有机物料还田对黑土胞外酶化学计量特征的影响

冷凉区有机物料（秸秆和有机肥）还田黑土胞外酶计量特征是否受年平均温度的影响，目前缺少定量研究和深入分析。根据气候条件，该研究在黑龙江省西部依据纬度特征选取了12个有机物料还田年限大于5 a的定位试验点，基于有机物料还田种类对土壤胞外酶计量学特征及驱动因子进行了区域性分析。结果表明土壤胞外酶C:N:P在1:0.97:0.61～1:1.13:0.71之间，即有机肥还田（M）和秸秆还田（S）处理下土壤微生物整体面临微生物碳和养分（氮）限制。研究发现随年均温度升高，M和S处理的碳获取酶活性降低，而氮获取酶活性增加。此外，年均温度升高还使得M处理磷获取酶活性降低，而S处理磷获取酶活性增加。总体而言，东北冷凉区有机物料还田黑土微生物能量和养分限制主要受年平均温度直接影响，间接受pH值，土壤C:P等影响。该研究为冷凉区黑土建立合理的碳氮磷施肥模式提供数据支撑，为土壤养分恢复提供理论依据。

Impact of organic material incorporation on the chemical stoichiometry characteristics of extracellular enzymes in black soil

Organic matter (straw (S) and manure (M)) has been widely applied to the black soil. This study aims to explore the effect of mean annual temperature on soil enzyme measurement in the cold region. According to the latitude in western Heilongjiang Province, China, 12 positioning test sites were selected with the application period of organic matter greater than five years. A mixed-effects model was established to analyze the relationship between mean annual temperature and soil enzyme activity that related to carbon (C), nitrogen (N), and phosphorus (P) acquisition. In addition, a systematic analysis was made to determine the relationship among the vector angle and vector length, soil nutrient, microbial biomass C:N ratio, and extracellular enzyme stoichiometry. The results show that the C acquisition enzyme activity of M and S treatment decreased, as the mean annual temperature increased, whereas, there was an increase in the N acquisition enzyme activity. There was a significant difference in the P acquisition enzyme activity of M and S treatment. The P acquisition enzyme activity decreased in the M treatment, as the mean annual temperature increased, whereas increased in the S treatment. Moreover, there was a negative correlation between the vector length and vector angle of soil extracellular enzymes. All soil samples were limited by microbial N, while some ones were limited by microbial C. In addition, the natural logarithmic ratio of NAG+LAP and BG+CBH was significantly negatively correlated in the M and S treatments. The combination of the Mantel test and the heat map showed that the soil C, N, and P acquisition enzyme activities were significantly correlated with the mean annual temperature. Redundancy analysis and hierarchical segmentation showed that the individual factors greater than 10% in the M treatment were the mean annual temperature, pH, and soil C:N ratio, accounting for 30.13%, 22.32%, and 12.27%, respectively. The extracellular enzyme N:P was positively correlated with the mean annual temperature and pH. The extracellular enzymes C: N and C:P were positively correlated with the soil C: N. The individual factors greater than 10% in the S treatment were pH, the application period of organic matter, C input, mean annual temperature, and soil C:P, accounting for 21.3%, 20.01%, 18.48%, 11.46%, and 11.31%, respectively. The extracellular enzyme C: N was positively correlated with pH, soil C:P, and mean annual temperature. The extracellular enzyme C:P was positively correlated with pH and soil C:P. The extracellular enzyme N:P was positively correlated with the C input, the application period of organic matter, and the mean annual temperature. In conclusion, the microbial N mainly limited the organic matter (straw and manure) application into black soil in the northeast cold region, according to the soil extracellular enzyme measurement and vector analysis. Both manure and straw application were driven by mean annual temperature, whereas the straw application was further influenced by carbon input and the application period. This finding can provide the data support and theoretical basis for the C, N, and P fertilization model for the black soil nutrient restoration in the cold region.