Samuelson Lisa J, Stokes Thomas A, Coleman Mark D
School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA.
Tree Physiol. 2007 May;27(5):765-74. doi: 10.1093/treephys/27.5.765.
Long-term hydraulic acclimation to resource availability was explored in 3-year-old Populus deltoides Bartr. ex Marsh. clones by examining transpiration, leaf-specific hydraulic conductance (G(L)), canopy stomatal conductance (G(S)) and leaf to sapwood area ratio (A(L):A(S)) in response to irrigation (13 and 551 mm year(-1) in addition to ambient precipitation) and fertilization (0 and 120 kg N ha(-1) year(-1)). Sap flow was measured continuously over one growing season with thermal dissipation probes. Fertilization had a greater effect on growth and hydraulic properties than irrigation, and fertilization effects were independent of irrigation treatment. Transpiration on a ground area basis (E) ranged between 0.3 and 1.8 mm day(-1), and increased 66% and 90% in response to irrigation and fertilization, respectively. Increases in G(L), G(S) at a reference vapor pressure deficit of 1 kPa, and transpiration per unit leaf area in response to increases in resource availability were associated with reductions in A(L):A(S) and consequently a minimal change in the water potential gradient from soil to leaf. Irrigation and fertilization increased leaf area index similarly, from an average 1.16 in control stands to 1.45, but sapwood area was increased from 4.0 to 6.3 m(2) ha(-1) by irrigation and from 3.7 to 6.7 m(2) ha(-1) by fertilization. The balance between leaf area and sapwood area was important in understanding long-term hydraulic acclimation to resource availability and mechanisms controlling maximum productivity in Populus deltoides.
通过检测三年生美洲黑杨（Populus deltoides Bartr. ex Marsh.）无性系对灌溉（除自然降水外，分别为13和551毫米/年）和施肥（0和120千克氮/公顷/年）的响应，研究了其对资源可利用性的长期水力适应情况。利用热消散探针在一个生长季内连续测量液流。施肥对生长和水力特性的影响大于灌溉，且施肥效果与灌溉处理无关。基于地面面积的蒸腾量（E）在0.3至1.8毫米/天之间，分别因灌溉和施肥增加了66%和90%。在参考蒸汽压亏缺为1千帕时，随着资源可利用性增加，特定叶水力导度（G(L)）、冠层气孔导度（G(S)）以及单位叶面积蒸腾量的增加与叶面积与边材面积比（A(L):A(S)）的降低相关，因此从土壤到叶片的水势梯度变化最小。灌溉和施肥同样增加了叶面积指数，从对照林分的平均1.16增加到1.45，但边材面积因灌溉从4.0增加到6.3平方米/公顷，因施肥从3.7增加到6.7平方米/公顷。叶面积和边材面积之间的平衡对于理解美洲黑杨对资源可利用性的长期水力适应以及控制最大生产力的机制至关重要。
