Water acquisition in spatiotemporal heterogeneous environments

Transcription

1 Water acquisition in spatiotemporal heterogeneous environments Boris Rewald & Sandra Korn Dept. of Plant Ecology

2 Soil-Plant-Atmosphere-Continuum

3 The root system Key component of forest water cycles

4 Key questions Are there species-specific and spatial differences in the hydraulic systems of tree roots? Are there functional adaptations within root systems in spatiotemporal environments?

5 Study site: Lüneburger Heide, NW Germany Tree species: Picea abies (Spruce), Quercus petraea (Sessile Oak), and Fagus sylvatica (Beech). Soil: Spodo-dystric Cambisol; Mean Temp.: 8.0 C; Precip.: 801 mm yr -1

6 Water uptake rate in different soil horizons 4 Organic layer 3 Root water uptake [g h -1 ] Mineral soil Spruce 1 0 S August 1999 Coners, 2001

7 Water uptake rate in different soil horizons 4 Organic layer 3 Beech Root water uptake [g h -1 ] Mineral soil Oak Spruce 1 0 B O S August 1999 Coners, 2001

8 Study site: Hainich National Park, Central Germany Distance: Mühlhausen-Göttingen 52km (North-West) Tree species: Acer pseudoplatanus (Sycamore), Fraxinus excelsior (Ash), Tilia cordata (Lime), Carpinus betulus (Hornbeam), Quercus robur (Pedunculate oak), and Fagus sylvatica (Beech). Soil: Luvisol; Mean Temp.: 7.5 C; Precipitation: 669 mm yr -1

9 Species-specific sap flow rates Sap flow rate per diameter -2-1 [g mm d ] Acer b b b a a a FraxinusTilia Carpinus Quercus Fagus Korn, 2004

10 Variation of sap flow rate within the root system of Beech Organic layer F. Organic sylvatica layer Surface specific flow rate [x10 gm d ] May Jun Jul Aug Sep Oct 2001 Korn, 2004

11 Study site: Ramat Negev Experimental Station, Israel Tree species: Olea europea (Olive), 3 different. Salt-resistent varieties Soil: Loess (Typic Torrifluvent); Temp. Max : 35 C, Temp. Min :5.5 C Precipitation: mm yr -1 (November - April)

12 Three differently salt tolerant Olive varieties and salinity treatments 3 Olive varieties: i) Barnea (very salt tolerant) ii) Arbequina (salt tolerant) iii) Proline (salt sensitive) 3 salinity treatments: i) EC 1.2 ds m -1 (fresh water) ii) EC 4.2 ds m -1 (moderate saline) iii) EC 7.5 ds m -1 (severe salinity)

13 Soil conditions under saline irrigation Oron et al., 1999

14 Influence of variety and salinity on the specific conductivity of Olive coarse roots Rewald, Wiesman & Ephrath, under review

15 Variety and salt stress induced distribution pattern of specific conductivities within the Olive root systems Rewald, Wiesman & Ephrath, under review

16 Functional specialization: High conductivity fine roots Example: Barnea fine roots, 7.5 ds m µm 500 µm Normal fine root High conductivity fine root Rewald, Wiesman & Ephrath, under review

17 Impact on future research Knowledge of species-specific water uptake rates would allow to improve current water cycle models Knowledge of root systems adaptabilities would allow to enhance current and future water cycle models in heterogeneous or changing environments

18 Many thanks to Heinz Coners, Jhonathan Ephrath, Christoph Leuschner, Moshe Silberbush, Sebastian Weissbein, Zeev Wiesman.

19 Determination of sap flow rate in fine roots Vol. Bodenwassergehalt Wurzelsaftfluss Wurzeloberfläche

20 Hydraulic conductivity measurement Sperry et al pressure gradient tap water, 0.2 µm filtered ΔPressure 6 kpa ΔTime = 300 s length 5 cm 2 root diameter classes: d = mm (fine roots) d = 2-10 mm (coarse roots) Sample size n = 15-35

21 Anatomical analyses Storage in 70% EtOH, embedding in PEG 2000 Preparation of microtomical slices: 7-10 µm, n = 8 Preparation of digital photos ( x) Determination of xylem conduits 1.) 2.) 3.) 4.)