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31.
Spatial and seasonal variation of salt ions under the influence of halophytes,in a coastal flat in eastern China 总被引：1，自引：0，他引：1
Yanyou Wu Rongcheng Liu Yuguo Zhao Pingping Li Congqiang Liu 《Environmental Geology》2009,57(7):1501-1508
The high salinity of coastal saline field is a key factor limiting the reclamation. Halophytes have been utilized in the reclamation
of saline land. The study area is in Yancheng, China. An analysis of the concentrations of Rb, Cs, Sr, and Ba, the ratio of
Rb/Cs, and Sr/Ba in soils in autumn shows that the soil of this study area has great homogeneity. Artemisia halodendron, Gossypium hirsutum, and Sesbania cannabina were selected as the reclamation plants in the present study. In order to know the spatial-temporal distribution of soil
salinity, the influence of plant-specific vegetation, and the difference of desalination among these halophytes in coastal
flat, the authors analyze the soil-layers and seasonal variation in salt ions. Sodium chloride was accumulated in 0–5 cm topsoil
with no vegetation during the winter and spring. The effect of desalinization of halophytes is significant. Of the three plant
species, Sesbania cannabina has the greatest desalinization. The difference of ions composition of soils covered with various plant species is significant.
It can be concluded that halophytes have better amelioration of coastal soil salinity. Special attention should be paid to
the selection of plant species and measures to plant and cultivate crops in the reclamation of saline land. 相似文献
32.
通过调查冷蒿的生物学特性,并以4种不同处理实验研究了耐牧性。处理方法分别为第1组模拟轻牧,剪去植株高度的一半(T1);第2组模拟重牧,把植株地上部分全部剪掉(T2);第3组埋土3~5cm(T3),以模拟沙质草场疏松的地表易被牲畜践踏活化而掩埋植物;第4组做对照(T4)。试验结果证明,春季对地上部分剪除不影响以后的营养生长和生殖枝的形成发育,但是7月以后做剪除处理则对其营养生长不利,对生殖枝的形成影响更大。生长季多次剪枝可获得更大生物量,不同处理组平均每株的地上部分收获生物量(干重)分别是25.2g(T1),27.4g(T2),24.7g(T3)和22.0g(T4)。冷蒿枝条密集,在无干扰条件下,平均每株有枝条近百枝。植株地上部被剪除后,不定芽萌发力强,1cm的残枝上可以萌芽2~4个。枝条的基部极易生不定根形成新植株。有性繁殖与无性繁殖并存保证了种群更新。 相似文献
33.
34.
Restoration treatments are based on the largely untested notion that desired recovery of plant communities following disturbance wouldn’t occur in the absence of active intervention. We identified rate of short-term (10 year) floristic changes following removal of plant functional groups in Wyoming big sagebrush plant communities in 1999-2005 and 2008. Treatments imposed on 6 × 6 m plots were: 1) removal of all plant functional groups, 2) perennial grass removal, 3) shrub removal and 4) control. Our data suggest recovery of the shrub component on shrub removal plots could take decades. Similarly, perennial grass cover and density on perennial grass removal plots was less than half that of unaltered plots 10 years after treatment. When all functional groups were removed, cover of annual forbs, annual grasses, and shrubs returned to unaltered levels within ten years or less. Perennial forbs were unaffected (p > 0.05) by treatment. The fact that natural recovery of some components occurred within a relatively short post-disturbance time interval (i.e. <10 years) suggests that intervention may not be necessary for some functional groups. Restoring shrubs in areas dominated by perennial grasses may require targeted reductions of competing perennial grasses. Conversely, shrub dominance may limit perennial grass re-establishment. 相似文献
35.
沙蒿是中国西北半干旱地区主要的固沙植物,其根系分布影响包气带水分运移过程,准确的植被特征和根系密度分布对根系吸水模型的建立十分重要。采用整体挖掘法获取不同层位的根系和根际土壤含水量,引入冠级和龄级的概念对沙蒿根系分布特征进行研究。分析结果表明：沙蒿种群以低龄级沙蒿占优,其根系生物量随龄级呈'S’型增长;根系长度分布和均一化根系密度分布均符合对数正态分布,最大值出现在浅层土壤20 cm处;沙蒿生长不依赖于地下水,其根系主要利用包气带中的水分,持续干旱条件下,为满足蒸腾作用根系出现两种调节方式：（1）横向生长增加根系量,利用横向土壤剖面的水分。（2）浅层根区由于水分胁迫造成的吸水量减少由深部相对湿润的根区补偿。因此沙蒿根系吸水模型中的根系密度分布函数应为对数正态分布,且吸水过程不仅依赖于根系密度分布,同时受土壤水分的影响。 相似文献
36.
The effects of climate change during the Terminal Pleistocene–Early Holocene transition on ecosystems and early Prearchaic hunter-gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from ~14 to ~7.5k cal a BP showing that Pinus-dominated woodlands were replaced by dry-adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking ~10.2–9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology. 相似文献
37.
不同演替阶段油蒿群落土壤水分特征分析 总被引：3，自引：0，他引：3
油蒿群落是毛乌素沙地最主要的群落类型之一,在维持当地生态系统稳定中起着重要作用。土壤水分是影响油蒿群落演替的重要环境因子,为深入分析不同油蒿演替阶段土壤水分特征,使用EC-5土壤水分传感器连续监测整个生长季内先锋物种阶段(流动沙地)、稀疏阶段(半固定沙地)和建成阶段(固定沙地)油蒿群落土壤水分动态。结果表明,3种样地土壤水分均存在时间和空间上差异,流动沙地各层土壤含水量均显著高于半固定沙地和固定沙地;土壤含水量受降水影响较大, 降水量是影响土壤水分补给深度的重要因素,小于10 mm的降水主要被表层土壤吸收,10～20 mm的降水对土壤水分的补给深度超过30 cm、不及60 cm, 30～40 mm的降水补给深度大于60 cm、不及100 cm;30 cm及其上层土壤水分波动剧烈,60 cm处土壤水分主要受大于30 mm降水事件影响,波动较小,100 cm和160 cm处土壤水分几乎不受降水的影响,土壤含水量较稳定;降水补给深度及植被根系需水的层次差异是导致3种样地土壤水分时间和空间上异质性的重要因素;土壤温度主要受大气温度影响,与土壤水分相关性不显著,且随土壤深度的增加而降低。 相似文献
38.
对青海共和盆地内的达连海湖泊流域54个样点进行植被调查及表土花粉分析,研究了植被与表土花粉之间的关系. 结果显示： 表土花粉组合可反映出该区植被的总体特征;达连海湖泊流域花粉沉积来源于整个流域植被,花粉与主要植被类型之间相关性良好,但不能完全反映出群落的建群种、优势种和盖度等. 蒿属和藜科花粉具有超代表性,禾本科表现为低代表性,蒿/藜比具有区域植被生态特点与气候指示意义,在不同的植被区域A/C变化明显;影响达连海湖泊流域表土花粉组合的主要控制因素是风力作用. 相似文献
39.
Seasonal patterns of soil respiration in three types of communities along grass-desert shrub transition in Inner Mongolia,China 总被引：1，自引：0，他引：1
The seasonal dynamics of soil respiration in steppe (S. bungeana), desert shrub (A. ordosica),
and shrub-perennial (A. ordosica + C. komarovii) communities were investigated during the growth season
(May to October) in 2006; their environmental driving factors were also analyzed. In the three communities,
soil respiration showed similar characteristics in their growth seasons, with peak respiration values in
July and August owing to suitable temperature and soil moisture conditions during this period. Meanwhile,
changes in soil respiration were greatly influenced by temperatures and surface soil moistures. Soil water
content at a depth of 0 to 10 cm was identified as the key environmental factor affecting the variation in
soil respiration in the steppe. In contrast, in desert shrub and shrub-perennial communities, the dynamics
of soil respiration was significantly influenced by air temperature. Similarly, the various responses of
soil respiration to environmental factors may be attributed to the different soil textures and distribution
patterns of plant roots. In desert ecosystems, precipitation results in soil respiration pulses. Soil carbon
dioxide (CO2) effluxes greatly increased after rainfall rewetting in all of the ecosystems under study.
However, the precipitation pulse effect differed across the ecosystem. We propose that this may be a result
of a reverse effect from the soil texture. 相似文献
40.
对腾格里沙漠东南缘不同的生境条件（包括始建于1964年的人工植被区和天然植被区）下油蒿（Artemisia ordosica）种群调查取样,按照植株的体积大小分为7个龄级（Ⅰ,0~2 cm3;Ⅱ,2~5 cm3;Ⅲ,5~10 cm3;Ⅳ,10~15 cm3;Ⅴ,15~20 cm3;Ⅵ,20~30 cm3;Ⅶ,>30 cm3）,分析了种群的组成、静态生命表和存活曲线。结果表明：人工植被区油蒿种群的总体规模大于天然植被区,幼龄个体占有很高的比例;天然植被区油蒿的死亡率低于人工植被区,天然植被区Ⅰ和Ⅱ龄级油蒿种群的死亡率最高,人工植被区Ⅴ~Ⅶ龄级的油蒿种群死亡率最高;天然植被区油蒿种群的稳定性维持主要通过幼苗的更新,而人工植被区可通过幼苗的自我更新和大龄植株的自疏作用;Ⅴ龄级的油蒿个体是种群中的生存质量最佳的个体;两种生境下油蒿种群均符合Deevey Ⅱ型存活曲线。 相似文献