1,720,974 research outputs found
ndonesia)
No full textNatural forests in South‐East Asia have been extensively converted into other land‐use systems in the past decades and still show high deforestation rates. Historically, lowland forests have been converted into rubber forests, but more recently, the dominant conversion is into oil palm plantations. While it is expected that the large‐scale conversion has strong effects on the carbon cycle, detailed studies quantifying carbon pools and total net primary production (NPPtotal) in above‐ and belowground tree biomass in land‐use systems replacing rainforest (incl. oil palm plantations) are rare so far. We measured above‐ and belowground carbon pools in tree biomass together with NPPtotal in natural old‐growth forests, ‘jungle rubber’ agroforests under natural tree cover, and rubber and oil palm monocultures in Sumatra. In total, 32 stands (eight plot replicates per land‐use system) were studied in two different regions. Total tree biomass in the natural forest (mean: 384 Mg ha−1) was more than two times higher than in jungle rubber stands (147 Mg ha−1) and >four times higher than in monoculture rubber and oil palm plantations (78 and 50 Mg ha−1). NPPtotal was higher in the natural forest (24 Mg ha−1 yr−1) than in the rubber systems (20 and 15 Mg ha−1 yr−1), but was highest in the oil palm system (33 Mg ha−1 yr−1) due to very high fruit production (15–20 Mg ha−1 yr−1). NPPtotal was dominated in all systems by aboveground production, but belowground productivity was significantly higher in the natural forest and jungle rubber than in plantations. We conclude that conversion of natural lowland forest into different agricultural systems leads to a strong reduction not only in the biomass carbon pool (up to 166 Mg C ha−1) but also in carbon sequestration as carbon residence time (i.e. biomass‐C:NPP‐C) was 3–10 times higher in the natural forest than in rubber and oil palm plantations
Mekanisme toleransi tanaman pada lahan salin: akumulasi prolin
Full text linkSalinitas menambah faktor penghambat pertumbuhan perkembangan tanaman serta meningkatkan penurunan produktivitas tanaman pada tanaman glikofit. Tingginya sodium dan klorin menstimulus produksi prolin (Pro) yang berperan sebagai osmoregulator dan buffer dalam mempertahankan turgor sel. Review ini membahas tentang mekanisme fisiologi adaptasi toleran terhadap salinitas melalui kajian biosintesis dan regulasi ekspresi gen, respon morfo-fisiologi dan peran fitohormon ABA terhadap akumulasi Pro. Prolin merupakan metabolit sekunder yang disintesis melalui metabolisme nitrogen dengan prekursor glutamat dan atau ornitin. Tanaman yang tercekam akan melakukan mekanisme pertahanan melalui (1) aktivasi gen P5CS, PDH, ProT, dan δ –OAT terkait metabolisme sintesis Pro yang tinggi pada akar, (2) peningkatan Pro pada akar di awal cekaman dan pada bunga di fase generatif, dan (3) penyerapan N tinggi pada akar. Peningkatan serapan N, NH4+, mendukung asimilasi N di akar sebagai respon tanaman dalam meningkatan pertumbuhan dan biomasa pada kondisi tercekam. Selain N, peningkatan ABA menstimulus gen-gen terkait stres salinitas. Dengan demikian, aplikasi NH4+ dan penambahan ABA memperbaiki produktivitas pertanian dengan meningkatkan resistensi tanaman terhadap salinitas
Prolin, Asam Askorbat, dan Kandungan Air Relatif pada Tanaman C3 dan C4 yang Tercekam Kekeringan
Full text linkDrought stress reduces plant growth and development that even reduces crop productivity. Plants activate various physiological defense mechanisms against water stress. This study aimed to compare the contents of proline (Pro), abscisic acid (ABA), and relative water content (KAR) in the leaves tissue of C3 plants from spinach (Amaranthus hybridus) and C4 from water spinach (Ipomea reptana) during drought stress of 2 days, 4 days, 6 days, and 8 days. The parameters measured were the content of Pro, ABA, and KAR in both leaves of A. hybridus and I. reptana at each stress period. The results of the study showed that the concentration of Pro was higher in water spinach at 6 days and 8 days of drought stress and the highest KAR value at 8 days of drought stress. The highest proline was synthesized by I. reptana at the longest-term stress of 8 days (1.54 µmol proline/g leaf). While the highest KAR value was shown by A. hybridus, namely 1.00% at 8 days stress. The high value of Pro in I. reptana was a physiological response to the decrease of KAR value. The high ABA concentration in A. hybridus as much as 3878.12/100 g leaf samples is a strategy for C3 plants to reduce the transpiration rate. On the other hand, the C4 plant of I. reptana demonstrated a defense mechanism by increasing the Pro osmoregulator to balance the osmotic cells when the KAR value decreased under prolonged stress.
Keywords— abscisic acid, C3, C4, proline, relative water conten
Kontrol auksin dan PIN1 dalam perkembangan dan venasi daun
Full text linkKontrol auksin dan PIN1 dalam perkembangan dan venasi dau
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
