Tropical cyclones shape mangrove productivity gradients in the Indian subcontinent

Abstract

Recent literature on the impact of cyclones on mangrove forest productivity indicates that nutrient fertilizations aided by tropical cyclones enhance the productivity of mangrove forests. We probe the implications of these predictions in the context of Indian mangroves to propose potential future directions for mangrove research in the subcontinent. First, we look at the time series trend (2000–2020) in satellite-derived gross primary productivity (GPP) datasets for seven mangrove forests across the country’s coastline. Second, we compare seasonal changes in soil nutrient levels for a specific site to further the arguments proposed in the literature and investigate the role of potential drivers of mangrove productivity. We find overall increasing trends for GPP over the past two decades for all seven mangrove sites with seasonal fluctuations closely connected to the tropical storm activities for three sites (Bhitarkanika, Pichavaram, and Charao). Additionally, organic carbon and nitrogen levels showed no significant trend, but phosphorus levels were higher during the post-monsoon-winter period for Bhitarkanika. Our findings expand the predictions of previous studies that emphasized the role of storm-induced nutrient fluxes and freshwater supply as primary drivers of productivity gradients in mangroves. Our study provides insights on how mangrove productivity may change with fluctuating frequency and magnitude of cyclones under a changing climate, implying the need for more mechanistic studies in understanding the long-term impact on mangrove productivity in the region.

Species Diversity, Biomass and Carbon Stock Assessment of Kanhlyashay Natural Mangrove Forest

“…where 0.04 is plot size in hectare and 25 is a constant used to extrapolate the measurement of the basal area from per plot (m 2 /plot) to per hectare (m 2 /ha). The Species Diversity index, determined in this study using the Shannon-Wiener's Index [25], indicated a quantitative description of mangrove habitat in terms of species distribution and evenness; this species diversity index was used in several studies [26][27][28] and was calculated using the following form: H = − ∑ P i lnP i (7) where: H = the value of the Shannon-Wiener diversity index Pi = the proportion of ith species individuals to total species individuals ln = the natural logarithm of P i Evenness Index, E = H /ln(S) (8) where, S = Number of species in the study area…”

“…Therefore, Shannon-Wiener's diversity index (H ) value of the mangrove community of LetKhutKon Village was very low compared to other natural mangrove forests since the mangrove stand in the study site possessed a low number of mangrove species and was dominated by the few species. In contrast to tropical lowland rainforest, the mangroves have very low diversity as few plants have their special adaptations, which are attributed to their unique stands formation and harsh coastal habitat [8].…”

“…The ecological benefits supported by the mangrove forests are bio-protection from littoral erosion [2,3], shoreline stabilizations, reducing the devastating impact of hurricanes, waves, and tsunamis, and protection from cyclones [3,4]. Additionally, mangrove ecosystems have a high carbon sequestration capacity, which is reflected in high aboveground biomass, high net primary production (NPP), the low decomposition rate of mangrove sediments, and belowground to aboveground biomass rations [5][6][7][8]. Mangrove forests have a critical role in climate change mitigation because they are able to absorb and store 3-5 times more carbon than other upland forests, mainly in soil [5].…”

Rapid, Landscape-Scale Assessment of Cyclonic Impacts on Mangrove Forests Using MODIS Imagery

“…We found an approximate three-year recovery period, which is in agreement with [36] but differs from others (Table 1). Tropical cyclones can enhance mangrove forest growth by delivering nutrient-rich sediments [56] and soil accretion [57] which can aid in faster recovery. However, frequent cyclones can compound the recovery period of a single disaster event (e.g., Rashmi and Aila struck within three years of Sidr) (Table S1).…”

Inclusion of social values, priorities, and motivations for mangrove conservation in Bhitarkanika, India

“…Mangrove forests are some of the most productive coastal ecosystems on the planet. They are found to sequester more carbon than their territorial counterparts and can reduce erosion and ooding risks during storms (Alongi, 2011;Rasquinha and Mishra, 2021). Apart from these important climate regulating services, they are also valued for their provisioning ( sh, fuelwood, materials), supporting (nutrient cycling, photosynthesis, and carbon assimilation, and refugia functions), and cultural services (recreational, religious, spiritual, aesthetic, educational and sense of place) across the globe (Walters et al, 2008).…”