Shift Of Seed Mass Spectrum And Seed Dispersal Spectrum Along Longitude Gradient In Inner Mongolia Plateau

Seed mass and dispersal syndrome, which reflect the breeding strategy of vegetation and adaptation to environment, are one of the centers in the process of plant evolution. Much more researches had been conducted about the variation of seed mass along the latitude and altitude gradient, while there were few studies about the shifts of seed mass and dispersal types along longitude in community context. We chose 20 big samples along longitude gradient of Inner Mongolia plateau, which differ hugly in precipitation, temperature and aridness.74 families,294 genera and 624 species were found in this region. Seed traits and environment factors (such as precipitation, temperature, and dryness) were correlated, providing scientific basis for studies on seed traits variation along the geographical gradient of across species. The main results are as follow:(1) Significant relationships between seed mass and longitude, precipitation, temperature were found, however, there existed opposite changed patterns. For desert and grassland ecosystems, negative correlations were found between seed mass and longitude, precipitation and dryness, and for forest ecosystems the correlations were positive. In the Inner Mongolia plateau, from desert to desert grassland to typical grassland, seed size shrunk gradually, while seed size increased in the forest, indicating that vegetation has different style of tactical reproduce.(2) Seed mass of five dominant families in the study region were compared along longitude and found that the correlation patterns in Leguminosae and Compositae are similar to that across species, while, the correlation was weak for other 3 families. It shows that in the Inner Mongolia plateau, the seed mass of Leguminosae and Compositae are sensitive for the ambient stress, while the seed mass in others families are relatively conservative.(3) Fruit type spectra (flesh fruit VS dry fruit) were found to be significantly associated with altitude, precipitation and dryness. Significantly positive correlation occurred between the proportions of species with fleshy fruits and precipitation, while the correlation with altitude was the contrary. In addition, there were weak relationships between proportions of fleshy fruited species and longitude, latitude as well as temperature.(4) Dispersal pattern was found to be significantly associated with precipitation and dryness. Significant positive correlation occurred between animal dispersal and precipitation, while there was a significant negatively correlation between wind dispersal and precipitation. In addition, the proportion of species with unassisted dispersal increased with rising altitude and descended with increasing temperature. It showed propagation modes were affected by environmental factors.(5) The proportion of species with wind dispersal propagules was the highest in each vegetation types, and decreased with the gradient of desert, desert steppe, typical steppe and forest. In desert and forest, the proportion of species with animal dispersal seeds was higher than in grassland. And in typical grassland, the proportion of animal dispersal was lowest. It showed that in different vegetation, plant colonize strategy was different because of the heterogeneity of abiotic factors (precipitation, temperature, wind, soil composition, etc.) and biological factors (species richness and community canopy density, the number of animal communicator, etc.).(6) Seed mass was closely related with other plant traits such as growth forms and dispersal modes. In comparison with shrubs, seed mass of trees and vines are largest and that of herbs are smallest in the whole growth forms. Seed mass of annual and biennial plants are found to be smaller than that of perennial plants. The sizes of seed with animal dispersal or flesh fruits were significantly greater than those with wind dispersal or dry fruits. In addition, there was a weak negative correlation between seed mass and specific leaf area, the pattern was different in different families yetIn summary, seed mass in community context displayed different response to limiting factors and environmental stress. It was important to explore the change patterns of seed mass and dispersal spectrum along geographical gradient as well as the relevance with other traits, which was helpful in understanding plant evolution.