变化环境影响下张承地区水源涵养和土壤保持服务及其权衡与协同关系研究

张家口-承德地区是京津冀环境优化的战略要地,开展水源涵养和土壤保持服务的定量评估对维护生态系统的安全运行意义重大。综合运用InVEST模型、空间偏相关统计制图及情景模拟等手段,分析了张承地区近20年水源涵养和土壤保持服务的时空变化特征及其复杂空间关系,定量评估二者对气候和土地利用变化的响应。结果表明:2000-2019年张承地区水源涵养量、土壤保持强度分别以0.97mm/a的速率增加和-0.50t hm^-2 a^-1的速率减少,空间上二者均呈西低(坝上高原)东高(冀北及燕山山地)的分布格局。冀北及燕山山地落叶阔叶林生态区水源涵养和土壤保持能力强,二者空间关系以协同为主;坝上高原草原与农业生态区则权衡关系更占优势。水源涵养和土壤保持服务关系复杂,空间上与区域土地利用类型、植被覆盖度和坡度关系密切。情景模拟结果表明,降水(r=0.90,P<0.01)对水源涵养服务的影响远大于潜在蒸散(r=-0.37,P>0.1),且降水变幅越大对水源涵养量的作用越强;而降水变化与土壤保持服务呈线性正相关关系,降水每增加(减少)10%引起土壤保持强度增加(减少)74.7t/hm²。预计2030年张承地区水源涵养能力将明显提升,土壤保持能力变化不大,届时人为干扰(如生态保护、规划控制)将对提升水源涵养服务产生重要影响。为改善张承地区水源涵养和土壤保持服务,需同时考虑多种因素的综合影响,以制定更合理的政策措施。建议继续加大国家重点生态工程建设,尽可能限制建设用地扩张,提高植被覆盖度,尤其加强保护关键坡度带是今后生态管理工作应关注的重点。

Water and soil conservation and their trade-off and synergistic relationship under changing environment in Zhangjiakou-Chengde area

Zhangjiakou-Chengde area (ZC area) is a strategic place for the environmental optimization of Jing-Jin-Ji Urban Agglomeration. The quantitative assessment of water conservation and soil conservation is of great significance to maintain the ecosystem safety. The Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, spatial partial correlation statistical mapping, and scenario simulation are used to comprehensively analyze the temporal and spatial change characteristics and complex relationships of water conservation and soil conservation services in ZC area in recent 20 years, and quantitatively evaluate their response to climate and land use change. The results showed that water conservation and soil conservation intensity in ZC area increased at the rate of 0.97 mm/a and decreased at the rate of -0.50 t hm^-2 a^-1 from 2000 to 2019, respectively, which were spatially low in the west (Bashang plateau) and high in the east (Yanshan Mountain). The water conservation and soil conservation were strong and mainly synergistic in the northern Hebei and Yanshan Mountains deciduous broad-leaved forest ecological zone; while the trade-off relationship was more dominant in the Bashang plateau grassland and agroecological zone. The spatial relationship between water conservation and soil conservation is complex, which is closely related to regional land use type, vegetation coverage and slope. The scenario simulation results showed that the impact of precipitation (r=0.90, P<0.01) on water conservation service was much greater than the potential evapotranspiration (r=-0.37, P>0.1), and the greater variation of precipitation, the stronger water conservation. There was a linear positive correlation between precipitation and soil conservation service, and each 10% increase (decrease) of precipitation caused the increase (decrease) of 74.7 t/hm² in soil conservation intensity. It is expected that water conservation capacity of ZC area will be significantly improved in 2030, while soil conservation capacity will not change much. By then, human activities (such as the policy measures related to ecological protection or planning control) will become the significant impact on improving water conservation service. In order to improve water conservation and soil conservation services in ZC area, the comprehensive impact of various factors should be considered to formulate more reasonable ecological protection policies. It is suggested to continue to strengthen the construction of national key ecological projects, to limit the expansion of construction land as much as possible and improve vegetation coverage to protect the natural ecosystem, especially to strengthen the protection of key slope zones, which should be the focus of water conservation and soil conservation services in the future.