喀斯特林地细根碳氮磷生态化学计量特征的季节变化及其影响因子

he ecological stoichiometry of fine root carbon (C), nitrogen (N), and phosphorus (P)is considered to reflect the strategies whereby plants adapt to the soil environment In order to gainan understanding of the seasonal changes in fine root CNP ratios in different forest types of akarst ecosystem, we measured the C, N, and P contents and ratios of living and dead fine roots inshrubbery and arbor forest vegetation, as well as the influence of abiotic and biotic factors. Theresults were as follows: (1) That C, N, and P contents in the fine roots of arbor forest vegetationwere higher than those of shrubbbery vegetation, thereby indicating that the fine roots of arborforest trees may by characterized by a stronger absorption and storage of nutrients than those ofshrubbbery vegetation. In addition, we established that the contents of C in living fine roots weresignificantly higher than those in dead fine roots (P < 0.05), whereas in contrast, N and P contentsin living fine roots were lower than those in dead fine roots. (2) It was found that the contents of Cin the living/dead fine roots of the two forest types were lower during the rainy season than duringthe dry season. Contrastingly, in shrubbery vegetation, whereas the N and P contents of living fineroots were higher during the rainy season than those in dry season, the opposite pattern wasobserved for the living fine roots of arbor forest vegetation. During the rainy season, the CN,CP, and NP ratios of living fine roots in shrubbery vegetation were lower than the valuesobtained during the dry season. Conversely, the CN and CP ratios of the living/dead fineroots of arbor forest vegetation were higher during the rainy season than in the dry season,whereas the values for the NP ratio were lower during the rainy season than during the dryseason. The lower rainy season NP ratios tend to indicate that plants in shrubbery and arborforest may be less P restricted during this season. (3) We also found that for both the living anddead fine roots of the two forest types, C contents were higher in plants growing on the upperslopes than in those growing on the middle and lower slopes, whereas the contents of N and Pwere higher in shrubs and forest trees growing on the lower slopes. Furthermore, the CN, CP,and NP ratios of living and dead fine roots were found to be relatively higher in shrubs growingon the upper slopes. In the case of arbor forest, the CN ratios of living and dead fine roots intrees growing on the lower slopes and the CP and NP ratios in trees growing on the upperslopes were higher than those of trees growing at other elevations, indicating that plants under these two forest types are strongly influenced by P limitation in the upper slopes, but only weaklyaffected on the middle and lower slopes. (4) Redundancy analysis revealed that forest type,available phosphorus, and season were the main factors influencing the contents and ratios of C, N,and P nutrients in fine roots, and could explain 18.8%, 6.6%, and 6.5% of the observed variation,respectively. These findings indicate that the effects of changes in the NP ratio associated withdifferences in forest type, season, and slope elevation should be taken into consideration whenvegetation restoration is promoted, which would contribute to accelerating the restoration of karstecosystems.