Problems in restoring native trees to barren tropical pasture

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Jeffry Dennis
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1 Problems in restoring native trees to barren tropical pasture Lynn Carpenter, Doland Nichols, Eduver Sandi, and Grad students: Mary Anderson, Riley Pratt, Calen May- Tobin, Kristin Young Undergraduate students: Laura Antonie and Sotheary Son 1

Goals and approaches of our project in 1992 Overall: Use native trees to reclaim extremely degraded pastureland Reason: to provide future information when more farms reach that state Goal 1:

2 Goals and approaches of our project in 1992 Overall: Use native trees to reclaim extremely degraded pastureland Reason: to provide future information when more farms reach that state Goal 1: jump-start forest succession Goal 2: restore economic value to farm Our approach was two-fold Basic science: Test ecological concepts such as successional facilitation Applied science: Develop practical methods with minimal capital outlay for local farmers 2

3 Our 6-wk search for the perfect study site Criteria: Lack of topsoil as judged by color Depth of cattle trails to 2m Extent of bare land 50% Site: southwestern Costa Rica Comparable to other projects? 3

4 Finca Cantarana m, 4400mm/yr rainfall History: Mid-1950 s: cleared for coffee Mid-1970 s: converted to pasture, overgrazed 1992: research began 4

5 Initial soil characteristics 5

6 Soil fertility and classification Infertile compared to other pasture sites in CR Las Alturas (Holl 1999) & Finca Cantarana (Nichols et al. 2001) Ultisol with andic influences Relevant units [(cmol(+)/l) or (%)] Finca Cantarana Las Alturas CIA ph Ca Mg K CEC Tot N OM Five 2-m soil profiles 6

7 Initial soil chemistry in cm (n=45) ph Ca Mg K Acidity AL CICE P PO4 (cmol(+)/l) % sat. (cmol(+)/l) (mg/kg) (ug/g) OM N NH4 NO3 Cu Fe Mn Zn % % (ug/g) (ug/g) (mg/kg) B93 Experiment on Finca Cantarana. Depth 0-15cm. Analyses done by CIA: ph in water; bases in ammonium acetate; P Olsen, PO4 resin membrane 7

8 First step: What tree species can grow? Ensayos 1994, 1996, 1998 (species assayed are in blue on next slide)

9 List of species planted (Arboles de Costa Rica vols. I-III) Non-natives (3) Eucalyptus deglupta (Myrtaceae) Pinus tecunumanii (Pinaceae) Inga edulis (Fabaceae) Native legumes (10) I. spectabilis (Fabaceae) Albizia carbonaria (Fabaceae) Calliandra calothyrsus (Fabaceae) Diphysa robinioides (Fabaceae) Gliricidia sepium (Fabaceae) Lonchocarpus sp. (Fabaceae) chaperno Platymiscium pinnatum (Fabaceae) Schizolobium parahyba (Caesalpinaceae) Samanea saman (Fabaceae) cenizaro Zygia longifolia (Fabaceae) soto caballo Other natives (19) Anacardium excelsum (Anacardiaceae) espavel Other natives (cont.) Annona muricata (Annonaceae) Aspidosperma spruceanum (Apocynaceae)? amargo Astronium graveolens (Anacardiaceae) Calophyllum brasiliense (Clusiaceae) Carapa guianensis (Meliaceae) Cecropia obtusifolia (Cecropiaceae) Cedrela odorata (Meliaceae) C. tonduzii (Meliaceae) Ceiba pentandra (Bombacaceae) Hyeronima oblonga (Euphorbiaceae) Juglans olanchana (Juglandaceae) Minquartia guianensis (Olacaceae) Tabebuia chrysantha (Bignoniaceae) Tabebuia rosea (Bignoniaceae) Terminalia amazonia (Combretaceae) Vochysia guatemalensis (Vochysiaceae) V. ferruginea (Vochysiaceae) 2 species of unidentified Lauraceae ( bambito, aguacatillo ) 9

10 Ensayo Results: Mortality Seedling and sapling mortality is high. hueco de infierno #2 10

11 Ensayo 1994 Mortality over 7yr (n small for calculating growth) Initial n = 87 of each species 11 V. guatemalensis Pinus Terminalia Calophyllum Cedrela odorata (Eucalyptus) (Tabebuia chrysantha) Proportion dead

12 Ensayo 1996 Mortality over 9.5 yr ( ) small n for calculating growth Initial n = 90 of each species, except Annona, Astronium, bambito, Platymiscium (n= 21-63) 12 I. spectabilis V, ferruginea I. edulis Astronium Terminalia Aspidosperma Platymiscium (Annona) (Cedrela tonduzii) (bambito) Proportion dead

13 Ensayo 1998 Mortality over 11 yr ( ) small for calculating growth Initial n = 90 for each species, except Calliandra and Gliricidia (n=45) Hyeronima I. edulis Terminalia Diphysa Calliandra Schizolobium (Gliricidia) (Albizia) (Platymiscium) Proportion dead

14 Ensayo results: Growth Slow compared to the minimum values found in the literature 14

15 Ensayo 1994 Growth comparisons with other sites FC 14yr Data for FC spp in ( ) are doubtful because of small n s FC Other 15 Growth (cm/yr) Pinus (Eucalyptus) V. guatemalensis Calophyllum Cedrela odorata Terminalia93 (Tabebuia chrysantha)

16 Ensayo 1996 Growth comparisons with other sites (FC 9.5 yr) Data for FC spp in ( ) are doubtful because of small n s FC LIT 16 I. edulis I. spectabilis Terminalia (Cedrela tonduzii) Aspidosperma (Annona) Astronium Platymiscium V, ferruginea Growth (cm/yr)

17 Ensayo 1998 Growth comparisons with other sites FC 4yr FC Other 17 Calliandra Hyeronima I. edulis Schizolobium Terminalia Diphysa Gliricidia Platymiscium Albizia Growth (cm/yr)

18 Mortality may worsen over time or nullify growth Note Schizolobium ( ), Albizia (!) (FC 4yr growth) Ensayo 1998 Mortality over 4 yr 18 Growth (cm/yr) Proportion dead! Albizia Calliandra Hyeronima I. edulis Schizolobium Terminalia Diphysa Gliricidia Platymiscium Schizolobium I. edulis Hyeronima Diphysa Calliandra Terminalia Albizia Platymiscium Gliricidia Ensayo 1998 Mortality over 11 yr ( ) small for calculating growth! Proportion dead Hyeronima I. edulis Terminalia Diphysa Calliandra Schizolobium (Gliricidia) (Albizia) (Platymiscium)

19 So, few natives establish and grow. Worse, terrain has been a factor Ridges > slopes > valleys 19

20 Soil characteristics of different terrains First, compare ridges and slopes. Then, slopes and valleys 20

21 Soil on ridges and slopes Soil chemistry Ridges vs. slopes cmol(+)/l mg/l mg/kg ** ** (Young and May-Tobin 2008) ** ** ph Ca Mg K CEC Cu P NO3- ** * * * Ridge Slope Measure 21

22 This student lost most trees in his four ridge blocks (half the experiment). No more grad student projects on ridges! 22

23 Soil on slopes and valleys (R. Pratt 2009) Also, AMF differed: Acaulospora on slopes, not valleys 23

24 Mortality and growth on different terrains Terminalia amazonia 24

25 Ensayo98: Mortality by location on slope Bottom Next Up Nr ridge Ridge Top ridge Proportion of mortality Albizia Calliandra Diphysa Gliricidia Hyeronima Inga Platymiscium Schizolobium Terminalia Tended to increase uphill: Hyeronima showed no pattern, and its mortality was lowest 25

26 Ensayo 98: Growth by location on slope Bottom Next up Near ridge Ridge Top (species in () have small n s) 12 Mean dbh (cm) (Albizia) (Calliandra) Diphysa (Gliricidia) Hyeronima I. edulis (Platymiscium) (Schizolobium) (Terminalia) Hyeronima and Inga tended to decrease growth uphill. Some other legumes show the trend but n s are small. 26

27 Soil moisture may be a factor Two experiments over the dry season 27

28 Calophyllum brasiliense Growth (sig. p<.001) Soil moisture (sig. p<.001) Flats on black plastic Flats on black plastic 28

Inga spectabilis Growth (sig. different @ p<.001) Soil moisture (sig.

29 Inga spectabilis Growth (sig. p<.001) Soil moisture (sig. p<.001) Flats on black plastic Flats on black plastic 29

30 At this point, I ll sum a few lessons we have learned 30

31 Experimental design Super-degraded sites require special consideration Block the experiment by terrain Expect high mortality, so balance # blocks (reps) and # trees per treatment within blocks For example: Ensayos had few trees per treatment per block (3) but a good # of blocks (30) B93 had too few blocks (5) and too many trees per treatment per block (93) 31

edulis But their performance may worsen over longer time periods All except

32 Best species for Finca Cantarana (of 23) Pinus tecunumanii Vochysia guatemalensis V. ferruginea Hyeronima oblonga Inga spectabilis I. edulis But their performance may worsen over longer time periods All except pine grow comparatively slowly None except pine can grow on high ridges or in hellholes. 32

33 One last question: Can these best species help others grow? Facilitation 33

34 The search for facilitator species Inga spp (N-fixing legume, Fabaceae) I. edulis increased N and growth in Terminalia p<.001) No other legume genus so far has potential as facilitators Vochysia spp A priori arguments about P availability Leaf mulch of V. guatemalensis increased growth in Astronium and Tabebuia p<.0001) Other experiments with seedling Vochysia n.s.: may need more time to grow Pinus tecunumanii We can allay fears about mycorrhiza pines did not inhibit AMF colonization (p>.28) Preliminary data (n.s.) suggest that 12yr old pines may facilitate. 34

35 Growth (cm/yr) Mean growth under V. guatemalensis and P. 3.5yr Tabebuia Calophyllum Platym iscium (Astronium) Control Vochysia Pinus Important to test for economic reasons: On FC, 1 15yr $90,000 (1 tree=$90) 35

36 In conclusion: returning to our 1992 goals Can we restore economic value to these lands? Pine may be the only option for the farmer when land is this bad Can we jump-start natural succession? Slopes and valleys are feasible Establishing cover begins the process. Legumes may facilitate. Main conclusion: the sooner the intervention, the better A valley 12 years 36

37 Thanks to: UCI, RAIN, Earthwatch, UREP, CIA, OTS for financial and logistical support. Incredible ticos for field and lab assistance as well as discussions of scientific and cultural import: Leonel Figueroa, Rolando Mendez, Diego Sandi, Yolanda Rojas, Ana Herra, Gloria Melendez, Carlos Henriquez, Luis Diego Gomez, and many others. Nancy Adrian and Martha Rosemeyer for their understanding And Manchita and Newton for moral support 37

38 List of species planted (Arboles de Costa Rica vols. I-III) Non-natives (3) Eucalyptus deglupta (Myrtaceae) Pinus tecunumanii (Pinaceae) Inga edulis (Fabaceae) Native legumes (10) I. spectabilis (Fabaceae) Albizia carbonaria (Fabaceae) Calliandra calothyrsus (Fabaceae) Diphysa robinioides (Fabaceae) Gliricidia sepium (Fabaceae) Lonchocarpus sp. (Fabaceae) chaperno Platymiscium pinnatum (Fabaceae) Schizolobium parahyba (Caesalpinaceae) Samanea saman (Fabaceae) cenizaro Zygia longifolia (Fabaceae) soto caballo Other natives (19) Anacardium excelsum (Anacardiaceae) espavel Other natives (cont.) Annona muricata (Annonaceae) Aspidosperma spruceanum (Apocynaceae)? amargo Astronium graveolens (Anacardiaceae) Calophyllum brasiliense (Clusiaceae) Carapa guianensis (Meliaceae) Cecropia obtusifolia (Cecropiaceae) Cedrela odorata (Meliaceae) C. tonduzii (Meliaceae) Ceiba pentandra (Bombacaceae) Hyeronima oblonga (Euphorbiaceae) Juglans olanchana (Juglandaceae) Minquartia guianensis (Olacaceae) Tabebuia chrysantha (Bignoniaceae) T. rosea (Bignoniaceae) Terminalia amazonia (Combretaceae) Vochysia guatemalensis (Vochysiaceae) V. ferruginea (Vochysiaceae) 2 species of unidentified Lauraceae ( bambito, acuacatillo ) 38

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