Ecosystem carbon exchange on conversion of Conservation Reserve Program grasslands to annual and perennial cropping systems
Ecosystem carbon exchange on conversion of Conservation Reserve Program grasslands to annual and perennial cropping systems
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DOI：
10.1016/j.agrformet.2018.02.016
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发表时间：
2018-05-01
影响因子：
6.2
通讯作者：
Robertson, G. Philip
中科院分区：
文献类型：
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作者：
Abraha, Michael;Hamilton, Stephen K.;Robertson, G. Philip
农业生产中的土地利用变化可能会对生态系统碳平衡产生长期影响。我们研究了生态系统的碳平衡8年后，22岁的保护区计划（CRP）草原和以前耕种的农田（AGR）转换为年度（连续免耕玉米）和常年（柳枝稷和恢复草原）农田。保留未转换的CRP字段（CRP Ref）作为历史参考。生态系统碳平衡评估使用调整后的净生态系统碳交换（NEEadj）计算增加碳去除收获的生物量NEE测量涡度协方差法。前CRP领域的玉米和多年生植物系统的累积NEEadj表明，这些系统是一个净碳源的大气在8年的时间，而前AGR领域，多年生植物系统的净碳汇和玉米系统近中性。CRP-Ref接近中性，直到干旱年才成为净源。CRP领域的玉米系统可能会达到一个新的低土壤碳平衡至少14年后转换，但将永远不会恢复转换后的碳损失在目前的免耕管理与残留物部分删除。另一方面，多年生系统可以在14年内完全恢复转换后失去的C。在相同的土地利用历史中，玉米系统的累积NEEadj表现出比多年生系统更高的C排放，反映了作物类型和管理在农业生态系统C平衡中的主导作用。结果表明，转换农田草地直接C收益的结果，而转换草地农田永久（免耕玉米与部分残留物去除）或临时（多年生草本作物）净碳损失到大气中。这对减缓全球气候变化具有重大意义，因为促进一年生和多年生作物的生物质生产，以避免化石燃料C排放（生物燃料）或从大气中去除CO2（生物能源C捕获和储存）。
Land use changes into and out of agricultural production may substantially influence ecosystem carbon (C) balance for many years. We examined ecosystem C balances for eight years after the conversion of 22 year-old Conservation Reserve Program (CRP) grasslands and formerly tilled agricultural fields (AGR) to annual (continuous no-till corn) and perennial (switchgrass and restored prairie) cropland. An unconverted CRP field (CRP Ref) was maintained as a historical reference. Ecosystem C balance was assessed using adjusted net ecosystem carbon exchange (NEEadj) calculated by adding C removed in harvested biomass to NEE measured using eddy covariance method. The cumulative NEEadj of the corn and perennial systems on former CRP fields showed that these systems were a net C source to the atmosphere over the 8-year period while on former AGR fields, the perennial systems were net C sinks and the corn system near-neutral. The CRP-Ref was near neutral until a drought year when it became a net source. The corn system on the CRP field will likely reach a new lower soil C equilibrium at least 14 years after conversion but will never regain the C lost upon conversion under current no till management with residue partially removed. On the other hand, the perennial systems could fully regain in 14 years the C lost following conversion. The cumulative NEEadj of the corn systems exhibited a higher C emission than did the perennial systems within the same land use histories, reflecting the dominant role of crop type and management in agricultural ecosystem C balance. Results suggest that converting croplands to grasslands results in immediate C gains whereas converting grasslands to croplands results in permanent (no-till corn with partial residue removal) or temporary (perennial herbaceous crops) net C loss to the atmosphere. This has a significant implications for global climate change mitigation where biomass production from annual and perennial crops is promoted to avoid fossil-fuel C emissions (biofuel) or to remove CO2 from the atmosphere (bioenergy C capture and storage).