Metla/3489/mhei/06.2012
Fig. 4. Mean longevity of short (A) and long (B) roots by treatment as a function of soil depth.
Fig. 2. The standing length (continuous line) and production volume (dashed) of live roots by treatment as a function of time for short (A) and long (B) roots.
Effects of soil frost on the growth and longevity of fine roots in Norway spruce
Tapani Repo
1, Seija Sirkiä
1, Jaakko Heinonen
1, Aurore Lavigné
2, Marja Roitto
1, Eija Koljonen
1, Sirkka Sutinen
1and Leena Finér
11Finnish Forest Research Institute, P.O. Box 68, FI- 80101 Joensuu, Finland, forename.lastname@metla.fi
2AgroParisTech/INRA, UMR 518 AgroParisTech/
INRA MIA, Paris, France
Results
•
In 2007 the standing length of short and long roots was less in FROST than in CTRL and OPEN, but in 2008 and 2009 it was more (Fig. 2).•
In 2007 the production of short and long roots (judged by elongation) was delayed, and in 2008 and 2009 it was higher in FROST than in CTRL and OPEN (Fig. 2).•
The survival function of roots in OPEN differed from that in CTRL and FROST (Fig. 3).•
The lifetime of the roots was longer for the long ones than the short ones and longer in OPEN than in CTRL and FROST (Fig. 3 and Fig. 4).•
Root longevity increased with soil depth (Fig. 4).Material and methods Conclusions
•
The standing length and production volume of roots were negatively affected by delayed soil thawing, but the roots were able to recover from these negative effects.•
Deep soil frost with a thin snow cover increased root longevity.•
Single winters with a thin snow cover may not be harmful for Norway spruce.Fig. 1. Air and soil temperature (A) and soil volumetric moisture content (B) (at the depth of 5 cm). In A, the snow cover in 2005/06 and 2006/07 is given for CTRL only, for the snow was removed in OPEN and FROST. The insulation periods in FROST are indicated with vertical bars in A.
Acknowledgements
The study was funded by the Finnish Forest Research Institute (Project 3489) and the Academy of Finland (Project 127924).
Introduction
The occurrence of soil frost, common in the northern hemisphere, depends on the quality of the snow cover, which is predicted to change in the future. We studied how soil freezing and its prolonged thawing affect the biomass, growth, and longevity of fine roots in 50-year-old Norway spruce (Picea abies L. Karst).
Temperature, Co
-30 -20 -10 0 10 20
30 Snow depth, cm
0 35 70
Vol. water content, %
0 10 20 30 40 50
Air
FROST
CTRL OPEN
2006 2007
A
B
2009 2008 Snow FROSTCTRL OPEN
2006 2007 2008 2009
Jan Apr Jul Oct
Jan Apr Jul Oct
Jan Apr Jul Oct Jan Apr Jul Oct
Jan Apr Jul Oct
Jan Apr Jul Oct
Jan Apr Jul Oct Jan Apr Jul Oct
•
The stand was in the boreal coniferous zone inEastern Finland (62°36’N, 29°43’E, 84 m a.s.l.).•
The treatments with three replicate plots in two winters 2005/06 and 2006/07:•
Natural snow cover (CTRL)•
Snow removal during winter (OPEN)•
As in OPEN, but the soil surface was insulated in late winter (FROST).•
The air and soil temperature and the soil moisture were monitored (Fig. 1).•
In autumn 2005, 27 minirhizotron tubes (3 tubes/plot) were installed at an angle of ca. 30°.
•
Imaging (Bartz BTC-100X) and image analysis by RootView at one-month intervals in the four growing seasons between 2006 and 2009.•
The standing length and production volume of short and long roots (divided by the total imaging area) and their mean longevity were calculated.•
On interval-censored data, the survival function was estimated by means of nonparametric maximum likelihood estimation (NPMLE).0.0 0.1 0.2 0.3 0.4
8/5/06 3/10/06 26/4/07 24/9/07 30/4/08 15/10/08 5/5/09 12/10/09 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
8/5/06 3/10/06 26/4/07 24/9/07 30/4/08 15/10/08 5/5/09 12/10/09
Short root Long root
Time Time
A B
Standing length and production, mm cm-2
CTRLFROST OPEN
300 400 500 600
Mean longevity, days
200 300 400 500
Soil layer
CTRL FROST OPEN
Long root Short root
Soil layer
A B
0–5 cm 5–15 cm 15–25 cm 0–5 cm 5–15 cm 15–25 cm
A 0.0 0.2 0.4 0.6 0.8 1.0
0 200 400 600 800 1000 0 200 400 600 800 1000
Short root Long root
Survival
Time, days Time, days
CTRL 282 FROST 276 OPEN 305
Longevity days
A B
CTRL 432 FROST 425 OPEN 464
Longevity days
0.0 0.2 0.4 0.6 0.8 1.0
Fig. 3. Survival function and mean root longevity for short (A) and long (B) roots by treatment.
