Browsing by Author "Behling, Hermann"

Human activities are increasingly threatening the integrity of Earth’s ecosystems. For successful conservation measures, one necessary prerequisite is an adequate level of understanding about the ecosystems and their constituting organisms. Currently, however, there are considerable deficits in our knowledge about which and how many species exist (Linnean shortfall), where these species are distributed geographically (Wallacean shortfall) and ecologically (Hutchinsonian shortfall), how abundant they are (Prestonian shortfall), and their evolutionary histories (Darwinian shortfall), among others. Many methods are available to fill these existing knowledge gaps but one of the undoubtedly crucial approaches is work on the ground in tropical hinterland regions, where high levels of biodiversity, important knowledge gaps, and often imminent threats to natural habitats coincide. One example for such a hinterland region is the Indonesian island of Sulawesi in the centre of the Malesian archipelago, whose large portions of relatively undisturbed tropical mountain forests harbour a rich and biogeographically unique, yet poorly known flora. With his thesis, I aim to contribute to a better understanding of the ecology of Sulawesi’s tropical mountain forest and its tree flora in relation to environmental factors and evolutionary history. To do so, I conducted extensive plot-based field work in the Lore Lindu National Park in Central Sulawesi, putting special emphasis on rigorous species identification. In the different chapters, I address the specific knowledge gaps or shortfalls outlined above. In an attempt to deal with the Linnean shortfall, I describe seven new endemic tree species from Sulawesi (Chapters 1–3), including information of their distribution, ecology, and conservation status. The species descriptions furthermore provide the necessary foundation for analyses carried out in later chapters. Chapter 1 contains the description of Magnolia sulawesiana (Magnoliaceae), a new Magnolia species from upper montane forests of Sulawesi, as well as an identification key for all ten species of the genus native to the island. Another montane species, Elaeocarpus firdausii (Elaeocarpaceae) of the species-rich and predominantly Australasian genus Elaeocarpus, is described in Chapter 2. In the third chapter, I propose five new species of Syzygium (Myrtaceae), one of the largest genera of woody plants worldwide. Although the genus is widespread, diverse, and often dominant, the taxonomy of Syzygium in Sulawesi is largely unresolved and taxonomic work on the genus is urgently needed. The newly proposed species are Syzygium balgooyi, Syzygium contiguum, Syzygium devogelii, Syzygium eymae, and Syzygium galanthum. In Chapter 4, I investigate patterns of tree species diversity, endemism, and composition along gradients of elevation and soil properties. I show that species diversity in Sulawesi at the plot level is similar to other Malesian regions and that it monotonically declines with elevation. Over 25% of the recorded tree species are new occurrence-records for (Central-) Sulawesi or undescribed species, highlighting how underexplored the region is. Levels of endemism found in this study clearly exceed estimates from previous studies, especially in high-elevation forests. The forest communities are mostly determined by elevation and can be grouped into three floristically distinct elevational belts whereas soil characteristics play only a minor role. I take a closer look at understorey trees species, a guild that is often neglected in standard forest or biodiversity inventories and highlight the important contribution of these understorey tree species to local species diversity. Given Sulawesi’s geographical position and geological history, the island’s tree flora needs to be viewed in a wider spatial and temporal context that includes Asia and Australia. I therefore widen the scope in Chapter 5 to address the Darwinian shortfall, which is defined as the lack of knowledge about the evolutionary history of Malesian tree species. The central part of Malesia only formed in the last 23 My and in that timespan, plants have colonized Malesia from Asia and Australia in a process termed the Malesian Floristic Interchange. I used my dataset from Central Sulawesi and published studies from other Malesia subregions and inferred the geographical origin of the tree lineages in the dataset based on phylogenetic and fossil information. I then related the relative abundance of Asian versus Australian trees per plot to environmental parameters to show that the colonization success of tree lineages in Malesia is strongly determined by habitat. The results showed a higher proportion of Australian tree species and individuals at higher elevations, over ultramafic bedrock, and east of Wallace’s line. The trend is stronger for tree individuals than for species meaning that montane forests and those on poor soils in Malesia are mainly dominated by Australian tree-lineages. These patterns are a consequence of the climatic and biogeographical history of Malesia and indicate that environmental similarities between source and sink habitats have largely determined the colonization success during the Malesian floristic interchange. In conclusion, I show that the rain forests of Sulawesi harbour a species-rich and unique tree flora, characterized by high proportions of small understorey trees and endemic species, many of which remain to be discovered and formally described. The biogeographical history changes from sub-montane communities dominated by Asian tree lineages to upper montane forests composed of mainly Australian lineages and many endemics. Although less-diverse than lowland rain forests, these upper montane communities therefore have high conservation values. At the same time, they remain among the least-studied ecosystems in Malesia. While with this thesis I hope to have bridged some knowledge gaps regarding Sulawesi’s trees and forests, repeated biodiversity inventories including phylogenetic and trait-based approaches will be indispensable to improve our baseline knowledge about plant diversity patterns in Sulawesi.

Understanding the organization of mutualistic networks at multiple spatial scales is key to ensure biological conservation and functionality in human-modified ecosystems. Yet, how changing habitat and landscape features affect pollen–bee interaction networks is still poorly understood. Here, we analysed how bee–flower visitation and bee–pollen-transport interactions respond to habitat fragmentation at the local network and regional metanetwork scales, combining data from 29 fragments of calcareous grasslands, an endangered biodiversity hotspot in central Europe. We found that only 37% of the total unique pairwise species interactions occurred in both pollen-transport and flower visitation networks, whereas 28% and 35% were exclusive to pollen-transport and flower visitation networks, respectively. At local level, network specialization was higher in pollen-transport networks, and was negatively related to the diversity of land cover types in both network types. At metanetwork level, pollen transport data revealed that the proportion of single-fragment interactions increased with landscape diversity. Our results show that the specialization of calcareous grasslands’ plant–pollinator networks decreases with landscape diversity, but network specialization is underestimated when only based on flower visitation information. Pollen transport data, more than flower visitation, and multi-scale analyses of metanetworks are fundamental for understanding plant–pollinator interactions in human-dominated landscapes.

We analysed pollen and macro-charcoal from a sediment core representing the last 9840 cal yr BP, collected at 2003 m a.s.l. in a patch of upper montane Atlantic Rain Forest (UMARF) embedded in a campos de altitude (high-elevation grassland) matrix in the Serra dos Órgãos National Park, southeastern Brazil. From 9840 to 4480 cal yr BP, campos de altitude (CDA) was the dominant vegetation at the site, indicating that the climate was relatively cool and dry. However, pollen data document that UMARF was near the core site throughout the recorded Holocene. Relatively frequent high-magnitude fires occurred during the Early Holocene but became rarer in the Mid-Holocene after 4480 cal yr BP, when the climate became wetter. In the Mid-Holocene, UMARF and tree fern taxa became slightly more frequent at the site, but CDA vegetation continued to dominate most of the high-mountain landscape. A climatic change to wetter and warmer conditions during the last 1350 cal yr BP is evidenced by an increase in UMARF and even lowland forest taxa in our core, as well as the near complete absence of fire after this date.

Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well‐known that semi‐natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear. We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff‐tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central Germany. We found that augmenting maize cover had a detrimental effect on pollen diversity collected by bumblebees, probably due to intensive management resulting in low plant diversity. This low pollen diversity translated into reduced colony growth, since colonies with high pollen diversity gained more weight than colonies with low pollen diversity. In contrast, OSR cover and configurational and compositional heterogeneity did neither affect colony growth nor pollen diversity. However, for OSR, the timing of the flowering period was important. When OSR fields had a high flower cover at the end of the OSR blooming period, colonies showed increased growth rates. Synthesis and applications. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass‐flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services. Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well‐known that semi‐natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear. We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff‐tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central Germany. We found that augmenting maize cover had a detrimental effect on pollen diversity collected by bumblebees, probably due to intensive management resulting in low plant diversity. This low pollen diversity translated into reduced colony growth, since colonies with high pollen diversity gained more weight than colonies with low pollen diversity. In contrast, OSR cover and configurational and compositional heterogeneity did neither affect colony growth nor pollen diversity. However, for OSR, the timing of the flowering period was important. When OSR fields had a high flower cover at the end of the OSR blooming period, colonies showed increased growth rates. Synthesis and applications. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass‐flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services.

Although it is well known that humans substantially altered the Malagasy ecosystems, the timing of the human arrival as well as the extension of their environmental impact is yet not well understood. This research aims to study the influence of early human impact and climate change on rainforests and wildlife in northern Madagascar during the past millennia. Results obtained from the lake sediment in a montane environment showed significant changes in vegetation within the lake catchment associated with a major drought that started approximately 1100 years ago. Human impact, revealed by fires, began at roughly the same time and occurred outside the lake catchment. Although this does not dismiss the impacts that humans had at a regional scale, this result demonstrates that the late Holocene natural drought also significantly impacted the ecosystems independently of anthropogenic activities. At a regional scale, a review of species demographic history revealed a substantial number of population bottlenecks during the last millennia, probably resulting from this combination of human-related impact and natural climate changes. This research highlights the importance of a multi-site and multi-proxy comparison for deciphering the nature and succession of environmental changes.

The increase of world population needs more food, feed, fuel, and fiber. Meanwhile, agricultural land supply is somewhat stationary or even decreasing. Ensuring food provision requires both intensification and expansion strategies. Considering internal circumstances, options may vary across countries. Indonesia, for instance, by population growth rate at 1.3 % year −1 and increasing middle income families, the need of diversity and improved quality of food become prevalent. Nevertheless, irrigated agricultural production decreased considerably, being converted to non-agricultural uses. The deterioration of agricultural land resources has occurred due to mismanagement while climate change has worsened the conditions globally. Narrowing yield gap in the existing agricultural land has been the primary efforts worldwide. Various farming systems have been established to minimize agro-inputs while generating high yields. The efforts differ across agro-ecosystems and being specific for each country. In Indonesia, the agro-ecosystems are divided into irrigated and rainfed agricultural lands, uplands (dry- and wet-climate agricultural lands), and wetlands (tidal and non-tidal agricultural lands, including peatlands). Each ecosystem requires specific land management which combines strategies and components previously studied. List of Conference Committee, Steering Committee, Delegate list are available in this pdf.

We studied the modern pollen rain in two different landscapes from Hyrcanian lowland forests up to the slopes of the Alborz Mountains in Gilan province for the first time. Pollen traps were installed for one year and moss samples were collected along two altitudinal transects from 100 to 1800 m and from 100 to 2300 m elevations. The results of pollen counting and environmental DNA barcoding (metabarcoding) of the collected pollen and moss samples were compared from 32 locations. In total, 81 vascular plant species from 36 families were identified by metabarcoding, and 68 taxa belonging to 39 families were identified by pollen counting. The pollen counting results reflect mainly wind-pollinated families, such as Betulaceae and Fagaceae while results from metabarcoding of the rbcL and ITS2 loci were more in line with the vegetation around the pollen traps and the moss samples. Furthermore, this study showed that the rbcL region is able to identify more taxa than the ITS2 region, while applying both markers provides higher confidence. Also using both metabarcoding and pollen data provides a better local and regional vegetation representation.

Abstract The Sundarban Mangrove Forest in the Sundarban Biosphere Reserve, located at the mouth of the Ganga–Brahmaputra Delta in India, is the most diverse mangrove ecosystem in the world. Sediment cores were taken from two widely separated islands in that reserve: Chamta (CMT) and Sudhyanyakhali (SDK). Pollen analysis and radiocarbon dating were used to study the Holocene development and dynamics of this unique ecosystem. Modern pollen rain study reveals a strong relation between modern pollen rain and the present vegetation, as well as a high rate of Phoenix palludosa pollen production.The pollen records indicate that man-grove existed at CMT from ~5960 and at SDK from ~1520 cal yr BP. Changes in relative sea level, including the frequency and intensity of inundation as well as fluctuating precipitation, have been the major factors along with geomorphic processes that control the development and dynamics of the mangrove in the area during the Holocene. The mid Holocene mangrove at CMT declined, to be progressively replaced by successive communities, and eventually reached climax stage, while the SDK site is transitional in nature. The mangrove responds rapidly to changes in environmental conditions at both locations. Because of large-scale anthropogenic interventions, it is unlikely that similar rapid responses will occur in the future.