Factors influencing plant growth under elevated atmospheric CO2 concentration

Numerous other factors, such as macro- and microelement contents in soil, water accessibility and temperature can influence the plant growth under the elevated CO2 concentration in the atmosphere. Improper value of only one of them can limit the biomass increase even if the CO2 concentration will be still rising.

This phenomenon is illustrated by the data presented in Table 3, which show the influence of the soil nitrogen concentration on the biomass growth examined under elevated CO2 concentration. The data show that a lower increase in shoot biomass due to an increase of the CO2 concentration was observed in the case of the soils with low nitrogen level compared to the soil with ample content of this macroelement. Sometimes, higher CO2 concentration did not compensate the N deficiency, and then the plant biomass was lower as compared to that obtained on the soil with ample nitrogen level. Is such case, the nitrogen is the limiting factor.

It is worth considering here the impact of others factors on the plant biomass productivity (and at the same time on the biomass primary productivity - Table 4) the changes of which arc also induced by increasing the CO2 levels in the atmosphere. The carbon dioxide emission contributes to climate warming, increasing the air temperature. Experimental data and model studies show that the stimulation of plant productivity by higher C02 level increase with rising temperatures, although this regularity applied to the plants growing in non-stress temperature ranges (Allen (1991; Luo et al. 2008; Bernacchi ct al. 2006). Therefore, it cannot be ruled out that if the critical temperature values arc exceeded for some physiological phenomena in plants, productivity will be reduced despite the increased ССЬ concentrations (Leakey ct al. 2012).

A temperature increase caused by elevated atmospheric ССЬ can reduce the moisture availability for plants, intensifying the evaporation process. On the other hand, at increased C02plants exhibit lower water requirements (by reducing transpiration), which improves their water use efficiency (Parry 1990). According to Leakey at al. (2012) reduced water use at increased CO2 levels enhances the plant productivity when they ameliorate water stress under the drought conditions - unfortunately at some level of drought stress, the biomass production can be limited to such extent that the impact of higher CO2 concentration will not

Table 3. The effect of increased CCL level on shoot biomass of plants at different nitrogen level under FACE conditions (Kimball et al. 2002).

Plant

C02 level" [jimol mol'1]

Increase due to growth of C02 concentration compared to the ambient C02 concentration [%]

References

Ample N

Low N

Ryegrass (Lolium perenne L.)

600

5.8

3.7

Hebeisen et al. 1997

Ryegrass (Lolium perenne L.)

600

8.0

-8.6

Hebeisen et al. 1997

Ryegrass (Lolium perenne L.)

600

10.9

1.6

Hebeisen et al. 1997

Ryegrass (Lolium perenne L.)

600

18.6

-6.2

Daepp et al. 2000

Ryegrass (Lolium perenne L.)

600

10.5

-0.3

Daepp et al. 2000

Rice (Oryza saliva L.)

589

10.8

8.1

Kim el al. 2001

Wheat (Triticum aestivum L.)

+200

11.7

2.8

Kimball el al. 2002

Ryegrass (Lolium perenne L.)

600

20.1

6.9

Daepp et al. 2000

a Explanation is the same as under Table 1

Table 4. The estimated effect of increased C02 level (~550 ppm) on net primary productivity (or seed yield) and photosynthelic ССЬ uptake of ecosystems (Leakey et al. 2012).

Biome

Primary functional groups

Change in:

net primary productivity/seed yield [%]

photosynthetic CO-. uptake) [%]

Temperate

forest

C3 trees

23±2a)

46±4c)

Temperate

grassland

Community

C3 grasses C4 grasses

13±4b)

  • 37±7c)
  • -2±9c)

Temperate

cropland

C3 crops C4 crops

  • 17±6b)
  • 6±9b)

13±5e) 11 ±6c)

  • a) Estimate based on four FACE experiments from Norby ct al. (2005)
  • b) Estimate based on updated meta-analysis of FACE data following methods of Ainsworth and Long (2005)
  • c) Estimates from Ainsworth and Rogers (2007)

compensate for the water deficiency. To summarize, it should be emphasized that the ССЬ fertilization effect in natural ecosystems is expected (Table 4) but its magnitude and duration is dependent on environmental factors, among which soil moisture, nutrients availability and temperature seem to be the most important (Leakey et al. 2012; Sneed 2018). Since the mentioned factors vary regionally, the response of biomes productivity to the elevated C02 is expected to be diverse (Rosenthal & Tomeo 2013). Accurately determining the impact of elevated carbon dioxide levels on the productivity of natural ecosystems requires further research, in particular regarding rainforests and tropical savannas that have a large share in the global carbon cycle (Leakey et al. 2012). Modelling studies indicate that tropical forest will respond more significantly to the elevated C02 concentration than temperate and boreal forests (Cernusak et al. 2013).

 
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