摘要
土壤干旱是北方地区杨树人工林生长和生态效益的重要限制因子。以群众杨(Populus×popularis‘35-44’)扦插苗为研究材料,采用盆栽称重法控制土壤水分,设置正常供水、中度干旱、重度干旱3种水分梯度。分别于2016年9月与2017年9月测定叶片气体交换参数、各器官干重、根冠比、叶经济性状等指标,研究了持续2年干旱胁迫下群众杨扦插苗光合特性与器官干物质分配的变化规律,分析了土壤干旱程度、树龄在"小老树"形成中的作用过程。2016年与2017年中度、重度干旱胁迫下功能叶净光合速率(P_n)受到非气孔限制,与正常供水相比分别降低了36.08%、56.42%;18.47%、5.13%。第一年干旱胁迫下群众杨气孔导度(G_s)和蒸腾速率(T_r)显著降低;第二年干旱胁迫下G_s与正常供水无显著差异,而T_r显著提高,有利于叶片C、N元素的运输分配进而维持较高的P_n。第一年随干旱胁迫程度加剧,群众杨叶片C/N显著提高,光合产物分配趋向于叶器官。第二年中度干旱胁迫下叶片C/N与正常供水相比无显著差异,各器官干重下降幅度均低于2016年,而根冠比显著增加,表明其光合产物主要用于地下部构建以适应中度干旱环境;持续重度干旱则光合产物向茎中的分配比例提高。干旱胁迫导致群众杨功能叶水分利用效率(WUE,Water use efficiency)与光合氮利用效率(PNUE,Photosynthetic nitrogen use efficiency)显著降低,整株氮利用效率(NUE,Whole plant nitrogen use efficiency)显著提高。严重土壤干旱下叶片耗水增强、PNUE下降以及茎木质部碳投资增加可能是群众杨小老树形成的重要原因。
Soil water content is a key limiting factor to development and ecological function of artificial poplar plantations in semi-arid area of northern China. To examine the effects of soil drought on a poplar variety Populus×popularis ‘35-44’,3 soil water levels,i.e.,normal( 75% "5% of field capacity),moderate drought( 50% "5%) and severe drought( 25% "5%),were set up using 1 year old cutting seedlings grown in pots. We measured leaf gas exchange parameters,organ dry mass and leaf economic traits both in September 2016 and September 2017 to analyze interannual changes in leaf gas exchange and biomass allocation in an attempt to elucidate the effects of soil water stress and ageing in formation of the"old dwarf trees"phenomenon. Compared with seedlings grown at the normal soil water level,leaf net photosynthetic rates( Pn)of seedlings grown at moderate and severe soil drought levels were reduced by 36.08% and 56.42% in 2016 respectively and also 18.47% and 5. 13% in 2017 respectively,mainly due to non-stoma limitation. In first year of soil water drought treatment,stomatal conductance( Gs) and transpiration rate( Tr) of seedlings grown at both soil drought levels decreasedsignificantly. However,no significant decrease of Gsat both soil drought levels were found in second year,while Tr increased at both drought levels significantly,which could be beneficial to transportation of C and N to leaves and therefore maintenance of Pn. In first year of treatment,with increasing severity of soil drought,leaf C/N ratio increased significantly and more biomass was allocated to foliage. However,no significant differences were found in leaf C/N ratio between normal soil water level and moderate soil drought level in second year of treatment,while the decreases of all component biomass at moderate soil drought level in 2017 were less than those in 2016 with a significantly higher root-shoot ratio,indicating that more dry matter were allocated to underground for root construction in acclimation to moderate soil drought. In compar
作者
赵瑜琦
高苗琴
李涛
王卫锋
ZHAO Yuqi;GAO Miaoqin;LI Tao;WANG Weifeng(College of Forestry,Shanxi Agricultural University,Taigu 030801,China)
出处
《生态学报》
CAS
CSCD
北大核心
2020年第5期1683-1689,共7页
Acta Ecologica Sinica
基金
国家自然科学基金项目(31400527,31700534)
山西省应用基础研究项目(201701D221190)
山西农业大学引进人才博士科研启动项目(2013YJ18)。
关键词
群众杨
干旱胁迫
气体交换参数
C、N含量
干物质分配
Populus×popularis’35-44’
soil water stress
leaf gas exchange
C and N content
biomass allocation
