【作者】 宋坤；

【导师】 达良俊；

【作者基本信息】 华东师范大学 ， 生态学， 2012， 博士

【摘要】 常绿阔叶林—落叶阔叶林交错带(以下简称交错带)地处我国亚热带向暖温带过渡区,对气候变化敏感,长期受人为活动影响,少量自然植被残存于偏远山区。此交错带在我国东部森林带划分中一直存有争议。缺乏对交错带植被特征和成因的了解是争议起因。安徽由南至北逐渐由常绿阔叶林向落叶阔叶林过渡,一直是交错带研究的热点区域。本研究以安徽交错带为对象,通过植被调查和生境、生物性状测定,阐明不同地形上森林群落由南至北的替代格局,揭示环境因子-性状特征-物种组成内在联系,探讨交错带森林植被特征及其成因,提出处理此交错带在我国东部森林植被带划分中的方案和建议。主要结论如下：安徽低山丘陵森林群落由南至北的替代格局在不同地形上存在差异。与下部坡面相比,上部坡面的常绿阔叶林在较低的纬度上被落叶阔叶林替代。这种地形上不对称的替代格局,决定交错带具有一定宽度。在群落水平上,随纬度增加,常绿阔叶物种丰富度降低速率较落叶阔叶物种丰富度增加速率快,因此总物种丰富度逐渐下降。气候因子,尤其表征低温胁迫和干旱胁迫的气候因子与群落的纬向替代格局相关性最大。按相关性大小依次为：最小月均潜在蒸散量、最冷季均温、寒冷指数、年实际蒸散量、最旱季降水。坡度、坡向和土壤总磷含量(SoilP)与其气候因子正交,表明它们与群落的地形分异有关。叶氮磷含量(Nmass/Pmass)、叶面积(LA)、叶灰分含量(LAC)和叶寿命(LL)与各类环境因子相关；木材密度(WD)和0℃处理下的叶相对电导率(ELO)仅与表征能量的气候因子相关。比叶面积(SLA)和叶干物质含量(LDMC)与环境因子无相关性。除LL外,性状指标与表征低温胁迫的因子相关性最高；LL与坡度和SoilP相关性最高。总体上,纬度越高,气温越低,Nmass、Pmass、LA、LAC、WD越大,LL和ELO越小。分布较北或海拔较高的常绿乔木,如青冈、苦槠、柯、灰柯、小叶青冈,Nmasss、LDMC偏大,LL、ELO偏小。常绿阔叶林和落叶阔叶林斑块镶嵌式混交是交错带的植被特征,是交错带植被在纬度、海拔、地形各纬度上常绿阔叶林—落叶阔叶林层级过渡格局的体现。纬度和海拔越低、越靠近坡面下部,常绿阔叶成分优势地位越大；反之,落叶阔叶成分优势地位越大。在水热条件较好的地段形成以苦槠、青冈为优势种的常绿阔叶林,在水热条件较差的地段形成以栓皮栎为优势种的落叶阔叶林,在两者过渡区域形成以栓皮栎和青冈为优势种的混交林。栓皮栎、青冈为优势种的混交林,是层级交错格局的产物。其混交模式为垂直混交,落叶成分在上层空间占优势,常绿成分在下层空间占优势。该群落可长期稳定存在,原因有两点：栓皮栎的最大高度和高生长速度远超青冈；栓皮栎和青冈分别以幼苗库和萌枝库持续更新。该群落轻度破坏后形成以化香、黄檀和马尾松为优势种的群落,随恢复进程栓皮栎和青冈分别成为乔木上层和乔木下层的优势种。综合上述结果,以常绿阔叶林和落叶阔叶林斑块镶嵌式混交格局存在与否作为交错带界划的依据,提出：交错带南界应为甜槠林等中生常绿阔叶林在基带上的分布北界,交错带北界应为青冈林等沟谷常绿阔叶林在基带上的分布北界。由此所划分的交错带在气候、区系和农林生产方式等方面接近亚热带常绿阔叶林区,因而建议在我国东部森林植被带划分中将其作为常绿阔叶林带的亚带处理。更多还原

【Abstract】 Evergreen-deciduous broadleaved forest ecotone (EDFE) locates in the transition area from subtropics to warm temperate zone, eastern China, and was sensitive to climate change. Under long-time anthropical disturbance, natural vegetation survived in mountain areas with small remnant area. The controversy about which bioclimatic zone EDFE should belongs to has been existed for a long time, due to little know about its vegetation characteristic and formation mechanism. Evergreen broadleaved forest (EBF) gradually transits to deciduous broadleaved forest (DBF) from south to north, in Anhui province, which has been the hot spot for EDFE studying. In this research, we conducted a vegetation survey from south to north in Anhui, with collecting habitat data and plant traits data at the same time. The following researching questions were addressed:1) How do forest communities transit across EDFE at different landforms?2) What kinds of environment factors drive forests transition and how plant traits responded to those environment factors at community level?3) How do communities distribute in EDFE and why there are mixed evergreen-deciduous broadleaved forests?4) How to determine the boundary of EDFE and which bioclimatic zone should EDFE belongs to?There were different vegetation transition patterns for low elevation forests from south to north among landforms in Anhui. Comparing to forests on the upper slope, EBFs were replaced by DBFs at lower latitude on lower slope. This asymmetric transition patterns among landforms caused a wide range of EDFE. At plot level, richness decreasing rate of evergreen broadleaved woody plants were greater than increasing rate of deciduous ones with increasing latitude, which causing total species richness decreased from south to north.Climate factors, especially those relating to the cold stress or drought stress, were most correlated with community transition along latitude gradient. According to correlation, minimum monthly potential evapotranspiration (PETmin) has the strongest explanation, followed by mean temperature of the coldest quarter (MTCQ)、coldness index (CI)、annual actual evapotranspiration (AET) and precipitation of driest quarter (PDQ). Slope, aspect and total soil phosphorus content (SoilP) were orthogonal to climate factors, suggesting them relating to the distribution pattern along landform gradient.According to RLQ analysis, leaf nitrogen and phosphorus per unit leaf mass (Nmass、Pmass), leaf area (LA), leaf ash content (LAC) and leaf life-span (LL) were correlated with all kinds of environment factors. Wood density (WD) and leaf relative electrolyte leakage at0℃(ELO) were just correlated with environmental energy factors. Specific leaf area (SLA) and leaf dry matter content (LDMC) had no significant relationship with environment factors. All traits except LL were most correlated with climate factors relating to the cold stress. LL was most correlated with SoilP. In general, with increasing latitude, Nmass, Pmass, LA, LAC, WD increased and LL, LDMC decreased due to temperature dropping. Evergreen broadleaved trees such as Cyclobalanopsis glauca, Castanopsis sclerophylla, Lithocarpus glaber, Lithocarpus henryi, Cyclobalanopsis myrsinifolia, which can distribute in higher latitude or higher altitude, possessed higher Nmass, LDMC and lower LL, ELO.EDFE showed a mosaic transition pattern intermixed by EBF and DBF patches, which caused by hierarchy EBF-DBF transition at latitude, altitude and landform levels. Evergreen broadleaved species dominated on the lower slope at lower latitude and lower altitude. In contrast, deciduous broadleaved species dominated on the upper slope at higher latitude and higher altitude. Generally, EBF dominated by evergreen species such as Cyclobalanopsis glauca and Castanopsis sclerophylla, occurred at sites with greater water-energy condition. DBF dominated by deciduous species such as Quercus variabilis, occurred at sites with weak water-energy condition. Mixed forest dominated by Quercus variabilis and Cyclobalanopsis glauca occurred at transition area between EBF and DBF.The mixed forest dominated by Quercus variabilis and Cyclobalanopsis glauca was an outcome of hierarchy EBF-DBF transition at muti-levels. Deciduous broadleaved tree species dominated at the upper tree layer and evergreen broadleaved tree species dominated at the lower tree layer, which raised a vertical evergreen-deciduous mixing pattern. Because Quercus variabilis had greater height growth rate and maximum height than Cyclobalanopsis glauca and both of them could maintain population by seedlings and resprouting, respectively, the mixed forest could persist for hundreds of years without disturbances. When being destroyed, it would degrade to a forest dominated by Platycarya strobilacea, Dalbergia hupeana and Pinus massoniana.According to all the above results, the mosaic pattern intermixed by EBF and DBF patches was proposed as the criterion to determine boundary of EDFE. Following this criterion, the northern boundary of EDFE was the northern distribution limit of mesophytic EBFs such as Castanopsis eyrei forest, and the southern boundary of EDFE was the northern distribution limit of valley EBFs, such as Cyclobalanopsis glauca forest. Because climate, floristic composition and agriculture-forestry management strategies in EDFE were similar with those in subtropical EBF zone, EDFE could be considered as a sub region of EBF zone in eastern China.更多还原