柳杉细根衰老过程中的养分内循环

将柳杉细根剥离土壤,加速细根衰老,测定并分析柳杉细根衰老期间不同根序细根的N,P,K及Ca浓度变化以及N,P,K浓度与Ca浓度比值的变化趋势。结果表明:1)在柳杉细根死亡过程中,N及K存在明显的内循环,Ca内循环不明显,P没有内循环;2)养分内循环首先出现在1级细根,其次是2和3级细根,表明细根衰老和死亡顺序与生长顺序相反;3)养分回输表现为阶段性,1级细根首先回输到2级细根,2级细根再回输到3级细根;4)柳杉细根中N,P,K浓度变化趋势和它们与Ca浓度比值的变化趋势基本一致。     

东北三大硬阔细根形态研究

细根根序的研究为进一步深入了解各级根序细根的功能及其对森林生态系统生态学过程和森林生产力的提高中的贡献提供了重要途径。水曲柳、黄波椤和胡桃楸为东北林区重要用材树种,研究其根系结构,了解细根的生理生态功能,对其科学经营管理,提高林分生产力有现实意义。     

徐州云龙山侧柏林细根形态与分布规律研究

为了提高徐州市石灰岩山地侧柏人工林的生态和景观质量,该研究以云龙山侧柏人工林为对象,利用Win-RHIZO根系分析仪对2个样地不同土层深度细根的形态参数、比根长、根长密度和生物量进行了综合分析。结果表明：（1）细根直径随根序等级的升高而增加,细根长度、比根长、表面积表现为下降趋势,而细根体积表现为先减小后增加的趋势;（2）在不同立地条件下,细根长度、比根长、表面积和体积均表现为表层高于底层,东坡高于西坡的规律;（3）单位面积上细根的生物量随根序的升高而增加,而根长密度则明显下降;表土层中细根生物量和根长密度都要高于底层,东坡高于西坡。     

胡桃楸、黄波罗和水曲柳细根形态研究

实验通过对胡桃楸、黄波罗和水曲柳一到五级根序之间的细根形态进行初探,以期了解温带树种细根形态各参数与根序的关系,为进一步研究细根形态与功能关系、细根寿命及周转提供科学依据。     

退耕还林地三倍体毛白杨与黑麦草复合模式细根和草根的分解动态

在天全县的退耕还林地中，对三倍体毛白杨＋黑麦草模式细根和草根的分解及其N、P、K、Ca、Mg养分释放动态进行研究。细根Ф0～1mm、Ф1～2mm、Ф0～2mm及草根的第1年干质量损失率分别为73．97％、69．80％、73．44％和79．53％，应用对数方程模拟细根和草根的分解过程，拟合程度较好（R^2〉0．9，P〈0．01），分解50％所需的时间分别为210、252、243和185d。细根分解过程中，P、K、Mg的含量下降，N、Ca的含量增加。草根分解过程中，养分元素的含量都呈现出不规则的波动变化，整体上没有明显的规律性。在细根分解过程中，P、K、Mg的养分释放率与其干质量损失率的变化趋势相似，分解前期增加较快，随后上升趋于平缓，而N、Ca的养分释放率增加整体比较平缓，元素分解速率均以P最快，其次是K、Mg，而N、Ca最慢；而草根分解过程中N、P、K、Ca、Mg的养分释放率初期增加都比较快，随后趋于平缓，并且元素分解速率呈现不规则变化，其中Ca分解率最慢，其他元素的分解率相近。由于细根和草根在垂直分布上的差异，整个生态系统中，土壤上下层地下凋落物的主要种类也有所不同，因而有利于三倍体毛白杨＋黑麦草生态系统的可持续发展。     

红松、云杉和水曲柳细根比较

对红松、云杉和水曲柳的细根生物量、不同根序细根平均根长和细根总长变化以及细根比根长变化进行比较研究。结果表明,红松、水曲柳生物量根序之间总体表现为随着细根级别增加而减少,云杉则没有上述树种所表现的规律性;根系统中由远端低级根序到近端的高级根序个体根的平均长度显著增加,但在同一个低级根序内根长差异不显著;红松、云杉和水曲柳由低级根序到高级根序细根的总长度逐渐下降;同一树种不同根序内,细根比根长由低级根序到高级根序逐渐降低;不同树种比根长构建方式明显不同,水曲柳比根长最高,云杉次之,红松比根长最低;水曲柳根生长的平均速率明显高于红松和云杉。     

刺槐无性系营养钵插根育苗试验研究

对刺槐无性系进行了营养钵插根育苗试验,结果表明：（１）粗根段（０．５～０．８ｃｍ）平均扦插成活率７８％,平均苗高２．３６ｍ,平均地径２．２６ｃｍ,分别比细根段（０．４ｃｍ以下）,提高２７．９％,２８．３％,２４．９％,（２）长根段（８～１２ｃｍ）平均扦插成活率为８３．３％,平均高２．４８ｍ平均地径２．２８ｃｍ,分别比短根段（４～５ｃｍ）提高２７．８％,１５．１％,９．７％。     

水杉人工林细根和粗根碳氮磷计量特征对N添加的响应

[目的]研究水杉细根和粗根碳（C）、氮（N）、磷（P）计量特征对N添加的响应，揭示细根和粗根N、P养分分配格局的变化，为科学认识水杉对N沉降的适应策略提供参考。[方法]在江苏省东台市林场水杉人工林进行长期N添加试验，设置对照(CK,0 kg·hm^-2·a^-1)、低N(LN,56 kg·hm^-2·a^-1)、中N(MN,168kg·hm^-2·a^-1)、高N(HN,280 kg·hm^-2·a^-1)4个N添加处理，测定水杉细根（直径<2 mm）和粗根（2 mm≤直径≤5 mm）C、N、P含量及土壤理化性质指标。[结果]（1）N添加对水杉人工林土壤有机碳和水解氮含量存在明显促进作用，且随着N添加量增加，这种促进作用有所减弱。N添加对土壤全磷含量、有效磷含量和p H均无显著影响。（2）随着N添加量的增加，水杉细根和粗根N含量、C:P、N:P显著增加，P含量和C:N显著下降。此外，细根和粗根N含量、C:N和N:P在HN处...     

胡桃楸、黄菠萝和水曲柳细根形态研究

研究了胡桃楸、黄菠萝和水曲柳一到五级根序之间的细根形态,以期了解温带树种细根形态各参数与根序的关系,为进一步研究细根形态与功能关系、研究细根寿命及周转提供科学依据。     

辽东楤木细根段育苗研究

本研究首次利用辽东格木的细根段（直径〈0．4cm）进行了育苗试验，结果表明：在细根段育苗时，根段截取长度应在9cm以上，否则后期养分不足，难以成苗。混沙催芽结合地膜覆盖可以明显提高细根段育苗的大田出苗率，本试验得到的结果为36.5％，而露地撒播的出苗率仅有10.5％。     

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.     

Nutrient retranslocation from the fine roots of <Emphasis Type="Italic">Fraxinus mandshurica</Emphasis> and <Emphasis Type="Italic">Larix olgensis</Emphasis> 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 Masson pine (Pinus massoniana) stands in the Three Gorges Reservoir Area, China, was studied in 30 m × 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 random 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 relationship between the spatial heterogeneous patterns of plant and soil properties.     

Root standing crop and chemistry after six years of soil warming in a temperate forest

Examining the responses of root standing crop (biomass and necromass) and chemistry to soil warming is crucial for understanding root dynamics and functioning in the face of global climate change. We assessed the standing crop, total nitrogen (N) and carbon (C) compounds in tree roots and soil net N mineralization over the growing season after 6 years of experimental soil warming in a temperate deciduous forest in 2008. Roots were sorted into four different categories: live and dead fine roots (≤1mm in diameter) and live and dead coarse roots (1-4 mm in diameter). Total root standing crop (live plus dead) in the top 10 cm of soil in the warmed area was 42.5% (378.4 vs. 658.5 g m(-2)) lower than in the control area, while live root standing crop in the warmed area was 62% lower than in the control area. Soil net N mineralization over the growing season increased by 79.4% in the warmed relative to the control area. Soil warming did not significantly change the concentrations of C and C compounds (sugar, starch, hemicellulose, cellulose and lignin) in the four root categories. However, total N concentration in the live fine roots in the warmed area was 10.5% (13.7 vs. 12.4 mg g(-1)) higher and C:N ratio was 8.6% (38.5 vs. 42.1) lower than in the control area. The increase in N concentration in the live fine roots could be attributed to the increase in soil N availability due to soil warming. Net N mineralization was negatively correlated with both live and dead fine roots in the mineral soil that is home to the majority of roots, suggesting that soil warming increases N mineralization, decreases fine root biomass and thus decreases C allocation belowground.     

Variations of fine root diameter with root order in Manchurian ash and Dahurian larch plantations

Fine root lifespan and turnover play an important role in carbon allocation and nutrient cycling in forest ecosystems. Fine roots are typically defined as less than 1 or 2 mm in diameter. However, when categorizing roots by this diameter size, the position of an individual root on the complex lateral branching pattern has often been ignored, and our knowledge about relationships between branching order and root function thus remains limited. More recently, studies on root survivals found that longevity was remarkably different in the same branching level due to diameter variations. The objectives of this study were: (1) To examine variations of fine root diameter from the first-to fifth-orders in Fraxinus mandshurica Rupr and Larix gmelinii Rupr roots; and (2) To reveal how the season, soil nutrient, and water availability affect root diameter in different branch order in two species. This study was conducted at Maoershan Forest Research Station (45°21′–45°25′N, 127°30′–127°34′E) owned by Northeast Forestry University in Harbin, northeast China. Both F. mandshurica and L. gmelinii were planted in 1986. In each plantation, fine roots of two species by sampling up to five fine root branch orders three times during the 2003 growing season from two soil depths (i.e., 0–10 and 10–20 cm) were obtained. The results showed that average diameters of fine roots were significantly different among the five branch orders. The first-order had the thinner roots and the fifth order had the thickest roots, the diameter increasing regularly with the ascending branch orders in both species. If the diameter of fine roots was defined as being smaller than 0.5 mm, the first three orders of F. mandshurica roots and the first two orders of L. gmelinii roots would be included in the fine root population. The diameter ranges of the fine roots from first-order to fifth-order were 0.15–0.58, 0.18–0.70, 0.26–1.05, 0.36–1.43, and 0.71–2.96 mm for F. mandshurica, and 0.17–0.76, 0.23–1.02, 0.26–1.10, 0.38–1.77, and 0.84–2.80 mm for L. gmelinii. The average coefficient of variation in first-order roots was less than 10%, second-and third-order was 10–20%, and fourth-and fifth-order was 20–30%. Thus, variation in root diameter also increased with the ascending root order. These results suggest that “fine roots”, which are traditionally defined as an arbitrary diameter class (i.e., <2 mm in diameter) may be too large a size class when compared with the finest roots. The finest roots have much shorter lifespan than larger diameter roots; however, the larger roots are still considered a component of the fine root system. Differences in the lifespan between root diameter and root order affect estimates of root turnover. Therefore, based on this study, it has been concluded that both diameter and branch order should be considered in the estimation of root lifespan and turnover. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(6): 871–877 [译自: 植物生态学报]     

Effect of nitrogen fertilizer, root branch order and temperature on respiration and tissue N concentration of fine roots in Larix gmelinii and Fraxinus mandshurica

Root respiration is closely related to root morphology, yet it is unclear precisely how to distinguish respiration-related root physiological functions within the branching fine root system. Root respiration and tissue N concentration were examined for different N fertilization treatments, sampling dates, branch orders and temperatures of larch (Larix gmelinii L.) and ash (Fraxinus mandshurica L.) using the excised roots method. The results showed that N fertilization enhanced both root respiration and tissue N concentration for all five branch orders. The greatest increases in average root respiration for N fertilization treatment were 13.30% in larch and 18.25% in ash at 6°C. However, N fertilization did not change the seasonal dynamics of root respiration. Both root respiration and root tissue N concentration decreased with increase in root branch order. First-order (finest) roots exhibited the highest respiration rates and tissue N concentrations out of the five root branch orders examined. There was a highly significant linear relationship between fine root N concentration and root respiration rate. Root N concentration explained >60% of the variation in respiration rate at any given combination of root order and temperature. Root respiration showed a classical exponential relationship with temperature, with the Q(10) for root respiration in roots of different branching orders ranging from 1.62 to 2.20. The variation in root respiration by order illustrates that first-order roots are more metabolically active, suggesting that roots at different branch order positions have different physiological functions. The highly significant relationship between root respiration at different branch orders and root tissue N concentration suggests that root tissue N concentration may be used as a surrogate for root respiration, simplifying future research into the C dynamics of rooting systems.     

Life cycles of individual roots in fine root system of Chamaecyparis obtusa Sieb. et Zucc.

Recent studies have remarked on differences in the life cycles of individual fine roots. However, the dynamics of individual roots with different life cycles, such as ephemeral and perennial, during root system development are still unknown. We examined individual roots during fine root system development in a mature stand of Chamaecyparis obtusa Sieb. et Zucc. (Cupressaceae) using the sequential ingrowth core method and an anatomical method. The visual classification, i.e., orange, red, brown, intact dead, and fragmented dead, of fine roots corresponded well with the anatomical classification. Orange and red roots contained passage cells, and brown roots contained cork cambium. The proportions of protoxylem groups differed among visual classes. Brown secondary roots were mainly triarch (43%) and tetrarch (40%) and rarely diarch (12%), whereas fragmented dead roots, which constituted more than 95% of the dead roots, were mainly diarch (67%). These results imply that triarch and tetrarch roots tend to form secondary roots, whereas diarch roots tend to become dead roots without secondary growth. Using the numbers of root tips and clusters, root system development could be classified into three stages: colonization, branching within the root system, and maintenance. During the colonization stage, mainly triarch and tetrarch roots, which tend to be secondary growth, invaded ingrowth cores. During the branching stage, primarily diarch roots, which tend to be ephemeral, emerged. Fine root system development involved the recruitment of different individual roots during the life cycle depending on the growth stage.     

长白山阔叶红松林群落的细根现存量及养分内循环

细根(直径≤2mm)是植物吸收水分和养分的重要器官,细根通过呼吸作用和周转过程向土壤输送有机质(Jackson et al.,1997;王政权等,2008)。细根生物量虽然仅占植物体总生物量的5%左右,但由于细根生长和周转迅速,其生长量可占森林初级生产力的50%～75%(Nadelhoffer et al.,1992),每     

Fine roots branch orders of <Emphasis Type="Italic">Abies faxoniana</Emphasis> respond differentially to warming in a subalpine coniferous forest ecosystem

Root is an important plant organ and has high heterogeneity. Global warming could change root and affect belowground ecological processes. There is little information on how fine roots branch orders responds to global change. This study examined the growth, morphological and physiological responses of fine roots of a subalpine coniferous species to warming. We investigated biomass, average diameter, specific root length (SRL), triphenyltetrazolium chloride (TTC) reducing capacity, carbon (C), total non-structural carbon (TNC) and fractions of the primal five branch order roots of Abies faxoniana in April, August, October and December. The decrease in total fine roots biomass after a growing season was significantly greater under warming treatment compared to control, suggesting that warming could accelerate the carbon input from root to soil, but the increment depended on tree species. Warming did not affect average diameter and SRL. Responses of biomass, TTC reducing capacity, C, TNC and fractions to warming significantly differed with root order and month. Significant warming effects were only observed in C and starch concentration of the first order and also TNC and soluble sugar concentration of the first three orders. The results indicated that the lower order roots (the first three orders) were more sensitive to warming, probably because they had more frequent, intense interactions with soil and low defense capability. Thus, global warming may dramatically alter root functions such as nutrients and water uptake as well as the cycle of C and nutrients at the whole subalpine coniferous forest ecosystem.     

杉木、观光木混交林群落细根N、P养分现存量动态变化

通过对杉木、观光木混交林和杉木纯林细根的养分现存量动态进行研究 ,结果表明 ,混交林细根N、P养分现存量分别是纯林的 1.3和 1.2倍 ;年归还量分别是纯林的 1.2 3倍和 1.14倍 ,且分别占混交林凋落物N、P养分年归还量的 38.3%和 6 7.4 % ;年分解量分别是纯林的 1.2 6和 1.2 3倍 ,而年累积量分别是纯林的 1.2 3和 1.14倍 ,可见混交林细根具有比纯林更高的养分累积和周转能力。混交林和纯林群落中林下植被细根在群落细根N、P养分循环中占有重要地位 ,而杉木和观光木 <0 .5mm径级细根则是其细根养分循环功能的主体。混交林和纯林杉木活细根N养分现存量动态变化呈单峰型 ,P则呈双峰型 ;死细根N、P养分现存量动态变化均呈倒“S”型。混交林中观光木细根的N、P养分现存量动态变化与杉木的较相似 ,但其活细根P养分现存量动态变化呈单峰型。混交林与纯林中林下植被活细根N、P养分现存量动态变化均呈双峰型 ,而死细根的动态变化则呈单谷型