不同养分环境下木荷种源生长和根系发育对邻株竞争响应的差异

研究同质和异质养分环境中邻株竞争对3个木荷种源生长和根系发育的影响,揭示了不同种源木荷生长竞争能力差异原因.结果表明: 与同质养分环境相比,3个木荷种源在异质养分环境中具有苗高生长量大、干物质积累量高和根系增生明显等特点.在异质养分环境下,福建建瓯种源木荷苗木生长量显著高于浙江龙泉和江西信丰种源,与杉木混植时尤为突出,这与其根系形态可塑性高和拓殖能力强有关,混植时,福建建瓯种源木荷的根长、根表面积和根体积等根系生长量较单植显著增长20.4 %～69.0%,其根系在富养表层大量增生的同时快速向深层贫养层拓殖,占有了更多的空间和资源,提高了觅养能力,使其生长优势更为明显,而浙江龙泉和江西信丰种源根系生长和深层土壤根系分布受邻株竞争影响不同程度的降低.纯植时,可能由于根系自我识别作用,3个木荷种源的根系生长发育均受到抑制,导致福建建瓯种源苗木生长量显著减小,而浙江龙泉种源苗高和干物质积累增长明显,这与其根系生理可塑性有关.建议生产上选用觅养效率高和竞争能力强的福建建瓯种源木荷,采用混交造林的方式提高木荷人工林生产力.     

Effects of localized nitrogen supply treatments on growth and root parameters in Pinus massoniana families under phosphorus deficiency

Aims A heterogeneous spatially distribution of nutrients in natural soil may affect plant growth. The objective of this study was to determine the effects of localized nitrogen (N) supply treatments on growth traits and root parameters among different families in Pinus massoniana.Methods Five families of P. massoniana seedlings from full-sib progenies were used as test materials (1, 25, 49, 52, and 57). This study included two conditions, (i.e. homogeneous phosphorus (P) deficiency vs. heterogeneous P efficiency) among soil layers in combination with four N supply treatments in a one-year pot experiment. These N supply treatments were: (1) Homogeneously high N along the soil profile (HHH); (2) high N-high N-low N (HHL); (3) low N-low N-high N (LLH); (4) low N-low N-on side with N addition and the other side without N supply (LLH/L).Important findings This study indicated that localized N supply treatment did enhance the growth of P. massoniana, and this enhancement mainly happened in the pattern of N applied to deep soil. The results showed: 1) Compared to the homogeneous low P condition, there were increase in the growth traits and root parameters of P. massoniana under heterogeneous low P condition. Particularly, the root length and root surface area under the heterogeneous P deficiency condition were 1.95 times and 2.11 times higher than that subjected to the homogeneous P deficiency. 2) Localized N supply treatment affected seedling growth, and there was a significant interaction among N supply pattern and P condition. In compared with homogeneous N supply treatment, the height, basal diameter and dry weight of seedlings increased significantly by localized N supply treatments (LLH and/or LLH/L) under both two P deficiency conditions. But when the seedlings parameters were enhanced under homogeneous P deficiency, they were inhibited under heterogeneous P deficiency subjected to HHL. 3) Within the two P conditions, LLH and LLH/L stimulated root proliferation significantly, and root parameters were significantly enhanced under the heterogeneous P deficiency condition. Specifically, the root length and root surface area subjected to LLH/L rather than HHH were significantly enhanced by 29.2% and 32.3%, respectively. However, the length and surface area of the roots were suppressed by HHL treatment. 4). There were significant differences in response to different N supply treatments among P. massoniana families Seedlings in the families of 49, 52, and 57 responded to the localized N supply treatments with increased root proliferation, which enhanced seedling dry mass. On the other hand, the seedling growth in the family of 25 were stimulated by N and (or) P concentration, while the response of seedlings in the family of 1 to local nitrogen supply was relatively slow and exhibited growth retardation.     

不同产地南方红豆杉各家系幼苗生长、光合生理与株高生长节律的差异分析

为充分了解不同产地南方红豆杉也Taxus wallichiana var. mairei ( Lemée et H. Lév.) L. K. Fu et Nan Li页各家系幼苗生长、光合生理及株高生长节律的差异,以产自江西分宜( FY)、浙江龙泉( LQ)、福建建瓯( JO)和福建明溪( MX)的20个家系的2年生容器苗为研究对象,对幼苗的株高和地径以及叶片的净光合速率和叶绿素含量进行比较,并对各家系的株高生长进行Logistic拟合回归分析以及拟合曲线参数和株高生长节律参数的计算和分析;在此基础上,分析了不同指标间的相关性并对供试的20个家系进行聚类分析。结果显示：不同产地间南方红豆杉的株高、地径、叶绿素含量和净光合速率均无显著差异,但这些指标在不同家系间均有极显著差异(P<0.01);各家系的株高、地径、净光合速率( Pn)以及叶绿素a( Chla)、叶绿素b( Chlb)和总叶绿素( Chl)含量的最大值较最小值分别高52.99%、29.63%、115.65%、39.81%、30.95%和37.24%。4个产地的株高生长均呈明显的“S型”曲线;各家系的最大生长速率( MGR)、线性生长速率( LGR)、线性生长总量( TLG)和线性生长持续时间( LGD)的最大值较最小值分别高60.00%、61.54%、63.73%和22.73%;从线性生长始期(t1)和线性生长终期(t2)来看,各家系的速生期为5月中旬或下旬至8月上旬。幼苗的株高与MGR、TLG、LGR、地径、Pn、Chlb和Chl等指标均极显著正相关,并与Chla显著正相关,而地径与MGR、TLG、LGR、Pn和Chlb等指标显著正相关,但株高和地径与LGD均无显著相关性。聚类分析结果表明：在欧氏距离10处,供试的20个家系被分成4个类型,其中,第Ⅳ类的6个家系的幼苗生长最佳且生长潜力最高。研究结果表明：不同产地南方红豆杉各家系的遗传变异丰富,且株高和地径生长主要受生长速率的影响;总体来看,家系LQ09、LQ11、FY21、FY26、MX12和MX18的幼苗生长潜力较高,可作为南方红豆杉的优良家系进行推广。     

不同养分环境下邻株竞争对木荷和杉木生长、细根形态及分布的影响

以木荷和杉木为试验材料,模拟异质和同质两种森林土壤养分环境,设计单植、两株纯植和两株混植3种栽植方式,开展盆栽试验研究木荷与杉木混交造林增产及木荷生长竞争优势形成的原因.结果表明: 与同质养分环境相比,异质养分环境中木荷与杉木混植时两树种均具有较高的苗高和干物质积累量,且木荷竞争优势明显,这与其根系可塑性强有关.混植的木荷各径级细根大量增生,其根系总长度、表面积和体积比杉木高80%～180%.木荷细根在垂直方向上采用了补偿性的生长策略,即除占据富养表层外,还在低养分斑块中大量增殖以获得更大的竞争优势.木荷与杉木的细根在土壤中的拓殖深度不同,生态位分化,缓解了两树种根系对养分的强烈竞争,提高了混植产量.纯植的木荷由于根系自我识别作用,抑制了根系的生长,使得纯植产量较低.细根在空间上错开和均匀分布可能是木荷纯林结构稳定的原因之一.建议在生产中采用块状整地和表层施肥等措施,改善土壤养分分布状况,营建混交林促进木荷和杉木生长,而对已营造的木荷人工纯林,可以及时调控林分密度促进林木生长.     

木荷稳定碳同位素分辨率的种源差异

利用设置在福建建瓯、浙江淳安和浙江庆元3个区试点的5年生木荷种源试验林,选取18个代表性种源测定叶片的稳定碳同位素分辨率(Δ值),研究其在种源间的差异和地理变异模式,以及造林立地环境和种源生长对其的影响.结果表明：木荷种源叶片稳定碳同位素分辨率存在很大差异,福建建瓯、浙江淳安和庆元3个区试点的叶片Δ值最高和最低种源分别相差6.9％、3.0％和3.7％.种源叶片Δ值与其产地纬度呈显著负相关,而与产地经度的相关性较小,表现为典型的纬向渐变模式,来自木荷分布区南部的种源叶片Δ值较大,说明其长期水分利用效率较低.随着造林立地环境的改善和年降雨量的增多,木荷叶片Δ值显著增加.种源叶片Δ值与其树高、胸径、一级侧枝总数和最大侧枝长等皆呈显著正相关,树冠浓密的速生种源具有较高的Δ值.此外, 在木荷中心产区(福建建瓯)和边缘产区(浙江淳安)分别初选出2个和4个水分利用效率高的速生优良种源,供推广应用.     

异质养分环境下邻株竞争对3个木荷种源干物质积累及氮磷效率的影响

为了探究不同木荷种源混交林和纯林生产力差异原因,采用盆栽试验,模拟异质和同质性森林土壤环境,并设计木荷单植、双株纯植和与杉木混植3种栽植模式,重点研究了异质养分环境下邻株竞争对3个木荷种源(福建建瓯、江西信丰和浙江龙泉种源)干物质积累及氮磷效率的影响。结果表明:与同质养分环境相比,木荷种源在异质养分环境中具有干物质量大,氮、磷吸收效率高的特点,尤以福建建瓯种源优势最大。邻株竞争对木荷种源的干物质量和氮、磷吸收效率影响显著。在异质养分环境中,与杉木邻株竞争时,木荷福建建瓯种源干物质积累量优于单植和双株纯植模式。这与其根冠比和生理可塑性较强有关,混植时,其根冠比明显降低,将更多的干物质分配至叶片,增强了光合能力;同时氮、磷吸收效率也显著提高,进而积累了较高的干物质量,提高了竞争力。相反,混植时江西信丰和浙江龙泉种源氮和磷吸收效率却不同程度地低于其单植或与之相近,根冠比较高,结果影响了干物质积累。同种邻株竞争虽促进了浙江龙泉和江西信丰种源的氮、磷吸收,但抑制了两元素的利用效率,而福建建瓯种源氮、磷效率受影响较小,且明显高于其他种源,从而形成较高的干物质量。以上研究结果表明,福建建瓯种源较高的生物量分配和生理可塑性是其生产力高和生长竞争优势明显主要原因。