Functional diversity of algal communities from headwater grassland streams: How does it change following afforestation?

Abstract

Pine afforestation of grassland streams may lead to changes in species traits and therefore functional diversity of epilithic algal community. Here, we studied trait-based responses in three grassland and three afforested streams in a mountain watershed of Córdoba, Argentina. We hypothesized that afforestation would reduce functional diversity through a simplification of periphyton architecture resulting from reduction in light availability, and that changes in hydrological periods would influence community responses. Algal samples were collected at each stream during two different hydrological periods (high flow and low flow), and physicochemical variables were recorded. Selected traits included strategies and morphological characters related to resource access and disturbance resistance (size, morphological guild, resource requirement, attachment mechanism and life-form). We calculated two indices of functional diversity: Rao's quadratic entropy (FD Q ) and functional variance. Most trait categories showed a significant effect of one or both factors; 26 % discriminated between vegetation types, 26 % reflect the changes between hydrological periods, and 47 % were sensitive to both of them. Our results revealed some categories of traits that can be used to distinguish changes in riparian vegetation, such as unicellular life-form and high-profile guild. Functional diversity of single traits was affected differently by pine afforestation. However, the most integrative index, the FD Q mean, partially supported our hypotheses. Afforestation reduced FD Q mean by 50 %, but only during low-flow period. FD Q mean was high and similar between streams at high flow, when environmental factors, such as discharge and temperature, could prevail on differences in riparian vegetation.

Succession of algal communities in headwaters: a comparison of pine afforested and natural grassland streams

“…Time had no effect on the variables measured in triplicated in each stream (P > 0.05). For variables measured only once at the beginning of the experiment, there might not have been differences throughout the experimental period based on previous studies in the area (see Cibils et al 2015;Ma´rquez et al 2015).…”

“…Evenness was calculated as H¢/H¢ max . Additionally, genera were grouped in categories of functional traits according to Cibils et al (2015): size, morphological guild, resources requirement, attachment mechanism and life-form (Table S1). Taxa were placed into five size classes, consisting of those with different biovolumes from class 1, which included smaller species, to class 5, which contained larger species.…”

The effect of agriculture on the seasonal dynamics and functional diversity of benthic biofilm in tropical headwater streams

“…Stream flow was also correlated with functional richness in our study, with higher values of functional indices occurring during high‐flow periods. In these periods, elevated flows often wash out accumulated fine sediment from the streambed surface, exposing rocks and other types of coarse substrata, thus creating a high degree of niche differentiation and therefore lowering competition (Cibils, Principe, Márquez, Gari, & Albariño, ; Mason, Mouillot, Lee, & Wilson, ). The same processes and outcome have been observed in subtropical streams (Cibils et al., ; Schneck & Melo, ), reinforcing our expectation that benthic diatom traits are mainly controlled by climatic characteristics in tropical streams.…”

Effects of intensive agriculture in the structure and functioning of tropical headwater streams

“…Streamflow also demonstrated effects on functional richness, with higher values of functional indices on high flow periods. In this period, instable flow washes the accumulated sediment on the streambed, exposing rocks and other types of substrata, creating a high degree of niche differentiation and therefore, low competition (MASON et al, 2005;CIBILS et al, 2015), favoring the establishment of species with different functions. The same result has been observed in subtropical streams (SCHNECK; MELO, 2012;CIBILS et al, 2015), reinforcing our expectations that benthic diatom traits are mainly controlled by climatic characteristics in the tropical headwater streams.…”

“…In this period, instable flow washes the accumulated sediment on the streambed, exposing rocks and other types of substrata, creating a high degree of niche differentiation and therefore, low competition (MASON et al, 2005;CIBILS et al, 2015), favoring the establishment of species with different functions. The same result has been observed in subtropical streams (SCHNECK; MELO, 2012;CIBILS et al, 2015), reinforcing our expectations that benthic diatom traits are mainly controlled by climatic characteristics in the tropical headwater streams. One of the issues that emerges from these findings is the observed relationship between converted lands and higher water temperatures and higher streamflow in different parts of the globe BROADMEADOW et al, 2011;SIMMONS et al, 2015), which demonstrated effects on functional dynamics of benthic diatom traits.…”