Asian Grasslands Research Articles

Root-Colonizing Endophytic Fungi of the Dominant Grass Stipa krylovii From a Mongolian Steppe Grassland.

In several terrestrial ecosystems such as grasslands, plants live together with various root-colonizing dark septate endophytes (DSEs), fungi that are relatively frequent colonizers of healthy belowground tissues of plants in these environments. They are important members of the plant microbiota and may have various effects on plant survival under different stress conditions; however, their general functions in relation to plants and the greater ecosystem remain elusive. Although an increasing number of studies has been published focusing on DSEs in Asian grasslands, our knowledge is limited. Especially in Mongolia, where the steppe region represents a significant area, information is not available on these root colonizers. In this study, we aimed to characterize DSEs of a common dominant gramineous plant species, Stipa krylovii in a semiarid grassland of Mongolia. Root samples were collected in a natural steppe and were processed for isolation of fungal endophytes. For molecular identification of the isolates, the internal transcribed spacer (ITS) region of the nrDNA was obtained for all the isolates investigated; furthermore, the partial translation elongation factor 1-α (TEF) gene and large subunit (LSU) and small subunit (SSU) of rDNA were also amplified and sequenced in case of representative isolates. In vitro tests were used to examine the rough symbiotic nature of the fungi, and root colonization was visualized. A majority of the 135 isolates examined in detail was found to belong to several orders of Ascomycota (110 isolates) and some to Basidiomycota (25 isolates). A significant number of the isolates represented presumably novel taxa, and dominant similarities of the lineages have been found with relatively frequent and known grass root endophytes of semiarid areas in other geographic regions. These endophytes included Periconia macrospinosa, Microdochium bolley, and Darksidea, the genus of which comprised one fourth of the isolates. We found numerous lineages, which have been detected not only from Asian steppe ecosystems, but also from prairies in North America and sandy grasslands in Europe. Therefore, our results strengthen the hypothesized worldwide presence of a common and dominant core group of a DSE community in arid and semiarid grasslands.

Conservation possibilities of the rare grasshopper Stenobothrus eurasius Zubovski, 1898 are hampered by wild game in its fragmented western outposts

The ecology of invertebrate steppe species requiring active conservation management has not been explored enough. Stenobothrus eurasius is a characteristic steppe species occurring very frequently in the Siberian and Central Asian grasslands, although on the western edge of its area it is present in small, isolated, endangered relict populations. We examined populations and habitats of St. eurasius in the Pannonian vegetation region to (1) seek predictor variables of its density and (2) explore potentially successful conservation management practices which could be used generally on declining steppe relict species. Our results showed that robust populations of St. eurasius are found in short, edaphic, relict steppe grasslands in which the proportion of coarse sand in the soil is high and which are free of significant disturbance by game (specifically by wild boar). According to our study, the most important approach for the enhancement of declining marginal populations of St. eurasius, existing as an umbrella species of steppe relicts, is to reduce individual numbers of game (mainly wild boar and mouflon) which have increased tenfold regionally in the last few decades (or at least to exclude them from the most vulnerable patches).

Dietary Stress From Plant Secondary Metabolites Contributes to Grasshopper (Oedaleus asiaticus) Migration or Plague by Regulating Insect Insulin-Like Signaling Pathway.

Diets essentially affect the ecological distribution of insects, and may contribute to or even accelerate pest plague outbreaks. The grasshopper, Oedaleus asiaticus B-Bienko (OA), is a persistent pest occurring in northern Asian grasslands. Migration and plague of this grasshopper is tightly related to two specific food plants, Stipa krylovii Roshev and Leymus chinensis (Trin.) Tzvel. However, how these diets regulate and contribute to plague is not clearly understood. Ecological studies have shown that L. chinensis is detrimental to OA growth due to the presence of high secondary metabolites, and that S. krylovii is beneficial because of the low levels of secondary metabolites. Moreover, in field habitats consisting mainly of these two grasses, OA density has negative correlation to high secondary metabolites and a positive correlation to nutrition content for high energy demand. These two grasses act as a ‘push-pull,’ thus enabling the grasshopper plague. Molecular analysis showed that gene expression and protein phosphorylation level of the IGF → FOXO cascade in the insulin-like signaling pathway (ILP) of OA negatively correlated to dietary secondary metabolites. High secondary metabolites in L. chinensis down-regulates the ILP pathway that generally is detrimental to insect survival and growth, and benefits insect detoxification with high energy cost. The changed ILP could explain the poor growth of grasshoppers and fewer distributions in the presence of L. chinensis. Plants can substantially affect grasshopper gene expression, protein function, growth, and ecological distribution. Down-regulation of grasshopper ILP due to diet stress caused by high secondary metabolites containing plants, such as L. chinensis, results in poor grasshopper growth and consequently drives grasshopper migration to preferable diet, such as S. krylovii, thus contributing to grasshopper plague outbreaks.

Infestations of Lice of Steppe Buzzards (Buteo buteo vulpinus) Differ from those of Common Buzzards (Buteo buteo buteo)

The Steppe Buzzard (Buteo buteo vulpinus), an eastern subspecies of the Common Buzzard (Buteo buteo), is a long-distance migrant raptor that breeds across eastern European and central Asian grasslands. The eastern European populations migrate through a geographic bottleneck in Israel and overwinter in eastern and southern Africa. To investigate how the metabolic demand of long-distance migration may affect their health, we trapped Steppe Buzzards (n = 28) at Eilat, Israel, during the spring migration of 2016 and 2017 and collected their parasitic lice (Insecta: Phthiraptera). We compared their louse infestation levels to published data on nonmigratory or short-distance migratory Common Buzzards (B. b. buteo). These Common Buzzards were divided into two groups, free-living birds (n = 59) and captive ones (n = 104). All the Steppe Buzzards we examined harbored 1–4 species of lice. The Amblyceran lice that feed partially on living tissues and are thought to be relatively more virulent (Laemobothrion maximum and Colpocephalum nanum) were significantly more prevalent on Steppe Buzzards than on Common Buzzards (either free-living or in captivity). In contrast, the less-harmful Ischnoceran lice (Craspedorrhynchus platystomus and Degeeriella fulva) were either similarly or less prevalent on Steppe Buzzards than on the nonmigratory Common Buzzards, either free-living or in captivity. We hypothesize that this difference may mirror the metabolic demands of long-distance migration or, alternatively, our Eilat sample of Steppe Buzzards might have been biased in favor of the heavily infested individuals. In the Steppe Buzzard sample, we also detected a formerly unknown negative correlation between the abundance of Laemobothrion maximum and Colpocephalum nanum.

Grazing decreased water use efficiency in Central Asia from 1979 to 2011

Accurate predictions of water vapor at large temporal and spatial scales are particularly important in global studies. In recent years, Central Asian grasslands have been subject to both intensive grazing and variability in climatic conditions. However, uncertainties about grazing on water cycling under climate change still exist. Therefore, the Biome-BGC grazing model was applied to assess the effects of grazing on evapotranspiration (ET) and water use efficiency (WUE). Three grassland types were studied during the period 1979–2011: forest meadow (FM), temperate grassland (TG) and desert grassland (DG). ET shows a gradual decreasing trend from FM (365.65 ± 36.86 mm m−2 yr−1) to DG (183.32 ± 21.15 mm m−2 yr−1), and WUE ranging from 0.62 ± 0.03 g C kg-1 H2O in FM to 1.12 ± 0.10 g C kg−1 H2O in TG, with an average of 0.83 ± 0.05 g C kg−1 H2O. Although there was a significant decrease in ET of 1.47–2.72 mm m−2 yr−1, WUE increased at a rate of 0.004 g C kg−1 H2O yr−1 in Central Asia. From 1979 to 2011, grazing lowered ET by 7.47% in Central Asia; the reduction rates for FM, TG and DG were 3.10%, 12.70% and 7.42%, respectively. In general, grazing decreased WUE by 3.60%. From non-grazed to grazed scenario, WUE increased by 6.86% for FM, but WUE decreased by 7.27% and 5.61% for TG and DG. An over-compensation of GPP under grazing might account for the higher WUE under certain grazing intensities. In order to achieve maximum utilization of water efficiency, proper grazing intensity for TG, DG and FM should be limited to 0.17, 0.39 and 0.38 head/ha, respectively.

Gut Transcriptome Analysis Shows Different Food Utilization Efficiency by the Grasshopper Oedaleous asiaticus (Orthoptera: Acrididae).

Oedaleus asiaticus B. Bienko is a persistent pest occurring in north Asian grasslands. We found that O. asiaticus feeding on Stipa krylovii Roshev. had higher approximate digestibility (AD), efficiency of conversion of ingested food (ECI), and efficiency of conversion of digested food (ECD), compared with cohorts feeding on Leymus chinensis (Trin.) Tzvel, Artemisia frigida Willd., or Cleistogenes squarrosa (Trin.) Keng. Although this indicated high food utilization efficiency for S. krylovii, the physiological processes and molecular mechanisms underlying these biological observations are not well understood. Transcriptome analysis was used to examine how gene expression levels in O. asiaticus gut are altered by feeding on the four plant species. Nymphs (fifth-instar female) that fed on S. krylovii had the largest variation in gene expression profiles, with a total of 88 genes significantly upregulated compared with those feeding on the other three plants, mainly including nutrition digestive genes of protein, carbohydrate, and lipid digestion. GO and KEGG enrichment also showed that feeding S.krylovii could upregulate the nutrition digestion-related molecular function, biological process, and pathways. These changes in transcripts levels indicate that the physiological processes of activating nutrition digestive enzymes and metabolism pathways can well explain the high food utilization of S. krylovii by O. asiaticus.

Biological and ecological evidences suggest Stipa krylovii (Pooideae), contributes to optimal growth performance and population distribution of the grasshopper Oedaleus asiaticus.

Oedaleus asiaticus Bey. Bienko is a significant grasshopper pest species occurring in north Asian grasslands. Outbreaks often result in significant loss in grasses and economic losses. Interestingly, we found this grasshopper was mainly restricted to Stipa-dominated grassland. We suspected this may be related to the dominant grasses species, Stipa krylovii Roshev, and hypothesized that S. krylovii contributes to optimal growth performance and population distribution of O. asiaticus. A 4 year investigation showed that O. asiaticus density was positively correlated to the above-ground biomass of S. krylovii and O. asiaticus growth performance variables (survival rate, size, growth rate) were significantly higher in Stipa-dominated grassland. A feeding trial also showed that O. asiaticus had a higher growth performance when feeding exclusively on S. krylovii. In addition, the choice, consumption and the efficiency of conversion of ingested food (ECI) by O. asiaticus was highest for S. krylovii compared with other plant species found in the Asian grasslands. These ecological and biological traits revealed why O. asiaticus is strongly associated with Stipa-dominated grasslands. We concluded that the existence of S. krylovii benefited the growth performance and explained the distribution of O. asiaticus. These results are useful for improved pest management strategies and developing guidelines for the monitoring of grasshopper population dynamics against the background of vegetation succession and changing plant communities in response to activities such as grazing, fire and climate change.

Effects of non-native Asian earthworm invasion on temperate forest and prairie soils in the Midwestern US

Effects of invasive European earthworms in North America have been well documented, but less is known about ecological consequences of exotic Asian earthworm invasion, in particular Asian jumping worms (Amynthas) that are increasingly reported. Most earthworm invasion research has focused on forests; some Amynthas spp. are native to Asian grasslands and may thrive in prairies with unknown effects. We conducted an earthworm-addition mesocosm experiment with before–after control-impact (BACI) design and a complementary field study in southern Wisconsin, USA, in 2014 to investigate effects of a newly discovered invasion of two Asian jumping worms (Amynthas agrestis and Amynthas tokioensis) on forest and prairie litter and soil nutrient pools. In both studies, A. agrestis and A. tokioensis substantially reduced surface litter (84–95 % decline in foliage litter mass) and increased total carbon, total nitrogen, and available phosphorus in the upper 0–5 cm of soils over the 4-month period from July through October. Soil inorganic nitrogen (ammonium– and nitrate–N) concentration increased across soil depths of 0–25 cm, with greater effects on nitrate–N. Dissolved organic carbon concentration also increased, e.g., 71–108 % increase in the mesocosm experiment. Effects were observed in both forest and prairie soils, with stronger effects in forests. Effects were most pronounced late in the growing season when earthworm biomass likely peaked. Depletion of the litter layer and rapid mineralization of nutrients by non-native Asian jumping worms may make ecosystems more susceptible to nutrient losses, and effects may cascade to understory herbs and other soil biota.

Vegetation and soil responses to livestock grazing in Central Asian grasslands: a review of Chinese literature

Grasslands in northern China and the Qinghai-Tibetan plateau are particularly important to both ecosystem functioning and pastoral livelihoods. Although there are numerous degradation studies on the effect of livestock grazing across the region, they are largely only published in Chinese, and most focus on single sites. Based on case studies from 100 sites, covering a mean annual precipitation gradient of 95–744 mm, we present a comprehensive, internationally accessible review on the impact of livestock grazing on vegetation and soils. We compared ungrazed or slightly grazed sites with moderately and heavily grazed sites by evaluating changes in two indicator groups: vegetation (plant species richness, vegetation cover, aboveground biomass, belowground biomass and root/shoot ratio) and soil (pH, bulk density, organic C, total N, total P and available P). Most indicators declined with intensified grazing, while soil pH, bulk density and belowground biomass increased. Available P showed no clear response. Variables within indicator groups were mostly linearly correlated at a given grazing intensity. Relative grazing effects on different indicators varied along specific abiotic gradients. Grazing responses of plant species richness, aboveground biomass, soil bulk density, total N and available P interacted with precipitation patterns, while grazing effects on belowground biomass were influenced by temperature. Elevation had impact on grazing responses of aboveground biomass and soil organic carbon. Complex grazing effects reflect both methodological inconsistency and ecological complexity. Further assessments should consider specific characteristics of different indicators in the context of the local environment.

Simulated grazing effects on carbon emission in Central Asia

Dryland grasslands in Central Asia were prone to concurrent high levels of grazing intervention and climatic variability in the past decades. However, the influences of grazing on carbon cycling under climate change are still uncertain in this region. We modeled the carbon dynamics in Central Asia for different grassland types (i.e., Temperate Grassland, TG; Desert Grassland, DG; Forest Meadow, FM) that varied in grazing intensity from 1979 to 2011 by using the modified Biome-BGC grazing model. In addition, an inventory approach was also employed to estimate the CO2-eq emission from meat and milk production. The regional simulation estimated that the grassland ecosystems in Central Asia acted as a net carbon source with a value of 0.83PgC for the last 33 years (1Pg=1015g). However, Central Asian grasslands had a weak carbon sink of 0.10Pg when the grazing effect was eliminated. Grazing resulted in the release of 0.93PgC in Central Asia according to the modeling approach and 0.25–1.39PgC to inventory approach. Nevertheless, proper grazing intensities for TG, DG, and FM at approximately 0.23, 0.35, and 0.35headha−1, respectively, can result in overcompensation, which means that plants have higher productivity after herbivory compared with ungrazed condition under proper grazing intensity. These results can be attributed to the decreasing evapotranspiration (ET) in grazed grasslands, which can effectively promote grass growth. Therefore, restricting the grazing intensity to less than 0.23, 0.35, and 0.35headha−1 for TG, DG, and FM, respectively, to mitigate the degradation and maintain its carrying capacity for livestock is important. Our research explored the possible implications for grazing management of grasslands in Central Asia and concluded that grazing can eventually be assembled into a set of biophysical tools for climate adaptation and mitigation.

Dendroecology in Asia

Though centered in a core area of human settlement and agricultural activity since prehistoric times, and despite tremendous forest losses due to overexploitation and conversion processes, Asia still hosts large areas and a wide variety of ecologically contrasting forests. While the monsoon regions of lowland southeast Asia are covered by tropical and subtropical evergreen humid or seasonal rainforests, the middle altitudinal belt of the Himalayas and western Chinese mountain regions are home of evergreen broadleaved forests. Around the margins of the Tibetan Plateau, high-altitude conifer forests form the highest treelines in the northern hemisphere. Finally, steppe forests with long-living juniper species form the transition to the central Asian grasslands and deserts, accompanied by riverine forests along streams that allow the growth of trees in a dry and tree-hostile environment. These contrasting environmental and climatic conditions offer plenty of opportunity to study relationships between trees and their adaptation to local climatic conditions. The papers of this special issue were presented during the Second International Asian Dendrochronological Conference held in Xi’an, China, during 20–23 August 2011, where more than 150 tree-ring researchers, mainly from Asian countries, participated. This collection of articles exemplifies quite well the variety and recent directions of dendroecological research in Asia. Zhang et al. use a drought-sensitive network of juniper ring-width chronologies to analyse spatial and temporal patterns of moisture availability on the margin of the Asian Summer Monsoon realm on the northeastern Tibetan Plateau during the past 150 years and report about climatic teleconnections with the North Atlantic climate. Cai et al. study the drought history of the past 130 years at the arid margin of forests in the Yellow River catchment area, the eastern limit of the Asian Summer Monsoon influence. Both papers illustrate how tree-ring networks can enable the detection of shifts in current atmospheric circulation patterns. Although the number of publications about reconstructions of various climatic parameters over Asia has literally boomed during the past years, there are still huge gaps of knowledge about climate–growth relationships in different climatological realms. One important issue is the lack of local climate stations in mountainous areas and their restriction to valley sites that may cause ambiguities and obstacles to calibrate climate–growth relationships of highelevation sites. On the other hand, the floristic composition of forest communities often stays relatively stable over hundreds of meters of elevation difference, raising the question whether there do exist differences in the growthlimiting climatic factors within one tree species along altitudinal gradients. The studies of Gao et al. and He et al. on different juniper species near the western distribution limit of tree growth on the Tibetan Plateau reveal a strong coherence of climate–growth relationships over altitudinal belts. On the other hand, these relationships may vary with time under different climatic conditions, which advise some caution regarding the inconsiderate application of present onto the past, a result confirmed by the study of Zhang et al. On the other hand, Liu et al. demonstrate that an extension of the growing season length due to temperature increase has not yet been accompanied by increasing growth of high-elevation Smith fir, giving credibility that temperature-limited sites on the southern Tibetan Plateau are still reliable indicators for temperature variations. This is of great interest, since phenology and tree height growth A. Brauning (&) Erlangen, Germany e-mail: abraeuning@geographie.uni-erlangen.de

不同起始状态对草原群落恢复演替的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同起始状态对草原群落恢复演替的影响 DOI: 10.5846/stxb201202220241 作者: 作者单位: 内蒙古大学生命科学学院,内蒙古大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划项目(2011BAC02B03);国家自然科学基金项目(31160476, 31060076);内蒙古自治区自然科学基金重点项目(2010Zd16) The effects of different original state on grassland community restoration succession Author: Affiliation: College Of Life Sciences Of Inner Mongolia University,College Of Life Sciences Of Inner Mongolia University 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:内蒙古典型草原,由于过度放牧利用,绝大部分草原处于退化状态。为了使退化草原得到较好的恢复,以锡林郭勒盟白音锡勒牧场典型草原为研究对象,比较分析了在不同起始状态下的草原群落,经过6a的自然恢复,其各自的群落组成,地上生物量及共有种的植株高度、节间长、叶长、叶宽,土壤紧实度和容重。结果表明:1)不同放牧率的植物群落,经过6a的禁牧恢复,群落类型发生了变化且群落趋于一致。2)当放牧率SR≤5.33羊/hm2(SR4)时,演替起始状态对草原群落地上生物量的恢复没有影响;当放牧率SR＞5.33羊/hm2时,演替起始状态对草原群落地上生物量的恢复产生影响,其结果是导致当前生物量降低,不利于草原的恢复。3)不同放牧率植物群落的植物个体特征趋于一致, "个体小型化"现象消失。同时,也说明群落恢复演替的起点不同,正常化的时间没有太大的变化。4)不同放牧率植物群落的土壤紧实度和容重经过6a的禁牧恢复,没有得到完全恢复,但均达到一致的水平。 Abstract:The Xilinggol steppe is one of the four biggest grasslands in China, and is representative of the semi-arid grasslands in Asia. To discover whether the initial state (6 years previously) of various degraded grassland communities has had an effect on recovery of these communities and in what way this effect is evidenced, research was undertaken on vegetation that has undergone 6 years of recovery through non-grazing, after varying degrees of degradation under different grazing rates. The experimental study site is in the middle reaches of the Xilin River, 500 meters west of the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences, from 43°26'-44°08'N and 116°04'-117°05'E. The following is the general situation of the surveyed land. The grazing experiment at the study site began in summer 1989. The sample plot is degraded grassland, in which Artemisia frigida and small grasses dominate, and the experimental grazing animal was sheep. There are 6 conditions, including five different stocking rates (1.33, 2.67, 4.00, 5.33 and 6.67 sheep/hm2) and a non-grazing control. Having been grazed at various rates for 16 years through 2005, the structure and function of the ecological system (plant community, soil physical and chemical properties) have experienced significant changes. Grassland ecological systems are in different degrees of degradation. To examine the recovery process of such grassland ecological systems after suspension of grazing, the grazing experiment was stopped in 2005. By 2011, the grassland ecosystems had recovered to their natural state. Investigation and sampling were conducted in August 2011. In recent years, under the influence of high use and adverse natural factors, the majority of the Inner Mongolian steppe has been in a state of degradation. In order to facilitate recovery of the degraded grasslands, the present research was conducted on a typical steppe at Baiyinxile Ranch in Xilinggol. The author analyzed a series of indicators of the state of various grassland communities (each after 6 years of natural recovery), which include plant community composition, aboveground biomass, plant height, internode length, main species leaf length, leaf width, soil compactness, and soil bulk density. The findings suggest that: 1) After 6 years of non-grazed recovery, communities of different stocking rates have changed their community type, and the communities tend to be consistent. 2) Initial successional stages have no significant effect on aboveground biomass recovery when the stocking rate is less than 5.33 sheep/hm2; however, if the stocking rate is more than 5.33 sheep/hm2, the initial successional stages lead to a decrease in current biomass. In other words, a higher stocking rate is unfavorable to the recovery of grassland. 3) Individual plant characteristics of communities at different grazing rates tend to be consistent, and the individual miniaturization phenomenon disappear. At the same time, this shows that even though the starting point of community recovery and succession is variable, the normalization time is nearly constant. 4) After 6 years of recovery, the soil compactness and bulk density of communities with different grazing rates did not fully recover, but tended to be consistent. 参考文献 相似文献 引证文献

Response of ecosystem respiration to soil water and plant biomass in a semiarid grassland

The Mongolian steppe zone constitutes a major part of East Asian grasslands. The objective of this study was to evaluate the quantitative dependence of ecosystem respiration (Reco) on the environmental variables of soil water and plant biomass in a semiarid grassland ecosystem. We determined Reco using opaque, closed chambers in a Mongolian grassland dominated by graminaceous perennial grasses during six periods: July 2004, May 2005, July 2005, September 2005, June 2006, and August 2009. Using the data collected when soil water content and aboveground biomass were relatively constant, values of Reco were fitted to an exponential temperature function, and the standardized rate of Reco at 20°C (R20) and temperature sensitivity (Q10) of Reco were calculated for each measurement plot and period. The results indicate that aboveground biomass significantly affected the variation in R20, and the relationship was expressed with a linear model. The R20 residuals of the linear biomass model were highly correlated with soil water content by a quadratic function. The Q10 values showed a weak positive relationship with soil water content. Temporal and spatial variations in Reco were well predicted by the exponential temperature model with R20, which relates to aboveground biomass and soil water content, and with Q10, which relates to soil water content.

Interactive effects of clipping and nutrient availability on the compensatory growth of a grass species

Resource availability is an important factor affecting the capacity of compensatory growth after grazing. We performed a greenhouse experiment with Poa bulbosa, a small perennial grass of the Mediterranean and Central Asian grasslands, to test the importance of nutrient availability for compensatory growth after clipping. We also compared the results with predictions of the limited resource model (LRM). Plants were grown at low and high fertilization levels and subjected to a clipping treatment. Contrary to the LMR, we found that in Poa plants compensatory growth occurred under the high fertilization level, while it did not occur under the low level. The LMR predicts a higher tolerance for grazing in the stressful environment. Our plants showed a significant decrease in their relative growth rates (RGR) after clipping. Although the plants allocated a 32–188% greater fraction of the mass to lamina growth after clipping, this greater allocation to the leaves did not fully compensate for the initial reduction in leaf area ratio (LAR). A sensitivity analysis showed for the clipped plants under the high fertilization treatment, that changes in leaf allocation (flam) enabled the plants to compensate for a part of the potential loss caused by defoliation. Probably, the increased biomass allocation comes largely from the bulbs. We conclude that the inconsistency of the LRM with our results originates in the lack of compensatory mechanisms in the model. To better understand how environmental conditions affect tolerance to herbivory, the effects of compensatory growth should be taken into account.

Carbon isotope discrimination of C3 vegetation in Central Asian grassland as related to long-term and short-term precipitation patterns

Abstract. The relationship between carbon isotope discrimination (13Δ) of C3 vegetation and long-term (30 years) and short-term (growing period) precipitation was investigated. Different species of Stipa, a dominant grass genus in the (semi-)arid Asian steppes, and other C3 species were collected along aridity gradients in Inner Mongolia in 2005 (11 sites, 71 samples) and in the Republic of Mongolia in 2006 (40 sites, 45 samples). The data set was expanded with published and unpublished data of Stipa and other C3 species (11 studies covering 8 years, including 64 observations of Stipa, and 103 observations of other C3 species) and C3 community bulk-samples (11 samples). Weather data were geostatistically interpolated for all sampling sites and years. 13Δ of Stipa followed different relationships for the individual years when related to mean annual precipitation due to large anomalies between annual and long-term average precipitation patterns. However, the 13Δ response to rainfall converged when the (long-term) mean annual precipitation was replaced by year-specific mean daily precipitation during the growing period (PG). Remarkably, the 13Δ-response to (PG) for C3 species as a whole (including herbaceous dicots, semi-shrubs and grasses) and also the C3 community-level response were virtually identical to that of Stipa. The relation was also valid outside the geographical and climatic range where it was developed, giving proof of its robustness.

Environmental controls on photosynthetic production and ecosystem respiration in semi-arid grasslands of Mongolia

The Mongolian steppe zone comprises a major part of East Asian grasslands. The objective of this study was to separately evaluate the quantitative dependencies of gross primary production (GPP) and ecosystem respiration ( R eco) on the environmental variables of temperature, moisture, radiation, and plant biomass in a semi-arid grassland ecosystem. We determined GPP and R eco using transparent and opaque closed chambers in a grassland dominated by Poaceae species in central Mongolia during five periods: July 2004, May 2005, July 2005, September 2005, and June 2006. Values of GPP were linearly related to live aboveground biomass (AGB) enclosed by the chamber. The amount of GPP per unit ground area differed among the study periods, whereas GPP normalized by the amount of AGB did not differ significantly among the periods, suggesting that plant production per unit green biomass did not depend on the phenological stage. GPP/AGB fit well a rectangular hyperbolic light–response curve for all the study periods. When the air and soil were dry, considerable reduction in GPP was observed. The GPP/AGB ratio was also expressed as individual functions of air temperature, vapor pressure deficit, and volumetric soil water content. R eco was exponentially related to the soil temperature and the relationship was modified by soil moisture. The amount of R eco and its temperature sensitivity ( Q 10) declined with decreasing soil moisture. Sharp increases of R eco after rainfall events were observed. The values of R eco, even including the rain-induced pulses, were expressed well as a bivariate function of soil temperature and soil moisture near the soil surface.

Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe.

A hypothesis has been advanced that the incursion of woody plants into world grasslands over the past two centuries has been driven in part by increasing carbon dioxide concentration, [CO(2)], in Earth's atmosphere. Unlike the warm season forage grasses they are displacing, woody plants have a photosynthetic metabolism and carbon allocation patterns that are responsive to CO(2), and many have tap roots that are more effective than grasses for reaching deep soil water stores that can be enhanced under elevated CO(2). However, this commonly cited hypothesis has little direct support from manipulative experimentation and competes with more traditional theories of shrub encroachment involving climate change, management, and fire. Here, we show that, although doubling [CO(2)] over the Colorado shortgrass steppe had little impact on plant species diversity, it resulted in an increasingly dissimilar plant community over the 5-year experiment compared with plots maintained at present-day [CO(2)]. Growth at the doubled [CO(2)] resulted in an approximately 40-fold increase in aboveground biomass and a 20-fold increase in plant cover of Artemisia frigida Willd, a common subshrub of some North American and Asian grasslands. This CO(2)-induced enhancement of plant growth, among the highest yet reported, provides evidence from a native grassland suggesting that rising atmospheric [CO(2)] may be contributing to the shrubland expansions of the past 200 years. Encroachment of shrubs into grasslands is an important problem facing rangeland managers and ranchers; this process replaces grasses, the preferred forage of domestic livestock, with species that are unsuitable for domestic livestock grazing.

State Policy and Pasture Degradation in Inner Asia

The pastoralists of the Inner Asian grassland have been administered in different ways by Russian, Mongolian and Chinese governments. A Cambridge-based international research project set out to compare the results of these various approaches in the light of the widespread pastoral degradation reported in Chinese and Russian parts of the region. The findings suggest that areas, such as Mongolia, which have retained mobile pastorialism have much lower levels of reported pastoral degradation than those that introduced static, highly-mechanised agro-industrial techniques.

The Imperata grasslands of tropical Asia: area, distribution, and typology

The rehabilitation or intensified use of Imperata grasslands will require a much better understanding of their area, distribution, and characteristics. We generated estimates of the area of Imperata grasslands in tropical Asia, and suggested a typology of Imperata grasslands that may be useful to define the pathways toward appropriate land use intensification. We conclude that the area of Imperata grasslands in Asia is about 35 million ha. This about 4% of the total land area. The countries with the largest area of Imperata grasslands are Indonesia (8.5 million ha) and India (8.0 million ha). Those with the largest proportion of their surface area covered with Imperata are Sri Lanka (23%), the Philippines (17%), and Vietnam (9%). Laos, Thailand, Myanmar, and Bangladesh evidently all have similar proportions of their land area infested with Imperata (about 3 to 4%). Malaysia (< 1%), Cambodia (1%), and the southern part of China (2%) have but a minor proportion of their total land area in Imperata. The species was found widely distributed on the full range of soil orders. It occupied both fertile (e.g. some of the Inceptisols and Andisols) and infertile soils (Ultisols and Oxisols) across a wide range of climates and elevations. Imperata lands fall into four mapping scale-related categories: Mega-grasslands, itmacro-grasslands, meso-grasslands, and micro-grasslands. The mega-grasslands are often referred to as ‘sheet Imperata’. They are the large contiguous areas of Imperata that would appear on small-scale maps of say 1:1,000,000. We propose that this basic typology be supplemented with a number of additional components that have a key influence on intensification pathways: land quality, market access, and the source of power for tillage. The typology was applied in a case study of Indonesian villages in the vicinity of Imperata grasslands. We propose an international initiative to map and derive a more complete and uniform picture of the area of the Imperata grasslands. This should include selected studies to understand conditions at the local level. These are critical to build the appreciation of change agents for the indigenous systems of resource exploitation, and how they relate to local needs, values and constraints.

The Impact of Desertification in the Mongolian and the Inner Mongolian Grassland on the Regional Climate

This is an investigation of the impact of and mechanisms for biosphere feedback in the northeast Asian grassland on the regional climate. Desertification in the Inner Mongolian grassland has dramatically increased during the past 40 years. The Center for Ocean-Land-Atmosphere Studies atmospheric general circulation model, which includes a biosphere model, was used to test the impact of this desertification. In the grassland experiment, areas of Mongolia and Inner Mongolia were specified as grassland. In the desertification experiment, these areas were specified as desert. Each experiment consists of six integrations with different atmospheric initial conditions and different specifications of the extent of the desertification area. All integrations were 90 days in length, beginning in early June and continuing through August, coincident with the period of the East Asian summer monsoon. The desertification had a significant impact on the simulated climate. During the past 40 years, the observed rainfall has decreased in northern and southern China but increased in central China, and the Inner Mongolian grassland and northern China have become warmer. The simulated rainfall and surface temperature differences between the desertification integrations and the grassland integrations are consistent with these observed changes. The water balance and surface energy balance were altered by the desertification. The reduction in evaporation in the desertification experiment dominated the changes in the local surface energy budget. The reduction in convective latent heating above the surface layer enhanced sinking motion (or weakened rising motion) over the desertification area and over the adjacent area to the south. Coincidentally, the monsoon circulation was weakened and the rainfall was reduced.