冠层光谱组成对红松和蒙古栎幼苗生长和光合荧光特性的影响

本研究选择长白山阔叶红松林优势树种红松和蒙古栎幼苗为对象,研究其植株形态、生长和光合荧光特性对5种光谱处理的响应。结果表明: 红松与蒙古栎的形态结构与生长主要受蓝光与紫外B区(UV-B)辐射调控。滤除蓝光后两种幼苗的植株叶面积比和相对生长速率均显著降低,而滤除UV-B辐射显著增加了红松的叶面积比和相对生长速率,分别上升了41.8%和47.7%,降低了蒙古栎的株高、总叶面积和生物量积累。滤除UV-B辐射显著降低了2种幼苗的光合荧光调节能力,红松的下降幅度较低,其非调节性耗散的量子产量(Φ_NO)升高31.6%,反映光合荧光调节能力的Φ_NPQ/Φ_NO值降低37.5%。2个树种幼苗具有明显不同的光谱适应策略,蒙古栎幼苗偏向于利用光谱变化调整自身形态增加光捕获能力,而红松更注重调整光合荧光特征以提高碳同化效率。     

Co-invading ectomycorrhizal fungal succession in pine-invaded mountain grasslands

Ectomycorrhizal (EM) fungal communities that associate with invading pines (Pinus spp.) are expected to be poor in species diversity. However, long-term successional trajectories and the persistence of dispersal limitations of EM fungi in the exotic range are not well understood. We sampled the roots and surrounding soil of Pinus elliottii and P. taeda trees invading mountain grasslands of Argentina. We also sampled the EM fungal spore bank in grassland soil near (∼150 m) and far (∼850 m) from the original pine plantations. We found 86 different co-invasive EM fungal OTUs. Differential dispersal capacities among EM fungi were detected in the spore bank of grassland soil, but not under mature pines. After thirty years of invasion, the age, but not the degree of spatial isolation of pine individuals affected the EM fungal composition. We showed how EM fungal succession occurs during pine invasions, which may have clear consequences for ecosystem functioning of co-invaded sites.     

Gopher Tortoise Response to Habitat Management by Prescribed Burning

ABSTRACT As quality of forested habitat declines from altered fire regimes, gopher tortoises (Gopherus polyphemus) often move into ruderal areas to the detriment of the animal and land manager. We evaluated effects of a dormant-and-growing-season prescribed fire on habitat and gopher tortoise use of degraded longleaf pine (Pinus palustris) forests surrounding military training areas. We burned 4 of 8 sites in winter 2001–2002 and again in April 2003. Changes in vegetation measured during 2001–2004 indicated that burn treatments did not increase herbaceous vegetation. Similarly, movement patterns, burrow usage, and home range of tortoises radiotracked from 2002–2004 did not differ between treatments. Woody cover initially was reduced in the forests postburn, and we found more new burrows in burned forest sites. Once shrub cover was reduced, tortoises started using forested habitat that had become overgrown. However, shrub reduction may be temporary, as woody stem densities increased postburn. Thus, the one-time use of fire to manage tortoise habitat may not rapidly restore the open canopy, sparse woody midstory, and abundant herbaceous vegetation that this species requires. Repeated prescribed fires or additional management techniques may be needed for complete restoration.     

Habitat Use of Sympatric Rattlesnake Species Within the Gulf Coastal Plain

Abstract: The eastern diamondback rattlesnake (Crotalus adamanteus) and timber rattlesnake (Crotalus horridus) are sympatric throughout most of southern Georgia, USA. We used rattlesnake sightings to quantify and compare habitat use by these 2 species in the Gulf Coastal Plain. At the largest scale examined, univariate statistics and logistic regression models indicated that eastern diamondback rattlesnakes were associated with roads but not with any of the specific habitat types we examined. In contrast, timber rattlesnakes were closely associated with hardwood habitat and riverine systems but not with roads and edges. To effectively conserve and manage both species in the Southeast, a habitat matrix of large intact patches of both hardwood and pine (Pinus spp.) forest may be necessary.     

Effect of laser pretreatment on germination and membrane lipid peroxidation of Chinese pine seeds under drought stress

The germination of laser-irradiated Chinese pine seeds was carried out under drought stress.The activities of superoxide dismutase (SOD) and peroxidase (POD),and the content of malondialdehyde (MDA) were determined.Results showed notably increased germination percentage,root length,vitality index and fresh weight.The SOD and POD protective enzyme system activity of the Chinese pine seedlings obviously rose.It can be concluded that the germination and juvenile resistance of Chinese pine seeds under drought stress are enhanced after laser processing.     

Spatial Distibution of Mountain Pine Beetle Outbreaks in Relation to Climate and Stand Characteristics:A Dendroecological Analysis

Principal components analysis, followed by K-means cluster analysis, was used to detect variations in the timing and magnitude of Pinus contorta Dougl. ex Loud. growth releases attributed to mountain pine beetle outbreaks in 31 stands of central British Columbia. Four major growth release patterns were identified from 1970 to 2000.Variations in the timing of growth releases among clustered stands corresponded well to aerial survey data indicating the timing of beetle outbreaks in the study area. Redundancy analysis was used to determine how variations in the timing and magnitude of growth releases attributed to beetle outbreaks changed with variations in climate or stand conditions over the study area. The first RDA axis, which accounted for 39% of the variations in growth patterns among stands, was significantly (P＜0.05) correlated with gradients in the percentage of pine in stands killed by mountain pine beetle, summer aridity, variation in summer precipitation, distance from initial infestation site, average pine age, and maximum August temperatures. The second RDA axis explained 6% of the variations and was significantly correlated with gradients in the beetle climate suitability index, extreme cold month temperatures, and site index. Comparisons of growth release patterns with aerial survey data and redundancy analyses indicated that dendrochronological techniques are useful for identifying mountain pine beetle outbreaks in central British Columbia, particularly among stands that had a density high enough to produce a growth release signal. Provided future studies account for interannual weather fluctuations, identification of growth increases due to stand thinning caused by beetle outbreaks will be useful for reconstructing the history of beetle outbreaks over much longer time periods.     

Effect of laser pretreatment on germination and membrane lipid peroxidation of Chinese pine seeds under drought stress

The germination of laser-irradiated Chinese pine seeds was carried out under drought stress. The activities of superoxide dismutase (SOD) and peroxidase (POD), and the content of malondialdehyde (MDA) were determined. Results showed notably increased germination percentage, root length, vitality index and fresh weight. The SOD and POD protective enzyme system activity of the Chinese pine seedlings obviously rose. It can be concluded that the germination and juvenile resistance of Chinese pine seeds under drought stress are enhanced after laser processing. Translated from Journal of Shaanxi Normal University (Natural Science Edition), 2006, 34(2): 40–43 [译自: 陕西师范大学学报 (自然科学版)]     

植被对土壤热扩散特征的影响——以长白山阔叶红松林为例

土壤温度变化及热传递是影响土壤和大气水热交换的重要过程,而植被是决定这种变化和影响的环境因子之一。通过比较林地与裸地土壤热特性的差异分析植被对土壤热扩散的影响。研究内容包括观测2007年长白山阔叶红松林区不同深度的土壤温度以及同期土壤含水量和叶面积指数。分析不同深度林地与裸地土壤温度年周期特征,根据热传导方程估算各土壤层温度的阻尼深度和热扩散率,并探讨引起林地与裸地土壤热特性差异的可能原因。结果表明,林地与裸地的土壤温度有明显的时空变化规律。随着深度的增加,土壤温度年周期的振幅逐渐减小、相位逐渐增大、平均值逐渐升高。林地土壤温度年平均值低于裸地,表层年平均温度相差约0.8℃;地表以下相同深度处,林地土壤温度年周期的振幅约低于裸地2.6—2.9℃,相位约小于裸地0.2—0.24 rad(角速度),这表明林地土壤温度极大值和极小值出现的时间比裸地滞后约11—14d。土壤温度阻尼深度和热扩散率随深度的增加而逐渐增大,而在1.6—3.2m则略有降低的趋势。林地与裸地土壤温度和热特性的时空特征和差异可能与土壤含水量和叶面积指数有关。     

择伐对阔叶红松林资源可持续利用的影响

科学评估目前的择伐方式对森林结构与功能的影响对区域森林资源的可持续利用具有重要意义。以择伐过的阔叶红松林为研究对象,并以原始林为对照,分析了择伐对物种组成、林分结构以及对木材生产的影响。结果表明,低强度择伐(≤20%)对物种组成和蓄积结构均没有显著影响,而高强度择伐则显著改变了物种组成和蓄积结构。择伐后林分蓄积量均显著小于原始林,不同择伐强度间没有显著差异。择伐显著影响了用材树种的数量和质量,导致择伐后样地中用材树种的株数和蓄积量均显著减少,严重影响了林分的木材持续生产能力。因此,从阔叶红松林木材可持续利用角度来看,需要重新思考红松不作为采伐树种的用材林经营技术模式。