旱区造林固碳有效性对降水的依赖效应研究——以陕西省为例

The dependent effect of carbon sequestration effectiveness of afforestation on precipitation in dryland:A case study of Shaanxi province

植被稀疏的干旱半干旱地区的造林和森林恢复具有很强的碳封存和生态修复能力,但是旱区造林的固碳有效性依赖于降水的空间分布。为了揭示旱区造林固碳有效性对降水的依赖效应,本文以中国陕西省为例,综合运用地理遥感技术、面板门槛回归和部分线性函数系数面板数据模型评估了不同降水条件下造林固碳的有效性,包含环境有效性和成本有效性两个方面。结果表明:在环境有效性方面,陕西省造林固碳具有显著的有效性。随着以造林为主的生态修复工程在陕西省大范围地实施,2000—2020年陕西省植被碳汇总量整体呈现出上升趋势,造林固碳的边际贡献为462.647 t/km^(2)。陕西省干旱地区的造林固碳边际贡献为512.868 t/km^(2),是其湿润地区的2.67倍。在面板门槛模型中,当降水量在366.468~525.470 mm之间,陕西省造林固碳的环境有效性处于最优区间内,造林固碳的边际贡献为511.493 t/km^(2)。在部分线性函数系数面板数据模型中,降水对陕西省造林固碳环境有效性的影响呈现倒“U”型的分布规律;当降水量达到495.539 mm的阈值时,造林固碳的最大边际贡献约为534.691 t/km^(2);当降水量超过该阈值时,造林固碳环境有效性逐渐减弱,其主要原因是在降水相对丰沛的区域,光照辐射相对较少,导致植被固碳效率降低。在成本有效性方面,陕西省造林固碳成本总体上随着降水的增加而逐渐上升,干旱地区的造林固碳更具有成本优势。陕西省造林固碳在干旱地区的成本为581元/t,比湿润地区低16.29%。因此,需要尊重“林-水-碳”交互作用规律,充分发挥旱区造林固碳的环境优势和成本优势,优化旱区造林空间活动以实现造林固碳收益的最大化。

Afforestation and forest restoration in arid and semi-arid regions with sparse vegetation have strong carbon sequestration and ecological restoration capabilities.However,the effectiveness of carbon sequestration in these dry areas heavily depends on the spatial distribution of precipitation.To explore the dependency of carbon sequestration effectiveness on precipitation in arid region afforestation,this study takes Shaanxi province,China,as a case study.It utilizes a combination of geographic remote sensing technology,panel threshold regression,and partially linear functional coefficient panel data models to evaluate the effectiveness of afforestation carbon sequestration under varying precipitation conditions,focusing on both environment-effectiveness and cost-effectiveness.The results indicate significant environment-effectiveness of afforestation carbon sequestration in Shaanxi.From 2000 to 2020,large-scale ecological restoration projects,primarily afforestation,were implemented across Shaanxi.As a result,the total vegetation carbon sequestration showed an overall upward trend,with the marginal contribution of afforestation carbon sequestration reaching 462.647 t/km^(2).In the arid regions of the province,the marginal contribution was 512.868 t/km^(2),2.67 times higher than in humid areas.The panel threshold model showed that when precipitation ranged from 366.468 to 525.470 mm,afforestation carbon sequestration effectiveness was optimal,with a marginal contribution of 511.493 t/km^(2).According to the partially linear functional coefficient panel data model,the environment-effectiveness of afforestation carbon sequestration in Shaanxi follows an inverted"U"-shaped pattern with increasing precipitation.The maximum marginal contribution,approximately 534.691 t/km^(2),reaches a precipitation threshold of 495.539 mm.Beyond this threshold,environmenteffectiveness diminishes due to reduced solar radiation in relatively wet areas,lowering vegetation carbon sequestration efficiency.In terms of cost-effectiveness,the cost of afforestation carbon sequestration tends to increase with higher levels of precipitation.Consequently,arid regions may offer greater cost advantages for such initiatives.The average cost in the arid regions of Shaanxi is 581 yuan/t,16.29%lower than in humid regions.Therefore,it is crucial to respect the"forest-water-carbon"interaction dynamics,carefully assess regional characteristics,and leverage the environmental and cost advantages of afforestation in arid regions.By strategically planning and optimizing spatial afforestation activities,carbon sequestration benefits can be maximized,so as to promote sustainable land management and enhancing the overall ecological and economic value of these regions.