[Seasonal dynamics of energy and nutrients of Pinus koraiensis seedlings in different successional stages of broadleaved Korean pine forest in Changbai Mountain, China.] / é•¿ç™½å±±é˜”å¶çº¢æ¾æž—ä¸åŒæ¼”æ›¿é˜¶æ®µæž—ä¸‹çº¢æ¾å¹¼è‹—èƒ½é‡ä¸Žå »åˆ†å­£èŠ‚åŠ¨æ€.

We examined the seasonal variations of growth and nutrient accumulation of two-year-old Korean pine (Pinus koraiensis) seedlings in the primary broadleaved Korean pine forest (primary forest) and poplar birch forest (secondary forest) in Changbai Mountain. The seasonal changes of photosynthetically active radiation (PAR), seedling biomass, nonstructural carbohydrate (NSC), total nitrogen (N), and total phosphorus (P) were measured in both forests. The effects of understory light and its seasonal variations in both forests on the growth and nutrient accumulation of understory Korean pine seedlings were also explored. The results showed that the seasonal variations of monthly cumulative PAR under both forests showed a double-peak pattern. In summer, light conditions under the two forests were poor because of the closed canopy. In spring and autumn, light conditions were better due to the deciduous characteristics of canopy broadleaved trees, with light conditions under the secondary forest being obviously better than that of the primary forest. The seasonal variations of biomass, NSC, total N and total P concentrations of Korean pine seedlings in the primary and secondary forests were basically consistent with that of understory light. All those variables increased significantly in spring and autumn, and decreased in summer. In spring, starch concentration increased. In summer, starch and soluble sugar concentrations decreased gradually, and touched bottom in August. In autumn, soluble sugar concentration increased significantly. The biomass and NSC concentration of seedlings under secondary forest were significantly higher than those under primary forest in spring and autumn, but without difference in summer. Therefore, the diffe-rence of understory light conditions in spring and autumn between the two forests might be the key factor driving nutrient accumulation, growth and regeneration of Korean pine seedlings.

[Response of radial growth of Pinus sylvestriformis and Picea jezoensis to climate warming in the ecotone of Changbai Mountain, Northeast China]. / 长白山群落交错带长白松和鱼鳞云杉径向生长对气候变暖的响应.

Changbai Mountain is a typical distribution area of temperate coniferous and broad-leaved mixed forests, with significant influence of global climate change. In order to understand the responses of forest ecosystem to climate change, we examined the responses of dominant arbor species in the community ecotone of broad-leaved Korean pine forest and spruce-fir forest (also known as dark coniferous forest), Pinus sylvestriformis and Picea jezoensis. The standard chronologies were established by obtaining tree ring width data in order to identity the key climatic factors that confine the radial growth of both species. The responses of P. sylvestriformis and P. jezoensis to climate factors were different.P. sylvestriformis was more sensitive than P. jezoensis, indicating that P. sylvestriformis was more suitable for dendroclimatological analysis. The radial growth of P. sylvestriformis was consistent with the increases of mean temperature, while the radial growth of P. jezoensis showed a "divergence problem" which decreased with the increases of mean temperature. The radial growth of P. sylvestriformis was mainly limited by temperature, especially the mean temperature in last July and August and current September. However, there was a negative correlation between standard chronologies of P. jezoensis and mean temperature in most months, which was limited by both temperature and precipitation. The correlation between radial growth of both species and climate factors after sudden temperature rise, was weaker than that before sudden temperature rise. The correlation between radial growth and climate factors changed from positive to negative in some months. Current temperature rise might not exceed the critical threshold of the radial growth of P. sylvestriformis, which could promote the radial growth. In addition, the wavelet analysis showed that the radial growth of trees in this area might be affected by large-scale coupling effects of atmospheric-ocean-land changes. In conclusion, climate warming was beneficial to the radial growth of P. sylvestriformis, while drought stress caused by warming was the main factor limiting the radial growth of P. jezoensis. If the global temperature continues to increase in the future, it will have an adverse impact on P. jezoensis. The results would help improve our understanding of the responses of radial growth of P. sylvestriformis and P. jezoensis to future climate change, and provide some basic data for climate reconstruction using both species.

Tailoring bacterial cellulose structure through CRISPR interference-mediated downregulation of galU in Komagataeibacter xylinus CGMCC 2955.

Diverse applications of bacterial cellulose (BC) have different requirements in terms of its structural characteristics. culturing Komagataeibacter xylinus CGMCC 2955, BC structure changes with alterations in oxygen tension. Here, the K. xylinus CGMCC 2955 transcriptome was analyzed under different oxygen tensions. Transcriptome and genome analysis indicated that BC structure is related to the rate of BC synthesis and cell growth, and galU is an essential gene that controls the carbon metabolic flux between the BC synthesis pathway and the pentose phosphate (PP) pathway. The CRISPR interference (CRISPRi) system was utilized in K. xylinus CGMCC 2955 to control the expression levels of galU. By overexpressing galU and interfering with different sites of galU sequences using CRISPRi, we obtained strains with varying expression levels of galU (3.20-3014.84%). By testing the characteristics of BC, we found that the porosity of BC (range: 62.99-90.66%) was negative with galU expression levels. However, the crystallinity of BC (range: 56.25-85.99%) was positive with galU expression levels; galU expression levels in engineered strains were lower than those in the control strains. Herein, we propose a new method for regulating the structure of BC to provide a theoretical basis for its application in different fields.

[Nectar productivity of Tilia amurensis in a broadleaved-conifer mixed forest in Changbai Mountains, China]. / 长白山针阔混交林紫椴的泌蜜量.

Tilia amurensis is one of (co-)dominant species in the broadleaved-conifer mixed forest in Northeast China, with high commercial and nectariferous values. We estimated the quantity of nectar secretion from individual trees to population or stand levels based on observation and statistical analysis. An equation for individual-tree nectar secretion was established, which was used to estimate nectar quantity at the stand level. We analyzed the relationships between nectar secretion and basal area or stem volume. The booming time for single flower was in average 6-8 days, with a nectar secretion period of about five days. The quantity for the entire period was estimated at 8.58 mg per flower. Sugar contents in the nectar, average 37.7%, showed diurnal variations, being high in the mid-noon and low in the early morning and late afternoon. The average diameter (DBH) of the species was approximately 40 cm, which was estimated to possess as much as 18×104 single flowers and 1.56 kg (or pure sugar 0.588 kg) of nectar. At the stand level, the nectar production potential was 79-147 kg (or 0.0686-0.1285 m3, pure sugar 29.78-55.42 kg) per hectare. There was a close correlation between nectar quantity and basal area or timber volume at both individual and stand levels, which could be used to estimate the nectar quantity for macro-scale forest area based on inventory data.

Long-term monitoring of tree population dynamics of broad-leaved Korean pine forest in Changbai Mountains, China.

Based on four investigations of a one-hectare permanent plot in Changbai Mountains from 1981 to 2016, the changes of tree species composition and structure of broad-leaved Korean pine forest were examined, and diameter distribution, spatial pattern distribution, and quantitative changes of each tree species were analyzed. The results showed that there were little changes in tree species composition and an overall decreasing trend in total density in 35 years. Both basal area and stand volume were 43-45 m2·hm-2 and 474-496 m3·hm-2, respectively. Pinus koraiensis was the most dominant species, whose basal area and volume accounted for 57.8%-59.7% and 62.5%-65.4% of the total in the community, respectively. All dominant species showed random distribution and changed little in 35 years. The DBH distribution of P. koraiensis was in a near-to-normal form. Total species showed a reversed "J" shape. The number of dead trees was the largest in small DBH class (10-26 cm) with the percentage of 30%. The percentage of dead trees was the largest in intermediate class (30-50 cm) with 30%-50%. Except Acer mono, all species in the tree layer showed little recruitment, with mortality rate being higher than recruiting rate. Specially, P. koraiensis had no saplings or recruitment, and the population was in decline. The regeneration of dominant species such as P. koraiensis and Tilia amurensis was hindered in the original broad-leaved Korean pine forest, the population maintenance of which might need natural disturbance.

[Response of radial growth of Pinus koraiensis and Picea jezoensis to climate change in Xiao-xing'anling Mountains, Northeast China]. / å°å ´å®‰å²­çº¢æ¾å’Œé±¼é³žäº‘æ‰å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å˜åŒ–çš„å“åº”.

Based on dendrochronological methods, we established residual chronologies of Pinus koraiensis and Picea jezoensis, with the dominant species of broadleaved Korean pine mixed forest at low altitudes chosen as the research object, to identify the key climatic factors affecting the radial growth of the two species in Xiaoxing'anling Mountains, Northeast China. The results showed that the responses of the two species to climate factors were different, and P. koraiensis was more sensitive, and hence more suitable for dendroclimatological analysis. Response function coefficients indicated that the radial growth of P. koraiensis negatively correlated with June mean temperature of current year, while positively correlated with precipitation in June of current year. There was no significant correlation between P. jezoensis and all climate variables. Spatial correlation analysis revealed that variations in chronology of P. koraiensis contained strong regional signals, and the highest correlation occurred in the vicinity of the study area. Warming caused drought stress, which was the main factor that limited the growth of P. koraiensis, and it might have adverse effects on the Korean pine if global temperature continues to increase. The coupling effects of large-scale atmospheric-oceanic variability may affect the radial growth of P. koraiensis in Xiaoxing'anling Mountains.

[Responses of Picea likiangensis radial growth to climate change in the Small Zhongdian area of Yunnan Province, Southwest China].

Picea likiangensis (Franch. ) Pritz. primary forest is one of the dominant forest types in the Small Zhongdian area in Shangri-La County of Yunnan Province. In this paper, the responses of P. likiangensis tree-ring width to climate change were analyzed by dendrochronological methods, and the dendrochronology was built by using relatively conservative detrending negative exponential curves or linear regression. Correlation analysis and response function analysis were applied to explore the relationships between the residual chronology series (RES) and climatic factors at different time scales, and pointer year analysis was used to explain the reasons of producing narrow and wide rings. In the study area, the radial growth of P. likiangensis and the increasing air temperature from 1990 to 2008 had definite 'abruption'. The temperature and precipitation in previous year growth season were the main factors limiting the present year radial growth, and especially, the temperature in previous July played a negative feedback role in the radial growth, while the sufficient precipitation in previous July promoted the radial growth. The differences in the temperature variation and precipitation variation in previous year were the main reasons for the formation of narrow and wide rings. P. likiangensis radial growth was not sensitive to the variation of PDSI.

[Soil nitrogen mineralization and primary productivity in Rhododendron aureum community of snowpacks in alpine tundra of Changbai Mountain].

Based on continuous observation of soil temperature and in situ incubation, this paper studied the effects of snow packs on soil temperature, soil nitrogen (N) mineralization, and primary productivity of Rhododendron aureum community alpine tundra in Changbai Mountain. During the snow-covered period of non-growth season (from last October to early May), test soil had an increasing N content, and accumulated sufficient mineralized N for plant growth in the coming year. The soil under snow packs in snow-covered period had a mean temperature -3.0 degrees C, and its N mineralization was more vigorous, with available N increased by 3.88 g x m(-2); while the soil with no snowpack had a mean temperature -7.5 degrees C, and the available N only increased by 1.21 g x m(-2). During growth season (from mid May to late August), soil N content decreased. In autumn when plants stopped growing, soil available N content tended to increase. In winter, the soil temperature under snowpacks kept at around 0 degrees C or a little lower, which promoted soil N mineralization, while that with no snowpack was in a frozen status. The difference in soil N mineralization was the key factor resulting in the higher primary productivity of snowpack Rh. aureum community and the driving force for the spatial variation of vegetation.

[Biomass of Quercus fabri population under different ecological restoration regimes in subtropical China].

In this paper, the tissue-specific biomass and above-ground biomass of Quercus fabri under different ecological restoration regimes in subtropical China were analyzed by establishing allometric models with different parameters. The best-fitted equations were adopted for estimating the biomass and its annual growth, and the below-ground biomass and its increment were estimated on the basis of its linear relationship with above-ground biomass. The results showed that the biomass of the branches and of the total above-ground tissues was best described by power-function models, and the best fitted independent variables were d2l and D2H, respectively. The tissue-specific biomass and total biomass of Q. fabri population were all greater in secondary forest than in Pinus elliottii plantation. The above-ground biomass and below-ground biomass of Q. fabri population in secondary forest were 3.592 and 1.723 t x hm(-2), respectively, in which, different tissue components were ranked in the order of stem > branch > leaf; while those in P. elliottii plantation were 0.666 and 0.462 t x hm(-2), respectively, in which, different tissue components were ranked in the order of stem > leaf > branch. From 2004 to 2006, the annual increments of above-ground, below-ground, and total biomass increased with time, and the increment of above-ground biomass had an ascent tendency, which was from 54.35% to 62.20% in P. elliottii plantation and from 67.27% to 68.94% in secondary forest. In comparing with that in secondary forest, the biomass increment of Q. fabri population in P. elliottii plantation was small, despite its relatively high growth rate.

[Estimation models of understory shrub biomass and their applications in red soil hilly region].

With 16 familiar species of understory shrub at Qianyezhou ecological experimental station in red soil hilly region under Chinese Academy of Sciences as test objects, crown area (A(c)) and projected volume (V(c)) were used as the variables for building quadratic and power allometric equations, respectively, to estimate the biomass of individual populations, and mixed-model was used to estimate the biomass of the 16 species. The best-fit models were applied to estimate the biomass of understory shrub in different forest types. The results showed that the biomass of shrub layer varied significantly among different stand types. With species-specific models, the biomass in deciduous, secondary, and coniferous forests was estimated as 4 773, 3 175 and 733 kg x hm(-2), respectively; while with mixed model, the estimation result was a little lower, being 3 946, 2 772 and 840 kg x hm(-2), respectively. Under the conditions of species-specific models being not established, mixed model was more convenient and practical in estimating the biomass of understory shrub.