植物功能性状对土壤反馈的不同响应促进近缘物种共存(2)
As for closely relatedspecies, they are supposed to have similar functional traits and occupy similar niches. In theother words, they should have more intensively competition which will lead to competitiveexclusion. Because of convergent and pergent evolution, however, there are also somespecies to have similar functional traits yet have far phylogenetic distance. A study conductedin the eastern Tibetan plateau has shown that plant functional persity can be independent ofspecies persity [7].In this study, we chose the alpine meadow in the eastern Tibetan plateau as the focal place.All species we used in this experiment are co-occurred there. Tibetan Plateau, the youngestalso the highest plateau in the world, supported an extraordinary level of biopersity anddesignated as a global hotspot for biopersity. Alpine meadow comprises the representativevegetation on the Tibetan plateau, and is also very fragile and sensitive to climate change andpastoral land use changes [8]. In the past few decades, because of increasing of humanpopulation and the following development of stock farming, this region has experiencedunprecedented extra nutrient inputs and anthropogenic disturbances [9]. We aimed to detecthow will closely related species perform under such disturbances, and which of functionaltrait and phylogenetic position is more related to the responses of species to environmentalchange. To learn the responses of different species to such environmental changes is crucialfor scientists to predict plant community dynamics and species coexistence pattern.To study the responses of species to environment changes (lack of soil microbial, warming,nitrogen deposition), a greenhouse experiment with 11 alpine plant species planted under 3treatments and the interaction of these treatments was conducted in Nanjing AgriculturalUniversity, Jiangsu, China (Table 1).
We proposed a hypothesis: under changed environments,closely related species will have similar responses to environmental factors independently offunctional traits.1 Material and methods1．1 Species and study siteWe selected 11 species which co-occurred in the eastern Tibetan Plateau (Table 2). Thesespecies can be classified into two functional groups, graminoids and forbs. We combinedthree Poaceae species (Elymus nutans, Stipa capillata L., Poa crymophila) and oneCyperaceae species (Kobresia capillifolia) as graminoids; and five Compositae species(Saussurea hieracioides, Saussurea nigrescens, Ligularia virgaurea, Aster diplostephioides,Anaphalis lactea) and two Scrophulariaceae species (Pedicularis semitorta, Pediculariskansuensis) combined as forbs. All seeds used in the experiment were collected from Maqu, Gansu Province, China (35°58′N, 101°53′E) and stored in refrigerator for no more than two years. Our experimentwas conducted in a Greenhouse at Nanjing Agricultural University from December 31, 2016to April 15, 2017. We planned to measure biomass for each species in the experiment, whichis known to capture important features (morphological and physiological) that representecological strategies and show us how will plants are affected by environmental factors [10]。1．2 Methods1．2．1 Greenhouse experiment We have three treatments including soil sterilization (S),nitrogen addition(N) and warming (W) and their interaction for all species (Table 1). Thisprovides a total of 2 × 2 × 2 = 8 treatments (CK, S, N, W, SN, SW, NW, SNW) separatedinto 6 blocks and each treatment has 10-20 replicates. The replicates are not unified becausesome species had very low seeds germination rate (Table 2).We started germinating the seeds for 11 species under c. 50% daylight and 25℃ in anincubator since December 31, 2016. We immersed seeds of K. capillifolia in 3% NaOHsolution for 3 hours to reduce germination inhibition. This treatment increased thegermination rates from 2% - 4% to about 40%. We transplanted seedlings into greenhouse atJanuary 22, 2017. Every pot contains about 300g sands and 10g soil. The soil was collectedfrom the field in September, 2016. We added non-sterile soil to pots as CK treatment andsterilized soil as soil sterilization treatment (S). To minimize the differences of soil physicalproperties, the sand and soil were sterilized by γ-ray radiation. We irrigated the seedlings withtap water once a day and fertilized them with diluted Hoagland nutrient solution weekly. Forhigh-nitrogen (N) treatment, the seedlings were fertilized with doubled nitrogen content ofHoagland’s. Open top chambers (OTC) were used to elevated atmospheric temperature(Warming treatment, W).