Effects of afforestation on water yield:: a global synthesis with implications for policy
Effects of afforestation on water yield:: a global synthesis with implications for policy
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DOI：
10.1111/j.1365-2486.2005.01011.x
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发表时间：
2005-10-01
影响因子：
11.6
通讯作者：
Jackson, RB
中科院分区：
文献类型：
--
作者：
Farley, KA;Jobbágy, EG;Jackson, RB
包括植树造林和重新造林在内的碳固存计划正在全球范围内获得关注，并将改变许多生态系统过程，包括水量。以前的一些分析讨论了毁林和产水量问题，而有些地区则考虑了植树造林对产水量的影响。然而，据我们所知，尚未对植树造林对产水量的影响进行系统的全球分析。为了在全球范围内评估和预测这些影响，我们分析了26个集水区数据集，其中包括504个观测值，包括年径流和低流量。我们研究了几个变量的变化，包括原始植被类型，种植园物种，种植园年龄和平均年降水量（MAP）。所有这些变量应该是有用的理解和模拟造林对产水量的影响。我们发现，年径流量平均减少44%（+/- 3%）和31%（+/- 2%）时，草地和灌丛绿化，分别。桉树比其他树种在绿化草地上的影响更大（P=0.002），减少径流量（90）75%（+/- 10%），而松树平均减少40%（+/- 3%）。无论是以绝对变化（mm）还是以预测径流量的比例（%）表示，在种植后至少20年，径流量随种植园年限的增加而显著增加（P < 0.001）。对于草地，年径流量的绝对减少量在湿润的地点最大，但比例减少量在干燥的地点显著更大（分别为P < 0.01和P < 0.001）。对低流量的影响与对年总流量的影响相似，但对低流量的影响比例更大（P < 0.001）。这些结果清楚地表明，在草地和灌木林造林后，径流量预计会减少，在干旱地区可能最为严重。我们的研究结果表明，在一个地区，天然径流量小于10%的MAP，植树造林应导致径流量的完全损失，天然径流量是降水量的30%，它可能会被削减一半或更多的树木种植时。植树造林可能会导致或加剧许多地方的水资源短缺，这是一种权衡，应该在碳固存计划中明确解决。
Carbon sequestration programs, including afforestation and reforestation, are gaining attention globally and will alter many ecosystem processes, including water yield. Some previous analyses have addressed deforestation and water yield, while the effects of afforestation on water yield have been considered for some regions. However, to our knowledge no systematic global analysis of the effects of afforestation on water yield has been undertaken. To assess and predict these effects globally, we analyzed 26 catchment data sets with 504 observations, including annual runoff and low flow. We examined changes in the context of several variables, including original vegetation type, plantation species, plantation age, and mean annual precipitation (MAP). All of these variables should be useful for understanding and modeling the effects of afforestation on water yield. We found that annual runoff was reduced on average by 44% (+/- 3%) and 31% (+/- 2%) when grasslands and shrublands were afforested, respectively. Eucalypts had a larger impact than other tree species in afforested grasslands (P=0.002), reducing runoff (90) by 75% (+/- 10%), compared with a 40% (+/- 3%) average decrease with pines. Runoff losses increased significantly with plantation age for at least 20 years after planting, whether expressed as absolute changes (mm) or as a proportion of predicted runoff (%) (P < 0.001). For grasslands, absolute reductions in annual runoff were greatest at wetter sites, but proportional reductions were significantly larger in drier sites (P < 0.01 and P < 0.001, respectively). Afforestation effects on low flow were similar to those on total annual flow, but proportional reductions were even larger for low flow (P < 0.001). These results clearly demonstrate that reductions in runoff can be expected following afforestation of grasslands and shrublands and may be most severe in drier regions. Our results suggest that, in a region where natural runoff is less than 10% of MAP, afforestation should result in a complete loss of runoff; where natural runoff is 30% of precipitation, it will likely be cut by half or more when trees are planted. The possibility that afforestation could cause or intensify water shortages in many locations is a tradeoff that should be explicitly addressed in carbon sequestration programs.