Remediation of lead (Pb)-contaminated soils is increasingly important because production of food crops in these soils is associated with human health risk. The present study investigated use of natural zeolite to remediate Pb-contaminated soil by quantifying changes in soil properties, soil nutrients and distribution of Pb in spinach plant parts. Natural zeolite was added to pots containing four different soil media that were artificially amended with Pb in a greenhouse. Zeolite was mixed with the media at four rates plus a zero control, and for three of the Zeolite rates a second application was made to the soil surface in the pot 30 days later for a total of eight zeolite treatments. The 32 treatments were replicated four times. Pb immobilization by zeolite was dose dependent, with greater immobilization at higher zeolite rates. Heterogeneous soil humus components exerted both mobilizing and stabilizing effects, so the medium nutrition was most effective for phytostabilization. So,split applications of zeolite were more effective than once, because the lag-phase time of split zeolite treatment applications was longer than for one application, to the same total dosage. This method might be an efficient way to remediate the lead-polluted soils with zeolite application twice.

草原是重要的自然资源和生态系统,具有十分重要的生态功能(如水源涵养、水分调节、水土保持、初级生产、气候调节和生物多样保护)和社会经济价值(如牧业生产、牧民生计维持、牧区文化传承等).科学保护、合理利用和有效恢复是草原资源和生态系统可持续管理的根本基础.2018年国家机构改革后草原主体功能从生产转向生态,草原在生态文明建设中的地位凸显.在新时代生态文明建设快速推进过程中,对标国家"山水林田湖草"生命共同体系统治理的总体战略,聚焦绿色发展和美丽中国建设的基本理念,提出基于地理分异和功能特征的草原分区方案,是推进草原资源高质量管理亟待解决的核心问题之一.利用文献调研、专家问卷调查和会议咨询等方法,构建以"生态保护优先、兼顾绿色发展"为主导思想的中国草原分区体系,提出生态地理单元分异原则、主体功能优先原则、产业布局协调性原则、历史传统相结合原则、行政边界完整性原则,提出了区、亚区和小区三级分区体系的主要指标、命名方式、功能判定及产业布局的厘定方法,将全国草原分为5个区(内蒙古高原草原区、西北山地盆地草原区、青藏高原草原区、东北华北平原山地丘陵草原区、南方山地丘陵草原区)、47个亚区、2899个小区,并给出了不同分区的主导生态功能及产业发展方向.分区结果具有综合性、协调性和时代性,可以为新时代草原生态文明建设和山水林田湖草系统治理提供科学支撑.

本研究选取河北坝上地区为研究区域,以不同放牧强度样地的群落优势种或亚优势种(马蔺(Iris lactea)、线叶蒿(Artemisia subulata)、糙隐子草(Cleistogenes squarrosa)、二裂委陵菜(Potentilla bifurca)、华北米蒿(A.giraldii)和羊草(Leymus chinensis))为研究对象,分析放牧强度对6个物种生物量分配格局的影响.结果表明:随放牧强度的增加,6个物种的单株总生物量和单株地上生物量均显著降低,单株地下生物量随放牧强度呈现不同的规律;与对照相比,重度放牧显著提高了糙隐子草的单株地下生物量,中度放牧则显著提高了二裂委陵菜的单株地下生物量;根冠比随放牧强度显著增加,且不同物种之间也呈现显著差异;羊草在群落中的重要值与根冠比呈显著负相关,其他5个物种的根冠比与其重要值呈显著正相关.本研究证实物种会通过调整其生物量分配格局来适应放牧干扰,研究结果有助于深入理解放牧退化草原群落物种组成的形成机制.

To study the effect of native arbuscular mycorrhizal fungi (AMF) on the growth and competition of grass species of different sizes, Elymus nutans and Poa crymophila were planted singly, in pairs, or in mixed pairs in an artificial grassland, which simulated non-competition, intraspecies competition, and interspecies competition conditions, respectively, and some of the plantings were inoculated with native AMF. The native AMF successfully colonized the roots of both E. nutans and P. crymophila and significantly improved the biomass, height, and tiller number of both plants. In contrast, the AMF significantly reduced the competitive ability (relative yield, relative yield total, and aggressivity index) of E. nutans, but increased that of P. crymophila. These results demonstrate that, even though AMF can promote the growth of both species in the absence of interspecific competition, it preferentially promotes the growth of P. crymophila under interspecific competition and may differentially contribute to the competitive ability of the two plant species in natural communities. The results also indicate that AMF plays an important role in the regulation of plant interspecific relationships and in the maintenance of community species diversity.

风险评估是预防外来物种入侵的有效手段,为科学评价外来牧草的入侵风险,防止盲目引种带来生态安全威胁,本研究将频度分析法与层次分析法结合,建立外来牧草入侵风险评估指标体系;该体系由5个一级指标和18个二级指标组成,包括外来牧草的入侵性、适应性、扩散性、生物学特性、危害性、防除难度等方面;本研究中,利用4种禾本科外来入侵牧草和3种禾本科外来牧草对构建的评估体系进行验证,并利用该体系对外来牧草柳枝稷(Panicumvirgatum L.)进行了入侵风险评估实例研究,得出其入侵风险为中等,主要体现在适应性强和扩散性强方面.本研究建立的评估体系,可初步明确柳枝稷入侵风险的主要来源,为外来牧草的引种管理提供参考.

Majority of plants are linked below-ground through common mycorrhizal networks (CMNs). The formation of CMNs between the roots of conspecific and heterospecific plant individuals influences the distribution of limiting nutrients, e.g., nitrogen (N) among the interconnected plants. In various ecosystems, the availability of N is being increased substantially; however, the effect of elevated N on the existence and functionality of CMNs in semi-arid regions of Inner Mongolia remains largely unexplored. Therefore, to verify the development of CMNs and their functionality under increasing N concentration, we incorporated different levels of N fertilizer, i.e., N0 = 0, N1 = 7.06, N2 = 14.12, and N3 = 21.18 mg kg−1, and established Leymus chinensis (L. chinensis) as a donor and the recipient plant in a specially designed portioned root-box. For the establishment of CMNs among the plants, compartments were separated via 37 μm mesh. The 15N isotope tracer technique and microscopic analysis evidenced the presence of CMNs because the extraradical hyphae originated from the donor side and crossed 37 μm mesh of the recipient plant compartment. The 15N recovery was highest at N1 in the donor (18.38%) and recipient (7.89%) plants, while the average transfer rate of 15N to recipient plant was 21–65% with a maximum transfer rate at N2 treatment. The establishment of CMNs significantly improved the donor and recipient plants chlorophyll contents and plant biomass at low N levels. Moreover, the AM fungal extraradical hyphae also released a special kind of protein called glomalin-related soil proteins (GRSPs) that improved the soil structure in terms of mean weight diameter (MWD), thereby improving the soil organic carbon (SOC). Interestingly, the mycorrhizal network had a more profound impact on its neighboring plants than the host plant. In short, the present investigation emphasizes the presence of CMNs in the typical steppe of Inner Mongolia with vital roles in nutrient transfer and improvement of plant growth and soil properties.

在线教学是“互联网+”时代远程教学的一种主要手段,是以网络为介质的教学方式.2020年抗击新型冠状病毒肺炎疫情的特殊时期,为了实现“停课不停教、停课不停学”,全国许多高校开展了在线教学.如何做好大学课程的在线教学工作,保证在线“教”与“学”的质量和效果,实现大学课程在线教学的长期化和常态化运行,是后抗疫时代“互联网+”大学教学改革的重要任务.本文以北京林业大学“草原生态修复学”在线课程为例,介绍“慕课+ SPOC+腾讯会议平台”的在线教学模式,探讨草学专业课程在线教学创新方法和保障途径.慕课(MOOC)可以实现大规模、开放式教学,SPOC可以实现精细化、专业化教学,腾讯课堂可以实现互动式、研讨式教学,基于慕课+ SPOC+腾讯会议平台的“草原生态修复学”在线教学,可以使三大教学平台的优势互补、相得益彰,共同保障“草原生态修复学”在线教学的质量.

为探究全球气候变化导致的青藏高原降雨增加对退化补播草地植被群落和土壤养分变化产生的影响,本试验依据当地植被生长季(5—9月)多年平均降水量对人工草地设置了5种增水处理,即增水6.25％(W1),12.5％(W2),25％(W3),50％(W4)以及不增水(CK)来研究不同增水对植被和土壤的影响.结果表明:短期增水可以有效增加高寒草甸生长季植被地上生物量和盖度,增水50％ 处理下生物量增产最高,可达200％;增水显著提高生长季初期(6月)植被物种丰富度指数,但对Shannon-Wiener指数、Simpson指数和Pielou指数的影响较小;不同增水处理下土壤微生物碳、土壤有效磷、土壤铵态氮、硝态氮等速效养分差异显著,增水量较多(W3,W4)处理下微生物碳含量较高.增水对土壤有机质、全氮、全磷含量有一定影响,但与对照处理差异不显著.可见,在高寒草甸进行短期增水处理可以显著提高植被生物量和盖度,在50％ 的增水处理下影响最为明显,各梯度增水处理对不同土壤养分类型的影响不一,但总体上促进了土壤养分的累积.

利用1955-2014年中国北方农牧交错带中段10个气象观测站的气温时间序列资料,在分析气温变化结构的基础上运行气候突变检验和小波分析,用以解释气温变化的多时间尺度的复杂结构,分析不同时间尺度下气候气温变化的突变点和周期性变化规律.结果表明:近60 a来研究区内平均气温呈现普遍升高趋势,尤其在20世纪80年代以后升高趋势更加显著,达到99％置信度,升温速率达到0.45℃·10a-1,高于全国和全球的气温增长率.2008年后区域进入降温过程,冬季降温尤为明显,其原因是全球变化发生停滞;气候突变检验表明区域年平均气温的升温突变发生在1986年,显著升温开始于1991年,冬季升温突变时间最早,发生在1978年,夏季升温突变时间滞后,出现于1991年;周期检验表明区域内气温存在5～10 a和30 a的多重时间尺度结构的变化特征,预计2008年后年平均气温和季节平均气温增加速度将变缓,甚至可能发生变暖停滞.

中外合作办学是我国高等院校进行国际合作，提升高等教育办学质量的重要途径之一。面对我国的中外合作办学现状，积极探索中外合作办学中所存在的诸多问题具有重要现实意义。本文通过对北京林业大学在中美合作办学项目的现状和面临问题分析的基础上，提出了优化合作项目的实施对策，可为促进我国高等教育中外合作办学的发展提供一定的借鉴。

知识经济时代对创新型人才的需求、全球生态环境的变化、国际竞争的加剧以及生态学科和生态学专业的快速发展等,都给生态学本科专业的人才培养带来了重大挑战.当前我国生态学本科专业的人才培养存在人才培养目标的定位不准确、课程设置不合理、教学内容重复、教学方法落后、实践教学环节薄弱、教学资源缺乏等问题.因此,为了提高生态学本科专业创新型人才的培养质量,应采取以下对策:一是确立基于全球视野的人才培养目标;二是注重专业课程建设,加强通识教育;三是改进教学方法,培养创新思维;四是加强教学资源建设;五是强化实践教学;六是实行本科生导师制,培养学生的探索精神.

利用非线性回归的生态界面测试分析法(BEDA),对华北农牧交错带农田草地景观土壤的速效氮界面在生长季(5-9月)的时空动态进行分析,为干旱、半干旱地区以植被恢复为主的大规模生态环境建设提供参考.结果表明:农田-草地边界的土壤速效氮生态界面位于草地内.在少雨的5月,农田-草地的边界影响域最小,仅为37.5m;而在雨水较为丰沛的8月,边界影响域最大,为57.5m.相对于少雨期,丰雨期的速效氮生态界面会更靠近草地内部.速效氮素在农田-草地界面上表现出地表生态流季节动态性.

气候变化、过度放牧和盲目开垦等不合理的人类活动,导致了新疆阿勒泰地区的植被退化和生态系统服务功能的减弱.为改善新疆阿勒泰地区的生态环境,本文选取在盐碱地和荒漠生境中生长良好的罗布麻为研究对象构建灌草复合系统,基于野外调查取样和室内分析方法,以平原荒漠区的原生植被为对照,对比分析1年和2年生罗布麻种植区与平原荒漠区的固碳增汇、防风固沙和水土保持等生态系统服务功能.结果表明,罗布麻植株相比对照平原荒漠的优势植物无叶假木贼,能显著提高植被的净光合速率和水分利用效率.2年生和1年生罗布麻样地的固碳量相比对照平原荒漠,分别增加了23.21％和21.56％;土壤风蚀模数分别降低了70.87％和88.72％,差异均显著;土壤可蚀性K值相比对照平原荒漠分别降低了 13.50％和18.33％.本研究证明在新疆阿勒泰平原荒漠区种植罗布麻,构建灌草复合系统,能显著改善研究区的群落结构,提高植被的水分利用效率,增强平原荒漠区的生态系统服务功能,能很好地实现阿勒泰地区生态效益和经济效益的双赢.

Elm (Ulmus pumila), widely distributed in the north temperate zone, contributes to a special savanna-like woodland in typical grassland region in the northeastern China. This woodland performs a variety of ecological functions and environmental significance, such as decreasing soil erosion, stabilizing sand dunes, preserving species diversity. However, in the last approximate 30 years, the species composition, productivity and distribution area of elm woodland has decreased severely. A series of studies have been carried out to find out whether the climate changes or human disturbances caused the degradation of elm woodland and how these factors affected elm woodland. In this study, undisturbed, plowing and grazing elm woodland were investigated in 1983 and 2011 by using Point-Centered Quarter method. The relationship between vegetation changes and environmental factors was analyzed by Bray-Curtis ordination. The results show that in 2011, species diversity and understory productivity of undisturbed elm woodland decrease slightly compared to those of undisturbed elm woodland in 1983. However, nearly 60% of the species is lost in the plowing and grazing elm woodland relative to the species undisturbed elm woodland in 1983. Interestingly, plowing stimulates the growth of elm and certain understory species through furrowing soil and accelerating soil nutrient turnover rate. Grazing disturbance not only leads to species loss and productivity decrease, but also induces changes in elm growth (small, short and twisted). The mean age of the elm was 29 ± 2 yr in undisturbed and plowing elm woodland, while only 15 yr in the grazing elm woodland. The results of Bray-Curtis ordination analysis show that all sample stands clustered to three groups: Group I including the undisturbed sample stands of 83UE (undisturbed elm woodland in 1983) and 11UE (undisturbed elm woodland in 2011); Group II including sample stands of PE (elm woodland disturbed by plowing); Group III including samples stands of GE (elm woodland disturbed by grazing). The results indicate that the long time disturbance of the plowing and grazing have converted elm woodland to different community types. Climate change is not the primary reason causing the degradation of elm woodland, but plowing and grazing disturbance. Both plowing and grazing decrease the vegetation composition and species diversity. Grazing further decreases vegetation productivity and inhibits the growth of elm tree. Therefore, we suggest that reasonable plowing and exclusive grazing would be favorable for future regeneration of degraded elm woodland.

In 2010,ten sampling sites were installed on the meadow steppe and typical steppes in the Guyuan County and Weichang County of Hebei Province and the Duolun County of Inner Mongolia,aimed to approach the relationships between the grassland biodiversity and the primary productivity and soil condition in the farming and pastoral regions of northern China.In the study areas,the Shannon-Wiener diversity index(H) and Pielou evenness index of the grasslands were significantly positively correlated(P0.05),and the H and Pielou evenness index had significant positive correlations with the primary productivity(P0.01).However,there was no significant correlation between the H and soil water content(P0.05).The H and Pielou evenness index had significant negative correlations with the total nitrogen in 0-30 cm soil layer(P0.05),and the H had a significant negative correlation with the total nitrogen(P0.01) but less correlation with the organic matter in 10-20 cm soil layer(P0.05).The results further proved that improving grassland biodiversity could increase the productivity and stability of grassland ecosystem.

To study the seasonal variability of soil inorganic nitrogen (N) across borders at the woodland-farmland ecotone and potential mechanisms, contents of soil inorganic N were measured during the dry season (May 20 and June 30) and the rainy season (August 10 and September 20) of 2006 in the Songnen Plain of Northeast China. The borders between farmland and woodland were determined by a border-and-ecotone detection analysis (BEDA). The ecotone limits, often referred to as the depth-of-edge influence (DEI), are critical for determining the scale at which edge effect operates. The results showed that the soil inorganic N border between the woodland and farmland was located further toward the woodland interior during the rainy season (DEI = 53.4 ± 8.7 m, August 10) than during the dry season (DEI = 35.0 ± 12.6 m, May 20). The seasonal variability in the soil inorganic N border was found to be associated with seasonal changes of deposition flux of N (the correlation coefficients between them for the dry season and rainy season were 0.61 and 0.67, respectively), which resulted from foliation patterns of trees and crops. Accordingly, the leaf area index at woodland edges was lower than that in the woodland interior, so woodland edges captured large amounts of atmosphere nitrogen deposition. The average DEI was 44.1 m, which was in accordance with the values of other temperate forest boundaries in literatures; therefore, BEDA was an appropriate method to estimate the borders of ecotones.

Using evaluation indexes of changing evaluation coefficient industrial structure and the industrial structure stability in the time series,the paper studied the change of agricultural structure characteristics of Minqin County.The result showed that agricultural structure presents simplification trend in 2003—2009 years,agricultural structure presents mutations instability mode under the influence of the environment of agricultural policies and agricultural market,the change of industrial structure presents mutability and instability.The adjustment of agricultural structure should meet ecological environment development and economic development needs,appropriately develop economic crops,increase the proportion of the forestry services and production value.

Seedling regeneration is critical to the stability and sustainability of plant community. In our early investigation of elm (Ulmus pumila L.) woodlands, which plays important roles in decreasing erosion, stabilizing sand dunes and maintaining species diversity in north China, we found that the most elm seedlings could not germinate in the second growing season. Therefore, early morphological and physiological traits of elm seedlings and survival were studied under different soil humidity, nutrients and clipping treatments under greenhouse conditions. Results showed that elm seedlings’ height and relative growth rate significantly increased with the increase of soil nutrient availability. A significant interaction of soil nutrients and clipping treatment was also tested for relative growth rate, which was highest at 50% clipping treatment when soil nutrient contents were high. Total biomass and biomass allocation obviously increased with increasing soil humidity and nutrients and there was significant interactive effect of soil humidity and nutrients. Leaf chlorophyll concentration and net photosynthesis rate markedly increased along the gradient of soil humidity. However, adequate soil nutrient availability did not induce high leaf chlorophyll concentration or net photosynthesis rate, and no significance of clipping treatment was found for the physiological traits of seedlings. Survival rate of elm seedlings was significantly increased with increasing soil humidity and nutrient availability, and a significant interactive effect of soil humidity and nutrients was also found. The clipping treatment did not show statistical significance for survival rate of elm seedlings. The results also showed that, when soil humidity was at the lowest level, both morphological and physiological traits of elm seedlings were lowest, especially the survival rate which was nearly zero. Therefore, we concluded that soil humidity was the primary factor limiting growth and survival of elm seedlings and 3% soil humidity was the minimum for elm regeneration. The joint influence of clipping and soil nutrient treatments markedly altered seedling growth and survival especially when soil nutrients were limited, and it also indicated that the actual infertile sandy habitat of native elm woodland would aggravate negative effects of frequent grazing. We suggested that strengthening of practical water and nutrient management, and removing grazing would be favorable for improving elm seedlings’ survival and regeneration of degraded native elm woodlands.

Elm(Ulmaceae) widely distributes in the temperate zone of northern Hemisphere,especially in Russia,England,America,Denmark etc.Depending on its drought tolerance,salinity adaptation and adaptation to various climates,elm(Ulmus pumila) contributes to the maintenance of savanna-like ligneous plant community in typical grassland region of the north China.This sparse elm community,generally provides with tree canopy covers less than 25% and average height of mature trees lower than 5 m,and appears a complex mosaic landscape as a whole.Elm woodlands are primarily located in the sandlands in Hunshandak,Kerqin and Ordos Plateau of Inner Mongolia,and in Songnen Plains of northeastern China.Elm woodlands offer wide expanses of grazing land for large herbivores.On the other hand,it can be utilized by agriculture cultivation.Some studies demonstrate that elm woodlands play important roles in decreasing soil erosion and stabilizing sand dune.At larger spatial scale,elm woodland is considered as a natural barrier to sandstorm in the eastern Asia.It greatly contributes to alleviating environmental deterioration and maintaining ecosystem stability.In the past two decades,most elm woodlands of the northern China have been over-utilized by grazing or cultivation.Such excessive utilization of elm woodland leads to the decrease in basal area and productivity,the scarcity of U.pumila juveniles,and the increase in species composition of community.This greatly weakens ecological protective functions of elm woodland.Some researchers assumed that the degradation of elm woodland is associated with drought climate,overgrazing and tree cutting.In order to anchor the essential reason that caused degradation of elm woodland,we carried out following experiments: in the Songnen grassland of China(40°30′-48°05′N,122°12′-126°20′E),we sampled an undisturbed Ulmus woodland in 1983,and we maintanenced that the Ulmus woodlands were seldom disturbed in past two decades.In 2004,we sampled five sites: the undisturbed site;two farming sites with 40% and 90% crop coverage;and two sites with light and heavy grazing as determined by distance to the nearest village(600 and 200 m,respectively).In each site,we sampled ten 4 m2 plots,and species′ names,number and aboveground biomass(measured as community productivity) were measured.Species diversity was calculated.We found that: 1) there were not significant species and productivity changes of elm woodland in 1983 and 2004,therefore we concluded that climate changes was not the main reason caused the degradation of elm woodland;2) in the contrast with the undisturbed elm woodland,the plowing and grazing elm woodlands showed great differences in species composition and productivity.These leaded us to such conclusion that human activities,such as plowing and grazing,directly decreased the productivity and species diversity of elm woodland,and also simplified the structure of elm woodland.3) Furthermore,high intensity of grazing caused the constructive specie(U.pumila) was thinner and shorter;therefore,elm represented much more shrub-like in grazing elm woodland.Finally,we concluded that human activities were the main and direct reason caused the degradation of elm woodland.