[Effects of different land use patterns on the soil microbial community diversity in montane region of eastern Liaoning Province, China.] / ä¸åŒåœŸåœ°åˆ©ç”¨æ¨¡å¼å¯¹è¾½ä¸œå±±åŒºåœŸå£¤å¾®ç”Ÿç‰©ç¾¤è½å¤šæ ·æ€§çš„å½±å“.

An experiment was conducted to examine the differences of soil microbial diversity across different land use patterns in montane region of eastern Liaoning Province, China. The relationships between soil physicochemical properties and soil microbial diversity in five different land use types, including Quercus mongolic forest, shrubland, Larix gmelinii plantation, Pinus koraiensis plantation, and Zea mays cropland were analyzed by Biolog-Eco method. The results showed that both soil total C and N contents were the highest in the Q. mongolica forest, which were 57.74 and 4.40 g·kg-1, followed by shrubland, but only 17.46 and 1.31 g·kg-1 in the Z. mays cropland, respectively. There were significant differences in microbial utilization rate of different land use types. The carbon utilization capacity by soil microbial communities was following the order of Q. mongolica forest > shrubland > L. gmelinii plantation > P. koraiensis plantation > Z. mays cropland, indicating that soil microbial metabolism and activity in Z. mays cropland were the lowest. The Shannon diversity index (2.997), Simpson diversity index (0.942) and McIntosh diversity index (5.256) of soil microbial community in the Z. mays cropland were significantly lower than those in other ecosystems. The average absorbance value (AWCD) was associated with Simpson diversity index and McIntosh diversity index. Esters, alcohols and amines were the primary carbon sources for the differentiation, which might be due to a joint action of many factors such as litter, soil nutrients, and specific soil microorganisms. The soil nutrient and soil microbial community diversity in forest land after reclamation sharply decreased, causing the loss of soil fertility and productivity. The region should keep the Q. mongolica forest, which could help restore soil fertility.

[Spatial distribution and scale effect of species diversity of secondary forests in montane region of eastern Liaoning Province, China.] / è¾½ä¸œå±±åŒºæ¬¡ç”Ÿæž—ç‰©ç§å¤šæ ·æ€§çš„ç©ºé—´åˆ†å¸ƒåŠå°ºåº¦æ•ˆåº”.

With secondary forest in the montane region of eastern Liaoning Province as research object, this paper analyzed the spatial distribution and scale effect of Gleason richness index, Simpson dominance index, Shannon diversity index and Pielou evenness index in a 4 hm2 plot. The results showed that spatial distributions of the four diversity indices showed higher spatial heterogeneity. Variance of the four diversity indices varied with increasing scale. Coefficients of variation of the four diversity indices decreased with increasing scale. The four diversity indices of the tree layer were higher than those of the shrub layer, and the variation tendency varied with increasing scale. The results indicated that sampling scale should be taken into account when studying species diversity in the montane region of eastern Liaoning Province.

[Dynamics of initial decomposition of Calamagrostis angustifolia litter in Sanjiang Plain of China].

A 28-day leaching-decomposition experiment was conducted to study the effects of microbial activity and leaching on the initial decomposition of Calamagrostis angustifolia litters taken from the boggy meadow and meadow in Sanjiang Plain of China. The results showed that the mass loss of the litters at their initial decomposition stage accounted for 59% and 22% of yearly mass loss, respectively, and the remaining dry mass decreased significantly after 28-day decomposition. By the end of the experiment, the N content in the litters decreased by 32.65% and 24.55% , and P content decreased by 36.71% and 45.15%, respectively. The N and P contents in the litters treated with chloroform were higher than those of the control, but the difference was not significant. No significant difference was also observed in the N and P release from the litters to the leachates between the treatment of chloroform and CK, which indicated that the initial decomposition of the litters was mainly affected by leaching. There was no significant difference in the decomposition rate and nutrient loss rate between the two litters.

[Effects of simulated wetland water change on the decomposition and nitrogen dynamics of Calamagrostis angustifolia litter].

From May 2005 to September 2006, the potential effects of wetland water change on the decomposition and nitrogen (N) dynamics of the typical meadow Calamagrostis angustifolia (TMC) and marsh meadow C. angustifolia (MMC) litters were studied by litterbag technique in the typical depressional wetland in the Sanjiang Plain. In this study, the natural water gradient in the depressional wetland was applied to simulate the changes of wetland water conditions, and six decomposition sub-zones were laid in turn in the six communities, Carex pseudocuraica (PF), Carex lasiocarpa (MG), Carex meyeriana (WL), Marsh meadow C. angustifolia (XII), Typical meadow C. angustfolia (XI), and Island forest (DZL), along the water gradient. The results show that water condition has significant effects on the decomposition of litters. If the hydrous environment is formed in C. angustfolia wetland due to the change of precipitation pattern in the future, the litter weightless rates of TMC and MMC will increase 4.33%-16.76% and 24.84%-53.97%, the decomposition rates will increase 10.51%-32.73% and 77.85%-93.92%, and the 95% decomposition time will decrease 0.72-1.85 a and 3.67-4.05 a, respectively. The changes of N contents and N accumulation indices of TMC and MMC litters are relatively consistent, but the change patterns indifferent sub-zones are different. In general, the N in litters in DZL, XI, WL, MG and PF sub-zones show the alternant change characteristics of release and accumulation, but the release process is predominated. In contrast with that, the N in litters in XII sub-zone show release at all times. The C/N ratios have important regulation functions to the changes of N in litters in decomposition process. The estimation results show that the N standing crops of TMC and MMC litters are 12.75 g x m(-2) and 8.29 g x m(-2), and the N annual returning amounts are larger than 1.95 g x (m2 x a)(-1) and 2.25 g x (m2 x a)(-1), respectively. The studies of affecting factors indicate that temperature has promotion effects on the relative decomposition rates of litters, while water condition has restraint effects on them. Further analysis shows that the relative decomposition rates, to some extent, depend on the substrate quality of litters if the nutrient status of decomposition environment does not change greatly. In reverse, if the nutrient status of decomposition environment changes greatly, the relative decomposition rates, to some extent, depend on the supply status of nutrient in decomposition environment.

[Phosphorus fractions under different land uses in Sanjiang plain].

Five land-uses type (soybean-filed, rice-field, abandoned cultivation, artificial forest, natural wetland) were obtained before planting and soil P fractions were determined by a modified Hedley fraction method. The result showed that the content of total P (TP) in natural wetland was higher than other soil. While the proportion of total inorganic P (TPi) in TP of farm land soil was higher than that of wetland. Adversely, the proportion of total organic P (TPo) was higher in wetland and least in rice-field. There was no obvious difference between that of abandoned field and artificial forest. The values of labile inorganic phosphorus (labile Pi) under different land-uses were similar. The contents of Resin-P and NaHCO3-Pi varied at a range of 32-36.3 mg x kg(-1) and 33.77-50.42 mg x kg(-1), respectively. The contents of NaOH-Pi and C.HCl-Pi in farmland were higher than those of wetland, especially in rice-field which was 152.4 mg x kg(-1). But for D.HCl-Pi, the content was higher in wetland with the value of 84.3 mg x kg(-1), and the contents of NaOH-Pi, C. HCl-Pi and D.HCl-Pi in abandoned field and artificial forest were in the middle of the above two land use patterns, which indicated that the restoration of soil P in abandoned farmland tended to approach the level of natural wetland. The value and percentage of Po was decreased greatly with the reclamation of wetland, and the decrease of C. HCl-Po was the most significant in all forms of organic P, and its values in soybean-filed and rice-field were only 25.96% and 19.26% of that in wetland. As the time went by the content of Po in abandoned arable land increased with very slow speed, which indicated that the restoration of wetland after reclamation would need a long time. The distribution of soil P in different P fractions has significant difference for the land-use change in Sanjiang plain.