A Study On The Sap Flow Rate Of Pinus Tabulaeformis Trees During Non-Growing Season In Taiyue Mountain, Shanxi Province, China

During the period of Sept.17,2009 to April 30,2010, I used TDP probes to conduct long-term monitoring survey on the sap flow rates of 11 Pinus tabulaeformis around the tower in the forestry farm in Lingkong Mountain in Shanxi province.1 also studied the relation between sap flow rates and the environmental factors in the non-growing season, comparing the sap flow rates in different directions on the same pine as well as the axial and radial variations of sap flow rates.The results showed that the sap flow of Pinus tabulaeformis was not stalled in non-growing seasons. The peak at noon gradually disappeared and the flows mainly showed at night with the maximum of 16.11cm/h, the minimum of 5.109×10-5 cm/h, and an average of 3.29cm/h. Sap flow rate curve in a clear day, in chronological order, showed five typical types, including a single peak and twin peaks type, transitional type, multi-peak typeⅠ, multi-peak typeⅡ, and non-peak. Besides, the sap flow rate difference of sunny and cloudy days in non-growing seasons was not that much compared with that in growing seasons.The main factors influencing the sap flow included photosynthetic active radiation, air temperature and relative humidity, and both significant positive and negative correlation were found between the three factors and the sap flow rate. Positive correlation showed between soil moisture and the rate in a long term.The sap flow rates of trees with different heights remained the same start and stop time. High position start increased fast with a high peak, general peak duration and a fastest decline; middle position start generally increased with a general peak and decline, but longest duration; low position start increased at a slower speed, with the earliest arrival at the peak and weaker duration, slowly declining after reaching the peak.