Effects Of Night Warming And Changing Precipitation On Plant Reproductive Phenology In Three Temperate Grasslands Of Northern China

Since the Industry Revolution,greenhouse gas concentration has been increasing rapidly due to intensified anthropogenic activities,which leads to climate warming with greater increases in night than day temperature.In addition to climate warming,changing precipitation has also been observed at global and regional scales.Plant phenology,including vegetative and reproductive phenology,is considered as a sensitive indicator of climate change.Previous studies have demonstrated that climate warming and changing precipitation could have profound impacts on vegetative and reproductive phenology,and may consequently result in variations in plant community stability and ecosystem functioning(e.g.,gross primary productivity).However,how climate warming and changing precipitation affect plant community structure and ecosystem functioning through altering plant reproductive phenology remains unclear.In addition,most previous studies were often conducted in one grassland type or experiment site,which faced the difficulty in extrapolating or upscaling the findings from local to regional and global scales.Here,using soil monolith(from desert,typical,and meadow steppes along a natural precipitation gradient)transplantation,the effects of night warming and changing precipitation on plant reproductive phenology and the relationship between plant reproductive phenology and community stability were examined in the three temperate steppes of Northern China.Over the two years,the flowering time of plants was advanced by 3.7 d under the night warming treatment in the typical steppe,but had no changes in the desert and meadow steppes.Decreased precipitation delayed the flowering time of plants by 4.6 d,3.5 d,and 2.0 d in the desert,typical and meadow steppes,respectively.Increased precipitation advanced the flowering time of the meadow steppe by 2.6 d.Across all species and the two years,the fruiting time of plants was advanced by 3.2 d under the night warming treatment in the typical steppe,but delayed by 1.4 d in the meadow steppe.Decreased precipitation delayed the fruiting time of desert and meadow steppes by 5.0 d and 2.3 d,respectively.The fruiting time of the meadow steppe was advanced by 1.9 d by increased precipitation,whereas the fruiting times of the desert and typical steppes did not change under the increased precipitation treatment.Reproductive duration was lengthened by 2.5 d under the night warming treatment in the desert steppe whereas there were no changes in the reproductive duration of plants under the night warming treatment in the typical and meadow steppes.Decreased precipitation shortened the reproductive duration of plants in the desert,typical,and meadow steppes by 3.9 d,4.5 d and 2.1 d,respectively.Increased precipitation did not affect the reproductive duration of plants in the desert and typical steppes,but lengthened that by 2.7 d in the meadow steppe.The reproductive overlap was lengthened by 1.8 d under the night warming treatment in the desert steppe,but had no change in the typical and meadow steppes over the two years.The reproductive overlap was shortened by 2.1 d under the decreased precipitation treatment in the meadow steppe.Increased precipitation stimulated the reproductive overlap by 6.1 d and 4.0 d in the typical and meadow steppes,respectively,but did not affect the reproductive overlap of the desert species.Positive dependences of the community stability on the reproductive overlap were found in the typical and meadow steppes,respectively.Community stability elevated with enhancing reproductive overlap in the typical and meadow steppes.However,no relationship between the community stability and reproductive overlap was found in the desert steppe.Changes in reproductive overlap may lead to variations in positive interactions between species,which could affect species co-existence,and consequently have impacts on community stability.Through reducing reproductive overlap,species may share the increased “risk” resulted from reduction of precipitation,suppressing positive interactions among species which could not benefit species co-existence,consequently,decreased precipitation declined the community stability.Increased precipitation enhanced the community stability by elevating the reproductive overlap and possibly stimulating positive interactions among species in typical and meadow steppes.The observations indicate that short-term increased precipitation could enhance resistance of temperate grassland to future climate change scenarios.The study clarified the effects of night warming and changing precipitation on plant reproductive phenology and the relationship between the community stability and reproductive overlap.The findings will improve our understanding of climate change impact on plant community stability of temperate grassland.