Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surfac

Tropical montane cloud forest

Tropical montane cloud forests (TMCFs) are covered in clouds and fog, by definition, and are abundant with mosses, lichens and epiphytes. The hydrology of these ecosystems is poorly understood due to the extreme wetness, complex topography, and remoteness, TMCF are also susceptible to several types of disturbance. The two main objectives of this thesis were to (i) study the fire history in a TMCF and (ii) investigate the changes in water input in a secondary TMCF. Field studies were conducted in southern Mexico and northern Costa Rica. The Chimalapas region of Oaxaca, Mexico was subjected to fires during the El Niño events of 1997 to 1998. Previous fires were evident from charcoal, which was collected in soil pits. Radiocarbon dating indicated that at least nine fire episodes have occurred in this area during the past 10, 000 years and the findings suggest that there have been repeated fires in the investigated TMCFs. The Costa Rican study aimed to estimate total soil water input from horizontal rain and fog (HP) in the edge and interior of a secondary TMCF. Net capture was defined as HP that reached the soil and was calculated as throughfall + stemflow - vertical precipitation. Over the 11-month measurement period, accumulated net capture decreased linearly from the forest edge (ca. 1200 mm) to the centre of the plot which was 20 m into the forest (ca.-1900 mm). Sixty-eight percent of the variability in weekly net capture could be explained by the plot position and the seasonal variation in HP input. In conclusion, the study demonstrated the potential to manage edges and emergent trees in landscapes with secondary TMCF for improved water input

Epiphytic bryophytes of Monteverde, Costa Rica

A survey of the literature and collections in the Monteverde Cloud Forest Preserve and adjacent pastureland yielded a total of 198 epiphytic bryophyte taxa (120 species of hepatics in 50 genera, 77 species of moss in 48 genera, and 1 hornwort): 178 in the primary forest, 63 in the secondary forest, and 84 in the pastureland

Forest cover estimation in Ireland using radar remote sensing: a comparative analysis of forest cover assessment methodologies

Quantification of spatial and temporal changes in forest cover is an essential component of forest monitoring programs. Due to its cloud free capability, Synthetic Aperture Radar (SAR) is an ideal source of information on forest dynamics in countries with near-constant cloud-cover. However, few studies have investigated the use of SAR for forest cover estimation in landscapes with highly sparse and fragmented forest cover. In this study, the potential use of L-band SAR for forest cover estimation in two regions (Longford and Sligo) in Ireland is investigated and compared to forest cover estimates derived from three national (Forestry2010, Prime2, National Forest Inventory), one pan-European (Forest Map 2006) and one global forest cover (Global Forest Change) product. Two machine-learning approaches (Random Forests and Extremely Randomised Trees) are evaluated. Both Random Forests and Extremely Randomised Trees classification accuracies were high (98.1–98.5%), with differences between the two classifiers being minimal (<0.5%). Increasing levels of post classification filtering led to a decrease in estimated forest area and an increase in overall accuracy of SAR-derived forest cover maps. All forest cover products were evaluated using an independent validation dataset. For the Longford region, the highest overall accuracy was recorded with the Forestry2010 dataset (97.42%) whereas in Sligo, highest overall accuracy was obtained for the Prime2 dataset (97.43%), although accuracies of SAR-derived forest maps were comparable. Our findings indicate that spaceborne radar could aid inventories in regions with low levels of forest cover in fragmented landscapes. The reduced accuracies observed for the global and pan-continental forest cover maps in comparison to national and SAR-derived forest maps indicate that caution should be exercised when applying these datasets for national reporting

Woody plant communities of isolated Afromontane cloud forests in Taita Hills, Kenya

In the Taita Hills in southern Kenya, remnants of the original Afromontane forest vegetation are restricted to isolated mountain peaks. To assess the level of degradation and the need for forest restoration, we examined how forest plant communities and their indicator species vary between and within remnant patches of cloud forest. We used ordinal abundance data to compare plant communities in eight forest fragments. We also analyzed data on the diversity and abundance of trees in 57 0.1 ha plots to compare tree communities within and between the largest two of these fragments, Ngangao (120 ha) and Mbololo (220 ha). The extant vegetation of the Taita Hills at landscape scale consists of secondary moist montane to intermediate montane forest. There was a high species dissimilarity between fragments (69%). Variation in species composition coincided with an abiotic gradient related to elevation. At plot level, secondary successional species and species of forest edges were most abundant and most frequent. Inferred clusters of plots almost entirely coincided with the two forest fragments. Indicator species associated with forest margins and gaps were more frequent in the smaller of the two forest fragments, while indicators for the larger fragment were more typical for less disturbed moist forest. Abiotic site variability but also different levels of disturbance determine site-specific variants of the montane forest. Conservation efforts should not only focus on maintaining forest quantity (size), but also on forest quality (species composition). Late-successional rainforest species are underrepresented in the woody plant communities of the Taita Hills and assisting restoration of viable populations of cloud forest climax tree species is urgently needed

The herpetofauna of the cloud forests of Honduras

The cloud forest amphibians and reptiles constitute the most important herpetofaunal segment in Honduras, due to the prevalence of endemic and Nuclear Middle American-restricted species. This segment, however, is subject to severe environmental threats due to the actions of humans. Of the 334 species of amphibians and reptiles currently known from Honduras, 122 are known to be distributed in cloud forest habitats. Cloud forest habitats are found throughout the mountainous interior of Honduras. They are subject to a Highland Wet climate, which features annual precipitation of >1500 mm and a mean annual temperature of <18°C. Cloud forest vegetation falls into two Holdridge formations, the Lower Montane Wet Forest and Lower Montane Moist Forest. The Lower Montane Wet Forest formation generally occurs at elevations in excess of 1500 m, although it may occur as low as 1300+ m at some localities. The Lower Montane Moist Forest formation generally occurs at 1700+ m elevation. Of the 122 cloud forest species, 18 are salamanders, 38 are anurans, 27 are lizards, and 39 are snakes. Ninety-eight of these 122 species are distributed in the Lower Montane Wet Forest formation and 45 in the Lower Montane Moist Forest formation. Twenty species are distributed in both formations. The cloud forest species are distributed among restricted, widespread, and peripheral distributional categories. The restricted species range as a group in elevation from 1340 to 2700 m, the species that are widespread in at least one of the two cloud forest formations range as a group from sea level to 2744 m, and the peripheral species range as a group from sea level to 1980 m. The 122 cloud forest species exemplify ten broad distributional patterns ranging from species whose northern and southern range termini are in the United States (or Canada) and South America, respectively, to those species that are endemic to Honduras. The largest segment of the herpetofauna falls into the endemic category, with the next largest segment being restricted in distribution to Nuclear Middle America, but not endemic to Honduras. Cloud forest species are distributed among eight ecophysiographic areas, with the largest number being found in the Northwestern Highlands, followed by the North-Central Highlands and the Southwestern Highlands. The greatest significance of the Honduran herpetofauna lies in its 125 species that are either Honduran endemics or otherwise Nuclear Middle American-restricted species, of which 83 are distributed in the country’s cloud forests. This segment of the herpetofauna is seriously endangered as a consequence of exponentially increasing habitat destruction resulting from deforestation, even given the existence of several biotic reserves established in cloud forest. Other, less clearly evident environmental factors also appear to be implicated. As a consequence, slightly over half of these 83 species (50.6%) have populations that are in decline or that have disappeared from Honduran cloud forests. These species possess biological, conservational, and economic significance, all of which appear in danger of being lost.Los anfibios y reptiles de los bosques nublados constituyen el segmento más importante de la herpetofauna de Honduras, debido a la prevalencia de especies endémicas y restringidas a la Mesoamérica Nuclear. Este segmento, sin embargo, está sometido a fuertes amenazas medioambientales debido a acciones humanas. De las 334 especies de anfibios y reptiles que se conocen en Honduras en el presente, 122 se conocen que están distribuidas en las habitaciones de los bosques nublados. Las habitaciones del bosques nublados se encuentran a través de las montañas del interior de Honduras. Ellos están sujetos a un clima lluvioso de tierras altas, el cual tiene una precipitación anual de más de 1500 mm y una temperatura anual promedia de menos de 18 grados centígrados. La vegetación de los bosques nublados cae entre dos formaciones de Holdridge, la de Bosque Lluvioso Montano Bajo y la de Bosque Húmedo Montano Bajo. La formación de Bosque Lluvioso Montano Bajo generalmente occure a elevaciones en exceso de 1500 m, aunque puede ocurrir tan bajo como 1300 m en algunas localidades. La formación Bosque Húmedo Montano Bajo generalmente ocurre a 1700 m o más de elevación. De las 122 especies de los bosques nublados, 18 son salamandras, 38 son anuros, 27 son lagartijas y 39 son culebras. Noventa y ocho de estas 122 especies están distribuidas en la formación Bosque Lluvioso Montano Bajo y 45 en la formación Bosque Húmedo Montano Bajo. Viente especies están distribuidas en ambas formaciones. Las especies de los bosques nublados están distribuidas entre categorías distribucionales restringidas, amplias, y periféricas. Las especies restringidas se encuentra como grupo en un rango de elevaciones de los 1340 a los 2700 m, las especies que tienen una distribución amplia en al menos entre una de las dos formaciones de los bosques nublados como grupo tiene un rango desde el nivel del mar hasta 2744 m, y las especies periféricas como grupo tiene un rango desde el nivel del mar hasta 1980 m. Las 122 especies de los bosques nublados ejemplifican 10 patrones distribucionales amplios con rangos de especies para las cuales los rangos terminales norteño y sureño están en los Estados Unidos (o Canadá) y América del Sur, respectivamente, hasta esas especies que son endémicas de Honduras. El segmento más grande de la herpetofauna cae en la categoría endémica, con el proximo segmento más grande siendo restringido en distribución a la Mesoamérica Nuclear, pero no endémico de Honduras. Las especies de los bosques nublados están distribuidas entre ocho áreas ecofisiográficas, con el grupo más grande encontrandose en las tierras altas hacia el noroeste y seguido por las tierras altas norte-central y las tierras altas del suroeste. La importancia más grande de la herpetofauna hondureña cae en sus 125 especies que son endémicas de Honduras o de otra manera restringidas a la Mesoamérica Nuclear, de las cuales 83 están distribuidos en los bosques nublados del país. Este segmento de la herpetofauna está seriamente amenazado a consequencia de la destrucción exponencial de sus habitaciones, el cual es el resultado de la destrucción de los bosques, aunque existen varias reservas bióticas establecidas en los bosques nublados. Otros factores medioambientales menos claramente evidentes parecen estar implicados. Como consequencia, un poco más de la mitad de estas 83 especies (50.6%) tiene poblaciones que están disminuyendo o que han desaparecidos de los bosques nublados hondureños. Estas especies poseen significancia biológica, de conservación, y económica, todas las cuales parecen estar en peligro de ser perdidas

Forests and Landscapes of Dominican Republic

Aims: This, in conjunction with the diversity of the substrates and the fact that the island is home to the highest mountains in the Caribbean and with a high rate of endemic species, allows them to be differentiated into three major groups –dry forest, cloud forest and the transition between dry and cloud forests. The forests in the Dominican Republic grow in a tropical climate with ombrotypes ranging from arid to humid-hyperhumid due to the moisture-laden Atlantic winds; and infra-, thermo-, meso- and supratropical thermotypes. Establish the diversity, ecology and forest types in Dominican Republic. Methods: We identified all species through field surveys and comparative analyzes of how forest types, structure, diversity and ecology.Results: We consided these forests to be endemic to the island of Hispaniola, as the dry forest presents 81 endemic species, of which 10 are trees, 65 shrubs, 5 creepers, and 1 herbaceous species; while the cloud forest has 19 trees, 20 shrubs, 8 creepers, 4 epiphytes and 6 herbaceous species. Conclusions: We highlight the absence of endemic epiphytes in the dry forests, which are in a poor state of conservation and subject to greater human pressure than the cloud forest