Dianlin Yang

Responses of plant diversity and primary productivity to nutrient addition in a Stipa baicalensis grassland, China

Nutrient addition can affect the structure and diversity of grassland plant communities, thus alter the grassland productivity. Studies on grassland plant community composition, structure and diversity in response to nutrient addition have an important theoretical and practical significance for the scientific management of grassland, protection of plant diversity and the recovery of degraded grassland. A randomized block design experiment was conducted with six blocks of eight treatments each: control (no nutrient addition) and K, P, N, PK, NK, NP, and NPK addition. We evaluated plant composition, height, coverage, density, and aboveground biomass to estimate primary productivity and plant diversity. Results showed that all treatments increased primary productivity significantly (P<0.05) with the exception of the K and the NPK treatments had the greatest effect, increasing aboveground biomass 2.46 times compared with the control (P<0.05). One-way ANOVA and factorial analysis were used for the species richness, Shannon-Wiener index, Pielou index and aboveground biomass, and the relationships between the diversity indices and aboveground biomass were determined through linear regression. We found that fertilization altered the community structure; N (but not P or K) addition increased the proportion of perennial rhizome grasses and significantly reduced that of perennial forbs (P<0.05), thus it presented a trend of decrease in species richness, Shannon-Wiener and Pielou indexex, respectively. Only the main effects of N had significant impacts on both the diversity indices and the aboveground biomass (P<0.05), and the interactions between N-P, N-K, P-K and N-P-K could be neglected. With fertilization, plant diversity (correlation coefficient, −0.61), species richness (−0.49), and species evenness (–0.51) were all negatively linearly correlated with primary productivity. The correlations were all significant (P<0.01). Scientific nutrient management is an effective way to improve grassland productivity, protect the plant diversity as well as recover the degraded grassland.

Effects of Rest Grazing on Organic Carbon Storage in Stipa grandis Steppe in Inner Mongolia, China

This study was aimed to evaluate the potential effects of rest grazing on organic carbon storage in Stipa grandis steppe of Inner Mongolia, China. Using potassium dichromate heating method, we analyzed the organic carbon storage of plant and soil in Stipa grandis steppe after rest grazing for 3, 6, and 9 yr. The results indicated that as the rest grazing ages prolonged, the biomass of aboveground parts, litter and belowground plant parts (roots) of the plant communities all increased, meanwhile the C content of the biomass increased with the rest grazing ages prolonging. For RG0, RG3a, RG6a, and RG9a, C storage in aboveground vegetation were 60.7, 76.9, 82.8 and 122.2 g C m−2, respectively; C storage of litter were 5.1, 5.8, 20.4 and 25.5 g C m−2, respectively; C storage of belowground roots (0–100 cm) were 475.2, 663.0, 1 115.0 and 1 867.3 g C m−2, respectively; C storage in 0–100 cm soil were 13.97, 15.76, 18.60 and 32.41 kg C m−2, respectively. As the rest grazing ages prolonged, the organic C storage in plant communities and soil increased. The C storage of belowground roots and soil organic C was mainly concentrated in 0–40 cm soil body. The increased soil organic C for RG3a accounted for 89.8% of the increased carbon in vegetation-soil system, 87.2% for RG6a, and 92.6% for RG9a. From the perspective of C sequestration cost, total cost for RG3a, RG6a, and RG9a were 2 903.4, 5 806.8 and 8 710.2 CNY ha−1, respectively. The cost reduced with the extension of rest grazing ages, 0.15 CNY kg−1 C for RG3a, 0.11 CNY kg−1 C for RG6a and 0.04 CNY kg−1 C for RG9a. From the growth characteristics of grassland plants, the spring was one of the two avoided grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. Organic C storage for RG9a was the highest, while the cost of C sequestration was the lowest. Therefore, spring rest grazing should be encouraged because it was proved to be a very efficient grassland use pattern.

Emergy Evaluation of three Rice Wetland Farming Systems in the Taihu Lake Catchment of China

Emergy analysis was performed to evaluate the sustainability of three rice farming systems (rice mono-cropping, rice-fish and rice-duck farming systems) in the Jiangsu province. The results showed that the three systems exhibit unique characteristics on each component. The emergy of rice seeding and the labour input were the most important costs, at 57.18 and 18.20 sej/ha/season, respectively, for the rice mono-cropping system. In the rice-fish and rice-duck systems, the feed input played a more important role, corresponding to values of 63.70 and 79.20 sej/ha/season, respectively. The machinery input was 45.21 sej/ha/season for the rice-fish system due to the construction of fish ponds and ditches. The rice-duck system exhibited lower environmental loading and a higher sustainability index than the rice mono-cropping and rice-fish systems, respectively. The ratios of the economic input to output were 0.41, 0.61 and 0.41 for the rice mono-cropping, rice-fish and rice-duck systems, respectively. The net profit of the rice-duck system was

Priority assessment of wetlands restoration in HuangHuaiHai region, China

3264.2 per hectare, which was nearly 40% higher than those of the other systems. Based on the results showing the highest economic efficiency and value on the sustainability index, the rice-duck system may be the optimal rice agriculture system from both ecological and economic perspectives.

Changes in soil microbial functional diversity under different vegetation restoration patterns for Hulunbeier Sandy Land

With vast area of wetlands (coastal estuaries, semi-arid rivers, lakes, and other typical wetlands) and rich biodiversity (especially water-birds), HuangHuaiHai Region (HHHR) has its uniqueness and irreplaceability at local, regional and global scales. HHHR not only provides huge suitable habitats for various wildlives, but also plays very import role in providing great ecosystem service for local people. However, due to intensive human activities in HHHR during the half past century, wetlands have long been suffering from large-scale destruction and increasing degradation. In spite of large invest for wetlands conservation and restoration, however, the efficacy was low. Therefore, its essential to identify the priority areas for wetlands restoration to limit wetlands degradation. Firstly, we conducted the wetlands evolutionary analysis during the period from 1980s to 2000s. Then, on the basis of it, combining with socio-economical factors, such as GDP, population, etc., using the priority theory of Systematic Conservation Planning (SCP) and Marxan space-optimized software used universally in the world, we established wetland restoration scenarios based on different levels, and established wetlands priority restoration pattern. The results showed that: on the whole, wetlands in HHHR tended to degrade from 1980s to 2000s, decreasing about 99.37km2. The priority areas for wetlands restoration involved 29 counties in all, 2 counties in Tianjin City, 3 counties in Shandong Province, 4 counties in Hebei Province, and 20 counties in Henan Province, respectively, mainly along the Yellow River in Henan Province and around the Bohai Sea, others distributed sparsely. Finally, these proposed protected areas should be well integrated together, thus we can form a wetlands priority restoration pattern for HHHR.