秦岭南坡的山体效应及对山地垂直带分布的影响

The Qinling Mountains, serving as the spatial boundary between warm temperate and subtropical zones in China,show obviously transitional, complex and diverse characteristics in geography and ecology. However, the precise boundary has been argued for decades. The primary reason is that most of the previous studies on Qinling Mountains focus on temperature variation of horizontal zones and difference in vegetation between southern and northern flanks, and little attention has been paid to azonal factors, especially mass elevation effect(MEE), leading to superficialunderstanding of the distribution and mechanism ofaltitudinal belt in the Qinling Mountains. This research aims at revealing MEEand its implication for altitudinal belt distribution in the southern flank of the Qinling Mountains. Field investigation and sampling are designed along three profiles, namely, “the southern slope of Mt. Taibai — Fuping national reserve — valley plain”, “the southern slope of Jingyunao — Yingzuishi — Shiquan Valley” and “southern Niubeiliang — Zhashui — Zhen’an” to acquire and analyze the distribution of montane altitudinal belts; then, on the basis of meteorological data obtained from remote sensing and meteorological stations, temperature difference between the Qinling Mountains and the peripheral free atmospheric at the same altitude is calculated, so as to quantify the MEE; and then contribution of MEE to the distribution of montane altitudinal belt limits is analyzed; finally, the mechanism of MEE is explored according to terrain factors derived from DEM. This study helps explain Qinling Mountains’ diversity and complexity so as to reach a more comprehensive and deeper understanding of Qinling Mountains’ horizontal and vertical zonality.

秦岭是我国暖温带和北亚热带的分界线，但对这一分界线的具体位置，长期以来存在较大的争议。其根本的原因是，过去的研究多集中在地带性的温度变化和坡向差异，对秦岭的非地带性，特别是对山体效应认识不足，致使对秦岭垂直带的分布和机理认识不够充分。本项目拟研究秦岭南坡的山体效应及对山地垂直带分布的影响。研究内容包括：基于遥感气候数据和气象台站数据，计算秦岭内外围同海拔自由大气温度的差异，获取山体效应的量值；通过秦岭南坡从边缘到山脊线的三个剖面进行野外调查采样，结合研究区的植被文献，分析山地垂直带的分布格局以及山体效应对山地垂直带分布的影响；根据DEM衍生的地形因子和山体效应的关系探索山体效应的机理。本研究对于我们更加全面的认识秦岭地区的过渡性、复杂性及非地带性规律具有重要的价值，对于地域分异规律的认识以及我国南北分界线位置确定等问题具有参考意义。

秦岭南坡的山体效应，作为非地带性分异关键因素，影响植被垂直分布和温度的空间格局。本项目拟进行秦岭南坡的山体效应的研究，包括山体效应的识别、山体效应对山地垂直带分布影响及山体效应机理探索。研究结果表明：.（1）秦岭南坡山地垂直带结构从东向西呈现先复杂后简单再复杂的特征，其优势带除流岭为山地针阔混交林带外，其它均为山地落叶阔叶林带。秦岭南坡山地落叶阔叶林带的上限从东向西随经度分布呈现了线性升高的趋势。.（2）秦岭南坡山体效应从东向西，从汉江谷地到山脊线，呈阶梯状升高的趋势，这与秦岭南坡整体地势由东向西、从汉江谷地到山脊线升高有关。 .（3）秦岭南坡山地落叶阔叶带上限与山体基面高度呈现显著的正相关，使用线性公式拟合二者关系的R2达到0.64。随着山体基面高度的增加，山地落叶阔叶林带建群种种类逐渐增多且形成更多的亚带，山体效应明显的太白山，其亚带可达3个。但是山体效应对山地常绿落叶阔叶混交林带，建群种种类没有明显的增加，对该山地垂直带上限也没有明显的抬升。.（4）秦岭南坡同海拔（1500m）气温自东向西，从南向北由汉江谷地向山脊线，呈现出明显的上升趋势，其中中段太白山比东段伏牛山同海拔温度年均温和7月份均温分别升高了3.5℃和2.5℃，比汉江谷地上升了2℃左右。同海拔温度的变化与山体基面高度呈现了明显的正相关，秦巴山地不同月份山体基面高度同海拔温度的偏相关系数超过了0.82，这就意味着在整个秦巴山地，山体基面高度越高，山体效应越强。.秦岭南坡山体效应的研究填补了秦岭南坡甚至整个秦巴山地山体效应研究的空白，使人们更科学、更准确的揭示秦岭山区地理和生态的过渡性、复杂性和多样性。有助于对秦岭地区山地垂直带界限和带谱结构做出科学的、合理的解释，使我们对山体效应（非地带性）对地带性因素，比如南北分界线的影响的强度和方向有一个更加清晰的认识，推动地域分异规律的认识。