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浅地下水埋深条件下胡杨、柽柳的早期竞争
吴桂林
学位类型硕士
导师李君
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业生态学
关键词演替、适应策略、河岸植物群落、波动生境、干扰
摘要干旱区河流径流多变,决定了干旱区河岸林水分生境波动的基本特征。植物萌发于水分充足,干扰强度大,靠近河道的河漫滩,河岸群落演替过程由此开始。植物苗期的竞争强烈且更容易遭受生境波动的干扰,不同物种对高干扰、低胁迫的河漫滩的适应能力决定其竞争能力,竞争的结果决定了河岸林的格局。由于干旱区植物对地下水具有高度的依赖性,因此,浅地下水埋深与干扰条件下植物的竞争能力决定了河岸植被的群落结构。本项研究以塔里木河河岸林优势种胡杨、柽柳幼苗群落为研究对象,在阿克苏站实验小区设置浅地水埋深模拟有利水分条件,同时,把地上生物量的丢失作为一种干扰,对不同条件下两物种的气体交换特征、生物量及其分配进行测定,对比两物种幼苗在水分充足条件下功能特征、适应策略、竞争能力,干扰前与干扰后竞争能力的变化,以及干扰后两物种恢复能力的差异。阐明水分有利生境与干扰条件下塔里木河河岸林早期演替的机理。主要结论如下: (1) 浅地下水埋深条件下,柽柳较低的Gs对LVPD的敏感度使其通过高耗水实现高碳同化策略,同时,柽柳叶片质量与叶片质量比均显著高于胡杨,这些特性使柽柳积累的单株地面生物量远高于胡杨,表现出明显的竞争优势。 (2) 对比地下水埋深条件下,与胡杨相比,柽柳在水分充足条件下Gs对LVPD的敏感度、WUE均较低,在水分亏缺条件下Gs对LVPD的敏感度相对较高,WUE增大的幅度较大,体现了柽柳在水分充足条件下通过高耗水充分利用水分快速生长,在水分亏缺条件下能够利用有限水分维持较高碳同化能力的策略,表现出对河漫滩多变水文生境较强的适应能力。 (3) 由于水分充足条件下,胡杨更高的根茎比,使其在受到干扰后幼苗的成活率与及恢复能力均高于柽柳。虽然,柽柳在平均单株生物量与平均单株株高上对胡杨仍有一定的优势,但与干扰前与非干扰条件相比,这一优势明显减弱。 综合本实验中有利水分条件与干扰条件下胡杨与柽柳幼苗的竞争能力差异,结合野外观测两物种从幼苗期至成熟期的分布格局,表明塔里木河幼苗群落的早期演替过程中胡杨的取胜的关键并非源于直接竞争,而是依赖于干扰减弱柽柳的竞争优势,从而促进胡杨的生长。 干旱区河流径流多变,决定了干旱区河岸林水分生境波动的基本特征。植物萌发于水分充足,干扰强度大,靠近河道的河漫滩,河岸群落演替过程由此开始。植物苗期的竞争强烈且更容易遭受生境波动的干扰,不同物种对高干扰、低胁迫的河漫滩的适应能力决定其竞争能力,竞争的结果决定了河岸林的格局。由于干旱区植物对地下水具有高度的依赖性,因此,浅地下水埋深与干扰条件下植物的竞争能力决定了河岸植被的群落结构。本项研究以塔里木河河岸林优势种胡杨、柽柳幼苗群落为研究对象,在阿克苏站实验小区设置浅地水埋深模拟有利水分条件,同时,把地上生物量的丢失作为一种干扰,对不同条件下两物种的气体交换特征、生物量及其分配进行测定,对比两物种幼苗在水分充足条件下功能特征、适应策略、竞争能力,干扰前与干扰后竞争能力的变化,以及干扰后两物种恢复能力的差异。阐明水分有利生境与干扰条件下塔里木河河岸林早期演替的机理。主要结论如下: (1) 浅地下水埋深条件下,柽柳较低的Gs对LVPD的敏感度使其通过高耗水实现高碳同化策略,同时,柽柳叶片质量与叶片质量比均显著高于胡杨,这些特性使柽柳积累的单株地面生物量远高于胡杨,表现出明显的竞争优势。 (2) 对比地下水埋深条件下,与胡杨相比,柽柳在水分充足条件下Gs对LVPD的敏感度、WUE均较低,在水分亏缺条件下Gs对LVPD的敏感度相对较高,WUE增大的幅度较大,体现了柽柳在水分充足条件下通过高耗水充分利用水分快速生长,在水分亏缺条件下能够利用有限水分维持较高碳同化能力的策略,表现出对河漫滩多变水文生境较强的适应能力。 (3) 由于水分充足条件下,胡杨更高的根茎比,使其在受到干扰后幼苗的成活率与及恢复能力均高于柽柳。虽然,柽柳在平均单株生物量与平均单株株高上对胡杨仍有一定的优势,但与干扰前与非干扰条件相比,这一优势明显减弱。 综合本实验中有利水分条件与干扰条件下胡杨与柽柳幼苗的竞争能力差异,结合野外观测两物种从幼苗期至成熟期的分布格局,表明塔里木河幼苗群落的早期演替过程中胡杨的取胜的关键并非源于直接竞争,而是依赖于干扰减弱柽柳的竞争优势,从而促进胡杨的生长。
其他摘要The physical environment of arid riparian zones is highly variable, which is determined by the variations of runoffs. Riparian plants commonly germinate on flood plains close active channels that are characterized by sufficient water supply and frequently subject to disturbances. After establishments, riparian plant communities begin the succession that is mediated by hydrological processes. Competition between species at seedling stage is more intensive and more subject to environment variations, i.e., the competitive ability of a given species is determined by its adaption to riparian environments, and thus the outcome of the competition determines the community structure of riparian forests. As riparian plants in arid zones are highly dependent on groundwater, riparian plant communities are expected to be determined by groundwater conditions and the competitive ability of plants affected by disturbances. The co-occurring dominant species of Tarim riparian forests, Populus euphratica and Tamarix ramosissima, were selected to test their competitive abilities at seedling stage under experimental high groundwater condition, the favorable environment in riparian zone, as well as under disturbance simulated by above-ground biomass removal. Gas exchange traits and biomass allocation for the two species were measured under different conditions, with the objectives to compare their competitive abilities under the favorable water condition, including the functional traits, adaptive strategies, as well as the changes of competitive ability before and after simulated disturbance. The study was aimed to explore the mechanisms of how hydrological processes mediate the early succession of Tarim riparian plant communities. The results indicated that: (1) Under high groundwater availability, stomatal sensitivity to leaf-to-air vapor pressure deficit (LVPD) for T. ramosissima was lower than that of P. euphratica, suggesting that T. ramosissima exhibits inert stomatal behavior under sufficient water supply, a strategy to gain more CO2 at the cost of high water use per leaf area; and on the other hand, T. ramosissima had greater leaf biomass and allocated more percentage of biomass to leaf than that of P. euphratica leading to much greater above-ground biomass of T. ramosissima that renders T. ramosissima overwhelm P. euphratica in above-ground biomass. (2) T. ramosissima had lower water use efficiency (WUE) and stomatal sensitivity to VPD under high groundwater availability, but relatively higher WUE and stomatal sensitivity to VPD under no groundwater availability, suggesting that T. ramosissima is able to gain more CO2 at expense of high water use under sufficient water supply and able to efficiently use water to maintain relatively high carbon gain when groundwater is unavailable. (3) Disturbance favored P. euphratica more than T. ramosissima because higher biomass allocation to roots in P. euphratica resulted in advantages over T. ramosissima in survival and recover after disturbance. Although T. ramosissima still had greater biomass and height per plant, the increased relative yield (RY) for P. euphratica and decreased RY for T. ramosissima following disturbance suggest that the overwhelming advantage of T. ramosissima over P. euphratica was narrowed. Comparisons in the competitive ability between the studied species under well-watered condition as well as under simulated disturbance indicate that, combined with the community structure observed in fields, that P. euphratica, as the final winner in the succession process in Tarim riparian zones, is more dependent on the unpredictable disturbance rather than on the direct competition against its competitor under the variable water environments of the Tarim riparian zones.
学科领域生态学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14673
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
吴桂林. 浅地下水埋深条件下胡杨、柽柳的早期竞争[D]. 北京. 中国科学院大学,2015.
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