Land use change (LUC), alters the multifarious biodiversity hotspots directly and indirectly through the loss of soil quality. A comparative study on soil carbon status and soil microbiome in undisturbed natural forest eco-systems with that of other land uses which gradually altered over time can serve as a suitable indicator for understanding LUC impact on carbon cycles. With this aim, the current investigation was initiated to infer the cyclic effects of LUC on the soil carbon status under six major ecosystems viz., cropland (CL), deciduous forest (DF), evergreen forest (EF), forest plantation (FP), scrubland (SL) and tea plantation (TP) of the Nilgiri Hill Region (NHR) (India's first biosphere reserve). The total organic carbon (TOC) and carbon stocks were highest in evergreen forest (10.25 %, 322.06 t ha-1) and they decreased with increasing depth of the soil profile across the pools of varying carbon lability. The proportion of active carbon pools (AP) in total carbon was higher in crop land and tea plantation (57.47 %, 58.38 %), however, in the case of evergreen forest, deciduous forest, forest plantation and scrub land the passive carbon pools (PP) (54.99 %, 61.28 %, 59.43 % and 60.70 %) was higher. We discovered LUC has altered the proportion of soil carbon pools, and the efficiency of soil microbiome and has resulted in higher carbon dioxide (CO2) emissions in tea plantation (71.87 t ha-1) and crop land (82.39 t ha-1). However, the native ecosystems (evergreen forest and deciduous forest) with higher recalcitrant carbon pools (46.96 g kg-1 and 34.89 g kg-1) prevent such carbon degradation and thereby hinder the soil carbon emissions as recorded in evergreen forest (48.43 t ha-1) and deciduous forest (56.47 t ha-1). Conclusively, our study demonstrates that LUC has substantially influenced the carbon cycle by altering the carbon stocks and CO2 emissions in relation to soil microbes. Henceforth, in order to maintain carbon footprints and attain carbon net neutrality under the current climate change scenario, suitable carbon management measures must be implemented in carbon-degraded ecosystems (crop land and tea plantation) of NHR.

Large-scale deforestation and increased land use change (LUC) over the past few years have shattered the ecological balance of the Western Ghats by deteriorating the soil quality and essential ecosystem services. This study was conducted in part of the Western Ghats comprising three different ecosystems, viz., agro ecosystem (AE), tea ecosystem (TE), and forest ecosystem (FE) to assess the impact of LUC on soil carbon dynamics. A total of 150 sites were chosen and soil samples were collected at three depth classes of 0–15, 15–30, and 30–45 cm to quantify the carbon pools, total organic carbon (TOC), total inorganic carbon (TIC), total carbon (TC), carbon stock, and carbon management index (CMI). The findings revealed that TOC concentration and carbon stock were significantly higher in FE than in TE and AE. On average (0–45 cm), the carbon stocks recorded in FE, TE, and AE were 77.94, 44.32, and 32.30 t ha−1 and decreased with the depth, while the concentration of total inorganic carbon (TIC) increased with depth. Among the various carbon pools, the very labile carbon (VLC) was higher in AE and TE while the non-labile carbon (NLC) was higher in FE. The active carbon pools (AP) in AE and TE were higher than passive carbon pools (PP), whereas the reverse trend occurred in FE. The results depict the shift in carbon dynamics under different ecosystems of Ooty. The magnitude of the shift is measured by the carbon management index (CMI), which revealed a higher CMI in FE than in AE and TE. The findings thus suggest the imperative need for immediate implementation of carbon management strategies in AE and TE to improve the carbon sequestration potential, achieve land degradation neutrality and improve the carbon footprints of the Ooty.

Accelerating land-use change (LUC) in the Nilgiri Hill Region (NHR) has caused its land to mortify. Although this deterioration has been documented, the destruction of buried gem soil has not been reported. Therefore, this study was conducted to assess the impact of LUC on soil-carbon dynamics in the six major ecosystems in the NHR: croplands (CLs), deciduous forests (DFs), evergreen forests (EFs), forest plantations (FPs), scrublands (SLs), and tea plantations (TPs). Sampling was conducted at selected sites of each ecosystem at three depth classes (0–15, 15–30, and 30–45 cm) to quantify the carbon pools (water-soluble carbon, water-soluble carbohydrates, microbial biomass carbon, microbial biomass nitrogen, dehydrogenase, and different fractions of particulate organic carbon). We found that the LUC significantly decreased the concentration of carbon in the altered ecosystems (49.44–78.38%), with the highest being recorded at EF (10.25%) and DF (7.15%). In addition, the effects of the LUC on the aggregate size of the organic carbon were dissimilar across all the aggregate sizes. The relatively high inputs of the aboveground plant residues and the richer fine-root biomass were accountable for the higher concentration of carbon pools in the untouched EFs and DFs compared to the SLs, FPs, TPs, and CLs. The results of the land-degradation Index (LDI) depicted the higher vulnerability of TP (−72.67) and CL (−79.00). Thus, our findings highlight the global importance of LUC to soil quality. Henceforth, the conservation of carbon pools in fragile ecosystems, such as the NHR, is crucial to keep soils alive and achieve land-degradation neutrality.

Land uses are pivotal in global carbon cycles. The native forest lands possess a greater potential to sequester higher carbon, which can directly address soil quality and climate change problems. Unfortunately, the rapid conversion of forests to other land use over the past few decades has significantly declined the concentration of carbon in the soils. Therefore, in order to estimate the impact of land-use change (LUC) on soil carbon status, this present study was attempted under major ecosystems (Forest (FOR), cropland (CRP), tea plantation (TEA)) of Conoor. Results from findings revealed that total organic carbon (TOC) concentration and carbon pools were significantly (p<0.05) higher in FOR than in CRP and TEA. TOC (0-45 cm) recorded in FOR, CRP and TEA was 32.88, 11.87 and 18.84 g kg-1 and it decreased along the depth increment. Carbon stock (t ha-1) in FOR, CRP and TEA (0-45cm) was 68.10, 26.04, 42.42. Microbial biomass carbon (MBC) was higher in FOR (283.08 mg kg-1) followed by TEA (94.64 mg kg-1) and CRP (76.22 mg kg-1). The microbial biomass nitrogen (MBN) followed; FOR > TEA > CRP. These results clearly indicate that the LUC has inflicted a greater impact on soil carbon status and its extent was quantified using the land degradation index (LDI). The LDI (0-45 cm) recorded in CRP (-38.65) and TEA (-61.75) signals the need for immediate implementation of carbon management strategies in the CRP and TEA ecosystem to keep the soils of Conoor alive and prevent land degradation.

The increased land-use change (LUC) from native lands to other land use at the Conoor region of western ghats in Tamil Nadu has severely declined soil carbon concentration. Therefore to quantify this decline, Carbon Management Index (CMI) was worked out under major land uses {(Forest (FOR), cropland (CRP), tea plantation (TEA)} using total organic carbon (TOC) and carbon pools under varying degrees of lability {a) NLC (non-labile carbon) b) VLC (very labile carbon) c) LC (labile carbon) d) LLC (less labile carbon)}. Results portray that the carbon pools were significantly (p < 0.05) higher in FOR than in TEA and CRP. The contribution of active pools {(very labile carbon (VLC) and labile carbon (LC)} towards TOC was higher in TEA and CRP, whereas in FOR, the passive pool {(less labile carbon (LLC) and non-labile carbon (NLC)} was higher. TOC (0-45 cm) was concentrated on the surface soils of FOR (32.88 g kg-1), CRP (11.87 g kg-1) and TEA (18.84 g kg-1) and it gradually declined with the increase in depth. The decline in TOC was maximum between 0 – 15 and 15 – 30 cm depth in CRP (30.62%) and FOR (22.17%), whereas it was maximum (37.16%) between 15 -30 and 30 -45 cm depth in TEA. Therefore, LUC spotlights the degradation of carbon pools and its extent was quantified using the carbon management index (CMI). The CMI (0 – 45 cm) recorded at CRP (12.93) and TEA (32.62) signals the need for an implementation of carbon management strategies at Conoor to keep the soils alive and protect biodiversity.