Summary1 Metabolic scaling theory predicts that the rate of resource use per unit area is independent of the average mass per individual and that the slope of the log masslog density relationship should be − 4/3. 2 Data were obtained from plant communities along a natural gradient of moisture and latitude in north-west China to test the generality of this theory. 3 The allometric exponents (slopes of the log mass-log density relationship) for aboveground biomass decreased with natural moisture levels and plant cover, deviating from the predictions of the energy equivalence theory. Allometric exponents for belowground and total biomass were similar among the three sites and were much closer to the predicted value of − 4/3. 4 Metabolic scaling theory may be applicable under many growth conditions, but not when restricted to above-ground biomass under drought stress. The rate of supply of the limiting resource per unit area determines which plant parts behave according to theory.

Listening comprehension constitutes a major problem for second language learners but little is known about the relative contribution of different factors to listening comprehension. Since there are still only very few studies in this area by comparison with studies focusing on the relationship between reading and vocabulary, there is a need for studies which can fill the gap in our knowledge about the specific contribution of generic and discrete-point measures of language ability to explaining listening. In the present study among 151 non-English major students at a university in Northwest China we explore what proportion of the variance in listening comprehension is explained by general language proficiency, vocabulary size and metacognitive awareness. Our results show that vocabulary size is the strongest predictor, followed by general language proficiency, while metacognitive awareness is less important. We discuss implications for the componential structure of the notion language ability, theories of listening and pedagogical practice in L2 classrooms.

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Abstract-The purpose of this study was to identify patterns of academic burnout in 730 Chinese middle school students, and to link the burnout patterns with academic motivation. Using cluster analysis, we identified four motivation groups: (a) distressed group, (b) persevering group, (c) laissez-faire group, and (d) well-functioning group. The results of optimal scaling procedures indicated that grade level and motivation variables (intrinsic and extrinsic motivation, and amotivation) were good discriminators among the four clusters. Specifically, variation on self-determination motivation characteristics was demonstrated among different academic burnout profiles: distressed students had the highest scores on a motivation and external motivation. In contrast, well-functioning students had the highest scores on intrinsic motivation. For persevering and laissez-faire students, there was no significant difference on intrinsic motivation. However, persevering students reported higher scores on a motivation and external motivation than laissez-faire students.