Quercus calliprinos IN THE PRESENCE OF MEDITERRANEAN DROUGHT?

Transcription

1 IS PINE FOREST CANOPY BENEFITIAL TO THE ESTABLISHMENT OF Quercus calliprinos IN THE PRESENCE OF MEDITERRANEAN DROUGHT? Orna Reisman-Berman, Shani Ben-Yair, Shimon Rachmilevitch, Boris Rewald, Ben Roshko, Bertrand Boeken 1

2 Introduction: Sustainable Mixed Forest Management Coniferous Planted Broad-leaved Native 2

3 Possible Transitions Between Various Forest States???? Pine Plantation Pine overstory Chaparral species understory Mixed Forest Natural woodland / Chaparral

4 1. Can Chaparral species naturally regenerate within pine plantations of Israel? 2. What management is required to facilitate regeneration (if any)?? 1. The eco-physiological aspect: Can woody broadleaved species establish and develop in forest shade? 2. The spatio-temporal temporal aspect: How does forest heterogeneity and its dynamics affect regeneration?

5 1. The eco-physiological aspect: Can woody broadleaved species establish and develop in forest shade? s Lower temperatures Higher soil moisture Lower light level Drought in Mediterranean environments Shade combined with Drought

6 1. The eco-physiological aspect Plant response to the combined effect of drought and shade: High Low Biomass allocation to shoots Biomass allocation to roots Increasing leaf area Decreasing leaf area Trade-off Hypothesis Smith & Huston 1989 Drought dramatically decreases the ability to tolerate shade Independent Effect Nobel 1999 Sack and Grubb 2002 The impacts of drought and shade are orthogonal Amelioration Effect Holmgren 2000 Shade improves water relation in the presence of drought

7 Is there a trade-off between drought and shade tolerance? In temperate species the combined tolerance to both shade and drought is rare - Niinemets & Valladares F Species of the Dry Mediterranean : Trade-off (in the forest shade) - Maestre et al No trade-off - Sanchez-Gomez et al 2006! Species specific - Sanchez-Gomez et al ! Depending on shading level, amelioration in intermediate shade - Reisman-Berman 2007.

8 The spatio-temporal temporal aspect: Forest heterogeneity & temporal variation affect woody species establishment Forest mosaics: Gaps and variable tree densities Forest heterogeneity Tree density modifies biota and environmental conditions, affecting availability of sites for establishment Temporal variation Variation among years (climate conditions) Forest development and Gap Dynamics affect the availability of sites for establishment 8

9 Managing for Biodiversity in the Forests of the Pacific Northwest US Sparse patches Dense patches Gaps Photos from Thomas A. Spies PNW Research Station Corvallis, OR, USA

10 Research questions Case study: Common Oak Quercus calliprinos Late successional, dominates the Chaparral Is forest canopy beneficial to the establishment and development of Q. calliprinos in the presence of droughts? Specifically: What is the effect of canopy openness??

11 Study site: Masua Forest 400 mm rainfall per year

12 Creating canopy openness gradient Spatial heterogeneity of pine density gradient Gap Gap margin Sparse forest Dense forest North & South facing slopes Gap Margin Sparse forest Dense forest 12

13 Dense forest Sparse forest Margin Gap 50% 70% 90% Experimental design 6 (North) +8 (South) blocks 7 plots per block 64 acorns per plot 13

14 Radiation (PAR) % Radiation per hr during the day * Over the canopy Gap (0%) Margin1 Margin2 Sparse forest Dense forest * Photosynthetic Photon Flux Density 14

15 Seedling emergence and establishment 0.8 N gap Establishment (p) N 50% N 70% N 90% N margin N sparse S gap S 50% S 70% 0.1 S 90% S dense S margin S sparse Establishment rate = Aspect ** Shading treatment ** Mortality rates surviving seedlings total seeds Aspect ** Shading treatment ns 15

16 Q. calliprinos establishment 27 months post sowing Establishment rate (p) Norht South 0 90% 70% 50% Gap (0%) Gap margin Sparse forest Dense forest Significant effect of shade and aspect Lowest establishment rates in forest gap (0% shade) and margin Highest establishment rate in 50% and 70% shading nets Higher establishment rate in the forest compared to the gap 16

17 Q. calliprinos development (27 month old) Basal diameter Significant effect of shading on seedling basal diameter (p< ) Highest in the open gap, lowest under canopy and deep shade 17

18 Q. calliprinos development (27 month old) Branching and number of leaves Number of branches Number of Leaves Significant effect of shading on number of leaves and branches Highest in gap, lowest under forest canopy and in deep shade. 18

19 Q. calliprinos development (27 month old) Height Height (mm) Significant effect of shading on seedling height (p< ) Highest under deep artificial shade, lowest under forest canopy. 19

20 Q. calliprinos development (27 month old) Height (mm) No. of Branches No. of Leaves Basal diameter (mm) 90 % 70 % 50 % gap, 0% margin sparse dense 20

21 Establishment vs. Development in Q. calliprinos Shade, if not deep, ameliorates seedling survival and establishment However, seedling development is best in full sunlight Suitable sites for establishment and development are different. 21

22 Trade -off Development Establishment

23 Q. Calliprinos Physiological Performance (34 month old) South North Fv/Fm Gap (0%) 50% 70% 90% forest Gap margin Light curve (North) Light curve (South) ETR Gap (0%) 50% 70% 90% Forest Margin ETR Gap (0%) 50% 70% 90% Forest Margin PAR PAR

24 Discussion and conclusions In an heterogeneous forest, Where is the best site for common oak recruitment? Individual development is most vigorous in forest gap. On the population level, seedling survival is the highest under the forest canopy. Gap Small, but developed population Forest canopy Larger, poorly developed 24

25 THANK YOU! Projects are funded by: KKL (JNF) BGU We would like to thank KKL staff fro assistance and many undergrads for spending long days in the forest 25