【作者】 许晓静；

【导师】 徐小牛；

【作者基本信息】 安徽农业大学 ， 园林植物与观赏园艺， 2007， 硕士

【摘要】 凋落物分解是陆地生态系统养分物质循环的基础,其过程深受凋落物性质及环境条件的强烈影响。与自然生态系统相比,城市生态系统有其独特的性质,决定了城市绿地生态系统凋落物分解以及分解过程中土壤呼吸和凋落物呼吸的特性。开展城市绿地生态系统凋落物分解特性的研究,以揭示城市立地环境在凋落物分解中的作用及其对分解过程中养分释放的影响,有助于绿地生态系统凋落物的有效控制。本研究根据合肥市3种园林树种,即重阳木(Biscofia polycarpa)、枫香(Liquidambar formosana)、马尾松(Pinus massoniana)的落叶,在蜀山森林公园和安徽农大校园绿地进行为期一年的分解试验,系统分析落叶分解速率和养分释放动态,同时结合分解过程中绿地土壤呼吸和落叶呼吸等方面的特性,探讨不同环境下落叶分解差异的主控因素,以及落叶分解速率与其环境土壤呼吸和落叶本身呼吸的关系。研究结果如下:1、分解速率在蜀山公园,落叶经过一年的分解,马尾松分解速率最快,失重率达到86.3%;枫香落叶分解速率最慢,失重率仅为48.9%;四种落叶分解的顺序为马尾松＞混合＞重阳木＞枫香。而在安徽农大校园,重阳木分解快,其失重率为73.7%,马尾松仅40.0%,学校内四种落叶分解快慢的顺序为重阳木＞混合＞枫香＞马尾松。通过Olson模型,模拟计算可知,在蜀山公园各落叶分解系数从大到小依次为马尾松(0.229)＞混合(0.099)＞重阳木(0.066)＞枫香(0.063)。完全分解所需的时间分别为:枫香3.97年、重阳木3.81年、混合落叶2.51年和马尾松1.09年。安徽农大校园内各落叶分解系数从大到小依次为重阳木(0.121)＞混合(0.096)＞枫香(0.050)＞马尾松(0.043);其完全分解所需的时间分别为:马尾松5.88年、枫香4.98年、混合落叶2.61年和重阳木2.07年。2、养分(N、P和Ca)动态不同树种落叶,分解过程中各元素浓度的变化有一定差异。无论在蜀山公园还是安徽农大校园,N含量小幅波动,总体上呈上升趋势;P含量初期呈现上升而后下降的趋势。Ca元素在不同环境下浓度变化规律不相同。在蜀山公园,各种落叶总体呈下降趋势;在安徽农业大学校园,经过一年的分解,各种落叶都有一定程度的Ca富集。Ca的这种动态变化可能与分解环境富Ca有关,校园土壤因建筑等干扰,土壤Ca含量远大于蜀山公园。3、土壤呼吸和落叶呼吸不同试验区土壤呼吸存在显著差异。对蜀山公园土壤呼吸和0～10cm土层含水量及0～5cm地温进行了多因子及互作项回归分析。结果表明,绿地土壤呼吸与0～5cm地温的相关系数达到显著水平r=0.984,(p＜0.0001),而与土壤含水率、含水率和地温互作项都没有达到显著水平(p＞0.05)。对安徽农大校园绿地土壤呼吸和0～10cm土层含水量及0～5cm地温进行了多因子及互作项回归分析结果表明,该处绿地土壤呼吸与0～5cm地温的相关系数达到显著水平r=0.985,(p＜0.0001),与含水率和地温互作项的相关系数也达到显著水平r=0.961,(p＜0.001);而与土壤含水率没有达到显著水平(p＞0.05)。充分说明表层土壤温度和含水量是影响土壤呼吸速率的主导因素。受地温和土壤含水率的影响,尽管不同树种的落叶呼吸大小不一,但是四种落叶都在5、6月份低,而4、10月较高。无论是四种落叶平均呼吸速率还是土壤呼吸在4月～12月平均呼吸速率都是:蜀山大于安农大校园,这可能是蜀山公园落叶分解速率比安徽农大校园快的重要原因。4、土壤呼吸和落叶呼吸与落叶分解的关系土壤呼吸和落叶呼吸与落叶分解都是由土壤微生物的数量、种类和活动强弱决定,环境影响也起重要调节作用,本试验显示土壤呼吸的季节变化同落叶分解失重率的季节变化基本同步。落叶呼吸速率和失重率之间不存在显著的相关性R~2=0.392(p=0.26)。更多还原

【Abstract】 Litter decomposition and related nutrient release are fundamental process of nutrient cycling in terrestrial ecosystems.This process is strongly influenced by the property of litter and environment conditions.In comparison with the natural ecosystems,the urban green-land ecosystem has its specific characteristics.This may determine the specificity of litter decomposition and the soil and litter respiration during the decomposition processes in urban environment.In order to determine the major controls on decomposition process, and to reveal the relationships between decomposition rate and the soil and litter respiration,litter decomposition experiment was conducted using the litter-bag method at urban(Campus of Anhui Agricultural University)and suburban(Shushan Forest Park)area in Hefei.In this study,four types of foliar litter from three tree species,Biscofia polycarpa, Liquidambar formosana,Pinus massoniana and L.formosala-P,massoniana mixture were used.The results are as follows.1.Decomposition rateResults from the study revealed that there existed the significant differences in decomposition rates amongst species and between sites as well.After one year decomposition,the rates of the initial weight loss for the four leaf litter decomposed in Shushan Park showed a decreasing order as:P.massoniana(86.3%)＞L.formosana-P. massoniana(65.7%)＞B.polycarpa(52.4%)＞L.formosana(48.9%).However,in Anhui Agricultural University Campus,the order was:B.polycarpa(73.7%)＞L.formosana-P. massoniana(63.6%)＞L.formosana(41.6%)＞P.massoniana(40.0%).In Shushan Park,the decomposition coefficients of the four litter types were P. massoniana,0.2288;L.formosana-P.massoniana,0.0994;B.polycarpa,0.0656;L. formosana,0.0629.However,in the Anhui Agricultural University Campus,the order of decomposition coefficients of the four litter types were:B.polycarpa 0.1208＞L. formosana-P.massoniana,0.0958＞L.formosana,0.0502＞P.massoniana,0.0425.The times for 95%decomposition for the litter types were,respectively,L.formosana,3.97 a in the park and 4.98 a in the campus;B.polycarpa 3.81 a and 2.07 a;L.formosana-P. massoniana,2.51 a and 2.61 a;and P.massoniana,1.09 a and 5.88 a.2.Nutrient dynamicsDuring the decomposition processes,notable differences in nutrient concentrations were observed amongst the four litter types.In general,N contents of the four litters had an increasing trend at both sites(Park and Campus)during the decomposition,whilst P contents fluctuated with an increasing trend at the initial phase and then decreased at the late phase.However,Ca contents showed evidently different patterns during the decomposition at the two sites.In Shushan Park,Ca contents of all litter types decreased from the initial phase.In the campus,Ca contents of four litter types increased constantly during decomposition.After one year decomposition,the Ca contents increased nearly 1.5 times for the four litters compared with the initial Ca contents.The possible reason for the enrichment of Ca at campus site was due to the high Ca concentration in the soil.3.Soil and litter respirationThe soil and litter respirations at two sites were measured during the decomposition. Soil respiration,soil water content(0-10 cm)and soil temperature(0-5 cm)at both sites were analyzed by multi-factor and interaction regression.The results showed that soil respiration rate in Shushan Park was positively correlated with soil temperature r=0.984, (p＜0.0001),while was not correlated with soil water content and their interaction(p＞0.05).-However,soil respiration rate in the Campus was positively correlated with soil temperature r=0.985,(p＜0.0001)and interaction between soil temperature and soil water content r=0.961,(p＜0.001),while was not correlated with soil water content(p＞0.05).Although the rates of respiration changed evidently with litter types at two sites,a similar pattern was observed for all litter types,with a greater respiration rate in May and June and a lower rate in April and October.The average respiration rates of both litters and soils were greater in Shushan Park than in the Campus.This could be one of the important cause contributing the rapid decomposition in Shushan Park.4.Relationship between decomposition rate and soil and litter respirationBoth soil and liter respirations were determined by microbial amount,species and physiological activities.Environmental conditions can also affect the soil and litter respirations.The results from the study showed that the seasonal course of both soil and litter respiration synchronized with that of the litter weight loss at the initial phase during decomposition.To a certain extent,the litter weight loss was not correlated with its respiration rate R~2 = 0.392(p=0.26).更多还原