鼎湖山季风常绿阔叶林水相沉积元素分布及其相关性研究

2001年2月~ 2002年3月在鼎湖山季风常绿阔叶林对大气降水、穿透水、土壤水 (30和 80cm层 ) 和溪水中的沉积元素进行监测, 拟通过不同水相元素浓度的比较及相关关系分析, 揭示系统的营养循环功能状况以及对区域化学条件变化的响应, 阐明因素在环境中的迁移转化规律。结果表明 :林冠与大气间强烈的相互作用, 极大地提高穿透水中Mn2 + 、Sr2 + 、K+ 、Mg2 + 、Ca2 + 浓度。水与土壤作用后, 极大地提高水相中Al3 + 的浓度。 30cm土壤溶液和溪水中的Al3 + 浓度分别是大气降水 (0.32 9mg·L-1) 的 4.8和 3.7倍。溪水中的Al3 + 主要来源于土壤的淋溶。大气降水平均Pb2 + 浓度为 0.0 6 2mg·L-1, 存在着一定程度的Pb2 + 污染, 其浓度分别是穿透水和溪水的 5倍和 10倍。林冠吸收和土壤过滤吸附是森林生态系统净化Pb2 + 等重金属污染物的主要过程。大气降水、穿透水、土壤水和溪水中Na+的浓度逐步增加, 但增幅不大。元素浓度的变异系数在 5 1.1%~ 2 36.7%之间。水相中的离子浓度与雨量有关, 大气降水、穿透水、土壤水中的沉积元素浓度大部分是干季大于湿季, 而溪水中是干季小于或近等于湿季。元素相关分析发现, 与元素Mg相关的元素最多, 穿透水所含相关元素对最多, 不同水相间元素相关状况差异与其元素的来源和外部环境条件有关系。Pb与金属元素Al、Mn在大气降水中极显著相关, Mn_Al、Mn_Mg、Mg_K在所有水相中显著相关, Al_Sr、Mn_Sr、Ca_K、Ca_Mg在除溪水外的所有水相中显著相关, Na_K、Na_Mg在除大气降水外的所有水相中显著相关, 而Pb_Na、Pb_K在所有水相中都无相关关系。结果说明, 季风常绿阔叶林系统已经遭受一定的外界环境压力, 但是其物质循环功能依然稳定。     

鼎湖山季风常绿阔叶林黄果厚壳桂群落植物元素含量特征

研究鼎湖山南亚热带季风常绿阔叶林黄果厚壳桂群落元素含量特征 ,分析了其中 9个种不同器官的 6种元素含量 ,结果表明 :1 )群落中植物不同器官的元素含量大小为 ,N:叶 >皮 >根 >枝 >茎 ,P:叶 >枝、皮 >根 >茎 ,K:叶 >皮 >枝 >根 >茎 ,Ca:皮 >叶 >枝 >根 >,Mg:叶 >皮 >根 >枝 >茎。 2 )椎栗、黄果厚壳桂、鼎湖钓樟和双盖蕨是群落中含 N量较高的种 ;椎栗、云南银柴和双盖蕨含 P量较高 ;各个种的含 K量相似。 3)养分含量表现出一定的层次性差异 ,上层种叶子含 P量高于下层种 ,但含 K量区别不显著。上层种茎 N、P、K含量显著低于下层种。黄果厚壳桂种群 ,其不同层次个体养分含量没有统计上的显著差异 ,但下层个体茎养分高 ,上层个体茎养分低。 4)群落不同元素间具有许多显著相关的元素对 ,其中 N与其它元素的相关性最大 ,其次是 Mg、P,再次是 K,而 Na不与其它任何元素相关 ,Ca相关性很少。从器官角度看 ,茎所含相关元素对最多 ,而枝、皮最少。     

鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干流的养分特征研究

对鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干茎流中的5种养分元素K、Ca、Mg、N、P进行了测定,结合水量分配规律,研究了森林降雨过程中养分在水相中的含量变化特征和输入规律。结果表明：(1)所有离子浓度均为大气降水<穿透雨<树干流,且增幅较大,而平均浓度以K+和总氮(TN)含量最高;总磷(TP)、磷酸盐(HPO42-)、总有机磷(TOP)含量均最低。(2) 大气降雨中的离子平均浓度中以总有机氮(TON)的变异系数最大,为1.282;最小的是NO3-(0.502);穿透雨中变异系数最大的是TOP(2.357);最小的是TN(0.621)。树干流中各养分元素浓度与树种的相关性不显著(P>0.05)。(3) 季风常绿阔叶林树干流和穿透雨各养分对森林土壤的年输入量为TN>K+>Ca2+>Mg2+>TP,树干流和穿透雨对森林土壤层Ca2+的输入大于凋落物分解输入。因此,大气降雨是养分从林冠层转移到土壤层的重要因素。     

模拟酸雨对鼎湖山季风常绿阔叶林土壤呼吸的初期影响

通过在鼎湖山季风常绿阔叶林(季风林)进行野外模拟酸雨试验,对不同酸雨强度处理下的林地土壤呼吸速率进行原位测定,探讨酸雨对南亚热带森林土壤呼吸的初期影响。结果表明:在两年的测定周期内,4个酸雨水平:CK(pH值4.5左右的天然湖水)、T1(pH值4.0)、T2(pH值3.5)和T3(pH值3.0)处理下的年平均土壤呼吸速率分别为(3.07±0.08)、(3.06±0.17)、(2.78±0.29)和(2.56±0.08)μmol·m~(-2)·s~(-1),其中T3处理显著低于CK和T1处理(P0.05),说明模拟酸雨抑制了季风林土壤呼吸。这种抑制作用大体上随处理时间的延长而逐渐显著,处理间的差异只在测定周期的第二年达到显著水平,且抑制作用的差异显著性只出现在湿季(P0.05)。模拟酸雨对土壤呼吸的抑制作用可能与其胁迫下土壤酸化而导致土壤微生物异养呼吸及凋落物CO_2释放量下降有关。表现为模拟酸雨导致土壤pH值降低,使得土壤酸化加剧;降低了土壤微生物量碳、氮含量,抑制了微生物活性;提高了凋落物质量残留率,抑制了凋落物分解。还与土壤呼吸结果相对应,上述指标对模拟酸雨的响应也大体上随处理时间的延长而逐渐显著。另外,土壤呼吸温度敏感系数Q_(10)值随处理pH值降低有下降的趋势,表明酸雨处理在一定程度上降低了土壤呼吸的温度敏感性。     

Change in water quality during the passage through a tropical montane rain forest in Ecuador

We studied five 20-m transects onthe lower slope under tropical lower montanerain forest at 1900–2200 m above sea level. We collectedsamples of soil and of weekly rainfall,throughfall, litter leachate, and stream waterbetween 14 March 1998 and 30 April 1999 anddetermined the concentrations of Al, totalorganic C (TOC), Ca, Cl^–, Cu, K, Mg, Mn,NH₄ ⁺-N, NO₃ ^–-N, total N (TN), Na, P, S, and Zn. The soils were shallowInceptisols; pH ranged 4.4–6.3 in the Ohorizons and 3.9–5.3 in the A horizons, totalCa (6.3–19.3 mg kg^–1) and Mgconcentrations (1.4–5.4) in the O horizon weresignificantly different between the transects.Annual rainfall was 2193 mm; throughfall variedbetween 43 and 91% of rainfall, cloud waterinputs were 3.3 mm a^–1 except forone transect (203). The volume-weighted mean pHwas 5.3 in rainfall and 6.1–6.7 in throughfall.The median of the pH of litter leachate andstream water was 4.8–6.8 and 6.8, respectively.The concentrations of Ca and Mg in litterleachate and throughfall correlatedsignificantly with those in the soil (r =0.76–0.95). Element concentrations inthroughfall were larger than in rainfallbecause of leaching from the leaves (Al, TOC,Ca, K, Mg), particulate dry deposition (TOC,Cu, Cl^–, NH₄ ⁺-N), and gaseousdry deposition (NO₃ ^–-N, total N, S).Net throughfall (= throughfall-rainfalldeposition) was positive for most elementsexcept for Mn, Na, and Zn. High-flow eventswere associated with elevated Al, TOC, Cu, Mn,and Zn concentrations.     

鼎湖山季风常绿阔叶林木本植物个体死亡动态

采用永久样地生物多样性长期监测的方法,在对1hm^2永久样地DBH≥1cm的植物进行4次测定的基础上,研究了鼎湖山季风常绿阔叶林植物个体死亡的动态及其成因,并对不同物种和不同径级植物死亡率的格局差异进行了分析。结果表明,从1992年到2004年,12a内该样地DBH≥1cm的植物共死亡2411株,为该样地现有活立木的69．34％。共有92种木本植物发生了个体死亡,占样地108种木本植物的85．19％,其中乔木70种,灌木22种;年平均死亡株数呈直线上升;死亡涉及木本植物种数也呈上升趋势;样地内种群数量最多的云南银柴（Aporosa yunnanensis）和柏拉木（Blastus cochinchinensis）死亡株数也最多（分别为445株和440株）,分别占所有死亡株数的18．46％、18．25％;优势树种黄果厚壳桂由于受虫害的影响,种群死亡率达90．83％;小径级树木死亡较多,其中DBH≤5cm死亡株数占样地死亡总株数的79．22％。自疏作用、灾害性天气、虫害和人为干扰直接影响到样地内植物个体的死亡动态。     

模拟酸沉降对鼎湖山季风常绿阔叶林地表径流水化学特征的影响

通过模拟酸沉降实验,研究了旱季期间(10-3月份)鼎湖山季风常绿阔叶林在4种不同pH模拟酸雨处理(对照、pH 4.0、pH 3.5、pH 3.0)下地表径流水化学输出特征.结果显示:(1)地表径流pH随酸处理强度增强呈“U”型变化模式,酸沉降对地表径流pH的影响不显著(P＞0.05),表明模拟酸沉降尚未引起地表水的酸化.(2)地表径流中NO3-、SO24-浓度随酸处理强度增强略有增加;HCO3-浓度的变化模式与地表径流pH类似.酸根离子浓度与地表径流pH相关性分析表明,SO24-、HCO3-有助于提高地表水抗酸化能力而NO3-则有助于促进地表水酸化.(3)地表径流中盐基离子对酸沉降的响应不尽相同.pH 3.0处理显著提高地表径流中Ca2+、Na+浓度;Mg2+浓度具有随酸处理梯度增强而增加的趋势;K+受模拟酸度的影响小.表明强酸(pH3.0)处理将导致土壤Na+、Ca2+、Mg2+盐基离子流失.(4)酸沉降具有诱发土壤可溶性有机碳(DOC)流失的倾向,增加地表水受有机污染的风险.     

鼎湖山森林生态系统演替过程中的能量生态特征

以时空替代的方法,将灌草丛、针叶林、针阔叶混交林和季风常绿阔叶林等４个处于同一空间下的群落当作同一样落演替进程中的４个阶段,研究了鼎湖山南亚热带森林演替过程中的能量生态特征。结果表明,鼎湖山南亚热带森林群落演替过程中,其垂直层次、叶面积指数、冠层对太阳辐射能的截获量、叶生物量、总生物量、总初级生产力、总呼吸量、净初级生产力、枯树木现存量和年输入量、昆虫啃食量、群落的能量现存量等随演替的进程而增加,     

云南普洱季风常绿阔叶林不同林层非结构性碳水化合物特征

在聚类分析的基础上,研究云南普洱季风常绿阔叶林主要物种非结构性碳水化合物(NSC)及其组分浓度、分配和季节性动态在林冠层、亚冠层和林下层间的变化特征.结果表明:亚冠层中可溶性糖及NSC浓度最高,分别为3.9%和13.3%,可溶性糖淀粉比在林下层最低,为0.76,而淀粉浓度则在各林层间无显著性差异.3个林层的可溶性糖均主要分配在叶片中,淀粉和NSC主要分配在根中.亚冠层中叶片和树干的可溶性糖浓度显著高于林冠层和林下层,枝和根的可溶性糖浓度在3个林层间无显著性差异;叶片的淀粉浓度则随林层高度降低而增加,但根淀粉浓度则是在林下层最低,为10.7%,枝和树干的淀粉浓度在3个林层间无显著差异;叶片NSC浓度为林冠层(10.7%)显著低于亚冠层(12.3%)和林下层(12.0%),但根的NSC浓度在林下层中最低,为14.2%;林下层叶片、枝、树干中可溶性糖淀粉比值均最低,但根的可溶性糖淀粉比值最低值出现在林冠层(0.79).3个林层NSC及其组分均存在显著的季节性变化,可溶性糖及可溶性糖淀粉比均为雨季显著高于旱季,而淀粉和NSC浓度则均在旱季中较高.不同林层NSC及其组分浓度的差异反映了不同高度树种碳利用策略的差异,部分地解释了物种的共存机制.     

西双版纳热带季节雨林林下土壤蒸发的稳定性同位素分析

利用2002年1月～2003年12月在西双版纳热带季节雨林样地测定的大气降雨、林冠穿透雨、林冠滴落雾水、溪流水水量及其氢、氧稳定性同位素比率δD和δ18O的测定结果,分析了热带季节雨林林下土壤的蒸发率.结果表明,热带雨林在雨水偏多的2002年和雨水偏少的2003年的蒸发散分别为1186 mm和987 mm,明显低于世界其它湿润热带雨林的蒸发散值;雾水的稳定性同位素比值明显重于雨水,表明雾水中包含区域再循环的蒸发水汽;由于森林林冠和林下土壤的蒸发作用,穿透雨水和溪水的稳定性同位素值又明显重于雨水的相应值.根据溪流水和穿透水（穿透雨水＋滴落雾水）的同位素差值,利用平衡状态下的瑞利蒸馏方程计算的森林土壤蒸发率表明,这两年的森林总蒸发散中分别有5.1%和3.1%来自林下土壤的蒸发.分析认为,持久、浓重的辐射雾是导致西双版纳地区热带雨林蒸发散和土壤蒸发率较低的重要因子.     

Estimation of evaporation rate from soil surface using stable isotopic composition of throughfall and stream water in a tropical seasonal rain forest of Xishuangbanna, Southwest China

Xishuangbanna is located at the northern edge of the distribution of tropical forests in Southeast Asia, and it has a very high frequency of radiation fog, especially during the dry season (November-April). In this study, rainwater, throughfall, intercepted fog water (fog drip) by forest canopy, and stream water were collected in January 2002 and December 2003 for stable isotopic analysis at a tropical seasonal rain forest site in Xishuangbanna, Southwest China. The objective of the study is to estimate the evaporation rate from the forest floor. The stable hydrogen (δD) and oxygen isotope composition (δ¹⁸O) of rainwater, throughfall, fog drip, and stream water was determined using an isotope ratio mass spectrometer. Stream water during the non-storm runoff period was considered to reflect the effect of evaporation from the forest floor. The evaporation rates from the forest floor were estimated using isotope composition values in stream water and the total throughfall was estimated using the Rayleigh distillation equation under equilibrium conditions. The results indicated that the annual weighted means of δD and δ¹⁸O in fog drip were consistently more enriched than those of rainwater and stream water, and the fog drip was thought to contain water that had evaporated and recycled. The weighted means of δD and δ¹⁸O in stream water during the non-storm runoff period were 5.69% and 0.39% more enriched than those of the total throughfall (rain throughfall + fog drip) in 2002, while in 2003 these were 5.05% and 0.28%, respectively. Evapotranspiration in the humid year 2002 and the dry year 2003, computed from the water balance, was 1186 mm and 987 mm, respectively, which was quite low when compared with the values reported in some humid tropical forests. Consequently, the evaporation rate from the forest floor was 5.1% of the evapotranspiration in 2002, and 3.1% in 2003. The lower evaporation rate was thought to be mainly a result of the influence of the high frequency of heavy radiation fog on the rain forest during the night in the dry season (November-April).     

Estimation of evaporation rate from soil surface using stable isotopic composition of throughfall and stream water in a tropical seasonal rain forest of Xishuangbanna, Southwest China

Xishuangbanna is located at the northern edge of the distribution of tropical forests in Southeast Asia, and it has a very high frequency of radiation fog, especially during the dry season (November-April). In this study, rainwater, throughfall, intercepted fog water (fog drip) by forest canopy, and stream water were collected in January 2002 and December 2003 for stable isotopic analysis at a tropical seasonal rain forest site in Xishuangbanna, Southwest China. The objective of the study is to estimate the evaporation rate from the forest floor. The stable hydrogen (δD) and oxygen isotope composition (δ¹⁸O) of rainwater, throughfall, fog drip, and stream water was determined using an isotope ratio mass spectrometer. Stream water during the non-storm runoff period was considered to reflect the effect of evaporation from the forest floor. The evaporation rates from the forest floor were estimated using isotope composition values in stream water and the total throughfall was estimated using the Rayleigh distillation equation under equilibrium conditions. The results indicated that the annual weighted means of δD and δ¹⁸O in fog drip were consistently more enriched than those of rainwater and stream water, and the fog drip was thought to contain water that had evaporated and recycled. The weighted means of δD and δ¹⁸O in stream water during the non-storm runoff period were 5.69% and 0.39% more enriched than those of the total throughfall (rain throughfall fog drip) in 2002, while in 2003 these were 5.05% and 0.28%, respectively. Evapotranspiration in the humid year 2002 and the dry year 2003, computed from the water balance, was 1186 mm and 987 mm, respectively, which was quite low when compared with the values reported in some humid tropical forests. Consequently, the evaporation rate from the forest floor was 5.1% of the evapotranspiration in 2002, and 3.1% in 2003. The lower evaporation rate was thought to be mainly a result of the influence of the high frequency of heavy radiation fog on the rain forest during the night in the dry season (November-April).     

鼎湖山南亚热带常绿阔叶林群落垂直结构及其物种多样性特征

群落结构在森林生态系统中具有重要作用, 其构建机制一直是森林生态学的研究核心。群落结构不仅包括水平方向上的物种分布格局, 还包括垂直方向上的物种分层结构。本文基于鼎湖山南亚热带常绿阔叶林塔吊样地, 利用林冠塔吊和测高杆精准测量样地内每个个体(胸径大于1 cm)的树高, 并划分群落的垂直层次, 研究了每层的群落多样性特征(α多样性)和林层间的群落多样性变化特征(β多样性)。结果表明: (1)样地群落垂直层次由下至上分为5层: 灌木层、亚冠层、林冠下层、林冠中层和林冠上层。(2)随林层向上, 物种丰富度、多度和Shannon-Wiener指数均下降, Pielou均匀度指数在林冠下层最大。(3)利用POD法计算并分解β多样性, 发现随林层向上, β多样性在灌木层与其他各层间呈递增趋势, 在相邻林层间呈单峰型, 不同林层间的物种组成差异主要由丰富度差异造成。 但在林冠下层与林冠中层间丰富度差异较小, 物种替换组分增大, 可能与林冠下层所处特殊位置有关。(4)各林层内微环境从灌木层向上, 趋于高温、强光照和低空气相对湿度, 但林冠下层平均日光强最低。综上, 鼎湖山南亚热带常绿阔叶林林冠下层可能存在强烈的环境筛选作用, 且光照可能是影响群落垂直结构形成的限制因子。