Above- and Belowground Plant Functional Composition Show Similar Changes During Temperate Forest Swamp Succession.

Plant functional composition, defined by both community-weighted mean (CWM) traits and functional diversity, can provide insights into plant ecological strategies and community assembly. However, our understanding of plant functional composition during succession is largely based on aboveground traits. Here we investigated community-level traits and functional diversity for six pairs of analogous leaf and fine root traits of understory plants in a temperate forest swamp during succession with a decrease in soil pH and nutrient availability. CWMs of traits related to resource acquisition (including specific leaf area, specific root length, leaf N, leaf P, root N, and root P) decreased with succession, whereas those related to resource conservation (leaf dry matter content, root dry matter content, leaf tissue density, leaf C, and root C) increased along the forest swamp successional gradient. Multi-trait functional dispersion (FDis) of both leaf and fine root traits tended to decrease along the successional gradient, but functional richness and evenness were highest at the middle successional stage. Moreover, FDis of individual plant traits except N showed the same pattern as multi-trait FDis. Soil pH and nutrient availability were the main drivers of successional changes in both CWM traits and FDis. The changes of community-level traits along succession indicated a shift from acquisitive to conservative strategy of understory plants during forest swamp succession. Similar trends in leaf and fine root functional diversity along succession may indicate above- and belowground functional diversity are coordinated during the processes of plant community assembly. These findings of linkages between above- and belowground plant functional composition have important implications for plant community dynamics and assembly rules.

[Spatial-Temporal Variation of Water Environment Quality and Pollution Source Analysis in Hengshui Lake].

To study the spatial-temporal variation of water environment quality in Hengshui Lake and determine the associated pollution sources, we used historical water monitoring data (from 2000 onwards) and data from 17 sites sampled in 2019 to determine the trophic level index (TLI), comprehensive water quality index (WQI), and water environment quality index (EQI). The results showed that the proportion of monitoring points reaching level Ⅲ increased from 2000 to 2019. The permanganate index, total nitrogen, and total phosphorus were the main water environmental indicators. Spatially, TLI, WQI, and EQI all generally decreased from the south to the middle and west of the lake, and then further decreased towards the northeast. After the establishment of the Hengshui Lake National Nature Reserve, a series of water body protection policies and measures were implemented. These interventions are reflected in reductions in the TLI, WQI, and EQI between 2000 and 2019 by 20.9%, 53.4%, and 49.2%, respectively. However, side seepage and sewage discharge, agricultural non-point source pollutants transported by water diversion, and the decay of plants in the lake present significant challenges for water quality in Hengshui Lake.

Is there coordination of leaf and fine root traits at local scales? A test in temperate forest swamps.

Examining the coordination of leaf and fine root traits not only aids a better understanding of plant ecological strategies from a whole-plant perspective, but also helps improve the prediction of belowground properties from aboveground traits. The relationships between leaf and fine root traits have been extensively explored at global and regional scales, but remain unclear at local scales. Here, we measured six pairs of analogous leaf and fine root traits related to resource economy and organ size for coexisting dominant and subordinate vascular plants at three successional stages of temperate forest swamps in Lingfeng National Nature Reserve in the Greater Hinggan Mountains, NE China. Leaf and fine root traits related to resource acquisition (e.g., specific leaf area [SLA], leaf N, leaf P, root water content, and root P) decreased with succession. Overall, we found strong linear relationships between leaf dry matter content (LDMC) and root water content, and between leaf and root C, N, and P concentrations, but only weak correlations were observed between leaf area and root diameter, and between SLA and specific root length (SRL). The strong relationships between LDMC and root water content and between leaf and root C, N, and P held at the early and late stages, but disappeared at the middle stage. Besides, C and P of leaves were significantly correlated with those of roots for woody plants, while strong linkages existed between LDMC and root water content and between leaf N and root N for herbaceous species. These results provided evidence for the existence of strong coordination between leaf and root traits at the local scale. Meanwhile, the leaf-root trait relationships could be modulated by successional stage and growth form, indicating the complexity of coordination of aboveground and belowground traits at the local scale.

Changes of the denitrifying communities in a multi-stage free water surface constructed wetland.

Microorganisms play crucial roles in the nitrogen removal processes of wetlands. However, the key functional genes and microbes related to the nitrogen removal remain largely unknown in the free water surface constructed wetland (FWS CW). Here we studied the abundances of denitrifiers by targeting the key functional genes (nirS, nirK and nosZ) and investigated the community compositions of denitrifiers and their correlations with the abiotic variables in a FWS CW. The increase of nosZ/(nirS + nirK) and nirS/nirK ratios in the outlet indicated a shift of denitrifiers' communities which tended to release less nitrous oxide at the genetic potential level. The denitrifiers dominated the bacterial community which also remarkably changed from the inlet to the outlet. PICRUSt analysis revealed that the denitrifiers contributed to 39.1% of the nitrogen metabolism, 38.9% of the amino acid metabolism and 25.6% of the amino acid related enzymes. Four bacterial genera including Hydrogenophaga, Hylemonella, Aquabacterium and Cellvibrio were detected as the putative keystone denitrifiers. The abundance (nirS, nirK and nosZ) and the relative abundance of putative keystone denitrifiers were significantly correlated with total organic carbon, oxidation-reduction potential and C/N ratio, which could be regarded as the determinants for the denitrification process in the free water.

Contrasting fine-scale genetic structure of two sympatric clonal plants in an alpine swampy meadow featured by tussocks.

Tussocks are unique vegetation structures in wetlands. Many tussock species mainly reproduce by clonal growth, resulting in genetically identical offspring distributed in various spatial patterns. These fine-scale patterns could influence mating patterns and thus the long-term evolution of wetland plants. Here, we contribute the first genetic and clonal structures of two key species in alpine wetlands on the Qinghai-Tibet Plateau, Kobresia tibetica and Blysmus sinocompressus, using > 5000 SNPs identified by 2b-RAD sequencing. The tussock-building species, K. tibetica, has a phalanx (clumping) growth form, but different genets could co-occur within the tussocks, indicating that it is not proper to treat a tussock as one genetic individual. Phalanx growth does not necessarily lead to increased inbreeding in K. tibetica. B. sinocompressus has a guerilla (spreading) growth form, with the largest detected clone size being 18.32 m, but genets at the local scale tend to be inbred offspring. Our results highlight that the combination of clone expansion and seedling recruitment facilitates the contemporary advantage of B. sinocompressus, but its evolutionary potential is limited by the input genetic load of the original genets. The tussocks of K. tibetica are more diverse and a valuable genetic legacy of former well-developed wet meadows, and they are worthy of conservation attention.

[Distribution Characteristics of Mercury in Reed Leaves from the Jiapigou Gold Mine in the Songhua River Upstream].

At the Jiapigou gold mine of the Songhua River upstream, reed leaves (Phragmites australis), soil, and water samples were collected from June (summer) and September (autumn) 2016 for the determination of mercury. Moreover, the mercury concentrations in the air were determined synchronously. Furthermore, the level of mercury pollution in the reed leaves was determined by a single factor pollution index method, and the relationships among mercury concentrations in the reed leaves and environmental factors were analyzed to research the distribution characteristics, influencing factors, and correlations around the gold mining area. The results show that, in terms of spatial distribution, the mercury concentrations in reed leaves, soil, and water gradually decay with the distance from the gold mining area, and the spatial distribution of the mercury concentrations in the air was not obvious. Regarding a temporal distribution, the mercury concentrations in the reed leaves in summer were lower than those in autumn in the heavy pollution areas, while the distribution in the light pollution areas was the opposite, as the mercury concentrations of air and soil in summer were higher than those in autumn. The influence of environmental factors on the mercury concentrations in the reed leaves was soil > air > water. In addition, after stopping gold mining and processing using mercury, the mercury source in the area was the soil.

[Contamination and Ecological Risk Assessment of Mercury in Hengshuihu Wetland, Hebei Province].

Investigation on the concentrations and the distribution characteristics of total mercury in atmosphere, water surface and soil/ sediments of Hengshuihu wetland was carried out based on a uniform set point sampling method. The geoaccumulation index and potential ecological risk index methods were simultaneously used to assess the mercury pollution in Hengshuihu wetland ecosystem. The results showed that: the total mercury content in Hengshuihu wetland atmosphere ranged from 1.0 to 5.0 ng · m⁻³, with an average of (2.9 ± 0.85) ng · m⁻³; the total mercury content in water surface ranged from 0.010 to 0.57 µg · L⁻¹, with the average value of (0.081 ± 0.053) µg · L⁻¹; the total mercury content in soil/sediment ranged from 0.001 0 to 0.058 mg · kg⁻¹, with an average of (0.027 ± 0.013) mg · kg⁻¹. The distribution features of total mercury in Hengshuihu wetland were as follows: the total mercury concentration in surface water of the shore was significantly higher than that in the center (P < 0.05), but the total mercury concentration of sediments in the center of the lake was significantly higher than that at the shore (P < 0.05); the total mercury in the soil of shore had a consistent trend with that in the atmosphere; high concentrations of total mercury pollution were accompanied by severe human activities. The geoaccumulation index showed that mercury pollution in Hengshuihu wetland was at clean level; potential ecological risk index showed mercury contamination had a low ecological risk in Hengshuihu wetland.

[Structure dynamics of insect communities in typical artificial and primeval forests during restoring stages in Xiaoxing'an Mountain, Northeast China].

In order to study the insect community structure of typical artificial and primeval forests during different restoring stages in Xiaoxing'an Mountains, we had systematically investigated the insect communities of four typical forests in Liangshui Natural Reserve. A total of 11712 specimens of 293 species were collected, which belonged to 81 families of 10 orders, with Hymenoptera, Diptera, and Coleoptera being the dominant groups. The community stability analysis on insect communities showed that the insect communities of Dahurian larch plantation and original broadleaved Korean pine forest were more stable than other forest types. The principal components analysis indicated that predatory and neutral insects played important roles in the community stability which increased with the increasing predatory insect species and quantities. Polar ordination analysis showed that there was little difference between the environmental factors of Korean pine plantation and the original Korean pine forest.