Relationship between net primary productivity and stand age in typical plantation forests in China.

Plantation forests play an important role in carbon sink in terrestrial ecosystems. Based on tree rings of five main plantation tree species (Robinia pseudoacacia, Quercus variabilis, Cunninghamia lanceolata, Pinus sylvestris var. mongolica, and Pinus tabuliformis) at 25 sites in China, we calculated the average annual NPP of standard trees in each study area by the biomass equations and extended to the stand scale. The relationships between NPP and stand age were fitted by the InTEC and Law models. The results showed that NPP of R. pseu-doacacia, C. lanceolata, and P. tabuliformis plantations increased to a peak and then leveling off with stand age, while that of Q. variabilis and P. sylvestris var. mongolica plantations reached a peak and then showed a decreasing trend. The inflection points of NPP-stand age curve for different planatations was 11 years for P. sylvestris var. mongolica, 14 years for C. lanceolata, 16 years for P. tabuliformis, and 20 years for R. pseudoacacia. The NPP peak was 6.65, 7.58, 4.70 and 2.59 t·hm-2·a-1, respectively. Both the InTEC and Law NPP-stand age models had high fitting accuracy at a large scale, with the lowest R2 of 0.95 and RMSE of 0.55 t·hm-2·a-1 for the P. sylvestris var. mongolica InTEC model and the highest R2 of 0.99 and RMSE of 0.26 t·hm-2·a-1 for the C. lanceolata InTEC model. The construction of NPP-stand age relationship for major plantations in China provided mechanistic support for the estimation of carbon sinks in plantations at long time scales and provided a reference for the diversification of afforestation tree species selection.

Spatial-temporal variations of forest and grassland phenology in the Yellow River Basin during 2000-2018.

The study of vegetation phenology is of great significance for understanding global climate change. The Yellow River basin has a wide spatial range and a complex ecological environment. The phenological characteristics of forest and grassland need further clarification. Based on the MODIS-EVI data from 2000 to 2018, we extracted the phenology of forest and grassland in the Yellow River basin using piecewise logistic and double logistic phenological models with the corresponding curvature change extremum method and derivative method, respectively. The temporal and spatial variations of phenological parameters were analyzed. The start of growing season (SOS) was at 90-165 day of year (DOY), and gradually delayed from southeast to northwest. The increase of 100 m elevation delayed SOS 0.94 d, and the SOS of forest was earlier than that of grassland. The end of growing season (EOS) was at 270-315 DOY, which delayed from west to southeast. For every 100 m increase in altitude, the EOS advanced 0.63 d, with EOS of forest being later than that of grassland. The length of growing season (LOS) was 110-230 d, which shortened gradually from southeast to northwest. The LOS of forest was larger than that of grassland. During the study, SOS showed an advance trend from 2000 to 2018 with a rate of 4.1 d·(10 a)-1, and the proportion of spatial advance area was 73.2%. There was an obvious advance in the central part of the basin. EOS generally showed a significant postponement trend with a rate of 2.3 d·(10 a)-1, and the proportion of spatially delayed area was 63.4%, the phenological advance and delay of forest was less stronger than that of grassland. LOS showed a significant prolongation trend with a rate of 6.4 d·(10 a)-1, and the proportion of spatial extension was 71.8%. The piecewise Logistic and double Logistic phenological models and the corresponding curvature extremum method and derivative method were suitable for the extraction of natural vegetation in the Yellow River Basin. The overall LOS of forest and grassland showed a prolonging trend, which was shortened with the increases of altitude. The LOS of forest was longer than that of grassland in the study area.

Brønsted-Acid-Catalyzed Synthesis of 3-Alkoxy and 3-Sulfamido Indanones via a Tandem Cyclization.

Brønsted-acid-catalyzed allylic substitution reactions of the in situ generated 3-hydroxy indanones with alcohols and sulfamides were investigated, which provided a facile route for the synthesis of a large variety of 3-alkoxy and 3-sulfamido indanones. The key intermediates, 3-hydroxy indanones, were obtained through the intramolecular Meyer-Schuster rearrangement of o-propargyl alcohol benzaldehydes. The resulting 3-benzyloxy indanone could be selectively modified by allylic sulfonamidation and reduction reactions.

[Simulation on photosynthetic light-responses of leaves of Quercus variabilis and Robinia pseudoacacia under different light conditions.] / ä¸åŒå ‰çŽ¯å¢ƒä¸‹æ “çš®æ Žå’Œåˆºæ§å¶ç‰‡å ‰åˆå ‰å“åº”æ¨¡æ‹Ÿ.

Photosynthesis can reflect the responses of plants to environmental changes. In this study, photosynthetic light-response curves were measured by the Li-6400XT photosynthetic system in Quercus variabilis and Robinia pseudoacacia plantations in Xiaolangdi Forest Ecosystem Research Station. Photosynthetic light-response curves were fitted by Ye model. The differences of photosynthetic parameters between inner and margin forests were examined. Stomatal conductance (gs) light-response curve were fitted using the mechanism model of gs coupled with a modified model of light-response of photosynthesis. The light-response characteristics of gs were investigated. Net photosynthetic rates (Pn) of Q. variabilis in the inner forest was higher than that in the margin. The initial light efficiency (Α) was 12.4% more in the inner forest than that in the margin in July and August when photosynthetically active radiation was less than 200 Μmol·m-2·s-1. The ability to capture and utilize weak light of Q. variabilis leaves in the inner forest was obviously higher than that in the margin. When photosynthetically active radiation was higher than 200 Μmol·m-2·s-1, Pn of Q. variabilis leaves in the margin forest was larger than that in the inner. Under weak light conditions (0-200 Μmol·m-2·s-1), Pn of R. pseudoacacia in the inner forest was higher than that in the margin. Pn of R. pseudoacacia in the inner forest was less than that in the margin when light intensity was higher than 200 Μmol·m-2·s-1. The dark respiration rate (Rd) and light compensation point (Ic) in the inner forest were 50.0% and 42.8% lower than those in the margin. The less Rd and Ic of the inner forest could reduce carbon loss and adapt to low photosynthetic rate. The stomatal conductance light-response of R. pseudoacacia in the inner forest significantly differed from that in the margin. The leaves of Q. variabilis and R. pseudoacacia had strong adaptability to the changes of light condition. The values of maximum net photosynthetic rate (Pn max) and Α of Q. variabilis leaves were mainly controlled by gs, and Rd and Ic were primarily affected by air temperature. Pn max and Α of R. pseudoacacia leaves had significant positive correlation with air temperature. The Ic and the light saturation point (Is) were remarkably correlated with leaf saturation vapor pressure deficit.

[Simulation on photosynthetic-CO2 response of Quercus variabilis and Robinia pseudoacacia in the southern foot of the Taihang Mountain, China.] / å¤ªè¡Œå±±å—éº“æ “çš®æ Žå’Œåˆºæ§å ‰åˆä½œç”¨-CO2响应模拟.

In this study, leaf photosynthetic CO2-response curves of Quercus variabilis and Robinia pseudoacacia were measured using a Li-6400XT photosynthetic measurement system in the southern foot of the Taihang Mountain, China. The rectangular hyperbola model (RH), nonrectangular hyperbola model (NRH) andYe model (YZP) were used to fit photosynthetic-CO2 response curves and compare photosynthetic parameters, including the maximum net photosynthetic rate (Amax), the initial carboxylation rate (η), light respiration rate (Rp), CO2 compensation point (CCP) and CO2 saturation point (CSP). Compared with the NRH and YZP models, Amax, η, Rp and CCP obtained by the RH model were higher, and were 59.8%, 128.6%, 133.4% and 19.8% higher than the measured values. The accuracy of the RH model was lower and its relative error was higher than that of the NRH and YZP models.Compared with the RH and YZP models, Amax fitted by the NRH model was higher, and was 11.1% higher than the measured value. η, Rp and CCP fitted by the NRH model were closer to the measured values. CO2 saturation phenomenon of photosynthesis could be simulated by the YZP model, and Amax and CSP were fitted well. Amax, Rp and CCP in the shaded leaves of Q. variabilis were 31.3%, 5.2% and 14.3% lower than those in the sunlit leaves. Amax, Rp and CCP in shaded leaves of R. pseudoacacia were 23.5%, 11.0% and 5.4% more than those in the sunlit leaves. η in the shaded leaves of Q. variabilis and R. pseudoacacia were 6.9% and 7.0% higher than those in the sunlit leaves, respectively. Rp and CCP of R. pseudoacacia leaves had linear relationships with temperature (T) and photosynthetic active radiation (PAR), and η had a significant relationship with stomatal conductance (gs). η of Q. variabilis leaves was linearly correlated with PAR and gs, and CCP was affected by T and relative humidity. Amax of Q. variabilis leaves had significant positive linear relationships with RH and gs.

Treatment of experimental non-alcoholic steatohepatitis by targeting α7 nicotinic acetylcholine receptor-mediated inflammatory responses in mice.

Non­alcoholic fatty liver disease (NAFLD) is one of the most common types of liver disease, affecting up to 30% of the general population worldwide. Non­alcoholic steatohepatitis (NASH) is a severe form of NAFLD without any effective therapies available. The present study showed that activation of α7­nicotinic acetylcholine receptor (α7 nAChR) may be a novel potential strategy for NASH therapy. Treatment with the α7 nAChR agonist nicotine for three weeks obviously attenuated hepatic steatosis in a high-fat diet­induced mouse model of NASH. Investigation of the underlying mechanism showed that nicotine reduced the secretion of the pro­inflammatory cytokines tumor necrosis factor α and interleukin 6 in vitro and in vivo. Inflammation is an integral part of NASH and is the most prevalent form of hepatic pathology found in the general population; therefore, the effect of α7 nAChR activation against NASH may be ascribed to its anti­inflammatory effects. In addition, the present study showed that nicotine­stimulated α7 nAChR activation led to a significant downregulation of nuclear factor kappa B (NK­κB) and extracellular signal-regulated kinase (ERK). It therefore appeared that activation of α7 nAChR suppressed the production of pro­inflammatory cytokines through NK­κB and ERK pathways. In conclusion, the present study indicated that targeting α7 nAChR may represent a novel treatment strategy for NASH.