Natural 13C abundance and soil carbon dynamics under long‐term residue retention in a no‐till maize system

Residue retention and reduced tillage are both conservation agricultural practices that may enhance soil organic carbon (SOC) stabilization in soil. We evaluated the long‐term effects of no‐till (NT) and stover retention from maize on SOC dynamics in a Rayne silt loam Typic Hapludults in Ohio. The six treatments consisted of retaining 0, 25, 50, 75, 100 and 200% of maize residues on each 3 × 3 m plot from the crop of previous year. Soil samples were obtained after 9 yrs of establishing the experiment. The whole soil (0–10 and 10–20 cm of soil depths) samples under different treatments were analysed for total C, total N, recalcitrant C (NaOCl treated sample) and ¹³C isotopic abundance (0–10 cm soil depth). Complete removal of stover for a period of 9 yrs significantly (P < 0.01) decreased soil C content (15.5 g/kg), whereas 200% of stover retention had the maximum soil C concentration (23.1 g/kg). Relative distribution of C for all the treatments in different fractions comprised of 55–58% as labile and 42–45% as recalcitrant. Retention of residue did not significantly affect total C and N concentration in 10–20 cm depth. ¹³C isotopic signature data indicated that C₄‐C (maize‐derived C) was the dominant fraction of C in the top 0–10 cm of soil layer under NT with maize‐derived C accounting for as high as 80% of the total SOC concentration. Contribution of C₄‐C or maize‐derived C was 71–84% in recalcitrant fraction in different residue retained plots. Residue management is imperative to increase SOC concentrations and long‐term agro‐ecosystem necessitates residue retention for stabilizing C in light‐textured soils.     

基于红外相机技术的广东曲江沙溪省级自然保护区兽类资源分析

2019年7月,使用网格法布设了11台红外相机首次对广东曲江沙溪省级自然保护区大中型兽类资源进行了调查研究,调查累计102天,累计回收1 123个相机工作日的数据,共拍摄到兽类独立有效照片数103张,鉴定出兽类3目6科9种,分别为黄腹鼬Mustela kathiah、鼬獾Melogale moschata、斑林狸Prionodon pardicolor、豹猫Prionailurus bengalensis、野猪Sus scrofa、小麂Muntiacus reevesi、赤腹松鼠Callosciurus erythraeus、倭花鼠Tamiops maritimus和红腿长吻松鼠Dremomys pyrrhomer,其中,斑林狸和红腿长吻松鼠为沙溪自然保护区新纪录种;发现相对多度指数最高的兽类是野猪,为29.39,分布最广泛的地栖兽类是鼬獾;建立兽类累积曲线发现前31天兽类种数上升较快,后71天趋于平缓;研究进一步证实了红外相机技术可以作为保护区兽类补充调查的重要手段,可以在保护区兽类物种编目、相对多度指数、分布现状与凭证标本等收集上发挥重大作用。     

Differences in bird species diversities between a natural mixed forest and a coniferous plantation

Bird species diversity and bird species richness were surveyed in a natural mixed forest (mature forest) and in a coniferous plantation (30–40 years old) monthly from 1990 to 1994. These forests were 20 km apart and had similar weather conditions and soil types. There were larch and cedar plantations, and hardwoods along streams in the coniferous plantation. In the natural mixed forest, 55 bird species were found, whereas 40 species were recorded in the coniferous plantation. The species diversity of bird communities was significantly higher in the natural mixed forest than in the coniferous plantation mixed with hardwood trees. This result indicates that the coniferous plantation mixed with hardwood trees, presumed to be a more simplified environment, is likely to be less inhabitable for many bird species than the natural mixed forest, suggesting a relationship between the diversity of the forest environment and the diversity of the bird community. A higher number of bird species was recorded in the small coniferous forest mixed with hardwood trees compared with those in the coniferous plantation. The mixing of broad-leaved trees in a coniferous plantation was suggested to be effective in increasing number of bird species. These tendencies were recorded all through the year during our study. In snow-covering periods, both the diversity and the bird species richness fell in all study sites every year. Snow cover would have greater effect on bird species diversity in the coniferous plantation than in other forest types probably due to diet shortages caused by the snow cover over the forest floor.     

昆明城市绿化中草本花卉多样性的现状与分析

就昆明市城市绿化中草本花卉的多样性进行了实地调查.调查结果表明:在调查的76处公共绿地、专用绿地和道路绿地中,所用草本花卉共32科62属73种、公共绿地应用种类较多、其次是专用绿地,道路绿地用得较少.从物种组成及丰富度、花色、观赏部位、生活型、适生环境、观赏季节、应用形式等方面对昆明城市绿化中草本花卉多样性的调查结果进行了分析,并针对存在的问题提出了改进建议.     

Restoring dry Afromontane forest using bird and nurse plant effects: Direct sowing of Olea europaea ssp. cuspidata seeds

To identify the perspectives of seed sowing for reforestation of degraded dry Afromontane savanna in exclosures in northern Ethiopia, seeds of a fleshy-fruited, secondary climax tree, Olea europaea ssp. cuspidata, were placed under two pioneer shrub species (Euclea racemosa and Acacia etbaica) and in open microhabitats. Seed removal and germination rates were examined. The effects of bird ingestion, manual pulp removal and mechanical endocarp treatments on germination rates were also studied.

Pulp removal promoted seed germination, in particular in seeds without endocarp manipulation. Seed removal, presumably by rodents, was concentrated in narrow strips along linear soil conservation structures, and not different between shrubs and open microhabitats. In the absence of water stress, humus types did not have a significant effect on germination rates. Under field conditions however, germination was higher under Euclea canopies. The observed facilitative effect of Euclea shrubs on germination may be attributed to moisture retention effects, related to the deep humus layer and canopy architecture, preventing desiccation and promoting imbibition of seeds. When readily available Olea seeds are not used for seedling production, direct sowing of seeds in the humus under dense Euclea shrubs could offer a cheap complement to planting of nursery-raised seedlings for forest restoration projects in recovering Afromontane savanna.     

The unstable fate of seedlings of the small-seeded pioneer tree species, Betula maximowicziana

The dynamics of the seedling population of the pioneer tree, Betula maximowicziana, were studied for 6 years under various site conditions, with special reference to mortality and mortality factors, in order to better understand their seedling bank formation process. We found that current year seedlings suffered high annual mortality of more than 80%, but that mortality fell with age. Canopy covers and cohorts maintained strong influences on seedling mortality during the first 3 years after emergence. The open site with disturbed soil surface was best suited for 3-year seedling survival. Since the seedlings of B. maximowicziana emerged regardless of canopy covers, high seedling mortality was thought to be the main factor that interrupted their regeneration under a canopy. The occurrence of various hazards together caused high seedling mortality. The major mortality factors, regardless of site conditions, were drought, cold hazard and debilitation, though occurrence of the three factors varied, dependent upon the climate of that particular year. Annual mortality and the occurrence of each mortality factor at a fine scale of 0.2 m² quadrate each showed certain spatio-temporal variations within the same site condition. The extremely high mortality of B. maximowicziana seedlings should be attributed to their inherently small, initial size. The poor root system of the small seedlings may be responsible for their low resistance to various hazards, such as drought and frost heaving.     

牡丹常见品种花瓣中主要营养成分与食用安全性分析

以洛阳牡丹常见的5个品种"凤丹白"、"日暮"、"赵粉"、"红株女"和"粉中冠"为试材,研究其盛花期花瓣中总糖、总蛋白、维生素C和5种元素(砷、铜、钒、硒、铬)的含量以及超氧化物歧化酶(SOD)的活力。结果表明:5个牡丹品种花瓣中均含有丰富的糖类、蛋白质和维生素C,并具有较高的SOD活力。"凤丹白"和"日暮"花瓣中砷元素、"赵粉"花瓣中硒元素、"红株女"和"粉中冠"花瓣中铬元素含量均略高于国家食品卫生标准中对蔬菜的限量标准,而作为粮食加工食品时,5个牡丹品种花瓣中的砷、铜、钒、硒、铬元素含量均低于或远低于国家限量标准。     

The apparent electrical conductivity as a surrogate variable for predicting earthworm abundances in tilled soils

Noninvasive geophysical methods have a great potential for improving soil‐biological studies at field or regional scales: they enable the rapid acquisition of soil information which may help to identify potential habitats for soil biota. A precondition for this application is the existence of close relationships between geophysical measurements and the soil organism of interest. This study was conducted to determine whether field measurements of apparent electrical conductivity (ECa) are related to abundances of earthworms in tilled soils. Relationships between ECa and earthworm populations were investigated along transects at 42 plots under reduced and conventional tillage at a 74 ha field on sandy‐loam soil in NE Germany. Relations were analyzed with linear‐regression and spatial analysis. The apparent electrical conductivity (ECa) was quantitatively related to earthworm abundances sampled 5 months after the geophysical measurements. No relationship was found, however, in plots under conventional tillage when analyzed separately. If earthworm abundances were known at every other location along the transects and if the state‐space approach was used for analysis, the analysis of ECa measurements and earthworm abundances indicated that 50% of the earthworm samples could have been substituted by ECa measurements. Further research is needed to fully evaluate the potential of ECa measurements for predicting earthworm habitats in tilled soil.     

N natural abundance of biologically fixed N2 in soybean is controlled more by the Bradyrhizobium strain than by the variety of the host plant

The ¹⁵N natural abundance technique is one of those most easily applied ‘on farm’ to evaluate the contribution of biological N₂ fixation (BNF) to legume crops. When proportional BNF inputs are high, the accuracy of this technique is highly dependent on an accurate estimate of the ¹⁵N abundance of the N derived from N₂ fixation (the ‘B’ value). The objective of this study was to determine the influence of soybean variety on ‘B’ value. Plants of five soybean varieties were inoculated separately with two Bradyrhizobium strains (one Bradyrhizobium japonicum and one Bradyrhizobium elkanii) grown in pots of soil virtually free of bradyrhizobia capable of nodulating soybean. The proportion of N derived from BNF (%Ndfa) was estimated in separate pots where a small quantity of enriched ¹⁵N ammonium sulphate was added. The %Ndfa was then used with the ¹⁵N natural abundance data of the nodulated soybean and non-N₂-fixing reference plants, to determine the ‘B’ value for each soybean variety/Bradyrhizobium association. The varieties nodulated by the B. japonicum strain showed significantly greater N content and %Ndfa than those nodulated by the B. elkanii strain, and in all cases the ‘B’ value of the shoot tissue (‘B_s’) was higher. The differences in ‘B_s’ values between varieties nodulated by the same Bradyrhizobium strain were insignificant, indicating that this parameter is influenced much more by the Bradyrhizobium strain than by the variety of the host plant.     

海南省典型咖啡园植株矿质养分状况评价

对海南省典型咖啡种植园植株样品(叶片)进行了测试分析。结果表明:调查区域植株叶片P、S、Fe含量均处于适宜范围,Mn、Zn含量均高于适宜范围,N、B含量在适宜或高量范围,K含量大部分也在适宜或高量范围,Ca、Mg含量较缺乏,Cu含量严重缺乏。