Alpine Grasses Research Articles

Seeding alpine grasses in low altitude region increases global warming potential during early seedling growth

Introduction of alpine grasses to low altitude regions has long been a crucial strategy for enriching germplasm diversity, cultivating and acclimating high-quality species, enhancing ecosystem resilience and adaptability, as well as facilitating ecosystem restoration. However, there is an urgent need to investigate the impacts of planting Gramineae seeds on greenhouse gas (GHG) emissions, particularly during the critical stage of early plant growth. In this study, four species of grass seeds (Stipa breviflora, Poa pratensis, Achnatherum splendens, Elymus nutans) were collected from 19 high-altitude regions surrounding the Qinghai-Tibet Plateau and sown at low-altitude. Measurements of GHG emissions at early seedling growth in the mesocosm experiment using static chamber method showed a strong increase in the cumulative emissions of CO2 (5.71%–9.19%) and N2O (11.36%–13.64%) (p < 0.05), as well as an elevated CH4 uptake (2.75%–5.50%) in sites where the four grass species were introduced, compared to bare soil. Consequently, there was a substantial rise in global warming potential (13.87%–16.33%) (p < 0.05) at grass-introduced sites. Redundancy analysis showed that seed traits, plant biomass, and seedling emergence percentage were the main driving biotic factors of three GHGs fluxes. Our study unveils the potential risk of escalating GHG emissions induced by introducing high altitude grasses to low altitude bare soil, elucidating the mechanism through linking seed traits with seedling establishment and environmental feedback. Furthermore, this offers a new perspective for assessing the impact of grass introduction on ecological environment of introduced site.

Hybridization in the Subtribe Alopecurinae Dumort. (Poaceae) According to Molecular Phylogenetic Analysis: Different Ploidy Level Tells Different Origin of the Groups.

We performed next-generation sequencing of the 18S rDNA-ITS1-5.8S rDNA region along with traditional Sanger sequencing of rbcL, matK, ndhF, and ITS1-5.8S rDNA-ITS2 to clarify the hybridization pattern in the subtribe Alopecurinae and in the genus Alopecurus in particular. Our data support the hybrid origin of Alopecurus × brachystylus from hybridization between A. geniculatus (sect. Alopecurium) and A. pratensis (sect. Alopecurus). Moreover, in the rDNA of hybrid A. × brachystylus, only A. aequalis-like ribotypes from tetraploid A. geniculatus participated. Surprisingly, we found the traces of introgression of A. arundinaceus-like ribotypes not only in hybrid A. × marssonii (A. geniculatus × A. arundinaceus) but in A. aequalis s. str. as well. A high-polyploid group from the section Alopecurus, A. aggr. alpinus has undoubted hybrid origin: e. g., A. brachystachyus has rDNA from the sect. Alopecurium. Alopecurus alpinus, with its allies, is clearly distinct from other members of the sect. Alopecurus (especially by maternal line) and thus we can re-establish a previous opinion about the separate group to which A. alpinus belongs. Species from the section Colobachne (presumably Alpine grasses from Ancient Mediterranean region) probably hybridized with the A. alpinus group. Even A. myosuroides (sect. Pseudophalaris) that could be referred to the separate genus has ribotypes common with the species of the section Alopecurium (A. aequalis, A. geniculatus) in one of the accessions. Additionally, we found that the possible polyphyletic origin of the genus Limnas. Limnas stelleri is very close to Alopecurus magellanicus according to NGS data, while L. malyschevii is more or less distinct from other studied species of the genus Alopecurus.

New species and new record of the genus Poa L. (Poaceae, Pooideae, Poeae) from India

Poa sachensis, a new species from the Sach Pass, Western Himalaya, is described and illustrated. It is a member of P. subg. Ochlopoa sect. Alpinae, and closely allied to P. alpina, but differs from the latter by its lower glume one‐nerved, callus scantly hairy, lemma (3.87–) 4.18–4.54 (–4.65) mm long, purplish, surface between nerves glabrous, palea proliferate and keels ciliate 1/2nd to 1/3rd part, and two stamens in fertile floret with anther (2.42–) 2.67–3.08 (–3.21) mm long. Further, we have added P. diaphora var. alpina for the first time to the flora of India based on specimens collected from the semiarid habitats of Spiti Valley. Information on the distribution, habitat, flowering, and fruiting cycles is provided along with a distribution map for each taxon.Keywords: alpine grasses, Poa alpina, P. subg. Pseudopoa, P. subg. Ochlopoa, Western Himalaya

Different patterns and drivers of fungal communities between phyllosphere and rhizosphere in alpine grasslands

Abstract Epiphytic fungi are vital in enhancing their host plant performance and can also cause plant diseases. Generally, phyllosphere fungal community are majorly driven by climate, while rhizosphere fungal community are determined by soil properties and spatial distance. However, the differences in the relative effects of environmental factors on fungal community compositions and network structures remain far from clear between phyllosphere and rhizosphere. In this study, we conducted a large‐scale field survey along a 1400 km transect in the Tibetan Plateau and explored the composition and structure of phyllosphere and rhizosphere fungal communities from two dominant grass species (Leontopodium nanum and Stipa purpurea). L. nanum is widely distributed in relatively wet areas of alpine grasslands but S. purpurea prefers relatively dry areas. The geographical distributions of these two species overlap in the middle of the transect First, we found that precipitation was more important than temperature to affect fungal alpha diversity. High precipitation significantly promoted fungal alpha diversity in both phyllosphere and rhizosphere. Second, climate and spatial variables explained more variations in fungal community in the phyllosphere than rhizosphere. Specifically, greater precipitation promoted the relative abundances of pathotrophic fungi in the phyllosphere and rhizosphere, whereas lower precipitation only stimulated the relative abundances of symbiotrophic fungi in the rhizosphere. Third, precipitation had different impacts on phyllosphere and rhizosphere fungal networks between host species. Drought caused lower node number of fungal networks in the phyllosphere and rhizosphere of L. nanum. However, for S. purpurea, drought led to more complex and positive fungal networks in the phyllosphere and rhizosphere. Overall, these results indicated that precipitation caused different fungal community compositions along the transect between phyllosphere and rhizosphere, but consistently shaped their fungal networks. This study is among the first to provide compelling evidence on the large‐scale spatial variations and controlling factors for epiphytic fungal community in alpine grasslands. These new findings help to understand the role of epiphytic fungal community in affecting the functions of alpine grasses to cope with extreme environments. Read the free Plain Language Summary for this article on the Journal blog.

Revisiting the subalpine Mesolithic site Ullafelsen in the Fotsch Valley, Stubai Alps, Austria – new insights into pedogenesis and landscape evolution from leaf-wax-derived &amp;lt;i&amp;gt;n&amp;lt;/i&amp;gt;-alkanes, black carbon and radiocarbon dating

Abstract. Archaeological research in high mountain regions has gotten a lot more attention since the discovery of the copper age mummy called “Ötzi” in the Ötztaler Alps in 1991. In the Tyrolean Stubai Alps, the Mesolithic site Ullafelsen at 1869 m a.s.l. (above sea level) close to the recent upper timberline in the Fotsch Valley represents, on the one hand, a very important archaeological reference site and offers, on the other hand, intriguing research questions related to, amongst others, pedogenesis. Given that no biomarkers and stable isotopes have been hitherto investigated, we aimed at contributing with respective analyses and additional radiocarbon dating to a better understanding of the landscape evolution and pedogenesis on and around the Ullafelsen. Our results for modern vegetation suggest that leaf-wax-derived n-alkanes allow us to chemotaxonomically distinguish between subalpine deciduous trees (nC27 predominance) versus (sub)alpine grasses, herbs and dwarf shrubs (nC29, nC31 and/or nC33 predominance). Except for Juniperus, conifers produce no or extremely low n-alkane contents. Although no clear vegetation changes could be inferred from the n-alkane patterns of the investigated soil profiles, the total n-alkane content (TAC) was developed for the first time as an unambiguous proxy for distinguishing between buried (= fossil) topsoils (2Ahb horizons) and humus-enriched subsoils such as Bh horizons of podzols. Based on this leaf wax proxy, we can rule out that the 2Ahb?/Bh? horizons under question on the Ullafelsen are buried topsoils as suggested previously. Dating of the H2O2-pretreated soil samples yielded 14C ages for the podzol Bh horizons ranging from 6.7 to 5.4 cal kyr BP. This is clearly younger than the overlying Mesolithic living floor (LL) (10.9 to 9.5 cal kyr BP) but pre-dates the assumed intensification of alpine pasturing from the Bronze Age onwards. Both the LL and the directly overlying OAh3 horizon yielded black carbon maxima and benzene polycarboxylic acid patterns reflecting fire-induced human impact during the Mesolithic. The discrepancy between the Mesolithic charcoal 14C ages (ages of ≥ 9.5 cal kyr BP) versus the 14C ages obtained for bulk n-alkanes ranging from 8.2 to 4.9 cal kyr BP suggests that non-alkane-producing conifers predominated the vegetation on and around the Ullafelsen after the Mesolithic occupation. Only with the anthropo-zoological lowering of the timberline associated with alpine pasturing since the Neolithic and especially the Bronze Age has an n-alkane-producing vegetation cover (grasses, herbs or dwarf shrubs) started to predominate.

The Little Thredbo River; Disputing With Lee

The Little Thredbo River The Little Thredbo River is all I need of nature its conversation over rocks the silence of its pools its manageable scale perhaps 14 Ks in all its clarity unspoiled water as it wants to be vegetation incidental alpine grasses alpine moss gums I’ve yet to learn the names of. The Little Thredbo river is not unlike a poem when it’s finally ‘abandoned’ a

Linking root traits and soil moisture redistribution under Achnatherum splendens using electrical resistivity tomography and dye experiments

The rooting traits of deep-rooted alpine grasses strongly control the redistribution of soil moisture (i.e., the changes in the soil volumetric water content, ΔSVWC), which is the most important water resource supporting vegetation growth in cold semiarid regions. However, due to the difficulty of developing appropriate methods to characterize the hidden structures of root-soil systems, the linkages between root traits and ΔSVWC remain challenging to detect. This study aims to identify how the roots of Achnatherum splendens (A. splendens) affect soil water infiltration and spatiotemporal variations in the rhizosphere under different root densities and rainfall patterns using electrical resistivity tomography (ERT) and dye experiments, as well as to determine the relationship between root traits and soil water redistribution. Manipulative rainfall experiments 5, 10, 20 and 40 mm simulated rainfall were applied to sample plots with no plants (control), single and double A. splendens plantings (BAS, SAS, DAS, respectively). The results of ERT and the dyeing profiles showed that the roots of A. splendens greatly affected infiltration processes and the soil water distribution. The soil water was vertically and laterally funneled along the roots. In SAS, which had a lower root length density (RLD), the soil water accumulated mainly in the shallow layer (0–20 cm), while in DAS, which had a higher total root mass density (RMD), the soil water mainly infiltrated rapidly into the deep soil (>20 cm), especially during the extreme (40 mm) rainfall event. The temporal increases in soil moisture below 20 cm under DAS were higher than that those under BAS and SAS after rainfall for 2 and 24 h. The RMD, specific root length (SRL), specific root surface area (SSA) and RLD were all negatively and significantly correlated with the ΔSVWC at 0–20 cm. At 20–40 cm, the RMD and RLD were positively and significantly correlated with ΔSVWC, whereas the SRL and SSA showed the opposite trend. These findings provide direct evidence of the linkages between A. splendens root traits and ΔSVWC using ERT and the dye tracing method, and this evidence is important for the development of soil-plant-atmosphere continuum (SPAC) models.

Soil microbes that may accompany climate warming increase alpine plant production.

Climate change is causing species with non-overlapping ranges to come in contact, and a key challenge is to predict the consequences of such species re-shuffling. Experiments on plants have focused largely on novel competitive interactions; other species interactions, such as plant-microbe symbioses, while less studied, may also influence plant responses to climate change. In this greenhouse study, we evaluated interactions between soil microbes and alpine-restricted plant species, simulating a warming scenario in which low-elevation microbes migrate upslope into the distribution of alpine plants. We examined three alpine grasses from the Rocky Mountains, CO, USA (Poa alpina, Festuca brachyphylla, and Elymus scribneri). We used soil inocula from within (resident) or below (novel) the plants' current elevation range and examined responses in plant biomass, plant traits, and fungal colonization of roots. Resident soil inocula from the species' home range decreased biomass to a greater extent than novel soil inocula. The depressed growth in resident soils suggested that these soils harbor more carbon-demanding microbes, as plant biomass generally declined with greater fungal colonization of roots, especially in resident soil inocula. Although plant traits did not respond to the provenance of soil inocula, specific leaf area declined and root:shoot ratio increased when soil inocula were sterilized, indicating microbial mediation of plant trait expression. Contrary to current predictions, our findings suggest that if upwardly migrating microbes were to displace current soil microbes, alpine plants may benefit from this warming-induced microbial re-shuffling.

Plant community strategies responses to recent eruptions of Popocatépetl volcano, Mexico

AbstractQuestionsWhat are the mechanisms operating behind the plant community structure changes over time after lahars activity of Popocatépetl volcano? We hypothesize that functional diversity matters more than species richness and that, after major disturbances, the pioneer plant community will first show a ruderal composition, that subsequently changes into successional stages in which competitive and stress‐tolerating species become dominant life‐forms. We expect this process to be revealed by the community's functional signature.LocationPopocatépetl volcano in Mexico (19°1′0″N, 98°37′0″W) which has undergone large eruptive activity that has caused lahars formation.MethodsIn 2002, survey plots were established in the bottom of the Huilóac gorge. Species composition and abundance data were thereafter collected for 10 years. In 2013, data on three functional traits leaf area (LA), leaf dry matter content and LA of 67 species were obtained and each species was assigned to a strategy according to the CSR (Competitive, Stress‐Tolerant or Ruderal) scheme. A community‐functional signature was calculated for each year. Also, a parallel ordination of plots strategies composition in time was performed to confirm functional shift trends.ResultsInitial successional phases were dominated by ruderal and competitive species. Thereafter, the communities went through a phase of increasing heterogeneity of strategies, which was followed by dominance of competitive and stress‐tolerant strategists in the later years. Parallel ordination confirmed the gradient of functional differentiation through time.ConclusionsThe change from ruderal/competitive to stress‐tolerant and competitive species with time suggests that the most recent lahar event played a major role in sorting species according to their tolerance for disturbances. Thereafter, a major trend has been the gradual shift from ruderal to stress‐tolerant species (conifers and alpine grasses).

Nitrogen (N) and phosphorus (P) resorption of two dominant alpine perennial grass species in response to contrasting N and P availability

Nutrient additions may affect plant nutrient resorption and hence alter plant community composition and nutrient cycling in ecosystems. However, there is still much debate about how changes in nutrient availability affects nutrient resorption. Field experiments were conducted in 2013 on the Kunlun Mountain alpine grassland in northwestern China to investigate the variation between two dominant grasses Stipa capillata and Seriphidium rhodanthum in term of their nutrient resorption response to contrasting N and P addition levels. Results showed increasing N addition reduced N resorption efficiency and proficiency, and the N:P resorption ratio for both grass species, but increased P resorption efficiency and proficiency for only S. rhodanthum. Phosphorus addition increased P and N resorption efficiency of S. rhodanthum. In contrast, P addition decreased P resorption efficiency but had no impact on N resorption efficiency of S. capillata. Our results suggest that nutrient resorption responses to nutrient availability differed between perennial grass species. For both species, P additions reduced P resorption proficiency but increased N resorption proficiency. Thus, nutrient resorption is sensitive to soil nutrient availability and is an important strategy for nutrient conservation strategy for alpine grasses.

近20年青藏高原东北部禾本科牧草生育期变化特征

近20年青藏高原东北部禾本科牧草生育期变化特征

Improved alpine grassland mapping in the Tibetan Plateau with MODIS time series: a phenology perspective

The Tibetan Plateau is primarily composed of alpine grasslands. Spatial distributions of alpine grasses, however, are not well documented in this remote, highly uninhabited region. Taking advantage of the frequently observed moderate resolution imaging spectroradiometer (MODIS) images (500-m, 8-day) in 2010, this study extracted the phenological metrics of alpine grasses from the normalized difference vegetation index time series. With the Support Vector Machine, a multistep classification approach was developed to delineate alpine meadows, steppes, and desert grasses. The lakes, permanent snow, and barren/desert lands were also classified with a MODIS scene acquired in the peak growing season. With ground data collected in the field and aerial experiments in 2011, the overall accuracy reached 93% when alpine desert grasses and barren lands were not examined. In comparison with the recently published national vegetation map, the alpine grassland map in this study revealed smoother transition between alpine meadows and steppes, less alpine meadows in the southwest, and more barren/deserts in the high-cold Kunlun Mountain in the northeast. These variations better reflected climate control (e.g. precipitation) of different climatic divisions on alpine grasslands. The improved alpine grassland map could provide important base information about this cold region under the pressure of rapidly changing climate.

Seasonal variations in the fatty acid profile of milk from yaks grazing on the Qinghai-Tibetan plateau

An experiment was conducted to study the seasonal changes in the fatty acid profile of milk from yaks (Bos grunniens) when kept at altitudes of 3000m above sea level (a.s.l.) and higher. Data and samples were collected in summer (July), autumn (September), winter (November) and spring (March) from ten lactating yaks (four in spring). The yaks grazed pastures adjacent to the farm building throughout the year. In spring only they received 0·6kg crop by-products per day (dry matter basis). Fresh alpine grasses, available in summer and autumn, showed high concentrations of α-linolenic acid (46-51g/100g lipids) compared with the dry, yellow vegetation of winter and spring (16g/100g lipids). In autumn and summer, the milk fat had higher concentrations of polyunsaturated fatty acids than in winter. These polyunsaturated fatty acids were comprised of vaccenic acid, rumenic acid and α-linolenic acid, which are all considered beneficial to human health. The rare fatty acid, γ-linolenic acid, was also detected in yak milk, especially in the milk obtained in spring. The results suggest that yak milk, which is the most important basic food of the Tibetan herders, has the most favourable fatty acid profile when yaks grazed green pasture, which also corresponds to the period of highest milk production.

Emigration of the plant pathogen Pseudomonas syringae from leaf litter contributes to its population dynamics in alpine snowpack

The recently discovered ubiquity of the plant pathogen Pseudomonas syringae in headwaters and alpine ecosystems worldwide elicits new questions about the ecology of this bacterium and subsequent consequences for disease epidemiology. Because of the major contribution of snow to river run-off during crop growth, we evaluated the population dynamics of P.syringae in snowpack and the underlying leaf litter during two years in the Southern French Alps. High population densities of P.syringae were found on alpine grasses, and leaf litter was identified as the main source of populations of P.syringae in snowpack, contributing more than the populations arriving with the snowfall. The insulating properties of snow foster survival of P.syringae throughout the winter in the 10 cm layer of snow closest to the soil. Litter and snowpack harboured populations of P.syringae that were very diverse in terms of phenotypes and genotypes. Neither substrate nor sampling site had a marked effect on the structure of P.syringae populations, and snow and litter had genotypes in common with other non-agricultural habitats and with crops. These results contribute to the mounting evidence that a highly diverse P.syringae metapopulation is disseminated throughout drainage basins between cultivated and non-cultivated zones.

Mortality of Australian alpine grasses (Poa spp.) after drought: species differences and ecological patterns

Aims Australian alpine ecosystems currently experience high precipitation in the snow-free season, but they are predicted to experience drier conditions under climate change. We observed high mortality of the dominant alpine grasses following drought in 2007. Our aims were as follows: to test the involvement of plant-available water (PAW) and other environmental variables in grass mortality in the field; to detect possible species differences in drought response and to link soil moisture to precipitation using soil properties and climate data. Methods The dominant tussock grasses of the Australian alpine zone, Poa hothamensis var. hothamensis N.G. Walsh, Poa hiemata Vickery and Poa phillipsiana Vickery (Poaceae), all exhibited mortality following drought in the Bogong High Plains, Victoria, Australia in 2007. PAW was calculated using soil water potential measurements, and past drought occurrence was modelled using climate data. We then tested the effects of PAW and soil depth on grass survival both at a large spatial scale spanning the elevational range of the alpine zone and at a smaller scale. Poa hothamensis and P. phillipsiana were compared in a common-garden experiment to test drought tolerance. Important Findings Poa hothamensis survival was predicted by dry-season PAW at the small spatial scale; at the large scale, soil depth and elevation were more important predictors of P. hothamensis survival, but dry-season PAW predicted P. hiemata survival. Common-garden experiments supported field observations that P. hothamensis is more droughtsensitive than is P. phillipsiana. We also present a simple polynomial relationship between rainfall and field soil moisture, which predicts that the alpine soils dry below wilting point several times a year. We suggest the timing of long rain-free periods may be more important than their duration.

Leaf respiration and alternative oxidase in field‐grown alpine grasses respond to natural changes in temperature and light

• We report the first investigation of changes in electron partitioning via the alternative respiratory pathway (AP) and alternative oxidase (AOX) protein abundance in field-grown plants and their role in seasonal acclimation of respiration. • We sampled two alpine grasses native to New Zealand, Chionochloa rubra and Chionochloa pallens, from field sites of different altitudes, over 1 yr and also intensively over a 2-wk period. • In both species, respiration acclimated to seasonal changes in temperature through changes in basal capacity (R₁₀) but not temperature sensitivity (E₀). In C. pallens, acclimation of respiration may be associated with a higher AOX : cytochrome c oxidase (COX) protein abundance ratio. Oxygen isotope discrimination (D), which reflects relative changes in AP electron partitioning, correlated positively with daily integrated photosynthetically active radiation (PAR) in both species over seasonal timescales. Respiratory parameters, the AOX : COX protein ratio and D were stable over a 2-wk period, during which significant temperature changes were experienced in the field. • We conclude that respiration in Chionochloa spp. acclimates strongly to seasonal, but not to short-term, temperature variation. Alternative oxidase appears to be involved in the plant response to both seasonal changes in temperature and daily changes in light, highlighting the complexity of the function of AOX in the field.

Short- and long-term effects of fire on the Collembola communities of a sub-alpine dwarf pine ecosystem in the Austrian Alps

We compared the Collembola communities of three sub-alpine sites in the Limestone Alps to evaluate the short- and long-term effects of natural forest fires. SITE 1 was burned in August 2003, SITE 2 was burned 50 years ago and sampled to assess the long-term effects of fire and the recovery of soil animals. A reference site (REF) was sampled to represent the undisturbed dwarf pine community. All sites are close to each other on a steep slope between 1 400 and 1 650 m above sea level. We found a total of 41 species of Collembola, as well as clear differences in the species composition and abundance between the sites. Most species (29) were found on the REF site. The highest abundance was found on SITE 1 (48 960 individuals*m-2, 22 species). We assume that some species survived the fire in deeper soil layers and others migrated or were passively dispersed from unburned patches and surrounding sites. The lowest abundance and species number (8 160 individuals*m-2, 18 species) were found on the 50-year-old site. This site was covered with a typical community for moving substratum, consisting mainly of alpine grasses, yet the dwarf pine vegetation had not yet recovered. The soil layer was still very thin and we therefore assume that a recovery of the Collembola community will take much longer than 50 years.

Relative contributions of leaf area ratio and net assimilation rate to change in growth rate depend on growth temperature: comparative analysis of subantarctic and alpine grasses

The present study shows that the relative contributions of leaf area ratio (LAR) and net assimilation rate (NAR) to variation among species in relative growth rate (RGR) depend on growth temperature. We grew three subantarctic and three alpine Poa species at daytime temperatures of 7, 12 and 17 degrees C, and analysed interspecific and temperature-related variation in RGRs by growth analysis. Variation in NAR accounted for most of the interspecific differences in RGR at low growth temperature, whereas variation in both NAR and LAR contributed strongly to interspecific differences in RGR at high growth temperature. For most species, the increase in RGR from 7 to 12 degrees C was attributable to an increase in LAR, whereas the increase in RGR from 12 to 17 degrees C was attributable to an increase in NAR. There were no differences between native subantarctic and alpine species in the plasticity of growth responses to temperature. However, Poa annua, a species introduced to the subantarctic, showed much greater growth plasticity than other species. There was little difference among species in tolerance of high-temperature extremes.

Seasonal pattern of antioxidant enzyme system in the roots of perennial forage grasses grown in alpine habitat, related to freezing tolerance

The relationship between active oxygen species (AOS) and membrane damage, and between antioxidant enzyme activity and chilling tolerance has been documented, but the mechanisms responsible for perennial forage grass to survive winter with temperatures at −30°C in temperate alpine regions is not well understood. In this study, the seasonal pattern of enzymatic antioxidant systems superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11) and lipid peroxidation in roots and leaves of alpine perennial grasses grown in their natural environment were investigated to understand the role of the enzymatic antioxidant system in freezing tolerance of perennial grasses. Four grasses, Poa sphyondylodes Trine., Bromus inermis Leyss., Bromus sinensis Keng. and Elymus nutans Griseb., were established in alpine conditions in 1993. The grasses were sampled at approximately semi‐monthly intervals in the autumn of 1995 and spring of 1996. The results showed that leaves were dead in the autumn and membrane damage seems to play a key role in the decline of this organ. Antioxidant enzyme activities of the roots strongly changed with declining temperature in the autumn and winter or increasing temperature in the spring. With the decrease in temperature in the autumn the antioxidant enzyme activities increased rapidly, reaching maximum values in early November and then slowly declining during the following winter period, although they were still higher than in September In the spring, antioxidant enzymes activities increased again in the roots with the rise of temperature from mid April to early May when the shoots began re‐growth. In contrast, thiobarbituric acid‐reactive substances content in the roots increased markedly in the autumn, reaching maximum values in early October and remaining constant with little fluctuation during the following winter. In the autumn when the roots experienced winter acclimation, the formation of freezing tolerance in the roots was correlated with the activities of the antioxidant enzyme, indicating that antioxidant activity systems in the roots played an important role in limiting the production of free radicals to protect membrane integrity. Freezing tolerance in alpine grasses correlated with an increased capacity to scavenge or detoxify activated AOS by the antioxidant enzymatic system. AOS accumulated with decreasing temperature in early cold acclimation may be an inducer in activating the antioxidant enzyme defence system for the formation of freezing tolerance in roots.

Simulation of Temporal and Spatial Distribution of Natural Vegetation Light Utilization Efficiency Based on 3s

Light utilization efficiency ( LUE ) directly influences the distribution of energy and rate of photosynthesis in all layers of vegetation. LUE is very valuable in deciding the integrated limits of environment to photosynthesis and plant growth allocation of aboveground, and is an important index in weighing functions of system. In China, the studies on LUE focus usually on crops, rarely on natural vegetations, and mostly calculate mean LUE over the country. The studies on LUE of natural vegetations in some regions are limited to one or two types of vegetation. Thus, it is very difficult to reflect the total conditions of all vegetations over these regions in different periods. In the study, leaf area index ( LAI ) that greatly influences LUE of vegetation was received from remote sensing images. The ecosystem productivity process model at landscape scale (EPPML) that described carbon cycle and water cycle of system was built by computer program (Visual C++), and seasonal dynamics and spatial distributions of total solar radiation, net primary productivity ( NPP ) and LUE in Changbai Mountain Nature Reserve were simulated. Geographical Information System (GIS) was used to process, analyze and display spatial data. Thus, we could extend and convert the studies on physiological ecology of plants from small scale to a larger scale. EPPML uses the principles of Century, BIOM_BGC, Forest_BGC and BEPS for quantifying the biophysical processes governing ecosystem productivity, but the original model is modified to better represent Changbai Mountain region. A numerical scheme is developed to integrate different data types: remote sensing data (TM), gridded vegetation, soil and topographic maps at 30_m resolution in Albers projection; daily meteorological data in Changbai Mountain station in 1995, including precipitation, maximal temperature, minimal temperature, mean temperature, solar zenith angle at noon, air pressure and wind speed; diameter data from field measurement and national forest survey; data from literatures for inputs to EPPML and validation of EPPML. Vegetation index is derived from remote sensing data for estimating daily LAI and biomass at landscape scale. The information about vegetation type, soil type, elevation, slope and aspect can be derived from vegetation, soil and topographic maps. EPPML uses the biochemical model for photosynthesis of leaves developed by Farquhar et al. (1980) to simulate the rate of photosynthesis. NPP is the organic matter eliminating respiration from gross photosynthetic productivity ( GPP ). In addition, EPPML uses the sub_module MT_Clim in Forest_BGC to calculate total solar radiation. In EPPML, the spatial scale is 30 m and temporal scale is daily and yearly. The whole simulating process is easily understood and realized. EPPML is run and values are cumulated in each pixel. The major outputs include seasonal dynamics and spatial distributions of some carbon cycle and water cycle variables including NPP and LUE . The results indicated that the seasonal variation of LUE of vegetations in Changbai Mountain was similar to that of NPP with peak value in July (2.9%). The LUE in spring, summer, autumn and winter averaged 0.551%, 2.680%, 0.551% and 0.047% respectively. The annual LUE of all vegetation types averaged 1.075%, varying from -3.272% to 3.556%. The maximal annual LUE appeared in mixed broad_leaved and korean pine forests (1.653%), minimum in alpine grasses (0.146%), others being Changbai larch forest (1.227%), spruce_fir forest (1.019%), meadow (0.983%), broad_leaved forest (0.728%), shrub (0.478%), alpine tundra (0.442%) and Betula ermanii forest (0.298%). Though the LUE of mixed broad_leaved and korean pine forests were very high, it still had great increasing potential. In conclusion, EPPML could well and truly simulate NPP and total solar radiation of main vegetations at landscape scale in Changbai Mountain Nature Reserve. Therefore, it could well reflect the seasonal dynamic a