【作者】 赵雪梅；

【导师】 孙向阳；

【作者基本信息】 北京林业大学 ， 土壤学， 2010， 博士

【摘要】 在中国河北省威县试验地,采用裂区试验设计对不同密度三倍体毛白杨人工林树木生长情况及林地土壤养分动态进行了研究,以三倍体毛白杨(B304、B305、B331、B333)和对照二倍体(1319)为研究对象,连续4a测定7种栽培密度下(2m×2m、2m×3m、2m×3.5m、2m×4m、2m×5m、3m×3m、3m×4m)三倍体毛白杨树木生长情况、叶片养分含量动态、林地土壤养分元素(N、P、K)和有机碳含量以及相关理化性质的变化,得出主要结论如下：(1)受无性系差异、种植密度、生长时间及各因素之间交互作用的影响,不同无性系三倍体毛白杨在胸径、树高、单株材积和蓄积量的生长上出现显著性差异。其中三倍体毛白杨无性系B331和B305在2m×5m和2m×4m种植密度下单株材积生长量较高。而对于毛白杨纸浆林的规模化栽种,宜选的种植密度为2m×2m(2500株·hm-2),可获得最高的林木蓄积量。(2)在4a生长期内林地土壤的pH值呈现碱性增强变化；不同种植密度和不同土层下土壤pH值变化有显著性差异,三个土层的土壤pH值均在3m×4m种植密度下增加最多,分别为0.51、0.74、0.87。(3)林地土壤有机质消耗量较多的种植密度是2m×2m、2m×3m,碱解N是2m×2m,有效P是2m×2m、2m×5m,即密集的种植密度下林地土壤养分消耗较多。但由于枯落物的养分归还,4a后林地土壤养分衰退情况有所恢复。(4)不同土壤层次的养分元素含量差异显著,尤其是0-20cm土层的土壤有机质、全N和碱解N含量在种植后的第二年(即2006年)显著下降；林地土壤养分含量受时间效应影响显著。在4a内有机质、N素及K素呈现先降低后升高的变化趋势,土壤P素呈现先升高后下降的变化特点。(5)在造林密度、生长时间及二者的交互作用的显著影响下,林地土壤有机碳含量呈现先降后升的变化特点,造林后第二年(即2006年)林地土壤有机碳含量最低。造林密度和时间效应对三倍体毛白杨林地(B304)土壤有机碳含量的影响大于二倍体(1319),在造林后第四年(即2008年)2m×3m密度下有机碳含量增加显著,所以此密度利于发挥林地土壤固碳增汇的生态功能。(6)有机碳／全氮(C／N)比值变化规律与有机碳含量变化规律一致,均在造林后第二年(2006年)达到最低值。三倍体毛白杨(B304)高密度林地(2m×2m、2m×3.5m)和普通二倍体(1319)的低密度林地(2m×5m、3mx3m)土壤有机碳与全N含量有显著正相关关系。同时,在2008年二倍体毛白杨2mx5m密度林地中有机碳与全N含量呈显著性负相关,这体现了有机碳与全N含量变化的复杂性。(7)毛白杨叶片养分元素的含量具有物候学的特点。在一年之中,叶片N、P、K、Fe和Cu元素的含量呈现下降变化,叶片S元素含量呈现上升变化。Ca和Mg元素的含量呈现先升后降的变化,Zn元素含量则先降后升。叶片各养分元素含量有显著的相关性,其中叶片Cu和S元素的含量在三倍体毛白杨生长时期内始终是呈正相关关系。在春季,叶片N-P,叶片Mg-Mn,叶片Zn-S/Cu之间有显著性正相关。夏季叶片中的K-Ca/Mn元素的含量呈现显著负相关,而Ca-Mn则呈现显著正相关。秋季叶片中的Zn-K/Fe/Cu之间有显著正相关关系,而叶片中Ca-Mg元素含量则呈现显著性负相关。所以在进行人工林管理时,根据其叶片养分动态特点宜在春季进行追肥。而且考虑到各养分元素之间的相关性特点,在施肥时应配比合理的施肥量。(8)在三倍体毛白杨B304叶片中,营养元素P、K、Mg、S、Fe、Cu、Zn含量高于其他毛白杨无性系,体现了对养分较强的吸收能力。(9)三倍体毛白杨(B304)DRIS营养诊断显示叶片养分元素最佳比例为N／P=13.07±1.76,N／K=6.27±1.77,P／K=0.48±0.10。由高产组三倍体毛白杨叶片养分元素含量得到的三种养分元素最佳比例为N：P：K=1：0.18：0.12。(10)根据DRIS营养诊断发现,在2mx2m和2m×3m种植密度下,叶片养分元素含量低,宜选用平衡施肥,保证各种养分的供应。在2mx3.5m、2mx4m、2mx5m和3mx3m种植密度下,K素不足是导致养分元素比例不平衡的限制因子,需肥顺序为K>P>N。(11)叶片养分元素与土壤养分和树木生长情况相关性复杂。在2mx2m和3mx4m种植密度下,叶片N含量与土壤全N呈显著性正相关,但在2mx5m种植密度下却呈现显著性负相关。在2mx3m种植密度下,叶片P含量与胸径生长量呈显著性负相关关系而在3mx3m种植密度下叶片P含量与树高生长量呈显著性正相关关系。更多还原

【Abstract】 From 2005～2008, a split-plot field experiment was carried out to study the tree’s growth, foliar nutrient concentrations, the soil organic carbon contents and the dynamic changes of soil nutrient (N, P, K) contents in three soil layers (i.e.,0-20cm,20-40cm and 40-60cm) of the triploid (cv. B304, B305, B331 and B333) and diploid (cv.1319) Populus tomentosa plantation under five growth densities (including 2m×2m,2m×3m,2m×4m,2m×5m and 3mx4m). The results showed that:(1) Significant increases of diameter at breast height (DBH), the total plant height, individual volumes (IDV) and growing stock (GRS) were found in triploid P. tomentosa. The largest IDV were found in B331 by 2m×5m and B305 by 2m×4m which were the optimal growth densities for triploid clones. Forevermore,2m×2m (2500 tree·hm-2) density for the large-scale planting for triploid clones can get maximum GRSs.(2) Singificant difference on soil pH values were found in different growth denisites and soil layers. Soil pH value increased after 4a and the largest increment were found in 3m×4m growth density with 0.51 for 0-20cm layer,0.74 for 20-40cm layer and 0.87for 40-60cm layer.(3) More soil nutrient contents decreased in the intensive growth densities, such as organic matter in 2m×2m and 2m×3m; available N in 2m×2m; available P in 2m×2m and 2m×5m.(4) Significant decreasing in the contents of organic matter, total and available N were found in 0-20cm soil layer in 2006. Growthing year showed significant effect on pH value, the content of P and K. The organic matter, total and available N and total and available K decreased first and then increased while the contents of P exhibited the totally different tendency.(5) Significant differences were indicated in the soil organic C content insulted by the treatments with growth density, sampling year and their interaction. Organic C content decreased in 2006 and then increased during the following two years. Form 2005 to 2008, more significant effects of growing density on soil organic C content was found in triploid clone than diploid one. The maximum content of organic carbon was found for the 2m×3m which was optional for the triploid clone to enhance the C sequestration in plantation soil.(6) The content changes in the ratio of soil organic C to total N had the same dynamic tendency of soil organic C, and the lowest C:N ratio was in 2006 for all the treatments of the triploid and diploid clones with seven growth densities. Significantly positive correlations between the soil organic C and the total N were found in triploid clone by 2mx2m and 2mx3.5m and diploid clone by 3mx3m and 2mx5m. Significantly negative correlation was also observed in the 2mx5m in 1319 which reflects the complex in the changes of soil organic C and total N in the plantation of triploid P. tomentosa.(7) Significant differences were found in foliar nutrients’ contents between the triploid (B304, B305, B331 and B333) and the diploid 1319 clones respectively, and an obvious phonological law was also found for them. Compared with the diploid clone 1319, significantly higher foliar P and K contents were found in B304 representing that B304 has stronger anti-drought capacity. The contents of foliar N, P, K, Fe and Cu all decreased from spring to fall while increasing for the foliar S content. Foliar Ca and Mg were also indicated remarkable phenological dynamics during the growing seasons. Moreover, significant positive correlations between the foliar N and P, the foliar Cu and S/Fe, and the foliar Zn and S/Cu/Fe, while significant negative correlations between the foliar Mg and Ca/Mn, and the foliar K and Ca/Mn were also found. According to the phenological change and correlations among the foliar nutrients elements, triploid Populus tomentosa B304 was the optimal one for local introduction and topdressing in spring was strongly recommended as well as the rational ratio of fertilizer should be considered during the plantation management.(8) Higher P, K, Mg, S, Fe, Cu and Zn contents were found in B304 and it was recommended to further study for significant higher P and K content in foliage.(9) According to DRIS, the optimum ratios were 13.07±1.76 for N/P,6.27±1.77 for N/K, and 0.48±0.10 for P/K for trioloid P. tomentosa.plantation. Based on means of the high-yielding group, the optimum N:P:K was 1:0.18:0.12.(10) Balanced fertilization was recommended for the triploid clone B304 P. tomentosa trees that are spaced at 2×2 and 2×3 m and that have low foliar nutrient concentrations. K was the limiting factor for the triploid clone B304 P. tomentosa plantation with spacings of 2x3.5,2x4,2x5, and 3x3 m, and the order of nutrient deficiencies was K>P>N.(11) Soil N concentrations and foliar N concentrations were positively correlated with spacings of 2x2 and 3x4 m but negatively correlated with a spacing of 2x5 m. Foliar P and K concentrations were negatively correlated with tree DBH with a spacing of 2x3 m, and foliar P concentrations and tree height were positively correlated with a spacing of 3x3 m.更多还原