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Impactos de la actividad humana sobre la calidad del suelo tropical en relacin con la productividad futura de la tierra y la biodiversidad
Impacts of human activity on tropical soil quality in relation to future land productivity and biodiversity
The high rates of tropical forest clearing followed by intensive agriculture may significantly degrade the soils original nutrient content and chemical composition, reducing future productivity and future restoration efforts. Land use impacts were determined by collecting soil samples from four sites in San Luis, Costa Rica. Three areas presented different agricultural uses, and the fourth was an area of forest, comparatively untouched by human activity. To evaluate existing nutrient levels, six tests were conducted from three soil samples from each site: ph, N, P, K, Al and Fe. Trends were found in that the site with the heaviest land use experienced the most change in nutrient levels compared to the forest soil. The three different agricultural areas displayed differing results, even as they were all within the same farming community, no more than 15m from one another.
Las altas tasas de deforestacin en los bosques tropicales debido a la agricultura pueden degradar significativamente el contenido original de los nutrientes y la composicin qumica de los suelos, reduciendo la productividad futura y los esfuerzos de restauracin. Los impactos del uso del suelo fueron determinados mediante la recopilacin de muestras del suelo en cuatro sitios en San Luis, Costa Rica.
Text in English.
Agricultural intensification--Costa Rica--Puntarenas--San Luis
Intensificacin agrcola--Costa Rica--Puntarenas--San Luis
Tropical Ecology 2008
Ecologa Tropical 2008
t Monteverde Institute : Tropical Ecology
Impacts of human activity on tropical soil quality in relation to future land productivity and biodiversity Lauren Bolte Department of Religion, University of Puget Sound ABSTRACT The high rates of tropical forest clearing followed by intensive agriculture may significantly degrade the soils original nutrient content and chemical compo sition, reducing future productivity and future restoration efforts. Land use impacts were determi ned by collecting soil samples from four sites in S an Luis, Costa Rica. Three areas presented different agricultural uses, and the fourth was an area of fo rest, comparatively untouched by human activity. To eval uate existing nutrient levels, six tests were condu cted from three soil samples from each site: ph, N, P, K Al and Fe. Trends were found in that the site wi th the heaviest land use experienced the most change in nu trient levels compared to the forest soil. The thre e different agricultural areas displayed differing re sults, even as they were all within the same farmin g community, no more than 15m from one another. RESUMEN Las altas tasas de deforestacion en los bosques tro picales debido a la agricultura pueden degradar significativa el contenido orignal de nutrientes y composicion quiumica de los suelos, reduciendo la productividad futura y los esfuerzos de restauracio n. El impacto del uso del suelo se determino colect ando muestras de suelo en cuatro sitios en San Lus, Cost a Rica. Tres areas presentan usos agricolas de dife rente impacto, y la cuarta es una area de bosque. Se enco ntraron tendencias a mayor cambio de nutrients en l os sitios con mayor explotacion en comparacion al suel o del bosque. Las tres areas agricolas mostraron diferentes resultados, inclusive estando en la mism a comunidad agricola. INTRODUCTION Soil in the Tropics Despite the fact that Tropical forests are among th e most productive ecosystems on the planet, tropical soils are extremely infertile (San chez, 1992). They lack important nutrients and are highly weathered (Terborgh, 2008) So-called mineral soil in the Tropics is nearly devoid of soluble minerals of any kind for roots to absorb (Richards, 1981). This poor soil state is a result of more th en millennia of torrential rain exposure (Terborgh, 1992). Rains that are mildly acidic are at the core of the problem. These rains percolate down through the soil, washing all dissol ved minerals away into streams. This leaching process does not leave behind much to bene fit the plants. What remains is a barren substrate comprised of masses of mostly iron aluminum oxides and other insoluble mineral, which are, not useful and are ev en toxic to most plants. Despite the great diversity of soil existing in the tropics almost two-thirds of all tropical soils are relatively infertile oxisols and utisols, containing clays with scant soluble minerals (Terborgh, 1992). These soils als o are generally deficient in bases and have high levels of acidity (Richards, 1981). The acidity disrupts the ability of roots to
absorb nutrients. These soils are deficient in key minerals such as potassium, phosphorous, carbon, magnesium and sulphur (Stallan d, 2006). The key factor concerning the tropics nutrient-poo r soil, yet high productivity lies in the litter carpeting the forests floor. T he nutrients of tropical ecosystems are mainly found in the living and recently dead organi c matter decomposing in the thin cap of topsoil (Richards, 1981). For many tropical for ests, the mineral soils deep beneath the topsoil mainly act as anchoring for trees and a wat er supply for roots (Terborgh, 1992). Issues of Tropical Agriculture As a result of relatively low soil fertility and hi gh weathering only around 20 percent of the soils of the humid tropical region a re capable of sustaining agriculture with current technology, and the majority of the land in the area has been intensively developed (Terborgh, 1992). At the same time, it i s relatively rare to find sites on which the natural vegetation and soils have not been dist urbed, to a great or lesser degree, by humans (Anderson et al., 1993). Tropical deforesta tion rates, though difficult to calculate, are also unquestionably high, and the va st majority of the forest clearing in Latin America is for agricultural purposes (Holl, 1 999). In particular this land creates pastureland for cattle grazing (Amelung & Diehl 199 2, Fearnside 1993). Pasture development in Latin America is responsible for abo ut 10 percent of tropical deforestation (Smith et al., 1992). For example, C osta Rica, which was once almost completely covered in forest, is now almost half (4 6%) cattle pasture (WRI, 1998). Agriculture plays a critical role in the economies of tropical countries and remains an essential part to a great population of local fa rmers (and their families), upon which their livelihoods depend. The warm temperatures and high precipitation can produce a wide range of crops year round, and farmers take fu ll advantage. However, these same conditions may degrade soil qua lity when coupled with deforestation and agriculture. Soil quality, thoug h broadly understood, emphasizes the capacity of soil to perform services including the production of plants and animals and the transport and regulation of matter, water and o ther compounds present in or added to soils (Wander et al., 2002). Additionally, soil qua lity, or SQ, is described as reflecting appreciation for soils fitness for use (Larson an d Pierce, 1994) and the capacity of soil to resist and recover from degradation (Blum, 1998 ; Greenland and Szabolcs, 1994). Compared to the natural ecosystems from which they were formed, the composition, abundance, and activity levels of the soil communit y in agricultural systems are notably different (Matson et al., 1997). Overall, it is gen erally understood that soils are depreciated by land transformation, and their abili ty to recover from such degradation is reduced. Tropical land use leaves behind a mosaic of forest patches, cattle pastures, row crop agriculture and fallow lands that may support secondary forests. What tropical biodiversity remains will live in this matrix and w ill ultimately depend on what soil fertility remains. This will not only determine fut ure human land use, but the fate of restoration/reforestation efforts. Studies of lowl and wet forest areas clearly show a decline in soil fertility that will compromise futu re land uses, including restoration (Martinez-Sanchez and Sanchez-Beltran, 2003). In m ontane areas, particularly those near volcanoes, the soils are more fertile Andisols (Clark et al., 2000). Here, I examine soil fertility for common land uses in Monteverde, Costa Rica. I compare major soil
nutrients between common land uses and forest to se e if Andisols suffer the same eventual fate as lowland Ultisols and Oxisols under agricultural use. METHODS Study Sites Four study sites were located in San Luis, Costa Ri ca within Finca la Bella. San Luis is a small farming community. The community is predomin antly comprised of individual small, rural, family farms, or larger coop farm env ironments. It has not been affected by the presence of tourism as seen in Monteverde and S anta Elena. The area was first settled in 1915, and more and more settlers began moving in to the area around 1930 (Nadkarani et al., 2000). The elevation of the Finca la Bella area is at 1100 meters, and the forest above and surrounding the farming communities is co nsidered formally premontane moist forest. Four sites were sampled, three typic al areas per site. The three different samples per site had to be at least 8 meters away f rom each other. The four sites were: 1) a coffee farm, 2) a cattle farm, 3) a organic veget able farm, and 4) the forest on the upper slopes of Finca la Bella. The first three samples represented various types of human land-use, while the forest represented a comparison for what the soils of the area were like without any human alteration. Basic Soil Features of Andisols Clark et al. (2000) characterize the soils of Monte verde as Andisols and further classify them as Udands because they formed under udic, or w et, conditions. Andisols have poorly to moderately differentiated soil horizons. Andisols are soils that have formed in volcanic ash or other volcanic ejecta. They differ from those of other orders in that they typically are dominated by glass and poorly crystal line colloidal materials such as allophane, imogolite, and ferrihydrite. As a result Andisols have andic properties unique chemical and physical properties that includ e high water-holding capacity and the ability to 'fix' (and make unavailable to plants) l arge quantities of phosphorus. Globally, Andisols are the least extensive soil order and onl y account for ~1% of the ice-free land area (http://soils.ag.uidaho.edu/soilorders/andisol s.htm). Because they are generally quite young, Andisols typically are very fertile except i n cases where phosphorus is easily fixed (this sometimes occurs in the tropics). They can usually support intensive cropping, with areas used for wet rice in Java supporting som e of the densest populations in the world. Other Andisol areas support crops of fruit, maize, tea, coffee or tobacco (http://soils.usda.gov/technical/classification/ord ers/andisols.html). Andisols are divided into 8 suborders: Aquands Gelands, Cryands Torrands Xerands Vitrands Ustands and Udands Monteverdes Ugand Andisols are highly weathered, with lots of clay and low available Phosphorus. Soil Sample Analysis For each sample taken, nutrient tests were conducte d to determine nutrient levels at each site. Six individual tests were performed upon each sample from each site. The samples
were tested for: 1) Ph, 2) Nitrogen nitrate, 3) Pot assium, 4) Phosphorous, 5) Aluminum, and 6) Iron. All tests were conducted using th e LaMotte STH Series Combination Soil Outfit test kit. pH was determined by combining a s mall soil sample with demineralizer solution and soil flocculating reagent and then tes ting the resulting liquid. Nitrogen, Potassium, Phosphorous, Aluminum and Iron were all tested using a general soil extract resulting from combining universal extract solution with a small sample of soil, shaking, and then filtering the soil. Here is a brief summa ry of the importance of each measure to soil fertility. pH: pH measurement is a simple means by which the pro duction potential of a soil can be evaluated (LaMotte, 1994). pH refers to the degree of effective acidity or alkalinity of a substance (LaMotte, 1994). The Ph scale ranges from 0-14 with a pH value of 7.0 being neutral, meaning neither ac id nor alkaline; pH values below 7.0 are acidic, and values above 7.0 are alka line (LaMotte, 1994). The tropics generally have more acidic soils (Stalland, 2006). Soil pH primarily affects soil organism growth and activity, which me ans that pH, affects the amount of available nutrients gained from organic m atter decomposition (Stalland, 2006). There is a large variation in op timal pH levels for different crops (LaMotte, 1994). Nitrogen: Nitrogen is required by nearly all biochemical proc esses that compose and sustain plant life (Stalland, 2006). In that s ense, nitrogen is an essential nutrient in the growth of plants. It aids in the a bsorption of essential nutrients (Stalland, 2006). Nitrogen is an indispensable n utrient element, as when used at the recommended rates, improves the quality of l eaf crops, and stimulates the utilization of potassium, phosphorous and other ess ential nutrient elements (LaMotte, 1994). Plants take up nitrogen in the fo rm of nitrate and ammonium and become part of the soil through fixation from a tmospheric N2 using bacteria associated with legumes (Stalland, 2006). The abov e-ground growth of plants is enhanced by nitrogen (LaMotte, 1994). In the tropi cs specifically, nitrogen in the form of nitrate is absorbed by plants, but has the potential for leaching out quickly (Kohnke, 1995). Phosphorous: Phosphorous is critical in the strong growth of the plant and activity of its cells (LaMotte, 1994). It promotes healthy root development (Stalland, 2006). Phosphorous stimulates the forma tion of fats, convertible starches, and healthy seed (LaMotte, 1994). With t he stimulation of rapid cell development in the plant, phosphorous can naturally increase disease resistance (LaMotte, 1994). Life, whether it is plant or anim al, cannot exist without phosphorous and the soil serves as the principal so urce (LaMotte, 1994). Animals utilize plants for food and by doing so secure phos phorous indirectly, while plants secure their phosphorous directly from the soil (La Motte, 1994). In the tropics, phosphorous deficiencies are common as a result of high leaching (Kohnke 1995). This deficiency causes many tropical farmers to inv est in commercial fertilizers (Nadkarni, 2000) The availability of phosphorous in the tropics also possesses a
connection to the Ph of soil, in that it becomes av ailable to plants only when soil acidity falls between 5.5 and 6.5 (LaMotte, 1994). Potassium: Potassium plays a vital role in the physiological and biochemical functions of plants (LaMotte, 1994). It improves t he general health of the plant, aids in photosynthesis, and the uptake of other nut rients (Stalland, 2006). By improving the health of the plant, it also develops stronger defense against disease. Deficiencies in potassium also contribute to the susceptibility of the soil to leaching (Stalland, 2006). Potassium and nitrog en work together to support optimal uptake of nutrients (Stalland, 2006). Pota ssium also is involved in production of amino acids, chlorophyll formation, s tarch formation, and sugar transport from leaves to root (LaMotte, 1994). Aluminum: Aluminum is widely distributed in nature, and in s ome plants can be toxic (LaMotte, 1994). In excess, aluminum can have significant impact on soil quality. Aluminum is common in acidic soils. As th e majority of tropical soils are acidic, it is interesting to evaluate their relatio nship. Iron: Although total iron in soil may be abundant, only a small portion is used by the plant. Solubility and mobility are the factors behind iron deficiencies in the plant (LaMotte, 1994). Once the iron is absorbed i t can act as a catalyst in the formation of chlorophyll, and is required in many o f the plants oxidationreduction reactions (LaMotte, 1994). RESULTS Forest in the San Luis valley showed a neutral pH of 7.2. This rating is similar to Andisols studied in tropical Mexico but is generall y high compared to tropical lowland soils, which range from 3.7 to 6.5, with Ultisols a round 4 (Martinez-Sanchez and Sanchez-Bertran, 2003). In general, tropical forest Andisols are intermedia te in total Nitrogen, low in Phosphorus, low in Potassium but typical in Aluminu m and Iron compared to other tropical soil types (Martinez-Sanchez and Sanchez-B ertran, 2003). The Nitrogen levels had a mean of 36.65 parts per million, and the mean Phosphorous was high with 100 parts per million. The mean Potassium was lowest of the four sites with 93.35 parts per million. And both the Aluminum (mean 2.5 ppm) and Iron (mean 3.5 ppm) levels were low. Coffee grown in the area had soil that differed from fore st soil in a number of ways. pH was slightly more acidic than the forest soil, as p H 6.3. Nitrogen and Phosphorus were lower than in forests, with average values of 28.35 parts per million Nitrogen, and 83.35 parts per million available Phosphorous. The Potas sium levels were lower than any other site with a mean of 93.35. The parts per million l evels of Aluminum and Iron were notably higher than any other site. The mean value s were 28.35 for Aluminum (compared to the 2.5 parts per million in the fores t), and 6.65 for Iron.
Cow farm had the greatest overall difference of nutrient lev els from the forest. The cow farm showed the lowest pH with 5.4, which is highly acidic. The Nitrogen levels were highest with a mean of 66.65 parts per million, whi ch is nearly double the amount found in the forest (36.65). The Potassium levels were a lso significantly higher than the other sites with a mean of 196.65 parts per million (whic h is especially higher when compared to the mean of 93.35 of the forest). The Phosphoro us levels were also lowest at 51.65 parts per million (practically half of the forests mean of 100. The Aluminum (mean 3.35) and Iron (mean 4.15) levels were not notably dissimilar compared to the organic farm and forest level. Organic farm tests results appeared to have the closet relation to the forest results. The pH level was 7.2 (closest to the forest pH of 7). The two had the same Phosphorous means of 100 parts per million, and the low levels of Aluminum (mean 3.5 ppm) and Iron (mean 2.5 ppm) were very close to similarly low lev els of Aluminum and Iron in the forest. The organic farm shared certain similariti es with the coffee farm having the same Potassium mean of 120 ppm, and a mean Nitrogen leve l of 26.65, near that of the Coffee farm. Comparing land uses soil from organic farms most closely resembled fo rest soils, cow pastures showed the greatest change in soil mineral composition and coffee plantations showed dramatic increases in Aluminum and Iron, whi ch are generally toxic to plants. Only organic farming maintained a neutral pH, all o ther land uses created more acidic soils. Cow pasture had much more acidic soils, pH 5.4, while coffee was less acidic at 6.3. Cow pasture also had the biggest change in ni trogen from forest and other land uses. Cow pasture had a mean of 66.65 ppm, which was twic e the nitrogen level of other land uses and nearly twice the forest nitrogen. Likewis e, cow pasture had far more potassium. Cow pasture had less phosphorus, unlike other land uses that were nearly equal to forest levels. Coffee differed from forest and other land uses most dramatically in the high levels of Aluminum and Iron. (See Figures 1-6). DISCUSSION The relationships seen in this study support the im portance of recognizing how different agricultural practices affect the land in different ways. For example, the practices used with the organic farm had very minim al impact on the soil when compared to the areas most pristine, humanly untouched, for est soil. The greatest impact to the soil in terms of soil nutrient composition change w as caused by the cow pasture. These heavier methods of agriculture can be dangerous to the future of the soil. Intensive uses, such as cattle farming, bulldozing and crop burning degrade the productivity of the soil for future land uses (Buschbacher et al., 1988). I n many cases the degradation is so significant that once farmed lands are abandoned, t heir soils are effectively sterile (Matson et al., 1997). The cow pasture had a significant impact on the soi ls composition. The soil in some areas experienced a depletion in nutrients, an d others experienced an appreciation. The lower pH level meant a lower level of acidity i n the soil. This affects the growth and
overall activity of growth of the organisms living in the soil. The alteration of the soils chemical composition along with its physical and bi ological processes can limit the species able to live within it, and do so on into t he future. Older, more nutrient poor tropical soils that have been abandoned demonstrate the soils inability to maintain long long-term livestock production (Martinez-Sanchez & Sanchez-Betrn, 2003). This is mainly due to the caused erosion and leaching of th e soils nutrient minerals. Low levels of Nitrogen, Potassium and Phosphorous c an limit the future productivity of a pasture (Martinez-Sanchez & Sanch ez-Betrn, 2003), the results for this test only showed a decrease in Phosphorous levels, both Nitrogen and Potassium were significantly higher than the other sites. The hig her levels of Potassium are related to the lower acidity levels, as well as a favorable influe nce of grass on potassium cycling to the soils surface compared with forest vegetation (Rei ners et al.,1994). The high levels of Nitrogen are probably due to the heavy content of c attle urine and excrements which return ~80% of the Nitrogen removed in the grasses eaten by the cows. And through the continuous trampling of soil, reducing large pore s paces and increasing bulk density, infiltration and percolation rates are affected, in particular altering nitrogen cycling causing slower rates in plant N uptake (Reiners et al.,1994). What might also account for these results may be du e to the specificity of the soil. Though tropical soils generally share the similar c haracteristics, various types of soil exist and certain types are more suitable for susta ining cattle. Pastures appear to be viable in the long term only on fertile soils like Andosols (Martinez-Sanchez & SanchezBetrn, 2003). The soil in and around the Montever de region has been classified as Andosols, clays over limestones and alluvial soils. This is beneficial, as it has been shown that moderate levels of fertilization, pastur es can be kept at a high level of production (Martinez-Sanchez & Sanchez-Betrn, 2003 ). Active pastures tend to be more fertile than forest soils (Reiners et al.,1994). Having high aluminum and iron levels can be quite t oxic to plant health and the coffee farm soil demonstrates the threat of such to xicity with long-term agricultural use. This poses particular concern in the future of trop ical agriculture, and biodiversity. Coffee production continues to grow rapidly through out Latin America as the conditions are ideal in tropical mountains at mid-elevation. F requently, coffee crops replace tropical and subtropical moist/wet forests, on poor soils. In addition, these poor soils generally have high possibility for erosion and are high area s of biodiversity. Combining these conditions with the development of high levels of i ron and aluminum greatly reduces the fertility of the soil. This makes regeneration and reforestation on lands once farmed for coffee difficult. Though reforestation and regeneration have proven challenging in abandoned agricultural land, efforts are being made, and thro ugh experience, knowledge of what works, and what does not is being gained. By looki ng at the results of this study through a wider lens, some conclusions can be made. Organi c farming appears to have the lowest impact on originally existing soil nutrients and is most similar to the conditions of the forest. Cow pastures, though significantly alter l evels of certain nutrients, can actually make soil more fertile. With proper treatment with fertilizer, these areas can maintain cattle and productivity for years. Long-term coffe e farming on an area has the potential of being perhaps the most detrimental. By taking o ver originally forested areas, erosion risks are greater, and higher levels of biodiversit y are threatened. The high levels of
aluminum and iron leave the soil more toxic, and re duce opportunity for successful productivity in the future. Though positive efforts towards regeneration and re forestation in abandoned agricultural land, such as planting native seedling s and implementing bird perches, continue to be made, they cannot bring forests back to life if the soil beneath has been too heavily depreciated. This would be the worst outco me for agriculture. Soil is the base upon which so much of life depends. Poor practices of farmers, and excessive human consumption for certain tropical products, could le ad to decreases in surrounding biodiversity and soil devoid of necessary nutrients Changes need to be made for future agriculture to be productive alongside the success of future biodiversity. Smarter choices need to be made concerning farming techniques, soil specific farming needs to be implemented whenever possible, and certain crops ne ed to be cultivated less as to not compromise what deserves to be offered equally to g enerations to come. ACKNOWLEDGEMENTS Thank you to Alan Masters who continued to be patie nt, helpful and flexible throughout my many project adjustments and alterations. Thank you to Milton B renes Salazar who never was hesitant to help my wit h all my projects and offer new ideas. Thank you to Pablo for general assistance, and thank you to Taeg an for kindly explaining how to write a scientific pap er. And thank you to the farmers of Finca la Bella in San Luis. LITERATURE CITED AMELUNG, T., & DIEHL, M., 1992. Deforestation of tropical rainforests: econom ic causes and impacts on development. Mohr, Tubingen, Germa ny. ANDERSON, J.M., & INGRAM, J.S.I.1993. Tropical Soil Biology and Fertility: A Handbo ok of Methods, Second Edition. CAB International. Wa llingford, UK. BLUM, W.H. 1998. Basic concepts: Degradation, resilience, and rehabilitation. p. 1-17. In R. Lal et al. (ed.) Methods for assessment of soil degradation. Advances in soil science. CRC Press, Boca Raton, FL. BUSCHBACHER, R., UHL, C., SERRAO, E. A. S., 1988. Abandoned Pastures in Eastern Amazonia II Nutrient Stocks in the Soil and Vegeta tion. Journal of Ecology. 76, 682-699. GREENLAND, D.J., WILD, A., & ADAMS, D. 1992. Organic Matter Dynamics in Soils of the Tropics-From Myth to Complex Reality. Myths and S cience of Soils in the Tropics. 29:17-34. HOLL, KAREN D. 1999. Factors Limiting Tropical Rain Forest Regen eration in Abandoned Pasture: Seed Rain, Seed Germination, Mi croclimate, and Soil. HOLL, KAREN D., LOIK, MICHEAL E., LIN, ELEANOR H., SAMUELS, IVAN A., 2000. Tropical Montane Forest Restoration in Costa Rica: Overcoming Barriers to Dispersal and Establishment. Restoration Ecology V ol. 8 No. 4, pp. 339-349. Biotropica 31(2): 229-242. LAMOTTE SOIL HANDBOOK, 1994. LaMotte Company. Chestertown, MD. LARSON, W.E., & PIERCE, F.J. 1994. The dynamics of soil quality as a measurement of sustainable management. P. 37-51. In J.W. Doran et al. (ed.) Defining soil quality
for a sustainable environment. SSSA Spec. Publ. 3 5. SSSA and ASA, Madison, WI. MARTINEZ-SANCHEZ, J.L., & SANCHEZ-BELTRAN, S. 2003. The effect of time of use of tropical pastures on soil fertility and cattle pro ductivity. Ecotropicos 16(1):17-26. MATSON, P. A., PARTON, W. J., POWER, A. G., SWIFT, M. J. 1997. Agricultural Intensification and Ecosystem Properties. SCIENCE. Vol. 277. REINERS, W.A., BOUMAN, A.F., PARSONS, W.F.J., KELLE R, M. 1994. Tropical rain forest conversion to pasture changes in vegetation and so il properties. Ecological Applications. 4(2)pp. 363-377. RICHARDS, P.W. 1981. The Tropical Rain Forest. University Press, C ambridge. SANCHEZ, P.A., 1976. Properties and management of soil in the Trop ics. John Wiley & Sons, New York, New York. SMITH, NIGEL J. H., WILLIAMS, J.T., PLUCKNETT, DONA LD L., TALBOT, JENNIFER P., 1992. Tropical Forests and their Crops. Cornell Universi ty Press, Ithaca and London. STALLAND, KATIE. 2006. Different Agricultural Management Practices Concerning Soil Fertility: case studies of six rural Monteverde fa rms. CIEE, Spring. University of Wisconsin-Madison. TERBORGH, JOHN, 1992. Diversity and the Tropical Rain Forest. Scien tific American Library, New York. WANDER, MICHELLE M., WALTER, GERALD L., NISSEN, TOD D M., BOLLERO, GERMAN A., ANDREWS, SUSAN S., CAVANAUGH-GRANT, and DEBORAH A. 2002. Soil Quality: Science and Process. Agron J. 94: 23-32. (http://soils.usda.gov/technical/classification/ord ers/andisols.html). FIGURES
nrrnrr FIGURE 1. Soil pH for different land uses and fores t in San Luis de Monteverde, Costa Rica. Three samples were taken per land use and an alyzed using LaMotte soil tests. Coffee (6.3); Cow (5.4); Organic (7.2); Forest (7). Standard error bars are shown. FIGURE 2. Soil nitrogen content for different land uses and forest in San Luis de Monteverde, Costa Rica. Three samples were taken p er land use and analyzed using LaMotte soil tests. Coffee (56.7); Cow (133.3); Or ganic (53.3); Forest (73.3). Standard error bars are shown
nrrnrr nrrnrr FIGURE 3. Soil Phosphorous levels for different lan d uses and forest in San Luis de Monteverde, Costa Rica. Three samples were taken p er land use and analyzed using LaMotte soil tests. Coffee (166.7); Cow (103.3); Or ganic (200); Forest (200). Standard error bars are shown. FIGURE 4. Soil Potassium levels for different land uses and forest in San Luis de Monteverde, Costa Rica. Three samples were taken p er land use and analyzed using LaMotte soil tests. Coffee (240); Cow (393.3); Org anic (240); Forest (73.3). Standard error bars are shown.
nrrnrr nrrnrr FIGURE 5. Soil Aluminum levels for different land u ses and forest in San Luis de Monteverde, Costa Rica. Three samples were taken p er land use and analyzed using LaMotte soil tests. Coffee (56.7); Cow (6.7); Orga nic (6.7); Forest (5). Standard error bars are shown. FIGURE 6. Soil Iron levels for different land uses and forest in San Luis de Monteverde, Costa Rica. Three samples were taken per land use and analyzed using LaMotte soil tests. Coffee (13.3); Cow (8.3); Organic (5); Fore st (6.7). Standard error bars are shown.