[Objective]In this study,the seasonal variation of carbon and nitrogen of microbial biomass in the Korean pine ( Pinus koraiensis) mixed forests at different altitudes was investigated. This study would provide a scientific basis for comprehending the role of soil microbial communities in carbon and nitrogen cycles.[Method]In this study,we set 5 sites along the altitude gradient of Changbai Mountain,starting from the highest distribution altitude of Korean pine and down in one hundred meters altitude intervals. At the same altitude,3 sample plots were set,and each of sample plot was 20 m × 20 m in size. A total of 10 sampling points in a size of 15 cm × 15 cm were randomly set up in an S type at each plot. We collected the samples in the plots on May 21,July 19,August 23,September 20 of 2013,respectively. We analyzed the dynamic variation and different mechanism of the soil microbial biomass carbon ( SMBC ) and microbial biomass nitrogen ( SMBN) in growing season. [Result]The SMBC,SMBN and the SMBC/SMBN had the same variation trend, that is,increased at first and then decreased with the increased altitude. The SMBC,SMBN and the SMBC/SMBN all reached to their maximum at 900 m (1287. 18 mg kg -1;224. 29 mg kg -1;9. 29). There were significant differences in the SMBC and SMBN among the elevations (P <0. 01). The microbial biomass carbon and nitrogen decreased with soil depth. The microbial biomass carbon in 0 -5 cm layers of the soil was 1. 15,1. 55,1. 29,2. 58,and 1. 32 times higher than those in the 5 -10 cm layers at the 5 elevations,respectively. The microbial biomass nitrogen was 1. 50,1. 23,1. 45,2. 64,and 1. 09 times higher than those in the 5 -10 cm layers,respectively. In the growing season ( from May to September) ,the SMBC and SMBN in the 0 -5 cm soil layers decreased at first,then increased and decreased again. The shape of the curve is inverted"N". However,the SMBC and SMBN first increased and then decreased and presented a unimodal shape of curve in the 5 -10 cm soil layer. The seasonal variation of microbial biomass carbon-nitrogen ratio among different altitudes and different soil layers were different. The microbial biomass carbon-nitrogen ratio was between 5 and 20 during the measuring periods except May. The results showed that fungi were more dominant than bacteria in microbial communities in the forests and the capability of soil humification was relative high. In August and September, the microbial biomass carbon-nitrogen ratios were highest,indicating that the capacity of carbon sequestration of soil was strongest. The content of soil available N,soil organic carbon,available P,available K and pH,and soil moisture was obviously different among the 5 elevations. Generally,all indexes increased gradually from 700 m to 900 m and reached to the maximum,and then decreased with the increased elevation. Soil microbial biomass carbon had extremely significant positive correlations with soil organic carbon,soil moisture,available N,available P and available K at different altitudes ( P<0 . 01 ) ,and had significant positive correlation with pH at different altitudes ( P <0 . 05 ) . Soil microbial biomass nitrogen had extremely significant positive correlations with pH at different altitudes ( P <0 . 01 ) ,and had significant positive correlations with soil organic carbon,soil moisture,soil available N,available P and available K at different altitudes (P < 0. 05). [Conclusion]The elevation gradient,soil depth and seasonal variation could impact on soil microbial biomass carbon and nitrogen content significantly. The physical and chemical properties of soil,and the difference of forest types were major factors which led to the changes of soil microbial biomass.

Patterns of precipitation have changed as a result of climate change and will potentially keep changing in the future. Therefore, it is critical to understand how ecosystem processes will respond to the variation of precipitation. However, compared to aboveground processes, the effects of precipitation change on soil microorganisms remain poorly understood. Changbai Mountain is an ideal area to study the responses of temperate forests to the variations in precipitation. In this study, we conducted a manipulation experiment to simulation variation of precipitation in the virgin, broad-leaved Korean pine mixed forest in Changbai Mountain. Plots were designed to increase precipitation by 30 % [increased (+)] or decrease precipitation by 30 % [decreased (−)]. We analyzed differences in the diversity of the bacterial community in surface bulk soils (0–5 and 5–10 cm) and rhizosphere soils between precipitation treatments, including control. Bacteria were identified using the high-throughput 454 sequencing method. We obtained a total 271,496 optimized sequences, with a mean value of 33,242 (±1,412.39) sequences for each soil sample. Being the same among the sample plots with different precipitation levels, the dominant bacterial communities were Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, and Chloroflexi. Bacterial diversity and abundance declined with increasing soil depth. In the bulk soil of 0–5 cm, the bacterial diversity and abundance was the highest in the control plots and the lowest in plots with reduced precipitation. However, in the soil of 5–10 cm, the diversity and abundance of bacteria was the highest in the plots of increased precipitation and the lowest in the control plots. Bacterial diversity and abundance in rhizosphere soils decreased with increased precipitation. This result implies that variation in precipitation did not change the composition of the dominant bacterial communities but affected bacterial abundance and the response patterns of the dominant communities to variation in precipitation.

An experiment was conducted to investigate the physiological responses of photosystem II in leaves of three arbors un-der Cd stress by the fast fluorescence transients technology including Fraxinus mandshurica Rupr., Phellodendron amu-rense Rupr.and Juglans mandshurica Maxim.in northeast China.With the rise ofCd content,the fluorescence parameters of Fv /Fm, Fv /Fo , Sm , Ψo , φPo , φEo and ETo/RC decrease gradually, while the parameters of VJ , Mo ,φ Do , ABS/RC and DIo /RC increased gradually.The electron transports in the receptor side of PSⅡ are impeded, and the QB site and PQ pool capacity in the receptor side of PSⅡelectron transport chain were reduced.The ability of leaves to capture light energy decreases, the proportion of heat dissipation increases, and the proportion of electron transports after Q-A decreases, so the photosynthetic performance in leaves of three kinds of arborsis reduced.The trend of TRo /RC increases at first then de-creased, so the energy dissipation efficiency of the rest of the active reaction center increases when Cd stress level is low. However, when the Cd content exceeds the limit, this mechanism, passive protection through the reaction center inactiva-tion, gradually loses its function.Different tree types have different adaptive mechanism and tolerance to Cd stress.The change trend of chlorophyll fluorescence parameters in leaves of Phellodendron amurense Rupr.and Juglans mandshurica Maxim.are similar with small change.Their photosystem II reaction center is with higher tolerance to Cd stress.The change of chlorophyll fluorescence parameters in leaves of Fraxinus mandshurica Rupr.under low Cd press is not obvious. However, when Cd is more than 0.8 mmol? L-1 , each index changes severely, and the leave photoinhibition occurs. Therefore, the photosystem II reaction center in leaves of Fraxinus mandshurica Rupr.has the weakest tolerance to Cd stress.

Broad-leaved Korean pine mixed forest is a kind of zonal climax vegetation with ecological significance in Northeast China, whereas Changbai Mountain is an ideal area to study the effects of precipitation variation on temperate forest. Taking the virgin broad-leaved Korean pine mixed forest in Changbai Mountain as the object, and based on T-RFLP method, this paper analyzed the spatial heterogeneity of fungal diversity in 0-5 cm and 5-10 cm soil layers and in rhizosphere soil at three different precipitation plots (30% increase, 30% decrease, and the control). Both the increase and the decrease of precipitation increased the diversity of soil fungi, but the dominant population changed. In 0-5 cm and 5-10 cm soil layers, the T-RFs over 500 bp increased with precipitation; in rhizosphere soil, the T-RFs responded to precipitation variation were 380 bp, 455 bp, and 487 bp, and the response mode was more complicated than that in surface soil layers. The results of CCA showed that the fungal community composition was significantly affected by soil pH, organic carbon, total nitrogen, and organic phosphorus.

The Pinus koraiensis genomic DNA in two different regions and the genomic DNA of three sonko plants in Northeast Forestry University were extracted using ITS molecular markers to study genetic diversity.After the sequencing and comparison in the GenBank,the phylogenetic tree were constructed by sequence maximum parsimony(Maximum Parsimony,MP),minimum evolution method(Minimum Evolution,ML) and the o-phase methods(Neighbor Joining,NJ),respectively.It turned out that Pinus koraiensis,Pinus sylvestnis and Pinus tabulaeformis,havig quite similar sequences were divided into a group,while Pseudotsuga menziesii,Abies alba,Picea mariana and Pseudolarix amabilis were divided into a group,and Larix olgensis was divided into another group.By comparing the results with previous studies,the possibility of ITS molecular markers for Phylogenetic Analysis of Pinaceae was explored.

Anthocyanin contents and distribution of photosynthetic energy in leaves of Prunus cerasifera Ehrhart f.atropurprea Jacq seedlings under full illumination or different shading(shading 25%,shading 50% and shading 75%) were investigated.The results indicate the anthocyanin contents in leaves of the seedlings were decreased under the on shading conditions,but the chlorophyll contents were increased;the initial fluorescence(Fo),maximum fluorescence(Fm) and non-photochemical quenching coefficient(qN) increased in leaves of the seedlings with the increase of the enhanced shading,while actual photosynthetic Ⅱ efficiency(Fv/Fm),photochemical quenching(qP) and electron transport rate(RETR) decreased,it is concluded that the tested seedlings were the intolerant tree species,and should be planted under natural light condition;the leaf photoresponse curve of ФPS Ⅱ and ETR showed that the ФPS Ⅱ decreased with the increase of light intensity,but RETR increased.Meanwhile,the proportion of the quantum yield of PS Ⅱ photochemistry(ФPS Ⅱ) had an obvious negative correlation with the shading degree,but the quantum yield of xanthophyll-regulated thermal energy dissipation(ФNPQ) and the quantum yield of thermal dissipation associated with the presence of non-functional PS Ⅱ(ФNF) increased with the increase of shading degree,and the non-functional PS Ⅱ significantly increased as shading degree reached 75%.The shading measures regulated the photosynthetic capacity by the way of influencing leaves photosynthetic pigment and anthocyanin contents and distribution of photosynthetic energy and then improved the adaptability of long-term weak light in Prunus cerasifera Ehrhart f.atropurprea Jacq seedlings.