Degradation selectivity for bamboo fiber and parenchyma lignin-carbohydrates complexes (LCC) esters.

The degradation of lignin-carbohydrate complex (LCC) esters has been proven to be crucial for the selective separation of lignocellulosic components. This study utilized Raman microspectroscopy to image the preferential degradation of lignin and LCC esters from the bamboo wall during successive NaOH (0.2 to 5.0 % w/w), H2SO4 (1 to 8 % v/v), and NaClO2 (5 to 20 min) treatments. Raman imaging showed that lignin and LCC esters were selectively removed from the middle lamella of fibers and the secondary wall of parenchyma during NaOH and NaClO2 treatments. In contrast, H2SO4 primarily caused the simultaneous removal of lignin and LCC esters from the fiber wall under harsh conditions (8 %), while the middle lamella of parenchyma was less affected, both morphologically and topochemically. Raman spectral analysis indicated that the band intensity at 1605 cm-1 for lignin and at 1173 cm-1 for LCC esters decreased by >87.0 % in the highly lignified parenchyma secondary wall after a 5.0 % NaOH treatment, while the decrease was <67 % in the fiber wall. Interestingly, a strong linear correlation was observed between LCC esters and carbohydrates in the parenchyma (R2 > 0.912). These findings provide important insights into the graded and classified utilization of bamboo resources.

Plant litter decomposition in wetlands is closely associated with phyllospheric fungi as revealed by microbial community dynamics and co-occurrence network.

Phyllospheric microbes play a crucial role in the biological decomposition of plant litter in wetland ecosystems. Previous studies have mainly focused on single stages of decomposition process, and to date there have been no reports on dynamic changes in the composition of phyllospheric microbes during the multiple stages of decomposition from living plant to death. Here we investigated fungal and bacterial community succession in the leaf litter of Schoenoplectus tabernaemontani, a wetland plant species using sequencing of the both fungal ITS and bacterial 16S genes. Our results revealed that, over the whole period of decomposition, the fungal communities underwent more distinct succession than did the bacterial communities. Proteobacteria dominated throughout the entire period, while, across different decomposition stages, the Ascomycete fungi were gradually replaced by the Ciliophora and Rozellomycota as the dominant fungi. Network analysis revealed higher degrees of species segregation and shorter average path lengths between species of fungi compared with species of bacteria. This suggests that fungal communities may harbor more niches and functional diversity and are potentially more susceptible to external interference than are bacterial communities. During decomposition, the contents of leaf cellulose, hemicellulose and lignin in the litter were significantly (p < 0.01) correlated with the fungal communities, and abiotic factors accounted for 89.8% of the total variation in the fungal communities. In contract, abiotic factors only explained 6.10% of the total variation in bacterial communities, suggesting external environments as drivers of fungal community succession. Overall, we provide evidence that the complex litter decay in wetlands is the result of a dynamic cross-kingdom succession, and this process is accompanied by distinct phyllospheric fungal community dynamics.

Carbon budgets of wetland ecosystems in China.

Wetlands contain a large proportion of carbon (C) in the biosphere and partly affect climate by regulating C cycles of terrestrial ecosystems. China contains Asia's largest wetlands, accounting for about 10% of the global wetland area. Although previous studies attempted to estimate C budget in China's wetlands, uncertainties remain. We conducted a synthesis to estimate C uptake and emission of wetland ecosystems in China using a dataset compiled from published literature. The dataset comprised 193 studies, including 370 sites representing coastal, river, lake and marsh wetlands across China. In addition, C stocks of different wetlands in China were estimated using unbiased data from the China Second Wetlands Survey. The results showed that China's wetlands sequestered 16.87 Pg C (315.76 Mg C/ha), accounting for about 3.8% of C stocks in global wetlands. Net ecosystem productivity, jointly determined by gross primary productivity and ecosystem respiration, exhibited annual C sequestration of 120.23 Tg C. China's wetlands had a total gaseous C loss of 173.20 Tg C per year from soils, including 154.26 Tg CO2 -C and 18.94 Tg CH4 -C emissions. Moreover, C stocks, uptakes and gaseous losses varied with wetland types, and were affected by geographic location and climatic factors (precipitation and temperature). Our results provide better estimation of the C budget in China's wetlands and improve understanding of their contribution to the global C cycle in the context of global climate change.

[Soil Degradation-Associated Microbial Community Structure Changes in an Alpine Meadow Under Tibetan Pig Herding].

Anthropic activities lead to a high risk of peatland degradation in the alpine regions. Along with the declined plant productivity and the impaired functioning of the soil carbon sink, the diversity and structure of soil microbial communities are also affected in a degraded peatland ecosystem. Tibetan pig herding is a unique peatland management strategy, which can significantly affect the peatland ecosystem, but it has been rarely studied. The changes in the microbial community structure and its responses to disturbances were studied using a 16S rRNA high throughput sequencing technique in an alpine meadow peatland under Tibetan pig herding disturbance and under control (without Tibetan pig herding) in the Northwestern Yunnan province. The results showed that Tibetan pig herding significantly reduced the α diversity of soil microbes, and the soil microbial community structures were significantly changed by pig herding. The soil microbial communities in the peatland soils were dominated by Proteobacteria, Acidobacteria, and Chloroflexi. Compared with those at the phylum level, the changes at the genus level under pig disturbance were more obvious. It was seen that the relative abundances of Sphingomonas and Hymenobacter significantly increased, while the abundances of Nitrospira and Rhodoplanes significantly decreased under pig herding. Venn diagram analysis revealed that there were 71 and 136 core OTUs in the soil under pig herding and in the control group soil, respectively. Burkholderiales, Pseudomonadales, and Sphingomonadales were the main taxa exclusively found under Tibetan pig herding, and could serve as indicators of soil disturbance. CCA ordination further showed that the distribution of Nitrospira and Rhodoplanes were mainly controlled by soil moisture, available phosphorus, and organic matter contents. Our findings provide an insight into the linkages between the soil microbial communities and the degradation of peatlands in alpine regions.

[Ecological restoration effect of closed and half-closed degraded wetlands in Northwest Yunnan Plateau, Southwest China].

Selecting the restoration site of Napahai, a representative degraded wetland in Northwest Yunnan Plateau, as test object, a comparative study was made on the changes of plant community species composition, water quality, and soil organic matter (OM) and total nitrogen (TN) contents within stream way, meadow, and lakeside before and after vegetation restoration, aimed to verify the effectiveness of integrated ecosystem restoration at catchment scale. In the early restoration period, the plants at the study site increased from 13 to 28 species, 12 to 22 genera, and 8 to 18 families, and the aboveground biomass increased from 318.56 g x m(-2) to 507.68 g x m(-2). The plant community structure and composition in lakeside and riverside had an obvious change before and after the vegetation restoration. Pollution-tolerant species diminished or disappeared, while the primary swamp communities of Sparganium stoloniferum and Batrachium bungei appeared after their disappearance for many years. After vegetation restoration, soil OM and TN contents increased from 28.85 g x kg(-1) and 0.79 g x kg(-1) to 50.26 g x kg(-1) and 1.45 g x kg(-1), respectively. The TN and TP contents and COD in the water decreased significantly, and their removal rates reached to 67.9%, 79.2%, and 71.2%, respectively. The transparency of water body increased to 179%, indicating that the structure and function of the wetland ecosystem had been substantially improved and restored. It was concluded that the vegetation restoration measures and technology used in closed or half-closed plateau wetland area were effective,

[Reinvasion of exotic plant species Spartina alterniflora in Chongming Dongtan Nature Reserve of Shanghai].

A demonstration plot in Chongming Dongtan for controlling exotic plant species Spartina alterniflora by using an integrated treatment technique of tussock cutting plus water level controlling was selected to make a 2-year monitoring on the reinvasion process of this plant species. A large number of S. alterniflora seedlings could proliferate and settle down in the hydrological restoring plots by tidal water in spring, and, after two years, the reinvasion community was established, with no obvious differences in its density as compared to the communities in neighboring areas. However, the distance of extension via vegetative propagation was limited. At the plots maintaining waterlogging, the distance of 2-year lateral extension was less than 1 m; at physically isolated plots, there was no any reinvasion of S. alterniflora. The rapid spreading of the seedlings in spring was the key of the fast reinvasion of S. alterniflora, and thus, to completely eradicate the spreading source from neighboring areas, to build isolation barrier to stop the spreading of this plant, and to adopt biological substitute by planting a native species such as Phragmites australis would be the main countermeasures to effectively prevent the reinvasion of S. alterniflora.