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.
Assuntos
Ecossistema , Microbiologia do Solo , Solo , Bactérias , China , Clima Desértico , Fungos , PradariaRESUMO
Changes in precipitation can influence soil water and nutrient availability, and thus affect plant nutrient conservation strategies. Better understanding of how nutrient conservation changes with variations in water availability is crucial for predicting the potential influence of global climate change on plant nutrient-use strategy. Here, green-leaf nitrogen (N) and phosphorus (P) concentrations, N- and P-resorption proficiency (the terminal N and P concentration in senescent leaves, NRP and PRP, respectively), and N- and P-resorption efficiency (the proportional N and P withdrawn from senescent leaves prior to abscission, NRE and PRE, respectively) of Leymus chinensis (Trin.) Tzvel., a typical perennial grass species in northern China, were examined along a water supply gradient to explore how plant nutrient conservation responds to water change. Increasing water supply at low levels (< 9000 mL/year) increased NRP, PRP and PRE, but decreased green-leaf N concentration. It did not significantly affect green-leaf P concentration or NRE. By contrast, all N and P conservation indicators were not significantly influenced at high water supply levels (> 9000 mL/year). These results indicated that changes in water availability at low levels could affect leaf-level nutrient characteristics, especially for the species in semiarid ecosystems. Therefore, global changes in precipitation may pose effects on plant nutrient economy, and thus on nutrient cycling in the plant-soil systems.
