RESUMO
Determining the differences in flower hydraulic traits and structural resource allocation among closely related species adapted to low mean annual precipitation (MAP) can provide insight into plant adaptation to arid environments. Here, we measured the maximum flower hydraulic conductance (Kmax-flower), water potential at induction 50% loss of Kmax-flower (P50-flower), flower pressure-volume parameters, dry mass of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) of six Caragana species growing in regions ranging from 110 to 1400 mm MAP. Compared with species from high-MAP environments, those from low-MAP environments presented lower Kmax-flower, more negative P50-flower, osmotic potential at full turgor (πo) and turgor loss points (πtlp), and a greater bulk modulus of elasticity (ε). Consequently, a negative correlation between Kmax-flower (hydraulic efficiency) and P50-flower (hydraulic safety) was observed across Caragana species. Furthermore, the dry masses of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) were greater in the species from the low-MAP environment than in those from the high-MAP environment. These findings suggest that greater flower hydraulic safety and drought tolerance combined with greater structural resource allocation promote drought adaptation in Caragana species to low-MAP environments.
RESUMO
Soil samples from four vegetation mini-patches (Artemisia scoparia, Glycyrrhiza uralensis, Sophora alopecuroides, Astragalus melilotoides) in a desert steppe in central Ningxia were collected. Soil physico-chemical properties including soil particle-size distribution, organic matter, pH, EC, total N, total K, total P of three depths were measured. The fractal dimension of particle size distribution characteristics of soils derived from four different vegetation mini-patches and their correlations with soil physico-chemical properties were examined. The results showed that patch vege-tation distribution affected the distribution of soil particle size, with the A. melilotoides mini-patch being the highest (D=2.51) and G. uralensis mini-patch being the lowest (D=2.46). There were significant positive correlation between fractal dimensions and the contents of clay and silt, and nega-tive correlation between fractal dimensions and sand content. Fractal dimensions were positively correlated with pH value and EC, negatively correlated with the contents of soil organic matter and total N, and had no correlation with the contents of soil total K and total P. The patchy vegetation distribution had potential trends of salinization and degradation.
Assuntos
Fractais , Solo , China , Argila , Nutrientes , Tamanho da PartículaRESUMO
Vegetation patch is one of the most basic characteristics of natural grazing grassland. To explore the effects of vegetation patch on soil microbial community, the changes of soil microbial biomass and community structure under four different vegetation patches in Ningxia desert steppe were quantified using phospholipid fatty acid (PLFA) analysis. The results showed that: 1) Soil microbial groups were abundant in vegetation patches, with the highest bacterial content, low fungal and actinomycete content, and the Gram-positive bacteria content being higher than that of Gram-negative bacteria in the patches of the four plant communities; 2) The total soil microbial biomass of Glycyrrhiza uralensis patch was significantly higher than that of Artemisia scoparia, Sophora alopecuroides, and Astragalus melilotoides patches; 3) Total PLFAs, Gram-positive bacteria, Gram-negative bacteria, fungi, anaerobic bacteria and fungi/bacteria were significantly positively correlated with soil organic C, and significantly negatively correlated with soil pH, indicating that soil organic C and pH were important factors affecting the growth and development of soil microorganisms in desert steppe.