Water use patterns of Pinus sylvestris var. mongolica trees of different ages in a semiarid sandy lands of Northeast China
Water use patterns of Pinus sylvestris var. mongolica trees of different ages in a semiarid sandy lands of Northeast China
复制标题
樟子松水分利用模式
DOI：
10.1016/j.envexpbot.2016.02.006
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发表时间：
2016
影响因子：
5.7
通讯作者：
Zhang Jinxin
中科院分区：
文献类型：
--
作者：
Song Lining;Zhu Jiaojun;Li Mingcai;Zhang Jinxin
蒙古松（Pinus sylvestrisvar）在中国北方半干旱沙地上，蒙古沙人工林在防治荒漠化中发挥着重要作用，但由于水分缺乏，人工林在种植后30 ~ 35年左右就会发生枯死。然而，不同年龄的蒙松所使用的水源的季节变化尚不清楚，这些变化影响了人工林的管理。在2012年和2013年连续2年，对10年、22年、32年和42年的蒙松人工林枝条木质部水分、不同深度（0-20、20-40、40-60和60-100 cm）土壤水分、降水和地下水中氢和氧的稳定同位素进行了分析，以确定不同季节（春、夏、秋）蒙松林木的用水来源。同时测定了针叶的土壤含水量、地下水位和δ13C，结果表明，在2年的观察中，10岁和22岁的树木只利用土壤水，而32岁和42岁的树木既利用土壤水又利用地下水。在土壤含水量较低的春季（5月下旬），10、22岁树龄利用20 ~ 60 cm土层水分，而32、42岁树龄利用40 ~ 100 cm土层水分和地下水。夏季（7月中下旬）土壤含水量较高时，不同树龄树木利用0 ~ 60 cm土层水分；秋季（9月中下旬）土壤含水量较高时（2012年），不同树龄树木利用20 ~ 100 cm土层水分。然而，当土壤含水量相对较低时（2013年），10岁和22岁的树木继续利用20-100 cm土层的水分，而32岁和42岁的树木同时吸收60-100 cm土层和地下水的水分。地下水对32年和42年树龄树木蒸腾的贡献随土壤湿度的降低而增加，当土壤湿度约为田间容量的20%（3.5%）时，地下水是主要的水源，占树木蒸腾的60.2%。此外，22年生松树的针叶δ13C显著高于4个年龄的松树，表明22年生松树的水分利用效率较高。这些研究结果表明，如果在干旱条件下地下水位突然下降，未来30-35岁的老蒙松人工林将经历更大的死亡率，但由于其根系无法到达饱和区，年轻蒙松人工林只会受到轻微的影响。
Mongolian pine (Pinus sylvestrisvar.mongolica) plantations in semiarid sandy lands play an important role in the prevention and control of desertification in northern China, but plantation dieback often occurs approximately 30–35 years after planting due to water deficiency. However, the seasonal changes in the water sources used by Mongolian pine trees of different ages remain unclear, and these changes influence the management of the plantations. During two consecutive years, 2012 and 2013, stable isotopes of hydrogen and oxygen from twig xylem water, soil water at different depths (0–20, 20–40, 40–60 and 60–100 cm), precipitation and groundwater were analyzed in 10-, 22-, 32- and 42-year-old Mongolian pine plantations to identify the sources of water used by the trees during different seasons (spring, summer and autumn). The soil water content, groundwater level and δ13C of the needles were measured concurrently, and the results showed that the 10- and 22-year-old trees only used soil water during the two years of observation, but the 32- and 42-year-old trees utilized both soil water and groundwater. In spring (late May), when soil water content was low, the 10- and 22-year-old trees used water from the 20–60 cm soil layer, but the 32- and 42-year-old trees utilized water from the 40–100 cm soil layer and groundwater. In summer (mid or late July), when soil water content was high, the trees of different ages used water from the 0–60 cm soil layer, and in autumn (mid or late September), when the soil water content was relatively high (2012), the trees of different ages used water from the 20–100 cm soil layer. However, when the soil water content was relatively low (2013), the 10- and 22-year-old trees continued to use water from the 20–100 cm soil layer, but the 32- and 42-year-old trees absorbed water from both the 60–100 cm soil layer and the groundwater. The contribution of groundwater to tree transpiration increased with decreasing soil moisture for the 32- and 42-year-old trees, and groundwater was the dominant water source (e.g., 60.2% of tree transpiration in the 42-year-old trees) when the soil moisture was approximately 20% of field capacity (3.5%). In addition, the significantly higher δ13C in the needles of the 22-year-old trees relative to the four ages of pine trees suggested higher water use efficiency in the 22-year-old trees. These findings suggest that the old Mongolian pine plantations (e.g., 30–35 years old) will experience greater mortality in the future if the groundwater level suddenly declines under drought conditions, but the young Mongolian pine plantations would suffer only slightly because their roots are unable to reach the saturated zone.