Unveiling hidden interactions: Microorganisms, enzymes, and mangroves at different stages of succession in the Shankou Mangrove Nature Reserve, China

Understanding the interactions between microorganisms, soil extracellular enzymes, and mangroves is crucial for conserving and restoring mangrove ecosystems. However, the unique environments associated with mangroves have resulted in a lack of pertinent data regarding the interactions between these components. Root, stem, leaf, and soil samples were collected at three distinct stages of mangrove succession. Stoichiometry was employed to analyze the carbon, nitrogen, and phosphorus contents of these samples and to quantify extracellular enzyme activities, microbial biomass, and various physicochemical factors in the soil. The results showed that the trends of C, N, and P in the mangrove plants were consistent. Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) were the highest in the Kandelia obovate community. Catalase (CAT) and β-D-G showed the highest content in K. obovate and Bruguiera gymnorrhiza, whereas cellulase showed the opposite trend. Urease was least abundant in the K. obovate community, whereas neutral protease (NPR) and acid phosphatase (ACP) were most abundant. The overall soil environment in mangroves exhibited a state of N limitation, with varying degrees of limitation observed across different succession stages. The demand for P became more intense in the later stages of succession, particularly in the K. obovate and B. gymnorrhiza communities. In conjunction with correlation analysis, it indicated that the input of mangrove plant litter had a significant regulatory influence on the C, N, and P contents in the soil. There was a significant positive correlation between MBC, MBN, and MBP, indicating synergistic effects of C, N, and P on soil microorganisms. Therefore, evaluating the nutrient ratios and sufficiency of mangroves allowed us to comprehensively understand the present environmental conditions. This study aims to develop sustainable management strategies for the conservation and restoration of mangroves.

The effect of soil depth on temperature sensitivity of extracellular enzyme activity decreased with elevation: Evidence from mountain grassland belts

Temperature sensitivity of soil extracellular enzyme activity (EEA), indicated by the temperature coefficient Q₁₀, is used to predict the effect of temperature on soil carbon (C), nitrogen (N), and phosphorus (P) cycling. At present, we lack understanding of elevation and soil depth variations in Q₁₀ of EEA. Here, we measured the Q₁₀ of three enzymes participating in C- (β-1,4-glucosidase, BG), N- (leucine aminopeptidase, LAP), and P- (acid phosphatase, AP) cycling along a vertical grassland belt of China. Soils from five depths (0-10, 10-20, 20-40, 40-60, and 60-100 cm) were sampled from three elevations (low, <1000 m; middle, 1000-2000 m; high, 2000-3000 m) and incubated at four temperatures (5, 15, 25, 35 °C). The average Q₁₀ of soil EEA ranged from 0.97 to 1.11 and the Q₁₀ of LAP was higher than that of BG and AP. Generally, the Q₁₀ of BG and LAP both increased from low to middle elevation and then decreased, while the Q₁₀ of AP was stable. Moreover, the effect of soil depth on Q₁₀ of EEA was weakened from low elevation to high elevation, and the factors driving Q₁₀ of soil EEA changed with elevation. This study improved the understanding of the vertical pattern of Q₁₀ of soil EEA in water-limited ecosystems, and highlighted that elevation could regulate the effect of soil depth on Q₁₀ of EEA.