Data on rates of atmospheric deposition is limited in many montane ecosystems, where high spatial variability in meteorological, topographic, and vegetation factors contributes to elevated atmospheric inputs and to the creation of deposition hotspots. Addressing the ecological consequences of increasing deposition in these areas will require a better understanding of surface controls influencing atmospheric deposition rates at both large and small-scales. The overarching objective of this thesis research was to understand the influence of vegetation structure and canopy exposure on small-scale patterns of atmospheric sulfate, nitrate, and chloride deposition inputs to a conifer forest in the Santa Cruz Mountains, California. Throughfall ion fluxes (i.e., ions delivered in water that pass from the forest canopy to the forest floor), bulk deposition (i.e., primarily wet deposition), and rainfall data were collected during the rainy period from October 2012 to May 2013. Throughfall SO42-, Cl-, and NO3- fluxes were measured beneath eight clusters of Douglas fir (Pseudotsuga menziesii) trees (three trees per cluster) differing in tree size (i.e., diameter at breast height; DBH) and canopy exposure. In each cluster, a throughfall collector was placed 1-meter from the bole of an individual tree, for a total of 24 individual collectors. The position of each throughfall collector was recorded with a Trimble® GPS. In addition, tree height, tree diameter, and leaf area index, were measured for all trees. LiDAR data were obtained from GeoEarthScope’s Northern California Airborne LiDAR project and used to model the elevation (DEM), canopy surface height (DSM), tree height (CHM), slope, and curvature of the canopy surface across the entire study area. Over the rainy season, total throughfall flux of SO42--S, a conservative tracer of total deposition (wet + dry + fog), to Douglas fir clusters ranged from 1.44 - 3.84 kg S ha-1 wet season-1, while dry and fog deposition ranged from 0.13 -2.37 kg S ha-1 wet season-1. Total deposition to exposed mature tree clusters was 1.7-2.7 times higher than other clusters. Patterns of total Cl- fluxes (17.10 – 54.14 kg Cl- ha-1 wet season-1) resembled patterns of total SO42--S inputs. Overall, net throughfall fluxes (throughfall – bulk deposition) to Douglas fir trees clusters were more variable than total throughfall fluxes. Net SO42--S and Cl- fluxes to individual collectors increased with tree DBH and the convexity of the canopy surface. Compared to SO42--S and Cl- in throughfall, total NO3--N fluxes (0.17 - 4.03 kg N ha-1 wet season-1) were low and appeared to vary with small-scale changes in elevation. Geospatial technologies and remote sensing tools, such as LiDAR, are promising in the study of relationships between atmospheric deposition and topography (including vegetation), and in scaling-up estimates of atmospheric deposition to larger spatial scales. Understanding small-scale surface controls on atmospheric deposition has implications for different areas of research within geography, including modeling the spread of emerging infectious disease and assessing the effects of nitrogen cycling on native and invasive plant species composition.

Nigeria is the most densely populated country in Africa and one of the most advanced economically in terms of both industry and soil and landscape utilization. This country is projected to have one of the largest urban growth rates by 2050. Thus, the demands of the rapidly increasing human population and its material consumption represent a severe threat to biodiversity. Nigeria has the highest deforestation rate of natural forest in the world, its original vegetation has largely been replaced by farming activities, urban development and other products of human activities. The principal causes of the decline and loss of biodiversity in Nigeria include human exploitation of natural resources, fragmentation of habitats and populations, conversion of wild areas to agriculture and other intensive human use and alterations in the structure and function of ecosystems. Amphibians are the vertebrate group with the highest number of species threatened with extinction and habitat loss and fragmentation are considered to be among the leading causes of their declines and extinctions. It has been recognized that one of the most severe problems in conservation biology is the scarcity of baseline data. Such lack prevents evaluation of the effect of the expanding anthropogenic impact and determination of potential population declines. The mountains of eastern Nigeria, within Taraba State, are regionally important in terms of biodiversity and endemism, however, its herpetofaunal diversity has received little attention. Moreover, no studies have investigated how habitat loss and fragmentation may affect dispersal and gene flow among small and isolated amphibian populations, and in the absence of such studies attempts at amphibian conservation are compromised. The aims of this project were threefold. Firstly, a comprehensive inventory of the amphibians and reptiles of Ngel Nyaki and Kurmin Danko Reserve on the Mambilla Plateau was compiled. The outcome, an annotated list of 21 amphibians and 11 reptiles, represent the most thorough inventory to date of the herpetofauna on the Mambilla Plateau. Based on this inventory four key anuran species were selected to conduct a population genetics study. Secondly, molecular tools specifically AFLP markers were developed and used to analyze the genetic population structures of the four frog species Cardioglossa schioetzi, Leptodactylodon bicolor, Astylosternus sp. 1 and Astylosternus sp. 2. differing in geographic distribution and life history traits within the study area. Thirdly, these species were assessed to understand dispersal and connectivity among fragmented and continuous populations on the Ngel Nyaki and Kurmin Danko Reserve. Genetic differentiation among the forest and the riparian fragment populations was observed for three of the target species, however, no significant genetic differentiation was detected among the populations located in continuous forest for any of the four frog species. In addition, geographic and genetic distances were not correlated significantly for any of the four target species, suggesting no isolation by distance at this fine geographic scale. Results from both the inventory and the genetic population structure study revealed that the riparian forest fragments are of utmost importance for the persistence and migration of Cardioglossa schioetzi, and potentially for many other amphibian species. The new scientific findings are now part of the valuable baseline data on the diversity and genetic population structure of amphibian species in Ngel Nyaki and Kurmin Danko Forest Reserve. These results will better inform conservation managers who need to make decisions around management of montane habitat for amphibian species.

The Cameroon Highlands that run along the Cameroon-Nigeria border are an important source of biodiversity. Not only are they rich in species and high in endemics, but biota from West Africa have not been studied as extensively relative to other parts of the Afrotropics, or the tropics in general. Threatening these rare and diverse habitats is anthropogenic pressure, which fragments forests and changes local animal communities. This thesis wished to address the impact of humans on seed dispersal and recruitment processes on selected tree species in forests on the Mambilla Plateau - a montane region in Nigeria's north-east. Research was conducted at Ngel Nyaki Forest Reserve, a conservation area established by the Nigerian Montane Forest Project. The reserve comprises a moderately-large forest patch (Ngel Nyaki Forest) and many small riparian fragments embedded in a grassland matrix. Cattle grazing and burning of this grassland are major threats to the survival of forest in this area.Hunting of local wildlife for bushmeat is also of concern, considering many of the region’s large-mammalian fauna are now locally extirpated (e.g. elephants) or at low abundances (many primate species). Loss of large-bodied frugivorous species has the potential to negatively impact the recruitment of large-seeded tree species that solely rely on them as seed dispersers. In this study, the ability for scatterhoarding rodents to act as surrogate dispersers for large-seeded species is tested. While much research has been carried out on secondary rodent dispersal in the Neotropics, work in the Afrotropics is still in its infancy. Because the outcome of plant-rodent interactions (i.e. predated or dispersed) may vary with season, habitat, or traits of the seed species in question, a number of experiments were established to quantify how local rodents at Ngel Nyaki may or may not be acting as effective dispersers. Additionally, the benefits of rodent dispersal were examined by creating an experiment that simulated secondary dispersal on seedling recruitment. The results of this study demonstrated that rodents can act as effective dispersers in Afromontane forests, but this is influenced by habitat, seasonal abundance of resources, and palatability of seed species. Furthermore, it was demonstrated that burial of seeds by rodents can increase the establishment probability of a seed by protecting it from removal by other rodents. However, while rodents play a strong driver of seed survival, it was also demonstrated that seedling mortality factors (such as herbivory) can also be heavy filters to seedling success. It is hoped that the results of this study will help to inform better management decisions and understand how the composition of the forest might change in the future.

O trabalho foi realizado na Floresta Ombrófila Densa Montana (Núcleo Santa Virgínia - Parque Estadual da Serra do Mar, São Paulo, situado entre 2317 a 2324S e 4503 a 4511W), com o objetivo de avaliar como as variações micro-ambientais de solo, liteira e topografia influenciam a composição e estrutura da comunidade de palmeiras. Em duas parcelas permanentes de um hectare, A e B, divididas em três transecções de 10x100 m e subparcelas de 10x10m, foram levantadas todas as palmeiras existentes com o propósito de conhecer a riqueza das espécies e estrutura das populações. Nas sub-parcelas amostras de solo foram coletadas para a determinação das propriedades química e física do solo; a espessura de liteira foi determinada em cinco pontos aleatórios; e a microtopografia de cada uma foi classificada em cume, vertente e vale. Nas duas parcelas (A e B) foram amostrados 3161 ind./0,6 ha e quatro espécies: Euterpe edulis, Geonoma gamiova, Geonoma pohliana e Geonoma schottiana. A fração dominante do solo ao longo de todos transectos foi a areia, em especial nos vales. A camada de liteira variou de espessura entre as classes topográficas. As variáveis K, P, Ca e Mg apresentaram baixos teores nas parcelas e conseqüentemente também foram baixos os teores da soma de bases. A saturação por bases foi baixa nas parcelas devido a alta concentração de Al e a baixa fertilidade do solo. A heterogeneidade micro-ambiental ocasionou variação na distribuição e composição de apenas algumas espécies de palmeiras, em especial o gênero Geonoma, apesar do maior número de indivíduos da E. edulis. A elevada densidade das espécies de palmeiras estudadas são indícios que as mesma estão adaptadas a condições de alta acidez, baixa fertilidade e umidade dolo, podendo ser indicadoras de alto potencial de seu emprego para recuperação de áreas degradadas em especial nas encostas e topos de morro. / The work was conducted in tropical montane rain forest (Núcleo Santa Virginia State Park of Serra do Mar, São Paulo, Brazil, situated in 23172324S and 45034511W), in order to assess how the micro-environmental variations of soil, topography and litter affect the composition and structure of the palm community. In two one hectare permanent plots, A and B, divided into three transects (10x100 m) and subplots (10x10m), it were surveyed all existing palms with the purpose of to know the richness of species and population structure. In sub-plots soil samples were collected to determine the chemical and physical properties of soil, thickness of litter was determined in five random points, and microtopography of each one was classified into ridge, slope and valley. In the two plots (A and B) were sampled 3161 individuals/0.6 ha and four species: Euterpe edulis, Geonoma gamiova, Geonoma pohliana and Geonoma schottiana. The soil dominant fraction in all transects was the sand, especially the valleys. The thickness of the litter layer ranged in between topographic classes. The variables K, P, Ca and Mg showed low levels in the plots and consequently were also low the levels of the basis sum. The saturation basis was low in the plots due to high concentration of Al and low soil fertility. The micro-environmental heterogeneity caused variation in the distribution and composition of a few species of palms, especially the genus Geonoma, despite the larger number of individuals of E. edulis. The high density of palm species studied are indications that the same are adapted to conditions of high acidity, low fertility, and moisture soil, which could indicate a high potential for their use for restoration of degraded areas especially on hillsides and hilltops.

Made available in DSpace on 2016-12-12T20:12:28Z (GMT). No. of bitstreams: 1 PGEF13MA006.pdf: 206072 bytes, checksum: 949b28c15cbcab9aa759abd7c53e055a (MD5) Previous issue date: 2013-10-04 / This study was conducted in different fragments in Planalto Sul Catarinense distributed in along an altitudinal gradient. The objective of the first chapter was to identify local rarity patterns and its proportions, basing on characteristics of habitat range and population size. For this, a vegetational matrix of tree species abundance, from 11 sampling units distributed in different forest fragments in Planalto Sul Catarinense region, was elaborated. In each of sampling plots all living tree individuals with diameter at breast height (dbh) greater than or equal to 5cm were counted and identified. The local rarity patterns were defined through a grid of descriptors used to classify the species in four categories: NE = non-specific species; R1 = scarce euryecious species; R2 = non-scarce stenoecious species; R3 = scarce stenoecious species. From all 144 analyzed tree species, 92 (63.89%) were classified as non-specific (NE). The rarity form R1 demonstrated 5 (3.47%) species, the rarity form R2 showed 33 (22.92%) species and the form R3 had 14 (9.72%) species. The most important conditioning of rarity was habitat preference, i.e., stenoecious species, represented in rarities forms R2 and R3. The species classified in rarity form R3 are those that require the most concentrated efforts in conservation measures. In the second chapter the present study aimed to analyze how the distribution and the richness of rare tree species occurs along an altitudinal gradient, in Araucaria Forests fragments. For this, tree species (diameter at breast height ≥ 5 cm) were sampled in 10 forest fragments located on different altitudinal floors in Planalto Sul Catarinense region, totaling 10ha of sampling area. The species with only one or two individuals in at least one fragment were classified as rare. The species distribution was verified by a dendrogram constructed through the Jaccard floristic distance index and the UPGMA clustering algorithm. The total species richness per forest fragment and the number of rare species was compared among montane and upper-montane sub-formation by the Mann-Whitney (U) test. The relationship between the altitude and the values of total richness and number of rare species in each fragment were determined by simple linear regressions. The results indicated the formation of two groups of rare species, in function of the altitude floor. Despite the total richness of communities decreases with increasing altitude, the number of rare tree species did not change significantly. We conclude that in the Planalto Sul Catarinense region, the fragments of Araucaria Forest have different set of rare species according to altitude and that the reduction of the richness of communities with increasing altitudinal floor is not accompanied by a reduction in the number of rare species / Este trabalho foi realizado na região fito-ecológica do Planalto Sul Catarinense em fragmentos localizados em diferentes cotas altitudinais. O primeiro capítulo teve como objetivo identificar os padrões de raridade local e suas proporções, com base nas características de amplitude de habitat e tamanho populacional. Para isso, foi elaborada uma matriz vegetacional de abundância de espécies arbóreas a partir de 11 unidades amostrais distribuídas em diferentes fragmentos florestais na região do Planalto Sul Catarinense. Em cada unidade amostral foram contados e identificados todos os indivíduos arbóreos que apresentaram diâmetro na altura do peito (DAP) igual ou superior a 5 cm. Para definir os padrões de raridade local foi utilizada uma grade de descritores que classificou as espécies em quatro categorias: NE= espécies não-específicas; R1= espécies escassas eurióicas; R2= espécies não-escassas estenóicas; R3= espécies escassas estenóicas. Das 144 espécies arbóreas analisadas, 92 (63,89%) foram não-específicas (NE). A forma de raridade R1 apresentou cinco (3,47%) espécies, a forma R2 apresentou 33 (22,92%) espécies e a forma R3 apresentou 14 (9,72%) espécies. O condicionante mais importante da raridade foi a preferência por habitat, ou seja, espécies estenóicas, representadas nas formas de raridade R2 e R3. As espécies classificadas na forma de raridade R3 são as que mais necessitam concentração de esforços em medidas de conservação. O segundo capítulo buscou verificar como a distribuição e a riqueza de espécies raras ocorrem em fragmentos de Floresta Ombrófila Mista, ao longo de um gradiente altitudinal. Foram amostradas espécies arbóreas (diâmetro na altura do peito ≥ 5cm) em 10 fragmentos florestais localizados em diferentes pisos altitudinais do Planalto Sul Catarinense, numa área total de 10ha. As espécies que apresentaram número de indivíduos igual ou inferior a dois em pelo menos um fragmento foram classificadas como raras. A distribuição das espécies foi verificada por meio de um dendrograma construído a partir do índice de distância florística de Jaccard e o algoritmo de agrupamento UPGMA. A riqueza total de espécies por fragmento florestal e o número de espécies raras foi comparada entre as subformações Montana e Alto-Montana por meio do teste de Mann-Whitney (U). As relações entre a altitude e os valores de riqueza total e número de espécies raras em cada fragmento foram determinadas por meio de regressões lineares simples. Os resultados indicaram a formação de dois grandes grupos de espécies raras, em função do piso altitudinal. Apesar da riqueza total das comunidades diminuir com o aumento da altitude, o número de espécies raras não apresentou alterações significativas. Conclui-se que na região do Planalto Sul Catarinense, os fragmentos de Floresta Ombrófila Mista apresentam diferentes conjunto de espécies arbóreas raras de acordo com altitude e que a redução da riqueza das comunidades com o aumento do piso altitudinal não é acompanhado pela redução do número de espécies raras

This project was aimed at investigating behaviour and condition of the Yellow-breasted Boubou, Laniarius atroflavus, in response to habitat differences across core, edge and riparian Afro-montane forest habitats at the Ngel Nyaki Forest Reserve, Nigeria. This species is little known and conservation effort will require direction in identifying the habitat of best quality for their survival. The determination of habitat association using correspondence analysis of census data suggested strongest association with the riparian habitat, even though this habitat held the least overall avian biodiversity as determined from a modified Shannon index. L. atroflavus appeared not to hold territories in the core habitat. Territoriality, vocalisation and time budget showed trends indicating L. atroflavus were more abundant and fared better in the riparian habitat. In this habitat, there was a greater density of territories and a smaller mean territory size, better call quality in frequency bandwidth and duration, and increased displaying and foraging time in the riparian habitat. Difference in size, colour and growth-based measures of condition showed difference between sexes, but did not show a strong habitat effect – males were larger than females, yet females appeared to have better quality of yellow breast feathers for equal carotenoid concentration. The effect of nest predation risk as a predictor of habitat quality revealed nests in the riparian habitat had the greatest daily survival probability, and within this habitat nests established at lower heights survived longest. While the evidence pointed towards the riparian habitat being most suitable for L. atroflavus, this habitat sadly continues to suffer anthropogenic disturbance and this species’ IUCN listing as Least Concern was suspected be an over-estimation.

The tropical montane forest of Ecuador is one of the ‘hot spots’ of species diversity. Despite this great species diversity, there are forests in our study area, namely in the Zamora-Chinchipe province in southern Ecuador, which are being depleted at an alarming rate. For example, large areas are being permanently deforested for use as ‘pastureland ’. This development is typically characterized by intensive slash and burn activities for vegetation clearance. After clear cut and slash burning, pasture species are planted of which Setaria sphacelata and Melinis minutiflora, are the most common. However, forest clearing by slash burn for pasture production occurs in the region simultaneously with subsequent invasion of bracken fern (Pteridium arachnoideum) and re-colonization of secondary succession vegetation on abandoned pasture land. In this study, we will examine the effects that the above phenomena have on ecosystems, namely the effects associated with the conversion of natural forestland to pasture land, and the succession that occurs as a result. We will also examine how land use change affects the nutrient status of the soil. This study focuses specifically on the area called the ‘San Francisco Valley’, (3°58’ 30”S latitude, 79°4’ 25”W longitude), which lies between Loja and the Zamora-Chinchipe provinces in Ecuador. Field work for this study was carried out at 1,798 and 2,226 m a.s.l in the following sites: 1) the San Francisco Natural Forest (this area refers to the eastern part of Podocarpus National Park); 2) active pastures Type I (this area refers to the pastureland in front of the San Francisco Scientific Station ECSF, and are pastures that have existed for 50 years or more); 3) active pastures Type II (this area refers to the pastureland in Sabanilla sites, and are pastures that have existed for approximately 17 years); and 4) abandoned pastureland (affected by succession over a period of at least twenty years). Each land-use type consists of five plots of approximately 20 x 20m2. Five points in each plot were then chosen and later sampled (two sub-samples) according to the defined horizons and depth units, namely the organic layer and mineral top soil horizons. Organic layer (only on forest and succession sampling plots) were designated as LOf1, Of2/Oh1 and mineral top soil was sampled to a depth of a 0-10, 10-20, 20-30 cm. To quantify the effects of the impact that land use change has on the chemical characteristics of soil in the selected areas, we analyzed the following bio-elements: the pH value, soil organic carbon (SOC), the total nitrogen (TN), the effective cation exchange capacity (ECEC), as well as stocks of total and available macronutrients. In addition, we examined the biological characteristics such as carbon and nitrogen microbial biomass (MBC, MBN), basal respiration (BR), and nitrogen mineralization (Nmin) in organic layers and top mineral soils (0-30 cm) of the following: the San Francisco Natural Forest, ECSF pastureland, Sabanilla pastureland, and abandoned pastures affected by succession. The main results of this study can be summarised as follows: The soil pH value increased after forest-to-pasture conversion and tended to decrease with soil depth. Moreover, pastureland in the study that was fifty years or more, showed evidence of a decrease in pH values. This decrease in pH value of the soil can be attributed to the reduction in exchangeable cations . However, they still remained higher than the pH values for the forest sites in the study. After the abandonment of pastureland, we observed a re-acidification in the soil of succession sites. This resulted in a decrease of base saturation . On the other hand, the total exchangeable base cation stocks were significantly higher for pasture soils compared with forest and succession soils. This was because of the addition of basic cations by ‘slash and burn activity ’. In this study, we observed that the greater values of soil organic carbon stocks occurred in forest sites. This can be explained by their high SOC value in the organic layer (73.9 Mg ha-1). However, the mineral layer (0 to 30 cm depth) of forest had a lower value than pasture and succession sites. This higher SOC stock of the mineral layer of our pasture sites are partly a result of carbon input from the former standing biomass. Likewise, in the mineral layers, we found that MBC content increases in a similar way to the SOC content. For example, when we compared the MBC content of forests with the pasture sites, we observed that pastures had approximately three times as much MBC. The results of nitrogen stored in the Microbial Biomass (MBN) showed the same tendency as the MBC values. Moreover, for organic layers, the total nitrogen stocks of forest were higher compared to succession sites. On the other hand, for mineral soil (0 to 30 cm depth), nitrogen stocks increased after forest to pasture conversion. This increase is partly due to the burning of aboveground biomass and the subsequent death of roots. Furthermore, the values of nitrogen stocks decreased again in succession sites (4.2 Mg N. ha-1), with similar values those of forests (4.4 Mg N. ha-1 ). Our results show that the slash-and-burn practice leads to a significant increase of P stock. We found that stocks of total phosphorus were significantly higher in the mineral topsoil (0–30 cm) of 50 year-old pastures (ECSF) than in the 17 year-old pastures (Sabanilla). It is important to note that the P stocks in the mineral soil of the abandoned pasture (20 year-old pasture sites) tend to return to forest values (399.9. Kg.ha-1). Nevertheless, the results show very low values of available P on both pastures and succession sites compared with forest sites. In the organic layers, our results show significant differences in the values of basal respiration between forest and succession sites. This indicates that the level of CO2 was greater in the selected forestland due to an increase of organic material. This essentially means that there was an increase of micro-organisms in the soil and subsequently an improved nutrient cycle . For the mineral soil, however, the results only showed a significant difference of 0-10 cm depth in the ECSF pastures and forests. In our study, we did not find any significant differences in the net nitrogen mineralization values in the four studied areas. Nevertheless, the results show that net nitrogen mineralization values decrease systematically according to the depth of the land uses. Summarizing, after the conversion of forest to pasture, there was an increase of the value of bio-elements in the mineral layers at both pasture sites. However, this increase was higher in 50 year old pastures (ECSF) than in the 17 year old pastures (Sabanilla). In addition, we noticed that after 20 years of the abandonment of pastures, most measured soil properties returned to the old-growth forest levels. / El bosque montano tropical de Ecuador es uno de los \"puntos calientes\" de diversidad de especies. Pero el bosque primario en el área de investigación (la provincia de Zamora Chinchipe al Sur de Ecuador) se está perdiendo a un ritmo alarmante. Grandes áreas están siendo permanentemente deforestadas para su uso como tierras de pastoreo. Este proceso se caracteriza por el uso intensivo de fuego para desmonte de la vegetación. Después de la quema y roza, se plantan especies de pastos entre las que Setaria sphacelata y Melinis minutiflora son las más comunes. Sin embargo, la quema y tala del bosque para la conversión a zonas de pastos ocurre simultáneamente con la subsecuente invasión del helecho común (Pteridium arachnoideum), produciéndose. La difusión de esta maleza y la decreciente productividad de los pastos (especialmente Setaria spacelata y Melinis minutiflora) conducen a que las tierras se utilizan en pastoreo hasta que la tierra se agota de nutrientes y luego se abandonan. En este estudio, se examinan los efectos que los fenómenos anteriormente mencionados tienen sobre los ecosistemas; a saber, los efectos asociados a la conversión de bosques naturales en tierras de pastoreo y la posterior sucesión de los pastizales; además de cómo el cambio de uso del suelo afecta el estado nutricional de los suelos del sur del Ecuador. El estudio se sitúa en la zona del valle de San Francisco (3°58’ 30”S latitud, 79°4’ 25”W longitud), entre Loja y Zamora Chinchipe, provincias que se encuentran en el sur de Ecuador. El trabajo de campo se llevó a cabo a una altura entre 1,798 y 2,226 m s.n.m.; en: 1) las áreas de bosque natural San Francisco (esta área se refiere a la parte oriental del Parque Nacional Podocarpus); 2) pasto activos Tipo I (esta área se refiere a los pastos en frente de la Estación Científica San Francisco ECSF, y son pastizales que tienen más de 50 años de edad); 3) pastos activos Tipo II (esta área se refiere a los pastos en los sitios de Sabanilla, y son pastizales que existen desde hace aproximadamente 17 años); y 4) pastos abandonados bajo vegetación de sucesión (más de 20 años de edad). Cada tipo de uso de la tierra consistió en cinco parcelas de aproximadamente 20 x 20 m2; se eligieron cinco puntos en cada parcela y se tomaron muestras (dos sub-muestras) de acuerdo con los horizontes orgánico y mineral. Las capas Orgánicas (solo presentes en el bosque y en los sitios de sucesión) se identificaron como LOf1, Of2/Oh1 y las capas minerales se muestrearon hasta los 0-30 cm de profundidad del suelo. Para cuantificar los efectos del impacto del cambio del uso de la tierra en las características químicas del suelo, se analizó los siguientes bio-elementos: pH, carbono orgánico del suelo (COS), nitrógeno total (Nt), la capacidad de intercambio catiónico efectiva (CICE), así como las reservas del contenido total y disponibilidad de los macro nutrientes. Además, las características biológicas, tales como el carbón (MBC) y nitrógeno (MBN) de la biomasa microbiana, la respiración basal (Rb) y la mineralización de nitrógeno (Nmin) en las capas orgánicas y en la capa mineral del suelo (hasta -30 cm) de los bosques naturales, pastos y pastizales abandonados bajo vegetación de sucesión. Los principales resultados del estudio se describen a continuación: El valor de pH del suelo indica una elevada acidez, después de la conversión de bosque a pastos y tiene una tendencia general a disminuir con la profundidad del suelo, cuando los pastos se hacen más viejos (más de 50 años de edad); los valores de pH del suelo disminuye como consecuencia de la lixiviación de cationes intercambiables, pero siguen siendo superiores a los valores de pH de los sitios del bosque. Tras el abandono de los pastos se observó una re-acidificación en el suelo de los sitios de sucesión, lo que resulta en una disminución de la saturación de bases. Los resultados además indican que las capas orgánicas, especialmente en los suelos de los bosques, almacenan una cantidad importante de potasio, calcio y magnesio. Sin embargo, las reservas totales de cationes básicos intercambiables fueron significativamente mayores en los suelos de los pastizales que en los bosques y que los suelos de sucesión, debido a la adición de cationes básicos producidos por la tala y quema usada en la conversión de bosques a pastizales. En este estudio, se encontró que los mayores valores de reservas de COS se producen en zonas forestales, que se corresponde con un alto valor en la capa orgánica (73,9 Mg C ha-1). Sin embargo, la capa mineral (hasta - 30 cm de profundidad) de los suelos del bosque tiene un valor menor en comparación con los valores de los pastos y sucesión. Este alto contenido de COS en los pastos, se debe en parte al ingreso de carbono desde la biomasa. Asimismo, en las capas minerales, se encontró que el contenido de carbono en biomasa microbiana (CBM) aumenta de una manera similar al contenido de carbono orgánico del suelo (COS). Por ejemplo, cuando comparamos el contenido de CBM de los bosques con los sitios de pastoreo, se observó que los pastos tenían aproximadamente tres veces más MBC. El resultado de nitrógeno almacenado en la biomasa microbiana (NBM) mostró la misma tendencia que los valores de CBM. En las capas orgánicas, las reservas totales de nitrógeno de los bosques fueron mayores en comparación con los sitios de sucesión. Por otro lado, en el suelo mineral (hasta -30 cm de profundidad) las reservas de nitrógeno aumentan después de la conversión de bosques a pastizales. Este incremento es parte debido a la quema de la biomasa superior y de la subsecuente muerte de las raíces. Además, los valores de las reservas de nitrógeno disminuyen de nuevo en los sitios de sucesión (4.2 Mg N. ha-1), a valores similares a las del bosque (4.4 Mg N. ha-1 ). Nuestros resultados muestran que las prácticas de quema y tala incrementan significativamente las reservas de fosforo, encontramos que las reservas de fosforo total fueron significativamente altas en las capas minerales (- 30 cm) de los pastos de 50 años (ECSF), seguido de los pastos de 17 años de edad (Sabanilla). Es importante notar que las reservas de fosforo en las capas minerales de los suelos de pastos abandonados (20 años de edad) tienden a retornar a los valores del bosque (399.9. Kg.ha-1). Sin embargo, los resultados muestran valores muy bajos de fosforo disponible en ambos sitios de pastos y sucesión comparado con el bosque. En las capas orgánicas, los resultados revelan diferencias significativas en los valores de la respiración basal (potencial) entre el bosque y la sucesión. Esto indica que el nivel de CO2 fue mayor en el los sitios de bosque debido a un aumento de la materia orgánica. Esto implica un aumento de los microorganismos en el suelo y, posteriormente, una mejora en el ciclo de nutrientes. En el suelo mineral, los resultados sólo muestran una diferencia significativa en la profundidad de 0-10 cm entre los pastos ECSF con los bosques. En nuestro estudio, no se encontró diferencias significativas en los valores de mineralización neta de nitrógeno entre las cuatro áreas estudiadas. Sin embargo, los resultados muestran que los valores netos de mineralización del nitrógeno disminuyen sistemáticamente con la profundidad en todos los usos de los suelos estudiados. En resumen, después de la conversión de bosques en pastizales, se produjo un incremento del valor de los bio-elementos en las capas minerales de ambos sitios de pastoreo. Sin embargo, este aumento fue mayor en los pastos de 50 años de edad (ECSF) que en los pastos de 17 años de edad (Sabanilla). Además, los resultados muestras que después de 20 años del abandono de los pastos, la mayoría de los parámetros medidos retornan a valores similares a los de los sitios de bosque. / Im globalen Kontext stellt der tropische Bergregenwald in Süd-Ecuador ein „Hotspot“ der Biodiversität dar. Im Untersuchungsgebiet ist die enorme Artenvielfalt durch die massive Zerstörung der natürlichen Waldökosysteme gefährdet. Der Wald wird durch intensive Brandrodung großflächig in Weideland umgewandelt. Im Laufe der Weidenutzung kommt es auf den Weideflächen zu einer zunehmenden Ausbreitung und Dominanz des tropischen Adlerfarns (Pteridium arachnoideum). Die Farnausbreitung und die abnehmende Produktivität der Weidegräser insbesondere von Setaria sphacelata und Melinis minutiflora, führt zum Verlassen der Weiden und zur Etablierung neuer Weideflächen durch fortgesetzte Brandrodung des Naturwaldes. Aufgelassene ehemalige Weideflächen unterliegen einer sekundären Sukzession. Innerhalb dieser Studie wurden die Effekte der Umwandlung des Naturwaldes in Weideland, der Weidenutzung sowie der Wirkungen der sekundären Sukzession nach dem Verlassen unproduktiver Weideflächen auf die Nährstoffsituation der Böden untersucht. Die Untersuchung erfolgte im Gebiet des „San Francisco Tales“, (3°58’ 30”S, 79°4’ 25”W), welches sich zwischen den beiden Provinzen Loja und Zamora-Chinchipe in Ecuador befindet. Feldarbeiten innerhalb dieser Studie wurden in einer Höhe zwischen 1798 und 2225 m NN in den folgenden Bereichen ausgeführt: 1) Naturwald in San Francisco; 2) aktive Weidefläche Typ I (seit circa 50 Jahren in Nutzung); 3) aktive Weidefläche Typ II (seit circa 17 Jahren in Nutzung); und 4) verlassenes Weideland (bestimmt durch sekundäre Sukzession seit mindestens 20 Jahren). Jeder Landnutzungstyp besteht aus fünf Plots mit einer Ausdehnung von circa 20 x 20 m. Fünf Punkte innerhalb eines jeden Plots wurden zur Beprobung ausgewählt. Die organische Auflage (Naturwald, verlassenes Weideland) wurde nach Auflagehorizonten (LOf1 und Of2/Oh) und der Mineralboden nach Tiefenstufen (0-10 cm, 10-20 und 20-30 cm) getrennt beprobt. Um die Effekte und den Einfluss des Landnutzungswandels auf chemische Bodenkennwerte zu quantifizieren, wurden die folgenden Indikatoren untersucht: pH, organischer Kohlenstoffgehalt des Bodens (SOC), Gesamtstickstoff (TN), effektive Kationenaustauschkapazität (CECeff) sowie Vorräte der gesamten und pflanzenverfügbaren Makronährelemente. Zusätzlich wurden bodenbiologische Indikatoren wie Kohlenstoff und Stickstoff der mikrobiellen Biomasse (MBC, MBN), Basalatmung (BR) und Stickstoffmineralisation (Nmin) in den organischen Auflagehorizonten und dem mineralischen Oberboden (0-30 cm) wie folgt untersucht: Naturwald in San Francisco, ECSF Weideflächen, Sabanilla Weideflächen und aufgelassene, von der Sukzession beeinflusste Weiden. Die hauptsächlichen Resultate der Untersuchung können wie folgt zusammengefasst werden: Der pH-Wert des Bodens erhöhte sich nach der Umwandlung von Wald zu Weide und zeigt mit zunehmender Tiefe einen abnehmenden Trend. Darüber hinaus nahmen die pH-Werte von der 17 Jahre alten zur 50 Jahre alten Weide ab. Diese Abnahme kann auf den Rückgang austauschbarer Kationen zurückgeführt werden. Dennoch verblieb der pH-Wert in den 50 Jahre alten Weiden oberhalb des pH-Wertes der im Wald beprobten Flächen. Nach dem Auflassen der Weiden wurde eine erneute Versauerung des Bodens im Stadium der Sukzession beobachtet. Dieser pH-Rückgang wird durch einen Abnahme der Basensättigung begleitet. Auf der anderen Seite waren die Vorräte an austauschbaren Basen der CECeff auf den Weideflächen signifikant über denen der Wald- und Sukzessionsflächen. Ursächlich dafür war die Freisetzung basischer Kationen während der Brandrodung des Naturwaldes. Innerhalb dieser Studie wurden die höchsten Vorräte an Bodenkohlenstoff im Naturwald ermittelt. Das kann durch hohe Vorräte an SOC in der organischen Auflage (73.9 Mg ha-1) erklärt werden. Allerdings waren die Vorräte im Mineralboden (0-30 cm) des Waldes geringer als auf den Weide- und Sukzessionsflächen. Diese höheren SOC-Vorräte im Mineralboden der Weideflächen sind teilweise das Resultat der höheren Kohlenstoffzufuhr durch Reste der oberirdischen Biomasse. Der Gehalt an mikrobiellem Biomassekohlenstoff nahm in ähnlicher Art und Weise wie der des bodenbürtigen organischen Kohlenstoffs zu. Beispielsweise wurde beim Vergleich von MBC und MBN-Gehalten des Waldes mit denen der Weide der dreifache Gehalt in der Weide gefunden. Außerdem waren die Stickstoffvorräte der organischen Auflagen im Wald höher als auf den Sukzessionsflächen. Andererseits nahmen die Stickstoffvorräte nach der Umwandlung von Wald zu Weide im Mineralboden (0-30 cm) zu. Diese Zunahme beruht zum Teil auf dem Abbrennen der oberirdischen Biomasse und dem anschließenden Absterben der Wurzeln. Des Weiteren verringerten sich die Stickstoffvorräte im Stadium der Sukzession (4.2 Mg N ha-1) und glichen sich wieder denen des Waldes (4.4 Mg N ha-1) an. Die Resultate zeigen, dass die Brandrodung zu einem signifikanten Anstieg der Phosphorvorräte führte. Vorräte des Gesamtphosphors waren in den mineralischen Oberböden (0-30 cm) der 50 Jahre alten Weide, gefolgt von der 17 Jahre alten Weide signifikant am höchsten. Zu betonen ist, dass die P-Vorräte im Mineralboden der aufgelassenen Weide dazu tendieren auf Werte des Waldes abzusinken (399.9 kg ha-1). Trotzdem zeigten die Ergebnisse sehr geringe Werte für pflanzenverfügbaren Phosphor in Weide und Sukzession im Vergleich zum Wald. In den organischen Auflagehorizonten wurden signifikante Unterschiede in der mikrobiellen Aktivität (Basalatmung) zwischen Wald und Weide gefunden. Das zeigt, dass das Niveau an C-Mineralisierung in der ausgewählten Waldfläche größer ist, was auf die erhöhte Verfügbarkeit der organischen Substanz zurückgeführt werden kann. Das bedeutet im Wesentlichen einen Anstieg der Mikroorganismen in den Böden und darauffolgend einen verbesserten Nährstoffkreislauf. Für den Mineralboden zeigten die Ergebnisse jedoch nur einen signifikanten Unterschied in einer Tiefe von 0-10 cm zwischen Wald und Weide. Signifikante Unterschiede in der Nettostickstoffmineralisation der vier untersuchten Gebiete konnten nicht gefunden werden. Nichtsdestotrotz zeigten die Ergebnisse, dass die Nettostickstoffmineralisation mit zunehmender Tiefe in den unterschiedlichen Landnutzungen abnimmt. Zusammenfassend kann festgestellt werden, dass nach der Brandrodung die Gehalte an Bioelementen im Mineralboden beider Weideflächen zunahmen. Dieser Anstieg war in den 50 Jahre alten Weideflächen (ECSF) sogar ausgeprägter als in den 17 Jahre alten Weideflächen (Sabanilla). Zusätzlich zeigte sich in den 20 Jahre alten Sukzessionsflächen, dass durch die Regeneration einer organischen Auflage ein positiver Effekt hinsichtlich erhöhter Vorräte an SOC und pflanzenverfügbarem Phosphor festgestellt werden konnte. Diese allmähliche Zunahme an Nährstoffen im Boden der Sukzession setzte sich fort, bis das Ausgangsniveau des Waldes wieder erreicht war.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20586号 / 農博第2238号 / 新制||農||1052(附属図書館) / 学位論文||H29||N5075(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 神﨑 護, 教授 北島 薫, 教授 井鷺 裕司 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Tropical soils are a globally important store of terrestrial carbon (C) and source of atmospheric carbon dioxide (CO2), regulated by the activity of soil microorganisms, through the mineralisation of plant residues and soil organic matter (SOM). Climatic warming will influence microbial activity, and this may accelerate the rate of C release from soils as CO2, contributing to alterations in current atmospheric composition, and generating feedbacks to climate change. Yet the magnitude of C loss from tropical soils remains uncertain, partly because we do not fully understand how non-climatic factors – including the chemistry of plant inputs, the availability of soil nutrients and the composition of the decomposer community – will interact to determine the response to changes in temperature. This thesis examines how these factors together regulate the rate of C cycling in contrasting soils across a 3400 m tropical elevation gradient in the Peruvian Andes, spanning a 20 ºC range (6.5 – 26.4 ºC) in mean annual temperature. Large-scale field-based manipulation experiments, translocating leaves and soil-cores across the elevation gradient (to impose an in-situ experimental warming treatment), were combined with controlled laboratory studies to examine the microbial-scale mechanisms which underlie the processes of decomposition and soil respiration observed in-situ. Results show that, across the gradient, rates of leaf-decomposition were determined principally by temperature and foliar chemical traits, while soil fertility had no significant influence. The effect of temperature was, however, stronger across higher-elevation sites, suggesting a greater vulnerability of the C-rich soils in montane systems to increased C loss under climatic warming. In lowland forests, the presence of invertebrate macrofauna also accelerated rates of decomposition, but leaf chemistry explained the greatest proportion of the observed variance, with a strong role for leaf chemical traits also identified under controlled conditions. Despite marked differences in microbial abundance and community composition among soils, these metrics were not associated with observed rates of decomposition. These results suggest that climate-related changes to plant species distributions (with associated changes to the chemistry of leaf-inputs), and upslope extension of macrofaunal ranges, could strongly influence future rates of leaf decomposition, independently of the direct response to warming. From the soil translocation study, root-soil interactions stimulated substantial net C loss from montane soils following translocation downslope (experimental warming treatment), indicating that warming-related changes to root productivity, exudation and/or species-composition could represent an important mode of future C loss from these soils. To examine more closely how inputs of plant-derived C influence the turnover of pre-existing SOM, and whether soil nutrient availability modulates the response, soils were amended with simple and complex 13C-labelled substrates in combination with inorganic nutrient treatments. Isotopic partitioning was used to determine the degree to which C and nutrient inputs accelerated (positive priming) or retarded (negative priming) the decomposition of SOM. Amendment of upper montane forest and montane grassland soils with nitrogen (N; alone and in combination with C) substantially retarded the decomposition of SOM, suggesting that microbial demand for N strongly regulates the turnover of organic matter in these soils. In contrast, amendment of lower montane and lowland forest soils with C stimulated positive priming of SOM, which was strongest in response to the simple C substrate and was not influenced by nutrient treatments, suggesting that microorganisms in these soils are primarily constrained by availability of labile C. Functional differences among microbial groups were also evident, with gram-negative bacteria and fungi using more labile sources of C while gram-positive bacteria used more complex C. Together, results from these studies considerably advance our understanding of soil C dynamics across lowland and montane systems, painting a rich picture of interacting processes which will determine the future soil C balance in tropical ecosystems. They show that the influence of temperature on the rate of soil C cycling is strongly affected by the nature and composition of plant-derived and atmospheric inputs, the principal additional constraints varying with elevation, leading to both opposing and reinforcing effects on rates of decomposition. The greater observed temperature sensitivity of decomposition at higher elevations is coupled with high microbial demand for N which regulates the turnover of SOM, whereas at lower elevations leaf decomposition is accelerated by active macrofaunal breakdown, while microbial decomposition of SOM is constrained by the availability of labile C. Under a global change scenario of increased temperature and N deposition, results therefore suggest that: (i) modified chemistry of plant inputs will influence rates of decomposition, independently of climate; (ii) increased availability of labile C will lead to more rapid decomposition of SOM at lower elevations; (iii) greater root productivity (associated with warming and plant-community shifts) will stimulate soil C loss across montane regions; but (iv) at higher elevations, a possible countervailing effect may be imposed on rapid warming-accelerated decomposition if increased N availability reduces microbial mineralisation of SOM. The net effect on the ecosystem C budget will depend on the balance of C gain from primary productivity and C loss from soils. Overall, however, the results presented here suggest that the large soil C stores in higher-elevation montane regions are particularly vulnerable to substantial reductions under exposure to short- and medium-term climatic warming.

Los suelos de los bosques tropicales desempeñan un papel importante en el clima de la Tierra mediante el intercambio con la atmosfera de grandes cantidades de gases de efecto invernadero (GEI). Sin embargo, esta importante función podría ser alterada por las actividades humanas causando el aumento en la deposición de nutrientes en los ecosistemas terrestres, especialmente en las regiones tropicales. Las causas de cómo el incremento de las cantidades de nutrientes está afectando los flujos de suelo de los GEI de los bosques tropicales es relativamente poco conocida, por ello los monitoreos de nutrientes in situ de los bosques montanos tropicales (BHT) son aún menos comprendidos. Ya que los BHT representan alrededor del 11-21% de la superficie forestal tropical, es de vital importancia predecir y cuantificar los cambios en los flujos de GEI del suelo en respuesta a la adición de nutrientes ya que podrían favorecer la retroalimentación a otros cambios globales. Esta tesis tiene como objetivo cuantificar el impacto de adición moderada de nitrógeno (N) y/o fósforo (P) en los flujos de tres GEI en suelo: dióxido de carbono (CO2), óxido nitroso (N2O) y el metano (CH4), a lo largo de un gradiente altitudinal (1000 m, 2000 m, 3000 m) de los BHT primarios en el sur de Ecuador. Desde hace más de cinco años, se ha medido los flujos de GEI del suelo en un experimento de manipulación de nutrientes (‘NUMEX’, por sus siglas en inglés), con replicas para control, y la adición de N (50 kg N ha-1 año-1), P (10 kg P ha-1 año-1) y N+P. Las mediciones in situ se realizaron mensualmente utilizando cámaras ventiladas estáticas, seguido por un análisis de cromatografía de gases para conseguir una perspectiva más profunda sobre los procesos implicados en el intercambio suelo-atmósfera de GEI. Se realizaron nuevas investigaciones incluyendo el monitoreo de factores básicos de control (i.e. temperatura del suelo, humedad y las concentraciones del N mineral), los diferentes componentes de los flujos de CO2 del suelo, tasas de reciclaje netos de N y fuentes de los flujos de N2O del suelo. Con este propósito, se utilizó la extracción de hojarasca y técnicas de excavación de zanjas (trenching technique), incubación de las muestras in situ (buried bag method) y el etiquetaje de 15N de corto plazo. Los flujos de GEI del suelo en los bosques que estudiados se mostraron en el rango de aceptado de los flujos de gases de otras BHT en elevaciones comparables, excepto para el N2O. Los flujos de N2O, que se derivan principalmente de la des nitrificación, fueron bajos para un TMF lo que se puede atribuir a los ciclos conservativos de N del suelo en nuestros sitios de estudios. Los suelos fueron fuentes de CO2 y N2O (la intensidad del recurso disminuye al aumentar la altitud) y en todas las elevaciones el CH4 es bajo. Encontramos efectos de los nutrientes en todos los flujos de GEI medidos en cada elevación. Las respuestas de los flujos de CO2 del suelo cambian con la duración y el tipo de nutrientes adicionado. En 1000 m, la adición del N no afecta los flujos de CO2 del suelo, mientras que las adiciones de P y N+P disminuyeron los flujos en el primer y cuarto a quinto año. En 2000 m., la adición de N y N+P incrementa los flujos de CO2 en el primer año; a partir de entonces, la adición del N disminuye los flujos mientras que la adición de N + P no mostro ningún efecto la adición de P carece de efectos. En 3000 m, la adición de N además incrementó los flujos de CO2 constantemente; la adición de P y N+P aumentaron los flujos sólo en el primer año a partir de entonces no existió ningún efecto. Los efectos diferenciales de los nutrientes estuvieron relacionados a un estatus del N y P y respuestas variadas de los componentes de la respiración del suelo. Las respuestas de los flujos de N2O y CH4 a la adición de nutrientes mostraron gran variabilidad entre años. Los flujos de N2O no se vieron afectados por la adición de tres a cinco años de N a pesar de las diferencias significativas observadas durante los dos primeros años del mismo experimento. Atribuimos la ausencia de las respuestas en años mas tardíos debido a los contenidos bajos de humedad del suelo en nuestro periodo de monitoreo 2010-2012. En todo el gradiente altitudinal, la adición de P disminuyó los flujos de N2O y las concentraciones de N mineral, presumiblemente debido a que alivió de la limitación del P en la producción primaria neta, lo que aumentó la captación de N a través de las plantas. La adición de N+P además mostró tendencias similares las respuestas a la adición de N solamente, pero con efectos menos fuertes debido a los efectos contrapuestos de la adición de P. Durante los dos primeros años de la adición de nutrientes, los flujos de CH4 no se vieron afectados en ninguna elevación, lo cual atribuimos a la combinación de cantidades moderadas de nutrientes añadidos, la fuerte inmovilización de nutrientes, y la separación de la más alta capacidad de absorción de CH4 en el subsuelo de la superficie del suelo donde se añaden fertilizantes. En el tercer a quinto año, la adición de nutrientes del suelo aumentaron la captación de CH4, aunque los efectos de N y P variaron a lo largo del gradiente altitudinal: en 1000 m, la adición de N y N+P aumentó la captación anual de CH4 a 20-60%; en 2000 m P y N+P incrementaron la captación a 21-50%; y en 3000 m la adición de P y N+P incrementó la captación de CH4 a 34-40%. Estos efectos diferenciales de la adición de nutrientes pueden estar relacionados con el estatus inicial de del suelo y respuesta diferenciales de otros componentes del ecosistema a la adición de nutrientes en cada elevación. Demostramos que los flujos de GEI del suelo y consecuentemente la red potencial de calentamiento global del suelo pueden cambiar considerablemente a lo largo de un gradiente de elevación, siguiendo una tendencia general de disminución con el aumento de la elevación. Los resultados indican además que la elevada deposición de N y P puede afectar los flujos de GEI del suelo en los BHT Andinos, pero las respuestas a los flujos de GEI a la adición de nutrientes depende del estatus inicial de los nutrientes del suelo, la duración de la adición de nutrientes y la variabilidad inter-anual de las condiciones climáticas. Puesto que los efectos de la adición de nutrientes fueron no lineares con el tiempo de exposición y a la par existen complejas interacciones con otros componentes del ecosistema, aún quedan muchas incertidumbres en la predicción exacta de los efectos de la deposición de nutrientes en los flujos de GEI. Sin embargo, ofrecemos los primeros datos sobre los efectos de nutrientes a medio plazo de N, P y N+P en los flujos de los tres principales gases de efecto invernadero del suelo a lo largo de un gradiente altitudinal de los BHT Andina. Nuestros resultados sugieren que la red potencial de calentamiento global de los suelos en todo el gradiente altitudinal podría aumentar ligeramente con la entrada contribución de N, mientras que podría disminuir con el aumento de la contribución de P y N+P.