川滇高山栎灌丛营养元素积累与生物循环特征

养分循环是森林生态系统的重要生态功能。以位于青藏高原东南缘的川西折多山东坡川滇高山栎(Quercus aquifolioides)灌丛为研究对象,分析了其营养元素的分布、积累和生物循环特征。结果显示:(1)川滇高山栎不同器官营养元素含量不同,叶片和枝条为NKCaMgP,树干和地下器官为CaKNMgP。(2)川滇高山栎灌丛生态系统各营养元素总贮量(kg/hm2)依次为:Ca(650.06)、N(252.67)、K(197.01)、Mg(51.18)、P(49.22),其中川滇高山栎灌层储量占88.61%~96.10%,林下草本层占0.64%~4.22%,凋落物层占2.54%~9.25%。(3)川滇高山栎灌层营养元素主要储存于地下根系,占灌层的67%~81%,丰富的根系营养元素储量有利于川滇高山栎灌丛在遭受火烧、砍伐等干扰后萌生更新。(4)川滇高山栎灌丛营养元素年积累量[kg/(hm2·a)]依次为:Ca(20.82)、N(7.46)、K(6.12)、P(2.33)、Mg(1.55);灌丛营养元素利用系数为0.09,循环系数为0.60,周转时间为22.87a。研究表明,川滇高山栎灌丛具有较低的营养元素利用率和较长的营养元素周转期。     

卧龙巴郎山川滇高山栎灌丛地上生物量及其模型

川滇高山栎广泛分布于横断山地区,属于亚高山硬叶栎林,是中国植被非常特殊的类型。采用标准地法和样方收获法,对卧龙自然保护区5个海拔梯度的川滇高山栎灌丛生物量进行调查。结果表明,用地径(D)、树高(H)估测单株林木器官生物量的适合模型均为指数模型和幂函数模型,且以指数模型为最佳,相关系数为0.941~0.988;而用D2H估测单株林木器官生物量的适合模型均为直线和指数模型,以直线模型为最佳,相关系数为0.982~0.996;川滇高山栎灌丛总生物量为3.3891×104kg.hm-2,各层生物量排序为川滇高山栎层>枯枝落叶层>伴生灌木层>苔藓层>草本层,其生物量占总生物量百分率分别为77.92%、17.64%、2.14%、1.23%和1.07%;川滇高山栎种群平均总生物量为2.6408×104kg.hm-2,各器官生物量大小排序为根>干>枝>叶>皮,其生物量占种群总生物量的百分率分别为31.03%、29.85%、18.54%、18.54%和6.91%。     

萌蘖调控对辽东栎留存萌生株生长与结实的影响

比较了不同调控措施对岷江上游辽东栎萌生灌丛生长与结实的影响.结果表明,人为调控对辽东栎萌生灌丛本生长阶段的高生长与有性繁殖有着显著影响.各调控措施对辽东栎灌丛萌生株的基径增长未产生明显影响;保留2支和3支萌生株的丛高生长优势明显.调控丛的新生枝数量、总长度、总生物量较未调控前有较大增加,保留2支萌生株的丛类型增加得尤为显著;叶片数量、叶片总生物量与未调控前相比增加明显,叶片面积按保留萌生株数量由多到少逐渐变小.调控后,每丛保留3支萌生株的丛产生的种子最多,但自然状态丛种子单粒重最大.     

科尔沁沙地小叶锦鸡儿地上-地下生物量分配格局

以科尔沁沙地18年生(成龄)和4年生(幼龄)人工小叶锦鸡儿以及天然小叶锦鸡儿灌丛为研究对象,采用分层挖取根系法调查不同植被区小叶锦鸡儿的根系分布特点,研究其在生物量分配、根冠比、根系分布等方面对干旱环境的响应.结果表明:1)小叶锦鸡儿倾向于把更多的生物量分配于地下,其中天然植被地下生物量比重最大,4年生植被地下生物量比重最小.2)小叶锦鸡儿灌丛根系生物量随着土层深度的增加而逐渐减少,其根系主要分布在0 ～ 100 cm土层中.3)4年生小叶锦鸡儿吸收根呈现浅层分布特性,在地下O～50 cm吸收根生物量显著高于18年生和天然植被(P＜0.05);18年生和天然植被吸收根更多分布于50 ～ 100 cm土层中.天然小叶锦鸡儿输导根生物量在50 ～ 100 cm土层中显著高于4年生和18年生植被(P＜0.05).4)小叶锦鸡儿灌丛地上-地下生物量符合异速生长模型的幂函数.     

长江三峡地区典型灌丛的生物量及其再生能力

 灌丛是三峡地区典型的退化生态系统类型。本文采用收获法和模拟砍伐实验研究了三峡地区铁仔灌丛、椎木灌丛、荆条灌丛和黄栌灌丛的生物量及黄栌灌丛、椎木灌丛地上部分砍伐后的再生能力。研究结果表明,这4种类型的灌丛总生物量分别为22.5±5.1、21.0±3.7、16.9±7.5和13.6±2.4t·hm-2,相当于同纬度地带性生态系统常绿阔叶林(30年林龄)的10％一25％ 4种灌丛灌木层占总生物量、地上部分生物量和地下部分生物量的90％以上。在生物量—物种序列中,前5种植物占总生物量的84％ 以上。不同地点灌丛生物量的比较表明,同一种类型灌丛,亚热带和暖温带地区总生物量没有明显差异。通过模拟砍伐实验,黄栌灌丛、被木灌丛地上部分全部砍伐后1年地上部分生物量就可以恢复到对照的42.7％和62.0％,说明这些灌丛类型具较高的生长速度和很大的恢复潜力。     

根际通气状况对盐胁迫下棉花幼苗生长的影响

以溶液培养的棉花(Gossypium hirsutum)幼苗为材料,测定了不同盐胁迫程度和不同通气状况下棉花幼苗株高、根系体积、根系和茎叶生物量以及灰分含量的变化,以探索根际通气状况对盐胁迫下棉花生长的影响。结果表明,盐胁迫抑制棉花植株生长,表现为植株变矮、叶面积减小和干物质积累下降;根际环境通气不良也会导致棉花幼苗生长受抑制、干物质积累下降和矿质元素吸收减少等。进一步比较盐胁迫和根际通气状况及两者组合作用对棉苗生长的影响,发现盐胁迫对株高和总生物量的影响较大,而根际通气状况对根系体积、根系生物量、根冠比和矿质元素吸收的影响较大。总体表现为:盐胁迫对茎叶生长的不利影响较大,而根际通气状况对根系生长的不利影响较大。同时,在根际环境通气良好的条件下,不同程度盐胁迫导致的棉花幼苗株高、根系体积、叶面积、根系生物量和总生物量的变化程度远小于根际环境通气不良条件下的变化程度。实验结果表明,根际环境通气良好可以减弱盐胁迫对棉花生长发育的抑制作用,而根际环境通气不良则会加重盐胁迫的不利影响。     

硝酸镧和兰科菌根真菌互作对石斛生长和有效成分积累的影响

利用盆栽的方式研究了不同硝酸镧水平下接种OM真菌对石斛生长、根系活力、N、P、K等营养元素吸收以及有效成分积累的影响,并分析了根际硝酸还原酶和磷酸酶活性变化。结果表明,添加适量的硝酸镧有利于OM真菌侵染和菌根发育,促进石斛生长,包括地下和地上的生物量。在接种OM真菌时,同时添加5.0 mg·L-1的硝酸镧,石斛的生物量达到最大,为对照组的4.76倍。在适量的硝酸镧水平下接种OM真菌还可以提高根系活力,并促进N、P和K的吸收和利用,提高根际硝酸还原酶和磷酸酶的活性;显著提高蛋白质、多糖以及石斛碱的含量。硝酸镧与OM真菌互作能促进石斛生长和有效成分的积累,提高其药用品质。     

羊草草原植物-土壤之间主要营养元素动态的研究

羊草草原土壤中N、P、K含量的季节变化规律是生长季初期较高,6—8月生长旺季较低,生长季末再度升高。营养元素在植物体内的分配是地下部分大于地上部分。地下部分N的贮量为地上部分的3.6倍,K为2.9倍,P为2.8倍。地上部分3种元素含量的季节变化曲线呈单峰型,从生长初期开始上升,最大值出现在8月,生长末期逐渐下降。地下部分的季节变化规律,大体上在整个生长季内呈上升趋势,随着根系的生长,营养元素的积累量不断增加。对植物—土壤之间营养元素动态分析结果表明,随着时间的推移,N、P、K在各状态中的比例趋于恒定。在稳定状态下,3种元素在土壤中的比例逐渐减少,与初始量相比N、P、K的含量分别减少21.23%、5.14%和2.99%。在其它状态中,3种元素的含量均有提高,特别在枯枝落叶和死根中增加的幅度较大。     

川滇高山栎种群不同海拔空间格局的尺度效应及个体间空间关联

川滇高山栎灌丛(Quercus aquifolioides)是我国西南高山典型的植被类型,研究其空间格局对于研究种群的生态学过程有重要意义。为了弄清川滇高山栎种群空间格局及其个体间空间关联对海拔,尺度和大小级等因素的响应情况,研究中应用点格局分析的方法,在巴郎山沿高山栎分布海拔范围设置4个海拔梯度,并根据体积大小将高山栎分为4个大小级等级,比较不同海拔、不同尺度、不同大小级间的高山栎种群空间格局及个体间空间关联。结果表明,川滇高山栎种群空间格局及其个体间关联与空间尺度、植株形体大小和海拔梯度密切相关:在小尺度上,种群趋向于聚集分布,个体间有较强的空间关联,随着空间尺度的增大,种群逐渐趋于随机分布,个体间空间关联减弱,区域无关联;个体间形体差异越小,个体间正关联就越强,个体间形体差异越大,正关联就越弱,负关联就越强;海拔因子对聚集分布的聚集规模和个体间关联的关联程度有较大影响。     

中山逍遥谷两奇树

广东省中山市五桂山区的“逍遥谷”，是２１世纪新开发的森林旅游区。这里生态环境优良，形形色色的热带、亚热带花草树木竞相生长，令游人赏心悦目。其中有两处奇树景观─— “十兄弟树”和“七姐妹树”，尤其引人入胜。 “十兄弟树”是由一株劫后余生的粘木长成：在一个远年被砍伐后留下的树桩上，茁壮地萌生出１０条树干，颇为奇特。粘木（Ｉｘｏｎａｎｔｈｅｓ　ｃｈｉｎｅｎｓｉｓ）是粘木科（或亚麻科）常绿乔木，春季开花，夏季果熟，萌芽能力甚强。 “十兄弟树”的伐根（树桩）直径逾１００厘米，萌条最大的直径１６厘米，高９米，…     

Biomass and nutrients in tree root systems–sustainable harvesting of an intensively managed Pinus pinaster (Ait.) planted forest

To develop sources of renewable energy and to reduce greenhouse gas emissions, increasing attention has been given to the extraction of forest biomass, especially in the form of harvest residues. However, increasing the removal of biomass, and hence nutrients, has raised concerns about the sustainability of site fertility and forest productivity. The environmental cost of harvesting belowground biomass is still not fully understood. The objectives of this study were to (i) estimate the stocks of belowground biomass that potentially can be collected; (ii) measure the nutrient (N, P, K, Ca, Mg) concentrations of the different root compartments (stumps, coarse and thin roots); and to (iii) quantify the biomass and nutrient exports under different scenarios, including harvests of above and belowground compartments. The study was carried out on Pinus pinaster stands located in south‐western France. Results showed that roots could be a significant fuelwood resource, particularly at forest clear cutting. Negative relationships between root diameter and root nutrient concentration were observed, independently of root function or tree age. Such relationships can be used to accurately simulate nutrient concentrations in roots as well as nutrient exports. Combining our original results on roots with previously published data on the aboveground compartments showed that nutrient losses were higher in canopy harvest scenarios than in root harvest scenarios. This was mainly due to high nutrient concentrations of needles. We concluded that stump and root harvest could be sustainable in our study context, conversely to foliage harvest. Because thin roots have higher nutrient concentrations than coarse roots and the proportion of thin roots increased with an increase in the distance from the tree, collecting roots only in the close vicinity of the stumps should limit nutrient exports (particularly N) without unnecessarily reducing fuelwood biomass.     

Nutrient cycling in Pinus sylvestris stands in eastern Finland

Nutrient cycling within three Pinus sylvestris stands was studied in eastern Finland. The aim of the study was to determine annual fluxes and distribution of N, P, K, Ca, Mg, Zn, Fe, B, and Al in the research stands. Special emphasis was put on determining the importance of different fluxes, especially the internal cycle within the trees in satisfying the tree nutrient requirements for biomass production. The following nutrient fluxes were included, input; free precipitation and throughfall, output; percolation through soil profile, biological cycle; nutrient uptake from soil, retranslocation within trees, return to soil in litterfall, release by litter decomposition. The distribution of nutrients was determined in above- and belowground tree compartments, in ground and field vegetation, and in soil.The nitrogen use efficiencies were 181, 211 and 191 g of tree aboveground dry matter produced per g of N supplied by uptake and retranslocation in the sapling, pole stage and mature stands, respectively. Field vegetation was more efficient in nitrogen use than trees. Stand belowground/aboveground and fine root/coarse root biomass ratios decreased with tree age. With only slightly higher fine root biomass, almost three times more nitrogen had to be taken-up from soil for biomass production in the mature stand than in the sapling stand.The annual input-output balances of most nutrients were positive; throughfall contained more nutrients than was lost in mineral soil leachate. The sulphate flux contributed to the leaching of cations, especially magnesium, from soil in the mature stand.Retranslocation supplied 17–42% of the annual N, P and K requirements for tree aboveground biomass production. Precipitation and throughfall were important in transferring K and Mg, and also N in the sapling stand. Litterfall was an important pathway for N, Ca, Mg and micro nutrients, especially in the oldest stands.     

Effect of root competition and shading on resprouting dynamics of Erica multiflora L.

Abstract. Resprouting from underground structures is one of the main regeneration strategies of Mediterranean shrubs after aerial biomass disturbance such as fire or clear-cutting to reduce fire risk. In order to study the effect of root competition and shading (simulated shoot competition) on Erica multiflora, growth, morphology, flowering performance and sprout size variability during resprouting, a factorial field experiment was conducted in which neighbours around target plants were eliminated and plants were shaded with mesh for two years. Root competition reduced sprout recruitment and sprout density (number of sprouts per unit stump area) more strongly than did shading. The negative effect of root competition on sprout biomass was constant with time, while the reduction due to shading increased with time. There was an interaction between root competition and shading on the biomass of sprouts 22 months after treatment: genets without root competition and shading were four times larger than in any other treatment. Both shading and root competition also decreased percentage branching but did not modify maximum sprout height. Only shading decreased the leaf/shoot biomass ratio and the percentage of flowering genets. One year after resprouting, root competition counteracted the effect of shading on inducing sprout biomass variability within the genet because it decreased sprout density. 22 months after treatment, sprout biomass variability was not affected by any main effect. The results suggest that competition among sprouts within the genet is asymmetric. However, shading by genet neighbours may not always increase sprout biomass variability if root competition is also severe.     

Effects of nutrient availability and neighbours on shoot growth,resprouting and flowering of Erica multiflora

Abstract. To test if low soil fertility and competition limit the performance of Mediterranean shrubs, and if the effects of competition on plant performance were modified by soil fertility, we subjected shrubs of Erica multiflora to a factorial field experiment of fertilization and removal of neighbours around target plants. After 18 months of treatment, fertilization had stimulated the growth of pre-existent sprouts and biomass allocation to stems into new sprouts, but decreased the frequency of sprout flowering. Removal of neighbours increased the number and biomass of new sprouts, the probability of sprout flowering and the biomass of flowers. Fertilization slightly enhanced sprout recruitment and the probability of sprout flowering when neighbours were removed, but did not modify the other parameters of plant performance. According to our results, both low soil fertility and competition limited plant performance. Competition was slightly more intense in fertilized plants, but only in determining sprout and flowering bud stimulation.     

异质养分环境中一年生分蘖草本黍根系的生长特征

为揭示黍（Panicum miliaceum L.)根系对异质养分环境的生长反应,作研究了黍根系从起始斑块向目标斑块水平生长时,时始斑块和目标斑块养分水平根生长的影响,就低养分起始珏块而言,粗根生物量,粗根长度,粗根表面积和细极长度在高养分目标斑块中的分配比例均小于其在低养分目标斑块中的分配比例,而细根长度及其密度,细根表面积指及其密度的变化恰好相反,就高养分起始斑块而言,高养分目标斑块的细根长度,细根长度密度,细根表面积指数和细根表面积密均不于低养分目标斑块,而粗根对目标斑块中养分状的反应不明显。当黍根系从桢的起始斑块进入不同的目标斑块后,目标斑块的养分状况对细根生物量及其分配无影响,而显影响细根长度和表现积,这指示细根是通过长度和表面积可塑性而不是生物量变化响应目标斑块中的养分差异。     

Root Growth of the Annual Tillering Grass Panicum miliaceum in Heterogeneous Nutrient Environments (in English)

To study growth responses of the roots of Panicum miliaceum L. to heterogeneous supply of nutrients. The authors analyzed the effects of the nutrient levels in both original patches (O) and destination patches (D) on the root growth of P. miliaceum when its roots were allowed to extend from original patch into destination patch. When the nutrient levels in the original patches were low, coarse root biomass ratio (coarse root biomass in the D/total coarse root biomass), coarse root length ratio (coarse root length in the D/total coarse root length), coarse root surface area ratio (coarse root surface area in the D/total coarse root surface area) and fine root length ratio (fine root length in the D/total fine root length) were greater in the destination patches with lower nutrient levels than in the destination patches with higher nutrient levels, while fine root length, fine root length density, fine root surface index, and fine root surface area density were smaller in the former than in the latter. When the nutrient levels in the original patches were high, fine root length, fine root length density, fine root surface area index and fine root surface density were greater in the destination patches with lower nutrient levels than in the destination patches with higher nutrient levels, coarse roots did not respond to the nutrient levels in the destination patches significantly. When the roots extended from the original patches with the same nutrient level into the destination patches with contrasting nutrient levels, fine root biomass and its percentage allocation did not respond to the nutrient levels in the destination patches significantly, whereas both root length and root surface area did. This indicates that the fine roots of P. miliaceum responded to difference in nutrient supply by plasticity in their length and surface area, rather than in their root biomass.     

不同栽植密度对斑叶稠李苗木培育质量的影响

以斑叶稠李（Padus maackii）1年生苗木为研究对象,通过4种不同栽植密度（60、80、100、120 株·m^-2）试验,测定其苗木形态、生物量、光合速率及养分含量,旨在探明不同密度对斑叶稠李苗木生长及养分含量的影响,为其高质量苗木培育提供理论依据。结果表明：（1）栽植密度显著影响苗木生物量,各密度下苗木根、茎、叶生物量由大到小顺序均为80 株·m^-2 > 60 株·m^-2 > 100 株·m^-2 > 120 株·m^-2;60和80 株·m^-2密度下斑叶稠李苗木质量指数显著高于100和120 株·m^-2密度处理。（2）栽植密度显著影响苗木侧根数,在80 株·m^-2的密度下达到最大;（3）80 株·m^-2密度较其它密度显著提高了苗木氮、磷、钾养分含量。（4）叶生物量、根生物量和侧根数与苗木各质量指标间Pearson相关性系数均达到了显著水平（P<0.1）,而光合速率和主根长与苗木各质量指标均不相关（P>0.1）。综合以上结果,斑叶稠李1年生苗木最适栽植密度为80 株·m^-2,且密度处理主要影响斑叶稠李苗木叶生物量、侧根数及根生物量指标,进而影响苗木质量。     

长期淹水环境下河竹鞭根系统形态、生物量和养分的适应性调节

为揭示长期淹水环境下基于形态、生物量和养分的河竹鞭根系统的生长策略,为河竹在水湿地和江河湖库消落带植被恢复中的应用提供参考,调查测定了人工喷灌供水和淹水处理3、6、12个月的河竹一年生竹鞭及其根系的形态和生理生化指标,分析了河竹鞭和鞭根形态特征和生物量分配及鞭根系统的养分吸收与平衡.结果表明: 长期淹水对河竹鞭节长、鞭径和土中根根径并无明显影响.淹水3个月整体上对鞭的形态特征影响小,水中翘鞭较少,但一定程度上抑制了根的生长.随着淹水时间的延长,水中鞭、根大量生长,同时促进了土中鞭、根的生长,但土中、水中鞭生物量和土中根生物量占总生物量的比例变化并不明显,而水中根生物量/总生物量和水中根生物量/土中根生物量显著升高,体现出河竹可以通过鞭根系统的生长调节和生物量合理分配来逐步适应淹水环境.长期淹水整体上降低了河竹土中根的根系活力,抑制了土中根对养分的吸收,但对土中根养分化学计量比的影响较小,而使水中根的根系活力显著增强,养分化学计量比产生明显的适应性调节,N/P升高,N/K和P/K降低.水中根不仅起到氧气吸收功能,还具有较强的养分吸收功能.这是河竹有效适应淹水环境的生长策略之一.     

模拟氮沉降对中亚热带杉木幼树根系生物量的影响

植物根系是全球陆地生态系统碳储量的重要组成部分,在全球生态系统碳循环中起着重要作用,日益加剧的氮沉降会影响根系生物量在空间和不同径级的分配,进而影响森林生态系统的生产力和土壤养分循环。以杉木幼树为研究对象,通过野外氮沉降模拟实验,研究氮沉降四年后对不同土层、不同径级根系生物量的影响。结果发现：（1）低氮和高氮处理总细根生物量较对照均无显著差异（P > 0.05）,高氮处理粗根生物量及总根系生物量较对照分别增加45%和40%（P < 0.05）;（2）与对照相比,施氮处理显著增加20-40 cm与40-60 cm土层细根和粗根生物量,且在低氮处理下,20-40 cm土层细根、粗根在总土层细根与粗根生物量的占比显著提高。（3）与对照相比,高氮处理显著增加了2-5 mm、5-10 mm及10-20 mm径级的根系生物量,低氮处理显著增加2-5 mm、5-10 mm径级根系生物量,且显著降低20-50 mm径级根系生物量。综上所述表明：氮沉降后杉木幼树通过增加较粗径级根系来增加对养分及水分的输送,同时通过增加深层根系生物量及其比例的策略来维持杉木幼树的快速生长;而根系生物量的增加,在一定程度上会增加根系碳源的输入,影响土壤碳循环过程。     

Soil nutrient heterogeneity and competitive ability of three grass species (<Emphasis Type="Italic">Festuca ovina,Arrhenatherum elatius</Emphasis> and <Emphasis Type="Italic">Calamagrostis epigejos</Emphasis>) in experimental conditions

We studied the effects of differences in root growth and nutrient pool on the competitive ability of Festuca ovina (short grass), Arrhenatherum elatius and Calamagrostis epigejos (tall grasses) grown in monocultures and in mixtures of homogeneous and heterogeneous environments during two growing seasons. Analysis of variance revealed a significant effect of plant species on nutrient concentrations in above-ground biomass and of substrate type on contents of N, K, Ca, Mg in biomass. The ANOVA also confirmed the significant effect of competitive environment on the concentration of N, K in above-ground biomass. In heterogeneous environments, both tall grasses (in competition with F. ovina) were able to produce more roots in the nutrient-rich patches and to accumulate more nitrogen in plant tissues, which was associated with higher yield of their above-ground biomass. Thus, the relative competitive ability for nutrients of both tall grasses was higher than that of F. ovina. This competitive ability of A. elatius to C. epigejos increased in heterogeneous treatments.