Satellite-based estimation of net primary productivity for southern China's grasslands from 1982 to 2012

Grassland productivity change, along with the factors driving this change, is central to the study of terrestrial ecosystems. To date, few studies have examined these factors in grassland areas in southern China. In this study, we investigated grassland productivity change in an area in southern China that constitutes nearly 25% of the country's total terrestrial area. Pairing GIMMS NDVI3g data with meteorological data from between 1982 and 2012, we estimated grassland net primary productivity (NPP) using the Carnegie-Ames-Stanford-Approach model. We then investigated the spatiotemporal changes in grassland NPP in response to several climate factors. Overall, we found an average annual grassland NPP of 309.6 g C m(-2) with a relatively large annual variation of 198.3 to 365.1 g C m(-2). Annual NPP exhibited an increasing trend, from 288 g C m(-2) yr(-1) in the 1980s to 323 g C m(-2) yr(-1) in the 2010s, with a mean annual increase rate of 0.39%. More than two-thirds of the grasslands (70.69%) showed relatively small fluctuations in annual NPP change. Collectively, our results indicate that grasslands in southern China were a relatively productive and stable ecosystem over the study period, accounting for approximately 1.8 to 5.5% of total annual Chinese terrestrial NPP. Our results also indicate interesting correlations between NPP and climate factors. During the study period, and across the study area, solar radiation and precipitation were positively correlated with NPP, while temperature was negatively correlated with NPP. Increases in NPP due to increasing radiation and precipitation combined with the decreases in NPP resulting from increasing temperature yielded an insignificant change in NPP overall

Nitrous oxide fluxes from the littoral zone of a lake on the Qinghai-Tibetan Plateau

Nitrous oxide (N(2)O) fluxes were measured in six littoral mirco-zones of Lake Huahu on Qinghai-Tibetan Plateau in the peak growing season of years of 2006 and 2007. The weighted mean N(2)O flux rate was 0.08 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1) (ranged from -0.07 to 0.35 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1)). The result was relatively high in the scope of N(2)O fluxes from boreal and temperate lakes. Emergent plant zones (Hippuris vulgaris and Glyceria maxima stands) recorded the highest N(2)O flux rate (0.11 +/- 0.24 and 0.08 +/- 0.17 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1), respectively). Non-vegetated lakeshore recorded the lowest N(2)O flux (0.03 +/- 0.11 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1)), lower than that from the floating mat zone of Carex muliensis (0.05 +/- 0.18 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1)), the floating-leaved plant zone of Polygonum amphibium (0.07 +/- 0.11 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1)), and the wet meadow (0.07 +/- 0.15 mg N m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1)). Standing water depths were important factors to explain such spatial variations in N(2)O fluxes. Significant temporal variations in N(2)O fluxes were also found. Such temporal variation in N(2)O flux in the littoral zone may be dependent on the interaction of water regime and thermal conditions, instead of the latter solely. These results showed the importance of the littoral zone of lake, especially the emergent plant zone, as a hotspot of N(2)O fluxes in such grazing meadows

Territorial ants depress plant growth through cascading non-trophic effects in an alpine meadow

Understanding non-trophic interactions is critical to mechanistically linking community structure and ecosystem functioning. Despite the widespread occurrence of territoriality across animal taxa and ecosystems, the cascading ecological consequences of non-trophic interactions between territorial animals and intruders have been poorly studied. We experimentally investigated the non-trophic interaction between territorial ants and members of a dung decomposer community (i.e. predatory arthropods, maggots and coprophagous beetles) in an alpine meadow. We further examined how this non-trophic interaction cascaded to influence ecosystem properties including dung removal rate, soil nutrient status and aboveground plant biomass surrounding dung pats. Results indicated that territorial interference of ants on key decomposers cascaded to affect plant growth. Specifically, ants significantly decreased the abundance of coprophagous beetles at the time of their peak-abundance and hence decreased dung removal rates and soil nitrogen concentrations, ultimately decreasing aboveground plant biomass. The strength of this non-trophic cascading effect was comparable to those reported in studies addressing trophic cascades triggered by predator-prey interactions. Our findings suggest that the non-trophic interactions and associated cascading effects stemming from territorial behavior should be incorporated into ecological network modeling and research addressing biodiversity-ecosystem functioning relationships

Spatial patterns of the soil seed bank and extant vegetation across the dry Minjiang River valley in southwest China

The medium-scale spatial patterns of soil seed banks (SSBs) and extant vegetation and the roles of abiotic factors are poorly understood. We selected the dry Minjiang River valley of southwest China to investigate SSB structure and corresponding extant vegetation in a medium-scale size (200-230 km long, 3-4 km wide) at eight sites across the valley using a germination method and field surveys. We found that, there was low seed density and species number in SSB and less coverage and litter thickness for community in extant vegetation at central sites compared with transitional sites across the dry valley; Quercus spp. occurred frequently in extant vegetation at transitional sites, while Caryopteris spp., Jasminum spp., Rabdosia parvifolia. Sophora davidii, Campylotropis spp., and Bauhinia faberi var. Microphylla was present frequently at central sites: Carex spp. and Artemisia spp. occurred frequently in SSB at transitional sites, while Ajania spp., Poa spp., and Fagopyrum caudatum was present more frequently at central sites. Hierarchical cluster analysis and Kendall's correlation showed that the spatial variation of both SSB and extant vegetation had significant correlation with rainfall and air evaporation. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved

BIOMASS ALLOCATION AND TRADEOFFS OF PEDICULARIS LONGIFLORA RUDOLPH. AT TWO SLOPE ASPECTS IN AN ALPINE MEADOW OF THE EASTERN TIBETAN PLATEAU

Pedicularis longiflora is a typical grassland plant located in the alpine habitat in wet meadows or besides streams. This paper addresses the response and adaptation of P. longiflora under heterogeneous environmental conditions at different slope aspects in an alpine wet meadow, eastern Tibetan Plateau. The results show that P. longiflora at the southeast slope benefited more for its development and population maintenance. It also showed a relatively greater leaf biomass. However, P. longiflora invested more biomass to reproductive organs at the southwest slope aspect, where this species has better population continuation. Isometric scaling existed in coupled organ biomasses of P. longiflora which indicated that genetic regulation plays a key role in biomass allocation. P. longiflora allocated more biomass to aboveground parts, vegetative biomass, and non-photosynthetic organs biomass according to tradeoff values, respectively. In addition, both biotic and abiotic factors influenced biomass production of P. longiflora. Thus, soil temperature and interspecies competition in different habitats needs to be clearly understood and paid more attention to for cultivation and better industrialization of this herbal medicinal plant

Allometric partitioning theory versus optimal partitioning theory: the adjustment of biomass allocation and internal C-N balance to shading and nitrogen addition in Fritillaria unibracteata (Liliaceae)

Fritillaria unibracteata is a classic perennial alpine herb. In this study, we examined it's responses to shading (SH) and nitrogen addition (NA), as well as its correlation with internal C-N balance to detect how it adjusted to the changes of habitat conditions. Randomized block experiment was carried out in the field in Chuanbeimu Research Station in Songpan County, Sichuan Province, China (32 degrees 09'54 '' N, 103 degrees 38'36 '' E, altitude 3300 m a.s.l.). Two growing seasons after NA and SH, Fritillaria unibracteata's total plant biomass decreased significantly, with the proportion of biomass allocated to aboveground significantly increased. In addition, in this study, under both SH and NA treatments, Fritillaria unibracteata increased its biomass allocation to above-ground, which consisted with optimal partitioning theory. Moreover, Fritillaria unibracteata's biomass allocation was significantly correlated with its internal C-N status, regardless of nitrogen and light condition. We conclude that Fritillaria unibracteata optimizes its biomass allocation between root and shoot by adjusting its internal C-N balance, which would not be changed by the specialized resource storage organ-bulb