# Drought characteristics and their impact on vegetation net primary productivity in the climate-sensitive transition zones of North China

## TL;DR

This study examines how droughts in North China's climate-sensitive regions affect plant productivity and carbon absorption, finding that grasslands are most vulnerable while forests show resilience.

## Contribution

The study introduces a multi-temporal drought analysis framework using SPEI and SSMI to assess NPP dynamics in climate-sensitive transition zones.

## Key findings

- Droughts showed a slight easing trend from 2001 to 2020, with frequent short-duration, high-intensity events.
- Grasslands exhibited the highest NPP growth rate (8.02g C·m-2a-1) and were most sensitive to drought.
- Forests showed drought resistance and delayed responses, with significant seasonal NPP-SPEI correlations.

## Abstract

Net Primary Productivity (NPP) serves as a key measure of ecosystem production capacity and carbon absorption ability. Evaluating the arid characteristics and their NPP impact in the climate-sensitive transition zones of North China (North China’s humid and semi-humid warm temperate regions) is vital for studying regional climate change, improving ecosystem adaptation, and promoting sustainable development. We analyze drought characteristics at multiple temporal scales (2001−2020) using the Standardized Potential Evapotranspiration Index (SPEI) and Standardized Soil Moisture Index (SSMI). The Carnegie-Ames-Stanford approach (CASA) model was employed to simulate and estimate NPP values, quantify NPP dynamics, and assess vegetation productivity responses to drought stress. We found that droughts showed a slight easing trend from 2001 to 2020. Over the long term, drought intensity and extent were relatively minor. Over the short term, there were frequent occurrences of short-duration, high-intensity droughts. Overall, NPP showed an upward trend, with a decreasing spatial distribution from the central and north-central regions toward the east and west. The fastest average annual growth rate was observed in grassland NPP (8.02g C·m-2a-1), followed by woodland (4.03g C·m-2a-1). Precipitation is an important factor that affects vegetation NPP. Areas with a high correlation between NPP and SPEI-12 are primarily grasslands. Significant relationships exist between NPP and seasonal SPEI-3: positive in summer and negative in winter. Grasslands are most sensitive to drought; forests, on the other hand, exhibit drought resistance and a delayed response to such conditions.