Microbial and metabolic profiling reveal strong influence of water table and land-use patterns on classification of degraded tropical peatlands

Abstract

Abstract. Tropical peatlands from southeast Asia are undergoing extensive drainage, deforestation and degradation for agriculture and human settlement purposes. This is resulting in biomass loss and subsidence of peat from its oxidation. Molecular profiling approaches were used to understand the relative influences of different land-use patterns, hydrological and physicochemical parameters on the state of degraded tropical peatlands. As microbial communities play a critical role in biogeochemical cascades in the functioning of peatlands, we used microbial and metabolic profiles as surrogates of community structure and functions, respectively. Profiles were generated from 230 bacterial 16 S rDNA fragments and 145 metabolic markers of 46 samples from 10 sites, including those from above and below water table in a contiguous area of 48 km2 covering five land-use types. These were degraded forest, degraded land, oil palm plantation, mixed crop plantation and settlements. Bacterial profiles were most influenced by variations in water table and land-use patterns, followed by age of drainage and peat thickness in that order. Bacterial profiling revealed differences in sites, based on the duration and frequency of water table fluctuations and on oxygen availability. Mixed crop plantations had the most diverse bacterial and metabolic profiles. Metabolic profiling, being closely associated with biogeochemical functions, could distinguish communities not only based on land-use types but also their geographic locations, thus providing a finer resolution than bacterial profiles. Agricultural inputs, such as nitrates, were highly associated with bacterial community structure of oil palm plantations, whereas phosphates and dissolved organic carbon influenced those from mixed crop plantations and settlements. Our results provide a basis for adopting molecular marker-based approaches to classify peatlands and determine relative importance of factors that influence peat functioning. Our findings will be useful in peatland management by providing a basis to focus early efforts on hydrological interventions and improving sustainability of oil palm plantations by adopting mixed cropping practices to increase microbial diversity in the long term.

Rare Species Shift the Structure of Bacterial Communities Across Sphagnum Compartments in a Subalpine Peatland

“…Environmental conditions strongly impact the structure of microbial communities (Bahram et al, 2018). The effects of water table and total nitrogen content on bacterial communities in SP samples (Table 3) matches well with previous studies in different types of peatlands (Mishra et al, 2014;Urbanová and Bárta, 2016;Zhong et al, 2017). Interestingly we further found that RT and CART also responded to water table and total nitrogen content.…”

Biogeographical distribution of Microbial Communities along the Rajang River-South China Sea Continuum

“…Anthropogenic disturbances, in particular settlements and logging (secondary forest), led to higher diversity indices (Fig .6). On the contrary, sites surrounded by oil palm plantations displayed the lowest diversity indices, supporting results by Mishra et al (2014) who found similar results in peatlands. Furthermore, the OTU overlapping of major anthropogenic activities (i.e settlements and oil palm plantations) in Supp.…”

“…2005; Kolmakova et al, 2014;Lemke et al, 2009;Newton et al, 2011;Read et al, 2015;Staley et al, 2013). While there are studies related to the freshwater-marine gradients of rivers such as studies by Crump and Hobbie (2005) and Fortunato et al (2013)and tropical peatlands (Kanokratana et al, 2011;Mishra et al, 2014;Yule et al, 2016;Too et al, 2018), to the author's knowledge, this is the first study which links both freshwater-marine gradients as well as tropical peatlands as a cohesive component (i.e tropical peat-draining river to coastal ecosystem). Due to the high diversity and fast generation time, the first responders to environmental changes (both natural and anthropogenic events such as storms, upwelling and pollutants) are microbial communities (Hunt and Ward, 2015).…”

Carbon Emissions From Oil Palm Plantations on Peat Soil

“…This was particularly apparent in Sebungan, where the canopy was closed and temperatures were lower. Sebungan had a lower mean WTD than the RSPO recommendations at the time of measurement and thus fresh peat may have been exposed to heterotrophic bacteria, increasing the rate of R h from Sebungan (Lim et al, 2012;Mishra et al, 2014;Carlson et al, 2015).…”

“…Modifying peatlands for agricultural management can alter the biogeochemistry and trace gas fluxes from these systems due to the introduction of artificial drainage ditches that lower the water table and create an aerated zone for root growth, raising the soil redox potential (Hirano et al, 2012;Mishra et al, 2014;Tonks et al, 2017). In these more oxic conditions, methanogenesis is inhibited and aerobic degradation pathways predominate, namely peat oxidation from heterotrophic respiration (R h ; Hooijer et al, 2012;Miettinen et al, 2017;Warren et al, 2017).…”