Effects of soil moisture on cotton root length density and yield under drip irrigation with plastic mulch in Aksu Oasis farmland

Effects of soil moisture on cotton root length density (total root length per unit soil volume) and yield under drip irrigation with plastic mulch were studied through field experiments. The results indicate that spatial distributions of root length density of cotton under various water treatments were basically similar. Horizontally, both root length densities of cotton in wide and narrow rows were similar, and higher than that between mulches. Vertically, root length density of cotton decreased with increasing soil depth. The distribution of root length density is different under different irrigation treatments. In conditions of over-irrigation, the root length density of cotton between mulches would increase. However, it would decrease in both the wide rows and narrow rows. The mean root length density of cotton increased with increasing irrigation water. Water stress caused the root length density to increase in lower soil layers. There is a significant correlation between root length density and yields of cotton at the flower-boll and wadding stages. The regression between irrigation amount and yield of cotton can be expressed as y = -0.0026x2+18.015x-24845 (R2 = 0.959). It showed that the irrigation volume of 3,464.4 m3/hm2 led to op-timal root length density. The yield of cotton was 6,360 .8 kg/hm2 under that amount of irrigation.

Root Length Density in Maize/Cowpea Intercropping under a Basin Tillage System in a Semi-Arid Area of Zimbabwe

A study to assess the effect of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L.) within the same basin or outside the basin on root length density (RLD) was conducted at the International Crop Research Institute for Semi-Arid Tropics (ICRISAT) Matopos Research Station from December 2009 to April 2010. The experiment was laid out in a Randomised Complete Block Design (RCBD) with four treatments replicated four times namely;sole maize, sole cowpea, maize-cowpea intercrop with cowpea and maize planted within the same basin and maize-cowpea intercrop with cowpea planted 20 cm outside the maize basin. There was significant difference (P < 0.001) in RLD, grain yield and stover yield. Maize-cowpea intercropped within the same basin achieved higher RLD, grain yield and stover yield than cowpea that was intercropped outside the basin and the sole crops. The land equivalent ratio (LER) in both intercrop designs showed that intercropping had better grain yield performance when compared to sole cropping. It can be concluded that intercropping maize and cowpeas within the same basin can result in an environment around the crop achieving higher RLD which translates to better grain yield compared to the sole cropping and intercropping cowpeas outside the basin.

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.

不同草本植物根系对土壤渗透性的影响

[目的]揭示当地排土场不同草本植物根系对土壤渗透性的影响,阐明预测草本植物根系提升土壤渗透性的最优指标,并得出草本植物根系提升土壤渗透性的最佳径级,为排土场生态修复植物选择提供重要依据。[方法]以海州露天矿排土场为研究地点,以轴根型紫花地丁、根蘖型苦荬菜和根茎型水麦冬为研究对象,采用图片像素换算法量化3种根系在不同土层深度范围内的根系分布特征;并结合渗透试验获取3种草本植物原状根土复合体的渗透参数,进而探究了根土复合体根系分布参数与渗透参数的关系。[结果]3种草本植物均能提升土壤的渗透性能,轴根型、根茎型和根蘖型根土复合体的初始入渗率、稳渗率、平均渗透速率、渗透总量相较于素土分别提升82.23%~254.99%,85.59%~307.63%,72.02%~325.91%,62.93%~246.98%。3种草本植物根系的根长密度和根表面积密度与根土复合体的渗透参数均呈现线性相关,根表面积密度的相关性强于根长密度。3种根系对土壤渗透性的增强作用主要归功于0.5 mm<D≤1.5 mm径级,它们均存在提升土壤渗透性的最佳径级。[结论]草本植物根系能够提升土壤渗透性,根表面积密度是最佳预测指标,且不同根系均存在最佳径级。

岷江上游干旱河谷地区油松和岷江柏细根生物量和根长密度

了解岷江上游干旱河谷地区12年生油松(Pinus tabulaeformis)和岷江柏(Cupressus chengiana)人工林细根(直径≤2 mm)生物量和根长密度在土层中的垂直分布状况,分析不同土层中细根系统的碳分配策略,为岷江上游干旱河谷地区植被恢复提供理论依据。以岷江上游干旱河谷地区的油松和岷江柏人工林为研究对象,采用土钻法进行取样,测定2种林分不同土层深度(h)(0 cm<h≤15 cm和15 cm<h≤30 cm)中吸收根(1~3级)和运输根(≥4级的细根)生物量和根长密度,以及吸收根占总细根生物量和根长密度比例。结果显示:油松和岷江柏吸收根生物量和根长密度在0 cm<h≤15 cm土层均显著高于15 cm<h≤30 cm土层,而运输根生物量和根长密度在土层间差异均不显著;油松和岷江柏吸收根占总细根生物量和根长密度比例在0 cm<h≤15 cm土层均显著高于15 cm<h≤30 cm土层(P<0.05);岷江柏吸收根占总细根生物量和根长密度比例在2个土层中均显著高于油松(P<0.05)。研究结果表明,在养分有效性最高的土壤表层,油松和岷江柏细根系统内将更多的碳分配到吸收根。

Effects of plant roots on soil preferential pathways and soil matrix in forest ecosystems

To characterize effects of plant roots on preferential flow（PF）,we measured root length density（RLD）and root biomass（RB） in Jiufeng National Forest Park,Beijing,China.Comparisons were made for RLD and RB between soil preferential pathways and soil matrices.RLD and RB declined with the increasing soil depth（0–10,10–20,20–30,30–40,40–50,50–60 cm） in all experimental plots.RLD was greater in soil preferential pathways than in the surrounding soil matrix and was 69.5,75.0 and72.2 % for plant roots of diameter（d） ／1,1 ／ d ／ 3 and3 ／ d ／ 5 mm,respectively.Fine root systems had the most pivotal influence on soil preferential flow in this forest ecosystem.In all experimental plots,RB content was the sum of RB from soil preferential pathways and the soil matrix in each soil depth.With respect to 6 soil depth gradient（0–10,10–20,20–30,30–40,40–50,50–60 cm） in each plot,the number of soil depth gradient that RB content was greater in soil preferential pathways than in the soil matrix was characterized,and the proportion was68.2 % in all plots.

Distribution and Quantity of Root Systems of Field-Grown Erianthus and Napier Grass

Cellulosic bioethanol produced from non-edible plants reduces potential food-fuel competition and, as such, is receiving increasing attention. In the raw material production of cellulosic bioethanol, the aboveground biomass of plants is entirely harvested;consequently, the plant roots represent the major source of organic matter incorporated into the soil. We selected Erianthus and Napier grass as the raw materials for cultivation in Asia. However, information about whether these 2 species provide sufficient root volume to sustain soil fertility is limited. Therefore, we examined the spatial distribution of the roots of these 2 plants, and quantified root mass and length. Erianthus and Napier grass were either grown in fields or greenhouses in Tokyo (Japan) and Lampung (Indonesia), and then their roots were exposed from adjacent soil profiles. Both species developed large, deep roots, penetrating 2.0-2.6 m deep into the soil. Root depth indexes showed that the roots of both species penetrated much deeper into the soil compared to monocot crop species, being more comparable to dicot species. Erianthus developed a root mass and length of 384-850 g·m-2 and 28.8-35.8 km·m-2, while the values for Napier grass were 183-448 g·m-2 and 15.6-43.6 km·m-2, respectively. These values exceeded the maximum values previously recorded for common crop species. Our study confirmed that Erianthus and Napier grass develop deep root systems, with substantially large biomass;hence, we suggest that both plants supply root biomass in large quantities, representing possible major sources of soil organic matter.

Maize-legume intercropping promote N uptake through changing the root spatial distribution,legume nodulation capacity,and soil N availability

Legume cultivars affect N uptake,component crop growth,and soil physical and chemical characteristics in maize-legume intercropping systems.However,how belowground interactions mediate root growth,N fixation,and nodulation of different legumes to affect N uptake is still unclear.Hence,a two-year experiment was conducted with five planting patterns,i.e.,maize-soybean strip intercropping(IMS),maize-peanut strip intercropping(IMP),and corresponding monocultures(monoculture maize(MM),monoculture soybean(MS),and monoculture peanut(MP)),and two N application rates,i.e.,no N fertilizer(N-)and conventional N fertilizer(N+),to examine relationships between N uptake and root distribution of crops,legume nodulation and soil N availability.Results showed that the averaged N uptake per unit area of intercrops was significantly lower than the corresponding monocultures.Compared with the monoculture system,the N uptake of the intercropping systems increased by 31.7-45.4%in IMS and by 7.4-12.2%in IMP,respectively.The N uptake per plant of intercropped maize and soybean significantly increased by 61.6 and 31.8%,and that of intercropped peanuts significantly decreased by 46.6%compared with the corresponding monocultures.Maize and soybean showed asymmetrical distribution of roots in strip intercropping systems.The root length density(RLD)and root surface area density(RSAD)of intercropped maize and soybean were significantly greater than that of the corresponding monocultures.The roots of intercropped peanuts were confined,which resulted in decreased RLD and RSAD compared with the monoculture.The nodule number and nodule fresh weight of soybean were significantly greater in IMS than in MS,and those of peanut were significantly lower in IMP than in MP.The soil protease,urease,and nitrate reductase activities of maize and soybean were significantly greater in IMS and IMP than in the corresponding monoculture,while the enzyme activities of peanut were significantly lower in IMP than in MP.The soil available N of maize and soybean was significantly greater increased in IMS and IMP than in the corresponding monocultures,while that of IMP was significantly lower than in MP.In summary,the IMS system was more beneficial to N uptake than the IMP system.The intercropping of maize and legumes can promote the N uptake of maize,thus reducing the need for N application and improving agricultural sustainability.

Soil nutrients in relation to vertical roots distribution in the riparian zone of Three Gorges Reservoir,China

Since the impoundment of the Three Gorges Reservoir(TGR), the riparian zone has been subjected to numerous environmental changes. This study was conducted to recognize the distribution of grass roots and its impacts on soil nutrients in the water level fluctuation zone of TGR. Roots of four predominant herbaceous plants in the study area, specifically, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, and their corresponding relation with soil nutrient contents were investigated. Root surface area density was determined with Win RHIZO, and the relationships of root distribution with soil depths and soil nutrient contents were studied. The results indicates that most roots are distributed in the top soil layer of 0-10 cm. Estimated root surface area density for the selected grass species ranges from 0.16 to 13.44 cm^2/cm^3, and decreases exponentially with an increase in soil depth. Soil organic matter and total nitrogen contents are significantly lower on bare control area than the corresponding values on the grasslands. Total nutrient contents on grasslands of C. dactylon and H. compressa are higher than those of other grass areas. Root length density and root surface area density are significantly correlated with soil organic matter and total nitrogen content for the four grasslands. The present results suggests that plant roots have significant effects on the distribution of soil nutrients in soil profiles in the riparian zone along the TGR. Nevertheless, additional investigations are needed to reveal the specific interactions between plant roots distribution, soil nutrients and water level fluctuations.

Roots and Nutrient Distribution under Drip Irrigation and Yield of Faba Bean and Onion

Drip irrigation proved to efficiently provide irrigation water and nutrients to the roots of plants, while maintaining high yield production. This research was established to study the root and nutrient distribution under drip irrigation. Faba bean and onion plants were cultivated in the experimental farm of the Faculty of Agriculture of Suez Canal University in Ismailia city with the application of normal fertilizers to soil. The data showed that soil moisture content in the soil planted with faba bean increased with the horizontal distance between drippers, contrariwise moisture content decreased with horizontal distance with the soil planted with onion. The data showed the vertical distribution of root length, root length density and specific root length of faba bean and onion decreased with increasing soil depth. The data showed that ammonium and nitrate pattern at the soil planted with the both plants increased between drippers and laterals. The peak concentration was recorded 35 mg/kg at 60 - 80 cm soil depth for faba bean and onion, indicating that the NO3-N leaching was low by drip irrigation. Available phosphorus was higher at the surface layer than the subsurface layer at the soil planted with faba bean and onion. Available potassium tended to move both horizontally and downward under drip irrigation.

草本植物根系类型和分布对根土复合体无侧限抗压强度的影响

为了探究草本植物根系类型和分布对根土复合体无侧限抗压强度的影响,采用图片像素转换法确定轴根型紫花地丁、根蘖型苦荬菜和根茎型水麦冬在不同土壤深度的根系分布特征;并利用无侧限抗压试验获取3种草本植物根土复合体的应力-应变曲线,量化根土复合体的抗压强度,探究根土复合体破坏面根系参数与黏聚力增量的关系。研究结果表明,在0~8 cm土壤深度范围内,随土壤深度的增加,轴根型紫花地丁和根茎型水麦冬的根长密度RLD、根表面积密度RASD、根面积比RAR逐渐减小,而根蘖型苦荬菜的RLD、RASD、RAR出现了先增大后减小的趋势。3种草本植物根系分布特征参数的量化结果均表现为紫花地丁>水麦冬>苦荬菜。根茎型水麦冬提升土体抗压强度的能力最优,其根土复合体黏聚力增量分别是紫花地丁和苦荬菜黏聚力增量的1.42、2.6倍。3种草本植物破坏面的RLD、RASD和RAR均表现为水麦冬最大,苦荬菜最小,紫花地丁居中。苦荬菜破坏面根系参数与黏聚力增量无相关性。对于轴根型和根茎型草本植物,根土复合体破坏面的3个根系分布参数中,RAR与黏聚力增量的相关性明显高于RLD和RASD。因此,RAR可以作为预测根茎型和轴根型草本植物提高土体抗压强度能力的重要参数。

基于Logistic模型的盐渍农田向日葵根长密度分布模拟

根长密度分布是反映作物根系潜在水分利用状态的重要指标,然而,当前关于水盐胁迫下作物根系量化的研究有限。以2016-2017年盐渍农田向日葵为研究对象,比较分析了不同盐分田块(低S1、中S2和高S3)的土壤水盐和作物根长密度分布变化,提出可以表征其动态变化的Logistic模型(LRDG),并对模型参数(α和β)进行量化。结果显示:高盐田块的作物根长密度整体高于低盐田块,且根系集中生长的现象显著,特别是在蕾期后,向日葵根系集中分布于30~75 cm土层,累积根长占比超过40%,其中2016年S3田块作物根长密度峰值达5 cm/cm^(3)以上。相比于标准根长密度的指数和幂函数模型,Logistic模型可较好地表征盐渍农田向日葵静态根长密度分布,R2为0.870,RRMSE为0.338;同时,Logistic模型参数α和β随土壤表层水盐和积温变化规律显著,由此具体量化了参数α和β的计算公式,参数量化验证RRMSE分别为0.425和0.297。这表明构建的LRDG模型能够准确表征土壤水盐胁迫下作物根长密度分布的动态响应,可为盐渍农田作物抗逆潜力挖掘和水肥科学管理提供工具支持。

永定河典型护岸植被土壤水分入渗特征及影响因素

为探究永定河岸坡缓冲带不同护岸植被覆盖下土壤水分入渗状况及植被根系对其影响,为区域河岸带生态修复和水资源保护提供参考,选取永定河流域典型护岸植被柳树林、荆条林、狗尾草地为研究对象,通过亮蓝染色法结合Photoshop、Image Pro6.0等图像处理技术,基于分形维数和多指标评价法定量评价了优先流发育程度,并探讨了不同植被根系对优先流的影响。结果表明:①研究区3种植被类型覆盖地土壤均存在水分优先入渗现象,土壤染色面积比随土层深度增加而逐渐减小,柳树林地平均染色面积比(38.32%)最大,为荆条林地和狗尾草地的1.11倍和1.37倍。狗尾草地的长度指数、优先流分数均显著低于柳树林地(P<0.05),3种植被覆盖地基质流深度无显著差异。②以优先流评价指数和分形维数评价优先流发育程度的结果呈一致,为柳树林地>荆条林地>狗尾草地,柳树林地的湿润锋迹线破碎化程度最高,优先流发育最显著。③有机质、非毛管孔隙度和根长密度对水分入渗均具有显著影响,总根长密度、非毛管孔隙度与染色面积比呈显著正相关,≥1 mm根系根长密度、有机质含量与分形维数呈显著正相关。3种植被覆盖地染色面积比和根长密度关系曲线拟合较好。总之,在外界条件相同的情况下,柳树林地水分优先入渗现象最明显;植物根系的径级、密度对优先流的发育具有显著影响,≥1 mm根系越丰富优先流现象越明显,而径级<1 mm的根系主要促进表层土壤水分均匀入渗。

漫灌下幼树期库尔勒香梨根系分布特征研究

【目的】研究幼树期库尔勒香梨根系分布特征,为制定科学高效的水肥管理措施提供理论依据。【方法】在南疆选择大水漫灌果园,选取1~6年生库尔勒香梨各3株为试材,在树干周围半径160 cm,挖掘0—100 cm深剖面,每20 cm取1个样品,利用WinRHIZO根系分析系统测定不同径级梨树根系根长、根表面积、根体积。【结果】梨树根长增长始终以吸收根为主,吸收根根长占总根长的86%~95%,且3、5、6年树龄根长显著增长。根表面积增长是不同径级根系共同作用的结果,其中吸收根根表面积占比为41%~77%,输导根占比22%~33%。根体积增长以粗根和输导根为主,4、6年粗根增长较快,3、5年输导根增长较快,两类根体积增长不同步。梨树根长密度整体上随土层加深先增大后减小,呈“单峰型”变化,随水平距离增加而减小。垂直方向上根长主要分布在0—60 cm深土层,占整个采样剖面总根长的76.46%以上;水平方向上,以0—20 cm土壤根长密度占比最高,1年和2年占比分别为71.93%、41.62%,随树龄增长呈下降趋势。2~4年,梨根系密度增幅较小,主要表现为延伸生长,并在距离树干较远处形成分散的根密集区。6年根长密集区连接成片,根长密度在水平方向上差异变小,形成垂直方向分层分布的特征。距离主干水平方向40 cm以内土壤吸收根生长旺盛,1~5年根长占比39.56%以上,对整个采样区域根长密度增长贡献较大。【结论】幼树期库尔勒香梨距主干较远处的根系具有较强的生长势,输导根和吸收根优先占据更大土壤空间,2~5年在距离树干较远处形成根系密集区域,有利于扩大养分吸收空间范围。6年生梨树根系密集区连接成片,水平方向较均匀分布,20—60 cm深度土层集中分布。实际生产中应根据树龄逐年扩大水肥管理范围,同时重视距主干40 cm水平范围内根系的作用。

深耕配合施用有机肥提高15—30cm土层小麦根长密度

【目的】耕作方式与有机物料影响小麦根系生长和产量,比较不同耕作方式和施用不同有机物料条件下小麦根系生长的特征,为建立合理的耕作方式与有机物料配合方案提供理论依据和技术支撑。【方法】田间定位试验位于安徽舒城,始于2016年。于2019年10月—2020年5月,选取其中旋耕+秸秆还田(RS)、深耕+秸秆还田(DS)、旋耕+有机肥(RM)、深耕+有机肥(DM)4个处理小区,监测小麦根系生长特征;小麦收获后测量土壤紧实度,并采集0—15和15—30 cm土样,分析土壤理化性质;每年小麦成熟期调查小麦产量。【结果】与旋耕相比,深耕处理显著降低了15—30 cm土层中土壤紧实度,平均降低幅度为18.02%,且增加了小麦根长密度,平均增加幅度为10.23%。深耕配合有机肥处理(DM)15—30 cm土层土壤有机质、全氮、有效磷含量最高,较其他处理的提升幅度分别为10.42%~16.56%、8.18%~45.12%、21.53%~29.13%;小麦根长密度提升幅度最大,小麦整个生育期平均较其他处理提升了10.88%~22.91%,其中在0—15、15—30、30—45 cm土层中的平均提升幅度分别为8.69%~18.67%、12.29%~27.99%、12.62%~30.61%。偏最小二乘法路径模型(PLSPM)分析表明,耕作方式主要是通过降低土壤紧实度,增施有机物料主要是通过提高土壤养分含量,来促进小麦根系生长,且在15—30 cm土层中土壤养分和紧实度对小麦根长密度的影响程度强于0—15 cm土层。【结论】深耕结合有机肥更有利于降低土壤紧实度、提高土壤养分含量、促进小麦根系生长,尤其在15—30 cm土层,小麦根长密度显著增加,这有利于深土层根系的增加,进而实现小麦的高产稳产。

不同根系构型草本与灌木复合对土壤饱和导水率的影响因素分析及模拟

[目的]探究不同根系构型草本与灌木复合时的根土性质的差异对土壤饱和导水率的影响,并综合考虑根系和土壤性质建立估算土壤饱和导水率的经验方程,为黄土高原植被恢复后的水文模型建立提供理论参考。[方法]选取不同根系构型草本与灌木的混合样地,分别为柠条锦鸡儿加冰草(须根系)和柠条锦鸡儿加铁杆蒿(直根系)。采用双环刀法测定不同样地土壤饱和导水率。[结果]样地类型和土层深度对土壤饱和导水率的影响达到显著水平,两者对土壤饱和导水率影响的因子贡献率分别为26%和52%。直根系铁杆蒿与柠条锦鸡儿混合样地的土壤饱和导水率高于须根系冰草与柠条锦鸡儿混合样地,并且不同样地的土壤饱和导水率随土层深度的增加均表现出降低的趋势。根长密度、团聚体以及土壤容重能够较好地模拟土壤饱和导水率,其拟合精度R 2可以达到0.86。[结论]直根系草本与灌木复合时较须根系草本与灌木复合相比具有更高的饱和导水率。在不同样地中,根长密度、团聚体以及土壤容重是影响饱和导水率的主要因素。

大田不同播种间距单株小麦根长密度动态研究

【目的】为探明单粒精播种植方式种间距对小麦根系的土层分布影响,构建了基于根系数字化仪实测根系3D拓扑结构数据下MATLAB分割分析复合型小麦根长密度(RLD)定量技术,获取大田条件不同种间距单株稻茬麦RLD在不同土层的分布特征和相对根长密度(NRLD)分布模型。【方法】选用宁麦13为试验材料,采用免耕等距单粒线播法,分别于2020和2021年进行稻茬小麦的免耕种植试验,设置单粒精播种间距1.5、3.0、4.5、6.7、9.0 cm共5个处理(JT1.5、JT3、JT4.5、JT6.7、JT9),行距20 cm。RLD分析采用根系构型数字化仪实测根系3D拓扑结构配合Pro-E软件数字重构,辅以MATLAB实现基于“空间voxel元技术”的根系生长空间3 cm^(3)精细分割和定量分析,跟踪各土层RLD分布动态和NRLD模型。【结果】不同处理的单株稻茬麦根长密度随土层深度的增加而逐步减小,0—9 cm土层深度内分布的稻茬麦根系达总根量95%以上,超过9 cm土层深度小麦根系急剧减小;单株小麦根系扩展面积随土层深度的增加先增加后减小,根构型以种子位作为中心点向四周拓展,且表现出明显的拓展方向性和约束性。群体稻茬麦RLD随种间距增加先增加后减小,且在JT4.5最大;RLD扩展面积随种间距的增大而不断增加,最大可达22972 mm^(2)。过高与过低的群体都造成不良的根构型影响,适宜的播种密度才能创建最佳的根系3D分布,实现土壤空间资源的高效利用。经归一化处理后0—20 cm土层NRLD分布同时符合三次多项式和指数模型,两模型的拟合效果均极好(R2>0.99,RMSE<0.1),但指数模型更符合随土层深度的RLD特征实际。【结论】融合根系数字化仪实测根系3D拓扑结构与MATLAB分割分析的复合型小麦根长密度定量技术实现了单粒精播稻茬麦不同种间距的单株及群体双尺度的根长密度分布动态的定量描述,所得结果可为今后开展小麦精确耕种、水肥精准运筹、根构型调控等研究提供方法学借鉴。

黄土旱塬区苹果园生草覆盖对深层土壤水分和根系分布特征的影响

研究苹果园长期生草覆盖后深层土壤水分及果树根系的分布规律,以期阐明旱作条件下果园根水互作关系,为黄土旱塬区果园生草覆盖实践的优化提供依据。试验于甘肃庆阳草地农业生态系统国家野外科学观测研究站苹果园中进行,设置果园生草覆盖(生草为鸭茅草,2014年建植)和清耕处理,以一年生作物田为对照;连续两年夏季测定果树行上和行间距离树干100和200 cm共4个位置0~500 cm土层的土壤水分和果树细根长密度,分析生草覆盖对果园深层水分亏缺及细根长密度的影响。清耕果园0~300 cm土壤水分较对照农田下降了6.7%~8.3%(P<0.01),而300~500 cm土层土壤水分与对照农田差异不显著(P>0.05);生草覆盖果园0~500 cm整个剖面的土壤水分均低于清耕果园,平均下降了11.5%~12.3%。果园生草覆盖6~7年后0~500 cm土层土壤较对照农田水分亏缺量为163.9~172.1 mm,是清耕果园水分亏缺量的3.2~4.2倍。果树根系在0~100 cm土层的细根长密度最高,平均密度为0.187 cm·cm^(-3),生草覆盖促进了0~100 cm土层果树根系的分布,对深层根系影响不显著。清耕果园和生草覆盖果园0~500 cm土层土壤水分的含量随果树细根长密度的增加而降低,二者呈线性负相关关系,生草覆盖后二者相关性提高,干旱年份二者相关性更高。黄土旱塬区苹果园长期生草可促进果树根系生长,降低深层土壤水分,加剧土壤干燥化,对苹果树的利用年限和农田水分循环具有负面效应。旱作条件下应加强果园生草覆盖管理以保障水分的可持续性。

Seasonal dynamics of fine root biomass, root length density, specific root length, and soil resource availability in a Larix gmelinii plantation

Fine root turnover is a major pathway for carbon and nutrient cycling in terrestrial ecosystems and is most likely sensitive to many global change factors.Despite the importance of fine root turnover in plant C allocation and nutrient cycling dynamics and the tremendous research efforts in the past,our understanding of it remains limited.This is because the dynamics processes associated with soil resources availability are still poorly understood.Soil moisture,temperature,and available nitrogen are the most important soil characteristics that impact fine root growth and mortality at both the individual root branch and at the ecosystem level.In temperate forest ecosystems,seasonal changes of soil resource availability will alter the pattern of carbon allocation to belowground.Therefore,fine root biomass,root length density(RLD)and specific root length(SRL)vary during the growing season.Studying seasonal changes of fine root biomass,RLD,and SRL associated with soil resource availability will help us understand the mechanistic controls of carbon to fine root longevity and turnover.The objective of this study was to understand whether seasonal variations of fine root biomass,RLD and SRL were associated with soil resource availability,such as moisture,temperature,and nitrogen,and to understand how these soil components impact fine root dynamics in Larix gmelinii plantation.We used a soil coring method to obtain fine root samples(≤2 mm in diameter)every month from May to October in 2002 from a 17-year-old L.gmelinii plantation in Maoershan Experiment Station,Northeast Forestry University,China.Seventy-two soil cores(inside diameter 60 mm;depth intervals:0-10 cm,10-20 cm,20-30 cm)were sampled randomly from three replicates 25 m×30 m plots to estimate fine root biomass(live and dead),and calculate RLD and SRL.Soil moisture,temperature,and nitrogen(ammonia and nitrates)at three depth intervals were also analyzed in these plots.Results showed that the average standing fine root biomass(live and dead)was 189.1 g·m^(-2)·a^(-1),50%(95.4 g·m^(-2)·a^(-1))in the surface soil layer(0-10 cm),33%(61.5 g·m^(-2)·a^(-1)),17%(32.2 g·m^(-2)·a^(-1))in the middle(10-20 cm)and deep layer(20-30cm),respectively.Live and dead fine root biomass was the highest from May to July and in September,but lower in August and October.The live fine root biomass decreased and dead biomass increased during the growing season.Mean RLD(7,411.56 m·m^(-3)·a^(-1))and SRL(10.83 m·g^(-1)·a^(-1))in the surface layer were higher than RLD(1474.68 m·m^(-3)·a^(-1))and SRL(8.56 m·g^(-1)·a^(-1))in the deep soil layer.RLD and SRL in May were the highest(10621.45 m·m^(-3) and 14.83m·g^(-1))compared with those in the other months,and RLD was the lowest in September(2198.20 m·m^(-3))and SRL in October(3.77 m·g^(-1)).Seasonal dynamics of fine root biomass,RLD,and SRL showed a close relationship with changes in soil moisture,temperature,and nitrogen availability.To a lesser extent,the temperature could be determined by regression analysis.Fine roots in the upper soil layer have a function of absorbing moisture and nutrients,while the main function of deeper soil may be moisture uptake rather than nutrient acquisition.Therefore,carbon allocation to roots in the upper soil layer and deeper soil layer was different.Multiple regression analysis showed that variation in soil resource availability could explain 71-73%of the seasonal variation of RLD and SRL and 58%of the variation in fine root biomass.These results suggested a greater metabolic activity of fine roots living in soil with higher resource availability,which resulted in an increased allocation of carbohydrate to these roots,but a lower allocation of carbohydrate to those in soil with lower resource availability.

绿色屋顶景天植物根系分布特征及其对饱和导水率的影响

为丰富我国绿色屋顶中景天属植物根系分布特征的研究及探讨根系特征参数与绿色屋顶基质层饱和导水率间的关系,选用景天属植物垂盆草、佛甲草种植于珍珠岩基质中,基质厚度为6、10、14 cm,结合武汉市降水特点对植物采用统一浇水制度进行培养,选取根长密度、根表面积密度、根体积密度来描述根系形态,并测定基质的饱和导水率;以无植物组为对照组,定量比较不同基质厚度下绿色屋顶景天属植物根系分布特征及其饱和导水率的变化差异。结果表明:1)景天属植物的根长密度、根表面积密度、根体积密度受珍珠岩基质厚度影响显著。6 cm基质中植物的总根长密度最大,这与基质中直径为0.2~0.4 mm根的根长密度占比大有关;14 cm基质中植物的总根表面积密度、根体积密度最大,这与基质中直径为1~2 mm根的根表面积密度、根体积密度占比大有关。2)景天属植物根系对珍珠岩基质饱和导水率的改变显著。相比无植物组,景天属植物根系的加入使得珍珠岩基质的饱和导水率改变了-98.95%~-95.15%,有植物组的饱和导水率远低于无植物组;而有植物组间,珍珠岩基质的饱和导水率与景天属植物直径为0.2~0.4 mm根的根长密度(P=0.050,R2=0.786)、根表面积密度(P=0.047,R2=0.818)、根体积密度(P=0.044,R2=0.824)呈显著正相关。