[Soil phosphorus forms and phosphorus solubilizing bacteria distribution after restoration from seriously burning in Greater Khingan Mountain areas, China]. / å¤§å ´å®‰å²­é‡åº¦ç«çƒ§è¿¹åœ°æ¢å¤åŽåœŸå£¤ç£·å½¢æ€ä¸Žè§£ç£·ç»†èŒåˆ†å¸ƒç‰¹å¾.

To understand the contents of various phosphorus forms, phosphorus solubilizing bacte-rial community structure and the relationship between them in soils after restoration from the seriously burning, we collected soil samples from artificial restoration (Pinus sylvestris var. mongolica plantation, Larix gmelinii plantation), artificial accelerated natural restoration (secondary forest) and natural restoration (natural secondary forest) stands in Greater Khingan Mountain area. Using methods of Sui et al. modified from Hedley phosphorus fractionation, we measured the contents of different phosphorus forms in rhizosphere soil and bulk soil (0-10, 10-20 cm). Abundances of phosphorus solubilizing bacteria were quantified by high-throughput sequencing method. The results showed that the contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Poin 0-10 cm bulk soil and NaHCO3-Po in rhizosphere soil followed the order of L. gmelinii plantation : P. sylvestris var. mongolica plantation : natural secondary forest : secondary forest. The contents of H2O-Pi, NaHCO3-Pi, NaHCO3-Po in 10-20 cm bulk soil and H2O-Pi, NaHCO3-Pi in rhizosphere soil followed the order of L. gmelinii plantation : P. sylvestris var. mongolica plantation : secondary forest : natural secondary forest. The ratios of contents of H2O-Pi, NaHCO3-Pi and NaHCO3-Po in rhizosphere to those in bulk soil (R/S) were higher than 1 in all forest stands. The moderately labile NaOH-P included NaOH-Pi and NaOH-Po. The content of NaOH-P was in order of L. gmelinii plantation : natural secondary forest : secondary forest : P. sylvestris var. mongolica plantation in 0-10 cm layer of bulk and rhizosphere soil, and ranked as L. gmelinii plantation : P. sylvestris var. mongolica plantation : secondary forest : natural secondary forest in 10-20 cm layer of bulk soil. There was rhizosphere effect of NaOH-P in the soil. The stable HCl-P included HCl-Pi and HCl-Po. The content of HCl-P followed the order of L. gmelinii plantation : natural secondary forest : P. sylvestris var. mongolica plantation : secondary forest in 0-10 cm layer of bulk soil,and ranked as L. gmelinii plantation : P. sylvestris var. mongolica plantation : natural secondary forest : secondary forest in the 10-20 cm layer. The content of residual-P in the soil was not sensitive to restoration methods. Bradyrhizobium, Streptomyces, Burkholderia and Bacillus were the main phosphorus solubilizing bacteria across all forest stands. The abundances of phosphorus solubilizing bacteria in soil of L. gmelinii plantation and P. sylvestris var. mongolica plantation were significantly higher than that of secondary forest and natural secondary forest. Results of redundancy analysis showed that the correlation between phosphorus solubilizing bacteria and various phosphorus forms was different. Our results showed that artificial afforestation was more conducive in improving the availability of phosphorus in soil and the abundance of phosphorus solubilizing bacteria.

Soil greenhouse gases fluxes and the affecting factors of natural secondary forest from seriou-sly burned area in Greater Khingan Mountains, China.

To learn the intensity of greenhouse gases (GHG) fluxes source/sink from soil and the influence factors of a natural secondary forest from seriously burned area in Greater Khingan Mountains, we used static chamber-GC technique to measure soil GHG (CO2, N2O, CH4) in situ during the growing season (from June to September). The results showed that: 1) The soil of natural secondary forest was atmospheric CO2 and N2O source and CH4 sink. The mean fluxes of soil GHG (CO2, N2O, CH4) during the growing season were 575.81 mg·m-2·h-1, 17.81 µg·m-2·h-1 and -68.69 µg·m-2·h-1, respectively. The CO2 and CH4 fluxes showed an obvious double-peak trend and the change of N2O fluxes was a single-peak pattern during the growing season, with all maximum fluxes occurred in August. 2) Soil temperature was the predominant factor controlling the soil GHG fluxes. The correlation of soil/atmospheric humidity and soil GHG fluxes was complicated and differed between diurnal scale and seasonal scale. 3) The soil GHG fluxes measured at 9:00-12:00 am could represent the diurnal average fluxes on the same day after proper correction in this area. The findings supplemented the soil GHG fluxes data of fired forest ecosystem in Greater Khingan Mountains, which could provide a basis for related research of soil GHG source/sink in this area.

[Monitoring and evaluation of the effects of Grain for Green Project in the upper and middle reaches of China's Yangtze River.] / 长江中上游地区退耕还林成效监测与评价.

Based on the comprehensive interpretation of GIS, we analyzed the normalized vegetation index (NDVI), land use types and digital elevation model (DEM), and revealed the results achieved by the Grain for Green Project in 84 prefecture-level regions in the middle and upper reaches of the Yangtze River. The results showed that the NDVI was growing in this area from 2000 to 2015. Compared with 2000, 2.1% of the farmland was no longer cultivated. 25% of the farmland with slope more than 35°, and 2.7% of the farmland with the slope of 25° to 35°, and the most part of moderate slope farmland had been converted. Arable land was mainly converted to woodland and grassland. The coverage of forest and grassland significantly increased, with an enhancement of 21.9%. The land area of low vegetation coverage was greatly reduced. The area with vegetation coverage less than 10% decreased by 95.3%, while the land area of high vegetation coverage significantly increased. The soil erosion intensity generally reduced. The land area with mild, strong, extremely strong soil erosion grade were all reduced by more than 10%, whereas severe soil erosion had not been alleviated. The proportion of forest coverage was 60% in this area. The magnitude of vegetation coverage changes varied in different periods. The spatial distribution was uneven, with higher coverage in the east than in the west. More works are needed to strenthen the management of Grain for Green Project in this area.

[Effects of root excision mulched with film on photosynthesis characteristics of poplar shelterbelts in black soil region]. / åˆ‡æ ¹è´´è†œå¯¹é»‘åœŸåŒºæ¨æ ‘å†œç”°é˜²æŠ¤æž—å ‰åˆç‰¹æ€§çš„å½±å“.

Root excision mulched with film is an effective method which can minimize decrease in crop production in negative-effect area. However, the measure may have adverse effects on the cropland shelterbelt. Taking no treatment as CK, the effects of root excisions mulched with film at distance 0.5, 1, 2 and 3 m from the trunk on photosynthesis characteristics of poplar shelterbelts in black soil region were discussed. The results indicated that root excision mulched with film had no significant effect on poplar leaf water content. Early in July, the time of peak and trough in the treatments were earlier than CK. Different treatments of root excision mulched with film made daily average value of net photosynthetic rate of poplar leaves significantly lower than CK, and there were significant difference among different treatments. During August to September, root excision mulched with film induced daily average value of net photosynthetic rate of poplar leaves still lower than CK, but the lowered range was somewhat reduced, root excision mulched with film at the distance 3 m from the trunk had no significant difference from CK. After root excision mulched with film, transpiration curve appeared in many forms. At the distances 2 and 3 m from the trunk, daily average value of transpiration rate of poplar leaves had no significant difference from CK. At the distances 0.5 and 1 m from the trunk, the decrease in transpiration rate in July was greater than that of photosynthetic rate, resulting in the significantly high water use efficiency than CK. Compared with CK, daily dynamics of water use efficiency in the other treatments had no change, however, daily average value of water use efficiency in the other treatments had significant change, and some of the changes were adverse. Comprehensive comparison indicated that root excision mulched with film at the distance 3 m from the trunk had no significant effect on the photosynthetic characteristics of poplar leaves, and this treatment was significantly superior to others.

[Distribution characteristics of soil organic carbon of burned area under different restorations.] / 火烧迹地不同恢复方式土壤有机碳分布特征.

The distribution characteristics of soil organic carbon (SOC), soil dissolved organic carbon (DOC) and soil microbial biomass carbon (MBC) under different restorations were studied in Larix gmelinii plantation, Pinus sylvestris var. mongolica plantation, artificial promotion poplar-birch forest and the natural secondary poplar-birch forest restored from burned area after the severe fire of Greater Xing' an Mountains in 1987. The results showed that the variations in SOC, DOC and MBC ranged from 9.63 to 79.72 g·kg-1, from 33.21 to 186.30 mg·kg-1 and from 200.85 to 1755.63 mg·kg-1, respectively, which decreased with soil depth increasing. There was significant diffe-rence in SOC, DOC and MBC among different restorations, with the maximum carbon contents for artificial promotion poplar-birch forest, followed by L. gmelinii plantation, natural secondary poplar-birch forest and P. sylvestris var. mongolica plantation successively. The soil microbial quotient va-ried from 1.1% under P. sylvestris var. mongolica plantation to 2.3% under artificial promotion poplar-birch forest, and its vertical distributions were different in the four restoration forests. Correlation analysis indicated that MBC had a significant positive correlation with SOC and DOC, respectively. The activity of soil organic carbon in artificial promotion poplar-birch forest was higher than in other forest stands, suggesting a stronger capacity of the soil carbon cycle through natural regeneration with artificial promotion on burned area in Greater Xing'an Mountains.

[Difference between carbon storage of burned area under different restorations in Greater Xing' an Mountains, Northeast China].

In order to explore forest restoration approach effect on carbon storage of severely burned area in Greater Xing'an Mountains, the carbon contents of tree, shrub, herb and litter from two plantations (Larix gmelinii and Pinus sylvestris var. mongolica) and natural secondary forest were determined, respectively, by using dry combustion method. The biomass of each component was obtained to estimate the distribution characterization of forest vegetation carbon storage by combing whole harvest method with average standard wood method. The results showed that, for both plantations and secondary forest, the average carbon content of shrub was higher than that of arbor and herb. In the L. gmelinii plantation, the average carbon contents of shrub, litter, arbor and herb were 45.8%, 45.3%, 44.4% and 33.6%, respectively. The average carbon content of shrub and arbor was more than 50% in P. sylvestris var. mongolica plantation, while that of arbor, shrub and litter was about 42% for the secondary forest. The biomass of arbor was higher than shrub and herb. In L. gmelinii plantation, the total biomass of vegetation and litter was 123.90 t · hm(-2), which was significantly higher than that of P. sylvestris var. mongolica plantation and secondary forest. The carbon storage of vegetation in L. gmelinii plantation was 50.97 t · hm(-2), among which the arbor was 49.87 t · hm(-2), accounting for 97.8% of the total carbon storage in forest vegetation, while the proportion of herb carbon storage only occupied 0.02%. The total carbon storage of plantations was higher than that of the secondary forest, suggesting a stronger capacity of carbon sink through artificial restoration on severely burned area in Greater Xing' an Mountains during this period.

[Population structure and understory species diversity of different aged Pinus sylvestris var. mongolica plantations in Nenjiang Sandy Land of Northeast China].

Taking the Pinus sylvestris var. mongolica sand-fixing plantations at different development stages (24-, 29-, 39-, and 43 years old) in Nenjiang Sandy Land as test objects, this paper studied their population structure, understory species composition, and species diversity. No regenerated seedlings were found in all the four P. sylvestris var. mongolica plantations. The mean individual height and DBH of the populations differed significantly with development stage. With the increasing age of the plantations, the proportion of small-sized individuals decreased obviously, while that of large-sized individuals increased, population tended to mature, and the diameter structure except 43 years old plantation was in normal distribution. A total of 33 understory plant species were recorded, belonging to 28 genera and 15 families. Setaria viridis was the dominant species, but its dominance decreased gradually with increasing age of the plantations. With the increase of plantation age, the proportion of annual plants decreased, while that of perennial plants increased. The Simpson index and Pielou index had no significant differences among the different aged plantations, but the richness index, Shannon index, and Alatalo index of 39 years old plantation were significantly higher than those of 24 years old stands, suggesting that the species diversity of the community improved with time.

[Responses of soil structure to seasonal freezing-thawing in a typical black soil cultivated region].

Taking the soil in a typical black soil cultivated region as test object, this paper analyzed its aggregate size distribution, wedge resistance, bulk density, porosity, saturation degree, and generalized structure index after a seasonal freezing-thawing cycle, and evaluated the effects of the freezing-thawing cycle on the soil structural characters. The seasonal freezing-thawing cycle aggravated the disruption of air-dried aggregates, but strengthened the aggregation of water-stable aggregates and lowered their destruction rate. After the freezing-thawing cycle, soil wedge resistance decreased by 15.45%, and soil bulk density remained relatively constant from 1.10 to 1.11 g x cm(-3). The volume percent of soil solid phase increased, and soil total porosity and capillary porosity decreased to different degree. Soil saturation degree was improved by 13.06%, which in turn decreased the soil potential storage capacity. Seasonal freezing-thawing cycle improved the soil structure and soil arability and increased the erosion resistance of soil aggregates, but decreased the soil erosion resistance and increased the risk of the water erosion of black soil.

[Effects of salt stress on mulberry seedlings growth, leaf water status, and ion distribution in various organs].

Taking the seedlings of mulberry (Morus alba) varieties Qiuyu and Tailai from Heilongjiang Province as test materials, this paper studied their growth, leaf water relations, and ion distribution in various organs under the stress of different salt concentration. The resu1ts showed that salt stress decreased the plant height and dry mass of the seedlings obviously, and the dry mass of young leaves was more affected than that of old leaves. With increasing salt stress, leaf water potential, osmotic potential, pressure potential, and relative water content decreased markedly, while the Na+ concentration in root and stem had an obvious increase. When the soil NaCl concentration was 150 mmol L(-1) or higher, the Na+ concentration in leaf, stem, and root reached saturated. Salt stress markedly decreased the K+ and Ca2+ concentrations in leaf, stem, and root as well as the Mg2+ concentration in leaf and stem, but had lesser effects on the Mg2+ concentration in root. The decrease of leaf Ca2+, K+, and Mg2+ concentrations under salt stress caused the ion deficiency in plant and limited plant growth, while the regionalized distribution of Na+ in root, stem, and older leaf could be one of the salt tolerance mechanisms of test varieties.