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Banaras Hindu University (2018)

Impact of rainfall variability on ecosystem processes in invaded and uninvaded grassland

Afreen,Talat

Titre : Impact of rainfall variability on ecosystem processes in invaded and uninvaded grassland

Auteur : Afreen,Talat

Université de soutenance : Banaras Hindu University

Grade : Doctor of Philosophy (PhD) in Botany 2018

Préface partielle
Tropical soils are nutrient limited and are markedly influenced by seasonality. The seasonal precipitation affects soil wet-dry cycle and has significant consequences for ecosystem functioning and processes. It has been predicted that in the tropical countries, a substantial change will occur in the annual mean temperature and precipitation regimes in the future. However, we have little knowledge as to how the soil properties and processes, will change with the change in the climatic conditions in tropics ? In this study, we have tried to collate studies related to the effect of changing climatic condition (temperature and precipitation) on the soil in tropics. The change in precipitation, than temperature, has more impact on the ecosystem processes in the tropics. Within the tropics the moist and dry ecosystems respond differently to the change in precipitation. Perhaps experimental studies using rain-out shelters may provide more precise information on the effect of changing pattern of precipitation and drought on the health and vigour of tropical soils. Changing climatic condition may also support the invasive species to get established in the area, further disturbing the equilibrium of an ecosystem. To fill kowledge gap, a study was designed with the objective to assess the impact of the change in the precipitation quantity on the soil properties and processes in a constructed grassland with and without an invasive plant (Hyptis suaveolens). Three rainout shelters each with respective rain doses of 800mm (20 % below average), 1100mm (average) and 1600mm (60% above average) and one unsheltered control plot (C) receiving ambient precipitation were established in the year 2014. All precipitation treatment plots were further divided into nine subplots of 1 x 1m and randomly assigned to three replicates each of (i) bare plots with no vegetation (B), (ii) uninvaded indigenous grassland plots (NIG) and (iii) invaded grassland plots with H. suaveolens (IG). After one year of the establishment of the plots seasonal sampling for the estimation of inorganic - N (NO3 - N + NH4 - N), N - mineralization rate, MBC, MBN, soil pH, soil CO2 flux, soil temperature and soil moisture were performed in 2015 - 2016. Monthly sampling of soil CO2 flux, soil temperature and soil moisture was also performed in 2016. Above ground net primary productivity (ANPP) of grassland and biomass of H. suaveolens were estimated in September in NIG and IG plots respectively. SOC, TN, BD and soil texture analyses were also performed.

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