Relative Contributions of Climate Change and Human Activities on Vegetation Productivity Variation in National Nature Reserves on the Qinghai–Tibetan Plateau

Abstract

National nature reserves (NNRs) are at the forefront of conservation efforts on the Qinghai–Tibetan Plateau (QTP). However, few studies have examined the vegetation dynamics and their driving forces at the whole QTP scale. In this study, we used potential Net Primary Productivity (PNPP), actual NPP (ANPP), and human-activity-induced NPP (HNPP) to analyze the vegetation dynamics of 42 NNRs on the QTP. Further, we determined the driving factors of vegetation dynamics from 2000 to 2020. The results indicate that, during the 21 years studied, ANPP increased at 83.4% of the NNRs area on the QTP. Additionally, the contributions of climate change and anthropogenic factors to ANPP variation were 59.53% and 40.47%, respectively. The contribution of temperature to ANPP variation was considered high and stable, whereas the contribution of precipitation was relatively lower and variable. Residual analysis showed that human activities had both positive (51.30%) and negative effects (48.70%) on ANPP. Using Hurst exponent analysis, we found that 31.60% of the vegetation for the NNRs on the QTP will likely remain a persistent trend, and 65.4% will be stochastic in the future. By contrast, 3.00% of the vegetation mainly located in southern QTP would show a reverse trend, with most of them distributing in southern QTP, which deserves more attention. This study may help policymakers understand the relative impacts of climate change and human activities on vegetation in the different nature reserves on the QTP.

Assessing the Distribution and Driving Effects of Net Primary Productivity along an Elevation Gradient in Subtropical Regions of China

“…The descending order of these indices was PNPP, HNPP, and ANPP. This concurred with previous research [49,61,62] and indicated the efficacy of these indicators in analyzing the study area.…”

“…The alteration in ANPP is primarily induced by human activities and climate fluctuations. Numerous preceding studies have utilized ANPP, HNPP, and PNPP to differentiate these two elements' effects on ANPP [18,48,49,61,62,86]. Our research findings indicate that a combined influence of climate change and human activities has led to the increase in ANPP in the study area, with their combined effect being greater than the individual impacts of climate change or human activities on the vegetation's ANPP.…”

“…The Thornthwaite memorial model, widely used for estimating PNPP [47], calculates PNPP based on the annual actual evapotranspiration [48][49][50]. This model, which takes temperature and precipitation data as inputs, is an improved version of the Miami model and is known for its accuracy [51].…”

“…Temperature and precipitation have always been the two most commonly used factors in studying the driving models between ANPP and meteorological elements [49,64,76,[96][97][98][99], as they largely affect the growth and distribution of vegetation. However, previous studies have not reached consistent conclusions regarding the impact of these two meteorological factors on ANPP.…”

Assessing the spatial occupation and ecological impact of human activities in Chengguan district, Lhasa city, Tibetan Plateau

“…However, they did not specify which human activities dominated nor did they provide specific ecological restoration measures. Similarly, Zhou 26 , Xiong 27 , and Wang 28 studied the long-term trend of grassland ecosystems, emphasizing the positive role of human activities in grassland conservation. However, quantifying the contributions of various factors to grassland productivity remains a challenge.…”