1Effect of different germination processes on belowground and aboveground productivity in mature Coffea 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 productivi ty of a mature Coffea arabica. It was thought by local farmers that a plant germinated in the ground and t hen transplanted would have more fine root biomass than a plant that is germinated in a polybag and th en transplanted. Traditional farming practices hav e shown that when coffee is transplanted from the gro und to another location; the main root is often cut yielding more secondary fine roots. In contrast, m any experiments have found that polybags increase a plantÂ’s 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 pl ant had more fine roots it should be more productiv e. Viewing the germination technique as a form of natu ral disturbance to the plant, this study measured t he plantÂ’s response in terms of productivity both belo wground 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 produ ctivity, though no affect was found on belowground productivity (p = 0.7055). RESUMEN ste es el primer estudio que investigo cmo se afe cta la productividad de Coffea arabica mediante el mtodo agrcola usado durante la fase d e la germinacin Una planta germinada en la tierra y despus trasplantada podra tener ms biomasa de la raz fina que una planta que se germina en una bol sa plstica y despus se trasplanta. Las prcticas ag rcolas tradicionales han demostrado que cuando el caf se trasplanta de la tierra a otra localizacin; la ra z principal se corta a menudo, rindiendo ms races finas secundarias. Las races finas son la fuente de nut rientes en una planta, as, si una planta tiene ra ces ms finas es ms productivo. Viendo la tcnica de la ge rminacin como forma de disturbio natural a la plan ta, este estudio midi la respuesta de la planta en tr minos de la productividad abajo y sobre la tierra. Se produjeron ms brotes de raz en las plantas que g erminaron en la tierra con respecto a las germinada s en las bolsas (p < 0.05) esto podria ser un indicador que la tcnica de la germinacin afecta productivid ad sobre tierra, aunque ningn efecto fue encontrado e n productividad de abajo la tierra (p = 0.7055). INTRODUCTION Currently there is a debate in ecology as to the im portance of belowground and aboveground interactions to overall productivity. Mutualisms involving mycorrhizae, detritivore and arthropod decomposition, and plant physiological processes above and below the soil surface influence growth. In additi on, above and belowground productivity is starting to be studied (De Deyne an d Van der Putten 2005, Harmand et al. 2003, Porazinska et al. 2003), though certain speci fic processes still remain a mystery. Plants are the main bridge between the subsurface a nd 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 occ ur. As an important agricultural product in many Lati n 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 chemicals, without chemicals, with compost, or with fertilizers, but the period of germination is crucially important for the developm ent of a strong dominant plant (Grubb 1977). Non-conventional farming such as Organic or Fairtrade often rely on natural remedies, instead of chemicals to maintain and incr ease their yields. In traditional coffee farming, there are two practices used during germin ation 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 after approximately 50 days; the n, 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 th e plant during transplantation (pers.conv Santa Maria 2008). The other method inv olves 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 se condary roots rather than vertical extension of a solitary root, which occurs with the bag-germinated plants (Hipps et al. 1996). Horizontal rooting and development of fine root mass can be important for essential nutrient uptake; especially in tropical r egions where the majority of nutrients are located in the top layers of the soil (Kothari et a l. 2005, Lynch 1995). The purpose of this project is to determine if dis turbance in the form of germination technique influenced the belowground an d thus aboveground productivity of Coffea arabica Measurements were made of the relative horizonta l fine root biomass of plants germinated in the ground and of plants germi nated in polybags. This was paired with information gathered on the aboveground produc tivity of the plants to determine if, in fact, bag-germination produces less belowground biomass and if this affects the overall aboveground productivity of the plant. METHODS Study Site The study took place on two coffee farms, the Santa Mara farm and the Torres farm, found in a tropical wet forest, approximately 1300 meters above sea level, in Caitas, Costa Rica. Both farms were transitioning from conventional farming to organic agricultural production, thus fostering similar mic rohabitats. Neither farm had used chemical additions for the past three years of cult ivation. The farms were producing five to seven year-old, full-sun variety Coffea arabica in approximately two-hectare plots. The only perceivable difference between the farms w as the method of plant germination; the Santa Maria farm germinated its plants in plast ic bags, and the Torres farm germinated its plants in the ground. Thus, ten mat ure 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 approximately 15 cm. At the time of sampling, the upper leaf debris and hum mus layer was removed and the four cores were pooled for each plant in a ZiplocTM bag. The soil was then dried at 70rC for twenty-four hours and massed. The roots were extra cted from the soil 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 u sing forceps. The roots were dried at 70rC and massed using an analytical balance (Dossa et al. 2007). In this way, the relative fine root biomass per gram of soil was determined f or all ten plants that were ground germinated and all ten that were container germinat ed. Aboveground Analysis Due to the age of the plants and to avoid damage, o nly 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 u sed to determine if there was a significant difference between the biomass of plants that are germinated differently. One test compared the fine root mass a nd another compared the number of shoots. A correlation analysis, SpearmanÂ’s Rank te st, was also used to determine if belowground biomass and above ground biomass were c orrelated. 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 th e aboveground 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 wa s
4 a difference in the medians (bag 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-linear distribution ( = 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 coffee productivity, it does promote furt her 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 effe cts are minimized. Another possibility is that germination technique does influence root grow th, but due to the difficulty of measuring belowground biomass these effects were no t 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 germ ination method does seem to affect aboveground productivity of coffee plants. A lthough increased belowground productivity for ground germinated plants was not f ound, the differences in aboveground productivity indicate that germination technique do es matter. Plants that were germinated
5 in protected ground or seedbanks and then transplan ted had more shoots than plants that were germinated in polybags and then transplanted. Thus, the traditional theory that transplantation from the ground encourages the plan t to uptake more nutrients is probable (Hipps et al. 1996). It is possible that ground ge rmination and transplantation does promote more horizontal root development, and there by more nutrient uptake, but this might only be seen in the early stages of the plant Â’s development. Over time, ground and bag germinated plants might become functionally equ ivalent belowground, but aboveground the ground germinated plants will show the advantage. In addition, germination technique might affect aboveground prod uctivity through processes other than nutrient sequestration. Ground germination is thought to be more disruptive, but this could be an advantage such that plants 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 k nown about the belowground and aboveground interactions of plants. The analysis o f germination technique effect on productivity of C. arabica suggests that disturbance can be reflected in abov eground but not belowground productivity. Furthermore, the effe ct of disturbance on overall plant productivity is of utmost importance to agriculturi sts that depend on maintaining aboveground productivity to meet a market demand. ACKNOWLEDGMENTS I would like to thank many people for their help w ith this project. I would like to thank Norman Santa Mara for information about coff ee germination processes as well 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 Caledrn for help gathering materials. Last ly, I would like to thank Dr. Alan Masters and Tania Chavarria for help with the devel opment 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 Chicago Press, Chicago, IL, pp. 86-8 8. De Deyn, G. B. and W. H. Van der Putten. 2005. Link ing 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. Aboveand belowground biomass, nutrient and carbon stocks co ntrasting an open-grown and a shaded coffee plantation. Agroforest Syst. 72: 1 03-115. Gera, M., N. Gera, S. Sharma, A. S. Bhandari. 1998. Improved seedling quality of polybag plants: Use of mounted angle iron beds. In dian Forester. 124.2: 116-133. Grubb, P. J. 1977. The maintenance of speciesrich ness in plant communities: the importance of the regeneration niche. Biological R eviews. 52.1: 107-145.
6 Harmand, J-M., C. Forkong Njiti, F. Bernhard-Revers at and H. Puig. 2003. Aboveground and belowground biomass, productivity and nutrient accumulation in tree improved fallows in the dry tropics of Cameroon. Forest Ecology 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 pseudoplantanus) s eedlings in nursery beds and after transplantation. Journal of Horticulture Sci ence. 71.5: 819-828. Kothari, S. K., C. Singh and Y. V. Kumar. 2005. Gro wth 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 product ivity. 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 th e AbovegroundBelowground Interface: Plants, Soil, Biota, and Soil Processes Ecological Monographs. 73.3: 337-395. Shu-guang, J., Y. Zhong-yi, J. Wei-jun. 2003. The e ffects of nutrition polybag on the growth, N-fixation and heavy metal accumulation of Sesbania rostrata grown on Pb/Zn tailings. Journal of Tropical and Subtropica l 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