秦岭北坡与黄土高原区森林植被自然带特征的比较研究

Aiming at clarifying the interrelated phyto-geographic zonation and the varied ecological processes behind the zonal features between the vertical zones along the northern slopes of Qinling Mountain Range and the south-northward horizontal zones across the Loess Plateau, this proposal suggests a comparative study on the characteristics of the zonal vegetation and the environmental factors influencing the vegetation within and between the two regions. By selecting field sampling areas in gridded pattern where covered with dense natural forests that could demonstrate the differentiation of phyto-geographical zonation of the two regions, the proposed study is planning to conduct a series of vegetation survey featuring with thorough investigations of species composition, flora elements, community structure, site conditions including topography, surface soil, ground substances, etc.. In particular, the field survey will also pay attention to the in-situ habitat observation on a few key climatic factors like temperature, humidity and so on, and the on-the-spot measurement of some plant functional traits such as leaf shapes and anatomy within and among certain dominant tree species. The surveyed and observed data in the field, as well as the analytic data from the laboratory and remote-sensing images, will be compiled and comparatively examined with the climatic data in time series collected from observatories, to find out the zonal differentiations and similarities between the two regions both in climate-vegetation-soil relationships and in ecological-geographical connections..The key issues to be discussed with scientific significances: 1) Which environmental factor, or a combination of factors, play(s) the key role in determining the differentiation of spatial distribution of a few edificato tree species and the main forests dominated by them in the two regions? 2) What are the similarities and dissimilarities in vegetation zonation and the related thermal and moist gradients between the two regions in both altitudinal and latitudinal dimensions? 3) How and in which extents do the thermal and moist as well as other environmental factors control the ecological-geographical processes in vertical and horizontal zones in the two regions, respectively and/or collectively?.The proposed study, if conducted, should be able to make contributions to clarifying the spatial differentiations and similarities between the two regions in natural vegetation, floristic composition, plant functional traits of a few main species, and key gradients of some climatic factors like temperature and moisture, elucidating the interrelated connections among the zonal geographical elements of climate-vegetation-soil within the two regions, revealing the coupled relationships between the vertical and the horizontal vegetation zones, and amending the zonation theory for the physical geography.

在秦岭北坡和黄土高原区以天然森林植被为对象，通过网格化结点式系统设置样地，经持续两生长季重复调查群落及其区系组成、生境特征，观测主要树种的叶功能性状；同点位以Hobo仪长持续测录水热光等气候因子，并将之与气象台站同时相观测记录及长序列气候数据、遥感影像数据、相关学科以往研究成果与资料积累等进行综合对比归纳分析，揭示两地的自然地带属性及其相似与分异对比特征。拟解决关键科学问题：1）何种生态因子或其组合主导着两地重要建群种及其所组成群落的空间分布分异？2）水热等生态因子和自然植被在两地垂直和水平空间上梯度变化有何异同特征？3）两地垂直带和水平带间相似和相异的生态地理过程背后蕴含着何种关键控制因素？研究可明确自然植被、区系组成乃至植物功能性状与气候水热等因子在两地的空间分异，揭示气候-植被-土壤等地带性要素在两地关联特征，探知两地植被垂直带变化与水平带更替间对应关系，深化自然地理地带性科学理论。

在秦岭北坡和黄土高原区以天然森林植被为对象，通过野外调查和仪器观测，从植物区系、群落结构、物种组成及多样性、植物叶属性、气候、地形及土壤等方面揭示了两地的自然地带属性及其相似与分异对比特征。取得的突破性成果和主要科学结论：1）调查得黄土高原地区天然森林群落中的维管植物共有108科473属1222种（含亚种和变种），这些物种的科与属（地理成分）分布区类型以“温带分布”特别是“北温带分布”为主，此特征在群落尺度上尤显突出。2）气温年较差和年均降水量为影响研究区α-多样性的关键因子；大尺度的多样性格局主要由纬度所代表的热量梯度所驱动；环境分异而非扩散限制主导着研究区森林群落分布的地理格局，这一结论从群落学角度定量证实了植被地理分布格局的纬向地带性与垂直地带性规律。3）扩散限制与生境过滤共同主导了秦岭西部森林群落的构建过程，且扩散限制所起作用更为显著。4）秦岭北坡与黄土高原森林中的落叶阔叶树均处于N相对富余、P相对缺乏的状态；海拔是反映太白山MAP和MAT的综合因子，在海拔1800-2000m以下，MAP对叶功能性状的影响占主导，而在1800-2000m以上，MAT对叶功能性状的影响占主导；在黄土高原地区，MAT和MAP分别是影响落叶阔叶树P、N含量最重要的环境因子。5）秦岭北坡的气温随海拔的升高呈显著下降趋势，年平均气温、年平均最低气温和年平均最高气温垂直递减率分别为0.45°C/100 m，0.44°C/100 m和0.40°C/100 m；以季节变化来看，平均最高气温直减率在冬季较高，春季较低，平均气温和平均最低气温直减率季节变化不明显。本研究明确了两地的自然植被、区系组成乃至植物功能性状与气候水热等因子的空间分异，揭示了气候-植被-土壤等地带性要素在两地关联特征及两地植被垂直带变化与水平带更替间对应关系，深化了自然地理地带性科学理论。