Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-26 Cooperative journals: 《广西植物》
Abstract： The 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 gain an understanding of the seasonal changes in fine root C∶N∶P ratios in different forest types of a karst ecosystem, we measured the C, N, and P contents and ratios of living and dead fine roots in shrubbery and arbor forest vegetation, as well as the influence of abiotic and biotic factors. The results were as follows: (1) That C, N, and P contents in the fine roots of arbor forest vegetation were higher than those of shrubbbery vegetation, thereby indicating that the fine roots of arbor forest trees may by characterized by a stronger absorption and storage of nutrients than those of shrubbbery vegetation. In addition, we established that the contents of C in living fine roots were significantly higher than those in dead fine roots (P < 0.05), whereas in contrast, N and P contents in living fine roots were lower than those in dead fine roots. (2) It was found that the contents of C in the living/dead fine roots of the two forest types were lower during the rainy season than during the dry season. Contrastingly, in shrubbery vegetation, whereas the N and P contents of living fine roots were higher during the rainy season than those in dry season, the opposite pattern was observed for the living fine roots of arbor forest vegetation. During the rainy season, the C∶N, C∶P, and N∶P ratios of living fine roots in shrubbery vegetation were lower than the values obtained during the dry season. Conversely, the C∶N and C∶P ratios of the living/dead fine roots of arbor forest vegetation were higher during the rainy season than in the dry season, whereas the values for the N∶P ratio were lower during the rainy season than during the dry season. The lower rainy season N∶P ratios tend to indicate that plants in shrubbery and arbor forest may be less P restricted during this season. (3) We also found that for both the living and dead fine roots of the two forest types, C contents were higher in plants growing on the upper slopes than in those growing on the middle and lower slopes, whereas the contents of N and P were higher in shrubs and forest trees growing on the lower slopes. Furthermore, the C∶N, C∶P, and N∶P ratios of living and dead fine roots were found to be relatively higher in shrubs growing on the upper slopes. In the case of arbor forest, the C∶N ratios of living and dead fine roots in trees growing on the lower slopes and the C∶P and N∶P ratios in trees growing on the upper slopes 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 weakly affected 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 N∶P ratio associated with differences in forest type, season, and slope elevation should be taken into consideration when vegetation restoration is promoted, which would contribute to accelerating the restoration of karst ecosystems.
Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-13 Cooperative journals: 《广西植物》
Abstract： In order to explore the effect of enzyme activities of plant root exudates on rhizosphere soil enzyme activities and nutrients in a karst ecosystem, the activities of β-1,4-glucosidase (βG), β-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and acidic phosphatase (ACP) of fine root exudates and rhizosphere soils in four vegetation restoration stages, which are shrub-grassland, shrubland, shrub-arbor forest and arbor forest, were measured. And, their relationships were also analyzed. The results showed that the four enzyme activities of rhizosphere soils and root exudates were significantly higher in the late stage of vegetation restoration than in the early stage of vegetation restoration. The enzyme activities C:P to N:P ratios of root exudates in arbor forest were significantly higher than those of other three stages, while the two parameters of rhizosphere soils were opposite. Correlation analysis showed that the enzyme activities of root exudates were positively correlated with the corresponding soil enzyme activity. Compared with the enzyme activities of root exudates, the correlation between soil enzyme activity and related nutrients had become significantly stronger. In addition, the activities of βG, NAG and LAP in rhizosphere soils and root exudates were positively correlated with organic carbon (SOC) and total nitrogen (TN) in rhizosphere soil, while the activity of ACP in rhizosphere soils and root exudates were positively correlated with available phosphorus (AP) in rhizosphere soil. The above results indicated that vegetation restoration had a positive effect on increasing activities of root exudates and soils. The enzymes of root exudates were the indispensable supplement for soils, and it played an important role in promoting carbon, nitrogen and phosphorus nutrient cycling. It will be that the regulation of root exudates and its enzyme activities may provide a new perspective for vegetation restoration in karst ecosystem.
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