CAJ | 학술논문

全球气候变化和人类活动的加剧,正导致古尔班通古特沙漠南缘原始盐生旱生荒漠地区的地下水位发生显著改变.大气污染导致该地区太阳辐射减少.以盐生荒漠建群种多枝柽柳(Tamarix ramosissima)为研究对象,选择地下水位在2.9-4.5m波动的典型原始生境,观测了生长期内光合有效辐射和地下水位变化时的光合作用、蒸腾作用和叶水势等生理活动的季节变化,调查了根系分布特征;并利用涡度相关系统测定了生态系统碳水通量,估算群落碳同化能力、蒸腾耗水量与叶面积指数的季节变化,旨在揭示光合有效辐射和地下水位等环境因素对柽柳属(Tamarix)荒漠灌木群落光合作用的影响.研究结果表明:降水造成的潜土层水分状况变化对多枝柽柳的碳平衡没有显著影响.深根系与气孔调节是多枝柽柳碳平衡适应荒漠环境水分状况的两个关键机制.特殊的气孔行为体现了多枝柽柳以高水分消耗为代价将其碳获取最大化的适应对策;多枝柽柳生理与群落尺度的水分平衡和碳获取均依赖于深根系获取的稳定地下水源,缓和的地下水位波动将不会扰动其现有的碳/水平衡,地下水位剧烈下降将危及多枝柽柳的生存.此外,光合有效辐射是另一个主要影响因素,与群落碳获取呈显著正相关关系.群落碳同化能力的季节变化是光合有效辐射和地下水位共同影响下光合作用物候学特征的体现.过度开采地下水和直接破坏原生植被的行为,将会严重地干扰多枝柽柳群落的生存,进而破坏该区域现有的生态水文过程.
전구기후변화화인류활동적가극,정도치고이반통고특사막남연원시염생한생황막지구적지하수위발생현저개변.대기오염도치해지구태양복사감소.이염생황막건군충다지정류(Tamarix ramosissima)위연구대상,선택지하수위재2.9-4.5m파동적전형원시생경,관측료생장기내광합유효복사화지하수위변화시적광합작용、증등작용화협수세등생리활동적계절변화,조사료근계분포특정;병이용와도상관계통측정료생태계통탄수통량,고산군락탄동화능력、증등모수량여협면적지수적계절변화,지재게시광합유효복사화지하수위등배경인소대정류속(Tamarix)황막관목군락광합작용적영향.연구결과표명:강수조성적잠토층수분상황변화대다지정류적탄평형몰유현저영향.심근계여기공조절시다지정류탄평형괄응황막배경수분상황적량개관건궤제.특수적기공행위체현료다지정류이고수분소모위대개장기탄획취최대화적괄응대책;다지정류생리여군락척도적수분평형화탄획취균의뢰우심근계획취적은정지하수원,완화적지하수위파동장불회우동기현유적탄/수평형,지하수위극렬하강장위급다지정류적생존.차외,광합유효복사시령일개주요영향인소,여군락탄획취정현저정상관관계.군락탄동화능력적계절변화시광합유효복사화지하수위공동영향하광합작용물후학특정적체현.과도개채지하수화직접파배원생식피적행위,장회엄중지간우다지정류군락적생존,진이파배해구역현유적생태수문과정.
Aims The groundwater table has changed and air pollution has been reducing solar radiation on the southern periphery of China's Gurbantonggut Desert. Our objective was to investigate the response and adaptation of Tamarix ramosissima, a native dominant desert shrub in Central Asia, towards variation in groundwater and pho-tosynthetically active radiation (PAR), in terms of ecophysiological activities, morphological characteristics and community carbon/water balances.Methods During the growing season from 2005 to 2007, we carried out experiments in the original habitat of T. ramosissima, where the groundwater table fluctuated from 2.9 to 4.5 m. Photosynthesis, transpiration, leaf water potential, water-use efficiency and root distribution were examined to reveal the water-use strategy of the species, and CO_2 and H_2O fluxes above an undisturbed T. ramosissima ecosystem were measured by eddy covariance method to evaluate net carbon assimilation, water loss and leaf area index (LAI).Important findings Physiological activity and community carbon uptake of T. ramosissima did not respond to sustained drought in upper soil or rainfall pulses, and its photosynthetic consistency is achieved by its water-use pattern. Special stomatal behavior and root distribution are two main mechanisms. Tamarix ramosissima tends to maximize its carbon gain at the cost of higher water consumption, attributable to its phreatophytic root system that ensures sufficient groundwater supply and avoids the effects of water deficiency in upper soil. Tamarix ramosissima can adapt to moderate fluctuation of groundwater table, but severe decline will threaten its survival, andhence the overexploitation of groundwater will cause severe degradation of Tamarix-dominated perennial vegetation and disturb the original ecohydrological processes in this arid region. PAR is another important environmental factor positively correlating with community carbon uptake. The LAI indicates that the seasonal pattern in community carbon assimilation represents the combined effects of groundwater table and PAR on the phenological photosynthesis capacity. It shows that the integrated study on different scales is an effective approach to further the understanding of desert shrub adaptive strategies and ecosystem processes under variable environmental conditions.