Hans Juergen Boehmer

Leibniz Universität Hannover · Institute of Earth System Sciences Geobotany Section

Aim: The relationship between native and naturalized alien species has been widely studied, particularly across large geographic scales. However, our knowledge of the spatial and temporal variations of their relationships is still limited, particularly for remote oceanic islands such as those of the southeast Pacific and across islands and archipel...

Das Schicksal unserer Wälder ist seit den 1980er Jahren ein Dauerthema in den Medien. Wurde das Phänomen „Waldsterben“ zunächst mit „Saurem Regen“ durch Luftverschmutzung in Zusammenhang gebracht, steht es seit dem Einsetzen immer häufigerer Dürren und Temperaturextreme um die Jahrtausendwende sinnbildlich für die Auswirkungen des Klimawandels. Dab...

Between 1954 and the mid-1980s, about 50,000 ha of native montane rainforest on the island of Hawai'i experienced a decline in canopy trees ("'ōhi'a dieback"), leading to great concern about the future of Hawai'i's rainforests. Dieback symptoms particularly affected the dominant tree species, the endemic Metrosideros polymorpha. Early hypotheses po...

Alu-elements comprise a large part of the human genome and some insertions have been shown to cause diseases. Here, we illuminate the protective role of an Alu-element in the 3’UTR of the human Factor 9 gene and its ability to ameliorate a poly(A) site mutation in a hemophilia B patient, preventing him from developing a severe disease. Using a mini...

Langfristige Aufzeichnungen und Vergleiche mit historischen Daten, sogenannten Legacy Data, sind entscheidend für die exakte Analyse der Reaktionen von Pflanzen- und Tierarten auf globale Veränderungen, unter anderem auf Klimawandel und biologische Invasionen. Die überzeugendsten Belege für Auswirkungen auf die Biodiversität stammen aus Langzeitstu...

Metrosideros polymorpha (‘ohi‘a, ‘ohi‘a lehua) is an important foundation species in Hawaiian forest habitats. The genus originated in New Zealand and was dispersed to the Hawaiian archipelago approximately 3.9 million years ago. It evolved into five distinct endemic species and one of these, Metrosideros polymorpha, further differentiated into eig...

Das Institut für Geobotanik der Leibniz Universität Hannover erforscht im globalen Netzwerk ITMN die komplexen Klimawandelfolgen in Regenwäldern des Pazifikraums.

Biological invasions drive biodiversity loss and ecosystem change on tropical islands. However, we know little about the implications of species losses on the functional structure of both resident and novel communities. Herein, we examined the potential effect of a non-native palm species, Pinanga coronata, on the taxonomic and functional assemblag...

The introduction and further spread of many alien species have been a result of trade and transport. Consequently, alien species are often found close to traffic infrastructure and urban areas. To contain and manage the spread of alien species, it is essential to identify and predict major routes of spread, which cannot be obtained by applying comm...

The South Pacific region is a hotspot of biodiversity but also has the world´s highest concentration of invasive alien plant species. Although the issue of biological invasions has been increasingly acknowledged by local governments and international agreements, invasive alien species are often not monitored properly. Knowledge of the potential imp...

In this popular science book (so far only available in German) I present in a generally understandable way how the world's forests react to global change and in particular to global warming. It includes a short history of research on the subject of "Forest Dynamics and Climate Change" with a focus on developments over the last decades up to the pre...

Ecosystems play a potentially important role in sustainably reducing the risk of disaster events worldwide. Yet, to date, there are few comprehensive studies that summarize the state of knowledge of ecosystem services and functions for disaster risk reduction. This paper builds scientific evidence through a review of 529 English-language articles p...

Science is expected to orient societal and individual action. But what does it mean to take responsibility for this orientation? The contributors to this book deal with general and subject-specific dimensions of geographical responsibility and formulate characteristics of a responsible scientific practice that follows good reasons. These good reaso...

Der Essay thematisiert den Widerspruch zwischen der Dokumentation von Umweltproblemen und der Verabschiedung internationaler Abkommen zum nachhaltigen Umgang mit globalen Ressourcen einerseits und dem Fortbestand eklatanter globaler Umweltprobleme andererseits. Dass auch der Umweltwissenschaft Physische Geographie längst eine nicht-nachhaltige Prax...

Von der Wissenschaft wird erwartet, dass sie gesellschaftliches und individuelles Handeln orientiert. Doch was heißt es, Verantwortung für diese Orientierung zu tragen? Die Beiträger*innen des Bandes gehen auf die allgemeine sowie die fachspezifische Dimension geographischer Verantwortung ein und formulieren Merkmale einer verantwortungsvollen und...

In island ecosystems, biological invasions are one of the major threats to native biodiversity and to ecosystem functioning. Invasive ornamental plants such as the alien palm tree Pinanga coronata in the Fiji islands can form mono‐dominant stands in rainforests and displace native species. Using a functional trait‐based approach, we investigated th...

The complexity of forest structures plays a crucial role in regulating forest ecosystem functions and strongly influences biodiversity. Yet, knowledge of the global patterns and determinants of forest structural complexity remains scarce. Using a stand structural complexity index based on terrestrial laser scanning, we quantify the structural compl...

Tropical forest tree inventories and plot projects have generated large amounts of data over many decades, but much of this data is in paper or older digitized formats, or still undiscovered. These legacy datasets are invaluable for understanding how tropical forests, biodiversity, and carbon storage change through time, including the cumulative im...

Tropical Pacific island countries, many of which are less-developed, are experiencing invasions of alien plant species at rates faster than areas of comparable size elsewhere. In this paper we examine the relationship between the presence, abundance, and richness of 14 invasive woody plant (IWP) species and level of urbanization and road type in th...

Die Vielfalt von Arten und Ökosystemen in Ozeanien ist durch biologische Invasionen, d. h. die unkontrollierte Ausbreitung gebietsfremder, von Menschen eingebrachter Tier- und Pflanzenarten bedroht, seit der Mensch vor Jahrtausenden die natürliche Ausbreitungsbarriere „Ozean“ überwunden hat. Biologische Invasionen spielen im Prozess der nachhaltige...

Unterrichtsmaterial "Insulare Biodiversität" mit Fokus auf die Problematik einer biologischen Invasion im Südpazifik. Die gebietsfremde Elfenbein-Rohrpalme (Pinanga coronata) aus Indonesien breitet sich massenhaft im fidschianischen Regenwald aus und bedroht seine natürliche Artenvielfalt. Dieses in Anlehnung an den Beitrag "Insulare Biodiversität...

Im Bereich der Ökologie wird redundante Forschung auf Tagungen und in Publikationen in wachsendem Maße als innovativ und bedeutsam dargestellt. Zudem sind viele Vorträge, Veröffentlichungen und Forschungsanträge bezüglich ihrer Berücksichtigung der jeweiligen disziplinären Grundlagen in Besorgnis erregendem Maße defizitär. So wird der Wissenschafts...

In this paper, we reinforce memory of the World´s first complex discussion on the natural causes of forest dieback as a showcase for the complexity of forest mortality research, and try to summarize what science has added to our knowledge on the links between tree mortality, forest dynamics and climate change in the Pacific islands in the meantime.

Long-term vegetation records are of crucial importance for investigating plant species´responses to global change, in particular to climate change and biological invasions. Some of the strongest evidence for the impacts on forest ecosystems comes from long-term studies through comparisons of current with previous data, based on methodological consi...

An die Geographie wird die Erwartung herangetragen, zukunftsweisende Antworten unter der Bedingung von Unübersichtlichkeit und Unvorhersehbarkeit zu geben – angesichts des gesellschaftlichen Imperativs der Digitalisierung, der Klimaänderung, weltweiter Ungerechtigkeiten und Migrationsbewegungen. Zugleich zeichnet sich die Geographie durch hochdiver...

Invasive alien ornamental plants are a global problem, especially on oceanic islands, and can have severe impacts on native biodiversity. Pinanga coronata, is an ornamental palm tree that can form mono-dominant stands in its native habitat and is widely cultivated throughout the tropics. Here we investigate the introduction, spread, impact and mana...

Questions (a) Have Metrosideros polymorpha trees become re‐established in Hawaiian forests previously impacted by canopy dieback in the 1970s? (b) Has canopy dieback expanded since the 1970s? (c) Can spatial patterns from this dieback be correlated with habitat factors to model future dieback in this area? Study Site An 83,603 ha study area on the...

Invasive ornamental plants are a global problem that can have severe impacts on native biodiversity, especially on islands. To determine whether the invasive, ornamental ivory-cane palm Pinanga coronata could be displacing native biodiversity, we investigated its co-distribution with native tree ferns in a Fijian rainforest. We recorded the abundan...

To investigate changes in vegetation and climate with altitude, we established forest plots and recorded climatic data at 100-m intervals between 550–1100 m asl on the western slopes of Mount Batilamu, Mount Koroyanitu range, Viti Levu, Fiji. Trees with a dbh ≥10 cm were identified and measured in 21 10 × 10-m plots, starting at 750 m altitude. Tem...

’Ohi‘a (Metrosideros polymorpha) is the most abundant tree species in the native wet and mesic forests throughout the main Hawaiian Islands. In the late 1960s and early 1970s large areas on the wet, eastern side of Hawai‘i island appeared to have extensive defoliation and death of the ’ohi‘a trees. The dieback on Hawai‘i island extended to approxim...

Ecological connectivity networks have been proposed as an efficient way to reconnect communities in fragmented landscapes. Yet few studies have evaluated if they are successful at enhancing actual functional connectivity (i.e. realized dispersal or gene flow) of focal species, or if this enhanced connectivity is enough to maintain genetic diversity...

Oceanic island ecosystems are considered to have a poor resilience against biological invasions. In many Pacific island forests, for instance, introduced plant species have become dominant in recent decades. A new and, regarding its invasiveness, unprecedented example in Fiji´s forests is the ivory cane palm, Pinanga coronata, which is native to Ja...

We studied the diversity, community composition and natural regeneration of woody species in an isolated but relatively large (> 1,000 ha) dry Afromontane forest in northern Ethiopia to assess its importance for regional forest biodiversity conservation. The principal human-induced disturbance regimes affecting this forest include logging and lives...

Diversity patterns of vascular plant species were studied along geographical gradients in the Afromontane regions of Ethiopia. Vegetation data were sampled from five moist evergreen Afromontane forest fragments, namely Harenna (southeast), Bonga, Maji, Berhane-Kontir and Yayu (southwest). In each forest, quadrats of 20x20 m were laid along transect...

The so-called ‘ohi‘a dieback, a landscape-level canopy tree decline on the island of Hawaii in the 1970s, has provided a unique opportunity to analyze the long-term dynamics of the rainforest canopy. Key questions include 1) Does a new landscape-level analysis support the conceptual model of Metrosideros polymorpha cohort dynamics as postulated in...

This essay, basically a review of the book "Hardware", is thought to be a reminder of Gerhard Hard´s brilliant contributions to the theory of vegetation science and plant geography.

Islands in the tropical Pacific have a rich and unique biota produced by island biogeographic processes and modified by recent anthropogenic influences. This biota has been shaped by four overlapping phases: natural colonization and dynamics (phase 1), impacts of indigenous (phase 2) and non-indigenous (phase 3) settlers, and increasing environment...

Response to habitat fragmentation may not be generalized among species, in particular for plant communities with a variety of dispersal traits. Calcareous grasslands are one of the most species-rich habitats in Central Europe, but abandonment of traditional management has caused a dramatic decline of calcareous grassland species. In the Southern Fr...

Directed dispersal by animal vectors has been found to have large effects on the structure and dynamics of plant populations in plants adapted to frugivory. Yet, empirical data are lacking on the potential of directed dispersal by rotational grazing of domestic animals to mediate gene flow across the landscape. Here, we investigated the potential e...

This paper addresses the question of transition states in the Hawaiian rainforest ecosystem with emphasis on their initial developments. Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering p...

Do long-term observations in permanent plots confirm the conceptual model of Metrosideros polymorpha cohort dynamics as postulated in 1987? Do regeneration patterns occur independently of substrate age, i.e. of direct volcanic disturbance impact? The windward mountain slopes of the younger Mauna Loa and the older Mauna Kea volcanoes (island of Hawa...

This paper evaluates the long-term effect of an ecological network of calcareous grasslands, a habitat type that experienced dramatic habitat loss and fragmentation during the 20th century, on species richness of habitat specialist plants. Calcareous grasslands are of special conservation concern as the habitat type with the highest diversity in pl...

In this book the authors of four generations (Dieter Mueller-Dombois, James D. Jacobi, Hans Juergen Boehmer, Jonathan P. Price) give an overview of five decades of intensive research carried out on the native Metrosideros polymorpha rainforests in Hawai‘i. Central in this book is the succession dynamics, specifically the processes through which the...

A brief history of the probably climate-induced forest decline called "Ohia dieback" (Big Island, Hawaii) in the 1970s and 80s, and its perception as reported from newspaper articles, memoranda, and symposia in the State of Hawaii.

Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering plants that over the millenia evolved into ca. 1000 endemic species. Outstanding among the forest builders were the tree ferns ( Cibotium...

Understanding plant species distribution patterns along environmental gradients is fundamental to managing ecosystems, particularly when habitats are fragmented due to intensive human land-use pressure. To assist management of the remaining vegetation of the Eastern Afromontane Biodiversity Hotspot, plant species richness and diversity patterns wer...

Background/Question/Methods For plants, seed dispersal is the process that determines population demographic connectivity, whereas both seed and pollen flow contribute to population genetic connectivity. The contribution of seeds to population genetic connectivity is typically expected to be negligible, as pollen may travel larger distances and i...

In fragmented landscapes, plant species persistence depends on functional connectivity in terms of pollen flow to maintain genetic diversity within populations, and seed dispersal to re-colonize habitat patches following local extinction. Connectivity in plants is commonly modeled as a function of the physical distance between patches, without test...

Forests are highly susceptible to dieback under ongoing climate warming. In degraded forests, dead standing trees, or snags, have become such prominent features that they should be taken into account when setting management interventions. This study investigated (1) the extent and spatial pattern of standing dead stems of Juniperus procera and Olea...

(Editorial Paper) Biologische Invasionen gelten neben der direkten Zerstörung von Lebensräumen durch Menschen als weltweit größte Bedrohung der biologischen Vielfalt. Vor allem die stete Zunahme von Fernhandel und Fernreisen im Zuge der Globalisierung lässt die Zahl von Einführungen gebietsfremder Arten in neue Lebensräume permanent ansteigen. Im...

Biological invasions are the second largest threat to global biodiversity after direct ecosystem destruction by man. Invasive alien species (IAS) are capable of completely changing the structure of invaded ecosystems, and of outcompeting native species by rapid population growth and controlling of nutrients and other essential resources. Furthermor...

Climate change increases the vulnerability of tropical montane rain forests e.g. by intensifying the frequency of climatic anomalies and extreme weather events, and increasing natural disturbances. A variety of human impacts additionally cause complex synergetic effects. The numerous consequences of these transformations include: changes in species...

Revised version of 2006 report on Fallopia japonica

Question: How does the floristic diversity of Afromontane rainforests change along an altitudinal gradient? What are the implications for conservation planning in these strongly fragmented forest areas that form part of the Eastern Afromontane Biodiversity Hotspot? Location: Bonga, southwestern Ethiopia. Methods: Based on evidence from other montan...

Hedychium gardnerianum is a major invader of native Hawaiian forests and suspected of smothering native understory species and preventing native tree seedlings’ establishment. In this study, effects on species composition in six vegetation layers of a Hawaiian rainforest were examined (Tree Layer 1, Tree Layer 2, Fern-Shrub Layer, Herb Layer, Bryop...

Coffea arabica occurs naturally in the montane rainforests of Ethiopia, but large areas of these unique forests have been converted to other land-uses. In the remaining forest, wild coffee is managed and harvested with increasing intensity because of rising coffee prices in the world market. This study evaluated the impact of coffee management on w...

Questions: Does the invasive alien Hedychium gardnerianum (1) replace native understory species, (2) suppress natural regeneration of native plant species, (3) increase the invasiveness of other non-native plants and (4) are native forests are able to recover after removal of H. gardnerianum. Location: A mature rainforest in Hawai'i Volcanoes Natio...

Large-scale analyses of the effects of climate change on the Earth´s biodiversity miss numerous local processes of crucial importance. This can be illustrated by using the sensitive forests of high-oceanic islands as model ecosystems. The montane rain forest on the island of Hawaii, for instance, was affected by a decline of the canopy trees in the...

Large-scale analyses of the effects of climate change on the Earth's biodiversity miss numerous local processes of crucial importance. This can be illustrated by using the sensitive forests of high-oceanic islands as model ecosystems. The montane rain forest on the island of Hawaii, for instance, was affected by a decline of canopy trees in the 197...

The main objective of this case study is to analyse the effects of the invasive alien North American beaver (Castor canadensis) on the autochtonous Nothofagus forest on Navarino Island in the Fuegian Archipelago (Archipiélago de Tierra del Fuego), Chile. On the study sites, (1) plant species diversity; (2) plant species composition; (3) proportion...

Revised version of 2006 report on Senecio inaequidens

Rainforest with wild Coffea arabica in the Bonga region is under severe land-use pressure and partly managed as semi-forest coffee (SFC) systems by local farmers. The objective of this study was to conduct vegetation surveys as a basis for conservation planning. Surveys were done in three forest fragments with natural and managed forest parts. In 7...

Biological invasions cause fundamental problems to many of the world’s ecosystems, particularly on islands. There is remarkable progress in international nature conservation efforts, but prevention of the problem could be improved on the national and regional level, e. g. by better public awareness through appropriate communication of the problem t...

A brief article suggesting biological invasions as a topic for high school education (in German).

Fallopia japonica has spread widely in Germany. It grows mainly on the banks of brooks and rivers, but also on ruderal sites. The massive appearance of F. japonica along rivers up to now is concentrated on distinct regions. At these locations it forms extended dense stands, exerting great competitive pressure upon the rest of the vegetation. F. ja...

Die Lösung zahlreicher Probleme der Praxis im Fluss- und Auenmanagement erfordert ein ausreichendes Verständnis dieser hochkomplexen, sehr artenreichen und vom Menschen in vielfältiger Weise beeinflussten Lebensräume. Ökologische Untersuchungen verwenden hierfür verschiedene Konzepte zu Umwelt-Organismen-Beziehungen. Je nach Fragestellung kommt es...

Das Flussbett der Elbe ist durch seine Ufer begrenzt, wobei die Uferlinie durch das Mittelwasser markiert wird. Durch die hydraulischen Kräfte bei Hochwasser können sich Uferkanten ausbilden und natürliche Uferwälle aus Sedimenten entstehen. Von der Niedrigwasserlinie, die die Grenze permanenter Wasserbedeckung beschreibt, steigt mit der Uferböschu...

Ein zentrales Ziel der biologischen Forschung innerhalb des BMBF-Forschungsverbundes „Elbe-Ökologie“ bestand darin, Faktoren im Fluss oder in der Aue aufzudecken, die das Vorkommen von Arten steuern, um auf dieser Grundlage ökologische Auswirkungen von Veränderungen der Lebensräume besser beurteilen und konkreter vorhersagen zu können. Daran orient...

Auf Organismen an Wasser wie an Land wirken unzählige Umweltfaktoren ein; diejenigen Faktoren, die entscheidend die Dynamik von Populationen und Lebensgemeinschaften bestimmen, sind von besonderem Interesse für die ökologische Forschung. Auf diese so genannten Schlüsselfaktoren, beispielsweise in Flüssen auf die Strömungsgeschwindigkeiten oder in A...

This study analyses changes in the landscape of a sector of Upper Franconia (Bavaria, Germany) by comparing land use changes over four time periods (1850, 1900, 1960, 2000). Geodetic and other data derived from the Bavarian real estate tax and land register were entered into various temporal layers of a land register-based vector GIS. This multitem...

Two case studies of cultural landscapes in Southern Germany were conducted to develop appropriate techniques for quantifying and analysing the landscape change since 1850. Methods were derived from geographical landscape change analysis, based on cadastral maps and land registers, and were rendered at a land plot level by the use of GIS. The databa...