Can the Study of Natural Vegetation Succession Assist in the Control of Soil Erosion on Abandoned Croplands on the Loess Plateau,China?

In the Loess Plateau, China, arable cultivation of slope lands is common and associated with serious soil erosion. Planting trees or grass may control erosion, but planted species may consume more soil water and can threaten long‐term ecosystem sustainability. Natural vegetation succession is an alternative ecological solution to restore degraded land, but there is a time cost, given that the establishment of natural vegetation, adequate to prevent soil erosion, is a longer process than planting. The aims of this study were to identify the environmental factors controlling the type of vegetation established on abandoned cropland and to identify candidate species that might be sown soon after abandonment to accelerate vegetation succession and establishment of natural vegetation to prevent soil erosion. A field survey of thirty‐three 2 × 2–m plots was carried out in July 2003, recording age since abandonment, vegetation cover, and frequency of species together with major environmental and soil variables. Data were analyzed using correspondence analysis, classification tree analysis, and species response curves. Four vegetation types were identified and the data analysis confirmed the importance of time since abandonment, total P, and soil water in controlling the type of vegetation established. Among the dominant species in the three late‐successional vegetation types, the most appropriate candidates for accelerating and directing vegetation succession were King Ranch bluestem (Bothriochloa ischaemum) and Lespedeza davurica (Leguminosae). These species possess combinations of the following characteristics: tolerance of low water and nutrient availability, fibrous root system and strong lateral vegetative spread, and a persistent seed bank.     

Vegetation succession of abandoned croplands in Ruanliang and Yingliang in the Ordos Plateau

Shrub encroachment has been a key phenomenon in arid and semi-arid grasslands over the last century. However, little research has been dedicated to vegetation dynamics in the abandoned croplands, which are surrounded by shrub-encroached grasslands. In this study, several abandoned croplands in Ruanliang and Yingliang in the Ordos Plateau were selected, and the biomass, coverage, density, root pattern, and plant litter dynamics were studied. The results showed that: (1) The abandoned croplands in Ruanliang experienced three community types, including weeds community, the subshrub Artemisia ordosica community, and the perennial grass community, while the abandoned croplands in Yingliang experienced three community types, including weeds community, perennial Stipa bungeana with Artemisia frigida community, and S. bungeana community. (2) The important value for the annual or biennial grass in abandoned croplands in Ruanliang declined during the restoration process, for the perennial grass it increased, and for the subshrub it first increased and then went down to zero. In Yingliang abandoned croplands, however, the perennial grass remained dominant during the succession process. (3) The root of A. ordosica in Ruanliang abandoned croplands was mainly distributed in soil depths of 0–30?cm; the root of the perennial grass was mainly in the 0–20?cm range, and S. bungeana was found at soil depths of 0–5?cm. To restore to a natural vegetation state, about 20?years would be needed to recover the total biomass, and 10?years would be needed to restore the vegetation coverage in Ruanliang abandoned croplands. For Yingliang abandoned croplands, about 15 and 20?years would be needed to restore the total biomass and vegetation coverage, respectively, to a state of natural vegetation.     

Temporal changes in species diversity and composition in abandoned fields in a <Emphasis Type="Italic">trans</Emphasis>-Himalayan landscape,Nepal

Secondary succession is an increasing phenomenon due to global changes in agriculture policies and practices. The empirical findings are biased towards the temperate zone. Abandonment of agriculture fields is less frequent in the subtropical and tropical zones where agriculture areas are, in general, expanding. But there are exceptions; a rapid rate of abandonment of agricultural fields have taken place in the arid trans-Himalayan region, due to today’s globalization of economy. We analysed agriculture fields that were abandoned between 1950 and 2003 in a large u-valley in central Nepal (3400 m a.s.l.). The potential forest vegetation is dominated by Pinus wallichina and shrubs of junipers and cotoneaster species. We tested the intermediate richness hypothesis in relation to vegetation cover, soil development and whether old-field succession is convergent or divergent with species data from 242 1 m² plots in 5 age-classes. The main species compositional turnover expressed by Detrended Correspondence Analyses (DCA) correlated, as expected, with time after abandonment. Fields that were abandoned a long time ago are closer to forest at the periphery of the agricultural landscape. Moisture of the soil significantly increased with age of abandonment, but total vegetation cover and pH were negatively related to age. Beta diversity expressed in DCA SD-units showed an increasing trend with age of abandonment, supporting the divergence pattern in old-field succession. The reason why the succession is not converging may be due to browsing by domestic animals that prevent a closed canopy of pines and juniper to develop. There was a significant hump-shaped pattern in species richness along the temporal gradient, which agrees with the intermediate species-richness hypothesis. There was a rapid increase in species richness in plots close to the villages that were used for haymaking which increased the seed input significantly.     

半干旱黄土高原苜蓿草地撂荒过程土壤水分变化特征

土壤水分是黄土高原植被恢复和生态建设的主要限制因子,明确土壤水分随植被演替的变化规律是阐明黄土高原植被与水分相互作用机制的重要基础。以半干旱黄土高原小流域苜蓿草地撂荒过程为研究对象,通过对2016-2018年生长季苜蓿群落、苜蓿+赖草群落、赖草群落和长芒草群落四种草地群落0-1.8 m土壤水分进行动态监测以及0-5 m深度土壤水分测定,分析不同演替阶段苜蓿草地土壤水分的动态特征,探讨土壤水分对苜蓿草地撂荒过程的响应。结果表明：（1）在苜蓿草地撂荒演替过程中,土壤水分随群落恢复时间的延长呈先增加后降低的变化,降水的年际动态显著影响不同演替群落的土壤水分响应;（2）0-0.4 m土壤水分主要受降水影响,使得各草地群落在这一层次没有显著差异（P>0.05）,而1 m以下的土壤水分含量则主要受植被类型的影响,各草地群落之间存在显著差异（P<0.05）;（3）0-5 m深层土壤水分随群落的演替,1 m以下各土层土壤水分含量逐渐增加,表明撂荒过程中使土壤水分得到了一定程度的恢复。研究结果揭示了苜蓿草地撂荒过程土壤水分的变化规律,可为黄土高原生态恢复提供理论依据。     

Drought and recovery effects on belowground respiration dynamics and the partitioning of recent carbon in managed and abandoned grassland

The supply of soil respiration with recent photoassimilates is an important and fast pathway for respiratory loss of carbon (C). To date it is unknown how drought and land‐use change interactively influence the dynamics of recent C in soil‐respired CO₂. In an in situ common‐garden experiment, we exposed soil‐vegetation monoliths from a managed and a nearby abandoned mountain grassland to an experimental drought. Based on two ¹³CO₂ pulse‐labelling campaigns, we traced recently assimilated C in soil respiration during drought, rewetting and early recovery. Independent of grassland management, drought reduced the absolute allocation of recent C to soil respiration. Rewetting triggered a respiration pulse, which was strongly fuelled by C assimilated during drought. In comparison to the managed grassland, the abandoned grassland partitioned more recent C to belowground respiration than to root C storage under ample water supply. Interestingly, this pattern was reversed under drought. We suggest that these different response patterns reflect strategies of the managed and the abandoned grassland to enhance their respective resilience to drought, by fostering their resistance and recovery respectively. We conclude that while severe drought can override the effects of abandonment of grassland management on the respiratory dynamics of recent C, abandonment alters strategies of belowground assimilate investment, with consequences for soil‐CO₂ fluxes during drought and drought‐recovery.     

The effect of management on productivity,litter accumulation and seedling recruitment in a Carpathian mountain grassland

The management regime may have a significant impact on the productivity and dynamics of grasslands, but the causal relationships influencing grassland conservation value are still not completely understood. Changes of selected community characteristics, such as standing crop, proportion of forbs in the standing crop, litter amount, litter decomposition and seedling recruitment, were investigated in a 4 year manipulative experiment in a mountain grassland in Slovakia. The aim of the research was to compare changes in newly abandoned sites and sites where restoration measures were applied after 20 years of abandonment. The sites were located in areas containing two vegetation types of the Arrhenatherion alliance (wet Poo-Trisetetum and dry Anthoxantho–Agrostietum) with different moisture regimes. The expected increase of the standing crop after abandonment was rather slow, and more pronounced towards the end of the experiment, and in the wet meadow type (~30% increase). The restoration mowing promoted forb proportions in the biomass, but it did not decrease the standing biomass in the restored grasslands. Strong litter accumulation after abandonment was observed in subsequent years after abandonment, when the amount of litter increased about 100% in abandoned plots. Decrease in litter was also significant after the start of restoration mowing (a decrease from 258 to 159 g m⁻² in wet type and from 287 to 147 g m⁻² in dry type was noted). Accumulated litter was negatively correlated to seedling recruitment (r = −0.63 at the end of the experiment). The litterbag experiment showed that the wet type has a higher rate of decomposition, with 20% more biomass decomposed during the litter-bag experiment. The experiment confirmed a negative role of litter accumulation on seedling recruitment, with the number of seedlings per m² decreasing from 413 to 321 individuals in the abandoned wet-type site. This may lead to a decrease in species richness. Mowing along with raking of mowed biomass may be a useful tool to restore degraded mountain grasslands and to remove accumulated litter from the stands.     

Restoration prospects of abandoned species‐rich sandy grassland in Hungary

Abstract. Secondary succession and seed bank formation was studied in a formerly grazed, abandoned, eastern Hungarian sandy steppe‐meadow (Pulsatillo‐Festucetum). The vegetation was sampled at different elevations of a sand dune which became partly invaded by the tree Robinia pseudo‐acacia ca. 10 yr ago. Pre‐abandonment vegetation records were used as historic references. Though composition of the non‐invaded grassland only changed moderately, dominance of tall grasses (Elymus hispidus, Poa angustifolia) increased significantly at the cost of annuals and low stature perennials. In the stand invaded by Robinia most grassland species were lost and replaced by nitrophytes. Vertical position influenced species abundance, but affected the composition only moderately. Fine‐scale zonation of the vegetation also changed with time. Species richness of the above‐ground vegetation and the seed density of soil samples at the lower elevation were slightly greater than at the higher sites. Seed banks of sensitive grassland specialists (e.g. Pulsatilla pratensis subsp. hungarica) disappeared during grass encroachment. Following extinction from above‐ground vegetation, restoration must rely on dispersal from adjacent areas. In contrast, several annuals and perennials, which survived this degradation stage in the above‐ground vegetation, possessed seed banks. Many of these species became extinct from the vegetation during the Robinia invasion but left viable persistent seeds. This fact is promising for restoration of the Potentillo‐Festucetum sandy pasture. Competitive weedy species and sprouting Robinia can, however, limit seedling establishment.     

黄土丘陵区氮磷添加对草地群落优势种养分利用特征的影响

为阐明黄土丘陵区氮磷添加对草地群落优势种养分利用特征的影响,探究群落结构和物种多样性的变化机制,选取5个典型优势种,即白羊草(Bothriochloa ischaemum)、长芒草(Stipa bungeana)、达乌里胡枝子(Lespedeza davurica)、铁杆蒿(Artemisia sacrorum)和猪毛蒿(Artemisia scoparia)为研究对象,采用裂区试验设计,以氮添加为主区处理, 包括:0(N0)、25(N25)、50(N50) 和100(N100) kg N hm^-2 a^-1;以磷添加为副区处理,包括:0(P0),20(P20),40(P40) 和80(P80) kg P₂O₅ hm^-2 a^-1,测定了各物种叶片氮磷比、氮磷重吸收效率、氮磷利用效率和相对生物量等参数。5种植物的氮和磷重吸收效率正相关,对氮磷添加量的响应具有耦合性。不同氮磷添加处理下,达乌里胡枝子叶片氮磷比最高,而氮磷重吸收效率最低;白羊草和长芒草的氮磷利用效率和重吸收效率高于其他物种。单施磷或N25与磷配施下,各物种相对生物量与氮磷比和磷利用效率呈正相关关系,与氮利用效率和氮磷重吸收效率呈负相关关系。单施氮、N50和N100与磷配施下,各物种相对生物量与氮磷利用效率和重吸收效率呈正相关,与氮磷比呈负相关。不施肥处理下,白羊草和长芒草相对生物量最高,低氮高磷下达乌里胡枝子相对生物量最高,高氮高磷下铁杆蒿和猪毛蒿相对生物量最高。不同优势种对氮磷添加的响应不同,生理生态过程各异,决定了其在群落中的优势度,这是氮磷添加后草地群落结构和物种多样性发生变化的关键机制。     

鄂尔多斯台地盐沼滩地微生物群落与土壤条件分析

[背景]我国北方内陆区与平原区土地盐碱化问题严重,针对微生物如何在极端盐碱地植被演替过程中发挥作用的研究鲜有报道.[目的]研究鄂尔多斯台地5种不同植被类型的盐沼湿地微生物群落与土壤条件的关系,筛选出耐盐碱菌群及影响耐盐碱菌群的土壤环境因子.[方法]采用高通量测序技术,对其微生物细菌群落组成进行了比对分析.[结果]鄂尔多...     

Soil erodibility,microbial biomass,and physical–chemical property changes during long-term natural vegetation restoration: a case study in the Loess Plateau,China

Soil erodibility (K factor) is an important index for measuring soil susceptibility to water erosion, and an essential parameter that is needed for the prediction of soil erosion. Field investigation and laboratory analysis were conducted to study the changes of soil characteristics during long-term vegetation restoration in the hilly gullied loess area. The soil erodibility K values were calculated using the EPIC model and the physico-chemical properties as well as microbial characteristics were evaluated along a chronosequence of natural vegetation recovery (0–50 years) in abandoned land in the Zhifanggou Watershed of Ansai County, northwestern Shaanxi Province, China. The results showed that natural vegetation recovery following abandonment resulted in improvement of the soil properties and structure and these improving effects were closely related to the date of abandonment. Specifically, the K value of the surface layer (0–20 cm) was significantly reduced with time, while the total organic carbon, total nitrogen and soil microbial biomass C, microbial N and microbial P and the water-stable aggregate increased quickly. During the first 10 years of abandonment, these changes occurred relatively quickly due to a significant increase in soil organic matter, after which they gradually fluctuated for approximately 20 years, reaching their uttermost or minimum levels finally. However, these values differed greatly under Platycladus orientalis forest, which suggests that soil rehabilitation is a long-term task that requires several generations to complete.     

Above- and belowground dynamics of plant community succession following abandonment of farmland on the Loess Plateau, China

Aboveground and belowground changes during vegetation restoration and vegetation successions need to be characterized in relation to their individual responses to changes in soil resources. We examined above- and belowground vegetation characteristics, soil moisture, and nutrient status at the end of the growing season in 2006 in plots with vegetation succession ages of 2, 4, 6, and 8 years (two replicates each) that had been established on abandoned cropland, where potatoes had been grown for 3 years, using hoe and plow cultivation, immediately prior to vegetation clearance and subsequent natural plant colonization. A plant community comprising pioneer species [e.g., Artemisia capillaries, (subshrub)] was characterized by low levels of species richness (7.5?±?1.4 species m^?2), plant density (35.7?±?4.2 stems m^?2), fine root length density (940.1?±?90.1 m m^?2), and root area density (2.3?±?0.3 m² m^?2) that increased rapidly with time. Aboveground and belowground characteristics of both A. capillaries and the later successional species, Stipa bungeana (C3 perennial grass), increased in the first 6 years, but in the following 2 years A. capillaries declined while S. bungeana thrived. Thus, the fine root length density of A. capillaries, 812.4 m m^?2 after 2 years, changed by a factor of 1.7, 2.0, and 0.4 in the 4th, 6th, and 8th years, whereas that of S. bungeana changed from 278.4 m m^?2, after 4 years, and by 1.7 and 23.3 times in the 6th and 8th years, respectively. Secondary vegetation succession resulted in reduced soil moisture contents. Soil available P and N mainly influenced aboveground characteristics, while soil moisture mainly influenced belowground characteristics. However, soil moisture had no significant affect on S. bungeana belowground characteristics at the population level in this semiarid region.     

Secondary Succession and Natural Habitat Restoration in Abandoned Rice Fields of Central Korea

Floristic composition and soil characteristics (moisture, pH, nutrient contents) in abandoned upland rice paddies of different ages were analyzed to clarify the regenerative aspects of succession as a tool for habitat restoration. The study sites represented five seral stages: newly abandoned paddy fields; successional paddy fields abandoned for 3, 7, and 10 years; and a 50‐year‐old Alnus japonica forest. A vegetation sere was apparent in changes of dominant plant species in the order Alopecurus aequalis var. amurensis (annual grass), Aneilema keisak (annual forb), Juncus effusus var. decipiens (rush), Salix koriyanagi (willow), and Alnus japonica (alder) communities. These temporal stages resemble the spatial zonation of vegetation in local riparian floodplain ecosystems, indicating a hydrosere, with soil moisture decreasing over time. Age distributions and life forms of the dominant plant species support a “tolerance” model of secondary succession, in which the established species persist into later successional stages. Persistence of earlier colonizers led to a net cumulative increase in species richness and a more even distribution of species cover with increasing field age. Between 10 and 50 years, vegetation stabilizes as an alder community. Soil moisture content decreased steadily with paddy field age after an initial rise immediately after their abandonment, whereas pools of organic matter, N, P, K, Ca, and Mg, increased with field age. The pace and direction of recovery of native vegetation and natural soil properties in these abandoned rice paddies resembled classic old field succession, a form of secondary succession that often serves as a template for guiding restoration efforts. Active intervention, in particular dismantling artificial levees, could accelerate the recovery process, but natural habitat recovery generally appears sufficiently robust to achieve “passive” restoration of this rare community without intervention.     

Feral horses dung piles as potential invasion windows for alien plant species in natural grasslands

Small scale disturbances could act as patches that provide sites for the colonization of competitively inferior species, promoting the establishment of non-native species in some cases. We analyzed the vegetation associated with feral horse dung piles in montane pampas grasslands in Mid-East Argentina and described the changes following their abandonment, evaluating whether dung piles act as invasion windows, allowing the entrance of alien plant species. We estimated the portion of the study area directly covered by horse manure and dung height was used to estimate the time elapsed after the abandonment of each pile. Vegetation replacement on dung piles of different ages was assessed and compared with grassland controls using discriminant analysis. We used regression analysis to look for changes in vegetation cover, species richness, species diversity and evenness in response to height (age) of the dung piles, and principal component analyses (PCA) to identify groups of plants associated with different successional stages. We compared cover of alien plant species on dung piles with grassland controls using one-way ANOVA. On average, 2.5% of the study area was covered by horse dung. Total vegetation cover, species richness, diversity and evenness increased after the piles were abandoned. Characteristic plant groups were associated with initial, middle and last phases of the studied succession. Vegetation on the dung piles significantly differed from that in grassland controls and two species were consistently associated with dung piles: the invasive Red Star Thistle, Centaurea calcitrapa, and a native grazing-intolerant grass, Nassella clarazii. Non-native species cover was also higher in dung piles than in control plots. Dung piles cover a significant portion of grassland area in our study site, produce significant changes in the vegetation and are associated with some invasive alien plants that could eventually colonize more pristine areas in the vicinity. On the other hand, they might represent refuges for palatable species, since horses seem to avoid them for grazing.     

Using the age of the oldest woody specimen for studying post-pasture successions in Corsica (Mediterranean island)

The aim of this research is to reconstruct the invasion history of sites by using core sampling and analysing the installation date of tree species. A total of 107 sample sites, abandoned since 0 to 45 years ago and distributed in eight valleys of central Corsica, were studied. Results show a high (r² = 0.86 P < 0.0001) correlation between the abandonment date derived from historic aerial photographs and the age of the oldest woody specimen in the site. For recent abandonment periods, the oldest woody species present in sample plots were grazing tolerant shrubs (short-lived species). When the abandonment period exceeded 20 years, the oldest species in sample plots were long-lived tree species. The use of category (short or long-lived species) and age of oldest woody species of sites allow to create a quantitative estimation of abandonment period available without old aerial photographs. This new chronological variable is relevant for studying intermediate (one to several decades) periods of abandonment in secondary succession processes. The use of such variable allows the analysis of succession of vegetal communities or the establishment of the dynamical response curves of species.     

Fungal communities differentially respond to warming and drought in tropical grassland soil

Climate change is predicted to cause more extreme events, such as heatwaves, and different precipitation patterns. The effects of warming and short‐term drought on soil microbial communities, in particular fungal communities, remain largely unexplored under field conditions. Here, we evaluated how the fungal community of a tropical grassland soil responds to these changes. A field experiment was carried out in a temperature free‐air controlled enhancement (T‐FACE) facility in Ribeirão Preto, Brazil. The isolated and combined effects of drought and a 2°C increase in temperature were investigated. Based on metabarcoding of the ITS2 region, a total of 771 operational taxonomic units were observed. While warming affected the community structure, drought affected the alpha diversity, and the interaction between warming and drought affected both diversity and structure. The change in community composition driven by warming affected only the less abundant species (>1% of the total sequences). The aspect of the fungal communities that was most affected was diversity, which was increased by drought (p < .05), mostly by reducing the dominance of a single species, as observed in the watered plots. In a phylogenetic context, some fungal taxa were favoured by changes in temperature (Hypocreales) and drought (Sordariales) or disadvantaged by both (Pleosporales). It was of note that a water deficit increased the abundance of phytopathogenic fungi, such as Curvularia, Thielavia and Fusarium species. Overall, our results provide evidence that fungal communities in tropical grassland soils have greater sensitivity to drought than to temperature, which might increase the incidence of certain soil‐borne diseases.     

阴山北麓农牧交错区退耕地草地生态系统碳交换及水分利用效率

内蒙古阴山北麓农牧交错区由于长期不合理的开垦造成了荒漠草地生态系统碳交换等生态功能的显著丧失。我国20世纪末开始实施的退耕还林还草工程产生了大量退耕地,随着自然恢复演替,这些退耕地的生态功能得到了有效的修复,其巨大的碳汇潜力成为了荒漠草地生态系统碳循环研究的热点。研究通过空间代替时间的方法,对内蒙古阴山北麓典型区域——武川县周边无干扰的荒漠草原以及3个退耕恢复阶段草地的生态系统CO₂交换(NEE、GEP和ER)、水分利用效率(WUE)以及生物量等指标进行了实地测量。结果表明：(1)随着退耕恢复演替时间的推移,生态系统CO₂交换呈显著上升趋势,演替晚期植被NEE与未受干扰的荒漠草地无明显差异;(2)生态系统水分利用效率的变化趋势与生态系统CO₂交换基本一致,但已退耕17年后的退耕地WUE仍没有恢复至未受干扰荒漠草地的水平;(3)导致以上结果的原因主要与退耕地地上植被生物量的恢复以及一、二年生植物和多年生植物比例的演替变化有关。结果表明荒漠草地退耕地恢复过程中生态系统功能的恢复可能并非是同时的,而是分阶段有选择进行的。     

干旱胁迫对高山离子芥试管苗抗氧化系统及其活性氧代谢的影响

该试验以高山离子芥试管苗(Chorispora bungeana)为试材,采用固液培养法,设置对照(不添加PEG-6000,CK),轻度干旱胁迫(5%PEG-6000)、中度干旱胁迫(20%PEG-6000)、重度干旱胁迫(40%PEG-6000)4个干旱处理水平,分析干旱胁迫对高山离子芥幼苗抗氧化系统、活性氧代谢等部分生理特征的影响,以揭示高山离子芥在干旱胁迫下的生理响应特征,为进一步探讨其对干旱环境的适应机制奠定基础。结果显示:(1)随着干旱胁迫程度的增加以及在各时间胁迫处理下,抗氧化酶SOD活性及可溶性糖含量显著升高,POD活性、丙二醛含量、CAT活性和APX活性均经历了先升后降的过程。(2)超氧阴离子(O-·2)的产生速率和过氧化氢(H2O2)的含量均显著升高;高山离子芥试管苗叶片相对电导率呈现出升-降-升的变化趋势。(3)相关分析结果显示,MDA与相对电导率、可溶性糖、SOD、APX、O-·2及H2O2呈极显著正相关关系,可溶性糖与SOD、POD、O-·2及H2O2呈极显著正相关关系;相对电导率以及保护酶系均与O-·2、H2O2呈极显著正相关关系。研究表明,高山离子芥具有较强的耐旱性,高山离子芥试管苗在响应干旱胁迫过程中,抗氧化酶系、活性氧代谢、脂质过氧化及渗透调节物等共同参与了高山离子芥试管苗对干旱胁迫的综合抗逆性形成,从而积极启动应对外界干旱环境的耐旱响应机制。     

Abandonment of traditionally managed mesic mountain meadows affects plant species composition and diversity

In recent years abandonment of traditional management of mountain grasslands has been observed throughout Central Europe. However, the impact of abandonment on vegetation of mountain grasslands is still unclear. In this study it was hypothesized that the cessation of traditional management of mesic mountain meadows causes changes in their species composition and a decrease in the biodiversity. In total, 260 plots were established in the Sudetes (SW Poland) on meadows with regular annual mowing, meadows with irregular mowing management, and abandoned meadows. Relevés (5 × 5 m) were performed, and the habitat properties were determined using Ellenberg indicator values. The study confirmed the hypothesis that the various ways of extensive management have an influence on species richness. The lowest species richness was observed on the irregularly managed meadows, while higher species numbers were found on the abandoned and regular managed meadows. The majority of patches on abandoned meadows exhibited degradation through the expansion of Solidago gigantea, Solidago canadensis, Lupinus polyphyllus, Heracleum sosnovsky, Calamagrostis epigejos, Deschampsia flexuosa, Festuca rubra and Hypericum maculatum. Meadows subjected to different management practices differed significantly in Ellenberg indicator values. The abandoned meadows had the highest values of the light index (L) and nitrogen availability (N), whereas the highest values of soil moisture (F) were noted on the irregularly managed meadows. The degradation of mountain mesic meadows requires regular mowing management, which stops ecological succession and preserves their high biodiversity.     

Long‐term effects of the abandonment of grazing on steppe‐like grasslands

Question: What are the consequences of grazing abandonment on the Stipa lessingiana dominated steppe‐like grasslands? What is the relative importance of management and environmental factors in causing variation in species composition and abundance in the continuously grazed and abandoned grassland stands? Location: Transylvanian Lowland, Romania. Methods: Repeated vegetation mapping of a grassland stand, where grazing was abandoned 35 years ago; re‐sampling six grassland stands surveyed 29–57 years ago. For revealing long‐term changes in species composition and rank abundance PCoA ordination was applied. The relative importance of management and environmental factors in structuring vegetation were explored by CCA ordination. Diversity, evenness and the relative number and abundance of red‐listed species were compared between managed and abandoned stands. Results: Our results pointed out that grasslands which were formerly grazed and dominated by S. lessingiana, in the long‐term absence of grazing, have been transformed into a S. pulcherrima dominated type. Management, probably by creating bare surfaces and preventing litter accumulation, had the strongest effect on the species composition and abundance in the grasslands. Abandoned grassland stands had lower diversity and evenness compared to continuously grazed stands. While at the same time, the relative number of threatened, rare species did not differ between managed and abandoned sites. Conclusion: Maintaining extensively grazed, as well as un‐managed, Stipa dominated grasslands would be important in order to create various habitat conditions for plant species, especially threatened and rare species, and promote diversity on the landscape scale.     

Seed germination responses to seasonal temperature and drought stress are species‐specific but not related to seed size in a desert steppe: Implications for effect of climate change on community structure

Investigating how seed germination of multiple species in an ecosystem responds to environmental conditions is crucial for understanding the mechanisms for community structure and biodiversity maintenance. However, knowledge of seed germination response of species to environmental conditions is still scarce at the community level. We hypothesized that responses of seed germination to environmental conditions differ among species at the community level, and that germination response is not correlated with seed size. To test this hypothesis, we determined the response of seed germination of 20 common species in the Siziwang Desert Steppe, China, to seasonal temperature regimes (representing April, May, June, and July) and drought stress (0, ?0.003, ?0.027, ?0.155, and ?0.87 MPa). Seed germination percentage increased with increasing temperature regime, but Allium ramosum, Allium tenuissimum, Artemisia annua, Artemisia mongolica, Artemisia scoparia, Artemisia sieversiana, Bassia dasyphylla, Kochia prastrata, and Neopallasia pectinata germinated to >60% in the lowest temperature regime (April). Germination decreased with increasing water stress, but Allium ramosum, Artemisia annua, Artemisia scoparia, Bassia dasyphylla, Heteropappus altaicus, Kochia prastrata, Neopallasia pectinata, and Potentilla tanacetifolia germinated to near 60% at ?0.87 MPa. Among these eight species, germination of six was tolerant to both temperature and water stress. Mean germination percentage in the four temperature regimes and the five water potentials was not significantly correlated with seed mass or seed area, which were highly correlated. Our results suggest that the species‐specific germination responses to environmental conditions are important in structuring the desert steppe community and have implications for predicting community structure under climate change. Thus, the predicted warmer and dryer climate will favor germination of drought‐tolerant species, resulting in altered proportions of germinants of different species and subsequently change in community composition of the desert steppe.