Controlling effects of forest belts on non-point source pollution of agricultural lands in Taihu Lake area, China

Taihu Lake area is one of the most developed areas in agricultural production. Application of fertilizers and pesticides in large quantities greatly aggravate environmental pollution of this area, and water pollution has worsened to an unbearable condition. Two sampling farms (respectively 1 hm2) under rape-rice rotation and wheat-rice rotation were selected as studied ecosystem and a 5-yr-old Poplar forest and 8-yr-old Metasequoia forest were chosen in the selected areas. By collecting samples of Nitrogen, Phosphorus in water, crops and underground of forest, the transfer and loss of N and P (main water pollutants) in faming ecosystem were studied, and the effects of forest belts on non-point source pollution of agricultural lands was analyzed. The results indicated that the transfer and loss of N and P vary with means of rotation, types of crops and the amount of fertilizer application. Buffering forest belts betweens farmlands and ditches can effectively stop and purify such elements as N and P in soil runoffs, thus controlling non-point source pollution of agricultural lands. When the width ratio of farmland to forest belt is 100 to 40, 50.05% losing N, 29.37% losing P can be absorbed by forest under rape-rice rotation and 30.98% N, 86.73% P can be absorbed by forest under wheat-rice rotation. When the width ratio of farmland to forest belt is 150 to 40, 33.37% losing N, 19.58% losing P can be absorbed by the forest under rape-rice rotation, and under wheat-rice rotation 20.65% lost N and 57.82% lost P can be absorbed. There is only some purification effect when the width ration of farmland to forest belt is 200 to 40. Based on model of buffering forest belts, the width ratio of farmland to forest is determined between 100 to 40 and 150 to 40, because it not only can purify water, but also occupy less farmland. It is suggested that Poplars, with the characteristics of fast-growing and high value, are suitable to be planted as shelter-forest in Taihu Lake Watershed.

Effects of sand-fixing and windbreak forests on wind flow:a synthesis of results from field experiments and numerical simulations

Sand-fixing and windbreak forests are widely used to protect or/and improve the ecological environments in arid and semi-arid regions. A full understanding of wind flow characteristics is essential to arranging the patterns of these protective forests for enhancing the effectiveness. In this study, the wind velocity over the underlying surface with sand-fixing forests and windbreak forests at the heights of 1–49 m was monitored from two 50-m high observation towers in an oasis of Minqin, Gansu Province of China. The wind velocities were simulated at different locations over these protective forests between those two towers by a two-dimensional Computational Fluid Dynamics（CFD） model. The results showed that at the heights of 1–49 m, the wind velocity profiles followed a classical logarithm law at the edge of the oasis and a multilayer structure inside the oasis. With increasing number of sand-fixing forest and windbreak forest arrays, the wind velocity at the heights of 1–49 m generally decreased along the downstream direction of the prevailing wind. Specifically, below the height of windbreak forests, the wind velocity decelerates as the airflow approaches to the windbreak forests and then accelerates as the airflow passes over the windbreak forests. In contrast, above the height of windbreak forests, the wind velocity accelerates as the airflow approaches to the windbreak forests and then generally decelerates as the airflow passes over the windbreak forests. Both the array number and array spacing of sand-fixing and windbreak forests could influence the wind velocity. The wind protection effects of sand-fixing forests were closely related to the array spacing of windbreak forests and increased with the addition of sand-fixing forests when the array of the forests was adequately spaced. However, if the array spacing of windbreak forests was smaller than seven times of the heights of windbreak forests, the effects were reduced or completely masked by the effects of windbreak forests. The results could offer theoretical guidelines on how to systematically arrange the patterns of sand-fixing and windbreak forests for preventing wind erosion in the most convenient and the cheapest ways.

The Altitudinal Belts of Subalpine Virgin Forest on Mt.Gongga Simulated by a Succession Model

How to accurately simulate the distribution of forest species based upon their biological attributes has been a traditional biogeographical issue.Forest gap models are very useful tools for examining the dynamics of forest succession and revealing the species structure of vegetation.In the present study,the GFSM(Gongga Forest Succession Model) was developed and applied to simulate the distribution,composition and succession process of forests in 100 m elevation intervals.The results indicate that the simulated results of the tree species,quantities of the different types of trees,tree age and differences in DBH(diameter at breast height) composition were in line with the actual situation from 1400 to 3700 MASL(meters above sea level) on the eastern slope of Mt.Gongga.Moreover,the dominant species in the simulated results were the same as those in the surveyed database.Thus,the GFSM model can best simulate the features of forest dynamics and structure in the natural conditions of Mt.Gongga.The work provides a new approach to studying the structure and distribution characteristics of mountain ecosystems in varied elevations.Moreover,the results of this study suggest that the biogeochemistry mechanism model should be combined with the forestsuccession model to facilitate the ecological model in simulating the physical and chemical processes involved.

Construction of Forest and Grass Industry Economic Belt Using Land Resources in Road Side Slope

The construction of expressway and high-speed rail is at the sacrifice of the soil ecological environment. It brings about much damaged land and bare slope. It is necessary to restore vegetation and rebuild landscape. In the design of target plant community and configuration plants,it is required to select as far as possible plants that can blossom and bear fruit or pods. Then seeds of these plants can be harvested,processed and sold,and applied for other projects,so as to develop into a complete forest and grass seed industry chain. This not only reasonably utilizes land resources,but also provides a new approach to the problem of insufficient fine forest seed sources in China. This paper discussed the use of land resources in road side slope and forest and grass seed selection and breeding technology,and elaborated the industrialized development paths for forest and grass seed industries in road side slope. Finally,it arrived at following recommendations.( i) The construction of forest and grass industry economic belt using land resources in road side slope can realize maximum land value. Building a road can help people there get rich,and the type of land and water cultivates its type of forest and grass.( ii) It can make up for the losses incurred from construction of expressway and high-speed rail or destroying forest land,and it can increase farmers' income.( iii) It can increase the supply of domestic seeds,reduce seed import,save foreign exchange,and partly solve the problem of insufficient supply of forest and grass seeds.( iv) It is able to form a complete forest and grass seed industry economic cycle chain,increase employment,and provide new approaches for enriching and benefiting farmers.

Characteristics of Environment Factors in Secondary Poplar-Birch Forests after Mutual-Belt Selective Cutting

The mutual-belt selective cutting was conducted in the secondary poplar-birch forests. The changes of environmental factors after cutting were observed. The environmental factors of effect belts(cutting belts) of 15m in width had great changes. 10-m effect belts had unnoticed changes in environmental factors. The reserved belts with 10-m effect belts had a greater increase in DBH growth rate and volume growth rate. The reserved belts for 6-m and 8-m effect belts had lower increase in DBH and volume. The environmental factors of 6-m and 8-m effect belts did not change much. comparing with their reserved belts. Cluster analysis and principal component analysis for environmental factors between each two belts were also made. and the results proved that 10-m cutting belt is the best way for management of the secondary poplar-birch forests.

Forest resources variation along with the main rivers in typical forest re-gion of Changbai Mountain

The restoration of the riparian vegetation disturbed by human activities is one of the hotspots of watershed ecology. Through interpreting the images of Remote Sensing in 1985 and 1999, the basic information of forest resources of Lushuihe Forest Bureau, which is a typical forest area of Changbai Mountain, was obtained with support of GIS. By dividing Land covers of Lushuihe area into 10 types (water body, residential land, stump land, farming land, wetland, mature conifer forest, midlife conifer forest, mature broadleaf forest, midlife broadleaf forest, and man-made young forest) and dividing the riparian zone into four buffers (in turn, 1000, 2000, 3000, 4000 m away from the river), the changes of riparian forest resources during 1985-1999 were analyzed. The results showed that the deforestation intension has obviously decreased and the whole environment has been evidently improved, but the riparian ecosystem was still flimsy. In buffer 1, 2, 3, the area of midlife conifer forest increased largely, but the areas of other types of land covers all decreased. Midlife conifer forest had a comparatively good status in the three buffers. In buffer 4, midlife conifer forest, mature conifer forest, and mature broadleaf forest formed a forest-age rank that is helpful to stabilize the forest ecosystem and exert its functions. Area percentage of wetland decreased in buffer 1, buffer 2, and buffer 3, even in buffer 4 in which forest ecosystem rehabilitated comparatively well, so protecting and rehabilitating wetland is a very difficult task.

Rebirth after death: forest succession dynamics in response to climate change on Gongga Mountain, Southwest China

Global climate change is having long-term impacts on the geographic distribution of forest species. However, the response of vertical belts of mountain forests to climate change is still little known. The vertical distribution of forest vegetation(vertical vegetation belt) on Gongga Mountain in Southwest China has been monitored for 30 years. The forest alternation of the vertical vegetation belt under different climate conditions was simulated by using a mathematical model GFSM(the Gongga Forest Succession Model). Three possible Intergovernmental Panel on Climate Change(IPCC) climate scenarios(increase of air temperature and precipitation by 1.8℃/5%, 2.8℃/10% and 3.4℃/15% for B_1, A_1B and A_2 scenarios, respectively) were chosen to reflect lower, medium and higher changes of global climate. The vertical belts of mountainous vegetation will shift upward by approximately 300 m, 500 m and 600 m in the B_1, A_1B and A_2 scenarios, respectively, according to the simulated results. Thus, the alpine tree-line will move to a higher altitude. The simulation also demonstrated that, in a changing climate, the shift in the vegetation community will be a slow and extended process characterized by two main phases. During the initial phase, trees of the forest community degrade or die, owing to an inability to adapt to a warmer climate. This results in modest environment for the introduction of opportunistic species, consequently, the vegetation with new dominant tree species becomes predominant in the space vacated by the dead trees at the expense of previously dominated original trees as the succession succeed and climate change advance. Hence, the global climate change would dramatically change forest communities and tree species in mountainous regions because that the new forest community can grow only through the death of the original tree. Results indicated that climate change will cause the change of distribution and composition of forest communities on Gongga Mountain, and this change may enhance as the intensity of climate change increases. As a result, the alternation of death and rebirth would finally result in intensive landscape changes, and may strongly affect the eco-environment of mountainous regions.

Wild foods(plants and animals)in the green famine belt of Ethiopia:Do they contribute to household resilience to seasonal food insecurity?

Background： The role of wild foods in combating problems of food shortage is paramount. However, existin, approaches to combat food insecurity shock have generally focused on reducing vulnerability via increasing productivity of domesticated foods. In contrast, approaches that enhance resilience mainly through wild fooc sources have been less focused. This study examined the contribution of wild foods to household resilience to food insecurity in the green famine belt of Ethiopia. Methods： A cross-sectional survey of 220 households was conducted using a structured questionnaire, key informant interviews, and semi-participant observations. Factor analysis was run using SPSS to analyze data. Correlation analysis was used to examine the direction and strength of association between wild foods and the income and food access （IFA）, a latent proxy indicator of resilience. Cross-tabulation was also run to determine the proportion of households in each ethno〈ulture group under each resilience category. Results： The mean amount of wild foods obtained by households was 156.61 kg per household per annum. This was about 5 % and 9 % of, gross and, net food available from all sources respectively. Wild foods contributed well to household resilience as the factor loading （Factor2 = 0.467） was large enough and were significantly correlated with IFA （r-- 0.174）. Wild vegetables were the most collected and consumed type of wild foods constituting 52.4 % of total amount of wild foods. The total amount of wild foods was smaller than that of domesticated sources of food. The majority of households （38.6 %） reported ＂reduced source of wild foods＂ as a reason for this. Smaller proportion of the indigenous （11.2 %） than the non-indigenous （34.1%） ethno-culture group reported one or more reasons for their lower level of dependence on wild foods. Conclusion： From the study we concluded that wild foods had important contribution to households＇ resilience to food shortages and are likely to continue to contribute in the future, this being more to indigenous than non-indigenous ethno-culture group. Therefore, a resilience building policy that incorporates wild foods should be adopted, and research that aims at exploring their current status and future prospect are urgently required.

Current vegetation dynamics of the “forest-mountain tundra” ecotones of Lake Baikal coastal ranges

During last decades, new trends appeared in the ecotones of the upper boundary of forests at the ridges surroundingLakeBaikal(Khamar-Daban and Baikal’sky Ridge): ones to advance of wood species (Pinus sibirica Du Tour, Abies sibirica Ledeb., Larix sibirica Ledeb., Larix dahurica Lawson) out of timber stands into the area of subgoltsy with Pinus pumila (Pallas) Regel. up to mountain tundras. In average, this is from 100 to 200 - 300 meters (maximum up to500 m) in linear distance from the margin of dense timber stand. A burst of forests renewal occurred in 1989-1995, it resulted probably from a high productivity of the seeds of wood species due to warmer winters in 1980ies-1990ies which favoured the formation of favourable climate-edaphic conditions for the development of forest communities above the forests boundary on the ridges surrounding Lake Baikal.

基于机器学习的“一带一路”投资国别风险预测研究

“一带一路”倡议提出十年间,中国对沿线国家的投资规模持续扩大。然而,企业在抓住机遇,进行“一带一路”沿线国家投资的同时,也需要重点关注“一带一路”投资国别风险。本文从政治、经济、社会和对华关系4个维度构建“一带一路”投资国别风险预测指标体系;运用灰色关联分析计算样本国家的综合风险评价值;基于2012~2022年间“一带一路”沿线国家的数据,利用机器学习构建GA-BP神经网络、支持向量回归和随机森林3种预测模型;通过对比预测精度,确定最佳预测模型,利用2021年的指标数据,对2022年的投资国别风险进行预测。研究结果表明:(1)在“一带一路”投资国别风险的研究背景下,支持向量回归模型预测效果最优,证明机器学习模型能够有效应用于风险管理领域;(2)“一带一路”投资国别风险存在明显的地区差异,中东欧地区和东南亚地区投资国别风险普遍较低,而南亚地区投资国别风险普遍较高,但都存在特例。本文研究结果可为“走出去”企业在“一带一路”沿线国家的投资决策提供参考。

基于空间分析的长江经济带森林乡村分布特征及影响机制

借助GIS空间分析方法探索长江经济带3 321个森林乡村的空间分布特征和地域分异规律,并辅之缓冲区和叠置分析、地理探测器模型探究森林乡村空间分布的主要影响因素。结果表明:长江经济带森林乡村空间分布呈现典型的集聚特征,上游地区分布多、下游地区分布少,核密度分布整体上呈“双核心—单核点—环核群”分布态势;长江经济带森林乡村空间分布具有显著的空间正相关性,表现为东热西冷、冷热交替的空间分异格局;长江经济带森林乡村空间分布格局受自然地理环境、生态环境质量、社会发展状况、经济发展水平的共同影响,其中耕地面积、常住人口、森林覆盖率是森林乡村空间分布的主要影响因子,其空间分异是影响因子共同驱动的结果。

“一带一路”背景下中国—东盟森林生态建设合作概况与对策

“一带一路”倡议是中国提出的一项重大国际合作倡议,旨在促进沿线国家间的互联互通和经济合作。森林生态建设是“一带一路”倡议中的重要组成部分,涉及森林资源的保护、可持续利用和生态环境的改善。中国与东盟国家都拥有丰富的森林资源,但由于经济发展和人口增长的压力,森林资源面临着被严重破坏和过度利用等一系列问题。基于此,文中总结当前中国-东盟森林生态建设合作的相关经验及面临的困境,并提出对策建议:1)加强政策沟通和合作机制建设;2)加强执法合作和提高执法能力;3)加强科技创新和能力建设;4)加强资金支持和投融资合作。

基于风洞试验的樟子松农田防护林防风效果研究

樟子松(Pinus sylvestris var. mongolica)是我国“三北”地区主要造林树种之一,樟子松防护林具有较强的防风固沙能力。本研究以樟子松防护林为研究对象,开展了5种行带式配置防护林防风效益风洞试验研究,测定了不同配置防护林防护区不同距离范围内风速及其流场特征,研究了樟子松防护林不同行带配置与防护效益关系,为常绿针叶树种农田防护林营造提供理论依据。结果表明:(1)防风效能随着林带行数的增加而增强,且林带后1 H~3 H内风速显著降低,形成风影区,风影区面积随着林带行数的增加而变大。(2)樟子松防护林带后风速流场发生显著变化,在12 m·s^(-1)风速条件下,1~5行1带的5种林带防风效能分别为15.1%、26.2%、37.5%、51.7%和51.9%,4行1带、5行1带结构配置防风效能均在50.0%以上。(3)樟子松防护林具有较强的防风效果,建议在干旱区农田防护林建设与更新中可采用樟子松造林,最适结构配置为4行1带。

和田—若羌铁路大风沙区绿化林带配置的风洞模拟试验

[目的]探究和田—若羌铁路大风沙区铁路科学的防沙林带宽度、间距及体系配置模式,为沙区铁路防护林带配置和建设提供理论依据。[方法]以梭梭和沙拐枣为林木模型,开展防沙林带配置的风洞试验研究。[结果]防护林带宽度为5行,防护林带间距为6 H(H为植物模型高度)时,第2条林带气流减弱效果明显,第3条阻沙林带之后区域,气流衰减显著,且不会随着风速的增大而增加,具有较好的防护效益,3条林带达到较好的防护作用。风速越大,林带背风侧防护区的范围越短。[结论]为保证体系在较大风速作用下有较好的防护作用,林带体系应选择5条防护林配置体系模式。

余姚瀑布仙茗生态茶园营林模式的探析

生态茶园是近年来茶产业发展的栽培趋势和方向,更是注重茶叶品质与安全的需要。而遮荫作为茶园管理中常用的农艺措施,可以改善茶园微环境,从色泽、香气和滋味等方面能提高茶叶的品质。文章以余姚瀑布仙茗为代表,结合其“三色”(黄、白、绿)绿茶品质特点,应用林业上复层林营造技术来综合优化茶园环境和丰富群落内生物链数量,来探析茶树的生理变化和生长势;同时,根据品牌系列产品以春茶为主呈现品质特点,以行道林带的架构,创新出“茶树+常绿乔木型”复层林和“茶树+落叶乔木型”复层林2种营林模式,成林后郁闭度控制在0.3~0.4,实现以生态提质增效及茶旅融合为特色的茶产业发展。

不同带间距对沙区河岸固沙林带的带间土壤水分和植被群落特征的影响

[目的]黄河沿岸地带是水土流失最严重的地区之一。研究沙区河岸固沙林带不同带间距下的土壤水分和植被群落特征,确定最优配置模式下的带间距,为建设沙区河岸固沙林带行带式造林提供依据。[方法]以内蒙古自治区鄂尔多斯市达拉特旗西柳沟不同带间距行带式固沙林为研究对象,对带间距8,16,22,28m的固沙林样地进行土壤取样和植被调查,统计不同带间距固沙林带的带间土壤物理性质以及植被群落特征,并分析土壤水分与植被间的相关性。[结果]①不同行带式固沙林中的土壤水分与植被指数整体上均随带间距增大而提升。②各样地带间0—100cm范围内不同土层土壤水分也随水平间距增加而升高,至11m后变化趋于稳定。③各样地带间土壤水分均与植被指数大体呈极显著正相关,但均匀度指数与丰富度指数有所差异。带间距越大,植被恢复效果越好,带间距22m时约达峰值。[结论]以低覆盖度行带式固沙林进行沙地治理时,植被恢复效果随带间距增大而增长,但带间距并非越宽越好。22m带间距的行带式固沙林带间植被恢复效应最佳,对沙地的近自然修复效果最优。

北京市绿化隔离地区空气负离子供给能力及影响因素分析

为探析北京市绿化隔离地区(简称“绿隔地区”)空气负离子的供给时空规律及其影响因素,基于植被生长季空气负离子监测数据定量评估了绿隔地区空气负离子供给能力,并分析了气象因子、植物群落因子对其供给影响的差异性。结果表明:①绿隔地区植被生长季空气负离子浓度呈先降后升再降的日变化特征,在14:00左右达到峰值。2022年绿隔地区森林植物群落空气负离子供给量为3.02×10^(21)个,供给能力为0.51×10^(16)个/m^(2),第二道绿化隔离地区(简称“二绿地区”)空气负离子供给能力和供给量均明显优于第一道绿化隔离地区(简称“一绿地区”),主要与森林面积比例、植物群落因子差异有关。②空气负离子浓度主要受温度影响,并与温度呈显著负相关,二绿地区对温度响应更显著,但相对湿度对其影响不显著。③空气负离子浓度受植物群落因子影响显著,植被覆盖度、林分阶段、群落结构为主要影响因子,并均与空气负离子浓度呈显著正相关。不同植物群落因子的空气负离子浓度差异明显,在林分阶段上表现为近自然林>人工林,在林分类型上表现为混交林>纯林,在群落类型上表现为针阔混交林>阔叶林>针叶林,在群落结构上表现为乔灌草>乔灌>乔木>乔草。研究显示,乔灌草结构的针阔混交林的空气负离子供给能力最高,而乔草结构的针叶林供给能力最低,未来应重点加强近自然林营建,构建混交、复层、异龄、多功能森林群落,其中,一绿地区应重点进行林分类型和群落结构调整,二绿地区应重点关注群落类型和群落结构优化以及植被覆盖度提升。

广东省县级生物防火林带阻隔网空间布局与规划

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