The impact of land use and cover change on soil organic carbon and total nitrogen storage in the Heihe River Basin: A meta-analysis

Abstract

Land use and cover change (LUCC) is an important indicator of the human-earth system under climate/environmental change, which also serves as a key impact factor of carbon balance, and a major source/sink of soil carbon cycles. The Heihe River Basin (HRB) is known as a typical ecologically fragile area in the arid/semi-arid regions of northwestern China, which makes it more sensitive to the LUCC. However, its sensitivity varies in a broad range of controlling factors, such as soil layers, LUCCs and calculation methods (e.g. the fixed depth method, FD, and the equivalent mass method, ESM). In this study, we performed a meta-analysis to assess the response of soil organic carbon (SOC) and total nitrogen (TN) storage to the LUCC as well as method bias based on 383 sets of SOC data and 148 sets of TN data from the HRB. We first evaluated the calculation methods and found that based on the FD method, the LUCC caused SOC and TN storage to decrease by 17.39% and 14.27%, respectively; while the losses estimated using the ESM method were 19.31% and 18.52%, respectively. The deviations between two methods were mainly due to the fact that the FD method ignores the heterogeneity of soil bulk density (BD), which may underestimate the results subsequently. We then analyzed the response of SOC and TN storage to various types of the LUCC. In particular, when woodland and grassland were converted into cultivated land or other land types, SOC and TN suffered from heavy losses, while other LUCCs had minor influences. Finally, we showed that increasing the depth of the soil layers would reduce the losses of SOC and TN storage. In summary, we identified a series of controlling factors (e.g. soil layer, the LUCC and calculation method) to evaluate the impact of the LUCC on SOC and TN storage in the HRB, which should be considered in future research.

Effects of land clearing for agriculture on soil organic carbon stocks in drylands: A meta‐analysis

“…In addition, SOC stocks were allocated to the surface and subsurface categories according to the proportion of the sampling layer that fell into each of the two categories. If the depth of the top layer was deeper than 30 cm (e.g., 0–50 cm), we converted the SOC stocks of irregular sample depths to stocks in each of the sample surface categories using the depth function (Jobbágy & Jackson, 2000; Tong et al, 2019; Yang et al, 2011): …”

“…In addition, SOC stocks were allocated to the surface and subsurface categories according to the proportion of the sampling layer that fell into each of the two categories. If the depth of the top layer was deeper than 30 cm (e.g., 0-50 cm), we converted the SOC stocks of irregular sample depths to stocks in each of the sample surface categories using the depth function (Jobbágy & Jackson, 2000;Tong et al, 2019;Yang et al, 2011): In Equations ( 3) and ( 4), Y is the cumulative ratio of SOC from the soil surface to the depth d (cm); β the relative reduction rate of SOC within the soil layer (SOC for 0.98) (Jobbágy & Jackson, 2000); SOC 0-30 is the expected SOC in the surface 0-30 cm soil layer; d the original soil depth (cm) available in each study; SOC d is SOC stocks (Mg C ha −1 ) measured at original depth d (cm). After that, 873 paired surface and subsurface observations were included in the meta-analysis.…”

Temporal and Spatial Evolution of Land Use in Gansu Section of The Yellow River Basin and Analysis of Driving Forces

“…The land-use transfer matrix and land-use change index reflect the response of land use to human activities during spatiotemporal change of land use. In recent years, many scholars have studied the evolution of land use in the Heihe River Basin [25], Huaihe River Basin [9] and Yellow River Basin [26] by using the above methods. The results show that the influence of human activities on land use in different regions gradually increases with the change of time, and most of them show the characteristics of decreasing cultivated land area and increasing construction area, which was similar to the evolution of land use pattern in Gansu section of the Yellow River Basin.…”

Impacts of Land-Use Change on the Spatio-Temporal Patterns of Terrestrial Ecosystem Carbon Storage in the Gansu Province, Northwest China

“…The terrestrial ecosystem CS are mainly divided into four major carbon pools (aboveground biomass carbon pool, below-ground biomass carbon pool, soil organic carbon pool, and dead organic matter carbon pool) [2,15,16]. The land use/cover change (LUCC) is an essential feature reflecting environmental changes [17] and a prime influencing factor of terrestrial ecosystem carbon storage [18,19]. Therefore, it is of great significance to quantify the effects of land-use change on ecosystem CS under climate change over the past and in the future [20].…”