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Global climate change has significantly changed precipitation patterns. Soil respiration (SR), as an important pathway through which CO

Studying the influence of precipitation patterns on plant community diversity, soil C:N:P ecological stoichiometric characteristics, and the relationships between key soil factors and plant community diversity is of great significance for the protection of plant community diversity in desert grasslands. This paper was studied in the desert steppe of the west of Loess Plateau using a three-year precipitation manipulation experiment (40% reduction in precipitation, 20% reduction in precipitation, natural precipitation, 20% increase in precipitation, and 40% increase in precipitation), explored the influence of changes in precipitation in dry and wet years on the diversity of plant community and soil C:N:P ecological stoichiometric characteristics. And we also explored the relationship between soil C:N:P ecological stoichiometric characteristics and the key soil factors and the diversity of plant community under changes in precipitation. The results showed that in a normal year and the drier year (2013 and 2015), Patrick richness and Shannon-Wiener diversity index were significantly low under the 20% reduction treatment compared with the control and 40% increase treatments, respectively. During the wetter year, Patrick richness and Shannon-Wiener diversity index were no different between any of the precipitation treatments. In the normal year and the drier year, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and the carbon-nitrogen ratio (C:N), carbon-phosphorus ratio (C:P), and nitrogen-phosphorus ratio (N:P) all decreased with an increase in precipitation (the decrease in the C:N ratio was statistically significant). During the wetter year, SOC, TN, C:P, and N:P increased with an increase in precipitation. During the normal year, precipitation treatments had no significant influence on soil water content, having a limited influence on the plant community. TN, N:P, SOC, C:N, and microbial biomass nitrogen (MBN) had a more prominent influence on plant community diversity. In the wetter year, precipitation was abundant leading to a rise in soil nutrients. Water was not the most important factor limiting to plant growth whereas soil water content, soil nutrients, and ecological stoichiometric characteristics jointly regulate plant community diversity. In the drier years, precipitation treatments had a significant impact on soil water content, whereby an increase in precipitation led to high losses of soil nutrients. Therefore, soil water content was the most important factor affecting plant community diversity during drier years. These observations indicate that under dry and wet years, plant community diversity and soil C:N:P ecological stoichiometric characteristics have variable responses to precipitation and soil C:N:P effect on plant community were also different. These results provide a theoretical basis for the protection and management of desert steppe systems under future projected changes in precipitation.

Under the background of global climate change, precipitation changes will have profound impacts on plant community dynamics. Through field experiment with precipitation manipulation in a desert steppe of western Loess Plateau, we examined the responses of species richness, density, coverage, height and aboveground biomass of different plant life-forms to precipitation changes. The results showed significant effects of precipitation on richness, density and coverage of annual herbs in the third year of manipulation experiment (2015), with lowest values in the decreased precipitation treatments. The height of annual herbs was more sensitive to precipitation changes, and was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of growth and aboveground biomass of annual herbs to decreased precipitation were larger than that to increased precipitation. Richness, density and coverage of perennial herbs in the decreased precipitation were significantly lower than those in the +40% precipitation in the 3rd year, but were insignificantly different from the control. The height of perennial herbs was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of richness, coverage and height of perennial herbs to decreased precipitation were larger than positive response to increased precipitation, while the positive response of aboveground biomass to the +40% precipitation treatment was stronger. The positive responses of richness, density, coverage and aboveground biomass of shrub to ±20% precipitation treatments were most obvious, which might be related to the relatively concentrated distribution of shrub in these treatments. The precipitation reduction inhibited the growth of herbaceous plants, particularly on the annual herbs, whereas increasing precipitation promoted perennial herbaceous growth and biomass accumulation to some extent. The annual herbaceous growth and biomass fluctuated with interannual variation of precipitation. Shrubs were relatively less affected by precipitation changes. Precipitation changes would have significant effects on plant community composition and function of desert steppe in western Loess Plateau.在全球气候变化背景下,降水变化对植物群落动态将产生深远的影响。以黄土高原西部荒漠草原为对象,通过野外降水控制试验,研究不同生活型植物丰富度、密度、盖度、高度和地上生物量对降水变化的响应。结果表明: 降水处理对一年生草本植物的丰富度、密度、盖度的影响在降水试验第3年(2015年)达到显著水平,以减水处理最低,植物高度对降水变化的响应更敏感,3年间,均以减水40%处理最低;植物生长和地上生物量对减水处理的负响应幅度大于对增水处理的响应。多年生草本植物的丰富度、密度和盖度在第3年以减水处理显著低于增水40%处理,但与对照无显著差异;植物高度3年间均以减水40%处理最低;丰富度、盖度、高度对减水处理的负响应幅度大于对增水处理的正响应,但地上生物量对增水40%处理的正响应较强。灌木的丰富度、密度、盖度和地上生物量对增减水20%处理的正响应最明显,可能与灌木在该处理分布相对集中有关。降水减少抑制了草本植物的生长,但对一年生草本植物的抑制作用更强,降水增加在一定程度上促进了多年生草本植物的生长和生物量积累。一年生草本植物的生长和生物量随降水年际变异波动明显,灌木受降水改变的影响相对较小,降水变化对黄土高原西部荒漠草原植物群落组成与功能将产生显著的影响。.

Major changes in precipitation regimes can be predicted, but the effects of such changes on terrestrial ecosystem functioning are largely unknown. To investigate the effects of changes in precipitation regimes on the plant community, soil properties, soil respiration and bacteria community composition in an arid grassland, we conducted a three-year precipitation manipulation experiment (i.e., ambient precipitation as a control, ±20% and ±40% of ambient precipitation) in a desert grassland in the western Loess Plateau, China. The species richness, density, mean height, aboveground biomass and litter biomass were reduced in the −40% precipitation treatment. Soil water content at a depth of 0–20 cm peaked in the +40% precipitation treatment. The influences of precipitation treatment on dissolved organic carbon (DOC), microbial biomass carbon (MBC) and soil nutrients were small. Soil respiration varied along the experimental precipitation gradient and peaked in the +40% precipitation treatment. NO3−-N was highest in the −40% precipitation treatment. Bacteroidetes had a higher relative abundance in the increased precipitation and control groups, while the abundance of Actinobacteria was higher in the decreased precipitation treatment in the wet year. The differences among precipitation treatments were not detected in the dry year. Thus, increased soil respiration along the precipitation gradient resulted from the positive responses of root growth, reflected in the plant community properties, and microbial respiration, reflected in the bacterial community composition. Different responses of ecosystem components to precipitation manipulation emphasize the necessity of studying the relationships between these components under climate change.

Cattle dung, firewood, and crop straw have being used as survival necessities by farmers and herdsmen for thousands of years in Tibet. Until recently such biotic energy source still constitutes more than 92 per cent of total rural energy consumption due to lack of petroleum, coal and new alternative energy sources. As a result, environmental degradation such as land desertification, soil erosion, grassland degradation and soil fertility reduction is increasingly aggravated, the area of desertified land has increased 1467.5 km2 from 1991 to 1997. Degraded area of grassland has reached 2.60 x 10(7) hm2, increased by 116.1% from 1987 to 1996. To prevent further deterioration of eco-environment in Tibet great efforts should be made to make full use of ample solar energy, wind energy and other biotic energy of the Qinghai-Tibet Plateau. The solar cooking stoves and solar hothouse, expand forest area and replace existing abiotic energy sources with firewood forest should be popularized. This is an urgent task to protect the eco-environment of Tibet today.