Floristic composition of a Swedish semi‐natural grassland during six years of elevated atmospheric CO₂

Abstract

Abstract. A semi‐natural grassland in Sweden was exposed to an elevated CO2 concentration during a six‐year open‐top chamber experiment. Vegetation composition was assessed twice a year using the point‐intercept method. The field had been grazed previously, but when the experiment started this was replaced with a cutting regime with one cut (down to ground level) each year in early August. From the third to the sixth year of the study the harvested material was divided into legumes, non‐leguminous forbs and grasses, dried and weighed. Elevated CO2 had an effect on species composition (as analysed by Principal Component Analysis) that increased over time. It also tended to increase diversity (Shannon index) in summer, but reduce it in spring. However, the effects of the weather and/or time on species composition and diversity were much more prominent than CO2 effects. Since the weather was largely directional over time (from dry to wet), with the exception of the fifth year, it was difficult to distinguish between weather effects and changes caused by a changed management regime. In all treatments, grasses increased over time in both mass and point‐intercept measurements, whereas non‐leguminous forbs decreased in mass, but not in point‐intercept measurements. Legumes increased in the point‐intercept measurements, but not in biomass, at elevated CO2, but not in the other treatments. Overall, we found that elevated CO2 affected species composition; however, it was only one of many factors and a rather weak one.

Response of an understory plant community to elevated [CO2] depends on differential responses of dominant invasive species and is mediated by soil water availability

“…During the drier year (2002) differences in composition were not as pronounced. Variation in compositional shifts under elevated [CO 2 ] caused by differential responses of species between years is not uncommon in community-level CO 2 -enrichment investigations (Vasseur & Potvin, 1998;Norton et al, 1999;Niklaus et al, 2001;Marissink & Hansson, 2002).…”

Climate warming and land‐use changes drive broad‐scale floristic changes in Southern Sweden

“…In studies focused on forest and grassland ecosystems from the same region and period, nitrogen deposition, sometimes in combination with soil acidification, has similarly been identified as the main driver of changes in the flora (Diekmann, Brunet, R€ uhling, & Falkengren-Grerup, 1999;Falkengren-Grerup, 1986, 1990Linusson et al, 1998). Similar, although less strong effects of eutrophication during the 1900s have been demonstrated further north in Sweden (Maad et al, 2009), as well as elsewhere in Europe and North America (Bobbink et al, 2010;von Numers & Korvenpaa, 2007;Walker et al, 2009 Furthermore, changes in land-use towards intensified agriculture and forestry have continued (Cousins et al, 2015), and new possible drivers of floristic changes such as increased atmospheric CO 2 levels (Marissink & Hansson, 2002;Sykes, 2007) and drastic declines in pollinating insects (Biesmeijer et al, 2006;Sorg, Schwan, Stenmans, & M€ uller, 2013; but see Carvalheiro et al, 2013) have been identified.…”

“…To summarize, recent and on-going changes in Scania and surrounding regions include (1) increasing forested area and numbers of trees in the landscape (Fredh et al, 2012), (2) decreasing numbers of grazing domestic animals and a smaller proportion of them being kept on low-productive semi-natural grasslands (Swedish Board of Agriculture, 2011), (3) rising temperatures (data from the Swedish Metrological and Hydrological Institute), (4) increasing atmospheric CO 2 levels (Marissink & Hansson, 2002) and (5) declining abundance of pollinating insects (Sorg et al, 2013). With the goal of being able to rank and evaluate the relative importance of these different potential drivers of floristic changes in the region, we present and analyse data from two readily comparable surveys (the Millora project).…”

Predicting adaptive evolution under elevated atmospheric CO2 in the perennial grass Bromus erectus

“…Current projections forecast a doubling or tripling of preindustrial CO 2 concentrations by the end of the 21st century (IPCC, 2001). In the last two decades, an enormous body of research has demonstrated that elevated CO 2 , the primary substrate for photosynthesis, can have profound effects on plant growth and reproduction (Jablonski et al, 2002;Poorter & Navas, 2003), species interactions and community dynamics (Niklaus et al, 2001;Marissink & Hansson, 2002;Polley et al, 2003;Poorter & Navas, 2003), and ecosystem processes (Kö rner, 2000;Niklaus & Kö rner, 2004). Surprisingly little work has been done, however, on the potential consequences of rising CO 2 for plant evolution (see e.g.…”