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Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: patterns, mechanisms, and open questions / Wolfgang W. Weisser in Basic and Applied Ecology, vol 23 (September 2017)
Titre : Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: patterns, mechanisms, and open questions Type de document : Article/Communication Auteurs : Wolfgang W. Weisser, Auteur ; Christiane Roscher, Auteur ; Sebastian Meyer, Auteur ; et al., Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Ecologie
[Termes IGN] azote
[Termes IGN] biomasse
[Termes IGN] carbone
[Termes IGN] écosystème
[Termes IGN] gaz à effet de serre
[Termes IGN] nutriment végétal
[Termes IGN] placette d'échantillonnage
[Termes IGN] potassium
[Termes IGN] puits de carbone
[Termes IGN] richesse floristique
[Termes IGN] sol
[Termes IGN] stabilité
Résumé : (auteur) In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research.
First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity-stability theory.
Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects often occurred mostly in addition to, but not instead of, effects of plant species richness.
Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances.
Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle.
Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity-ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions.
Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments where particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes.
Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services.
A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments.
To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible.
Numéro de notice : A2017-352 Affiliation des auteurs : non IGN Thématique : BIODIVERSITE/FORET Nature : Article DOI : 10.1016/j.baae.2017.06.002 Date de publication en ligne : 26/06/2017 En ligne : https://doi.org/10.1016/j.baae.2017.06.002 Format de la ressource électronique : URL article Permalink :
in Basic and Applied Ecology > vol 23 (September 2017)[article]Spatial variability of soil nutrients and GIS-based nutrient management in Yongji County, China / Qian Zhang in International journal of geographical information science IJGIS, vol 24 n°7-8 (july 2010)
Titre : Spatial variability of soil nutrients and GIS-based nutrient management in Yongji County, China Type de document : Article/Communication Auteurs : Qian Zhang, Auteur ; Z. Yang, Auteur ; Y. Li, Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : pp 965 - 981 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale
[Termes IGN] azote
[Termes IGN] Chansi (Chine)
[Termes IGN] krigeage
[Termes IGN] phosphore
[Termes IGN] potassium
[Termes IGN] sol arable
[Termes IGN] système d'information géographique
[Termes IGN] variabilité
[Termes IGN] variable régionalisée
Résumé : (Auteur) Integrated nutrient management is important for sustainable agricultural production and protecting environment quality and has been widely investigated around the world. In this article the spatial variability of soil nutrients was investigated and a regionalized nutrient management system was developed using geostatistics and geographic information system technologies. A total of 511 GPS-referenced soil samples were taken in Yongji County, Shanxi province, China, and analysed for major soil nutrients: soil total nitrogen (TN), Olsen extractable phosphorus (OLSENP) and extractable potassium (EXTK). Low concentrations of nitrogen (N) and phosphorus (P) were found and they are likely to be the main limiting nutrients for crop growth in this county. Within the county moderate spatial dependence was found for all three soil variables, but at different spatial scales. The spatial distributions of TN, OLSENP and EXTK were estimated by using kriging interpolation. The cropped areas of the county were divided into fertilizer management categories consisting of four classes of TN, three classes of OLSENP and two classes of EXTK. For the targeted crop yields, regionalized fertilization maps of N, P and K in the county were produced using geographic information system. In 3-year field verification trials in two villages the crop yields of the wheat-maize rotation system increased by 10-20%, and farmers' cash income increased by 1550-2610 RMB ha-1 year-1 where regional fertilization recommendations were implemented, in comparison with traditional farmers' practices. The regionalized maps are a practical alternative to site-specific soil nutrient management approaches in areas where it is not practical, because of small farm size or other constraints, to use intensive soil sampling and chemical analyses. Numéro de notice : A2010-315 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article DOI : 10.1080/13658810903257954 En ligne : https://doi.org/10.1080/13658810903257954 Format de la ressource électronique : URL article Permalink :
in International journal of geographical information science IJGIS > vol 24 n°7-8 (july 2010) . - pp 965 - 981[article]
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Code-barres Cote Support Localisation Section Disponibilité 079-2010041 RAB Revue Centre de documentation En réserve L003 Disponible 079-2010042 RAB Revue Centre de documentation En réserve L003 DisponiblePredicting in situ pasture quality in the Kruger National Park, South Africa, using continuum-removed absorption features / Onisimo Mutanga in Remote sensing of environment, vol 89 n° 3 (15/02/2004)
Titre : Predicting in situ pasture quality in the Kruger National Park, South Africa, using continuum-removed absorption features Type de document : Article/Communication Auteurs : Onisimo Mutanga, Auteur ; Andrew K. Skidmore, Auteur ; Herbert H.T. Prins, Auteur Année de publication : 2004 Article en page(s) : pp 393 - 408 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] Afrique du sud (état)
[Termes IGN] azote
[Termes IGN] biochimie
[Termes IGN] carbone
[Termes IGN] forêt tropicale
[Termes IGN] image hyperspectrale
[Termes IGN] parc naturel national
[Termes IGN] paturage
[Termes IGN] phosphore
[Termes IGN] potassium
[Termes IGN] prairie
[Termes IGN] réflectance végétale
[Termes IGN] régression linéaire
[Termes IGN] savane
[Termes IGN] spectroradiomètre
[Termes IGN] zone intertropicale
Résumé : (Auteur) The remote sensing of pasture quality as determined by nitrogen, phosphorous, potassium, calcium and magnesium concentration is critical for a better understanding of wildlife and livestock feeding patterns. Although remote sensing techniques have proved useful for assessing the concentration of foliar biochemicals under controlled laboratory conditions, more investigation is required to assess their capabilities in the field where inconsistent results have been obtained so far. We investigated the possibility of determining the concentration of in situ biochemicals in a savanna rangeland, using the spectral reflectance of five grass species. Canopy spectral measurements were taken in the field using a GER 3700 spectroradiometer. We tested the utility of using four variables derived from continuum-removed absorption features for predicting canopy nitrogen, phosphorous, potassium, calcium and magnesium concentration: (i) continuum-removed derivative reflectance (CRDR), (ii) band depth (BD), (iii) band depth ratio (BDR) and (iv) normalised band depth index (NBDI). Stepwise linear regression was used to select wavelengths from the absorption-feature-based variables. Univariate correlation analysis was also done between the first derivative reflectance and biochemicals. Using a training data set, the variables derived from continuum-removed absorption features could predict biochemicals with R2 values ranging from 0.43 to 0.80. Results were highest using CRDR data, which yielded R2 values of 0.70, 0.80, 0.64, 0.50 and 0.68 with root mean square errors (RMSE) of 0.01, 0.004, 0.03, 0.01 and 0.004 for nitrogen, phosphorous, potassium, calcium and magnesium, respectively. Predicting biochemicals on a test data set, using regression models developed from a training data set. resulted in R2 values ranging from 0. 15 to 0.70. The error of prediction (RSE) in the test data set was 0.08 (+ 10.25% of mean), 0.05 (+ 5.2% of mean), 0.02 (+ 11.11% of mean), 0.05 (+ 11.6% of mean) and 0.03 (+ 15% of mean) for nitrogen, potassium, phosphorous. calcium and magnesium, respectively, using CRDR. When data was partitioned into species groups, the R2 increased significantly to >0.80. With high-quality radiometric and geometric calibration of hyperspectral imagery, the techniques applied in this study (i.e. continuum removal on absorption features) may also be applied on data acquired by airborne and spacebome imaging spectrometers to predict and ultimateIy to map the concentration of macronutrients in tropical rangelands. Numéro de notice : A2004-020 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2003.11.001 En ligne : https://doi.org/10.1016/j.rse.2003.11.001 Format de la ressource électronique : URL article Permalink :
in Remote sensing of environment > vol 89 n° 3 (15/02/2004) . - pp 393 - 408[article]