Publications by authors named "Jason P Martina"

Article Synopsis
  • * Sites with warmer, wetter conditions and more species generally saw increased biomass, while arid, species-poor areas experienced declines, alongside notable changes in seasonal plant growth patterns.
  • * Factors like grazing and nutrient input didn't consistently predict biomass changes, indicating that grasslands are undergoing substantial transformations that could affect food security, biodiversity, and carbon storage, particularly in dry regions.
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Little is currently known about how climate modulates the relationship between plant diversity and soil organic carbon and the mechanisms involved. Yet, this knowledge is of crucial importance in times of climate change and biodiversity loss. Here, we show that plant diversity is positively correlated with soil carbon content and soil carbon-to-nitrogen ratio across 84 grasslands on six continents that span wide climate gradients.

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Eutrophication usually impacts grassland biodiversity, community composition, and biomass production, but its impact on the stability of these community aspects is unclear. One challenge is that stability has many facets that can be tightly correlated (low dimensionality) or highly disparate (high dimensionality). Using standardized experiments in 55 grassland sites from a globally distributed experiment (NutNet), we quantify the effects of nutrient addition on five facets of stability (temporal invariability, resistance during dry and wet growing seasons, recovery after dry and wet growing seasons), measured on three community aspects (aboveground biomass, community composition, and species richness).

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Maintaining reproductive seasonality can be vital to the fitness of wild animals. Certain species, however, may display aseasonal reproduction and may produce multiple yearly litters when maintained in captivity. Wild fennec foxes (Vulpes zerda), for example, produce a single litter in March or April although their reproductive behaviors are reportedly variable in captivity.

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Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant biodiversity, species composition and ecosystem processes like aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance.

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Nutrient enrichment can simultaneously increase and destabilise plant biomass production, with co-limitation by multiple nutrients potentially intensifying these effects. Here, we test how factorial additions of nitrogen (N), phosphorus (P) and potassium with essential nutrients (K+) affect the stability (mean/standard deviation) of aboveground biomass in 34 grasslands over 7 years. Destabilisation with fertilisation was prevalent but was driven by single nutrients, not synergistic nutrient interactions.

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Coastal wetlands intercept significant amounts of nitrogen (N) from watersheds, especially when surrounding land cover is dominated by agriculture and urban development. Through plant uptake, soil immobilization, and denitrification, wetlands can remove excess N from flow-through water sources and mitigate eutrophication of connected aquatic ecosystems. Excess N can also change plant community composition in wetlands, including communities threatened by invasive species.

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Maternal deprivation can cause long-term behavioral changes in captive mammals. Studies regarding captive ungulates have also indicated behavioral shifts in the presence of the animal keeping staff; however, little is known about these effects in captive giraffes (Giraffa camelopardalis). To examine this, we observed a population of reticulated giraffes composed of maternally raised and maternally deprived individuals by direct and camera observations at Binder Park Zoo, Battle Creek, Michigan.

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Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply.

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