Container volume and growing density influence western larch (Larix occidentalis Nutt.) seedling development during nursery culture and establishment

Larch tree species (Larix Mill.) are both ecologically and commercially valuable in their native range and are the focus of many restoration, afforestation, and commercial reforestation efforts in the boreal forests of the northern hemisphere. Land use change, shifting climate, and poor natural regeneration are making it increasingly difficult to establish the species; therefore, artificial regeneration is critical to ensure this timber species maintains its productive role on the landscape. New stocktypes are continually being developed to aid target seedlings for difficult sites, and critical, non-confounding evaluations of them are needed for target seedling development. This research evaluates the effect of container parameters on potential target seedlings. It examines tolerance thresholds of western larch (Larix occidentalis Nutt.) with respect to moisture and temperature status in the rhizosphere during early establishment. A suite of morphological measurements was used to assess seedling quality and relative performance following transplant. Modifying a commercially available container developed four distinct stocktypes of 111, 143, 175 and 207 ml that were paired with a volume-dependent nutrient regime at two culturing densities. Seedling phenotype was affected to a greater extent by container density than by container volume. Despite changes to container volume, root:shoot were found to be similar, indicating benefits of a tailored nutrient regime during nursery culture. Simulated field trials revealed that a low density growing arrangement improved post-transplant seedling growth, specifically root growth. Also, the 207 ml container facilitated greater growth in dry soil conditions compared to smaller containers. Lower (10 °C) rhizosphere temperature hindered root growth; however, seedling survival was 100 %, warranting the testing of earlier outplanting windows for this species. This evaluation of stocktype performance contributes to a greater body of work with this species and its congeners, which will ultimately benefit reforestation and afforestation efforts alike.     

Photosynthetic decline and pigment loss during autumn foliar senescence in western larch (Larix occidentalis)

We measured needle pigment content and photosynthetic rates of 1-year-old western larch (Larix occidentalis Nutt.) during autumn foliar senescence. Chlorophyll (Chl) and carotenoid (xanthophyll + b-carotene) contents of needles declined 11 and 17%, respectively, before CO(2) assimilation rate began to decline. Chlorophyll a/b ratio, Chl/carotenoid ratio, photochemical efficiency (F(v)/F(m)), and photochemical quenching did not begin to decline until late in senescence. Internal CO(2)/ambient CO(2) did not change during needle yellowing. In seedlings in warmed soil (average 3 degrees C above natural conditions), the decline in needle chlorophyll content was delayed by 10 days and the decline in CO(2) assimilation rate was delayed by 5 days, compared with seedlings in soil at ambient temperature. In seedlings exposed to an extended 16-h photoperiod, the decline in needle chlorophyll content was delayed by 32 days, and the decline in CO(2) assimilation rate was delayed by 21 days, compared with seedlings exposed to natural day lengths. In addition to delaying the onset of needle senescence, the treatments affected the sequence of events during senescence. Differences among treatment groups provide evidence that the onset of pigment loss and photosynthetic decline and the sequence of events during needle senescence are affected by soil temperature and day length.     

Carbon storage in old-growth and second growth fire-dependent western larch (Larix occidentalis Nutt.) forests of the Inland Northwest,USA

There is limited understanding of the carbon (C) storage capacity and overall ecological structure of old-growth forests of western Montana, leaving little ability to evaluate the role of old-growth forests in regional C cycles and ecosystem level C storage capacity. To investigate the difference in C storage between equivalent stands of contrasting age classes and management histories, we surveyed paired old-growth and second growth western larch (Larix occidentalis Nutt)–Douglas-fir (Pseudostuga menziesii var. glauca) stands in northwestern Montana. The specific objectives of this study were to: (1) estimate ecosystem C of old-growth and second growth western larch stands; (2) compare C storage of paired old-growth–second growth stands; and (3) assess differences in ecosystem function and structure between the two age classes, specifically measuring C associated with mineral soil, forest floor, coarse woody debris (CWD), understory, and overstory, as well as overall structure of vegetation. Stands were surveyed using a modified USFS FIA protocol, focusing on ecological components related to soil, forest floor, and overstory C. All downed wood, forest floor, and soil samples were then analyzed for total C and total nitrogen (N). Total ecosystem C in the old-growth forests was significantly greater than that in second growth forests, storing over 3 times the C. Average total mineral soil C was not significantly different in second growth stands compared to old-growth stands; however, total C of the forest floor was significantly greater in old-growth (23.8 Mg ha⁻¹) compared to second growth stands (4.9 Mg ha⁻¹). Overstory and coarse root biomass held the greatest differences in ecosystem C between the two stand types (old-growth, second growth), with nearly 7 times more C in old-growth trees than trees found on second growth stands (144.2 Mg ha⁻¹ vs. 23.8 Mg ha⁻¹). Total CWD on old-growth stands accounted for almost 19 times more C than CWD found in second growth stands. Soil bulk density was also significantly higher on second growth stands some 30+ years after harvest, demonstrating long-term impacts of harvest on soil. Results suggest ecological components specific to old-growth western larch forests, such as coarse root biomass, large amounts of CWD, and a thick forest floor layer are important contributors to long-term C storage within these ecosystems. This, combined with functional implications of contrasts in C distribution and dynamics, suggest that old-growth western larch/Douglas-fir forests are both functionally and structurally distinctive from their second growth counterparts.     

The study on site quality evaluation for dahurian larch (Larix gmelinii Rupr.)

Site quality of larch (Larix gmelinii Rupr.) in Da Xingan Mountain in Inner Mongolia was studied systematically with about 1000 temporary plots and computer software. The nature of site class and site index curve was discussed in view of general mathematical model of height growth. The height growth of dominant tree of four divisions of forest stands were studied and site index tables were constructed respectively. In order to unify the comparing standard and convenience for management in this region, site index table was constucted too. Based on discussing the action and accuracy of forest type, a series of site quality evaluation (forest type-site index class-site index) was suggested. This subject of study is supported by the National Natural Scientific Fund (No. 39270549).     

Endophytic fungi in Siberian larch (Larix sibirica) needles

Endophytic fungi were isolated from surface‐sterilized needles of the Siberian larch. Samples were collected from a native growing site of the Siberian larch in north‐western Russia and from sites in Russia, Finland and Iceland where the Siberian larch has been introduced. The isolated fungi were classified to operational taxonomic units (OTUs) using colony morphology and molecular characteristics. Needle colonization rates were 50–99% and in total 79 OTUs were found. There were five common OTUs, which covered 86.2% of all isolates. The most common OTU lacked from the youngest plantations in Finland (Solböle) and in Iceland (Kjarnaskógur). The highest similarity in regard to the frequency of OTUs occurred among the stands established long ago in Finland, and the UPGMA clustering using similarity indices separated the seven stands into two major groups.     

Self-thinning in prince Rupprecht's larch (Larix principis-rupprechtii Mayr) stands

Prince Rupprecht's larch (Larix principis-rupprechtii Mayr) stands growing at three different densities were investigated to determine characteristics of self-thinning. Tree density decreased with increasing stand age, and the higher density stand had higher mortality than the lower one. Mean stem volume increased with increasing stand age, and the higher density stand had higher relative growth rate of mean stem volume than the lower one. Mean stem volume (ν) increased with decreasing tree density (ρ), resulting in self-thinning line being expressed as ln ν=lnK-α ln ρ, whereK and α are coefficients. The slope of self-thinning line, —α, over the whole study period for all sites was similar with a mean value of —2.13. The ν-ρ trajectories before reaching the self-thinning slope of—3/2 could be described by Tadaki's model. The phase self-thinning line tended to decrease toward a slope of—3/2 with increasing stand age, which trends agreed with those of the published data of aPinus strobus stand andP. densiflora stands.     

华北落叶松与日本落叶松杂交试验

通过华北落叶松与日本落叶松的杂交,在22个控制授粉杂交组合中,球果长在1.74 cm~2.92 cm之间,球果径在0.98 cm~1.46 cm之间;在30个组合中,单粒球果质量介于0.52 g~1.63 g之间;球果种鳞数在23枚~47枚之间;种子连翅长在0.75 cm~1.07 cm之间;种子千粒重在2.6 g~5.0 g之间。     

Resilience of European larch (<Emphasis Type="Italic">Larix decidua</Emphasis> Mill.) forests to wildfires in the western Alps

European larch is a dominant species in the subalpine belt of the western Alps. Despite recent increases in wildfire activity in this region, fire ecology of European larch is poorly understood compared to other larch species around the world. This study aims to assess whether European larch forests are resilient to fires, and to find out the factors that drive such resilience. We assessed the recovery of larch forests along a gradient of fire severity (low, moderate, high) based on the abundance and dominance of post-fire larch regeneration. We established 200 plots distributed among burned larch forests in nine wildfires that occurred between 1973 and 2007 in the western Alps. We included variables regarding topography, climate, fire severity, fire legacies, ground cover, grazing intensity, and time since fire. To evaluate potential drivers of larch recruitment, we applied generalized linear mixed models (GLMM) and random forests (RF). Larch regeneration was much more abundant and dominant in the moderate- and high-severity fire classes than in the low-severity class. More than half of the plots in the moderate- and high-severity classes were classified as resilient, i.e., post-fire larch regeneration was enough to recover a larch stand. GLMM and RF produced complementary results: fire severity and legacies, such as snags, canopy cover and distance to seed source, were crucial factors explaining post-fire larch recruitment. This study shows that fire has a positive effect on larch regeneration, and we conclude that European larch forests are highly resilient to mixed-severity fires in the western Alps.     

Frost hardening in first-year eastern larch (Larix laricina) container seedlings

Eastern larch (Larix laricina [du Roi] K. Koch) container seedlings were tested to determine shoot frost hardiness development under short or long days and warm (15 to 25 °C) or cool (10/5 °C, day/night) temperatures, to aid in the development of greenhouse hardening strategies. Seedlings were sampled sequentially over time (25 seedlings per week) from a population of 1000 trees. Frost hardiness increased significantly after one week of fluctuated over the next 6 weeks, and increased thereafter through week 14. Seven weeks of warm, intermittent short days, followed by 6 weeks of cool, continuous short days, resulted in greater frost hardiness than 13 weeks of warm, intermittent short days. In contrast, seedlings exposed to 7 weeks of warm, intermittent short days, followed by six weeks of warm, long days were significantly less frost hardy. Stems with needles attached had lower Index of Injury than stems without needles.     

Production of hybrid seed in a seed orchard of two larch species,Larix sibirica and Larix decidua

The larch seed orchard studied is intended to produce interspecific hybrid seed between Larix sibirica and Larix decidua. Only the L. sibirica clone (half of the grafts) in the orchard was intended to act as the seed parent, and the six L. decidua clones are pollinators. The proportion of hybrid seed produced was determined using Mdh3 locus as a genetic marker. The mean percentage of hybrid seed produced by the grafts of L. decidua was 93, but that of the hybrid seed produced by L. sibirica was only 18. The results can be explained by differences in flowering abundance. The grafts of L. sibirica produced several times more pollen than those of L. decidua. Contrary to the original plans, L. decidua should be used as the seed parent and L. sibirica only as the pollen parent in the studied seed orchard.     

Shrinkage variation in Japanese larch (Larix kaempferi, [Lamb.]Carr.) progenies/provenances trials in Eastern Canada

Twelve-year-old Japanese larch (Larix kaempferi [Lamb.]Carr.) trees of 20 different progenies and/or provenances were sampled at one site in the Mauricie region of Quebec. Two standard samples were obtained at breast height and closer to the bark from each tree. Partial and total radial, tangential, and volumetric shrinkages, and tangential/radial (T/R) shrinkage ratios were assessed. All of these variables were significantly affected by the progeny/provenance. Drying defects are one of the main reasons for downgrading larch lumber; thus, T/R shrinkage ratio was considered for the selection of progenies/provenances for lumber production purposes. Lowest partial and total T/R shrinkage ratios were obtained with progenies/provenances 8964, 8904, 8962, 8957, 8907, 8927, 7283, and 7795. Among them, lowest partial and total tangential, radial, and volumetric shrinkages were found in progenies/provenances 8964, 8962, and 8907 as well. Other physico-chemical (mechanical properties, density, extractive content) and silvicultural (growth rate) attributes should also be taken into consideration for an adequate selection of progenies/provenances according to the specific final utilization.     

Effects of deforestation on microbial diversity in a Siberian larch(Larix sibirica) stand in Mongolia

For evaluating microbial community changes in a Siberian larch stand disturbed by forest fire or clearcutting,357 clones were randomly selected and sequenced using a culture-independent approach and 16S rRNA sequencing to characterize the bacterial composition and diversity from the different disturbed Siberian larch stands.Interestingly,the burned larch stand had an increase in the relative amounts of b-proteobacteria and Firmicutes and a decrease in Acidobacteria,while Gemmatimonadetes increased Verrucomicrobia decreased in the harvested larch stand.Microbial diversity and richness were higher in the undisturbed larch stand than the disturbed(burned or clear-cut)larch stands,and the influence of clear-cutting was more negative than that of the forest fire.This study indicates that evaluating the microbial diversity of undisturbed,burned,and clear-cutting Siberian larch stands provides information about the impact of forest disturbances on soil microbial communities,which may be helpful for understanding and evaluating soil health and devising reafforestation strategies for larch.     

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.     

兴安落叶松不同器官中的黄酮含量的动态变化

黄酮是植物体内一类重要的次生代谢产物,具有重要的生态作用和经济价值.但目前对兴安落叶松黄酮的研究很少.本论文研究了自然条件下兴安落叶松黄酮动态变化的特征,并对黄酮与温度和光照的相关关系进行初步探讨.对兴安落叶松不同器官黄酮含量的分析结果表明:(1)树皮,茎木质部,针叶和枝中黄酮含量的高低顺序为:树皮(7.78%) >针叶(2.79%)>枝条(1.72%)>茎木质部 (1.19%).(2)树皮,茎木质部,针叶和枝中黄酮含量具有明显的季节变化,但各器官(树皮,树叶,树枝,茎木质部)黄酮含量对温度的依赖性并不相同.就树皮而言,随着温度的升高,黄酮的含量与温度呈现较明显的正相关关系(R2=0.75).但其它器官黄酮含量对温度的依赖性不强;(3).随着季节的变化,黄酮含量的最高值出现在夏秋季节,含量是冬春季节的3-4倍.这种现象可能归因于夏季落叶松遭受的多种环境胁迫,例如紫外辐射,高温等可能促进了黄酮的积累.(4)不同高度和方向的针叶中,黄酮含量阳生叶比阴生叶多,上部叶比下部叶多,说明阳光辐射促进了黄酮的积累(R2=0.76).总而言之黄酮在落叶松抵御自然环境的胁迫中发挥了积极的作用,保护落叶松免受高温和强光的伤害,但是不同器官的黄酮可能发挥着不同的作用.     

Clonal variation of carbon content in wood of Larix kaempferi (Japanese larch)

Variations in carbon content in wood among 102 clones, selected from almost the entire natural distribution area, were investigated in Larix kaempferi. The average carbon content was 50.50%, 50.94%, and 50.80% in sapwood, heartwood, and whole wood, respectively. The difference in carbon content between clones was significant. The clonal repeatabilities were 0.46, 0.38, and 0.44 in heartwood, sapwood and whole wood, respectively. The coefficients of variation in the clonal mean carbon content were only 0.43%, 0.42%, and 0.41% in heartwood, sapwood, and whole wood, respectively. This small genetic variation and resulting small relative genetic gain of carbon content indicate that the genetic improvement of carbon content by selection has a small effect on the genetic improvement of carbon sequestration capacity by selection in L. kaempferi.     

Effects of high drying temperatures and restraint on twist of larch (Larix)

Abstract

During drying, timber changes its shape, mainly as a result of specific properties such as shrinkage anisotropy, radial differences in longitudinal shrinkage and spiral grain. The distortion, causing severe downgrading, can be reduced by restraining the timber and by using special drying schemes. The research described here is related to a project on the improvement of shape stability of Norway spruce. In the present part, different larch species from three stands were dried at high temperatures (80, 120 and 170°C). The effects of restraint during presteaming, drying and steaming on short-term twist reduction were investigated. The permanency of drying distortions was investigated in subsequent moisture cycling. Results showed a clear dependency of twist on the distance to pith. Restrained specimens sawn close to pith experienced reduced twist. This twist reduction was permanent during subsequent moisture variations. Drying temperature did not significantly influence twist and twist amplitude in moisture cycling.     

Effects of high drying temperatures and restraint on twist of larch (Larix)

During drying, timber changes its shape, mainly as a result of specific properties such as shrinkage anisotropy, radial differences in longitudinal shrinkage and spiral grain. The distortion, causing severe downgrading, can be reduced by restraining the timber and by using special drying schemes. The research described here is related to a project on the improvement of shape stability of Norway spruce. In the present part, different larch species from three stands were dried at high temperatures (80, 120 and 170°C). The effects of restraint during presteaming, drying and steaming on short-term twist reduction were investigated. The permanency of drying distortions was investigated in subsequent moisture cycling. Results showed a clear dependency of twist on the distance to pith. Restrained specimens sawn close to pith experienced reduced twist. This twist reduction was permanent during subsequent moisture variations. Drying temperature did not significantly influence twist and twist amplitude in moisture cycling.     

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     

落叶松(日本、长白)经营技术措施图的编制

利用落叶松（日本、长白）各年龄阶段与林分密度、直径、树高、优势高、林分蓄积、生物量的相关性，得到各项因子经验式，依据经验式，编制了经营技术措施图。