Transient responses to increasing CO2 and climate change in an unfertilized grass–clover sward

Abstract

Mechanisms controlling transient responses to elevated CO 2 concentration and climate change in an unfertilized grassland on the Swiss Plateau were examined in light of simulations with PROGRASS, a process-based model of grass-clover interactions. Daily weather for a series of transient climate scenarios spanning the 21st century were developed for the study site with the help of the LARS-WG weather generator. Changes in the length of dry and wet spells, temperature, precipitation and solar radiation defining the scenarios were obtained from regional climate simulations carried out in the framework of the PRUDENCE project. Compared to 1961-1990, the latter indicated that for 2071-2100 there would be a noticeable increase in temperature (roughly 3°C in winter and 5°C in summer), a significant drop in summer precipitation (of the order of -30%) and a nearly 2-fold increase in the length of dry spells. Assuming that clover is less drought-tolerant than grass, we examined whether clover abundance would decrease as a consequence of increasing heat and water stress, or be promoted on account of CO 2 stimulation. Results indicated that: (1) at our site, climate change alone did not curtail biological N 2 fixation to the point as to alter the composition of the sward but nevertheless entailed a decrease in grassland productivity; (2) increasing CO 2 clearly promoted clover growth (via feedbacks on nitrogen acquisition) and grassland productivity; and (3) even with CO 2 stimulation, the additional N input from symbiotic N 2 fixation was not sufficient to substantially improve the mineral N status of the system and promote grass competitiveness.

Differential long-term effects of climate change and management on stocks and distribution of soil organic carbon in productive grasslands

“…Corresponding changes in monthly precipitation amounts, average length of wet and dry spells, minimum and maximum temperature, temperature standard deviation, and solar radiation nominally valid for the end of the 21st century already given in Lazzarotto et al (2010) are reproduced here in Table 3 for the sake of clarity.…”

“…were adjusted using the anomalies specified in Table 3 (for details see Semenov, 2007). These adjustments were assumed to be valid in 2100; linear interpolation in time was internally applied to infer a transient evolution of the monthly climate (Lazzarotto et al, 2010). Ultimately, 110 years of synthetic weather data were generated for each scenario.…”

Nitrogen cycle and ecosystem services in the Brazilian La Plata Basin: anthropogenic influence and climate change

“…Climate change alone did not restrain biological nitrogen fixation, however this additional input from symbiotic BNF was not enough to improve the mineral nitrogen status of the system. Unfortunately, such a regional study is not applicable for the BLPB since there are different environmental circumstances affecting the basin and moreover, Lazzarotto et al (2010) state that changes in plant, soil microbial biomass activity and soil organisms could significantly alter the ecosystem responses to the effects of climate change.…”

“…However Lazzarotto et al (2010) developed climate scenarios projecting rising temperatures, high CO 2 concentration in the atmosphere and extended drought periods during late spring, summer and early autumn in an unfertilised grassland (grass and clover) sward on the Swiss Plateau. They observed an overall positive response of BNF to high CO 2 levels.…”

Risk management strategies to cope with climate change in grassland production: an illustrative case study for the Swiss plateau

“…To this end, we use the process-based grassland model PRO-GRASS (Lazzarotto et al 2009(Lazzarotto et al , 2010 which is combined with an economic valuation approach that accounts for mean profitability and production risks of grassland production. Our analysis also accounts for the role of direct payments and cross-compliance requirements for production decisions.…”