山地流域土地利用时空演变的地形梯度特征——以乌江北源为例

地形因子是丘陵山区土地利用空间分布格局的重要影响因素之一,对土地的利用方式和空间格局有着直接作用。以乌江北源2000年、2005年和2010年Landsat TM/ETM遥感影像为数据源,采用高程、坡度、地形位指数3个指标,分析了山地流域土地利用时空演变的地形梯度特征。结果表明:（1）2000—2010年,林地、建设用地和水域用地面积增加,耕地和草地面积减少。土地利用类型以林地和耕地为主,反映了山地流域土地利用结构特点;（2）研究区土地利用类型的地形梯度特征明显。耕地、建设用地、水域用地在低地形梯度上有明显分布优势。林地、未利用地分布优势在高地形梯度上;（3）耕地、建设用地优势分布主要受坡度梯度的影响,高程梯度决定了水域用地的分布,这与其他平原、丘陵地区有所不同。地形因素是山地流域土地利用结构演变的决定性因素,其他社会、经济、人文因素都对该区域土地利用格局的转变起到推动作用。在对山地流域土地开发利用过程中,应兼顾生态效益和社会经济效益,保障河流源区生态经济的持续发展。     

不同林龄柠条锦鸡儿土壤有效磷的变化

研究柠条锦鸡儿(Caragana Microphylla Lam.)林地不同土层深度土壤有效磷的变化规律,为进一步深入研究北方农牧交错带土壤性质及地区植被建设提供依据。笔者通过野外调查和数据处理,对赤峰市敖汉旗风沙土区不同林龄(5、11、17、23、29年)柠条锦鸡儿不同土层的土壤有效磷进行了分析。研究表明:相同林龄不同立地条件的土壤有效磷含量随土层厚度的增加呈现减小的趋势;相同林龄不同立地条件的土壤有效磷含量大小表现为丘间低地阴坡阳坡;相同立地条件不同林龄的土壤有效磷含量随林龄的增加而增加。柠条锦鸡儿的种植有利于土壤性质向良性方向发展。     

基于SRTM的地形因子提取方法研究

地形是影响土壤侵蚀的重要因子,在侵蚀估算模型中常用坡度和坡长(LS)来衡量,在大区域上常基于数字高程模型(DEM)提取.SRTM作为大区域尺度上质量高、易获取的高程数据,在全球土壤侵蚀评价中得到广泛应用.但现有地形因子提取算法要求高程和栅格单元的单位(通常为m)一致,需对SRTM进行坐标变换才能使用.针对大区域上SRT...     

Characteristics of phosphorus uptake kinetics of poinsettia and marigold

In a previous experiment it has been found that maximum uptake rate (I_max), Michaelis constant (K_m), and minimum nutrient concentration (C_min) as plant physiological characteristics may be important for phosphorus (P) uptake in peat-substrate. Thus, variation of P uptake parameters was evaluated with a series of depletion studies for poinsettia (Euphorbia pulcherrima) and marigold (Tagetes patula) under fluctuating climatic conditions and different developmental stages.     

Changes in fox squirrel anti-predator behaviors across the urban–rural gradient

Predator stimuli created by humans in the urban environment may alter animals’ anti-predator behaviors. I hypothesized that habituation would cause anti-predator behaviors to decrease in urban settings in response to humans. Additionally, I hypothesized that populations habituated to humans would show reduced responses to other predator stimuli. I observed three populations of squirrels (urban, suburban and rural) responses to human approaches, red-tailed hawk vocalizations (Buteo jamaicensis) and coyote (Canis latrans) vocalizations. Mahalanobis distances of anti-predator behaviors in response to human approaches were consistent with the urban–rural gradient. Flight initiation distances (X ² = 26.33, df = 2, P < 0.001) and amount of time dedicated to anti-predator behavior (X ² = 10.94, df = 2, P = 0.004) in response to human approaches were also consistent with the urban–rural gradient. Supporting the habituation hypothesis, naive juvenile squirrels increased flight initiation distances (X ² = 35.89, df = 1, P < 0.001) and time dedicated to anti-predator behaviors (X ² = 9.46, df = 1, P = 0.002) relative to adult squirrels in the same urban environment. Time dedicated to anti-predator behaviors differed among all three sites in response to both coyote (X ² = 9.83, df = 2, P = 0.007) and hawk (X ² = 6.50, df = 2, P = 0.035) vocalizations. Responses to both vocalizations on rural sites (coyote = 45%, hawk = 55%) greater than twice that found on the urban sites (coyote = 11%, hawk = 20%). This is possibly the first case of a transfer of habituation demonstrated under field conditions.     

遮荫处理对侧柏种子萌发的影响

在不同光照梯度55.44%自然全光照(Natural sonlight,NS)、21.12%NS、3.47%NS 和0.86%NS的人工遮荫条件下,研究了侧柏(Platycladus orientalis)种子萌发的特点.结果表明:4个光照梯度处理的侧柏种子的萌发率分别为68.9%、82.2%、44.4%和42.2%;随着光照强度的减弱,种子萌发进程减慢;萌发指数和幼苗活力指数均在21.12%NS处理最大,分别为1.89和770.8.     

不同基质及生根剂浓度对五种园林植物扦插生根的影响

以5种园林植物为材料,进行不同基质与不同生根剂浓度对植物扦插生根的比较研究.结果表明:月季、大叶黄杨最适宜的基质是河沙,小叶女贞、八角金盘最适宜的基质是珍珠岩,鹅掌柴最适宜的基质是混合基质.月季、大叶黄杨最合适的生根剂浓度为3 000 mg/kg,小叶女贞最合适的生根剂浓度为5000mg/kg,八角金盘、鹅掌柴最合适的生根剂浓度为1000mg/kg.     

不同基质配比对黄瓜幼苗生长的影响

为提高农业废弃物利用率,减少环境污染,以黄瓜品种津绿3号为试验材料,研究牛粪、花生壳、草炭、蛭石、珍珠岩等不同基质成分配比对黄瓜幼苗生长及光合作用的影响。结果表明:不同基质配比对黄瓜的生长有显著影响。其中C处理(花生壳︰蛭石︰珍珠岩体积比7︰3︰3)效果最好,育苗40 d后,黄瓜幼苗叶片大而肥厚,叶色浓绿,株高、茎粗、地上和地下部分鲜质量均达到了最大值,分别为17.21 cm、5.4 mm、6.82 g和2.26 g,分别是对照的2.1倍、1.5倍、2.7倍和1.1倍;光合速率为13.95μmol/(m2·s),比A处理稍低,但无显著差异,且显著高于其他处理。综合各项指标,C处理成本低,原料来源方便,建议在黄瓜育苗中应用。     

Review on the roles and effects of growing media on plant performance in green roofs in world climates

Growing media (substrate) is a fundamental part of a green roof, providing water, nutrients and support to plants. However, little research has reviewed how it affects plant performances in different climatic regions. This study aims to analyse published research on green roof growing medium across world’s climate zones. Findings are structured according to Köppen–Geiger climate classification, aiming to investigate the prevalence of research conducted in different climate zones. Results from full-scale studies and laboratory or greenhouse experiments were reviewed. The later were included as they provide systematic knowledge on the effect of individual factors on system performances although cannot provide climate specific information. Studies discussed effects of major substrate components and depths on plant survival and establishment using standard test procedures. Results showed that most research in the subject were in temperate (group C climate classification), continental (group D) and dry climates (group B), respectively. Considerable number of investigations was conducted in controlled laboratory or greenhouse environments. Based on the results, future green roof research and guidelines should consider climate specifications of the region in designing growing medium, depths and attribute of green roof substrates in order to ensure enhanced plant performance. Especially, for more fragile but less investigated dry climate, considerations should be made to tackle heat fluctuations and drought stress by enhancing water holding capacity and thermal isolation of the substrate. To move forward, sustainable building solutions as a part of future urban forms, climate-adaptive green roof systems should be included into future research, practice and guidelines.     

多尺度DEM提取河流比降的对比分析

研究旨在用DEM计算河流比降,分析DEM分辨率与阈值对比降的影响,并提取最佳分辨率与最佳阈值。以延河流域的ASTER GDEM和SRTM3 DEM为原始数据源,利用Arc GIS分别提取60、150、200、300 m分辨率下延河流域的主河道,并据此计算流域平均比降。结果表明:延河的平均比降为3.39‰;DEM分辨率与汇流阈值对比降影响较大,当DEM分辨率小于150 m时,比降随阈值增大而减少;DEM分辨率大于150 m,比降逐步增大。延河流域河流比降分析的DEM分辨率不宜超过150 m,其中DEM分辨率为90 m时,计算的比降结果较为符合延河流域实际情况;DEM分辨率为30、60、90、150、200、300 m时,计算比降的最佳阈值分别为65000、60000、30000、70000、40000、20000;利用85%的主河道折线段信息,进行比降计算,其结果接近真实值。研究实现了基于DEM的河流比降计算,有助于DEM在水文学等流域的应用。