Function and structure of the farmland shelterbelts in northern area of Shanxi Province

From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suitable tree species and design of logical shelterbelts structure. In order to provide a profound basis for the efficient establishment of shelterbelts, the study on function and structure of the farmland shelterbelts was conducted in Shuozhou and Datong areas, both are semi-arid areas in Northern Shanxi Province during 1996-2001. The wind-control effects of shelterbelts with different structures (close-spaced, wider-spaced, and widest-spaced) were investigated by portable wind vane and anemometer, wet and dry bulb thermometer, ground thermometer, glass service instrument. The results showed that the wind-control capacity of the shelterbelts during the leafing period should be thought as the criteria index in shelterbelts established. The wider-spaced shelterbelt that was made of 4-6 rows of trees, with a spacing of 2.0 m×3.0 m, had the best wind-control result.

Study on specifications of farmland shelterbelt net in Northeastern Plain of China

s: The farmland shelterbelts in Northeastern Plain of China have formed relatively complete net system. The func-tions of shelterbelt net in omnibearing wind check and prevention of frostbite as well as the field of integrated climate effect within shelterbelt net were analyzed, through located observation of meteorological factors. Within the shelterbelt net, the area with more than 10% efficiency of omnibearing wind check was determined as benefited area. The analysis of yield and quality of crops indicated that the sheltering range of shelterbelt net was 25 times tree height. The mature heights of the various varieties of poplar composed the shelterbelts were determined according to their height growth. Based on the comprehensive analysis above, the suitable size of farmland shelterbelt net in Northeastern Plain of China was decided to be 400 m×400 m.

A Method for Spatial Heterogeneity Evaluation on Landscape Pattern of Farmland Shelterbelt Networks:A Case Study in Midwest of Jilin Province,China

On the basis of landscape ecology, combining the Spot 5 high resolution satellite imagery with GIS, a method evaluating the spatial heterogeneity of shelterbelts distribution at landscape scale is put forward in this paper. The distance coefficients of reasonable and existing landscape indexes of farmland shelterbelt networks were com-puted, and then through the classification of the distance coefficients, and the establishment of evaluation rules, the spatial heterogeneity of farmland shelterbelts was evaluated. The method can improve the evaluating system of previ-ous studies on shelterbelts distribution, resolve the disadvantages of lacking spatiality of overall evaluation, and make the evaluation results have more directive significance for shelterbelt management. Based on this method, spatial het-erogeneity of shelterbelt networks was evaluated in the midwest of Jilin Province, China. The results show that the re-gions with fewer shelterbelts and no closed network account for 34.7% of the total area, but only 4.9% of the area has relative reasonable pattern of shelterbelt networks. Many problems exist in the distribution pattern of shelterbelts, therefore, much attention should be paid to construct farmland shelterbelts in the study area.

An overview of the “Three-North” Shelterbelt project in China

The ＂Three-North＂ Shelterbelt is the largest and most distinctive artificial ecological engineering project in China. It has been conducted since November 25, 1978 in the ＂Three-North＂ （i.e., Northeast China, North China and Northwest China） regions. In this study, the background and the essential benefits of the ＂Three-North＂ Shelterbelt project are summarized. The basic status and future development of the ＂Three-North＂ Shelterbelt project are also studied. As well, we tried to discuss the problems existing in the current shelterbelt system and the strategies to conduct this ecological project rationally.

Protection efficiency assessment and quality of coastal shelterbelt for Dongshan Island at the coastal section scale

The coastal shelter forest in China is under threat of destruction and degradation because of the impact of human activities. Protection efficiency assessment of the coastal shelterbelt is an important component of shelterforest remediation planning and sustainable management. In this study, a protection efficiency index （PEI） model was established using the projection pursuit method to assess the protective quality of the coastal shelter forest at the coastal section scale of Dongshan Island, China. Three criteria were used, including forest stand structure, forest belt structure, and windbreak effect; each criterion further comprised multiple factors. Based on survey data of 31 plots in the coastal shelter forest of Dongshan Island, we calculated PEI values using a projection of a pursuit model. The result showed 64.5 % of the PEIs fell at or below the middle level, which can indicate the status of the coastal shelterbelt is unsatisfactory. To further explore whether the different bays and land use types create significant differences in PEIs and evaluation indices, we used an ANOVA to test the influence of various bays and forms of land use on coastal shelterbelts. The results showed that PEI and most of the indices differed significantly by bay; mean tree height, mean DBH, mean crown width, stand density, vegetation coverage, and wind velocity reduction differed significantly by land use. Therefore, relevant measures for different locations, bays and surrounding land use can be proposed to improve the existing conditions of the coastal shelterbelt. The results of this study provide a theoretical and technical framework for future changes and sustainable management of coastal shelterbelt on Dongshan Island.

Changes in and evaluation of surface soil quality in Populus×xiaohei shelterbelts in midwestern Heilongjiang province,China

To examine changes in surface soil quality over time in Populus×xiaohei shelterbelts,we collected soil samples from five shelterbelts of different ages and also from former cropland left fallow for 25 years.Twenty-one surface soil(0–20 cm)properties were measured,and variation in soil quality was assessed using one-way ANOVAs and multiple comparison tests.Based on this analysis,16 soil indexes were used in a model evaluating soil quality,with each index given weight as determined by the correlation coefficient.Compared with the control,the postmature forest had greater soil moisture content but lower bulk density(P<0.05).The mature forest also had higher soil pH,total organic carbon,alkali-hydrolyzed nitrogen,available phosphorus,and biomass nitrogen content,but reduced nitrate-nitrogen and total phosphorus content than the control(P<0.05).Total porosity was highly positively correlated with aeration,nitrate-nitrogen,alkali-hydrolyzed nitrogen,available phosphorus,microbial biomass carbon and microbial biomass nitrogen.Soil total organic carbon,ammonium nitrogen,nitrate-nitrogen,alkali-hydrolyzed nitrogen,total nitrogen,available phosphorus,microbial biomass carbon and microbial biomass nitrogen were all strongly correlated.In the soil quality evaluation model,total organic carbon was assigned the highest weight and total potassium content the lowest.The soil quality index was lowest in the near-mature forest and greatest in the postmature forest.Generally,soil quality in P opulus×xiaohei shelterbelts varied with age and was higher in the 10–20 cm versus 0–10 cm soil layer.After a single forest generation,surface soil quality was significantly improved.

Effect of farmland shelterbelts on gully erosion in the black soil region of Northeast China

The black soil region of northeast China is one of the most important grain-producing areas in China. Increasingly severe gully erosion in this region has destroyed much farmland and reduced grain production. We analyzed SPOT5 imagery from 2007 and TM imagery from 2008 to describe the distributions of gullies and farmland shelterbelts in Kedong County and to assess the effect of farmland shelterbelts on gully erosion. The ima- gery revealed 2311 gullies with average density of 418.51 m km-2, indicating very serious gully erosion. With increasing slope gradient there was an inverse trend between gully density and shelterbelt density, indicating that farmland shelterbelts can prevent gully erosion. The defense effect of farmland shelterbelts against gullyerosion varied with distance： for distances 〈120 m, the defense effect was consistent and very strong; for distances of 120-240 m, a weak linear decrease was found in the defense effect; and for distances 〉240 m, the defense effect of the shelterbelts was significantly weaker. We recommend an optimal planting density of farmland shel- terbelts for the prevention of gully erosion at 1100-1300 m km-2.

Assessment of the effects of the shelterbelt on the soil temperature at regional scale based on MODIS data

At present, the most researches on the protected effect of shelterbelt are on the basis of the two scales of forest belts and networks. However, with the further research on the global environmental change, more attention was paid to the regional climate effect of shelterbelt. In present study, we analyzed the temperature effect of the shelterbelt at regional scale by using the land surface temperature （LST） data from the moderate resolution imaging spectroradiometer （MODIS） at Yushu, Nong＇an, Dehui, and Fuyu in Jilin Province of China from March to October in 2008. Results show that the shelterbelt can increase the soil temperature of the protected farmland as compared with no shelterbelt zone, with the increment of 0.57oC per day in fine shelterbelt and 0.38oC per day in the normal shelterbelt. Moreover, the correlation analysis of the air temperature, precipitation and the soil type and the shelterbelt effect shows that the air temperature and precipitation are negatively correlated with the shelterbelt effects, that is, the more the temperature and precipitation are, the less the effect produced. While the impact of the soil types on the shelterbelt＇s effect is not very obvious as a whole. This paper draws significance in terms of analyzing the effects of the shelterbelt on the soil temperature at regional scale utilizing the remotely sensed data and GIS technique.

A retrieval and validation method for shelterbelt vegetation fraction

Shelterbelts are important in defending against natural disaster and maintaining ecological balances in farmland. Understanding of the shelterbelt vegetation fraction is fundamental to regional research of shelterbelts using remote sensing. We used SPOT5 imagery with 10×10m spatial resolution in combination with knowledge of the characteristics of shelterbelts to develop a method for retrieval of the vegetation fraction of shelterbelts by the pixel un-mixing model. We then used the method to retrieve values for shelterbelts in study area. By combining the parameters of photographic images with characteristics of shelterbelts, we developed a method for measuring the vegetation fraction of shelterbelts based on an advanced photographic method. We then measured the actual values to validate the retrieval result. The multiple correlation coefficients between the retrieved and measured values were 0.715. Our retrieval and measuring methods presented in this paper accurately reflect field conditions. We suggest that this method is useful to describe shelterbelt structure using remote sensing.

Evaluating the Role of Shelterbelt in Vegetation Development in a Semi Arid Zone of Yobe State, Nigeria

This study evaluates the role of shelterbelts on the development and dynamics of vegetation in relation to livelihoods in the study area using geo-information techniques. The study covered the period between 1972 and 2007. The results show that in 1972 vegetation cover in the study area extended over an area of 6955 hectares (i.e.?shrubs, grasses and trees) which represents 65% of the area;however there was a decrease in 1986 to an area of 5779 hectares (54%). Despite the establishment of shelterbelt in the area in 1987, the trend did not change. This is obvious in the reduction of vegetation cover between 1986 and 2000 to a total area of 3893 hectares (37%). The vegetation cover further decreased to 2791 hectares (26%) in 2005 and 1659 hectares (16%) in 2007 respectively. The study concludes that the establishment of shelterbelts alone cannot guarantee the success of vegetation cover development in the area without a sustainable plan which recognizes the local communities as critical stakeholders. Thus, variables like population growth and GDP have a role to play in vegetation cover depletion. The study recommends that efforts geared towards enlightenment of the local communities on the need for conservation should be encouraged by Government and Non-Governmental Organisations.

Effects of Spatial Density of Farmland Shelterbelts on NDVI on the Northern Slope of Tianshan Mountains

[Objectives]To explore the effects of spatial density of farmland shelterbelts on NDVI on the northern slope of Tianshan Mountains.[Methods]Taking the economic belt of the northern slope of the Tianshan Mountains as the research area and using the grid method,the spatial density distribution of farmland shelterbelts can be known.Combining the grid method with NDVI data,the average value of normalized difference vegetation index(NDVI)during the growing period of crops can be obtained.In addition,the protection benefits of the shelterbelts on crops were analyzed through comparing the growth of crops within the protection zone with and without protection.[Results]The grids with shelterbelt distribution were better than the grids without shelterbelt distribution,and the shelterbelt played a great role in promoting crop growth.In the middle stage of crop growth,the protection benefit of shelterbelt was significant.The spatial density of shelterbelts was unevenly distributed in the range of 0.6 to 0.8,and the protection benefits were poor.[Conclusions]It is expected to explore the effects of shelterbelts on crop growth at a larger regional scale,so as to provide a basis for the management and design of shelterbelts in the future,and to provide a theoretical basis for studying the protective effect of farmland shelterbelts on crops.

"3Ns" Shelterbelt Network Project

In China’s three northern regions of the Northwest, North and Northeast (3Ns), there are 1.33 million sq km of desert and sand land, forming a 5,000-km-long wind-sand belt. In 1978, the Chinese government decided to build the "3Ns" shelterbelt network. The project covers 13 provinces, autonomous regions and cities including Xinjiang, Qinghai, Gansu, Ningxia, Shaanxi, Inner Mongolia, Shanxi, Hebei, Beijing, Tianjin, Liaoning, Jilin and Heilongjiang, eovering an area of 4.06 million sq km, 42％ of the country’s total land. It plans to complete the project in 73 years, in three phases: the first phase

Comparison of the water consumption levels of four shelterbelt tree species in a typical arid oasis in Northwest China

The shelterbelt is an indispensable barrier to the ecological and economic development of an oasis.Soil moisture,groundwater and irrigation greatly affect the shelterbelt water consumption and development.In this study,the transpiration rate of shelterbelt trees,soil moisture and meteorological data were collected to determine the effects of soil moisture and meteorological factors on the water consumption of different shelterbelt tree species via multivariate statistical methods.The results showed that the water consumption rate was positively correlated with solar radiation,air temperature and precipitation.Moreover,the leaf transpiration rate exhibited the trend of P.Russkii Jabl.˃P.alba˃P.simonii Carr.>P.nigracv,while the average daily water consumption decreased in the order of P.alba>P.Russkii Jabl.>P.simonii Carr.>P.nigracv.The average daily water consumption levels of P.alba,P.Russkii Jabl.,P.simonii Carr.and P.nigracv were(9.15±0.92)kg/(tree∙d),(6.95±1.41)kg/(tree∙d),(4.43±1.32)kg/(tree∙d),and(1.58±0.18)kg/(tree∙d),respectively.Over the growing season,the soil water consumption levels of P.alba,P.Russkii Jabl.,P.simonii Carr.,and P.nigracv in each shelterbelt tree stand reached 674.8,336.9,358.1 and 161.7 kg,respectively.More than 96%of the soil moisture lost was provided by the upper 120-cm soil layer.Understanding the influence and contribution of soil water and meteorological factors to shelterbelt water consumption is beneficial for shelterbelt management and protection.

The Three-North Shelterbelt Program and Dynamic Changes in Vegetation Cover

The Shelterbelt Forest System Program in northeast, north and northwest China （the Three-North Shelterbelt Program, TNSP） is the largest ecological reforestation program in the world. TNSP vegetation research has important ecological meaning and profound social and economic signiifcance. Here, spatio-temporal variation in vegetation cover under the TNSP was examined using the NDVI average method, major climatic factors such as temperature and precipitation, and linear regression trend analysis from 1982 to 2006. We found that in the past 25 years, NDVI vegetation in the study area has consistently risen at a rate of 0.007 per decade. Vegetation cover, temperature and precipitation are positively correlated. The area of vegetation associated with precipitation is larger than the area related to temperature;precipitation is the key factor affecting vegetation growth across the TNSP. From 1982 to 2006, regions with improved vegetation cover were found in the central and southern part of the Greater Khingan Mountains, central part of the Lesser Khingan Mountains, northeastern part of the Changbai Mountains, Yanshan Mountians, Western Liaoning Hilly Region, Altai Mountains, Tien Shan Mountains, eastern part of the Qilian Mountains, eastern part of the northwest desert as wel as southern part of the Gul y Region of the Loess Plateau. However, vegetation cover declined on both sides of the Greater Khingan Mountains, western part of the Hulun Buir Plateau, northern part of the Sanjiang Plain, southern part of Horqin Sandy Land, southern part of the northwest desert and northern part of the Gul y Region of the Loess Plateau.

Carrying Capacity of Water Resources for Three-North Shelterbelt Construction in China

Water shortage is an important constraint factor in the construction of the Three-North Shelterbelt （TNS）. Here, we analyzed temporal-spatial patterns in water resources and trends in the Three-North region. We evaluated the water resource carrying capacity （WRCC） of 623 counties in the project area during the fifth phase of the TNS Development Program. Results show that 387 counties are appropriate for forestation, 185 counties can be planted, and 60 counties are inappropriate for forestation because of water resource constraints.

豫东沙土农区杨树-农作物复合生态系统中温室气体排放的研究

为了探讨农林复合系统农田土壤温室气体排放的贡献率,在豫东沙区杨树—农作物复合生态系统中选取了2种典型的防护林网密度——大网格BT(防护林间距1000 m×1000 m)、小网格ST(防护林间距200 m×200 m),并用周边5~10年生的人工纯林地作对照,采用静态箱—气相色谱法对不同防护林网密度的杨树—农作物复合生态系统中土壤温室气体(CO_(2)、N_(2)O、CH_(4))季节排放通量进行田间原位测定。结果表明:豫东农区农田土壤是CO_(2)、N_(2)O的排放源、CH_(4)的吸收汇。不同农林复合模式对土壤温室气体的排放或吸收的强度都有不同的特征,大网格、小网格、林地土壤CO_(2)日排放通量均在7月达到最大值,分别为1163.17、1005.91、923.53 mg/(m^(2)·h);大网格的土壤N_(2)O日排放通量在7月达到最大值,小网格和林地则在8月达到最大值,土壤N_(2)O排放通量为4.29~313.28μg/(m^(2)·h);3种模式下土壤CH_(4)的吸收峰值均在7月达到最大值,其中大网格的吸收峰值最大,为4.41 mg/(m^(2)·h)。不同农林复合经营模式通过影响土壤、空气温度和湿度等来影响农田土壤温室气体排放,其中增温干燥强化了土壤CO_(2)和N_(2)O排放源的特征,但同时也增加了土壤作为大气CH_(4)吸收汇的功能,大网格、小网格、林地的全球增温潜势(GWP)分别为1.50×10^(5)、1.03×10^(5)、0.885×10^(5)kg C/hm^(2),单位面积GWP值以林地的最小、大网格的最大。总的来看,适当增加防护林网密度有利于减少农林系统的增温潜能。

农田防护林林网景观结构定量评价与分析

以东北地区的“三北”防护林工程重点建设区为研究对象,选取林网的带斑比、连接度、环度、优势度等作为评价指标,利用高分辨率的ZY-3影像,根据景观生态学原理及地理信息系统技术,对2021年实际林网和合理状态下林网的景观指标值进行定量评估及对比,并分析现有农田防护林景观结构参数的空间分布差异性。结果表明:该区域的防护林数量与面积基本达到优质林网的要求,并且分布较均匀,但是主副林带条数不足,成型状况较差,且形成的闭合网格太少,削弱了林网的防护功能。从林网数量、分布以及成型状况等方面对防护林工程进行了宏观评价,指明了下阶段建设工作方向,为该区域防护林的管理和更新提供参考。

海南热带海岸海防林植被恢复的探索与实践

文章分析了海南岛热带海岸存在植被生态退化问题,针对主要的退化问题钛锆砂矿废弃地的植被退化和单一树种的人工木麻黄海防林的缺陷,提出了分三步走恢复海岸海防林植被的学术思路,即恢复和巩固木麻黄海防林;建立引入乡土树种的混交林型海防林;促进混交林演替成具地带性植被特征的天然林型海防林。按照这个思路开展了近20年的海岸植被生态恢复的实证研究和应用实践,验证了其可行性,实现了初步构建乡土林型的海防林植被,达到了研究构想预期的效果。研究成果为海南岛以及华南沿海热带海岸的海防林生态恢复提供了可借鉴的范例。

木麻黄基干林带对台风“杜苏芮”的防风效应

为了解海防林对台风的防护效应,以惠安赤湖国有防护林场监测站收集的“杜苏芮”台风登陆前后的气象数据为材料,分析了台风登陆前后近地层的风速、风向、湍流强度、防风效能和气流加速率等的特征规律。结果表明:(1)台风登陆前后的平均风速和风向时程变化特征满足了台风眼区经过的条件,平均风速曲线呈“M”形双峰分布,通过采集到的台风眼区、眼壁和外围强风的完整风况数据,完整展示了台风经过林带前后风速、风向的演变过程。(2)湍流强度的时程整体变化趋势随着台风靠近和离去呈现增大-减小-剧增-回落的过程,尤其台风后风圈影响的区域,湍流强度剧烈增大,强度可增大2倍以上。(3)向岸风在垂直方向上,弱风或强风的防风效能随高度增加而降低,高度相同,林带后弱风的防风效能小于强风;水平方向上,林内及林带后1H和5H处防风效能最好,在高度3 m平均防风效能为49.57%~93.93%,在高度9 m平均防风效能为44.04%~90.10%。离岸风在垂直方向上,随着气流靠近林带,弱风或强风的气流加速率随高度增加而增大,林带后1H高度3 m气流加速率平均为0.2193,高度9 m气流加速率平均为0.3242,林内气流加速率达到最低值;而风越过林带后,弱风风速恢复到88%左右,强风的气流则有个加速的过程。

Wind Velocity Reduction of Coastal Shelterbelt System in Shanghai,East China

Wind velocity reduction of coastal shelterbelt system was monitored for 1 month in 3 weather stations in Nanhui,Shanghai,and the benefits of shelterbelt system and trunk shelterbelt forest were compared in this paper.The results showed the wind velocity at the first weather station(W1),which located in front of trunk shelterbelt forest by the seaside,was the biggest,with the average of 9.36 m/s;the wind velocity at the second weather station(W2) was lower than that at W1,with the range of 0 to 18.2 m/s and the average of 6.39 m/s,and the wind velocity at the third weather station(W3) was the lowest,with the average of 2.58 m/s.Both the ratio of W2 to W1 and the ratio of W3 to W1 ranged from 0 to 100%,but most of the ratio of W2 to W1(89.59%) was above 20%,and most of the ratio of W3 to W1(95.52%) was below 50%,which shows bigger wind velocity reduction in shelterbelts system than in trunk shelterbelt forest.With the wind scale increased from 1 to 8 scale at W2 and W3,the wind velocity increased.But the reduction in wind velocity decreased.