【作者】 刘洋；

【导师】 张一平；

【作者基本信息】 中国科学院研究生院（西双版纳热带植物园） ， 生态学， 2008， 博士

【摘要】 探讨和解释生物多样性的空间分布格局一直是生态学家和生物地理学家所关注的问题,预测气候变化对植物多样性的潜在影响已成为生态学研究的焦点。本研究以纵向岭谷区不同纬度的西双版纳(热带山地)、哀牢山、无量山、高黎贡山和白马雪山(亚热带山地)等5个区域为研究对象,分析了不同区域山地气候要素的时空分布特征、山地面积和植物多样性的垂直分布格局,从气候的角度解释了植物多样性的垂直分布格局,预测了区域气候变化对植物多样性的潜在影响。研究结果表明:纵向岭谷区不同纬度山地气温和地表温年较差随海拔的升高而减小,随纬度的增加而增大;地表温年较差高于气温年较差。雨季平均相对湿度在75%以上,干季平均相对湿度在60%以上。降雨的年内变化呈单峰型,有明显的干、湿季之分,雨季降雨量占全年降雨的70%以上。整体而言,纵向岭谷区不同纬度山地,5～10月气温、地表温、相对湿度较高,降雨较多,11～4月气温、地表温、相对湿度较低,降雨较少,体现了纵向岭谷区雨热同期的气候特征。相近海拔高度处东坡的热量状况优于西侧坡面,西坡的水分状况优于东侧坡面。山地气温垂直递减率在0.54～0.78℃/100m之间,地表温垂直变率在0.62～0.66℃/100m之间。气温垂直递减率随纬度的增加而增大,山地东坡的气温垂直递减率大于西坡。气温和地表温垂直变率呈现了雨季>干季、最热月>最冷月的变化特征。降雨随海拔的升高均为线性递增型,均未发现最大降雨高度。除高黎贡山地区以外,随纬度的增加降雨呈减小趋势,山地年降雨量的垂直变率也呈减小趋势,山地东坡降雨垂直变率大于西坡。除西双版纳山区外,相对湿度均随海拔高度的升高而增大,山地东坡相对湿度的垂直变率大于西坡。哀牢山地区山顶自然保护区内同样存在显著的增温趋势。山区气候的长期变化特征显著,年、季和月平均气温均呈现显著的升高趋势,气温的显著升高主要发生在干季,增温率为干季>年>雨季。最冷月均温增温率最大,最热月均温变化幅度较小,气温年较差呈减小趋势。∑t≥0℃的有效积温和∑t≥10℃的活动积温显著增加。气温的变化具有显著的空间差异,增温速率为东侧盆地>山顶>西侧盆地。山地迎风坡面(西坡)气温垂直递减率显著减小,背风坡面(东坡)气温垂直递减率整体呈增大趋势。降雨整体呈增加趋势,不同季节间降雨的变化差异显著,年降雨量的变化趋势主要受雨季降雨控制,干季降雨呈微弱上升或下降趋势,降雨的增加率为东侧盆地>山顶>西侧盆地。以哀牢山地区群落样方调查数据为基准,乔木层和灌木层物种多样性沿海拔梯度呈单峰型分布格局,中山湿性常绿阔叶林乔木层树高、胸径和物种多样性最大;灌木层物种多样性最大值出现在中山湿性常绿阔叶林与季风常绿阔叶林和半湿性常绿阔叶林的过渡区域;草本层物种多样性沿海拔梯度呈整体减小的趋势;累加乔、灌、草三层的物种多样性指数,哀牢山地区东、西坡不同海拔梯度植物群落的Shannon-Wiener指数和物种丰富度最大值出现在海拔2000m左右。相同海拔高度处,西坡植物群落的物种多样性高于东坡,季风常绿阔叶林的物种多样性大于半湿性常绿阔叶林,干热河谷植被的物种多样性最小。群落间相似性沿海拔梯度呈“S”型分布格局,存在两个明显的转换点,其中一个出现在由季风常绿阔叶林或半湿性常绿阔叶林向中山湿性常绿阔叶林转换的过程中,另一个出现在由干热河谷植被向半湿性常绿阔叶林的转换过程中。纵向岭谷区山地种子植物多样性沿海拔梯度存在由平缓至递减(热带山地:西双版纳)和先增后减的单峰型(亚热带山地:哀牢山、无量山、高黎贡山、白马雪山)两种分布格局;随着纬度的增加种子植物多样性沿海拔梯度最大值出现的位置呈升高趋势。西双版纳山区、哀牢山和白马雪山蕨类植物多样性沿海拔梯度均呈单峰型分布格局;蕨类植物最大值出现的海拔高度高于种子植物。以物种分布中心为基准与以物种分布幅度为基准统计分析的物种丰富度垂直分布格局结果一致。物种分布幅度随海拔的升高均呈现先增大后减小的变化趋势,山顶和山谷物种分布幅度较小,最大物种分布幅度出现在中间海拔处。在所选取的西双版纳山区、哀牢山、无量山、高黎贡山和白马雪山5个研究区中,面积与物种丰富度的垂直分布格局不同(西双版纳),物种丰富度最大值并未出现在面积最大的海拔范围内(5个地区);在去除面积的影响后,植物分类群密度与丰富度垂直分布格局相同;面积作为单一因子不能很好的解释植物多样性的垂直分布格局。作为环境水分和能量状况的综合体现,实际蒸散量能较好的解释不同地区山地植物物种丰富度垂直分布格局及其异同。从气候的角度而言,亚热带山地植物物种丰富度单峰型分布格局主要受制于山地下部高温、少雨的气候特征,水分的胁迫是山地下部物种丰富度减小的主要原因,随着山地下部环境干燥程度的加剧物种丰富度迅速减小。亚热带山地下部干热河谷植被的形成以及不同坡向相同植被类型分布范围的差异与环境的水热平衡状况有很强的相关性。山地的不同位置都呈显著的升温趋势,河谷地区的干燥程度将进一步加剧。气候变化将对植物的分布产生显著的影响,植物的分布范围将沿海拔梯度向上迁移,然而影响的强度在山地的不同坡向及不同位置有所不同。按照“能量-生物多样性理论”,山地的中上部物种丰富度将增加,河谷地区物种丰富度将减小,山顶和河谷地区狭域分布的植物类群将有灭绝的危险。更多还原

【Abstract】 One of the most significant intellectual challenges to ecologists and biogeographers is to understand spatial patterns in biodiversity. Identifying the potential effects of climate change on plant species richness has become the focus of ecological research. Five mountains in LRGR were selected. Xishuangbanna belongs to the tropical area. Ailao mountains, Wuliang mountains, Gaoligong mountains and Baima snow mountains are subtropical mountains. The elevation patterns of species richness, area and climatic variables are analyzed. This study has explained the variation in species richness patterns along the elevation gradients by climatic variables and explored the potential effects of climate change on plant species richness along elevation gradients. The results have shown that:Annual variation of air temperature and soil surface temperature of mountains at different latitude in LRGR decrease monotonically with increasing elevation, and have positive relations with latitude. Annual variation of soil surface temperature is larger than annual variation of air temperature at the same station. Average relative humidity is larger than seventy-five percent in the rainy season and larger than sixty percent in the dry season. The patterns of annual variation of precipitation are unimodal. A major feature in the LRGR region is the clear-cut changes between the two seasons: the dry season (November-April) and the rainy season (May-October). Precipitation of the rainy season makes more than seventy percent of the whole year. In general, air temperature, soil surface temperature and relative humidity are higher from May to October, and are lower from November to April. The main climate condition in the LRGR region is that more energy and precipitation present to the same period. With the parallel elevation, the east slope receives more energy inputs than west slope, and water condition of west slope is better than the east. Lapse rates of air temperature are between 0.54℃/100m and 0.78℃/100m. Lapse rates of soil surface temperature fall into the range between 0.62℃/100m and 0.66℃/100m. Lapse rate of air temperature has a positive relationship with latitude and is larger on the east slope than that on the west slope. Lapse rate of air temperature and soil temperature are very different in monthly and seasonal scale and it is bigger in the rainy season and hottest month than it in the dry season and coldest month. Precipitation has a positive relationship with increasing elevation, maximum precipitation-elevation is not observed. Except for Gaoligong Mt., precipitation tends to decrease with increasing latitude. Lapse rates of precipitation also show the same pattern and it’s larger on the east slope than it on the west. Except for Xishuangbanna, relative humidity increase with increasing elevation and the lapse rates are larger on the east slope.The field station on the mountaintop is experiencing remarkable temperature increase. Air temperature increases significantly at all the stations owing to the increase in the dry season and the incremental rate is biggest in the dry season, moderate for the whole year and the least in the rainy season. The incremental rate in the hottest month is faster than that in the coldest month and the difference of air temperature in annual scale shows a downward trend. There is also a remarkable increase in the∑t≥0℃accumulative temperature and∑t≥10℃accumulative temperature. The lapse rate of air temperature shows a statistical significant upward trend on the windward slope (west) and it has a slight increase on the leeward slope (east). Precipitation tended more or less to increase owing to the increase in the rainy season. Comparing to the west valley, the east valley is experiencing a much hotter period, then it comes to the mountaintop.Based on sample data, the patterns of plant diversity of trees and shrubs along elevation gradients are hump-shaped, the maximum values of height, DBH and biodiversity index present to the transition between mid-mountain humid evergreen broad-leaved forests, monsoon evergreen broad-leaved forests and semi-humid evergreen broad-leaved forests. Plant diversity of herbs tend to decrease with increasing elevation. Maximum total Shannon-Wiener index and species richness (including herbs, shrubs and trees) are observed at 2000m. With the parallel elevation, biodiversity index is higher on the west slope than it on the east slope and biodiversity index of monsoon evergreen broad-leaved forests is higher than that of semi-humid evergreen broad-leaved forests, the minimum biodiversity index is observed in dry and hot valley vegetation. There are two obvious transition of similarity index along elevation gradients, one is between monsoon evergreen broad-leaved forests, semi-humid evergreen broad-leaved forests and mid-mountain humid evergreen broad-leaved forests, the other is between dry and hot valley vegetation and semi-humid evergreen broad-leaved forests.The patterns of species richness along elevation gradients can be divided to two types in LRGR. Species richness is higher in the lowlands and then decreases monotonically with increasing elevation in the tropical mountains and has unimodal relationships with elevation in the subtropical mountains. The elevation peaks in family richness, genus richness and species richness of seed plants emerge at higher elevation in the mountains with the increasing latitude. The patterns of fern species along elevation gradients are hump-shaped in Xishuangbanna, Ailao Mt. and Baima Snow Mt.. Elevation peaks of fern species are higher than that of seed plants. The patterns of species richness based on elevation mid-point show good agreement with the results from those based on interpolation. Elevation ranges of species are narrower at both the tops of mountains and the bottom of the gradients, wider elevation ranges are observed at the middle of the gradients.As the patterns of area and species richness along elevation gradients are not the same in Xishuangbanna and species richness does not peak at the elevation where the area is largest for all the five mountains. After adjusted of its area, the patterns of species density are the same as that in species richness along elevation gradients. So the effect of area on the patterns of species richness along elevation gradients is not remarkably. Among the climate variables, actual evapotranspiration (AET) as a measurement of water-energy balance has strong relationships with species richness. The decline in species richness is due to the higher temperature and less precipitation in the lowlands of the subtropical mountains. Species richness decreases significantly with increasing MI as the reinforcements of the arid climate conditions in the lowlands of the subtropical mountains.Water-energy balance should be an exclusive elucidative climatic variable for the distributive ranges of vegetation type. Air temperature increased significantly at all the locations of the mountains and the valleys are experiencing a much more severe dry and hot period especially in the dry season. Climate change would be expected to affect species distribution along the whole elevation gradient as the reinforcement of the“inferior”climatic conditions (temperature increase and drought development), but the intensity would not be uniform among different locations in the mountains. As a result of climate change, plant species may be pushed upwards along elevation gradient and may be eliminated if already at mountains’summit. Based on the“Species-Energy Theory”, species richness may decrease in the lower part of the mountains. Some species with narrow elevation ranges currently found in the valleys may be extinct.更多还原