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Long-term vegetation monitoring, an update.

Long-term vegetation monitoring, an update. Pierre Hiernaux, Eric Mougin, Josiane Seghieri, François Lavenu, Nogmana Soumaguel, Lassine Diarra. Post-drought dynamics on sandy and clayed soils. An asset to study long term vegetation dynamics in the sahel.

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Long-term vegetation monitoring, an update.

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  1. Long-term vegetation monitoring, an update. Pierre Hiernaux, Eric Mougin, Josiane Seghieri, François Lavenu, Nogmana Soumaguel, Lassine Diarra

  2. Post-drought dynamics on sandy and clayed soils

  3. An asset to study long term vegetation dynamics in the sahel • Asset:12 years of vegetation monitoring over 24 rangeland sites sampled in a South_North transect across the Gourma from 1984 to 1995. • The monitoring developed to assess the seasonal and interannual changes in rangeland ressource, on sites sampled to be representative of the range climates, soils and intensity of grazing pressure in the Gourma. • Measured initiated in 1984, matching with the peak of the worse drought that stroke the Sahel, and kept active till 1993 with a few measures in 1994 and 1995. Then, observations resumed by AMMA in 1998 and sites are monitored till now. • From the onset, the sampling methods on the field were designed to match with a remote sensing approach (NOAA-AVHRR in collaboration with NASA, Agrhymet, Institut de Geographie, CESBIO…). The minimum size of the field sites are 1x1km, when possible located within a larger area with similar ecology. Landscape pattern and vegetation heterogeneity considered through enbedded stratified sampling, and distinct methods for the annual herbaceous community, and woody plants and in a few cases perennial herbaceous.

  4. Vegetation monitoring in 2005 • Data set organisation: data entry, checking, standardisation, systematic statistical analysis • 2006 plans

  5. Vegetation patterns: the facies, the stratas

  6. Observations, measures and indicators on annual herbaceous mean, variance by strata weighted mean, random resampled mean by facies, site Field data Observed/measured on 1x1 m plots Visual estimate of herb cover (%) (green/dead, standing/litter, grass/dicots) cover, mass means and variances cover, mass weighted means and variances Desctuctive measure of herb mass (g/m²) (green/dead, standing/litter, grass/dicots) List of species with visual estimate of cover (%) Species weighted contribution to cover Observed/measured on 0.2x0.2 m sub-plots Direct measure of leaf area (cm²) Indirect with hemispherical photo Leaf area, root mass means and variances LAI, root mass weighted means and variances Root masses by layers of 10 cm (g/m²) Species weighted contribution to seed stock Soil seed stock by 2cm layers extracted and counted, in and ex-situ germination

  7. Calendar of measures on the herbaceous layer in Gourma sites in 2005-06

  8. Weighted means of standing herbaceous cover (%) dry mass –kg/ha) and plant density (#/m²),site 17 in 2005

  9. Species contribution to cover at site 17 the 26/06/05 and during the 2005 rainy season

  10. Contribution of taxonomic or functionnal species groups to herbaceous vegetation cover in the Gourma sites in 2005

  11. Calendar of vegetation and soil observations in the IER sites in Bamba district.

  12. Comparing cover and masses of annuals, perennial grasses and woody plants foliage in the Haoussa sites

  13. Observations, measures and indicators on perennial and woody plants density and Crown cover assessment Field data weighted mean, of foliage and wood masses using allometry relations pre-established for each species Observed/measured populations Record of individuals in circular plots (per category or per species) density mean and variance by category Record the four closest individuals and measure distance from random points Record individuals which crown intercept the 1000m site axis, measure interception crown cover estimate Observed/measured on individuals Measure crown heighth, length and width (m) crown cover mean and variance by category Foliage, wood, masses weighted means and variances Measure basal circonference of stems or basal crown (cm) Species weighted contribution to cover, masses.. Record species name of all individuals

  14. Sampling woody plant populations (trees and shrubs) in circular plots, which area is fitted to the population density Linear transect B A Large Circular Plot used to record low density Tree: ~ 10/ha Small circular Plot used to record Densely populated shrubs: ~100/ha

  15. Assessing plant population densities and structure by measuring the distance of closest plant to random points

  16. Root system Acacia raddiana, Agoufou (site 17), 2005 Source:Josiane Seghieri

  17. Vegetation monitoring in 2005 • Data set organisation: data entry, checking, standardisation, systematic statistical analysis • Upscaling: mapping vegetation, soil, water balance and landuse • 2006 plans

  18. Flow chart of the data files and program codes for the statistical analysis of the data on herbaceous layers Stratification Mass, cover… Species composition stratosXX mesvegXX compflorXX Row field Data files stratosXX msvegXX ctspXX Standardized data files biomassXX spcompXX SAS code files herb_str_XX herb_fac_XX Herb_sit_XX resucla_XX Standardized statistics and indicator files alpltXX alfacXX alsitXX Herbfac Herbsit Ctsp Resucla Interannual data base

  19. Weighted means of standing herbaceous at Agoufou (site 17) from 1990 to 2005 No observations

  20. Flow chart of the data files and program codes for the statistical analysis of the data on woody populations Circular plots Distance Crown linear intercept circgoXX pcqgoXX intlingoXX Row field Data files circXX pcqXX intlinXX Standardized data files intlinXX circXX pcqXX SAS code files circdnXX circmfXX circboiXX pcqdnXX pcqmfXX pcqboiXX linrcXX Standardized statistics and indicator files linrc Interannual data base Circdn/mf/boi Pcqdn/mf/boi

  21. Changes in woody plants canopy cover and species composition from 1988 to 2005, sites 14 and 21

  22. Seasonal and internnual changes in leaf mass, Acacia senegal, 1984-92

  23. Vegetation monitoring in 2005 • Data set organisation: data entry, checking, standardisation, systematic statistical analysis • Upscaling: mapping vegetation, soil, water balance and landuse • 2006 plans

  24. Monitoring of herbaceous annuals Frequency and type of measures will be adapted to season and site priority: • Five ranks in priority: • Agoufou (17) • Other flux station sites (21, 40, A3) • Other super-site sites (18, 19, 20, 22, 31) • Other Gourma sites (1,2,4,5,6,8,9,10,12,14,16,25,28,30,32,37,38) • Other Bamba sites (A1, A2, B5, B6, B8, B13, R3, R5, R6, R7, R8, R9, R10, R11) • Two seasons: • Wet season (from June to October): every 10d, 15d, month • Dry season (from November to May): every 2 months (11, 01, 03, 05) • Nature of observation or measure: • Stratification, cover and mass • species composition (once at the end of the wet season except in 17 ? • Leaf area ? • Root mass ? • Germination-soil seed stock ?

  25. Monitoring perennial grasses and woody plants Frequency of observations and measures depends on the type of observation and the component: • Population studies (CIRC or PCQ): • Woody plants: every 5 years thus next in 2010 • Perennial plants (sites 32 and twelve of the Bamba sites): every year ? • Quantitative phenololy (standard branchlets; sampled tussocks): • Wet season (from June to October): every month • Dry season (from November to May): every two months (11/01/03/05) • List of species populations and sites to monitor for leaf/flower/frut pheno • List of species populations and sites to monitor LAI • List of species populations and sites to monitor root masses

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