[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.

[Effects of mulberry/soybean intercropping on the plant growth and rhizosphere soil microbial number and enzyme activities].

A root separation experiment was conducted to investigate the plant growth and rhizosphere soil microbes and enzyme activities in a mulberry/soybean intercropping system. As compared with those in plastic barrier and nylon mesh barrier treatments, the plant height, leaf number, root length, root nodule number, and root/shoot ratio of mulberry and soybean in non-barrier treatment were significantly higher, and the soybean's effective nodule number was larger. The available phosphorous content in the rhizosphere soils of mulberry and soybean in no barrier and nylon mesh barrier treatments was increased by 10.3% and 11.1%, and 5.1% and 4.6%, respectively, as compared with that in plastic barrier treatment. The microbial number, microbial diversity, and enzyme activities in the rhizosphere soils of mulberry and soybean were higher in the treatments of no barrier and nylon mesh barrier than in the treatment of plastic barrier. All the results indicated that there was an obvious interspecific synergistic effect between mulberry and soybean in the mulberry/soybean intercropping system.

[Effects of Morus alba and Setaria italica intercropping on their plant growth and diurnal variation of photosynthesis].

A field investigation was conducted to study the effects of intercropping Morus aIba and Setaria italica on their dry matter production, land use efficiency, and diurnal variation of leaf photosynthesis. Under intercropping, the plant height, basal diameter, root length, and branch number of M. alba increased by 6.0%, 13.7%, 6.8%, and 14.8%, respectively, and the leaf yield of M. alba was increased by 31.3%, as compared with monoculture M. alba. In contrast, the plant height and root length of intercropped S. italica had no significant difference with those of monoculture S. italica. Intercropping enhanced the equivalent ratio and use efficiency of arable land. For both M. alba and S. italica in monoculture or intercropping, their leaf photosynthetic depression all occurred at midday (12 :00), but the leaf photosynthetic depression of monoculture M. alba was heavier than that of intercropped M. alba. Intercropping promoted the leaf stomatal conductance (g(s)) and water use efficiency (WUE) of M. alba at midday, increased the photosynthetic carbon assimilation of M. alba, and inhibited the decline of M. alba leaf actual photochemical efficiency of PS II (phi(PS II)), photosynthetic electron transport rate (ETR), and the maximal photochemical of PS II (F(v)/F(m)) , which might contribute to alleviate the leaf photosynthetic depression of M. alba at midday. It was concluded that M. alba and S. italica intercropping could obviously improve the leaf photosynthetic capacity of M. alba.

[Effects of mulberry-soybean intercropping on carbon-metabolic microbial diversity in saline-alkaline soil].

Aiming at the characteristics that mulberry-soybean intercropping could alleviate the damage of saline-alkaline soil, Biolog technique was adopted to study the effects of this intercropping on the diversity of carbon-metabolic microbial community in the rhizosphere of saline-alkaline soil. Under mulberry-soybean intercropping, the average well color development (AWCD) symbolizing the metabolic activity of soil microbes was obviously higher, as compared with that under mulberry or soybean monocropping, being the lowest under mulberry monocropping. The McIntosh index was also higher under intercropping than under monocropping, but the Shannon index and Simpson index had less difference between intercropping and monocropping, indicating that intercropping changed the composition and enhanced the diversity of the microbial community in the rhizosphere of saline-alkaline soil. Principal component analysis (PCA) showed that the carbon source utilization mode of the soil microbial community differed between intercropping and monocropping, and the main carbon sources were carbohydrate, carboxylic acid, and polymers. Soil pH and salinity were the main factors limiting the diversity of the microbial community in saline-alkaline soil, and intercropping could effectively decrease the soil pH and salinity and promote the improvement of soil microbial community diversity.

[Effects of NaCl and Na2CO3 stresses on the growth and photosynthesis characteristics of Morus alba seedlings].

Taking 1-year old Morus alba variety 'Qinglong' seedlings as test materials, this paper studied their growth and photosynthetic characteristics under the stresses of different concentration neutral salt NaCl and alkali salt Na2CO3. Salt stresses decreased the plant height and the leaf number, biomass, and photosynthetic capacity of the seedlings markedly. With increasing concentration Na+, the leaf stomatal conductance, transpiration rate, net photosynthetic rate, actual photochemical efficiency, electron transport rate, and photochemical quenching (qP) decreased obviously, the energy dissipation rate increased, and the light use efficiency and photosynthetic capacity dropped down. At low concentrations Na+ (< 150 mmol x L(-1)), the seedlings growth and leaf photosynthetic capacity were slightly inhibited, and the adaptability of the seedlings to the salt stresses increased via the increase of root/shoot ratio. However, this protection mechanism was impaired by increasing salt concentration. Na2CO3 stress (Na+ concentration > 50 mmol x L(-)) had stronger inhibitory effects on the seedlings growth and leaf photosynthetic capacity, and the effect increased with increasing Na+ concentration. It was concluded that at Na+ concentration < 150 mmol x L(-1), the photosynthetic adaptability of M. alba to neutral salt stress was mainly dependent on the plant morphology and photosynthetic metabolism, but at Na+ concentration > 150 mmol x L(-1), the photosynthetic adaptability of M. alba to alkali salt stress was mainly dependent on the photosynthetic metabolism.

[Effects of Festuca arundinacea on the microbial community in crude oil-contaminated saline-alkaline soil].

By using the routine soil physical and chemical analysis methods and the Biolog technique, this paper studied the effects of Festuca arundinacea growth on the pH value, total salt content, and microbial community in the rhizosphere of crude dil-contaminated saline-alkaline soil in Songnen Plain of Northeast China. Crude oil contamination resulted in the increases of average well color development (AWCD), Shannon index (H), and carbon source utilization richness index (S), and altered the utilization patterns of carbon sources by the microbes. F. arundinacea had greater potential to remediate crude oil-contaminated soil. This plant could decrease the soil pH and soil total petroleum hydrocarbon (TPH) content, and increase the soil water content. The AWCD and S in F. arundinacea rhizosphere soil were obviously higher than those in the soil of naked land, providing a suitable environment for the growth and development of rhizosphere soil microbes.

[Effects of combined fertilization of N, P, and K on nicotine content of filling type flue-cured tobacco].

An orthogonal regression field experiment was conducted to study the effects of combined fertilization of N, P, and K on the nicotine content in the upper leaves of filling type flue-cured tobacco (Nicotiana tobacum) variety "Longjiang 911" from Northeast China. The regression effect models of N, P, and K fertilization rates and upper leaf nicotine content were established, and the effects of the fertilization rates and their interactions were analyzed. Based on these, an optimized NPK fertilization scheme was drawn up to reduce the nicotine content in the upper leaves of "Longjiang 911". The model analyses showed that the nicotine content in the upper leaves of "Longjiang 911" decreased after an initial increase with the increasing fertilization rate of N, increased with the increasing fertilization rate of P, and had a sharp decrease with the increasing fertilization rate of K. The two-factor effects of NKP on the nicotine content were in the order of NK >PK>NP. Within a certain range of fertilization rates, NP and PK had negative correlations with the nicotine content, suggesting the antagonistic effects between N and P and between P and K, while NK was on the contrary, suggesting the synergistic effects between N and K. A comprehensive analysis on the regression effect models of N, P, and K fertilization rates and upper leaf nicotine content showed that the basal fertilization rates of N, P, and K for the tobacco production on warp soil were recommended as 33.5-47.8 kg x hm(-2), 40.2-63.6 kg x hm(-2), and 78.0-119.6 kg x hm(-2), respectively.