1 Effect of different germination processes on belowground and aboveground productivity in mature Coffe a arabica. Emily Giles Department of Ecology and Evolutionary Biology, The University of Tennessee ABSTRACT This was the first study in Monteverde, Costa Rica to look at how the agricultural method used during the germination phase affects the productivity of a mature Coffea arabica. It was thought by local farmers that a p lant germinated in the ground and then transplanted would have more fine root biomass than a plant that is germinated in a polybag and then transplanted. Traditional farming practices have shown that when coffee is transplanted from the ground to anoth er location; the main root is often cut, yielding more secondary fine roots. In contrast, many experiments have found that polybags increase a plantÂ€s productivity by protecting root growt h Shu guang et al. 2003, Gera et al. 1998. Fine roots are the source of nutrient uptake in a plant, thus, if a plant had more fine roots it should be more productive. Viewing the germination technique as a form of natura l disturbance to the plant, this study measured the plantÂ€s response in terms of productivity both belowground and aboveground. More shoots were produced by plants germinated in the ground in comparison to those germinated in bags p < 0.05 indicate that the germination technique does affect aboveground productivity, though no affect was found on belowground productivity p = 0.7055. RESUMEN Ã‰ste es el primer estudio que investigo cÃ³mo se afecta la productividad de Coffea arabica mediante el mÃ©todo agr Ãcola usado durante la fase de la germinaciÃ³n Una planta germinada en la tierra y despuÃ©s trasplantada podrÃa tener mÃ¡s biomasa de la raÃz fina que una planta que se germina en una bolsa plÃ¡stica y despuÃ©s se trasplanta. Las prÃ¡cticas agrÃcolas tradiciona les han demostrado que cuando el cafÃ© se trasplanta de la tierra a otra localizaciÃ³n; la raÃz principal se corta a menudo, rindiendo mÃ¡s raÃces finas secundarias. Las raÃces finas son la fuente de nutrientes en una planta, asÃ, si una planta tiene raÃces mÃ¡s finas es mÃ¡s productivo. Viendo la tÃ©cnica de la germinaciÃ³n como forma de disturbio natural a la planta, este estudio midiÃ³ la respuesta de la planta en tÃ©rminos de la productividad abajo y sobre la tierra. Se produjeron mÃ¡s brotes de raÃz en las pl antas que germinaron en la tierra con respecto a las germinadas en las bolsas p < 0.05 esto podria ser un indicador que la tÃ©cnica de la germinaciÃ³n afecta productividad sobre tierra, aunque ningÃºn efecto fue encontrado en productividad de abajo la tierr a p = 0.7055. INTRODUCTION Currently there is a debate in ecology as to the importance of belowground and aboveground interactions to overall productivity. Mutualisms involving mycorrhizae, detritivore and arthropod decomposition, and plant physiologi cal processes above and below the soil surface influence growth. In addition, above and belowground productivity is starting to be studied De Deyne and Van der Putten 2005, Harmand et al. 2003, Porazinska et al. 2003, though certain specific processes s till remain a mystery. Plants are the main bridge between the subsurface and aboveground realms De Deyn and
2 Van der Putten 2005, thus studying their response to various local perturbations can help elucidate when, why, and how these interactions occur. As an important agricultural product in many Latin American countries, the cultivation of Coffea arabica plays an integral role in local economies Boucher 1993. There are various methods of growing coffee such as in full sun, in shade, with chemical s, without chemicals, wi th compost, or with fertilizers, but the period of germination is crucially important for the development of a strong dominant plant Grubb 1977. Non conventional farming such as Organic or Fairtrade often relies on natural remedies, instead of ch emicals to maintain and increase their yields. In traditional coffee farming, there are two practices used during germination and the early stages of the plantÂ€s life. In one method, the seed is placed in a plastic bag , or polybag, until it has reached maturation aft er approximately 50 days; then, it is transplanted into the ground. The polybag is thought to protect the seedling from root predators, unfavorable soil conditions, and it also minimizes disturbance to the plant during transplantation pers.conv Santa Maria 2008. The other method involves placing the seed in a protected area on the ground, or seed bank, and after 50 days it is transplanted into the area of cultivation. During transplantation the roots are partially cut with a machete and must regenerate. While this process can compromise the plant if the roots are not re grown quickly, it also encourages surface extension of secondary roots rather than vertical extension of a solitary root, which occurs with the bag germinated plants Hipps et al. 1996 . H orizontal rooting and development of fine root mass can be important for essential nutrient uptake; especially in tropical regions where the majority of nutrients are located in the top layers of the soil Kothari et al. 2005, Lynch 1995. The purpose of thi s project i s to determine if disturbance in the form of germination technique influenced the belowground and thus aboveground productivity of Coffea arabica . Measurements were made of the relative horizontal fine root biomass of plants germinated in the ground and of plants germinated in polybags . This was paired with information gathered on the aboveground productivity of the plants to determine if, in fact, bag germination produces less belowground biomass and if this affects the overall aboveg round productivity of the plant. METHODS Study Site The study took place on two coffee farms, the Santa MarÃa farm and the Torres farm, found in a tropical wet forest, approximately 1300 meters above sea level, in CaÃ±itas, Costa Rica. Both farms were t ransitioning from conventional farming to organic agricultural production, thus fostering similar microhabitats. Neither farm had used chemical additions for the past three years of cultivation. The farms were producing five to seven year old, full sun va riety Coffea arabica in approximately two hectare plots. The only perceivable difference between the farms was the method of plant germination; the Santa Maria farm germinated its plants in plastic bags, and the Torres farm germinated its plants in the gr ound. Thus, ten mature coffee plants were selected from each farm for analysis.
3 Belowground Analysis Four soil samples were taken using a standard soil corer at random intervals approximately ten centimeters from the focal plant to a depth of approxima tely 15 cm. At the time of sampling, the upper leaf debris and hummus layer was removed and the four cores were pooled for each plant in a Ziploc TM bag. The soil was then dried at 70 Â C for twenty four hours and massed. The roots were extracted from the s oil by soaking the pooled soil samples in water and sieving through a two millimeter screen. Two successive washings of the remaining soil followed this. The roots were rinsed in distilled water, and were separated from the organic debris using forceps. Th e roots were dried at 70 Â C and massed using an analytical balance Dossa et al. 2007. In this way, the relative fine root biomass per gram of soil was determined for all ten plants that were ground germinated and all ten that were container germinated. Aboveground Analysis Due to the age of the plants and to avoid damage, only the shoots were counted to assess aboveground biomass. Coffea arabica does not fruit until approximately eight years of age. Using a hand counter, the shoots were counted on the same twenty plants from which soil was taken. These numbers were then used to reflect the aboveground productivity of the differently germinated plants. Statistical Analysis A Mann Whitney non parametric comparison test was used to determine if there wa s a significant difference between the biomass of plants that are germinated differently. One test compared the fine root mass and another compared the number of shoots. A correlation analysis, SpearmanÂ€s Rank test, was also used to determine if belowgrou nd biomass and above ground biomass were correlated. RESULTS There was no difference in productivity between germination treatments for belowground biomass Fig 1,U = 45, p = 0.7055, n = 10, but there was a difference in productivity found for the ab oveground biomass between treatments Fig 2, U=0, p = 0.0001573, n = 10. The median values of belowground biomass for each treatment were very similar bag germinated = 0.0022, ground germinated = 0.0018 and there was complete overlap of the data range with high variability of root biomass for bag germinated plants Fig . 1. The boxplots of aboveground biomass show that the ground germinated C. arabica had more shoots than the coffee germinated in bags Figure 2. There was a difference in the medians bag
4 germinated = 57.5, ground germinated = 92.5 despite moderate variation in the ranges of the data. There was no correlation between belowground and aboveground biomass for the germination treatments Figure 3. The figure shows a scattered, non li near distribution Â‚ = 0.17, p = 0.4733, n = 10 with only 17% of the variation in belowground biomass explaining variation in aboveground biomass. DISCUSSION While the results of this study did not validate a direct effect of germination method on coff ee productivity, it does promote further speculation about the belowground and aboveground interactions of C. arabica . The belowground biomass was not different for differently germinated coffee plants. This leads one to believe that germination method does not affect the development of fine rootmass. Explanations for this could be that either transplantation effects, from the ground or a bag, are equally disruptive, or over time, differences in these effects are minimized. Another possibility is that germination technique does influence root growth, but due to the difficulty of measuring belowground biomass these effects were not detected. Very little fine root biomass was obtained from the coring, and, though, there was little to no growth around the coffee plants, the roots were not identified to species, possibly influencing the results. One interesting outcome of this study is that germination method does seem to affect aboveground productivity of coffee plants. Although increased belowground prod uctivity for ground germinated plants was not found, the differences in aboveground
5 productivity indicate that germination technique does matter. Plants that were germinated in protected ground or seedbanks and then transplanted had more shoots than plants that were ge rminated in poly bags and then transplanted. Thus, the traditional theory that transplantation from the ground encourages the plant to uptake more nutrients is probable Hipps et al. 1996 . It is possible that ground germination and transplantation does promote more horizontal root development, and thereby more nutrient uptake, but this might only be seen in the early stages of the plantÂ€s development. Over time, ground and bag germinated plants might become functionally equivalent belowground, but aboveground the ground germinated plants will show the advantage. In addition, germination technique might affect aboveground productivity through processes other than nutrient sequestration. Ground germination is thought to be more disruptive, but this could be an advantage such that pl ants that survive to adulthood are more hardy, fast growing, or productive as a result of disturbance. The results of this study indicate how little is known about the belowground and aboveground interactions of plants. The analysis of germination techni que effect on productivity of C. arabica suggests that disturbance can be reflected in aboveground but not belowground productivity. Furthermore, the effect of disturbance on overall plant productivity is of utmost importance to agriculturists that depend on maintaining aboveground productivity to meet a market demand. ACKNOWLEDGMENTS I would like to thank many people for their help with this project. I would like to thank Norman Santa MarÃa for information about coffee germination processes as wel l as for the use of his farm as one of my study sites. I would also like to thank Venicio Torres for the use of his farm for my other study site. I would like to thank Pablo Allen and Moncho CaledrÃ³n for help gathering materials. Lastly, I would like to thank Dr. Alan Masters and Tania Chavarria for help with the development of this project and for help with statistical analysis. LITERATURE CITED Boucher, D. H. 1983. Coffee. In : Costa Rican Natural History , D. H. Janzen, ed. The University of Chicag o Press, Chicago, IL, pp. 86 88. De Deyn, G. B. and W. H. Van der Putten. 2005. Linking aboveground and belowground diversity. Trends in Ecology and Evolution . 20.11: 625 633. Dossa, E. L., E. C. M. Fernandez, W. S. Reid and K. Ezui. 2008. Above and b elowground biomass, nutrient and carbon stocks contrasting an open grown and a shaded coffee plantation. Agroforest Syst . 72: 103 115. Gera, M., N. Gera, S. Sharma, A. S. B handari. 1998. Improved seedling quality of polybag plants: Use of mounted angle iron beds. Indian Forester. 124.2: 116 133.
6 Grubb, P. J. 1977. The maintenance of species richness in plant communities: the importance of the regeneration niche. Biological Reviews. 52.1: 107 145. Harmand, J M., C. Forkong Njiti, F. Bernhard Reversat and H. Puig. 2003. Aboveground and belowground biomass, productivity and nutrient accumulation in tree improved fallows in the dry tropics of Cameroon. Forest Ec ology and Management. 188.3: 249 265. Hipps, N. A., K. H. Higgs, L. G. Collard. 1996. The effect of irrigation and root pruning on the growth of sycamore Acer pseudo plantanus seedlings in nursery beds and after transplantation. Journal of Horticulture Science. 71.5: 819 828. Kothari, S. K., C. Singh and Y. V. Kumar. 2005. Growth and yield of Spilanthes acmella roots and its cultivation economies as influenced by nitrogen and phosphorus application under semi arid tropics. Journal of Me dicinal and Aromatic Plant Sciences. 27.2: 283 286. Lynch, J. 1995. Root architecture and plant productivity. Plant Physiology. 109: 7 13. Porazinska, D. L., R. D. Bardgett, M. B. Blaauw, H. W. Hunt, A. N. Parsons, T. R. Seastedt and D. H. Wall. 2003. Relationships at the Aboveground Belowground Interface: Plants, Soil, Biota, and Soil Processes. Ecological Monographs. 73.3: 337 395. Shu guang, J., Y. Zhong yi, J. Wei jun. 2003. The effects of nutrition polybag on the growth, N fixation and heavy metal accumulation of Ses bania rostrata grown on Pb/Zn tailings. Journal of Tropical and Subtropical Botany. 11.1: 34 40.
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Efecto de los diferentes procesos de germinacin en la productividad debajo de la tierra y por encima de la tierra en Coffea arabica madura
Effect of different germination processes on belowground and aboveground productivity in mature Coffea arabica
This was the first study in Monteverde, Costa Rica to look at how the agricultural method used during the germination phase affects the productivity of a mature Coffea arabica. It was thought by local farmers that a plant germinated in the ground and then transplanted would have more fine root biomass than a plant that is germinated in a polybag and then transplanted. Traditional farming practices have shown that when coffee is transplanted from the ground to another location; the main root is often cut, yielding more secondary fine roots. In contrast, many experiments have found that polybags increase a plants productivity by protecting root growth (Shu-guang et al. 2003, Gera et al. 1998). Fine roots are the source of nutrient uptake in a plant, thus, if a plant had more fine roots it should be more productive. Viewing the germination technique as a form of natural disturbance to the plant, this study measured the plants response in terms of productivity both belowground and aboveground. More shoots were produced by plants germinated in the ground in comparison to those germinated in bags (p < 0.05) indicate that the germination technique does affect aboveground productivity, though no affect was found on belowground productivity (p = 0.7055).
Este fue el primer estudio en Monteverde, Costa Rica para ver cmo el mtodo agrcola utilizado durante la fase de germinacin afecta la productividad de Coffea arabica madura.
Text in English.
Coffee--Traditional farming--Costa Rica--Puntarenas--Monteverde Zone
Caf--agricultura tradicional--Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology 2008
Ecologa Tropical 2008
t Monteverde Institute : Tropical Ecology