different organs of larch (Larix gmelinii) at different light and temperature conditions were investigated in this study. Results showed that the order of flavonoids content in different organs from high to low was 7.78% (stem bark)>2.79% (leaves) >1.72% (branches) >1.19% (stem xylem)and different organs had a great seasonal variation in flavonoids content, but the change of flavonoids content at different temperature was not obvious in different organs., The content of flavonoids in barck had, a positive correlation with temperature (R ²=0.75), but that in other organs had slight variation with the change of temperature. For all the tested organs, the flavonoids content in summer and autumn was approximately 3–4 times higher than in spring and winter. This is attributed to the great stress from environmental physical variables such as UV radiation, high temperature that induce the accumulation of flavonoids. The flavonoid content of sun leaves was evidently higher than that of shade leaves, and leaves at upper part of canopy had a higher flavonoids content compared with that at other parts. This result indicates that sun radiation could improve flavonoids production in leaves (R ²=0.76). The flavonoids may actively evolve in plant defenses to environmental stress, protecting larch from the damage of high temperature and radiation, and its main function is different in different organs. Foundation item: This paper is supported by the National Natural Science Foundation of China (30300271) and the Key Project of Chinese Ministry of Education (104191). Biography: WANG Wen-jie (1974-), male, Lecturer in Key Laboratory of Forest Plant Ecology, Northeast Forestry University, Harbin 150040, P. R. China. Responsible editor: Zhu Hong     

Use of GIS-derived environmental factors in predicting site indices in Japanese larch plantations in Hokkaido

The objectives of this study were (1) to evaluate the effects of environmental factors derived from GIS on tree-height growth of Japanese larch (Larix kaempferi) and (2) to develop a best-fit regression model for its site index. Based on data from 40 sample plots situated in an even-aged (38 years), pure, and undamaged Japanese larch stand, multiple regression models for a site index of Japanese larch were constructed using environmental factors as independent variables. The average slope gradient, effective relief, distance from ridge, flow accumulation, degree of exposure, shading, solar radiation index, and gravitational water index were used as environmental factors and calculated on GIS using digital elevation model data. These factors were related to the Japanese larch site index through multiple-regression analysis. The result showed that the most effective factor for estimating site index was the degree of exposure. Through a backward stepwise procedure, the degree of exposure, shading, and average slope gradient were selected for a best-fit regression model. This model explained 72% of the variance in site index, with standard error estimates of 1.75 m. This strong relationship suggests that GIS-derived environmental factors can be used to predict site indices of Japanese larch. This study was supported by the experimental forest of Kyushu University.     

Effect of collar insertion on soil respiration in a larch forest measured with a LI-6400 soil CO2 flux system

Little information is available on the effect of root cutting by the collar pre-insertion technique on soil respiration. In this study, we found that soil respiration rates decreased with increasing depth of collar insertion in both the with live roots intact and with live roots severed treatments, but the rate of decrease was substantially higher in the former. The cutting of roots, especially fine roots, may be responsible for this result.     

皮层和中柱对水曲柳和落叶松吸收根直径变异的影响

采用植物解剖学和通径分析方法研究皮层和中柱对水曲柳和落叶松人工林根系前2级根(最末端的根尖为1级根)直径变异的影响。结果表明：1)根直径、皮层厚度和中柱直径具有明显的季节变化,三者具有相同的变化规律;2)随着皮层厚度或中柱直径的增加,根直径显著增加,皮层厚度可以解释直径变异的85%～95%,中柱直径可以解释直径差异的92%～97%,表明皮层和中柱均对直径变异有重要的影响;3)通径分析结果显示,水曲柳根直径变异和季节变化主要是皮层变化起直接作用,中柱仅起间接作用;而落叶松则是皮层起间接作用,中柱起直接作用。研究结果为认识木本植物吸收根种内直径变异的机制提供重要基础。     

大兴安岭兴安落叶松林树木生物量对氮沉降的响应

[目的]研究兴安落叶松生物量增长率对氮沉降是否存在响应,年际间是否存在差异;不同径级是否会影响兴安落叶松生物量增长率对氮沉降的响应。[方法]通过人工氮添加的方法模拟大气氮沉降变化,探究兴安落叶松林连续3年(2014—2016)树木生物量的变化对氮沉降的响应。从2012年开始,共设置4个氮添加水平,分别为对照(CK,0 g·m-2·a-1)、低氮(TL,2.5 g·m-2·a-1)、中氮(TM,5 g·m-2·a-1)和高氮(TH,7.5 g·m-2·a-1),每年的生长季(5—10月)按月将NH4NO3溶于32 L蒸馏水,利用背喷式喷雾器均匀喷洒于样方内,对照样地喷洒等量纯净水。[结果](1)3年间各施氮处理生物量增长率均显著高于对照组(P0.05)、各年份生物量增长率均存在显著差异(P0.05),而且2016年生物量增长率明显高于前两年(P0.05)。(2)2014年各处理间无显著差异;2015年TL处理的生物量增长率显著高于TM和TH处理(P0.05),2016年TL处理的生物量增长率显著高于TH处理(P0.05)。(3)不同处理对年际间不同径级生物量增长率也产生不同影响。TL处理对2014和2016年的10 15cm径级的兴安落叶松生物量增长率有显著促进作用(P0.05);TM处理对所有年份10 15 cm和15 20 cm径级兴安落叶松生物量增长率均有显著促进作用(P0.05);TH处理对所有年份胸径大于10 cm的3个径级(1015、15 20、20 cm)兴安落叶松生物量增长率均有显著促进作用(P0.05)。[结论](1)长期氮添加有可能导致树木生长率的增量逐渐减少甚至出现抑制,将改变现有北方森林生态系统碳源汇动态;(2)由于不同径级树木对氮沉降的响应不同,为提高氮沉降对北方森林碳库影响的模型预测精度,应按不同径级分别模拟。     

Discrepancy in fine root turnover estimates between diameter-based and branch-order-based approaches: a case study in two temperate tree species

Fine root turnover plays a key role in carbon(C) budgets and nutrients cycles in forest ecosystems.However,the difference between branch-order-based and diameter-based approaches in estimating fine root turnover is still unclear.We studied root biomass turnover based on multiplying root standing biomass by turnover rate(inverse of median root longevity) in two Chinese temperate tree species,Fraxinus mandshurica Rupr.and Larix gmelinii Rupr.The minirhizotron(MR) technique was used to estimate longevities for first and second order roots,and total roots(R total) apparent on the MR tube surface.The corresponding biomass for each root group was estimated by soil monolith.The difference in biomass turnover between R total and the sum of the first and second order roots was used to represent the discrepancy between diameter-and order-based approaches.First order roots had shorter life spans and higher biomass turnover rates than the second order roots in both species.Biomass turnover estimated by the order-based method for F.mandshurica and L.gmelinii were 155.4 g m-2 a-1 and 158.9 g m-2 a-1,respectively,in comparison with 99.5 g m-2 a-1 and 117.7 g m-2 a-1 estimated by the diameter-based method,indicating that the diameter-based approach underestimated biomass turnover.The most probable reason was that the order-based method enhanced separation of the heterogeneous root population into relatively homogenous root groups with varying turnover rates.We conclude that separating fine root pool into different branch orders can improve the accuracy of estimates for fine root turnover,as well as the understanding of the belowground C allocation and nutrient cycling at ecosystem level.     

Fine root dynamics of shaded cacao plantations in Costa Rica

Root turnover may contribute a significant proportion of recycled nutrients in agroforestry systems and competition between trees and crops for nutrients and water may depend on temporal fine root regrowth patterns. Fine root biomass ( 2 mm) and fine root productivity were measured during one year in plantations of cacao (Theobroma cacao) shaded by Erythrina poeppigiana or Cordia alliodora planted on a deep alluvial soil in Turrialba, Costa Rica. Fine root biomass of approximately 1.0 Mg ha^–1 varied little during the year with maximum values at the beginning of the rainy season of 1.85 Mg ha^–1 in the cacao-C. alliodora system compared to 1.20 Mg ha^–1 for cacao-E. poeppigiana. Fine root productivity of C. alliodora and E. poeppigiana (maximum of 205 and 120 kg ha^–1 4 week^–1, respectively) was greatest at the end of the rainy season, while for cacao it was greatest at the beginning of the rainy season (34–68 kg ha^–1 4 week^–1), which suggests that if nutrient competition occurs between the shade trees and the cacao, it could be minimized by early fertilization during the beginning of the rains immediately after pruning the shade trees. Annual fine root turnover was close to 1.0 in both systems. Assuming that fine root biomass in these mature plantations was constant on an annual basis, nutrient inputs from fine root turnover were estimated as 23–24 (N), 2 (P), 14–16 (K), 7–11 (Ca) and 3–10 (Mg) kg ha^–1 year^–1, representing 6–13% and 3–6% of total nutrient input in organic matter in the C. alliodora and E. poeppigiana systems, respectively.     

Characteristics of reproductive biology forLarix originating in Japan

The paper summarized the life cycle, environmental features and distributions ofLarix origination in Japan. The time of blooming and fruiting and the ways of cone collection and seeds storage were introduced. The treating methods of seeds germination and the sowing time for both Japanese larch (Larix kaempferi Carr) and Dahurian larch (Larix gmelinii var.japonica Pilger) were discussed. Responsible Editor: Zhu Hong     

大兴安岭不同区域落叶松相容性材积方程及异方差研究

[目的]对不同区域立木相容性材积方程以及不同异方差校正方法进行详细对比分析,建立相容性材积方程预估大兴安岭不同区域落叶松的立木材积。[方法]以大兴安岭3个不同区域的落叶松为研究对象,采用误差变量联立方程组的方法构建不同区域立木相容性材积方程。采用非线性额外平方和的方法(F检验)进行区域性检验。使用多种权函数分别对3个区域存在异方差的材积方程进行加权回归。[结果]表明:任何2个区域的立木材积方程都有显著不同(P0.000 1),区域1和区域3的材积相差较大,区域2与区域1和区域3的材积相差较小。不同区域立木材积方程的错误应用会导致较大的预测误差。在参数稳定性和评价指标方面,加权估计会优于普通最小二乘估计。基于平均相对误差(MRE)和总相对误差(TRE),区域1(-0.11、0.97)、区域2(0.04、0.08)和区域3(1.04、0.93)的最优权函数分别为1/F(x)、1/D4.99、1/D3.38。[结论]立木材积方程是森林调查和林分生长与收获模型的主要组成部分,本文所构建3个区域的相容联立方程组模型预测误差均不超过±3%。建立相容性立木材积方程时应考虑其异方差的影响。最优权函数没有统一的形式。为尽可能得到稳定的参数估计,在加权回归估计过程中应选用多种权函数进行对比分析。     

A model for vertical distribution of fine roots in Robinia pseudoacacia plantations on the Loess Plateau

Based on a detailed investigation of vertical distributions of fine roots in Robinia pseudoacacia plantations at the Ansai Soil and Water Conservation Station, Shaanxi Province, a model was developed for the deep distribution of fine roots of R. pseudoacacia, which reflects the growth of fine roots affected by the mixed process of infiltration water and deep soil water. The maximum depth of the distribution h _max and the depth of the highest fine root density (FRD) h _p were determined and the maximum depth of infiltration water supplied for fine root growth h _q could also be calculated, h _q was considered as the approximate boundary between infiltration water and deep soil water in support of the growth of fine roots. According to the model, the soil water of R. pseudoacacia woodland in the profile could be classified into three layers: the first layer from the soil surface to h _p was the active water exchange layer, very much affected by precipitation; the second was the soil water attenuation layer, between h _p and h _q and largely affected by the vertical distribution of fine roots; the third was the relatively stable soil water layer below h _q, below which soil water did not change much. The percentage of infiltration water supplied for the growth of fine roots reached a level of 88.32% on the shaded slopes and 85.21% on sunny slopes. This indicated infiltration of precipitation played a crucial role in the growth of R. pseudoacacia in the gully region of the Loess Plateau. The research of interaction between the distribution of fine roots and soil water in the profile will help to explain the reasons for the complete drying out of soils and provide a theoretical basis for continuing the policy of matching tree species with sites on the Loess Plateau. Translated from Scientia Silvae Sinicae, 2006, 42(6): 40–48 [译自: 林业科学]     

基于非线性混合模型的东北兴安落叶松树高和直径生长模拟

以黑龙江省带岭林业局大青川林场80株人工兴安落叶松解析木数据为例,采用Richards生长模型作为基础模型,利用S-PLUS软件中的NLME过程,分别拟合非线性树高和直径生长模型。采用AIC、BIC、对数似然值和似然比检验等模型评价统计指标对不同模型的精度进行比较分析。结果表明:当对树高-年龄关系进行拟合时,b1、b3同时作为混合参数时模型拟合最好;当对直径-年龄关系进行拟合时,b1、b3同时作为混合参数时模型拟合最好。把相关性结构包括一阶自回归结构AR(1)、一阶移动平均结构MA(1)及一阶自回归与移动平均结构[ARMA(1,1)]加入到树高和直径最优混合模型中,一阶自回归结构AR(1)显著提高了树高混合模型的拟合精度,一阶移动平均结构MA(1)显著提高了直径混合模型的拟合精度。模型检验结果表明:混合模型通过校正随机参数值能提高模型的预测精度。因此,混合模型在应用上不但能反映树高和直径的平均预测趋势,还能用方差协方差结构和误差相关性结构校正随机参数来反映个体之间的差异。     

Stand structure and composition of a 60-year-old larch (Larix kaempferi) plantation with retained hardwoods

Tree retention is understood as a key practice in creating complexity, leading to heterogeneity in resources and habitats in managed stands. In this article, we clarify the long-term effects of tree retention on stand structure and tree-species composition in a 60-year-old Larix kaempferi plantation in central Japan. In our study plot (1.5 ha) there were 18 stems/ha of retained trees (determined by tree-ring analysis), mostly Quercus crispula. We conducted spatial analyses and tested the hypothesis that tree abundance, size structure, and species composition and diversity change with distance from the retained trees. Near the retained trees, L. kaempferi showed a reduction of 40%–60% in basal area, due presumably to the shading effect. In contrast, the nearby area showed greater species diversity in the canopy layer. The retained trees created patches of different species composition in the understory. The spatial gradient of shade and colonization opportunity provided by retained trees greatly affect the distribution of the colonized species, according to their shade tolerance and seed-dispersal ability, which resulted in the stand structure with a heterogeneous shrub-layer vegetation. Retention proved particularly important for the enhancement and long-term maintenance of structural and compositional complexity in L. kaempferi plantations.     

Relationship between resistance to vole browsing and content of ether extract in the bark of larch species and hybrids

We determined the survival rate of tree families produced by the intra- and interspecific crossing of larch species damaged by browsing of vole (Clethrionomys rufocanus bedfordiae Thomas) and the contents of ether extracts (EE) in their bark. The average survival ofLarix gmelini var.japonica Pilg. (L. gmelini)×L. gmelini (G×G) was highest, followed by the hybridL. gmelini×L. leptolepis Gordon (G×L). The families of the hybrid G×L, which is considered suitable for silviculture in Hokkaido, Japan, showed significant differences in survival rates, suggesting that it is possible to produce improved varieties of the hybrid which are more resistant to vole browsing. The EE contents of the bark were under strong hereditary control, and the rank of the EE content among the various families hardly fluctuated between the location of the test fields. The correlation coefficient between the survival rates and the EE contents was highly significant (r=0.89,n=24,p<0.01), indicating that the EE content in the bark may be used as a possible index of resistance or susceptibility to vole browsing in larch plantations. A part of this report was presented at the 106th Annual Meeting of the Japanese Forestry Society, at Sapporo, April, 1995.     

Blue stain fungi associated withIps cembrae (Coleoptera: Scolytidae) in Japanese larch in connection with their brood development

The association between blue stain fungi andIps cembrae Heer (Coleoptera: Scolytidae) was investigated in the Japanese larch,Larix leptolepis Gordon, in the Nagoya University Forest, Aichi Prefecture, central Japan.I. cembrae had one or two generation(s) in a year in this study area. Two blue stain fungi,Ophiostoma piceae andLeptographium sp., were isolated from the body surface of both male adults in mating chambers and female adults in parent galleries, suggesting that this beetle species was a vector of these fungi. Although no blue stain fungi were isolated from non-stained wood, both fungi were isolated from the mating chambers, the center and the uppermost end of the galleries throughout the season. The fact thatO. piceae was consistently isolated with high frequency from adults and from their galleries strongly suggested that this species would be the principal blue stain fungus infecting the beetle-attacked larch trees.     

马尾松细根研究进展

根系是植物长期适应陆地条件而形成的一个重要的地下器官,在整个生态系统中扮演者重要的角色。细根作为根系系统中最重要部分,对森林生态系统碳平衡和养分循环具有重要作用。马尾松是我国速生特有种,集经济价值和生态价值为一体。文中综述了马尾松细根生物量、周转和寿命的研究进展,并对今后的研究提出展望,以期为我国树木根系生态学研究提供参考。