保护性耕作下小麦田土壤呼吸及碳平衡研究

Soil Respiration and Carbon Balance in Wheat Field Under Conservation Tillage

为了研究小麦农田生态系统土壤碳排放与作物碳蓄积特征,采用LI6400-09在重庆北碚西南大学教学试验农场对平作(T)、垄作(R)、平作+覆盖(TS)、垄作+覆盖(RS)这4种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中小麦生长季节的土壤呼吸及植株生长动态进行了观测.利用根系生物量外推法(root biomass regression,RBR)和根排除法(root exclusion,RE)这2种方法比较分析根系呼吸对土壤总呼吸的贡献,并估算小麦农田碳收支状况.结果表明,土壤呼吸介于0.62~2.91μmol·(m2·s)-1,平均值为1.71μmol·(m2·s)-1.T、R、TS、RS各处理日均土壤呼吸速率分别为1.29、1.59、1.99、1.96μmol·(m2·s)-1,表现为T<R<RS<TS.小麦拔节期以前垄作对土壤呼吸的影响不显著,拔节期开始垄作处理提高了土壤呼吸速率.秸秆覆盖对土壤呼吸的影响最大,始终保持较高的土壤呼吸速率.在小麦生长的169 d里,T、R、TS、RS这4个处理的土壤呼吸总量为2266.82、2799.52、3483.73、3443.89 kg·hm-2,地上部分生物量累计为51800.84、59 563.20、66 015.37、71 331.63 kg·hm-2.与对照相比,R、TS、RS这3个处理分别增产14.99%、27.44%和37.70%.RBR方法测得根系呼吸贡献为47.05%,根系呼吸速率在0.201~1.226μmol·(m2·s)-1之间,RE法下则为53.97%.在小麦生长初期农田表现为弱的碳源,拔节期开始随着小麦植株的生长,农田碳汇能力越来越强,在灌浆期达到最大,随后进入成熟期,农田又呈现出碳源特征.小麦生长季T、R、TS、RS各处理总的碳收支分别为5924.512、6743.807、8350.741、8876.115kg·hm-2,因此,以垄作和秸秆覆盖为主的保护性耕作能显著提高农田生态系统的碳汇能力,增汇幅度达13.83%~49.82%.

In order to study the characteristics of carbon sources and sinks in the winter wheat farmland ecosystem in southwest hilly region of China,the LI6400-09 respiratory chamber was adopted in the experiment conducted in the experimental field in Southwest University in Chongqing. The soil respiration and plant growth dynamics were analyzed during the growth period of wheat in the triple intercropping system of wheat-maize-soybean. Four treatments including T( traditional tillage),R( ridge tillage),TS( traditional tillage + straw mulching),and RS( ridge tillage + straw mulching) were designed. Root biomass regression( RR) and root exclusion( RE) were used to compare the contribution of root respiration to total soil respiration. The results showed that the average soil respiration rate was 1. 71 μmol·( m2·s)-1with a variation of 0. 62-2. 91 μmol·( m2·s)-1. Significant differences in soil respiration rate were detected among different treatments. The average soil respiration rate of T,R,TS and RS were 1. 29,1. 59,1. 99 and 1. 96μmol·( m2·s)-1,respectively. R treatment did not increase the soil respiration rate significantly until the jointing stage. Straw mulching treatment significantly increased soil respiration,with a steadily high rate during the whole growth period. During the 169days of growth,the total soil respiration was 2 266. 82,2 799. 52,3 483. 73 and 3 443. 89 kg·hm-2while the cumulative aboveground biomasses were 51 800. 84,59 563. 20,66 015. 37 and 7 1331. 63 kg·hm-2. Compared with the control,the yield of R,TS and RS increased by 14. 99%,27. 44% and 37. 70%,respectively. The contribution of root respiration to total soil respiration was 47. 05%by RBR,while it was 53. 97% by RE. In the early growth period,the carbon source was weak. The capacity of carbon sink started to increase at the jointing stage and reached the maximum during the filling stage. The carbon budget of wheat field was 5 924. 512,6 743. 807,8 350. 741,8 876. 115 kg·hm-2,respectively. The results indicated that ridge tillage and straw mulching conservation tillage significantly improved the carbon sink in the wheat farmland ecosystem.