不同耕作方式对茶园土壤物理性状及茶叶产量的影响

研究了免耕、旋耕和深松3种耕作方式对茶园土壤紧实度、土壤含水率、土壤容重、茶叶产量构成因素及茶叶产量的影响.结果表明: 3种耕作方式对土壤容重和土壤紧实度的影响效果为深松>旋耕>免耕.旋耕和深松能够打破粘盘层,降低深层土壤紧实度.0～30 cm耕层深松土壤容重较免耕下降16.4%,土壤紧实度下降13.4%～27.5%;深松可以显著增加土壤的储水空间,进而增强土壤持水能力,扩大土壤水库容,深松15～30 cm层含水量与免耕相比增加7.7%.不同耕作方式对土壤孔隙度影响不大.旋耕和深松方式下土壤比表面积增加,土壤气体和液体的比例均明显升高.茶叶的光合速率和蒸腾速率的日变化曲线均为“双峰”型,气孔因素是导致“午休”的主要原因.在深松方式下,茶树叶片蒸腾速率降低,芽叶密度增加,百芽干质量和水分利用效率升高,茶叶产量分别比免耕和旋耕增加17.6%和6.8%.深松是皖东地区茶园较为适宜的耕作方式.     

短期深旋松对黄淮海沙姜黑土耕层结构及小麦生长的影响

针对黄淮海平原由于连年旋耕所导致的犁底层加厚上移、耕层变浅的问题,引入一种全新的耕作技术——深旋松耕,以改良耕层障碍因素,提高冬小麦产量.设置深松20 cm(SS₂₀)、深旋松30 cm(DVR₃₀)两个处理,以深松20 cm为对照,研究深旋松耕作对土壤物理特性及小麦开花期光合特性的影响.结果表明: DVR₃₀处理能够充分破除犁底层,DVR₃₀处理10～20和20～30 cm土层容重分别较SS₂₀处理降低了9.5%和11.2%,DVR₃₀处理20～30 cm穿透阻力较SS₂₀处理降低了42.3%.DVR₃₀能够增强水分入渗能力,提高土壤深层贮水量.随着深度的增加,DVR₃₀处理土壤含水量显著增加,30～40和40～50 cm土层含水量分别较SS₂₀处理提高16.9%和10.6%,且差异达到显著水平,0～50 cm土壤贮水量提高3.3%.DVR₃₀处理创造了良好的耕层环境,促进了小麦开花期光合能力的提高,与SS₂₀处理相比,DVR₃₀处理小麦开花期叶片相对叶绿素含量(SPAD)及净光合速率分别提高1.3%和15.5%,小麦地上部、地下部干物质累积量亦有显著增加,同时DVR₃₀处理通过提高小麦有效穗数,提高了产量,实际增产12.4%.综上,短期深旋松耕作能够充分破除犁底层、深松活土,为构建合理耕层结构、充分挖掘耕层潜力提供了一种新的技术手段.     

深松和秸秆还田对甘肃引黄灌区土壤物理性状和玉米生产的影响

通过在甘肃引黄灌区灰钙土2015—2017年的田间试验,研究深松35 cm秸秆还田、深松35 cm秸秆不还田与传统旋耕秸秆不还田对土壤紧实度、容重、入渗率和0～100 cm土层土壤水分、玉米产量、养分吸收量的影响.结果表明: 与深松35 cm秸秆不还田及旋耕秸秆不还田相比,深松35 cm秸秆还田使0～40 cm土层土壤紧实度和容重降低最明显,2017年收获后紧实度与容重较2015年试验前分别下降42.6%、7.0%,且2016和2017年播种前与收获后0～40 cm土层紧实度和容重的变幅最小,紧实度变异系数平均为6.1%,容重为3.2%,土壤入渗率较旋耕秸秆不还田提高33.6%;深松35 cm秸秆还田可显著提高春秋两季0～100 cm土层剖面含水量,降低剖面水分变异,0～100 cm土层土壤贮水量较旋耕秸秆不还田春季增加15.5%,秋季增加5.6%,水分利用效率提高32.4%;此外,深松35 cm秸秆还田能促进玉米生产,较旋耕秸秆不还田的经济产量两年平均分别增产25.6%,生物产量提升33.3%,玉米氮、磷、钾养分吸收量分别提高49.6%、51.5%和37.6%.综上,深松35 cm秸秆还田能改善物理土壤特性,稳定耕层物理性状,提高0～100 cm土层剖面水分含量及春秋两季土壤平均贮水量,降低水分变异,是促进玉米水肥高效利用,实现高产的最优措施,为甘肃引黄灌区耕层构建技术的深入研究提供理论依据.     

宁南旱区耕作覆盖对马铃薯产量及土壤水热特征的影响

为探究耕作覆盖对土壤水热及旱作马铃薯产量的影响,连续2年在宁南旱区不同耕作深度结合覆盖模式下开展了研究工作。结果表明: 耕作深度、覆盖材料对马铃薯播种期0～100 cm土层土壤贮水量有极显著影响,而二者交互作用无显著影响;2019年土壤贮水量以深松30 cm覆盖地膜处理最高,2020年以深松40 cm覆盖秸秆处理较高,分别较翻耕15 cm不覆盖处理(对照)显著提高16.9%和33.4%;耕作深度、覆盖材料可显著影响马铃薯关键生育期土壤贮水量;同一耕作深度下土壤贮水量以秸秆、地膜覆盖处理效果较好,同一覆盖材料下以深松30～40 cm处理最佳。覆盖材料、耕作深度与覆盖材料二者交互作用对播种-现蕾期0～25 cm土层土壤有效积温影响显著;同一耕作深度下覆盖地膜处理土壤有效积温平均较不覆盖处理显著增加9.3%,而覆盖秸秆处理较不覆盖处理显著降低18.7%;2019和2020年各处理全生育期土壤有效积温分别以深松30 cm和深松40 cm覆盖地膜处理最高。2019年马铃薯总产量和经济效益以深松30 cm覆盖秸秆处理较高,分别较对照显著提高84.6%和107.9%;2020年以深松40 cm覆盖秸秆处理最佳,分别较对照显著提高81.7%和105.7%。耕作深度、覆盖材料对作物水热利用效率均有显著影响,水分利用效率以深松30～40 cm覆盖秸秆处理较高,而积温利用效率不同耕作深度结合秸秆覆盖各处理均较翻对照显著提高。相关分析表明,块茎形成期的土壤水分和有效积温对马铃薯总产量的形成至关重要,而全生育期土壤水分对总产量的影响高于土壤有效积温。可见,深松30～40 cm覆盖秸秆处理可改善土壤水热状况,实现马铃薯增产增收和水热资源的高效利用,在宁南半干旱区马铃薯生产中有一定的应用推广价值。     

西北半干旱区深旋松耕作对马铃薯水分利用和产量的影响

探明深旋松耕作技术(VRT)对西北黄土高原半干旱区马铃薯阶段性耗水、个体和群体生长状况、产量、水分利用效率和经济收益的影响,可为寻求抗旱增产、资源高效利用的耕作方法提供依据.本研究采用随机区组设计,于2016和2017年设置旋耕15 cm (TT)、深松40 cm (DLT)、深旋松耕40 cm (VRT) 3种耕作方式,测定马铃薯不同生育时期0～200 cm土层土壤贮水量、叶片SPAD值、叶面积指数、植株干物质量和产量等指标,计算阶段耗水量、水分利用效率(WUE)、商品率、商品产量、纯收益和新增收益等指标,探究深旋松耕作对马铃薯生产效率和经济效益的影响.结果表明: 与TT和DLT相比,VRT能显著促进马铃薯在盛花期和块茎膨大期的耗水,2016和2017年分别较DLT、TT增加了46.7、35.7和27.2、47.3 mm.由于VRT促进马铃薯耗水,叶片SPAD值、干物质量和叶面积指数均显著提高,证明它能促进马铃薯个体和群体发育.基于较高的个体和群体生长量,VRT的马铃薯块茎产量显著提高,分别在2016和2017年较DLT和TT增加了156.8%、47.8%和24.8%、41.0%,WUE相应地提高了92.3%、19.2%和18.9%、26.6%.深旋松耕作使马铃薯商品薯产量显著增加,纯收益和新增纯收益显著提高,在2016和2017年分别达到 12631.9、11019.1和29498.3、18245.5元·hm^-2.深旋松耕作促进马铃薯花期和块茎膨大期耗水,使马铃薯叶片SPAD值、干物质量和叶面积指数显著提高,导致块茎产量和水分利用效率明显升高,并提高了商品薯产量和纯收益,是适宜于西北黄土高原半干旱区马铃薯种植的耕作技术.     

耕作深度对蔗地土壤物理性状及甘蔗产量的影响

探讨蔗地机械化耕作深度对耕层土壤物理性状及甘蔗产量构成因子的影响,阐明深松作业的针对性土壤区位和障碍因子,可为甘蔗良好耕层的构建和土壤改良策略的制定提供科学依据.本研究设置3种深松作业深度(35、40和45 cm),以不深松为对照,对蔗地土壤物理性状(紧实度、容重、含水率、孔隙度、三相容积率)和甘蔗产量构成因素及蔗茎产量等指标进行研究.结果表明: 耕作作业深度与蔗地土壤结构特性及甘蔗产量的改善提升效应呈显著正相关.深松能够打破犁底层,显著降低土壤紧实度和容重,减小机械作业相应的贯入阻力和抗剪强度,尤其对20～30 cm土层的上述因子具有显著改善效应,对甘蔗高产意义重大.深松显著提高了30 cm以内土层的液相容积率,增大了土壤水分库容,使10～30 cm土层的水分指标显著改善.10～30 cm土层是深松对耕层土壤固相容积率改善效应最显著的区位.耕作深度的增加对甘蔗有效茎数、株高、蔗茎产量及蔗糖含量具有显著的促进效应.鉴于蔗区当前较普遍的机具装备水平,我国适宜蔗区实施机械化深松的作业深度标准应不小于40 cm.     

渭北旱塬农田不同耕作模式对土壤性状、玉米产量和水分利用效率的影响

通过渭北旱塬黑垆土8年定位试验,研究了秸秆还田下6种耕作方式,即连年翻耕(CT/CT)、免耕(NT/NT)、深松(ST/ST)和免耕/深松(NT/ST)、翻耕/免耕(CT/NT)、翻耕/深松(CT/ST)对土壤团聚体、有机碳、作物产量和水分利用效率(WUE)的影响.结果表明:与CT/CT相比,NT/NT、ST/ST及3种轮耕措施减小了土壤力稳性团聚体的平均质量直径;NT/NT、ST/ST和NT/ST措施增加了20～50 cm土层>0.25 mm水稳性团聚体的含量(WR_0.25)和平均质量直径,降低了土壤团聚体结构破坏率(PAD).在0～10 cm土层,NT/ST、CT/NT、NT/NT和ST/ST处理土壤有机碳含量显著高于CT/CT处理.随着土层加深,各耕作处理土壤有机碳含量下降,但3种单一耕作处理(ST/ST、NT/NT和CT/CT)下降幅度大于3种轮耕处理(CT/NT、ST/CT和NT/ST).与CT/CT相比,其他5种耕作方式均增加了农田0～200 cm土层的土壤蓄水量、作物产量和水分利用效率,其中,NT/ST处理作物产量和WUE分别显著提高了15.1%和27.5%.相关分析表明,玉米产量、WUE与0～200 cm土层生育期和休闲期的蓄水量呈显著正相关,且生育期蓄水量与0～50 cm土层的WR_0.25呈显著正相关,与PAD呈显著负相关;其中,20～50 cm土层的WR_0.25、PAD与玉米产量、生育期蓄水量以及WUE关系最密切;生育期蓄水量和WUE还与0～10 cm土层的有机碳含量呈显著正相关.综合考虑不同耕作措施对土壤结构、作物产量和水分利用效率的影响,免耕/深松是最适宜于渭北旱塬区黑垆土春玉米种植的耕作方式.     

不同耕作方式对旱地全膜双垄沟播玉米产量和水分利用的影响

为明确新型耕作技术--立式深旋耕作对西北黄土高原半干旱区土壤水分含量、玉米产量和水分利用效率的影响,采用随机区组设计,于2016和2017年设置立式深旋耕作40 cm （VRT）、深松40 cm （SS）、旋耕15 cm （TT）和免耕（ZT）4种耕作方式,测定0-300 cm土层土壤含水量、地上生物量、叶面积指数（LAI）和SPAD、产量等指标,计算阶段耗水量、水分利用效率（WUE）等。结果表明,VRT在2017年播前0-40 cm土层的土壤贮水量分别较SS、TT、ZT增加了7.7、8.6、6.6 mm,在0-100 cm土层增加了18.2、22.8、20.2 mm,均达到显著差异。VRT显著促进干旱年的花前耗水和平水年的花后耗水,提高玉米地上生物量、LAI和SPAD,其中地上生物量较SS、TT、ZT分别增加了14.7%-18.3%、12.7%-18.8%和22.8%-29.1%。基于较为优势的植株生长,VRT籽粒产量较SS、TT和ZT分别增加了12.0%-13.0%、13.7%-33.6%、24.0%-47.4%。因此,虽然VRT提高了玉米耗水,并与ZT达到显著差异水平,导致收获后土壤贮水量低于其他三种耕作方式,但2017年播前0-100 cm土层土壤贮水量显著高于其他3种耕作处理;尽管0-300 cm土层土壤贮水量较SS、TT和ZT下降了11.4、14.8、20.5 mm,但它们之间无显著差异。以上结果表明,VRT能够同时促进玉米耗水和降水入渗,维持土壤水分平衡,是一种有效的抗旱增墒耕作方法,可在半干旱区玉米生产中推广应用。     

半干旱区立式深旋耕和有机无机肥配施对饲用玉米水分利用效率和产量的影响

合理的耕作和施肥管理措施是提高黄土高原半干旱区饲用玉米产量和水分利用效率的关键。本研究于2017—2019年在甘肃省农业科学院定西试验站开展大田试验,设置了传统旋耕+有机无机肥配施(TOF)、深旋耕+有机无机肥配施(DOF)和立式深旋耕+有机无机肥配施(VROF)3个处理,并以传统旋耕+单施无机肥(TF)为对照,测定了饲用玉米干物质量、土壤含水量、产量,计算了土壤耗水量、水分利用效率和经济效益等指标,探究不同处理对饲用玉米产量、水分利用效率和经济效益的影响。结果表明: 与其他处理相比,VROF花期0～300 cm土层土壤贮水量降低了16.9～79.9 mm,干旱年份花前耗水量增加了9.7～22.4 mm、花后耗水量增加了11.0～19.8 mm,总土壤耗水量提高了8.6%～12.4%;立式深旋耕+有机无机肥配施能够促进饲用玉米生育期耗水,使得成熟期干物质量增加3.9%～13.4%,株高、穗长、穗粒数、百粒重和双穗率也明显增加,秃顶长显著降低,籽粒产量增加4.3%～51.5%、生物产量增加4.3%～25.7%,籽粒和生物量水分利用效率分别提高2.7%～36.9%和3.6%～13.5%,单位总产值增加5.1%～32.9%、纯收益提高6.9%～80.5%。可知,立式深旋耕结合有机无机肥配施能够调控饲用玉米生育期耗水,使饲用玉米干物质积累、株高、百粒重等农艺和经济性状指标明显增加,显著提升产量和水分利用效率,并提高总产值和纯收益,是适宜于西北黄土高原半干旱区饲用玉米种植的抗旱增产增效技术。     

不同降水年型下耕作方式结合覆盖对旱地土壤物理性质和马铃薯产量的影响

2018—2021年连续3年在宁夏南部旱作区开展大田定位试验,设置4种耕作方式(翻耕15 cm、深松30 cm、深松40 cm、深松50 cm)和3种覆盖措施(燕麦秸秆覆盖、塑料地膜覆盖、不覆盖),以翻耕15 cm不覆盖处理为对照,探讨不同降水年型下耕作方式结合覆盖对旱地土壤容重、团聚体含量、生育期土壤蓄水量和马铃薯产量的影响。结果表明：与试验处理前相比,3年耕作结合覆盖均能有效降低0～60 cm土层土壤容重;同一耕作方式下,不同降水年型均以秸秆覆盖最佳;丰水年20、40 cm土层以深松30 cm覆盖秸秆处理最佳,60 cm土层以翻耕15 cm覆盖秸秆处理最佳,平水年和枯水年20、40、60 cm土层均以深松40 cm覆盖秸秆处理最佳。在0～20 cm土层,>0.25 mm土壤团聚体含量3年均以深松40 cm覆盖秸秆处理最高;20～40 cm土层,丰水年以翻耕15 cm覆盖秸秆处理最高,平水年和枯水年以深松40 cm覆盖秸秆处理最高;在40～60 cm土层,丰水年、平水年、枯水年分别以翻耕15 cm覆盖地膜处理、深松30 cm覆盖地膜处理、深松30 cm覆盖秸秆处理最高,较对照分...     

Effect of alginite amendment on microbial activity and soil water content in forest soils

The effect of the amendment with alginite, an organic rock originating from the biomass of fossilized unicellular algae, on microbial activity of forest soils was tested using a pot experiment. Five variants of soil-alginite mixtures were tested in three replicates with two forest soils: a loose sandy soil and a sandy loam. Gravimetric moisture closely correlated with the dose of alginite in both soils. Basal respiration and catalase activity increased with the dose of alginite in the sandy soil, but not in the sandy loam, where the highest response was observed at intermediate doses of alginite. The correlations of microbial activity parameters with moisture in the sandy soil were also much closer than in the sandy loam. The amendment with alginite was thus effective in improving some of the selected microbial activity indicators, but the optimum dose of alginite strongly depends on soil texture.     

水热因子对沙漠地区土壤呼吸的影响

利用Li-6400-09土壤呼吸室和Li-6400便携式光合测定仪,在植物生长季对腾格里沙漠东南缘植被区和流沙区的土壤呼吸进行了连续测定,并分析了温度和水分对土壤呼吸的影响.结果表明:(1)植被区和流沙区土壤呼吸速率的日变化特征相似,即夜间土壤呼吸速率保持在较低的水平,而白天则呈现单峰变化趋势;而季节变化趋势明显不同,即植被区内的土壤呼吸有明显的季节变化,流沙则没有明显的季节变化;(2) 植被区和流沙区0～5cm土壤含水量与土壤呼吸速率均呈显著的线性关系,但植被区的相关性好于流沙区.当0～5cm土壤含水量大于测定期间的平均值 (植被区为6.78%、流沙区6.94%)时,植被区和流沙区的土壤呼吸速率都明显高于土壤含水量小于平均值时的土壤呼吸速率,其土壤呼吸速率平均值之比分别为:2.6、1.5;(3) 土壤呼吸速率与地表5cm处土壤温度呈显著的指数关系,当土壤含水量小于测定期间的平均值时,植被区与流沙区的Q10值分别为1.23和1.43;当土壤含水量大于测定期间的平均值时,植被区与流沙区的Q10值分别为2.23和1.72.由此可见,土壤水分不仅影响了土壤呼吸速率的大小,而且还影响了土壤呼吸速率的温度敏感性.     

The effect of water supply on seed-bank analysis using the seedling-emergence method

1. When using the seedling-emergence method to analyse a soil seed bank the greenhouse conditions should match the germination requirements of the species involved. Although the seedling-emergence method is common practice in ecological studies, the germination characteristics of many species are not known, or are only partly known.
2. Before carrying out a large-scale seed-bank study in a wet dune slack, we tested the water requirements of the species in the seed bank, comparing a waterlogged soil with a moist soil. Four species germinated in significantly larger numbers in a waterlogged soil, seven species in a moist soil and 11 species showed no significant difference. When a species was present in low densities, it was often missed using the less appropriate treatment.
3. These results emphasize the need for a preliminary study before carrying out a seed-bank analysis and show the danger of using a 'standard' method to analyse soil samples from different habitats.     

Aeration status in the root zone of maize in relation to soil water content

The aeration status of a silt loam placed in microcolumns was measured in the maize root zone using an oxygen microelectrode. At soil moisture saturation, the O₂ concentration was found to be zero. Maize evapotranspiration led to a fast increase in O₂ concentration against time (2% O₂ after 2 days, atmospheric concentration after 7 days). Surprisingly, for specified soil moisture levels, no significant O₂ concentration differences were observed between planted and fallow soils. These results are discussed to explain observations on the denitrification process in the root zone of plants.     

Interactions between elevated CO2 concentration, nitrogen and water: effects on growth and water use of six perennial plant species

Two experiments are described in which plants of six species were grown for one full season in greenhouse compartments with 350 or 560 μ mol mol^–1 CO₂. In the first experiment two levels of nitrogen supply were applied to study the interaction between CO₂ and nitrogen. In the second experiment two levels of water supply were added to the experimental set-up to investigate the three-way interaction between CO₂, nitrogen and water. Biomass and biomass distribution were determined at harvests, while water use and soil moisture were monitored throughout the experiments. In both experiments a positive effect of CO₂ on growth was found at high nitrogen concentrations but not at low nitrogen concentrations. However, plants used much less water in the presence of low nitrogen concentrations. Drought stress increased the relative effect of elevated CO₂ on growth. Available soil moisture was used more slowly at high CO₂ during drought or at high nitrogen concentrations, while at low nitrogen concentrations decreased water use resulted in an increase in soil moisture. The response to the treatments was similar in all the species used. Although potentially faster growing species appeared to respond better to high CO₂ when supplied with a high level of nitrogen, inherently slow-growing species were more successful at low nitrogen concentrations.     

黄土高原水土保持林对土壤水分的影响

黄土高原植被恢复的限制因素主要是土壤水分,植被与土壤水分关系的研究对黄土高原植被恢复具有重要意义.2008年7月1日至2009年10月31日间采用EnviroSMART土壤水分定位监测系统以每30min监测1次的频度,对晋西黄土区刺槐人工林地、油松人工林地、次生林地的土壤水分变化进行了研究.研究得出:次生林地0-150 cm土层中平均蓄水量为331.95mm,刺槐人工林地为233.85 mm,有整地措施的油松人工林地为314.85mm,刺槐人工林比次生林多消耗的98.10mm土壤水分主要来源于80 cm以下土层.次生林主要消耗0-80 cm土层的水分,而人工林不但对0-80 cm土层水分的消耗量大于次生林,对深层土壤的消耗也较次生林大,这将有可能导致人工林地深层土壤的“干化”.在土壤水分减少期(11-1月)刺槐人工林土壤水分的日均损耗量为0.86mm、油松人工林为0.82 mm、次生林为0.84 mm.土壤水分缓慢恢复期(2-5月)刺槐人工林地土壤水分的恢复速度0.90mm/d,油松人工林地为0.53 mm/d、次生林地为0.79 mm/d.土壤水分剧烈变化期(5-10月)刺槐人工林地土壤水分含量的极差为95.71mm,油松人工林地为179.1mm,次生林地为72.03mm.在干旱少雨的黄土高原进行植被恢复时,应多采取封山育林等方式,依靠自然力量形成能够与当地土壤水资源相协调的次生林,是防止人工植被过度耗水形成“干化层”、保障水土保持植被持续发挥生态服务功能的关键.     

黄土丘陵区不同土地利用模式对深层土壤含水量的影响

对陕北米脂人工经济林、神木退耕还林和榆林榆阳区防风固沙林具有代表性植被类型0～20 m土壤剖面水分特征的差异进行了研究,分析黄土丘陵区不同土地利用模式对深层土壤剖面水分分布和储存特征的影响及生态环境效应.结果表明: 在0～20 m土层,不同位点具有代表性土地利用方式均影响土壤含水量的垂直分布;在整个剖面中,人工经济林土壤储水量有显著差异,为矮化枣树 ＞ 未矮化枣树,储水量相差587.9 mm;神木退耕还林和榆林榆阳区防风固沙林土壤剖面中土壤储水量无较大差异,在神木整个剖面中土壤储水量的大小为退化人工草地 ＞ 柠条林,储水量相差98.8 mm;在榆阳为荒草地 ＞ 樟子松,储水量相差7.5 mm.与未矮化枣树相比,人工经济林矮化枣树减少了对土壤水分的消耗,矮化枣树冠幅较小,降低了蒸腾作用,从而更加有利于土壤水分的可持续利用;人工柠条林和退化人工草地土壤水分含量无明显差异,这是因为退化人工草地过去为苜蓿地,根系分布深以及生物量大,对土壤深层水分利用较大所致;防风固沙林樟子松与荒草地整个剖面中的平均土壤含水量较低,土壤砂粒含量较高,土壤持水性差,土壤含水量随土壤深度的增加而增加,平均土壤含水量分别为3.4%和3.6%,且该地植物对深层土壤水分影响有限.综上,土壤剖面中土壤水分除了受土壤质地的控制,不同土地利用模式由于植物根系不同,对土壤水分也产生较大的影响.为此,选择合适的植物对于土壤深层水的保护和持续利用非常重要.     

冬季土壤含水量对糯米糍荔枝花芽分化的影响

冬季适度干旱有利于糯米糍荔枝的花芽分化,对砂壤土而言,土壤含水量的最适范围为12%~15%,低于10%或高于16%都不利于花芽分化。     

Influence of large termitaria on soil characteristics, soil water regime, and tree leaf shedding pattern in a West African savanna

Termitaria are major sites of functional heterogeneity in tropical ecosystems, through their strong influence on soil characteristics, in particular soil physico-chemical properties and water status. These factors have important consequences on nutrient availability for plants, plant spatial distribution, and vegetation dynamics. However, comprehensive information about the influence of termite-rehandled soil on soil water regime is lacking. In a humid shrubby savanna, we characterized the spatial variations in soil texture, soil structure and maximum soil water content available for plants (AWC max) induced by a large termite mound, at three deepths (0–0.10, 0.20–0.30 and 0.50–0.60 m). In addition, during a three month period at the end of the rainy season, soil water potential was surveyed by matrix sensors located on the termite mound and in the surrounding soil at the same depths and for the 80–90 cm layer. Concurrently, the leaf shedding patterns of two coexisting deciduous shrub species exhibiting contrasted soil water uptake patterns were compared for individuals located on termite mounds and in undisturbed control areas. For all the soil layers studied, clay and silt contents were higher for the mound soil. Total soil clods porosity was higher on the mound than in control areas, particularly in the 0.20-0.60 m layer, and mound soil exhibited a high shrinking/swelling capacity. AWC_max of the 0-0.60 m soil layer was substantially higher on the termite mound (112 mm) than in the surroundings (84 mm). Furthermore, during the beginning of the dry season, soil water potential measured in situ for the 0.20-0.90 m soil layer was higher on the mound than in the control soil. In contrast, soil water potential of the 0-0.10 m soil layer was similar on the mound and in the control soil. In the middle of the dry season, the leaf shedding pattern of Crossopteryx febrifuga shrubs (which have limited access to soil layers below 0.60 m) located on mounds was less pronounced than that of individuals located on control soil. In contrast, the leaf shedding pattern of the shrub Cussonia barteri (which has a good access to deep soil layers) was not influenced by the termite mound. We conclude that in this savanna ecosystem, termite mounds appear as peculiar sites which exhibit improved soil water availability for plants in upper soil layers, and significantly influence aspects of plant function. Implications of these results for understanding and modelling savanna function and dynamics, and particularly competitive interactions between plant species, are discussed.