Landscape metrics as functional traits in plants: perspectives from a glacier foreland.

Spatial patterns of vegetation arise from an interplay of functional traits, environmental characteristics and chance. The retreat of glaciers offers exposed substrates which are colonised by plants forming distinct patchy patterns. The aim of this study was to unravel whether patch-level landscape metrics of plants can be treated as functional traits. We sampled 46 plots, each 1 m × 1 m, distributed along a restricted range of terrain age and topsoil texture on the foreland of the Nardis glacier, located in the South-Eastern Alps, Italy. Nine quantitative functional traits were selected for 16 of the plant species present, and seven landscape metrics were measured to describe the spatial arrangement of the plant species' patches on the study plots, at a resolution of 1 cm × 1 cm. We studied the relationships among plant communities, landscape metrics, terrain age and topsoil texture. RLQ-analysis was used to examine trait-spatial configuration relationships. To assess the effect of terrain age and topsoil texture variation on trait performance, we applied a partial-RLQ analysis approach. Finally, we used the fourth-corner statistic to quantify and test relationships between traits, landscape metrics and RLQ axes. Floristically-defined relevé clusters differed significantly with regard to several landscape metrics. Diversity in patch types and size increased and patch size decreased with increasing canopy height, leaf size and weight. Moreover, more compact patch shapes were correlated with an increased capacity for the conservation of nutrients in leaves. Neither plant species composition nor any of the landscape metrics were found to differ amongst the three classes of terrain age or topsoil texture. We conclude that patch-level landscape metrics of plants can be treated as species-specific functional traits. We recommend that existing databases of functional traits should incorporate these type of data.

Conservation tillage affects species composition but not species diversity: a comparative study in Northern Italy.

Conservation tillage (CT) is widely considered to be a practice aimed at preserving several ecosystem functions. In the literature, however, there seems to be no clear pattern with regard to its benefits on species diversity and species composition. In Northern Italy, we compared species composition and diversity of both vascular plants and Carabids under two contrasting tillage systems, i.e., CT and conventional tillage, respectively. We hypothesized a significant positive impact of CT on both species diversity and composition. We also considered the potential influence of crop type. The tillage systems were studied under open field conditions with three types of annual crops (i.e., maize, soybean, and winter cereals), using a split-plot design on pairs of adjacent fields. Linear mixed models were applied to test tillage system, crop, and interaction effects on diversity indices. Plant and Carabids communities were analyzed by multivariate methods (CCA). On the whole, 136 plant and 51 carabid taxa were recorded. The two tillage systems studied did not differ in floristic or carabid diversity. Species composition, by contrast, proved to be characteristic for each combination of tillage system and crop type. In particular, CT fields were characterized by nutrient demanding weeds and the associated Carabids. The differences were especially pronounced in fields with winter cereals. The same was true for the flora and Carabids along the field boundaries. For studying the effects of CT practices on the sustainability of agro-ecosystems, therefore, the focus should be on species composition rather than on diversity measures.

Large clones on cliff faces: expanding by rhizomes through crevices.

BACKGROUND AND AIMS: Large clones of rhizomatous plants are found in many habitats, but little is known about whether such clones also occur on cliff faces where environmental conditions are extremely harsh and heterogeneous. METHODS: Using molecular (intersimple sequence repeat, ISSR) markers, the genotypic composition of a cliff-face population of Oxyria sinensis in Sichuan, China, was investigated. KEY RESULTS: The 98 O. sinensis ramets sampled belonged to 12 different genotypes (clones). The three most frequent clones were represented with 45, 22 and 12 ramets, respectively; the remaining nine were represented with only one to five ramets. The three largest clones spanned at least 2.7 m in the vertical direction and 4.6-6.9 m in the horizontal direction on the cliff face. CONCLUSIONS: On the cliff face, large clones of O. sinensis are formed by rhizomes growing along the crevices. Expansion by rhizomes may help O. sinensis to exploit the patchy resources and support establishment and growth of new ramets. Moreover, rooted ramets connected by rhizomes may effectively reduce the susceptibility of O. sinensis to rock fall and erosion and thus greatly improve the chances for long-term survival. The multi-clone structure indicates that sexual reproduction is also important for the long-term persistence of O. sinensis populations on cliffs.

The fate of flowers and fruits of Cornus sanguinea L. in three contrasting Mediterranean habitats.

In the Mediterranean region of southern France, the fate of flowers and fruits of Cornus sanguinea, a deciduous shrub, was studied in three contrasting habitats: (1) an abandoned olive grove, (2) the edge and (3) the interior of a deciduous forest. Abundance of flowering and fruiting of C. sanguinea differed widely between the three habitats. The fate of the flowers, on the other hand, did not differ significantly between habitats. Taking all three habitats together, 77% of the flowers aborted, 23% initiated fruits, 6% developed mature fruits, and 3% produced ripe fruits that were eaten by birds. Likewise, there were for the most part no significant differences in the fate of immature and mature fruits between the habitats. On average, 58% of the immature fruits were abscised undamaged, 24% matured, 10% were damaged by insects and 8% dried up. Of the mature fruits, on average, 51% were eaten by birds, 23% damaged by insects, 20% dried up and 6% fell to the ground undamaged. Independent of habitat conditions, C. sanguinea seems to regulate the quantity of its seed crop primarily by limiting the number of flowers and secondarily by aborting surplus immature fruits, and the number of flowers is mainly controled by resource availability and genetic factors. In the case of C. sanguinea, both the fruit/flower ratio and the proportion of flowers producing mature fruits that are eaten by birds remain constant over a wide range of environmental conditions.