<b>Description: </b>We deployed 18 mesocosms into each of the ecosystem types (logged forest and oil palm) in mid-May 2016, to give the soil one month to recover from the disturbance. We constructed mesocosms from black plastic containers, 40 cm diameter and 25 cm high after removing the base. We dug mesocosms 20 cm into the ground leaving 5cm above the surface. We arranged them in a 6 x 3 grid with a minimum of 3 m between each mesocosm to minimise interaction between the soil nutrient cycling in each mesocosm. As proximity of the seedlings to mature trees may increase competition for nitrogen and other nutrients we recorded the distance of each mesocosm to the nearest mature tree (any species with diameter at breast height &gt; 30 cm) for inclusion in our analyses. We randomly selected 12 of the mesocosms, to receive 15N-labelled dung patties weighing 300 ± SD 2.27 g in logged forest and 410 ± SD 2.04 g in oil palm. We populated six randomly selected mesocoms from within those 12 treated with dung with a standardised dung beetle communities (Fig. 1, Table S2). The remaining six mesocosms were left as soil only controls. We covered each mesocosm with a fine nylon mesh secured with a rubber belt to prevent beetles leaving or colonising the mesocosms, and to standardise any microclimatic effects between treatments. However, after 48 hours we opened the dung beetle treatments for a 24 hours period to allow the beetles to emigrate rather than forcing them to artificially stay in the same pat (cf. Roslin 2000; Slade et al. 2017), and then re-covered the mesocosms with netting.We sampled soil seven times from logged forest over the course of the experiment. Any remaining surface dung was removed prior to soil sampling, and replaced thereafter, in order to reduce the possibility of contamination. If a soil core was unsuccessful (most likely due to beetle channels) a second core was taken directly beside. On each sample day, a core of 10cm depth was taken and split into vertical horizons 0- 2cm, 2-5 cm and 5-10cm. We sampled leaves eight times over the eight-month duration of the experiment, with high frequency during the first month, aimed to capture the initial assimilation of DDN into the plants. We collected one leaf from the Dipterocarpaceae or palm seedlings for each sample event. For dipterocarp seedlings we alternated collection of the terminal leaf from top and bottom (leaving the topmost, newest leaf) between consecutive sample days, and for palm seedlings we sampled the two penultimate leaflets from alternating sides of the mid-stem, from the youngest fully formed frond. As assimilated 15N did not plateau in logged forest during the 8-month timeframe of the experiment, we took a sample after 21 months in order to determine whether all DDN had been turned over in the plant biomass after this time.The leaf and soil samples were dried at 60°C for a minimum of 48 hours. We then ground samples to a fine powder using a ball mill (Retsch UK Ltd., Hope, UK). We weighed ground samples into 6 x 4 mm ultraclean tin capsules (Elemental Microanalysis Ltd., Okehampton, UK) using an ultra-microbalance with readability 1 μg (Mettler-Toledo, Greifensee, Switzerland) to provide sufficient elemental carbon and nitrogen for analysis by continuous flow isotope ratio mass spectrometry (SERCON, Crewe, UK). Isotope ratios are expressed in per mil (‰) relative to international reference standards (Rstandard), which are Atmospheric Nitrogen and Vienna PeeDee Belemnite (VPDB) for nitrogen and carbon, respectively. The delta value describes the isotopic composition of each sample, which signifies a measurement of difference relative to laboratory standards. The calculation of δ values is given by: δHX = [(RSAMPLE /RSTANDARD −1)]*1000<b>Project: </b>This dataset was collected as part of the following SAFE research project: <b>Using stable isotopes to link biogeochemical processes to biodiversity of conservation concern</b><b>Funding: </b>These data were collected as part of research funded by: NERC (Research grant, NE/K016148/1)This dataset is released under the CC-BY 4.0 licence, requiring that you cite the dataset in any outputs, but has the additional condition that you acknowledge the contribution of these funders in any outputs.<b>Permits: </b>These data were collected under permit from the following authorities:Sabah Biodiversity Centre (SABC) (Research licence JKM/MBS.1000-2/2 (374) )Sabah Biodiversity Centre (SABC) (Research licence JKM/MBS.1000-2/2 JLD.4 (41))Sabah Biodiversity Centre (SABC) (Research licence JKM.1000-2/2 JLD.5 (153))<b>XML metadata: </b>GEMINI compliant metadata for this dataset is available here<b>Files: </b>This consists of 1 file: 3_Kemp_15N_mesocosms_data.xlsx<b>3_Kemp_15N_mesocosms_data.xlsx</b>This file contains dataset metadata and 3 data tables:<b>OP leaf</b> (described in worksheet OP_leaf)Description: Details the δ15N of leaves sampled in oil palm from palm seedlings across eight sample days up to day 233. Number of fields: 13Number of data rows: 144Fields: <b>Name</b>: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)<b>Day</b>: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)<b>Day2</b>: Experimental day as a factor (Field type: id)<b>Mesocosm</b>: Unique identifier for each of the 18 mesocosms (Field type: id)<b>Treatment</b>: Treatment assignment (Field type: categorical)<b>DistMature</b>: Distance from the nearest mature tree (any species with diameter at breast height &gt; 30 cm). (Field type: numeric)<b>Weight</b>: Sample weight (Field type: numeric)<b>Beam.Area.N</b>: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)<b>ugN</b>: Measure of the elemental nitrogen content of the sample (Field type: numeric)<b>d15N</b>: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)<b>Beam.Area.C</b>: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)<b>ugC</b>: Measure of the elemental carbon content of the sample (Field type: numeric)<b>d13C</b>: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)<b>LFE leaf</b> (described in worksheet LFE_leaf)Description: Details the δ15N of leaves sampled in logged forest, taken from dipterocarp seedlings across nine sample days, up to day 625.Number of fields: 13Number of data rows: 147Fields: <b>Name</b>: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)<b>Day</b>: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)<b>Day2</b>: Experimental day as a factor (Field type: id)<b>Mesocosm</b>: Unique identifier for each of the 18 mesocosms (Field type: id)<b>Treatment</b>: Treatment assignment (Field type: categorical)<b>DistMature</b>: Distance from the nearest mature tree (any species with diameter at breast height &gt; 30 cm). (Field type: numeric)<b>Weight</b>: Sample weight (Field type: numeric)<b>Beam.Area.N</b>: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)<b>ugN</b>: Measure of the elemental nitrogen content of the sample (Field type: numeric)<b>d15N</b>: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)<b>Beam.Area.C</b>: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)<b>ugC</b>: Measure of the elemental carbon content of the sample (Field type: numeric)<b>d13C</b>: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)<b>LFE soil</b> (described in worksheet LFE_soil)Description: Details the δ15N of soil sampled in logged forest across seven sample days up to day 64Number of fields: 14Number of data rows: 375Fields: <b>Name</b>: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)<b>Day</b>: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)<b>day2</b>: Experimental day as a factor (Field type: id)<b>Mesocosm</b>: Unique identifier for each of the 18 mesocosms (Field type: id)<b>Treatment</b>: Treatment assignment (Field type: categorical)<b>DistMature</b>: Distance from the nearest mature tree (any species with diameter at breast height &gt; 30 cm). (Field type: numeric)<b>Depth</b>: The depth which the soil sample was taken from, i.e. 0002 is the horizon between the ground surface and 2 cm belowground (Field type: numeric)<b>Weight</b>: Sample weight (Field type: numeric)<b>Beam.Area.N</b>: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)<b>ugN</b>: Measure of the elemental nitrogen content of the sample (Field type: numeric)<b>d15N</b>: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)<b>Beam.Area.C</b>: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)<b>ugC</b>: Measure of the elemental carbon content of the sample (Field type: numeric)<b>d13C</b>: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)<b>Date range: </b>2016-05-01 to 2017-02-01<b>Latitudinal extent: </b>4.5000 to 5.0700<b>Longitudinal extent: </b>116.7500 to 117.8200