氮磷添加下黄土丘陵区退耕草地土壤呼吸速率日变化特征

为探究黄土丘陵区退耕草地土壤呼吸及其组分日变化对氮磷添加的响应,采用裂区试验设计,主区施氮[0,50和100kg N/(hm2·a)]和副区施磷[0,40和80kgP2O5/(hm2·a)],于2019年5～8月每月测定各处理下土壤呼吸速率、异养呼吸速率及土壤温度和含水量日变化.结果表明,土壤呼吸速率及其组分日变化均呈...

Effects of nitrogen and phosphorus addition on diurnal variations of soil respiration rate in the grassland and farm withdrawing cultivation on Loess Hilly-gully Region

In order to explore the response characteristics of soil respiration (R_s) and its components (heterotrophic respiration, R_h; and autotrophic respiration, R_a) to N and P additions in the grassland and farm withdrawing cultivation, a field split-plot experiment was performed including: [main-plots with 0, 50, and 100kg N/(hm²·a)]; and [subplots: with 0, 40 and 80kg P₂O₅/(hm²·a)]. Such treatments were made every month from May to August in 2019 and for each treatment, these treatments were made: diurnal variations of R_s and R_hand R_a, soil temperature (T_s) and soil water content. Results showed that the diurnal variations of R_s and its two components (i.e. R_h and R_a) showed single-peak curves across all N and P addition treatments, and all reached the maximum values between 12:00~14:00. Compared with no fertilization treatment (CK), R_s, R_h and R_a increased significantly under N addition by 7.31%~13.13%, 1.12%~12.43% and 7.64%~46.26%, respectively, and increased significantly under P addition by 16.84%~18.42%, 11.48%~14.22% and 17.15%~29.59% respectively. N and P combined addition increased R_s, R_h and R_a by 24.17%~27.30%, 21.94%~32.43% and 34.05%~41.26%, respectively. The daytime proportions of whole day carbon emissions from R_s, R_h and R_a under different N and P addition treatments accounted for 52.68%~61.37%, 50.92%~58.70% and 51.39%~76.35%, respectively. The cumulative CO₂emission was the highest at 2012g/m² under a treatment of 50kg N/(hm²·a) combined with 80kg P₂O₅/(hm²·a), and the lowest appeared under no fertilization treatment at 1531g/m². R_s and its two components (R_h and R_a) were significantly positively correlated with the soil temperature (T_s), and their temperature sensitivity (Q₁₀) ranged from 1.19 to 1.86, 1.08 to 1.81, and 1.11 to 3.67, respectively. N and P decreased the Q₁₀ values of R_h, but increased the Q₁₀ values of R_a. In summary, N and P additions increase the rates of R_s and its two components, but decreased the temperature sensitivity of R_h, and the effect of N and P addition on soil respiration rate were related to N and P addition amounts and their ratios.