Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

The South Ecuadorian Andes are one of the hottest global hotspots of biodiversity and currently threatened by land use and climate change. Forest structure and composition are crucial factors for understanding the capacity of forest support species in changing environments. In order to prioritize limited conservation resources a better understanding of tree diversity patterns is needed. The use of image texture measures, as a proxy for spatial and forest structure has shown useful possibilities in explaining patterns of tree diversity and species richness. My goal was to evaluate the performance of different texture measures on NDVI, EVI and two broad-band combinations on high resolution (0.3m) aerial photography to predict tree diversity. Bayesian Model Averaging (BMA) was used to relate in situ measurements of tree diversity to measures of image texture. Texture explained up to 44.7% of the variability of tree diversity with measures related to habitat heterogeneity, particularly variance, providing highest explanatory power. Image texture measures bear considerable potential for predicting tree diversity in the tropics and can contribute to improvements on conservation efforts and management planning.

Abstract:

The comparatively long research history within the study area allowed to develop well-grounded hypotheses on how the hydrological system within the study area should behave (Bogner et al., 2014; Boy et al., 2008; Bücker et al., 2011, 2010; Crespo et al., 2012, 2011; Fleischbein et al., 2006; Goller et al., 2005). Based on those earlier findings made within the study area and the hydrological research conducted elsewhere in tropical mountain cloud forests (see Bonell and Bruijnzeel, 2004; Bruijnzeel, 2004; Bruijnzeel et al., 2011 for recent overviews) provided the background to shape the research conducted within this dissertation around the focal point of global change impacts on the hydrological cycle inside the study area (see chapter 1.3).Separated into three chapters, each representing a scientific research paper, this thesis will address the issue on how to evaluate effects of land-use change on the hydrological cycle (chapter 2), how stable water isotopes are distributed over space and time within the study area (chapter 3) and how stable water isotopes can be used in hydrological models to assist this analysis of global change impacts in the future (chapter 4). All of the research conducted for this dissertation was performed in the Rio San Francisco catchment within South Ecuador.

Abstract:

The present study is composed of three interlinked research papers described in three respective chapters: Chapter 2: “Understanding uncertainties when inferring mean transit times of water trough tracer-based lumped-parameter models in Andean tropical montane cloud forest catchments” deals with the estimation of mean transit times and explores the most reliable transit time distribution functions for 32 sampled sites in the catchment, which included 18 soil water sites, 2 streamwater sites in the main river, 7 streamwater tributaries, 2 small creeks and 3 springwaters. For the analysis, seven lumped-parameters models were tested. Besides, for each simulation, uncertainties were accounted through applying the Generalized Likelihood Uncertainty Estimation approach (GLUE). Chapter 3: “Sampling frequency trade-offs in the assessment of mean transit times of tropical montane catchment waters under semi-steady-state conditions”. This chapter describes the effect of sampling resolution data on the results provided by lumped-parameter models. Based on the insights from results described in Chapter 2, only selected models and sampled sites were screened for intercomparison. The results of this topic were aimed to account the degree of reliability of mean transit time estimations. Chapter 4: “Multi-criteria assessment of water dynamics reveal subcatchment variability in a seemingly homogeneous montane rainforest catchment”. By considering a nested catchment approach (main river outlet and its seven tributaries), mean transit times and other diverse catchment characteristics data (e.g., hydrometric and topographic indices, physicochemical properties of stream waters) were used to perform diverse statistical and modelling techniques, such as bivariate and multivariate analysis, Principal Component Analysis (PCA), Cluster Analysis, EMMA, Hydrological and Chemical modelling. All of which allowed to gain insights on the key factors governing the flow processes in each analysed site.

Abstract:

In-Situ-Konzentrationsmessungen sind ein wichtiges Werkzeug in der Hydrologie. Die Ver-wendung entsprechender Geräte erlaubt die Aufnahme von hochfrequenten und gleichzeitig langfristigen Zeitreihen. Nitratkonzentrationen unterliegen in natürlichen Fließgewässern ta-geszeitabhängigen Schwankungen. In dieser Arbeit werden Konzentrationsmessungen aus dem Rio San Francisco in Ecuador aus-gewertet. Ergänzt werden diese durch Wettermessungen und Pegelstandsmessungen aus dem gleichen Gebiet. Der Nitratdatensatz verläuft über etwa viereinhalb Jahre und enthält viertel-stündliche Messungen. Diese werden aufbereitet, gefiltert, und nach Tageszyklen hin unter-sucht. Zum Einsatz kommt dabei eine hierarchische Clusteranalyse mit Dynamic-Time-War-ping-Distanzen. Um Zusammenhänge der Zyklen mit den anderen Variablen aufzudecken, wird eine Lineare Diskriminanzanalyse (LDA) mit einer Variablenauswahl nach Wilks-Lambda durchgeführt. Zusätzlich werden unabhängig von Tageszyklen kurzfristige Residuen der Nit-ratkonzentration per multimodal normalverteiltem Mischungsmodell untersucht. Die Clusteranalyse zeigt, dass es einen Cluster A mit einem regelmäßigen Tageszyklus sowie einen Cluster B mit unregelmäßigen Konzentrationsverläufen gibt. Die Trennung von A und B scheint mit der Lufttemperatur, der relativen Luftfeuchtigkeit, dem Niederschlag, und dem Pe-gel zusammen zu hängen. Ein LDA-Modell mit den Tagesvariablen Pegelamplitude, Nieder-schlagssumme, und mittlere relative Luftfeuchtigkeit ordnet erfolgreich die meisten Tage dem Cluster A zu, versagt jedoch bei der Zuordnung in Cluster B. Die Analyse mit dem Mischungsmodell ergibt keine eindeutigen Ergebnisse. Es scheint aber einen negativen Zusammenhang zwischen den Residuen der Nitratkonzentration mit der Luft-temperatur und der Globalstrahlung zu geben. Die Ergebnisse dieser Arbeit entsprechen teilweise jenen, welche auch in der Literatur aufzu-finden sind. Der Tagesverlauf mit einem Maximum am Morgen und einem Minimum am Abend scheint typisch für Fließgewässer zu sein. Jedoch findet sich in den Daten kein Hinweis auf eine saisonale Verschiebung des Zyklus.

Abstract:

Mit Hilfe des Snapshot Samplings wurde an drei Tagen entlang des 14,2 km langen Flusses Quinoas in 50 m Abständen Wasserproben gesammelt. Das Untersuchungsgebiet liegt in den ecuadorianischen Anden (auf ca. 3.300-3.900 m) und die Hauptvegetation des EZGs ist Páramo. Alle Wasserproben wurden auf ihre Nitrat-N-, BSB- und EL-Konzentrationen untersucht. Die gemessenen Konzentrationen wurden auf ihre Korrelation zu den prozentualen Landnutzungsflächen (vor allem Páramo, Wald und Weide) der jeweiligen EZG analysiert, als Maßzahl wurde der Rangkorrelationskoeffizient nach Spearman gewählt. Bei Nitrat-N waren im Durchschnitt die Korrelationen zu Wald und Weide am höchsten. Der starke Zusammenhang zwischen Nitrat-N und Wald konnte nicht eindeutig geklärt werden. Der Anstieg der Nitrat-N-Konzentration durch einen höheren Anteil an Weide im EZG ist vermutlich durch Düngerausbringung zu erklären. Es zeigte sich, dass Nitrat-N vermutlich vermehrt aus tieferen Bodenschichten ausgewaschen wird. Die Korrelation zwischen Nitrat-N und Páramo ist mittelmäßig stark und negativ. Nährstoffe in diesen Böden liegen oft stark gebunden oder in Pflanzen gespeichert vor und können nur schwer ausgewaschen werden. Aus den Waldflächen des EZG wird relativ gesehen wenig BSB ausgewaschen. In den Wäldern wird nur nach Perioden mit vielen Niederschlägen etwas organische Materie in den Fluss geschwemmt. Der Großteil der organischen Materie der Páramoböden liegt gebunden vor und daher ist der Zusammenhang zwischen BSB und Páramo zwar positiv, aber nicht besonders stark. Die Korrelationen zwischen BSB und Weide sind im Durchschnitt negativ. Die Weideflächen im EZG werden nur extensiv bewirtschaftet und die Tieranzahl ist sehr gering. Im Gegensatz zu den anderen Parametern zeigten sich bei BSB basierend auf verschiedene Wetterverhältnisse sehr unterschiedliche Ergebnisse zwischen den drei Messterminen. Wie bei Nitrat-N ist die Korrelation zwischen EL und Páramo negativ und zwischen EL und Wald, sowie Weide positiv. Bei EL sind die Spearmans Rangkorrelationskoeffizienten im Allgemeinen sehr hoch. Allerdings kann hier nicht ausgeschlossen werden, dass eigentlich andere Faktoren (wie Geologie oder Bodentyp) vorrangig entscheidend sind. Einflüsse von Forellenfarmen konnten basierend auf den Ergebnissen dieser Arbeit nicht gefunden werden. Einige große Zuflüsse können einen Teil der Parameterkonzentrationsschwankungen im Flussverlauf erklären. Ob die Parameterkonzentrationen der Zuflüsse sich auf Grund ihrer Landnutzung vom Hauptfluss unterscheiden konnte nicht eindeutig geklärt werden.

Abstract:

Future climate and land use change may have a great impact on essential ecosystem functions such as carbon storage and water supply of the Andean p´aramo ecosystem. As hydrogeochemical processes in the p´aramo and possible reactions to these changes are still largely unknown, nutrient fluxes during storm flow events in a p´aramo catchment in the Cajas National Park of south Ecuador were studied. From February to June 2014, discharge and stream concentrations of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity and nitrate (NO3-N) were monitored in five minute intervals in the Quinuas River. In order to study the catchment’s response to rainfall events, rotational patterns of concentration-discharge hysteresis effects were analysed. In total, 35 events were suitable for analysing hysteresis effects of BOD, COD, and turbidity. Nitrate concentrations were studied in 20 events. Precipitation events led to an increase of concentration of all parameters. Hysteresis patterns showed a high consistency. COD, turbidity, and nitrate rotated mainly clockwise, BOD counterclockwise. Therefore, a fast response of the sources of COD, nitrate, and turbidity is suggested. This might be mainly due to a fast subsurface flow through the upper organic soil horizons. BOD sources, mainly soil surface and litter layer, predominate later in the storm flow event

Abstract:

This report examines the impact of climate changes and variations in land use based on water samples taken from the alpine grassland ecosystem Páramo in the South of Ecuador. For this purpose, two monitoring points were identified, which hold a different level of anthropogenic influences. Predominantly, the Virgin area exists of natural Páramo. In contrast, the area of Chirimachay is by far more versatile since its components are natural Páramo, nature forest, livestock as well as trout farming. In order to analyse the climate in a diurnal and seasonal cycle, date of temperature and precip-itation has been evaluated. For the purpose of this report, fluxes of nitrogen-nitrate (N-NO3), chemical and biochemical oxygen demand (COD / BOD) and turbidity were analysed. In order to examine the fluxes, concentrations of the mentioned parameters were measured in a five minutes routine in the first step. Afterwards, they were multiplied with current discharge data. Analysis of the data does not illustrate a correlation between nutrient fluxes and air temperature. In terms of precipitation, however, it was possible to identify a relation to COB and BOD (given R=0,829 each in Chirimachay area) by using a linear correlation matrix. Additionally, in the Chirimachay area, evidence for a relation between precipitation and turbidity was found. Even though there is no linear correlation between N-NO3 and precipitation, it is still possible that there is another relation based on the characteristics of moving in soil during different environ-mental conditions. Furthermore, land use has different effects on each parameter. By using scatter plots and statis-tical tests it was possible to analyse the extent of differences in fluxes due to the specific land use. Therefore, N-NO3 fluxes are not influenced while COD, BOD, and on a minor scale, tur-bidity, are correlating to each other.

Abstract:

In 2008, a booklet “The Mountain Rainforest: Scientific Discoveries in a Highly Diverse Eco - system in Southern Ecuador” was published by a German Research Unit, informing the public about 10 years of biodiversity and ecosystem research in the Eastern range of the tropical Andes of Ecuador. The authors (K. Kiss & A. Bräuning) had compiled 14 contributions on diversity, dynamic processes and potential use of the primary forest and of its agricultural replacement systems. Another 8 years of research in the area have immensely widened the understanding of the ecosystem and its value for science in general and for the region in particular. The new book “Biodiversity Hotspot: Tropical Mountain Rainforest”, starting with an introductory chapter on the research area as the second hottest biodiversity hotspot worldwide, presents in an apprehensible way the major results of 16 collaborative projects addressing questions of basic as well as applied research. Understanding ecosystem components and processes is the prerequisite for an assessment of its stability under climate and land use changes. With this book the authors acknowledge the long-standing support of the work by the German Research Foundation and by the foundation Naturaleza y Cultura Internacional in Loja and San Diego, as well as the fruitful collaboration with our Ecuadorian partners, the Universidad Tecnica Particular de Loja, the Universidad Nacional de Loja, the Universidad de Cuenca and the Universidad de Azuay, and the local weather service INAMHI. We also appreciate very much the important contributions of our non-university research partners beyond NCI, ETAPA EP (Empresa Pública Municipal de Telecomunicaciones, Agua potable, lcantarillado y Saneamiento de Cuenca - Ecuador), Gobierno Municipal de Zamora and the regional water fund FORAGUA (Fondo Regional del Agua).

Abstract:

Quality control is a particularly demanding problem for micrometeorological studies in complex environments. With the transition to electronic sensing and storage of climate data in high temporal resolution, traditional approaches of homogenization are insufficient for addressing the small-scale variability and spatial heterogeneity of the data. This problem can be successfully addressed by introducing a new class of control procedures based on the physical and climatological relations between different climate variables. The new approach utilizes knowledge about the interdependency of air temperature, precipitation, radiation, relative air humidity, cloud cover, and visibility to develop empirical functions for determining the probability margins for the co-occurrence of specific conditions in tropical mountains and deserts. It can also be applied to other geographic settings by adjusting the parameters derived from the data itself. All procedures are integrated into a processing chain with feedback loops and combined with conventional logical and statistical checks, which enables it to detect small errors that normally pass unnoticed. The algorithms are also adapted to incorporate the short time steps of the original data to retain the potential for detailed process analyses.

Abstract:

Human activities during the last decades provoked a notable reduction in global forest cover. Knowing that forest stands act as stock and sinks for carbon and other greenhouse gases, it is important to determine the existing forest cover at country level and to calculate annual deforestation rates. This work uses NOAAsatellite images in a resolution of 1 km x 1 km to classify the surface of continental Ecuador in “forest” – “non-forest” pixels and to estimate the annual deforestation rate from 1986 to 2001 as well as from 2001 to 2008. The method is based on a decision tree algorithm that includes different spectral bands of the NOAA-AVHRRsensor and additional topographic and meteorological parameters. The results show that the total forest cover of continental Ecuador was reduced from 48.1 % in 1986 to 36.8 % in 2008. The calculated annual deforestation rates indicate that forest reduction increased during the last decade. The most affected area is the Coastal Lowland, due to the enhanced population pressure, followed by the Amazon Basin, not only caused by the governmental supported oil and mining industry, but also due to the uncontrolled timber extraction. The Andean Highland has been less affected, because the major parts of this region were deforested before, during the Pre-Columbian-Era.

Abstract:

Sea salt (NaCl) has recently been proven to be of the utmost importance for ecosystem functioning in Amazon lowland forests because of its impact on herbivory, litter decomposition and, thus, carbon cycling. Sea salt deposition should generally decline as distance from its marine source increases. For the Amazon, a negative east–west gradient of sea salt availability is assumed as a consequence of the barrier effect of the Andes Mountains for Pacific air masses. However, this generalized pattern may not hold for the tropical mountain rainforest in the Andes of southern Ecuador. To analyse sea salt availability, we investigated the deposition of sodium (Na+) and chloride (Cl?), which are good proxies of sea spray aerosol. Because of the complexity of the terrain and related cloud and rain formation processes, sea salt deposition was analysed from both, rain and occult precipitation (OP) along an altitudinal gradient over a period between 2004 and 2009. To assess the influence of easterly and westerly air masses on the deposition of sodium and chloride over southern Ecuador, sea salt aerosol concentration data from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis data set and back-trajectory statistical methods were combined. Our results, based on deposition time series, show a clear difference in the temporal variation of sodium and chloride concentration and Na+???Cl? ratio in relation to height and exposure to winds. At higher elevations, sodium and chloride present a higher seasonality and the Na+???Cl? ratio is closer to that of sea salt. Medium- to long-range sea salt transport exhibited a similar seasonality, which shows the link between our measurements at high elevations and the sea salt synoptic transport. Although the influence of the easterlies was predominant regarding the atmospheric circulation, the statistical analysis of trajectories and hybrid receptor models revealed a stronger impact of the north equatorial Atlantic, Caribbean, and Pacific sea salt sources on the atmospheric sea salt concentration in southern Ecuador. The highest concentration in rain and cloud water was found between September and February when air masses originated from the north equatorial Atlantic, the Caribbean Sea and the equatorial Pacific. Together, these sources accounted for around 82.4?% of the sea salt budget over southern Ecuador.

Abstract:

As a consequence of the remote location of the Andean páramo is knowledge on their hydrologic functioning limited, notwithstanding this alpine tundra ecosystem act as water towers for a large fraction of the society. Given the harsh environmental conditions in this region is year-round monitoring cumbersome, and it would be beneficially if the monitoring needed for the understanding of the rainfall-runoff response could be limited in time. To identify the hydrological response and the effect of temporal monitoring a nested (n?=?7) hydrological monitoring network was set up in the Zhurucay catchment (7.53?km2), south Ecuador. The research questions were: (1) can event sampling provide similar information in comparison to continuous monitoring, and (2) if so, how many events are needed to achieve a similar degree of information? A subset of 34 rainfall runoff events was compared to monthly values derived from a continuous monitoring scheme from December 2010 to November 2013. Land cover and physiographic characteristics were correlated with eleven hydrological indices. Results show that despite some distinct differences between event and continuous sampling, both datasets reveal similar information; more in particular the monitoring of a single event in the rainy season provides the same information as continuous monitoring, while during the dry season 10 events ought to be monitored.

Abstract:

Few high-elevation tropical catchments worldwide are gauged, and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53?km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900?m?a.s.l. Water samples for stable isotopic analysis were collected during 2?years (May 2011–May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that andosol soils predominantly situated on hillslopes drain laterally to histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily composed of pre-event water stored in the histosols, which is replenished by rainfall that infiltrates through the andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non-exceedance flows?<?Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year-round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high-intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high-elevation tropical ecosystem, (1) subsurface flow is a dominant hydrological process and (2) (histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged.

Abstract:

This study focuses on the investigation of the mean transit time (MTT) of water and its spatial variability in a tropical high-elevation ecosystem (wet Andean páramo). The study site is the Zhurucay River Ecohydrological Observatory (7.53?km2) located in southern Ecuador. A lumped parameter model considering five transit time distribution (TTD) functions was used to estimate MTTs under steady-state conditions (i.e., baseflow MTT). We used a unique data set of the ?18O isotopic composition of rainfall and streamflow water samples collected for 3 years (May 2011 to May 2014) in a nested monitoring system of streams. Linear regression between MTT and landscape (soil and vegetation cover, geology, and topography) and hydrometric (runoff coefficient and specific discharge rates) variables was used to explore controls on MTT variability, as well as mean electrical conductivity (MEC) as a possible proxy for MTT. Results revealed that the exponential TTD function best describes the hydrology of the site, indicating a relatively simple transition from rainfall water to the streams through the organic horizon of the wet páramo soils. MTT of the streams is relatively short (0.15–0.73 years, 53–264 days). Regression analysis revealed a negative correlation between the catchment's average slope and MTT (R2?=??0.78, p?<?0.05). MTT showed no significant correlation with hydrometric variables, whereas MEC increases with MTT (R2?=??0.89, p?<?0.001). Overall, we conclude that (1) baseflow MTT confirms that the hydrology of the ecosystem is dominated by shallow subsurface flow; (2) the interplay between the high storage capacity of the wet páramo soils and the slope of the catchments provides the ecosystem with high regulation capacity; and (3) MEC is an efficient predictor of MTT variability in this system of catchments with relatively homogeneous geology.

Abstract:

Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest–pasture–urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.

Abstract:

Im Páramo der ecuadorianischen Anden wurden in einer Höhe zwischen 3000 m und 4000 m Plantagen mit Pinus patula angelegt. Dadurch wurden im Páramo normalerweise nicht vorkommende Ektomykorrhizapilze eingeführt. Mithilfe morphologischer und molekularer Methoden wurden die Ektomykorrhiza-Arten in drei Plantagen in der Nähe von Cuenca untersucht. Insgesamt wurden fünf verschiedene Ektomykorrhizapilze gefunden, von denen drei bis auf die Art bestimmt werden konnten: Thelephora terrestris, Suillus luteus, Inocybe jacobi, eine Sebacina-Art und eine nicht identifizierte Art. Thelephora terrestris war in allen drei Plantagen die am häufigsten vorkommenden Ektomykorrhiza-Art. Die Ektomykorrhizagemeinschaft dieser Plantagen ist also sehr artenarm im Vergleich zu natürlichen Standorten. Diese Beobachtung wird von anderen Studien in Kiefernplantagen der südlichen Hemisphäre bestätigt.

Abstract:

Summary
Community analyses of arbuscular mycorrhizal fungi (AMF) using ribosomal small subunit (SSU) or internal transcribed spacer (ITS) DNA sequences often suffer from low resolution or coverage. We developed a novel sequencing based approach for a highly resolving and specific profiling of AMF communities.
We took advantage of previously established AMF-specific PCR primers that amplify a c. 1.5-kb long fragment covering parts of SSU, ITS and parts of the large ribosomal subunit (LSU), and we sequenced the resulting amplicons with single molecule real-time (SMRT) sequencing.
The method was applicable to soil and root samples, detected all major AMF families and successfully discriminated closely related AMF species, which would not be discernible using SSU sequences. In inoculation tests we could trace the introduced AMF inoculum at the molecular level. One of the introduced strains almost replaced the local strain(s), revealing that AMF inoculation can have a profound impact on the native community.
The methodology presented offers researchers a powerful new tool for AMF community analysis because it unifies improved specificity and enhanced resolution, whereas the drawback of medium sequencing throughput appears of lesser importance for low-diversity groups such as AMF.

Abstract:

The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuousmap of forest tree density at a global scale. This mapreveals that the global numberof trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.

Abstract:

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ?40,000 and ?53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ?19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimumof ?4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

Abstract:

The relationship between canopy-level evapotranspiration (ETSci) and leaf-level transpiration (Tleaf) as well as photosynthesis (Pleaf) for a homogeneous tropical montane pasture was analyzed over five days using a combination of methods involving a laser scintillometer and a porometer. Weather conditions ranged from overcast to sunny during the period of study. The gas exchange of the leaves of the dominant pasture grass Setaria sphacelata (transpiration vs. photosyn¬thetic CO2 net uptake ) was measured with a porometer and physiologically interpreted on the background of microclimate variables (photosynthetic active radiation (PAR) as proxy for total light intensity, temperature, water vapor deficit of the air) and soil moisture data. Water use efficiency (WUE, photosynthetic CO2 net uptake vs water loss by leaf transpiration) of the pasture was used to analyze the grass’ range of response to the environmental variables of the research area. PAR and water vapor deficit of the air (VPD) appeared to be the determinant factors for Tleaf and ETSci. WUE for the Setaria sphacelata pasture ranged from 1.9 to 5.8 ?mol CO2 mmol-1 H20 day-1 and is particularly low during periods of high VPD combined with enhanced insolation during cloudless periods. ET measurements collected by the scintillometer demonstrated a strong correlation with water flux calculated using the Penman-Monteith approach (TPM) (r² = 0.95). Also, Tleaf measured with the porometer showed reasonable coincidence with the ET observations (r² = 0.78). Values of ETSci ranged from 2.26 to 4.96 mm day-1 and Tleaf ranged from 0.83 to 2.41 mm day-1, but only ETSci showed good correspondence with the available energy (net radiation). The lower correlation between Tleaf and canopy-level ETSci compared to that between ETSci and TPM was tested against contaminations from the adjacent fetch area of the scintillometer path, but no effects were found. Likewise, soil water limitations of Tleaf could be ruled out. Therefore, different correlations of ETSci and Tleaf with the incoming energy and VPD may be traced back to a direct effect of the VPD on ET in contrast to its indirect effect on Tleaf which is additionally regulated by physiological processes in the leaf stomata.

Abstract:

Phylogenetic niche conservatism (PNC) is the tendency of species within a clade to retain ancestral traits and to persist in their primary ecological niches on geological time scales. It links evolutionary and ecological processes and has been hypothesized to explain patterns of species richness and the composition of species assemblages. Decreasing patterns of species richness along latitudinal gradients were often explained by the combination of ancient tropical climates, trait retention of tropical lineages and environmental filtering. PNC also predicts decreasing phylodiversity and family age with decreasing tropicality and has been invoked to explain these patterns along climatic gradients across latitudinal as well as elevational gradients. However, recent studies on tree assemblages along latitudinal and elevational gradients in South America found patterns contradicting the PNC framework. Our study aims to shed light on these contradictions using three different metrics of the phylogenetic composition that form a gradient from recent evolutionary history to deep phylogenetic relationships. We analyzed the relationships between elevation and taxonomic species richness, phylodiversity and family age of tree assemblages in Andean rainforests in Ecuador. In contrast to predictions of the PNC we found no associations of elevation with species richness of trees and increasing clade level phylodiversity and family age of the tree assemblages with elevation. Interestingly, we found that patterns of phylodiversity across the studied elevation gradient depended especially on the deep nodes in the phylogeny. We therefore suggest that the dispersal of evolutionarily old plant lineages with extra-tropical origins influences the recent composition of tree assemblages in the Andes. Further studies spanning broader ecological gradients and using better resolved phylogenies to estimate family and species ages are needed to obtain a deeper mechanistic understanding of the processes that drive the assembly of tree communities along elevational gradients.

Abstract:

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000mm/yr (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000mm/yr.

Abstract:

Questions: How does the structure of liana communities (diameter, density and biomass) in tropical montane forests vary along elevation and topographic gradients? How do patterns of tree infestation vary with elevation? Is tree diameter growth reduced by lianas in tropicalmontane forest? Location: Tropical Andean forests (1000–3000 m a.s.l.) in the San Francisco Reserve and in the Podocarpus National Park, southern Ecuador. Methods: All lianas (DBH ? 1 cm) were censused in 54 permanent plots (20 9 20 m) equally distributed between three study sites (1000, 2000 and 3000 m a.s.l.) and three topographic positions (lower, mid and upper slope) per site (six replicate plots at each site by position combination). The DBH and number of lianas hosted was recorded for all trees (DBH ? 10 cm). Liana biomass was estimated using allometric equations. ANOVAs were used to test for effects of elevation and slope positions on liana parameters and proportion of trees infested. The relationships between liana biomass and tree parameters and environmental parameters were analysed with partial least squares regression. We used the available literature data to perform a regression analysis of liana biomass in response to elevation in humid tropical old-growth forests between sea level and 3000 ma.s.l. Results: Liana diameter, density and biomass all decrease with elevation. The decreasing liana biomass agrees with results from previous studies of liana biomass in other humid tropical forests, indicating a decrease of 0.18 Mg/ha liana biomass per 100 m of elevation gain. Topographic variation leads to thinner but more abundant stems upslope; there was no effect of topographic position on liana biomass. Liana biomass and liana infestation are both positively correlated with host tree DBH at every elevation. Tree diameter growth is reduced by liana infestation; the proportion of infested trees is lower in Andean montane forests than in tropical lowland forests. Conclusions: Liana biomass distribution and tree infestation vary significantly with elevation. Biomass of lianas and relative contribution of lianas to total above-ground biomass both decrease with elevation. Topographic effects likely result fromhigher soil fertility at lower slope positions.