基于生态风险评估的锡林河流域退化草地优化管理

利用遥感监测和空间信息分析技术,通过对退化草地的退化等级评估、风险度评估以及易恢复度评估,构建了草地生态优化管理指数(EMI),探讨了退化草地生态优化管理的实践途径;并以锡林河流域为例, 分析了退化草地生态优化管理指数.结果表明,通过构建退化草地优化管理模型,定量分析流域内不同优化管理等级退化草地的退化程度、危害性和易恢复性,可以有针对性地采取合理的治理措施,有利于退化草地治理中的资源优化配置.该模型能整合退化草地的各种相关信息,具有较强的普适性.     

青藏高寒区退化草地生态恢复:退化现状、恢复措施、效应与展望

青藏高寒区属于独特而典型的高原生态系统,草地生态系统作为其重要组成部分,在对高寒区生态安全以及农牧民生计的维系中,占有举足轻重的地位。目前,青藏高寒区的草地生态系统退化严重,因此该区退化草地的生态恢复工作是国家生态工作的重中之重。近年来,已有大量研究提出了各种有效的恢复手段,但缺乏因地制宜的系统性总结和论述。基于此,在已有研究的基础上,阐述了青藏高寒区退化草地现状,总结了高寒区各生态类型分区的主要生态问题,明确了不同集成技术与模式的适用区域和范围,同时对这些技术、措施和模式的恢复效果和恢复机制进行分析和讨论。并对未来高寒草地生态系统的研究进行了展望,以期为青藏高寒区退化草地的恢复治理、高寒草地生态系统结构和功能稳定性维系提供系统的理论基础与技术支撑。     

21世纪初我国草地生态学研究展望

草地退化是我国天然草地面临的突出问题,在21世纪初期,我国的草地生态学将围绕解决草地退化这一核心问题展开深入的研究。其热点领域应在草地恢复生态学,草地界面生态学,草地放牧生态学,草地的健康诊断和草地的价值评估等5个方面。其中草地恢复生态学是治理退化草地的基础;草地界面生态学是剖析退化草地的切入点;草地放牧生态学是调控退化草地的手段;草地健康诊断有助于对草地退化进行客观评价;草地的价值评估则是对草地生态系统效益和服务的估算。     

退化草地生态恢复研究案例综合分析:年限、效果和方法

草地生态系统退化严重影响着全球生态安全、草原区域居民生计和草原文化多样性的发展。退化草地恢复工作依赖于对有效研究案例的借鉴,不同研究年限的案例对生态恢复实践的目标、恢复方案的制定有不同借鉴和参考作用,而获得有指导价值的研究案例通常是长期开展的研究工作。在调查国内外149个退化草地生态恢复案例基础上,该文综合分析了退化草地生态恢复的研究年限分布、恢复目标、恢复方法,效果及长期研究数据获取方法等,主要有以下几方面总结。(1)年限小于10a的案例数量较多,且更侧重于连续性研究;较长时间研究更多依赖于以前研究案例重访性研究。(2)相对而言,较长期的研究结果可靠性更高,其恢复技术的说服性更强,对于生产力的研究一般比生态功能研究的案例年限短些。(3)在退化草地生态恢复中,恢复目标排在前三位的分别是生物多样性,植被覆盖度和土壤碳库。(4)在调查的研究案例中关于动物群落的研究非常少。(5)退化草地恢复方法中应用最多是人工播种,围栏封育,放牧应用。(6)跨度时间较长的研究工作大多采用案例重访的方式,获取和以前可对比的数据资料。最后,建议特别应该重视案例重访方法的应用,尽可能更多的开展实地性数据获取再进行大数据综合,这样更可靠。     

氮添加对内蒙古退化草地植物群落多样性和生物量的影响

人为干扰及气候变化导致内蒙古草地发生了大面积退化, 氮添加是促进退化草地生产力恢复的一项重要措施。该文基于2011年建立的氮肥添加实验平台, 以3个不同退化程度(中度退化、重度退化、极度退化)草地群落为研究对象, 设置对照、10、20、30、40和50 g·m ^-2·a ^-1 6种氮添加处理, 分析氮添加对退化草地恢复过程中群落多样性和生物量的影响。结果表明: (1)氮添加降低了中度、重度退化草地恢复进程中物种丰富度和多样性, 对极度退化草地恢复进程中物种丰富度和多样性无明显影响。(2)氮添加促进了3个不同退化程度草地恢复进程中群落地上生物量的增加。(3)氮添加显著增加了群落中禾草的地上生物量及其在群落地上生物量中所占的比例, 降低了杂类草在群落地上生物量中的比例, 但对杂类草地上生物量无显著影响。研究表明在利用施肥措施治理退化草地的过程中, 需要充分考虑草地退化程度以及由氮添加引起的群落多样性和生产力的改变对草地生态系统功能的影响。     

Effects of nitrogen addition on the plant diversity and biomass of degraded grasslands of Nei Mongol,China

人为干扰及气候变化导致内蒙古草地发生了大面积退化, 氮添加是促进退化草地生产力恢复的一项重要措施。该文基于2011年建立的氮肥添加实验平台, 以3个不同退化程度(中度退化、重度退化、极度退化)草地群落为研究对象, 设置对照、10、20、30、40和50 g·m ^-2·a ^-1 6种氮添加处理, 分析氮添加对退化草地恢复过程中群落多样性和生物量的影响。结果表明: (1)氮添加降低了中度、重度退化草地恢复进程中物种丰富度和多样性, 对极度退化草地恢复进程中物种丰富度和多样性无明显影响。(2)氮添加促进了3个不同退化程度草地恢复进程中群落地上生物量的增加。(3)氮添加显著增加了群落中禾草的地上生物量及其在群落地上生物量中所占的比例, 降低了杂类草在群落地上生物量中的比例, 但对杂类草地上生物量无显著影响。研究表明在利用施肥措施治理退化草地的过程中, 需要充分考虑草地退化程度以及由氮添加引起的群落多样性和生产力的改变对草地生态系统功能的影响。     

侵蚀退化红壤自然恢复下土壤生物学质量演变特征

为了探讨严重侵蚀退化红壤区自然植被恢复过程中土壤生物学质量演变特征,对南方严重侵蚀退化红壤自然植被恢复的4个演替阶段（裸地,地衣地,苔藓地和草地）,以及该地区人工马尾松林地的土壤微生物量、酶活性和线虫数量进行了比较研究。结果表明：在侵蚀红壤自然恢复过程中土壤生物学性质演变特征明显。在恢复初期,地衣和苔藓对土壤生物学性质的改善主要体现在土壤表层。在0～2cm土层地衣地土壤微生物量碳、氮、蔗糖酶和脲酶活性高于裸地,但差异不显著;苔藓地表层微生物量氮、脲酶和酸性磷酸酶活与人工马尾松林地已无显著差异,表明苔藓地是严重侵蚀退化红壤自然恢复过程中土壤质量改善的重要阶段。裸地、地衣地和苔藓地土壤线虫恢复程度低于微生物量和酶活性。草地土壤微生物量碳、氮和3种酶活性以及线虫数量则显著高于自然恢复初期各阶段。与人工恢复林相比较,自然恢复草地表层土壤生物学质量优于人工马尾松林地,但对深层土壤的改善效果不如林地。相关分析表明自然恢复过程中土壤微生物与酶活性的改善程度比较一致,而土壤线虫对自然植被恢复响应与微生物和酶活性不尽相同。     

退化荒漠草地恢复对土壤有机碳及其驱动因子的影响

揭示中国北方退化荒漠草地土壤有机碳分布积累对草地恢复的响应规律和驱动机制,可为科学治理退化草地、阐明草地恢复的土壤碳汇效应提供科学依据。以鄂尔多斯高原不同恢复阶段(流动沙地、恢复前期、恢复中期和恢复后期)的退化草地为研究对象,分析了0-10 cm,10-20 cm和20-40 cm的土壤有机碳对草地恢复的响应,并采用多种统计方法分析土壤有机碳的驱动因素。结果表明:(1)草地恢复显著增加了不同深度的土壤有机碳(P ＜ 0.05),恢复后期可使0-10 cm、10-20 cm和20-40 cm土壤有机碳分别增加8.28倍、6.44倍和9.46倍。(2)不同深度土壤有机碳的驱动因素不同:植被盖度和植物多样性共同控制0-10cm土壤有机碳的积累,而下层土壤(10-20 cm和20-40 cm)有机碳积累受到养分限制(土壤氮素)的影响,并且这种影响会随着土壤深度的增加而加强。研究结果可为合理恢复退化草地提供理论依据,同时还为通过草地恢复促进土壤碳循环以实现双碳目标提供了证据。     

植物-土壤反馈与草地群落演替:菌根真菌和土壤病原菌的调控作用

由植物引起的根际土壤生物或非生物环境的改变能够反馈影响群落中不同植物的生长,直接改变共存植物的相对竞争关系,推动群落结构的动态变化。作为土壤生物群落的重要组成部分,土壤微生物在植物-土壤反馈关系中起到重要的调控作用,对解释植物群落的演替进程和方向有着重要的意义。在草地植物群落演替的早期阶段和外来物种入侵的过程中,宿主植物对丛枝菌根真菌（AMF）的依赖性较低,受本地病原菌的影响较小,一般不存在负反馈。在演替后期,植物对AMF更具依赖性,而积累的病原菌则产生较强的负反馈效应,从而促进群落物种共存和植物多样性,提高草地生产力和稳定性。研究微生物-植物反馈机制不仅有助于完善草地退化与恢复理论,还对退化草地恢复治理的实践有着指导意义。未来关于根际微生物-植物反馈在草地群落演替中的作用应该加强以下几方面的研究：（1）在实验方法上,开展专性微生物-植物反馈研究;（2）在测定指标上,进一步量化不同微生物在反馈关系中的功能差异;（3）在研究对象上,加强土壤微生物在植物群落水平的反馈研究;（4）在应用上,明晰植物-土壤反馈在退化草地恢复过程中的作用,指导草地管理实践。     

温带草原退化对土壤剖面微生物学特征的影响

【目的】草地退化已成为我国草原当前面临的最主要问题。土壤微生物量和土壤酶活性是反映土壤养分和土壤环境质量的重要指标。揭示退化程度对温带草原土壤剖面微生物学特征的影响规律。【方法】以内蒙古温带草原为研究对象,选取成熟自然草地以及中、重度退化草地和极度退化草地4种典型不同退化程度的草地,按不同土壤深度分层采样并进行土壤微生物量和土壤微生物酶活性的测定。【结果】表层土壤微生物生物量及其酶活性在不同退化样地中呈现出一致的趋势:成熟自然样地中度退化样地重度退化样地极度退化样地;10-20 cm土层土壤微生物学特征与表层的差异随着退化程度的加深逐渐减少,甚至在极度退化样地中10-20 cm层土壤微生物指标高于表层。【结论】表层土壤微生物生物量及其酶活性随着退化程度的加深而减少。同时,退化程度越严重,表层与10–20 cm土层之间土壤微生物学特征的差异越小。这一结果为评价草地退化程度提供了新思路,为温带草原的恢复和重建提供了重要的理论依据。     

三江源区“黑土滩”型退化草地人工恢复植物群落的演替动态

选取青藏高原三江源区"黑土滩"型退化草地上建植的人工草地为研究对象,对不同建植年限人工草地植物群落及其各功能群的物种组成、平均高度、盖度和地上生物量及植物多样性等进行实地调查和对比分析,探讨"黑土滩型"退化草地在人工恢复过程中植物群落组成和多样性变化,以期回答人工恢复的草地植物群落何时才能接近天然草地、人工恢复的时间阈值应为多长等问题,从而为三江源区"黑土滩"型退化草地的恢复重建提供科学的理论指导。研究结果表明:草地恢复前5年内,禾本科植物的数量大量增加,植物群落的高度增加了847.6%,植物群落盖度增加了134.5%;不同恢复年限的草地植物群落的多样性指数都有相似的变化趋势,恢复8年后植物群落组成达到阶段性的稳定状态,在恢复时间达16—18年后,逐渐向更稳定的状态转化;恢复18年的草地与天然草地植物群落的Jaccard及Sorensen相似度指数分别为0.596、0.747,Cody差异度指数为9.5。由此可见,建植人工草地的方式恢复退化草地,可在建植8年后达较好的恢复效果;恢复时间达16年以上的人工草地采取适度的调控措施,有利于其向天然草地恢复演替;建植18年的人工草地物种组成情况与天然草地最接近,但仍有差异。因此,"黑土滩"型退化草地的人工促进恢复,到未退化的状态至少需要18年以上。     

内蒙古典型草原地带退化草原的恢复动态

对退化草原自然恢复演替过程的监测,是认识其恢复过程、机理、探讨恢复的限制因子和进一步制定快速、低投入生态恢复措施的基础。通过对内蒙古典型草原地带退化草原［星毛委陵菜（Potentila acaulis）、冷蒿（Artemisia frigida）和寸草苔（Carex duriuscula）等为主］封育恢复动态 8年的监测表明：在退化草原群落自然恢复过程中,植物高度上升;植被盖度和生物量先增加,尔后基本稳定,或略有下降的趋势。群落的物种丰富度增加微弱,这可能与该区草原植物和野生动物协同进化有关,同时与数千年的家畜放牧史有关。即植物物种对放牧有较大的耐性,停止放牧,物种的丰富度也增加较少;群落结构的变化主要表现在不同种群优势度的消长上。群落均匀度指数的动态过程分析表明,恢复8年的草原群落尚未达到天然草原状态,尚需进一步的监测研究。     

浑善达克退化沙地草地生态恢复试验研究

选择草地退化十分严重的浑善达克沙地腹地开展恢复生态学研究 ,试图寻求沙地草地生态恢复的新途径。采取“以地养地”模式 ,在小范围的土地上 ,建立高产饲草基地 ,使牲畜的压力逐步向高效地集中 ,同时改变畜群结构 ,解决当地牧民生活出路 ;而大面积的退化草地 ,主要借助自然力恢复。结果表明 ,自然力在浑善达克沙地退化生态系统恢复中起到巨大的作用 ,群落生物量、平均高度和总盖度 2年后均随恢复时间增加而增加 ( P<0 .0 5 )。流动沙丘的裸沙 ,经 2 a自然恢复后 ,生物量达 1 0 1 2 g/m,总盖度高达 60 %。与对照相比 ,封育 2 a后固定沙地群落盖度增加近 3倍 ;滩地群落生物量提高了 9倍 ,平均高度增加 4倍。植被组成方面 ,恢复前固定沙地以冷蒿 ( Artemisia frigida)、糙隐子草 ( Cleistogens squarrosa)和寸草苔 ( Carexduriuscula)等为主 ,恢复 2 a后冰草 ( Agropyron cristatum)、褐沙蒿 ( Artemisia intramongolica)等占优势 ;滩地植被中 ,羊草 ( L eymus chinensis)、披碱草 ( Elymus dahuricus)等逐步取代了灰绿藜 ( Chenopodiumglaucum)和尖头叶藜 ( Chenopodium acuminatum)等。生态恢复不仅使自然生态系统得以保护 ,而且带动了社会经济的发展 ,项目中的正蓝旗巴音胡舒嘎查牧民 ,在实验示范前后     

Transfer seeds,hay, or soil blocks? The importance of the completeness of biological inputs to address dispersal and establishment limitations during the restoration of plant assemblages in floodplain grasslands

This study investigated different techniques of grassland restoration to overcome dispersal or establishment limitation, which are key processes influencing early-successional plant community assembly. A fully randomized in situ experiment was set up in a former arable land in a floodplain along the Garonne river (south-western France) to test for the effect of (1) the type and completeness of the biological input (any biological material—seed, hay, and soil—transferred to the site under restoration), (2) soil disturbance by deep tillage, and (3) their interaction on plant community dynamics for 5 years. All inputs influenced the plant community structure and composition. The effects depended on the type of the input but not necessarily in link with its completeness. High density and diversity seed mixture led to high levels of richness and relative abundance of target species like soil blocks, the input considered as the most complete. During the first year, hay transfer mostly influenced community assembly through negative litter effects. Delayed germination of several species contributed to buffer these early effects. This study supports the importance of dispersal limitation during early succession in degraded grassland ecosystems whereas soil disturbance had only subtle effects on the seed bank and standing plant community, indicating that competition and establishment limitation were of secondary importance in our study system. Our results suggest that even low-frequency immigration events (e.g. when a few seeds are transferred within hay) can be of great importance providing that a sufficiently long time period is considered for grassland restoration.     

Plant community and soil available nutrients drive arbuscular mycorrhizal fungal community shifts during alpine meadow degradation

Arbuscular mycorrhizal fungi (AMF) play an important role in maintaining the function and sustainability of grassland ecosystem, but they are also susceptible to environmental changes. In recent decades, alpine meadows on the Tibetan Plateau have experienced severe degradation due to the impact of human activities and climate change. But it remains unclear how degradation affects the AMF community, a group of functionally important root associated microorganisms, which potentially limit the development and application of microbial technologies in the restoration of degraded grasslands. In this study, we investigated AMF communities richness and composition in non-degraded (ND), moderately degraded (MD) and severely degraded (SD) alpine meadows on the Tibetan Plateau, and then explored their main biotic and abiotic determinants. Alpine meadow degradation significantly reduced plant community biomass, richness, soil organic carbon, total nitrogen, total phosphorus, available nitrogen and available phosphorus, but increased soil pH. AMF community composition and the iesdominant family and genera differed significantly among different degradation stages. Grassland degradation shifted the AMF community composition in favor of Claroideoglomus over Rhizophagus, and resulted in a marked loss of Glomeraceae and the dominance of Diversisporaceae. Alpine meadow degradation significantly increased AMF hyphal density and richness, likely working as a plant strategy to relieve nutrient deficiencies or loss as a result of degradation. The structural equation model showed that AMF community richness and composition were significantly influenced by plant community, followed by soil available nutrients. Soil available nutrients was the key contributor to the increased AMF hyphal density and richness during grassland degradation. Our findings identify the effects of alpine meadow degradation on AMF richness and highlight the importance of the plant community in shaping the AMF community during alpine meadow degradation. These results suggest that plant community restoration should be the primary goal for the ecological restoration of degraded alpine meadows, and these soil functional microorganisms should be simultaneously integrated into ecological restoration strategies and management.     

Success of active restoration in grasslands: a case study of birds in southern Brazil

Grasslands in southeastern South America have been extensively converted to various land uses such as agriculture, threatening regional biodiversity. Active restoration has been viewed as a management alternative for recovery of degraded areas worldwide, although most studies are conducted in forests and none has evaluated the effect of active restoration of grasslands in southeastern South America. From 2015 through 2017 we monitored a federally owned tract of grassland from the beginning of the active‐restoration process. We compared the bird community in this active‐restoration area (AR) with a reference area (NG) in Pampa grasslands in southern Brazil. We sampled birds by point counts and surveyed vegetation structure in plots. Over the 3 years of active restoration, bird species richness and abundance were higher in AR (30 species, 171 individuals) than NG (22 species, 154 individuals). The species composition also differed between the two habitats. Grassland bird species were present in both AR and NG. The vegetation structure differed between AR and NG in five attributes: height, short and tall grasses, herbs, and shrubs. Since it has been found that active restoration is useful in promoting species diversity, we encourage studies of the use of long‐term restoration efforts. Our study, even on a local scale, showed a rapid recovery of the bird community in the active‐restoration compared to native grassland, and suggests the potential for recovery of the degraded grasslands of the Brazilian Pampa biome.     

Spider community responses to grassland restoration: balancing trade‐offs between abundance and diversity

Spiders (Araneae) play key roles in ecosystems, not only as common and abundant generalist predators, but also as major contributors to biodiversity in many areas. In addition, due to their short generation times and high mobility, spiders respond rapidly to small changes in their environment, potentially making them useful indicators for restoration monitoring. However, few studies have focused on spider responses to grassland restoration in the United States. We compared degraded, native, and restored grassland sites to examine how spider communities and habitat respond to arid grassland restoration. We also examined how responses varied with the age of the restoration project. Spider communities in native sites differed from those in restored and degraded sites in several ways: native sites had fewer spiders and a different community composition than degraded and restored sites. However, native and restored sites had more species than degraded sites. Chronosequence data showed trends for lower abundance, higher species richness, and changing community composition as restoration projects mature. Several habitat variables were closely linked to variation in spider communities including cover of invasive annual grasses, litter, and biological soil crusts. Our data suggest that spider and vegetation responses to grassland restoration efforts can be successful in the long term—with resulting communities becoming more similar to native ones—and that spiders are useful indictors of grassland restoration. Our results also suggest that restoration may involve balancing trade‐offs between ecosystem services, with potential losses in predatory control offset by increases in biodiversity with restoration effort.     

Grazing Gradient versus Restoration Succession of Leymus chinensis (Trin.) Tzvel. Grassland in Inner Mongolia

Grazing‐induced degradation of grasslands is the primary impediment to the socioeconomic development of Inner Mongolia. It affects the entire environment of northern China. Understanding grassland dynamics is necessary for restoration and sustainable management of these degraded ecosystems. The recovery dynamics of a degraded Leymus chinensis (Trin.) Tzvel. grassland after removal of grazing was studied in comparison with its spatial variation along a grazing gradient, using its climax community as a benchmark. The species composition, diversity, and biomass of the grassland vegetation, as well as the attributes (height, density, and individual mass) of major species, were examined on the eight sites along the grazing gradient and in the recovering grassland over 11 years. The spatial pattern of grassland vegetation along the grazing gradient closely reflected its recovery trajectory over time. Both the spatial and the temporal processes exhibited the same shift in species dominance in association with grazing removal or less grazing intensity. Grassland degradation was accompanied by an increase in species density and a decrease in species size; this trend was reversed during recovery. This result suggested that the degraded grassland is highly resilient and that restoration could occur naturally by reducing or excluding grazing animals. However, some differences existed between the spatial and the temporal processes. Species richness was high on the light‐ or no‐grazing sites along the gradient, but varied little during the recovery of the degraded grassland. Species evenness was high under moderate to light grazing along the gradient and was high at the beginning of the recovery period but not at the end. Although standing biomass improved significantly during the recovery period, it did not change significantly along the grazing gradient. These observed discrepancies were related to the intrinsic difference in the spatial versus temporal processes and are discussed together with the advantage/disadvantage of the grazing gradient versus dynamic monitoring methods in grassland dynamics studies.