Carbon Storage And Carbon Budget Of Poplar-Crop Intercropping Ecosystem In The Northern Jiangsu Plain Agricultural Areas

Poplar-crop intercropping is a main way developing poplar plantation in plain. In order to evaluate the carbon absorptive function of poplar- crop ecosystem, the carbon storage and carbon budget were systematically studied with a practical measurement method for sample plots among three poplar-crop intercropping patterns in the northern Jiangsu plain. The main results of the research are as follows:(1) The carbon storage in various parts of the agroforestry system was in the order of soil >crop > poplar > litter-fall for all the three poplar-crop intercropping patterns. The percentage of soil carbon storage to the whole system was 69⁸3%, while the percentage was 12²7% for crop, 4¹3% for poplar, and 0.15⁰.42% for litter-fall, respectively. The carbon storage in soil was 2.24⁴.76 times in the biomass carbon storage. The carbon storage in poplar-crop intercropping ecosystem in K pattern were 88.40 t·hm^-2 with wheat + corn, 86.16 t·hm^-2 with wheat + bean and 89.47 t·hm^-2 with wheat + rice, respectively, while those of P pattern accounted for 58.38 t·hm^-2, 56.89 t·hm^-2 and 58.53 t·hm^-2, as well as those of W pattern accounted for 61.70 t·hm^-2,58.25 t·hm^-2 and 58.87 t·hm^-2.(2) After a carbon balance formula was developed, the balance of carbon was studied in the three poplar-crop intercropping patterns. Results showed that NEP was above zero in 2006 and 2007, and poplar-crop intercropping ecosystem also showed absorptive and solidifying function of CO2. NEP in K pattern with poplar plantations of 5-year-old was 3.33 tC·hm^-2·a^-1 for intercroping of wheat + corn and 3.10 tC·hm^-2·a^-1 for intercroping of wheat + bean respectively, but amounting to 4.65 tC·hm^-2·a^-1at the 6-year-old for intercroping of wheat + rice. NEP in P pattern in the 5-year-old was 4.54 tC·hm^-2·a^-1 for intercroping of wheat + corn and 4.17 tC·hm^-2·a^-1 for intercroping of wheat + bean respectively, but amounting to 4.47 tC·hm^-2·a^-1at the 6-year-old for intercroping of wheat + rice. NEP in W pattern in the 5-year-old was 3.65 tC·hm^-2·a^-1for intercroping of wheat + corn, and 2.99 tC·hm^-2·a^-1 for intercroping of wheat + bean respectively, while in the 6-year-old NEP was 2.97 tC·hm^-2·a^-1 for for intercroping of wheat + rice. The results suggested carbon storage was influenced by the management patterns, intercrops and periods of intercropping.(3) The dynamics of carbon was studied in K, P and W patterns in 2007. The results showed that net carbon production by the photosynthesis inputing to the plant carbon pool was 14.93 t·hm^-2·a^-1,14.31 t·hm^-2·a^-1 and 13.97 t·hm^-2·a^-1. The carbon from the plant carbon pool to the soil carbon pool was 3.37 t·hm^-2·a^-1,3.19 t·hm^-2·a^-1 and 3.08 t·hm^-2·a^-1.for K, P and W patterns, respectively. The soil releasesed 1.88 t·hm^-2·a^-1,1.99 t·hm^-2·a^-1 and 1.63 t·hm^-2·a^-1 through heterotrophic respiration, while the carbon output by the way of crop harvest was 8.39 t·hm^-2·a^-1, 7.84 t·hm^-2·a^-1, 9.38 t·hm^-2·a^-1 for the three patterns, respectively.