Study On Cold Resistance Of Common Plants In Alpine Meadow Of Qinghai-Tibet Plateau

Due to the impact of global climate change,plants in alpine meadows on the Qinghai Tibet Plateau are highly susceptible to extreme cooling during the growing season,which severely inhibits plant growth and reproduction.Therefore,a series of studies on the cold resistance of the common plants in the alpine meadow of the Qinghai Tibet Plateau and the related cold resistance are particularly important for the recovery and management of the alpine meadow of the Qinghai Tibet Plateau under the future global change.This study selected 20 common plants from the alpine meadow near the Nagqu Observation Station in Nagqu City,Tibet Autonomous Region.After using a frost box to simulate cooling,the relative conductivity was measured using the conductivity method and combined with a logistic model to calculate the cold resistance(LT₅₀);Afterwards,the K-value method andλ-value method is used to calculate the phylogenetic signals and analyze the phylogenetic relationship of cold resistance of alpine meadow plants in the Qinghai Tibet Plateau;And combined with six plant functional traits,including specific leaf area（SLA）,leaf dry matter content（LDMC）,plant height（Height）,leaf carbon content（LCC）,leaf nitrogen content（LNC）,and leaf phosphorus content（LPC）,the adaptation strategies of common plants in alpine meadows on the Qinghai Tibet Plateau to extreme cooling were analyzed.The results indicate that:（1）Out of 20 species,6 species had poor logistic model fitting results and were unable to calculate LT₅₀.Among the remaining 14 species,the species with the strongest cold resistance is Oxytropis proboscideas(LT₅₀=-20.84℃),while the species with the weakest cold resistance is Thalictrum alpinum(LT₅₀=2.42℃).Compared to the actual extreme cooling temperatures during the growth season from2011 to 2019,except for Oxytropis proboscideas and Potentilla fruticosa var.pumila,other species are susceptible to extreme cooling during the growth season;The highest coefficient of variation within 14 species for cold resistance is Lancea tibetica,with a coefficient of variation of 128.77%;The smallest is Potentilla fruticosa var.pumila,with a coefficient of variation of 3.81%;And there is a negative correlation between the intra species variation coefficient of cold resistance and its cold resistance,indicating that the stronger the cold resistance,the more stable the LT₅₀ of the species.The contribution of intra specific variation（6.65%）to the total variation of cold resistance is much smaller than that of inter specific variation（93.35%）,but there are still four species（Lancea tibetica:128.77%,Saussurea stoliczkai:125.68%,Elymus nutans:105.05%,and Thalictrum alpinum:99.07%）with intra specific variation coefficients greater than inter specific variation coefficients（98.49%）,In future research on the cold resistance of alpine meadow plants in the Qinghai Tibet Plateau,intra species variation cannot be simply ignored.（2）The cold resistance(LT₅₀)of common plants in alpine meadows on the Qinghai Tibet Plateau is significantly influenced by phylogenetic history,and the results of phylogenetic signals（K=1.003,p<0.05;λ=0.999 p<0.05）comprehensively indicates that there is a significant and strong phylogenetic signal for cold resistance,that is,the species with closer relationships on the phylogenetic tree of common plants in alpine meadows on the Qinghai Tibet Plateau have more similar cold resistance.（3）The cold resistance of common plants in alpine meadows on the Qinghai Tibet Plateau is negatively correlated with specific leaf area,and positively correlated with leaf dry matter content.The contribution rates of specific leaf area and leaf dry matter content to the explanation of cold resistance changes are higher（42.24%and33.38%）.Species with stronger cold resistance have slower photosynthetic and growth rates,but stronger adaptability to resource protection and extreme environments;Cold resistance is not significantly correlated with the content of carbon,nitrogen,phosphorus in plant leaves,and plant height,and these four traits have a low contribution rate to cold resistance changes.Based on the PCA ranking results,we divided 14 species into two groups.The species represented by Oxytropis proboscideas and Potentilla fruticosa var.pumila have extremely strong or strong cold resistance,with a lower specific leaf area;The content of dry matter in leaves is relatively high,and the height of some plants is relatively high.Species represented by Thalictrum alpinum have weak cold resistance,larger leaf area,and most species have lower leaf dry matter content and plant height.Based on the leaf economics spectrum,we believe that these species have formed two divergent ecological strategies when adapting to extreme cooling during the growing season,namely the"slow investment return"strategy represented by Oxytropis proboscideas and Potentilla fruticosa var.pumila,and the"fast investment return"strategy represented by Thalictrum alpinum.In summary,this study found that common plants in the alpine meadows of the Qinghai Tibet Plateau,such as Oxytropis proboscideas and Potentilla fruticosa var.pumila,have extremely strong cold resistance.Species with similar phylogenetic relationships to these two species may have similar characteristics,and this part of species needs to be focused on in the future;At the same time,in order to adapt to the frequent extreme cooling on the Qinghai Tibet Plateau,we believe that the plants in the alpine meadows on the Qinghai Tibet Plateau have formed two divergent ecological strategies.This study analyzed the cold resistance of common plants in alpine meadows on the Qinghai Tibet Plateau and their phylogenetic relationships,as well as the trade-off between cold resistance and other functional traits.It reveals the sensitivity of alpine meadow plants on the Qinghai Tibet Plateau to extreme cooling in the growing season and their growth and survival strategies,further explores the internal mechanism of plant physiological and ecological processes in the alpine meadow ecosystem,and provides a theoretical basis for exploring the internal mechanism of ecological niche differentiation and species coexistence in the future,and predicting the impact of global change on alpine meadow plants.