Land‐use change and water losses: the case of grassland afforestation across a soil textural gradient in central Argentina
Land‐use change and water losses: the case of grassland afforestation across a soil textural gradient in central Argentina
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DOI：
10.1111/j.1365-2486.2005.00975.x
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发表时间：
2005-07
影响因子：
11.6
通讯作者：
M. Nosetto;E. Jobbágy;J. Paruelo
中科院分区：
文献类型：
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作者：
M. Nosetto;E. Jobbágy;J. Paruelo
植被变化，特别是那些涉及树木和草为主的覆盖之间的过渡，往往会改变蒸发水分损失的结果，植物介导的水分进入和需求的变化。在南半球特别重要的天然草原上大规模植树造林，可能对水文循环产生强烈但难以量化的影响。我们探讨了在巨桉种植园和本土潮湿的草原，他们取代在阿根廷中部的用水模式。为了揭示土地覆被类型、土壤质地和气候变异对蒸发水分损失和水分利用效率的交互作用，我们估算了117个不同土壤质地梯度的人工林和草地样地的日蒸散量（粘土质地的变性土到桑迪质地的变性土），使用来自七个陆地卫星场景的辐射信息，现有的木材生产记录，和树干中的13 C测量。在任何时候和所有地点，植树造林的地表温度都比草地低（平均-5 °C），蒸发的水也比草地多（平均+80%）。草地和人工林之间的绝对ET差异范围为0.6至2 mm/天，每种植被类型的年增长建议值分别为0.630和0.1150 mm/年。ET的时间变异性显着低于人工林相比，草地（变异系数36%比49%）。每日ET增加的水分平衡变得更加积极（前18天的累积平衡）与饱和响应在草地与连续线性增加的人工林，表明较低的生态生理限制，以减少水分流失的树冠相比，原生植被。土壤质地对种植园蒸散的影响比草地蒸散大，粗质地土壤蒸散最大，其次是中质地和细质地土壤蒸散。木材生产力，以及13 C浓度在茎中达到峰值，在中等质地的网站，表明极端的纹理较低的水分利用效率，并建议水的限制是不负责生产力下降到更细，更粗的土壤。我们的研究强调了植被类型对蒸散的关键作用，因此，在水文循环。考虑到植树造林可能会继续在草原上扩张，植树造林的蒸发性水分损失增加，可能会导致水管理以及当地气候发生问题性变化。
Vegetation changes, particularly those involving transitions between tree‐ and grass‐dominated covers, often modify evaporative water losses as a result of plant‐mediated shifts in moisture access and demand. Massive afforestation of native grasslands, particularly important in the Southern Hemisphere, may have strong yet poorly quantified effects on the hydrological cycle. We explored water use patterns in Eucalyptus grandis plantations and the native humid grasslands that they replace in Central Argentina. In order to uncover the interactive effects that land cover type, soil texture and climate variability may have on evaporative water losses and water use efficiency, we estimated daily evapotranspiration (ET) in 117 tree plantations and grasslands plots across a soil textural gradient (clay‐textured Vertisols to sandy‐textured Entisols) using radiometric information from seven Landsat scenes, existing timber productions records, and 13C measurements in tree stems. Tree plantations had cooler surface temperatures (−5°C on average) and evaporated more water (+80% on average) than grasslands at all times and across all sites. Absolute ET differences between grasslands and plantations ranged from ∼0.6 to 2 mm day−1 and annual up‐scaling suggested values of ∼630 and ∼1150 mm yr−1 for each vegetation type, respectively. The temporal variability of ET was significantly lower in plantations compared with grasslands (coefficient of variation 36% vs. 49%). Daily ET increased as the water balance became more positive (accumulated balance for previous 18 days) with a saturation response in grassland vs. a continuous linear increase in plantations, suggesting lower ecophysiological limits to water loss in tree canopies compared with the native vegetation. Plantation ET was more strongly affected by soil texture than grassland ET and peaked in coarse textured sites followed by medium and fine textured sites. Timber productivity as well as 13C concentration in stems peaked in medium textured sites, indicating lower water use efficiency on extreme textures and suggesting that water limitation was not responsible for productivity declines towards finer and coarser soils. Our study highlighted the key role that vegetation type plays on evapotranspiration and, therefore, in the hydrological cycle. Considering that tree plantations may continue their expansion over grasslands, problematic changes in water management and, perhaps, in local climate can develop from the higher evaporative water losses of tree plantations.