Ruijun Long

Methane emissions by alpine plant communities in the Qinghai-Tibet Plateau

For the first time to our knowledge, we report here methane emissions by plant communities in alpine ecosystems in the Qinghai–Tibet Plateau. This has been achieved through long-term field observations from June 2003 to July 2006 using a closed chamber technique. Strong methane emission at the rate of 26.2±1.2 and 7.8±1.1 μg CH4 m−2 h−1 was observed for a grass community in a Kobresia humilis meadow and a Potentilla fruticosa meadow, respectively. A shrub community in the Potentilla meadow consumed atmospheric methane at the rate of 5.8±1.3 μg CH4 m−2 h−1 on a regional basis; plants from alpine meadows contribute at least 0.13 Tg CH4 yr−1 in the Tibetan Plateau. This finding has important implications with regard to the regional methane budget and species-level difference should be considered when assessing methane emissions by plants.

The relationship of vegetation and soil differentiation during the formation of black-soil-type degraded meadows in the headwater of the Qinghai-Tibetan Plateau, China

In alpine meadow ecosystems, considerable spatial heterogeneity in forb-dominant vegetation exists as a result of severe grassland degeneration; however, there is limited quantitative information on the vegetative differences between degenerated and pristine grasslands. Therefore, a field study, which seeks to identify the edaphic factors driving the variation in plant composition and distribution, was conducted in a severely degraded alpine meadow located in the Qinghai-Tibetan Plateau, NW China. Five meadows, an original meadow and four degraded meadows, were used to determine the differentiation and relationships between the vegetation and soil of degraded alpine meadows. The dominated species of these degraded meadows are Ligularia virgaurea–Artemisia gmelinii (LA), Oxytropis ochrocephala–Leontopodium nanum (OL), Aconitum pendulum–Potentilla anserina (AP) and Stellera chamaejasme–Artemisia nanschanica (SA), respectively. The results indicate that vegetation cover, grass biomass, species number and diversity indices clearly decrease from the original to the degraded meadow. Soil water, clay and nutrient content are also reduced with grassland degradation in surface and subsoil layers. The joint study of floristic and edaphic variables confirms that the soil features, especially the bulk density, sand content, pH, salinity, N and K, mainly determine the establishment of vegetation in the severely degraded fields of this study. These results may be useful for alpine grassland ecosystem restoration and management.

Grazing behavior of lactating and non-lactating yaks in the summer season of the Qinghai-Tibetan plateau

The effect of the physiological states of lactating vs. non-lactating (dry) on grazing behavior and herbage intake by yaks was examined in the summer season in the Qinghai alpine area under continuous stocking management. Intake rates were estimated over periods of 1 h by weighing the animals before and after grazing, retaining the feces and urine excreted, and applying a correction for insensible weight loss (the 1-h weight changes of yaks when non-eating before or after the intake rate measurement). It is hypothesized that the lactating yaks should eat more and spend more time eating than nonlactating yaks, because they expend more energy. In our experiment, there were no differences in the effect of physiological state (lactating vs. dry) of yaks observed on the rate of insensible weight loss, intake rate, grazing jaw movement rate, bites per grazing jaw movement, or bite mass. The dry yaks tended to eat more and spend more time eating than lactating yaks, but not significantly so. Compared with the dry yaks, the lactating yaks had a significantly lower bite rate and bites per bolus.

Trolox equivalent antioxidant capacities and fatty acids profile of 18 alpine plants available as forage for yaks on the Qinghai-Tibetan Plateau

Traditionally, yaks (Poephagus grunniens) raised on the Qinghai-Tibetan plateau graze only natural pasture and much of their diet consists of sedges, in particular Kobresia spp. These ruminants are subjected to an extremely harsh environment of strong UV radiation, hypoxia and severe cold, which can lead to high oxidative stress. Consequently, it was predicted that sedges would contain high concentrations of functional antioxidants when compared with other alpine plants, and that this would help them survive the harsh conditions. To test the prediction, 18 alpine plants on the Qinghai-Tibetan plateau, which are available to yaks as forage, were examined. These plants, including four sedges, five grasses, five forbs and four shrubs, were analysed for gross constituents, Trolox equivalent antioxidant capacity, phenol content, and fatty acids composition. Based on their Trolox equivalent antioxidant capacity, the 18 plants were divided into three groups: low, medium and high. Three of the four sedges were ranked in the medium group and one in the low group, whereas three of four shrubs were ranked in the high group. The total phenol content of the plants ranged between 1.1 and 12.4 g gallic acid equivalents per 100 g DM, with the shrubs containing the highest concentrations. The prediction that sedges would contain higher antioxidant capacity than other alpine plants was not supported. It was concluded that other factors such as anti-nutritional contents and biomass availability are also important in determining dietary selection in yaks.

Recruitment of seedlings versus ramets as affected by pasture degradation in alpine meadows and the implications for ecological restoration

Background: The degradation of alpine meadows on the Qinghai-Tibetan Plateau (QTP) has an impact on vegetation recruitment from seedlings and ramets. Aims: Understanding the relative contribution of recruitment by seedling and ramet in alpine meadows is for the ecological restoration of degraded grasslands on the QTP. Methods: An experiment was conducted to investigate seedling and ramet densities, species composition and their relationships with standing vegetation in plots representative of non-degraded (ND), lightly (LD), moderately (MD) and severely degraded (SD) alpine meadows. Results: With increasing degradation and the reduction in vegetation cover, the number of seedlings and ramets declined. The proportion of young plants arising from seedlings was low, with the majority of species reproducing clonally. The establishment of seedlings of forbs in SD meadows led to species-rich, forb-dominant vegetation in these areas. Conclusions: LD and MD meadows appear to be able to be managed by reduced grazing for the restoration of grass- and sedge-dominated pastures. In contrast, restoration of SD meadows will require additional intervention, such as of seeding and weed eradication.

Effects of Soil Resources on Species Composition, Plant Diversity, and Plant Biomass in an Alpine Meadow, Qinghai-Tibetan Plateau

We investigated the effects of soil resources on species composition, plant diversity, and plant biomass in four alpine Kobresia meadow communities. Species diversity was lower in the Kobresia tibetica swamp meadow community than in the other three communities, but this community was characterized by the highest aboveground and belowground biomass and soil nutrients. Aboveground biomass was positively correlated with soil organic matter and soil total nitrogen in all four alpine meadow communities. The proportion of light fraction organic carbon (LFOC) was positively correlated with soil total organic carbon in all types of grassland. In alpine meadows, belowground biomass mostly occurred at 0-10 cm soil, as did soil nutrients. Community differences in plant species composition were reflected in biomass distribution. The highest total biomass (13,759 ± 497 g/m2) including above- and belowground biomass appeared in the sedge-dominated Kobresia tibetica swamp meadow community. Intermediate biomass (3,235 ± ...

Inhibitory action of allelochemicals from Artemisia nanschanica to control Pedicularis kansuensis, an annual weed of alpine grasslands

The inhibitory action of allelochemicals can be used effectively for biological weed management and can minimise environmental impacts related to herbicides. The aim of the present study was to identify allelochemicals of Artemisia nanschanica Krasch, a typical weed with strong allelopathic effects, that could potentially control Pedicularis kansuensis Maxim, the key pioneer weed that causes rapid degradation of alpine pastures. Gas chromatography and mass spectrometry were used to identify the compounds of six extracts from A. nanschanica. Two ethyl acetate extracts were the most effective in reducing the seed germination rate and in inhibiting seedling shoot and root growth of P. kansuensis. Three chemical compounds from the ethyl acetate extracts were identified for their allelopathic inhibitory effects, a sesquiterpene and two aromadendrene oxides, with the sesquiterpene being the most effective. The three compounds showed the best inhibitory effect through synergistic action. We concluded that the three allelochemicals of A. nanschanica, either alone or in combination, can be used to biologically control P. kansuensis in alpine pastures on the Tibetan plateau.

Trolox-equivalent antioxidant capacity and composition of five alpine plant species growing at different elevations on the Qinghai–Tibetan Plateau

Background: Alpine plants on the Qinghai–Tibetan Plateau are exposed to an extremely harsh environment, namely severe cold, strong ultraviolet radiation, hypoxia and low CO2 partial pressure. These conditions are sources of oxidative stress, which increase in severity with increasing elevation. Aims: To examine whether antioxidant capacity and chemical composition of alpine plants change with increasing elevation. Methods: We measured the Trolox-equivalent antioxidant capacity (TEAC) and chemical composition of five alpine plant species at 3016, 3814 and 4621 m a.s.l. Results: With increasing elevation: (1) the TEAC increased and total phenols and tannins tended to increase in two forb and two shrub species but not in a sedge species; (2) concentrations of protein and fat increased in all five plant species; (3) polyunsaturated fatty acids (PUFA) increased and (4) mineral concentrations tended to decrease, but trends were inconsistent. Conclusions: We conclude that with increasing elevation, TEAC and total phenols and tannins increased which we interpreted as an adaptation to higher oxidative stress; and protein and fat contents increased to support high metabolic activity. The increase in PUFA and the trend for minerals to decrease with increasing elevation require further investigation.