水分处理对油菜叶位光合速率、蒸腾速率及水分利用效率的影响

通过对不同水分处理下油菜不同叶位叶片光合速率(Pn)、蒸腾速率(E)和水分利用效率(WUE)的测定表明,油菜主茎叶片的光合速率、蒸腾速率和水分利用效率随叶位的降低而降低;干旱胁迫下油菜水分利用效率显著提高,光合速率变化不明显,但上部、下部叶间光合速率差异大。充分供水时叶片的蒸腾速率提高,水分利用效率则降低,从上到下叶片水分利用效率、光合速率降低不剧烈,而蒸腾速率表现为上部和下部叶高,而中部叶低。据测定,干旱处理下油菜单株生物量为37.45g,充分供水时为38.76g,干旱导致油菜生物量降低;水分胁迫能提高作物水分利用效率;在充分供水条件下叶片蒸腾速率较高,这可能是气孔行为的结果。

不同时间尺度径流对植被变化的响应

植被覆盖对陆地生态系统的水分循环起着重要作用。径流对植被变化在不同时间尺度的响应研究,对区域生态环境建设及水资源管理具有重要的参考价值。该文介绍基于对比流域法,在多年平均、年际、季节等不同时间尺度径流对植被变化响应的研究结果。多年平均尺度上,由植被类型更替引起的径流绝对变化量,湿润区较干旱区大,其相对变化量在干旱区严重;年际尺度上,因植被变化,径流从一种平衡状态到另一种平衡状态的响应时间因抚育措施和地区不同而不同,造林情况下,湿润地区一般需要15~20 a,干旱地区约需25 a甚至更长,森林自然恢复情况下则需要上百年;季节尺度上,径流对植被变化的响应在季风影响区较四季湿润地区强烈。流量历时曲线研究表明,干旱地区造林,其基流无论在量或发生概率的变化上均较湿润区强烈。

黄土丘陵区柳枝稷光合生理生态特性的初步研究

研究了黄土丘陵区引种草种柳枝稷 ( Panicum virgatum)的光合生理生态特性 ,比较了不同叶位叶片光合速率 ( Pn)、蒸腾速率 ( Tr)、水分利用效率 ( WUE)的日变化以及环境因子的作用。结果表明 ,柳枝稷叶片 Pn日变化曲线为双峰型 ,中午“光合降低”主要是由于叶温过高导致呼吸高引起的净光合速率降低。叶龄增大 ,叶片 Pn日变化相对较平缓 ,其中壮龄叶Pn日变化最为平缓。幼龄叶 Tr的日变化为双峰型 ,随叶龄增大 (叶位下降 )而成为单峰型。WUE的日变化可划分为上午的降低和下午的波动 2个阶段 ,最上充分展开叶 (旗叶 )的WUE始终最高。

地下滴灌埋管深度对冬小麦根冠生长及水分利用效率的影响

在试验室内 ,进行了地下滴灌埋管深度对不同生育时期冬小麦根系生长和地上部分生长影响的试验研究。结果表明 :2 0 cm和 4 0 cm埋管深度的水分分布特征 ,在生育早期抑制地上部分营养生长 ,促进冬小麦蹲苗 ;而中后期则促进生殖生长 ,产量和水分利用效率较高。不考虑犁底层影响时 ,在重壤土上 4 0 cm是冬小麦进行地下滴灌的较好埋深

燕沟基本农田粮食稳产高产综合配套技术及试验示范

提出了以新修梯田耕作栽培技术和作物抗旱节水技术为中心的燕沟流域基本农田粮食高产综合配套技术体系 ,并在燕沟流域经过 3年试验示范 ,使粮食生产潜力实现率由原来的 2 3%～ 48% ,平均已达到 5 4 %～ 64% ,典型的抗旱节水综合试验示范地块的潜力实现率提高到 78%～ 87% ;作物平均单产和水分利用效率较原来分别提高了 63%和 5 9.1 % ,粮食单产平均较 1 997年翻了两番 ,粮食产量较 1 997年提高了 33.7%～ 62 .1 % ,人均产粮达到了 5 0 0 kg以上 ,基本实现了减地不减产和增产增效的效果

保墒灌溉对渠灌类型区冬小麦产量构成及生理特性的影响

以传统耕作栽培方式为对照,研究了5种保墒灌溉栽培方式下冬小麦产量构成的差异,并对冬小麦灌浆期旗叶叶绿素含量、MDA含量、SOD含量、水分利用效率进行了研究。结果显示:不同保墒灌溉栽培方式对冬小麦均有增产作用,平均增产13.46%,穗长平均增加7.15%,不孕小穗数平均降低21.78%,结实小穗平均增加11.42%,穗粒数平均增加10.82%,千粒重平均增加11.05%。保墒灌溉栽培方式的冬小麦灌浆期旗叶叶绿素含量降低减缓,MDA含量降低、SOD含量增高,水分利用效率平均提高24.03%。结果表明,以免耕留茬方式增产幅度最大,水分利用效率最高。

土壤水分状况对长白山阔叶红松林主要树种叶片生理生态特性的影响

Potted seadlings of Pinus koraiensis , Fraxinus mandshurica,Juglans mandshurica,Tilia amurensis, and Quercus mongolica ,which are five dominant species in the Korean pine broadleaf forest at Changbai mountain,were grown in different soil moistures.We designed three soil moisture scenarios:85%～100%(high water,CK),65%～85% (medium water,MW) and 45%～65% (low water,LW) of field water holding capacity.The results show that characteristics of typical drought resistance on the leaves are significantly developed.The net photosynthetic rate and water use efficiency of F. mandshurica were higher compared with CK at MW.The net photosynthetic rate and water use efficiency of other 4 tree species at CK were lower than those at MW and LW.The transpiration rate of 5 tree species responses differently to various soil water status.

Carbon Dioxide Exchange Between the Atmosphere and an Alpine Shrubland Meadow During the Growing Season on the Qinghai-Tibetan Plateau

In the present study, we used the eddy covariance method to measure CO2 exchange between the atmosphere and an alpine shrubland meadow ecosystem (37°36'N, 101°18'E; 3 250 m a.s.l.) on the Qinghai-Tibetan Plateau, China, during the growing season in 2003, from 20 April to 30 September. This meadow is dominated by formations of Potentilla fruticosa L. The soil is Mol-Cryic Cambisols. During the study period, the meadow was not grazed. The maximum rates of CO2 uptake and release derived from the diurnal course of CO2 flux were -9.38 and 5.02 μmol•m-2•s-1, respectively. The largest daily CO2 uptake was 1.7 g C•m-2•d-1 on 14 July, which is less than half that of an alpine Kobresia meadow ecosystem at similar latitudes. Daily CO2 uptake during the measurement period indicated that the alpine shrubland meadow ecosystem may behave as a sink of atmospheric CO2 during the growing season. The daytime CO2 uptake was correlated exponentially or linearly with the daily photo synthetic photon flux density each month. The daytime average water use efficiency of the ecosystem was 6.47 mg CO2/g H2O. The efficiency of the ecosystem increased with a decrease in vapor pressure deficit.

Characterization of photosynthetic pathway of plant species growing in the eastern Tibetan plateau using stable carbon isotope composition

The photosynthetic pathway of plant species collected at Menyuan, Henan, and Maduo sites, east of Tibetan Plateau, China, during the growing season were studied using stable carbon isotopes in leaves. The 232 samples leaves analyzed belonged to 161 species, 30 families, and 94 genera. The delta(13)C values (from -24.6 to -29.2 %o) indicated that all the considered species had a photosynthetic C-3 pathway. The absence of plant species with C-4 photosynthetic pathway might be due to the extremely low air temperature characterizing the Tibetan Plateau. The average delta(13)C value was significantly (p < 0.05) different between annuals and perennials at the three considered study sites. Hence the longer-lived species had greater water-use efficiency (WUE) than shorter-lived species, that is, longer-lived species are better adapted to the extreme environmental conditions of the Tibetan Plateau.

Short-term variation of CO2 flux in relation to environmental controls in an alpine meadow on the Qinghai-Tibetan Plateau

[1] The alpine meadow ecosystem on the Qinghai-Tibetan Plateau may play a significant role in the regional carbon cycle. To assess the CO2 flux and its relationship to environmental controls in the ecosystem, eddy covariance of CO2, H2O, and energy fluxes was measured with an open-path system in an alpine meadow on the plateau at an elevation of 3,250 m. Net ecosystem CO2 influx (Fc) averaged 8.8 g m(-2) day(-1) during the period from August 9 to 31, 2001, with a maximum of 15.9 g m(-2) day(-1) and a minimum of 2.3 g m(-2) day(-1). Daytime Fc averaged 16.7 g m(-2) day(-1) and ranged from 10.4 g m(-2) day(-1) to 21.7 g m(-2) day(-1) during the study period. For the same photosynthetic photon flux density (PPFD), gross CO2 uptake (Gc) was significantly higher on cloudy days than on clear days. However, mean daily Gc was higher on clear days than on cloudy days. With high PPFD, Fc decreased as air temperature increased from 10degreesC to 23degreesC. The greater the difference between daytime and nighttime air temperatures, the more the sink was strengthened. Daytime average water use efficiency of the ecosystem (WUEe) was 8.7 mg (CO2)(g H2O)(-1); WUEe values ranged from 5.8 to 15.3 mg (CO2)(g H2O)(-1). WUEe increased with the decrease in vapor pressure deficit. Daily albedo averaged 0.20, ranging from 0.19 to 0.22 during the study period, and was negatively correlated with daily Fc. Our measurements provided some of the first evidence on CO2 exchange for a temperate alpine meadow ecosystem on the Qinghai-Tibetan Plateau, which is necessary for assessing the carbon budget and carbon cycle processes for temperate grassland ecosystems.

喀斯特石漠化区植物水分利用的时空变化研究----以贵州清镇王家寨小流域为例

本研究以西南喀斯特地区的王家寨小流域为研究对象，以植物叶片δ13C值为植物水分利用效率的指示值，结合利用氢氧同位素对植物的水分来源进行确认，通过研究小流域中不同土壤类型石漠化样地、不同季节、不同等级石漠化样地及喀斯特不同小生境中常见植物种水分利用效率及水分来源的差异，旨在从小生境、植物种、植物群落等不同尺度上探讨石漠化发生过程对植物长期水分利用的影响，了解不同水源的利用对植物水分利用效率的影响，了解喀斯特生态系统特有生境中植物对水分的竞争和利用策略，以加深对生态系统水分平衡的认识。通过研究，得出了以下几点认识： 1 喀斯特石漠化区植物叶片δ13C值的时空变化 （1）在本研究区，不同土壤类型区域植物群落δ13C值均随着石漠化的进行趋正，方差分析结果显示黄壤序列植物群落叶片δ13C值存在显著差异（F（3，80）0.01=2.720.05)。整个生长季中，常见种叶片δ13C值与土壤含水量的相关关系研究表明大多数种在大多数时间随土壤水分的减少其WUE提高。 （4）本研究区小生境类型主要有石面、石沟、石缝、及土面。各小生境内植物叶片δ13C值基本上随石漠化进行趋正，即小生境尺度上植物叶片δ13C值随石漠化进行趋正。基于石漠化梯度和小生境类别的双因素方差分析表明，生长于不同石漠化等级及不同小生境的植物叶片δ13C 值总体差异显著。土面上生长的植株叶片δ13C值最负，说明较厚的土层、较多的土量能供给植物较为充足的水分、养分，避免或减小了植物的水分胁迫。对各小生境植物叶片δ13C值与各小生境主要环境因子进行相关分析，结果表明植物叶片δ13C值与小生境土壤厚度、0-10cm土壤平均含水量以及日均大气相对湿度呈显著负相关，而与日均光照强度呈显著正相关。 （5）石漠化过程中常见植物种叶片解剖结构中的栅栏组织厚度、上角质层厚度、下角质层厚度、最大导管直径均呈现逐渐增大的趋势，而海绵组织厚度则呈现逐渐减少的趋势，方差分析结果显示各解剖结构均呈现显著性差异（p<0.05）。另外，对叶片解剖结构指标与叶片δ13C值的相关分析表明，所研究的植物种叶片上述解剖形态结构中除下角质层厚度与叶片δ13C值相关关系不显著（p>0.05）外，其余指标均与其叶片δ13C值呈现显著的正相关关系（p<0.05），说明植物的WUE与植物叶片解剖结构的变化存在着内在的相关关系。 2 喀斯特石漠化区植物水分来源的时空变化 （1）由于07年降雨丰富，其喀斯特皮下水显著低于06年，但是06年喀斯特皮下水的季节变化却不大，这是由于06年为特大欠水年，观测期内降雨仅721mm，为正常年份的60%，“活塞效应”不明显。2006年对各等级石漠化样地植物水分来源研究结果表明：（12月）土壤水及小枝木质部水分的δD及δ18O值明显高于夏季（7、9月）。降雨较多的7月，强、中度石漠化大多数植物主要利用土壤水，轻、无石漠化样地植物则利用土壤水和喀斯特皮下水。9月，由于干旱严重，各石漠化样地大多数植物均不同程度的利用了喀斯特皮下水。 （2）对研究区各小生境植物水分来源的研究表明：各小生境土壤水分δD、δ18O各不相同，石缝小生境土壤水分δD、δ18O最负，石面土壤水分δD、δ18O最正，土面、石沟居中。强度石漠化土壤剖面水分δD、δ18O值>中度石漠化样地>轻度石漠化样地>无石漠化样地，显示随着石漠化的进行，样地蒸发越强烈。整体上，石缝中植物比其他生境更容易利用喀斯特皮下水，无石漠化样地的植物比石漠化样地的植物更容易利用喀斯特皮下水，常绿植物比落叶植物利用更多的喀斯特皮下水，乔木比灌木利用更多的喀斯特皮下水。 3 植物稳定性氢氧同位素与碳同位素耦合 通过对研究区植物叶片δ13C值和不同水源和植物木质部δD、δ18O值的测定，结果表明无石漠化样地植物具有更负的δ13C值，即其水分利用效率（WUE）低于石漠化样地，这是由于无石漠化样地喀斯特水赋存的二元结构，植物除了可以利用浅薄土层的水分，还拥有稳定的浅层地下水即喀斯特皮下水，这已通过植物木质部水分δD、δ18O值的测定得到佐证。落叶种具有比常绿种更正的δ13C值，即其水分利用效率（WUE）高于常绿种，这是由于常绿种比较稳定的利用了浅层地下水，具有稳定的水分来源，使得常绿种的水分利用效率（WUE）较低。土面生境植物具有比其他生境更负的δ13C值，是因为较大的土面面积、较厚的土厚，较多的土量提够给植物较多的水分，养分，土壤水分较充足，避免或减少了植物的水分胁迫，植物WUE较低。

Conversion of natural forests to managed forest plantations decreases tree resistance to prolonged droughts

© 2015 Published by Elsevier B.V.Throughout the southern US, past forest management practices have replaced large areas of native forests with loblolly pine plantations and have resulted in changes in forest response to extreme weather conditions. However, uncertainty remains about the response of planted versus natural species to drought across the geographical range of these forests. Taking advantage of a cluster of unmanaged stands (85-130year-old hardwoods) and managed plantations (17-20year-old loblolly pine) in coastal and Piedmont areas of North Carolina, tree water use, cavitation resistance, whole-tree hydraulic (Ktree) and stomatal (Gs) conductances were measured in four sites covering representative forests growing in the region. We also used a hydraulic model to predict the resilience of those sites to extreme soil drying. Our objectives were to determine: (1) if Ktree and stomatal regulation in response to atmospheric and soil droughts differ between species and sites; (2) how ecosystem type, through tree water use, resistance to cavitation and rooting profiles, affects the water uptake limit that can be reached under drought; and (3) the influence of stand species composition on critical transpiration that sets a functional water uptake limit under drought conditions. The results show that across sites, water stress affected the coordination between Ktree and Gs. As soil water content dropped below 20% relative extractable water, Ktree declined faster and thus explained the decrease in Gs and in its sensitivity to vapor pressure deficit. Compared to branches, the capability of roots to resist high xylem tension has a great impact on tree-level water use and ultimately had important implications for pine plantations resistance to future summer droughts. Model simulations revealed that the decline in Ktree due to xylem cavitation aggravated the effects of soil drying on tree transpiration. The critical transpiration rate (Ecrit), which corresponds to the maximum rate at which transpiration begins to level off to prevent irreversible hydraulic failure, was higher in managed forest plantations than in their unmanaged counterparts. However, even with this higher Ecrit, the pine plantations operated very close to their critical leaf water potentials (i.e. to their permissible water potentials without total hydraulic failure), suggesting that intensively managed plantations are more drought-sensitive and can withstand less severe drought than natural forests.

Un modelo de optimización del uso del suelo y del agua con fines agrícolas en el partido de Tandil

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Los grandes sistemas de abastecimiento de agua en el litoral de Alicante

El litoral de Alicante ha sufrido grandes transformaciones territoriales desde las décadas de 1960 y 1970 a raíz de la actividad turística. Uno de los servicios que necesita esta actividad, entre otros, es el abastecimiento de agua potable. En este sentido, por su papel estratégico, el suministro de agua en alta es decisivo para abastecer a los municipios turístico-residenciales. El objetivo de este estudio es conocer y analizar los diferentes sistemas de abastecimiento de agua en alta en la costa de Alicante, sus características, infraestructuras, recursos hídricos disponibles y medidas de gestión llevados a cabo. Algunas de las conclusiones extraídas son el papel estratégico que ejercen en el territorio, especialmente con el agua, un recurso escaso y de vital importancia para la orla costera alicantina, sobre todo en los meses estivales.