Dinâmica de crescimento em Tabebuia rosea (Bertol.) Bertero ex A.DC. (Bignoniaceae): fenologia apical e cambial caulinar

O estudo da dinâmica de crescimento em espécies arbóreas permite melhor compreender a adaptação de uma espécie ao ambiente em que se desenvolve. Dados dessa natureza ainda são escassos no Brasil considerando-se a diversidade de espécies e fitofisionomias existentes. Esse tipo de estudo tem sido apontado como de grande relevância principalmente diante das situações atuais de desmatamento e mudanças climáticas, que exigem recuperação de áreas degradadas e prospectar como as espécies nativas sobreviveram diante deste ambiente de aceleradas mudanças. Nesta perspectiva, o objetivo deste trabalho foi investigar a dinâmica de crescimento de Tabebuia rosea, por meio do monitoramento mensal da fenologia apical e cambial caulinar e dos teores dos pigmentos fotossintetizantes: clorofilas a, b, totais e carotenoides. Os resultados obtidos foram correlacionados entre si e também com a sazonalidade das variáveis ambientais: temperatura, precipitação e fotoperíodo. No que se refere aos teores dos pigmentos fotossintetizantes, foi também avaliada as oscilações observadas nas folhas obtidas nas orientações geográficas: norte, sul, leste e oeste. O trabalho foi desenvolvido no Campus da Universidade do Estado do Rio de Janeiro, RJ, Brasil. A fenologia dos ápices caulinares foi acompanhada mensalmente a partir de observações qualitativas e quantitativas em 15 indivíduos. As amostras contendo a zona cambial foram obtidas por método não destrutivo e processadas segundo as técnicas usuais em histologia vegetal. A extração dos pigmentos fotossintéticos foi realizada em acetona 80%, com posterior centrifugação e análise ao espectrofotômetro em diferentes comprimentos de onda. Tabebuia rosea apresentou aumento na largura da zona cambial em número de camadas celulares e em micrômetros, diminuição do diâmetro radial da célula inicial fusiforme e aumento em micrômetros da camada de células em processo de alongamento e diferenciação do xilema secundário no mesmo período em que a copa das árvores estava ocupada por folhas adultas e com os teores mais elevados de clorofilas nas folhas, coincidindo com o período em que as variáveis ambientais apresentaram-se elevadas, corroborando os resultados já obtidos para outras espécies nativas da Mata Atlântica se desenvolvendo no estado do Rio de Janeiro. A maior concentração de carotenoides foi observada no período em que as variáveis ambientais apresentavam índices elevados e as plantas estavam mais expostas à radiação luminosa, possivelmente em função de um maior investimento em fotoproteção. Cabe destacar que o lado oeste da copa das árvores mostrou uma tendência em apresentar maiores concentrações dos pigmentos fotossintéticos estudados, resultado ainda não observado na literatura até o momento, o que pode ser uma estratégia da espécie em compensar níveis baixos de radiação solar com acúmulo de clorofilas.

Analysis of the retailer value chain segment in five governorates

This study is the third output of the SDC-funded “Improving Employment and Income through Development of Egyptian Aquaculture” (IEIDEAS), a three-year project being jointly implemented by the WorldFish Center and CARE International in Egypt with support from the Ministry of Agriculture and Land Reclamation. The aim of the study is to gather data on the retailer segment of the aquaculture value chain in Egypt, namely on the employment and market conditions of the women fish retailers in the five target governorates. In addition, this study provides a case study in Minya and Fayoum of the current income levels and standards of living of this target group. Finally, the study aims to identify the major problems and obstacles facing these women retailers and suggest some relevant interventions.

开垦和放牧对内蒙古草原土壤碳库和温室气体通量的影响

本文采用野外观测和室内测定相结合的方法，研究了内蒙古草原两种主要的土地利用方式（开垦和放牧）对土壤碳库和温室气体通量的影响，结果如下： 1．内蒙古草甸草原开垦后30年后，与天然草原相比，在休闲年份0～20 cm土壤有机碳和土壤微生物量碳含量均没有显著下降，但开垦导致土壤易分解碳下降了24%。土壤易氧化碳受季节性水热因子的驱动，表现出明显的季节变化动态。因此，土壤易分解碳的较土壤碳库的其他组分对开垦更敏感，是表征土壤管理措施引起有机质变化的一个重要指标。 草原开垦后，土壤-植物系统氧化大气甲烷的能力明显提高，农田和天然草原CH4平均吸收通量分别是48.9 和 29.0 μg C m-2 h-1，开垦后增加了1.7倍。开垦没有改变CH4吸收通量 “夏季高秋季低” 的季节变化规律（由降水决定）;开垦使N2O的平均释放通量增加了47%，农田和天然草原N2O平均吸收通量分别是56.6 和 38.6 ugN m-2 h-1;开垦同时也增大了通量的变异幅度;但没有改变N2O季节变化规律，只是出现高峰的时间较天然草原推后约10天左右。 2．开垦后的农田土壤在模拟添加厩肥后，刺激了土壤微生物的呼吸代谢，使CO2的释放量增加了5-7倍。试验期间总体排放的CO2中，约60%来源于羊粪，40% 来源于土壤。两种土壤即羊草顶级草原土壤（高碳高氮）和冷蒿－小禾草退化草原土壤（低碳低氮），在CO2的释放总量和释放比例上都没有显著性差异。添加厩肥均造成两种土壤碳库的净碳损失，并且退化草原土壤（7.0%）的土壤净碳损失要大于羊草草原（2.6%）。说明与开垦后的高C土壤相比，在已经退化草原的低C土壤上施厩肥将趋向于土壤更大的净碳损失。 3．自由放牧22年后，羊草草原0～10 cm土壤有机碳、微生物量碳和易分解碳分别下降了14.1%、27.9%和22.0%;大针茅草原0～5 cm土壤有机碳和微生物量碳分别下降了27.6%和38.2%。两类草原土壤碳组分的季节变化受水热因子的驱动，大针茅草原季节波动出现高峰的时间较羊草草原迟。土壤微生物量碳在表征羊草草原和大针茅草原土壤碳素的动态变化时，要敏感于土壤总有机碳。放牧对冷蒿-小禾草草原土壤各碳素组分影响不明显。在表征放牧对冷蒿-小禾草草原土壤的影响指示上，MB-C/ Org-C和Lab-C/ Org-C要比MB-C和Lab-C更加敏感。这说明在研究放牧对草原土壤碳库影响时，不同的草原类型应使用不同的指标来表征其变化。 内蒙古羊草草原是大气CH4的汇，自由放牧增加土壤对CH4的吸收。CH4平均吸收通量增加了27%，但CH4吸收的季节变化形式没有改变;放牧使。自由放牧还增大了N2O的排放通量，将原来N2O源、汇的双重功能改变为单一的源功能;放牧使N2O平均释放通量增加了1倍;放牧显著增加了羊草草原向大气排放CO2的量（p<0.05），并且年度排放量范围也有所增大。 4．草原羊尿斑土壤的pH和NH4+浓度在施后显著升高，但土壤微生物C和N没有明显变化，尿斑N素会发生大量的流失。粪斑和厩肥斑中各有46%和27%的N素分解后转移到植物中。羊草种群斑块上粪尿斑引起CO2和N2O通量的变化，要大于星毛委陵菜种群斑块。与植被类型的影响相比，羊粪尿斑尤其是尿斑对温室气体通量的影响更大。尿斑既降低了土壤对CH4的吸收，又增加了CO2和N2O的释放，使粪尿斑上相当于CO2的净排放量比对照土壤增加了15%。 在内蒙古草原中等放牧条件下，家畜粪尿斑在放牧草地上的覆盖面积约只有2%，与未被家畜排泄物覆盖的草原土壤 相比，粪尿斑对内蒙古草原温室气体总体收支产生的影响可以忽略不计。因此内蒙古草原地区温室气体减排措施的重点，应放在家畜的食性食量对温室气体的影响以及厩肥的科学利用上。但随放牧强度的加大，家畜排泄物覆盖草地的面积将大大增加，加之放牧生态系统中家畜瘤胃代谢产生的的大量温室气体，其对草原温室气体的核算将会产生的影响也是不容忽视的。

The role of satellite lakes in conservation of fish species diversity in the Lake Kyoga basin

Lakes Victoria and Kyoga had, a diverse fish fauna, which was important as food for local population and valuable in scientific studies. Over the past twenty years, the diversity of fish in these lakes had declined due to over-exploitation, introduction of new fish species including the piscivorous Nile perch and degradation of fish habitat. Studies of satellite lakes in the Victoria and Kyoga lake basins suggested that some of these lakes harboured species which had been lost from the main lakes. In order to better understand the extent, to which these satellite lakes may serve as refugia, a faunal survey was undertaken to determine the distribution and nature of the taxa found. Seven satellite lakes and the eastern end of the main Lake Kyoga adjacent to these minor lakes were surveyed over a two-year period for fish species diversity. A total of 68 fish species were recorded of which 41 were haplochromines. Almost all the native non cichlids which occurred in the main lakes (Victoria and Kyoga) before the Nile perch upsurge recorded. Lakes Nawampasa, Gigati, Kawi, Agu and Nyaguo had the highest fish species and trophic diversity. The trophic diversity of haplochromines (based on Shannon Weaver Index) was highest in Lake Nawampasa (1.28), followed by Gigati (1.25), Kawi (1.18), Agu (0.8), Lemwa (0.81), Nyaguo (0.35) and was lowest in the main Lake Kyoga. Potential threats to these lakes were from collectors of ornamental fish species, especially the haplochromines, the spread of the predatory Nile perch and the water hyacinth, which are already in Lake Kyoga, and the destruction of macrophytes through harvesting of papyrus and reclamation for agriculture. The human population around these lakes harvested the fishes for food but the levels of exploitation were still low because the lakes were adjacent to main Lake Kyoga, the major supply of fish. Ornamental fish dealers were encouraged to start captive breeding of the fish for export to reduce pressure on the lakes and demonstrations for breeding were set up at FIRI in Jinja. Meetings and seminars were held with some of the communities living around the lakes sampled and the importance of fish species found in these lakes and the dangers of destructive practices discussed. Representatives of all taxa of fish caught from the lakes were preserved, catalogued and stored in the FIRI Museum. Results from this survey support the motion that these satellite lakes are important refugia for endemic diversity. Based on survey, we recommend that SaIne of these lakes like Nawampasa, Gigati, Kawi, Agu and Nyaguo could be designated as conservation areas of species threatened in the main lakes. One of the factors that seem to have prevented the spread of Nile perch into Kyoga Minor lakes seems to have been the presence of extensive swamps around these lakes and the low oxygen levels that exist in these habitats. Clearing of swamps and vegetation that separate Kyoga minor lakes from the main lake should be avoided to prevent Nile perch from spreading into these lakes.

东北3省人类活动与水土流失关系的演进

受人类对土地过度垦殖及不合理耕作利用的影响,水土流失正在成为制约我国东北地区耕地可持续利用和粮食生产的主要因素。在对历史资料甄别与整理的基础上,分析近代以来东北3省区人口、土地利用变化及其与水土流失关系的演变。结果表明:到20世纪中期,东北地区人口压力达到60~70人/km2,伴随着生活方式的转变,机械化技术的应用,林草湿地被垦殖,森林覆盖率降到30%,垦殖率达30%,使区域性水土流失问题日益严重。

神府东胜煤田复垦区土壤入渗特性的试验研究

土壤入渗性能是最基本的土壤物理特性之一。复垦区土壤的结构组成复杂,入渗特性有别于非矿区土壤。本文以神府东胜煤田马家塔复垦区为研究对象,利用圆盘入渗仪分别测定了复垦区乔木、林地、荒地、灌木林地和草地的土壤入渗特性,用经典统计学方法对复垦区土壤入渗性能的空间变异性进行了分析。实测结果表明,不同土地利用方式下的土壤入渗特性有较大的差异;在测定范围内,乔木林地、荒地、草地和灌木林地的稳定入渗率均表现出0 cm>—3 cm>—15 cm的规律性,其中草地稳定入渗率随吸力的变化更明显。研究表明:乔木林地稳定入渗率和累积入渗量的变异系数分别为0.58和0.49.属于中等变异。

宁夏黄土区不同植物群落土地利用方式对土壤质量的影响

本文研究了宁夏南部山区典型植物群落土地不同利用方式下土壤质量的变化。结果表明:(1)典型长芒草群落土地,开垦地比封禁地土壤有机质、全氮、全磷、速效氮、速效磷、速效钾养分含量明显降低,降低幅度分别为19.5%、20.1%、17.6%1、3.0%、77.8%和47.5%。脲酶活性为开垦地>封禁地,蔗糖酶则表现为封禁地>开垦地,中性磷酸酶差异不明显。(2)铁杆蒿群落土地三种利用方式下:放牧地土壤有机质、全氮、全磷、速效钾等养分含量较封禁地与开垦地有一定幅度的增加;放牧地的土壤脲酶、蔗糖酶和中性磷酸酶活性均高于封禁和开垦的同土层土壤,封禁地的脲酶和蔗糖酶次之,开垦地的脲酶和蔗糖酶活性最小,开垦地的中性磷酸酶活性高于封禁地。脲酶活性在土层之间变化较小,最高为放牧地表层177.6 mg/(kg.h),最低为开垦地表下层114.5 mg/(kg.h),蔗糖酶活性层次之间变化明显,其中放牧地表层为表下层的3倍左右。长芒草群落土壤表层各级微团聚体表现为封禁地远大于开垦地,铁杆蒿群落土地不同利用方式下各级微团聚体表现不同,结构系数表现为表层>表下层,保持率则为表层<表下层。结构系数与保持率均表现为封禁地>放牧地>开垦地。(3)在...

Spatial patterns and driving forces of land use change in China during the early 21st century

Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science (LCS) in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km x 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the "Grain for Green" policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of "Western Development", "Revitalization of Northeast", coupled with rapidly economic development during this period.

Impacts of LUCC processes on potential land productivity in China in the 1990s

Using meteorological data and RS dynamic land-use observation data set, the potential land productivity that is limited by solar radiation and temperature is estimated and the impacts of recent LUCC processes on it are analyzed in this paper. The results show that the influence of LUCC processes on potential land productivity change has extensive and unbalanced characteristics. It generally reduces the productivity in South China and increases it in North China, and the overall effect is increasing the total productivity by 26.22 million tons. The farmland reclamation and original farmlands losses are the primary causes that led potential land productivity to change. The reclamation mostly distributed in arable-pasture and arable-forest transitional zones and oasises in northwestern China has made total productivity increase by 83.35 million tons, accounting for 3.50% of the overall output. The losses of original farmlands driven by built-up areas invading and occupying arable land are mostly distributed in the regions which have rapid economic development, e.g. Huang-Huai-Hai plain, Yangtze River delta, Zhujiang delta, central part of Gansu, southeast coastal region, southeast of Sichuan Basin and Urumqi-Shihezi. It has led the total productivity to decrease 57.13 million tons, which is 2.40% of the overall output.

Study on spatial pattern of land-use change in China during 1995-2000

It is more and more acknowledged that land-use/cover dynamic change has become a key subject urgently to be dealt with in the study of global environmental change. Supported by the Landsat TM digital images, spatial patterns and temporal variation of land-use change during 1995 -2000 are studied in the paper. According to the land-use dynamic degree model, supported by the 1km GRID data of land-use change and the comprehensive characters of physical, economic and social features, a dynamic regionalization of land-use change is designed to disclose the spatial pattern of land-use change processes. Generally speaking, in the traditional agricultural zones, e.g., Huang-Huai-Hai Plains, Yangtze River Delta and Sichuan Basin, the built-up and residential areas occupy a great proportion of arable land, and in the interlock area of farming and pasturing of northern China and the oases agricultural zones, the reclamation I of arable land is conspicuously driven by changes of production conditions, economic benefits and climatic conditions. The implementation of "returning arable land into woodland or grassland" policies has won initial success in some areas, but it is too early to say that the trend of deforestation has been effectively reversed across China. In this paper, the division of dynamic regionalization of land-use change is designed, for the sake of revealing the temporal and spatial features of land-use change and laying the foundation for the study of regional scale land-use changes. Moreover, an integrated study, including studies of spatial pattern and temporal process of land-use change, is carried out in this paper, which is an interesting try on the comparative studies of spatial pattern on change process and the change process of spatial pattern of land-use change.

STUDY ON THE SPATIAL PATTERNS OF LAND-USE CHANGE AND ANALYSES OF DRIVING FORCES IN NORTHEASTERN CHINA DURING 1990-2000

Land-use change is an important aspect of global environment change. It is, in a sense, the direct result of human activities influencing our physical environment. Supported by the dynamic serving system of national resources, including both the environment database and GIS technology, this paper analyzed the land-use change in northeastern China in the past ten years (1990 - 2000). It divides northeastern China into five land-use zones based on the dynamic degree (DD) of land-use: woodland/grassland - arable land conversion zone, dry land - paddy field conversion zone, urban expansion zone, interlocked zone of farming and pasturing, and reclamation and abandoned zone. In the past ten years, land-use change of northeastern China can be generalized as follows: increase of cropland area was obvious, paddy field and dry land increased by 74. 9 and 276. 0 thousand ha respectively; urban area expanded rapidly, area of town and rural residence increased by 76. 8 thousand ha; area of forest and grassland decreased sharply with the amount of 1399. 0 and 1521. 3 thousand ha respectively; area of water body and unused land increased by 148. 4 and 513. 9 thousand ha respectively. Besides a comprehensive analysis of the spatial patterns of land use, this paper also discusses the driving forces in each land-use dynamic zones. The study shows that some key biophysical factors affect conspicuously the conversion of different land- use types. In this paper, the relationships between land- use conversion and DEM, accnmlated temperature(>= 10 degrees C) and precipitation were analysed and represented. We conclude that the land- use changes in northeast China resulted from the change of macro social and economic factors and local physical elements. Rapid population growth and management changes, in some sense, can explain the shaping of woodland/grassland - cropland conversion zone. The conversion from dry land to paddy field in the dry land - paddy field conversion zone, apart from the physical elements change promoting the expansion of paddy field, results from two reasons: one is that the implementation of market-economy in China has given farmers the right to decide what they plant and how they plant their crops, the other factor is originated partially from the change of dietary habit with the social and economic development. The conversion from paddy field to dry land is caused primarily by the shortfall of irrigation water, which in turn is caused by poor water allocation managed by local governments. The shaping of the reclamation and abandoned zone is partially due to the lack of environment protection consciousness among pioneer settlers. The reason for the conversion from grassland to cropland is the relatively higher profits of fanning than that of pasturing in the interlocked zone of farming and pasturing. In northeastern China, the rapid expansion of built-up areas results from two factors: the first is its small number of towns; the second comes from the huge potential for expansion of existing towns and cities. It is noticeable that urban expansion in the northeastern China is characterized by gentle topographic relief and low population density. Physiognomy, transportation and economy exert great influences on the urban expansion.

淤泥质潮滩地貌的遥感研究－以苏北辐射沙洲海岸为例

本文以具有典型特征的苏北淤泥质潮滩海岸作为研究区，利用1975-2003年间14景覆盖该地区的Landsat和SPOT卫星影像作为主要数据源，结合地面调查和验证工作，在遥感影像处理和地理信息系统分析技术的支持下，对区内潮滩、岸线、水边线和盐沼植被等进行遥感解译，分析苏北辐射沙脊群和沿岸地貌的空间分布特征和动态演变趋势。研究结果表明：苏北辐射沙脊群海域的潮汐水位过程的不同步现象普遍存在，限制了常规遥感数据在苏北潮滩地貌研究中的适用范围和解译精度；在人工判别的辅助下，多光谱遥感的非监督分类方法可以有效解译淤泥质潮滩的水边线；利用修改型土壤调整植被指数（MSAVI）可以较好地提取潮滩上的盐沼植被信息；苏北沿岸潮滩的快速淤长促进了盐沼植被带向海侧快速扩展，近年来持续的潮滩围垦工程则不断从陆侧侵占盐沼植被带，使盐沼植被带宽度减小乃至消失；在大规模人类活动和自然条件的共同影响下，苏北辐射沙脊群海岸的岸线发育趋于平直化，无序的潮滩围垦项目使得可垦滩地资源被过度消耗；1975～2002年间，研究区北部和南部沿岸的高潮滩整体上处于淤长状态，中部沿岸潮滩和离岸沙洲高潮滩则被大面积侵蚀；1999年以来，研究区内低潮滩部位开始形成有序排列的滩面地物，并表现出逐年大面积蔓延的趋势，可能是滩涂紫菜养殖区扩展的结果。

浑善达克沙地的光释光测年研究

Eolian deposits are important for paleoclimatic and paleoenvironmental reconstructions in arid and semi-arid regions. In China active sand dunes mainly occur in the northwest inland basins ,whereas deserts dominated by semi-stabilized sand dunes are mainly distributed in the northeastern semi-arid and sub-humid regions. Recent studies indicate that prompt desertification in northeastern China has been serious.Thus northeastern China is one of the key sites on which to study the history of past environmental changes. However, previous studies focused mainly on big scale environmental changes, whereas changes in the environment during the Holocene have not been well studied. This research uses optically stimulated luminescence to date fossil sand dunes in Hunshandake desert in order to offer the accurate time scale to reconstruct the history of eolian activity in the region. Furthermore,we compare this region with other deserts in northern China.The main conclusions is following: Active dune formation in northeastern China lasted from the Last Glacial Maximum to about 10 000aB.P. It has also been shown that the warm climate of the Holocene was interrupted by a cold/dry dune-forming episode at about 2 800-1 800aB.R. The Holocene Optimum occurred between 10 000-2 800aB.R, and a later warm/humid dune stabilization phase lasted from at least 1 900-1 500aB.R. The youngest age on the uppermost soil unit in Hunshandake desert yielded an age of 90aB.P.,on which the younger sand deposits,and the youngest age on the sand in Hulun Buir desert is 40aB.R. The mean annual precipitation of these regions is up to 450 mm. But these deserts locate in middle latitudes regions, where the climate is sub-humid, semi-arid continental monsoon.Under present climatic conditions, there should be no active sand dunes in northeastern China. So the appearance of active sand in northeastern China is not due to natural factors,but to extensive land reclamation and cultivation.

热察绥地区过去300年土地利用覆被变化

The historical land use and land cover changes is one of the key issues in LUCC research. However, the achievement of China in this field doesn't match her position in the world yet. And the reliability of the quantitive records in Chinese historical literature, the basic data for historical land use research, has been doubted. This research focuses on Re-Cha-Sui, a typical area for the farming-pastoral region in the north of China, to make a detailed case study in this field. Based on a deep mining and calibration on the data from massive historical documents and land-use surveys, the author gives a detailed analysis on the administrative region evolution, historical population dynamics, reclamation policy, and the land statistic system. According to textual researches, parallel validation and physical geographical analysis, a unified land use series for recent 300 years, which founded on the results of modern land-use surveys, is constructed. And the thematic maps on the cultivation index for different counties in several temporal sections are plotted. Based on the endeavor above, the dynamic of forest and steppe is reconstructed as well. The temporal-spatial patterns of land use/land cover changes in the area is analyzed. And the influence of different driving forces are discussed. The main conclusions of the research are as followed: 1. The quantitive records in literatures on Re-Cha-Sui area are reflection of real amounts of croplands. It is practical to reconstruct a result comparable with the modern land-use surveys, based of a deep mining and considerate validation on historical documents. The unexceptional negative attitude towards the numerical records in historical documents is unnecessary. 2. In recent 300 years, 3 climax of reclamation appeared in Re-Cha-Sui area and altered the pure pastoral area into a farming-pastoral region. The interval were respectively the early time till mid time of the Qing dynasty, the end of the Qing dynasty till early time of the Republic of China(ROC), and the time after A.D. 1949. After the first expansion, the area of cropland in this region reached 2.0 million ha. Among them, Guisui area, which was most densely cultivated, had a cultivation index over 30%, which is similar with modern situation. The second expansion covered broader area, and the amount of cropland reached 3.5 million ha. The increase of farming area after 1949 is due to the recultivation of abandoned farmland. The current area of cropland in this region is 5.6 million ha. In the southern area where the land was reclaimed early, the amount on of the cropland has some fluctuation in 300 years. While in the new reclaimed area in the north, the area of cropland has kept the trend of increasing. 3. Due to the different natural conditions, most forests in Re-Cha-Sui area distribute in the mountain area of North Hebei province, and the upland of West Liaoning province, especially the former, which has a forest coverage near 70%. However, most of these forests were destroyed before the end of the Qing dynasty. In 1949, the natural forest near Chengde was nearly cleared up. They were partly renewed after 1949 due to plantation. 4. In the steppe zone such as northern Rehe, Suiyuan and Chahar, the area of steppe has a negative correlation with that of cropland. With the expansion of cropland, the percentage of steppe has shrunk from over 80% to 53%. In the mountain area of North Hebei province, steppe expanded with the shrinkage of forest, though cropland was expanding. The percentage once reached 60%, and then fell with the renew of forest. However, in the upland of West Liaoning province, the steppe shrink slowly from original 50% to current 26%, with the expansion of cropland. 5. The land use and land cover change in Re-Cha-Sui area in recent 300 years is driven by various factors, including human dimensions such as population, policy of the government, disorder of the society, cultural tradition, and natural factors such as climate change and natural disasters. Among them, pressure from surplus population is the basic driving force.