Effects of past and current crop management on soil microbial biomass and activity

Because soil biota is influenced by a number of factors, including land use and management techniques, changing management practices could have significant effects on the soil microbial properties and processes. An experiment was conducted to investigate differences in soil microbiological properties caused by long- and short-term management practices. Intact monolith lysimeters (0.2 m² surface area) were taken from two sites of the same soil type that had been under long-term organic or conventional crop management and were then subjected to the same 2.5-year crop rotation [winter barley (Hordeum vulgare L.), maize (Zea mais L.), lupin (Lupinus angustifolius L.), and rape (Brassica napus L. ssp. oleifera)] and two fertilizer regimes (following common organic and conventional practices). Soil samples were taken after crop harvest and analyzed for microbial biomass C and N, microbial activity (fluorescein diacetate hydrolysis, arginine deaminase activity, and dehydrogenase activity), and total C and N. The incorporation of the green manure stimulated growth and activity of the microbial communities in soils of both management histories. Soil microbial properties did not show any differences between organically and conventionally fertilized soils, indicating that crop rotation and plant type had a larger influence on the microbial biomass and enzyme activities than fertilization. Initial differences in microbial biomass declined, while the effects of farm management history were still evident in enzyme activities and total C and N. Links between enzyme activities and microbial biomass C varied depending on treatment, indicating differences in microbial community composition.     

Linking past land use, recent disturbance, and dispersal mechanism to forest composition

Many areas in north-eastern North America were historically cleared for agriculture and subsequently abandoned. The resulting woodlots are exposed to varying degrees of recent disturbance. This paper examines the contributions of land use history and recent disturbance on the species richness and community composition of wooded areas in an agricultural landscape. Woodlots were categorized according to land clearance history, past grazing, and recent disturbance, such as the presence of roads or selective cutting. Vegetation surveys resulted in the identification of 250 herbaceous plant species, 44 of which were classified as exotic. While no influence of recent disturbance on community composition was detected, past land use influenced species richness for all plant groups examined. General linear models indicated that herbaceous, native, and forest species richness was highest in historically partially cleared sites; while exotic and invasive species richness was greatest in historically cleared sites. Non-metric multi-dimensional scaling (NMS) ordination was used to identify associations between community assemblage, land use history, and dispersal mechanism. The two axes of the NMS ordination explained 79.2% of the variation in the data, and indicated that woodlots completely cleared in the past were associated with wind dispersed species indicative of disturbed habitats. In contrast, historically uncleared sites contained short-distance dispersed species indicative of rich woods. Although no effects of recent disturbance were detected, the long lived impacts of past land use and the increase of exotic and invasive species in historically cleared indicate that undisturbed woodlots should be considered of highest conservation importance.     

The usefulness of a long-term perspective in assessing current forest conservation management in the Apuseni Natural Park, Romania

The forest ecosystem of the Apuseni National Park (ANP) in NW Romania is recognized for its high species and genetic diversity and is protected through various conservation measures. As ANP is the most populated natural park in Romania, the focus is on the need for communities to manage, sustain and prosper by using, exploring and sustaining the natural resources. But what activities are the most appropriate for the conservation of a highly diverse natural forest? This paper presents results from a long-term ecological study using fossil pollen, microscopic and macroscopic charcoal and AMS¹⁴C dating on a site in the ANP in order to examine how the interaction between climate change, human activities and other disturbances have shaped the present protected landscapes over the last 5700 years in this part of the reserve. Results from this study show that the landscape in this region has been continuously forested over the last 5700 years BP, but the forest composition and structure have been dynamic throughout much of the time. In particular, distinct changes in forest composition have occurred over the last 700 years of the record. Fagus sylvatica was the major taxon between 5200 and 200 years BP and its dominance is associated with the highest forest stability. The formation of the current Picea abies forests started 400 years ago and spruce became the dominant forest species during the last two centuries as a result of selective forest clearance, intensive grazing, and more recently, plantations. This led to a large reduction in forest diversity, decline of F. sylvatica and local extinction of several species including Abies alba, Ulmus, Tilia, and Acer. Our results show the high conservation values of A. alba and F. sylvatica in the ANP. Current management practices that allow the anthropogenic activities of timber production and fast tree regeneration, usually involving the plantation of P. abies in this part of the ANP are not in keeping with the NATURA 2000 objectives of ensuring the persistence of the most vulnerable species and habitats.     

The functional structure of ectomycorrhizal communities in an oak forest in central France witnesses ancient Gallo-Roman farming practices

The activities of nutrient-mobilising enzymes secreted by ectomycorrhizas of sessile oak (Quercus petraea) have been measured in 24 plots in a forested area in central France where many rural Gallo-Roman settlements (first to fifth centuries AD) have been discovered. Data have been related with tree growth and soil chemical properties. Although soil near the past settlements is still enriched in N and P, this does not always correspond to the higher productivity of oak trees. However, when this is the case, the ectomycorrhizal community displays higher chitinase, protease and phosphatase activities (involved in N and P mobilisation from soil organic matter). A few specialised ectomycorrhizal fungal species are responsible for this adaptation to the long-lasting modification of soil conditions.     

衡阳市黄巢公园及周边地段开发规划

对规划设计的项目地域特征及现状进行分析,探讨了如何利用此地段的历史因素与自然因素,突出"怀古"与"思今"的规划主题,创造独具魅力的景观环境。     

什么是农民,什么是土地——农民分化视野下的土地问题

本文简单梳理了近百年农民由分化到齐平再到分化的生存状态,并根据在豫南周村的调研资料详细探讨了当下农民的分化情况.本文将当下农民划分为"纯务农农民"、"半工半农农民"和"非农农民","非农农民"又可分为"常年在外务工农民"和"在外经商农民",这四类农民对土地的依赖依次降低,因此在相关土地制度设计时要予以考虑,要保障占农民...     

Impact of attendees’ motivation and past experience on their attitudes toward the National Cherry Blossom Festival in Washington,D.C

Motivation and past experience have been frequently examined in the literature. However, most studies have examined the two concepts separately in a destination loyalty model, and few have made analyses at three levels: univariate or multivariate analysis, structural equation model (SEM) analysis, and SEM multi-group analysis. This study examined the two concepts at the three levels in the context of a cherry blossom festival, based on data collected from 950 visitors. Results indicate that repeaters were more motivated by the blossoms and more positive in their cognitive, affective, and behavioural attitudes toward the festival than were first timers. However, first timers exhibited a stronger relationship between motivation and cognition and between cognition and loyalty than repeaters. It seemed that cognition played a central role in the loyalty model, thus, it is necessary to place priority on increasing the public’s knowledge/awareness about the festival. Theoretical, methodological, and managerial implications are discussed.     

价格认知对不同类型农民消费者购买意愿的影响机理——基于辽宁省调查数据的分析

将农民分为远离城市的全职农民、靠近城市的兼职农民和在城市生存的农民3类。在Fishbein合理行为模型的基础上,加入价格认知、过去的购买行为2个变量,从心理认知层面对不同类型农民价格认知如何影响购买意愿进行结构方程分析。结果表明:1主观规范、个体态度、过去的购买行为对购买意愿均有直接的正向影响,并且在3类农民中,过去的购买行为影响最大,主观规范和个体态度的影响存在差异。2主观规范还通过个体态度对购买意愿产生正向影响。3远离城市的农民的价格认知通过个体态度间接对购买意愿产生正向影响,靠近城市的兼职农民的价格认知主要通过主观规范间接对购买意愿产生正向影响,在城市生存的农民的价格认知通过个体态度和主观规范间接对购买意愿产生正向影响。     

Soybean yield physiology and development of high-yielding practices in Northeast China

Soybean (Glycine max (L.) Merrill), one of the most important crops in China, has been known to man for over 5000 years. Soybean production in China increased from 7.5 million Mg in 1978 to 26 million Mg in 2005. The largest production areas in China are in the Northeast China's three provinces, where soybean is spring seeded and grown as a full-season crop. Development of research programs and rapid adoption of technologies emerging from agricultural research by producers including a better understanding of the physiological processes of growth and development, improved cultivars and cultural practices, and a higher demand of the soybean processing industry has contributed much to the upward trend in on-farm yield and total production. Research on leaf area index (LAI), light interception and canopy photosynthesis, source–sink relationships, phytohormones, environmental stresses (drought and cold damage), development of cultivar selection, tillage systems, cultivation practices as well as weeds, insects and diseases during the last half century in Northeast China were reviewed. The intent is to document a summary of the understanding of soybean physiology and culture for high yields mainly from Chinese scientists’ perspective.