With Village Yaoledianzi,an ecological demonstration village in the ecotone between agriculture and animal husbandry in north China as an example,the land use history from 1950 to 1999 has been reconstructed on the basis of PRA,GPS and field measurement.The characteristics of the changes in land use has also been analyzed by spatial overlay in GIS.Factor analysis and stepwise regression are used to probe into effects of human activities on land use.It is found that before 1985 cultivated land and sand land expanded both at the cost of grassland;land use turned in reverse and to be more logical after 1985.

Carrying capacity of the land in Gezhen′er watershed has been calculated.The results show that all the farmland with slope exceeding 15° should be surrendered to forestry,and the acreage of basic cropland per capita should be kept no less than 0.066 hm 2.In this case,after returning land for farming to forestry,the maximum land carrying capacity of the watershed is 2 802 persons,much higher than the predicted population,and the remaining farmland is adequate to ensure food supply.Thus the policy of returning land for farming to forestry can be implemented.

The composition,growth and withering,dominant species and eco niches of the weeds in rice fields in Shenyang were investigated.The results showed that Echinochloa crusgalli,Bidens frondosa,Ammannia arenaria,Ludwigia prostrata,Eleocharis acicularis,Myosoton aquaticum,Rorippa islandica and Centipeda minima.Echinochloa crusgalli and Bidens frondosa are the main eco damaging populations in paddy fields of the area.Based on the calculation of time,horizontal and vertical breadth eco niches of the weed community, Echinochloa crusgalli and Bidens frondosa are the dominant species.Their niches overlap extensively.Mono application of barnyardgrass killing herbicide can induce spreading of broadleaf weeds such as Bidens frondosa .

By making reference to the latest accomplishments in the study of comprehensive evaluation of regional sustainable development at home and abroad,according to AHP,an index system and a measuring model for comprehensive evaluation of sustainable development of ecological demonstration zones has been designed,proceeding from the following six aspects:economic development,social development,resources and ecological security,sustainable development capacity,sustainable development degree and system coordination.The results of a quantitative evaluation of the development of Baota District of Yan′an in the period from 1992 to 1999 show that the sustainable development of Baota District is,though increasing steadily in level,still in the stage of weak sustainable development,and the regional development system is not well coordinated.

Land treatment system is an effective technology for de harming and recycling wastewater in arid semiarid ecotone region.The design and operation of the land treatment system in Huolinhe Mining Field,Inner Mongolia showed that this region was well conditioned for extension of the land treatment technology,which should be based on recycling wastewater through slow rate filtration.Treatment of wastewater has to be combined with ecological construction.The application of wastewater is helpful in increasing stability of the complex eco system with mosaic structure,accelerating canopy closure and timber growing stock of the artificial forests,and improving the eco environment of the arid semiarid region.The social,economic and environmental benefits of the land treatment system are very remarkable.

Effects of enhanced UV-B radiation on germination of maize and growth of its seedlings was investigated.The results show that compared with the maize growing under natural light last year and this year,the germination and seedling growth of maize under enhanced UV-B radiation last year was decreased significantly,but the effects this year was not so significant on the seeds from the crop growing under enhanced UV-B radiation last year.The results of the experiment also show that maize seedlings out of the seeds yielded from the crop exposed to enhanced UV-B radiation last year have significantly more flavonoid content than those always growing under natural light,which might be in part attributed to the adaptation of the crop with the enhanced UV-B radiation.

Effects of light stress on function and structure characteristics of photosynthetic membranes (thylakoid membranes and PS Ⅱ particles) in leaves of wheat( Triticum aestivum L.cv.Yangmai No.5)seedling were studied by measuring changes in O 2 evolving activity,fluorescence emission spectra and membrane protein polypeptide components. Results showed that light stress (2 500 μmol·m ^-2 ·s ^-1 ) induced decline of electron transport activities of thylakoid membranes and PS Ⅱ particles and decrease in fluorescence emission intensities. When PS Ⅱ particles in wheat leaves were illuminated with higher light intensity (2 500 μmol· m ^-2 ·s ^-1 ) at 25 ℃, the extrinsic protein (OEC 33 000,23 000,17 000 u) and the chlorophyll binding protein CP43 of PS Ⅱ complex were degraded. It seems that OEC 33 000 u polypeptide plays a role in regulating stabilization of the PS Ⅱ reaction center structure under light stress.

Autumn irrigation is a particular irrigation system designed to wash soil salt into deeper layers and retain a higher water content for the following spring crops in the Hetao Irrigation District of China.The effects of autumn irrigation on leaching of soil salt in different types of farmland in the Hetao Irrigation District are discussed on the basis of field determination of amounts of soil salt leached in 5 types of farmland.Before irrigation,the soil moisture content was the highest in the cabbage field and the lowest in the sunflower field. Autumn irrigation increased soil moisture in all the fields,showing no significant difference between them.After the autumn irrigation,the leaching of soil salt from the soil profiles was in a decreasing order of surface layer(0-40 cm),middle layer(40-80 cm)and deep layer(80-120 cm)in all the fields except the sunflower field,and in a decreasing order of cabbage field,sunflower field,maize field,spring wheat maize inter planting field and spring wheat field.It can be concluded that the leaching of soil salt during the autumn irrigation in fields without crops is significantly correlated with the increase in soil moisture content in 0-100 cm( r =0.990 2),but not with the content of salt in the soil before irrigation.

Fertilities of the soil samples gathered from 79 soil sampling points in the saline soil region in the North China plain in 1999 were compared with those collected in 1980 of the same points.The results showed that the amount of organic matter,total N and Olsen-P in 1999 increased by 41%,102% and 351% compared with that in 1980,respectively.However,NH 4Ac-K decreased by 38%.The reasons of the changes were mostly related to increase in input of N and P fertilizer and inadequacy in input of K fertilizer.Nutrient content was also highly related to soil texture. But,as a result of human activities,the nutrient contents tended to be uniform.The correlative analysis between organic matter content and salinity of the surface layer showed significant negative correlation in soils with coarse texture;but not as significant in other cases.

Contents of heavy metal elements of As,Cd,Co,Cr,Cu,Hg,Fe,Mn,Mo,Ni,Pb and Zn in soils of vegetable greenhouses 1,5,8 and 11 years old and a plot of conventional cultivated dryland(CK)have been investigated.The results showed that the content distributions of heavy metal elements within the soil layer(0-40 cm in depth)of the greenhouses of same age varied slightly;different heavy metal elements showed different tendencies in variation;generally,the contents of heavy metal elements in the soils of the greenhouses utilized for 5,8 and 11 years were higher,but not yet up to the extent of being called pollution;High rate of fertilization(compound fertilizers)is considered as the main reason for the increases in contents of heavy metal elements in the soils of these greenhouses.

Effects of sodium borate,potassium sulfate,manganese sulfate,magnesium sulfate,zinc sulfate and cobalt sulfate on nitrate contents in vegetable have been studied by pot experiment with Brassica chinensis .The results showed that nitrate contents in Brassica chinensis decreased by 14.84%-19.56% after application of sodium borate for 20 days,and also decreased significantly by using K、Mn、Mg、Zn and Co.Nitrate content decreased by 18.96% 10 days after application of zinc sulfate and by 21.42% 20 days after application of potassium sulfate.Application rate of the mineral elements showed significant effects on the accumulation of nitrate in Brassica chinensis .

Chinese agriculture is displaying such new tendencies in its development after entering the 21st century,as modernization,industrialization,structural optimization,standardization,informatization and ecologicalization.Under the background of the globalization of the world economy and China entering WTO,agricultural ecology in China is facing new challenges and tasks such as:(1)ecological issues during agricultural restructuring;(2)agricultural biological security;(3)food safety and eco agriculture construction;(4)protection of agricultural resources and biodiversity;(5)agro ecological management and ecological compensation;(6)eco environmental construction and restoration in agricultural and rural areas;(7)ecological issues in the process of migration of agricultural population and urbanization;(8)agro ecological economy and sustainable development in poor rural areas.

Since the 1980s,national park and nature reserve planning has entered a new phase in both ideology and practice.The progresses in the research of nature reserves of the world in association with their cultural value,funds,native people,scientific basis and planning are discussed.It has been pointed out that there tends to be a new direction for construction of and research on nature reserves of the natural ecological type to maintain and protect ecosystem integrity. 更多还原 AbstractFilter('EnChDivSummary','ChDivSummaryMore2','ChDivSummaryReset2');

Acute toxicity of pesticides to birds was described.Their toxicity to different birds and toxic effects of pesticides of different kinds and formulations on birds were also discussed.On such a basis,safety of pesticides to birds was evaluated.

On the basis of the current situation of the industry development in Rizhao City,a preliminary idea of developing an eco industrial park in Rizhao and its incubation mechanism have been proposed.

Sustainable utilization is now being considered as a leading thought and a common principle in regard to ecological system of wetland.The environment problem in wetland utilization has also seriously affected the equilibrium of related regional ecosystem.It is intended to provide a systematic pathway to find a reasonable measure for sustainable utilization of wetland in Lixiahe region.The present utilization of wetland has resulted in some serious environment problems in the region,including shrinkage of the area of wetland,frequent natural disasters,deterioration of the environment,serious pollution caused by production and domestic life,degradation of wetland in function,decline in benefit of agricultural production and resultant decrease in farmers′ production input.For keeping the equilibrium of ecological system of wetland,the following strategies for sustainable utilization of wetland in the study area are put forward in light of the above problems:1)establish new indexes and standards for evaluation of sustainable utilization; 2)establish an early warning and analysis system; 3)increase overall comprehensive social,economic and environmental benefits,based on modern wetland ecological engineering technique.