冀西北高原不同植被的土壤水分动态变化研究

冀西北高原为高寒半干旱地区,降水是此地区土壤水分的唯一给源,研究土壤水分的动态变化对高效利用降雨有至关重要的作用。研究采用定点观测的方法,对不同植被土壤含水量的动态变化进行了比较研究。结果表明,3种植被生长期内不同土层土壤水分变化存在差异。生长前期,3种植被0￣30cm土层土壤含水量,农田耕翻地最高,水分条件最好,人工草地与退耕还林地互有高低,30￣60cm土层退耕还林地最高,人工草地最少。生长前期,农田耕翻地表层土壤水分较好,能满足春季作物生长要求。生长中期,0￣30cm土层农田耕翻地最低,人工草地与退耕还林地互有高低。30￣60cm土层农田耕翻地最高,人工草地最低。生长后期,0￣60cm土层农田耕翻地土壤含水量最高;人工草地土壤含水量与退耕还林地相比较,0￣40cm土层差异不大,40￣60cm土层退耕还林地高于人工草地。     

黄土丘陵区达乌里胡枝子人工草地生产力与土壤水分特征研究

对黄土丘陵区川地和坡地达乌里胡枝子(Lespedeza davurica)人工草地生产力与土壤水分状况的季节变化动态进行比较研究。结果表明,川地达乌里胡枝子人工草地生产力显著高于山坡地,单位面积干重约为山坡地的3倍。不同立地下达乌里胡枝子耔实部分约占地上部分最终生物量得到30%~40%。川地与山地叶片水分利用效率相近,因而川地达乌里胡枝子在维持高生产力情况下,260cm以下土壤层出现雨季期间及休闲期后均不能够恢复的稳定低湿层。     

植物篱模式下土壤水分特征变化研究

通过对不同土地利用类型下土壤水分空间变化进行研究,结果表明:土壤含水量与土壤容重呈负相关,相关系数为-0.095;不同土层土壤水分变化呈中等变异性,40-60 cm土壤水分变异性达0.989;不同土地利用类型下,土壤含水量差异显著(P>0.05),植物篱不种植农作物(T3)土壤含水量最高(21.25),其次为草地(T4)(20.62),而受人类活动严重干扰下的植物篱+农作物(T1)、农作物(T2)土壤含水量最低;T2田间持水量随深度增加呈递减趋势,其余利用类型土地田间持水量在0～40 cm土层呈下降规律,至40 cm附近为最低值,然后随深度进一步增加呈缓慢升高趋势.     

内陆沙区丘间地土壤水分时空变化分析

土壤水分是沙漠沙生植物成活和生长的最主要因子,不同的地形类型下土壤水分空间分布差异明显。利用智能中子水分仪定时测定土壤水分的方法,测定并分析了巴丹吉林沙漠东南缘不同地形下0~200 cm深土壤共10 个层次的水分时空变化特征。结果表明：巴丹吉林沙漠东南缘土壤水分空间分布具有一定规律性,土壤水分丘间地下部＞丘间地中部＞丘间地上部＞沙丘上中下部,沙丘上中下部的年季变化不大,总体处于平稳状态;丘间地土壤水分变化较其他地形大,春季土壤水分不是很丰富,土壤水分波动不大;夏季受植物生长、太阳蒸腾和降雨的影响,土壤水分时空变化差异明显,20 cm以上水分增多,40~180 cm表现为水分变化活跃层;秋季水分整体含量增加。巴丹吉林沙漠东南缘不同地形下土壤水分时空变化研究为大规模的沙漠生态平衡治理、生态系统人工修复以及沙区可持续发展等提供了科学的依据。     

宁南黄土丘陵区不同生态恢复与重建中的土壤水分变化研究

针对宁南黄土丘陵区存在的生态脆弱、环境恶化的突出问题,对黄土丘陵区不同生态恢复过程中的土壤水分变化进行了研究。研究结果表明：在退化山地的植被恢复过程中, 0~60cm土层,土壤水分含量随恢复年限的增长而增加,在60cm土层以下,土壤含水量随着退耕年限的不断增长不断减小;对于不同恢复方式的土壤水分含量,88542水平沟>人工草地>鱼鳞坑>天然草地;对于不同植被类型的土壤水分含量,草地>灌木地>林地;对于不同地形的土壤水分含量,阴坡>半阴坡>阳坡,坡下部>坡中部>坡上部,并且随着坡度的不断增加,土壤水分含量不断减小。     

不同土地利用方式下土壤水分动态及对降水的响应——以青海省互助县浅山旱地为例

摸清青海旱作农业区土壤水分动态变化对保障农作物产量形成和粮食生产安全具有重要意义。采用野外采样结合统计学方法,探究青海互助浅山旱地不同土地利用方式下土壤水分季节动态、垂直剖面特征及土壤水分对降水的响应。结果表明：（1）不同土地利用方式下耕作层(0~30 cm)土壤含水量季节动态存在明显的干湿周期变化,土地利用方式对土壤水分季节变化影响不显著(P>0.05),降水事件、降水量级是影响耕作层(0~30 cm)土壤含水量季节动态的主导驱动力;（2）0~30 cm土层是雨养耕作层,典型土壤含水期分为干旱期、湿润期、常态期和过渡期,土壤干旱发生一般由表层开始,随着土壤水分耗损加重土壤干旱逐渐向深层土壤延伸;（3）4种土地利用方式的土壤水分动态变化与前期累计降水量变化基本一致,亚表层(10~20 cm)和深层(20~30 cm)土壤含水量与前期累计降水量极显著相关性(P<0.01)。因此,在干旱事件频繁的青海旱作区发展“浅埋滴灌技术”是寻求土壤供水平衡的有效路径。     

偏旱年休闲期施肥覆盖对旱地小麦播前土壤水分的影响及其与产量的相关分析

为了改善旱地小麦的土壤水分状况,提高旱地小麦的产量,采用大田试验,研究了休闲期施肥覆盖对播前土壤水分含量的影响及其与产量的关系。结果表明：休闲期施有机肥提高了休闲期降雨补给率,但不显著,休闲期地膜覆盖与纸覆盖均可显著提高休闲期降雨补给率。休闲期施有机肥、覆盖均可提高播前0~100 cm、100~200 cm、0~300 cm土层土壤含水量,施肥与覆盖对播前200~300 cm土层土壤含水量的影响较小。结果还表明：地膜覆盖对播前不同土层土壤含水量的增加效果均大于纸覆盖,施肥可增大地膜覆盖对土壤水分的影响范围,在有机肥条件下地膜覆盖可增加40~160 cm各土层土壤含水量,不施肥条件下可增加40~140 cm各土层土壤含水量。休闲期施肥、覆盖均可显著增产。相关分析表明：播前0~100 cm、100~200 cm、0~300 cm土壤含水量与旱地小麦穗粒数、产量均显著正相关,在20~ 140 cm各土层土壤含水量与产量和穗粒数的相关性均达到显著或极显著水平。总之,休闲期施肥与覆盖均有利于旱地小麦播前土壤水分状况的改善和产量的提高,且以有机肥条件下地膜覆盖效果最好。     

朔州市玉米生长季土壤储水量动态研究

为了掌握朔州市玉米生长季土壤储水量变化规律,提高本地区农业种植土壤水分利用率。作者利用1995—2015年山西省朔州市玉米生长季土壤湿度及相关气象要素数据,在研究了土壤储水量与相关气象因子的相关性、土壤储水量旬变化、土壤储水量垂直变化后,分析了朔州市玉米生长季土壤储水量变化规律。结果显示：朔州市玉米生长季,降水量变异系数大于15%,降水量每增加1 mm,土壤储水量增加约0.2 mm。10、20 cm土壤层中,降水量、气温、相对湿度、蒸发等气象因子与土壤储水量的相关性达到60%以上,30 cm以上各层的复相关系数显著下降;0~50 cm土壤储水量旬变化曲线可分为,旱季土壤水分快速消耗期、雨季降水补充期、秋季土壤水分平稳期3个阶段;玉米生长季（5—9月）各月的土壤水分垂直规律相似,0~20 cm土壤储水量变异系数都在20%以上,气象因子对该层的影响较大,30~50 cm变异系数在20%以下,降水无法渗入土壤深层,其他气象要素对深层土壤的影响较小,导其土壤储水量变异系数较小。     

放牧对草地土壤含水量与容重及地下生物量的影响

摘要：对滇东北人工草地不同放牧压下土壤含水量、土壤容重和地下生物量的变化进行研究,结果表明：（1）放牧利用对主要影响表层（0-5cm）土壤含水量和土壤容重,表层土壤含水量随着放牧压的增大而减小,土壤容重则以GPI0.76最大,GPI0.57下土壤容重随放牧时间波动较小,说明适度的放牧利用有利于稳定土壤结构;（2）草地植被地下生物量主要分布在0-10cm土层,占0-30cm土层的64-74%,地下生物量随放牧压增加而减少。     

不同灌水次数对日光温室番茄土壤水分动态变化规律的影响

根据番茄在整个生育期内土壤水分变化特点,充分利用有限水资源,调节土壤水分状况。在相同灌水量条件下,利用时域反射仪研究不同灌水次数对土壤含水量的变化的影响。结果表明：各处理土壤贮水量变化的深度一般在0~100 cm内,尤其在0~60 cm变化最为激烈,100~180 cm范围内土壤水分变化不明显。按土壤水分运移规律进行划分,将土壤水分的垂直变化分为4层,即活跃层（0~30 cm）、次活跃层（30~60 cm）、缓变层（60~100 cm）和均稳层（100~180 cm）。灌水次数越少对土壤水分消耗的越多,易造成活跃层和次活跃层土壤水分亏缺;反之,则土壤水分消耗较少。     

Pasture restoration improvement methods for temperate degraded pastures and consequences of the climatic seasonality on soil–pasture complex

Short persistence of renovated pastures is a major problem for pastoral production systems. Pasture species establishment, species performance and persistency and their relationships with soil–water attributes following pasture improvement methods were evaluated over two years. Fertilised naturalised pasture (FNP), non-fertilised naturalised pasture (NFNP), Lolium perenne–Trifolium repens cultivated pasture (CP), L. perenne–T. repens direct-drilled pasture (DP), and Bromus valdivianus, Holcus lanatus, Dactylis glomerata, L. perenne and T. repens direct-drilled pasture (DDP) were established as a randomised complete block design. Pastures were limed, fertilised and sheep-grazed. Plant growth compensatory mechanisms, by decreasing tiller number and increasing tiller size, equalised pasture yield during the establishment. In both years, the improved pastures yield was greater than that of NFNP. In the second year, DDP and FNP reached the higher pasture growth rate, with a seasonality diminishment. During the second summer, soil matrix potential at 0–20 cm soil profile exceeded the permanent wilting point, resulting in the pasture growth rate of NFNP and the sown pastures ranging from 0.0 to 3.6 kg DM/ha per day, while for FNP, it was 17.8 kg DM/ha per day. Sown species, fast-growing species spontaneous colonisation and growth were all stimulated in the improved pastures over species that tolerate stress, improving agronomical and ecological pasture features.     

微灌技术对环湖区退化人工草地的影响

旨在采用微灌技术对环湖区混播人工草地进行节水灌溉试验的观测研究,探索环湖区人工草地对灌溉条件响应,为环湖区混播人工草地管理和持续高效利用提供参考依据。采用光伏扬水系统进行微喷灌节水灌溉试验,调查群落结构,计算地上和地下植物量。研究表明：植物群落多样性、均匀度、生态优势度指数均为灌溉区大于对照区;水分充足条件下能促进植物茎叶的生长,而干旱有利其根部的发育;灌溉可有效提高环湖区人工草地的优良牧草产量。可见水分的增加抑制了退化草地指标种生长,有利于草地恢复,环湖区人工草地对灌溉条件具有较好响应。     

A Comparison of Methods Used to Determine Biomass on Naturalized Swards

An experiment was conducted in 2000 to compare simple visual estimate, sward height and rising plate meter (RPM) methods for determining forage biomass in mixed-species, naturalized, rotationally grazed dairy and beef pastures. Measurements were taken pre- and post-grazing on 10 sampling dates at the dairy pasture, and post-grazing at 13 sampling dates at the beef pasture. For each sampling date, the effectiveness of each method for estimating the actual biomass from a quadrat was evaluated using regression analysis. The results for the visual estimate method were not consistent, with non-linear relationships occurring early and late in the season. While the meter stick was most effective in the dairy pasture, the RPM was most effective in the beef pasture. Species composition and structural characteristics of the stand were important factors affecting accuracy of biomass estimation. Equations developed for each method and site using data from all dates had low R²-adjusted values, and were unreliable predictors of biomass. The results from individual sites and dates were extremely variable, with no single method effective in all circumstances. To estimate forage biomass in mixed-species, naturalized pastures, standard quadrat harvesting remains the most reliable method, provided that enough quadrats are clipped to adequately represent a given area.     

Light absorption and water loss in overwintered and spring–sown evening primrose (Oenothera spp.) crops

Evening primrose (Oenothera spp.) is a high-value oilseed crop for temperate areas which may be either overwintered or spring–sown. Light absorption, light use efficiency, water loss and biomass water ratio were compared between overwintered and spring–sown crops of cv. Merlin in two years of field trials. An overwintered crop of cv. Peter was also studied in year two. The energy content of evening primrose plant material was shown to be similar to other crops. Both overwintered and spring–sown crops can achieve full canopy closure and maintain high fractional photosynthetically active radiation (PAR) interception for long periods but canopy closure occurred much later than in other temperate seed crops. In spring–sown evening primrose, maximum PAR interception did not occur until August, by which time incident light levels were declining and consequently the proportion of incident light energy captured during the main growing season was low. Most light was intercepted by green leaves and very little shading by senescent tissue and flowers occurred. Light conversion efficiencies for the main growing period were comparable with other temperate C₃ crops, but in year two a steep decline in light conversion efficiency was observed as the crops matured and the soil water deficit exceeded 60 mm. In year one, water loss from both the overwintered and spring–sown crops were low and the soil water deficit increased relatively slowly. By contrast, in the year two crop water loss was high and the soil water deficit built up very rapidly between the end of June and crop maturity. No significant differences in biomass water ratio (water use efficiency) were recorded between overwintered and spring–sown crops but ratios were 50% higher in year one than in year two. Although no relationship was detected between biomass water ratio corrected for vapour pressure deficit (“normalised”) and soil water deficit, after canopy closure normalised daily water loss declined with increasing soil water deficit. Earlier canopy closure, particularly in the spring crop, and the avoidance of soil water deficits through irrigation, would lead to substantial improvements in the size and consistency of seed yields of evening primrose crops.     

Effects of contrasting seasonal growth patterns on composition and persistence of mixed grass‐legume pastures over 5 years in a semi‐arid Australian cropping environment

Perennial grass‐based pastures are uncommon in phased cropping rotations in south‐eastern Australia, where rainfall often limits production and persistence. The high reliance on pure legume‐based pastures limits overall pasture productivity and has adverse effects on environmental parameters such as weed incursion and ground cover. A field experiment was monitored over 5 years to examine the relative productivity of the temperate perennial grasses, phalaris (Phalaris aquatica) and cocksfoot (Dactylis glomerata) and determine whether contrasting seasonal activity enhances their persistence when grown in mixtures with lucerne (Medicago sativa) and annual legumes. Phalaris swards were shown to increase cumulative aboveground biomass by up to 96% and 32%, and in year 5 reduce annual grass emergence by between sevenfold and threefold compared to annual legume and lucerne/annual legume mixed swards, respectively. Only swards that included phalaris maintained ground cover above 70% in each autumn of the experimental period. Swards based on the highly summer dormant cocksfoot cultivar, Kasbah, were generally less productive over all, despite the cocksfoot showing a high level of persistence and good recovery following drought. Grass‐based swards that included lucerne were observed to produce ~35% greater legume biomass than a sward sown only to annual legumes. Cumulative legume biomass was greatest in lucerne swards in the absence of perennial grasses. The experiment was unable to demonstrate a consistent benefit in production and persistence associated with contrasting seasonal growth patterns. However, mixtures containing a range of functional types were consistently shown to enhance productivity over the duration of the experiment compared to less diverse swards. The potential to substantially increase forage productivity and ground cover, while reducing incursion by annual grass weeds, by including well‐adapted perennial grasses in mixtures with lucerne and annual legumes should be utilized.     

黄土高原丘陵沟壑区不同土地利用模式对土壤机械组成和速效养分影响分析

通过对黄土高原丘陵沟壑区不同土地利用模式土壤机械组成和速效养分的测定,论述黄土高原丘陵沟壑区不同土地利用模式对土壤机械组成和速效养分的影响。结果表明：草地的在两个土层速效养分含量差别不大,而其他土地利用模式0-20cm土层的速效养分含量均高于20-40cm土层。关中土壤的速效养分明显高于黄土高原丘陵沟壑区,草地的速效养分都低于其它土地利用模式。黄土高原丘陵沟壑区土壤机械组成分布大致为：粉粒>细砂粒>粗砂粒≈粘粒。速效养分只与0-20cm的粘粒含量承显著正相关。     

Persistence of Legumes in Hill Land Pasture Following Sod Seeding

Unimproved hill land pastures are often characterized by low production and poor forage quality. The introduction and persistence of a legume component in the sward may increase both forage quality and quantity. Persistence of red clover ( Trifolium pratense L.), birdsfoot trefoil ( Lotus corniculatus L.) and white clover ( T. repens L.) sod-seeded into a rotationally grazed hill land pasture was examined. Legumes were introduced by broadcasting by hand, sod-seeding with a zip seeder, and sod-seeding with a Power-till seeder. The effects of paraquat (1, 1-dimethyl 4–4'-bipyridinium ion), lime and P on legume persistence also were examined. The pasture was mostly Kentucky bluegrass ( Poa pratensis L.) with 5 % white clover initially. Percentage legume in the pasture followed the same trend over time irrespective of whether sod-seeded or not, or method of sod-seeding. There was 30 % legume in control plots the year after sod-seeding and 15 % at the end of 4 years. Application of lime and P resulted in an increase in legume content of at least 5 % through the 4 year period. Paraquat, legume species, and sod-seeding method had no effect on legume persistence. It is concluded that management, soil fertility and time are the most important determinants of legume persistence in hill land pastures.     

黄土丘陵区小流域横断面土壤水分的空间分布特征

以黄土丘陵区的纸坊沟小流域为研究对象,研究了横断面上土壤水分空间变化特征,得出如下规律：①从总体来看,土壤水分含量大致是阴坡高于阳坡,坡下高于坡上,地形起着决定性作用,但植被的影响也非常重要。②在小流域断面水分分布中,乔木林地的平均含水量最低,灌木林次之,草本植被最高。表明丘陵区最适宜的植被应是草本植被和灌木群落。③植被的生长弱化了断面地形变化的影响,刺槐的阴阳坡、上下坡的土壤水分含量趋于接近,柠条的生长良好时的大耗水量也使阴坡和坡下的水分优势减弱,长势良好的草本群落使梁峁坡上的土壤水分状况优于其他坡位。④纸坊沟小流域除阴坡草本植被外,全部有土壤干层的存在,但并不影响植被的正常生长,因此,在植被恢复良好的地区,干层的产生是正常的。