Chronological dataset of soil respiration fluxes from a seasonally dry forest in Northwest México

Soil respiration (CO2 emission to the atmosphere from soils) is an important component of the global carbon cycle. In highly seasonal ecosystems the magnitudes and the underlying mechanisms that control soil respiration (RS) are still poorly understood and measurements are underrepresented in the global flux community. In this dataset, systematic and monthly measurements of RS were conducted with an infrared gas analyzer coupled to a static chamber during 2015, 2016, 2017 and 2019 in a tropical dry forest with a land use history from Northwestern México. These data is useful to assess the intra-annual and seasonal variations of RS at a highly seasonal dry forests and serves as a base line to benchmark soil carbon models in regional and global contexts. The data presented supports the research manuscript: “Soil respiration is influenced by seasonality, forest succession and contrasting biophysical controls in a tropical dry forest in Northwestern Mexico” from Vargas-Terminel et al. [1].

Dataset link: Chronological dataset of soil respiration fluxes from a seasonally dry forest in Northwest México (Original data) a b s t r a c t Soil respiration (CO 2 emission to the atmosphere from soils) is an important component of the global carbon cycle.In highly seasonal ecosystems the magnitudes and the underlying mechanisms that control soil respiration (R S ) are still poorly understood and measurements are underrepresented in the global flux community.In this dataset, systematic and monthly measurements of R S were conducted with an infrared gas analyzer coupled to a static chamber during 2015, 2016, 2017 and 2019 in a tropical dry forest with a land use history from Northwestern México.These data is useful to assess the intra-annual and seasonal variations of R S at a highly

Value of the Data
• Even though, about half of the tropics display a seasonally dry climate [6] , there is still an uncertainty about the contribution of soil greenhouse gases from tropical dry forest to ecosystem C balance [7] and the present database contributes to fill this gap.• The present soil respiration dataset is worthy to reduce the gaps of knowledge in the seasonal, intra-annual and inter-annual variability of tropical dry forest soils under contrasting environmental settings and across forest succession [1] .• This dataset compiles the effort s of monitoring systematically soil respiration in a seasonally dry forest from Northwestern México in order to serve as a baseline information to test, calibrate and validate process-based ecosystem models for water limited regions [8 , 9] .
• Soil respiration from seasonally dry ecosystems in Northwestern México can contribute to the effort s f or strengthening soil-atmosphere flux gas research networks such as MexFlux [10] and AmeriFlux [11] and to consolidate the creative commons access to global databases and software such as Continuous SOil Respiration (COSORE) as described in Bond-Lamberty et al. [12] and the Soil Respiration Database (SRDB) reported in Jian et al. [13] .• Assessing the magnitude of soil carbon fluxes in natural protected areas contribute to define the ecosystem potential to serve as a nature climate solution [14] .

Data Description
The dataset contains a four-year measurement period of soil respiration along a forest succession from a seasonally dry forest in the municipality of Álamos, Sonora, México.Climate in the zone is classified as BS1(h')w [15] with a mean annual temperature of 24 °C and a mean annual precipitation of 706 mm [16] .The study area confers a well-defined seasonality that depicts a dry season (November to May) and a wet season, which ∼80% of the total annual precipitation is distributed in this period [17] .
The information located in this repository [18] is described in Table 1 , while Fig. 1 shows the monthly mean inter-annual and seasonal variations of soil respiration during 2015, 2016, 2017 and 2019 in an old-growth, mid-secondary and early-secondary tropical dry forests.

Experimental Design, Materials and Methods
Soil respiration (R S ) was measured in the northmost limit of the TDF in the Americas.Here, three sites were selected according to the TDF succession pathway in the Pacific Coast of México from Álvarez-Yépiz et al. [5] .The TDF succession sites include an early secondary forest (ES; 26.999202 °N, -108.785681°W), which was cleared for intensive livestock and agriculture and abandoned for ∼10 years, followed by a mid-secondary forest (MS, 27.00 60 65 °N, -108.779109°W) with a recovery period of ∼40 years since the last land clearing and finally, an old-growth forest (OG, 26.996829 °N, -108.789193°W) a well-conserved site that never has been cleared and maintains the representative species composition from TDF.The landscape within the sites shows a mean height above mean sea level (hamsl) of 378 m ( Fig. 2 ).
Monthly R S measurements were conducted from March 2015 to December 2017 at OG, MS and ES, while, from March to December 2019 only OG and MS sites were sampled.The experimental design at each site consisted in establishing four permanent transects of 60 m radiating away from a central micrometeorological tower in the direction of each cardinal point, at each  transect 10 cm diameter PVC collars were distributed every 20 m ( Fig. 3a ).Each collar was 8 cm tall and a portion of about 4 cm was buried.R S measurements were conducted using a portable infrared soil gas analyzer (LI-8100, LI-COR Biosciences, Lincoln, Nebraska, USA) connected to a static chamber (model: 8100-102, LI-COR Biosciences, Lincoln, NE, USA) ( Fig. 3b ).In each soil collar, the CO 2 concentration was recorded by the analyzer for 180 s and between each measurement a pre-purge and a post-purge were conducted with the aim of removing the trace gas inside the chamber [19] .Also, in an adjacent zone to each soil sampling collar, simultaneous soil temperature and volumetric water content measurements were carried out at 10 cm depth with thermocouple thermometer (Barnant Co., Barrington, IL, USA) and a soil moisture sensor (Theta Probe ML2x, Delta Services, Cambridge, UK).Finally, soil respiration flux rates were calculated using SoilFluxPro R (version 4.0.1,LI-COR Biosciences, Lincoln, NE, USA).A detailed information of experimental design and measurements can be found in Vargas-Terminel et al. [1] .

Limitations
In total, 48 soil collars were installed and distributed among four transects; 12 collars within each site.However, in order to avoid drastic changes in environmental conditions during measuring periods, a window of maximum 3 h was scheduled to complete a measurement cycle.Site features (vegetation growth) and access conditions (flooding) during some sampling campaigns precluded the entrance to soil collars in each site.Under these circumstances, a minimum of 8 collars per site were aimed.

Fig. 1 .
Fig. 1.Monthly means of soil respiration (R S ) in an old-growth (OG), mid-secondary (MS) and early-secondary (ES) tropical dry forest in Northwestern Mexico modified from Vargas-Terminel et al. [1] (see Fig. 1 in the related research article).The data are presented as mean ± standard.Early-secondary (ES) site was not sampled during 2019.Shaded areas show the wet season in the tropical dry forest.

Fig. 2 .
Fig. 2. Location of tropical dry forest sampling sites in Northwestern México.

Fig. 3 .
Fig. 3. Experimental design for soil respiration (R S ) sampling collars.Soil collars were installed in permanent 60 m transect distributed along the four cardinal points (a) and R S measurements were conducted monthly during 2015, 2016, 2017 and 2019 with a soil portable infrared gas analyzer (b).
[1] forests and serves as a base line to benchmark soil carbon models in regional and global contexts.The data presented supports the research manuscript: "Soil respiration is influenced by seasonality, forest succession and contrasting biophysical controls in a tropical dry forest in Northwestern Mexico" from Vargas-Terminel et al.[1].©2023 The Author(s).Published by Elsevier Inc.

Table 1
Soil respiration data set description from tropical dry forest in Northwestern Mexico.
SiteStudy site: Álamos, Sonora Text Ecosystem Ecosystem type: tropical dry forest Text Forest Forest succession stage: old-growth, mid-secondary and early-secondary