| 781. |
- Xiong, Shaojun, et al.
(författare)
-
Responses of riparian plants to accumulation of silt and plant litter : the importance of plant traits
- 2001
-
Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 12, s. 481-490
-
Tidskriftsartikel (refereegranskat)abstract
- A 2-yr field experiment was used to determine the response of riparian plants to accumulation of litter or silt in a river flood-plain meadow in northern Sweden. Such disturbances occur regularly in free-flowing rivers but are likely to change as a result of global changes in land use or climate. We anticipated that plants with different traits would differ in their response to litter and silt accumulation. We quantified plant response as relative change in above-ground biomass, and regressed it on either litter mass or silt depth, and on plant traits such as lateral spread, plant height, relative growth rate, seed mass and seed persistence in soil. The relative changes in riparian plant biomass following litter or silt accumulation were negatively related to litter mass and silt depth, and positively related to most examined plant traits Such as seed mass. seed persistence and lateral spread. The vegetation recovery in the second season was largely determined by plant traits; litter or silt accumulation had no significant effect. Litter accumulation selected for large-seeded species, but silt accumulation selected for species with strong ability of lateral spread. Seed persistence was a useful variable in predicting species recovery from both litter and silt accumulation. Plant height was negatively related to plant recovery, but relative growth rate was not significantly related to relative change in plant biomass after silt or litter accumulation. Our results imply that plant traits are important variables to consider for predicting the responses of riparian vegetation to deposition of organic and inorganic matter.
|
|
| 782. |
|
|
| 783. |
|
|
| 784. |
- Zardán Gómez de la Torre, Teresa, et al.
(författare)
-
Detection of rolling circle amplified DNA molecules using probe-tagged magnetic nanobeads in a portable AC susceptometer
- 2011
-
Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 29:1, s. 195-199
-
Tidskriftsartikel (refereegranskat)abstract
- Here, the volume-amplified magnetic nanobead detection assay (VAM-NDA) is for the first time applied for detection of rolling circle amplified (RCA) DNA molecules in a portable, commercial AC susceptometer that operates at ambient temperatures and with an analysis time of about 20 min. The performance of the assay is investigated using three different magnetic nanobead sizes: 50, 130 and 250 nm. The performance of the assay using the AC susceptometer is compared to the performance achieved using a superconducting quantum interference device (SQUID). It is found that the performance of the assay is comparable in the two setups with a quantitative detection limit of ∼4 pM for all bead sizes under study. The findings show that the VAM-NDA holds promise for future wide-spread implementation in commercial AC susceptometer setups thus opening up for the possibility to perform magnetic bead-based DNA detection in point-of-care and outpatient settings.
|
|
| 785. |
- Zettervall, Niklas, et al.
(författare)
-
Small Skeletal Kinetic Reaction Mechanism for Ethylene-Air Combustion
- 2017
-
Ingår i: Energy and Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 31:12, s. 14138-14149
-
Tidskriftsartikel (refereegranskat)abstract
- Ethylene is a fuel considered for high-speed ram- and scramjet combustion applications, mainly because of the short ignition delay time resulting from its high reactivity. Further research and development on these combustion systems would benefit from simulations of large eddy (LES) type, which allow some chemical detail to accurately predict combustion characteristics and pollutant formation. In the present work, a chemical kinetic mechanism suitable for LES is presented, consisting of 66 irreversible reactions between 23 species. The mechanism is extensively validated for combustion characteristics related to ignition and flame propagation over a wide range of pressure, temperature, and equivalence ratios that previously published mechanism of this size have not covered. Agreement with a detailed reference mechanism is good for ignition delay, flame temperature, and laminar burning velocities. In addition, overall concentration profiles of major stable products are in overall good agreement with a reference mechanism. The skeletal mechanism shows an overall good performance in combination with a numerical stability and short computation time, making it highly suitable for combustion LES.
|
|
| 786. |
- Zhang, Feng, et al.
(författare)
-
Evaluation of restoration approaches on the Inner Mongolian Steppe based on criteria of the Society for Ecological Restoration
- 2020
-
Ingår i: Land Degradation and Development. - : John Wiley & Sons. - 1085-3278 .- 1099-145X. ; 31:3, s. 285-296
-
Forskningsöversikt (refereegranskat)abstract
- Ecological restoration is becoming an increasingly common management tool worldwide. However, a challenge still exists on how to effectively monitor restoration outcomes and evaluate restoration success for ecological restoration managers. In this review, the goal is to evaluate whether the research in a degraded area has been sufficient for fostering efficient restoration measures and follow-up of restoration success based on the Society for Ecological Restoration (SER) criteria. We selected the Inner Mongolian Steppe (IMS) in China as a model system. This area has been the subject of substantial research over the most recent years to understand degradation processes and restoration outcomes. We put together the variables used to assess degradation and restoration needs in the IMS and analyzed restoration results based on SER's nine criteria for evaluating restoration success. We found that the accomplished research in the IMS only partially supplied the data needed for evaluation of restoration success. The available results were sufficient for a proper evaluation of species composition and tentatively supported assessments of another seven criteria but not self-sustainability. Grazing exclusion led to the fastest and most successful recovery of degraded steppe, but landscape-scale processes during restoration in the IMS are still incompletely known. Our review supports large-scale restoration of the IMS and emphasizes the need for long-time monitoring for a more complete evaluation of the outcome of the IMS restoration following all SER's criteria.
|
|
| 787. |
- Zhang, Feng, et al.
(författare)
-
Evapotranspiration and crop coefficient for a temperate desert steppe ecosystem using eddy covariance in Inner Mongolia, China
- 2012
-
Ingår i: Hydrological Processes. - Malden : Wiley-Blackwell. - 0885-6087 .- 1099-1085. ; 26:3, s. 379-386
-
Tidskriftsartikel (refereegranskat)abstract
- Evapotranspiration (ET), which links water, energy and the carbon cycle in terrestrial ecosystems, is an important eco-hydrological process, especially in arid and semi-arid regions. To determine the crop coefficient (K-c) over a 2-year period for a temperate desert steppe in Inner Mongolia, China, ET was measured using the eddy covariance method and the reference evapotranspiration (ET0) was estimated from site meteorological data. The results showed that the seasonal variation of ET differed on an annual timescale between the 2 consecutive years, exhibiting a multi-peak curve in 2008 and a single peak in 2009. The mean daily K-c values were 0.15 and 0.17 in 2 years, varying from 0.009 to 0.75 in 2008 and from 0.005 to 0.58 in 2009. The 5-day moving average for K-c values was mainly affected by SWC10cm and R-n, and the regression coefficients (R-2) were 58.9 and 69.5%, respectively. These results will aid in making accurate and quantitative assessments of the vulnerability of the sparse vegetation to climate change.Copyright (C) 2011 John Wiley & Sons, Ltd.
|
|
| 788. |
- Zhang, Feng, et al.
(författare)
-
Remote estimation of the fraction of absorbed photosynthetically active radiation for a maize canopy in Northeast China
- 2015
-
Ingår i: Journal of Plant Ecology. - : Oxford University Press (OUP). - 1752-9921 .- 1752-993X. ; 8:4, s. 429-435
-
Tidskriftsartikel (refereegranskat)abstract
- Aims Accurate remote estimation of the fraction of absorbed photosynthetically active radiation (fAPAR) is essential for the light use efficiency (LUE) models. Currently, one challenge for the LUE models is lack of knowledge about the relationship between fAPAR and the normalized difference vegetation index (NDVI). Few studies have tested this relationship against field measurements and evaluated the accuracy of the remote estimation method. This study aimed to reveal the empirical relationship between NDVI and fAPAR and to improve algorithms for remote estimation of fAPAR.Methods To investigate the method of remote estimation of fAPAR seasonal dynamics, the CASA (Carnegie-Ames-Stanford Approach) model and spectral vegetation indices (VIs) were used for in situ measurements of spectral reflectance and fAPAR during the growing season of a maize canopy in Northeast China.Important Findings The results showed that the fAPAR increased rapidly with the day of year during the vegetative stage, it remained relatively stable at the stage of reproduction, and finally decreased slowly during the senescence stage. In addition, fAPAR(green) [fAPAR(green) = fAPAR x (green LAI/green LAI(max))] showed clearer seasonal trends than fAPAR. The NDVI, red-edge NDVI, wide dynamic range vegetation index, red-edge position (REP) and REP with Sentinel-2 bands derived from hyperspectral remote sensing data were all significantly positively related to fAPAR(green) during the entire growing season. In a comparison of the predictive performance of VIs for the whole growing season, REP was the most appropriate spectral index, and can be recommended for monitoring seasonal dynamics of fAPAR in a maize canopy.
|
|
| 789. |
- Zinko, Ursula, et al.
(författare)
-
Plant species number predicted by a topography based groundwater-flow index
- 2005
-
Ingår i: Ecosystems (New York. Print). - New York, N.Y. : Springer. - 1432-9840 .- 1435-0629. ; 8:4, s. 430-441
-
Tidskriftsartikel (refereegranskat)abstract
- The lack of a clear understanding of the factors governing the often-great variation of species numbers over entire landscapes confounds attempts to manage biodiversity. We hypothesized that in a topographically variable boreal forest landscape the availability of shallow groundwater is a major determinant of plant species numbers. We then developed a topographically derived hydrologic index based on multidirectional flow algorithms to account for the variation in availability of such groundwater in the landscape. We found a positive correlation between species numbers of vascular plants in plots ranging from 0.01 to 200 m2 and the hydrologic index. Generally, the landscape was relatively dry and species-poor, but interspersed patches with shallow groundwater had high species numbers and high proportions of regionally uncommon plant species. The index explained 30% of the variation in vascular plant number and correlated quite well (rs = 0.50) with groundwater level, but not as well with a community H+concentration value (instead of community pH, rs = −0.31), based on species composition. In addition, we found a very strong correlation between species number and the community H+ concentration value (rs−0.84). The hydrologic index is a useful tool for the identification of spatial of species number patterns across entire landscapes. This is an important step in identifying the areas most in need of protection or restoration, designing survey techniques, and understanding the fundamental processes that control the spatial distribution of species.
|
|
| 790. |
- Zinko, Ursula, 1969-
(författare)
-
Plants go with the flow : predicting spatial distribution of plant species in the boreal forest
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objectives of this thesis are to study if a topographic wetness index (TWI) could be used as a tool for predicting the spatial distribution of vascular plant species richness in the boreal forest as well as to study congruence in species richness between vascular plants, liverworts, mosses and lichens. A wetness index ln(a/tanβ) based on topography was used to assign a specific TWI-value to every 20 x 20m grid in two 25 km2 boreal forest landscapes (differing in average soil pH) in northern Sweden. Soil pH is known to be influenced by groundwater and to affect plant species richness in other biomes. Therefore, the relationships between plant species richness, TWI and soil pH were also studied. The results showed that the majority of the investigated boreal forest landscapes were relatively dry and species-poor, whereas interspersed patches linked to areas with relatively high TWI had species-rich vegetation including the species of the drier parts of the landscape. There was a positive relationship between species richness of vascular plants and the TWI in both landscapes, but varied with average soil pH. TWI explained 30 % and 52 % of the variation in plant species richness in the landscape with lower and higher pH, respectively. The proportion of regionally uncommon plants also increased with TWI. Testing different calculation methods of the TWI resulted in a large variation in correlation strengths between the various TWI-values and different measured variables (species richness of vascular plants, soil pH, groundwater flow and soil moisture). The relationship between plant species richness and TWI could be further improved with some of the calculation methods. When studying correlations in species richness using data sets from boreal forest in northern Sweden, strong positive correlations among vascular plants, mosses and liverworts were found, but no significant correlation between macrolichens and any of the other groups. This result could be explained by that the species number of each of the three related groups increases with ambient moisture, whereas the species number of macrolichens is weakly associated with moisture. In conclusion, the TWI could become a useful tool in conservation management for identifying areas of special interest prior to field inventories. Since vascular plants can be used as an indicator taxon for species richness of mosses and liverworts, high TWI-values indicate areas of species hotspots of these taxa.
|
|
