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  • Volume 6 Issue 4
    Species-rich alpine meadow in the Research Station of Alpine Meadow and Wetland Ecosystems of Lanzhou University on the eastern edge of Qinghai-Tibetan plateau. Photo taken by Shurong Zhou.
    Research Articles
    Helmut Brandl
    2013, 6 (4): 265-269.
    Abstract ( 101 )   PDF   Save
    Aims The goal of the study was to apply Fourier transform infrared (FTIR) spectroscopy followed by chemometrical data treatment for the differentiation of fungi-infected perennial ryegrass (Lolium perenne) from uninfected grass.
    Methods FTIR was used to rapidly discriminate between leaves of perennial ryegrass (L. perenne) infected by a fungal endophyte (Epichlo?; asexual forms: Neotyphodium) and uninfected leaves. Besides drying and grinding of the sampled leaves, no other preparation steps were needed. FTIR measurements were performed in the attenuated total reflection (ATR) mode. Aliquots of powdered leaf samples were placed on a ZnSe crystal and the spectra were collected, followed by chemometrical analysis (multidimensional factor analysis, hierarchical cluster analysis).
    Important findings ATR-FTIR allowed a rapid detection of fungal infections in the plant material and proved to be a fast and reliable tool for the differentiation of plant biomass without the need of time-consuming sample preparation.
    Zhaoyong Shi, Xiaogai Hou, Yinglong Chen, Fayuan Wang, Yanfang Miao
    2013, 6 (4): 270-276.
    Abstract ( 77 )   PDF   Save
    Aims Mycorrhizas play key roles in important ecosystem processes and functions. Carbon (C), nitrogen (N) and phosphorus (P) concentrations and their ratios are very important foliar traits and their cycling constrains most ecosystem processes. Thus, this study addresses the influence of mycorrhizal strategies on these foliar nutrients and their response to climate change.
    Methods A new database was established including mycorrhizal types and leaf C mass, N mass, P mass, C: N and N: P of each plant species based on He et al. [(2008) Leaf nitrogen: Phosphorus stoichiometry across Chinese grassland biomes. Oecologia 155:301–10]. The predominant type of mycorrhizal association of each plant species was classified according to the published literature and our own observations. We analyzed leaf C mass, N mass, P mass, C: N and N: P among 112 plant species in 316 samples of ascertained mycorrhizal type in the major grassland biomes of China.
    Important findings The results show highly significant variation among different mycorrhizal strategy types for foliar C mass, N mass and N: P. The highest foliar C mass was observed in ectotrophic mycorrhiza (ECM) type (469.8mg g-1) followed by that in arbuscular mycorrhiza (AM) type (443.884mg g-1) and nonmycorrhizal (NM) type (434.0mg g-1). The foliar N concentration was significantly higher in NM type (31.0mg g-1). However, the AM type had the greater C:N value (19) than the other types although less variation in C mass and N:P among abuscular types on AM strategy was observed. Foliar traits showed significant variation in response to precipitation (mean growing season and annual precipitation (GSP and MAP)) and temperature (mean growing season and annual temperatures (GST and MAT)) depending on different mycorrhizal strategies and arbuscular types. When the responses of all folia parameters to precipitation and temperature were compared, the influence of GSP on leaf traits was greater than the influence of GST.
    Jiajia Liu, Deyan Wu, Xiaoyu Peng, Shurong Zhou, Corey J. A. Bradshaw
    2013, 6 (4): 277-285.
    Abstract ( 79 )   PDF   Save
    Aims We aim to quantify the relative importance of various endogenous and exogenous processes influencing the spatial distribution of the individuals of plant species at different temporal and spatial scales in a species-rich and high-cover meadow in the eastern Tibetan Plateau.
    Methods We calculated Green's index of dispersion to infer the spatial distribution patterns of 73 herbaceous species at two scales (0.25 and 1.0 m 2). We constructed a series of generalized linear models to test the hypotheses that different species traits such as mean plant stem density, per capita dry biomass, maximum plant height and mean seed mass contribute to their spatial distribution. We used the first principal component of soil C, N and P to explain abundance variation across quadrats and sub-plots.
    Important findings The individuals of the species studied were highly spatially aggregated. At both spatial scales, biomass and stem density explained the most variation in aggregation, but there was no evidence for an effect of mean seed mass on aggregation intensity. The effects of soil carbon, nitrogen and phosphorus at different depths affected plant abundance mostly at the broader spatial scale. Our results demonstrate that self-thinning and habitat heterogeneity all contribute to determine the spatial aggregation patterns of plant individuals in alpine meadow vegetation in the eastern Tibetan Plateau.
    G.O. K'Otuto, D.O. Otieno, B. Seo, H.O. Ogindo,, J.C. Onyango
    2013, 6 (4): 286-297.
    Abstract ( 89 )   PDF   Save
    Aims Humid savannas, as a result of high precipitation amounts, are highly productive. They are also hotspots for land use change and potential sources of carbon dioxide (CO2) due to the large soil carbon (C) stocks. Understanding how ecosystem CO2 exchange is influenced by changes arising from agricultural land use is vital in future management of these ecosystems and in responding to the ongoing shifts in management and climate. The aim of this study was to identify how ecosystem CO2 exchange and biomass productivity of the herbaceous layer of a humid savanna in Kenya respond to current management practices.
    Methods We used flux chambers to quantify CO2 fluxes, while monthly harvests were undertaken to determine biomass development of the herbaceous layer of three sites that were (i) fenced to exclude livestock grazing, (ii) subjected to grazing by livestock and (iii) abandoned after being cultivated for maize production and also open to grazing by livestock.
    Important findings The peak aboveground biomass ranged between 380 and 1449g m ?2 and biomass production was significantly (P < 0.05) lower in the grazed and abandoned plots. The maximum gross primary production (GPP) and net ecosystem CO2 exchange (NEE) ranged between 21.8±1.3 to 32.5±2.7 and ?9.6±0.7 to-17.9±4.8 μmol m ?2 s-1, respectively. Seasonal NEE fluctuations ranged between 10 and 21 μmol m ?2 s-1, while spatial (among sites) differences ranged between 2 and 10 μmol m ?2 s-1. Ecosystem respiration (R eco) fluctuated between 5 and 10 μmol m ?2 s-1 during the growing season. R eco was, however, not significantly different among the sites. Unlike in other similar ecosystems where ecosystem respiration is determined by the ambient temperature, we did not find any relationship between R eco and temperature in this savanna. Instead, soil moisture accounted for 38–88% of the spatial and seasonal fluctuations in ecosystem CO2 fluxes and aboveground biomass production. Management influenced the maximum GPP and NEE rates through modification of soil moisture, plant species composition and aboveground biomass. We concluded that soil moisture is the key determinant of ecosystem CO2 exchange and productivity in this tropical savanna. Management, however, significantly modifies C fluxes and productivity through its influence on soil moisture, plant species composition and aboveground green biomass and should be taken into consideration in future similar studies.
    Gurbir S. Bhullar, Peter J. Edwards, Harry Olde Venterink
    2013, 6 (4): 298-304.
    Abstract ( 94 )   PDF   Save
    Aims and Methods Vascular plants are known to influence the production, transport and oxidation of methane in wetland soils, but these processes are not well understood. Using plants grown in intact peat cores, we compared the influence upon methane emissions of 20 forb and graminoid species from European wetlands. We measured plant-mediated transport of methane (conduit or chimney effect) using a novel agar-sealing technique that prevented methane exchange from the bare soil to the atmosphere.Important Findings The plant-mediated transport (chimney effect) represented between 30% and almost 100% of the total methane flux, with graminoids exhibiting greater internal transport than forbs. In general, plants with less dense root tissues and a relatively larger root volume exhibited a larger chimney effect. Most species (12 out of 20) significantly reduced methane emissions compared to bare soil and only one species, Succisa pratensis, increased them. We suggest that characterising vegetation in terms of plant functional traits and plant processes offers an effective method for estimating methane emissions from wetlands. However, we found no correlation between the magnitude of the chimney effect and the overall influence of different plant species on methane emissions. Besides introducing a useful tool to study plant-mediated transport, this work suggests that characterising vegetation in terms of functional traits could improve estimates of methane emissions from wetlands, which in turn could help in designing mitigation strategies.
    Heike Kawaletz, Inga Mölder, Stefan Zerbe, Peter Annighöfer, André Terwei, Christian Ammer
    2013, 6 (4): 305-315.
    Abstract ( 97 )   PDF   Save
    Aims Invasive species continue to be a worldwide threat to ecosystems mainly as a cause for biodiversity loss. Forest ecosystems, for example, are subject to a change in species composition due to the invasion of exotic species. Specifying the attributes that cause the strong competitiveness of several exotic species may improve the ability to understand and effectively manage plant invasions in the future. In this study the following hypotheses were tested: (1) biomass production of below- and aboveground plant components of the exotic tree species is higher than that of the natives, resulting in a higher competitiveness of the exotics; (2) the exclusion of root competition has a positive effect on the biomass production of the inferior native species; and (3) mixtures of native and exotic species yield a higher biomass production than the respective monocultures.
    Methods A pot experiment, containing about 2000 tree seedlings, was established. We investigated the biomass productivity and growth reactions of two native (Quercus robur L., Carpinus betulus L.) and two exotic tree species (Prunus serotina Ehrh., Robinia pseudoacacia L.) in different intra- and interspecific, competitive situations with and without the influence of root competition.
    Important findings The biomass production of both exotic species was significantly higher and led to a strong competitive advantage, resulting in a biomass decrease of the less competitive native species. The high belowground biomass of both exotic species had a negative effect on the biomass production. The competitive pressure of exotic tree seedlings on the native ones was largely driven by root competition. Furthermore, mixtures of native and exotic tree species had a higher productivity than their growth in monocultures would have predicted. Competition was lower for exotic species in mixtures with the less productive native species compared to the competition in monocultures or in mixture with the other highly productive exotic species. Accordingly, both highly competitive exotic species produced less biomass in mixture with each other compared to monocultures. Despite the significantly higher biomass of P. serotina in all mixtures and in monoculture, R. pseudoacacia seemed to be the dominating species. Due to its strong root competition, R. pseudoacacia significantly reduced the biomass production of P. serotina .
    Xiangjian Zhao, Wenyao Liu, Meng Zhou
    2013, 6 (4): 316-322.
    Abstract ( 83 )   PDF   Save
    Aims Crofton weed, with a subtropical origin, has successfully invaded in diverse habitats that belong to different climate zones in Southwest China. We tested whether local adaptation plays an important role in the successful invasion of crofton weed in heterogeneous environments.
    Methods Five populations from different habitats with an altitude ranging from 678 to 2356 m were selected. Plant height, biomass, seed yield and seed germination capability of these populations were investigated in the field. Greenhouse and reciprocal transplant experiments with the five populations were conducted, and all the above characters were measured and compared among these populations.
    Important findings Plant height, biomass, seed yield and seed germination rate were each significantly different among the five populations in field. However, there was no difference among these populations in the greenhouse experiment. In the reciprocal transplant experiment, plants from the five populations responded similarly to different habitats in the field, indicating lack of local adaptation. Instead, phenotypic plasticity likely plays a key role in the invasion success of crofton weed in different habitats.
IF: 1.780
5-year IF: 2.674
Wen-Hao Zhang
Bernhard Schmid
CN 10-1172/Q
ISSN 1752-9921(print)
ISSN 1752-993X(online)