[Effects of radiation changes on net ecosystem exchange of carbon dioxide in a middle subtropical Chinese fir plantation]. / 辐射变化对中亚热带杉木人工林净CO2交换的影响.

Total solar radiation is an important factor affecting carbon exchange in forest ecosystem. In order to understand the effects of radiation change on carbon exchange in Chinese fir plantation, long-term monitoring data of carbon dioxide flux and meteorological factors measured by open eddy covariance system and meteorological gradient observation system were used in this study. The clearness index (kt) was used to represent the condition of solar radiation. We analyzed the effects of kt on net ecosystem exchange of carbon dioxide (NEE) in the central subtropical Chinese fir plantation during the growing season (from April to October). The results showed that total solar radiation in clear sky was usually higher in the morning than that in the afternoon, and that NEE was lower in the morning than in the afternoon. Such difference in NEE reached the maximum when the solar elevation angle was about 50°. At the medium kt(0.42-0.52), carbon absorption of Chinese fir plantation was the strongest. The ave-rage maximum relative change of NEE in 10 years in different solar elevation angles ranged from 11.0% to 29.4%, while the minimum and maximum critical values appeared at 35°-40° and 45°-50°, respectively. When kt was at the moderate degree due to the existence of clouds, carbon absorption and diffuse photosynthetically active radiation of Chinese fir plantation reached the maximum, and the latter might be the main reason for the former. Moderate radiation condition with the presence of cloud clould promote NEE of Chinese fir plantation and lead to largest carbon absorption.

[Leaf nitrogen and phosphorus stoichiometry of shrubland plants in the rocky desertification area of Southwestern Hunan, China.] / æ¹˜è¥¿å—çŸ³æ¼ åŒ–åœ°åŒºçŒä¸›æ¤ç‰©å¶N、P化学计量特征.

In this paper, we took the leaves of shrubland plants in rocky desertification area in Southwestern Hunan as the research object to analyze the nitrogen (N) and phosphorus (P) stoichiometry characteristics for different functional groups and different grades of rocky desertification, i.e., light rocky desertification (LRD), moderate rocky desertification (MRD) and intense rocky desertification (IRD). The results showed that the average contents of N and P were 12.89 and 1.19 g·kg-1, respectively, and N/P was 11.24 in common shrubland plants in the study area, which indicated that the growth of most plants were mainly limited by N. The content of N was declined in order of deciduous shrubs > evergreen shrubs > annual herbs > perennial herbs. The content of P and N/P were higher in deciduous shrubs than in perennial herbs. Significant differences were found among the main families of plants in terms of the contents of N, P and N/P in the study sites. The plants of Gramineae had the lowest contents of N and P, andtheir growth was mostly restricted by N, while Leguminosae had the highest content of N and N/P, and their productivity was majorly controlled by P. The contents of N and P in the leaves were significantly higher in dicotyledon plants and C3 plants than in monocotyledon plants and C4 plants, but the N/P was not significantly diffe-rent between these two plant categories. The nitrogen-fixing plants had higher content of N and N/P than the non-nitrogen-fixing plants, but the P content was not significantly different between these two plant groups. There were significant correlations between contents of N and P, N/P and N in all study plots. No significant correlation was found between N/P and P content in the examined rocky desertification sites, except for that in MRD. There were no significant differences of the contents of N, P and N/P under different grades of rocky desertification.

[Spatial heterogeneity and influencing factors of soil phosphorus concentration in a mid-subtropical Choerospondias axillaris deciduous broad-leaved forest, China.] / ä¸­äºšçƒ­å¸¦å—é ¸æž£è½å¶é˜”å¶æž—åœŸå£¤ç£·ç´ ç©ºé—´å˜å¼‚åŠå ¶å½±å“å› ç´ .

In order to investigate spatial variations in soil phosphorus (P) concentration and the influencing factors, one permanent plot of 1 hm2 was established and stand structure was surveyed in Choerospondias axillaries deciduous broadleaved forest in Dashanchong Forest Park in Changsha County, Hunan Province, China. Soil samples were collected with equidistant grid point sampling method and soil P concentration and its spatial variation were analyzed by using geo-statistics and geographical information system (GIS) techniques. The results showed that the variations of total P and available P concentrations in humus layer and in the soil profile at depth of 0-10, 10-20 and 20-30 cm were moderate and the available P showed higher variability in a specific soil layer compared with total P. Concentrations of total P and available P in soil decreased, while the variations increased with the increase in soil depth. The total P and available P showed high spatial autocorrelation, primarily resulted from the structural factors. The spatial heterogeneity of available P was stronger than that of total P, and the spatial autocorrelation ranges of total P and available P varied from 92.80 to 168.90 m and from 79.43 to 106.20 m in different soil layers, respectively. At the same soil depth, fractal dimensions of total P were higher than that of available P, with more complex spatial pattern, while available P showed stronger spatial correlation with stronger spatial structure. In humus layer and soil depths of 0-10, 10-20 and 20-30 cm, the spatial variation pattern of total P and available P concentrations showed an apparent belt-shaped and spot massive gradient change. The high value appeared at low elevation and valley position, and the low value appeared in the high elevation and ridge area. The total P and available P concentrations showed significantly negative correlation with elevation and litter, but the relationship with convexity, species, numbers and soil pH was not significant. The total P and available P exhibited significant positive correlations with soil organic carbon (SOC), total nitrogen concentration, indicating the leaching characteristics of soil P. Its spatial variability was affected by many interactive factors.

[Plant and soil nutrient characteristics in the karst shrub ecosystem of southwest Hunan, China]. / æ¹˜è¥¿å—å–€æ–¯ç‰¹åœ°åŒºçŒä¸›ç”Ÿæ€ç³»ç»Ÿæ¤ç‰©å’ŒåœŸå£¤å »åˆ†ç‰¹å¾.

This research was conducted in light (LRD), moderate (MRD, abandoned land) and intense (IRD) rocky desertification shrub ecosystems in Shaoyang, Hunan Province. We collected plant samples and soil at 3 layers (0-15, 15-30, 30-45 cm), and analyzed the distribution patterns of soil and plant nutrients and the relationships among them. Our results showed that the contents of soil organic carbon (SOC) and total N in different soil layers were various and decreased with soil depth, while the contents of total P, K, Ca and Mg had no obvious variation among the different soil layers. The contents of total N, P, Ca and Mg in soil were significantly different among the 3 rocky desertification shrub ecosystems, and the SOC, total N and total P in MRD were relatively higher than in the others. The rank of macroelement contents in soils for LRD and IRD was SOC>total K>total Ca>total Mg>total N>total P, while it was SOC>total K>total Ca>total N>total Mg>total P for MRD. The rank of macroelement contents in plants from the 3 rocky desertification shrub ecosystems was Ca>N>K>Mg>P, and the contents of N and P in plants were significantly positively correlated with the corresponding contents of total N and total P in soils. Soil nutrients were closely related to vegetation growth. According to the soil nutrient status of desertification plots of different grades, we should integrate the forest reservation with artificial afforestation and targeted fertilization methods for managing karst rocky desertification.

[Ecological footprint of farmers and herdsmen in Tibet Autonomous Region, China].

Based on relevant statistical yearbook and with an integrated method, the ecological footprint and ecological carrying capacity of farmers and herdsmen during the period from 2000 to 2012 in Tibet Autonomous Region, China were studied. The results showed that the ecological status of farmers and herdsmen were in a surplus state during the study period, but the surplus amount exhibited a decreasing tendency. The ecological capacity decreased from 7.49 hm2 in 2000 to 6.35 hm2 in 2012, with a decrease of 15.3%, while the ecological footprint increased gradually from 1.03 hm2 in 2000 to 1.26 hm2 in 2012.

Development and Evaluation of Models for the Relationship between Tree Height and Diameter at Breast Height for Chinese-Fir Plantations in Subtropical China.

Tree diameter at breast height (dbh) and height are the most important variables used in forest inventory and management as well as forest carbon-stock estimation. In order to identify the key stand variables that influence the tree height-dbh relationship and to develop and validate a suit of models for predicting tree height, data from 5961 tree samples aged from 6 years to 53 years and collected from 80 Chinese-fir plantation plots were used to fit 39 models, including 33 nonlinear models and 6 linear models, were developed and evaluated into two groups. The results showed that composite models performed better in height estimate than one-independent-variable models. Nonlinear composite Model 34 and linear composite Model 6 were recommended for predicting tree height in Chinese fir plantations with a dbh range between 4 cm and 40 cm when the dbh data for each tree and the quadratic mean dbh of the stand (Dq) and mean height of the stand (Hm) were available. Moreover, Hm could be estimated by using the formula Hm = 11.707 × l n(Dq)-18.032. Clearly, Dq was the primary stand variable that influenced the height-dbh relationship. The parameters of the models varied according to stand age and site. The inappropriate application of provincial or regional height-dbh models for predicting small tree height at local scale may result in larger uncertainties. The method and the recommended models developed in this study were statistically reliable for applications in growth and yield estimation for even-aged Chinese-fir plantation in Huitong and Changsha. The models could be extended to other regions and to other tree species only after verification in subtropical China.

Reverse mutation of the virulence-associated S2 gene does not cause an attenuated equine infectious anemia virus strain to revert to pathogenicity.

The contribution of S2 accessory gene of equine infectious anemia virus (EIAV) to the virulence of pathogenic strains was investigated in the present study by reverse mutation of all four consensus S2 mutation sites in an attenuated EIAV proviral strain, FDDV3-8, to the corresponding sequences of a highly pathogenic strain DV117. The S2 reverse-mutated recombinant strain FDDVS2r1-2-3-4 replicated with similar kinetics to FDDV3-8 in cultivated target cells. In contrast to the results of other studies of EIAV with dysfunctional S2, reverse mutation of S2 only transiently and moderately increased the plasma viral load of inoculated horses, and induction of transient immunosuppression did not boost viral pathogenicity. In addition, inoculation of FDDVS2r1-2-3-4 induced partial protection to a challenge pathogenic virus. These results suggest that the attenuated EIAV vaccine strain with multiple mutations in multiple genes will not easily revert to a virulent phenotype.

Spatial patterns and climate drivers of carbon fluxes in terrestrial ecosystems of China.

Understanding the dynamics and underlying mechanism of carbon exchange between terrestrial ecosystems and the atmosphere is one of the key issues in global change research. In this study, we quantified the carbon fluxes in different terrestrial ecosystems in China, and analyzed their spatial variation and environmental drivers based on the long-term observation data of ChinaFLUX sites and the published data from other flux sites in China. The results indicate that gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP) of terrestrial ecosystems in China showed a significantly latitudinal pattern, declining linearly with the increase of latitude. However, GEP, ER, and NEP did not present a clear longitudinal pattern. The carbon sink functional areas of terrestrial ecosystems in China were mainly located in the subtropical and temperate forests, coastal wetlands in eastern China, the temperate meadow steppe in the northeast China, and the alpine meadow in eastern edge of Qinghai-Tibetan Plateau. The forest ecosystems had stronger carbon sink than grassland ecosystems. The spatial patterns of GEP and ER in China were mainly determined by mean annual precipitation (MAP) and mean annual temperature (MAT), whereas the spatial variation in NEP was largely explained by MAT. The combined effects of MAT and MAP explained 79%, 62%, and 66% of the spatial variations in GEP, ER, and NEP, respectively. The GEP, ER, and NEP in different ecosystems in China exhibited 'positive coupling correlation' in their spatial patterns. Both ER and NEP were significantly correlated with GEP, with 68% of the per-unit GEP contributed to ER and 29% to NEP. MAT and MAP affected the spatial patterns of ER and NEP mainly by their direct effects on the spatial pattern of GEP.

Isolation and genetic characterization of bovine parainfluenza virus type 3 from cattle in China.

Bovine parainfluenza virus type 3 (BPIV3) is one of the most important of the known viral respiratory pathogens of both young and adult cattle. However BPIV3 has not been detected or isolated in China prior to this study. In 2008, four BPIV3 strains were isolated with MDBK cells from cattle in China and characterized by RT-PCR, nucleotide sequence analysis, transmission electron microscope observation, hemadsorption and hemagglutination tests. Nucleotide phylogenetic analysis of partial hemagglutinin-neuraminidase (HN) gene for four isolates and the complete genome for the SD0835 isolate implicated that the four Chinese BPIV3 strains were distinct from the previously reported genotype A (BPIV3a) and genotype B (BPIV3b) and might be a potentially new genotype, which was tentatively classified as genotype C (BPIV3c). This is the first study to report the isolation and genetic characterization of BPIV3 from cattle in China.

Genetic evolution of equine influenza viruses isolated in China.

China experienced an outbreak of equine influenza during 2007-2008. Meanwhile, its neighbor countries, such as Mongolia, India and Japan, have also been affected by various influenza virus strains in each country. Phylogenetic analysis showed that the newly emerging Chinese strains belong to Florida sublineage clade 2, as well as the Indian strain Jammu-Katra/6/08 and the Mongolian strain Mongolia/1/08. All of these strains were derived from European strains of this clade, such as the Newmarket/1/07 and Cheshire/1/07 strains, but these were not related to Japanese strains isolated around the same time (Florida sublineage clade 1) or to Chinese strains isolated in the 1990s (European lineage). Some unique amino acid changes were found in the antigenic sites in Asian strains of Florida sublineage clade 2. Moreover, the loss of a glycosylation site was found in the Liaoning/9/08 strain. From these studies, we have determined that equine influenza viruses in China have evolved with some new characteristics during recent years, and this emphasizes the importance of continued equine influenza virus surveillance in China.

[Construction and in vitro evaluation of an infectious clone of the equine infectious anemia virus vaccine strain EIAV(FDDV) with four reverse-mutated vaccine-specific sites in the S2 gene].

To elucidate the function of the S2 gene in equine infectious anemia virus (EIAV) and its role in the attenuation of the Chinese attenuated EIAV vaccine strains, the S2 in the EIAV vaccine strain EIAV (FDDV) was reverse-mutated and the in vitro replication character of the resultant virus was evaluated. Based on the sequence variation of the S2 gene between the EIAV virulent strains and vaccine strains, all the four vaccine-specific sites in the S2 of an EIAV(FDDV) infectious clone, pFDDV3-8, were reverse-mutated to the sequences of the virulent strain EIAV(DV115). The reverse-mutated molecular clone pFDDVS2r1-3-4-5 was used to transfect fetal donkey dermal (FDD) cells for rescuing the derived virus vpFDDVS2r1-3-4-5. The production and replication of vpFDDVS2r1-3-4-5 in FDD cells were proved by RT-PCR, immune fluorescence assay and reverse transcriptase activity assay. Typical virons of EIAV were clearly observed under the electron microscopy. The parallel analysis of the dynamic replication of the reverse-mutated viral clone vpFDDVS2r1-3-4-5 and its parental virus vpFDDV3-8 showed that the virus with four reverse mutations in the S2 replicated only slightly slower than its parental vaccine strain in FDD cells. This result implicates that the mutations in the S2 of the EIAV vaccine strains did not significantly alter the viral replication in vitro. Further studies on the in vivo replication of the reverse-mutated viral clone are required for understanding the relationship between the S2 and the attenuated pathogenesis of EIAV attenuated vaccines.

[Elevation of IFN-gamma transcription level in peripheral blood mononuclear cells of EIAV vaccinated horses].

AIM: To evaluate the relationship between the transcriptional level of IFN-gamma mRNA in peripheral blood mononuclear cells (PBMC) and immune protective response driven by inoculated horses with donkey leukocyte attenuated vaccine of EIAV(DLV), and to elucidate the immune mechanism of DLV. METHODS: A real-time PCR method was established for quantitative detection of IFN-gamma mRNA level from horse PBMCs. Twelve horses were divided into vaccination group, healthy control group, challenging control group and EIAV natural infection group. The transcriptional level and distribution of IFN-gamma mRNA in PBMCs were analyzed. The temperature and other parameters of the inoculated horses were monitored or a daily basis. Horses inoculated with DLV vaccines were challenged post-inoculated 8 months, and the change of transcriptional level of IFN-gamma mRNA during pre/post-challenge was evaluated. RESULTS: Compared with the healthy control and natural infection group. The transcriptional level of IFN-gamma mRNA was much higher in vaccination group (P<0.01), and kept increasing even after challenging with virulent EIAV strains. In the challenging control group, the transcriptional level of IFN-gamma mRNA fluctuated with the development of disease and reduced markedly during febrific episodes. CONCLUSION: This study for the first time reveals that EIAV-attenuated vaccine could induce high level transcription of IFN-gamma mRNA, with is associated closely with immune protective response induced by DLV. This finding provides some clues to elucidate the mechanism of immunity protection of DLV at the molecular level.

[Induction of EIAV-specific cellular immune response by attenuated EIAV vaccine].

AIM: To elucidate cellular immune protective mechanism of EIAV. METHODS: Four horses were immunized with (DLV) by subcutaneous injection and 2 horses with 0.85% sodium chloride as the negative control. Rectal temperatures and clinical features were recorded daily. Whole blood samples were collected, from which PBMC were separated and used for CTL assay and lymphocyte proliferation assay. RESULTS: The target cells were activated by PWM and treated with DLV or recombinant vaccinia vectors expressing DLV and LN Gag or Env separately. The percentage of EIAV-specific CTL lysis was under 5% in the negative control group, however, that was 20% to 30% in the group of immunized horses. The stimulation index (SI) from proliferation assay was 3 in the group immunized with attenuated DLV vaccine. CONCLUSION: The results indicated that EIAV-specific cellular immune-response induced by DLV immunization may contribute to the immune protective effect against EIAV virus infection.