Potentilla Bifurca Research Articles

The decline in plant biodiversity slows down soil carbon turnover under increasing nitrogen deposition in a temperate steppe

Abstract Nitrogen (N) deposition not only alters the physiological processes of individual plant, but also leads to world‐wide biodiversity loss. However, little is known about how the hierarchical responses from individual physiological processes to plant community structure would have cascading effects on soil carbon (C) cycling. Here, we assessed whether changes in plant chemical composition and community composition under increasing N input would affect the turnover rate of litter layer and soil C loss via heterotrophic respiration (Rh) in a temperate grassland. We showed that more than a decade’s N addition significantly decreased plant species richness, litter layer turnover rate and Rh. The 13C‐NMR results showed that, for individual species, N addition either increased the abundance of recalcitrant C groups such as alkyl and methoxyl, or decreased labile C groups such as carbohydrate, resulting in decreases in carbohydrate C‐to‐methoxyl C ratio (CC/MC) for most species. Our data also showed that with the increase in N deposition, the abundance of relatively high degradable dominant species, such as Agropyron cristatum and Artimesia frigida declined rapidly, and the relatively recalcitrant species such as Potentilla bifurca and Leymus chinensis become dominant. Changes in individual species’ chemical composition and plant community composition significantly decreased litter quality at community level, as indicated by the lower community‐level CC/MC at higher N addition rates. The result of step‐AIC model selection further showed that plant diversity loss and the decrease in community‐level CC/MC jointly explained the decrease in Rh after N addition best, and further relative importance partition result showed that these two factors respectively contributed 65.1% and 34.9% of the explained variation. Overall, we demonstrated that changes in plant chemical composition and diversity loss due to N addition reduced the quality of plant C input to soil, which further slowed down litter layer turnover rate and inhibited soil heterotrophic respiration. Our study complements the intermediate links of how shifts in plant community structure regulate soil C cycle under global changes. A plain language summary is available for this article.

青藏高原东北部二裂委陵菜叶片生态化学计量随海拔变化的特征

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原东北部二裂委陵菜叶片生态化学计量随海拔变化的特征 DOI: 10.5846/stxb201805231128 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（41461109）；甘肃省自然科学基金重大项目（18JR4RA002）；中国科学院内陆河流域生态水文重点实验室开放基金（KLEIRB-ZS-16-01） Variation characteristics of Potentilla bifurca leaf stochiometry along the elevation gradient on the northeastern Qinghai-Tibetan Plateau Author: Affiliation: Fund Project: The Key Program of the Chinese Academy of Sciences,China Postdoctoral Science Foundation,Joint Research Fund for Hong Kong and Macao Young Scholars 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:海拔对陆地生物地球化学循环过程具有重要影响。研究植物叶片碳（C）、氮（N）、磷（P）生态化学计量沿海拔的变化特征，有助于深入了解植物对环境的适应策略。通过对青藏高原东北缘不同海拔（2980-3280，3281-3580，4180-4480，4481-4780 m）二裂委陵菜（Potentilla bifurca）叶片C、N、P含量及其计量比的首次研究，对其生态适应性和限制元素进行了初步探讨，结果发现：（1）二裂委陵菜叶片C、N、P平均含量分别为411.58 g/kg、22.47 g/kg和1.35 g/kg；C：N、C：P、N：P的均值分别为18.51、321.81和17.33。（2）随着海拔升高，二裂委陵菜叶片C含量和N：P呈上升趋势，分别从400.40 g/kg增加到418.08 g/kg、12.73增加到18.81；N、P含量呈先降后增趋势，其最大和最小值分别为23.88 g/kg和20.48 g/kg、1.89 g/kg和1.12 g/kg；C：N、C：P呈先增后降趋势，分别从20.42减少到17.79、372.18减少到334.72。（3）二裂委陵菜叶片C与N、C：N不相关，与P显著负相关，而与C：P、N：P显著正相关；N与N：P不相关，与P显著正相关，而与C：N、C：P显著负相关；P与C：N、C：P、N：P显著负相关；C：N与C：P显著正相关，与N：P不相关；C：P与N：P显著正相关。（4）二裂委陵菜生长主要受P限制。 Abstract:Elevation has a major impact on the terrestrial biogeochemical processes cycle. Exploring the variations in leaf ecological stoichiometry along the elevation gradient will enable an understanding of the adaptative strategy of the plant. The leaf C, N, and P concentrations of the leaf and its corresponding ecological stoichiometry of Potentilla bifurca at different elevations, including from 2980 to 3280 m, 3281 to 3580 m, 4180 to 4480 m, and 4481 to 4780 m, on the northeastern Qinghai-Tibetan Plateau, were investigated. Its ecological adaptability and restricted elements were also discussed for the first time. The results showed that the concentrations of leaf C, N, and P were 411.58 g/kg, 22.47 g/kg, and 1.35 g/kg, respectively, and leaf C:N, C:P, and N:P values were 18.51, 321.81, and 17.33, respectively. The concentrations of leaf C and the N:P of Potentilla bifurca increased with an increase in elevation, with the value of leaf C increasing from 400.40 g/kg to 418.08 g/kg, and the value of leaf N:P increasing from 12.73 to 18.81. The contents of leaf N and P first decreased and then increased with the elevation increase, with maximum and minimum values of 23.88 g/kg and 20.48 g/kg, and 1.89 g/kg and 1.12 g/kg, respectively. However, leaf C:N and C:P first increased and then decreased with the elevation increase; C:N decreased from 20.42 to 17.79, while C:P decreased from 372.18 to 334.72. The concentration of leaf C was neither related to leaf N nor leaf C:N, while it was significantly and negatively related to leaf P and significantly and positively related to leaf C:P and N:P. The concentration of leaf N was not related to leaf N:P, but was significantly and positively related to leaf P and significantly and negatively related to leaf C:N and C:P. The concentration of leaf P was significantly and negatively related to leaf C:N, C:P, and N:P, leaf C:N was significantly and positively related to leaf C:P, and leaf C:N was unrelated to leaf N:P. Leaf C:P was significantly and positively related to leaf N:P. The growth of Potentilla bifurca on the Qinghai-Tibetan Plateau was primarily limited by phosphorus. 参考文献 相似文献 引证文献

Частотность и применение некоторых терминообразующих суффиксов монгольского языка

The article calculates the meanings and frequency use of some Mongolian term-forming suffixes by the aid of TextStat program. The present paper deals with meanings, functions, frequency and application of some Mongolian term-forming suffixes, such as -тан4 , -нцар2, -гана4, -лзай3, -ж, ‑жин, -ч, -чин, -ийнхан2. The study examines terms to denote plants, animals, minerals and geological objects related to natural sciences in the Russian-Mongolian Terminological Dictionary (editions of 1964, 1970, and 1979) containing 120,000 terms. The study includes two main sections. Firstly, it summarizes works by scientists to have studied the meanings of the suffixes mentioned above, and examines which of the meanings are more frequently used to create terms. Among the scientists who have investigated the Mongolian suffix -тан, T. A. Bertagaev described its meaning as follows: 1. ‘massive’, e.g., цэргийн эрхтэн ʽmilitary authorities, militaristsʼ; 2. ‘singular / plural’, e.g., цагаантан ʽwhite guardsman, white guardsmen; 3. ‘singularity’, e.g., сэхээтэн ʽintellectualʼ. In term formation, -тан4 is commonly used to create terms denoting plant and animal species. For example, in animal names — битүү тууртан ʽodd-toed ungulatesʼ (1); in plant names — Луулийн язгууртан ʽChenopodiaceaeʼ; in names of microorganisms — багц шилбүүртэн ʽlofotrihiʼ (1); in bird names — жигүүртэн ʽbirdsʼ, etc. The suffix -нцар is primarily used to form terms with meaning ‘diminutive’, e. g., үндсэнцэр ʽsmall rootʼ, навчинцар ‘leaflets’ (7); and meanings of similarity, e.g., манинцар ‘hermaphroditism’ (3), болронцор чулуу ‘quartzite’ (2), and the meaning ‘piece of a big thing’, e. g., элэгний хэлтэнцэр ‘hepatic lobule’ (2), etc. Thus, those are suffixes used for semantic extension of the vocabulary. The study also reveals that the suffix -гана4 contains 5 different meanings when it comes to term formation: a) the suffix is mostly added to a noun to create one characterized by specific terminology of the subject. For example, улаагана ‘red currant’ (3), хонхорт харгана ‘cingil silver’ (3), алтгана ‘golden karagana’; b) it is used to create terms denoting shape and form. For example, өргөст бударгана (өргөст хамхуул) ‘Salsola pestifera Nels’ (2); c) it is added to onomatopoetic words imitating animal sounds, such as tsuur tsuur, hed hed to create corresponding terms. For example, цүүргэнэ ‘locust’ (3), хэдгэнэ ‘wasp’ (3), etc. d) it is used to create term with the meaning of similarity. For example, сүүгэнэ ‘Euphorbia’ (1), салаагана ‘chorispora’ (2), гичгэнэ ‘Potentilla bifurca’ (1), e) it is added to roots of loan words to create new plant and fish names. For example, тавилгана — (tavolga + гана) (1), Суладай, нагана — Нагана (Suladai, Nagana — Nagana) (1), etc. The second section of the paper mainly focuses on the frequency of the suffixes -тан4, -нцар2, -гана4, -лзай3, -ж, -жин, -ч, -чин, -ийнхан2 in the Russian-Mongolian Terminological Dictionary analyzed using the TextStat corpus linguistic software. The study concludes the suffix -тан4 to be traced 292 times in the structure of single and compound terms; -нцар — 218; -гана — 68; -ч, -чин — 53; -ж, -жин — 45; -ийнхан — 11.

New species and records of phytoptids (Eriophyoidea, Phytoptidae) from cinquefoils (Rosaceae, Potentilla) from Serbia and southern Russia

Two new vagrant species of the genus Phytoptus Dujardin (Eriophyoidea, Phytoptidae, Phytoptinae) from Serbia are described: Phytoptus argenteus n. sp. from Potentilla argentea and P. serbicus n. sp. from Potentilla tommasiniana. Remarks on morphology of Phytoptus alchemillae Jočić et al. 2011 collected from Alchemilla plicata in Serbia and supplementary description of infrequently encountered species Phytoptus potentillae Chen et al. 2005 from Potentilla bifurca (Poaceae) based on mummies recovered from dry plant material from southern Russia are given. Sequences of mtCOI barcode region (658 bp) of three Phytoptus species (P. alchemillae, P. argenteus n. sp., and P. serbicus n. sp.) are provided. A brief comparison of pairwise genetic distances between congeneric eriophyoid mites across taxa of Eriophyoidea (including genus Phytoptus) indicates that COI sequences of congeneric eriophyoid mites do not precisely reflect phylogenetic relations of their hosts. This fact may be explained by (a) different rate of the COI evolution in different mite clades associated with phylogenetically related and unrelated hosts or by (b) similar timing of the associations between mites and plants (while having the same rate of COI evolution).

Effects of grazing on the acquisition of nitrogen by plants and microorganisms in an alpine grassland on the Tibetan plateau

Nitrogen (N) limitation leads to intense competition between plants and soil microorganisms for available N. However, it is unclear how grazing affects the acquisition of N by plants and microorganisms. We conducted short-term 15N tracer experiments during the growing season (June, early growing season; July, mid-growing season; and September, late growing season) in an alpine grassland on the Tibetan Plateau to investigate the effects of grazing on the acquisition of NO3 −-N, NH4 +-N, and glycine-N by plants and soil microorganisms. Three dominant plant species (one graminoid, Kobresia pygmaea, and two forbs, Potentilla bifurca and Potentilla multifida) were selected for the study. As these species represented >90% of the vegetation, the plant recovery of 15N reflected competition at the plant community. Grazing decreased the recovery of 15N by soil microorganisms and plants by 46 and 69%, respectively, indicating that grazing strongly reduced the uptake of 15N by plants and microorganisms and altered the partitioning of 15N between them. Significant interactions were found between grazing, season and the different forms of N. In the absence of grazing, plants acquired relatively more N than soil microorganisms for the three forms of N in July and September, whereas the microorganisms obtained relatively more 15N glycine in July and all three forms of N in September under grazing conditions. Under grazing, the plant root biomass played an important role in controlling plant–microbial N acquisition. Grazing alters the partitioning of inorganic and organic N between plants and soil microorganisms by reducing microbial 15N recovery to a lesser extent than plant 15N recovery. This indicates that heterotrophic microorganisms play an important part in N cycling in N-limited ecosystems.

Floodplain steppe meadows of the Eastern part of the Altai-Sayan mountain region

In South Siberian mountains floodplain steppe meadows can be found only within steppe and forest-steppe belts. In the eastern part of the Altai-Sayan mountain region (ASMR) these belts occupy large intermontane depressions, making up the submeridional range at 56–50° N (Fig. 1). The northern part of this range consists of four large depressions (the Nazarovo, North Minusinsk, Middle Minusinsk and South Minusinsk). To the north, the Nazarovo depression merges into the West Siberian plain. The southern border of the South Minusinsk depression is the West Sayan. The southern part of range includes the Turan-Uyuk and Central Tuvinian depressions. This study is based on the analysis of 260 geobotanical relevés made in the valleys of 47 rivers (21 — in Minusinsk depressions, 26 — in Tuvinian depressions). The set includes the relevés of steppe meadow of different river types (large, medium, small), located in different parts of the studied region. The typical feature of these communities is the permanent coexistence of steppe and meadow species with negligible part of meadow-steppe herbs. All steppe meadows under discussion are similar in appearance. Tall grasses, various in different associations, form a sparse upper sublayer. Depending on the intensity of use, the main part of the herbage can be located in the middle sublayer or in the bottom one. In the middle sublayer, grasses predominate (Bromopsis inermis, Poa angustifolia, Elytrigia repens). Herbs tolerant to grazing (Potentilla bifurca, Amoria repens) make up the bottom sublayer. We have revealed 6 associations of steppe meadows. Ass. Potentillo bifurcae–Poetum angustifoliae, Potentillo bifurcae–Leymetum dasystachyos, Potentillo bifurcae–Hordeetum brevisubulati are typical for Tuvinian depressions, ass. Artemisio laciniatae–Koelerietum delavignei, Trifolio pratensis–Koelerietum delavignei и Trifolio pratensis–Festucetum valesiacae — for Minusinsk ones (Table 1). The basic bioclimatic barrier of ASMR — the West Sayan divides their areas. The ordination of new associations along the gradients of moisture supply (horizontal axis) and richness-salinity of soils (vertical axis) demonstrates that areas of associations form two ranges — the Minusinsk and Tuvinian. Every association of the Minusinsk range has corresponding association of the Tuvinian range (Fig. 2). DCA-ordination (Fig. 3) and cluster analysis (Fig. 4) of syntaxa from the South Urals, West Siberia, Yakutia and new associations have detected the specificity of the last ones, so a new alliance Potentillo bifurcae–Poion angustifoliae (order Galietalia veri, class Molinio-Arrhenatheretea) has been described. It comprises steppe meadows of the Eastern part of ASMR.

Generic delimitation between Fragariocoptes and Sierraphytoptus (Acari: Eriophyoidea: Phytoptidae) and a supplementary description ofFragariocoptes gansuensis with remarks on searching for mummified eriophyoid mites in herbaria under UV light.

Generic concepts of Fragariocoptes Roivainen, 1951 and Sierraphytoptus Keifer, 1939 are discussed and the correct delimitation between these two genera is given. A supplementary description of Fragariocoptes gansuensis Wei, Chen & Luo, 2005 is included based on fresh specimens from Astrakhan, Russia and dried mummies found in old herbaria collected in 1919 from southern European Russia of the cinquefoil, Potentilla bifurca L. (Rosaceae) with pathological stem proliferation. The male of this species is described for the first time. The cuticle of eriophyoid mummies emitted a faint glow under UV light wavelength equal to 365 nm of a common UV Light-Emitting diode (LED) lamp showing that this characteristic could be useful for quickly detecting eriophyoids in old herbaria which would otherwise be almost indistinguishable against the background under the regular white light source of a stereomicroscope. This was only possible for plant material stored in appropriate conditions enabling the autofluorescent signal of the dried mite cuticle to remain strong enough for observation.

青藏高原高寒草甸区铁路工程迹地植被恢复过程的种间关联性

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原高寒草甸区铁路工程迹地植被恢复过程的种间关联性 DOI: 10.5846/stxb201502030276 作者: 作者单位: 北京林业大学,北京林业大学,北京林业大学,西北农林科技大学林学院,中国林业科学研究院荒漠化研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项经费资助项目（201504401）；国家自然科学基金资助项目（30870231） Analysis of the interspecific associations present in an alpine meadow community undergoing revegetation on the railway-construction affected land of the Qinghai-Tibet Plateau Author: Affiliation: Beijing Forestry University,Beijing Forestry University,Beijing Forestry University,College of Forestry, Northwest A&F University,Institute of Desertification, Chinese Academy of Forestry 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:为了研究大型工程建设对脆弱生态系统的影响，以青藏高原高寒草甸区铁路工程迹地植被为对象，分别在青藏铁路建设期（2005年8月）、运行期（2009年8月、2013年8月）对工程迹地进行了3次植被群落调查，样地大小10m×40m，在此基础上利用种间关联性分析的方法，通过对群落特征的方差比率（VR）检验、χ2检验和Spearman秩相关系数检验，来探讨群落物种总体关联性和主要种种对间关联性。结果显示：（1）2005年群落平均盖度（35.21±4.41）%，群落内共有物种71种，2009年群落平均盖度（33.42±3.01）%，共有物种78种，2013年群落平均盖度（43.41±3.26）%，共有物种85种。（2）对群落物种总体关联性检验发现群落物种总体关联性均表现为显著正相关，关联程度排列为VR2005 > VR2009 > VR2013，群落趋向松散，抗干扰能力弱。（3）对群落主要物种种对间关联性检验发现成对物种间的正、负联结比例总体呈下降趋势，并且达到显著或极显著的种对数百分比也呈下降趋势，群落内物种间联结强度逐渐降低。（4）在高寒草甸区工程迹地植被恢复8a时间里，部分相同种对之间的关联程度发生变化，中生或者湿生植物减少，耐旱植物种类增加，表明铁路沿线由于生境小气候干旱化和土壤紧实度增加，群落组成发生适应性改变，群落处于从逆向演替向正向演替的过渡阶段，应尽量降低放牧等二次干扰，加速其自然恢复进程。研究旨为探索青藏铁路工程迹地植被恢复规律提供参考。 Abstract:The construction of the Qinghai-Tibet Railway is a centennial project of the People's Republic of China. A large part of this railway is located on alpine meadows (typical vulnerable ecotones characterized by high altitude, low temperatures, and scarce annual precipitation) between the Tanggula Mountains Pass and Damxung County. Because the construction of this railway is inevitably a source of disturbance to the surrounding environment, it is vital to study the revegetation of these severely affected alpine meadows. To understand the community dynamics of the affected alpine meadows, we investigated the vegetation present on the impacted land during the railway construction period (2005), as well as 4 years (2009), and 8 years (2013) after the construction period. Eight 10 m×40 m plots uniformly located between the Tanggula Mountains Pass (91° 43' 31.4" E, 33° 04' 36.3" N) and Wumatang (91° 32' 11.95" E, 30° 37' 51.05" N) were sampled, each with 9 quadrants 1 m×1 m in size. The data collected included species composition, species coverage, species height, and the population size of each species. To this end, a series of variance ratio (VR) tests, χ2 tests, and Spearman's rank correlation coefficient tests were conducted. The results show that the community coverages were (35.21±4.41)%, (33.42±3.01)%, and (43.41±3.26)%, and 71, 78, and 85 species recorded in the year 2005, 2009, and 2013, respectively. After dropping the species with importance values lower than 0.01, we used the 23, 27, and 21 dominant species in our subsequent analyses for the respective periods. Overall, species richness and community coverage increased over time, with the overall interspecific association indices (VR) being larger than 1 (from 2005 to 2013). In addition, the results of the W statistics (χ0.95N2 < W < χ0.05N2) showed that the overall associations between species in the community were all significantly positive (P<0.05). The sequential order of association was VR2005 > VR2009> VR2013, suggesting that the intensity of the community associations gradually declined over time. Finally, the proportion of positive and negative interspecific associations between the dominated species pairs declined, and the proportion of species pairs achieving significant and highly significant levels tended to increase during the 8 years of revegetation. In addition, the associations between the same species pairs varied significantly among years of investigations(e.g., the association between Potentilla bifurca and Anemone imbricate was not significant during the railway construction period, but was significant in 2009 (P<0.05) and highly significant (P<0.01) in 2013). Lastly, the number of mesophyte and hygrophyte species such as Taraxacum leucanthum and Saxifraga tibetica declined, while that of drought-tolerant plants such as Ceratoides compacta increased. Overall, the results indicated that the alpine meadows affected by the Qinghai-Tibet Railway construction project fluctuated greatly during the first 8 years of revegetation. Future research can be done to more precisely determine the patterns present during the time in which the alpine meadow community becomes stabilized. 参考文献 相似文献 引证文献

Grazing modifies inorganic and organic nitrogen uptake by coexisting plant species in alpine grassland

To study how grazing affects the uptake of inorganic and organic N forms, three focal plant species (i.e., the graminoid species Kobresia pygmaea, which decreases with grazing, and the forbs Potentilla bifurca and Potentilla multifida, which increase with grazing) were selected in ungrazed and grazed plots in an alpine meadow on the Tibetan Plateau. Three times during the growing season (i.e., June, July, and September), these plots were injected with 15N-labeled NO3 −-N, NH4 +-N, or glycine-N, or with only water as a control. Two hours after 15N injection, exchangeable NH4 +-N, glycine-N, and NO3 −-N as well as plant and soil samples were collected and analyzed for 15N/14N and total N content. Our result showed that all three plant species took up glycine-N, but uptake of inorganic N was generally predominant. The graminoid K. pygmaea took up all three N forms equally in June but preferred NO3 −-N in July (particularly under grazing) and exchangeable NH4 +-N in September. The forbs P. bifurca and P. multifida preferentially took up exchangeable NH4 +-N in July (particularly under grazing), while NO3 −-N was the dominant form of N uptake in September. P. bifurca generally preferred exchangeable NH4 +-N, but preference shifted toward NO3 −-N under grazing in June. P. multifida preferred glycine-N in ungrazed plots and shifted its preference to NO3 −-N under grazing in June. In conclusion, the three plant species showed niche partitioning for uptake of three forms of N across the season, which was modified by grazing. These findings indicate that plant N uptake patterns should be considered for better understanding the mechanisms of grazing effects on plant diversity and species coexistence.

Effects of soil fertility on the N:P stoichiometry of herbaceous plants on a nutrient-limited alpine steppe on the northern Tibetan Plateau

Plant nutrient concentrations and their correlations with soil nutrient conditions are regarded as effective tools for exploring plant adaptation and resource utilisation strategies in a severe environment. However, few comparative studies have addressed the nutrient traits of different organs along natural fertility gradients. We quantified the nitrogen (N) and phosphorus (P) concentrations and N:P ratios in roots and leaves of 139 plant samples from 14 species on a nutrient-limited alpine steppe on the Tibetan Plateau. Next, we explored the correlation between root and leaf nutrient traits of different plant functional groups as well as soil fertility. Soil P had a significant impact on plant N:P stoichiometry, whereas soil N had little effect on plant nutrient traits. Leaf P and the N:P ratio of legumes exhibited more sensitive responses to soil P than roots. Among non-legume species, however, root N and P concentrations of Stipa purpurea and Orinus thoroldii (grasses) were more sensitive than N and P concentrations of leaves to variations in soil P availability. In contrast, leaf P and the N:P ratio of Leontopodium nanum, Potentilla bifurca and ect. (forbs) exhibited more sensitive responses to soil P than roots. Both root and leaf nutrient traits of Carex moorcroftii (sedges) were uncorrelated with soil fertility. The N:P stoichiometry of different functional groups showed disparate responses to soil P, and even the roots and leaves of the same functional group exhibited inconsistent correlations with soil nutrients. The distinct response patterns to soil nutrient conditions across functional groups helped elucidate the diversification of alpine plant adaptations to nutrient-poor environments and offered insights into quantifying the trade-off of different organs in co-existing species between resource use/conservation “strategies” and soil fertility.

δ13C values of plants as indicators of soil water content in modern ecosystems of the Chinese Loess Plateau

We selected typical restored grassland along a chronosequence of natural vegetation restoration on the Chinese Loess Plateau (CLP) and determined the soil water content once each month from April to October as well as the stable carbon isotope composition of six plant species (C3), for both the aboveground (δ13CAP) and belowground (δ13CBP) portions, to examine the sensitivity of plant δ13C values to soil water content in modern ecosystems. The study sites include three restored grasslands, which have been restored for 3 years (RG1), 13 years (RG2) and 23 years (RG3) since farmland abandonment. Results showed that the soil water content increased significantly with vegetation restoration, with means of 7.3%, 10.7% and 13.1% for RG1, RG2 and RG3, respectively. The multispecies mean δ13CAP and δ13CBP values were −27.1‰, −27.5‰, −28‰ and −26.9‰, −27.4‰, −27.6‰ in RG1, RG2, RG3, respectively, decreasing significantly with vegetation restoration. Further analysis indicates that the multispecies mean δ13CAP and δ13CBP values were negatively correlated with soil water content, with r2 values of 0.72 and 0.98, respectively. The δ13CAP and δ13CBP values of all individual species were also significantly and negatively correlated with soil water content, except for Saussurea japonica, for which the δ13CBP value increased with soil water content. Of all the plant species, the responses of both the δ13CAP and δ13CBP values to soil water content were more sensitive for Potentilla bifurca. We suggest that the δ13CAP and δ13CBP values of individual plant species are likely reliable indicators of the soil water content of the specific year of sampling and a longer-term (several years) integrated signal, respectively.

Independent effects of warming and nitrogen addition on plant phenology in the Inner Mongolian steppe

Phenology is one of most sensitive traits of plants in response to regional climate warming. Better understanding of the interactive effects between warming and other environmental change factors, such as increasing atmosphere nitrogen (N) deposition, is critical for projection of future plant phenology. A 4-year field experiment manipulating temperature and N has been conducted in a temperate steppe in northern China. Phenology, including flowering and fruiting date as well as reproductive duration, of eight plant species was monitored and calculated from 2006 to 2009. Across all the species and years, warming significantly advanced flowering and fruiting time by 0·64 and 0·72 d per season, respectively, which were mainly driven by the earliest species (Potentilla acaulis). Although N addition showed no impact on phenological times across the eight species, it significantly delayed flowering time of Heteropappus altaicus and fruiting time of Agropyron cristatum. The responses of flowering and fruiting times to warming or N addition are coupled, leading to no response of reproductive duration to warming or N addition for most species. Warming shortened reproductive duration of Potentilla bifurca but extended that of Allium bidentatum, whereas N addition shortened that of A. bidentatum. No interactive effect between warming and N addition was found on any phenological event. Such additive effects could be ascribed to the species-specific responses of plant phenology to warming and N addition. The results suggest that the warming response of plant phenology is larger in earlier than later flowering species in temperate grassland systems. The effects of warming and N addition on plant phenology are independent of each other. These findings can help to better understand and predict the response of plant phenology to climate warming concurrent with other global change driving factors.

Nitrogen fertilization and fire act independently on foliar stoichiometry in a temperate steppe

Nitrogen (N) fertilization, as a grassland management strategy, has been widely used to improve forage quality and increase the productivity of grasslands degraded by overstocking. It is widely accepted that N addition will alter ecosystem structure and function, and that these effects may be altered by natural disturbances, such as fire. We examined the effects of annual burning and N fertilization (17.5 g N m−2 year−1, at a surplus rate in order to simulate agriculture treatment) on foliar chemistry and stoichiometric ratios of eight dominant species (Leymus chinensis, Stipa grandis, Cleistogenes squarrosa, Potentilla bifurca, Thalictrum squarrosum, Artemisia frigida, Kochia prostrata and Caragana microphylla) in a temperate steppe in northern China. After 3 years of treatments, annual burning significantly increased soil extractable phosphorus (P) concentration but showed no effects on soil inorganic N concentration, whereas N fertilization caused a significant increase in inorganic N concentration but not of extractable P. Species differed substantially with respect to all nutritional and stoichiometric variables. Both annual burning and N fertilization caused significant increases in foliar N and P concentrations and thus decreases in carbon (C):N and C:P ratios. While annual burning showed no effects on N:P ratios, N fertilization produced higher N:P ratios. However, species responded idiosyncratically to both fire and N fertilization in terms of foliar N concentration, C:N and N:P ratio. In addition, there was no interaction between fire and N fertilization that affected all variables. This study suggests that both annual burning and N fertilization have direct impacts on plant elemental composition and that fire- and N addition-induced changes of community composition may have important consequences for plant-mediated biogeochemical cycling pathways in temperate steppe ecosystem.

Population structure of Potentilla bifurca L. in the Altai-Sayan Mountain Region

Pollen characters were analyzed in 16 cenopopulations of Potentilla bifurca L. in five provinces of the Altai-Sayan Mountain Region. As a result, two groups of cenopopulations, western and eastern, have been recognized. Both groups are characterized by a high intrapopulation (44.7–63.9%) and a lower interpopulation (11.4–42.2%) variability. The observed similarity between groups of cenopopulations of P. bifurca from different geobotanical provinces is determined by their common origin from the Pliocene-Pleistocene steppe communities.

Floristic compositions of Inner Mongolian grasslands under different land‐use conditions

AbstractThe severe degradation of grasslands caused by overgrazing and other diverse human operations has become widespread in Inner Mongolia, China. In this study, the vegetations of several grasslands under different land‐use conditions were compared to examine the relationships between the vegetation and the disturbance of the grassland. Floristic and life‐form compositions of the stands representing the six different sites were researched by the quadrat method: a non‐grazed grassland (G1), a lightly grazed grassland (G2), a path (P), an abandoned field (AF) and two artificial meadows (M1 and M2). P, AF, M1 and M2 were located in a part of the grazed grassland. AF, M1 and M2 had been tilled when planted. The dominant species found in G1 and G2 were Potentilla fragarioides, Poa annua, and Cleistogenes squarrosa. Artemisia annua, Chenopodium album, Cannabis sativa f. ruderalis and Calystegia hederacea were found in P and AF, being scarce in the grassland areas. Amaranthus retroflexus, Kochia scoparia and Setaria viridis, which are cosmopolitan weeds, were dominant only in AF. Leymus chinensis, Agropyron cristatum, Potentilla bifurca, and Potentilla tanacetifolia were widely observed across all the surveyed sites. The land‐use change from grassland to path caused a decrease of perennial species and an invasion of annual species by heavy trampling. A similar vegetational change occurred with the land‐use change from grassland to abandoned field due to the destruction of original vegetation by tillage. Human disturbance such as tillage and trampling also resulted in a decrease in the species with the tufted‐ and branched‐form and an increase in the species with the erect‐form. Tillage could produce a more serious impact on the grassland vegetation as compared to grazing.

Soil erosion and vegetation succession in alpine Kobresia steppe meadow caused by plateau pika—A case study of Nagqu County, Tibet

This paper evaluated the impacts of mounds created by the plateau pika (Ochotona curzoniae) on the vegetation composition, structure, and species diversity of an alpine Kobresia steppe meadow in Nagqu County, Tibet Autonomous Region, China. Based on mound height or the depth of erosion pit, we defined five stages of erosion and compared the floristic features of communities at these stages with those in undisturbed sites. In the study area, the mounds and pits covered up to 7% of the total area. Lancea tibetica, Lamiophlomis rotata, and Potentilla bifurca were the dominant species in erosion pits, and Kobresia pygmaea, the dominant species in undisturbed sites, became a companion species in eroded areas. In the process of erosion, the original vegetation was covered by soil ejected by the pika, then the mounds were gradually eroded by wind and rain, and finally erosion pits formed. The vegetation coverage increased with increasing erosion stages but remained significantly lower than that in undisturbed sites. Improved coverage eventually reduced soil erosion, and pit depth eventually stabilized at around 20cm. Aboveground biomass increased with increasing erosion stage, but the proportion of low-quality forage reached more than 94%. The richness index and Shannon-Wiener index increased significantly with increasing erosion stage, but the richness index in mound and pit areas was significantly lower than that in undisturbed sites.

Effect of Exclosure and Topography on Rehabilitation of Overgrazed Shrub‐Steppe in the Loess Plateau of Northwest China

AbstractThe purpose of this study was to clarify the effect of grazing exclosures on the recovery and rehabilitation of overgrazed steppe vegetation on varying slope aspects in the Loess Plateau of northwest China. The annual precipitation in the area studied was 400–480 mm. Soil samples were taken on nine slopes in the five‐year exclosure and on five slopes outside the exclosure after a vegetation survey; they were then analyzed chemically. Mean number of species recorded per 0.25 m2 was lower on the south‐facing slope than all other slopes. The reverse trend was observed for aerial biomass. Species diversity estimated by information content was higher in the grazing zone than in a 3200‐ha protected zone within an exclosure. From species ordination by principal component analysis, species with lower coverage in the grazing zone were Poa sphondylodes, Roegneria purpurascens, Hierochloe odorata, and Potentilla bifurca, which are all recognized as indicator species for rehabilitation efforts. In the soil surface layer, calcium contents were low, and the total contents of carbon and nitrogen were high on the north‐facing slope in the exclosure. The protection by exclosure of overgrazed steppe was seen to be effective because the accumulation of soil organic matter increased and water balance improved.