The Spatial And Temporal Variation Of Plant Leaf And Fine Root Traits In The Yanhe River Catchment, Shaanxi, China

Abiotic and biotic processes may both affect plant community assembly. Ecologicalsuccess under varied environmental conditions and interactions between organisms mayrequire plants to share certain common functional traits, which allow for the possibilities ofthe classification of plant functional types (PFTS). In recent decades, the vegetationrestoration work on Loess Plateau had made great progress, however, there were still someproblems not solved. How to promote the survival rate and eco-efficiency of vegetation andrestore vegetation in the fragile habitats in sustainable way remained major problems to besolved.Our objectives were to analysis the variation of plant leaf and fine root traits alongspatial and temporal environmental gradients, explore the relative influence of environmentand phylogenic background on variations in plant functional traits, and to explore theadaptation strategies of different plant functional types and the changes in number of speciesin each functional type along succession in the Yanhe River catchment, Shaanxi, China, withemphasis on the plant functional types dynamics and variations during vegetation restorationon abandoned farmlands in this area. The results may be significant to understanding plantadaptation strategies variation and interactions influencing plant adaptation as they relate toenvironmental factors.on the spatial scale, this study measured six leaf traits and three fine root traits of107species belonging to35families in31sample plots in three vegetation zones (forest,forest-steppe, steppe) on the Loess Plateau. One-way ANOVA was used to find the variationamong three vegetation zones and plant families. We then used redundancy analysis (RDA) toanalyze the relationships between plant functional traits and meteorological factors. Principalcomponent analysis (PCA) was used to detect important relationships between plantfunctional traits and plant families. Finally, we used a General Line Model (GLM) to evaluatethe relative contribution of environmental factors and plant phylogenic background tovariations in plant functional traits.The results showed that:(1) there were no significant differences in leaf nitrogen concentration per mass (LN) and fine root nitrogen concentration per mass (RN), butsignificant differences were found in leaf thickness (LT), specific leaf area (SLA), leaf tissuedensity (LTD), leaf phosphorus concentration per mass (LP), the ratio of leaf nitrogenconcentration per mass and leaf phosphorus concentration per mass (LN:LP), specific rootlength (SRL), fine root tissue density (RTD）between the three vegetation zones. The values ofthese various parameters increased from the south to the north as climatic aridity intensified,by which plants could adapt to different environmental conditions. Plants in the forest zonehad higher competitive ability with more rapid leaf growth rates and with roots having ahigher resistance to stress and damage. Plants in the forest-steppe zone had higher root growthrates and had leaves with greater resistance to stress and damage;(2) Plants from differentplant families used different strategies to adapt to environment; different species performdifferently when provided with the same resources and environmental gradients. for example,leaf nitrogen concentration per mass and root nitrogen concentration per mass ofLeguminosae was far greater than that of other families, but the nutrient absorption efficiencyof species in the Leguminosae was not high.(3) Average annual precipitation and the meantemperature of the warmest month were two main factors which had significant effects onvariations in traits along environmental gradients in the area; for example,16.26%of theobserved variance in SLA can be explained by average annual precipitation and4.02%can beexplained by plant family. The explained variance of plant functional traits varied as thosesame functional traits varied and there were obvious environmental screening effects in theprocess of the formation of plant communities in the Yanhe River watershed. Six traits, LT,SLA, LTD, LP, SRL, and RTD were sensitive to climatic aridity at the species level; thespatial variation was caused primarily by environmental differences. In conclusion,environmental heterogeneity must be considered during vegetative restoration on the LoessPlateau.on the temporal scale, this study measured44species belonging to16families in35plant communities in5vegetation restoration stages in a forest-steppe zone in the YanheRiver catchment. All species were classified into3functional types by the7functional traitsusing Clustering analysis. One-way ANOVA was used to describe the variation among threePFTs. We then analyzed each type’s adaptation strategies, and made a comparison of thechanges in the functional types composition along vegetation restoration stages.The results showed that:(1)based on the seven functional traits, all plants can beclassified into three functional types. Seven plant attributes across all the39species showedlarge variations.(2) plants of PFTⅠhave bigger LTD, and lesser LT, LN and RN; plants ofPFTⅡ have bigger RTD, LN and RN, and lesser SLA and SRL; plants of PFT Ⅲ have bigger LT, SLA and SRL, lesser LTD and RTD.(3) according to C-S-R Triangle theories ofGrime, PFTⅠinvested more substance for defensive, and its growth rate is in an intermediatelevel, adopted “stress tolerance-ruderals” strategy; PFT Ⅱ adopted “stresstolerance-competitiveness” strategy, which can survive in resource-poor environment bymaintaining the nutrient balance in the body; while PFTⅢ devoted large quantities ofnutrients for growing, belonged to “competitiveness” strategy.(4) PFTⅠwas the dominantfunctional type throughout the vegetation restoration gradient and showed an increasing trendin the entire time series of vegetation restoration (from61%to80%), but the percentage ofPFTⅡ decreased from25%to15%along the vegetation restoration gradient, and PFTⅢgradually decreased from14%to5%. The dominant species in PFTⅠ also changed as timegoes on, SLA of dominant species in PFTⅠ decreased markedly, and LN and RN ofdominant species in early restoration period were bigger than in late stage. Totally, Althoughthe nutrient content of soil is rising overall along the vegetation restoration, but theenvironment had not been improved to that there was no interference with stress, in the fortyor fifty years early of vegetation restoration, PFTⅠwas in a dominant position, the adaptationstrategies of dominant species transformed from rapid growth to the increase of the toleranceto stress.These results can be helpful to the species selection and restoration planning.