The Study On The Flowering Phenology Of Alpine Meadow Communities In The East Qinghai-Tibet Plateau

Phenology studies the seasonal timing of life cycle events, it is the fundamental of ecology, and affects nearly all aspects of ecology and evolution, an exhaustive research of phenolgy is crucial to the understanding of plant community assembly and its functions in variable environments. The Qinghai-Tibet grassland ecosystem is the integrate part of terrestrial ecosystems in China, due to unique ecogeography of the ecosystems, study of phenology of Qinghai-Tibetan grassland can be use to infer the phonological trends of other terrestrial ecosystem in global changes. Moreover, studying on the grassland phenology in the Qinghai-Tibetan plateau can be use to address many fundamental topics, e.g species coexist and community assembly, as well as exploring the relationship between vegetation process and ecosystem functioning in rapidly changing environment. We carried out during 2006 and 2007 two years intensively comparative experiment in the field grassland of the Research Station for Alpine Meadow and Wetland Ecosystems of Lanzhou university in East Qinghai-Tibetan Plateau, namely Walaka site. By monitoring the phenology and species abundance of 53,28 and 18 comonpent species in enclosed (Ck), nomadic grazed communities (Gr) and fertilized community(Fr), respectively, we gained the following results:1.The environmental cues seasonally distribute in the alpine habitats, which influence the distributions of community flowering phenology.The daily average temperature, date and precipitations are the most important climate factors in determining to plant phonology, with cumulative proportion is 97.11% under the principal component analysis (PCA). The precipitations concentrated from the end of May to early August, the daily maximum temperatures occurred in the mid July, the days of annual daily minimum temperatures above 0℃were 100d during 2006 and 2007.With the increases in canopy covers and heights from mid to end of growing periods, photosynthetic active radiation (PAR)decreased dramatically from top to bottom, in Fr canopy PAR reduced more significantly under 60cm than Ck canopy, in Gr canopy PAR reduced less significantly under 30cm than Ck canopy, the PAR distributions significantly varied across canopies.2. The distributions of the peak flowering days are aggregated in the alpine meadow communities. The tests for 53 species in Ck,28 species in Gr and 18 species in Fr support that distributions of the peak flowering days(PFD) in communities are aggregated, PFDs within families are randomly distributed in Ck and Gr communities, whereas graminoids are aggregated, the other families are randomly distributed in Fr community. In the light of flowering species seasonal distribution rates, the most species bloom at the mid of growing season in Ck, Gr and Fr habitats.3. Species adapt the different flowering strategies. In view of annual variances of species flowering phases, the first flowering days (FFD) and last flowering days(LFD) of the early flowering species such as Gentiana spathulifolia, Leontopodium souliei and Scirpus distigmaticus, inter-annually varied significantly, where as FFDs and LFDs of the mid and late flowering species inter-annually changed insignificantly, only their flowering duration days(FDD) and flowering synchronies shifted inter-annually.4.In Ck community, the average FDDs the 53 observed species are 8.1±3.22d, both FDDs and flowering synchronies are negatively correlated with FFDs. Generally, the early flowering species manifest short FDDs and high flowering synchronies, the late flowering species do long FDDs and low flowering synchronies.5. The species trait influences the flowering phenology across growth forms. In the alpine meadows, the peak flowering phases across growth forms are separated. The most cushions bloom in early spring with short FDDs and low synchrony, usually the PFDs are randomly distributed, flowering phases inter-annually vary significantly, the FDDs are positively correlated with the FFDs, the synchronies are negatively correlated with FFDs. Sedges bloom in early growing periods, among them the early blooming species have short FDDs and high synchronies, flowering phases inter-annually vary significantly; the late blooming species have long FDDs and low synchronies, the variances of flowering phases are inter-annually stable; the FDDs are posivtively correlated with FFDs, the synchronies are negatively correlated with the FFDs. Creepers bloom in mid growing periods, the FDDs are negatively correlated with the FFDs, the synchronies are negatively correlated with the FFDs. Rosettes bloom from mid to end of growing periods, the FDDs are negatively correlated with FFDs. Graminoids bloom in mid growing periods, FDDs are negatively correlated with FFDs, the synchronies are negatively correlated with FFDs. Clusters bloom from mid to late growing periods, FDDs are negatively correlated with FFDs.6. The flowering phases differ among plants with different pollination modes. The FFDs of anemophilouos commence significantly earlier than entomophilouos, FDDs of anemophilouos continue significantly shorter than entomophilouos. The most anemophilouos species bloom in early growing periods, the most entomophilouos species bloom in mid growing periods. In the early growing periods the species with the white or yellow corollas bloom, in mid growing seasons besides species white and yellow corollas, the species with blue and purple corolla flower. The corolla color diversity and evenness in mid growing seasons are higher than those of both early and late growing seasons in alpine meadows.7. The community flowering times are correlated to biomass and height. PCA for Ck community 38 species biomass in flowering phase show that biomass, stem biomass, leaf biomass and height are the main components representing flowering time, their cumulative proportion is 83.03%.The community flowering days are positively correlated to biomass, and height. In the point of flowering time and biomass relationships across growth forms, creepers are positively correlated to biomass, negatively correlated to both flower biomass and height; rosettes are negatively correlated to height; clusters are positively correlated to flower biomass and height; sedges are positively correlated to height, and biomass, graminoids are positively correlated to height, and stem biomass. Within growing seasons, community level leaf biomass allocation rates are negatively correlated with FFDs, stem biomass allocation rates are positively correlated with FFDs, flower biomass allocation rates are high at early and late growing periods, which are low at mid growing season.8. Growth forms showed different responses to fertilization effects. In the fertilized community, the FFDs, PFDs and LFDs of sedges, rosettes and clusters are slightly accelerated or delayed, and the FDDs are truncated or prolonged in a small scale, whereas PFDs and LFDs of graminoids are significantly postponed, but their FDDs have no significant shifts.9. According to the flowering distributions of 28 species in Gr plots, under nomadic grazing the FFDs of cushions, sedges and creepers significantly accelerated, LFDs significantly retarded, FDDs significantly prolonged, whereas the flowering phases of clusters and graminoids are stable.In summary, under the influences of phylogeny, stress and biological interactions, the PFDs of alpine meadows are aggregated in growing seasons. The phonological complementarities promote niche differentiation in commuty, traits are the fundamentals of niche seperations.