Horticultural Section, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand.
Rubber Development Department, General Directorate of Rubber, Ministry of Agriculture, Forestry and Fisheries, Penh, Cambodia.
Tree Physiol. 2019 Jun 1;39(6):1061-1070. doi: 10.1093/treephys/tpz017.
Transient thermal dissipation (TTD) systems provide a simple way to measure xylem sap flow with dual or single Granier-type probe, which gives lower energy consumption and higher accuracy due to its lessor sensitivity to thermal interferences. A new system, TTD heat within 5 min (TTD5), proposed on the reduction of the heating duration. This evolution captured interest through decreased energy consumption and increased temporal resolution. Within our study, the first objective was to test and calibrate this new system with a single probe for young rubber tree - Hevea brasiliensis. The second objective was to explore the sources of variability in calibration such as species, individual cut-stems and probe-wood contact. The complementary species consisted of two diffuse-porous species (mango tree - Mangifera indica, eucalyptus tree - Eucalyptus camaldulensis) and one ring-porous species (teak tree - Tectonia grandis). Twenty-eight response curves were assessed over a large range of flux densities from 0.5 to 10 l dm-2 h-1. The incremental rise of temperature from 30 to 300 s (T300-30) after commencement of heating was sensitive to flux density over the complete range. Compared with the full signal at 300 s, the incremental signal markedly reduced the variability between response curves within species and between species. Moreover, a new index K2, defined as (T0 - Tu)/T0, normalized the responses between 0 and 1. However, the responses had a non-linear trend above 5 l dm-2 h-1. Within diffuse-porous wood type, the species did not differ in calibration, whereas the ring-porous species was markedly different. A sigmoid function provided the best fit for the diffuse-porous species. Individual stems were identified as the main source of within-species variability in calibration. The normalizing K2 index removed the influence of probe-wood contacts, controlled through drilling difference; however, there was still an effect of individual stems interacting with flux density (P = 0.019). Replications of cut-stems and response curves are necessary to assess a reliable averaged calibration. In conclusion, the applicability of the TTD5 system with a single probe has been confirmed and several sources of variability in calibration have been evaluated.
瞬态热耗散（TTD）系统为使用双探头或单探头格兰杰型探头测量木质部液流提供了一种简单的方法，由于其对热干扰的敏感性较小，因此能耗更低，精度更高。一种新的系统，TTD 加热 5 分钟（TTD5），通过减少加热时间提出。由于能耗降低和时间分辨率提高，这种新系统引起了人们的兴趣。在我们的研究中，第一个目标是使用单探头测试和校准该新系统，以测量年轻橡胶树——巴西橡胶树的木质部液流。第二个目标是探索校准中的可变性来源，如物种、个体切割茎和探头-木材接触。补充的物种包括两种散孔材（芒果树-芒果、桉树-桉树）和一种环孔材（柚木-柚木）。在从 0.5 到 10 l dm-2 h-1 的较大通量密度范围内评估了 28 条响应曲线。从 30 到 300 s（T300-30）的温度递增上升在整个范围内对通量密度敏感。与 300 s 时的全信号相比，增量信号明显降低了物种内和物种间响应曲线之间的可变性。此外，定义为（T0-Tu）/T0 的新指数 K2 将响应在 0 到 1 之间归一化。然而，响应在 5 l dm-2 h-1 以上呈非线性趋势。在散孔材中，物种在校准方面没有差异，而环孔材则明显不同。Sigmoid 函数为散孔材提供了最佳拟合。个体茎被确定为校准中物种内可变性的主要来源。标准化 K2 指数消除了探头-木材接触的影响，该影响通过钻孔差异控制；然而，个体茎与通量密度的相互作用仍有影响（P = 0.019）。为了评估可靠的平均校准，需要对切割茎和响应曲线进行重复。总之，已经证实了使用单探头的 TTD5 系统的适用性，并评估了校准中的几个可变性来源。
