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.

Zugl.: Berlin, Freie Univ., Diplomarbeit, 2003 u.d.T.: Piechowski, Daniel: Vegetationsstrukturanalyse unterschiedlich beeinflusster submontaner Regenwälder in Ecuador

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.

No description available.

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.

No description available.

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

Peat from the temperate regions has been used for paleoenvironmental reconstruction using diverse proxies for over a century now. Peat is rare and severely understudied in the tropics. The montane peat bogs of the Nilgiris, southern India have been found to preserve global climatic signals including the Holocene Optimum and the Last Glacial Maximum (LGM). At Sandynallah, one of the oldest peat accumulations in the world at >40 kyr BP, we had undertaken a high resolution paleoenvironmental reconstruction using multiple proxies which are yet to be evaluated in the tropical context. The study consists of 3 main objectives, i. Establishing an accurate high resolution chronology for the peat profile using radiocarbon dating, ii. Extracting vegetation and climate information from C/N ratio and Rock-Eval indices and iii. Using elemental profiles to establish the utility of inorganic geochemical proxies for processes such as weathering and dust transport. High resolution chronology for the site was built using Accelerator Mass Spectrometry (AMS) radiocarbon dates. To improve accuracy of the age-depth model, we also tested 4 samples for the effects of the AAA (Acid-Alkali-Acid) extraction method, the most common pre-treatment method for peat in the world. We compared ages on bulk samples (acid washed) and AAA treated samples from 4 different depths. We find that for all depths, the ages of the untreated samples do not lie within the internal uncertainty window and differ from the AAA treated sample age by at least an order of magnitude of the internal error, if not more. Based on these results we argue that the internal error should be used in conjunction with a reliable estimate of external error in an age-depth model for more realistic dating of paleoclimatic events. C/N ratios were explored for their paleoclimatic potential in conjunction with Rock-Eval indices and it was found that decomposition in tropical peat, as opposed to temperate peat, may not be sensitive to climatic perturbations. Inorganic geochemical proxies were also evaluated through this study. We see that the major and trace elements, except the lanthanide series do not show many significant trends for paleoenvironmental interpretation. But the lanthanides show some promise for identifying potential sources of dust and weathered material. Our study has addressed the gap in knowledge about the utility of recent geochemical proxies in tropical peat and has attempted to provide a solution to improve reliability in constructing age-depth models.

We reconstructed historical fire regimes of montane forest-grassland ecotones in the ~40,000 ha Valles Caldera National Preserve, New Mexico. We used a targeted approach to sample ancient fire-scarred trees along the ecotone, and compared variations in historical fire occurrence within and among valles in the grassland-forest. The resulting tree-ring record extends from 1240-2008 C.E., comprised of 2,443 fire scars from 330 trees representing 238 fire years during the period of analysis, 1601-1902 C.E. Our results confirm pre-1900 historical occurrence of high-frequency, low-severity surface fires over multiple centuries in the ecotone. Mean fire intervals for all fires were 5.5-22.5 years (~6-123 ha) at individual sites, 2.7-10 years (~67-4955 ha) in individual valles, and 1.6 years (~10 386 ha) across the landscape. Synchronous fires burned extensively and occurred at ~10 year intervals during years with significantly low PDSI. Results will be useful in planning forest/grassland restoration actions and reinstituting fire regimes.

Tropical montane cloud forests (TMCF) are one of the most fascinating, but least understood ecosystems in the world, and the interest in the carbon (C) cycle of TMCFs with regard to carbon sequestration and storage practices has increased rapidly in recent years. One feature that prevails in all TMCFs is a decrease in aboveground net primary productivity (ANPP) and standing biomass and leaf area index (LAI) with increasing altitude, together with the stunted growth form of the trees. This thesis focuses on the input part of the TMCF C-cycle, and investigates the controlling factors on photosynthesis on a leaf, canopy, and ecosystem level in the Kosñipata valley in south east Peru, on the eastern slope of the Andes (13º11’28’’S / 71º35’24’’W). Leaf traits are known to relate to foliar C-exchange, and compared with other altitudinal transect studies of TMCFs, the studied sites had similar altitudinal trends for foliar nitrogen (N) content (though not for phosphorus) and leaf mass per area (LMA), with N content decreasing and LMA increasing with altitude. N concentrations were relatively high and LMA values relatively low, but this observed relationship was consistent with those found in global leaf trait surveys. Examining plant stoichiometry (i.e. N:P ratios), the data suggests that unlike the general hypothesis, the Kosñipata forests are not N limited, except for the study site at 2990 m a.s.l. At the 2990 m a.s.l. site, which is the focal study site of the thesis, photosynthetic parameters Vcmax (the carboxylation efficiency of the Rubisco protein) and Jmax (the electron transport efficiency) proved to be similar to those found in lowland tropical rainforest leaves when expressed on an area basis and standardised to 25 °C (55.6 ± 2.6 and 106.5 ± 5.2 mmol m-2 s-1, for Vcmax and Jmax, respectively). However, when standardised to the mean ambient TMCF temperature of 12.5 °C, both photosynthetic parameters were much lower than ambient tropical rainforest Vcmax and Jmax values. The TMCF Jmax -Vcmax relationships were steeper than found in other tropical biomes, indicating a possible adaptation to the lower light availability in TMCFs because of frequent cloud cover, or a consequence of little atmospheric evaporative demand, which is also due to the humid conditions in this forest type. Although N-Vcmax relationships were significant (P<0.05), the fit was not very strong and the relationship between nitrogen use efficiency (NUE) and Vcmax indicates that TMCF species can be regarded as a different plant functional type compared with other tropical forest types. Diurnal measurements of net photosynthesis (A), stomatal conductance (gs) and leaf water potential (Yleaf) showed that different TMCF species experienced non-contrasting diurnal patterns of Yleaf and gs in the dry season. The observed patterns suggest that some TMCF species can be classified as isohydric species, while others behave anisohydrically. Additionally, in situ gs was not very responsive to these to the range of experienced photosynthetically active radiation (PAR), vapour pressure deficit (VPD) or soil water content (SWC), leading to the conclusion that in the studied TMCF, drought stress does not play a role in C-uptake. When using the measured photosynthetic parameters for up-scaling C-uptake to stand scale with a Soil-Plant-Atmosphere model, simulated annual gross primary productivity (GPP) was 16.24 ±1.6 T C ha-1 yr-1, which is about half the GPP observed in neotropical lowland rainforests. Analyses of the modelled results showed that GPP in this TMCF is mostly controlled by temperature, PAR and leaf area index (LAI) and when increasing these three factors to values found in tropical lowland forest, GPP increased up to 75%. In addition, the modelled results indicate that hydraulic limitations on TMCF C-uptake are very unlikely under current climatic conditions. The modelled results also showed that increases in radiation as a result of less cloud cover do not translate to straightforward increases of GPP. The cloudy conditions of TMCFs, which reduced incident PAR in TMCFs, should therefore not be regarded simply as a negative control on TMCF GPP. Instead, the increase in fraction of diffuse radiation partially offsets the decrease in GPP following the reduction in PAR. Overall, the results of this study show that leaves of Andean TMCF forests have similar C-uptake capacity to tropical lowland rainforests when standardized to similar temperatures, but that for in situ C-uptake temperature, radiation and LAI are the key controls.