华北平原小麦-玉米农田生态系统服务评价

本研究于2006 年和2007 年在中国科学院栾城农业生态系统试验站田间试验基础上, 评价了华北平原小麦-玉米农田的初级产品生产、气体调节、土壤有机质累积、水调节和氮素转化等5 项生态系统服务。研究表明, 华北平原小麦-玉米农田初级产品量包括籽粒产量5.04~5.71 t·hm^-2·a^-1(小麦)和6.69~8.24t·hm^-2·a^-1(玉米), 秸秆量8.58~9.72 t·hm^-2·a^-1(小麦)和6.97~8.58 t·hm^-2·a^-1 (玉米); 农田气体调节包括释放O₂ 24.99~28.64 t·hm^-2·a^-1, 固定CO₂ 34.23~39.22 t·hm^-2·a^-1, 排放N₂O 0.72~1.13 kg·hm^-2·a^-1, 吸收CH₄ 3.39~5.70 kg·hm^-2·a^-1; 农田耕层土壤有机质累积量为1.13~2.39 t·hm^-2·a^-1; 水资源消耗量为2 890~3 830 m³·hm^-2·a^-1; 农田土壤氮素几乎都处于亏缺状态, 变化范围为-107.73~5.33 kg(N)·hm^-2·a^-1, 不施氮肥农田亏缺较多。综合评价发现, 小麦-玉米农田提供生态服务的经济价值为5.48~6.25 万元·hm^-2·a^-1, 是粮食生产价值的3 倍左右。氮肥施用对农田生态系统服务及其产生福利的影响较为复杂, 这主要是由于施加氮肥明显增加了氮素转化功能导致的经济损失, 而同时可能会增加初级产品生产、气体调节中作物固定CO₂ 和释放O₂ 功能的经济价值。尽管目前有关生态系统服务评价研究主要关注生态系统产生的正效应, 但仍有必要对农田产生的负效应做出评价, 以便客观看待农田生态系统价值, 正确认识农田生态系统对人类福利的影响。

Ecosystem services of wheat-maize cropland systems in the North China Plain

Field investigations were conducted at Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in Hebei Province for the period from 2006 to 2007. The field data were then used to evaluate ecosystem services of wheat-maize croplands in the North China Plain. Ecosystem services analyzed in the study included primary products, gas regulation, soil organic matter (SOM) accumulation, water regulation and nitrogen transformation. The results showed that primary products from croplands accounted for 5.04~5.71 t·hm^-2·a^-1 of wheat grain, 6.69~8.24 t·hm^-2·a^-1 of maize grain, 8.58~9.72 t·hm^-2·a^-1 of wheat straw and 6.97~8.58 t·hm^-2·a^-1 of maize straw. As for cropland gas regulation, O₂ and N₂O emissions were 24.99~28.64 t·hm^-2·a^-1 and 0.72~1.13 kg·hm^-2·a^-1, whereas CO₂ and CH₄ assimilations were 34.23~39.22 t·hm^-2·a^-1 and 3.39~5.70 kg·hm^-2·a^-1, respectively. While cropland SOM accumulation was calculated at 1.13~2.39 t·hm^-2·a^-1, that of water consumption was 2 890~3 830 m³·hm^-2·a^-1. Soil nitrogen content dropped considerably at the rate of -107.73~5.33 kg(N)·hm^-2·a^-1 after one crop rotation. Total economic value of cropland ecosystem services was estimated at 5.48×104~6.25×104 Yuan·hm^-2·a^-1, which was three times the value of food production. Based on the results, effects of nitrogen fertilizer on the welfare of cropland ecosystem services was complicated. Nitrogen application led to economic loss due to increasing nitrogen transformation, simultaneously, increased economic value of primary production, gas regulation, CO₂ fixation, and O₂ releasing. Most ecosystem services studies have focused on the positive effects of ecosystems on human welfare. But a balanced and reasonable approach was to analyze both the positive and negative effects of cropland ecosystem services on human welfare.