干旱区绿洲城市草坪草截留特征研究

以干旱区绿洲城市草坪草为试材,进行人工降雨截留试验,综合运用统计分析和模型回归分析方法,研究了降雨时间、降雨强度和植被覆盖度对草坪草截留的影响。结果表明:不同降雨强度下,随着降雨时间的持续,截留量先是快速增长,随后趋向稳定;建立截留量和降雨时间拟合方程,多项式方程模拟最好;截留量与植被覆盖度呈正相关关系,截留量随降雨强度的增大而减小;通过多元回归分析,建立基于降雨时间、降雨强度和植被覆盖度为参数的草坪草截留量模型,模拟效果显著。     

森林植被林冠截留降水模型初探

林冠层是大气降水进入森林后的第一个作用面,其对大气降水的分配直接影响水分在森林生态系统中的整个循环过程,国内外有关学者为深入研究林冠截留降水规律,模拟出了诸多林冠截留降雨模型,本文并对这些截留模型研究进行了总结并提出改进方法。     

不同农田土壤压实层深度对水分入渗和分布的影响

以2种土壤包括耕层土(SCK)和压实土(NCK)为研究对象,设置了3个土壤压实层深度5 cm(T1)、10 cm(T2)和15 cm(T3)进行一维入渗土柱模拟试验,研究了水分入渗过程和水分剖面分布情况及土壤不同压实层深度对水分入渗的影响,以期为田间耕作保墒和节水灌溉提供参考依据.结果 表明:入渗过程中,初始入渗率较高,后呈幂函数式下降直至稳定入渗率,入渗相同深度时,SCK处理的入渗率显著大于NCK处理,其它处理随着压实层深度的增大,入渗率偏大,但达到稳定入渗率时,随压实深度的加深而逐渐减小;累积入渗量呈先快速增长后稳定增长的趋势,入渗相同深度时,SCK处理的累积入渗量显著大于NCK处理,入渗初期,相同入渗深度,累积入渗量随压实层深度的加深而增大,如水分入渗至5 cm时,T1、T2和T3累积入渗量分别为13.7、13.8、14.1 cm,在入渗后期,相同入渗深度,累积入渗量随压实层深度的增加而减少,如当水分入渗至15～20 cm时,以上处理的累积入渗量则分别为4.7、4.3、4.1 cm;入渗完成后土壤含水量随土层深度的加深而减小,相对于耕层土对照(SCK),压实层的存在显著提高了上层土壤的含水量,并且随着压实土层深度的增加,促进了水分在上层的储存.     

基于叶面积指数分析毛竹林林冠生态水文效应

对不同月份叶面积指数时空分布及其对林冠截留、透流及干流的影响进行观测研究。结果表明:2～8月份叶面积指数一直在递增,9～1月份叶面积指数一直在递减,8月份叶面积指数达最大值7.5,2月份叶面积指数达最小值为3.1。各月林冠截留、干流与叶面积指数呈正相关性,透流与叶面积指数呈负相关性。当降雨量小时,随叶面积指数的递增则林冠截留、干流递增缓慢;当降雨量和降雨强度较大时,随叶面积指数的递增则林冠截留、干流递增加快。     

丘陵缓坡山地‘金果’猕猴桃耗水规律研究

以五年生‘金果’猕猴桃为试材，采用智能Insentek测定土壤墒值，分析果园气象与物候期相关性，与产量构建水分生产函数，探明丘陵缓坡山地猕猴桃不同物候期水分动态循环及植株耗水规律，以期为果园精准节水灌溉管理提供参考依据。结果表明：‘金果’猕猴桃全物候期为211 d,试验年降雨量属于丰年，物候期中果实膨大期最长，其降雨量达1 214.89 mm,且有效降雨量占总量的73.68%;果园土壤10～30 cm含水量变化幅度较大，土层越深土壤含水量越高，晴天白天土壤含水量高于夜间，呈现阶梯状下降趋势；物候期ET峰值出现在5月，日耗水量达43.11 mm,日耗水量高水平持续到果实膨大后期，且该时期需水模数最高为0.74;参考作物腾发量物候期呈先升高后下降趋势，峰值出现在7—8月，作物系数物候期内呈先减小后增大趋势，且值均大于1;猕猴桃产量与耗水量拟合方程优度大于临界值，可作为水分生产函数使用，且随耗水量增大产量呈先增加后减少趋势。猕猴桃果实膨大期持续时间长、耗水量大，虽降雨总量占年降雨总量比率高，但出现了季节性干旱胁迫，是猕猴桃高产灌溉补水的关键时期。     

PEG-6000模拟干旱胁迫对冷季型草坪种子萌发特性影响

在室内采用不同浓度的聚乙二醇(PEG-6000)模拟干旱胁迫的方法对3种冷季型草坪草萌发期的抗旱性进行比较。结果表明:不同强度PEG-6000胁迫对冷季型草坪草种子萌发均有一定的抑制作用,并随胁迫强度的增加下降明显。不同品种草坪草对于PEG-6000胁迫的适应有差异。3种抗旱性强弱依次为:高羊茅多年生黑麦草匍匐剪股颖。     

不同叶面积指数下截留、透流和干流动态过程研究

通过对长江三角洲城市森林生态定位站的北亚热带次生毛竹林林冠降雨再分配的观测研究,探讨了不同叶面积指数下场降雨林冠截留、透流和干流动态过程。结果表明:叶面积指数对小雨时林冠截留过程影响不大,对中、大雨时林冠截留过程影响显著;对透流雨和干流的影响主要表现在波峰值的大小和峰值形成时间上的差异;随叶面积指数的递增,则透流雨的峰值减小,形成时间滞后,而干流峰值显著增加,形成时间超前。     

PEG诱导水分胁迫对柑桔幼苗细胞质膜透性及脯氨酸含量的影响

柑桔叶片相对含水量(RWC)随聚乙二醇(PEG)处理渗透势的降低而依次降低;叶片细胞质膜透性随PEG处理浓度的增加而依次增大;幼苗叶片累积脯氨酸的数量随水分胁迫时间和强度递增。     

南疆矮砧密植滴灌苹果生长、耗水及产量研究

【目的】提高南疆苹果水分利用率和制定高产高效的灌溉模式。【方法】2019—2020年以5年生矮砧密植皇家嘎拉为研究对象,设置W1(13.5 mm)、W2(18 mm)、W3(22.5 mm)、W4(27 mm)及W5(31.5 mm)5个灌水定额,研究不同灌水定额对苹果生长、耗水特性、产量及水分利用效率的影响。【结果】苹果新梢长度随灌水定额的增加而增加,达显著水平(p 0.05);各灌水处理间耗水量、耗水强度及作物系数均随灌水定额的增加而增大,呈显著差异性(p 0.05),且随生育期推进,耗水量、耗水强度及作物系数呈单峰曲线,果实膨大期达到峰值;苹果产量以W4处理最高,W3处理次之,两年均值分别为30 540.8 kg·hm-2和31 144 kg·hm-2,两处理产量无显著差异,水分利用效率以W1处理最高,W4和W3处理较高,两年均值分别为6.59 kg·m-3、6.46 kg·m-3和5.49 kg·m-3,灌溉水利用效率与水分利用效率变化规律一致,并通过拟合分析可知,水分利用效率和灌溉水利用效率随灌水量增加呈下降趋势,产量、WUE和IWUE与灌水量拟合曲线交点所对应的灌水量区间为400～500 mm。【结论】综合苹果生长、耗水、产量及水分利用效率分析可知,生育期灌水定额为22.5 mm,灌水次数21次为南疆矮砧密植苹果适宜的灌溉模式。     

不同灌水次数对温室黄瓜耗水规律及水分利用效率的影响

在膜下滴灌条件下.灌溉定额为600mm时,研究了不同灌水次数对日光温室黄瓜耗水规律及水分利用效率的变化规律.研究结果表明,灌水次数达18次时,黄瓜耗水强度整体随着生育期的延后逐渐增大,在结果盛期达到最大,随后逐渐下降;土壤贮水量随灌水量的增加而增加,而土壤水分的消耗则随着灌水量的增加而明显减少;灌水15～18次,既能满...     

Quantifying urban tree canopy interception in the southeastern United States

Urban stormwater is a major contributor to surface water degradation in the United States, prompting cities to invest in ways to naturally capture, store, and slowly release runoff through green infrastructure (GI). An often overlooked, yet integral, component of GI is urban tree canopy, which functions as GI through the process of rainfall interception (i.e., rainfall captured and stored within the canopy prior to returning to the atmosphere via evaporation). Nine trees from three native species commonly found in urban areas in the southeastern United States were studied in three parks in Knoxville, TN, USA to quantify interception. Throughfall (rainfall that passes through the canopy) and stemflow (rainfall that travels down the trunk) data were collected with continuous measurements by a network of automatic rain gauges positioned underneath each tree canopy. Data were collected from January 2018 to May 2019 which resulted in 98 storm events collected for each red maple (Acer rubrum) and willow oak (Quercus phellos), and 97 storm events collected for each white pine (Pinus strobus). Annually, red maples, white pines, and willow oaks intercepted 24.4%, 52.4%, and 33.2% of gross throughfall, respectively. Seasonally, white pines performed the most consistently with interception varying only from 49.2% to 57.0% between seasons compared to an interception range of 13.2–39.7% and 17.5–54.2% for red maples and willow oaks, respectively. Results demonstrated the effect of event duration, rainfall intensity, and seasonality on the interception potential of each species. Overall, these observations are a step toward allowing the storage capacity of urban trees to be properly credited as part of efforts to reduce stormwater runoff.     

The effect of street trees and amenity grass on urban surface water runoff in Manchester,UK

It is well known that the process of urbanization alters the hydrological performance of an area, reducing the ability of urban areas to cope with heavy rainfall events. Previous investigations into the role that trees can play in reducing surface runoff have suggested they have low impact at a city wide scale, though these studies have often only considered the interception value of trees.This study assessed the impact of trees upon urban surface water runoff by measuring the runoff from 9 m² plots covered by grass, asphalt, and asphalt with a tree planted in the centre. It was found that, while grass almost totally eliminated surface runoff, trees and their associated tree pits, reduced runoff from asphalt by as much as 62%. The reduction was more than interception alone could have produced, and relative to the canopy area was much more than estimated by many previous studies. This was probably because of infiltration into the tree pit, which would considerably increase the value of urban trees in reducing surface water runoff.     

Fine-scale vegetation patches decline in size and cover with increasing rainfall in Australian savannas

Fine-scale vegetation patches (<5 m in width) are critically important in many landscapes because they function to obstruct surface flows of water and wind. These obstructions increase the infiltration of runoff and the capture of nutrients in runoff sediments and in wind-blown soil and litter. The importance of redistribution of runoff into runon patches from spaces between patches (fetches) is likely to be greater in drier than in wetter environments. In this paper we examine the hypothesis that the ratio of fetch to patch decreases as rainfall increases, and that this trend will be most evident on intermediate-textured soils because these soils are more prone to runoff. We measured fine-scale patches on 38 sites with sand, loam or clay soils. Sites were located along a 1000-mm rainfall gradient in the savannas of northern Australia. The width and intercept length of patches and the fetch between patches was measuring along line transects of 100–120 m oriented down slope. We found that the ratio of fetch to patch area did not decrease with decreasing rainfall, but increased on both sand and loam soils. This result was because with increasing rainfall mean spacing between patches disproportionally increased while mean patch size and cover declined. The cover of patches was negatively correlated with tree canopy cover, which significantly increased with rainfall. This negative correlation suggests that in higher rainfall savannas the size and spacing of ground-layer patches is controlled by the tree layer, and that as rainfall decreases this control decreases and runoff-runon processes increasingly structure the landscape. For savannas on clay soils these trends were not significant except that on the highest rainfall sites the cover of ground-layer patches was nearly 100% while trees were absent.     

Rainfall interception and stem flow by eucalypt street trees – The impacts of canopy density and bark type

Understanding how trees influence water movement in an urban landscape is important because in an ‘engineered xeriscape’ small changes in rainfall frequency or magnitude have significant implications to plant water availability and mortality at one extreme, and stormwater runoff and flooding at the other. This study relates direct measures of tree canopy interception and discusses their implication for catchment hydrology in different urban landscape contexts. We measured canopy throughfall and stemflow under two eucalypt tree species in an urban street setting over a continuous five month period. Eucalyptus nicholii has a dense canopy and rough bark, whereas Eucalyptus saligna has a less-dense canopy and smooth bark. E. nicholii, with the greater plant area index, intercepted more of the smaller rainfall events, such that 44% of annual rainfall was intercepted as compared to 29% for the less dense E. saligna canopy (2010). Stemflow was less in amount and frequency for the rough barked E. nicholii as compared to the smooth barked E. saligna. However, annual estimates of stemflow to the ground surface for even the smooth barked E. saligna would only offset approximately 10 mm of the 200 mm intercepted by its canopy (2010).Tree canopy and bark characteristics should be considered when planting in pervious green space, or impervious streetscapes, because of their profound impact upon tree and surrounding water availability, soil water recharge or runoff. This study provides an evidence base for tree canopy impacts upon urban catchment hydrology, and suggests that rainfall and runoff reductions of up to 20% are quite possible in impervious streetscapes. Street tree canopies can function as a cost-effective compliment to water sensitive urban design for stormwater reduction benefits.     

Forest gradient response in Sierran landscapes: the physical template

Vegetation pattern on landscapes is the manifestation of physical gradients, biotic response to these gradients, and disturbances. Here we focus on the physical template as it governs the distribution of mixed-conifer forests in California's Sierra Nevada. We extended a forest simulation model to examine montane environmental gradients, emphasizing factors affecting the water balance in these summer-dry landscapes. The model simulates the soil moisture regime in terms of the interaction of water supply and demand: supply depends on precipitation and water storage, while evapotranspirational demand varies with solar radiation and temperature. The forest cover itself can affect the water balance via canopy interception and evapotranspiration. We simulated Sierran forests as slope facets, defined as gridded stands of homogeneous topographic exposure, and verified simulated gradient response against sample quadrats distributed across Sequoia National Park. We then performed a modified sensitivity analysis of abiotic factors governing the physical gradient. Importantly, the model's sensitivity to temperature, precipitation, and soil depth varies considerably over the physical template, particularly relative to elevation. The physical drivers of the water balance have characteristic spatial scales that differ by orders of magnitude. Across large spatial extents, temperature and precipitation as defined by elevation primarily govern the location of the mixed conifer zone. If the analysis is constrained to elevations within the mixed-conifer zone, local topography comes into play as it influences drainage. Soil depth varies considerably at all measured scales, and is especially dominant at fine (within-stand) scales. Physical site variables can influence soil moisture deficit either by affecting water supply or water demand; these effects have qualitatively different implications for forest response. These results have clear implications about purely inferential approaches to gradient analysis, and bear strongly on our ability to use correlative approaches in assessing the potential responses of montane forests to anthropogenic climatic change.     

Interception of moving organisms: influences of patch shape,size, and orientation on community structure

Island biogeographers have predicted that in oceanic systems, oblong islands oriented perpendicular to the dispersal paths of organisms should intercept more species and individuals than (1) circular islands of the same size, and (2) oblong islands of equal area oriented parallel to the direction of travel. Landscape ecologists expect similar relations with habitat patches in a terrestrial matrix. Yet in neither situation is there adequate empirical information to permit conclusions about the prevalence of such effects. To test the hypothesis that intercept-related patch variables influence community structure on the landscape scale, we studied relations between the richness and abundance of cavity-nesting birds and patch shape, size, and orientation relative to a northerly migration path. The influences of other patch features on nest abundances were removed analytically. Multiple regression indicated that the mean and total number of nesting species, and nest abundances for migrants were significantly associated with patch orientation or a patch area x orientation interaction, but not patch shape. Nest abundances for permanent residents were not associated with patch shape or orientation, although area effects, possibly reflecting dispersal interception, were evident. These results are consistent with the hypothesis that stochastic interception of migrating or dispersing organisms influences patch community structure. In addition to richness and abundance effects apparent in this analysis, the sex ratio, age structure, growth rate, social structure, and genetic features of patch populations may also be influenced. The interception of moving organisms by patches may thus be a key factor influencing population and community persistence in reserves. If so, landscape structure could be manipulated to maximize the interception of dispersing or migrating organisms, or minimize it if the effects are undesirable.     

渭北旱塬苹果园土壤水分环境效应

塬面苹果园、农田和其它主要土地利用方式的比较研究表明,苹果园的水分环境效应表现为土壤高入渗率、降雨低产流率和强烈的蒸腾耗水作用形成的土壤低湿层,使土壤水库对干旱的调节作用丧失,导致苹果产量随年际降雨呈现较大波动。随着苹果种植面积的扩大,这种水分环境效应将加强土壤、植物、大气间的水分小循环,削弱降雨转化为地表水和地下水的比例,最终影响区域水资源的数量和果业的持续发展。     

Integrated vegetation designs for enhancing water retention and recycling in agroecosystems

Long term studies have shown strong links between vegetation clearing and rainfall declines and more intense droughts. Many agroecosystems are exposed to more extreme weather and further declines in rainfall under climate change unless adaptations increase the retention of water in landscapes, and its recycling back to the lower atmosphere. Vegetation systems provide vital feedbacks to mechanisms that underpin water vapour recycling between micro- and meso-scales. Various heterogeneous forms of vegetation can help generate atmospheric conditions conducive to precipitation, and therefore, increase the resilience of agroecosystems to drought and climatic extremes. The aim of this paper is to demonstrate how vegetation can be designed for agroecosystems to enhance recycling of water vapour to the atmosphere through the regulation of surface water and wind, and heat fluxes. The structure of the paper revolves around five functions of integrated vegetation designs that can help underpin the restoration of water recycling through enhanced retention of stormwater, protection from wind, moistening and cooling the landscape, production of plant litter, and contribution toward regional scale climate and catchment functioning. We also present two supplementary functions relevant to land and natural resource managers which may also be integrated using these designs.