Photosynthesis data and carbon isotope Results graphs and statistical analysis




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Photosynthesis data and carbon isotope - Results graphs and statistical analysis

Here, we are interesting about tree species Psoralea lanceotum (leguminous), Rosa acicularis and Artemisia frigida (sage). These three plants growth in inter-dune and vegetated dune. Only Psoralea lanceotum growths on active dune.

We can notice many difference about DOY 185. During this day, there was a high temperature and VPD is particularly high. Indeed the maximum of leaf temperature and leaf VPD is on DOY 185 for each species.

Comparison of two species




Psoralea lanceotum

Rosa acicularis

Rosa acicularis

A : 157, 185, 208,

230


E : 185

230





Ci/Ca : 157


13C : 185, 208, 230

Artemisia frigida

A : 185


E : 185, 230

A : (157), 208, 230

E :

Ci/Ca : 230


13C : 157, (230)

Ci/Ca : 157, 230

13C : 157, 185, 208

For example (in green, on the table): the mean of the values for DOY 157 of Ci/Ca of Psoralea lanceotum is significant different (p<5%) of the mean of values for DOY 157 of Ci/Ca of Rosa acicularis. Parentheses means values are significant different for p<10%.

Photosynthesis data (A) and carbon isotope (13C) of Rosa acicularis are significant different for almost each date, of photosynthesis data and carbon isotope of Psoralea lanceotum and Artemisia frigida. Indeed photosynthesis values are lower for Rosa acicularis for each date. This species seems to be less photosynthetic active. But its photosynthetic activities increase in July and August whereas data about photosynthetic activity of Psoralea lanceotum and Artemisia frigida are more spread and decrease at the end of July and August.

Moreover carbon isotopes of Rosa acicularis are always constant and higher than carbon isotope of the other species. Rosa acicularis discriminates less 13C than other species studied. Carbon isotope in Psoralea lanceotum (without the first data) and Artemisia frigida increase in July and August.

According to photosynthetic data and carbon isotope Psoralea lanceotum and Artemisia frigida undergo a drought from middle of July, whereas Rosa acicularis don’t seems to be reach by the drought.



Comparison of two places (vegetated dune, inter-dune, and active dune)

Artemisia frigida

Vegetated dune

Interdune

A : (230)

E :

Ci/Ca : (230)

13C :

For Artemisia frigida, measures in vegetated dune and inter-dunes are not significant difference.

Rosa acicularis

Vegetated dune

Interdune

A : 230

E : 230

Ci/Ca : 185, 208

13C :

At the end of the season (DOY 230) there is a significant difference about photosynthesis, and transpiration. Leaf temperature of Rosa acicularis on vegetated dune and inter-dune are also significant different. Leaf interdune is warmer and photosynthesis in higher in inter-dune. So, high temperatures activate photosynthesis even at the end of August.

(We can notice the inverse effect for Artemisia frigida for last measure DOY 230, indeed leaf temperature are significant different - p<10% -, leaves in inter-dune are warmer. But photosynthesis in inter-dune is lower. Maybe at this end of the summer stomata start to close in inter-dune because it’s too warm.)



Psoralea lanceotum

Active dune

Interdune

Interdune

A :

E :




Ci/Ca :

13C :

Vegetated dune

A :

E : 230

A :

E :

Ci/Ca :

13C : (208)

Ci/Ca :

13C : 157, (208)

Measure in active dune and inter-dune are very close, but plants in vegetated dune don’t show a big difference in these measures.

Comparison of two dates

Psoralea lanceotum

157

185

208

185

A :


E :







Ci/Ca : significant

13C : significant

208

A :

E :

A :

E : significant




Ci/Ca : significant

13C : significant

Ci/Ca : significant

13C :

230

A :

E : significant

A :

E : significant

A :

E : significant

Ci/Ca : significant

13C : significant

Ci/Ca : (significant)

13C :

Ci/Ca :

13C :

Means of transpiration of DOY 230 (last measure) shows always a significant difference with all the other date. Transpiration is lower. On the middle of August stomata of Psoralea lanceotum begin to close.

The first mean of carbon isotope is significant difference about all the other measure of carbon isotope. This measure seems very high for vegetated dune, active dune and interdune.



Photosynthetic data never show a significant difference between two dates. These data are very spread above all at the beginning of the summer. The differences between each plant are more important than the difference in one sector or the mean of one date.

Rosa acicularis

157

185

208

185

A : (significant)

E : significant






Ci/Ca : significant

13C : significant

208

A :

E : significant

A : significant

E :




Ci/Ca : significant

13C :

Ci/Ca :

13C : significant

230

A :

E : significant

A : significant

E :

A :

E : (significant)

Ci/Ca : significant

13C :

Ci/Ca :

13C :

Ci/Ca :

13C : (significant)

For DOY 157, transpiration are significant different and higher. At the beginning of the season, there is more water more available and Rosa acicularis open his stomata. From the beginning of July transpiration of Rosa acicularis decrease to be stabilized around 4 mmol.m-2.s-1, there is less water available on the soil, but the stomata doesn’t closed so much as I explain before.

Artemisia frigida

157

185

208

185

A :


E :







Ci/Ca : significant

13C :

208

A :


E :

A :

E :




Ci/Ca : significant

13C : significant

Ci/Ca : (significant)

13C : significant

230

A :

E : significant

A :

E :

A :

E : (significant)

Ci/Ca : significant

13C : significant

Ci/Ca :

13C : significant

Ci/Ca : significant

13C : significant

13C are not significant difference between the two first measures (DOY 157 and DOY 185), but always significant difference for all the other comparison. Indeed 13C increase on July. RubisCo “choose” less isotope of carbon at the end of the summer, stomata are more closed as a period of drought. Artemisia frigida suffered of drought from the beginning of July. However, photosynthesis data are very spread on June and on the beginning of July and stay constant during all the summer, even if 13C (and a little bit transpiration that decrease all the time) shows a drought, Artemisia frigida continue photosynthetic activity.

For the tree species, Ci/Ca in DOY 157 are always significant different of the other dates. At the beginning of the season Ci/Ca is closer than 1. Stomata don’t show a big resistance, like if the stomata are more open and RubisCo are slower to transform all CO2 in organic carbon on the middle of June, but after we can imagine stomata start to close in function of temperature and VPD.



General linear model- repeated measures




A

E

Ci/Ca

13C

date




×

×

×

date*plant

(species)










×

date*position

(active dune, vegetated dune, inter-dune)













date*plant*position

(×)










Differences about photosynthetic activity don’t show any difference about the DOY. For Psoralea lanceotum and Artemisia frigida these measures are much spread and depend on each plant. We cannot notice about Rosa acicularis a real increasing of photosynthetic activity.

However, measure of transpiration, Ci/Ca and carbon isotope show a significant difference for each date. Measures of transpiration decrease to reach its minimum on the middle of August. Ci/Ca don’t shows the same evolution for each plant, even if we can notice a lower data for DOY 185 (at this DOY leaf VPD is really high).

Measures between plants show a real difference only for carbon isotope. Indeed carbon isotope in Artemisia frigida increases regularly, whereas carbon isotope in Rosa acicularis is more or less constant and the first data of carbon isotope of Psoralea lanceotum is really high.

Data about photosynthetic activity, transpiration and Ci/Ca are significant comparable for this three species.

Areas (vegetated dune, inter-dune, active dune) never change the photosynthetic way (photosynthesis, transpiration, Ci/Ca, or carbon isotope) of these tree species. We know too soil nitrogen (table below) is not limiting, and its repartition don’t depend of the area. (In each area, soil nitrogen is really variable even if in inter-dune the mean is really higher.)

August (NO3)

soil nitrogen



means

standard error

range

active dune

14.0

2.6

5-32

inter-dune

76.2

31.9

14-275

vegetated dune

28.2

6.4

8-57

Punctually, there is a significant difference between two areas (vegetated dune and inter-dune or active dune and vegetated dune for Psoralea lanceotum) but this difference seems to be more due to difference of leaf temperatures or leaf VPD than the area, the environment or the soil.

Comparison of two species about oxygen isotope and hydrogen isotope




Psoralea lanceotum

Rosa acicularis

Rosa acicularis

2H :

18O :




Artemisia frigida

2H : 230

18O : 230

2H :

18O :

There are two significant comparisons, between Psoralea lanceotum and Artemisia frigida. Indeed values of Psoralea lanceotum are lower than value of Rosa acicularis and Artmisia frigida. Differences aren’t always significant because data are very spread for Rosa acicularis and Artemisia frigida. For Rosa acicularis, and Artemisia frigida I can’t conclude anything about the deep of the roots (value are so spread) but maybe these values shows that these species can have short root and really deep root. Values of Psoralea lanceotum are not spread (around -100 for 2H, and around 0 for 18O), maybe this species has deep root regardless soil conditions, water conditions.



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