扎龙湿地异质生境芦苇种群根茎动态及年龄结构

无性系植物根茎不仅具有营养繁殖和扩展种群的功能,也是无性系家族中芽和分株生理整合的通道。采用单位土体挖掘取样,对扎龙湿地单优种群落芦苇种群根茎进行调查,比较了湿生生境和水生生境根茎长度、生物量和干物质贮量的季节变化。结果表明:芦苇种群根茎长度、生物量和干物质贮量均以湿生生境显著大于水生生境;8月前,根茎长度缓慢增加,8月后,根茎长度迅速增加,以3龄最长,6龄最短;根茎生物量、干物质贮量先下降后上升,8月最低,至10月休眠期均已超过营养生长初期,生物量以3龄最大,1龄最小,干物质贮量以5龄最高,1龄最低;不同龄级根茎长度及年龄谱与月份间呈线性相关(R~20.81,P0.05),不同龄级根茎生物量与月份间呈二次曲线关系(R~20.98,P0.05),生物量年龄谱与月份间呈线性相关(R~20.80,P0.05),5个生育期根茎干物质贮量与龄级之间呈二次曲线关系(R~20.86,P0.05)。芦苇种群根茎长度、生物量、干物质贮量有着相同的季节变化规律,不同龄级根茎的寿命与养分的输出消耗和养分的再输入补偿密切相关。整个生育期内,生境异质性对芦苇种群根茎动态及年龄结构的影响均存在,且引起的差异也相对较稳定。     

扎龙湿地保护区异质生境芦苇种群分株构件的数量特征

采用单位面积取样,计数和测量的调查与统计方法,对扎龙湿地保护区4个生境单优群落芦苇种群分株构件数量特征进行比较分析。结果表明,4个生境芦苇种群从5月10日左右返青后进入营养生长期,分株高度和分株密度均持续增加到生殖生长初期的8月份,其中6-8月份差异均达到显著水平(P0.05),8-10月份差异均未达到显著水平(P0.05),芦苇进入生殖生长期后,分株便停止高度生长,地下芽的输出也不再形成分株补充现实种群;分株生物量和种群生物量均持续增加到生殖生长旺盛期的9月份,至休眠期的10月份均有所降低,各月份间的差异均达到显著水平,芦苇种群在生长季末期,具有将生产的物质分配转移到地下储藏与营养繁殖器官的形成与生长上的特性。芦苇种群分株数量特征与返青后实际生长时间之间均较好地符合对数函数关系,R~2在0.818-0.994之间,拟合方程均达到了P0.05的显著水平。4个生境芦苇种群分株密度以湿生生境最大,依次为水生生境、旱生生境,盐碱生境最小,分株高度、分株生物量和种群生物量均以水生生境最大,依次为湿生生境、旱生生境,盐碱生境最小。因此,4个生境芦苇种群分株构件数量特征均表现出基本一致的生育期节律性,同时,芦苇种群的个体生长和种群动态存在明显的环境效应,土壤含水量、pH是影响该地区芦苇分株数量特征的主要因子。     

扎龙湿地不同生境芦苇种群根茎构件的年龄结构

芦苇是典型的长根茎型克隆植物,天然种群主要依靠根茎的营养繁殖进行更新。采用单位土体挖掘取样,按实际生活年限划分根茎龄级的方法,对扎龙湿地芦苇种群不同龄级根茎进行调查。结果表明,6月份,4个生境芦苇种群根茎构件均由2—6a的5个龄级组成,7—10月份均由1—6a的6个龄级组成。6—10月份,1a根茎长度比率逐渐增加;除盐碱生境略有增加外,其他3个生境2a、3a比率均小幅减少;4—6a比率逐渐减小,根茎长度比率均以3a最大,依次是2a,4a,1a,5a,最高的6a最小。1—3a根茎生物量比率逐渐增加;4—6a比率逐渐减小,均以3a根茎生物量比率最大,依次是4a,2a,5a,6a,以最低1a最小。不同龄级根茎长度和生物量比率与返青后实际生长时间之间均较好地符合直线函数关系(R²>0.91,P<0.01;R²>0.81,P<0.05),6—9月份,根茎长度呈衰退型年龄结构,10月份又转为稳定型结构,整个生长季根茎生物量均为衰退型结构。不同龄级根茎构件在芦苇种群中的地位和作用不同,根茎构件的年龄结构蕴含着种群调节的重要信息。     

扎龙湿地芦苇种群不同龄级根茎构件的季节动态

克隆植物根茎具有营养繁殖和扩展种群的功能,也是芽和分株生理整合的通道。根茎构件具有出生、死亡及年龄等种群统计特征,不同龄级根茎的季节动态可以反映根茎的存活和衰老过程。采用单位土体挖掘取样,对扎龙湿地4个生境芦苇种群根茎构件进行野外调查,比较不同龄级根茎长度、生物量和干物质贮量的季节动态。结果表明:7—10月份,1a根茎长度、生物量和干物质贮量均呈指数函数增加,在生长季中后期有一个持续时间较长的生长和物质积累时期。6—10月份,2a、3a根茎长度呈线性函数增加,4—6a根茎长度呈线性函数减少;2—4a根茎生物量和2—5a根茎干物质贮量呈二次函数先减少后增加,5a、6a根茎生物量和6a根茎干物质贮量呈幂函数减少。整个生长期内,根茎长度和根茎生物量均以3a最大,根茎长度以最高的6a最小,根茎生物量以最低的1a最小;根茎干物质储量以5a最大,以最低的1a最小。4个生境芦苇种群根茎长度、生物量和干物质贮量在龄级间的差异及差异序位稳定,在新根茎的产生、老根茎的存活以及根茎寿命与养分消耗和储藏上均具有稳定的生物学特性,不同龄级根茎在种群中的地位和作用以及对种群的贡献不同。     

扎龙湿地不同生境芦苇功能性状变异及其对土壤因子的响应

物种的遗传特征和外在环境条件的差异共同决定了植物功能性状的表达,植物功能性状可以反映物种对环境条件的适应策略。采用大样本抽样调查与统计分析方法,比较研究扎龙湿地4种生境（盐碱生境、旱生生境、湿生生境和水生生境）芦苇分株和叶功能性状,分析不同生境芦苇功能性状的分异规律及其对土壤因子的响应。结果表明：（1）不同生境芦苇功能性状均表现出中等程度变异。其中分株和叶性状均以盐碱生境最低（P<0.05）,分株及除叶面积和比叶面积以外的叶性状均以水生生境最高;株高和株重在种群内的变异系数为15.96%-48.61%和38.65%-87.82%,种群间的变异系数为46.58%和66.39%;叶性状在种群内的变异系数为13.21%-72.37%,种群间的变异系数为26.46%-57.03%;（2）不同生境芦苇功能性状间存在协同变化特征。芦苇的株高、株重、叶长、叶宽、叶面积和叶重之间均呈极显著正相关关系（P<0.01）,比叶面积与其他性状的相关性因生境不同存在一定变化;（3）不同生境芦苇的原位土壤因子表现出异质性特征,芦苇功能性状的变异是含水量、pH、有机质和速效氮等土壤因子综合作用的结果。其中含水量、有机质和速效氮为正向驱动,而pH为负向驱动。因此,芦苇通过自我调节功能性状更好地适应不同的生存环境,局域尺度不同生境的土壤因子是引起芦苇功能性状产生分异的导因。     

扎龙湿地不同生境的昆虫多样性

为了探讨湿地不同生境对昆虫物种多样性的影响,对扎龙湿地8种生境的昆虫进行了系统调查.共捕获昆虫5822只,分属11目58科143种,其中直翅目、双翅目、蜻蜒目为扎龙湿地的优势类群.不同生境中,草原草甸昆虫多样性最高,湖边生境多样性指数和均匀度指数均较高,杂草甸均最低.聚类分析和主分量分析结果表明,不同生境的昆虫群落相似性与水资源状况和植被类型有关,捕食性类群种类数和个体数量对昆虫群落稳定性具有重要的调控作用.湖边生境昆虫群落稳定性最强,湿草甸稳定性最弱.湿地水资源状况能影响昆虫生存生境,进而影响昆虫群落的组成和分布格局.     

扎龙芦苇湿地生长季的甲烷排放通量

为研究高寒地区天然淡水芦苇湿地的甲烷排放特征,采用静态箱-气相色谱法,测定了扎龙不同水位芦苇湿地生长季的甲烷排放通量.结果表明:观测期内,扎龙芦苇湿地甲烷排放通量平均为7.67 mg·m^-2·h^-1（-21.18～46.15 mg·m^-2·h^-1）,其中深水区(平均水深100 cm)和浅水区(平均水深25 cm)的平均甲烷排放通量分别为5.81和9.52 mg·m^-2·h^-1,排放峰值分别出现在8月和7月,最低值均出现在10月.深水区夏季(6-7月)的甲烷排放通量显著低于浅水区,而春(5月)、秋(8-10月)季节显著高于浅水区.生长季甲烷排放通量的变化为夏季>秋季>春季;昼夜排放量为12:00和14:00最高,0:00最低.温度和水位是高寒地区淡水芦苇湿地甲烷排放通量变化的主要影响因子.     

黄河口芦苇湿地不同恢复阶段种群生态特征

采用时空替代法,选择黄河口未恢复区(R0)、恢复5a区(R2007)和恢复10a区(R2002)的芦苇湿地为研究对象,研究了建群种芦苇的株高、密度、立枯物量、地上生物量的动态变化趋势。结果表明,不同恢复阶段的芦苇株高整体均呈增加趋势,且R2002与其它两个恢复阶段差异显著(P0.01);不同恢复阶段的芦苇密度亦具有明显季节动态,R0与其它两个恢复阶段差异显著。不同恢复阶段芦苇地上及不同器官生物量整体均表现为R2002R2007≈R0,其季节动态符合抛物线模型(y=b0+b1t+b2t2,R2≥0.90,P0.01)。不同恢复阶段芦苇地上器官对地上生物量的平均贡献率均无显著差异,但均以茎的贡献率最高,且表现为R2002R2007R0。不同恢复阶段芦苇的立枯物量随时间变化均符合指数增长模型(y=A0ebT+B0,R20.95,P0.01),整体表现为R2002R2007R0,但其差异不显著。研究发现,不同恢复阶段的湿地水文情势(积水深度和水质)是导致芦苇种群生态特征和地上生物量差异的重要因素,故建议下一步湿地恢复工程蓄水应采取少量多次补水措施,并应避开水质较差时间。     

松嫩平原旱地生境芦苇种群不同龄级根茎的干物质贮藏及水溶糖含量

通过对松嫩平原旱地生境单优种群落芦苇种群不同龄级根茎的调查测定,分析了一个生长季内3个生育期芦苇种群各龄级根茎干物质贮量和水溶糖含量的季节变化.结果表明:各生育期低龄级芦苇种群根茎中干物质贮量和水溶糖含量均较少,且与高龄级的差异较大;随着生长季的进程,低龄级根茎中干物质贮量和水溶糖含量迅速增加,且与高龄级的差异逐步缩小.在整个生长季,芦苇种群各龄级根茎均具有养分消耗和再贮藏乃至超补偿性贮藏的活性,其中,幼龄级根茎的活性更大.高龄级根茎的干物质贮量和水溶糖含量有一个逐年累积的增加过程.根茎干物质贮量在龄级间和龄级内的差异均达到了极显著水平(P<0.01),并且龄级间的差异大于龄级内.水溶糖含量仅在龄级间差异达到显著水平(P<0.05).随着龄级的增加,芦苇种群根茎的干物质贮量和水溶糖含量均呈二次曲线变化.     

扎龙湿地丹顶鹤繁殖生境质量变化

基于1996和2004年扎龙湿地丹顶鹤生境因子专题图,通过建立生境适宜性模型和种群格局最邻近体模型,定量分析了扎龙湿地丹顶鹤繁殖生境质量的变化.结果表明：研究期间,扎龙湿地丹顶鹤繁殖适宜生境经历了面积丧失和功能丧失过程;2004年,研究区内丹顶鹤繁殖适宜性生境已大量丧失,核心区繁殖适宜生境已经严重斑块化.丹顶鹤繁殖生境选择行为对生境质量变化的响应表现为两个过程：一是丹顶鹤巢址不断向核心区集中的过程,二是在核心区的分布格局经历了从均匀分布到成群分布的生态过程.     

扎龙湿地芦苇分株生态可塑性及其对土壤因子的响应

扎龙湿地的芦苇既可形成大面积的单优群落,也可形成不同群落斑块。采用大样本抽样调查与统计分析方法,对湿地内水生生境、湿生生境、旱生生境和盐碱生境芦苇种群分株高度和生物量进行比较。结果表明,6—10月份,4个生境芦苇种群分株高度及生物量均以水生生境最高,盐碱生境最低,水生生境株高为盐碱生境的1.5—2.3倍,分株生物量为2.0—5.1倍,生境间的差异性以及差异序位均相对稳定。4个生境株高生境间变异系数(19.45%—31.56%)均高于生境内变异系数(8.07%—17.61%),分株高度在生境间的可塑性更大;分株生物量中水生生境、湿生生境和盐碱生境3个生境间的变异系数(33.43%—55.61%)均低于生境内变异系数(44.85%—79.82%),分株生物量在生境内的可塑性更大。不同生境条件下芦苇种群分株,在生长和生产上均存在较大的生态可塑性,表现出明显的环境效应,其中土壤含水量是该地区芦苇分株生态可塑性变异的主要驱动因子(R0.80),为正向驱动。     

Rhizome development ofPhragmites australis in a reed community

Variations in the height, shoot density, biomasses of above- and below-ground parts and rhizome distributions ofPhragmites australis were investigated along a line-transect in a reed community at Yufutsu Mire, Hokkaido. Relationships of performance of the reed plants to soil conditions and species compositions were also examined. Three types of rhizome development were recognized in reed plants; (1) the central part of the reed community, characterized by well developed rhizomes and dense aerial shoots, (2) the intermediate part, characterized by development of rhizomes along both the peat and surface layers and very dense aerial shoots, and (3) the marginal part, characterized by development of rhizomes only along the peat layer and sparse aerial shoots. Observation showed that rhizomes in the surface layer actively produced aerial shoots, whereas rhizomes in the peat layer contributed to the spreading of their distribution range. With the growth of rhizomes, organic debris originating from dead rhizomes and roots accumulated in the mineral soil to promote organic soil formation. In dense parts of the reed stand, species composition was poor because of the shading and litter accumulation by reed plants. The effects of microtopography and water level on the establishment of reed seedlings were also considered.     

Effects of rhizome age on the decomposition rate of Phragmites australis rhizomes

The change in dried rhizome samples that were left to decompose was investigated to elucidate the effects of rhizome age on the decomposition rate of Phragmites australis. Rhizomes were classified into five age categories and placed 30 cm below the soil surface of a reed stand. After 369 days of decay, new (i.e., aged less than one year) rhizomes had lost 84% of their original dry mass, compared with a loss of 41–62% for that of older rhizomes. The exponential decay rates of older rhizomes were nearly identical to that of aboveground biomass. The nitrogen (N) concentration increased to two times its original values, but the phosphorus (P) concentration remained constant after an initial loss by leaching. The carbon to nitrogen (C:N) and carbon to phosphorus ratios (C:P) leveled out at 22:1 to 38:1 and 828:1 to 1431:1, respectively, regardless of rhizome age. The results are important to understand the nutrient cycles of reed-dominant marsh ecosystems.     

Blocking Phragmites australis reinvasion of restored marshes using plants selected from wild populations and tissue culture

This study tested a vegetation strategy for controlling Phragmites australis invasion into brackish marshes as an alternative to the current technique of repeated herbicide sprays followed by burning. This strategy involves blocking P. australis by planting desired plants selected from wild populations and/or tissue culture regenerants at key points on the major routes of P. australis invasion. The planting of native species was conducted at three sites in a herbicide-treated P. australis marsh near Salem, NJ. Wild population selections of three upland marsh shrubs, Myrica cerifera, Baccharis halimifolia, and Iva frutescens, as well as two grass species, Spartina alterniflora and Spartina patens, and two rushes, Juncus gerardi and Juncus roemerianus, were planted according to their normal zonation positions. Tissue culture regenerated plants of the two grasses and two rushes, and the sedge species Scirpus robustus, were also planted. Plant growth at each site was monitored each year after planting for up to 3 years. Most plants of B. halimifolia, I. frutescens, J. roemerianus, and S. patens demonstrated a consistent vigorous growth at all three sites, whether or not the plants were collected from wild populations or were tissue culture regenerants. These multi-layered walls of plants demonstrated effectiveness in controlling the P. australis by restricting or inhibiting its spread. Upon screening 48 regenerated plants of S. patens at one of the three sites, we found that some regenerants showed enhanced characteristics for blocking P. australis, such as greater expansion and a high stem density. The availability of the tissue culture-regenerated plants of the native marsh species makes it possible to select lines from local genotypes that have desirable characteristics for wetland restoration projects, such as blocking P. australis reinvasion.     

张掖湿地芦苇比叶面积和水分利用效率的关系

密度制约下植物比叶面积与水分利用效率的关系,对于认识土壤-植物-大气的物质循环和能量流动机制具有重要意义。采用样方调查法,研究了3种密度(高密度Ⅰ:210—230株/m~2;中密度Ⅱ:130—150株/m~2;低密度Ⅲ:50—70株/m~2)条件下芦苇种群比叶面积(SLA)和水分利用效率(WUE)的关系。结果表明:随着芦苇种群密度的逐渐降低,湿地群落的土壤含水量逐渐减小,芦苇的株高、叶面积、叶干重、SLA和蒸腾速率(Tr)均呈逐渐减小的趋势,净光合速率(Pn)、叶厚度和WUE呈逐渐增加的趋势;不同密度条件下湿地植物芦苇比叶面积(SLA)与水分利用效率(WUE)的关系存在显著差异(P0.05),在高密度(Ⅰ)与低密度(Ⅲ)样地,芦苇SLA与WUE呈极显著负相关关系(P0.01);在中密度(Ⅱ)样地,二者呈显著负相关关系(P0.05)。不同种群密度的湿地生境中,芦苇通过调整叶片形态构造,使比叶面积和水分利用效率形成了相反的变化趋势,反映了植物适应光照条件、土壤含水量等异质性环境因子的资源利用策略和光合产物积累模式。     

Factors affecting iron plaque on the roots ofPhragmites australis (Cav.) Trin. ex Steudel

Phragmites australis (the common reed) was collected at six sites in southern Québec and Ontario, Canada, in order to study the accumulation of iron plaque on the roots. The deposition of iron oxides on roots ofP. australis did not correlate directly with soil measurements; however, the amounts of iron-bound-to-carbonates fraction of the soil/sediment, responsible for the iron plaque accumulation, correlated with the % of water, % of organic matter, % of clay and pH of the substrate. Plants located very near flowing water accumulated more iron plaque on the roots than plants in other habitats through the summer; it is hypothesized that carbonates associated with iron come from the flowing water. In wetlands or sites near flowing water, most root iron was found on the surface, as iron plaque, while there was more iron inside the root in dry environments. Radial oxygen loss from the roots is probably the most important source of oxygen for the oxidation of iron.