基于Copula模型的黄河流域植被干旱损失概率与致损阈值研究

Vegetation drought loss probability and disaster-triggering thresholds in Yellow River Basin based on Copula model

摘要

【目的】黄河流域是中国重要的生态屏障和农业产区,生态环境脆弱,对气候变化响应敏感。探究该区域植被对干旱事件的响应特征,量化不同干旱情景下的植被损失概率,识别植被损失的干旱触发阈值,对区域生态安全与可持续发展具有重要意义。【方法】因此,基于1982—2020年逐月降水与叶面积指数(LAI)数据,采用标准化降水指数(SPI)识别干旱,构建二元Copula条件概率模型评估植被损失概率并逆向识别致损阈值。【结果】结果表明:(1)黄河流域94.3%的网格LAI与SPI呈显著正相关,植被对干旱的最优干旱累积时间尺度南北分异显著,南部4~9个月,东北部超过17个月。流域平均植被损失概率由轻度干旱的52.0%升至极端干旱的67.7%(LAI≤40th),中北部草原集中区显著高于东南部森林与农田区(差异达12%~18%);(2)4种植被类型干旱阈值差异显著,草原触发LAI≤40th损失的SPI均值仅为-0.70,落叶阔叶林需达-1.12,二者敏感性差异达1.6倍;(3)随损失等级从40th降至10th,可识别阈值的区域占比骤降,表明极端植被损失主要受局部草原干旱主控。【结论】黄河流域植被干旱脆弱性受植被类型与区域水分条件共同控制,草原植被是干旱风险最高的生态系统类型,中北部草原集中分布区是干旱致损的重点防控区域。研究成果可为流域干旱风险分区管理、生态保护优先级划定及水资源优化调配提供科学依据。

Abstract

[Objective] The Yellow River Basin serves as a critical ecological barrier and major agricultural production area in China, characterized by a fragile ecological environment and high sensitivity to climate change. Investigating the response characteristics of vegetation to drought events in this region, quantifying the probability of vegetation loss under different drought scenarios, and identifying the drought thresholds that trigger vegetation loss are of great significance for regional ecological security and sustainable development. [Methods] Based on monthly precipitation and leaf area index(LAI) data from 1982 to 2020, the standardized precipitation index(SPI) was used to identify drought events, and a bivariate Copula-based conditional probability model was constructed to assess vegetation loss probability and inversely identify disaster-triggering thresholds. [Results] 1) LAI was significantly positively correlated with SPI across 94. 3% of the grid cells in the Yellow River Basin, and the optimal cumulative time scale of vegetation response to drought exhibited a pronounced north-south divergence, ranging from 4—9 months in the southern region to over 17 months in the northeastern region. The basin-wide average probability of vegetation loss increased from 52. 0% under mild drought to 67. 7% under extreme drought(LAI ≤ 40 th percentile), with values in the grassland-dominated central and northern areas substantially exceeding those in the forest-and cropland-dominated southeastern areas(by 12% ~18%).(2) Drought thresholds differed markedly among the four vegetation types. The mean SPI required to trigger LAI ≤ 40 th percentile loss was only-0. 70 for grasslands, whereas deciduous broadleaf forests required an SPI as low as-1. 12, indicating a 1. 6-fold difference in drought sensitivity between the two.(3) As the loss level decreased from the 40 th to the 10 th percentile, the proportion of areas with identifiable thresholds declined sharply, suggesting that extreme vegetation loss was predominantly governed by localized drought events in grassland regions. [Conclusion] Vegetation drought vulnerability in the Yellow River Basin is jointly governed by vegetation type and regional moisture availability. Grasslands represent the most drought-prone ecosystem type, and the grassland-dominated central and northern areas constitute priority regions for drought disaster prevention and control. These findings provide a scientific basis for drought risk zoning and management, ecological conservation prioritization, and optimized water resource allocation across the river basin.

关键词

黄河流域 / 干旱 / 叶面积指数 / 植被损失概率 / 致损阈值 / Copula函数 / 植被差异 / 植被脆弱性

Key words

Yellow River Basin / drought / leaf area index / vegetation loss probability / disaster-triggering threshold / Copula function / vegetation differences / vegetation vulnerability

基金资助

国家自然科学基金项目(52279016)

河南省自然科学基金面上项目(262300421317)

河南省科技研发计划联合基金(252103810062)

河南省科技研发计划联合基金(252103810074)

水灾害防御全国重点实验室开放基金项目(2025490911)