Global Environmental Change: Implications for Agricultural Productivity

全球環境變遷：對農業生產力的影響

Bruce A. Kimball

《作物、環境與生物資訊》 1卷4期 (2004/12) Pp. 251-263

https://doi.org/10.30061/CEB.200412.0003

摘要

大氣的二氧化碳濃度持續在上升中，而且許多氣候模式的預測亦顯示將因此造成全球溫暖化及降水模型的改變。二氧化碳、溫度及降水的改變將直接影響植物的生長，可能也將引起農作物生產力的變異。提高二氧化碳濃度通常將可促進多數作物的產量，此一結果在生長箱、溫室及幾年前的田間高二氧化碳環境試驗(free-air CO2enrichment，FACE)中獲得證實，惟高二氧化碳濃度對產量的正面提升需要充分營養元素供應的相互配合。在高二氧化碳濃度環境下，葉片氣孔開度趨於部分關閉，使得植被溫度升高，需水量略為下降，然而不同作物表現並不一致。當氣溫一如模式預測伴隨二氧化碳濃度升高，作物的需水量可能將高於目前的情境。單獨考量全球溫暖化因素下，其對植物生長的快速或和緩促進作用則視當時氣溫係高或低於該植物的生長適溫而定。由於氣溫隨時改變於一天當中的任一時刻及一季當中的任一天，因此某一時段的植物生長可能低於、高於或處於最適速率。植物生長模式即納入此種溫度變異對生理作用的效應及生長隨時間的估測，較單純的模式輸入生長季節的逐日資料，細緻的模式則需要輸入每小時的資料以進行每日模型的模擬。目前的模式多已忽略許多詳細而重要的生理機制及交感作用，藉由模式的驗證程序提高其應用於估測未來農業生產力的能力。據最近以能夠解釋高二氧化碳影響許多生理效應的模式進行多種全球變遷情境的模擬結果，在採行適應全球變遷的農場經營策略下（如調整栽植期），已開發國家的穀物產量可以在2080年左右提高3-8%；反之，處於熱帶氣候的開發中國家產量將減少2-7%。如此一來，原本生產條件已較為遜色的開發中國家，將更苦於農業生產力下降的新情境。

關鍵字

全球變遷 ； 二氧化碳 ； 生產力 ； 產量 ； 水分使用 ； 作物 ； 植物 ； 農業

並列摘要

Atmospheric concentrations of CO2 are increasing, and predictions from climate models suggest there will be a consequent global warming and changes in precipitation patterns. Altered levels of CO2, temperature, and water all directly affect plant growth, so there likely will be changes in the productivity of agricultural crops. Increased levels of CO2 generally have increased the yields of most crops, as determined from many years of work using chambers or greenhouses and confirmed more recently using free-air CO2 enrichment (FACE) technology in open fields. Yield responses to elevated CO2 are generally higher when there are ample nutrients than when nutrients are limiting. Elevated CO2 also tends to partially close leaf stomata, thereby causing plant canopy temperatures to warm while reducing water requirements slightly, with the reduction varying by crop species. However, if air temperatures rise along with CO2 concentration as predicted, water requirements are likely to increase slightly in comparison to present-day conditions. Considering global warming alone, whether plants will grow faster or slower depends on whether they are below or above their optimum growth temperature. Temperatures change with season and time of day, so at any given time, plants may be below, at, or above their optimum. Plant growth models integrate such changing temperature effects on physiological processes and growth through time. Simpler models step through growing seasons day by day, whereas the more sophisticated models have an hourly time step and simulate diurnal patterns. Most present-day models ignore many processes and interactions that may be important. Nevertheless, they have had some respectable validations, and they are useful tools for estimating future agricultural productivity. Some recent simulations, which accounted for physiological effects of elevated CO2 and for farm-level adaptations to global change (e.g., change planting date), with various global change scenarios suggested that cereal yields in developed countries may increase 3-8% by the 2080s. On the other hand, yields in developing countries, which tend to be in more tropical climates, may decrease 2-7%. Therefore, the hardship of lower agricultural productivity may fall on those least able to cope.

並列關鍵字

global change ； CO2 ； productivity ； yield ； water use ； crop ； plant ； agriculture