How much genetic variation is stored in the endangered and fragmented shrub Tetraena mongolica Maxim?

Tetraena mongolica Maxim (Zygophyllaceae) is an endangered species endemic to western Inner Mongolia and China, and is currently threatened by habitat loss and human over-exploitation. We explored the genetic background, its genetic diversity, population structure, and demographic history, based on 12 polymorphic nuclear microsatellite loci. Our results indicated high genetic diversity in extant populations, but no distinguishable gene cluster corresponding with a specific biogeography. Population demography analysis using a MSVAR indicated a strong, recent population decline approximately 5,455 years ago. These results suggest that the Yellow River and Zhuozi Mountain range may not prevent pollination between populations. Finally, we surmised that the population demography of T. mongolica was likely to have been affected by early mankind activities.

Sediment type affects competition between a native and an exotic species in coastal China.

Different types of sediments in salt marsh have different physical and chemical characters. Thus sediment type plays a role in plant competition and growth in salt marsh ecosystems. Spartina anglica populations have been increasingly confined to upper elevation gradients of clay, and the niche sediment has changed. Because the niches of S. anglica and the native species Scirpus triqueter overlap, we conducted a greenhouse experiment to test the hypothesis that plant competition has changed under different types of sediments. Biomass and asexual reproduction were analyzed, and inter- and intraspecific competition was measured by log response ratio for the two species in both monoculture and combination under three sediment types (sand, clay and mixture of sand and clay). For S. anglica, biomass, ramet number and rhizome length in combination declined significantly compared with those in monoculture, and the intensity of interspecific competition was significantly higher than that of intraspecific competition under all sediments. For S. triqueter, the intensities of intra- and interspecific competition were not significantly different. This indicates that S. triqueter exerts an asymmetric competitive advantage over S. anglica across all sediments, but especially clay. Thus the sediment type changes competition between S. anglica and S. triqueter.

Nitrogen level changes the interactions between a native (Scirpus triqueter) and an exotic species (Spartina anglica) in Coastal China.

The exotic species Spartina anglica, introduced from Europe in 1963, has been experiencing a decline in the past decade in coastal China, but the reasons for the decline are still not clear. It is hypothesized that competition with the native species Scirpus triqueter may have played an important role in the decline due to niche overlap in the field. We measured biomass, leaf number and area, asexual reproduction and relative neighborhood effect (RNE) of the two species in both monoculture and mixture under three nitrogen levels (control, low and high). S. anglica showed significantly lower biomass accumulation, leaf number and asexual reproduction in mixture than in monoculture. The inter- and intra-specific RNE of S. anglica were all positive, and the inter-specific RNE was significantly higher than the intra-specific RNE in the control. For S. triqueter, inter- and intra-specific RNE were negative at the high nitrogen level but positive in the control and at the low nitrogen level. This indicates that S. triqueter exerted an asymmetric competitive advantage over S. anglica in the control and low nitrogen conditions; however, S. anglica facilitated growth of S. triqueter in high nitrogen conditions. Nitrogen level changed the interactions between the two species because S. triqueter better tolerated low nitrogen. Since S. anglica is increasingly confined to upper, more nitrogen-limited marsh areas in coastal China, increased competition from S. triqueter may help explain its decline.

China's natural wetlands: past problems, current status, and future challenges.

Natural wetlands, occupying 3.8% of China's land and providing 54.9% of ecosystem services, are unevenly distributed among eight wetland regions. Natural wetlands in China suffered great loss and degradation (e.g., 23.0% freshwater swamps, 51.2% costal wetlands) because of the wetland reclamation during China's long history of civilization, and the population pressure and the misguided policies over the last 50 years. Recently, with an improved understanding that healthy wetland ecosystems play a vital role in her sustainable economic development, China started major efforts in wetland conservation, as signified by the policy to return reclaimed croplands to wetlands, the funding of billions of dollars to restore degraded wetlands, and the national plan to place 90% of natural wetlands under protection by 2030. This paper describes the current status of the natural wetlands in China, reviews past problems, and discusses current efforts and future challenges in protecting China's natural wetlands.

[Characteristics analysis of micro-element contents in western Erdos soil and in Tetraena mongolica plant].

This paper studied why the ex-situ conservation of Tetraena mongolica isn't successful. Through measuring and analyzing the micro-element contents in the soil where Tetraena mongolica is naturally distributed and where Tetraena mongolica is introduced in western Erdos. The results showed that among the areas where Tetraena mongolica is native to and the ex situ protection area, the average contents of 9 micro-elements, except B, are not only obviously higher than the average values in China's soil, but also higher than the values in desert areas. The contents of all micro-elements, except Cu, in the ex situ protection area are higher than desert and the natural distribution areas of Tetraena mongolica. Among the contents of the micro-elements in Tetraena mongolica plant, Fe, Cu, Zn, B, Se and Co are quite higher than that in other plant species on steppes, and Mo is higher than that in other plant species but is only 50% to the desert plants. The correlation coefficient for the contents of micro-elements between soil and plants (including adults and seedlings) are not significant and the contents in Tetraena mongolica plant are much higher than available contents of the counterparts in soil. By comparing the contents of micro-elements in Tetraena mongolica, grassland plants on steppe and desert and the contents in soil, it can be seen that every micro-element was enriched by Tetraena mongolica during its growth. The results do not support the suggestion that the contents of micro-elements in soil is the factor restricting the growth of Tetraena mongolica in the ex situ protection area.