No abstract

Urban forest ecosystems, the structure and functions therein, are subjected to anthropogenic disturbances. Native and sensitive species from those forests might be lost due to such disturbances. At the same time, supplemented anthropogenic resources might create opportunities for exotic and invasive species. Although, invasive species are considered as one of the major threats to the urban biodiversity and ecosystems, the researches on invasion dynamics in the Himalayas have mostly focused on the impacts of invasion on forest structure and productivity. This study aims to understand the influence of forest structure and anthropogenic factors in invasion success that are poorly covered in the existing literature. We selected 11 urban forest patches for the study considering the presence-absence of selected invasive species and structural attributes. We used Principal Component Analysis (PCA) to reduce co-linearity in the covariates and generalized linear mixed effects model (GLMM) to identify the factors affecting the invasion success. We found that the structural attributes of the forests and anthropogenic disturbances regulated invasion success in urban forests. This implies that maintaining urban forest structural attributes, especially maintaining the stands with large-sized trees, are essential to regulate and control invasion in the context of urbanization.

Prevailing climate change is expected due to carbon dioxide emission to the atmosphere through soil respiration and perhaps the alteration in the terrestrial carbon cycle. The measurements to establish the effect and sensitivity of soil temperature, soil water content and plant biomass on soil respiration was performed in the sub-tropical grassland located in Central Nepal. Field measurements of soil respiration was conducted by using the closed-chamber method, and soil temperature, soil water content and plant biomass were monitored in the years 2015 and 2016. The soil respiration showed positive significant exponential function which accounted for 74.6% (R2=0.746, p<0.05) of its variation with the soil temperature. The temperature sensitivity of soil respiration, Q10 value obtained was 2.68. Similarly, soil respiration showed a positive significant exponential function that accounted for 37.2% (R2=0.372, p<0.05) of its variation with the soil water content. Remarkable seasonal and monthly variations were observed in soil respiration, soil temperature and soil water content, and the plant biomass as well followed the seasonal trend in variation of the soil respiration. Average soil respiration during measurements period was observed 325.51 mg CO2 m-2 h-1 and the annual soil respiration of the grassland in the years 2015 and 2016 was estimated 592.35 g C m-2 y-1. The study confirmed that soil temperature is the most influential primary factor in controlling soil respiration along with the soil water content and plant biomass. This research indicates that through emissions under the increasing temperature and precipitation, in the changing climate, the sub-tropical grassland could be an additional source of carbon dioxide to the atmosphere that might spur risk for further warming.

Societal Impact StatementPlant–pollinator relationships are fundamentally important for the conservation of the terrestrial biodiversity that rural communities in low‐income countries rely upon. In Nepal, a country that is biologically rich but economically poor, Rhododendron forests provide a range of ecosystem services that are under threat from overexploitation and climate change. Here, we suggest a vital role for pollinating birds in ensuring the sexual reproduction, and thus the long‐term survival, of Rhododendron populations. In this respect, the pollinators are an important link between people and the plants on which they depend. However, we also highlight how little we know about these interactions, with significant knowledge gaps for even the most basic aspects of their ecology.