Abstract
Depending on the strength of environmental filtering and competitive exclusion, successful colonizers of plant communities show varying degrees of similarity to resident species with respect to functional traits. For the present study, colonizer’s performance was assessed in relation to the degree of fit with the resident community, and in addition, in relation to the community’s trait profile and the environmental factors at the study locations. The two-year field experiment investigated the relative growth rates of 130 species that had been transplanted into German grassland communities varying in intensities of land-use. The transplanted species were selected in accordance with the following scenarios: species with highly similar or dissimilar traits to residents, species with highest degree of co-occurrence with resident species and species chosen randomly from the local species pool. The performance of transplanted phytometers depended on the scenario according to which the species were selected, on community trait diversity, and in addition, often on the interaction of both and on land use intensity. The total amount of explained variance in performance was low, but increased considerably when species identity was taken into account. In general, individuals in the co-occurrence scenario performed better than those selected based on trait information or those selected randomly. Different predictors were important in different seasons, demonstrating a limited temporal validity of performance models.
Highlights
The assessment of trait dispersion patterns of species within communities is commonly used as a tool to understand community assembly mechanisms[1], with trait requisites being determined by a set of filters constraining colonization, establishment and persistence in a given habitat[2]
Before the six phytometer species were planted into the plots, mean multi-trait distance did not differ among the resident species that grew in the respective subplots, which had been randomly assigned to the four different scenarios (Fig. 1)
Variation explained by plot ranged from 4% for relative growth rates (RGR) of leaf number in the first monitoring interval to 39% for RGR height in the 3rd interval, between 0% and 0.4% explained by scenario and between 9% and 38% explained by species identity
Summary
The assessment of trait dispersion patterns of species within communities is commonly used as a tool to understand community assembly mechanisms[1], with trait requisites being determined by a set of filters constraining colonization, establishment and persistence in a given habitat[2]. It is not clear whether species that are more similar to a resident community perform better than dissimilar species, or vice versa In grasslands, this question depends on land-use intensity. Under heavy land-use intensity, and the associated strong abiotic filtering regime combined with higher competition intensity, newcomers with a higher trait similarity to the extant community should perform better and species with more divergent trait values should perform worse. Plants in a community with low leaf dry matter content (LDMC) tended to show higher growth rates than in those with high LDMC36 Such functional attributes of the community are not independent of each other, as FD and CWM can be the result of external environmental filtering processes, such as land-use intensity and, in turn, may indirectly contribute to environmental filtering themselves. CWMs of SLA have been found to increase with increasing fertilization or disturbance intensity[37,38,39], which should result in a high photosynthetic capacity and overall improved growth conditions, thereby intensifying the competition intensity for light
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