Vascular changes of the choroid and their correlations with visual acuity in diabetic retinopathy.

Objective: To investigate changes in the choroidal vasculature and their correlations with visual acuity in diabetic retinopathy (DR). Methods: The cohort was composed of 225 eyes from 225 subjects, including 60 eyes from 60 subjects with healthy control, 55 eyes from 55 subjects without DR, 46 eyes from 46 subjects with nonproliferative diabetic retinopathy (NPDR), 21 eyes from 21 subjects with proliferative diabetic retinopathy (PDR), and 43 eyes from 43 subjects with clinically significant macular edema (CSME). Swept-source optical coherence tomography (SS-OCT) was used to image the eyes with a 12-mm radial line scan protocol. The parameters for 6-mm diameters of region centered on the macular fovea were analyzed. Initially, a custom deep learning algorithm based on a modified residual U-Net architecture was utilized for choroidal boundary segmentation. Subsequently, the SS-OCT image was binarized and the Niblack-based automatic local threshold algorithm was employed to calibrate subfoveal choroidal thickness (SFCT), luminal area (LA), and stromal area (SA) by determining the distance between the two boundaries. Finally, the ratio of LA and total choroidal area (SA + LA) was defined as the choroidal vascularity index (CVI). The choroidal parameters in five groups were compared, and correlations of the choroidal parameters with age, gender, duration of diabetes mellitus (DM), glycated hemoglobin (HbA1c), fasting blood sugar, SFCT and best-corrected visual acuity (BCVA) were analyzed. Results: The CVI, SFCT, LA, and SA values of patients with DR were found to be significantly lower compared to both healthy patients and patients without DR (P < 0.05). The SFCT was significantly higher in NPDR group compared to the No DR group (P < 0.001). Additionally, the SFCT was lower in the PDR group compared to the NPDR group (P = 0.014). Furthermore, there was a gradual decrease in CVI with progression of diabetic retinopathy, reaching its lowest value in the PDR group. However, the CVI of the CSME group exhibited a marginally closer proximity to that of the NPDR group. The multivariate regression analysis revealed a positive correlation between CVI and the duration of DM as well as LA (P < 0.05). The results of both univariate and multivariate regression analyses demonstrated a significant positive correlation between CVI and BCVA (P = 0.003). Conclusion: Choroidal vascular alterations, especially decreased CVI, occurred in patients with DR. The CVI decreased with duration of DM and was correlated with visual impairment, indicating that the CVI might be a reliable imaging biomarker to monitor the progression of DR.

Above- and belowground biodiversity drives soil multifunctionality along a long-term grassland restoration chronosequence.

Restoring degraded land is an efficient strategy for improving biodiversity and ecosystem functioning. However, the effects of aboveground and belowground biodiversity on multiple ecosystem functions (multifunctionality) during ecological restoration are not well understood. Here, the relationships between plant and microbial communities and soil multifunctionality were assessed in a 30-year natural grassland restoration chronosequence on the Loess Plateau, China. Soil multifunctionality, in relation to the carbon, nitrogen, phosphorus, and sulfur cycles, was quantified. Soil bacterial and fungal communities were analyzed by high-throughput sequencing using the Illumina HiSeq platform. The results showed that soil multifunctionality was significantly increased with the increasing period of grassland restoration. Plant and bacterial diversity, rather than fungal diversity, were significantly and positively correlated with soil multifunctionality based on single functions, averaging, and multiple threshold approaches. Random forest and structural equation modeling analyses showed that soil multifunctionality was affected by both biotic and abiotic factors. Plant diversity and bacterial community composition had direct effects, whereas plant community composition had both direct and indirect effects on soil multifunctionality. Restoration period and soil pH indirectly affected soil multifunctionality by altering plant and bacterial communities. This work demonstrates the importance of aboveground and belowground biodiversity in driving soil multifunctionality during grassland restoration. The results provide empirical evidence that conserving biodiversity is crucial for maintaining ecosystem functions in restored areas.

Global change effects on plant communities are magnified by time and the number of global change factors imposed.

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity-ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

Conservation of genetic diversity hotspots of the high-valued relic yellowhorn (Xanthoceras sorbifolium) considering climate change predictions.

Genetic structure and major climate factors may contribute to the distribution of genetic diversity of a highly valued oil tree species Xanthoceras sorbifolium (yellowhorn). Long-term over utilization along with climate change is affecting the viability of yellowhorn wild populations. To preserve the species known and unknown valuable gene pools, the identification of genetic diversity "hotspots" is a prerequisite for their consideration as in situ conservation high priority. Chloroplast DNA (cpDNA) diversity was high among 38 natural populations (H d = 0.717, K = 4.616, Tajmas' D = -0.22) and characterized by high genetic divergence (F ST = 0.765) and relatively low gene flow (N m = 0.03), indicating populations isolation reflecting the species' habitat fragmentation and inbreeding depression. Six out of the studied 38 populations are defined as genetic diversity "hotspots." The number and geographic direction of cpDNA mutation steps supported the species southwest to northeast migration history. Climatic factors such as extreme minimum temperature over 30 years indicated that the identified genetic "hotspots" are expected to experience 5°C temperature increase in next following 50 years. The results identified vulnerable genetic diversity "hotspots" and provided fundamental information for the species' future conservation and breeding activities under the anticipated climate change. More specifically, the role of breeding as a component of a gene resource management strategy aimed at fulfilling both utilization and conservation goals.

Change in dominance determines herbivore effects on plant biodiversity.

Herbivores alter plant biodiversity (species richness) in many of the world's ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis-that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.

Natural revegetation of a semiarid habitat alters taxonomic and functional diversity of soil microbial communities.

Revegetation of degraded lands has a profound impact on the maintenance and stability of ecosystem processes. However, the impacts of this land use change on functional diversity of soil microbial communities are poorly understood. Here, using 16S rRNA gene amplicon and shotgun metagenomic sequencing, we compared the taxonomic and functional communities of soil microbiome, and analyzed the effects of plant diversity and soil chemical properties, in a chronosequence of restored ex-farmland that had been naturally revegetated to grassland over periods of 5, 15 and 30years with adjacent farmland, on the Loess Plateau, China. We found that microbial taxonomic diversity was positively correlated with plant diversity and was higher in the revegetated sites. Functional diversity increased significantly in the oldest grassland. Actinobacteria, commonly considered a copiotrophic phylum, was more abundant in the revegetated sites, while Acidobacteria, an oligotrophic phylum, was more abundant in farmland. Furthermore, the structure of taxonomic and functional communities was significantly different between revegetated sites and farmland, and organic matter was the best environmental predictor in determining these microbial communities. Compared with the farmland, revegetation increased the proportion of genes associated with energy metabolism, carbohydrate metabolism and xenobiotics biodegradation and metabolism. Notably, the higher proportion of carbohydrate degradation gene subfamilies in the revegetated sites indicated higher levels of soil nutrient cycling. These results elucidate the significant shifts in belowground microbial taxonomic and functional diversity following vegetation restoration and have implications for ecological restoration programs in arid and semi-arid ecosystems.

Chi-Ju-Di-Huang-Wan protects rats against retinal ischemia by downregulating matrix metalloproteinase-9 and inhibiting p38 mitogen-activated protein kinase.

BACKGROUND: Retinal ischemia is a retinal disorder related to retinal vascular occlusion, glaucoma, diabetic retinopathy and age-related macular degeneration. The study aimed to evaluate the protective effects and underlying mechanisms of Chi-Ju-Di-Huang-Wan (CJDHW) against retinal ischemia in rats. METHODS: High intraocular pressure (HIOP)-induced retinal ischemia was established in Wistar rats by raising their intraocular pressure to 120 mmHg for 60 min with in an eye whose anterior chamber was cannulated with a 30-guage needle adapted to a normal saline bottle through an intravenous line. This ischemic insult was followed by 1 or 7 days of reperfusion. The effects of CJDHW were studied by (i) electroretinogram (ERG); (ii) real-time polymerase chain reaction to determine the retinal mRNA levels of Thy-1 and matrix metalloproteinase-9 (MMP-9); (iii) Western blot analysis to determine the retinal protein levels of B cell lymphoma 2 (Bcl-2), heme oxygenase-1 (HO-1), phosphorylated-p38 mitogen-activated protein kinase (P-p38 MAPK) and MMP-9; (iv) hematoxylin and eosin (HE) staining; (v) fluorogold retrograde labeling; and (vi) terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) apoptosis assay. Moreover, after fixation with 4 % paraformaldehyde and 30 % sucrose, the isolated retinas were sectioned and immunolabeled with goat anti-choline acetyltransferase (ChAT) polyclonal antibody, mouse anti-vimentin monoclonal antibody and rabbit anti-glial fibrillary acidic protein (GFAP) polyclonal antibody. The retinal sections were then incubated with rhodamine-conjugated rabbit anti-goat antibody, fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG or FITC-conjugated goat anti-rabbit IgG. A daily oral intake of 3 mL of water (vehicle; Group 2) or CJDHW (2.8 or 4.2 g/kg/day; CJDHW2.8 or CJDHW4.2; Group 3 or 4) was given for 7 consecutive days either before (preischemic drug administration) or after HIOP-induced retinal ischemic injury (postischemic drug administration). In Group 5, an intravitreal injection of 4 µL of 0.5 mM SB203580 (p38 MAPK inhibitor) was performed on the ischemic eye 15 min before retinal ischemia. The control rats received a sham procedure (Group 1) where the saline reservoir was not raised. RESULTS: The ischemia-induced changes (Group 2) were significantly modulated by pretreating the rats with 4.2 g/kg/day of CJDHW (Group 4; ERG: P < 0.001 on I/R day 7; HE stain: P < 0.001 on I/R day 7; TUNEL: P = 0.05 on I/R day 7; retrograde labeling: P = 0.007 on I/R day 7; Thy-1 mRNA: P = 0.02; MMP-9 mRNA: P < 0.001; Bcl-2 protein: P = 0.02; HO-1 protein: P = 0.03; P-p38 MAPK protein: P < 0.001; MMP-9 protein: P = 0.02). These modulations included the following features (Group 2 vs. 4), increased ERG b-wave amplitudes (0.38 ± 0.04 vs. 0.81 ± 0.03), increased inner retinal thickness (45.08 ± 2.85 vs. 67.98 ± 5.48 µm), increased ChAT immunolabeling, decreased vimentin/GFAP immunoreactivity, less numerous apoptotic cells in the ganglion cell layer (1.40 ± 0.55 vs. 0.60 ± 0.55), and more numerous retinal ganglion cells (887.73 ± 158.18 vs. 1389.02 ± 53.20). Moreover, increased Thy-1 (0.31 ± 0.15 vs. 0.78 ± 0.32) and decreased MMP-9 mRNA levels were found (4.44 ± 0.84 vs. 1.13 ± 0.34), respectively. Furthermore, the Bcl-2 protein level (0.78 ± 0.08 vs. 1.80 ± 0.34) was increased while the HO-1 (0.99 ± 0.20 vs. 4.15 ± 2.08), P-p38 MAPK (1.12 ± 0.18 vs. 0.57 ± 0.18) and MMP-9 levels were decreased (0.70 ± 0.23 vs. 0.39 ± 0.10). The ischemia-associated increases in P-p38 and MMP-9 protein levels were also attenuated by 0.5 mM SB203580 (P-p38 MAPK: 1.12 ± 0.18 vs. 0.18 ± 0.07, P < 0.001; MMP-9: 0.70 ± 0.23 vs. 0.21 ± 0.07, P = 0.002). This was also the case to the MMP_enzyme activity (Group 2 vs. 4: 5.03 ± 1.57 vs. 1.59 ± 0.47, P = 0.002; Group 2 vs. 5: 5.03 ± 1.57 vs. 1.35 ± 0.41, P = 0.001). CONCLUSION: Treatment of the rats suffering from retinal ischemia with CJDHW inhibited apoptosis, increased antioxidative activity, downregulated MMP-9 and inhibited p38 MAPK.

Response of soil CO2 efflux to precipitation manipulation in a semiarid grassland.

Soil CO2 efflux (SCE) is an important component of ecosystem CO2 exchange and is largely temperature and moisture dependent, providing feedback between C cycling and the climate system. We used a precipitation manipulation experiment to examine the effects of precipitation treatment on SCE and its dependences on soil temperature and moisture in a semiarid grassland. Precipitation manipulation included ambient precipitation, decreased precipitation (-43%), or increased precipitation (+17%). The SCE was measured from July 2013 to December 2014, and CO2 emission during the experimental period was assessed. The response curves of SCE to soil temperature and moisture were analyzed to determine whether the dependence of SCE on soil temperature or moisture varied with precipitation manipulation. The SCE significantly varied seasonally but was not affected by precipitation treatments regardless of season. Increasing precipitation resulted in an upward shift of SCE-temperature response curves and rightward shift of SCE-moisture response curves, while decreasing precipitation resulted in opposite shifts of such response curves. These shifts in the SCE response curves suggested that increasing precipitation strengthened the dependence of SCE on temperature or moisture, and decreasing precipitation weakened such dependences. Such shifts affected the predictions in soil CO2 emissions for different precipitation treatments. When considering such shifts, decreasing or increasing precipitation resulted in 43 or 75% less change, respectively, in CO2 emission compared with changes in emissions predicted without considering such shifts. Furthermore, the effects of shifts in SCE response curves on CO2 emission prediction were greater during the growing than the non-growing season.

Niche and Neutral Processes Together Determine Diversity Loss in Response to Fertilization in an Alpine Meadow Community.

Fertilization via nutrient deposition and agricultural inputs is one of the most important factors driving decreases in plant diversity. However, we still do not fully understand which processes (niche process or neutral process) are more important in leading to decreases in plant diversity caused by fertilization. A hypothesis-based approach was used to test the relative importance of niche versus neutral processes along a fertilization gradient in an alpine meadow community on the eastern Tibetan plateau, China. Niche overlap values were calculated for species biomass, and the null model was used to generate the values of niche overlap expected at random. A linear regression modeling was used to evaluate the relationship between functional traits (specific leaf area, leaf dry matter content, and leaf total nitrogen concentration) and species relative abundance. Our results demonstrated that observed niche overlap for species biomass was significantly higher than expected at lower fertilization gradients. Moreover, we also found a significantly negative correlation between species relative abundance and specific leaf area and leaf dry matter content, but a significantly positive correlation between relative abundance and leaf nitrogen concentration at lower fertilization gradients. However, these relationships were not significant at higher fertilization gradients. We concluded that community assembly is dynamic progression along the environmental gradients, and niche and neutral processes may together determine species diversity loss in response to fertilization.

Plant Functional Diversity Can Be Independent of Species Diversity: Observations Based on the Impact of 4-Yrs of Nitrogen and Phosphorus Additions in an Alpine Meadow.

Past studies have widely documented the decrease in species diversity in response to addition of nutrients, however functional diversity is often independent from species diversity. In this study, we conducted a field experiment to examine the effect of nitrogen and phosphorus fertilization ((NH4)2 HPO4) at 0, 15, 30 and 60 g m-2 yr-1 (F0, F15, F30 and F60) after 4 years of continuous fertilization on functional diversity and species diversity, and its relationship with productivity in an alpine meadow community on the Tibetan Plateau. To this purpose, three community-weighted mean trait values (specific leaf area, SLA; mature plant height, MPH; and seed size, SS) for 30 common species in each fertilization level were determined; three components of functional diversity (functional richness, FRic; functional evenness, FEve; and Rao's index of quadratic entropy, FRao) were quantified. Our results showed that: (i) species diversity sharply decreased, but functional diversity remained stable with fertilization; (ii) community-weighted mean traits (SLA and MPH) had a significant increase along the fertilization level; (iii) aboveground biomass was not correlated with functional diversity, but it was significantly correlated with species diversity and MPH. Our results suggest that decreases in species diversity due to fertilization do not result in corresponding changes in functional diversity. Functional identity of species may be more important than functional diversity in influencing aboveground productivity in this alpine meadow community, and our results also support the mass ratio hypothesis; that is, the traits of the dominant species influenced the community biomass production.

[Carbon sequestration status of forest ecosystems in Ningxia Hui Autonomous Region].

Based on the data of Ningxia Hui Autonomous Region forest resources inventory, field investigation and laboratory analysis, this paper studied the carbon sequestration status of forest ecosystems in Ningxia region, estimated the carbon density and storage of forest ecosystems, and analyzed their spatial distribution characteristics. The results showed that the biomass of each forest vegetation component was in the order of arbor layer (46.64 Mg x hm(-2)) > litterfall layer (7.34 Mg x hm(-2)) > fine root layer (6.67 Mg x hm(-2)) > shrub-grass layer (0.73 Mg x hm(-2)). Spruce (115.43 Mg x hm(-2)) and Pinus tabuliformis (94.55 Mg x hm(-2)) had higher vegetation biomasses per unit area than other tree species. Over-mature forest had the highest arbor carbon density among the forests with different ages. However, the young forest had the highest arbor carbon storage (1.90 Tg C) due to its widest planted area. Overall, the average carbon density of forest ecosystems in Ningxia region was 265.74 Mg C x hm(-2), and the carbon storage was 43.54 Tg C. Carbon density and storage of vegetation were 27.24 Mg C x hm(-2) and 4.46 Tg C, respectively. Carbon storage in the soil was 8.76 times of that in the vegetation. In the southern part of Ningxia region, the forest carbon storage was higher than in the northern part, where the low C storage was mainly related to the small forest area and young forest age structure. With the improvement of forest age structure and the further implementation of forestry ecoengineering, the forest ecosystems in Ningxia region would achieve a huge carbon sequestration potential.

Value of postoperative radiation therapy for regional control after dissection in head and neck squamous cell carcinoma cases.

OBJECTIVE: We aimed to define clinicopathologic risk factors associated with regional recurrence (RR) and thus the effectiveness of postoperative radiotherapy (PORT) for neck control for head and neck squamous cell carcinomas (HNSCCs) with differing cervical lymph node status. METHODS: A retrospective study was performed in 196 HNSCC patients with pathologically positive neck node (N+) to evaluate the high-risk factors for RR and to define the role of PORT in control after neck dissection and postoperative radiotherapy (PORT). RESULTS: Overall, the RR rate after neck dissection and PORT was 29%. Extracapsular spread (ECS) was confirmed to be the only independent risk factor for RR. There were no significant risk factors associated with RR in the ECS- group. The 5-year disease-specific survival rate was 45%, which descended to 10% with the emergence of RR. CONCLUSIONS: ECS remains a determined risk factor for RR after neck dissection and PORT in patients with N+. PORT alone is not adequate for preventing RR in the neck with ECS after neck dissection. More intensive postoperative adjuvant therapies, especially combined chemotherapy and radiotherapy, are needed to prevent regional failure in HNSCC patients with ECS.

[Fine root biomass of four main vegetation types in Daluo Mountain of Ningxia, Northwest China].

By the method of soil core sampling, this paper studied the fine root biomass, soil water content, and soil bulk density in 0-40 cm soil layer of four main vegetation types (Picea crassifolia forest, Pinus tabulaeformis forest, deciduous shrubs, and desert grassland) in Daluo Mountain of Ningxia, and the fine root biomass in the 0-40 cm soil layer of P. crassifolia forests with the ages of 50-, 70-, and 100 a. The fine root biomass of the four vegetation types was mainly distributed in 0-20 cm soil layer, with the rank of P. tabulaeformis forest > P. crassifolia forest > deciduous shrubs > desert grassland, and the fine root biomass of P. tabulaeformis forest was significantly higher than that of the other three vegetation types. The fine root biomass of the P. crassifolia forests with different ages was 70 a > 100 a > 50 a, and there were no significant differences in the live fine root biomass ratio and dead fine root biomass ratio among the three P. crassifolia forests. The soil water content in the 0-40 cm soil layer of the four vegetation types was P. crassifolia forest > P. tabulaeformis forest > deciduous shrubs > desert grassland, while the soil bulk density followed an opposite pattern, and was significantly negatively correlated with the fine root biomass.

Ecosystem carbon and nitrogen accumulation after grazing exclusion in semiarid grassland.

The grazing exclusion in degraded grassland has been extensively used to prevent the loss of grassland resources and to improve grassland services. The effects of grazing exclusion on C and N balance, however, have not been well addressed but are essential for assessing grassland C sinks, the sustainable use of grassland resources and the support of grassland services. To understand the response of ecosystem C and N to grazing exclusion in semiarid grassland, we determined the C and N in litter, aboveground biomass, roots and soils from ungrazed grassland fenced at different times in northwest China. Our results showed that the aboveground biomass, root biomass and plant litter were 70-92%, 56-151% and 59-141% higher, respectively, in grazer excluded grassland than in grazed grassland. Grazing exclusion significantly increased C and N stored in plant biomass and litter and increased the concentrations and stocks of C and N in soils. Grazing exclusion thus significantly increased the C and N stored in grassland ecosystems. The increase in C and N stored in soil contributed to more than 95% and 97% of the increases in ecosystem C and N storage. The highest C and N stocks in ecosystems were observed in 17-year grazer excluded grassland. The results from this study indicate that grazing exclusion has the potential to increase C and N storage in degraded semiarid grassland and that the recovery of ecosystem C and N was mainly due to the accumulation of C and N in soils.

Comparing the effect of naturally restored forest and grassland on carbon sequestration and its vertical distribution in the Chinese Loess Plateau.

Vegetation restoration has been conducted in the Chinese Loess Plateau (CLP) since the 1950s, and large areas of farmland have been converted to forest and grassland, which largely results in SOC change. However, there has been little comparative research on SOC sequestration and distribution between secondary forest and restored grassland. Therefore, we selected typical secondary forest (SF-1 and SF-2) and restored grassland (RG-1 and RG-2) sites and determined the SOC storage. Moreover, to illustrate the factors resulting in possible variance in SOC sequestration, we measured the soil δ(13)C value. The average SOC content was 6.8, 9.9, 17.9 and 20.4 g kg(-1) at sites SF-1, SF-2, RG-1 and RG-2, respectively. Compared with 0-100 cm depth, the percentage of SOC content in the top 20 cm was 55.1%, 55.3%, 23.1%, and 30.6% at sites SF-1, SF-2, RG-1 and RG-2, suggesting a higher SOC content in shallow layers in secondary forest and in deeper layers in restored grassland. The variation of soil δ(13)C values with depth in this study might be attributed to the mixing of new and old carbon and kinetic fractionation during the decomposition of SOM by microbes, whereas the impact of the Suess effect (the decline of (13)C atmospheric CO(2) values with the burning of fossil fuel since the Industrial Revolution) was minimal. The soil δ(13)C value increased sharply in the top 20 cm, which then increased slightly in deeper layers in secondary forest, indicating a main carbon source of surface litter. However the soil δ(13)C values exhibited slow increases in the whole profile in the restored grasslands, suggesting that the contribution of roots to soil carbon in deeper layers played an important role. We suggest that naturally restored grassland would be a more effective vegetation type for SOC sequestration due to higher carbon input from roots in the CLP.

[Allelopathic effects of Artemisia sacrorum population in typical steppe based on niche theory].

By using modified Levins niche width index and Pianka niche overlap index, this paper analyzed the ecological competition between constructive and dominant species in a typical steppe. The stem- and leaf extracts from the constructive species (Artemisia sacrorum) were utilized to study their allelopathic potential on the seed germination and plant growth of the dominant species (Stipa bungeana, Thymus mongolicus, S. grandis, and Leymus secalinus), and the ecological position of A. sacrorum in the steppe succession. In the steppe, S. bungeana had the widest niche width (0.99), followed by T. mongolicus (0.94), A. sacrorum (0.82), S. grandis (0.76), and L. secalinus (0.73). The niche overlap value between A. sacrorum and S. bungeana, S. bungeana and T. mongolicus, T. mongolicus and S. grandis, and A. sacrorum and T. mongolicus was 0.90, 0.95, 0.94, and 0.86, respectively. The allelopathic effects of A. sacrorum extracts varied with their concentration. For the seed germination, root growth, and shoot growth of the dominant species, A. sacrorum extracts showed a trend of promoting at low concentrations and inhibiting at high concentrations. The extracts of A. sacrorum had a stronger promotion effect on the root growth of S. bungeana than on that of T. mongolicus, but a stronger inhibition effect on the shoot growth of T. mongolicus than on that of S. bungeana. Methanol extracts had stronger allelopathic effects than aqueous extracts. The high niche overlap between A. sacrorum and S. bungeana, and T. mongolicus and S. grandis indicated that the steppe community would continue succession to S. bungeana, while A. sacrorum population was only an important transitional stage during the succession. The allelopathic effect of A. sacrorum played a driving role in the succession process.

[Outcomes of salvage laryngectomy after initial radiation failure in laryngeal squamous cell carcinoma].

OBJECTIVE: To investigate survival outcomes of salvage surgery preformed for laryngeal squamous cell carcinoma that recurred or progressed after radiotherapy alone. METHODS: A review of 72 patients who underwent salvage laryngectomy for laryngeal cancer failed in initial radiation therapy between 1996 and 2005 was performed. The tumor persistence occurred in 50 cases and recurrence in 22 cases. All patients received salvage total laryngectomy and radical neck dissection. Survival analysis was performed by using Kaplan-Meier method, Log-rank test and Cox proportional hazard model. RESULTS: Thirty patients developed a postoperative complication after salvage surgery. Pharyngocutaneous fistula occurred in 15(20.8%) patients. During 5 years after salvage surgery, the rates of tumor recurrence, distant metastasis and second malignancy were 34.7%, 22.2% and 6.9%, respectively. Kaplan-Meier analysis showed that overall 3 year and 5 year survival rates of those patients after operation were 45.8% and 36.1%, respectively. Univariate analysis indicated that N restage, tumor persistence/recurrences after radiotherapy, surgical margin status, level of tumor invasion, pathologic N stage, extracapsular nodal spread and invasion of nonlymphotic structures were significantly associated with overall survival. Multivariate analysis showed the most significant prognostic factors were tumor persistence or recurrence after radiotherapy, surgical margin status and level of tumor invasion. CONCLUSIONS: Surgical salvage remains the gold standard for management after failure of initial radiation therapy. The extent of tumor invasion must be assessed sufficiently before operation, and the surgical margin status must be identified in operation by using a frozen sectioning approach, especially in patients with tumor invasion to muscle/cartilage and tumor persistence after radiotherapy.

[Distribution responses of Lespedeza davurica community on Loess Plateau to climate change].

Field survey and position monitoring were conducted from 2000 to 2009 to study the effects of climate change on the distribution and growth of Lespedeza davurica community on Loess Plateau. As affected by air temperature, the appropriate growth region of L. davurica community on the Plateau had an obvious zonal distribution from northwest to southeast. For the distribution of L. davurica community, the suitable air temperature was 7.4 degrees C-10 degrees C, average population density was 13.9 plants x m(-2), and reproductive branch was averagely 11.4 per cluster. As affected by precipitation gradient, the horizontal distribution of L. davurica community changed from a constructive or predominant species in typical grassland region into a companion species in forest steppe region, and then, the community gradually became dominant species. The L. davurica community appeared as an occasional species on the half sunny slope of gullies and valleys and the sand dunes in desert steppe region, and extended gradually from its optimal region with yearly precipitation 300 -500 mm to the region with yearly precipitation 270-600 mm. Also, the L. davurica community extended from its optimal altitude 1100-1700 m to 600-1950 m. Under the background of global climate change, the eco-breadth of L. davurica community expanded gradually.

[Clinicopathologic aspects of locoregional recurrence of hypopharyngeal cancer and their implication on the survival of patients].

OBJECTIVE: To investigate the clinicopathologic aspects of locoregional recurrence and their implication on the survival in patients with hypopharyngeal cancer. METHODS: A retrospective review of 101 patients with hypopharyngeal cancer that were treated with surgical management and postoperative radiotherapy from 1998 to 2004 was performed. The clinicopathologic risk factors for locoregional recurrence were evaluated by using univariate chi(2) tests and multiple stepwise Logistic regression models. Survival analysis was performed by using Kaplan-Meier method, Log-Rank test and Cox proportional hazard model. RESULTS: The overall incidence of locoregional recurrence in this series of hypopharyngeal cancer was 43.6% (44/101). The rates of recurrence were local 13.9% (14/101), regional 31.7% (32/101). In a multivariate Logistic regression analysis, it was confirmed that number of levels with pathologic lymph node (OR = 0.334, P = 0.0242) was the most significant risk factors for locoregional recurrence. The same for regional recurrence was capsule rupture of pathologic lymph node (OR = 0.353, P = 0.0389) and multilevel positive nodal involvement in neck (OR = 0.259, P = 0.0069). The overall survival of hypopharyngeal cancer was 23.2%, and reduced to 11.4% for locoregional recurrence. The recurrences were managed by salvage surgery in 12 cases, which included local recurrences after partial pharyngolaryngectomy, ipsilateral regional recurrences after selective neck dissection, and contralateral regional recurrences at initially uninvolved neck. The overall survival of those patients sustained 33.3%. A multivariate Cox regression analysis revealed that the factors impacting the prognosis were recurrent time (RR = 0.317, P < 0.0001) and treatment modality after locoregional recurrence (RR = 6.119, P = 0.0001). CONCLUSIONS: Locoregional recurrences are frequent and have a very negative impact on patient survival in hypopharyngeal cancer, which most commonly have a regional recurrence. Salvage surgery in suitable cases seems to improve survival rates. Much attention should be paid to cervical pathological factors for locoregional recurrences in hypopharyngeal cancer, especially multilevel and capsule rupture of pathologic lymph node.

[Water potential productivity and soil desiccation effect of alfalfa grasslands in different type arid areas of Loess Plateau: a simulation study].

Based on model validation and database establishment, the dynamic changes of water potential productivity, available water amount in 0-10 m soil layer, and moisture distribution in soil profiles on the alfalfa grasslands at Changwu of semi-humid area, Guyuan of semi-arid area, and Haiyuan of semi-arid prone drought area on Loess Plateau were simulated with WinEPIC model in a 20-30 years period. The results showed that the simulated water potential productivity of alfalfa grasslands at Changwu, Guyuan and Haiyuan fluctuated but declined with precipitation, and the mean value was 8.81, 3.83 and 2.48 t x hm(-2), respectively. The simulated monthly available water amount in 0-10 m soil layer also declined obviously but with fluctuation. On the 4-8 years old alfalfa grasslands, soil desiccation was quite serious, and soil available water amount fluctuated at low level with precipitation for a long period. With the increasing year of alfalfa growth, the thickness and distribution depth of desiccated soil layer increased gradually, and the duration for the desiccated soil depth over 10 m was 6 years at Changwu, 6 years at Guyuan, and 4 years at Haiyuan. After then, the soil layer beneath rainfall infiltration depth lasted permanently in a desiccated status. The reasonable duration for water sustainable use on alfalfa grasslands was 8-10 years on semi-humid area, 6-8 years on semi-arid years, and 4-6 years on semi-arid prone drought area.