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

Abstract

摘 要 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 6.69~8.24 t·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 O 2 24.99~28.64 t·hm −2 ·a −1 , 固定 CO 2 34.23~39.22 t·hm −2 ·a −1 , 排放 N 2 O 0.72~1.13 kg·hm −2 ·a −1 , 吸 收 CH 4 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 m 3 ·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 CO 2 和释放 O 2 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。 关键词 农田生态系统 小麦−玉米农田 生态系统服务 正效应 负效应 华北平原 中图分类号: S181 文献标识码: A Abstract 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, O 2 and N 2 O emissions were 24.99~28.64 t·hm −2 ·a −1 and 0.72~1.13 kg·hm −2 ·a −1 , whereas CO 2 and CH 4 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 m 3 ·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 5.48×10 4 ~6.25×10 4 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, CO 2 fixation, and O 2 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.