Variation patterns of fine root biomass, production and turnover in Chinese forests

China's forests cover 208.3 million ha and span a wide range of climates and a large variety of forest types, including tropical, temperate, and boreal forests. However, the variation patterns of fine root (< 2 mm in diameter) biomass, production, and turnover from the south to the north are unclear. This study summarizes fine root biomass (FRB), production (FRP) and turnover rate (FRT) in China's forests as reported by 140 case studies published from 1983 to 2014. The results showed that the mean values of FRB, FRP and FRT in China's forests were 278 g m(-2), 366 g m(-2) a(-1), and 1.19 a(-1), respectively. Compared with other studies at the regional or global scales, FRB in China's forests was lower, FRP was similar to estimates at the global scale, but FRT was much higher. FRB, FRP, and FRT in China's forests increased with increasing mean annual precipitation (MAP), indicating that fine root variables were likely related to MAP, rather than mean annual temperature or latitude. This is possibly due to the small variation in temperature but greater variation in precipitation during the growing season. These findings suggest that spatiotemporal variation in precipitation has a more profound impact on fine root dynamics in China's forests, and this will impact carbon and nutrient cycles driven by root turnover in the future.

Vertical Distribution and Seasonal Dynamics of Fine Root Parameters for Apple Trees of Different Ages on the Loess Plateau of China

The vertical distribution pattern and seasonal dynamics of fine root parameters for the apple trees of different ages （3, 10, 15, and 20 years old） on the Loess Plateau of China were studied. Soil coring method was used to determine the vertical distribution and seasonal dynamics of fine roots at different root radial distances （1.0, 1.5, and 2.0 m from the main tree trunk）. The fine root biomass density （FRD）, fine root length density （RLD）, and specific root length （SRL）, as well as soil water content and soil temperature were also measured. The FRD and RLD for the 10, 15, and 20 years old trees reached peak values in the 20-30 cm soil layer. For the 3 years old tree, the highest FRD and RLD were observed in the 10-20 cm soil layer. The FRD and RLD decreased with increased soil depth from the 10-20 or 20-30 cm soil layer for all age apple trees. The SRL declined with the increase of tree age. The FRD at the 1.0 m radial distance from the main tree trunk was higher than that at other radial distances in the 3 and 10 years old orchard. However, in the 15 and 20 years old orchards, especially the 20 years old orchard, the FRD at the 2.0 m radial distance was nearly equal to or higher than that at the 1.0 and 1.5 m radial distances. For all the root radiuses or the tree ages, the FRD, RLD, and SRL were the highest in spring and the lowest in autumn. The age of an apple tree does not affect the vertical distribution pattern but the biomass of fine roots and the SRL. Radial distance affects the root horizontal distribution of 3 and 10 years old trees but the 15 and 20 years old trees. Additionally, effects of soil temperature and soil moisture on fine root distribution or seasonal dynamics are not significant.

Estimating the production and mortality of fine roots using minirhizotrons in a Pinus densiflora forest in Gwangneung,Korea

The aim of this study was to estimate fine root production （FP） and fine root mortality （FM） at 0-10, 10-20, and 20-30 cm soil depths using minirhizotrons in a 75-year-old Pinus densiflora Sieb. et Zucc. forest located in Gwangneung, Korea. We developed the conversion factors （frame cm-2） of three soil depths （0.158 for 0-10 cm, 0.120 for 10-20 cm, and 0.131 for 20-30 cm） based on soil coring and minirhizotron data. FP and FM were estimated using conversion factors from March 26, 2013 to March 2, 2014. The annual FP and FM values at the 0-30 cm soil depth were 3200.2 and 2271.5 kg ha-1 yr -1, respectively. The FP estimate accounted for approximately 17 % of the total net primary production at the study site. FP was highest in summer （July 31-September 26）, and FM was highest in autumn （September 27-November 29）. FP was positively correlated with seasonal change in soil temperature, while FM was not related to that change. The sea- sonality of FP and FM might be linked to above-ground photosynthetic activity. Both FP and FM at the 0-10 cm depth were significantly higher than at 10-20 and 20-30 cm depths, and this resulted from the decrease in nutrient availability with increasing soil depth. The minirhizotron approach and conversion factors developed in this study will enable fast and accurate estimation of the fine root dynamics in P. densiflora forest ecosystems.

Definition of fine roots on the basis of the root anatomy, diameter,and branch orders of one-year old Fraxinus mandshurica seedlings

Fine roots are important in root absorption of nutrient and water,and in root turnover.Accurate definition of fine roots is a prerequisite to improved estimation of the physiological and ecological functions of forest ecosystems.Root development and physiological functions are reflections of root anatomical structure.In this study,the anatomical structures of different root orders were analyzed by examining paraffin sections of one-year old Fraxinus mandshurica seedlings.One-year-old F.mandshurica seedlings had over five root orders.The root anatomical structures of all orders showed more differences.First and second order roots consisted of four sections： the epidermis,cortex,pericycle,and vascular bundles.Fourth and fifth order roots were mainly composed of the skin and peripheral vascular bundles（including the xylem and phloem）.Third order roots had root epidermal and cortical structures,but the quantity and integrity of the cortical cells were inferior to those of the first and second order roots,and superior to those of the fourth and fifth order roots.All the first and second order roots and some third order roots with discontinuous cork layer（〈0.4 mm in diameter）,but not the fourth and fifth order roots,were the fine roots of one-year old F.mandshurica seedlings.Although they had similar diameters,different portions of root systems had different anatomical structures and therefore,vary in capacity to absorb water and nutrients.Fine roots were accurately defined by root diameter,branch orders,and anatomical structural features of one-year old F.mandshurica seedlings.

Nutrient retranslocation from the fine roots of Fraxinus mandshurica and Larix olgensis in northeastern China

Nutrient retranslocation in trees is important in nutrient budgets and energy flows in forest ecosystems. We investigated nutrient retranslocation in the fine roots of a Manchurian Ash （Fraxinus mandshurica） and a Larch （Larix olgensis） plantation in northeastern China. Nutrient retranslocation in the fine roots was investigated using three methods, specifically, nutrient concentration, the ratio of Ca to other elements （Ca/other elements ratio） and nutrient content. The method based on nutrient content proved most suitable when investigating nutrient retranslocation from fine roots of the two species. The nutrient-content-based method showed that there were retranslocations of N, P, K and Mg from the fine roots of Manchurian Ash, with retranslocation efficiencies of 13, 25, 65, and 38 %, respectively, whereas there were no Ca retranslocations. There were retranslocations of N, P, K, Ca and Mg from the fine roots of Larch, with retranslocation efficiencies of 31, 40, 52, 23 and 25 %, respectively.

Spatial heterogeneity of fine root biomass of Pinus massoniana forests in the Three Gorges Reservoir Area, China

Environmental heterogeneity is a constant presence in the natural world that significantly affects plant behavior at a variety of levels of complexity. In order to estimate the spatial pattern of fine root biomass in the Three Gorges Reservoir Area, the spatial heterogeneity of fine root biomass in the upper layer of soils （0-10 cm） in three Mas- son pine （Pinus massoniana） stands in the Three Gorges Reservoir Area, China, was studied in 30 m x 30 m plots with geostatistical analysis. The results indicate that 1） both the live and dead fine root biomass of stand 2 were less than those of other stands, 2） the spatial variation of fine roots in the three stands was caused together by structural and ran- dom factors with moderate spatial dependence and 3） the magnitude of spatial heterogeneity of live fine roots ranked as： stand 3 〉 stand 1 〉 stand 2, while that of dead fine roots was similar in the three stands. These findings suggested that the range of spatial autocorrelation for fine root biomass varied considerably in the Three Gorges Reservoir Area, while soil properties, such as soil bulk density, organic matter and total nitrogen, may exhibit great effect on the spatial distribution of fine roots. Finally, we express our hope to be able to carry out further research on the quantitative relation- ship between the spatial heterogeneous patterns of plant and soil properties.

Comparing growth and fine root distribution in monocultures and mixed plantations of hybrid poplar and spruce

Disease prevention, biodiversity, productivity improvement and ecological considerations are all factors that contribute to increasing interest in mixed plantations. The objective of this study was to evaluate early growth and productivity of two hybrid poplar clones, P. balsamifera x trichocarpa （PBT） and P. maximowiczii x balsamifera （PMB）, one improved family of Norway spruce （Picea glauca （PA）） and one improved family of white spruce （Picea abies （PG）） growing under different spacings in monocultures and mixed plots. The plantations were established in 2003 in Abitibi-Témiscamingue, Quebec, Canada, in a split plot design with spacing as the whole plot factor （1 × 1 m, 3 × 3 m and 5 × 5 m） and mixture treatments as subplot factor （pure： PBT, PMB, PA and PG, and 1：1 mixture PBT：PA, PBT：PG, PMB：PA and PMB：PG）. Results showed a beneficial effect of the hybrid poplar-spruce mixture on diameter growth for hybrid poplar clones, but not for the 5 × 5 m spacing because of the relatively young age of the plantations. Diameter growth of the spruces decreased in mixed plantings in the 1 × 1 m, while their height growth increased, resulting in similar aboveground biomass per tree across treatments. Because of the large size differences between spruces and poplars, aboveground biomass in the mixed plantings was generally less than that in pure poplar plots. Leaf nitrogen concentration for the two spruce families and hybrid poplar clone PMB was greater in mixed plots than in monocultures, while leaf nitrogen concentration of clone PBT was similar among mixture treatments. Because of its faster growth rate and greater soil resources demands, clone PMB was the only one showing an increase in leaf N with increased spacing between trees. Fine roots density was greater for both hybrid poplars than spruces. The vertical distribution of fine roots was insensitive to mixture treatment.

Spacial Patterns of Fine Root Abundance in Mixed Larch-Ash Plantation

Horizontal and veftical distributions of fine root abundance (mass per unit ground surface arca) were investi-gated in a densely planted larch - ash -stripe - mixed tbrest on dark broxvn forest soil in northeast China. There was evidencefor some degree of below-ground niche partitioning (or differentiation) betmpen the two species in hoth the horizontal andvertical directions. The ash fine roots largely penetrated into the larch belt (larch Sub-community) in surttrce soil (0-20 cm),indicating a possible inductive effect of larch ecological field on ash roots, while the penetration of larch tine roots into ashbelt (ash sub-community) was much restricted- which reflected a negative influence of ash ccological tield on Iarch roots. Inthe vertical direction of marginal soil the ash tine roots were mainly distributed in topsoil with a vertical gradient similar tothat as in the internal ash sub-community. but the larch fine roots were relatively compelled to deepcr soil layers by the com-petition (or exclusion) of marginal ash trees. All the dit1brences or complemcntarity wcre considered to the result of inter-specitic competition, which was important to the coexistence of the two tbrest species and the sustainability of mixed planta-tion.

Fine Roots Dynamics in Two Forest Strata of a Semi-Deciduous Forest in Northern Republic of Congo

The belowground biomass is represented by coarse and fine roots. Concentrated in the superficial horizons of the soil, the fine roots play a crucial role in the functioning of a forest ecosystem. However, studies on their dynamics in natural forests are almost non-existent in the Republic of Congo. Here, we estimated the biomass, production, turnover and fine root lifespan of two forest strata of a semi-deciduous forest: the Gilbertiodendron dewevrei (De Wild.) J. Léonard forest (GF) and the mixed forest (MF) of land. The ingrowth cores method was used to estimate the biomass, production, turnover and lifespan of fine roots. The results of this study revealed that the biomass, production and fine root turnover of the two forest strata studied significantly decreased with increasing soil depth, with an increase in lifespan. The annual fine root biomass of GF (2284.50 ± 37.62 and 1034.61 ± 14.52 ) was slightly lower than that of MF (2430.07 ± 40.68 and 1043.10 ± 11.75 ) in the 0-15 cm and 15-30 cm horizons, respectively. The annual production of fine roots from these latter horizons was respectively 1300.19 ± 32.17 and 539.18 ± 11.55 in GF and 1362.24 ± 39.59 and 492.95 ± 14.38 in the MF. Root turnover was higher in the GF (1.68 ± 0.05 and 1.35 ± 0.03 ) than in the MF (1.57 ± 0.05 and 1.13 ± 0.02 ). The lifespan of fine roots increased with the depth of the soil. The difference in fine root dynamics observed between the forest strata studied was influenced by the Evenness index and the above-ground biomass.

Morphological Characteristics and Nutrient Content of Fine Roots of 2-Year-Old and 3-Year-Old Eucalyptus grandis Plantation

[ Objective] This study aimed to explore the morphological characteristics and nutrient content of f＇me roots of 2-year-old and 3-year-old Euca/yptus grand/s plantation and investigate the correlation. [ Method] Fine roots of 2-year-old and 3-year-old Eucalyptus grandis plantation were collected as experimental materials, to determine the root diameter （D）, root length （L）, specific root length （SRL） and contents of major nutrient elements N, P, K, Ca, Mg and C of fine roots （level 1 -5）, study the morphological characteristics and major nutrient element content and investigate the correlation. [ Result] The results showed that morphological differences of fine roots （ level 1 - 5 ） of Eucalyptus grandis plantation were great with the increase of root order, to be specific, D and L increased and SRL decreased with the increasing root order; SRL, L and D of 3-year-old Eucalyptus grauclis plantation were greater than those of 2-year-old Euca/yptus grand/s plantation. Contents of N, Ca, Mg and C of fine roots of 2-year-old and 3-year-old Eucalyptus grandis plantation showed consistent orders with the increase of root order： N and Mg contents were reduced, while Ca and C contents were enhanced; P and K contents varied with different forest ages; both 2-year-old and 3-year- old Eucalyptus grandis showed an order of C 〉 K 〉 Ca （Mg） 〉 N. Major nutrient element content and morphological characteristics of Eucalyptus grand/s fine roots （level 1 -5 ） were extremely significantly correlated （P 〈0.01 ）, SRL, L and D could be adopted as reference indices to evaluate nutrient status of Eucalyptus grand/s. Required nutrients and fine root morphology of Eucalyptus grandis plantation changed with the increase of forest age, and the nutrient cycling and energy flow patterns also changed; major nutrient dements in fine roots of 2-year-old and 3-year-old Eucalyptus grandis plantation transferred in a different order from the growth order, therefore N fertilizer could be applied to improve the growth of fine roots. [ Condusion] This study laid the foundation for understanding the fine root morphology and nutrient variation pattern of Eucalyptus grandis plantation and enriching the response and adaptation mechanism theory of roots to environment, pos- sessing important reference significance for the sustainable development of Eucalyptus grand/s plantation.

Fine Root Mortality Increased by Earthquake Induced Landslides

This study determined the effects of earthquake induced landslide on fine root mortality. It is useful to understand underground soil process after earthquake. We established 9 plots at each of non-moved and landslide site in Cupressus funebris and Cryptomeria fortunei forest stands near the fault belt of the Wenchuan Earthquake. Fine roots were sampled at 0 - 10 and 10 - 15 cm soil layer using aluminum cylinders (100 cm3). We found that earthquake induced landslide significantly increased fine root mortality in Cupressus funebris and Cryptomeria fortunei forest stands. Fine root biomass also decreased by landslide at 0 - 10 cm soil layer. We observed that the fine root biomass and mortality were various with forest type. There were higher fine root mortality rate (68.4%) and lower fine root biomass (0.48 t/hm2) in Cupressus funebris than the Cryptomeria fortunei soils (0.97 t/hm2 and 37.4%).

木麻黄细根形态和化学计量特征对P添加的塑性响应

探究不同发育阶段木麻黄防护林细根形态和化学计量特征对磷(P)添加的塑性响应规律,为滨海沙地土壤低磷限制下进行木麻黄不同发育阶段有针对性的施肥抚育提供科学依据。以福建省平潭岛木麻黄幼龄林(5 a)、中龄林(12 a)和成熟林(25 a)为研究对象,以内生长土芯法开展P添加试验,细根在内生长芯生长一年后,采用功能划分法对细根形态性状和化学计量特征进行测定。结果表明:(1)P添加显著提高木麻黄细根根长和根表面积,其中,总根长和总表面积总体提高7.79倍、8.69倍,比根长和比表面积总体提升15.1%、19.5%;(2)不同根系功能类群间,细根形态对P添加的塑性响应具有较显著差异,形态塑性以吸收根为主,且吸收根对P养分资源的响应更为敏感,P添加使吸收根P含量总体提高56.0%,C/P和N/P总体降低18.7%和38.7%,组织密度总体降低31.4%;(3)对于土壤P养分资源的变化,不同林龄木麻黄采取不同的塑性响应策略,P添加后,幼龄林主要通过吸收根化学计量特征变异,改变自身生理性状获取P元素,中龄林细根形态和化学计量特征无显著变异,成熟林主要通过改变吸收根形态,扩大根系吸收面积获取P元素。外源P添加可以协调木麻黄细根形态与化学计量特征的内部关系,而不同林龄木麻黄细根在获取P资源时会选择性投资。故在木麻黄施肥抚育时,应根据不同林龄采取针对性的抚育方案。

微根管和根箱法在亚热带细根寿命研究中的应用

由于研究方法的限制,植物细根寿命的准确估算仍较为困难,因此寻求一种准确的研究方法对细根寿命进行研究显得十分重要。微根管法和根箱法能够在不干扰细根生命过程的前提下连续观测植物细根动态,是一种非破坏性观测方法,被较多地应用于野外观测。结合课题组多年来运用微根管技术和根箱技术研究中亚热带代表性植物细根寿命的实例,对微根管法和根箱法的具体应用进行了介绍和分析,主要包括两种方法的具体实验设计、图片采集及分析、数据处理等,以期为促进对森林生产力和碳源汇控制机理的理解提供借鉴。

西北干旱区荒漠植物叶片和细根碳、氮、磷化学计量特征

植物的叶片和细根是植物地上部分和地下部分最重要的营养器官,其碳(C)、氮(N)、磷(P)化学计量特征反映了植物的养分限制状况及叶片与细根间的协同作用,开展叶片与细根化学计量关系的研究,对认识植物养分利用策略及元素间平衡关系有重要意义。对西北干旱区21种荒漠植物叶片与细根C、N、P含量进行了测定,分析了C、N、P含量及其计量比在不同生活型及不同器官间的关系。结果表明:1)西北干旱区荒漠植物叶片与细根C含量相对稳定,叶N、P含量高于细根,说明在干旱生境中,植物对养分的分配侧重于地上部分,以完成其正常的生命活动;叶片与细根的N∶P无显著差异,有明显的保守性,表明植物地上与地下部分养分吸收策略与分配规律具有一致性;2)不同生活型植物叶片和细根的C、N、P含量及C∶N、C∶P存在显著差异,灌木与禾草具有较高的C∶N和C∶P,杂类草具有较高的N、P含量,说明灌木与禾草倾向于保守型养分适应策略,杂类草倾向于快速生长的资源竞争策略;3)21种荒漠植物叶片与细根N、P含量间均存在显著的正相关关系,表明西北干旱区荒漠植物体内N、P元素间存在相互作用;4)植物叶片与细根间C、N、P含量及C∶N、C∶P存在等速生长关系,表明植物光合产物和养分在地上与地下部分间的分配具有平行的比例关系,但这种关系受生活型影响。上述结果表明西北干旱区不同生活型植物在恶劣生境中存在不同的养分适应策略,且地上与地下部分的养分利用策略及分配规律存在协同作用,这为进一步认识西北干旱区荒漠植物的养分利用策略提供了试验基础。

闽江福州段湿地草本植物叶片与细根功能性状对水盐梯度的响应

叶片和细根是植物获取资源最重要的器官,探究叶片、细根功能性状之间的相互关系及其对环境梯度变化的响应,有利于揭示植物对资源的利用情况以及对环境变化适应的生态策略。本文以湿地草本植物为研究对象,闽江流域福州段4个典型湿地为研究区域,设置了3条垂直于河道的调查样带,108个样方,选取7个叶功能性状以及5个细根功能性状指标,运用单因素方差分析、相关性分析、冗余分析等方法分析湿地草本植物叶片与细根功能性状对水盐梯度的响应。结果显示:(1)叶形指数和根组织密度变异系数最大;(2)叶厚、叶干物质含量、根体积、比根长随着水盐条件的增加而增加,比叶面积和根组织密度则随着水盐条件的增加而减小,冗余分析表明土壤含水量的影响更为关键;(3)比叶面积与叶面积、叶厚等呈极显著负相关;叶组织密度和叶干物质含量均与比根长、比根面积均呈极显著正相关;(4)地上和地下部分的功能性状在不同的水盐梯度下,一部分成对性状会呈现协同一致的趋势。研究结果说明,湿地草本植物对于水盐条件变化的适应能够通过叶、细根功能性状的相互调节而实现,具有较强的性状可塑性。

根土微环境对早实核桃细根时空分布、养分特征的影响

以长势基本一致且处于稳产期的‘新新2号’早实核桃(Juglans regia L.)后代为研究对象,按照小格子法将根土连续体划分为144个采样小区。于2022年每月采集根、土样品,测定细根生物量并构建二维空间分布图,研究细根形态指标、养分特征以及土壤水、养质量分数并分析其对早实核桃细根时空分布、养分特征的影响。结果表明:早实核桃细根主要分布在垂直方向的0~0.4 m土层和距树干水平方向1.5 m范围内,占细根分布总量的80%。细根形态参数值(生物量、根长密度、根表面积密度、根体积密度)和养分质量分数均随土层加深呈下降趋势,细根在微环境水平变异时差异不明显。夏、秋季细根形态参数值均显著高于春、冬季。土壤全氮、全磷质量分数随土层加深逐渐减少,土壤全钾质量分数在整个空间分布上无明显差异。土壤含水率随土层加深而增加,距树干距离越远含水率越低。土壤各养分质量分数的季节性差异较大,全氮质量分数在夏、秋季较高,在春季最低;全磷质量分数在春季最高;全钾质量分数在冬季最高;土壤含水率在秋、冬季最高。细根形态、养分质量分数与土壤全氮、全磷、含水率的关系更密切,相关性存在一定季节差异。细根生长在细微变异的环境下仍具有一定的趋水趋肥性。对早实核桃进行肥水精细化管理时,可根据根土的时空关系,在根区适时灌溉,季节性调整肥料养分,施肥则以氮、磷肥为主。

扫描根窗法在落叶松人工林细根动态研究中的应用

植物根系深藏于地下,由于缺乏有效的观测方法,制约了对根系的了解。以落叶松人工林为研究对象,根据扫描根窗法对落叶松人工林细根长期观测案例,介绍扫描根窗法在野外原位观测细根动态的过程。结果表明:在深秋季节安装根窗,根窗安装扰动后恢复期为1 a,经过冻融交替和一个生长季后,细根现存量迅速恢复且趋于稳定;通过观察发现吸收根现存量峰值多出现在春季和初夏,而运输根峰值多出现在秋季;野外根窗法与微根管法相比可清晰的观测到细根的完整分枝结构,将高度异质性的细根群体细分为不同根序或功能类型,为区分不同细根功能和分枝等级提供了手段。

不同种源和家系红皮云杉细根形态与生物量垂直分布特征

为揭示不同种源和家系红皮云杉(Picea koraiensis)细根(直径≤2 mm)形态和生物量垂直分布特征,以黑龙江省林口县青山林场4个种源(纬度从低到高分别为穆棱、林口、金山屯、乌伊岭)30个家系的24年生红皮云杉试验林为研究对象,采用根钻法研究了不同土壤深度(h)(表层:0<h≤10 cm,亚表层:10 cm<h≤20 cm,底层:20 cm<h≤30 cm)细根形态和生物量垂直分布规律。结果表明:不同种源红皮云杉细根形态特征存在显著差异,而同一种源不同家系间比根长和根组织密度存在显著差异。在种源水平,所有土层根平均直径均以穆棱种源最粗,比根长和根组织密度则均是林口种源最大。在家系水平,0<h≤10 cm土层根直径W035最粗、CK-2最细,比根长CK-2最大、W043最小,根组织密度J082最高、M515最低。不同种源和家系红皮云杉根组织密度和比根长均随土层加深而减小,而根直径随土层的加深有增大的趋势。4个种源的细根总生物量平均值为33.56 g·m^(-2),其中林口种源细根生物量最大(39.04 g·m^(-2)),金山屯种源细根生物量最小(32.52 g·m^(-2)),呈现出非连续的地理变异。细根生物量均随土层的加深而减小,土壤表层根系生物量占总生物量的比例平均为77%。相比较,低纬度的穆棱种源各家系细根生物量在土壤亚表层和底层分布比例较高,高纬度的乌伊岭和金山屯种源各家系细根生物量在土壤表层分布比例较高,表明温度较低地区的红皮云杉倾向于将细根分布在资源丰富的土壤表层。

封育年限对武夷山毛竹细根功能性状的影响

自然封育是培育森林资源重要且有效的途径,细根作为植物体重要的资源获取型器官,在森林群落发挥生态功能中扮演重要角色。为明晰自然封育对毛竹细根功能性状的影响,采用空间代替时间的研究方法,以武夷山国家公园内正常经营和封育年限为3、5、10、15年和40年的毛竹林作为研究对象,揭示不同封育年限下毛竹细根功能性状的差异以及对土壤理化性质变化的适应规律。结果表明:(1)封育年限对毛竹细根的功能性状具有显著影响。随着封育年限的增长,毛竹细根的比根长、比根面积、全碳、全氮和全磷含量均呈现先上升后下降的变化趋势,组织密度、碳氮比和碳磷比呈现先下降后上升的趋势,同其他封育毛竹林群落相比,封育10和15年的毛竹林群落中细根比根长、比根面积和养分含量得到显著提高。土壤层次和细根径级对细根功能性状同样具有显著影响。(2)毛竹细根功能性状间随封育年限的变化存在显著的相关性。比根长、比根面积、全碳含量、全氮含量和全磷含量彼此之间存在显著的正相关关系,与碳氮比、碳磷比和组织密度存在显著的负相关关系。(3)随着封育演替进程,毛竹林群落中土壤因子的变化驱动着细根功能性状发生改变,土壤容重同细根养分含量呈显著的负相关关系,土壤碳磷含量与细根比根长和比根面积存在显著的正相关关系,土壤养分含量与细根养分含量呈现极显著正相关关系。综上,自然封育促使毛竹细根通过自身表型可塑性合理权衡不同功能性状之间的资源配置,当封育10—15年,毛竹细根将更多养分集中于资源获取型性状的构建,吸收能力和效率显著提高,林分生产力和生态功能较优,在封育10—15年后适当进行科学的人为经营活动有助于毛竹林的可持续健康发展。

淡竹蔸根和鞭根细根寿命特征

植物细根寿命是影响细根周转的重要因素,在陆地生态系统碳和养分循环中扮演着重要角色。但是,目前对竹类植物根寿命的直接观测资料和研究仍显不足,尤其缺乏关于竹类植物蔸根和鞭根两种类型根寿命特征的研究。利用根箱对淡竹(Phyllostachys glauca)蔸根和鞭根细根生长动态开展研究,结果表明:(1)淡竹蔸根和鞭根细根寿命间没有显著差异,但是根序对根寿命有显著影响。1级根寿命显著低于2级根寿命,2级根寿命显著低于3级根寿命。(2)蔸根和鞭根的出生和死亡具有不同的季节模式。鞭根新根出生集中于7、8、9月,在7月达到峰值,死亡高峰发生在春季(3—5月)。蔸根新根发生没有单一峰值,在3月、7月、11月各有一次新根发生的小高峰,死亡高峰发生在夏季(6—8月)。(3)淡竹蔸根和鞭根的细根寿命与出生时间的关系不同。蔸根夏季出生的细根中值寿命最长,春季出生的细根中值寿命最短。鞭根春季出生的细根中值寿命最长,冬季(12—2月)出生的细根中值寿命最短。发现淡竹蔸根和鞭根的细根具有不同的生长规律,其寿命与根序级别、出生时期密切相关,研究结果可为竹林生产和管理提供理论依据。