Effects of natural small-scale scale disturbances on light conditions and regeneration patterns in an old-growth

Transcription

1 Effects of natural small-scale scale disturbances on light conditions and regeneration patterns in an old-growth Nothofagus betuloides forest in Tierra del Fuego,, Chile Alvaro Promis 1, Albert Reif 1, Stefanie Gärtner 1, Gustavo Cruz 2 Contact: alvaro.promis@waldbau.uni-freiburg.de 1 Institute of Silviculture, University of Freiburg 2 Department of Silviculture, University of Chile The "Old Forests, New Management" Conference - Hobart, Tasmania, Australia February

2 CONTENT I. Theoretical Background II. Objectives III. Study Area IV. Methods and Results 1. Natural canopy gaps 2. Understorey solar radiation transmittances 3. Regeneration patterns V. Summary 2 alvaro.promis@waldbau.uni-freiburg.de

3 I. Theoretical Background Canopy Gaps (small-scale disturbances) the availability of many resources typically increases with gap formation (e.g. light, soil moisture, nutrients) a gradient of resources for tree seedlings and plants would exist between closed canopy forests, and the edges and centers of canopy gaps 3 alvaro.promis@waldbau.uni-freiburg.de

4 I. Theoretical Background The old-growth evergreen Nothofagus betuloides forests most of the N. betuloides forests in Patagonia and Tierra del Fuego are uneven-aged the allowed silvicultural systems by the Chilean Forest Law for this forest type are either a Shelterwood or Selection System both silvicultural systems are designed to promote natural regeneration after logging a Gap-based Approach might be a basis for the promotion of New Silvicultural Practices in the Region, in order to ensure the maintenance of multi-layer structures and high diversity 4 alvaro.promis@waldbau.uni-freiburg.de

5 II. Objectives To detect the effects of natural small-scale disturbances on: the understorey light conditions, the regeneration patterns (density and growth rates) in an old-growth evergreen Nothofagus betuloides forest 5 alvaro.promis@waldbau.uni-freiburg.de

6 III. Study Area It is covered by natural N. betuloides forests localized at the Río Cóndor on the west side of Tierra del Fuego The climate is cold-temperate with high humidity 600 forest surface (ha) Nothofagus betuloides density (trees ha -1 ) basal area (m 2 ha -1 ) DBH (cm) dominant tree height (m) 1, Density (trees ha -1 ) y= *x n=20; R 2 = ; RM= ; p< DBH(cm)

7 IV. Methods and Results Small-scale disturbances in the Nothofagus betuloides Forest 7

8 IV. Methods and Results canopy gap ( 20 m 2 ) All gaps were recorded along 36 transects expanded gap shape area Gaps were considered closed when the vegetation growing below the opening was 2-3 m tall 8 alvaro.promis@waldbau.uni-freiburg.de

9 IV. Methods and Results canopy gap ( 20 m 2 ) expanded gap average average 51 m m 2 25 canopy gaps in 20 ha gap fraction 2.0% expanded gap fraction 4.6% 9 alvaro.promis@waldbau.uni-freiburg.de

10 IV. Methods and Results Disturbance dynamics (frequency and intensity of disturbances over time) was studied on the basis of radial growth patterns of trees, with increment cores from juvenile trees increment cores Major and moderate release criteria were classed An average growth increase 100 % lasting for at least 15 years 50 % sustained for at least 10 years major release moderate release 10 alvaro.promis@waldbau.uni-freiburg.de

11 IV. Methods and Results Number of releases Major disturbance Moderate Decade The higher frequency of moderate than major releases show the stability of the canopy, which is only affected by fine-scale disturbances, leading to the creation of small canopy gaps 11 alvaro.promis@waldbau.uni-freiburg.de

12 IV. Methods and Results Understorey Solar Radiation in the Nothofagus betuloides Forest 12

13 IV. Methods and Results Measuring understorey solar radiation transmittances (13) (13) (13) (13) (13) Gap Gap Edge Centre Gap Edge North A gradient of light conditions was established per 13 canopy gaps (21 92 m 2 ; average 47 m 2 ) 65 hemispherical photographs were taken (2006) South 13 alvaro.promis@waldbau.uni-freiburg.de

14 IV. Methods and Results Understorey solar radiation transmittances 10 Gap Edge Gap Centre Gap Edge Solar Radiation Transmittances (%) % a 7.9% a 8.6% a Global 6.6% a 6.9% a 14 alvaro.promis@waldbau.uni-freiburg.de

15 IV. Methods and Results Regeneration patterns of Nothofagus betuloides 15

16 IV. Methods and Results Regeneration patterns of N. betuloides (13) (13) (13) (13) (13) 4 m 2 Gap Gap Edge Centre Gap Edge all seedlings and saplings were counted Height classes (cm) germinant and non-lignified Seedlings lignified and 20 cm tall the tallest seedling per quadrat harvested: age annual height increments annual radial growths was cm tall cm tall Saplings cm tall and 5 cm dbh 16 alvaro.promis@waldbau.uni-freiburg.de

17 IV. Methods and Results Density of N. betuloides (n plants m -2 ) Height classes (cm) Total Density (plants m -2 ) germinated and non-lignified 20 cm tall cm tall cm tall cm tall Gap Edge Gap Centre Gap Edge a a a a a 0.8 a 1.6 a 0.9 a 0.4 a 0.9 a 12.2 a 15.9 a 12.5 a 13.5 a 19.0 a 2.5 a 2.4 a 3.3 a 3.6 a 2.7 a 0.5 a 1.0 a 1.8 a 1.8 a 1.1 a 0.9 a 0.3 a 0.4 a 0.9 a 0.7 a 17

18 IV. Methods and Results Relative Annual Height Incremen Ratio of Annual Height Increment to Total Height ( x GSR x ) y = age x GSR years old years old years old years old 0.30 > 40 years old R 2 = 0.519; RM = 0.045; n = 58 (5-65 years old) 5 years old 10 years old 20 years old 30 years old 50 years old GSR Transmittance (%) 18 alvaro.promis@waldbau.uni-freiburg.de

19 Relative Annual Radial Incremen IV. Methods and Results Ratio of Annual Radial Increment to Total Radius ( x GSR x ) y = x + GSR age GSR Transmittance (%) 5-10 years old years old years old years old > 40 years old R 2 = 0.767; RM = 0.014; n = 58 (5-65 years old) 5 years old 10 years old 20 years old 30 years old 50 years old 19 alvaro.promis@waldbau.uni-freiburg.de

20 IV. Methods and Results Ratio of Annual Radial Increment to Total Radius Apparent competition of two native shrub species; Berberis ilicifolia and B. buxifolia Relative Annual Radial Incremen years old years old years old years old > 40 years old Coverage of Berberis spp Coverage of Berberis spp. (%) GSR Transmittance (%) 20

21 IV. Methods and Results Relative Annual Radial Incremen years old years old years old years old > 40 years old Coverage of Berberis spp Coverage of Berberis spp. (%) Relative Annual Height Incremen years old years old years old years old > 40 years old Coverage of Berberis spp Coverage of Berberis spp. (%) Etiolation? GSR Transmittance (%) 0 21 alvaro.promis@waldbau.uni-freiburg.de

22 V. Summary Small canopy gaps are the prevalent disturbance type in this N. betuloides forest The availability of light in the understorey is much more continuous for the regeneration The regeneration appears to be more continuous and apparently do not require great gaps to establish It is possible to regenerate under low light conditions Understorey light and the age of seedlings and saplings explain: 74-77% of the variation in their relative annual radial increment, 51-57% of the variation in their relative annual height increment 22

23 ACKNOWLEDGEMENTS DAAD (German Academic Exchange Service) CONICYT (Chilean National Commission for Scientific and Technological Research) FONDEF Project D02I1080 IPP Forestry in Transition Pd.D. Program of the Faculty of Forest and Environmental Sciences of the University Freiburg, Germany Müller-Fahnenberg-Stiftung WCS (Wildlife Conservation Society) - Chile Programa Bosques Patagónicos of the University of Chile Mr. Joaquín Soto (Owner of the forest) Dipl. Biol. Michael Lüth for the introduction in the identification of Mosses and Liverworts Elizabeth Barrera and Víctor Ardiles from the Botanical Section of the National Museum of Natural History (Santiago, Chile), for helping me in the identification of Liverworts. Dr. Guillermo Martínez Pastur (CADIC) for advice 23 alvaro.promis@waldbau.uni-freiburg.de

24 Thank you! Alvaro Promis,, Albert Reif, Stefanie Gärtner,, Gustavo Cruz Contact: Poster 10 Whoever eats the calafate returns for more (Moore, 1983) Berberis buxifolia (calafate) Silviculture treatments for old-growth mixed deciduous - evergreen Nothofagus pumilio N. betuloides forests in southern Patagonia, Chile Cruz, G., Promis,, A. & Schmidt, H. 24

25 Small-scale disturbance in the N. betuloides forest Forest Composition N Gaps Surface (m2) Gap Exp. Gap Gap fraction (%) Gap Exp. Gap References Tierra del Fuego N. betuloides This research N. betuloides N. pumilio Promis et al. N. betuloides D. winteri N. betuloides gaps were not apparent Rebertus and Veblen (1993) N. pumilio N. betuloides N. pumilio N. pumilio Cuevas (2005) N. pumilio , Cavieres and Fajardo (2005) New Zealand N. menziesii Weinmannia racemosa , Stewart (1986) N. fusca N. menziesii Stewart et al. (1991)

26 Understorey solar radiation transmittances in the N. betuloides forest Gap Non-cosine-corrected Solar Radiation Transmittances (%) Gap Edge Centre Gap Edge 9.5% 8.0% 8.2% 5.5% a Direct a a Diffuse b Global 8.2% a 26

27 Understorey solar radiation transmittances in the N. betuloides forest Gap Non-cosine-corrected Solar Radiation Transmittances (%) Gap Edge Centre Gap Edge 6.1% 7.8% 8.7% 7.1% b Direct a a Diffuse ab Global 6.3% b 27

28 Understorey plant species diversity in the Nothofagus betuloides forest 28

29 Understorey plant species diversity in the N. betuloides forest (13) (13) (13) (13) (13) 4 m 2 Gap Gap Edge Centre Gap Edge Vegetation: Phytosociological relevés Percentage species cover were visually estimated following the Londo scale... lichens mosses liverworts ferns herbs woody plants seedlings 29 BACKGROUND OBJECTIVES STUDY AREA RESULTS SUMMARY

30 Plant species diversity in the N. betuloides forest (13) (13) (13) (13) (13) Gap Edge Centre Gap Edge Shannon s diversity Senecio acanthifolius 1 Lepidogyna menziesii 1 Leptoscyphus chiloscyphoideus 1 Riccardia prehensiles 1 Hypnum cupressiforme 2 Leptostomum menziesii 1 Riccardia patens 1 Frullania sp. 1 Gap Pernettya mucronata 1 Adenocaulon chilense 2 Codonorchis lessonii 3 Hymenophyllum tortuosum var. Glomeratum 1 Hennediella sp 1 Ulota pygmaeothecia 1 GAP Closed Forest 4 m GAP EDGE

31 Mean coverage per quadrat by taxonomical groups (13) (13) (13) (13) (13) a a a a a 4 m 2 Gap 50 Gap Edge Centre Gap Edge Marchantiophyta 40 Average coverage (%) Bryophyta Pteridophyta Monocotyledons Dicotyledons Anthocerotophyta Similar letters mean no significant difference among places, n= 13 (Kruskal- 31 Wallis H Test, p > 0.05)

32 Mean N of species per quadrat by taxonomical groups (13) (13) (13) (13) (13) a a a a a 4 m 2 8 Gap Edge Gap Centre Gap Edge Average N Species per quadrat Marchantiophyta Bryophyta Pteridophyta Monocotyledons Dicotyledons Anthocerotophyta Similar letters mean no significant difference among places, n= 13 (Kruskal- 32 Wallis H Test, p > 0.05)