Relationship between plant diversity and spatial stability of aboveground net primary productivity (ANPP) across different grassland ecosystems

Theory predicts that greater biodiversity is expected to enhance stability of ecosystem. In field experiment, we created some diversity-level assemblages by removing functional groups across two grassland ecosystems and evaluated the responses of spatial stability of aboveground net primary productivity (ANPP) to varying functional trait diversity. The results revealed that higher diversity promoted greater spatial stability in the semi-shrub grassland ecosystem except SGB, whereas the similar pattern in diversity-stability relationship had been scarcely found in the typical steppe ecosystem. Additionally, we found that factors-influencing spatial stability varied across different grassland types. In the typical steppe ecosystem, spatial stability was only accounted for by positive sampling effect induced by high dispersal rate of rhizomatous grass. By contrast, in the semi-shrub grassland ecosystem, diversity level together with positive sampling effect commonly contributed to spatial stability, moreover, effect of particular trait overshadowed that of diversity. We also found that the positive diversity-stability relationship did not exist when compared with two grassland types. Research provides new insights into understanding the relationship between biodiversity and ecosystem functioning in varying environments. This relationship is not consistent across different ecosystems and is often system-dependent. Critical trait of species is particularly an important determinant for ecosystem functioning.Key words: Biodiversity experiment, spatial variability, functional trait diversity, ecosystem type

Warming shows differential effects on late-season growth and competitive capacity of Elodea canadensis and Potamogeton crispus in shallow lakes

Submerged macrophytes are likely to be affected by climate changes through changes in water temperatures and length of growing season. We conducted a lab experiment to examine the influence of a late-season temperature increase on growth, biomass allocation, and acclimation of 2 submerged macrophyte species, Elodea canadensis and Potamogeton crispus. We also ran competitive interaction experiments between the 2 species with mono- and mixed-species cultures in pots placed in outdoor heated mesocosms (5 years at ambient temperature and a higher temperature following the IPCC A2 scenario downscaled to local conditions but enhanced by 50%). In the lab, macrophytes collected in the 2 types of mesocosms were grown at ambient temperatures (12 °C in September and 8 °C in October) and 4 °C higher. Warming had an overall stronger effect on E. candensis than P. crispus, particularly within the low temperature range studied. Hence, the relative growth rate (RGR) of E. canadensis acclimated to ambient mesocosm conditions increased 6-fold from low (8 °C) to high (16 °C) temperature whereas the RGR of P. crispus increased <2-fold. In the competitive interaction experiment, warming increased the biomass and RGR of E. canadensis in the monoculture. In addition, warming increased shoot elongation of the plant in both the monoculture and mixed culture. P. crispus was generally unaffected by warming when grown in both monoculture and mixed culture, but competition decreased the elongation of shoots pre-adapted to ambient conditions and grown in the warmer mesocosms. The decomposition rate of E. canadensis accelerated with warming but was unaffected in P. crispus. We conclude that E. canadensis is a stronger competitor than P. crispus under warmer late-season conditions; however, it may have a higher demand for oxygen due to the increased decomposition rates at higher temperatures, particularly in the peripheral growing season, with potential profound effects on lake ecosystems. Although acclimatisation was evident, we suggested that temperature changes will affect the growth pattern of the 2 plant species and thereby perhaps induce a switch in macrophyte species dominance

Cassava genome from a wild ancestor to cultivated varieties

Cassava is a major tropical food crop in the Euphorbiaceae family that has high carbohydrate production potential and adaptability to diverse environments. Here we present the draft genome sequences of a wild ancestor and a domesticated variety of cassava and comparative analyses with a partial inbred line. We identify 1,584 and 1,678 gene models specific to the wild and domesticated varieties, respectively, and discover high heterozygosity and millions of single-nucleotide variations. Our analyses reveal that genes involved in photosynthesis, starch accumulation and abiotic stresses have been positively selected, whereas those involved in cell wall biosynthesis and secondary metabolism, including cyanogenic glucoside formation, have been negatively selected in the cultivated varieties, reflecting the result of natural selection and domestication. Differences in microRNA genes and retrotransposon regulation could partly explain an increased carbon flux towards starch accumulation and reduced cyanogenic glucoside accumulation in domesticated cassava. These results may contribute to genetic improvement of cassava through better understanding of its biology

Low power diamond rock coring parameters

An experimental rock coring study was conducted on a low power diamond drilling system. In this laboratory experiment, two surface-set and two impregnated diamond bits were tested on six types of rock ranging from granite to limestone under the same conditions. In this paper, authors present the testnng equipment, rock strength and index tests, and the result of the coring test

Introduction - Ecology and Indigeneity: An Exploration of ASEAN Literatures

The Journal of Ecocriticism811-