摘要
对第 2代杉木幼林生态系统的降雨、穿透水、茎流、地表和地下径流等水文过程中 N、P、K、Ca、Mg、Cu、Fe、Zn和 Mn9种养分元素含量进行了连续 5 a的测定 ,结果表明 :降雨通过林冠后其化学特性发生明显变化 ,p H值出现酸化现象 ,穿透水中 Zn和 Org-N为负淋溶 ,其余各元素浓度有所增加。树干茎流的富集作用比穿透水强 ,其中 Zn为负 ,其它元素的浓度均比林外降雨的高。地表径流中 Zn>Org-N>NO3 -N,与降雨中含量相比较为淋失迁移型 ,Ca>K>Cu>Mg>P>NH4 -N>Mn>Fe为内贮型 ,p H值增大。地下径流中 Zn>Org-N>NH4 -N>K>Mn为淋失迁移型、Ca>Mg>Cu>NO3 -N>P>Fe为内贮型。该系统的水循环中 Ca>Mg>Fe>P为净损失、Zn>K>Org-N>NH4 -N>Mn>NO3 -N>Cu为净积累 ,与第 1代杉木林相比 ,第 2代杉木幼林水化学过滤与吸贮功能较差 ,系统稳定性也较弱 。
Chinese fir or Cunninghamia lanceolata is a dominant native species for timber production in southern China. With the rapid expansion of planting acreage and extensive practice of successive rotations, the urgent need to sustain long-term productivity of the forested land with this species has attracted nationwide attention. The present project is concerned with the nutrient flux in the process of hydrological cycling in a forest ecosystem, which is believed to be an important aspect enabling the system to maintain its ability to be productive and stable. The project site is situated in Huitong Located Forest Ecosystem, a field location established in 1978 by the authors and their colleagues for the purpose of working out solutions to sustain the productivity of Chinese fir plantations. There are 8 small watersheds in the station, paralleling one another with the distance no wider than 100 m in between, and the present study was conducted in Watershed No.3. The second-rotation Chinese fir plantation under observation was established in 1989 when the first rotation crop was clear cut. The planting density was 2 490 trees/hm+2, and the average tree height at the time of the first observation was 9 m, with the mean dbh approximating 8 cm. From 1995 to 2000 such hydrological data as the rainfall, throughfall, stemflow, surface runoff and groundwater were automatically measured. Specifically, water samples were collected for chemical analysis each month after the rain. Precipitation samples were collected from the gauge fixed on the two measuring towers above the forest canopy at the top and foot of the valley. Throughfall samples were taken from three receivers installed in the valley slope and foot of the hill. Stemflow samples were collected from receivers fixed at the stem ground, and the samples of surface and ground runoff were collected from the watershed weirs. The volume of each water sample was around 2000 ml. In order to prevent algae from growing, 5 drops of methane trichloride (CH-4Cl-3) were added into each sample before sampling. The methods used for analyzing water samples were as follows: electric potential method for pH value, naxon-agent colorimetric method for NH 4-N, phthol disulforic acid colorimetric method for NO 3-N, vaporization colorimetric method for organic N, molybdic-blue colorimetric method for P, and atomic spectrometer for K, Ca, Mg, Fe, Cu, Zn and Mn. The data collection lasted 5 years, and the analytical results are shown as follows. For rainfall, K ranked the top in concentration among the 9 nutrient elements tested, i.e. N, P, K, Ca, Mg, Fe, Cu, Zn and Mn, being 2^016mg/L; P and Cu were the lowest in concentration, both being 0^018mg/L. For throughfall and stemflow, Cu was the lowest in concentration in both samples, but the concentrations of Ca and K ranked the highest in both the throughfall and the stemflow, respectively. The hydrochemical characteristics changed obviously after the rainfall passed through the forest canopy, and acidification was found in the throughfall and stemflow. The concentrations of Zn and Org-N in the throughfall were lower than those in the rainfall, while the concentrations of other elements were higher. The leaching coefficient of the elements in the throughfall was in the descending order of Mg, Mn, Fe, Ca, P, NH 4-N, Cu, NO 3-N, K, Org-N, and Zn. In the stemflow a stronger nutrients enrichment was identified than in the throughfall. The concentration of Zn in the stemflow was lower than that in the rainfall but other elements (N, P, K, Ca, Mg, Cu, Fe and Mn) showed higher concentrations. The order of leaching coefficient in stemflow was, descendingly, Mn, Mg, NH 4-N, P, Ca, Fe, K, NO 3-N, Cu, Org-N, and Zn. The concentration of Ca amounted to 8^021mg/L and 6^222mg/L in the surface runoff and groundwater, respectively, which was the highest of the 9 nutrient elements tested. The concentration of Cu in the surface runoff and groundwater was the lowest with the amount being 0^033mg/L and 0.026mg/L, respectively. The pH values in the surface runo
出处
《生态学报》
CAS
CSCD
北大核心
2002年第6期859-865,共7页
Acta Ecologica Sinica
基金
国家重点野外台站资助项目 ( 2 0 0 0 -0 76 )
国家林业局重点科研资助项目 ( 2 0 0 1 -7)
湖南省科委重大资助项目( 99JZY1 0 0 4 )
关键词
养分含量
降雨
穿透水
径流
第2代杉木幼林
生态系统
水化学特征
young second-rotation Chinese fir plantation
nutrient concentration
rainfall
stemflow
throughfall
runoff
