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.

阿勒泰柯姆地区树轮宽度年表与灰度年表的建立

通过对比柯姆采点的8个标准化宽度和灰度树轮年表的多项特征参数,表明宽度年表在多项年表特征参数上均大大高于灰度年表。通过相关普查得出,标准化晚材灰度年表与当年7月至8月的降水量的相关系数最高,为0.426,显著性水平达0.001,而标准化早材灰度年表与上年12月至当年2月的月平均温度的相关系数最高,为0.362,显著性水平达0.02,且二者的相关具有明确的树木生理学意义。在0.10的显著性水平上,3个宽度年表均具有14a和3.4a左右的变化准周期,而5个灰度年表均存在2.2～2.4a的变化准周期。

树轮δ^(13)C记录的阿勒泰地区近160a夏季气温变化

利用阿尔泰山南坡东中西部3个采点的西伯利亚落叶松树轮样本,建立了3个树轮δ13C序列,结合阿勒泰地区6个气象站的气象资料,分析了阿尔泰山树轮δ13C对气候的响应,并重建了阿勒泰地区过去160 a夏季气温变化。研究表明,位于阿勒泰科勒迭难布拉克森林上线的树轮δ13C序列对阿勒泰地区夏季气温响应较好,与7月平均气温明显正相关,相关系数达到0.608(p<0.000 1);利用树轮δ13C可较好的重建阿勒泰地区过去160 a的夏季气温;近160年来,阿勒泰地区夏季温度19世纪末有缓慢上升趋势,20世纪初,夏季温度整体偏高,40年代以后,夏季温度明显下降,直到60年代,60年代成为近160 a夏季温度最低的时期,60年代至今,阿尔泰山南坡夏季气温经历了160 a来最长和最为强烈的升温时期。虽然有气象观测记录以来,阿勒泰地区夏季气温升温明显,但是20世纪初夏季温度要高于近30 a平均气温;重建的阿勒泰地区夏季温度序列不仅能代表整个阿尔泰山夏季温度变化,也能够较好的代表包括北疆、中亚部分地区和俄罗斯南部大范围的夏季温度变化。