Dynamics of multiple elements in litter decomposition under various disturbances

Both artificial disturbance and climate change regimes can strongly affect soil carbon (C) sequestration and nutrient dynamics through decomposition processes of above- and belowground residues in terrestrial ecosystems. This requires new directions in managing future forests. I conducted decomposition experiments on foliage and root litter in different ecosystems and different types of disturbance, including nitrogen deposition, elevation gradients, and clearcutting. My thesis aims to: i) investigate the decomposition and nutrient release pattern of contrasting litter species in response to N deposition in already nitrogen-rich subtropical forests; ii) compare the carbon decomposition of belowground root litter (humification and mineralization) in response to an elevation gradient in an alpine forest; and iii) explore the role of litter affinity, in particular home-field advantage, on litter decomposition and nutrient mineralization after clearcutting in a temperate forest that is managed to achieve a conversion from monospecific plantations to more natural deciduous forests in a temperate climate. I collected leaf and root samples from local ecosystems and conducted litterbag experiments in individual forest ecosystems, respectively. Three main experiments were performed. In the first experiment, one-year in situ decomposition of low-quality Michelia wilsonii and high-quality Camptotheca acuminata with N additions (0 kg N ha-1 yr-1, 20 kg N ha-1 yr-1 and 40 kg N ha-1 yr-1) at the western edge of the Sichuan Basin of China was studied. In particular, mass loss rate, carbon, nitrogen and phosphorus dynamic were studied. The second experiment was a two-year litterbag experiment with root litter of three diameter classes (0-2, 2-5 and 5-10 mm) of two common subalpine tree species (Picea asperata and Abies faxoniana) at two elevations (3037 m and 3580 m, varied in soil temperature, moisture and snowpack) on the eastern Tibetan Plateau, China. This experiment focused in particular on humification, humified substance was extracted with modified alkaline extraction. Thirdly, a transplant reciprocal litter decomposition experiment of Norway spruce (Picea abies) and European Beech (Fagus sylvatica) within the forest and clear-cut area and for two soil types (Cambisols and Gleysols) in Eifel National Park (Wüstebach Germany) was performed; decomposition home-field advantage, carbon, nitrogen, phosphorus, calcium, and of the stable isotopes d13C and d15N were determined. My results indicated that nitrogen addition negatively affected low-quality M. wilsonii litter decomposition, but not high-quality C. acuminata litter. Nitrogen addition caused immobilization of nitrogen and phosphorus in M. wilsonii which decreased the carbon-to-phosphorus ratios in the later decomposition stages. Nitrogen addition had no effect on carbon mineralization for both species. When considering the climatic condition, elevation gradients did not affect formation of humic substances from roots. Snowpack and freeze-thaw cycles change with elevation. This offsets the expected temperature effect on the belowground root humification process in an alpine forest. However, root diameter increases with cellulose and carbon-to-phosphorus ratio, leading to decreased mass loss rate and concentrations of humic substance, humic acid and fulvic acid. Clearcutting management significantly elevated soil moisture and temperature status, changed the field-litter affinity of spruce forest (masked decomposition home-field advantage in a spruce forest). Increased beech decomposition rate and litter nitrogen release further promoted soil carbon and nitrogen cycling in the clearcut site. This phenomenon was more evident in the comparable acidic and moisture-deficient Cambisols than in Gleysols present in the catchment. In summary, my study clearly demonstrated that the decomposition rate, as well as carbon, nitrogen and phosphorus release from leaf and root litter are highly related to litter substrate quality in forest ecosystems. I especially saw a diversity of responses in term of litter quality and extreme disturbance condition. Therein, nitrogen deposition and elevation had less influence on carbon loss of native litter, whereas clearcutting management promoted the decomposition of non-dominant species. Suppression of nutrient release from high-lignin litter under disturbance and warming condition underlined the necessity to reconsider the current forest structure and management. This study illustrates how disturbance and climate change impact, together with plant species and edaphic conditions at local levels, can help explain external-induced changes in ecosystem functions such as soil organic matter formation and nutrient cycling and provide a basis for further development of sustainable forest management.Sowohl künstliche Störungen als auch der Klimawandel können die Kohlenstoffsequestrierung im Boden und die Nährstoffdynamik aufgrund von Zersetzungsprozesse von Wurzel- und Blattstreu in terrestrischen Ökosystemen stark beeinflussen. Dies erfordert neue Wege bei der Bewirtschaftung künftiger Wälder. Ich habe Zersetzungsexperimente mit Laub- und Wurzelstreu in verschiedenen Ökosystemen und unter verschiedenen Störungsarten durchgeführt, darunter Stickstoffdeposition, Höhengradienten und Kahlschlag. Meine Dissertation zielt darauf ab: i) die Zersetzungs- und Nährstofffreisetzungsmuster verschiedener Streuarten als Reaktion auf Stickstoffeinträge in bereits stickstoffreichen subtropischen Wäldern zu untersuchen; ii) den Kohlenstoffabbau von unterirdischer Wurzelstreu (Humifizierung und Mineralisierung) als Reaktion auf einen Höhengradienten in einem alpinen Wald zu vergleichen; und iii) die Rolle der Streuaffinität, insbesondere des Heimvorteils, auf den Streuabbau und die Nährstoffmineralisierung nach einem Kahlschlag in einem Wald der gemäßigten Zonen zu untersuchen, der bewirtschaftet wird, um eine Umstellung von monospezifischen Plantagen auf natürlichere Laubwälder in einem gemäßigten Klima zu erreichen. Ich sammelte Blatt- und Wurzelproben aus lokalen Ökosystemen und führte in den einzelnen Waldökosystemen jeweils Streuabbauversuche durch. Es wurden drei Hauptexperimente durchgeführt. Im ersten Experiment wurde die einjährige In-situ-Zersetzung von weniger hochwertigem Michelia wilsonii und hochwertigem Camptotheca acuminata mit N-Zusätzen (0 kg N ha-1 yr-1, 20 kg N ha-1 yr-1 und 40 kg N ha-1 yr-1) am westlichen Rand des Sichuan-Beckens in China untersucht. Untersucht wurden insbesondere die Massenverlustrate sowie die Dynamik von Kohlenstoff, Stickstoff und Phosphor. Der zweite Versuch war ein zweijähriges Streuabbau-Experiment mit Wurzelstreu dreier Durchmesserklassen (0-2, 2-5 und 5-10 mm) von zwei verbreiteten subalpinen Baumarten (Picea asperata und Abies faxoniana) in zwei Höhenlagen (3037 m und 3580 m, mit unterschiedlichen Bodentemperaturen, Feuchtigkeit und Schneedecken) auf dem östlichen tibetischen Plateau, China. Dieser Versuch konzentrierte sich insbesondere auf die Humifizierung; die humifizierte Substanz wurde mit einer modifizierten alkalischen Extraktion extrahiert. Drittens wurde ein Experiment zur wechselseitigen Streuzersetzung von Fichte (Picea abies) und Rotbuche (Fagus sylvatica) im Wald und im Kahlschlaggebiet und für zwei Bodentypen (Cambisole und Gleysole) im Nationalpark Eifel (Wüstebach Deutschland) durchgeführt; Heimvorteil bei der Zersetzung, Kohlenstoff, Stickstoff, Phosphor, Kalzium und die stabilen Isotope d13C und d15N wurden bestimmt. Meine Ergebnisse deuten darauf hin, dass die Zugabe von Stickstoff die Zersetzung der Streu von M. wilsonii negativ beeinflusst, nicht aber die der hochwertigen Streu von C. acuminata. Der Stickstoffzusatz bewirkte eine Immobilisierung von Stickstoff und Phosphor in M. wilsonii, wodurch sich das Verhältnis von Kohlenstoff zu Phosphor in den späteren Zersetzungsstadien verringerte. Die Stickstoffzugabe hatte bei beiden Arten keine Auswirkungen auf die Kohlenstoffmineralisierung. Unter Berücksichtigung der klimatischen Bedingungen wirkten sich die Höhenunterschiede nicht auf die Bildung von Huminstoffen aus den Wurzeln aus. Die Schneedecke und die Frost-Tau-Zyklen ändern sich mit der Höhenlage. Dadurch wird die erwartete Auswirkung der Temperatur auf den unterirdischen Humifizierungsprozess der Wurzeln in einem alpinen Wald kompensiert. Der Wurzeldurchmesser nimmt jedoch mit dem Zellulose- und P-Kohlenstoff-Phosphor-Verhältnis zu, was zu einer Verringerung der Massenverlustrate und der Konzentrationen von Huminstoffen, Huminsäure und Fulvosäure führt. Durch die Kahlschlagbewirtschaftung wurden die Bodenfeuchtigkeit und die Bodentemperatur signifikant erhöht und die Streuaffinität von Fichtenwäldern verändert (maskierter Heimvorteil bei der Zersetzung im Fichtenwald). Die erhöhte Zersetzungsrate der Buche und die Freisetzung von Stickstoff aus der Streu förderten den Kohlenstoff- und Stickstoffkreislauf des Bodens im Kahlschlaggebiet weiter. Dieses Phänomen war in den feuchtigkeits- und nährstoffarmen Braunerden deutlicher zu beobachten als in den im Einzugsgebiet ebenfalls vorhandenen Gleyböden. Zusammenfassend lässt sich sagen, dass meine Studie deutlich gezeigt hat, dass die Zersetzungsrate sowie die Freisetzung von Kohlenstoff, Stickstoff und Phosphor aus der Blatt- und Wurzelstreu in hohem Maße von der Qualität des Streusubstrats in Waldökosystemen abhängt. Vor allem bei der Streuqualität und extremen Störungsbedingungen konnte ich eine Vielfalt von Reaktionen feststellen. Dabei hatten Stickstoffdeposition und Höhenlage weniger Einfluss auf den C-Verlust der einheimischen Streu, während die Kahlschlagbewirtschaftung die Zersetzung der nicht dominanten Arten förderte. Die Unterdrückung der Nährstofffreisetzung aus Streu mit hohem Ligningehalt unter Störungs- und Erwärmungsbedingungen unterstreicht die Notwendigkeit, die derzeitige Waldstruktur und -bewirtschaftung zu überdenken. Diese Studie veranschaulicht, wie Störungen und die Auswirkungen des Klimawandels zusammen mit Pflanzenarten und edaphischen Bedingungen auf lokaler Ebene dazu beitragen können, von außen verursachte Veränderungen der Ökosystemfunktionen wie die Bildung organischer Substanz im Boden und den Nährstoffkreislauf zu erklären und eine Grundlage für die weitere Entwicklung einer nachhaltigen Waldbewirtschaftung zu schaffen

The complementary graphene growth and etching revealed by large-scale kinetic Monte Carlo simulation

To fully understand the kinetics of graphene growth, large-scale atomic simulations of graphene islands evolution up to macro sizes (i.e., graphene islands of a few micrometers or with billions of carbon atoms) during growth and etching is essential, but remains a great challenge. In this paper, we developed a low computational cost large-scale kinetic Monte Carlo (KMC) algorithm, which includes all possible events of carbon attachments and detachments on various edge sites of graphene islands. Such a method allows us to simulate the evolution of graphene islands with sizes up to tens of micrometers during either growth or etching with a single CPU core. With this approach and the carefully fitted parameters, we have reproduced the experimentally observed evolution of graphene islands during both growth or etching on Pt(111) surface, and revealed more atomic details of graphene growth and etching. Based on the atomic simulations, we discovered a complementary relationship of graphene growth and etching-the route of graphene island shape evolution during growth is exactly the same as that of the etching of a hole in graphene and that of graphene island etching is exactly same as that of hole growth. The complementary relation brings us a basic principle to understand the growth and etching of graphene, and other 2D materials from atomic scale to macro size and the KMC algorithm is expected to be further developed into a standard simulation package for investigating the growth mechanism of 2D materials on various substrates

Genomic Analyses Reveal Mutational Signatures and Frequently Altered Genes in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide and the fourth most lethal cancer in China. However, although genomic studies have identified some mutations associated with ESCC, we know little of the mutational processes responsible. To identify genome-wide mutational signatures, we performed either whole-genome sequencing (WGS) or whole-exome sequencing (WES) on 104 ESCC individuals and combined our data with those of 88 previously reported samples. An APOBEC-mediated mutational signature in 47% of 192 tumors suggests that APOBEC-catalyzed deamination provides a source of DNA damage in ESCC. Moreover, PIK3CA hotspot mutations (c.1624G>A [p.Glu542Lys] and c.1633G>A [p.Glu545Lys]) were enriched in APOBEC-signature tumors, and no smoking-associated signature was observed in ESCC. In the samples analyzed by WGS, we identified focal (<100 kb) amplifications of CBX4 and CBX8. In our combined cohort, we identified frequent inactivating mutations in AJUBA, ZNF750, and PTCH1 and the chromatin-remodeling genes CREBBP and BAP1, in addition to known mutations. Functional analyses suggest roles for several genes (CBX4, CBX8, AJUBA, and ZNF750) in ESCC. Notably, high activity of hedgehog signaling and the PI3K pathway in approximately 60% of 104 ESCC tumors indicates that therapies targeting these pathways might be particularly promising strategies for ESCC. Collectively, our data provide comprehensive insights into the mutational signatures of ESCC and identify markers for early diagnosis and potential therapeutic targets

How Precisely Can Prostate Cancer Be Managed?

Progress has been made in applying genetic information to disease management in the postgenomic era, and precision medicine is emerging in prostate cancer management. The prostate health index, the 4-kallikrein (4K) score, and the PCA3, TMPRSS2-ERG, and Prostarix tests have potential for refining prostate cancer screening in conjunction with traditional prostate-specific antigen testing. The Confirm MDx and PCA3 tests have shown promise in identifying men who need be rebiopsied after a primary negative biopsy. Oncotype DX, Prolaris, the biopsy-based Decipher prostate cancer test, and ProMark may improve predictive risk stratification in addition to the traditional Gleason score and tumor stage. Decipher and Prolaris may predict biochemical recurrence and metastasis after radical prostatectomy and possibly help identify patients who need adjuvant therapy. Androgen receptor splice variant 7 appears effective in guiding the selection of second hormonal manipulation with abiraterone or enzalutamide versus chemotherapy when treating metastatic castration-resistant prostate cancer

The Design and Development of a Mobile Phone Application for STEM based on a Novel Engineering Approach

STEM education provides students with interdisciplinary knowledge to improve problem-solving ability. The purpose of this study is to explore whether students could achieve the goal of STEM education by mobile learning. This study developed a mobile application which was named Borrowing Your Enemy’s Arrows to support mobile learning about science, technology, engineering, and math (STEM). According to the textbooks for Grades 5-7，the teaching content of the APP was designed to help students get a better grasp of teaching contents and to help teachers save time in preparing classes. The central narrative，like cartoon or the dialogue of cartoon is used for APP to bridge the teaching contents. Therefore，learners can construct a real-life situation by App. To inspire learners' interest in STEM courses, the APP used games to test how well students did in learning. A shipbuilding task with the narrative background was set to improve learners' skills and interest in engineering learning. The educator could make the assessment of learners based on all their performance in the process of learning, including the design sketches, final products, the messages from students and the grade of game. For the purpose of improving the APP, teachers and students were interviewed to investigate users’ feedback in this study

Retrospectively Analysis of Factors Influencing the Relapse (or Progression) of Newly Diagnosed Nonoperative Small Cell Lung Cancer

Background and objective Most small cell lung cancer (SCLC) patients relapse or progress and have low survival rate although they have significant response to initial chemotherapy and radiotherapy. This study intends to explore the factors affecting the relapse (or progression) of nonoperative SCLC and to explore the correlations between progression-free survival (PFS) and overall survival (OS). Methods Clinical data of 182 patients diagnosed with SCLC between January 2009 and December 2011 at Shanghai Chest Hospital has been reviewed and retrospectively analyzed. All of these patients accepted chemotherapy combined (or not combined) with radiotherapy, and relapsed or progressed after first-line therapy. Univariate Kaplan-Meier survival estimates as well as multivariate Cox regression survival analysis were used to locate the potential factors affecting PFS. The correlation between PFS and OS was analyzed via Bivariate Correlation Analysis method. Results The univariate estimates showed that the TNM stage, liver metastasis or not, brain metastasis or not, first-line chemotherapy cycles, effect of initial chemotherapy, and thoracic radiotherapy combined or not were the significant contributive factors to PFS. In the subgroup of the patients without brain metastases, those received prophylactic cranial irradiation (PCI) had longer PFS. Cox regression indicated that the three independent variables of first-line chemotherapy cycles, effect of initial chemotherapy and thoracic radiotherapy combined or not were closely related to PFS. In addition, significant positive correlation between PFS and OS had been observed. Conclusion PFS could be prolonged by having more first-line chemotherapy cycles (>4 cycles), obtaining better effect of initial chemotherapy (partial response or complete response), combining with thoracic radiotherapy and implementing PCI for patients without brain metastasis