Study on water use efficiency characteristics of dorminate species in communities in shallow mountain area on the north slope of Kunlun Mountain

研究区位于昆仑山北坡前山带，以昆仑山北坡前山带群落优势种塔里木沙拐枣、驼绒藜和昆仑绢蒿为研究对象。通过群落调查，描述了研究区植物群落结构、物种多样性和群落相似性特征，结果显示，在调查区域内发现21种植物，参与建群种15种，其他6种为偶见种。21种植物分属于10科20属，其中菊科(Compositae)和藜科(Chenopodoideae)植物13种；五个植物群落，优势种分别为塔里木沙拐枣(Calligonum roborowasikii)、琵琶柴(Scorzonera muriculata)、河西苣(Hexinia polydichotoma)、蒿类植物(昆仑蒿Artemisia nanschanica + 昆仑绢蒿Seriphidium korovinii)与驼绒藜(Ceratoides latens)；植物群落沿海拔高度变化地带性更替明显，低山砾质壤土母质上为塔里木沙拐枣和琵琶柴群落，集中分布范围分别为2200－2300m和2250－2400m，中部沙质土壤母质上为蒿类植物和河西苣群落，蒿类植物群落分布于海拔2400－2500m，河西苣群落集中于2500m高大沙丘丘间低地，驼绒藜群落在砾质土壤和沙质土壤母质上均有分布，海拔范围在2380－2800m；群落结构简单，整体盖度小于10%，物种密度为4-13株(丛)/m2，灌木层优势种单一，密度很小(1.2株(丛)/m2)，草本层冠幅水平低，盖度小(小于5%)；群落间高度(H)、盖度(C)、密度(D)存在不同程度差异，物种丰富度指数dMA和生物多样性指数(D、H'、Jsw、Jgi)差异并不明显，总体处于较低水平。群落盖度、密度、高度和物种数随海拔高度变化趋势不同，生物多样性指数随着海拔高度增加呈增加趋势。群落相似性比较显示低海拔地区植物群落间的相似性高于高海拔地区植物群落间的相似性。利用气体交换法测定植物分析了植物WUE时间变化、沙丘不同部位植物WUE差异性及海拔高度变化对植物WUE及叶片δ13C的影响。结果显示，（1）沙丘起伏增加了植物水分利用效率日变幅，植物光合速率、蒸腾速率沿着坡位升高规律性升高，而水分利用效率在不同坡位的变化并不规律，尽管如此，沙丘的起伏没有造成植物光合速率、蒸腾速率和水分利用效率的显著变化；（2）气体交换参数计算的植物水分利用效率结果显示，海拔越高植物水分利用效率越低，驼绒藜水分利用效率海拔变化达到显著水平（F=6.00，P=0.019），塔里木沙拐枣水分利用效率海拔差异不明显（F=2.17，P=0.14）；而稳定性同位素结果显示海拔越高δ13C越高，两者顺序相反，其原因有待进一步分析；（3）气体交换法测定植物水分利用效率大小顺序为：塔里木沙拐枣（2.89±0.79）>昆仑绢蒿（2.23±1.39）>驼绒藜（1.73±1.20）；植物WUE种间差异显著程度季节变化不均，6月份差异极显著(F=27.98, P天山北坡阜康荒漠地区>甘肃金塔地区。The research was conducted in Shallow Mountain Area of Northern Slope of Kunlun Mountain. Vegetation in this area typically belongs to arid and semi-arid ecosystem, composition and structure of communities are simple. Dominate species in five communities are Calligonum roborowasikii, Scorzonera muriculata, Hexinia polydichotoma, Artemisia nanschanica + Seriphidium korovinii, Ceratoides latens. Calligonum roborowasikii community and Scorzonera muriculata community distributed on gravelly loam at low altitude, altitude distribution are 2200－2300m and 2250－2400m, Hexinia polydichotoma community and Artemisia nanschanica + Seriphidium korovinii community distributed on sandy loam, altitude distribution are 2400－2500m and 2500m, respectively. Ceratoides latens community distributed both on gravelly loam and sandy loam, altitude distribution are 2380－2800m. Plant species there were sparse, amount to 21 in all, 38% of them are Chenopodoideae and Compositae. Coverage of communities are lower than 10%, species density of communities are about 4-13/m2. Different levels of differences in Coverage, height and density exist in coummunities investigated, however, the richness index (dMA)and the species diversity(D、H'、Jsw、Jgi) are low with no significant differences among plant communities at 5% or 1% level. Species diversity values increased along altitude elevation, changes of Coverage, height and density of communities along altitude elevation are not regular. Comparing the similarity coefficient, it’s similarer among communities at low altitude region than communities at high altitude region. Environmental condition in shallow mountain area of Kunlun Mountain is significantly different from desert around oasis in the southern margin of the Taklimakan Desert, to study plant water use efficiency here, dominate species, Ceratoides latens, Seriphidium korovinii(C3) and Calligonum roborowasikii (C4), in natural communities were taken as the research object. Leaf photosynthesis rate A (molCO2m-2s-1) and leaf transpiration rate E (mmolH2Om-2s-1) was measured using Li-6400 Portable Photosynthesis System, instantaneous plant WUE is calculated by A/E. The plots were layouted along road perpendicular to Mountain Ridge, seasonal changes of plant WUE at different dune part in 65km, 63km, 60km were measured. The intention of our research was as follows: (1) to detect the interspecific variations of WUE among plants investigated, (2) seasonal changes of plant WUE and interspecific difference, (3) the influence of sand-dune undulation on plant WUE and interspecific heterogeneity, (4) vertical variation of plants WUE at different elevation in shollow mountain area. The results showed that (1) sand-dune undulation produce regular effect on Photosynthetic Rate and Transpiration Rate, but not regular on WUE, however, the difference of photosynthetic rate, transpiration rate and WUE among different part on the sand-dune were not significant, sand-dune undulation increases daily variations of plants WUE, plants WUE at upper slope is lower than middle slope and base slope without significant difference,（2）the higher the altitude is, the lower the WUE of plants are, variations of WUE of Ceratoides latens at different altitude is significant, variations of WUE of Seriphidium korovinii at different altitude is not significant, the higher the altitude is, the higher δ13C are, the cause of this opposite phenomenon of size order between WUE calculated by gas exchange parameters and leaf δ13C need further need further research, (3) WUE of C4-plant Calligonum roborowasikii is significantly greater than C3-plant Seriphidium korovinii and Ceratoides latens (F=27.98, P