景泰川灌区次生盐渍化及其防治

景泰川灌区位于甘肃省北部,景泰县内。1974年景泰电力提水工程建成,最大提水高度406.2米,设计流量10.5米/秒,有效灌溉面积30万余亩。本区为干旱区大陆性气候,年平均降水量186毫米,蒸发量3600毫米,且风沙多。过去由于没有灌溉条件,大面积土地长期荒芜。景电工程的建成,彻底改变了本区的自然面貌和生产条件,短短的十四年间,这里建成了荒漠中的大片绿洲。但是,随着土壤灌溉,灌区的次生盐渍化已经露头。根据第二次土壤普查统计,己经盐化面积30482亩,占总耕地面积的10.16%。因此,充分发挥提黄河水灌溉的效益,并防治土     

云南山地民族刀耕火种生态学定位与山地森林资源可持续利用

通过对云南省永仁县直苴村刀耕火种农业的景观生态学研究，发现在一个相当长的时期内，正是刀耕火种使山地民族社区人和森林都实现了自身的可持续发展，并同时实现了二者的和谐发展，但随着人口、资源和环境的变化，刀耕火种存在的条件不断消失，刀耕火种也必然消失，这说明任何一种物质生产方式都有其时空尺度的局限性，都必须以一定的环境条件和资源条件为基础，以区域内生态系统的健康、持续性发展为前提，     

Condition of Quercus robur L. along a natural Luvisol microtoposequence on loess in Central Belgium

Abstract. This research aims to assess how the variability in soil morphology of Luvisols along a microtopographic sequence influences the condition of pedunculate oak ( Quercus robur ). The condition of 205 pedunculate oaks was observed during one growth season and related to morphological soil properties. Results show that the presence of a consolidated argillic B horizon or fragipan in Luvisols, has a negative influence on the condition of Q.robur .     

黄土丘陵区沙棘林几个水分生理生态特征研究

为探讨沙棘对半干旱黄土丘陵区水分条件的适应性,1998年对沙棘的水分生理生态及抗旱性进行了分析研究.试验结果表明(1)沙棘适应半干旱黄土丘陵区生境形成了耐旱、御旱的双重抗旱方式.在旱季,沙棘体内束缚水含量随干旱加剧而上升,束缚水与自由水比值随干旱加剧而增大,叶片维持较高的含水量,蒸腾减弱,叶水势降低,临界饱和亏增大,表现出较强的抗旱性.(2)沙棘光合速率具明显的日变化,1000 1200出现第1次峰值,1400 1500出现第2次峰值.沙棘光合速率与环境因子(气温、相对湿度和光合有效辐射)间有显著的相关关系,相关系数为0.8466 0.9351,其中光合有效辐射对光合速率影响最显著,气温次之,相对湿度最小;沙棘光合速率与气孔导度及细胞间CO2浓度间有十分显著的相关关系,相关系数为0.9852 0.9856.(3)沙棘蒸腾速率与气孔导度具明显的日变化,两者的变化趋势相似,5、7月日变化曲线呈单峰型,6、8、9月日变化曲线呈双峰型.在生长季(5-     

黄土高原寒区青海云杉人工林地土壤水分物理特性研究

对黄土高原高寒区的青海云杉人工林林地的土壤水分物理性质进行了实地观测和分析(主要采用野外实测土壤水分再分布的方法,对入渗后不同土层土壤的水分再分布过程及低吸力段土壤水分特征作了研究),发现该林地在枯落物及林下植被层的作用下,使得0~10 cm表层土壤的持水性最好;因放牧践踏导致林地10~30 cm土层的土壤板结密实,持水性较差;30~50 cm土层土壤的持水性居中。通过研究还拟合得出了该林地土壤水分再分布、土壤水分特征曲线及土壤比水容量的参数。为该地区退耕还林还草、林业生态建设和森林水文效益评价提供了可靠依据。     

Pruning of néré trees (Parkia biglobosa (Jacq.) Benth.) on the farmlands of Burkina Faso, West Africa

This study of the pruning of néré (Parking biglobosa) trees in central Burkina Faso included detailed surveys of 83 trees and their owners in 21 villages. Pruning is not widespread, but appears to be a practice with various motives and techniques. The motives are mainly aimed at deliberate management of the trees, in order to enhance their fruit production, and are rarely aimed at reducing tree impact on crop productivity. The characteristics of tree pruning techniques (e.g., frequency, intensity and seasonality) and their corresponding motives appear to change as an adaptation to land degradation processes and the deterioration of tree condition. The results demonstrate that indigenous silvicultural management techniques contribute to a sustainable use of tree resources.

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Résumé Cette étude sur la taille du néré (Parkia biglobosa) a été faite par des observations détaillées de 80 nérés et les entretiens avec leurs propriétaires dans 21 villages au Plateau Central du Burkina Faso. La taille du néré n'est pas générale, mais révèle diverses motivations et techniques. La plupart des motivations est orientée vers une gestion consciente de l'arbre en vue d'une amélioration de la production furitière, et rerament en vue d'une reduction de l'influence de l'arbre sur les cultures. Les caracteristiques des techniques de taille (fréquence, intensité, période de taille) et les motivations impliquées paraissent s'adapter à la dégradation de l'environnement et al détérioration de la viabilité des arbres. Les résultats montrent la durabilité des pratiques concernant la gestion des arbres.

     

黄土高原坡地林草复合系统景观边界植物多样性特征

以黄土高原坡地刺槐林—草地复合系统景观边界为研究对象,按一定的生态梯度调查分析了边界植物种的分布特点。结果表明,草地、林地斑块内都有自身的植物种类分布;草地斑块内有较高的植物多样性。在草地斑块内,距林缘8~16m区域为边界植物多样性边缘效应的显著区;林地斑块内β多样性变化剧烈,林缘处的群落相异系数(CD)、Cody指数都最大,共有度指数(CP)最小,CD、Cody与CP成反比。     

A Study on Water Exchange in Root Zone of ProtectiveForest Ecosystem in Loess Area

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Plant diversity of secondary forests in response to anthropogenic disturbance levels in montane regions of northeastern China

The effects of anthropogenic disturbances on forest structure and plant diversity of secondary forest ecosystems were evaluated based on the classification by site factors in the montane regions of northeastern China. Forty-five sample plots containing 720 sub-plots of overstory species (8 m × 8 m), 1,440 quadrats of understory species (2 m × 2 m), and 1,440 quadrats of herbaceous layer species (1 m × 1 m) were clustered into five groups (G1, G2, G3, G4 and G5) by site variables with Hierarchical Cluster Analysis. Meanwhile, the disturbance levels corresponding to the five groups were determined according to the factors influencing human disturbances (D0-G2, D1-G1, D2-G3, D3-G5, and D4-G4). Species diversities of overstory, understory, herbaceous layer and overall species were evaluated using species number, Margalef index, Pielou index, Shannon–Wiener index, and Simpson index; and β-diversities (Whittaker index, Cody index). Basal area of stands exhibited a decreasing trend along the disturbance level due to a gradual increase in the extraction of timber by the human disturbances. The indices of species diversity suggested that overstory and understory species were distributed evenly among the groups or disturbance levels. There were no absolutely dominant tree species in the secondary forest ecosystems. The differences in site factors and the current disturbance intensities were not intense enough to lead to loose changes in overstory and understory species. The species diversity indices exhibited the maximum values at D3 (G5) for herbaceous layer species; this may suggest that the current disturbance intensities were intense enough to lead the changes of herbaceous layer species. Three rare and endangered species (Juglans mandshurica, Fraxinus mandshurica and Acanthopanax senticosus) were found within the secondary forests. These rare and endangered species appeared in each clustered group or disturbance level, which suggested that the current disturbance intensity in the study area was not strong enough to influence the distribution of rare and endangered species. The current disturbances in the secondary forests may not lead to a decrease in stability and complexity of the overstory and understory species, but the higher disturbance level may be intense enough to change the habitat fitness for the herbaceous species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized authors.