Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations

Soil pH declined from 5.9 to 5.0 in 8 years beneath plantations of Eucalyptus saligna (Sm.) in Hawaii. In stands of Albizia falcataria, (L.) Fosberg, the soil pH change was more dramatic, declining from 5.9 to 4.6. We measured several components of soil acidity beneath four mixtures of the two tree species to gain insight on the processes responsible for the decline in soil pH. These components were studied using an empirical method of comparing acid quantity, degree of neutralization (depletion of base cations), and acid strength. The decline in soil pH differed between species as a result of differences in the degree of neutralization of the soil exchange complex; the larger decrease in soil pH under Albizia was produced by greater acidification of the exchange complex. Empirical titration curves suggested that differences in acid strength moderated the divergence in soil pH beneath the species. Had the acids accumulating in the soil under Albizia been as strong as those in the Eucalyptus soil, the difference in soil pH would have been greater. Though the two species had contrasting effects on soil pH, the differences in degree of neutralization, responsible for the pH decline, were small compared with differences in the amount of cations stored in tree biomass. Continued supply of nutrient cations (from weathering or fertilization) will ultimately control both the extent of soil pH decline and the level of productivity sustained by the forest.     

Decomposition of tree root litter in a climatic transect of coniferous forests in northern Europe: A synthesis

The purpose of this study was to understand the variation in root litter mass‐loss rates in a climatic transect across a large region ranging from the Arctic Circle (66°N) in Scandinavia to Berlin (52°N) in north‐east Germany, dominated by coniferous monocultural forests. To investigate the combined influence of litter quality and climate, data were used from 37 sites and plots at which root litters of three coniferous species (Pinus sylvestris, Pinus contorta and Picea abies) had been incubated. In spite of the considerable climatic differences among sites, there were no strong relationships between any climatic variable and the lst‐yr mass loss (range 17.0–40.9%). For the lst‐yr mass loss, the average annual temperature was the most rate‐regulating factor for all litter combined, with a value for R ² _adj of 0.186. Substrate quality also had an influence. Thus, for the whole region lignin concentration was significant, with a value for R ² _adj of 0.142. For the separated groups of pine and spruce stands the value for r ² increased but the factor average temperature still dominated and for pine the R ² _adj reached a value of 0.346. Over the region N concentration in the fresh pine root litter was significant (R² _adj = 0.232). For the root litter of P. abies the average temperature in July was the strongest rate‐regulating climatic factor, with a value for R ² _adj of 0.381. A combination of temperature in July and the initial P concentration in the litter gave an R ² _adj value of 0.713 for P. abies litter, thus explaining about 71% of the variation.     

松根颈树皮象生物学特性和防治方法的研究

松根颈树皮象广泛分布在云南省,幼虫主要为害云南松、思茅松和华山松中幼林。幼虫钻蛀松树根颈的形成层和韧皮部,当松树受害轻时针叶变为黄褐色,受害严重时致死。松根颈树皮象二年完成一代,以成虫和5—7龄幼虫越冬。成虫在8月中开始羽化,两次越冬并生活达2年。整个成虫期都有交尾活动,但在羽化的当年不产卵。幼虫期10—14个月,主要为7—8龄,7月下旬开始化蛹,蛹期约27天。由于虫口密度较低,老熟幼虫做蛹室至成虫羽化要经过两个多月,虫期整齐,很容易用手清除。从8月下旬到9月中是最好的防治时期。     

Pseudomonas associated with Bursaphelenchus xylophilus,its insect vector and the host tree: A role in pine wilt disease?

In this study, we characterized the diversity of Pseudomonas associated with Bursaphelenchus xylophilus, its insect vector (Monochamus galloprovincialis) and its host (Pinus pinaster), by a culture‐independent approach using rpoD clone libraries. Clone libraries of Pseudomonas rpoD were obtained from B. xylophilus, M. galloprovincialis and infected P. pinaster. Most M. galloprovincialis and B. xylophilus sequences grouped together in the P. fluorescens group. Genes related to xenobiotics degradation and phenylacetate synthesis were present in the genomes of the type strains closely related to sequences retrieved from the nematode libraries. Results demonstrated that the nematode, during its life stages inside the tree, maintains a diverse Pseudomonas community that is closely related to the one associated with the insect vector. These bacteria might contribute to degradation of xenobiotics and tree weakening during the nematode tree infection.     

松阳县古松树的松材线虫病现状调查与分析

古松树是历史的见证,是文化的承载,其保护工作具有重要意义,但因松材线虫的传播侵染,其生存状况不容乐观。本研究以松阳古松树为对象,基于分子检测技术,对其松材线虫病现状进行了调查与分析。结果表明,有12个乡镇近60%的古松树均已感病,疫情较为严重,需及时开展抗病保护工作。     

新疆博尔塔拉蒙古族草原那达慕大会表层文化变迁探析

草原那达慕大会是蒙古族文化的重要组成部分,新疆博尔塔拉蒙古自治州举行的草原那达慕大会具有独特的地域特点。随着时代的发展,关于新疆博尔塔拉蒙古自治州草原那达慕大会举办地点、举办内容、功能和组织形式等内容发生了很大的变化。其表层文化变迁具有与时俱进的特点。     

防治松萎蔫病的新策略及林间防效初报

在松萎蔫病是由松材线虫与其携带的致病细菌诱导的一种复合侵染病害的新学说的指导下,根据松萎蔫病在疫区病树呈聚集分布,提出了防治松萎蔫病的新策略,即利用我们研究开发防治松萎蔫病的新药剂α-三噻吩与杀细菌剂恶喹酸对在以病死树中心周围半径50 m的范围内所有寄主树进行注干处理。经过2010—2011年在面积近20 hm2的处理黑松林地的防治试验,至2011年12月已经取得了良好的防效。处理林地中没有再发生病死树,对照区内却有24株病死树。防治仍在继续,新结果将继续报道。     

白河林业局红松分布数量预估模型1）

根据长白山地区白河林业局的772块固定标准地调查数据,以及最小二乘法（ OLS）,建立逻辑斯蒂（Logistic）模型来预估该局现时状态有林地的红松分布概率,并采用泊松（Poisson）和负二项分布（Negative binomi-al,NB）模型预估该局现时状态有林地红松的分布数量,并对模型进行了拟合效果评价及独立性检验。结果表明, Logistic模型与数据的拟合效果很好,独立性检验中预测精度也在可接受的范围内,可以利用Logistic模型来预估该局有林地红松的分布概率。与Poisson模型相比,负二项分布模型能够解决因变量的不均匀分布（即过度散布）的问题,因此能够更好地拟合数据。但在独立性检验中,Poisson模型和NB模型的预测精度接近,且都在可接受的范围内,两个模型均可以用来预估该局有林地红松的分布数量。