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While taxonomic diversity mediates changes in ecosystem function is well-studied, how deeper dimensions of biodiversity, specifically phylogenetic and functional, independent of taxonomic diversity, drive important processes is understudied. The overarching goal of this work was to determine the role of these dimensions of biodiversity independently and/or interactively explain carbon processing in rivers. Here, we explicitly link community structure and subsequent traits of riparian forests to adjacent ecosystem processing of carbon (e.g., leaf litter). This was accomplished by examining how forests are actually structured in addition to experimental manipulations of phylogenetic and functional diversities of riparian forest community inputs of leaf litter to streams. Experimental field manipulations were carried out in three Piedmont headwater streams to answer the following questions: (1) Does existing variation in taxonomic, functional and phylogenetic diversity of riparian communities differentially drive decomposition in rivers? And (2) Independent of taxonomic diversity, how does functional and phylogenetic diversity of leaf litter assemblages influence rates of decomposition in rivers? We observed significant interspecific variation in breakdown among 30 riparian tree species, in addition to significant relationships between breakdown rate and important foliar tissue chemistries. Breakdown of mixtures that reflected the composition of the riparian species composition did not vary with functional nor phylogenetic diversity, but breakdown of litter mixtures was higher than that of single species. In a separate study, when manipulated independently, functional and phylogenetic diversity were positively related to breakdown, and explained similar degrees of variation. These results are important to understand in light of deepening knowledge of the role different dimensions of biodiversity take in explaining ecosystem function, as well as how these measures can be used as tools in habitat restoration practice. 

The harsh geophysical template characterized by the urban environment combined with people’s choices has led ecologists to invoke environmental filtering as the main ecological phenomena explaining urban biodiversity patterns. Yet, dispersal is often overlooked as a driving factor, especially on expanding vacant land. Does overcoming dispersal limitation by seeding native species in urban environments and increasing the functional or phylogenetic diversity of the seeding pool increase native plant species diversity and abundance in urban vacant land? We took an experimental approach to learn how different dimensions of plant biodiversity within an augmented regional species pool, via seed additions, can explain variation in community structure over a 3-year period. Vacant lots were cleared and manipulated with seeding treatments of high or low phylogenetic and functional diversities from a pool of 28 native species. Establishment success, total native cover and native species richness were followed and compared to cleared, unseeded control lots as well as un-manipulated lots. Seeding increased native plant abundance and richness over uncleared plots, as well as cleared and unseeded control plots. Phylogenetically diverse seed mixtures had greater establishment success than mixtures composed of closely related species. Diversifying seed mixtures increased the likelihood of including species that are better able to establish on vacant land. However, there were no differences in varying levels of either functional or phylogenetic diversity. Augmenting the regional species pool via diverse seed mixtures can enhance native plant cover and richness under the harsh environmental conditions conferred by land abandonment. 

Habitat alteration and destruction are a primary driver of biodiversity loss. There is a plethora of research documenting similarly strong patterns of decline across ecosystem types and spatial scales. However, evolutionary dimensions remain largely unexplored in many systems. For example, little is known about how habitat alteration/loss can lead to phylogenetic deconstruction of ecological assemblages at the local level. That is, while species loss is evident, are some lineages favored over others? Using a long-term dataset of a globally, ecologically important guild of invertebrate consumers, stream leaf “shredders,” we created a phylogenetic tree of the taxa in the regional species pool, calculated mean phylogenetic distinctiveness for > 1000 communities spanning > 10 y period, and related species richness, phylogenetic diversity and distinctiveness to watershed-scale impervious cover. Using a combination of changepoint and compositional analyses, we learned that increasing impervious cover produced marked reductions in all three measures of diversity, and in particular, aid in understanding both phylogenetic diversity and average assemblage phylogenetic distinctiveness. Our findings suggest that, not only are species lost when there is an increase in watershed urbanization, as other studies have demonstrated, but that those lost are members of more distinct lineages relative to the community as a whole. 

Humans promote and inhibit other species on the urban landscape, shaping biodiversity patterns. Institutional racism may underlie the distribution of urban species by creating disproportionate resources in space and time. Here, we examine whether present‐day street tree occupancy, diversity, and composition in Baltimore, MD, USA, neighborhoods reflect their 1937 classification into grades of loan risk—from most desirable (A = green) to least desirable (D = “redlined”)—using racially discriminatory criteria. We find that neighborhoods that were redlined have consistently lower street tree α‐diversity and are nine times less likely to have large (old) trees occupying a viable planting site. Simultaneously, redlined neighborhoods were locations of recent tree planting activities, with a high occupancy rate of small (young) trees. However, the community composition of these young trees exhibited lower species turnover and reordering across neighborhoods compared to those in higher grades, due to heavy reliance on a single tree species. Overall, while the negative effects of redlining remain detectable in present‐day street tree communities, there are clear signs of recent investment. A strategy of planting diverse tree cohorts paired with investments in site rehabilitation and maintenance may be necessary if cities wish to overcome ecological feedbacks associated with legacies of environmental injustice.