The net primary productivity, carbon (C) stocks and turnover rates (i.e. C dynamics) of tropical forests are an important aspect of the global C cycle. These variables have been investigated in lowland tropical forests, but they have rarely been studied in tropical montane forests (TMFs). This study examines spatial patterns of above‐ and belowground C dynamics along a transect ranging from lowland Amazonia to the high Andes in SE Peru. Fine root biomass values increased from 1.50 Mg C ha−1 at 194 m to 4.95 ± 0.62 Mg C ha−1 at 3020 m, reaching a maximum of 6.83 ± 1.13 Mg C ha−1 at the 2020 m elevation site. Aboveground biomass values decreased from 123.50 Mg C ha−1 at 194 m to 47.03 Mg C ha−1 at 3020 m. Mean annual belowground productivity was highest in the most fertile lowland plots (7.40 ± 1.00 Mg C ha−1 yr−1) and ranged between 3.43 ± 0.73 and 1.48 ± 0.40 Mg C ha−1 yr−1 in the premontane and montane plots. Mean annual aboveground productivity was estimated to vary between 9.50 ± 1.08 Mg C ha−1 yr−1 (210 m) and 2.59 ± 0.40 Mg C ha−1 yr−1 (2020 m), with consistently lower values observed in the cloud immersion zone of the montane forest. Fine root C residence time increased from 0.31 years in lowland Amazonia to 3.78 ± 0.81 years at 3020 m and stem C residence time remained constant along the elevational transect, with a mean of 54 ± 4 years. The ratio of fine root biomass to stem biomass increased significantly with increasing elevation, whereas the allocation of net primary productivity above‐ and belowground remained approximately constant at all elevations. Although net primary productivity declined in the TMF, the partitioning of productivity between the ecosystem subcomponents remained the same in lowland, premontane and montane forests.

Abstract. The elevational gradient in plant and animal diversity is one of the most widely documented patterns in ecology and, although no consensus explanation exists, many hypotheses have been proposed over the past century to explain these patterns. Historically, research on elevational diversity gradients has focused almost exclusively on plant and animal taxa. As a result, we do not know whether microbes exhibit elevational gradients in diversity that parallel those observed for macroscopic taxa. This represents a key knowledge gap in ecology, especially given the ubiquity, abundance, and functional importance of microbes. Here we show that, across a montane elevational gradient in eastern Peru, bacteria living in three distinct habitats (organic soil, mineral soil, and leaf surfaces) exhibit no significant elevational gradient in diversity (r 2 , 0.17, P . 0.1 in all cases), in direct contrast to the significant diversity changes observed for plant and animal taxa across the same montane gradient (r 2 . 0.75, P , 0.001 in all cases). This finding suggests that the biogeographical patterns exhibited by bacteria are fundamentally different from those of plants and animals, highlighting the need for the development of more inclusive concepts and theories in biogeography to explain these disparities.

Masting, the highly variable and synchronous production of seeds across a population of perennial plants, is an ecologically important, but still poorly understood, phenomenon. While much is known about the fitness benefits of masting and its effects on seed consumers and trophic interactions, less is understood about the proximate mechanisms of masting. The resource budget model (RBM) posits that masting requires more resources than plants can gain in a single year. Individual plants store resources until a threshold is reached and then produce seeds, which depletes resources so that plants cannot reproduce again for 2 or more years. Individuals are synchronized by pollen coupling or environmental forcing. We review the assumptions of these models and assess the extent to which they are consistent with general patterns in plant populations. We discuss the implications of the RBM for how plants respond to changes in the external environment. Overall, the RBM is a likely cause of synchrony in many, but not all, masting species. This mechanistic hypothesis also leads to specific, but not always intuitive, expectations about how plant resources affect mast seeding.

Altitudinal gradients are often used as natural laboratories to study ecosystem dynamics, biodiversity, and species' distribution response to climate gradients. However, the underlying climate gradients are rarely described in detail, especially in the tropics. In this study, we describe the diurnal and seasonal patterns in microclimate across a 3900 m altitudinal gradient in and adjacent to the Kosñipata Valley in Manu National Park, Peru, on the eastern slope of the tropical Andes. We focus on the understudied altitudinal range between 1500 and 3500 m using micrometeorological data associated with a permanent tree plot network designed to study cloud forest biodiversity and ecosystem dynamics. Data from this plot network were supplemented with data in the public domain across a 20 000 km 2 area with time series at individual sites lasting from 2 to 17 yr. Observed diurnal and seasonal trends in microclimate variables were explained by diurnal and seasonal variation in solar radiation and atmospheric moisture flux. Altitudinal trends in microclimate varied seasonally, with solar radiation, vapor pressure deficit, and temperature reaching their annual maximum earlier at higher altitudes, likely because of seasonally shifting cloud dynamics. Cloud dynamics were important in determining diurnal, seasonal, and altitudinal trends in several microclimate variables, suggesting that changes to cloud frequency and altitudinal occurrence associated with global climate change could have important impacts on cloud forest ecosystem dynamics, in addition to those of rising temperatures.

The hydrology of tropical mountain catchments plays a central role in ecological function, geochemical and biogeochemical cycles, erosion and sediment production, and water supply in globally important environments. There have been few studies quantifying the seasonal and annual water budgets in the montane tropics, particularly in cloud forests. We investigated the water balance and hydrologic regime of the Kosnipata catchment (basin area: 164.4 km(2)) over the period 2010-2011. The catchment spans over 2500 m in elevation in the eastern Peruvian Andes and is dominated by tropical montane cloud forest with some high-elevation puna grasslands. Catchment-wide rainfall was 3112 +/- 414 mm yr(-1), calculated by calibrating Tropical Rainfall Measuring Mission (TRMM) 3B43 rainfall with rainfall data from nine meteorological stations in the catchment. Cloud water input to streamflow was 316 +/- 116 mm yr(-1) (9.2% of total inputs), calculated from an isotopic mixing model using deuterium excess (Dxs) and delta D of waters. Field streamflow was measured in 2010 by recording height and calibrating to discharge. River runoff was estimated to be 2796 +/- 126 mm yr(-1). Actual evapotranspiration (AET) was 688 +/- 138mm yr(-1), determined using the Priestley and Taylor-Jet Propulsion Laboratory (PT-JPL) model. The overall water budget was balanced within 1.6 +/- 13.7 %. Relationships between monthly rainfall and river run-off follow an anticlockwise hysteresis through the year, with a persistence of high run-off after the end of the wet season. The size of the soil and shallow groundwater reservoir is most likely insufficient to explain sustained dry-season flow. Thus, the observed hysteresis in rainfall-run-off relationships is best explained by sustained groundwater flow in the dry season, which is consistent with the water isotope results that suggest persistent wet-season sources to stream-flow throughout the year. These results demonstrate the importance of transient groundwater storage in stabilising the annual hydrograph in this region of the Andes