[Seedling regeneration and spatial correlation between seedlings and seed trees in Castanopsis hystrix plantation by large diameter wood cultivation in south subtropical China]. / å—äºšçƒ­å¸¦çº¢é”¥å¤§å¾„æåŸ¹è‚²æž—å¹¼è‹—æ›´æ–°åŠå ¶ä¸Žæ¯æ ‘çš„ç©ºé—´å ³è”æ€§.

Using the paired correlation equation g(r) in the spatial point patterns, we investigated the regeneration characteristics and spatial patterns of Castanopsis hystrix seedlings and the spatial correlation with the seed trees in the plantation by large diameter wood cultivation in south subtropical China. The results showed that natural seedling regeneration in C. hystrix plantation was good, which were widely distributed in the whole plantation. The seedling regeneration were mainly contributed by root sprouts, accounting for 73.6% of the total. The number distribution of C. hystrix seedlings in different age classes showed a pyramidal shape, with the contribution of diameter class1, 2 and 3 being 64.3%, 29.3% and 6.4% of the total, respectively. The C. hystrix seedlings mainly presented aggregated distribution in small scale (<15 m). With the increases of size classes and spatial scales, the aggregation strength gradually weakened and finally presented random distribution. The spatial correlation between seedlings and seed trees was not significant with the increases of size classes or spatial scale.

Differential controls on soil carbon density and mineralization among contrasting forest types in a temperate forest ecosystem.

Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models.

Soil microbial responses to forest floor litter manipulation and nitrogen addition in a mixed-wood forest of northern China.

Changes in litterfall dynamics and soil properties due to anthropogenic or natural perturbations have important implications to soil carbon (C) and nutrient cycling via microbial pathway. Here we determine soil microbial responses to contrasting types of litter inputs (leaf vs. fine woody litter) and nitrogen (N) deposition by conducting a multi-year litter manipulation and N addition experiment in a mixed-wood forest. We found significantly higher soil organic C, total N, microbial biomass C (MBC) and N (MBN), microbial activity (MR), and activities of four soil extracellular enzymes, including ß-glucosidase (BG), N-acetyl-ß-glucosaminidase (NAG), phenol oxidase (PO), and peroxidase (PER), as well as greater total bacteria biomass and relative abundance of gram-negative bacteria (G-) community, in top soils of plots with presence of leaf litter than of those without litter or with presence of only fine woody litter. No apparent additive or interactive effects of N addition were observed in this study. The occurrence of more labile leaf litter stimulated G-, which may facilitate microbial community growth and soil C stabilization as inferred by findings in literature. A continued treatment with contrasting types of litter inputs is likely to result in divergence in soil microbial community structure and function.

[Bacterial community structure and diversity in soils of different forest ages and types in Bao- tianman forest, Henan Province, China].

To compare the microbial compositions and diversities in soils of different forest ages and types in Baotianman forest, Henan Province, China, genomic DNA of forest soils was extracted for amplifying the 16S rRNA V4 hyper variable region by PCR and sequencing by Illumina MiSeq. The BIPES, UCHIME and QIIME were employed to analyze the soil bacterial community. It was shown that 60 phyla were identified, with Proteobacteria, Acidobacteria, and Verrucomicrobia representing the most dominant lineages and accounting for 29%, 18.5% and 10% of all sequences, respectively. At the genus level, 1209 genera were identified, the most abundant phylotypes were DA101 (6.3%), Acidobacteria-2 (5.9%), Candidatus Solibacter (2.9%) and Candidatus Nitrososphaera (2.6%). Different forest age and type soil samples had unique compositions and specific high and rare genus. Forest type and age both impacted the soil microbial community structure, and the influence of the former was stronger than the latter. The soil microbial diversity of the 80-year-old Quercus aliena forest was the lowest among all age and type forest soil samples. Soil pH, soil nitrogen and organic carbon contents were the most important factors affecting soil bacterial community structure.

[Effects of forest floor litter and nitrogen addition on soil microbial biomass C and N and microbial activity in a mixed Pinus tabulaeformis and Quercus liaotungensis forest stand in Shanxi Province of China].

From September 2010 to October 2011, a field experiment with randomized block design was conducted in a mixed Pinus tabulaeformis and Quercus liaotungensis forest stand in Lingkong Mountain of Shanxi Province to study the effects of forest floor litter and nitrogen addition on the soil microbial carbon (MBC) and nitrogen (MBN) and microbial activity (MR). The litter treatments included complete litter removal, doubling of leaf litter (L), doubling of woody litter (B), and doubling of mixed leaf and woody litter (LB), and the nitrogen addition rates were 0 (N0), 5 g x m(-2) x yr(-1) (N1), and 10 g x m(-2) x yr(-1) (N2). Except that the treatment of complete litter removal without nitrogen addition decreased the soil organic carbon content significantly, all the other treatments had no significant differences in the effects on soil organic carbon. The soil MBC, MBN, and MR varied in the ranges of 262.42-873.16 mg x kg(-1), 73.55-173.85 mg x kg(-1), and 2.38-3.68 mg x kg(-1) x d(-1), respectively, and the MBC and MBN had significant positive correlations with the MR. Nitrogen addition did not show any effect on the MBC, MBN, and MR, whereas litter treatments affected the MR significantly, with the highest MR in treatment LB, followed by treatments L and B, and the lowest in treatment of complete litter removal. There were no interactive effects between litter and nitrogen addition treatments on any of the variables studied. It was suggested that short-term nitrogen addition and forest floor litter change could have limited effects on soil microbial processes.

[Total analysis of organic rubber additives].

In the present paper, after middle pressure chromatograph separation using both positive phase and reversed-phase conditions, the organic additives in ethylene-propylene rubber were identified by infrared spectrometer. At the same time, by using solid phase extraction column to maintain the main component-fuel oil in organic additves to avoid its interfering with minor compounds, other organic additves were separated and analysed by GC/Ms. In addition, the remaining active compound such as benzoyl peroxide was identified by CC/Ms, through analyzing acetone extract directly. Using the above mentioned techniques, soften agents (fuel oil, plant oil and phthalte), curing agent (benzoylperoxide), vulcanizing accelerators (2-mercaptobenzothiazole, ethyl thiuram and butyl thiuram), and antiagers (2, 6-Di-tert-butyl-4-methyl phenol and styrenated phenol) in ethylene-propylene rubber were identified. Although the technique was established in ethylene-propylene rubber system, it can be used in other rubber system.