| Moso bamboo(Phyllostachys pubescence) is Chinese important economic bamboo species which is the most widespread and the largest area of plantation, it shows prominent benefit but was argued by its effect on water conservation. However, research of bamboo was mainly focused on its usage, cultivation and photosynthetic characteristics, few studied was reported on leaf traits response to soil moisture was less. In China moso bamboo is mostly planted in slope and high altitude hill or reservoir drainage, therefore planting bamboo might effect on soil water function and meanwhile the soil moisture variation would influence on bamboo growth.The site of this study locates at moso plantation forest of upstream of Qingshitan reservoir, Lijiang River drainage. The experenment design based on appropriate water spraying (simulated rainfall), which we displace4water treatment:A, no water but covered with plastic to stop soil evaporation; B,5mm water and covered with plastic; C,10mm water and covered with plastic; D,20mm water and covered with plastic. Meanwhile we placed CK (control, nature condition) and HM (native community, Schima superba-Sapium sebiferum). We measured the soil moisture and photosynthetic variables and analysis the leaf water trait, physiecological traits and their response to soil moisture, thereafter to understand leaf photosynthesis productivity, transpiration and water use efficiency under different water condition, presuming the strategy of moso bamboo water physiecological adaptation.The main results were as follow:1、Soil physical properties of Moso forest:soil bulk density, soil density and soil capillary porosity of Moso is significantly higher than native community. Different water treatment show significant influence on soil water content but not on soil bulk density and soil density. Soil water content decrease temporally which D,C,B was rapid and A, CK and ZM was slow.2、Moso bamboo leaf trait and its response to water condition:leaf water content in bamboo is significantly higher than two native species. Re Moso, leaf water in B and C treatment is significantly higher than other treatment. However, leaf water content in D is not significantly different from that in CK. leaf area, specific leaf area (SLA) in C treatment is significantly higher than that in other treatments. No significantly different of bamboo leaf thickness, leaf dry mass among the treatment.3^Photosynthetic characteristics of bamboo leaf response to soil water:Net photosynthetic rate and stomatal conductance, transpiration rate and water use efficiency of bamboo leaf is significantly higher than native species Schima superba. Re Moso, maximum net photosynthesis is highest in treatment C, and lowest in D indicating appropriate water treatment can enhance net photosynthesis but too much water may lead to a native result. SPAD chlorophyll index variation temporally, which no significantly different before treatment, but on the5th day, B and D significantly increase, and maintain to the15th day. SPAD chlorophyll index of D slightly increase but decreased after the10th day. Transpiration is maximum in C but minimum in D which similar to the native species, however D has a highest water use efficiency. The reason might be due to low stomatal countenance and low transpiration in D. Net photosynthesis and transpiration is correlated with stomatal conductance.4> Leaf water potential response to soil water conditions:The leaf water potential was high at predawn and evening, but decreased by-1.88MPa to-2.66MPa at moon time. Leaf water potential S. superba was higher than moso at predawn but S. superba was lower than moso at noon time except C treatment. That is to say, degree of diurnal water potential variation is higher in bamboo than S. superba. Medium water treatment C, leaf water potential at noon is lowest; but maximum water treatment D, leaf water potential at noon is highest. This might due to the stomatal conductance high in the previous but low in the last treatment. While continually monitoring the leaf water potential in a12-day period, we also found it was low in S. superba than Moso at10:00. Soil water condition influences on leaf water potential, that leaf water potential increase along with water content increase except D treatment. With water spray in A and CK, the decrease of leaf water potential is slighter in A (with plastic) than CK, and the variation trend is similar to that of soil water.Conclusion:(1) the soil physical properties are significantly different between Moso and S. superba forest. Maso and cultivation method may have influence on soil water function. The soil bulk density and soil capillary porosity et al of Moso is significantly higher than native community which might imply water retention of Moso is better than native community. However literature and local people observer would indicate that the time of stream water was getting shorter, meaning water retention in Moso is decline. These two conclusions seems conflict. But if we considered soil flow velocity, the conflict may be explained, but it needs a further study.(2) under a nature condition, maximum water capacity is significantly higher in Moso than that in S. superba forest, but transpiration rate of Moso is significantly high than that of S. superba in a leaf level, indicating the total transpiration of Moso stand may not always higher than that S. superba stand. As we observe that the crown density meaning LAI of S. superba is higher than Moso. During our experiment period, high transpiration rat in leaf level did not result in a significantly soil water decrease.(3) The net photosynthesis and water use efficiency of Moso is significantly higher than S. superba, and the net photosynthesis is closely correlated to stomatal conductance. Although our experiment was conducted in dry season, but2013is a wet year, that our initial soil water is as high as around27%, when spraying a simulate rainfall10mm, can increase the net photosynthesis and transpiration, but decrease water use efficiency; but while increase the simulated rainfall to20mm, stomatal conductance decrease resulting into net photosynthesis and transpiration decrease, demonstrating too water logging seem not to benefit for Moso growth. |
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