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

Abstract:

Ecological patterns are difficult to extract directly from vegetation data. The respective surveys provide a high number of interrelated species occurrence variables. Since often only a limited number of ecological gradients determine species distributions, the data might be represented by much fewer but effectively independent variables. This can be achieved by reducing the dimensionality of the data. Conventional methods are either limited to linear feature extraction (e.g., principal component analysis, and Classical Multidimensional Scaling, CMDS) or require a priori assumptions on the intrinsic data dimensionality (e.g., Nonmetric Multidimensional Scaling, NMDS, and self organized maps, SOM). In this studywe explored the potential of Isometric FeatureMapping (Isomap). This new method of dimensionality reduction is a nonlinear generalization of CMDS. Isomap is based on a nonlinear geodesic inter-point distance matrix. Estimating geodesic distances requires one free threshold parameter, which defines linear geometry to be preserved in the global nonlinear distance structure.We compared Isomap to its linear (CMDS) and nonmetric (NMDS) equivalents. Furthermore, the use of geodesic distances allowed also extending NMDS to a version that we calledNMDS-G. In additionwe investigated a supervised Isomap variant (S-Isomap) and showed that all these techniques are interpretable within a single methodical framework. As an example we investigated seven plots (subdivided in 456 subplots) in different secondary tropical montane forests with 773 species of vascular plants. A key problem for the study of tropical vegetation data is the heterogeneous small scale variability implying large ranges of β- diversity. The CMDS and NMDSmethods did not reduce the data dimensionality reasonably. On the contrary, Isomap explained 95% of the data variance in the first five dimensions and provided ecologically interpretable visualizations; NMDS-G yielded similar results. The main shortcoming of the latterwas the high computational cost and the requirement to predefine the dimension of the embedding space.The S-Isomap learning scheme didnot improve the Isomap variant for an optimal threshold parameter but substantially improved the nonoptimal solutions. We conclude that Isomap as a new ordination method allows effective representations of high dimensional vegetation data sets. The method is promising since it does not require a priori assumptions, and is computationally highly effective.

Abstract:

Aims: Inferring environmental conditions from characteristic patterns of plant co-occurrences can be crucial for the development of conservation strategies concerning secondary neotropical forests. However, no methodological agreement has been achieved so far regarding the identification and classification of characteristic groups of vascular plant species in the tropics. This study examines botanical and, in particular, statistical aspects to be considered in such analyses. Based on these, we propose a novel data-driven approach for the identification of characteristic plant co-occurrences in neotropical secondary mountain forests. Methods: Floristic inventory data were gathered in secondary tropical mountain forests in Ecuador. Vegetation classification was performed by coupling locally adaptive isometric feature mapping, a non-linear ordination method and fuzzy-c-means clustering. This approach was designed for dealing with underlying non-linearities and uncertainties in the inventory data. Important Findings: The results indicate that the applied non-linear mapping in combination with fuzzy classification of species occurrence allows an effective identification of characteristic groups of co-occurring species as fuzzy-defined clusters. The selected species indicated groups representing characteristic life-form distributions, as they correspond to various stages of forest regeneration. Combining the identified ?characteristic species groups? with meta-information derived from accompanying studies indicated that the clusters can also be related to habitat conditions. In conclusion, we identified species groups either characteristic of different stages of forest succession after clear-cutting or of impact by fire or a landslide. We expect that the proposed data-mining method will be useful for vegetation classification where no a priori knowledge is available.

Abstract:

The investigated area is located in the upper valley of the San Francisco river at about 2000 m asl. at the border of the Podocarpus National Park (PNP) in southern Ecuador. The area belongs to the worldwide outstanding biodiversity hotspots. The 7 investigated secondary forest (plots C1; C2, C3, C4, D5, F1 and F2) were subdivided in regular subplots (usually 5 x 5 m). Depending on the size and shape of the plots, between 60 and 91 subplots were established and a total of 457 subplots were analyzed. The plots were classified referring to analysis of aerial photographs taken in 1962, 1976, 1989, and 2003. Four plots (C1-C4) represent regenerations stages after different clearing intensities during the fifties and sixties of the past century for the construction of a water pipe and a path to a nearby power plant. These plots border the primary forest. The plot D5 is a young regeneration stage of a forest on accumulated material of a landslide in a ravine and the plots F1 and F2 are forests which recover from a fire 15 years ago. Some still active, but mainly already abandoned pastures that are covered with ferns and bushes surround these three plots. A total of 779 vascular plant species were recorded on the seven plots. The number of species varies significantly between plots and subplots, especially in the number of tree species. With a total of 217 species the plot F1 was the most bio-diverse. The plots C4 (73) and F1 (72) showed the highest diversity of tree species. Diversity of shrubs (54 species) and lianas (35 species) was also highest in plot F1, whereas C3 was the plots with the highest diversity of herbs (60 species). The total number of plant species did not correlate with the assumed age of the vegetation on the plot and the same holds for the species richness of one of the 4 plant life-forms. But the ?alpha? diversity was inversely proportional with the individual cover abundance of species per plot. According to the ISOMAP results, the arrangement of plot depends on two major factors: i) The time-span of regeneration, which is reflected by the maturation of forest and is obvious from the sequential order of C1, C2, C3 and C4 along the abscissa of a two-dimensional graph, and, ii) The soil quality, i.e. the nutrient availability, which is indicative of the impact on the original forest. While D5 regenerates on a very poor subsoil of a land-slide, C1 develops on a former agriculturally used area und F1 and F2 exploit the nutrient richness of a soil after a fire. These plots follow a sequence along the y-axis of the mentioned plot. The low values of the Soerensen indexes between subplots demonstrate the high heterogeneity of the plant cover of the plots. Plot C1 showed the highest similarity (0.4) between all its subplots, however a decreasing Soerensen index (similarity) with an increase of the species richness of the subplots. This contrasts with the situation in C2, C3, C4, F1 and D5 where similarity increased with a higher ?alpha? diversity. The similarity was also analyzed as a function of distance (in meters) between the subplots. The determined correlation values were low in all forests and only for plots C1 and F1 an increasing similarity with a decreasing distance could be observed. At the species level every plot presents a high number of species, which do not have a high cover abundance and not necessarily do occur in other plots. The number of frequent and dominant species was low. Apparently, the floristic composition of secondary mountain forest depends more on the type of impact than on the successional stage, as the numbers of species in plots and subplots vary independently of age and size of examinated area. An effect of impact intensity and frequency is observed in the species richness. Plots F1 and F2, which were burnt about 15 years ago, show a higher species richness than C1 and C2, where a the forest was clearcut more than 30 years ago. In addition, D5 which developed on new landslide material 10 years ago has la lower species richness than F1 and F2. Similarly, F1 shows higher species richness than C3 and C4, which represent advanced stages of secondary forest without indications of detrimental impacts. As shown by the results of ISOMAP, these secondary forests in general constitute a very heterogenous vegetation, which is composed of a small-scale mosaic of areas with low similarity of the plant cover. The degree of heterogeneity increased with the distance between these areas, but on the other hand was positively correlated with the values of their ?alpha-diversity?. Plots F1, F2, C1 and C2 can be considered as successional mid-stage forests, dominated by a species-rich tree stratum with a high proportion of pioneer species. D5 was characterized as young secondary forest with rich shrub and herbal strata, and C3 and C4 represent advanced secondary forests with a dominance of shade tolerant species.

Abstract:

The investigated area is located in the upper valley of the San Francisco river at about 2000 m asl. at the border of the Podocarpus National Park (PNP) in southern Ecuador. The area belongs to the worldwide outstanding biodiversity hotspots. The 7 investigated secondary forest (plots C1; C2, C3, C4, D5, F1 and F2) were subdivided in regular subplots (usually 5 x 5 m). Depending on the size and shape of the plots, between 60 and 91 subplots were established and a total of 457 subplots were analyzed. The plots were classified referring to analysis of aerial photographs taken in 1962, 1976, 1989, and 2003. Four plots (C1-C4) represent regenerations stages after different clearing intensities during the fifties and sixties of the past century for the construction of a water pipe and a path to a nearby power plant. These plots border the primary forest. The plot D5 is a young regeneration stage of a forest on accumulated material of a landslide in a ravine and the plots F1 and F2 are forests which recover from a fire 15 years ago. Some still active, but mainly already abandoned pastures that are covered with ferns and bushes surround these three plots. A total of 779 vascular plant species were recorded on the seven plots. The number of species varies significantly between plots and subplots, especially in the number of tree species. With a total of 217 species the plot F1 was the most bio-diverse. The plots C4 (73) and F1 (72) showed the highest diversity of tree species. Diversity of shrubs (54 species) and lianas (35 species) was also highest in plot F1, whereas C3 was the plots with the highest diversity of herbs (60 species). The total number of plant species did not correlate with the assumed age of the vegetation on the plot and the same holds for the species richness of one of the 4 plant life-forms. But the ?alpha? diversity was inversely proportional with the individual cover abundance of species per plot. According to the ISOMAP results, the arrangement of plot depends on two major factors: i) The time-span of regeneration, which is reflected by the maturation of forest and is obvious from the sequential order of C1, C2, C3 and C4 along the abscissa of a two-dimensional graph, and, ii) The soil quality, i.e. the nutrient availability, which is indicative of the impact on the original forest. While D5 regenerates on a very poor subsoil of a land-slide, C1 develops on a former agriculturally used area und F1 and F2 exploit the nutrient richness of a soil after a fire. These plots follow a sequence along the y-axis of the mentioned plot. The low values of the Soerensen indexes between subplots demonstrate the high heterogeneity of the plant cover of the plots. Plot C1 showed the highest similarity (0.4) between all its subplots, however a decreasing Soerensen index (similarity) with an increase of the species richness of the subplots. This contrasts with the situation in C2, C3, C4, F1 and D5 where similarity increased with a higher ?alpha? diversity. The similarity was also analyzed as a function of distance (in meters) between the subplots. The determined correlation values were low in all forests and only for plots C1 and F1 an increasing similarity with a decreasing distance could be observed. At the species level every plot presents a high number of species, which do not have a high cover abundance and not necessarily do occur in other plots. The number of frequent and dominant species was low. Apparently, the floristic composition of secondary mountain forest depends more on the type of impact than on the successional stage, as the numbers of species in plots and subplots vary independently of age and size of examinated area. An effect of impact intensity and frequency is observed in the species richness. Plots F1 and F2, which were burnt about 15 years ago, show a higher species richness than C1 and C2, where a the forest was clearcut more than 30 years ago. In addition, D5 which developed on new landslide material 10 years ago has la lower species richness than F1 and F2. Similarly, F1 shows higher species richness than C3 and C4, which represent advanced stages of secondary forest without indications of detrimental impacts. As shown by the results of ISOMAP, these secondary forests in general constitute a very heterogenous vegetation, which is composed of a small-scale mosaic of areas with low similarity of the plant cover. The degree of heterogeneity increased with the distance between these areas, but on the other hand was positively correlated with the values of their ?alpha-diversity?. Plots F1, F2, C1 and C2 can be considered as successional mid-stage forests, dominated by a species-rich tree stratum with a high proportion of pioneer species. D5 was characterized as young secondary forest with rich shrub and herbal strata, and C3 and C4 represent advanced secondary forests with a dominance of shade tolerant species.

Abstract:

Orchids depend on fungi for germination and protocorm development, but also form mycorrhizas during life time. Mycorrhizal fungi are, therefore, discussed as driving force in orchid evolution and speciation. However, for serious discussion reliable data on fungal identity are crucial. Application of molecular phylogeny and transmission electron microscopy congruently revealed distinct fungal groups as orchid mycobionts. Sebacinales Group B, Tulasnellales, and Ceratobasidiales were found associated with terrestrial orchids in open grasslands and arbuscular mycorrhizal forests and with epiphytes, while Sebacinales Group A, Thelephorales, Russulales, some Euagaricales and Tuberales form mycorrhizas with terrestrial orchids in ectomycorrhizal forests. Enzyme and isotope analyses revealed that the former obtain carbon from rotten organic material to nourish the protocorm while the latter take carbon from ectomycorrhizas of woody plants to feed protocorms and adult heterotrophic or mixotrophic plants. Mycobionts of terrestrial orchids appeared to be of narrower host range than previously expected, and co-speciation was discussed. The few investigations on mycobionts of epiphytic orchids so far indicated sharing of hosts. Further information is needed of mycobionts from tropical terrestrial and epiphytic orchids at well resolved molecular level of fungal identity, in situ prove, host range, and ecology to finally evaluate if association strategies differ between epiphytic and terrestrial orchids or between temperate and tropical habitats.

Abstract:

The sampling of epiphytes is fraught with methodological difficulties. We present a protocol to sample and analyse vascular epiphyte richness and abundance in forests of different structure (SVERA). Epiphyte abundance is estimated as biomass by recording the number of plant components in a range of size cohorts. Epiphyte species biomass is estimated on 35 sample-trees, evenly distributed over six trunk diameter-size cohorts (10 trees with dbh >30 cm). Tree height, dbh and number of forks (diameter >5 cm) yield a dimensionless estimate of the size of the tree. Epiphyte dry weight and species richness between forests is compared with ANCOVA that controls for tree size. SChao1 is used as an estimate of the total number of species at the sites. The relative dependence of the distribution of the epiphyte communities on environmental and spatial variables may be assessed using multivariate analysis and Mantel test. In a case study, we compared epiphyte vegetation of six Mexican oak forests and one Colombian oak forest at similar elevation. We found a strongly significant positive correlation between tree size and epiphyte richness or biomass at all sites. In forests with a higher diversity of host trees, more trees must be sampled. Epiphyte biomass at the Colombian site was lower than in any of the Mexican sites; without correction for tree size no significant differences in terms of epiphyte biomass could be detected. The occurrence of spatial dependence, at both the landscape level and at the tree level, shows that the inclusion of spatial descriptors in SVERA is justified.

Abstract:

Ziel dieser Arbeit war es, die Epiphytenvegetation bezüglich ihrer Abundanz, Diversität und floristischen Zusammensetzung in einem Bergregenwald in Südecuador zu untersuchen. Dafür wurde zum einen ein junger Sekundärwald mit Primärwald und zum anderen Unterwuchs und Kronendach eines gestörten bzw. älteren sekundären Waldes miteinander verglichen. Es wurden verschiedene Umweltparameter aufgenommen, um einen Einfluss dieser auf die Epiphytenvegetation zu untersuchen. Lediglich bei den Umweltparametern Hangneigung, Kronendachöffnung und Moosdeckung im jungen Sekundärwald konnte ein möglicher Einfluss auf Abundanz und Artenzahl der Epiphyten festgestellt werden. Nach Einteilung der Untersuchungsgebiete in vertikale Zonen konnte insbesondere im Unterwuchs des gestörten bzw. älteren sekundären Waldes eine vertikale Stratifizierung festgestellt werden. Die Abundanz und Artenzahl war in der Zone 1 (>0,25m - 1,25m) signifikant höher als in der Zone 2 (>1,25m - 2,25m). Dies wurde hauptsächlich auf mikroklimatische Unterschiede zurückgeführt. Auch hinsichtlich der floristischen Zusammensetzung gab es Unterschiede zwischen den beiden Zonen. Die Abundanz der Farne nahm mit zunehmender Höhe besonders stark ab. Lichtliebende und trockentolerante Gattungen der Familien Orchidaceae und Bromeliaceae hatten hingegen in der Zone 2 eine höhere Abundanz. Im jungen Sekundärwald stellte sich die durchschnittlich 4,5m hohe Zone 3 (>2,25m - Kronenhöhe) verglichen mit den beiden Zonen 1 und 2 als arten- und individuenärmer heraus. Dies wurde insbesondere auf das geringe Alter und das Fehlen von geeigneten Etablierungsmöglichkeiten für vaskuläre Epiphyten sowie auf deren oft langsames Wachstum zurückgeführt. Beim Vergleich der Epiphytenvegetation des Unterwuchses und des Kronendaches stellte sich heraus, dass trotz einer etwa doppelt so hohen Abundanz im Kronendach, die Anzahl der Arten im Unterwuchs und im Kronendach fast gleich hoch war. Hinsichtlich der Artenzusammensetzung unterschieden sich Unterwuchs und Kronendach stark voneinander. Von den insgesamt 229 aufgenommenen Arten kamen etwa 40% ausschließlich im Unterwuchs vor und nur 20% waren sowohl im Unterwuchs als auch im Kronendach vertreten. Im Vergleich des jungen Sekundärwaldes mit Primärwald zeigten sich ebenfalls starke Unterschiede. Im jungen Sekundärwald waren Abundanz und Artenzahl sowie der Anteil zoochor ausgebreiteter Arten um ein Vielfaches niedriger als im Primärwald. Die monokotylen Epiphyten, darunter insbesondere Orchidaceen, hatten im Primärwald die höchste Abundanz und Artenzahl. Im jungen Sekundärwald waren die monokotylen Epiphyten zwar auch die artenreichste Klasse, ihre relative Abundanz war jedoch wesentlich geringer. Trotz der hohen relativen Abundanz der Farne im jungen Sekundärwald hatten besonders feuchtigkeitsliebende Farnfamilien eine sehr geringe Abundanz. Dies wurde auf das weniger konstant-feuchte Mikroklima des jungen Sekundärwaldes mit seinem noch nicht so stark geschlossenen Kronendach (hohe Kronendachöffnung) zurückgeführt. So war beispielsweise die feuchigkeitsliebende Farnfamilie Hymenophyllaceae, die im Primärwald nach den Orchidaceen die zweithöchste Abundanz hatte, im jungen Sekundärwald mit einer nur sehr geringen Abundanz vertreten. Diese Ergebnisse verdeutlichten zum einen die Bedeutung der Unterwuchsepiphyten für die Diversität der gesamten Epiphytenvegetation tropischer Bergregenwälder. Zum anderen zeigte sich die besondere Sensibilität dieser Unterwuchsepiphyten gegenüber den mikroklimatischen Bedingungen ihrer Standorte. Dies zeigte die Abnahme ihrer Abundanz und Artenzahl mit Abnahme der konstanten Luftfeuchtigkeit in höheren Stammbereichen. Charakteristische Unterwuchsepiphyten sind wahrscheinlich deshalb im jungen Sekundärwald noch vergleichsweise schwächer vertreten als charakteristische Kronendachepiphyten, weil sich die mikroklimatischen Bedingungen, wie sie in älteren Wäldern und besonders in Primärwäldern im Unterwuchs vorherrschen noch nicht wieder eingestellt haben. Selbst der untersuchte etwa 30 bis 40 Jahre alte, gestörte bzw. sekundäre Wald (Gebiet ECSF) hatte im Vergleich zum Primärwald eine immer noch deutlich geringere Abundanz und Artenzahl. Dies deutet darauf hin, dass die Sukzession der Epiphytenvegetation ein sehr langsamer Prozess ist. Es stellt sich die Frage, ob es möglich ist und wie lange es in diesem Fall dauert, bis sich wieder eine primärwaldähnliche floristische Zusammensetzung und eine hohe epiphytische Diversität entwickelt.

Abstract:

Pteridophytes, understood as taxonomic group containing ferns, horsetails, and clubmosses, are especially diverse and abundant in the tropical mountain ranges of South America. My work aims to understand better the diversity of these plants, how they have evolved, and how they function in the ecosystems. Tree ferns are conspicuous elements of tropical montane rainforest. About 200 species of scaly tree ferns of the family Cyatheaceae occur in the Neotropics, ranging from small trunkless ferns of rocky outcrops to almost 20 m tall giants in dense forests. My work on these plants led to the recognition of 19 new and several formerly synonymized species in the genera Alsophila and Cyathea. The confusing nomenclature of the family was partially clarified by the correction of the typification of Cyathea pallescens (Sodiro) Domin. A checklist with keys to the Bolivian tree ferns was also accomplished during these studies. The revision of the genus Melpomene revealed 27 species with 10 varieties, most of them small ferns with deeply pinnatifid fronds, which are mostly epiphytes in upper montane forests or characteristic terrestrial elements of treeless páramo vegetation. The phylogenetic analysis based on morphology and chloroplast DNA shows that this genus as currently morphologically circumscribed is monophyletic and originated in South America. The radiation of the core group is apparently directly connected with the uplift of the northern Andes, which is the center of diversity of this genus. My ecologically orientated field studies of fern communities in southern Ecuador initiated several projects that aimed on different aspects. I found 248 different species of pteridophytes in our main study area, the Reserva Biológica San Francisco (RBSF), Prov. Zamora-Chinchipe, but this number is likely to increase in the future. The study area is part of the Amotape-Huancabamba zone, a stretch of low elevation in the Andes located a the overlap of several biogeographic subunits and thus rich in endemic and widespread species alike. I found that the upper limit in the elevational distribution of most of the widespread ferns follows this dent in the mountain range, indicating that probably a downward shift of all vegetation belts may be found. The mountain ridges in the RBSF support a unique heath forest dominated by the otherwise rare tree Purdiaea nutans Planch., but these peculiarities are not reflected in the fern composition. Ridge habitats in the study area, including two comparative sites close to the RBSF, are less diverse than adjacent slopes, and there was no higher representation of localized species on ridges. Overall, widespread species were weakly but significantly more abundant than localized species, and terrestrial ? but not epiphytic ? species were more abundant on ridges compared to slopes. The observed influence of soils on the distribution of ferns in the Ecuadorian study area, where terrestrial and phylogenetically more derived taxa increase in diversity along a nutrient gradient caused by a downhill flux from the ridges to the gorges, encouraged me to look at the soil preferences of pteridophytes worldwide and see if it contains a phylogenetic signal. It seems that more derived lineages are better represented on rich soils, but have also a higher percentage of epiphytes. Looking at the mediator between soils and plant roots, the mycorrhizal fungi, I found that the published reports cover only a small fraction of the fern diversity and often give contradicting results. Focusing on neglected taxa, like the epiphytic Hymenophyllaceae, grammitid ferns (Polypodiaceae), and the genus Elaphoglossum (Dryopteridaceae), the investigation of root samples gathered in the Ecuadorian study area increased the known number of fern species with ascomycete infection considerably. The finding of this more derived type of mycorrhiza is in concordance with the phylogenetic position and life form of the host plants. Terrestrial and especially phylogenetically basal groups of pteridophytes have predominantly vesicular-arbuscular mycorrhiza, which is a very common and supposedly old form symbiosis.

Abstract:

Die Bergregenwälder und Bergnebelwälder Ecuadors gehören zu den artenreichsten und gleichzeitig auch zu den am meisten bedrohten Gebieten der Erde. Bisher ist nur recht wenig über die Stoffkreisläufe in dieser Region bekannt. Meine Arbeit beschäftigt sich mit der Mineralisation, in einem tropischen Bergwald in Südecuador. Die Mineralisation ist für die Erforschung der Stoffkreisläufe von wesentlicher Bedeutung, da sie die Nährstoffnachlieferung in tropischen Bergregenwäldern beschreibt. Die Bestimmung der Mineralisation war bisher mit großem Untersuchungs- und Zeitaufwand verbunden. Deshalb wurde in dieser Arbeit nicht nur die Freisetzung von Nährstoffen bestimmt, sondern auch untersucht ob es möglicherweise mit geringem Untersuchungsaufwand zu bestimmende Proxydaten für die Mineralisation gibt. Es wurde dabei untersucht, (i) ob die Freisetzung von Nährstoffen in Tälern und auf Hangrücken sich unterscheiden; (ii) ob und wenn ja welche Elemente die Mineralisation und damit möglicherweise den Pflanzenwuchs limitieren. Weiterhin soll untersucht werden, ob (iii) Bodenparameter wie Auflagemächtigkeit, C/N-Verhältnis, C/S-Verhältnis, beziehungsweise (iv) die Verhältnisse der Isotopensignaturen (δ13C, δ15N) der organischen Auflage- bzw. der mineralischen Horizonte als Proxies für die Stickstofffreisetzung genutzt werden können. Hierzu wurde ein Inkubationsexperiment im Labor unter optimalen Bedingungen durchgeführt, bei welchem die Umsätze von NH4+, NO3-, DON, o-PO43-, DOP, Cl-, Ca, K, Mg, Na sowie Mn und Zn wöchentlich über einen Zeitraum von 92 Tagen bestimmt wurden. Dies erfolgte für jeweils 10 Profile auf einem Grat (T2) und in einem Tal (Q2). Beprobt wurden die L-, A- und Horizonte sowie ein Mischhorizont aus Of und Oh. Parallel dazu wurden die Isotopensignaturen dieser Horizonte bestimmt. Grat und Tal unterschieden sich signifikant hinsichtlich NH4+- und NO3-- Freisetzung pro Jahr. Im Tal wurde mehr NO3--N freigesetzt (0,143 kg m-2 a-1; SE 0,034 gegenüber 0,038 kg NH4+-N m-2 a-1; SE 0,012 auf dem Grat) und auf dem Grat wurde mehr NH4+-N freigesetzt (0,122 kg m-2 a-1; SE,014 gegenüber 0,056 kg NO3--N m-2 a-1; SE 0,028 im Tal). Als limitierende Faktoren für die Mineralisation kommen o-PO43-, Ca und K in Frage. Die nötigen Zugaben an ortho-Phosphat, welche zu einer P-Sättigung nötig waren, betrugen in den OHorizonten, welche den höchsten Bedarf aller Horizonte aufwiesen, 3,55 M/kg im Tal und 4,40 M/kg auf dem Grat, bei Ca und K jeweils 15,99 M/kg im Tal, bzw. 19,80 M/kg auf dem Grat. Bei K und Ca war nicht auszuschließen, dass der im Experiment gemessene Bedarf auf abiotischen Faktoren zurückzuführen ist und nicht auf eine Limitation der an der Mineralisation beteiligten Organismen.

Abstract:

Der Gefährdung der Ressourcen im tropischen Regenwald durch den zunehmenden Nutzungsdruck kann nur durch nachhaltiges Management begegnet werden (Bruijnzeel, 1990). In meiner Arbeit untersuchte ich den Einfluss einer experimentellen Forstmanagement-Maßnahme auf den Wasserhaushalt von kleinen Wassereinzugsgebieten unter tropischem Bergregenwald in Ecuador. Dazu bilanzierte ich die Wasserflüsse im Kronenraum und in den gesamten ca. 10 ha großen Einzugsgebieten. Außerdem analysierte ich den zeitlichen Verlauf der Wasserflüsse in den ersten beiden Jahren nach dem forstlichen Eingriff (06.05.2004-03.05.2006). In einer achtwöchigen Vorlaufphase zeigte sich, dass das ungestörte Vergleichseinzugsgebiet Q2 einen mit Q5, dem forstlich gemanagten Einzugsgebiet, vergleichbaren Wasserhaushalt aufwies. Bei der Prüfung der einzelnen Parameter des Wasserhaushaltes auf Veränderungen durch den Einfluss der Durchforstungsmaßnahme konnten keine signifikanten Veränderungen zwischen Q2 und Q5 festgestellt werden. Im Durchschnitt der beiden Wassereinzugsgebiete und der beiden untersuchten Jahre betrugen die mittleren Jahressummen des Freilandniederschlages 2.550±257 mm (Q2: 2609 mm/ Q5: 2647 mm), des Bestandesniederschlages 1590±240 mm (Q2: 1452 mm/ Q5: 1728 mm) und des Abflusses 1058±251 mm (Q2: 1006 mm/ Q5: 1110 mm). Die Evapotranspirationsrate betrug 1485±243 mm (Q2: 1524 mm/ Q5: 1445 mm), wobei der Interzeptionsverlust 1043±234 mm (Q2: 1161 mm/ Q5: 924 mm) und die Transpirationsrate 442±51 mm (Q2: 363 mm/ Q5: 521 mm) ergaben. Der Nebeleintrag war vernachlässigbar. Im Hinblick auf den Wasserhaushalt kann das angewandte Forstmanagement als nachhaltig angesehen werden.

Abstract:

In den südecuadorianischen Anden wird derzeit der Erfolg eines Naturwaldmanagementexperimentes geprüft. Ziel dieses Experimentes ist es den Farmern eine Nutzungsalternative zum Brandroden anzubieten, die keinen Einfluss auf die Funktionalität und (Bio-) Diversität des Bergregenwaldes hat. Diese Alternative besteht darin, dass Bäume gefällt werden, die in Konkurrenz mit ökonomisch wertvollen Bäumen stehen, um eine Leistungssteigerung dieser Wertbäume zu erzielen. Ziel meiner Arbeit ist es festzustellen, ob dieser Forsteingriff ökologisch nachhaltig ist und ob das Wachstum und die Erträge der Zielbäume im Untersuchungsgebiet auf diese Weise gesteigert werden können. Da sich ein nachhaltiges Ökosystem über einen geschlossenen Nährstoffkreislauf definiert, muss festgestellt werden, ob der Einund Austrag an Nährstoffen auf Einzugsgebietsebene durch den Forsteingriff verändert wird. Die Wirksamkeit des Experimentes im Sinne einer Förderung der Wertbäume hingegen setzt unter anderem gestiegene Nährstoffkonzentrationen in der Bodenlösung voraus. Die Untersuchungen werden in zwei Wassereinzugsgebieten im Bergregenwald (zwischen 1900 und 2200m ü. NN) an der Ostseite der östlichen Andenkordillere durchgeführt. Das Projekt wurde im Juni 2004 nach sechs Wochen Vorlauf etabliert. Beprobt werden im wöchentlichen Intervall Freiland- und Bestandesniederschlag, Oberflächenabfluss, sowie die Bodenlösung unterhalb der organischen Auflage und in 15cm bzw. 30cm Mineralbodentiefe. Diese Proben werden in je drei Messplots in dem Einzugsgebiet mit dem Forsteingriff und in einem naturbelassenen Referenzeinzugsgebiet gezogen, dann auf ihren pH-Wert und ihre elektrische Leitfähigkeit, sowie NO3-, NH4-, TN-. o-PO4-, TP-, Cl-, K-, Na-, Mg- und Ca- Konzentrationen und -Flüsse hin analysiert. Festgestellt wurde, dass sich Stoffein- und ?austrag durch die Forstmaßnahme nicht verändern, was für die Nachhaltigkeit des Experimentes spricht. In der organischen Auflage wurde eine verstärkte Nährstoffmineralisation vor allem von Stickstoff festgestellt, der direkt von den Pflanzen aufgenommen werden kann, was einen Erfolg des Experimentes belegt, da eine ansteigende Mineralisierung und somit mehr vorhandenen Nährstoffe im obersten Bereich des Bodens festzustellen sind.

Abstract:

- Presently, molecular ecological studies of arbuscular mycorrhizal fungi (AMF) are only possible above species-level when targeting entire communities. To improve molecular species characterisation and to allow species-level community analyses in the field, a set of newly designed AMF specific PCR primers is successfully tested. - Nuclear rDNA fragments from diverse phylogenetic AMF lineages were sequenced and analysed to design four primer mixtures, each targeting one binding site in the small (SSU) or large subunit rDNA (LSU). To allow species resolution, they span a fragment covering the partial SSU, whole internal transcribed spacer rDNA region (ITS), and partial LSU. - The new primers are suitable to i) specifically amplify AMF rDNA from material that may be contaminated by other organisms, e.g., samples from pot cultures or the field, ii) characterise the diversity of AMF species from field samples, and iii) amplify a SSU-ITS-LSU fragment that allows phylogenetic analyses with species-level resolution. - The described PCR primers can be used for monitoring of entire AMF field communities, based on a single rDNA marker region. Their application will improve the base for deep sequencing approaches, and moreover they can be efficiently used as DNA barcoding primers.