气象要素对华北地区夏季植被覆盖度的影响

植被覆盖对气候变化极其敏感,华北区地处我国半干旱—半湿润过渡地区,气象因子对该地区植被覆盖有重要的影响,但缺少有效的数理模型定量刻画气象要素对植被的影响。因此,本文基于华北区2000~2018年中分辨率成像光谱仪的植被覆盖数据和主要气象要素数据,开展了多气象要素影响植被覆盖度的研究,初步建立了华北夏季植被覆盖度与气象要素的关系。研究表明:(1)华北存在向暖干转变的趋势,且夏季植被覆盖度与降水、相对湿度呈正相关,与气温、日照时数和地温呈负相关。(2)影响华北地区植被覆盖度最重要的气象要素是相对湿度,体现了温度和降水的共同作用。(3)基于多元回归法和最小二乘法可以定量描述气象要素变化对植被覆盖度的可能影响。其中,五变量影响模型对植被覆盖度模拟的相关系数略偏高,因此,基于五变量气象要素可以更好的模拟植被覆盖度的变化。研究结果有利于了解气象要素如何影响植被生态系统,进而为国家生态文明建设提供理论参考依据。

种内竞争时滞对植被周期振荡模式的影响研究

考虑到干旱、半干旱地区的幼年植被与成年植被之间存在竞争水资源的现象,该文构建一个具有种内竞争时滞的植被-土壤水动力学模型.分析出系统存在植被灭绝平衡点和植被生存平衡点,并给出了平衡点局部稳定的条件,分别给出非空间系统和空间系统产生Hopf分支周期解的条件.通过数值模拟展示出两种系统对应的植被随时间演化做周期振荡模式,并通过参数敏感性分析发现降雨量和植被的增长率对这种模式的产生和模式的振幅、周期有显著影响,但蒸发量的影响效果最不显著,表明降雨量和植被本身的特征对干旱、半干旱地区植被的演化发展产生了深刻的影响.同时发现空间扩散的引入会抑制这种模式的发生,但对振幅和周期没有任何影响.所获得的结果解释了自然界中广泛观察到的植被周期振荡现象,为植被系统的可持续发展提供了理论支撑.

Relationship between Urban Industrial Land Use Size and Sulfur Dioxide Emissions:Evidence from 294 Cities in China

Although the relationship between the size of urban industrial land use and pollutant emissions has been widely discussed from different perspectives(e.g.,the scale and crowding effects),the results of various studies have revealed positive,negative,and combined impact relationships.However,how the expansion of urban industrial land use affects SO_(2) emissions remains unknown.We need to clarify this relationship in order to facilitate the realization of China’s pollution reduction and emission reduction goals.This study used the panel data from 294 cities spanning from 2011 to 2019 to construct a spatial econometric model.The objective was to explore the correlation between the scale of urban industrial land and sulfur dioxide emissions in China.The results show that a large scale of urban industrial land use corresponds to lower sulfur dioxide emissions per unit of industrial added value.By gaining a deeper understanding of the relationship between the scale of urban industrial land use and sulfur dioxide emissions,policymakers can further reduce pollutant emissions by rationalizing the planning of urban industrial land use and industrial layout.In addition to promoting industrial agglomeration and economies of scale in cities with extensive industrial land use,this strategy can support the development of efficient and environmentally friendly industries in areas with limited industrial land use.Optimizing the technology and encouraging the development of green industries can help reduce environmental pollution and promote sustainable urban development.