1,721,002 research outputs found
Differences in Root Nitrogen Uptake Between Tropical Lowland Rainforests and Oil Palm Plantations
No full textConversion of lowland tropical rainforests to intensely fertilized agricultural land-use systems such as oil palm (Elaeis guineensis) plantations leads to changes in nitrogen (N) cycling. Although soil microbial-driven N dynamics has been largely studied, the role of the plant as a major component in N uptake has rarely been considered. We address this gap by comparing the root N contents and uptake in lowland rainforests with that in oil palm plantations on Sumatra, Indonesia. To this aim, we applied 15N-labeled ammonium to intact soil, measured the 15N recovery in soil and roots, and calculated the root relative N uptake efficiency for 10 days after label application. We found that root N contents were by one third higher in the rainforest than oil palm plantations. However, 15N uptake efficiency was similar in the two systems. This finding suggests that lower N contents in oil palm roots were likely caused by plant internal utilization of the absorbed N (e.g., N export to fruit bunches) than by lower ability to take up N from the soil. 15N recovery in roots was primarily driven by the amount of root biomass, which was higher in oil palm plantation than rainforest. The oil palms unveiled a high capacity to acquire N, offering the possibility of enhancing sustainable plantation management by reducing N fertilizer application.Open-Access-Publikationsfonds 202
Correction to: Fungal succession, litter decomposition and root nitrogen supply in a tropical oil palm plantation
No full textShifts in root and soil chemistry drive the assembly of belowground fungal communities in tropical land-use systems
No full textChanges in Trophic Groups of Protists With Conversion of Rainforest Into Rubber and Oil Palm Plantations
No full textProtists, abundant but enigmatic single-celled eukaryotes, are important soil microbiota providing numerous ecosystem functions. We employed high-throughput sequencing of environmental DNA, targeting the V4 region of the 18S rRNA gene, to characterize changes in their abundance, species richness, and community structure with conversion of lowland rainforest into rubber agroforest (jungle rubber), and rubber and oil palm plantations; typical agricultural systems in Sumatra, Indonesia. We identified 5,204 operational taxonomic units (OTUs) at 97% identity threshold of protists from 32 sites. Protists species richness was similar in rainforest, jungle rubber and oil palm plantations but significantly lower in rubber plantations. After standardization, 4,219 OTUs were assigned to five trophic groups, and inspected for effects of land-use change, and potential biotic and abiotic driving factors. The most abundant trophic group was phagotrophs (52%), followed by animal parasites (29%), photoautotrophs (12%), plant parasites (1%), and symbionts (<1%). However, the relative abundance and OTU richness of phagotrophs and photoautotrophs increased significantly with increasing land-use intensity. This was similar, but less pronounced, for the relative abundance of symbionts. Animal and plant parasites decreased significantly in abundance and species richness with increasing land-use intensity. Community compositions and factors affecting the structure of individual trophic groups differed between land-use systems. Parasites were presumably mainly driven by the abundance and species richness of their hosts, while phagotrophs by changes in soil pH and increase in Gram-positive bacteria, and photoautotrophs by light availability. Overall, the results show that relative species richness, relative abundance, and community composition of individual trophic groups of protists in tropical lowland rainforest significantly differ from that in converted ecosystems. This is likely associated with changes in ecosystem functioning. The study provides novel insight into protist communities and their changes with land-use intensity in tropical lowland ecosystems. We show, that trophic groups of protists are powerful indicators reflecting changes in the functioning of ecosystems with conversion of rainforest into monoculture plantations
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Fungal succession, litter decomposition and root nitrogen supply in a tropical oil palm plantation
Full text linkBackground and Aims Industrial oil palm plantation
management degrades tropical soils and disrupts
ecosystem functions. Applying oil palm leaf litter can
help restore soil fertility, but the underlying fungaldriven
decomposition and nitrogen recycling remain
understudied. This study examines fungal succession
in degrading oil palm leaf litter, the fate of litterderived
nitrogen in soil and roots, and the potential
for the restoration of fungal biodiversity.
Methods We produced 15N-labelled oil palms and
exposed dry leaf litter in 2-mm and 37-μm mesh bags within a plantation. The finer mesh allowed microbial
access but restricted roots and most detritivores.
We measured litter mass loss, carbon and nitrogen
dynamics, and fungal communities via ITS barcoding
over six months. Root ingrowth and soil chemistry
were also analyzed.
Results Litter mass decreased by 70% in both mesh
types, with soil accumulating litter-derived 15N. Fine
roots grew into the mesh after three months and took
up 15N, demonstrating nitrogen recycling. Fungal succession
displayed clear temporal patterns: early colonizers
thrived with higher C/N ratios (Hypocreales,
Pleosporales, Chaetothyriales), while late colonisers
(e.g., Sordariales, Pleosporales, Chaetosphaeriales) correlated with C degradation. Arbuscular mycorrhizal
fungi increased with declining C/N ratios and
coincided with root growth.
Conclusions Oil palm litter enhances nitrogen
availability, fosters AMF diversity, and improves
degraded soils. The numerous uncharacterized fungi
in litter decomposition highlight the need for further
research into their functional roles for sustainable soil
restoration
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Summary of research results, management recommendations and farmer workshops from cacao agroforestry landscapes in Indonesia
No full textSoftcover, 17,6x25Cacao agroforestry systems are common in Indonesia, but differences in local management affect
biodiversity and related ecosystem services. Importantly, birds and bats alike strongly contribute
to biological pest control in cacao, thereby promoting yields and sustainable farming. Our findings
from many years of ecological field research, in close collaboration with Indonesian cacao farmers,
are summarized and discussed in this bilingual book, written in both English and Indonesian. It is
designed to communicate scientific information as well as to facilitate transdisciplinary discussions
and more biodiversity-friendly management in tropical agroforestry systems.
We consider this book as a tool to improve the collaboration of local communities, farmers and
scientists, as well as to improve the application of scientific knowledge in agricultural practice -
particularly in tropical land use areas.
Bea Maas, the first author of this book, is postdoctoral researcher at the University of Vienna
(Austria), working in the fields of biology, ecology and conservation. She conducted the research and
workshops presented here in close collaboration and with support from the University of Göttingen
(Germany) and the University of Tadulako (Indonesia).Sistem agroforestri kakao adalah hal umum di Indonesia, tetapi perbedaan pengelolaan setempat
akan mempengaruhi keanekaragaman hayati dan layanan ekosistem. Terutama, burung dan kelelawar
sama-sama memberikan kontribusi tinggi pada pengendalian hama biologis di kakao, sehingga
dapat meningkatkan hasil panen dan pertanian yang berkelanjutan. Temuan kami dari penelitian
lapangan ekologi bertahun-tahun, yang bekerjasama erat dengan petani kakao Indonesia, dirangkum
dan dibahas dalam buku bilingual ini, tertulis dalam bahasa Inggris dan bahasa Indonesia. Buku
ini dirancang untuk mengkomunikasikan informasi ilmiah dan juga untuk memfasilitasi diskusi
transdisipliner dan pengelolaan keanekaragaman hayati yang ramah pada sistem agroforestri tropis.
Kami menganggap buku ini sebagai alat untuk meningkatkan kolaborasi masyarakat lokal, petani
dan ilmuwan, serta untuk meningkatkan penerapan pengetahuan ilmiah dalam praktik pertanian -
terutama di wilayah penggunaan lahan tropis.
Bea Maas, penulis pertama buku ini, adalah peneliti postdoctoral di Universitas Wina (Austria),
bekerja di bidang biologi, ekologi dan konservasi. Dia melakukan penelitian dan lokakarya yang
disampaikan dalam buku ini dengan kerjasama yang erat dan dukungan dari Universitas Göttingen
(Jerman) dan Universitas Tadulako (Indonesia)
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