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91.
Interactions among fire legacies, grazing and topography predict shrub encroachment in post-agricultural páramo 总被引:1,自引:1,他引:0
Woody encroachment in grasslands is a global phenomenon driven by complex interactions between climate, grazing and fire management. Alpine shrub encroachment is of particular concern for biological conservation because high-elevation grasslands harbor high levels of biodiversity and species endemism. Páramo grasslands of the high Andes are exceptionally high in floral diversity, but traditional agricultural practices have resulted in widespread livestock grazing and anthropogenic burning. Fire suppression has frequently been identified a driver of woody expansion in other grasslands, and conservation initiatives that aim to decrease burning and grazing in páramos may inadvertently lead to shrub encroachment. We tested whether interactions among fire and grazing legacies, topography and edaphic conditions predicted the patchy distribution of encroaching shrubs in an Ecuadorian páramo 10 years after release from burning and grazing. Interviews with land-users identified proximity to roads, footpaths and riparian areas as proxies for fire frequency and grazing pressure. A recursive partitioning model of shrub cover revealed that woody abundance was generally lower at lower elevations, especially near the access road (where fire frequency and grazing pressure were high). Within the low-elevation areas, shrub cover was highest near streams (where grazing pressure was high). These results suggest that (1) the effects of fire and grazing legacies depend on the spatial patterns of grazing, and (2) legacy effects interact with topography to help explain patchy shrub encroachment. 相似文献
92.
93.
Rachel N.T.M. Kabuyah Bart E. van Dongen Alastair D. Bewsher Clare H. Robinson 《Soil biology & biochemistry》2012
The degradation of organic macromolecules, including lignin, in plant-derived soil organic matter, is important to the global carbon cycle. In grasslands, saprotrophic (decomposer) fungi are major decomposers of such organic material. The aim of this study was to characterise lignin degradation, particularly with respect to lignin oxidation typical of white-rot basidiomycete fungi. Lignin breakdown products, analysed by gas chromatography–mass spectrometry (GC–MS) with TMAH thermochemolysis, in initial wheat (Triticum aestivum var. Swatham) straw samples were compared with those in samples which had been buried as a “model” resource for 46 months in a sand-dune grassland at Ainsdale National Nature Reserve, Lancashire, UK.Our results showed that lignin oxidation occurred in the straw over the 46 month period, as there were general increases in the [Ac/Al]S and [Ac/Al]G ratios and a clear decrease in the [S/G] ratio. These data provide tentative support for the theory that white-rot basidiomycete fungi are involved in the degradation of lignin in grasslands. 相似文献
94.
95.
Syarifah Aisyafaznim Sayed Abdul Rahman Zulqarnain Mohamed Rofina Yasmin Othman Rony Swennen Bart Panis Dirk De Waele Serge Remy Sebastien Christian Carpentier 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(3):343-351
The polyphagous obligate parasites Meloidogyne spp. devastate a wide range of crop plants including bananas and plantains. Their infestations impact agriculture worldwide. Therefore,
an effective combating regime against this nematode species and an in-depth understanding of plant-nematode interaction are
essential. Early detection of infection by visual inspection is not possible. This hampers early control strategy efforts
and makes in-depth research of the early infection and plant defence unfeasible. A simple and robust in planta PCR-based nematode detection method is described here as the first crucial step. This PCR-based detection assay exploits
the existence of the Internal Transcribed Spacer 1 (ITS 1) region of the ribosomal DNA (rDNA) gene family in the nematodes
for early detection of nematode penetration into the roots. The results demonstrate that this detection assay is suitable
to serve as a molecular screening tool for plant root diagnostic purposes. 相似文献
96.
Terzano R Al Chami Z Vekemans B Janssens K Miano T Ruggiero P 《Journal of agricultural and food chemistry》2008,56(9):3222-3231
Zinc distribution and speciation within different organs (root, petiole, and leaf) of the edible plant Eruca vesicaria L. Cavalieri were determined using synchrotron microbeam X-ray techniques (XRF microtomography and mu-XANES) for plants grown in polluted soil with or without compost amendment. Data on soil derived from different extraction procedures and using mu-XANES analyses on rhizospheric soil indicated that compost amendment did not significantly influence the Zn speciation and availability in soil. However, major differences were observed within the plants. Plants grown in the presence of compost were able to partly block zinc immediately outside the root endodermis in the form of zinc-phytate, while a smaller Zn fraction was allowed to xylem transport as zinc-citrate. In the leaves, zinc was largely excluded from leaf cells, and about approximately 50% was in the form of phosphate precipitates, and the other 50% was complexed by cysteine and histidine residues. The reported data provide new information concerning the mechanisms of zinc tolerance in E. vesicaria L. Cavalieri, a very common edible plant in Mediterranean regions, and on the role of compost in influencing the molecular strategies involved in zinc uptake and detoxification. 相似文献
97.
Bartłomiej Świątek Marcin Chodak Marcin Pietrzykowski 《Communications in Soil Science and Plant Analysis》2019,50(4):474-481
Fine roots play an important role in organic matter accumulation in reclaimed mine soils. However, estimation of the increment of fine root biomass is difficult and none of the existing methods is universal. The paper examined two methods for measurement of fine roots biomass increment (FRBI): i) with using the root-ingrowth core method (RIC) and ii) the monolith sampling method (MSC). The study was conducted under alder plantings (Alnus incana, A. glutinosa and A. viridis) introduced on technosols at a combustion waste disposal site and a former open-cast sand mine. The FRBI determined using MSC method was significantly lower (33–481 g m?2 yr?1) and less variable than the FRBI measured with RIC (85–2317 g m?2 yr?1). However, the results obtained with both methods were correlated (r = 0.70, P = 0,05). Consequently, MSC is better to qualitatively compare the habitats of tree species in terms of their ability to produce fine roots. However, in the initial soils where plants very often produce more fine roots, RIC seems to be more suitable. This method shows the actual ability of trees to produce roots in order to satisfy their life needs when acquiring a new habitat on reclaimed soils. Such information is particularly important in oligotrophic soils where nutrient deficiency may be balanced only by the efficient circulation and decomposition of organic matter (SOM) including the fine roots that die off after each growing season. 相似文献
98.
Els Bobelyn Anca-Sabina Serban Mihai Nicu Jeroen Lammertyn Bart M. Nicolai Wouter Saeys 《Postharvest Biology and Technology》2010,55(3):133-143
The effect of cultivar, season, shelf-life and origin on the accuracy of near infrared (NIR) calibration models for the soluble solids content (SSC) and firmness of apple was studied based on a large spectral data set based on approximately 6000 apple fruit from different cultivars, origins, shelf-life exposure time and seasons. To interpret the variance in the spectra with respect to biological variability, functional analysis of variance (FANOVA) was used. From the FANOVA analysis it was concluded that the effects of cultivar, origin and shelf-life exposure time on the NIR spectra were all significant. The largest differences in the spectra were found around the water absorption peaks (970, 1170 and 1450 nm). External validations using independent data sets showed that the accuracy of the models increased considerably when more variability was included in the calibration data set. In general the RMSEP for predictions of the SSC were in the range 0.6–0.8 °Brix, while for Magness Taylor firmness it was 5.9–8.8 N, depending on the cultivar. It was shown that atypical data can lead to large validation errors. It is, therefore, important to collect a calibration data set which is sufficiently representative for future samples to be analyzed with the developed calibration models and to develop simple procedures for model adaptation during practical use. 相似文献
99.
Sultanul Arafin Shemeen Ahmad Amrit N Bart Yang Yi James E Rakocy James S Diana 《Aquaculture Research》2010,41(6):904-912
This is the first controlled experiment to quantify the effect of introduced tilapia on indigenous species. This experiment was conducted in small earthen ponds (100 m2) to assess the impact of mixed‐sex or all‐male Nile tilapia (Oreochromis niloticus) on small indigenous species (SIS) commonly found in south Asia, mola (Amblypharyngodon mola), chela (Chela cachius) and punti (Puntius sophore). Ponds were fertilized, then stocked with 0.56 fish m?2 of water surface area in the mixed‐sex and all‐male tilapia treatments and 0.42 fish m?2 in the treatment without tilapia. No additional nutritional inputs were applied after stocking. Treatments were: mixed‐sex tilapia with SIS, mono‐sex male tilapia with SIS and SIS without tilapia (control). All treatments were stocked with 14 fish per species. All species reproduced during the 21‐month culture duration. The number of recruits varied by species, Tilapia reproduced in greater numbers than SIS. Tilapia numbers at harvest were the highest (451 ± 25/100 m2) in the mixed‐sex treatment compared with mola (221 ± 22/100 m2), chela (94 ± 8/100 m2) and punti (100 ± 7/100 m2). The number of mola was higher (399 ± 33/100 m2) in the all‐male tilapia treatment. There was reduction in the number of mola and chela in the treatment containing mixed‐sex tilapia. Gut content analysis combined with water sampling revealed that all fish species fed selectively. Significant interspecies dietary overlap was found between Nile tilapia and SIS and among SIS. Thus, there is potential for tilapia to compete with indigenous fish species when space and other resources are limiting, but a longer duration study with varying level of management is needed to determine how successfully tilapia competes with locally adapted SIS. 相似文献
100.
Katelijn H. Lievens Ronan van Rijsbergen Frederik R. Leyns Bart J. Lambert Paul Terming Jean Swings Henk J.-P. Joos 《Pest management science》1989,27(2):141-154
A search for micro-organisms associated in high numbers with roots or leaves of corn, grapevine, chicory, soybean, sunflower, barley and sugarbeet yielded a collection of over 10 000 bacterial strains. Within this collection, antifungal strains have been selected, using direct or indirect in-vitro assays against one target fungus per crop. The target fungi were selected based on their agronomic relevance as pests. Isolates with antifungal activity were tested for their spectrum of activity against a set of phytopathogenic fungi. In 15 bacterial strains with broad-spectrum activity, belonging to the species Erwinia herbicola. Serratia plymuthica, Pseudomonas fluorescens, P. aureofaciens, P. cepacia and Bacillus subtilis, the active compounds have been identified. Bacterial strains belonging to the same taxon, but isolated from different ecological niches and/or different places in Europe, produce identical compounds. In two bacterial taxa (Erwinia and Serratia) this was reflected in a genetic conservation of the regions coding for antifungal activity. In both cases, the biosynthetic pathways proved to be genetically complex. All of the compounds identified in this study have been described previously in bacterial strains isolated from analogous or completely different ecosystems. 相似文献