Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert.

Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

[Variation in soil Mn fractions as affected by long-term manure amendment using atomic absorption spectrophotometer in a typical grassland of inner Mongolia].

The effect of sheep manure amendment on soil manganese fractions was conducted in a 11 year experiment at inner Mongolia grassland, using sequential extraction procedure in modified Community Bureau of Reference, and determined by atomic absorption spectrophotometer. Five treatments with dry sheep manure addition rate 0, 50, 250, 750, and 1500 g x m(-2) x yr(-1), respectively, were carried out in this experiment. Results showed that the recovery rate for total Mn was 91.4%-105.9%, as the percentage recovered from the summation of the improved BCR results with aqua regia extractable contents, and it was 97.2%-102.9% from certified soil reference materials. Plant available exchangeable Mn could be enhanced by 47.89%, but reducible and total Mn contents decreased significantly under heavy application of manure at depth of 0-5 cm. The effect of manure amendment on Mn fractions was greater in 0-5 cm than in 5-10 cm soil layer. The results are benefit to micronutrient fractions determination and nutrient management in grassland soils.

[Effects of plant functional groups removal on the soil carbon, nitrogen pools in a Leymus chinensis community of typical steppe in Inner Mongolia].

A field plant functional groups (PFGs) removal experiment was conducted in 2005-2007 to study the effects of plant diversity in a Leymus chinensis community of typical steppe in Inner Mongolia on the topsoil (0-10 cm) carbon (C) and nitrogen (N) pools. In the three successive years, the topsoil total C and N contents had a slight change (< 15%). They changed little in 2005, but were significantly higher in 2006 than in 2007 (P < 0.05). The topsoil NH4(+)-N content had a greater inter-annual change, being 80% higher in 2006 than in 2007, while the NO3(-)-N content had less significant change (P > 0.05). There was a positive linear relationship (P < 0.05) between the number of removed PFGs and the content of soil NO3(-)-N, which meant that the decrease of plant diversity increased soil NO3(-)-N content, and consequently, led to a possible soil nitrogen loss through leaching.