Studies in tree hydrology: Strategies of water use in co-occurring exotic and indigenous species Munessa Forest

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1 Studies in tree hydrology: Strategies of water use in co-occurring exotic and indigenous species Munessa Forest Masresha Fetene Addis Ababa University Ethiopia

2 Geographic coordinates 3 24` and 14 53` North; 32 42` and 48 12` East Area Total: 1,127,127 km 2 Land: 1,119,683 km 2 Water: 7,444 km 2

3 Elevational differences Lowest point: Danakil, -125 m Highest point: Ras Dejen, 4,533 m

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8 Location Kuke Ecological gradient from semi-arid Zuway-Shalla Basin to subhumid Arsi Highland Geological substrate is homogenous, intermediate volcanic rock

9 The study area Ecological gradient

10 Forest plantations alongside degraded natural forest Exotic tree plantations of - Eucalyptus spp. - Cupressus lusitanica - Pinus patula Turnover time 25 to 35 yrs. Degraded forest Consequences for - sustainability - carbon storage - soil degradation - re-establishment of native species - utilization by people are unknown Photos by Klaus Müller-Hohenstein

11 Project nature Multidisciplinary Forest Ecosystem Study Cooperation among several research groups: Soil scientists, botanists/biogeographers, foresters, ecologists, ecophysiologists, and microbiologists among others

12 Goals Understanding of the functioning of mountain forests Knowledge and integration of ecological key processes - Water fluxes - Nutrient fluxes - Diversity - Regeneration Needs and utilization of forest by local population Interdisciplinary approach is necessary Development of concepts for sustainable forest management

13 Contribution of individual tree species in the water balance of a mixed forest Hydrological and microclimatological processes of tropical montane forests knowledge on the water cycle of tropical forest ecosystems

14 Studies on plantations as foster systems for natural forest regeneration

15 Specific Objectives water-use and pattern of sap-flow dynamics cooccurring indigenous and exotic tree species Seasonal differences in whole tree transpiration among the species Relate soil dryness, root architecture and soil water partitioning among species

16 What are the techniques used to estimate forest transpiration? Porometry Weighing lysimeters Large-tree potometers Ventilated chambers Radiotracers Stable isotopes Energy balance, heat dissipation and heat-pulse techniques

17 Methods The thermal heat dissipation method developed by Granier (1985) was used.

18 Methods Sap flux density (in g m -2 s -1 ) is related to ΔT by: Js =.119U U = (ΔT ΔT)/ΔT, where ΔT is the value of ΔT, when there is no sap flow E = Js x SW cross-section area

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25 3 Podocarpus 5 Daily curves Croton Stem flux density (g m -2 s -1 ) Cupressus Eucalyptus Time of day Time of day

26 S1 Croton 2 Natural Forest Rainy Season Sap flow density [ml cm -2 min -1 ] /4/6 : 12/4/6 : 14/4/6 : 16/4/6 : 18/4/6 : Time Croton 1 Eucalyptus-Croton-Plot Rainy Season sap flow density [ml cm -2 min -1 ] /9/5 : 25/9/5 : 26/9/5 : 27/9/5 : 28/9/5 : 29/9/5 : 3/9/5 : 1/1/5 : time

27 Rainy Season Sap flow den [ml cm -2 min - 1 ] /4/6 : 12/4/6 : 14/4/6 : 16/4/6 : 18/4/6 : Time Dry Season Sap flow density [ml cm -2 min - 1 ] /11/ 5 : 26/11/ 5 : 27/11/ 5 : 28/11/ 5 : 29/11/ 5 : 3/11/ 5 : 1/12/ 5 : 2/12/ 5 : time

28 ,4 Sap flow density [ml cm -2 min -1 ],3,2, : : : : : Podo 1 S3 Eucalyptus 1 Eucalyptus 2 Eucalyptus 3 Eucalyptus 9 Eucalyptus 1 Sap flow density in the Eucalyptus site of five Nurse Trees of Eucalyptus saligna (between 3 and 4 m high) and one Podocarpus falcatus sapling (6. m high) measured in the rainy season (April 12 th 26) with the Granier system

29 PAR (micro mol PAR m -2 s -1 ) 16 1,6 Vapour 12 pressure deficit, PAR and stem 1,2 8 flux density, , Croton,4, VPD (kpa) Stem-flux (g m -2 s -1 ) Stem flux (g m -2 s -1 ) Eucalyptus Time of Day

30 14 December ,6 2 March PAR (micro mol m -2 s -1 ) ,2,8,4, VPD (kpa) PAR (micro mol m -2 s -1 ) Stem flux (g m -2 s -1 ) Cupressus Stem flux (g m -2 s -1 ) Podocarpus Time of Day Time of Day

31 4 VPD (kpa) 3 Croton r 2 =.77 2 Stem flux and VPD regressions 1 r 2 =.5 Eucalyptus 4 Stem flux density (g m -2 s -1 ) Cupressus r 2 = Podocarpus 1,,2,4,6,8 1, 1,2 1,4 1,6 1,8

32 Total daily transpiration (g H 2 O -day ) dbh (cm) Eu Eu Eu Eu4 32. Eu Wet season Total daily transpiration (Eucalyptus) Dry season Eu1 Eu2 Eu3 Eu4 Eu5 Eu1 Eu2 Eu3 Eu4 Cu5 Total daily transpiration (g H 2 O -day ) Wet season Total daily transpiration (Croton) dbh (cm) Cr Cr2 1.8 Cr3 8.8 Cr4 7.8 Cr5 1.8 Dry season Cr1 Cr2 Cr3 Cr4 Cr5 Cr1 Cr2 Cr3 Cr4 Cr5

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36 Soil-plant hydrology: Soil matric potential 5 *** *** ** *** * *** *** *** 21 wet year Soil depth (cm) *** *** *** *** ** ** *** *** 22 dry year C. lusitanica E. globulus Mean difference in matric potential to P. falcatus (hpa) Soil under C. lusitanica is much drier than under P. falcatus Soil under E. globulus is moist taps from deeper ground

37 Soil-plant hydrology: Living fine roots and root architecture Podocarpus Cupressus Eucalyptus 1 b 1 a Dry season (1m distance) 1 c Wet season (1m distance) Soil depth (cm) 35 6 Total LFR: 1.34 kg m -2 Soil depth (cm) 35 6 Dry season (2m distance) Wet season (2m distance) Total LFR:.88 kg m -2 Soil depth (cm) 35 6 Total LFR:.27 kg m P. falcatus 85 C. lusitanica 85 E. globulus LFR (g m -3 ) LFR (g m -3 ) LFR (g m -3 )

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39 C. lusitanica P. falcatus E.globulus 4 Oct. 11 Oct. 18 Oct. 25 Oct. 6 Nov. 2 Nov. 5 Dec Xylem cm cm cm cm Span Xylem cm cm cm cm Span / Xylem cm cm cm cm Span Δ 18 O values

40 Summary and Conclusions Characteristic diurnal patterns of water uptake and loss. However, pattern did not vary significantly with size of trees Croton - highest daily transpiration (up to 7 kg per day per tree) Eucalyptus drains water from deep soil layers especially in the dry season Podocarpus transpired much less than Eucalyptus, Cupressus and Croton and reduced its transpiration during dry periods, displaying a better control of its water use.

41 The study revealed that Podocarpus, through a high water use efficiency, may be capable of competing sucessfully with Eucalyptus in a shared environment

42 And beyond? The Munessa Project Field Station at Kuke Opportunities for qualification BSc/MSc/PhD studies Training activities Summer schools Field courses Training for professionals Provides accommodation Enables easy access to field sites Offers basic working facilities

43 Thank You for Your Attention