Post-fire resource redistribution and fertility island dynamics in shrub encroached desert grasslands: a modeling approach

A common form of land degradation in desert grasslands is associated with the relatively rapid encroachment of woody plants, a process that has important implications on ecosystem structure and function, as well as on the soil hydrological and biogeochemical properties. Until recently this grassland to shrubland transition was thought to be highly irreversible. However recent studies have shown that at the early stages of shrub encroachment in desert grasslands, there exists a very dynamic shrub–grass transition state with enough grass connectivity between the shrub islands to allow for fire spread. In this state fire could play a major role in determining the dominance of grasses and their recovery from the effects of overgrazing. Using a spatially explicit cellular automata model, we show how the patch-scale feedbacks between fires and soil erosion affects resource redistribution and vegetation dynamics in a mixed grass–shrub plant community at landscape to regional scales. The results of this study indicate that at its early stages, the grassland-to-shrubland transition can be reversible and that the feedbacks between fire and soil erosion processes may play a major role in determining the reversibility of the system.     

MAP kinase phosphatase as a locus of flexibility in a mitogen-activated protein kinase signaling network

Intracellular signaling networks receive and process information to control cellular machines. The mitogen-activated protein kinase (MAPK) 1,2/protein kinase C (PKC) system is one such network that regulates many cellular machines, including the cell cycle machinery and autocrine/paracrine factor synthesizing machinery. We used a combination of computational analysis and experiments in mouse NIH-3T3 fibroblasts to understand the design principles of this controller network. We find that the growth factor-stimulated signaling network containing MAPK 1, 2/PKC can operate with one (monostable) or two (bistable) stable states. At low concentrations of MAPK phosphatase, the system exhibits bistable behavior, such that brief stimulus results in sustained MAPK activation. The MAPK-induced increase in the amounts of MAPK phosphatase eliminates the prolonged response capability and moves the network to a monostable state, in which it behaves as a proportional response system responding acutely to stimulus. Thus, the MAPK 1, 2/PKC controller network is flexibly designed, and MAPK phosphatase may be critical for this flexible response.     

Ovipositional responses of the pulse beetle, Bruchus chinensis (Coleoptera: Bruchidae) to extracts and compounds of Capparis decidua

Extracts of Capparis decidua stems and flowers showed insecticidal and oviposition inhibitory activities against Bruchus chinensis. The LC50 values of these extracts were found to increase with the increase in the polarity of the extract at different exposure periods. For instance, after 96 h, the LC50 values were found to be 3.619, 7.319, and 10.151 microg for CD1, CD2, and CD3, respectively. Extract CD7 was effective only at higher doses. The toxicity was found to be dose- and time-dependent. The females laid lesser number of eggs, when exposed to sublethal doses of different extracts and pure compounds, as compared to control. The maximum oviposition deterrence index was found for extract CD1 followed in decreasing order by CD2, CD3, and CD7. From extract CD1, two compounds were isolated and characterized as triacontanol (C1) and 2-carboxy-1,1-dimethylpyrrolidine (C2). When the females were exposed to sublethal doses of these compounds, they laid lesser number of eggs as compared to the control. C2 was found to have a slightly greater oviposition inhibition effect than C1. From fraction CD7, one novel compound labeled as CDF1 has been isolated and identified as 6-(1-hydroxy-non-3-enyl)tetrahydropyran-2-one. CDF1 has also shown insecticidal and oviposition inhibitory activities against B. chinensis at low concentrations.     

Formation of regulatory patterns during signal propagation in a Mammalian cellular network

We developed a model of 545 components (nodes) and 1259 interactions representing signaling pathways and cellular machines in the hippocampal CA1 neuron. Using graph theory methods, we analyzed ligand-induced signal flow through the system. Specification of input and output nodes allowed us to identify functional modules. Networking resulted in the emergence of regulatory motifs, such as positive and negative feedback and feedforward loops, that process information. Key regulators of plasticity were highly connected nodes required for the formation of regulatory motifs, indicating the potential importance of such motifs in determining cellular choices between homeostasis and plasticity.     

Multi-agent simulation of alternative scenarios of collaborative forest management

International calls for sustainable development advocate that forest management should be carried out in a multi-stakeholder environment. The importance of community participation is acknowledged in theIndonesian Act No. 41 on Forestry (1999). However, it is not clear how to achieve this in areas already allocated to a concession holder. Current regulations offer little flexibility for concessionaires to develop site-specific management, or to involve local communities in forest management. The research reported here examines the application of simulation techniques to explore scenarios of sustainable forest management addressing those limitations. Several scenarios have been developed using multi-agent simulation to examine social and biophysical issues. Of the four scenarios examined in this study, collaborative forest management involving both the concessionaire and the local community appears to offer the most promising pathway toward sustainability. The authors wish to acknowledge that this paper has been produced with financial support from Department for International Development of the UK, and the Asian Development Bank under RETA Grant 5812 and CIFOR. The views expressed here are those of the authors and can in no way be taken to reflect the official opinion of the donors or of CIFOR. The authors also thank Bruce Campbell for his inputs to the paper.     

ROC analysis of prepartum feeding time can accurately predict postpartum metritis development in HF crossbred cows

Receiver operating characteristic (ROC) analysis is a useful statistical tool to visualize, organize, and select diagnostic variables. Accuracy of the test is represented by the area under the ROC curve (AUC), sensitivity (Se), and specificity (Sp). In the present study, ROC analysis of prepartum feeding time (day ?11 to day ?2) of 20 pluriparous Holstein-Friesian crossbred cows were recorded, and the cows were followed up for detecting postpartum metritis development if any. Prepartum daily feeding time data during whole study was grouped into 2 periods (P1 [day ?11 to day ?7] and P2 [day ?6 to day ?2]). The AUC of feeding time for the P1 and P2 periods was 0.64 (P = 0.29) and 0.86 (P = 0.006), respectively. Cows with daily feeding times below the optimum threshold value of 284.5 min/d during P2 (Se = 75% and Sp = 91.67%) had more chance of developing postpartum metritis compared with those with daily feeding time above the threshold value (positive likelihood ratio = 9.0). Furthermore, relative risk (RR) analysis revealed that the risk of development of postpartum metritis increased as feeding time decreased below the optimum threshold value during P2 (RR = 5.571, P = 0.004). Thus, the optimum threshold value of feeding time during P2 may be used to predict risk of postpartum metritis, allowing for preventive measures to be implemented in the early postpartum period to reduce the likelihood of postpartum complications.     

Sensitivity of isolates of Macrophoma theicola from untreated and DMI treated tea to hexaconazole

Journal of Plant Diseases and Protection - Stem canker disease caused by Macrophoma theicola is a serious disease of tea in low country tea gardens in Sri Lanka. There is no evidence for the...