宁夏燃煤电厂周边土壤、植物和微生物生态化学计量特征及其影响因素

大气酸沉降增加对陆地生态系统的影响已得到了广泛证实，但有关酸沉降累积下工业排放源周边植被-土壤系统元素平衡特征及其影响机制的研究较少。燃煤电厂是主要的工业酸排放源之一。因此，以宁东能源化工基地3个燃煤电厂为观测点，研究了电厂周边土壤-植物叶片-微生物生态化学计量特征，分析了叶片和微生物生物量生态化学计量特征与降水降尘S、N沉降量及土壤性质的关系。结果表明：土壤和微生物生物量C ： N ： P生态化学计量特征变异系数较大，叶片各指标的变异系数较小。与受人类活动影响较少的其他同类型区相比，研究区具有较高的土壤有机C水平和N、P供给，且P相对于N丰富。植物可能主要受N限制，而微生物主要受P限制；土壤及微生物元素间均存在极显著的线性关系（P<0.001）。叶片全C与全N、全P均无显著的关系（P>0.05）。叶片全N、全P和N ： P具有高的内稳性。微生物生物量N ： P内稳性较强，但生物量N和P内稳性较弱，对土壤环境的变化反应敏感；SO₄^2-沉降有助于促进叶片对P的摄取和微生物对C、N、P的固持。少量NO₃^-沉降有利于叶片N摄取，但持续增加的NO₃^-沉降可能会使土壤P受限性增强，进而抑制叶片P摄取和微生物生物量积累。土壤酶活性、Ca²⁺和含水量亦显著影响着植物和微生物元素生态化学计量关系（P<0.05）。因此，今后还需结合多个电厂的土壤性质和植被状况，从较长时间尺度上深入揭示酸沉降增加对工业排放源周边植被-土壤系统元素平衡特征的影响机制。

C: N: P ecological stoichiometry in soils, plants, microbes, and their influencing factors around the coal-fired power plants in Ningxia

Recently, with the practice of emission control measure on air pollutant and the transformation of economic structure, atmospheric acid (mainly S and N) deposition shows a downward trend in most areas of China, but keeps increasing in the northwest region. The effects of increasing atmospheric acid deposition on terrestrial ecosystems have been widely confirmed. However, there are few studies on the elemental ecological stoichiometry and its influencing mechanisms in the plant-soil systems around industrial emission sources under accumulating acid deposition. Coal-fired power plant is one of the main industrial sources of acid emission. In this paper, C:N:P ecological stoichiometry in soils, leaves of common plants, and microbes were thus measured around three coal-fired power plants in Ningdong Energy and Chemical Industry Base. The relationships were analyzed between leaf C:N:P ecological stoichiometry and environmental factors (monthly mean deposition of S and N in precipitation and dustfall and soil properties) and also between microbial biomass C:N:P ecological stoichiometry and environmental factors. The results showed that, the variation coefficients were generally higher in soil and microbial biomass C:N:P ecological stoichiometry than those in leaves. The levels of soil organic C, total N, and total P in the study area were higher than those in the same type areas, and the supply of P was more abundant than that of N. Plants might be mainly limited by N, whereas microbes might be P-limited; significantly linear relationships were detected among the three elements in both soils and microbes (P<0.001), whereas insignificant relationships were observe between C and N and also between C and P in leaves (P>0.05). The homeostasis of total N, total P, and N:P were high in leaves. The homeostasis of biomass N:P was higher while those of N and P were lower in microbes, resulting in high sensitivities of microbes to environmental changes in soils; SO₄^2- deposition simulated leaf P uptake and microbial C, N, and P immobilization. Low amount of NO₃^- deposition was beneficial for leaf N absorption, whereas continually increased NO₃^- deposition might intensify P limitation and thus inhibited leaf P uptake and microbial biomass accumulation. Soil enzymatic activity, Ca²⁺, and water content also significantly regulated the C:N:P ecological stoichiometry in leaves and microbes (P<0.05). Therefore, it is necessary to deeply reveal the influencing mechanisms in plant-soil systems around industrial emission sources under accumulating acid deposition with the comprehensive consideration of the soil properties and plant conditions in more power plants on a longer time scale.