Stem Radius Variation in Response to Hydro-Thermal Factors in Larch

The response mechanism of the tree stem radius variation to hydro-thermal factors is complex and diverse. The changes of TWD (tree water deficit-induced stem shrinkage) and GRO (growth-induced irreversible stem expansion) are respectively driven by different factors, so that their responses to hydro-thermal factors are different. The stem radius variation and its matching hydro-thermal factors experimental data was measured and determined at 0.5 h time scale in larch (Larix gmelini Rupr.) forest of the Daxing’anling region of the most northeastern part of China. Response characteristics of the stem radius variation to hydro-thermal factors have been found by analyzing the data under different time windows. The stem radius variation mainly responded to the changes in precipitation and relative humidity. The main driving factors for TWD were sap flow density and solar radiation. The response of GRO to hydro-thermal factors was complex, varied a lot under different time scales. During the analysis of the response of tree radial growth, changes of the stem radius can be divided to TWD and GRO to implement separate studies on their responses to hydro-thermal factors. In this way, it becomes easier to discover the response of TWD under drought stress and the responding mechanism of GRO to hydro-thermal factors.

Ophiostoma olgensis, a new species associated with Larix spp. and Ips subelongatus in northern China

A new ophiostomatoid species, Ophiostoma olgensis sp. nov., isolated from Larix olgensis and Larix gmelini infested by Ips subelongatus in northern China, is described and illustrated. The fungus produces abundant short-necked perithecia in phloem as well as on artificial substrates. The short-necked perithecia are characteristic of the Ophiostoma minus complex and more specifically, of Ophiostoma kryptum, isolated from European larch. However, O. olgensis can be distinguished from O. kryptum on the basis of combined morphological traits and phylogenetic data from ITS, partial β-tubulin, EF-1α, and actin gene region analyses of single-spore isolates. The most obvious morphological differences between both species are the asexual forms and the conidial morphology. The pathogenicity of O. olgensis and O. kryptum was evaluated in situ on local mature Larix spp. by stem inoculation. All inoculations of O. olgensis and O. kryptum resulted in serious lesions on the inner bark, and thus the new species is considered to be a pathogen on Larix spp. (L. olgensis, L. gmelini, L. principis-rupprechtii and L. kaempferi ).

Method on Distinguishing Permafrost and Talik Regions in the Great Khingan Mountains by Analyzing the Characteristics of Specific Plants

In the fieldwork in the Great Khingan Mountains, it is practical and easy to distinguish permafrost region or talik region by analyzing the characteristics of the plants growing on them. Generally speaking, permafrost there tends to degenerate from south to north, but there are some individual places where remind original ecology of permafrost. After permafrost degenerate into the talik region, the condition of plant growth has changed. We can distinguish permafrost and talik region by the difference of plants growing status there. Some common species that specifically grow in permafrost or talik region have also been listed and introduced in this paper. Specifically, plants growing in permafrost region include larix gmelini, birch, vaccinium uliginosum, ledum palustre, vaccinium vitis-idaea, bilberry, pinus sylvestnis var. mongolica litv, low birch thicket, adina racemosa and so on. Meanwhile the plants live in talik region include peridium aquilinum, xylosma racemosum, daylily, milkvetch. The list of plants can be used to distinguish permafrost region and talik in the field. It is crucial for constructions to recognize if the construction area is permafrost or talik region. The change of talik has its two sides to constructions. On the upside, it can increase groundwater storage, and we can regard the future projects as thawing projects. On the downside, existing projects would arise thawing settlement.