Potentilla Tanacetifolia Research Articles

Delay impacts of ant nests on plant reproductive phenology in a temperate steppe.

Increasing ant abundance associated with climate warming has been observed in temperate ecosystems. However, how enhanced ant activity affects plant development and phenology remains unclear. In this study, individuals of a perennial forb (Potentilla tanacetifolia) during flowering with and without an ant (Proformica) nest were marked to explore the impacts of ant nests on plant growth and phenology in a temperate steppe on the Mongolian Plateau. Ant nests delayed the start and end flowering dates simultaneously and, consequently, had no effect on flowering duration. However, presence of an ant nest postponed the fruiting date of individuals. Nests further increased numbers of aborted flowers and thus decreased fruit set. These observations suggest that the delayed flowering phenology disrupted synchrony between plant reproduction and pollinators and thus reduced pollination efficiency under ant nests. Given the increasing abundance of ants with rising temperatures under climate warming, plant delayed reproductive phenology and reduced reproductive output will potentially have negative consequences for plant fitness and plant-arthropod interactions, with consequent impacts on resistance and resilience of perennial species in temperate steppes under climate change.

Phosphorus addition alleviates the inhibition of nitrogen deposition on photosynthesis of Potentilla tanacetifolia

Atmospheric nitrogen(N) deposition increased soil active N, and excessive N content led to the increase of the ratio of nitrogen to phosphorus (N: P), which changed plant growth from N limitation to phosphorus(P) limitation. Potentilla is not only an important native greening material, but also a common diversity component in various grasslands in China. Its population fluctuation in the process of N deposition will affect the species diversity and productivity of grassland ecosystem. Potting experiment was conducted for 2 years with Potentilla tanacetifolia, a common species in the northern warm steppe, as the material. Through the interactive treatment of different N addition (0, 10, 20, 40 kg N ha yr−1) and P addition (4, 6, 8 kg P ha yr−1) gradients, to analysis the feedback effect between leaf N and P content and net photosynthetic rate (Pn). We explored the N: P threshold of N and P limitation from the perspective of Pn. The results showed that: 1) Under low soil N concentration, P addition can promote N absorption of P.tanacetifolia, while the high soil N concentration can reduce the N: P by increasing the leaf P content to weaken the limiting effect caused by nutrient imbalance of plants. 2) In N addition environment, proper P addition increased Pn by increasing stomatal conductance (Gs), while excessive P addition decreased Gs and inhibited Pn. 3) The Pn showed a single peak normal distribution characteristic with the enhancement of the N: P of leaves, and the Pn was at a high level between 14.5–17.0. It was preliminarily believed that the threshold value of N: P in leaves of P.tanacetifolia was 14.5–17.0. Plant photosynthesis is very sensitive to the environment and easy to be affected by the external environment. The results of N and P addition showed that Pn of broad-leaf forbs was easily affected by N and P restriction, and P addition increased Pn of broad-leaf forbs under N restriction. There was a certain relationship between N:P and Pn. It was preliminarily believed that the N: P of P.tanacetifolia leaves is not limited by nitrogen and phosphorus in the range of 14.5-17.0.

Clipping decreases plant cover, litter mass, and water infiltration rate in soil across six plant community sites in a semiarid grassland

Water infiltration in the soil is a crucial hydrological function in the land water cycle, especially in the semiarid region where water is relatively scarce. The semiarid grassland in Northern China represents the regional vegetation in the vast area of Eurasian continent and is sensitive to land use change. However, no clear patterns exist regarding the comprehensive examination of water infiltration in relation to clipping across six plant community sites. This study aimed to test the effect of clipping and plant community sites, which were dominated by Agropyron cristatum, Stipa krylovii, Leymus chinensis, Potentilla tanacetifolia, Artemisia frigida, or Lespedeza davurica, on the water infiltration rate in the semiarid grassland. Clipping significantly decreased the water initial, steady, and average infiltration rates by 39.13, 4.36, and 12.46 mm h−1, respectively, across the six plant community sites. Clipping-induced changes in the average infiltration rate positively correlated with the changes in the plant cover (r = 0.60, P < 0.01), litter mass (r = 0.53, P < 0.01), forb functional group ratio (r = 0.46, P = 0.03), and total porosity (r = 0.49, P = 0.02), and negatively with water-holding capacity (r = −0.45, P = 0.03). Further, the water infiltration rate significantly differed among the six plant community sites. The L.davurica site had the highest water initial infiltration rate with a value of 137.63 ± 17.76 mm h−1, while the L. chinensis site had the lowest rate with a value of 74.08 ± 5.26 mm h−1. Principal component analysis showed that the total porosity, litter mass, plant cover, and forb functional group ratio were the main factors affecting water infiltration rates in the control grassland. Overall, our findings suggested that local governments and herders should implement unclipping as a potential sustainable management for improving hydrological function in the semiarid grassland.

Erratic precipitation and clipping frequency reshape the community structure and species stability of Leymus chinensis steppe

Leymus chinensis steppe is subject to degradation under the combined stresses of climate change and human disturbance. This study aimed to determine the independent and compound effects of precipitation and clipping frequency on the community structure and species temporal stability of L. chinensis steppe. Six treatments were applied in a 9-year field study, comprising three precipitation regimes (precipitation reduced by 50%, R1; unchanged from ambient precipitation, R2; and increased by 50%, R3) and two clipping frequencies (clipping once or twice per year, C1 and C2). We evaluated the soil hydrothermal status, dry matter, importance value and temporal stability of five important species (L. chinensis, Artemisia eriopoda, Cleistogenes squarrosa, Potentilla tanacetifolia, and Stipa krylovii) in the L. chinensis community. The results showed: Change in the soil volumetric water content (±2.4%) altered the competitive capability of L. chinensis relative to its associated species. Drought was beneficial to S. krylovii, wet status was favorable to C. squarrosa and P. tanacetifolia, whereas drought and a wet regime both reduced the importance value and temporal stability of L. chinensis. Erratic precipitation, rather than clipping frequency, decreased the temporal stability of L. chinensis. Net primary productivity and dry matter of L. chinensis were strongly correlated under drought or wet regimes. Restoration of the key species L. chinensis and controlling grazing intensity in severe drought or wet conditions are recommended strategies for sustainable management of L. chinensis steppe.

ANALYSIS OF ECOLOGICAL AND GEOCHEMICAL INDICES FOR PLANTS OF THE SPECIES POTENTILLA TANACETIFOLIA GROWING IN THE CONDITIONS OF THE CITY OF CHITA AND THE CHITA REGION

The use of biogeochemical research methods is necessary when studying the technogenic migration of toxic elements in urban ecosystems. Using the values of the ecological and geochemical indices, we assessed the degree of accumulation and movement of zinc, lead, cadmium, and copper from the soil to the organs of plants of the species Potentilla tanacetifolia. The content of elements was determined by the method of inverse voltammetry on a «TA-Universal» analyzer. According to the results of the studies and the values of environmental and geochemical coefficients, it was found that, according to the level of soil pollution, the studied areas of the city of Chita and the Chita region were classified as territories with a low level of pollution. According to the values of ecological and geochemical indices for plants of the P. tanacetifolia species, intense absorption of cadmium by the root system and active movement of zinc and copper from the root layer of soils were noted. The translocation coefficient (TF) values indicated the intake of copper, lead, and cadmium into the aboveground organs in almost all the studied sites. According to the value of the discrimination coefficient, it was found that this species intensively accumulates cadmium. The results presented by us indicate that plants of the P. tanacetifolia species can be attributed to accumulator species with a rather high degree of accumulation of heavy metals at a low concentration in the medium.

Beneficial effects of nitrogen deposition on carbon and nitrogen accumulation in grasses over other species in Inner Mongolian grasslands

Globally, chronic nitrogen (N) deposition into terrestrial ecosystems has resulted in changes in community composition, depending on the responses of co-existing species to increasing soil N availability. The levels of plant non-structural carbohydrates (NSCs) produced by photosynthesis are associated with leaf N content, and together they represent the capital of a plant for its life including competitive ability. However, the specific ways that concentrations of plant NSCs, and also N, influence the growth of plants, and thus their productivity, are still abscue. Here, we explored the effect of variations in plant leaf NSCs (starch and soluble sugars) and N concentrations on the growth of plants with different soil N uptake capacities, i.e. two grasses (Leymus chinensis and Stipa baicalensis), two forbs (Potentilla tanacetifolia and Galium verum), and one legume (Thermopsis lanceolate) in Inner Mongolian grasslands subjected to three N addition rates (i.e., 0, 10, or 20 g N m−2 yr−1) and three N forms [i.e., NH4NO3, (NH4)2SO4, or CO(NH2)2] for four years. Irrespective of N addition rate and N form, N addition significantly increased aboveground biomass of the grasses, but not that of the forbs or the legume. The grasses had higher increase in N concentrations than the forbs and the legume. N addition increased the starch concentrations of grasses, but decreased that of forbs and the legume. Changes in the aboveground biomass of all tested plant species were significantly positively correlated with changes in concentrations of both NSCs and N. Our results indicate that, irrespective of the N addition rates and N forms, greater increase in NSCs and N concentrations contributed to higher aboveground productivity in grasses, but not in forbs and legumes. These results imply that future nitrogen deposition will benefit grasses over other plant forms, and thus the former may become more dominant in grasslands in northern China.

The complete chloroplast genome sequence of Potentilla tanacetifolia Willd. ex Schltdl.

Potentilla tanacetifolia Willd. ex Schltdl. is a perennial herb in China, which has high ecological and economic values. Its complete chloroplast genome was reported in this study for the first time. The whole chloroplast genome was 157, 051 base pairs in length with 129 genes, including 84 protein-coding genes, 37 tRNAs, and 8 rRNAs. In addition, phylogenetic analysis showed a sister relationship between P. tanacetifolia and P. chinensis.

Joint forcing by heat waves and mowing poses a threat to grassland ecosystems: Evidence from a manipulative experiment

AbstractThe frequency and intensity of heat waves (HWs) have increased in recent years, but it remains unclear how grassland ecosystems respond to such extreme weather. A 3‐year manipulative field experiment was conducted to simulate HWs under different mowing intensities in a Stipa krylovii steppe on the Mongolian Plateau to examine their effects on plant morphology, phenology, and community. At the species level, the morphology and phenology of the three main herb species (S. krylovii, Melilotoides ruthenica, and Potentilla tanacetifolia) showed species‐specific responses to the HW and mowing treatments. The major dominant species S. krylovii shed ~50% of the tiller outer layer to protect the internal tiller from HW stress thereby directly decreasing the heat load and water loss from green plant tissue and indirectly increasing the litter biomass. HWs also caused increases of community index (richness, diversity, and evenness) but also associated with a 30% decrease in the importance value of S. krylovii, whereas mowing enhanced this value by 27%. When HWs were combined with mowing, the joint forcing of mechanical damage and low carbon accumulation aggravated negative effects of stress on plant health and growth, which further decreased community index. We constructed a framework to fully describe the effects of HWs and mowing and their interrelationship on different ecological levels and explain how short‐term effects, such as extreme climate, produce long‐term effects on ecosystems. In conclusion, we found that synergisms between climate extremes (HWs) and human activities (mowing) can reduce ecosystem stability posing a threat to the grasslands.

Seasonal distribution of increased precipitation in maternal environments influences offspring performance of Potentilla tanacetifolia in a temperate steppe ecosystem

Precipitation is predicted to increase in arid and semiarid regions under climate change, with greater changes in intra- and inter-annual distribution in the future. As a major limiting factor in these regions, changes in precipitation undoubtedly influence plant growth and productivity. However, how the temporal shifts in precipitation will impact plant populations are uncertain. A 3-year field experiment and a greenhouse experiment were conducted in a temperate grassland in northern China to examine the impacts of seasonal (spring and summer) increased precipitation on offspring performance of a common species, Potentilla tanacetifolia. Our results showed that the amounts and timing of increased precipitation both played important roles in regulating offspring performance of P. tanacetifolia in the temperate steppe ecosystem. Increased precipitation in spring at maternal stage stimulated seed production, germination percentage and seedling biomass, whereas increased precipitation in summer at maternal stage stimulated seedling biomass. The timing of increased precipitation influenced seed attributes, whereas the amount of increased precipitation influenced offspring seedling biomass. Our results indicate that population development of P. tanacetifolia may be underestimated under future increased precipitation regime, if the transgenerational effect is not taken into account.

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.

Monitoring of heavy metal contamination of soil and plants (for example, &lt;i&gt;Potentilla tanacetifolia&lt;/i&gt; Willd. ex Schlecht.) of natural ecosystems in Chita urban areas

The paper presents data on the content of gross and mobile forms of zinc, cadmium, lead and copper in the soils of Chita and its surroundings. The paper contains a comparative analysis of the accumulation (Kn) and movement (KP) coefficients of these microelements in organs ( Potentilla tanacetifolia Willd. ex Schlecht.), relative to their gross content and mobile forms in soils. The authors have revealed that soil samples of the studied sites contain unequal gross amount of heavy metals. In some points (6 and 3) the content of cadmium and zinc exceeded the Mac, that is why such soils have been attributed to heavily polluted. The index of biological activity on mobile forms of heavy metals in all sites significantly exceeded the same index on gross forms. It was found that Potentilla tanacetifolia are accumulators of heavy metal ions. Aboveground bodies accumulate and absorb cadmium and copper especially intensively, thus the content of mobile forms of these metals in the soil is insignificant. Excessive adsorption of trace elements in the phytomass of plants can be connected with surface contamination. According to the content of zinc and lead, the accumulation values in the organs of P. tanacetifolia were characterized by small coefficient values, against the background of their high concentration in the soil.

The antioxidation-related functional structure of plant communities: Understanding antioxidation at the plant community level

In the case of ecological stresses, reactive oxygen species (ROS) can be overproduced in plant cells, leading to lipid peroxidation that causes damage or death to cells. To prevent damage, plant tissues contain several antioxidants that scavenge ROS. However, antioxidation at the plant community level still remains unknown and may provide an insight into ecosystem functioning regarding stress resistance. To understand the property, we established the antioxidation-related functional structure based on the concept of the functional structure and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), reduced glutathione (GSH), carotenoid (Car) and proline (Pro) and the relative abundance of component species in natural plant communities on the Chinese hilly-gullied Loess Plateau. An information-theoretic (I-T) approach was used to infer the effects of antioxidation-related functional components and stresses that we investigated on lipid peroxidation at the plant community level quantified by the community-weighted mean of malondialdehyde (MDA). We found that the induction of lipid peroxidation was more closely associated with a soil available nitrogen deficiency than it was with an available phosphorus deficiency. However, the inducing effect of soil available nitrogen was finite. The prevention of lipid peroxidation was more closely associated with the community-weighted means of GSH and Pro (CWM GSH and CWM Pro) than it was with other antioxidation-related functional components. However, the efficiency of CWM Pro was quite low; CWM GSH exhibited inefficiency. In addition, antioxidation-related functional components were affected by neither soil available nitrogen nor available phosphorus. Furthermore, by estimating the relative weights of the antioxidants and considering the feasibility of community assemblages, we proposed that Stipa grandis, Leymus secalinus, Stipa bungeana, Phragmites australis, Potentilla tanacetifolia, Artemisia gmelinii, Artemisia scoparia, Heteropappus altaicus and Syringa oblata could be utilized in community assemblages to achieve an antioxidation-functional target. Additionally, appropriate phosphorus application for A. gmelinii and H. altaicus might contribute to maintaining their antioxidation.

Nitrogen deposition influences the response of Potentilla tanacetifolia to phosphorus addition

Phosphorus is an essential macronutrient for all livingplants and plant production. Simultaneously, atmospheric nitrogendeposition also affects plant productivity at a global scale. However,few studies have investigated how plants respond to P addition whilesimultaneously considering N deposition. We investigated plant biomass,nutrient status and stoichiometric ratios on Potentilla tanacetifoliain response to P fertilization under contrasting N addition ratesin a typical meadow steppe in Inner Mongolia, China. Abovegroundbiomass of P. tanacetifolia increased under increasing levels of P fertilizationunder conditions of N addition. However, there was no significantchange in biomass when only phosphorus was added. Plantleaf and stem P concentrations increased linearly with P additionwhen there was no N addition. Our results suggest that increasedplant P nutrition under P addition will not turn into plant growthenhancement unless N demands are also satisfied. Nitrogen additionsignificantly increased leaf N concentrations, and leaf and seed N:Pratios, when there was no P fertilization. Nevertheless, the effects ofN addition were weakened, and eventually disappeared when P fertilizationrates increased. This indicates that N-induced alterationsof the plant nutrition status and stoichiometric ratios were P availability-dependent. Overall, our results suggest that multiple-nutrientconstraints and their interactions must be considered when assessingplant nutrient and growth responses to nutrient enrichment.

Estimation of herbage intake and digestibility of grazing sheep in Zhenglan Banner of Inner Mongolia by using n-alkanes.

To reveal the seasonal dynamics of herbage intake, diet composition and digestibility and clarify the relationship of those with herbage nutrient and botanical composition of grazing sheep in Zhenglan Banner of Inner Mongolia, the n-alkane technique was used to test in sheep grazed during June, August and December. The results showed that the sheep mainly ate Fringed sagebrush, Stipa krylovii and Carex in proportions of 33.5, 17.9 and 21.2%, respectively, in spring. In summer, the sheep consumed cleistogenes, Potentilla tanacetifolia, Thyme, etc; the intake of Fringed sagebrush, Carex and Stipa declined. In winter, Fringed sagebrush accounted for 50.1% of herbage intake, and the intakes of Cleistogenes and Stipa krylovii increased to 15.3 and 18.4%, respectively. Herbage intake by the sheep in spring was 1.8 kg DM/d, and digestibility was 71.4%. Herbage intake and digestibility decreased slightly to 1.7 kg DM/d and 68.4% during the summer, respectively and decreased significantly to 1.2 kg DM/d and 36.4% in winter. There were significant correlations between diet composition and CP content in winter, diet composition and botanical composition in summer. A highly positive correlation between herbage intake and digestibility was observed in grazing sheep.

Characteristics of seedling survival in habitats of hill and gully slopes in hill-gully Loess Plateau region of northern Shaanxi

Aims Seedling is the fundament of vegetation restoration succession and plays a very important role in ecosystems. The objective of this paper was to explore the characteristics of seedling survival in habitats of hill and gully slopes in a hill-gully Loess Plateau region. Methods Fifteen permanent plots in Zhifanggou and Songjiagou watershed in Ansai County were established for sentinel dynamic monitoring, and one-way ANOVA and hierarchical cluster analysis were used to analyze seedling density and survival rate in different habitats. Important findings There were significant differences in the characteristics of seedling survival among different habitats, with smaller seedling density and higher survival rates observed on the sunny slopes and larger seedling density but lower survival rate found on the shady slopes. In competition for survival, Artemisia gmelinii, Potentilla tanacetifolia, and Heteropappus altaicus etc. took advantage of quality and were characterized by a higher seedling survival rate, while Artemisia scoparia, Ixeris chinensis, Siphonostegia chinensis etc. adopted a strategy of "quantity" and characterized by a higher seedling density. The same species in different habitats had different survival curves, and the same survival curves in different habitats applied to different species. The seedlings of Artemisia gmelinii, Potentilla tanacetifolia, Stipa bungeana, Heteropappus altaicus, and Lespedeza davurica etc. had a strong survival capability in the rainy season and were easy to overwinter successfully, whereas the seedling survival capability in Artemisia scoparia, Dracocephalum moldavica, and Artemisia hedinii etc. was strong priorto the rainy season but weak in winter. The characteristics of seedling survival in different micro-environments also differed. A change in micro-environment affected seedling growth, survival, and overwintering to some extent. Thus, a proper tending for seedlings according to the survival characteristics of species is conducive to the seedling establishment and vegetation succession in the hill-gully Loess Plateau region.

Effects of increased nitrogen deposition and precipitation on seed and seedling production of Potentilla tanacetifolia in a temperate steppe ecosystem.

BackgroundThe responses of plant seeds and seedlings to changing atmospheric nitrogen (N) deposition and precipitation regimes determine plant population dynamics and community composition under global change.Methodology/Principal FindingsIn a temperate steppe in northern China, seeds of P. tanacetifolia were collected from a field-based experiment with N addition and increased precipitation to measure changes in their traits (production, mass, germination). Seedlings germinated from those seeds were grown in a greenhouse to examine the effects of improved N and water availability in maternal and offspring environments on seedling growth. Maternal N-addition stimulated seed production, but it suppressed seed mass, germination rate and seedling biomass of P. tanacetifolia. Maternal N-addition also enhanced responses of seedlings to N and water addition in the offspring environment. Maternal increased-precipitation stimulated seed production, but it had no effect on seed mass and germination rate. Maternal increased-precipitation enhanced seedling growth when grown under similar conditions, whereas seedling responses to offspring N- and water-addition were suppressed by maternal increased-precipitation. Both offspring N-addition and increased-precipitation stimulated growth of seedlings germinated from seeds collected from the maternal control environment without either N or water addition. Our observations indicate that both maternal and offspring environments can influence seedling growth of P. tanacetifolia with consequent impacts on the future population dynamics of this species in the study area.Conclusion/SignificanceThe findings highlight the importance of the maternal effects on seed and seedling production as well as responses of offspring to changing environmental drivers in mechanistic understanding and projecting of plant population dynamics under global change.

Pollen limitation and variation in floral longevity in gynodioecious Potentilla tanacetifolia

Abstract Pollination limitation is common in flowering plants and is thought to be a factor driving the evolution of floral traits. The plasticity of floral longevity to pollination may be an adaptation of plants to pollen limitation. However, this adaptation is less critical in short-lived flowers. To evaluate pollen limitation and the plasticity of floral longevity to pollination in Potentilla tanacetifolia, a gynodioecious herb with short-lived flowers, we analyzed its breeding system, tested sex-differential pollen limitation, and compared variations in floral display size in natural populations in Duolun County, Inner Mongolia, China. Hand pollination experiments and pollinator exclusion treatments revealed that P. tanacetifolia is self-compatible and non-autonomously apomictic and shows sex-differential pollen limitation. The plasticity of floral longevity to pollination was observed; the floral duration of female plants was prolonged by approximately 3–4 hours with pollination exclusion treatment. Moreover, the percentage of flowers displayed on female plants during pollination exclusion treatment was significantly higher than that during natural pollination. Under natural pollination conditions, the percentage of flowers displayed on female plants was significantly higher than on hermaphrodite plants. Furthermore, approximately 50% of the pollen grains spread out of the anthers of hermaphrodite flowers within 2 h of anthesis; the number of pollen grains adhering to the stigmas of hermaphrodite flowers was significantly higher than that adhering to female flowers when flowers shed their petals. These results indicate that variation in floral longevity may be an adaptive strategy to pollination conditions for gynodioecious P. tanacetifolia.

Nitrogen and water addition reduce leaf longevity of steppe species.

Changes in supplies of resources will modify plant functional traits. However, few experimental studies have addressed the effects of nitrogen and water variations, either singly or in combination, on functional traits. A 2-year field experiment was conducted to test the effects of nitrogen and water addition on leaf longevity and other functional traits of the two dominant (Agropyron cristatum and Stipa krylovii) and three most common species (Cleistogenes squarrosa, Melilotoides ruthenica and Potentilla tanacetifolia) in a temperate steppe in northern China. Additional nitrogen and water increased leaf nitrogen content and net photosynthetic rate, and changed other measured functional traits. Leaf longevity decreased significantly with both nitrogen addition (-6 days in 2007 and -5·4 days in 2008; both P < 0·001) and watering (-13 days in 2007 and -9·9 days in 2008; both P < 0·001), and significant differences in leaf longevity were also found among species. Nitrogen and water interacted to affect leaf longevity and other functional traits. Soil water content explained approx. 70 % of the shifts in leaf longevity. Biomass at both species and community level increased under water and nitrogen addition because of the increase in leaf biomass production per individual plant. The results suggest that additional nitrogen and water supplies reduce plant leaf longevity. Soil water availability might play a fundamental role in determining leaf longevity and other leaf functional traits, and its effects can be modified by soil nitrogen availability in semi-arid areas. The different responses of species to resource alterations may cause different global change ramifications under future climate change scenarios.

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.

RELATIONSHIP BETWEEN PLANT COMMUNITY AND SOIL ON THE INTER_DUNE LOWLAND IN THE MIDDLE OF OTINGDAG SAND LAND

Aims Vegetation and soil surveys were conducted in the summer of 2004 to study the relationship between vegetation types and soil of inter-dune lowland of Otindag sand land. Of 102 vegetation samples collected, 99 were herb-dominated, the others shrub-dominated. We analyzed soils for total nitrogen, soil organic matter, soluble sodium, soluble potassium and pH. Vegetation samples were classified based on species composition and species functional groups. We used detrended canonical correspondence analysis (DCCA) to determine the main environmental factors related to the distribution of plant communities. Methods The 102 samples were classified into twenty-eight groups dominated by Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis, A. scoparia, A. frigida, Carex duriuscula, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Leymus chinensis, L. secalinus, Bromus inermis, Saussurea amara, Potentilla tanacetifolia, Achnatherum splendens, Iris lactea, Salix microstachya, Phragmites australis, Calamagrostis epigejos, Potentilla anserine, Halerpestes ruthenica, Puccinellia tenuiflora, Scirpus tabernaemontani and Suaeda glauca. Importunt findings The Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis and A. scoparia associations are mostly distributed on sites often covered by quicksand. The level of the groundwater is low, the lixivium of the soil is neutral and the average soluble K+, Na+, total nitrogen and organic matter are low. Artemisia frigida, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Potentilla tanacetifolia, Leymus secalinus, Carex duriuscula and L. chinensis associations are rooted mostly in stable sand, where soil water, organic matter and total nitrogen are high. Bromus inermis, Saussurea amara, Puccinellia tenuiflora, Phragmites australis and Potentilla anserine associations grow in wet sites, where organic matter and total nitrogen are relatively high. Achnatherum splendens, Iris lacteal, Calamagrostis epigejos, Salix microstachya and Halerpestes ruthenica associations are on saline sites that have high groundwater and alkalinity. The Suaeda glauca association occurs in a highly saline lake, where water and salinity levels are very high. The Scirpus tabernaemontani association occurs in a marsh. The first DCCA axis denoted gradients in ground water level (GWL) and factors related to ground water level such as pH, soluble sodium and soluble potassium. The second axis reflected gradients of total nitrogen and soil organic matter. The third axis reflected a pH gradient. Ground water level, pH, soluble sodium, soluble potassium, total nitrogen and soil organic matter significantly correlated with the distribution of plant communities.