Grassland Ecology Research Articles

Grassland fire ecology has roots in the late Miocene

That fire facilitated the late Miocene C4 grassland expansion is widely suspected but poorly documented. Fire potentially tied global climate to this profound biosphere transition by serving as a regional-to-local driver of vegetation change. In modern environments, seasonal extremes in moisture amplify the occurrence of fire, disturbing forest ecosystems to create niche space for flammable grasses, which in turn provide fuel for frequent fires. On the Indian subcontinent, C4 expansion was accompanied by increased seasonal extremes in rainfall (evidenced by δ18Ocarbonate), which set the stage for fuel accumulation and fire-linked clearance during wet-to-dry seasonal transitions. Here, we test the role of fire directly by examining the abundance and distribution patterns of fire-derived polycyclic aromatic hydrocarbons (PAHs) and terrestrial vegetation signatures in n-alkane carbon isotopes from paleosol samples of the Siwalik Group (Pakistan). Two million years before the C4 grassland transition, fire-derived PAH concentrations increased as conifer vegetation declined, as indicated by a decrease in retene. This early increase in molecular fire signatures suggests a transition to more fire-prone vegetation such as a C3 grassland and/or dry deciduous woodland. Between 8.0 and 6.0 million years ago, fire, precipitation seasonality, and C4-grass dominance increased simultaneously (within resolution) as marked by sharp increases in fire-derived PAHs, δ18Ocarbonate, and 13C enrichment in n-alkanes diagnostic of C4 grasses. The strong association of evidence for fire occurrence, vegetation change, and landscape opening indicates that a dynamic fire-grassland feedback system was both a necessary precondition and a driver for grassland ecology during the first emergence of C4 grasslands.

Recent advances in understanding grasslands.

Grasslands are a vitally important ecosystem, supporting a wide range of ecosystem services and high levels of biodiversity. As a consequence, they have long been a focus for ecologists, playing host to some of the world’s longest-running ecological experiments and providing the inspiration for many long-standing theories and debates. Because the field of grassland ecology is broad, encompassing many areas of ecology, this article picks some areas of particular debate and development to look at recent advances. The areas include relationships between diversity and productivity, ecosystem stability and ecosystem service provision, global change threats from nutrient addition, invasive species, climate change, and plant soil interactions.

Taxonomic and Functional Responses of Soil Microbial Communities to Annual Removal of Aboveground Plant Biomass.

Clipping, removal of aboveground plant biomass, is an important issue in grassland ecology. However, few studies have focused on the effect of clipping on belowground microbial communities. Using integrated metagenomic technologies, we examined the taxonomic and functional responses of soil microbial communities to annual clipping (2010–2014) in a grassland ecosystem of the Great Plains of North America. Our results indicated that clipping significantly (P < 0.05) increased root and microbial respiration rates. Annual temporal variation within the microbial communities was much greater than the significant changes introduced by clipping, but cumulative effects of clipping were still observed in the long-term scale. The abundances of some bacterial and fungal lineages including Actinobacteria and Bacteroidetes were significantly (P < 0.05) changed by clipping. Clipping significantly (P < 0.05) increased the abundances of labile carbon (C) degrading genes. More importantly, the abundances of recalcitrant C degrading genes were consistently and significantly (P < 0.05) increased by clipping in the last 2 years, which could accelerate recalcitrant C degradation and weaken long-term soil carbon stability. Furthermore, genes involved in nutrient-cycling processes including nitrogen cycling and phosphorus utilization were also significantly increased by clipping. The shifts of microbial communities were significantly correlated with soil respiration and plant productivity. Intriguingly, clipping effects on microbial function may be highly regulated by precipitation at the interannual scale. Altogether, our results illustrated the potential of soil microbial communities for increased soil organic matter decomposition under clipping land-use practices.

WATCHING GRASS GROW- A PILOT STUDY ON THE SUITABILITY OF PHOTOGRAMMETRIC TECHNIQUES FOR QUANTIFYING CHANGE IN ABOVEGROUND BIOMASS IN GRASSLAND EXPERIMENTS

Abstract. Grassland ecology experiments in remote locations requiring quantitative analysis of the biomass in defined plots are becoming increasingly widespread, but are still limited by manual sampling methodologies. To provide a cost-effective automated solution for biomass determination, several photogrammetric techniques are examined to generate 3D point cloud representations of plots as a basis, to estimate aboveground biomass on grassland plots, which is a key ecosystem variable used in many experiments. Methods investigated include Structure from Motion (SfM) techniques for camera pose estimation with posterior dense matching as well as the usage of a Time of Flight (TOF) 3D camera, a laser light sheet triangulation system and a coded light projection system. In this context, plants of small scales (herbage) and medium scales are observed. In the first pilot study presented here, the best results are obtained by applying dense matching after SfM, ideal for integration into distributed experiment networks.

Distribution modelling of pre-Columbian California grasslands with soil phytoliths: New insights for prehistoric grassland ecology and restoration.

Historical reconstructions of plant community distributions are useful for biogeographic studies and restoration planning, but the quality of insights gained depends on the depth and reliability of historical information available. For the Central Valley of California, one of the most altered terrestrial ecosystems on the planet, this task is particularly difficult given poor historical documentation and sparse relict assemblages of pre-invasion plant species. Coastal and interior prairies were long assumed to have been dominated by perennial bunchgrasses, but this hypothesis has recently been challenged. We evaluated this hypothesis by creating species distribution models (SDMs) using a novel approach based on the abundance of soil phytoliths (microscopic particles of biogenic silica used as a proxy for long-term grass presence) extracted from soil samples at locations statewide. Modeled historical grass abundance was consistently high along the coast and to a lesser extent in higher elevation foothills surrounding the Central Valley. SDMs found strong associations with mean temperature, temperature variability, and precipitation variability, with higher predicted abundance in regions with cooler, equable temperatures and moderated rainfall, mirroring the pattern for modern perennial grass distribution across the state. The results of this study strongly suggest that the pre-Columbian Central Valley of California was not dominated by grasses. Using soil phytolith data as input for SDMs is a promising new method for predicting the extent of prehistoric grass distributions where alternative historical datasets are lacking.

Reference gene selection for qRT-PCR assays in Stellera chamaejasme subjected to abiotic stresses and hormone treatments based on transcriptome datasets.

BackgroundStellera chamaejasme Linn, an important poisonous plant of the China grassland, is toxic to humans and livestock. The rapid expansion of S. chamaejasme has greatly damaged the grassland ecology and, consequently, seriously endangered the development of animal husbandry. To draft efficient prevention and control measures, it has become more urgent to carry out research on its adaptive and expansion mechanisms in different unfavorable habitats at the genetic level. Quantitative real-time polymerase chain reaction (qRT-PCR) is a widely used technique for studying gene expression at the transcript level; however, qRT-PCR requires reference genes (RGs) as endogenous controls for data normalization and only through appropriate RG selection and qRT-PCR can we guarantee the reliability and robustness of expression studies and RNA-seq data analysis. Unfortunately, little research on the selection of RGs for gene expression data normalization in S. chamaejasme has been reported.MethodIn this study, 10 candidate RGs namely, 18S, 60S, CYP, GAPCP1, GAPDH2, EF1B, MDH, SAND, TUA1, and TUA6, were singled out from the transcriptome database of S. chamaejasme, and their expression stability under three abiotic stresses (drought, cold, and salt) and three hormone treatments (abscisic acid, ABA; gibberellin, GA; ethephon, ETH) were estimated with the programs geNorm, NormFinder, and BestKeeper.ResultOur results showed that GAPCP1 and EF1B were the best combination for the three abiotic stresses, whereas TUA6 and SAND, TUA1 and CYP, GAPDH2 and 60S were the best choices for ABA, GA, and ETH treatment, respectively. Moreover, GAPCP1 and 60S were assessed to be the best combination for all samples, and 18S was the least stable RG for use as an internal control in all of the experimental subsets. The expression patterns of two target genes (P5CS2 and GI) further verified that the RGs that we selected were suitable for gene expression normalization.DiscussionThis work is the first attempt to comprehensively estimate the stability of RGs in S. chamaejasme. Our results provide suitable RGs for high-precision normalization in qRT-PCR analysis, thereby making it more convenient to analyze gene expression under these experimental conditions.

Current status of grassland degradation and measures for grassland restoration in northern China

Grasslands in northern China are traditionally important bases for livestock production and ecological barriers for China. However, these grasslands degraded extensively due to global climatic change and poor management during the past half century. Such grassland degradation leads to dramatic declines in multiple ecosystem functions. Here we first analyzed the current status of these grasslands, with emphasizing on production and ecological functions. In general, the capability of annual aboveground biomass production in these grasslands has been greatly impaired in comparison with that in 1980s and not recovered to normal level despite application of some restoration measures. As indicated by large inter-annual variation in grasses production, the capability of feedback regulation to buffer the negative impacts of climatic change was greatly eroded. Carrying capability for animals of grasslands at the national level displayed an increasing trend in recent years, while the actual stocking capacity remained higher than its potential. Total water resources in these grasslands have declined greatly as evidenced by rapid losses of lakes and drying up of rivers. We next reviewed the major measures for restoration and management of grasslands in northern China during the past decades and analyzed their advantages and constrains, respectively. Fencing (prohibition of grazing) has been used in some area, but was difficult to extend to a larger area mainly due to economic reasons. Seasonal grazing and rotational grazing have been recommended by local governments. However, the outcomes of these measures are limited. Tillage and harrowing have also been suggested for restoration of the degraded grasslands, but it has rarely been largely used due to higher costs and inconsistent results. Reseeding grasses and/or legumes in natural grasslands are potentially useful for grassland restoration, but frequent droughts limit its application. Rotational mowing is a good measure for hey production system. Moreover, the yearly shift between grazing and mowing is much better than successive grazing or mowing. Fertilization has often been used in grassland management in most developed countries. However, this measure has not been widely applied in China due mainly to the lack of information on the types, rates and applied methods. Finally, based on our long-term studies on grassland ecology and practices in grassland restoration, especially the demonstration work in Hulunbuir grasslands, we propose some proposition on policy making and development of technical measures related to sustainable management of the grasslands in northern China. Ecological monitoring and evaluation of native grasslands should be done, and local farmers should be compensated for based on the evaluation results. Establishing cultivated pastures with high productivity and quality of forage grasses are key measures for protection and restoration of the degraded natural grasslands. As above-mentioned measures on grassland restoration usually take long time (from several years to decades) to restore the natural grasslands, new technical measures to restore the degraded natural grasslands are urgently needed. This review has important implications for improving the production and ecological functions of natural grasslands in general and for the sustainability of grass-based animal husbandry in particular.

Game Analysis of Intergovernmental Interests in the Sharing of Grassland Ecological Civilization across Regions

The party has made a strategic decision to promote the construction of ecological civilization vigorously in the 18th CPC National Congress, and the impact of ecological civilization construction and sharing on the economic development of our country is also growing. This paper is based on the study of the coordination of local government interests in the process of joint construction and sharing of grassland ecological civilization. First of all, it explained the conflicts of interest between local governments in the process of co-construction and sharing of ecological civilization in the grass-roots steppe. Secondly, it conducted a game analysis of the interests among local governments in the process of co-construction and sharing of grassland ecological civilization across regions, and on this basis, the corresponding countermeasures were put forward. Cross regional ecological civilization sharing refers to all the administrative regions (can be the smallest village as the basic unit) in the process of its development in a reasonable, fair, sustainable, harmonious as the basic value idea, to resource sharing, shared responsibility, development and win-win for the construction of ecological civilization of grassland basic mode. In this process, we must strengthen the different departments within the administrative region of the regional cooperation and build a win-win situation, emphasizing the administrative regional construction, symbiosis, sharing, win-win situation. The core obstacle in the process of sharing the ecological civilization across the grassland is the interest barrier, especially the interests among the local governments. If the interests of the regions cannot be effectively coordinated, it will cause great obstacles to the process of sharing the ecological civilization across the region and make it difficult to effectively carry out. The conflict of interests that the government faces will affect its decision-making and execution in the process of sharing ecological civilization, which leads to the difficulty of sharing the ecological civilization of the grassland across the region. Only by creating a community of interests, improve the cooperation between local governments, to mobilize the enthusiasm of the local government in the process of cross regional grassland ecological civilization sharing, coordinate the behavior of local government, to promote its development planning and use of resources, protecting the ecological environment of grassland, grassland construction and ecological civilization, so it is of great significance to study.

Impact of grassland conversion to forest on groundwater recharge in the Nebraska Sand Hills

Study regionNebraska National Forest in the High Plains Aquifer, Nebraska Sand Hills, U.S.A. Study focusThis research aimed to investigate the effects of grassland conversions to forest on recharge rates in a century-old experimental forest. The DiffeRential Evolution Adaptive Metropolis (DREAMZS) global optimization algorithm was used to calibrate the effective soil hydraulic parameters from observed soil moisture contents for 220 cm deep uniform soil profiles. The historical recharge rates were then estimated by applying the numerical model HYDRUS 1-D for simulation of two plots representing grasslands and dense pine forest conditions. New hydrological insightsThe results indicate that conversion from grasslands to dense pine forests led to vegetation induced changes in soil hydraulic properties, increased rooting depth, and greater leaf area index, which together altered the water budget considerably. The impacts of land use change, expressed in percent of gross precipitation, include a 7% increase in interception associated with an increase in leaf area index, a nearly 10% increase in actual evapotranspiration, and an overall reduction of groundwater recharge by nearly 17%. Simulated average annual recharge rates decreased from 9.65 cm yr−1 in the grassland to 0.07 cm yr−1 in the pine plot. These outcomes highlight the significance of the grassland ecology for water resources, particularly groundwater recharge, in the Nebraska Sand Hills and the overall sustainability and vitality of the High Plains Aquifer.

Grassland ecology in China: perspectives and challenges

During the last few decades, there have been an increasing number of studies on grassland ecology in China, involving the classic ecology concepts or theories and the applicable ecological principles of grassland conservation or management. This paper reviews the main progress in the following aspects. (1) Research on grassland species adaptation and resistance, population dynamics and foraging behavior, and biodiversity and community stability. (2) Research on managed grassland ecosystems (grassland grazing ecology) including grazing effects on grassland ecosystem function and foraging behavior by large herbivores. (3) Global climate change and grassland processes and functioning. (4) Applied research on grassland restoration and ecosystem health assessments such as vegetation restoration, restoration of ecosystem functioning, and assessment methods. There have been significant advances in grassland ecology, including the functions of ecosystem biodiversity, the ecological stoichiometry mechanisms affecting grassland community stability, grazing regulation of plant diversity and nutrient cycling. Grassland ecologists have succeeded in making these advances through observational, experimental and theoretical studies. Nevertheless, there are still significant challenges for the grassland ecology research, including understanding of grassland spatial processes, grassland grazing and multi-functionality, integrated effects of global climate change across grassland areas, as well as the ecological methodology and experimental techniques in grassland ecology.

模拟氮沉降和降雨变化对贝加尔针茅草原土壤细菌群落结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 模拟氮沉降和降雨变化对贝加尔针茅草原土壤细菌群落结构的影响 DOI: 10.5846/stxb201612092539 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31170435） Effects of simulated nitrogen deposition and precipitation change on soil bacterial community structure in a Stipa baicalensis steppe Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究氮沉降和降雨变化对土壤细菌群落结构的影响，对未来预测多个气候变化因子对草地生态系统影响的交互作用具有重要意义。以施氮和灌溉分别模拟氮沉降和降雨增加，采用高通量测序技术，研究8个氮添加水平（0、15、30、50、100、150、200、300kg N hm-2a-1）和2个水分添加水平（不灌溉、模拟夏季增雨100 mm灌溉）对土壤细菌群落结构的影响。结果表明，氮素和水分输入增加后，土壤细菌群落组成、丰度均显著变化（P < 0.05）。在群落中占主导的细菌门类有疣微菌门Verrucomicrobia（30.61%-48.51%）、变形菌门Proteobacteria（21.37%-29.97%）、酸杆菌门Acidobacteria（9.54%-20.67%）和拟杆菌门Bacteroidetes（4.96%-9.74%）。在常规降雨和水分添加两种条件下，随着氮添加水平的增加，占主导的细菌门类（相对丰度 > 1%）表现出不同的变化趋势。疣微菌门相对丰度在常规降雨N100-N300条件下显著降低，但在氮素和水分同时添加条件下随氮添加水平升高而逐渐升高，在N200-N300时显著升高。变形菌门和拟杆菌门相对丰度在常规降雨高氮添加条件下呈升高趋势，但在水分添加时却无明显变化。酸杆菌门相对丰度在常规降雨高氮添加条件下升高，但在水分添加后呈明显下降趋势。放线菌门Actinobacteria相对丰度在常规降雨N100-N300条件下显著升高，但在水分添加后高氮添加时显著降低。厚壁菌门Firmicutes相对丰度在常规降雨条件下无显著变化，但在水分和高氮添加条件下降低。浮霉菌门Planctomycetes相对丰度在两种不同的水分添加条件下均呈先升高后降低的趋势。氮素和水分添加对土壤细菌群落结构的变化存在明显的互作效应（P < 0.0001）。在不同氮素和水分输入条件下共有19个土壤细菌门类相对丰度有显著差异。土壤细菌群落结构的变化主要来自于疣微菌门和酸杆菌门的相对丰度变化，两者可作为土壤细菌群落结构变化的指示种。综上，氮素和水分添加显著改变了土壤细菌群落结构，氮素和水分对土壤细菌不同门类相对丰度变化存在明显的互作效应。 Abstract:Nitrogen (N) deposition and precipitation change are important phenomena in global climate change and they can strongly influence grassland ecology. There have been many studies on the response of plant and soil microbial communities to N addition. However, the interactive effects of N addition and irrigation on soil microbial communities are still largely unknown. Studying the effects of nitrogen (N) deposition and precipitation change on soil microbial community structure is of great significance for predicting the interactive effects of multiple climate factors on grassland ecosystems in the future. Here, we simulated N deposition and precipitation change by N addition (0, 15, 30, 50, 100, 150, 200, 300 kg N hm-2a-1) and irrigation (no irrigation and irrigation equivalent to 100 mm extra summer rainfall) at a test area on the Stipa baicalensis steppe. A split-plot design was adopted. Soil samples were collected with a soil probe after four years of experimental treatments. Using high-throughput sequencing technology, we evaluated the interactive effects of N addition and irrigation on the soil bacterial community structures. Statistical analyses showed that N addition and irrigation significantly (P < 0.05) shifted the composition and relative abundance of the soil bacterial community.The dominant bacterial phyla were Verrucomicrobia (30.61%-48.51%), Proteobacteria (21.37%-29.97%), Acidobacteria (9.54%-20.67%), and Bacteroidetes (4.96%-9.74%). Under normal precipitation, the relative abundance of Verrucomicrobia significantly decreased in N100-N300 (P < 0.05), but the relative abundance of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes increased with high N addition levels. However, the relative abundance of Firmicutes did not significantly change. When water was added with N, the relative abundance of Verrucomicrobia increased following the increase of N addition rates and significantly increased in N200-N300, but the relative abundance of Acidobacteria, Firmicutes and Actinobacteria decreased after N addition. The relative abundance of Proteobacteria and Bacteroidetes did not significantly change under N addition combined with irrigation. The ANOVA of the split-plot design showed that N addition and irrigation interactively affected the structure of the soil bacterial community. The results of the Linear Discriminant Analysis (LDA) showed that the relative abundance of 19 bacterial phyla significantly shifted under different N and water addition rates. The changes in soil bacterial community structure were mainly related to changes in the relative abundance of the phyla Verrucomicrobia and Acidobacteria. Hence, phyla Verrucomicrobia and Acidobacteria could be used as indicator species for changes in soil bacterial community structure. In all, N addition and irrigation significantly changed the structure of the soil bacterial community. N and water addition interactively affected the relative abundance of different soil bacterial phyla. 参考文献 相似文献 引证文献

The South Brazilian grasslands – A South American tallgrass prairie? Parallels and implications of fire dependency

Fire has long been recognized as an important driver of vegetation patterns, and is of particular importance for biodiversity maintenance in many grassland systems, including the North American tallgrass prairie. Here, it has been successfully used as a conservation and restoration tool. In southern Brazil, grasslands appear to present many similarities to tallgrass prairie in terms of composition and ecology, but the role of fire has been poorly studied and it is not usually used in conservation. Here, we compare plant genera and family composition of tallgrass prairie and South Brazilian grassland sites. We find striking similarities in terms of dominant families, genera, and functional types. The similarities between plant communities suggest similarities in ecological processes and should lead to a re-thinking of conservation strategies in South Brazilian grasslands. Research on the role of fire is needed, and comparative North–South studies on grasslands in the Americas likely will provide important insights for grassland ecology and management.

Research on the Mechanism of Cross Regional Grassland Ecological Compensation

In recent years, grassland environmental damage has become serious, and grassland resources protection task has become heavy, grassland ecological compensation has become an effective way to solve this problem; but the current grassland ecological compensation standards were low, the effect is poor. The fundamental reason is the model of administrative division destroys the integrity of grassland. Based on the analysis of the status quo of grassland compensation, this paper tries to protect the grassland integrity, breaks the administrative division restriction, implements the space regulation, constructs the framework of cross-regional grassland ecological compensation mechanism, describes its operation process. It provides new way to realize the sustainable development of the grassland environment.

Soil ecology and ecosystem services of dairy and semi-natural grasslands on peat

Peat wetlands are of major importance for ecosystem services such as carbon storage, water regulation and maintenance of biodiversity. However, peat drainage for farming leads to CO2 emission, soil subsidence and biodiversity losses. In the peat areas in the Netherlands, solutions are sought in reducing drainage, adapting farming to wetter soils, and converting productive dairy grasslands to less intensively managed semi-natural grasslands. Our objective was to compare the soil ecology and related ecosystem services of dairy and semi-natural grasslands on peat soils (Terric Histosols). Soil biotic and abiotic parameters were measured in twenty dairy and twenty semi-natural sites, with particular focus on (i) soil faunal diversity (ecosystem service “maintenance of biodiversity”), (ii) CO2 emission (“climate regulation”), (iii) water infiltration (“water regulation”) and (iv) soil fertility (“grass production”). Mean soil faunal taxonomic richness per site (alpha diversity) was higher in dairy grasslands compared to semi-natural grasslands. However, the total observed number of taxa (gamma diversity) in dairy grassland was 13% lower for soil fauna and 21% lower when including plant species. Potential C mineralization rate in the topsoil – used as a proxy for CO2 emission – was not influenced by land use but was limited by drought. Additionally, potential C mineralization depended on different C sources and microbial groups in the two grassland types. Water infiltration rate differed by a factor of five between land use types (dairy > semi-natural), and correlated with soil porosity. As expected, soil fertility was higher in dairy than in semi-natural grasslands. However, potential N mineralization was similar in dairy and semi-natural grasslands and was correlated negatively with bacterial biomass apparently indicating N immobilization, and positively with bacterial growth that depended on labile C and N in soil. Our study on peat soils shows that dairy versus semi-natural grassland use influences biodiversity, climate regulation, water regulation and (potential for) grassland production. We conclude with recommendations for land management to optimize the delivery of those ecosystem services.

Fire, Smoke, and Expertise in South Africa’s Grasslands

Fire as a management practice in South Africa’s grasslands inflamed heated debate throughout the twentieth century. Imported ecological ideas meshed with homegrown sectoral land management traditions to reinforce a powerful anti-burning narrative among experts. Farmers, however, developed their own theories on burning, and the history of fire research, policy, and management reveals a series of entanglements between ecological theory, management policies and recommendations, and practice that complicate narratives grounded in historiographical traditions focused on critiquing settler and colonial expertise. This article recommends three distinctions to make when thinking about the history of scientific expertise: first, between an individual’s abstract theorizing and his or her “thinking in the field”; second, between the influence of accepted scientific findings and the thinking guiding official policies of land management sectors; and third, between official policies and actual land management practices. This article provides overviews of long-term fire use in the country’s grasslands, the ecology of grasslands and fire in South Africa, of early debates over fire, and scientific fire research and management in the country.

Nitrogen deposition combined with elevated precipitation is conducive to maintaining the stability of the soil fungal diversity on the Stipa baicalensis steppe

Changes in nitrogen (N) deposition and precipitation can strongly influence grassland ecology. However, the combined effects of N and water addition on soil fungal genetic diversity, and especially the underlying influencing factors, are not well understood. We investigated the response of soil fungal α diversity to experimental N and water addition in a northern Chinese steppe. We found that N addition alone exceeding N100 (100 kg N·ha−1·yr−1) significantly increased soil fungal α diversity. However, when water was added, soil fungal diversity did not significantly change following N enrichment. Structural equation modelling (SEM) results indicated that N addition increased soil fungal α diversity, while N addition combined with irrigation maintains soil fungal diversity that would otherwise be enhanced by N addition. This results from reversing the correlation between soil fungal diversity and plants\\\\soil physicochemical properties. Our results provide evidence that the effects of N deposition regarding soil fungal diversity might be overestimated if we ignore variations in water availability.

Elevated precipitation modifies the relationship between plant diversity and soil bacterial diversity under nitrogen deposition in Stipa baicalensis steppe

Nitrogen (N) deposition and precipitation change are important phenomena in global climate change and they can strongly influence grassland ecology. Previous studies primarily focused on the impact of N deposition or precipitation on plant community and soil microorganisms separately. They did not account for the relationship between plant and soil microbial communities. To better understand how future climate change may affect the relationship between plant and soil microbial diversity, we simulated N deposition and precipitation change through artificial fertilization (0, 15, 30, 50, 100, 150, 200, 300kg N ha−1·yr−1) and irrigation (no irrigation and irrigation equivalent to 100mm extra summer rainfall) at a test area on the Stipa baicalensis steppe. We found that the plant primary productivity increased following N enrichment but the plant diversity declined. The composition, abundance and diversity of soil bacteria changed in the test scenarios. Under normal precipitation, the bacterial OTU richness increased at N100 (100kg N ha−1·yr−1) and the bacterial diversity increased at N100–N300 (100–300kg N ha−1·yr−1). When irrigation was applied, the bacterial OTU richness and diversity were improved at low N levels (15–50kg N ha−1·yr−1) but decreased at high N levels (N100–N300). This is probably due to water addition lead to the dissolution of more nitrates in soil and thus decreased the soil pH. A significant negative relationship was observed between plant diversity and bacterial diversity under normal precipitation. Under irrigation, the correlation was also negative at low N levels (N15–N50), but became significantly positive when the N level exceeded N100, which contributed to decrease in bacterial diversity resulting from significant decrease of soil pH. Our results clearly showed the elevated precipitation modified the relationship between plant and soil bacterial diversity under N deposition. We predict that as the global climate change further intensifies, the interaction between climate change factors may exercise complex impact on ecological properties and lead to unexpected consequences on the feedback in plant-microbe-soil system.

Numerical studies on groundwater-grassland relations in an inland arid region in China

In this study, a 2-D numerical model was developed to assess the impacts of groundwater on grassland ecology in the Hulun Lake Basin. An extreme dry climate scenario and water resource management scenario and their interactions in the Hulun Lake Basin were designed, and their influence on groundwater was evaluated. The results show that the grassland ecology is heavily dependent on groundwater, and a distribution of groundwater with a depth of 8 m correlates well with the distribution of grassland. Under the water resource management scenario, the groundwater level will increase to a maximum value of 2.5 m after 15 years around Hulun Lake. The groundwater level will decrease dramatically under the extreme dry climate scenario, thus affecting the environment.

Winter ecology of a subalpine grassland: Effects of snow removal on soil respiration, microbial structure and function

Seasonal snow cover provides essential insulation for mountain ecosystems, but expected changes in precipitation patterns and snow cover duration due to global warming can influence the activity of soil microbial communities. In turn, these changes have the potential to create new dynamics of soil organic matter cycling. To assess the effects of experimental snow removal and advanced spring conditions on soil carbon (C) and nitrogen (N) dynamics, and on the biomass and structure of soil microbial communities, we performed an in situ study in a subalpine grassland in the Austrian Alps, in conjunction with soil incubations under controlled conditions. We found substantial winter C-mineralisation and high accumulation of inorganic and organic N in the topsoil, peaking at snowmelt. Soil microbial biomass doubled under the snow, paralleled by a fivefold increase in its C:N ratio, but no apparent change in its bacteria-dominated community structure. Snow removal led to a series of mild freeze-thaw cycles, which had minor effects on in situ soil CO2 production and N mineralisation. Incubated soil under advanced spring conditions, however, revealed an impaired microbial metabolism shortly after snow removal, characterised by a limited capacity for C-mineralisation of both fresh plant-derived substrates and existing soil organic matter (SOM), leading to reduced priming effects. This effect was transient and the observed recovery in microbial respiration and SOM priming towards the end of the winter season indicated microbial resilience to short-lived freeze-thaw disturbance under field conditions. Bacteria showed a higher potential for uptake of plant-derived C substrates during this recovery phase. The observed temporary loss in microbial C-mineralisation capacity and the promotion of bacteria over fungi can likely impede winter SOM cycling in mountain grasslands under recurrent winter climate change events, with plausible implications for soil nutrient availability and plant-soil interactions.

Disturbance ecology of Tasmanian highland grassland — an overview and implications for conservation management

Active manipulation of disturbances such as fire and grazing is often necessary to maintain or enhance biodiversity values in grasslands. However in many instances information is lacking on the disturbance regimes most likely to achieve conservation aims. This paper provides an overview of the effects of fire and grazing in Tasmanian highland grasslands, and the implications of these for conservation management of this vegetation. In Tasmania, highland grassland is defined as occurring above 600 m above sea level. The vegetation is typically dominated by species of Poa. Highland grassland is grazed by a suite of native herbivores and has a history of stock grazing, which continues at some sites of high biodiversity value. There is evidence that Indigenous Tasmanians regularly burnt highland grasslands and that Indigenous burning was instrumental in maintaining grassland at sites that otherwise would be forest. For highland grasslands below 1000 m asl, a reduction in the biomass of dominant grasses through disturbance is necessary in order to maintain plant species diversity. The use of periodic fire, together with native grazing, is likely to be beneficial in this regard. The combination of fire and grazing is also likely to prevent woody plant invasion and maintain vegetation structural heterogeneity. The near ubiquity of native grazing species means there is no ecological imperative for stock grazing. Low productivity of grasslands occurring above 1000 m means that competitive exclusion of interstitial species by grasses is unlikely and therefore active application of disturbance as a management tool will rarely, if ever be necessary. Disturbance management should be accompanied by a well-designed monitoring program and regular review of the management strategy