The association of arable weeds with modern wild cereal habitats: implications for reconstructing the origins of plant cultivation in the Levant

Reconstructing the origins of plant cultivation in southwest Asia is crucial for understanding associated processes such as the emergence of sedentary communities and domesticated crops. Among the criteria archaeobotanists developed for identifying the earliest plant cultivation, the presence of potential arable weeds found in association with wild cereal and legume remains has been used as a basis for supporting models of prolonged wild plant cultivation before domesticated crops appear. However, the proposed weed floras mainly consist of genus-level identifications that do not differentiate between arable weeds and related species that characterise non-arable habitats. Here we test, for the first time, whether the potential arable weed taxa widely used to identify wild plant cultivation also occur in non-cultivated wild cereal populations. Based on modern survey data from the southern Levant we show that the proposed weed taxa characterise both grasslands and fields. Our findings, therefore, do not support the use of these taxa for reconstructing early cultivation. Instead, for future studies we suggest an approach based on the analysis of plant functional traits related to major agroecological variables such as fertility and disturbance, which has the potential to overcome some of the methodological problems

A new functional ecological model reveals the nature of early plant management in southwest Asia

The protracted domestication model posits that wild cereals in southwest Asia were cultivated over millennia before the appearance of domesticated cereals in the archaeological record. These ‘pre-domestication cultivation’ activities are widely understood as entailing annual cycles of soil tillage and sowing and are expected to select for domestic traits such as non-shattering ears. However, the reconstruction of these practices is mostly based on indirect evidence and speculation, raising the question of whether pre-domestication cultivation created arable environments that would select for domestic traits. We developed a novel functional ecological model that distinguishes arable fields from wild cereal habitats in the Levant using plant functional traits related to mechanical soil disturbance. Our results show that exploitation practices at key pre-domestication cultivation sites maintained soil disturbance conditions similar to untilled wild cereal habitats. This implies that pre-domestication cultivation did not create arable environments through regular tillage but entailed low-input exploitation practices oriented on the ecological strategies of the competitive large-seeded grasses themselves

An ecohydrological approach to managing dryland forests: integration of leaf area metrics into assessment and management

We review the use of leaf area metrics (LAM) for assessing and managing dryland forests. We propose a framework integrating individual tree to whole-ecosystem metrics representing a variety of forest features and review theory, empirical evidence and knowledge gaps. Four basic concepts underlie the LAM framework: (1) Max-LAI - an ecosystem can be characterized by an upper potential leaf area index (LAI) dictated mainly by water availability, (2) Leaf area distribution - the distribution of leaf area is proportional to the distribution of resources among vegetation components, (3) Safe-LAI - maintaining Ecosystem-LAI below Max-LAI is a way to reduce drought stress and (4) tree leaf area (TLA) - the leaf area of an individual tree as a proportion of its potential TLA, represents its vigour. Implementation of the LAM strategy requires the following: (1) better understanding how edaphic conditions and vegetation characteristics interact with climate in determining Max-LAI, (2) better understanding how leaf area is related to water use across species, vegetation strata and light regimes, (3) better understanding the interaction between LAI development and stand dynamics, (4) better capability of measuring or estimating individual tree leaf area and (5) development of species-specific references for tree vigour based on leaf area. The LAM strategy is promising for managing dryland forests under increasing drought stress