黑河下游胡杨季节尺度径向生长变化研究

利用半径型树木生长测量仪, 于2009-2010年生长季对西北内陆河-黑河流域下游荒漠河岸林优势树种-胡杨径向生长进行了监测, 结合环境气象、 水文因子同步监测资料, 对胡杨季节变化节律和环境影响因素进行了研究.结果表明: 按照胡杨径向生长日变化特征, 将其分为增长型(ΔR+)、 负增长型(ΔR-)和持续增长型(ΔR++)3种类型.在生长季, 胡杨径向生长季节变化呈"S"型, 可分为前期缓慢增长(P1)、 迅速增长(P2)和后期微弱增长(P3) 3个阶段; ΔR+/++类型在这3个阶段中所占比例分别为63.64%, 85.51%和48.61%; 5月末至8月初是胡杨年轮形成的主要阶段, 在该阶段气温和地下水位埋深均表现出显著的相关关系, 但地下水位埋深应是最根本的因素. 因此, 在树木年轮学应用方面, 胡杨可以用来反演区域水环境变化, 包括河道径流和地下水位变化等. 在荒漠河岸林管理方面, 满足春夏季地下水位条件和适度频率的春汛, 是保证该地区胡杨河岸林正常生长和保持合理种群结构的前提.

Study of Seasonal Stem Radial Growth of Populus euphratica in the Lower Reaches of the Heihe River

Using the point-dendrometer,the stem radial growth of Populus euphratica,a dominant tree species of the desert riparian forest in the lower reaches of the Heihe River,an inland river in Northwest China,was measured in the growing season in the years of 2009-1010.The seasonal rhythm of stem radial growth of P.euphratica and its relationship to environment factors was analyzed coupling with the synchronous instrumental records of air temperature and groundwater level.According to the stem radial growth characteristics,the whole diurnal cycle can be assorted to three types:(A) the stem diameter expands over the last maximum when it start to contract(ΔR+),(B) the stem diameter’s expansion can not reach the last maximum(ΔR-) and(C) the stem diameter expands continually from the last maximum and the contraction phase absents in the daily cycle(ΔR++).In the growth season(from May to early October),the cumulative stem radial growth shows "S" style.The annual total growth is about 2.89±0.91 mm and similar to the average ring width of P.euphratica.The whole period can be subdivided into three phases.The Phase 1 shows slow growth rate,0.46~9.17 μm·d-1,before later May,the Phase 2 is the highest growth period with the rate of 29.90-50.62 μm.day-1 from the later May to early August,and then the growth rate decreases to-0.23~2.78 μm·d-1 in the Phase 3 from early August to the end of growth season.In the three phases,the ΔR+ type accounts for 63.64%,85.51% and 48.61%,respectively.It can be sure that the period from later-May to early August is the main period for the growth ring formation.Although both air temperature and groundwater level have significant correlation to the stem radius growth in this period,the groundwater level should be the substantial factor.Therefore,for the dendrochronological study,the tree ring of P.euphratica can be used for reconstructing the regional water regime process,such as river flow and groundwater level changes.For the management of desert riparian forest,keeping the suit groundwater level in the spring and summer,with some frequent spring floods,is the precondition for the tree’s health growth and maintaining suitable forest stand structure.