Quantifying responses of net primary productivity to agricultural expansion in drylands

Abstract

There is a limited understanding of agricultural land dynamics across global drylands and the impacts of transitions between agricultural land and land cover on net primary productivity (NPP) changes. This study attempted to fill this gap by examining agricultural land changes and NPP responses in drylands. A data-driven assessment of effects on the NPP of individual agricultural land displacement was carried out using three methods: the mean difference method, a newly introduced ridgeregression method, and a proposed method based on actual change excluding climate impact. Increases in NPP were accompanied by agricultural land transitions from natural land cover and expected forests. The agricultural expansion mainly replaced sparse vegetation and grassland and increased the overall NPP of the dryland ecosystem. The mean difference method and ridge-regression method overestimated the NPP increase caused by agricultural land expansion. Land use change contributed more than 70% to NPP increase in the new agricultural area. However, land use change has less effect on total NPP in drylands than climate change. Monitoring agricultural land dynamics and distinguishing NPP changes caused by different agricultural land transitions is helpful for targeted management and sustainable development of agriculture in drylands.

Where Anthropogenic Activity Occurs, Anthropogenic Activity Dominates Vegetation Net Primary Productivity Change

“…In addition, considering the complexity of each driving mechanism, the relative contributions of climate change and other factors to the NPP variation are calculated according to Table 1 [58,59] Pan et al [60] proposed a method to quantify the effects of an individual LULC change on NPP. The LULC data for Xinjiang were obtained from the National Land Use Dataset on 1 June 2021 (NLUD), which is established from the remote sensing surveys of resources and the environment by the Chinese Academy of Sciences (https://www.resdc.cn/Datalist1.aspx?…”

“…To solve the problem of uncertainty in quantitative analysis of the contributions of factors affecting vegetation productivity, we proposed the RES-CON method. Based on the research of Wu et al [61] and Pan et al [60], six different scenarios were established through residual analysis, and the contribution of climate change to NPP was evaluated. The control variable method was used to determine the impact of anthropogenic activities on NPP.…”

Mapping South America’s Drylands through Remote Sensing—A Review of the Methodological Trends and Current Challenges

“…RS-based tools and LULC maps, coupled with social and demographic variables, could help enhance the adaptative capacity of dryland populations and promote the sustainable management of ecosystems. Investigation on erosion detection [162,163], drought-vulnerability [164,165] and cropland/pastureland [166] mapping is vital to inform policymaking to combat food insecurity and poverty [112]. These policies can also help to balance possible trade-offs between ecosystem services and economic growth in drylands.…”

Regional differentiation in the ecological effects of land cover change in China

“…The ecological effects of land cover changes have been widely discussed (Chen et al, 2019;Ding et al, 2020;Pan et al, 2021).…”

“…), while Gao, Liang, & He (2019) indicated that cultivated land had the strongest greening effect. Pan et al (2021) found that the impact of land use changes on the total net primar productivity (NPP) of drylands was relatively small, and Wang et al (2017) showed that the practice of converting farmland to forest resulted in an average annual net carbon sequestration was as much as 1813.74 kg C ha À1 yr À1 . Regarding to the temperature effect, concluded that the conversion of open land into forest would bring about a cooling effect, while Gibbard et al (2005) found that replacing the current global vegetation with trees would lead to average global warming of 1.3 C. It can be found that in addition to different opinions, most of the previous studies focused on a single effect and lacked the comparison of multiple ecological effects.…”