Using Leaf Traits to Rank Native Grasses According to Their Nutritive Value

International audience1. Dry matter digestibility is a critical component of herbage nutritive value, a major service delivered by grasslands. The aim of this study was to test whether the dominance hypothesis applies to assess the impacts of environmental gradients and management regimes on thiscomponent of herbage nutritive value in permanent grasslands. 2. At the plant level, digestibility has been related to a number of functional traits, but whether this can be scaled up to the community level in species-rich grasslands and how such relationships are modulated by environmental conditions and management regimes remainunknown. Our primary objective was to test whether community-weighted means – species trait values weighted by the species abundance – of morphological, phenological and chemical traits could be used to explain variations in digestibility over a large range of climatic contexts,soil resource levels and management regimes. Our second objective was to explain variations in community digestibility within and among nine contrasting sites along large natural and man-induced environmental gradients.3. Over the whole data set, digestibility and most community-weighted means of traits responded to climatic factors and management regimes, but relations were not always significant when each site was considered separately. Community digestibility was significantly related to one or more plant traits within each site and to all of the measured traits when considering all the sites. Leaf dry matter content (LDMC) had the most consistent effects on digestibility, with a strikingly similar negative effect within each site. Potential evapotranspiration was negatively related to digestibility and contributed to explain a large part of the among-site variance. In addition, a low return interval of disturbance and a high disturbance intensity (biomass removal) were both associated with a high digestibility.4. Synthesis and applications. Disturbance regime, plant traits and local climate impacted dry matter digestibility roughly equally in grasslands. The effects of community composition on digestibility and its response to abiotic factors could be successfully captured by community weightedmeans of leaf dry matter content. This functional marker can be used to develop indicators and grassland management rules to support farmers in the refinement of their practices towards specific needs, such as target production outputs

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“…Al Haj Khaled et al . ) or plant height (Alexander et al . ), and in monospecific swards, Pontes et al .…”

Section: Discussionmentioning

confidence: 99%

Plant trait–digestibility relationships across management and climate gradients in permanent grasslands

Gardarin

Garnier

Carrère³

et al. 2014

Journal of Applied Ecology

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“…As we had assumed, the selected mesic grasslands were differentiated by higher community weighted means of forage indicator value and SLA, and a lower community weighted mean of LDMC (Table 2) – i.e. indicators of higher forage quality [27], [47]. The supposed higher forage quantity (availability) in mesic grasslands was not due to vegetation height, as the community weighted mean of canopy height was in a similar range in both grassland types, probably because all sites had been unmanaged for a long time and tall species were favored.…”

Section: Discussionmentioning

confidence: 99%

Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

et al. 2013

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BackgroundCurrent plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.Methodology/FindingsWe assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.ConclusionsOur findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.

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“…2005). At the leaf lamina scale, digestibility was correlated negatively with LDMC and positively with SLA (Al Haj Khaled et al . 2006).…”

Section: Discussionmentioning

confidence: 99%

Leaf traits affect the above‐ground productivity and quality of pasture grasses

Pontes¹,

Soussana²,

Louault³

et al. 2007

Functional Ecology

111

137

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Summary1. By comparing plant species under the same experimental field conditions, the direct effects of plant traits on ecosystem processes can be studied. We have analyzed the role of leaf traits (leaf lamina dry matter content, LDMC; leaf lamina N content, LNC and specific leaf lamina area, SLA) for the annual above-ground primary productivity (ANPP) and quality (pepsin-cellulase digestibility, crude protein content) for herbivores of 13 perennial C 3 pasture grass species. 2. These relationships were investigated over 2 years with monocultures grown in a fully factorial block design crossing the plant species, the cutting frequency and the N supply factors. 3. The within species variation in leaf traits, ANPP, digestibility and protein content was less than between species variation. Species ranks for leaf traits were conserved among N supply and cutting frequency levels. Highly significant ( P < 0·001) between species allometric relationships were found for LNC × SLA and SLA × LDMC, with common slopes but differences in intercept and shifts among factor levels. 4. The between species variation in ANPP was strongly ( P < 0·001) and negatively correlated with the fresh-matter based leaf N content (i.e. LDMC × LNC) and was not affected by SLA, apparently because of a trade-off between SLA and leaf lamina fraction. Digestibility increased with SLA and declined with LDMC. Protein content increased with both fresh and dry-matter based LNC. 5. N supply increased LNC and SLA but reduced LDMC. Cutting frequency increased LDMC and reduced LNC. In response to cutting frequency, changes in digestibility and in fresh-matter based LNC were positively correlated. 6. We conclude that the between species variation in the annual production of digestible energy and of proteins by pasture grasses is controlled in an additive way by two leaf traits: LNC and LDMC.

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Using Leaf Traits to Rank Native Grasses According to Their Nutritive Value

Cited by 55 publications

References 38 publications

Plant trait–digestibility relationships across management and climate gradients in permanent grasslands

Plant trait–digestibility relationships across management and climate gradients in permanent grasslands

Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

Leaf traits affect the above‐ground productivity and quality of pasture grasses

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