[Innovative design of global change network control experiment: A case design of water and heat factors of grassland ecosystem in China]. / å ¨çƒå˜åŒ–è”ç½‘æŽ§åˆ¶å®žéªŒçš„åˆ›æ–°æ€§è®¾è®¡:ä»¥æˆ‘å›½è‰åœ°ç”Ÿæ€ç³»ç»Ÿæ°´çƒ­è¦ç´ è”ç½‘æŽ§åˆ¶å®žéªŒä¸ºä¾‹.

Global changes have profound impacts on the structure and function of terrestrial ecosystems. It is a prerequisite to realize the sustainable use of ecosystem to clarify the response and adaptation mechanism of ecosystems to global changes. Network of control experiment is an important way to understand the response and adaptation of the structure and function of ecosystems to global change factors at regional and global scales. The scientific top-level design is conducive to the integration, comparison and analysis of integrative network-data, and then supports the development of universal ecological theory. We comprehensively expounded the theoretical basis, methodological principles and brand-new concepts of experimental network design for future global change control experiment networks design from several aspects, such as research progress, development needs, innovative design and research prospects. Taking Chinese grassland ecosystems as an example, based on the concept of space reference points (mean point of water and heat), the innovative design technology system of China's grassland ecosystem networking experiment was proposed, in order to promote the development of networking research of control experiments at both regional and global scales in the future.

[Ecosystem carbon uptake was co-limited by nitrogen and phosphorus in alpine meadow on the Qinghai-Tibet Plateau]. / æ°®ç£·å ±é™åˆ¶é’è—é«˜åŽŸé«˜å¯’è‰ç”¸ç”Ÿæ€ç³»ç»Ÿç¢³å¸æ”¶.

Alpine grassland is threatened by the import of chemicals, fertilizers and other external resources with increasing human activities on the Qinghai-Tibet Plateau. It is unclear how carbon cycle of alpine grasslands is affected by the inputs of external resources such as nitrogen, phosphorus, and potassium (N, P, K) and their interactions. We conducted a 3 year experiment on the interactive addition of N, P and K with alpine grassland as the research object to clarify ecosystem carbon exchange process in response to resource addition by measuring community coverage and ecosystem carbon exchange. The results showed the alpine meadow was represented by carbon sequestration during the growing season. The mean value of net ecosystem CO2 exchange (NEE) was -13.0 µmol·m-2·s-1 under the control treatment. NEE, ecosystem respiration (ER), and gross ecosystem productivity (GEP) showed no significant responses when N, P and K were added separately. NEE was significantly increased by 95.3% and 63.9%, GEP was significantly increased by 45.5% and 33.0% under the combined addition of NP and NPK, but ER remained stable. The combined addition of NP or NPK mainly increased NEE and GEP by increasing the coverage of plant communities and affecting ecosystem water use efficiency. Plant community coverage was increased by 18.1% and 21.4%, respectively. The addition of NP increased productivity and autotrophic respiration in alpine meadow. It might cause soil acidification to inhibit heterotrophic respiration, thereby did not change ER due to the two aspects canceling each other out. The addition of N, P, K alone and NK and PK did not change ecosystem carbon exchange, while the combined addition of NP increased NEE and GEP on the nutrient-deficient alpine meadows, indicating that ecosystem carbon uptake was co-limited by N and P in alpine meadow.

Interface Engineering for the Enhancement of Carrier Transport in Black Phosphorus Transistor with Ultra-Thin High-k Gate Dielectric.

Black phosphorus (BP) is the most stable allotrope of phosphorus which exhibits strong in-plane anisotropic charge transport. Discovering its interface properties between BP and high-k gate dielectric is fundamentally important for enhancing the carrier mobility and electrostatics control. Here, we investigate the impact of interface engineering on the transport properties of BP transistors with an ultra-thin hafnium-dioxide (HfO2) gate dielectric of ~3.4 nm. A high hole mobility of ~536 cm(2)V(-1)s(-1) coupled with a near ideal subthreshold swing (SS) of ~66 mV/dec were simultaneously achieved at room temperature by improving the BP/HfO2 interface quality through thermal treatment. This is attributed to the passivation of phosphorus dangling bonds by hafnium (Hf) adatoms which produces a more chemically stable interface, as evidenced by the significant reduction in interface states density. Additionally, we found that an excessively high thermal treatment temperature (beyond 200 °C) could detrimentally modify the BP crystal structure, which results in channel resistance and mobility degradation due to charge-impurities scattering and lattice displacement. This study contributes to an insight for the development of high performance BP-based transistors through interface engineering.

Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier.

Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec).

[Changes and analysis of soil quality under different land use types in oasis rim].

The aggravation process of oasisization leads to changes of land use type in oasis rim. In order to discuss the effects of different land use types on soil properties and soil quality, the four land use types located Cele oasis rim in south margin of Tarim Basin, which are the cotton field, orchard, and Caligonum mongolicum Turcz land use type reclaimed by people and nature state land use type covered by Alhagi sparsifolia SHAP, were selected as study object. The relative soil quality index (RI) and the soil quality synthesis index (SQI) were used to analyse the changes of soil quality between four land use types within 0-20 cm, 2040 cm, 40-60 cm soil depth, respectively. Meantime, the fractal theory was used to analyse the particle-size distribution (PSD) property of top soil under different land use types. The results indicated that there was a significant difference in the soil organic matter and total nitrogen in same soil depth between four land use types; the order ranked according to RI was same to the order ranked according to SQI in each soil depth between four land use types. The cotton field and orchard have an obviously positive effect on soil quality of the top soil, however, the soil quality of Alhagi sparsifolia SHAP land use type was gradually increasing along with the increasing soil depth. The soil properties and soil quality of Caligonum mongolicum Turcz land use type were at the lowest level according to the comparison results among all land use types, and the calculation results of PSD fractal dimension also indicated the Caligonum mongolicum Turcz land use type had the worst ability on maintaining soil fine fractions.