PRODUCTION, DISTRIBUTION AND NUTRIENT RETURN OF FINE ROOTS IN A MIXED AND A PURE FOREST IN SUBTROPICAL CHINA

研究了福建三明 2 7a生杉木观光木混交林和杉木纯林群落细根 (d <2mm)的生产力、分布和养分归还 .结果表明 ,混交林细根生物量、N、P养分现存量分别为 5 .381thm-2 、4 8.0 85kghm-2 和 4 .174kghm-2 ,分别比杉木纯林增加17.4 %、2 7.2 %和 2 0 .0 % .混交林细根的年净生产力达 4 .12 4thm-2 a-1,比纯林高出 16 .9% .混交林杉木和观光木细根均在表层土壤富集 ,而在较深层土壤两者分布具镶嵌性 ;与混交林杉木相比 ,纯林杉木土壤表层细根量较少 ,最大分布层次下移 .混交林中观光木细根的周转速率为 1.16 ,杉木为 0 .96和 0 .95 ;而林下植被层细根周转速率 (1.4 6～ 1.5 2 )均高于相应的乔木层 .混交林细根的年死亡量、N和P养分年归还量分别达 2 .119thm-2 、18.5 5 9kghm-2 和 1.5 6 5kghm-2 ,分别是纯林的 1.2 1倍、1.2 3倍和 1.14倍 ,其中林下植被细根占有较为重要位置 .对细根分布与土壤性质的相关分析表明 ,细根的垂直分布与土壤全N的相关性最强 (0 .87～ 0 .89) .图 1表 4参 32The studies on production, distribution and nutrient return of fine roots ( d <2 mm) in a mixed Chinese fir ( Cunninghamia lanceolata ) Tsoong' tree ( Tsoongiodendron odorum ) forest and a pure Chinese fir forest at age 27 were carried out in Sanming of Fujian, China. The standing crops of dry matter, N and P in fine roots of the mixed stand were 5.381 t hm -2 , 48.085 kg hm -2 and 4.174 kg hm -2 , 17.4 %, 27.2% and 20.0% higher than those of the pure stand, respectively. The fine root production in the mixed forest was up to 4.124 t hm -2 a -1 , 16.9% higher than that in the pure stand. Fine roots of Chinese fir and Tsoong' tree in the mixed forest both concentrated in the surface soil, and showed a vertical stratification in the subsoil. Compared with those in the mixed forest, fine roots of Chinese fir in the pure forest had a deeper rooting zone, with a lower root density in the superficial soil. The turnover rates of fine roots for Tsoong' tree and Chinese fir in the mixed stand, and Chinese fir in the pure stand, were 1.16, 0.96 and 0.95, respectively. The undergrowth species had higher root turnover rates than their respective tree layers (1.46 in the mixed forest and 1.52 in the pure stand). The annual mortality, annual return of N and P of fine roots in the mixed forest amounted to 2.119 t hm -2 , 18.559 kg hm -2 and 1.565 kg hm -2 , 1.21, 1.23 and 1.14 times as much as that in the pure forest respectively. Bulk density, moisture content, total N and humic C were strongly correlated with fine root density along the soil profile in the two forests, with total N giving the highest coefficients of determination. Fig 1, Tab 4, Ref 32中国博士后科研基金;; 福建省科委重大基础研究项目 (2 0 0 0F0 0 4 );; 高等学校骨干教师资助计划;; 福建省自然科学基金 (B0 1 1 0 0 2 5)资助

LITTER DECOMPOSITION AND NUTRIENT RELEASE IN A MIXED FOREST OF CUNNINGHAMIA LANCEOLATA AND TSOONGIODENDRON ODORUM

通过福建省中亚热带杉木观光木混交林 (CunninghamialanceolataandTsoongiodendronodorummixedforest)和杉木纯林 (PureC .lanceolataforest)凋落物的分解和养分释放动态试验研究表明 ,凋落物各组分分解过程中干物质损失速率随时间而减小 ,分解 1年时以观光木叶的干重损失最大。各组分分解过程中N、P元素浓度增加而K和C元素浓度下降。混交林中各组分的养分释放速率大小为观光木叶 >混合样品 (等重量的观光木叶和杉木叶混合 )>杉木叶 >杉木小枝。不同元素的释放速率与干重损失速率大小为 :K >C >干重 >N≈P。混交林凋落物的年养分释放量 (kg·hm-2 ·a-1)为N 17.92 1,P 0 .715 ,K 10 .315 ,分别是纯林的 2 .0 3倍、1.73倍和 1.34倍。与纯林相比 ,混交林较高的年凋落物养分归还量和养分释放量有利于促进养分的再循环 ,这对维持混交林的地力有重要作用。Rate of litter weight loss and release of nutrient elements were investigated in a mixed forest of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and Tsoong' tree (Tsoongiodendron odorum Chun) and a pure stand of Chinese fir in Sanming, Fujian. Chinese fir needle, branch, Tsoong' tree leaf and the mixture of Chinese fir needle and Tsoong' tree leaf were involved in the 510 day period of litter bag studies. Rate of weight loss slowed with time for all litter components, with the highest percent initial weight loss of 74.54% for leaf litter of Tsoong' tree at the first year. Concentrations of N and P appeared to increase and concentrations of K and C appeared to decrease during the decomposition. The four litter components could be arranged with respect to nutrient release rate in this sequence: leaf of Tsoong' tree > the mixed leaves > needle of Chinese fir > branch of Chinese fir. Nutrient elements and weight loss followed the release pattern: K >C >dry weight> N≈P. The total annual nutrient release of litter fall was N,17.921 kg·hm -2 ·a -1 ; P, 0.715 kg·hm -2 ·a -1 and K,10.315 kg·hm -2 ·a -1 respectively in the mixed forest, being 2.03, 1.73 and 1.34 times as much as that in the pure forest. It was concluded that the higher yield of litter production and the greater amount of nutrient release from litter in mixed forest were beneficial to nutrient cycling. Thus, a higher level of soil fertility would be expected for mixed forest than for pure forest.ThePost_doctorResearchFoundationofChina,theFoundationforUniversityKeyTeacherbytheMinistryofEducation,andtheResearch ProjectofBasicTheoryofFujianProvince ( 2 0 0 0F0 0 4

Effects of soil moisture on photosynthetic rate, transpiration rate and water use efficiency of rape in different leaf positions.

通过对不同水分处理下油菜不同叶位叶片光合速率(Pn)、蒸腾速率(E)和水分利用效率(WUE)的测定表明,油菜主茎叶片的光合速率、蒸腾速率和水分利用效率随叶位的降低而降低;干旱胁迫下油菜水分利用效率显著提高,光合速率变化不明显,但上部、下部叶间光合速率差异大。充分供水时叶片的蒸腾速率提高,水分利用效率则降低,从上到下叶片水分利用效率、光合速率降低不剧烈,而蒸腾速率表现为上部和下部叶高,而中部叶低。据测定,干旱处理下油菜单株生物量为37.45g,充分供水时为38.76g,干旱导致油菜生物量降低;水分胁迫能提高作物水分利用效率;在充分供水条件下叶片蒸腾速率较高,这可能是气孔行为的结果

北疆早熟棉区高产优质栽培技术体系集成与示范推广

本成果因地制宜实施、总结、改进棉花栽培技术规程,建立高产优质高效适耗栽培模式与技术体系;建立棉花目标产量,因土优化平衡施肥适用技术与棉花专用长效复合肥合理使用技术,把原来的氮、磷配比1:0.57调整为N：P_2O_5为1:0.42～0.5;选育、示范、扩繁抗病、早熟、高产、优质、强适的主栽品种,选择方向与科学调整产量结构;探索提出棉花播种适期及改进宽播技术,一播全苗;示范应用病毒农药及其生物防治技术,实施综合有效防治棉花病虫害措施,重点遏控棉铃虫加剧发生和枯黄萎病蔓延危害;研究、监测、跟踪高产棉田群体生育动态,改进肥水运筹、化学调控、调节灌溉、栽培管理的综合调控技术